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Rescue bisphosphonate treatment of alveolar bone improves extraction socket healing and reduces osteonecrosis in zoledronate-treated mice
Abstract
Bisphosphonate (BP)-related osteonecrosis of the jaw, previously known as BRONJ, now referred to more broadly as medication-related osteonecrosis of the jaw (MRONJ), is a morbid condition that represents a significant risk for oncology patients who have received high dose intravenous (IV) infusion of a potent nitrogen containing BP (N-BP) drug. At present, no clinical procedure is available to prevent or effectively treat MRONJ. Although the pathophysiological basis is not yet fully understood, legacy adsorbed N-BP in jawbone has been proposed to be associated with BRONJ by one or more mechanisms. We hypothesized that removal of the pre-adsorbed N-BP drug common to these pathological mechanisms from alveolar bone could be an effective preventative/therapeutic strategy. This study demonstrates that fluorescently labeled BP pre-adsorbed on the surface of murine maxillo-cranial bone in vivo can be displaced by subsequent application of other BPs. We previously described rodent BRONJ models involving the combination of N-BP treatment such as zoledronate (ZOL) and dental initiating factors such as tooth extraction. We further refined our mouse model by using gel food during the first 7 days of the tooth extraction wound healing period, which decreased confounding food pellet impaction problems in the open boney socket. This refined mouse model does not manifest BRONJ-like severe jawbone exposure, but development of osteonecrosis around the extraction socket and chronic gingival inflammation are clearly exhibited. In this study, we examined the effect of benign BP displacement of legacy N-BP on tooth extraction wound healing in the in vivo model. Systemic IV administration of a low potency BP (lpBP: defined as inactive at 100 μM in a standard protein anti-prenylation assay) did not significantly attenuate jawbone osteonecrosis. We then developed an intra-oral formulation of lpBP, which when injected into the gingiva adjacent to the tooth prior to extraction, dramatically reduced the osteocyte necrosis area. Furthermore, the tooth extraction wound healing pattern was normalized, as evidenced by timely closure of oral soft tissue without epithelial hyperplasia, significantly reduced gingival inflammation and increased new bone filling in the extraction socket. Our results are consistent with the hypothesis that local application of a rescue BP prior to dental surgery can decrease the amount of a legacy N-BP drug in proximate jawbone surfaces below the threshold that promotes osteocyte necrosis. This observation should provide a conceptual basis for a novel strategy to improve socket healing in patients treated with BPs while preserving therapeutic benefit from anti-resorptive N-BP drug in vertebral and appendicular bones.
... We have previously reported that N-BP adsorption to bone minerals is not permanent but rather establishes an equilibrium 14,15 . Thus, we hypothesized that the legacy N-BP adsorbed on the jawbone might be displaced and replaced by a pharmacologically inactive N-BP through the equilibrium-based molecular competitive binding, leading to the attenuation of abnormal oral wound healing. ...
... Steadystate release of adsorbed N-BP drugs from bone is slow, as shown by studies determining their half-lives in the skeleton, which range from months to several years 17 . However, we have shown that N-BPs can be rapidly displaced from synthetic HAp or bone mineral surfaces by the application of competing BPs in solution 14,15 . This led us to explore the idea that displacement of legacy N-BP from the jawbone by local treatment with a pharmacologically inactive N-BP prior to the high-risk dentoalveolar surgical manipulations would abate the development of abnormal wound healing. ...
... We have previously used the mouse model described above to examine the effect of intra-oral injection of non-nitrogen containing BP for the attenuation of abnormal or delayed tooth extraction wound healing of ZOL-treated mice 14 , based on which we determined the number of mice per group to be n = 8 by the preliminary results. The primary outcome measure was not used to determine the sample size. ...
Background
Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a rare but serious side effect of nitrogen-containing bisphosphonate drugs (N-BPs) frequently prescribed to reduce skeletal-related events in bone malignancies and osteoporosis. BRONJ is associated with abnormal oral wound healing after dentoalveolar surgery and tooth extraction. We previously found that N-BP chemisorbed to bone mineral hydroxyapatite was dissociated by secondary applied N-BP. This study investigated the effect of the surface equilibrium-based removal of N-BP from jawbone on tooth extraction wound healing of zoledronate (ZOL)-treated mice.
Methods
A pharmacologically inactive N-BP derivative (the 4-pyridyl isomer of risedronate equipped with a near-infrared 800CW fluorescent imaging dye, 800CW-pRIS) was designed and synthesized. 800CW-pRIS was intra-orally injected or topically applied in a deformable nano-scale vesicle formulation (DNV) to the palatal tissue of mice pretreated with ZOL, a potent N-BP. The female C56BL6/J mice were subjected to maxillary molar extraction and oral wound healing was compared for 800CW-pRIS/ZOL, ZOL and untreated control groups.
Results
800CW-pRIS is confirmed to be inactive in inhibiting prenylation in cultured osteoclasts while retaining high affinity for hydroxyapatite. ZOL-injected mice exhibit delayed tooth extraction wound healing with osteonecrosis relative to the untreated controls. 800CW-pRIS applied topically to the jaw one week before tooth extraction significantly reduces gingival oral barrier inflammation, improves extraction socket bone regeneration, and prevents development of osteonecrosis in ZOL-injected mice.
Conclusions
Topical pre-treatment with 800CW-RIS in DNV is a promising approach to prevent the complication of abnormal oral wound healing associated with BRONJ while retaining the anti-resorptive benefit of legacy N-BP in appendicular or vertebrate bones.
... N-BP chemisorption to bone results from its high affinity to hydroxyapatite (HAp), the mineral component of bone (Nancollas et al., 2006). Recent investigations in our laboratories revealed that pre-adsorbed N-BPs can be displaced from HAp by exposure to a second N-BP/BP in aqueous buffer both in vitro and in vivo (Hokugo et al., 2013;Hokugo et al., 2019). This led us to envision a new experimental model based on the selective removal of pharmacologically active legacy N-BP locally from jawbone by intra-oral application of a second BP with low pharmacological potency (lpBP). ...
... The nitrogencontaining side chain of N-BPs, an essential pharmacophore in all potent N-BP antiresorptive drugs, is absent in HMDP which, however, retains an α-OH group together with two phosphonate groups, conferring high affinity to HAp ( Figure 1A). Thus, we postulated that HMDP in solution might be able to decrease the amount of legacy N-BP at the jaw bone surface by a competitive displacement mechanism as we reported (Hokugo et al., 2013;Hokugo et al., 2019). ZOL IV injection to mice increased femur trabecular bone volume over the saline vehicle solution injection control, whereas HMDP IV injection with the same dose did not alter the bone architecture ( Figure 1B and C). ...
... ZOL IV injection to mice increased femur trabecular bone volume over the saline vehicle solution injection control, whereas HMDP IV injection with the same dose did not alter the bone architecture ( Figure 1B and C). The lack of pharmacological effect of HMDP in vivo was consistent with our previous study using a standard in vitro prenylation assay (Hokugo et al., 2019) and confirmed HMDP to be an lpBP. Next, we tested the ability of HMDP to displace the pre-adsorbed N-BP from bone mineral surface. ...
Bisphosphonate-related osteonecrosis of the jaw (BRONJ) presents as a morbid jawbone lesion in patients exposed to a nitrogen-containing bisphosphonate (N-BP). Although it is rare, BRONJ has caused apprehension among patients and healthcare providers and decreased acceptance of this anti-resorptive drug class to treat osteoporosis and metastatic osteolysis. We report here a novel method to elucidate the pathological mechanism of BRONJ by the selective removal of legacy N-BP from the jawbone using an intra-oral application of hydroxymethylene diphosphonate (HMDP) formulated in liposome-based deformable nanoscale vesicles (DNV). After maxillary tooth extraction, zoledronate-treated mice developed delayed gingival wound closure, delayed tooth extraction socket healing and increased jawbone osteonecrosis consistent with human BRONJ lesion. Single cell RNA sequencing of mouse gingival cells revealed oral barrier immune dysregulation and unresolved pro-inflammatory reaction. HMDP-DNV topical applications to nascent mouse BRONJ lesions resulted in accelerated gingival wound closure and bone socket healing as well as attenuation of osteonecrosis development. The gingival single cell RNA sequencing demonstrated resolution of chronic inflammation by increased anti-inflammatory signature gene expression of lymphocytes and myeloid-derived suppressor cells. This study suggests that BRONJ pathology is related to N-BP levels in jawbones and demonstrates the potential of HMDP-DNV as an effective BRONJ therapy.
... BPs could bind to hydroxyapatite crystals of the bone tissue via chelation of calcium ions by their two phosphate groups (Hokugo et al., 2019;Kates and Ackert-Bicknell, 2016). During bone resorption by osteoclasts, BPs incorporated in the bone are detached and released from the binding sites into the acidic lacuna and taken-up by osteoclasts (Barton et al., 2020). ...
... Non-nitrogen-containing BPs could induce osteoclast apoptosis by incorporating into ATP decreasing osteoclast resorption by reducing the number of active osteoclasts on the bone surface. On the other hand, nitrogen-containing BPs inhibit pyrophosphate synthase resulting in cytoskeletal changes in osteoclasts, and thus they inhibit osteoclast activity and provoke osteoclast apoptosis (Hokugo et al., 2019;Barton et al., 2020;Lechner et al., 2021). ...
... Although osteonecrosis of the jaw bone is regarded as an adverse impact of long-term BP administration, many studies have produced promising outcomes of reducing or preventing this unfavorable condition (Mauceri et al., 2018;Hokugo et al., 2019;Otto et al., 2021). For instance, in a current study, Nakagawa et al. (2021) revealed osteonecrosis following long-term subcutaneous administration of zoledronic acid in an osteoporotic rat model. ...
This study was carried out to assess the effect of different cage stocking densities on the production performance of Nandanam quail III reared up to 42 days. Three hundred day old Nandanam quail III were randomly assigned to 2.5 x 1.5 ft cages and distributed with 3 treatments (20, 25 and 30 quails per cage or 0.17, 0.14 and 0.11 sq. ft per quail, respectively) and 4 replicates. There were significant differences among treatments for bi-weekly body weight, feed consumption, feed conversion ratio and net profit per bird. There was a reduction (P>0.05) in body weight with the increase in stocking density and the 4th and 6th week body weight were 144.17±3.84, 128.55±3.63 and 108.03±2.69 g; and 216.86±5.95, 207.76±4.01 and 197.27±3.81 g, respectively. The feed consumption per bird (g) up to 42 days were 665.69±0.01, 532.19±0.01 and 443.23±0.01 respectively. Better feed conversion ratio (2.57 and 2.25) and net profit per bird (Rs. 4.48 and 7.15) were observed where the birds reared at the cage stocking density of 0.14 sq.ft and 0.11 sq.ft per bird, respectively. This study concluded that the cage stocking density between 0.11 and 0.14 sq.ft per bird will be more economical for rearing Nandanam quail III in cage system of rearing up to 42 days of age.
... One of the reasons for the disparate findings between the current study and prior literature may be the choice of bisphosphonate. While the class of nitrogen-containing BPs (e.g., alendronate, zoledronate, pamidronate) exhibit anti-resorptive abilities due to their inhibition of FPPS, other bisphosphonates can be engineered to have minimal to no FPPS inhibition (Sung et al., 2020) while still maintaining their affinity for hydroxyapatite minerals, as is the case with OFS-3 (Hokugo et al., 2019;Okawa et al., 2022). Furthermore, BPs conjugated to other molecules, like OFS-3, may demonstrate even further attenuated antiresorptive effects compared to BPs used in isolation (Sun et al., 2016). ...
... Also noteworthy, our findings are specific to OFS-3, a novel modified pamidronate-based BP molecule. Different bisphosphonates can have significantly different degrees of osteoclast inhibition (Hokugo et al., 2019;Okawa et al., 2022), which may have alternative effects on outcome measures. Finally, this investigation is an early-phase translational investigation of a method for targeting molecules to the site of tendon-bone repair. ...
Background: Osteoadsorptive fluorogenic sentinel 3 (OFS-3) is a recently described compound that contains a bone-targeting bisphosphonate (BP) and cathepsin K (Ctsk)-triggered fluorescence signal. A prior study in a murine Achilles repair model demonstrated its effectiveness at targeting the site of tendon-to-bone repair, but the intrinsic effect of this novel bisphosphonate chaperone on tendon-to-bone healing has not been previously explored. We hypothesized that application of this bisphosphonate-fluorophore cargo conjugate would not affect the biomechanical properties or histologic appearance of tendon-bone repairs.
Materials and Methods: Right hindlimb Achilles tendon-to-bone repair was performed on 12-week old male mice. Animals were divided into 2 groups of 18 each: 1) Achilles repair with OFS-3 applied directly to the repair site prior to closure, and 2) Achilles repair with saline applied prior to closure. Repaired hindlimbs from 12 animals per group were harvested at 6 weeks for biomechanical analysis with a custom 3D-printed jig. At 4 and 6 weeks, repaired hindlimbs from the remaining animals were assessed histologically using H&E, immunohistochemistry (IHC) staining for the presence of Ctsk, and second harmonic generation (SHG) imaging to evaluate collagen fibers.
Results: At 6 weeks, there was no significant difference in failure load, stiffness, toughness, or displacement to failure between repaired hindlimbs that received OFS-3 versus saline. There was no difference in tissue healing on H&E or Ctsk staining on immunohistochemistry between animals that received OFS-3 versus saline. Finally, second harmonic generation imaging demonstrated no difference in collagen fiber parameters between the two groups.
Conclusion: OFS-3 did not significantly affect the biomechanical properties or histologic appearance of murine Achilles tendon-to-bone repairs. This study demonstrates that OFS-3 can target the site of tendon-to-bone repair without causing intrinsic negative effects on healing. Further development of this drug delivery platform to target growth factors to the site of tendon-bone repair is warranted.
... In this study, the high-prevalence of BRONJ in the animal model was used and modified as previously described. 15 Briefly, before tooth extraction, C57BL/6 J mice were intravenous injection of 600 μg/Kg zoledronate (Zometa, designated as Z; Novartis, Stein, Switzerland) as previously described. 15,16 No steroids were administered. ...
... 15 Briefly, before tooth extraction, C57BL/6 J mice were intravenous injection of 600 μg/Kg zoledronate (Zometa, designated as Z; Novartis, Stein, Switzerland) as previously described. 15,16 No steroids were administered. The animals were grouped as follows: (1) the Ctl group, in which only the right maxillary first molars were removed; (2) Z group, which received zoledronate injection and tooth extraction; (3) Z + Nit group, which received zolendronate and 4 mM of sodium nitrate. ...
Bisphosphonate‐related osteonecrosis of the jaw (BRONJ) is a serious complication that occurs in patients with osteoporosis or metastatic bone cancer treated with bisphosphonate. There is still no effective treatment and prevention strategy for BRONJ. Inorganic nitrate, which is abundant in green vegetables, has been reported to be protective in multiple diseases. To investigate the effects of dietary nitrate on BRONJ‐like lesions in mice, we utilized a well‐established mouse BRONJ model, in which tooth extraction was performed. Specifically, 4 mM sodium nitrate was administered in advance through drinking water to assess the short‐ and long‐term effects on BRONJ. Zoledronate injection could induce severe healing inhibition of the tooth extraction socket, while addition of pretreating dietary nitrate could alleviate the inhibition by reducing monocyte necrosis and inflammatory cytokines production. Mechanistically, nitrate intake increased plasma nitric oxide levels, which attenuated necroptosis of monocytes by downregulating lipid and lipid‐like molecule metabolism via a RIPK3 dependent pathway. Our findings revealed that dietary nitrate could inhibit monocyte necroptosis in BRONJ, regulate the bone immune microenvironment and promote bone remodelling after injury. This study contributes to the understanding of the immunopathogenesis of zoledronate and supports the feasibility of dietary nitrate for the clinical prevention of BRONJ. (A) Schematic overview of study procedures: 4 mM nitrate was added to the drinking water of C57/BL6 mice 1 week before injection of zoledronate up to 1 or 5 weeks after extraction of the right upper first molar. (B) Proposed model: Dietary nitrate could regulate monocyte necrosis stimulated by zoledronate by producing NO in vivo, thus regulating immunity and promoting bone remodelling after injury.
... All mouse studies were performed in accordance with Institutional Guidelines on Animal Experimentation at Keio University of The Keio University Institutional Animal Care and Use Committee. Various doses of zoledronate administered to promote ONJ development have been reported in mouse studies: some utilized a single injection at doses from 0.1 to 0.54 mg/kg before tooth extraction 24,25,45,46 , and others administered zoledronate ranging from 0.1 to 0.6 mg/ kg/week before and after tooth extraction 17,26,[47][48][49][50][51][52][53][54][55] . Also, zoledronate has been administered to mice either intravenously 48,52 , intra-peritoneally or subcutaneously 47,49,50,56 . ...
... Also, zoledronate has been administered to mice either intravenously 48,52 , intra-peritoneally or subcutaneously 47,49,50,56 . In general, higher doses of zoledronate are administered to mice than to humans 17,26,45,50,56 , as bone turnover in mice is reportedly faster than in humans 57 . Here, we performed experiments using our established ONJ model 17 . ...
Invasive dental treatment such as tooth extraction following treatment with strong anti-bone resorptive agents, including bisphosphonates and denosumab, reportedly promotes osteonecrosis of the jaw (ONJ) at the extraction site, but strategies to prevent ONJ remain unclear. Here we show that in mice, administration of either active vitamin D analogues, antibiotics or anti-inflammatory agents can prevent ONJ development induced by tooth extraction during treatment with the bisphosphonate zoledronate. Specifically, tooth extraction during treatment with zoledronate induced osteonecrosis in mice, but administration of either 1,25(OH)2D3 or ED71, both active vitamin D analogues, significantly antagonized osteonecrosis development, even under continuous zoledronate treatment. 1,25(OH)2D3 or ED71 administration also significantly inhibited osteocyte apoptosis induced by tooth extraction and bisphosphonate treatment. Administration of either active vitamin D analogue significantly inhibited elevation of serum inflammatory cytokine levels in mice in response to injection of lipopolysaccharide, an infection mimetic. Furthermore, administration of either anti-inflammatory or antibiotic reagents significantly blocked ONJ development following tooth extraction and zoledronate treatment. These findings suggest that administration of active vitamin D, anti-inflammatory agents or antibiotics could prevent ONJ development induced by tooth extraction in patients treated with zoledronate.
... Since then, additional fluorescent bisphosphonates were prepared, expanding the "toolkit" to cover all clinically used N-heterocyclic BPs (ZOL, MIN) and related analogues, as well as a wider spectroscopic window from visible to near-infrared range (Fig. 17) [109]. These probes have been used in various imaging studies in skeletal-related fields [127][128][129][130], and further expanded in non-skeletal fields in recent years, including dental research [131][132][133][134][135][136], otology [137][138][139], drug distribution studies [140,141], cancer research [142,143], nephrology [144] and brain calcification studies [145]. ...
... For example, McKenna and collaborators have exploited the fact that one bisphosphonate can displace another on the bone surface, which has led to the development of an "antidote" procedure [131]. By utilizing relatively inactive (low potency) bisphosphonates (e.g., some fluorescent bisphosphonates) that maintain their bone binding affinity, it has been shown that this strategy may aid the prevention and treatment of related symptoms of zoledronate associated osteonecrosis of the jaw in a rodent model [136]. In addition, a recent significant study by McDonald, et al. reported a novel cellular program for osteoclast reuse through their fission, transport, and reassembly process (osteoclast-osteomorph recycling) [146]. ...
The bisphosphonates ((HO)2P(O)CR¹R²P(O)(OH)2, BPs) were first shown to inhibit bone resorption in the 1960s, but it was not until 30 years later that a detailed molecular understanding of the relationship between their varied chemical structures and biological activity was elucidated. In the 1990s and 2000s, several potent bisphosphonates containing nitrogen in their R² side chains (N-BPs) were approved for clinical use including alendronate, risedronate, ibandronate, and zoledronate. These are now mostly generic drugs and remain the leading therapies for several major bone-related diseases, including osteoporosis and skeletal-related events associated with bone metastases. The early development of chemistry in this area was largely empirical and only a few common structural features related to strong binding to calcium phosphate were clear. Attempts to further develop structure-activity relationships to explain more dramatic pharmacological differences in vivo at first appeared inconclusive, and evidence for mechanisms underlying cellular effects on osteoclasts and macrophages only emerged after many years of research. The breakthrough came when the intracellular actions on the osteoclast were first shown for the simpler bisphosphonates, via the in vivo formation of P-C-P derivatives of ATP. The synthesis and biological evaluation of a large number of nitrogen-containing bisphosphonates in the 1980s and 1990s led to the key discovery that the antiresorptive effects of these more complex analogs on osteoclasts result mostly from their potency as inhibitors of the enzyme farnesyl diphosphate synthase (FDPS/FPPS). This key branch-point enzyme in the mevalonate pathway of cholesterol biosynthesis is important for the generation of isoprenoid lipids that are utilized for the post-translational modification of small GTP-binding proteins essential for osteoclast function. Since then, it has become even more clear that the overall pharmacological effects of individual bisphosphonates on bone depend upon two key properties: the affinity for bone mineral and inhibitory effects on biochemical targets within bone cells, in particular FDPS. Detailed enzyme–ligand crystal structure analysis began in the early 2000s and advances in our understanding of the structure-activity relationship, based on interactions with this target within the mevalonate pathway and related enzymes in osteoclasts and other cells have continued to be the focus of research efforts to this day. In addition, while many members of the bisphosphonate drug class share common properties, now it is more clear that chemical modifications to create variations in these properties may allow customization of BPs for different uses.
Thus, as the appreciation for new potential opportunities with this drug class grows, new chemistry to allow ready access to an ever-widening variety of bisphosphonates continues to be developed. Potential new uses of the calcium phosphate binding mechanism of bisphosphonates for the targeting of other drugs to the skeleton, and effects discovered on other cellular targets, even at non-skeletal sites, continue to intrigue scientists in this research field.
... Various experimental therapies were proposed for BRONJ treatment, aiming to promote gingival wound healing, as local application of adipose-derived stem cells, of growth factors, of platelet rich fibrine, or low-level laser therapy [10][11][12]. Improved extraction socket healing was achieved by local application of a rescue bisphosphonates treatment able to decrease its bioavailability in the jawbone surfaces [13]. The background of these therapies is the assumption that bisphosphonates impair keratinocyte and fibroblast function and reduces soft tissue capacity of healing and vascularization. ...
... Materials 2020,13, 1955 ...
Bisphosphonate-associated osteonecrosis of the jaw (BRONJ), a post-surgical non-healing wound condition, is one of the most common side effects in patients treated with nitrogen-containing bisphosphonates. Its physiopathology has been related with suppression of bone turnover, of soft tissue healing and infection. Biphasic calcium phosphates (BCP) are used as a drug delivery vehicle and as a bone substitute in surgical wounds. Due to their capacity to adsorb zoledronate, it was hypothesized these compounds might have a protective effect on the soft tissues in BRONJ wounds. To address this hypothesis, a reproducible in vivo model of BRONJ in Wistar rats was used. This model directly relates chronic bisphosphonate administration with the development of osteonecrosis of the jaw after tooth extraction. BCP granules were placed in the alveolus immediately after tooth extraction in the test group. The animals were evaluated through nuclear medicine, radiology, macroscopic observation, and histologic analysis. Encouragingly, calcium phosphate ceramics were able to limit zoledronate toxicity in vivo and to favor healing, which was evidenced by medical imaging (nuclear medicine and radiology), macroscopically, and through histology. The studied therapeutic option presented itself as a potential solution to prevent the development of maxillary osteonecrosis.
... In the mAb alone group, there was no epithelial defect in the extraction socket, but half of the group showed abnormal healing with a thickened epithelium (Fig. 1B). Such epithelial hyperplasia has also been reported in a murine BRONJ model [23,24]. Kuroshima et.al reported that the administration of an anti-RANKL antibody to gingival fibroblasts did not affect the proliferative capacity or apoptosis [25]. ...
Medication-related osteonecrosis of the jaw is a serious disease occurring in patients with cancer and osteoporosis, who are undergoing treatment with antiresorptive agents (ARAs) such as bisphosphonate (BP) or denosumab, an antibody targeting receptor activator of NF-κB ligand. Recently, stem cell-based therapy has been shown to be effective in preventing the development of bisphosphonate-related osteonecrosis of the jaw. However, studies on denosumab-related osteonecrosis of the jaw (DRONJ) remain limited. Here, the efficacy of treatment with dental pulp stem cell conditioned media (DPSC-CM) in preventing DRONJ in a murine model was evaluated. Local administration of DPSC-CM into the extraction socket of a mouse with DRONJ decreased the number of empty osteocyte lacunae and the prevalence of ONJ. In tissues surrounding the extraction sockets in the DPSC-CM-treated group, the expression of inflammatory cytokines was attenuated and that of osteogenesis-related molecules was enhanced compared to that in the control group. Further, the expression of Wnt signaling molecules, which had been suppressed, was improved. These findings collectively suggest that DPSC-CM prevents ONJ development in a murine DRONJ model.
... Liu et al. 25 29 In addition, given the widespread use of BP both therapeutically (e.g., osteoporosis) 30 and diagnostically (e.g., bone scintigraphy), 31 the transient use of these agents appears safe. Furthermore, it is possible to engineer BP molecules that bind HAP without significantly impairing local osteoclast activity 32,33 as is the case with OFS-3. ...
Tendon injuries are common and often treated surgically, however, current tendon repair healing results in poorly organized fibrotic tissue. While certain growth factors have been reported to improve both the strength and organization of the repaired enthesis, their clinical applicability is severely limited due to a lack of appropriate delivery strategies. In this study, we evaluated a recently developed fluorescent probe, Osteoadsorptive Fluorogenic Sentinel-3 (OFS-3) that is composed of a bone-targeting bisphosphonate moiety linked to fluorochrome and quencher molecules joined via a cathepsin K-sensitive peptide sequence. Using a murine Achilles tendon-to-bone repair model, bisphosphonate-based and/or Ctsk-coupled imaging probes were applied either locally or systemically. Fluorescence imaging was used to quantify the resultant signal in vivo. After tendon-bone repair, animals that received either local or systemic administration of imaging probes demonstrated significantly higher fluorescence signal at the repair site compared to the sham surgery group at all time points (p<0.001), with signal peaking at 7 to 10 days after surgery. Our findings demonstrate the feasibility of using a novel bisphosphonate-based targeting and Ctsk-activated delivery of molecules to the site of tendon-to-bone repair and creates a foundation for further development of this platform as an effective strategy to deliver bioactive molecules to sites of musculoskeletal injury. This article is protected by copyright. All rights reserved.
... Regardless of the via of administration (oral or injectable), there is a high deposition of the drug in the jaws, leading to impaired post-trauma repair. Another important factor for the occurrence in the jaws is the presence of thin mucosa, susceptible to trauma, and presence of oral biofilm (HOKUGO et al., 2019). ...
This study aimed to clinically evaluate the effect of platelet- and leukocyte-rich fibrin (L-PRF) membranes in preventing bisphosphonate-related osteonecrosis of the jaw (BRONJ) in rats. In this study, twelve Wistar rats (six males and six females) were used. A split-mouth study was performed; the right-side was used as treatment, with treatment of platelet- and leukocyte-rich fibrin membranes (L-PRF group, LPRFG), and the left-side received no intervention as control (control group, CG). The rats received intravenous Zolendronate (Zol) (80 ug/kg/week) injections during nine weeks to induce the BRONJ. The surgical extractions were divided into two stages: in the eighth week of Zol injections, the first lower molars on both sides were removed followed by bone decorticalization. In the ninth week of Zol injections, extractions of the second lower molars were performed on both sides, followed by bone decorticalization. L-PRF membranes were made of 1 ml of blood by cardiac puncture. The following clinical variables were analyzed: presence of bone exposure, inflammation (edema, erythema), suppuration, bony sequestrum and epithelialization of the alveoli. In addition, the mesiodistal (MD) and buccolingual (BL) dimensions of bone exposure were obtained using a millimeter probe. Statistical analysis was performed using Fisher's exact test, with a significance level of 0.05. There were no significant differences between the sides regarding the presence of bone exposure, inflammation, suppuration, bony sequestrum and epithelialization of the alveoli (p > 0.05). However, lower bone exposure was observed in the MD (p = 0.002) and BL (p = 0.03) dimensions in the LPRFG. Thus, the use of L-PRF membrane decreased bone exposure contributing to the alveoli healing of BRONJ in rats.
... It is, nevertheless, a matter of concern that the medical-related osteonecrosis of the jaw (MRONJ) condition, caused by powerful BPs direct toxicity to bone and soft tissue cells, is fostered by treatment duration and concomitant oral surgery [36]. Fortunately, there is evidence of the use of intra-oral formulation of low potency BPs (lpBP) to dramatically reduce the osteocyte necrosis area when locally administered in Zoledronate-pretreated mice [37]. Therefore, beyond the need for new drugs to treat osteoporosis where CatK inhibitors can play a central role as new therapies for this disease, its role in patients with MRONJ needs to receive further dedicated studies [38]. ...
Introduction:
Cathepsin K (CatK) is a lysosomal cysteine protease and the predominant cathepsin expressed in osteoclasts, where it degrades the bone matrix. Hence, CatK is an attractive therapeutic target related to diseases characterized by bone resorption, like osteoporosis.
Areas covered:
This review summarizes the patent literature from 2011 to 2021 on CatK inhibitors and their potential use as new treatments for osteoporosis. The inhibitors were classified by their warheads, with the most explored nitrile-based inhibitors. Promising in vivo results have also been disclosed.
Expert opinion:
As one of the most potent lysosomal proteins whose primary function is to mediate bone resorption, cathepsin K remains an excellent target for therapeutic intervention. Nevertheless, there is no record of any approved drug that targets CatK. The most notable cases of drug candidates targeting CatK were balicatib and odanacatib, which reached Phase II and III clinical trials, respectively, but did not enter the market. Further developments include exploring new chemical entities beyond the nitrile-based chemical space, with improved ADME and safety profiles. In addition, CatK's role in cancer immunoexpression and its involvement in the pathophysiology of osteo- and rheumatoid arthritis have raised the race to develop activity-based probes with excellent potency and selectivity.
... We have recently found promising results using locally delivered chelating agents such as EDTA, which improved socket healing and prevented osteonecrosis in zol-treated animals. [22] Another study showed that the displacement of pre-adsorbed nitrogen-containing bisphosphonates using a weaker BP significantly attenuated osteonecrosis [28]. Thus, future research should Antibiotics 2021, 10, 1380 9 of 13 be focused on therapeutic approaches that locally remove matrix bound bisphosphonates from the bone surface. ...
(1) Background: The aim of this study was to test whether matrix-bound zoledronate (zol) molecules enhanced the oral biofilm colonization of a mineralized matrix, rendering the alveolar bone more susceptible to medication-related osteonecrosis of the jaw (MRONJ) following invasive dental procedures. (2) Methods: We tested the effect of matrix-bound zol on the growth and attachment of Porphyromonas gingivalis (Pg), Fusobacterium nucleatum (Fn) and Actinomyces israelii (Ai), and whether the nitrogen-containing component of zol contributed to such effect. The role of oral bacteria in the induction of osteonecrosis was then tested using an extra-oral bone defect model. (3) Results: The attachment of biofilm to hydroxyapatite discs increased when the discs were pre-treated with zol. Bacterial proliferation was not affected. Matrix-bound zol was more potent than non-nitrogen-containing etidronate in enhancing the colonization. Stimulation was dampened by pre-treating the bacteria with histidine. The delivery of oral biofilm to a tibial defect caused osteonecrosis in zol-treated rats. (4) Conclusions: We conclude that matrix-bound zol enhances the oral biofilm colonization of hydroxyapatite. This enhancement depended on the presence of the nitrogen-containing group. The oral biofilm rendered the extra-oral bone susceptible to medication-related osteonecrosis, suggesting that it has an important role in the induction of MRONJ.
... Some previous studies that investigated the effects of ZOA and Dex combination therapy on wound healing of tooth extraction sockets showed that BP-related ONJ (BRONJ)-like lesions were induced in up to 50% of ZOA-treated mice [22,23]. Hokugo et al. considered that the ONJ-like bone exposure in mice was often associated with food impaction and showed that a gel diet resulted in wound healing with no bone exposure in ZOAtreated mice [31]. Recently, Kozutsumi et al. focused on a report that 50% of BRONJ stage 0 (i.e., without bone exposure/necrosis) progressed to a higher stage [32], and created a mouse model of BRONJ stage 0-like lesions to investigate the effect of high-dose BPs on extraction socket healing [33]. ...
Osteonecrosis of the jaw (ONJ) is a serious adverse event that is associated with antiresorptive agents, and it manifests as bone exposure in the maxillofacial region. Previous clinical reports suggest that mechanical trauma would trigger ONJ in a manner that is similar to tooth extractions. To the best of our knowledge, there have been few detailed pathophysiological investigations of the mechanisms by which occlusal/mechanical trauma influences ONJ. Here, we developed a novel mouse model that exhibits ONJ following experimental hyperocclusion and nitrogen-containing bisphosphonate (N-BP) treatment. This in vivo model exhibited ONJ in alveolar bone, particularly in the mandible. Moreover, the experimental hyperocclusion induced remarkable alveolar bone resorption in both mouse mandible and maxilla, whereas N-BP treatment completely prevented alveolar bone resorption. In this study, we also modeled trauma by exposing clumps of mesenchymal stem cells (MSCs)/extracellular matrix complex to hydrostatic pressure in combination with N-BP. Hydrostatic pressure loading induced lactate dehydrogenase (LDH) release by calcified cell clumps that were differentiated from MSCs; this LDH release was enhanced by N-BP priming. These in vivo and in vitro models may contribute further insights into the effect of excessive mechanical loading on ONJ onset in patients with occlusal trauma.
... The key clinical feature of BRONJ is the retarded gingival healing with necrosis exposure [30], however, it is still unclear why such the lesion should present with loss of oral soft tissue as the primary clinical feature. As mentioned in the literature, oral mucosa as a unique soft tissue is superior in terms of preventing wound infection and promoting the underlying bone remodeling [31]. ...
Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a clinical condition that specifically occurs in the oral cavity, characterized by retarded wound healing in oral mucosa accelerating the exposure of bone. Moreover, the pathological mechanism remains poorly understood. Gingival mesenchymal stem cells (GMSCs) play a critical role in gingival healing and soft tissue regeneration. Although previous studies have showed that bisphosphonates (BPs) are highly toxic to healthy GMSC, there is overall lack of direct evidence demonstrating the characterization of GMSCs derived from BRONJ patients. In present study, we isolated GMSCs for the first time from the central area of BRONJ patients’ gingiva (center-BRONJ GMSCs) and the peripheral area (peri-BRONJ GMSCs), and found that they exhibited decreased proliferation, adhesion, migration capacities and underwent early apoptosis in vitro compared control GMSCs. Notably, the central and peripheral BRONJ GMSCs transplantation in a mice excisional skin model also displayed lower cell survival rate and poor healing effects than that of controls. Mechanistically, TGF-β1 signaling pathway was suppressed not only in BRONJ patients’ gingival lesions but also in BRONJ GMSCs transplantation animal model. The results above suggested that under the microenvironment of BRONJ patients, the dysfunction of GMSCs and the suppressed TGF-β1 signaling pathway may be the vital factors in impaired gingival healing, thus contributing to persistent exposure of underlying bone and development of BRONJ. This study provides new insights into the prevention for BRONJ by improving the functions of GMSCs and upregulating TGF-β1 in accelerating gingival wound healing.
Graphical Abstract
Schematic illustration of the dysfunction of BRONJ GMSCs in vitro and BRONJ GMSCs transplantation in a mice skin model delaying cutaneous wound healing mainly via suppressing TGF-β1 signaling pathway.
... For example, they included the systemic transplantation of MSCs[19, 181], a stromal vascular fraction of adipose tissue [182], and peripheral blood mononuclear cells (PBMCs) [183] to induce immunomodulatory effects and acceleration of tissue repair in mice with MRONJ. Other curative treatments tested in murine models included PTH [184], intraoral injections of a low potency BP that reduced the necrotic bone area of MRONJ lesions [185], and the local injection of the tetrahedral framework of nucleic acids into the mucosa adjacent to MRONJ lesions to promote healing of the oral lesions [186]. ...
Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). pARs, including nitrogen-containing bisphosphonates (N-BPs; e.g., zoledronic acid, alendronate) and anti-RANKL antibodies (e.g., denosumab), are used to manage bone metastases in patients with cancer or to prevent fragility fractures in patients with osteoporosis.
Though significant advances have been made in understanding MRONJ, its pathophysiology is still not fully elucidated. Multiple species have been used in preclinical MRONJ research, including the rat, mouse, rice rat, rabbit, dog, sheep, and pig. Animal research has contributed immensely to advancing the MRONJ field, particularly, but not limited to, in developing models and investigating risk factors that were first observed in humans. MRONJ models have been developed using clinically relevant doses of systemic risk factors, like N-BPs, anti-RANKL antibodies, or AgIs. Specific local oral risk factors first noted in humans, including tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection, etc.), were then added. Research in rodents, particularly the rat, and, to some extent, the mouse, across multiple laboratories, has contributed to establishing multiple relevant and complementary preclinical models. Models in larger species produced accurate clinical and histopathologic outcomes suggesting a potential role for confirming specific crucial findings from rodent research. We view the current state of animal models for MRONJ as good. The rodent models are now reliable enough to produce large numbers of MRONJ cases that could be applied in experiments testing treatment modalities. The course of MRONJ, including stage 0 MRONJ, is characterized well enough that basic studies of the molecular or enzyme-level findings in different MRONJ stages are possible.
This review provides a current overview of the existing models of MRONJ, their more significant features and findings, and important instances of their application in preclinical research.
... HEDP exhibited short-term compatibility with NaOCl solutions at clinical strength, thus retaining the desired antimicrobial and proteolytic effects of NaOCl while adding an element of decalcification to the mixture [39]. Nishimura et al. demonstrated another interesting dental application of BPs to prevent ONJ in vivo, where local application of a rescue BP (a BP with low or no antiresorptive activity, low potency BPs -lpBPs) given prior to dental surgery decreased the amount of a legacy BP drug (via equilibrium displacement of existing drug) in proximate jawbone surfaces below the threshold for induction of ONJ lesions in mice [40]. ...
Studies of the potential role of bisphosphonates in dentistry date back to physical chemical research in the 1960s, and the genesis of the discovery of bisphosphonate pharmacology in part can be linked to some of this work. Since that time, parallel research on the effects of bisphosphonates on bone metabolism continued, while efforts in the dental field included studies of bisphosphonate effects on dental calculus, caries, and alveolar bone loss. While some utility of this drug class in the dental field was identified, leading to their experimental use in various dentrifice formulations and in some dental applications clinically, adverse effects of bisphosphonates in the jaws have also received attention. Most recently, certain bisphosphonates, particularly those with strong bone targeting properties, but limited biochemical effects (low potency bisphosphonates), are being studied as a local remedy for the concerns of adverse effects associated with other more potent members of this drug class. Additionally, low potency bisphosphonate analogs are under study as vectors to target active drugs to the mineral surfaces of the jawbones. These latter efforts have been devised for the prevention and treatment of oral problems, such as infections associated with oral surgery and implants. Advances in the utility and mechanistic understanding of the bisphosphonate class may enable additional oral therapeutic options for the management of multiple aspects of dental health.
... The key clinical feature of BRONJ is the retarded gingival healing with necrosis exposure (24), however, it is still unclear why such the lesion should present with loss of oral soft tissue as the primary clinical feature. In present study, we found that BRONJ patients' gingiva appeared as disordered lamina propria and displayed notably depressed expressions of collagen. ...
Background: Retarded gingival healing is the hallmark of bisphosphonate-related osteonecrosis of the jaw (BRONJ) and poses a great challenge to maxillofacial surgeons. Although previous studies have showed that bisphosphonates (BPs) are highly toxic to healthy gingival mesenchymal stem cells (GMSCs) in vitro, there is overall lack of direct evidence demonstrating the regeneration capacity of oral mucosa in BRONJ patients. In present study, we aim to isolate GMSCs from BRONJ patients’ gingiva and assessed their phenotypes and functions in vitro, as well as their therapeutic effects for wound healing in a mice excisional skin model.
Methods: BRONJ patients’ gingival samples were used for microarray analysis, histological detection and cell culture. The stem cells isolated from the central gingiva (center-BRONJ GMSCs) and the peripheral lesions (peri-BRONJ GMSCs) were analyzed by Cell Counting Kit-8 (CCK-8), cell adhesion, scratch and flow cytometry. Luciferase/GFP (Green Fluorescent Proteins)-labeled GMSCs combined with Hydrogel were transplanted in a mice excisional skin model, and mice were divided into a hydrogel alone group, a hydrogel/control GMSCs group, a hydrogel/center-BRONJ GMSCs group and a hydrogel/peri-BRONJ GMSCs group. Bioluminescence imaging trace cell survival in vivo. Healing effects were evaluated by wound area measurement, histology, immunohistochemistry (IH) and immunofluorescence (IF).
Results: Center-BRONJ GMSCs and peri-BRONJ GMSCs were all fibroblast-like cells, but they became slender and more wrinkled compared control GMSCs. Notably, they exhibited decreased proliferation, adhesion, migration capacities and underwent early apoptosis in vitro. In animal model, BRONJ GMSCs transplantation also displayed lower cell survival rate and poor healing effects than that of control group. Mechanistically, we found that the expression of TGF-β1 signaling pathway was suppressed not only in BRONJ patients’ gingival lesions but also in BRONJ GMSCs transplantation animal model.
Conclusions: In BRONJ patients’ microenvironment, the regeneration ability of oral mucosa was dramatically decreased. Our mice skin model demonstrated for the first time that BRONJ GMSCs transplantation displayed poor effects on wound healing mainly via suppressing TGF-β1 signaling pathway. This study provides new insights into the prevention for BRONJ by improving the functions of GMSCs in accelerating gingival wound healing.
... In addition, another report has identified a cat diagnosed with bilateral patellar fractures and radiographically thickened cortices following 8 years of oral BP (alendronate) treatment [32], an atypical fracture in this species. Moving forward, the problem of ONJ may be resolved as many rodent models have been developed to mimic symptoms of BP associated ONJ, raising the likelihood of developing a potential BP antidote to treat the condition [33]. ...
Bisphosphonates (BPs) are characterized by their ability to bind strongly to bone mineral and inhibit bone resorption. However, BPs exert a wide range of pharmacological activities beyond the inhibition of bone resorption, including the inhibition of cancer cell metastases and angiogenesis and the inhibition of proliferation and apoptosis in vitro. Additionally, the inhibition of matrix metalloproteinase activity, altered cytokine and growth factor expression, as well as reductions in parameters of pain have also been reported. In humans, clinical BP use has transformed the treatment of post-menopausal osteoporosis, rare bone diseases such as osteogenesis imperfecta, as well as multiple myeloma and metastatic breast and prostate cancer, albeit not without infrequent but significant adverse events. Despite the well-characterized health benefits of BP use in humans, the evidence-base for the therapeutic efficacy of BPs in veterinary medicine is, by comparison, limited. Notwithstanding, BPs are used widely in small animal veterinary practice for the medical management of hyperparathyroidism, idiopathic hypercalcemia in cats, as well as for the palliative care of bone tumors which are common in dogs, and in particular, primary bone tumors such as osteosarcoma. Palliative BP treatment has also recently increased in veterinary oncology to alleviate tumor-associated bone pain. In equine veterinary practice, non-nitrogen-containing BPs are FDA-approved to control clinical signs associated with navicular syndrome in adult horses. However, there are growing concerns regarding the off-label use of BPs in juvenile horses. Here we discuss the current understanding of the strengths, weaknesses and current controversies surrounding BP use in veterinary medicine to highlight the future utility of these potentially beneficial drugs.
... Recently, Hokugo et al. showed a unique strategy to reverse the adverse effect of zoledronate in mice. It was observed that the local administration of a "rescue" BP other than zoledronate dramatically reduced the development of osteonecrosis symptoms [58]. Since the course of BRONJ is progressive and greatly influenced by exposure to surrounding microorganisms in the oral cavity, which leads to uncontrolled inflammation, MPMBP may be a useful compound as a "rescue" BP, due to the most potent antioxidant and anti-inflammatory activities among currently available BPs. ...
Bisphosphonates (BPs) are classified into two groups, according to their side chain structures, as nitrogen-containing BPs (NBPs) and non-nitrogen-containing BPs (non-NBPs). In this study, we examined the effects of NBPs and non-NBPs on inflammatory responses, by quantifying the inflammatory mediators, prostaglandin E2 (PGE2) and nitric oxide (NO), in cultured neonatal mouse calvaria. All examined NBPs (pamidronate, alendronate, incadronate, risedronate, zoledronate) stimulated lipopolysaccharide (LPS)-induced PGE2 and NO production by upregulating COX-2 and iNOS mRNA expression, whereas non-NBPs (etidronate, clodronate, tiludronate) suppressed PGE2 and NO production, by downregulating gene expression. Additionally, [4-(methylthio) phenylthio] methane bisphosphonate (MPMBP), a novel non-NBP with an antioxidant methylthio phenylthio group in its side chain, exhibited the most potent anti-inflammatory activity among non-NBPs. Furthermore, results of immunohistochemistry showed that the nuclear translocation of NF-κB/p65 and tyrosine nitration of cytoplasmic protein were stimulated by zoledronate, while MPMBP inhibited these phenomena, by acting as a superoxide anion (O2−) scavenger. These findings indicate that MPMBP can act as an efficacious agent that causes fewer adverse effects in patients with inflammatory bone diseases, including periodontitis and rheumatoid arthritis.
... There appears to be consensus that actual bisphosphonates were not implicated in the historical occupational disease syndrome: the hypothesis linking MRONJ and phossy jaw now largely rests upon the proposal that pyrophosphate (present or generated in situ) was the causative agent in the latter (Hinshaw and Quin, 2013;Hinshaw and DeLong, 2016), a claim that has been cited as lacking scientific foundation (Orriss et al., 2016;Kwaasi et al., 2016). Current investigations of MRONJ focus on the potential for the mitigation of adverse symptoms, or even prophylaxis against MRONJ triggered by tooth (Hokugo et al., 2013(Hokugo et al., , 2019. Finally, it has been suggested that BPs have a beneficial effect on bone-forming osteoblasts, osteocytes, and perhaps stem cells; the mechanism of this phenomenon is also currenty 1' being investigated (Bellido and Plotkin, 2011;Misra et al., 2016). ...
“Bisphosphonate” (BP) is a commonly used generic term for a pyrophosphate (PPi) analogue containing a pCR¹R²p group. This replacement of the bridging O atom in PPi by a carbon atom greatly enhances stability to hydrolysis and make possible substitution (R¹, R²) derivatives that exhibit diverse chemical, biological and pharmacological properties, while sharing the ability to chelate metal dications. The synthesis and characteristics of representative BPs are briefly described. Certain BPs are useful in the treatment of resorptive bone diseases, including osteoporosis and bone cancers, and new applications for BPs are emerging in biology and medicine.
... 155 Alternative strategies to reversing BP treatment have been to outcompete existing previously administered BP with locally applied weaker BP compounds that have fewer side effects. 156 Both of these effective methods may be used to potentially prevent ONJ in patients who have been exposed to this subset of antiresorptives. ...
It is well established that alterations in phosphate metabolism have a profound effect on hard and soft tissues of the oral cavity. The present-day clinical form of osteonecrosis of the jaw (ONJ) was preceded by phosphorus necrosis of the jaw, ca. 1860. The subsequent removal of yellow phosphorus from matches in the early 20th century saw a parallel decline in “phossy jaw” until the early 2000s, when similar reports of unusual jaw bone necrosis began to appear in the literature describing jaw necrosis in patients undergoing chemotherapy and concomitant steroid and bisphosphonate treatment. Today, the potential side effect of ONJ associated with medications that block osteoclast activity (antiresorptive) is well known, though the mechanism remains unclear and the management and outcomes are often unsatisfactory. Much of the existing literature has focused on the continuing concerns of appropriate use of bisphosphonates and other antiresorptive medications, the incomplete or underdeveloped research on ONJ, and the use of drugs with anabolic potential for treatment of osteoporosis. While recognizing that ONJ is a rare occurrence and ONJ-associated medications play an important role in fracture risk reduction in osteoporotic patients, evidence to date suggests that health care providers can lower the risk further by dental evaluations and care prior to initiating antiresorptive therapies and by monitoring dental health during and after treatment. This review describes the current clinical management guidelines for ONJ, the critical role of dental-medical management in mitigating risks, and the current understanding of the effects of predominantly osteoclast-modulating drugs on bone homeostasis.
Natural polymers have been particularly appealing for constructing hemostatic materials/devices, but it is still desirable to develop new natural polymer-based biomaterials with balanced hemostatic and wound-healing performance. In this work, a natural polyphenol-functionalized chitosan/gelatin sponge (PCGS) was prepared by the lyophilization of a chitosan/gelatin mixture solution (under a self-foaming condition to prepare the CGS) and subsequent chemical cross-linking with procyanidin (PC). Compared with the original CGS, PCGS exhibited an enhanced liquid-absorption ability, reduced surface charges, and similar/low hemolysis rate. Benefiting from such a liquid-absorption ability (∼4000% for whole blood and normal saline) and moderate surface charges, PCGS exhibited high in vitro hemostatic property and promising hemostatic performance in an in vivo femoral-artery-injury model. In addition, PCGS possessed higher antioxidant property and slightly decreased antibacterial ability than CGS, owing to the incorporation of PC. The feasibility of PCGS for treating infected wounds was further confirmed in an in vivo infected-tooth-extraction model, as the typical complication of intractable tooth-extraction bleeding. The present work demonstrated a facile approach for developing multifunctional hemostatic materials through the flexible management of natural polymers and polyphenols.
Since the initial description of medication-related osteonecrosis of the jaw (MRONJ) almost two decades ago, the potential pathophysiology and risk factors have been elaborated on in many investigations and guidelines. However, the definitive pathophysiology based on scientific evidence remains lacking. Consequently, the optimal clinical treatment and prevention strategies for MRONJ have not been established. Despite their different mechanisms of action, many drugs, including bisphosphonates, denosumab, angiogenesis inhibitors, and other medications, have been reported to be associated with MRONJ lesions in cancer and osteoporosis patients. Importantly, MRONJ occurs predominantly in the jawbones and other craniofacial regions, but not in the appendicular skeleton. In this up-to-date review, the currently available information and theories regarding MRONJ are presented from both clinical and basic science perspectives. The definition and epidemiology of MRONJ, triggering medication, and histopathology are comprehensively summarized. The immunopathology and the potential pathophysiology based on immune cells such as neutrophils, T and B cells, macrophages, dendritic cells, and natural killer cells are also discussed. In addition, antiangiogenesis, soft tissue toxicity, necrotic bone, osteocyte death, and single-nucleotide polymorphisms are examined. Moreover, other possible mechanisms of MRONJ development are considered based on the unique embryological characteristics, different cell behaviors between jawbones and appendicular skeleton, unique anatomical structures, and sustained bacterial exposure in the oral cavity as a basis for MRONJ site specificity. Based on the literature review, it was concluded that multiple factors may contribute to the development of MRONJ, although which one is the key player triggering MRONJ in the craniofacial region remains unknown.
Medication-related osteonecrosis of the jaw (MRONJ) is primarily associated with administering antiresorptive or antiangiogenic drugs. Despite significant research on MRONJ, its pathogenesis and effective treatments are still not fully understood. Animal models can be used to simulate the pathophysiological features of MRONJ, serving as standardized in vivo experimental platforms to explore the pathogenesis and therapies of MRONJ. Rodent models exhibit excellent effectiveness and high reproducibility in mimicking human MRONJ, but classical methods cannot achieve a complete replica of the pathogenesis of MRONJ. Modified rodent models have been reported with improvements for better mimicking of MRONJ onset in clinic. This review summarizes representative classical and modified rodent models of MRONJ created through various combinations of systemic drug induction and local stimulation and discusses their effectiveness and efficiency. Currently, there is a lack of a unified assessment system for MRONJ models, which hinders a standard definition of MRONJ-like lesions in rodents. Therefore, this review comprehensively summarizes assessment systems based on published peer-review articles, including new approaches in gross observation, histological assessments, radiographic assessments, and serological assessments. This review can serve as a reference for model establishment and evaluation in future preclinical studies on MRONJ.
Bisphosphonates (BPs) are major anti-bone-resorptive drugs. Among them, the nitrogen-containing BPs (NBPs) exhibit much stronger anti-bone-resorptive activities than non-nitrogen-containing BPs (non-NBPs). However, BP-related osteonecrosis of the jaw (BRONJ) has been increasing without effective strategies for its prevention or treatment. The release of NBPs (but not non-NBPs) from NBP-accumulated jawbones has been supposed to cause BRONJ, even though non-NBPs (such as etidronate (Eti) and clodronate (Clo)) are given at very high doses because of their low anti-bone-resorptive activities. Our murine experiments have demonstrated that NBPs cause inflammation/necrosis at the injection site, and that Eti and Clo can reduce or prevent the inflammatory/necrotic effects of NBPs by inhibiting their entry into soft-tissue cells. In addition, our preliminary clinical studies suggest that Eti may be useful for treating BRONJ. Notably, Eti, when administered together with an NBP, reduces the latter’s anti-bone-resorptive effect. Here, on the basis of the above background, we examined and compared in vitro interactions of NBPs, non-NBPs, and related substances with hydroxyapatite (HA), and obtained the following results. (i) NBPs bind rapidly to HA under pH-neutral conditions. (ii) At high concentrations, Eti and Clo inhibit NBP-binding to HA and rapidly expel HA-bound NBPs (potency Eti>>Clo). (iii) Pyrophosphate also inhibits NBP-binding to HA and expels HA-bound NBPs. Based on these results and those reported previously, we discuss (i) possible anti-BRONJ strategies involving the use of Eti and/or Clo to reduce jawbone-accumulated NBPs, and (ii) a possible involvement of pyrophosphate-mediated release of NBPs as a cause of BRONJ.
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The objective of this chapter is to review the published literature on the effects of various drugs and nutrition supplements consumed by patients for treatment of systemic diseases on the process of orthodontic tooth movement. The increase in the number of adults seeking orthodontic treatment has introduced more medical conditions and medication use, causing an additional set of factors in orthodontic tooth movement, with potential implications for mechanotherapy and retention protocols. Orthodontic tooth movement is first initiated by placing carefully directed forces upon teeth. These forces cause many biological processes and mediators to occur within the periodontal ligament causing inflammation and bone turnover. Medications, nutrition supplements, and molecules produced in various diseased tissues and organs can reach the mechanically stressed paradental tissues through the circulation and interact with local target cells. The combined effect of mechanical forces and one or more of these agents may be inhibitory, additive, or synergistic. All the medications reviewed have systemic therapeutic effects. However, the potential adverse effects on OTM are probably overshadowed by the medical benefit. These adverse effects may change the desired outcome of tooth position or health of surrounding tissues. Therefore, it is imperative that the orthodontist pays close attention to the medical and drug consumption history of each patient before and during orthodontic treatment. The medication benefits and risks for tissue systems must be explored to determine the best orthodontic mechanotherapy and health outcome for our patients.
Despite extensive research since the first report of medication-related osteonecrosis of the jaw (MRONJ) in 2003, the optimal treatment and preventive modalities for the condition are not clear. Therefore, its management has been a concern in dentistry, oral and maxillofacial surgery, as well as departments involved in the treatment of cancers and/or bone diseases worldwide. Several cases of MRONJ could not be cured by conventional treatment strategies, as per the recommendations in various position papers. Therefore, a number of studies, including randomized controlled trials, have been conducted to examine the efficacy of novel therapies. However, no definite treatment modality has been determined. Several types of cell therapies have been documented. 10 animal studies and 5 case reports have been documented, in which autologous transplantation of cells has been carried out in MRONJ patients. Although these reports showed the efficacy of cell therapy, they were not large-scale, statistically accurate clinical studies; hence, the efficacy of cell therapy for this condition is not certain. However, the efficacy of MRONJ treatment using mesenchymal stromal cell (MSC) sheets has been investigated since 2013. This has been confirmed through various experiments in which MSC sheets were transplanted into model rats and beagle dogs exhibiting MRONJ-like lesions. Based on these results, a clinical study of MRONJ treatment using periodontal ligament-derived MSC sheets is being currently planned.
Compromised osteoblast attachment on hydroxyapatite could be involved in the development of bone healing failure. We developed a bone-compatible scaffold that mimics bone structure with sub-micron hydroxyapatite (HA) surfaces, so that we could evaluate the effects of nitrogen-containing bisphosphonate (N-BP) on osteoblast behavior and bone healing. Human osteoblasts were seeded onto the bone-compatible scaffold with or without N-BP, and cell attachment and spreading behavior were evaluated 4 and 24 h after seeding. Then, mineralization was evaluated at 7 and 14 days. The osteoconductive activity of the scaffold was evaluated by implantation for 3 and 6 weeks into a rat cranial bone defect. The numbers of osteoblasts and their diameters were significantly less in N-BP-binding scaffolds than in untreated scaffolds at 4 and 24 h. Mineralization were also significantly less in the N-BP-binding scaffolds than in controls at 7 and 14 days. In vivo study revealed bone formation in N-BP-binding scaffolds was significantly less than in untreated scaffolds at 3 and 6 weeks. These results suggest that N-BP-binding to HA inhibited osteoblast attachment and spreading, thereby compromising bone healing process in the injured bone defect site.
Since the first report in 2003, bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been increasing, without effective clinical strategies. Osteoporosis is common in elderly women, and bisphosphonates (BPs) are typical and widely used anti-osteoporotic or anti-bone-resorptive drugs. BRONJ is now a serious concern in dentistry. As BPs are pyrophosphate analogues and bind strongly to bone hydroxyapatite, and the P-C-P structure of BPs is non-hydrolysable, they accumulate in bones upon repeated administration. During bone-resorption, BPs are taken into osteoclasts and exhibit cytotoxicity, producing a long-lasting anti-bone-resorptive effect. BPs are divided into nitrogen-containing BPs (N-BPs) and non-nitrogen-containing BPs (non-N-BPs). N-BPs have far stronger anti-bone-resorptive effects than non-N-BPs, and BRONJ is caused by N-BPs. Our murine experiments have revealed the following. N-BPs, but not non-N-BPs, exhibit direct and potent inflammatory/necrotic effects on soft-tissues. These effects are augmented by lipopolysaccharide (the inflammatory component of bacterial cell-walls) and the accumulation of N-BPs in jawbones is augmented by inflammation. N-BPs are taken into soft-tissue cells via phosphate-transporters, while the non-N-BPs etidronate and clodronate inhibit this transportation. Etidronate, but not clodronate, has the effect of expelling N-BPs that have accumulated in bones. Moreover, etidronate and clodronate each have an analgesic effect, while clodronate has an anti-inflammatory effect via inhibition of phosphate-transporters. These findings suggest that BRONJ may be induced by phosphate-transporter-mediated and infection-promoted mechanisms, and that etidronate and clodronate may be useful for preventing and treating BRONJ. Our clinical trials support etidronate being useful for treating BRONJ, although additional clinical trials of etidronate and clodronate are needed.
Medication-related osteonecrosis of the jaw (MRONJ) represents a complication of bisphosphonate treatment that responds poorly to standard treatment. In a retrospective cohort study we investigated a possible role of Actinomyces spp. in the pathogenesis of MRONJ. Deep biopsies of necrotic bone were collected during surgical treatment of MRONJ and evaluated by histology and microbiology for the presence of Actinomyces spp. Microbiological, demographic and clinicpathological data were analyzed for risk of Actinomyces-associated MRONJ. Between 2005 and 2014, 111 patients suffering from histologically-confirmed MRONJ were identified. Actinomyces spp. were detected in 99 cases (89%) by histology and in six further patients by microbiological culture. A diverse microbial flora was found in all specimens without association with Actinomyces spp. Demographic and clinicopathological characteristics did not separate significantly Actinomyces-positive from Actinomyces-negative cases. Our observations confirm previous reports of a high prevalence of Actinomyces spp. in MRONJ in the single largest cohort available up to now. The high prevalence of Actinomyces spp. and the lack of clinicopathological risk factors underline the prominent role of Actinomyces spp. in MRONJ and may change the current understanding of MRONJ. Established prolonged antimicrobial treatment regimens against Actinomyces spp. infection could therefore be a mainstay of future MRONJ management.
Injury to the barrier tissue initiates a rapid distribution of myeloid immune cells from bone marrow, which guide sound wound healing. Bisphosphonates, a widely used anti-bone resorptive drug with minimal systemic side effects, have been linked to an abnormal wound healing in the oral barrier tissue leading to, in some cases, osteonecrosis of the jaw (ONJ). Here we report that the development of ONJ may involve abnormal phenotypic plasticity of Ly6G+/Gr1+ myeloid cells in the oral barrier tissue undergoing tooth extraction wound healing. A bolus intravenous zoledronate (ZOL) injection to female C57Bl/6 mice followed by maxillary first molar extraction resulted in the development of ONJ-like lesion during the second week of wound healing. The multiplex assay of dissociated oral barrier cells exhibited the secretion of cytokines and chemokines, which was significantly modulated in ZOL mice. Tooth extraction-induced distribution of Ly6G+/Gr1+ cells in the oral barrier tissue increased in ZOL mice at week 2. ONJ-like lesion in ZOL mice contained Ly6G+/Gr1+ cells with abnormal size and morphology, as well as different flow cytometric staining intensity. When anti-Ly6G (Gr1) antibody was intraperitoneally injected for 5 days during the second week of tooth extraction, CD11b+GR1hi cells in bone marrow and Ly6G+ cells in the oral barrier tissue were depleted and the development of ONJ-like lesion was significantly attenuated. This study suggests that local modulation of myeloid cell plasticity in the oral barrier tissue may provide the basis for pathogenesis and thus therapeutic as well as preventive strategy of ONJ.
The aim of this study is to establish osteoclasts as key immune effectors capable of activating the function of Natural Killer (NK) cells, and expanding their numbers, and to determine in vivo and in vitro effect of bisphosphonates (BPs) during NK cell interaction with osteoclasts and on systemic and local immune function. The profiles of 27 cytokines, chemokines and growth factors released from osteoclasts were found to be different from dendritic cells and M1 macrophages but resembling to untreated monocytes and M2 macrophages. Nitrogen-containing BPs Zoledronate (ZOL) and Alendronate (ALN), but not non-nitrogen-containing BPs Etidronate (ETI), triggered increased release of pro-inflammatory mediators from osteoclasts while all three BPs decreased pit formation by osteoclasts. ZOL and ALN mediated significant release of IL-6, TNF-` and IL-1β, whereas they inhibited IL-10 secretion by osteoclasts. Treatment of osteoclasts with ZOL inhibited NK cell mediated cytotoxicity whereas it induced significant secretion of cytokines and chemokines. NK cells lysed osteoclasts much more than their precursor cells monocytes, and this correlated with the decreased expression of MHC class I expression on osteoclasts. Intravenous injection of ZOL in mice induced pro-inflammatory microenvironment in bone marrow and demonstrated significant immune activation. By contrast, tooth extraction wound of gingival tissues exhibited profound immune suppressive microenvironment associated with dysregulated wound healing to the effect of ZOL which could potentially be responsible for the pathogenesis of Osteonecrosis of the Jaw (ONJ). Finally, based on the data obtained in this paper we demonstrate that osteoclasts can be used as targets for the expansion of NK cells with superior function for immunotherapy of cancer.
BACKGROUND:
Osteonecrosis of the jaw (ONJ) is a rare but serious adverse drug effect linked to long-term and/or high-dose exposure to nitrogen-bisphosphonates (N-BP), the standard of care for the treatment of bone fragility disorders. The mechanism leading to bisphosphonate-associated ONJ (BAONJ) is unclear and optimal treatment strategies are lacking. Recent evidence suggests that BAONJ may be linked to drug-induced immune dysfunction, possibly associated with increased susceptibility to infections in the oral cavity. The objective of this investigation was to comprehensively assess the relationship linking immune function, N-BP exposure, the oral microbiome and ONJ susceptibility.
METHODS:
Leukocyte gene expression of factors important for immunity, wound healing and barrier function were assessed by real-time quantitative PCR and the oral microbiome was characterized by 454 pyrosequencing of the 16S rRNA gene in 93 subjects stratified by N-BP exposure and a history of ONJ.
RESULTS:
There were marked differences in the systemic expression of genes regulating immune and barrier functions including RANK (p = 0.007), aryl hydrocarbon receptor (AHR, p < 0.001), and FGF9 (p < 0.001), which were collectively up-regulated in individuals exposed to N-BP without ONJ relative to treatment controls. In contrast, the expression levels of these same genes were significantly down-regulated in those who had experienced BAONJ. Surprisingly, the oral microbiome composition was not directly linked to either BAONJ or N-BP exposure, rather the systemic leukocyte expression levels of RANK, TNFA and AHR each explained 9% (p = 0.04), 12% (p = 0.01), and 7% (p = 0.03) of the oral bacterial beta diversity.
CONCLUSIONS:
The oral microbiome is unlikely causative of ONJ, rather individuals with BAONJ lacked immune resiliency which impaired their capacity to respond adequately to the immunological stress of N-BP treatment. This may be the common factor linking N-BP and anti-RANK agents to ONJ in at-risk individuals. Preventive and/or therapeutic strategies should target the wound healing deficits present in those with ONJ.
Osteonecrosis of the jaw (ONJ), an uncommon comorbidity in patients treated with bisphosphonates (BP), occurs in the segment of jawbone interfacing oral mucosa. This study aimed to investigate a role of oral mucosal barrier γδ T cells in the ONJ pathogenesis. Female C57Bl/6J (B6) mice received a bolus zoledronate intravenous injection (ZOL, 540 μg/kg), and their maxillary left first molars were extracted one week later. ZOL treated mice (WT ZOL) delayed oral wound healing with patent open wound 4 weeks after tooth extraction with characteristic oral epithelial hyperplasia. γδ T cells appeared within the tooth extraction site and hyper plastic epithelium in WT ZOL mice. In ZOL-treated γδ T cell null (Tcrd-/- ZOL) mice, the tooth extraction open wound progressively closed; however, histological ONJ-like lesions were identified in 75% and 60% of WT ZOL and Tcrd-/- ZOL mice, respectively. While the bone exposure phenotype of ONJ was predominantly observed in WT ZOL mice, Tcrd-/- ZOL mice developed the pustule/fistula disease phonotype. We further addressed the role of γδ T cells from human peripheral blood (h-γδ T cells). When co- cultured with ZOL-pretreated human osteoclasts in vitro, h-γδ T cells exhibited rapid expansion and robust IFN-γ secretion. When h-γδ T cells were injected to ZOL-treated immunodeficient (Rag2-/- ZOL) mice, the oral epithelial hyperplasia was developed. However, Rag2-/- ZOL mice did not develop osteonecrosis. The results indicate that γδ T cells are unlikely to influence the core osteonecrosis mechanism; however may serve as a critical modifier contributing to the different oral mucosal disease variations of ONJ.
Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
Bisphosphonates are effective for the treatment of osteoporosis despite recent reports of safety concerns such as atypical femur fracture. We conducted an ecological analysis of relevant media reports, oral bisphosphonate use, and fracture outcomes in the United States. Trends in media reports and public interest of bisphosphonates were quantified using data from Google Trends. Data from the Medical Expenditure Panel Survey (MEPS) and the National Inpatient Sample (NIS) were used to estimate the trends in oral bisphosphonate use among patients aged 55 years and older and hospitalizations for intertrochanteric and subtrochanteric fractures, respectively. These trends in the prevalence of oral bisphosphonate use and the age-adjusted incidence rate of intertrochanteric and subtrochanteric fractures were examined from 1996 to 2012. A series of spikes in Internet search activity for alendronate (Fosamax) occurred between 2006 and 2010 immediately following media reports of safety concerns. Oral bisphosphonate use declined by greater than 50% between 2008 and 2012 (p < 0.001) after increasing use for more than a decade. The decline was more common in patients with lower education levels. Intertrochanteric hip fractures declined from 1996 through 2006 (p < 0.001) and continued to decline from 2008 to 2012 (p < 0.05). Subtrochanteric and diaphyseal fractures showed a steady and significant increase from 2002 to 2011 (p < 0.05). However, the incidence decreased from a peak of 30.5 per 100,000 in 2011 to 26.7 per 100,000 in 2012. The plateauing and subsequent decline in oral bisphosphonate use since 2006 coincided with reports of safety concerns of bisphosphonates, despite the fact that U.S. Food and Drug Administration (FDA) and American Society of Bone and Mineral Research (ASBMR) reports did not recommend any safety restrictions on their use. This decline in oral bisphosphonate use was followed by the decline in the incidence of subtrochanteric and diaphyseal fractures.
Osteonecrosis of the jaw (ONJ) is a serious complication associated with oral and intravenous bisphosphonate therapy. Its pathogenesis is not well understood and its management is difficult. Microbiological investigations have detected a variety of oral pathogens such as Actinomyces, Enterococcus, Candida albicans, Aspergillus, Haemophilus influenzae, alpha-hemolytic streptococci, Lactobacillus, Enterobacter, and Klebsiella pneumoniae. To better treat it, it is important to understand its causes and complications. Materials and Methods. Our present study addresses a microscopic observation of curetted jaw necrotic lesions related to bisphosphonates. Results. A mycotic infestation has been found in all of the 18 cases studied. Discussion. An identification of the fungal agent and its incrimination in the pathogenesis of bisphosphonates related osteonecrosis of the jaw could change radically the management of this condition.
Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a well-characterized oral complication of systemic therapy with bisphosphonates. Pseudoepitheliomatous hyperplasia was observed in some of the lesions. Because podoplanin expression has been linked to malignant lesions of the oral mucosa, we aimed to investigate podoplanin expression in the pseudoepitheliomatous hyperplasia. We analyzed archival paraffin- and plastic-embedded specimens from BRONJ using both conventional and immunohistochemical (AE1/AE3, D2-40) staining methods. Eleven out of seventeen BRONJ cases showed pseudoepitheliomatous hyperplasia. All these cases were positive for AE1/AE3 and pseudoepitheliomatous hyperplasia displayed a strong basal and parabasal reaction against podoplanin. The podoplanin expression in pseudoepitheliomatous hyperplasia in BRONJ specimens should not be considered a sign of malignancy. We discuss the current and possible future roles of surgical pathologists in diagnosing morphological changes associated with the development and therapy of BRONJ lesions.
Bisphosphonates have been widely used in the treatment of osteoporosis with robust data from numerous placebo-controlled trials demonstrating efficacy in fracture risk reduction over 3-5 years of treatment. Although bisphosphonates are generally safe and well tolerated, concerns have emerged about adverse effects related to long-term use. For most patients with osteoporosis, the benefits of treatment outweigh the risks. Because these agents accumulate in bone with some persistent antifracture efficacy after therapy is stopped, it is reasonable to consider a 'drug holiday.' There is considerable controversy regarding the optimal duration of therapy and the length of the holiday, both of which should be based on individual assessments of risk and benefit.
Necrotic bone exposure in the oral cavity has recently been reported in patients treated with nitrogen-containing bisphosphonates as part of their therapeutic regimen for multiple myeloma or metastatic cancers to bone. It has been postulated that systemic conditions associated with cancer patients combined with tooth extraction may increase the risk of osteonecrosis of the jaw (ONJ). The objective of this study was to establish an animal model of bisphosphonate-related ONJ by testing the combination of these risk factors. The generation of ONJ lesions in rats resembling human disease was achieved under the confluence of intravenous injection of zoledronate (ZOL; 35 microg/kg every 2 weeks), maxillary molar extraction, and vitamin D deficiency [VitD(-)]. The prevalence of ONJ in the VitD(-)/ZOL group was 66.7%, which was significantly higher (p < .05, Fisher exact test) than the control (0%), VitD(-) (0%), and ZOL alone (14.3%) groups. Similar to human patients, rat ONJ lesions prolonged the oral exposure of necrotic bone sequestra and were uniquely associated with pseudoepitheliomatous hyperplasia. The number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end label-positive (TUNEL(+)) osteoclasts significantly increased on the surface of post-tooth extraction alveolar bone of the VitD(-)/ZOL group, where sustained inflammation was depicted by [(18)F]fluorodeoxyglucose micro-positron emission tomography (microPET). ONJ lesions were found to be associated with dense accumulation of mixed inflammatory/immune cells. These cells, composed of neutrophils and lymphocytes, appeared to juxtapose apoptotic osteoclasts. It is suggested that the pathophysiologic mechanism(s) underpinning ONJ may involve the interaction between bisphosphonates and compromised vitamin D functions in the realm of skeletal homeostasis and innate immunity.
Osteonecrosis of the jaw (ONJ) associated with bisphosphonate therapy is a rare but severe side effect in osteoporosis patients. Recently, the number of osteoporosis patients with ONJ has dramatically increased in Japan. This has contributed to an increase in the number of patients avoiding extractions. However, there has been no prospective study providing definitive incidence data for ONJ in Japanese patients. The purpose of this study was to elucidate the true as well as suspected incidence of ONJ. A total of 3229 subjects (1612 subjects in the minodronic acid group and 1617 subjects in the raloxifene group) in the Japanese Osteoporosis Intervention Trial protocol number 4 participated in this study. ONJ was diagnosed by experienced dentists. Suspected Stage 0 and 1 (bone exposure of the jaw) ONJ was assessed by a structured questionnaire at baseline and at 6, 12, 18, and 24 months. No established ONJ cases were diagnosed during the study. The incidence of suspected Stage 0 and/or Stage 1 ONJ was 6.14 per 1000 patient-years in the minodronic acid group and 3.38 per 1000 patient-years in the raloxifene group [hazard ratio (95% confidence interval) = 1.82 (0.84–3.93), P = 0.13]. Approximately 50–60% of bone exposures that appeared during the study had disappeared at the next observation. Although the subjects in this study may have developed a greater interest in the health of the oral cavity, the incidence of ONJ after minodronic acid treatment would be lower than the expected incident rate.
Objective:
The aim of this study was to explore the radiographic appearance of stage 0 medication-related osteonecrosis of the jaws (MRONJ) and examine 5 radiographic parameters (trabecular sclerosis, cortical erosion, periosteal reaction, sequestration, and crater-like defect) as predictors of progression to bone exposure.
Study design:
Twenty-three patients with a history of antiresorptive therapy, no bone exposure, and nonspecific signs and symptoms were included. Intraoral photographs, panoramic and cone beam computed tomography (CBCT) images at initial visit, and follow-up intraoral photographs were reviewed. Three patients had dental disease (DD), 10 patients with stage 0 MRONJ did not progress to bone exposure (NBE), and 10 patients progressed to bone exposure (BE). Radiographic parameters were scored as absent (0), localized (1), or extensive (2), and their sum formed the composite radiographic index (CRI).
Results:
DD patients demonstrated minimal radiographic findings, and their CRI was significantly lower than that of NBE and BE patients. Additionally, BE patients demonstrated a higher radiographic index compared with NBE patients. Intriguingly, sequestration was observed in the initial CBCT of 9 (90%) of 10 BE patients, whereas 80% of NBE patients showed absence of sequestration at initial CBCT examination.
Conclusions:
CBCT imaging can aid in the differentiation of stage 0 MRONJ from dental disease. Radiographic sequestration at initial presentation can serve as a predictor of future bone exposure in patients with stage 0 MRONJ.
Purpose:
Medication-related osteonecrosis of the jaw (MRONJ) is a rare but severe side effect of antiresorptive medications. Most animal models use tooth extraction as an instigating local factor to induce MRONJ, with varied results. However, these teeth are healthy and absent of dental disease, a rare finding that does not reflect clinical practices. The authors hypothesized that extraction of teeth with periapical inflammation would lead to MRONJ in rats treated with high-dose bisphosphonates.
Materials and methods:
Rats were pretreated with zoledronic acid (ZA) for 1 week. Pulp exposure (PE) was established by exposing the pulpal chamber of the first and second molars. Experimental periapical disease (EPD) was induced by PE and bacterial inoculation into pulp chambers of the first and second mandibular molars. The mandibular molars were extracted 4 weeks after PE or EPD, and animals were euthanized 4 weeks after tooth extraction. Extraction sockets were assessed clinically, radiographically, and histologically.
Results:
Clinically, radiographically, and histologically, socket healing was observed in all vehicle-treated animals and in ZA-treated animals after extraction of healthy teeth or teeth with PE. In contrast, bone exposure, lack of socket healing, and osteonecrosis were present in most ZA-treated animals after extraction of teeth with EPD. Bacterial presence was noted in areas of osteonecrotic alveolar bone.
Conclusion:
These data support a synergistic contribution of severe dental disease and tooth extraction to MRONJ pathogenesis. Importantly, this model is amenable to manipulation of methodologic conditions for the dissection of parameters involved in MRONJ pathogenesis.
Medication-related osteonecrosis of the jaw (MRONJ) is a rare but detrimental intraoral lesion that predominantly occurs in patients with long-term use of anti-resorptive agents such as bisphosphonate and denosumab, a human anti-RANKL monoclonal antibody (Ab). Surgical intervention such as tooth extraction is a known risk factor for MRONJ, which is often performed to eliminate pre-exiting pathological inflammatory condition such as periodontal diseases. Nonetheless, it remains unknown whether pre-existing periodontal disease condition exacerbates, or removal of such condition ameliorates, MRONJ development following tooth extraction. In this study, we combined the ligature-induced periodontitis and the tooth extraction mouse models under the administration of zoledronate (ZOL) or anti-RANKL Ab, and provide experimental evidence that pre-existing pathological inflammatory condition exacerbates MRONJ development following tooth extraction in mice. Under zoledronate (ZOL) administration, tooth extraction alone induced ONJ lesion; however, extraction of a ligature-placed tooth further exacerbated ONJ development. When the ligature was removed and inflammatory condition was deescalated, ONJ development was ameliorated. Anti-RANKL Ab administration resulted in similar outcomes. Interestingly, unlike ZOL-administered mice, anti-RANKL Ab-administered mice exhibited complete absence of osteoclasts, suggesting that physical presence of osteoclasts is not directly involved in ONJ development. Collectively, our study demonstrated that periodontal disease is a functionally linked risk factor that predisposes ONJ development following tooth extraction in the presence of bisphosphonate and denosumab.
Purpose
From 2011 to 2013, a nationwide retrospective cohort study was conducted by the Japanese Society of Oral and Maxillofacial Surgeons and the Japanese Society of Dentistry in medically compromised patients, to assess the development of Bisphosphonate (BP)-related osteonecrosis of the jaws (BRONJ), and to elucidate the outcomes and factors associated with remission.
Materials and Methods
A written questionnaire, including the clinical characteristics, management and outcomes of patients with BRONJ, was sent to 501 institutions.
Results
This large-scale study included 4.797 cases, with a preponderance of females. BRONJ occurred twice as often in the mandible as compared to the maxilla. Most patients were BRONJ stage 2 (61.4%), followed by stage 1 (20.7%) and stage 3 (16.8%); stage 0 was excluded. The most common primary disease was malignant neoplasm (46.5%), followed by osteoporosis (including prevention, 45.3%). The proportion of patients on oral BPs has increased, with the incidence now approaching that receiving BP parenterals. Surgical therapy rates of patients with BRONJ stages 1, 2 and 3 were 14.0, 37.6, and 53.5%, respectively.
Outcome assessment in a total of 936 patients with BRONJ stage 2 who underwent surgical therapy indicated remission in 46.3% of cases, improvement in 30.6%, disease progression in 5.4%, and no change in 6.1%. Good prognosis (remission or improvement) was seen in 76.9% of cases and poor prognosis (disease progression or no change) in 11.5%. Analysis showed that risk factors for onset of BRONJ (p = 0.031), surgical procedure (p < 0.024), condition of the wound (p = 0.017), and discontinuation of BP (p < 0.001) were factors affecting prognosis.
Conclusion
The number of patients with BRONJ has increased in Japan. Attention to oral BP and proper treatment is required to minimize the number of cases. Surgical therapy seems to be effective for BRONJ stage 2 disease.
Unlike other antiresorptive medications, bisphosphonate molecules accumulate in the bone matrix. Previous studies of side-effects of anti-resorptive treatment focused mainly on systemic effects. We hypothesize that matrix-bound bisphosphonate molecules contribute to the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ). In this study, we examined the effect of matrix-bound bisphosphonates on osteoclast differentiation in vitro using TRAP staining and resorption assay, with and without pretreatment with EDTA. We also tested the effect of zoledronate chelation on the healing of post-extraction defect in rats. Our results confirmed that bisphosphonates bind to, and can be chelated from, mineralized matrix in vitro in a dose-dependent manner. Matrix-bound bisphosphonates impaired the differentiation of osteoclasts, evidenced by TRAP activity and resorption assay. Zoledronate-treated rats that underwent bilateral dental extraction with unilateral EDTA treatment showed significant improvement in mucosal healing and micro-CT analysis on the chelated sides. The results suggest that matrix-bound bisphosphonates are accessible to osteoclasts and chelating agents and contribute to the pathogenesis of BRONJ. The use of topical chelating agents is a promising strategy for the prevention of BRONJ following dental procedures in bisphosphonate-treated patients.
Introduction Oral bisphosphonates are the most commonly prescribed anti-resorptive drugs used in the treatment of osteoporosis, but osteonecrosis of the jaw is a serious complication. The early diagnosis of this destructive side effect is crucial in preventing excessive bone loss, pain and infection.
Objective To aid dental practitioners in the early identification of bisphosphonate-related osteonecrosis of the jaw.
Method A scoping review was carried out.
Data sources We searched MEDLINE via OVID, EMBASE via OVID, Dentistry and Oral Sciences Source (DOSS), Proquest Dissertation and Theses Search, to identify references that described clinical and radiological findings in medication-related osteonecrosis of the jaw (MRONJ).
Data selection Nineteen references mentioned the earliest radiological changes in MRONJ with a description of the observations and were included in the analysis.
Data synthesis The radiographic signs included osteosclerosis/lysis, widening of the periodontal ligament and thickening of the lamina dura and cortex. To assess the quality of original data on which recommendations had been made, these 19 studies were subjected to a quality appraisal.
Conclusion Using bone exposure as a criterion for diagnosis of MRONJ, leads to delayed diagnosis and a poor response to treatment. In those patients at risk of bone exposure with MRONJ, insufficient information is present in the literature to allow the general dental practitioner to reliably identify the radiographic features indicating imminent bone exposure. A well-designed prospective study is needed.
Objective:
The purpose of this study was to identify the patient populations at risk of medication related osteonecrosis of the jaw (MRONJ) and determine which medical and dental comorbidities are significant risk factors for this disease.
Methods:
An electronic search of Embase, MEDLINE, Cochrane Central Register of Controlled Trials, WHO International Clinical Trials Registry Platform and ProQuest Dissertations and Theses Global was conducted to identify all human studies that reported risk factors for MRONJ. Only a qualitative analysis was performed due to significant heterogeneity in the collected data.
Results:
The search strategy identified 2872 records, of which 219 studies were eligible for inclusion. 4106 patients with MRONJ were identified, 39 different systemic diseases were implicated, and 14 medical and 11 dental risk factors were reported, although no statistical analysis of the significance of each of these factors was possible.
Conclusions:
The clinical reach of MRONJ may be wider than anticipated, and more data on the significance of each potential risk factor is needed to guide the identification and management of at-risk patients. This article is protected by copyright. All rights reserved.
Background:
The effectiveness of management strategies used for the treatment of medication-related osteonecrosis of the jaw (MRONJ) remains poorly understood. The authors evaluated systematically the effectiveness of the various treatment modalities used for MRONJ.
Types of studies reviewed:
The authors conducted a comprehensive search of MEDLINE, Embase, the Cochrane Library, and Scopus to identify randomized controlled trials, nonrandomized controlled trials, and prospective cohort studies to evaluate comparatively the effectiveness of management strategies for the treatment of MRONJ. The authors conducted the identification of eligible studies in duplicate and synthesized the extracted data by means of a meta-analysis, when feasible.
Results:
The authors found 13 studies with a medium-to-high risk of bias that met the inclusion criteria of this review. The authors found that, compared with medical treatment of local antimicrobials with or without systemic antimicrobials, the study investigators associated surgical treatment with higher odds of complete resolution of the condition (2 studies; 76 participants; unadjusted odds ratio, 3.55; 95% confidence interval, 1.12 to 11.19). The effectiveness of other therapies, such as bisphosphonate drug holidays, teriparatide, and hyperbaric oxygen, was uncertain.
Conclusions and practical implications:
On the basis of the results of an unadjusted analysis, the results of the studies that were deemed to be medium to low quality and to have medium-to-low statistical power suggested that there are higher odds of resolving MRONJ with surgical treatment compared with medical treatment. High-quality research is required for conclusive statements to be made regarding treatment strategies for management of MRONJ.
Objective
The pathogenesis of medication-related osteonecrosis of jaw (MRONJ) is poorly understood. The aim of this prospective study was to determine the effect of chronic dental inflammation on the development of stage 0 MRONJ based on histopathological findings.
Methods
The study involved patients with a history of bisphosphonate use and an indication for tooth extraction. Before surgery, C-terminal telopeptide test (CTX) values were collected from all patients. All tooth extractions were performed according to a determined protocol. To detect whether any medication-related osteonecrotic changes were present in the non-exposed bone, biopsy samples were taken from the alveolar bone.
Results
A total of 50 patients were included in the study (39 women and 11 men). The patients were mean age of 57.4 ± 12.1 years. In total, 74 teeth were extracted (29 maxillary and 45 mandibular). Histologic examination of three patients (6%) revealed stage 0 MRONJ. Postoperatively, the complete mucosal healing success rate was 96%. MRONJ risk was not significantly correlated with low CTX value (p = 0.285).
Conclusions
Chronic inflammation may contribute to stage 0 MRONJ; however, its role may not be sufficient alone for its development. Application of a predetermined protocol for dentoalveolar processes will help to prevent MRONJ development.
Objective:
Although over a decade has passed since first introduction of BRONJ, the exact pathophysiology of this disease is still unclear. The present experimental study aimed to determine whether the oral mucosa or alveolar bone serves as the starting point for BRONJ development.
Subjects and methods:
Sixty male Wistar rats were randomly assigned into study and control groups (each, n = 30), and received intraperitoneal injection of 0.06 mg/kg zoledronate and saline, respectively, once a week for 12 weeks. At the end of the week 4 of the experiment, all 60 rats underwent unilateral mandibular first molar extraction. A 4 mm defect was made in the contralateral canine alveolar mucosa. At the end of the experiment, rats were sacrificed, and the three areas of interest including extraction, soft tissue defect, and the non-intervention (canine area on the same side of extraction) sites were assessed clinically for presence of bone exposure/fistula, and histologically for status of bone remodeling (only at extraction site) and osteonecrosis.
Results:
In the study group, the frequency of bone exposure/fistula was 80%, 0%, and 0%; and the rate of histological bone necrosis was 83.3%, 20%, and 0%; at the extraction, soft tissue defect, and non-intervention sites, respectively. No clinical and histological sign of bone necrosis was found in the control group. Normal bone remodeling was observed in 0% and 100% of the extraction sockets in the study and control groups, respectively.
Conclusion:
Injury to alveolar bone was a stronger trigger for BRONJ development compared to oral mucosal damages.
Bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) can occur when enhanced bone-resorptive diseases are treated with nitrogen-containing BPs (N-BPs). Having previously found, in mice, that the non-N-BP etidronate can (i) reduce the inflammatory/necrotic effects of N-BPs by inhibiting their intracellular entry and (ii) antagonize the binding of N-BPs to bone hydroxyapatite, we hypothesized that etidronate-replacement therapy (Eti-RT) might be useful for patients with, or at risk of, BRONJ. In the present study we examined this hypothesis. In each of 25 patients receiving N-BP treatment, the N-BP was discontinued when BRONJ was suspected and/or diagnosed. After consultation with the physician-in-charge and with the patient’s informed consent, Eti-RT was instituted in one group according to its standard oral prescription. We retrospectively compared this Eti-RT group (11 patients) with a non-Eti-RT group (14 patients). The Eti-RT group (6 oral N-BP patients and 5 intravenous N-BP patients) and the non-Eti-RT group (5 oral N-BP patients and 9 intravenous N-BP patients) were all stage 2–3 BRONJ. Both in oral and intravenous N-BP patients (particularly in the former patients), Eti-RT promoted or tended to promote the separation and removal of sequestra and thereby promoted the recovery of soft-tissues, allowing them to cover the exposed jawbone. These results suggest that Eti-RT may be an effective choice for BRONJ caused by either oral or intravenous N-BPs and for BRONJ prevention, while retaining a level of anti-bone-resorption. Eti-RT may also be effective at preventing BRONJ in N-BP-treated patients at risk of BRONJ. However, prospective trials are still required.
Graphical Abstract Fullsize Image
A bone imaging toolkit of 21 fluorescent probes with variable spectroscopic properties, bone mineral binding affinities, and antiprenylation activities has been created, including a novel linking strategy. The linking chemistry allows attachment of a diverse selection of dyes fluorescent in the visible to near-infrared range to any of the three clinically important heterocyclic bisphosphonate bone drugs (risedronate, zoledronate, and minodronate or their analogues). The resultant suite of conjugates offers multiple options to "mix and match" parent drug structure, fluorescence emission wavelength, relative bone affinity, and presence or absence of antiprenylation activity, for bone-related imaging applications.
Objective:
We present clinical and radiologic data of periodontal tissue involvement preceding the appearance of osteonecrosis of the jaw (ONJ) in 5 patients with solid tumors, who received antiresorptives alone or in combination with targeted therapies.
Study design:
Five patients with osteonecrosis before dental extraction were studied.
Results:
Periodontal involvement was evidenced by pain, bleeding, fistula, purulence, swelling, periodontal pocket, and tooth mobility. Combined endoperiodontal lesions were considered in 1 patient. Duration of symptoms before ONJ diagnosis lasted 8 to 24 weeks. Routine therapy was performed in 2 of 5 patients. Widening of the periodontal ligament was observed in 4 patients, and dense alveolar bone was seen in 1 patient. Local complications of ONJ required dental extractions in 4 of 5 patients. Spontaneous tooth exfoliation was observed in 1 patient. Alveolar bone biopsies, after the extraction in 2 patients, confirmed osteonecrosis. Osteonecrosis healed in 2 patients-1 after the dental extraction and 1 after 3 dental extractions and surgical debridement. Postextraction socket healed in 1 patient, and the area with exposed bone remained asymptomatic. Osteonecrosis progressed in 2 patients.
Conclusions:
Clinical and radiologic signs of periodontal tissue involvement, before dental extraction in patients treated with antiresorptives alone or in combination with targeted therapy, may represent developing osteonecrosis.
Osteonecrosis of the jaw (ONJ) is a multifactorial disease in patients with primary or metastatic bone malignancy or osteoporosis undergoing systemic antiresorptive therapy, where pathophysiology has not yet been fully determined. The staging of ONJ is based on severity of symptoms and extent of clinical and radiographic findings. Treatment strategies range from conservative local wound care to aggressive resective surgery of all necrotic bone. The first ONJ cases were reported in 2003 and 2004, and although significant progress has been made in our understanding of the disease, much more work needs to be done to completely explain its pathophysiology.
Osteonecrosis of the jaws (ONJ) is a significant complication of antiresorptive medications, such as bisphosphonates and denosumab. Antiresorptive discontinuation to promote healing of ONJ lesions remains highly controversial and understudied. Here, we investigated whether antiresorptive discontinuation alters ONJ features in mice, employing the potent bisphosphonate zoledronic acid (ZA), or the RANKL inhibitor OPG-Fc, utilizing previously published ONJ animal models. Mice were treated with veh, ZA or OPG-Fc for 11 weeks to induce ONJ, and antiresorptives were discontinued for 6 or 10 weeks. Maxillae and mandibles were examined by μCT imaging and histologically. ONJ features in ZA and OPG-Fc groups included periosteal bone deposition, empty osteocyte lacunae, osteonecrotic areas and bone exposure, each of which substantially resolved 10 weeks after discontinuing OPG-Fc, but not ZA. Full recovery of TRAP+ osteoclast numbers occurred after discontinuing OPG-Fc, but not ZA. Our data provide the first experimental evidence demonstrating that discontinuation of a RANKL inhibitor, but not a bisphosphonate, reverses features of osteonecrosis in mice. It remains unclear whether antiresorptive discontinuation increases the risk of skeletal-related events in patients with bone metastases, or fracture risk in osteoporosis patients, but these preclinical data may nonetheless help to inform discussions on the rationale for a "drug holiday" in managing the ONJ patient. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
This paper provides a systematic review of the literature from January 2003 to April 2014 pertaining to the incidence, pathophysiology, diagnosis and treatment of osteonecrosis of the jaw (ONJ), and offers recommendations for its management based on multidisciplinary international consensus. ONJ is associated with oncology-dose parenteral anti-resorptive therapy of bisphosphonates (BP) and denosumab (Dmab). The incidence of ONJ is greatest in the oncology patient population (1-15%) where high doses of these medications are used at frequent intervals. In the osteoporosis patient population, the incidence of ONJ is estimated at 0.001% to 0.01%, marginally higher than the incidence in the general population (<0.001%). New insights into the pathophysiology of ONJ include anti-resorptive effects of BPs and Dmab, effects of BPs on gamma delta T-cells and on monocyte and macrophage function, as well as the role of local bacterial infection, inflammation and necrosis. Advances in imaging include the use of cone beam computerized tomography assessing cortical and cancellous architecture with lower radiation exposure, magnetic resonance imaging, bone scanning and positron emission tomography, although plain films often suffice. Other risk factors for ONJ include glucocorticoid use, maxillary or mandibular bone surgery, poor oral hygiene, chronic inflammation, diabetes mellitus, ill-fitting dentures, as well as other drugs, including anti-angiogenic agents. Prevention strategies for ONJ include elimination or stabilization of oral disease prior to initiation of anti-resorptive agents, as well as maintenance of good oral hygiene. In those patients at high risk for the development of ONJ, including cancer patients receiving high-dose BP or Dmab therapy, consideration should be given to withholding anti-resorptive therapy following extensive oral surgery until the surgical site heals with mature mucosal coverage. Management of ONJ is based on the stage of the disease, size of the lesions, as well as the presence of contributing drug therapy and comorbidity. Conservative therapy includes topical antibiotic oral rinses and systemic antibiotic therapy. Localized surgical debridement is indicated in advanced non-responsive disease and has been successful. Early data have suggested enhanced osseous wound healing with teriparatide in those without contraindications for its use. Experimental therapy includes bone marrow stem cell intralesional transplantation, low-level laser therapy, local platelet-derived growth factor application, hyperbaric oxygen, and tissue grafting. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Background:
The National Institutes of Health.funded Trial to Assess Chelation Therapy (TACT) randomized 1708 stablecoronary disease patients aged .50 years who were .6 months post.myocardial infarction (2003.2010) to 40 infusions ofa multicomponent EDTA chelation solution or placebo. Chelation reduced the primary composite end point of mortality,recurrent myocardial infarction, stroke, coronary revascularization, or hospitalization for angina (hazard ratio, 0.82; 95%confidence interval, 0.69.0.99; P=0.035).
Methods and results:
In a randomly selected subset of 911 patients, we prospectively collected a battery of quality-of-life(QOL) instruments at baseline and at 6, 12, and 24 months after randomization. The prespecified primary QOL measures were the Duke Activity Status Index (Table I in the Data Supplement) and the Medical Outcomes Study Short-Form 36 Mental Health Inventory-5. All comparisons were by intention to treat. Baseline clinical and QOL variables were well balanced in the 451 patients randomized to chelation and in the 460 patients randomized to placebo. The Duke Activity Status Index improved in both groups during the first 6 months of therapy, but we found no evidence for a treatment-related difference (mean difference [chelation.placebo] during follow-up, 0.9 [95% confidence interval, .0.7 to 2.6; P=0.27]).There was no statistically significant evidence of a treatment-related difference in the Mental Health Inventory-5 during follow-up (mean difference, 1.0; 95% confidence interval, .0.1 to 2.0; P=0.08). None of the secondary QOL measures showed a consistent treatment-related difference.
Conclusions:
In stable, predominantly asymptomatic coronary disease patients with a history of myocardial infarction,EDTA chelation therapy did not have a detectable effect on QOL during 2 years of follow-up.
Clinical trial registration:
URL: http://clinicaltrials.gov. Unique identifier: NCT00044213.
Strategies for management of patients with, or at risk for, Medication-Related Osteonecrosis of the Jaw (MRONJ) were set forth in the American Association of Oral and Maxillofacial Surgeons (AAOMS) Position Papers in 2007 and 2009. The Position Papers were developed by a Special Committee appointed by the Board and composed of clinicians with extensive experience in caring for these patients and basic science researchers. The knowledge base and experience in addressing MRONJ has expanded, necessitating modifications and refinements to the previous Position Paper. This Special Committee met in September 2013 to appraise the current literature and revise the guidelines as indicated to reflect current knowledge in this field. This update contains revisions to diagnosis, staging, and management strategies, and highlights current research status. AAOMS considers it vitally important that this information be disseminated to other relevant health care professionals and organizations.
Patients undergoing extraction are at risk for bisphosphonate-related osteonecrosis of the jaws (BRONJ). A C-terminal crosslinking telopeptide (CTX) level lower than 150 pg/mL has been suggested as a predictor of BRONJ risk. The authors aimed to increase the precision of estimates of the risk of BRONJ in osteoporosis after extraction and to assess value of CTX testing at extraction time in cases of BRONJ in a large prospective cohort.
All patients on oral bisphosphonates for osteoporosis referred for extractions over a period of 6.5 years were included in a standard protocol. Pre-extraction fasted CTX levels were obtained. All patients were followed until healing. If the CTX level was lower than 150 pg/mL, they were offered a drug holiday. If they declined, if the CTX level was above 150 pg/mL at baseline, or after the drug holiday, they had extractions performed under local anesthesia. Age-matched controls not on bisphosphonates were identified.
Nine hundred fifty patients had 2,461 extractions. One hundred eighty-one patients had a CTX level lower than 150 pg/mL. Four patients developed BRONJ; all had a CTX level lower than 150 pg/mL. All were on alendronate. The case-control comparison approached significance (<150 pg/mL; P = .073). Alendronate was associated with a low CTX level (P < .05). A CTX level lower than 150 pg/mL had a sensitivity of 100% and specificity of 81%. Bayesian analysis yielded a population expected risk of BRONJ of 0.29% (95% confidence interval, 0.12-0.52); the expected risk was 0.42% for a CTX level lower than 150 pg/mL and 0.13% for a CTX level higher than 150 pg/mL.
The risk of BRONJ for patients with osteoporosis on bisphosphonates having extractions is approximately 0.2%. A CTX level lower than 150 pg/mL is sensitive and is associated with an approximately 3-fold greater risk of BRONJ.
Evidence of the incidence and risk of osteonecrosis of the jaw (ONJ) in Asian osteoporosis populations receiving different osteoporosis medications is lacking. We found that there is no excess incidence of or risk for ONJ in osteoporosis patients >50 years old using alendronate as compared with patients using raloxifene or calcitonin under real-world conditions in Taiwan.
To provide information on ONJ in Asian populations, this study compares the incidence and risk of ONJ between patients receiving alendronate and those receiving non-bisphosphonate osteoporosis medications in Taiwan.
Enrollees in the National Health Insurance Research Database (NHIRD) from 2003 to 2007, aged above 50 years, with vertebral/hip fracture, and new to osteoporosis therapy were recruited. Patients with Paget's disease or cancer during the baseline period were excluded. Patients were classified into either the alendronate or the calcitonin/raloxifene (control) group according to their exposure during follow-up. Previously proposed possible ONJ diagnosis codes were adopted as potential ONJ cases, but qualifying cases also had a repeated ONJ diagnosis within 8 weeks of the first diagnosis and received one or more broad-spectrum oral antibiotics. Cox modeling compared the risk of ONJ between the alendronate and the control groups, which were matched using propensity scores. Results were examined in series sensitivity analyses, including different cumulative dose groups.
We found 25 potential ONJ cases in the alendronate (N = 18,030) and 21 in the control groups (N = 25,615). Over the 6-year follow-up period, no increased risk of ONJ in the alendronate group in the original (hazard ratio (HR), 0.87; 95 % confidence interval (CI), 0.47-1.58) or propensity score-matched cohorts (HR, 0.86; 95 % CI, 0.44-1.69) was found. All comparison groups exhibited a similar incidence of ONJ, ranging from 6.9 to 8.2/10,000 person-years.
Under real-world conditions, there is no excess risk for ONJ in osteoporosis patients >50 years old using alendronate as compared with patients using raloxifene or calcitonin.
Bisphosphonates (BPs) are chemically stable analogs of pyrophosphate exhibiting strong affinity to bone and have been used for the treatment of diseases characterized by excessive bone resorption. Contrary to the widely accepted BP accumulation model in bone after repeated applications, we report here that an equilibrium-dependent BP–crystalline bone mineral interaction may better explain BP bio-distribution and anti-catabolic bone remodeling and may be relevant to the appearance of osteonecrosis of the jaw (ONJ) in rats. Fluorescent-labeled BP analogs were synthesized and used to evaluate the mode of bone adsorption. After fluorescent-labeled BP adsorbed on crystalline calcium phosphates in vitro, subsequent BP application replaced the previously absorbed BP depending on the dose and the relative binding affinity to hydroxyapatite. The in vivo intravenous zoledronate (ZOL) injection of repeated fractional doses resulted in lower serum CTX and TRAP5b measurements than a single bolus injection in spite of the equivalent cumulative dose. Repeated injections resulted in the distribution of fluorescent-labeled BP on the large area of bone surfaces; whereas the single bolus injection gave rise to the intense BP bio-distribution at selected bone sites such as the alveolar process of jawbones. Necrotic maxillary alveolar bone was predominantly observed in vitamin D deficiency rats treated with bolus ZOL injection. The palatal necrotic bone was characteristically sequestrated by the fistulation of hyperplastic oral epithelium, suggesting the initial development of ONJ-like lesions in rats. Our results suggest that equilibrium-dependent BP–bone interaction may, in part, determine the effectiveness and influence side effects of long-term and repeated applications of BPs.
Osteonecrosis of the jaw (ONJ) is a well-recognized complication of antiresorptive medications, such as bisphosphonates (BPs). Although ONJ is most common after tooth extractions in patients receiving high dose BPs, many patients do not experience oral trauma. Animal models utilizing tooth extractions and high BP doses recapitulate several clinical, radiographic and histologic findings of ONJ. We and others have reported on rat models of ONJ utilizing experimental dental disease in the absence of tooth extraction. These models emphasize the importance of dental infection/inflammation for ONJ development. Here, we extend our original report in the rat, and present a mouse model of ONJ in the presence of dental disease. Mice were injected with high dose zoledronic acid and pulpal exposure of mandibular molars was performed to induce periapical disease. After 8 weeks, quantitative and qualitative radiographic and histologic analyses of mouse mandibles were executed. Periapical lesions were larger in vehicle- vs. BP treated mice. Importantly, radiographic features resembling clinical ONJ, including thickening of the lamina dura, periosteal bone deposition and increased trabecular density, were seen in the drilled site of BP treated animals. Histologically, osteonecrosis, periosteal thickening, periosteal bone apposition, epithelial migration and bone exposure were present in the BP treated animals in the presence of periapical disease. No difference in TRAP+ cell numbers was observed, but round, detached, and removed from the bone surface cells were present in BP animals. Although 88% of the BP animals showed areas of osteonecrosis in the dental disease site, only 33% developed bone exposure, suggesting that osteonecrosis precedes bone exposure. Our data further emphasize the importance of dental disease in ONJ development, provide qualitative and quantitative measures of ONJ, and present a novel mouse ONJ model in the absence of tooth extraction that should be useful in further exploring ONJ pathophysiological mechanisms. © 2013 American Society for Bone and Mineral Research.
Osteonecrosis of the jaw (ONJ) following the use of bisphosphonates has become of increased interest in the scientific community, due in particular to its as-yet-unsolved pathogenesis. An experimental model of ONJ was induced in normal male rats [alendronate (ALN); 1 mg/Kg/day; n = 10] and matched controls (saline solution; n = 10). After 60 days of drug treatment, all animals were subjected to extractions of the left first lower molars and were euthanized at 3 and 28 days postsurgery. The following analyses were performed: (i) descriptive and quantitative (scores) histological evaluation, (ii) stereometry of distal sockets and (iii) biochemical measurement of C-telopeptide cross-linked collagen type I (CTX) and bone-specific alkaline phosphatase (BALP). The results showed that 28 days postsurgery the animals treated with ALN had areas of exposed and necrotic bone, associated with significant infection, especially in the interalveolar septum area and crestal regions, compared with controls. The levels of CTX, BALP and bone volume, as well as the degrees of inflammation and vascularization, were significantly reduced in these animals. Therefore, analysis of the data presented suggests that ALN therapy is associated with the development of osteonecrosis in the jaws of rodents after tooth extraction.
To quantify the incidence of osteonecrosis of the jaw (ONJ) by bisphosphonate exposure among two cohorts of patients.
In a retrospective cohort study, we identified cohort members via health insurance claim diagnosis codes and identified potential cases of ONJ that were confirmed with medical record review. One cohort included patients aged ≥40 years with breast or prostate cancer or multiple myeloma; the other cohort included men aged ≥60 years and women ≥50 years with osteoporosis. For each cohort, we calculated sex- and age-standardized incidence of ONJ by exposure to oral bisphosphonates and intravenous bisphosphonates.
In the cancer cohort (n = 46 542), sex- and age-standardized incidence of ONJ (n = 26 probable or possible cases) adjusted for abstraction proportion was 0.29 per 1000 person-years (95% confidence interval [CI], 0.07-0.52) among those unexposed to bisphosphonates and 5.3 (95%CI, 1.9-8.7) after intravenous bisphosphonate use. Controlling for covariates, the rate ratio for intravenous use versus no use was 8.8 (95%CI, 2.0-38). Patients with multiple myeloma had a rate 4.5 times that of patients with breast cancer. In the osteoporosis cohort (n = 31 244), sex- and age-standardized ONJ (n = 11 probable or possible cases) incidence was 0.26 per 1000 person-years (95%CI, 0.06-0.47) among those unexposed to bisphosphonate and 0.15 (95%CI, 0.00-0.36) after oral bisphosphonate use.
Among patients with selected cancers, incidence of ONJ was higher among those with multiple myeloma and users of intravenous bisphosphonates.
Though osteonecrosis of the jaw (ONJ) is temporally-associated with the use of nitrogen-containing bisphosphonates (N-BPs), a cause-and-effect relationship has not yet been established. We hypothesize that ONJ is a two-stage process in which: (1) risk factors initiate pathologic processes in the oral cavity that lead to a supranormal rate of hard tissue necrosis; and (2) powerful antiresorptives reduce the rate of removal of necrotic bone sufficiently to allow its net accumulation in the jaw. To test this hypothesis, we used the rice rat model of periodontitis. At age 28 days, rats (n = 15/group) were placed on a high-sucrose and casein diet to exacerbate the development of periodontitis. Animals were injected subcutaneously (SC) biweekly with vehicle or alendronate (ALN, 15 µg/kg), or IV once monthly with vehicle, a low dose (LD) of zoledronic acid (ZOL), or a high dose (HD) of ZOL and sacrificed after 6, 12, 18, and 24 weeks. Mandibles and maxillae were analyzed to determine the effects on the: (1) progression of periodontitis; (2) integrity of alveolar bone; (3) status of bone resorption and formation; (4) vascularity; and (5) osteocyte viability. We found that only HD-ZOL induced ONJ-like lesions in mandibles of rice rats after 18 and 24 weeks of treatment. These lesions were characterized by areas of exposed necrotic alveolar bone, osteolysis, a honeycomb-like appearance of the alveolar bone, presence of bacterial colonies, and periodontal tissue destruction. In addition, inhibition of bone formation, a paradoxical abolition of the antiresorptive effect of only HD-ZOL, increased osteocyte necrosis/apoptosis, and decreased blood vessel number were found after 18 and/or 24 weeks. Our study suggests that only HD-ZOL exacerbates the inflammatory response and periodontal tissue damage in rice rats, inducing bone lesions that resemble ONJ. © 2012 American Society for Bone and Mineral Research.
The ability of bisphosphonates ((HO)(2)P(O)CR(1)R(2)P(O)(OH)(2)) to inhibit bone resorption has been known since the 1960s, but it is only recently that a detailed molecular understanding of the relationship between chemical structures and biological activity has begun to emerge. The early development of chemistry in this area was largely empirical and based on modifying R(2) groups in a variety of ways. Apart from the general ability of bisphosphonates to chelate Ca(2+) and thus target the calcium phosphate mineral component of bone, attempts to refine clear structure-activity relationships had led to ambiguous or seemingly contradictory results. However, there was increasing evidence for cellular effects, and eventually the earliest bisphosphonate drugs, such as clodronate (R(1)=R(2)=Cl) and etidronate (R(1)=OH, R(2)=CH(3)), were shown to exert intracellular actions via the formation in vivo of drug derivatives of ATP. The observation that pamidronate, a bisphosphonate with R(1)=OH and R(2)=CH(2)CH(2)NH(2), exhibited higher potency than previously known bisphosphonate drugs represented the first step towards the later recognition of the critical importance of having nitrogen in the R(2) side chain. The synthesis and biological evaluation of a large number of nitrogen-containing bisphosphonates took place particularly in the 1980s, but still with an incomplete understanding of their structure-activity relationships. A major advance was the discovery that the anti-resorptive effects of the nitrogen-containing bisphosphonates (including alendronate, risedronate, ibandronate, and zoledronate) on osteoclasts appear to result from their potency as inhibitors of the enzyme farnesyl pyrophosphate synthase (FPPS), a key branch-point enzyme in the mevalonate pathway. FPPS generates isoprenoid lipids utilized in sterol synthesis and for the post-translational modification of small GTP-binding proteins essential for osteoclast function. Effects on other cellular targets, such as osteocytes, may also be important. Over the years many hundreds of bisphosphonates have been synthesized and studied. Interest in expanding the structural scope of the bisphosphonate class has also motivated new approaches to the chemical synthesis of these compounds. Recent chemical innovations include the synthesis of fluorescently labeled bisphosphonates, which has enabled studies of the biodistribution of these drugs. As a class, bisphosphonates share common properties. However, as with other classes of drugs, there are chemical, biochemical, and pharmacological differences among the individual compounds. Differences in mineral binding affinities among bisphosphonates influence their differential distribution within bone, their biological potency, and their duration of action. The overall pharmacological effects of bisphosphonates on bone, therefore, appear to depend upon these two key properties of affinity for bone mineral and inhibitory effects on osteoclasts. The relative contributions of these properties differ among individual bisphosphonates and help determine their clinical behavior and effectiveness.
Bisphosphonates (BPs) are medications used commonly to treat primary and metastatic bone cancer, as well as osteoporosis. Although BPs improve bone mineral density, reduce fracture risk, and reduce hypercalcemia of malignancy, some patients develop BP-related osteonecrosis of the jaws (BRONJ). This devastating complication is defined as clinically exposed bone in the maxillofacial region for more than 8 weeks. Despite an increasing number of BRONJ cases since first reported, the disease pathophysiology remains largely unknown. Since published studies suggest a significant role for dental disease in the pathophysiology of BRONJ, we developed a BRONJ animal model where aggressive periodontal disease is induced by ligature placement around the crown of the right maxillary first molar in the presence of vehicle (veh) or zoledronic acid (ZA), a potent BP. Ligature placement induced significant alveolar bone loss, which was attenuated by ZA treatment. Osteonecrosis was observed associated with ligature-induced periodontitis in the ZA-treated group. This was seen as sequestration and extensive periosteal alveolar bone formation on micro-computed tomography (µCT) in the ligated site of BP-treated animals. Histologic examination confirmed these findings, seen as necrotic bone with diffuse loss of osteocytes and empty lacunae, rimming of the necrotic bone by squamous epithelium and inflammation, and exposure to the oral cavity. Importantly, the rat lesions were strikingly similar to those of BRONJ patients. Our data suggest that dental disease and potent BP therapy are sufficient for BRONJ development in the rat.
We report on an observational longitudinal noncontrolled study of a case series of consecutive patients treated with zoledronate who underwent tooth extractions. The tooth extractions were performed after a preventive protocol to minimize the risk of bisphosphonate-related osteonecrosis of the jaw.
A total of 43 patients who had received zoledronate and required single or multiple dental extractions were treated. The preventive protocol provided a surgical approach for dental extractions, characterized by the removal of alveolar bone (alveolectomy), and supported by correct antimicrobial therapy (antibiotics and mouthwash).
A total of 102 tooth extractions in 43 patients were performed. The follow-up was 12 months. No signs of inflamed tissue or necrotic exposed bone in any patient were observed.
With the limits of the present study, we observed that the removal of the alveolar bone after the tooth extractions and correct antimicrobial prophylaxis (antibiotics and mouthwash) could reduce the risk of occurrence of osteonecrosis in patients taking zoledronate.
Bisphosphonates are used in the treatment of hypercalcemia of malignancy, skeletal complications associated with metastastic bone disease, Paget's disease, and osteoporosis. Osteonecrosis of the jaw (ONJ) is a recently described clinical condition that has been associated with the use of nitrogen-containing bisphosphonates. Reports describing this entity first appeared in the literature in 2003. While there have been significant numbers of case reports and a limited number of retrospective and prospective studies examining risk factors associated with ONJ, the pathophysiology of this condition remains elusive. In this review, we explore proposed mechanisms underlying ONJ development and identify potential areas for future investigation.
Bisphosphonate effects on the skeleton have been studied in the context of a broad range of disciplines, including endocrinology, orthopedics, oncology, and dentistry. The emergence of osteonecrosis of the jaw as a rare but serious side effect of bisphosphonate treatment has stimulated interest in understanding how this drug class affects the oral skeleton. This review focuses on recent work describing how bisphosphonates affect bone remodeling, tissue properties, and postsurgical healing in the oral cavity.
To report a case series of patients with the nonexposed variant of bisphosphonate-associated osteonecrosis of the jaw-a form of jaw osteonecrosis that does not manifest with necrotic bone exposure/mucosal fenestration.
Among 332 individuals referred to 5 clinical centers in Europe because of development of jawbone abnormalities after or during exposure to bisphosphonates, we identified a total of 96 patients who presented with the nonexposed variant of osteonecrosis. Relevant data were obtained via clinical notes; radiological investigations; patients' history, and referral letters.
The most common clinical feature of nonexposed osteonecrosis was jaw bone pain (88/96; 91.6%); followed by sinus tract (51%), bone enlargement (36.4%); and gingival swelling (17.7%). No radiological abnormalities were identified in 29.1% (28/96) of patients. In 53.1% (51/96) of the patients; nonexposed osteonecrosis subsequently evolved into frank bone exposure within 4.6 months (mean; 95% confidence interval; 3.6-5.6).
Clinicians should be highly vigilant to identify individuals with nonexposed osteonecrosis, as the impact on epidemiological data and clinical trial design could be potentially significant. Although the present case series represents approximately 30% of all patients with bisphosphonates-associated osteonecrosis observed at the study centers, further population-based prospective studies are needed to obtain robust epidemiological figures.
Radiographic features in patients with bisphosphonate-related osteonecrosis of the jaw (BRONJ) are well described, but less is known in bisphosphonate-exposed individuals with stage 0 disease (clinical symptoms without exposed necrotic bone) considered at risk for BRONJ. We sought to characterize radiographic findings in a subgroup of patients with concerning clinical symptoms and bisphosphonate exposure to identify imaging features that may presage development of BRONJ.
A dental symptom survey was returned by 8,572 Kaiser Permanente Health Plan members receiving chronic oral bisphosphonate therapy, and 1,005 patients reporting pertinent dental symptoms or complications after dental procedures were examined. Those without BRONJ but with concerning symptoms were referred for clinical evaluation, including imaging. Among the subset who received maxillofacial imaging, we identified those with stage 0 disease and abnormal radiographic features.
There were a total of 30 patients without exposed bone but with concerning symptoms who received maxillofacial imaging (panoramic radiography or computed tomography) in the context of clinical care. Among these 30 patients, 10 had stage 0 disease with similar radiographic features of regional or diffuse osteosclerosis in clinically symptomatic areas, most with extension beyond the involved site. Other findings in these 10 patients included density confluence of cortical and cancellous bone, prominence of the inferior alveolar nerve canal, markedly thickened and sclerotic lamina dura, uniform periradicular radiolucencies, cortical disruption, lack of bone fill after extraction, and a persisting alveolar socket. None had exposed bone develop during 1-year follow-up. The remaining 20 patients had normal or localized radiographic findings consistent with odontogenic pathology.
In 10 of 30 symptomatic patients referred for clinical evaluation and imaging, a consistent finding was conspicuous osteosclerosis in clinically symptomatic areas characteristic of stage 0 disease. These data support the need to better understand radiographic features associated with bisphosphonate exposure and to determine whether osteosclerosis is a specific finding indicative of the risk for progression to BRONJ.
We report synthesis of the first fluorescently labeled conjugates of risedronate (1), using an epoxide linker strategy enabling conjugation of 1 via its pyridyl nitrogen with the label (carboxyfluorescein). Unlike prior approaches to create fluorescent bisphosphonate probes, the new linking chemistry did not abolish the ability to inhibit protein prenylation in vitro, while significantly retaining hydroxyapatite affinity. The utility of a fluorescent 1 conjugate in visualizing osteoclast resorption in vitro was demonstrated.
Osteonecrosis of the jaw (ONJ) can be a severe complication of patients with multiple myeloma (MM) treated with bisphosphonates. Dental procedures are a major risk factor for ONJ occurrence. We retrospectively analysed the data of 178 patients with MM to evaluate if antibiotic prophylaxis before dental procedures may prevent ONJ. A correlation between dental procedures, antibiotic prophylaxis, incidence of ONJ and relevant clinical features was performed. Overall nine out of 178 patients developed ONJ (5 year crude cumulative incidence: 7.7%). Only one case of ONJ was not correlated with dental procedures. Seventy-five patients received at least one dental procedure and 43 received antibiotic prophylaxis. Eight cases of ONJ were observed, all in the group of patients without antibiotic prophylaxis. The only variable significantly associated with ONJ was antibiotic prophylaxis (p = 0.012), which had a protective effect. Thus, we speculated that antibiotic prophylaxis may prevent ONJ occurrence after dental procedures.