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Biochemical and Morphological Abnormalities of Subchondral Bone and Their Association with Cartilage Degeneration in Spontaneous Osteoarthritis

August 2021
Calcified Tissue International 109(8)

August 2021
109(8)

DOI:10.1007/s00223-021-00834-3

Authors:

Niu Haijun

Beihang University (BUAA)

Haipeng Cen

Beihang University (BUAA)

Show all 6 authorsHide

This study aims to investigate how biochemical composition in subchondral bone (SB) relates to the sulfated glycosaminoglycan (sGAG) content of articular cartilage (AC) in the knee joint of guinea pigs from the early to moderate osteoarthritis (OA). Male Dunkin Hartley strain guinea pigs were grouped according to age (1, 3, 6, and 9 months, with 10 guinea pigs in each group). The biochemical properties of the AC and SB in the tibial plateau of the guinea pigs were determined through histology and Raman spectroscopy, respectively. Furthermore, the microstructures of the SB were investigated using micro-computed tomography (micro-CT) and histology. Increased thickness and bone mineral density (BMD) and decreased porosity were observed in the subchondral plate (SP) with the progression of spontaneous OA, accompanied by a decreasing trend in sGAG integrated optical density (IOD) of AC. Compared with the changes in the microstructure of subchondral bone, the content of sGAG was more correlated to the changes in the mineral/matrix ratio of subchondral bone. The mineralization of the matrix was significantly correlated to the content of sGAG compared with crystallinity/maturity and Type B carbonate substitution. PO43− ν1/Amide III was more correlated to the content of sGAG than PO43− ν1/Amide I, PO43− ν1/CH2 wag during the progression of spontaneous osteoarthritis. This study demonstrated that the mineralization of subchondral bone plays a crucial role in the pathogenesis of OA. Future studies may access to the mineralization of subchondral bone in addition to its microstructure in the study for pathogenesis and early diagnosis of osteoarthritis.

Synopsis of the tests performed in tibial AC and subchondral bone regions, and sketch map of spectra acquisition areas and sites in sagittal plane of knee joint. According to the sample size, 3–5 semi-circles with 0.5 mm diameter were selected as spectra acquisition areas of subchondral plate (A), and 3–5 circles with 0.8 mm diameter were selected as spectra acquisition areas of trabecular bone (B). The red crosses in the sketch map were spectra acquisition sites, and 2–3 sites were selected in each spectra acquisition area

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BMD and microarchitecture parameters of tibial subchondral plate and subchondral trabecular bone at medial and lateral sides from 1-, 3-, 6-, and 9-month-old guinea pigs (n = 40). a Images of top and coronal views of ROI selection of medial and lateral tibia subchondral plate and subchondral trabecular bone for bone analysis; b BMD; c thickness; d BMD; e BV/TV; f TBPf; g Tb.Th; h SMI; i DA. *p < 0.001

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Typical histology images of AC in tibial plateau from 1-, 3-, 6-, and 9-month-old guinea pigs with HE staining and safranin orange-fast green staining, and sGAG IOD of AC in tibial plateau. a Typical HE images from 1-, 3-, 6-, and 9-month-old guinea pigs, respectively. Arrows indicate the histological changes, i.e., the number of chondrocytes in the superficial zone of the AC decreased at age of 3 month; at age of 6 months, fibrillation expanded to the transitional zone; at age of 9 months, more fissures appeared and tidemark disappeared; scale bar 250 μm; b Ratio of pore area/total area variation with animal age; c Ratios of bone area/total area variation with animal age. d Typical histology images with safranin orange-fast green from 1-, 3-, 6-, and 9-month-old guinea pigs, respectively; scale bar 100 μm; e sGAG integrated optical density variations with animal age; f Modified Mankin score variations with animal age.*p < 0.05, compared with 1-month group; #p < 0.05, compared with 3-month group; θp < 0.05, compared with 6-month group

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Mineral-to-matrix ratios, crystallinity, and type B carbonate substitution of subchondral plate (SP) and subchondral trabecular bone (ST) measured by Raman spectroscopy in tibial plateau from 1-, 3-, 6-, and 9-month-old guinea pigs (n = 40). a PO4³⁻ ν1/Amide III, PO4³⁻ ν1/CH2, and PO4³⁻ ν1/Amide I of SP and ST variation with animal age; b Crystallinity/maturity of SP and ST was not different between groups; c Type B carbonate substitution of SP and ST was not different between groups; *p < 0.05, compared with 1-month group; #p < 0.05, compared with 3-month group

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Vol.:(0123456789)

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Calciﬁed Tissue International (2021) 109:179–189

https://doi.org/10.1007/s00223-021-00834-3

ORIGINAL RESEARCH

Biochemical andMorphological Abnormalities ofSubchondral Bone

andTheir Association withCartilage Degeneration inSpontaneous

Osteoarthritis

PenglingRen1,2· HaijunNiu1· HaipengCen1· ShaoweiJia1· HeGong1,2· YuboFan1

Received: 19 November 2020 / Accepted: 25 February 2021 / Published online: 13 March 2021

Abstract

This study aims to investigate how biochemical composition in subchondral bone (SB) relates to the sulfated glycosamino-

glycan (sGAG) content of articular cartilage (AC) in the knee joint of guinea pigs from the early to moderate osteoarthritis

(OA). Male Dunkin Hartley strain guinea pigs were grouped according to age (1, 3, 6, and 9months, with 10 guinea pigs in

each group). The biochemical properties of the AC and SB in the tibial plateau of the guinea pigs were determined through

histology and Raman spectroscopy, respectively. Furthermore, the microstructures of the SB were investigated using micro-

computed tomography (micro-CT) and histology. Increased thickness and bone mineral density (BMD) and decreased poros-

ity were observed in the subchondral plate (SP) with the progression of spontaneous OA, accompanied by a decreasing trend

in sGAG integrated optical density (IOD) of AC. Compared with the changes in the microstructure of subchondral bone, the

content of sGAG was more correlated to the changes in the mineral/matrix ratio of subchondral bone. The mineralization of

the matrix was signiﬁcantly correlated to the content of sGAG compared with crystallinity/maturity and Type B carbonate

substitution. PO43− ν1/Amide III was more correlated to the content of sGAG than PO43− ν1/Amide I, PO43− ν1/CH2 wag

during the progression of spontaneous osteoarthritis. This study demonstrated that the mineralization of subchondral bone

plays a crucial role in the pathogenesis of OA. Future studies may access to the mineralization of subchondral bone in addi-

tion to its microstructure in the study for pathogenesis and early diagnosis of osteoarthritis.

Keywords Articular cartilage· Subchondral bone· Microarchitecture· Biochemical composition

Introduction

Osteoarthritis (OA) is the most common joint disorder that

leads to pain and chronic disability, especially in the elderly

[1, 2]. It is generally accepted that OA is not only related

to articular cartilage (AC) itself, but also involving the sur-

rounding tissues, especially subchondral bone (SB) [3–6].

Currently, the entire bone–cartilage unit, not merely the AC

or SB, is attracting considerable attention. The AC layer

and SB bear the most severe mechanical load. Studies have

shown that the mechanical properties of AC and SB changed

during the progression of osteoarthritis [7–10]. Biomechani-

cal property of tissue is determined by its biochemical com-

position and microstructure. The interrelationship between

SB and cartilage in morphological structure and biochemi-

cal components may aﬀect the mechanical properties of

the entire bone–cartilage unit [4, 6, 7]. Recently, exten-

sive investigations have been carried out on the biochemi-

cal composition of AC and microstructure of SB [3, 4, 7].

Results have shown that there was a signiﬁcant correlation

between the biochemical composition and the microstructure

of SB in OA, but few studies have explored the change of

biochemical composition of SB, as well as the relationship

between biochemical composition of SB and AC during the

progression of OA. A better understanding of these altera-

tions and relationships may contribute to the development

of bone-targeting therapies.

* He Gong

bmegonghe@buaa.edu.cn

1 Key Laboratory forBiomechanics andMechanobiology

ofMinistry ofEducation, Beijing Advanced Innovation

Center forBiomedical Engineering, School ofBiological

Science andMedical Engineering, Beihang University,

Beijing, People’sRepublicofChina

2 Department ofRadiology, Beijing Friendship

Hospital, Capital Medical University, Beijing,

People’sRepublicofChina

Content courtesy of Springer Nature, terms of use apply. Rights reserved.

Early Degenerative Changes in a Spontaneous Osteoarthritis Model Assessed by Nanoindentation

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Understanding early mechanical changes in articular cartilage (AC) and subchondral bone (SB) is crucial for improved treatment of osteoarthritis (OA). The aim of this study was to develop a method for nanoindentation of fresh, unfixed osteochondral tissue to assess the early changes in the mechanical properties of AC and SB. Nanoindentation was performed throughout the depth of AC and SB in the proximal tibia of Dunkin Hartley guinea pigs at 2 months, 3 months, and 2 years of age. The contralateral tibias were either histologically graded for OA or analyzed using immunohistochemistry. The results showed an increase in the reduced modulus (Er) in the deep zone of AC during early-stage OA (6.0 ± 1.75 MPa) compared to values at 2 months (4.04 ± 1.25 MPa) (*** p < 0.001). In severe OA (2-year) specimens, there was a significant reduction in Er throughout the superficial and middle AC zones, which correlated to increased ADAMTS 4 and 5 staining, and proteoglycan loss in these regions. In the subchondral bone, a 35.0% reduction in stiffness was observed between 2-month and 3-month specimens (*** p < 0.001). The severe OA age group had significantly increased SB stiffness of 36.2% and 109.6% compared to 2-month and 3-month-old specimens respectively (*** p < 0.001). In conclusion, this study provides useful information about the changes in the mechanical properties of both AC and SB during both early- and late-stage OA and indicates that an initial reduction in stiffness of the SB and an increase in stiffness in the deep zone of AC may precede early-stage cartilage degeneration.

Naturally Occurring Osteoarthritis Features and Treatments: Systematic Review on the Aged Guinea Pig Model

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INT J MOL SCI

To date, several in vivo models have been used to reproduce the onset and monitor the progression of osteoarthritis (OA), and guinea pigs represent a standard model for studying naturally occurring, age-related OA. This systematic review aims to characterize the guinea pig for its employment in in vivo, naturally occurring OA studies and for the evaluation of specific disease-modifying agents. The search was performed in PubMed, Scopus, and Web of Knowledge in the last 10 years. Of the 233 records screened, 49 studies were included. Results showed that within a relatively short period of time, this model develops specific OA aspects, including cartilage degeneration, marginal osteophytes formation, and subchondral bone alterations. Disease severity increases with age, beginning at 3 months with mild OA and reaching moderate–severe OA at 18 months. Among the different strains, Dunkin Hartley develops OA at a relatively early age. Thus, disease-modifying agents have mainly been evaluated for this strain. As summarized herein, spontaneous development of OA in guinea pigs represents an excellent model for studying disease pathogenesis and for evaluating therapeutic interventions. In an ongoing effort at standardization, a detailed characterization of specific OA models is necessary, even considering the main purpose of these models, i.e., translatability to human OA.

Axial alignment is a critical regulator of knee osteoarthritis

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Although osteoarthritis (OA), a leading cause of disability, has been associated with joint malalignment, scientific translational evidence for this link is lacking. In a clinical case study, we provide evidence of osteochondral recovery upon unloading symptomatic isolated medial tibiofemoral knee OA associated with varus malalignment. By mapping response correlations at high resolution, we identify spatially complex degenerative changes in cartilage after overloading in a clinically relevant ovine model. We further report that unloading diminishes OA cartilage degeneration and alterations of critical parameters of the subchondral bone plate in a similar topographic fashion. Last, therapeutic unloading shifted the articular cartilage and subchondral bone phenotype to normal and restored several physiological correlations disturbed in neutral and varus OA, suggesting a protective effect on the integrity of the entire osteochondral unit. Collectively, these findings identify modifiable trajectories with considerable translational potential to reduce the burden of human OA.

Inhibition of complement C3 prevents osteoarthritis progression in guinea pigs by blocking STAT1 activation

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Osteoarthritis (OA) is one of the leading causes of disability, affecting over 500 million adults worldwide. Previous studies have found that various inflammatory factors can contribute to the pathogenesis of OA, including complement factors in the synovial fluid of OA patients. However, the pathogenesis of this disease is still not known, and the only therapy of severe OA is total joint replacements. Total joint replacements are invasive, expensive, and affect quality of life. Here we show that when human articular chondrocytes are stimulated with pro-inflammatory mediator interleukin-1β (IL-1β) there is an increase in inflammatory factors including complement component 3 (C3). We also found the transcription factor, signal transducer and activator of transcription 1 (STAT1), is responsible for increased C3 expression after IL-1β stimulation in human articular chondrocytes. A specific STAT1 inhibitor, fludarabine, attenuates the hyper-expression of C3 and delays/prevents spontaneous OA in Dunkin-Hartley guinea pigs. Since fludarabine is already clinically used for chemotherapy, this study has great translational potential as a unique disease-modifying osteoarthritis drug (DMOAD) in treating primary OA.

SDF-1α promotes subchondral bone sclerosis and aggravates osteoarthritis by regulating the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells

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Background Subchondral bone sclerosis is a major feature of osteoarthritis (OA), and bone marrow mesenchymal stem cells (BMSCs) are presumed to play an important role in subchondral bone sclerosis. Accumulating evidence has shown that stromal cell-derived factor-1α (SDF-1α) plays a key role in bone metabolism-related diseases, but its role in OA pathogenesis remains largely unknown. The purpose of this study was to explore the role of SDF-1α expressed on BMSCs in subchondral bone sclerosis in an OA model. Methods In the present study, C57BL/6J mice were divided into the following three groups: the sham control, destabilization of the medial meniscus (DMM), and AMD3100-treated DMM (DMM + AMD3100) groups. The mice were sacrificed after 2 or 8 weeks, and samples were collected for histological and immunohistochemical analyses. OA severity was assessed by performing hematoxylin and eosin (HE) and safranin O-fast green staining. SDF-1α expression in the OA model was measured using an enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (q-PCR), and immunohistochemistry. Micro-CT was used to observe changes in subchondral bone in the OA model. CD44, CD90, RUNX2, and OCN expression in subchondral bone were measured using q-PCR and immunohistochemistry. In vitro, BMSCs were transfected with a recombinant lentivirus expressing SDF-1α, an empty vector (EV), or siRNA-SDF-1α. Western blot analysis, q-PCR, and immunofluorescence staining were used to confirm the successful transfection of BMSCs. The effect of SDF-1α on BMSC proliferation was evaluated by performing a CCK-8 assay and cell cycle analysis. The effect of SDF-1α on the osteogenic differentiation of BMSCs was assessed by performing alkaline phosphatase (ALP) and alizarin red S (ARS) staining. Cyclin D1, RUNX2 and OCN expression were measured using Western blot analysis, q-PCR, and immunofluorescence staining. Results SDF-1α expression in the DMM-induced OA model increased. In the DMM + AMD3100 group, subchondral bone sclerosis was alleviated, OA was effectively relieved, and CD44, CD90, RUNX2, and OCN expression in subchondral bone was decreased. In vitro, high levels of SDF-1α promoted BMSC proliferation and increased osteogenic differentiation. Cyclin D1, RUNX2, and OCN expression increased. Conclusion The results of this study reveal a new molecular mechanism underlying the pathogenesis of OA. The targeted regulation of SDF-1α may be clinically effective in suppressing OA progression.

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INT J MOL SCI

Osteoarthritis (OA) is a degenerative disease, and there is currently no effective medicine to cure it. Early prevention and treatment can effectively reduce the pain of OA patients and save costs. Therefore, it is necessary to diagnose OA at an early stage. There are various diagnostic methods for OA, but the methods applied to early diagnosis are limited. Ordinary optical diagnosis is confined to the surface, while laboratory tests, such as rheumatoid factor inspection and physical arthritis checks, are too trivial or time-consuming. Evidently, there is an urgent need to develop a rapid nondestructive detection method for the early diagnosis of OA. Vibrational spectroscopy is a rapid and nondestructive technique that has attracted much attention. In this review, near-infrared (NIR), infrared, (IR) and Raman spectroscopy were introduced to show their potential in early OA diagnosis. The basic principles were discussed first, and then the research progress to date was discussed, as well as its limitations and the direction of development. Finally, all methods were compared, and vibrational spectroscopy was demonstrated that it could be used as a promising tool for early OA diagnosis. This review provides theoretical support for the application and development of vibrational spectroscopy technology in OA diagnosis, providing a new strategy for the nondestructive and rapid diagnosis of arthritis and promoting the development and clinical application of a component-based molecular spectrum detection technology.

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Human Adipose- and Amnion-Derived Mesenchymal Stromal Cells Similarly Mitigate Osteoarthritis Progression in the Dunkin Hartley Guinea Pig

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Recent studies have shed light on the cellular and molecular mechanisms that link subchondral bone remodelling and angiogenesis in knee osteoarthritis (KOA). Type H vessels are newly identified bone blood vessel characterized by high expression of CD31 and Endomucin (Emcn) and are coupled with osteogenesis. Factors including mechanical loading, TGF-β1, platelet-derived growth factor type BB (PDGF-BB), the OPG/RANKL/RANK system, osteopontin (OPN), mTOR, VEGF, stromal cell-derived factor l (SDF-1), and prostaglandin E2 (PGE2) participate in the formation of type H vessels in osteoarthritic subchondral bone. In this review, we summarize the current understanding of type H vessels in KOA, as well as the signalling pathways involved and potential therapeutic medicines. In future, the pathogenesis of KOA could be further clarified by the bridge of type H vessels and the design of new disease-modifying osteoarthritis drugs (DMOADs). However, further experiments are needed to determine the upstream signals regulating type H vessel formation in osteoarthritic subchondral bone.

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The pathological changes in osteoarthritis—a degenerative joint disease prevalent among older people—start at the molecular scale and spread to the higher levels of the architecture of articular cartilage to cause progressive and irreversible structural and functional damage. At present, there are no treatments to cure or attenuate the degradation of cartilage. Early detection and the ability to monitor the progression of osteoarthritis are therefore important for developing effective therapies. Here, we show that indentation-type atomic force microscopy can monitor age-related morphological and biomechanical changes in the hips of normal and osteoarthritic mice. Early damage in the cartilage of osteoarthritic patients undergoing hip or knee replacements could similarly be detected using this method. Changes due to aging and osteoarthritis are clearly depicted at the nanometre scale well before morphological changes can be observed using current diagnostic methods. Indentation-type atomic force microscopy may potentially be developed into a minimally invasive arthroscopic tool to diagnose the early onset of osteoarthritis in situ

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Although cartilage degradation is the characteristic feature of osteoarthritis (OA), it is now recognized that the whole joint is involved in the progression of OA. In particular, the interaction (crosstalk) between cartilage and subchondral bone is thought to be a central feature of this process. The interface between articular cartilage and bone of articulating long bones is a unique zone, which comprises articular cartilage, below which is the calcified cartilage sitting on and intercalated into the subchondral bone plate. Below the subchondral plate is the trabecular bone at the end of the respective long bones. In OA, there are well-described progressive destructive changes in the articular cartilage, which parallel characteristic changes in the underlying bone. This review examines the evidence that biochemical and biomechanical signaling between these tissue compartments is important in OA disease progression and asks whether such signaling might provide possibilities for therapeutic intervention to halt or slow disease development.

Subchondral Bone Plate Changes More Rapidly than Trabecular Bone in Osteoarthritis

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Sep 2016
INT J MOL SCI

Osteoarthritis (OA) is the most common joint disorder, characterised by focal loss of cartilage and increased subchondral bone remodelling at early OA stages of the disease. We have investigated the temporal and the spatial relationship between bone remodelling in subchondral bone plate (Sbp) and trabecular bone (Tb) in Dunkin Hartley (DH, develop OA early) and the Bristol Strain 2 (BS2, control which develop OA late) guinea pigs. Right tibias were dissected from six male animals of each strain, at 10, 16, 24 and 30 weeks of age. Micro-computed tomography was used to quantify the growth plate thickness (GpTh), subchondral bone plate thickness (SbpTh) and trabecular bone thickness (TbTh), and bone mineral density (BMD) in both Sbp and Tb. The rate of change was calculated for 10–16 weeks, 16–24 weeks and 24–30 weeks. The rate of changes in Sbp and Tb thickness at the earliest time interval (10–16 weeks) were significantly greater in DH guinea pigs than in the growth-matched control strain (BS2). The magnitude of these differences was greater in the medial side than the lateral side (DH: 22.7 and 14.75 µm/week, BS2: 5.63 and 6.67 µm/week, respectively). Similarly, changes in the BMD at the earliest time interval was greater in the DH strain than the BS2, again more pronounced in the disease prone medial compartment (DH: 0.0698 and 0.0372 g/cm3/week, BS2: 0.00457 and 0.00772 g/cm3/week, respectively). These changes observed preceded microscopic and cellular signs of disease as previously reported. The rapid early changes in SbpTh, TbTh, Sbp BMD and Tb BMD in the disease prone DH guinea pigs compared with the BS2 control strain suggest a link to early OA pathology. This is corroborated by the greater relative changes in subchondral bone in the medial compared with the lateral compartment.

Characterization of nano-structural and nano-mechanical properties of osteoarthritic subchondral bone

Article

Full-text available

Aug 2016
BMC MUSCULOSKEL DIS

Background Although articular cartilage is the primary tissues affected by osteoarthritis (OA), the underlying subchondral bone also undergoes noticeable changes. Despite the growing body of research into the biophysical and mechanical properties of OA bone there are few studies that have analysed the structure of the subchondral sclerosis at the nanoscale. In this study, the composition and nano-structural changes of human osteoarthritis (OA) subchondral bone were investigated to better understand the site-specific changes. MethodsOA bone samples were collected from patients undergoing total knee replacement surgery and graded according to disease severity (grade I: mild OA; grade IV: severe OA). Transmission electron microscopy (TEM), Electron Diffraction, and Elemental Analysis techniques were used to explore the cross-banding pattern, nature of mineral phase and orientation of the crystal lattice. Subchondral bone nano-hydroxyapatite powders were prepared and characterised using high resolution transmission electron microscopy (HR-TEM) and fourier transform infrared spectroscopy (FTIR). Subchondal bone mechanical properties were investigated using a nano-indentation method. ResultsIn grade I subchondral bone samples, a regular periodic fibril banding pattern was observed and the c-axis orientation of the apatite crystals was parallel to the long axis of the fibrils. By contrast, in grade IV OA bone samples, the bulk of fibrils formed a random and undulated arrangement accompanied by a circular oriented pattern of apatite crystals. Fibrils in grade IV bone showed non-hierarchical intra-fibrillar mineralization and higher calcium (Ca) to phosphorous (P) (Ca/P) ratios. Grade IV OA bone showed higher crystallinity of the mineral content, increased modulus and hardness compared with grade I OA bone. Conclusions The findings from this study suggest that OA subchondral sclerotic bone has an altered mineralization process which results in nano-structural changes of apatite crystals that is likely to account for the compromised mechanical properties of OA subchondral bones.

Raman Spectroscopy Detection of Molecular Changes Associated with Osteoarthritis.

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Jan 2009

Karen Esmonde-White

Vibrational spectroscopic methods are minimally invasive, and are appropriate for use in clinical contexts. Methods were developed in this dissertation for evaluating joint damage and disease using Raman spectroscopy. Subtle changes in the molecular structure of joint tissue and synovial fluid precede morphological changes in the joint. The goal of this research is to develop Raman spectroscopic methods for the examination of joint tissue and biological fluids, for monitoring and detecting molecular alterations associated with osteoarthritis. We identified Raman spectroscopic markers of altered molecular structure in subchondral bone and relevant biological fluids. Using Raman spectroscopy the molecular structure of joint tissues was measured, and the results were compared to the results from micro computed tomographic and histopathologic analysis. Raman spectra of subchondral bone collected from Del1 (+/-) transgenic mice, a mouse model for early-onset osteoarthritis, indicated lower bone mineralization in transgenic mice (5.73 ?? 0.28 vs. 6.87 ?? 0.225 in wild-type mice, p=0.003). A fiber-optic Raman probe for arthroscopic measurements was developed to demonstrate the feasibility of measuring the molecular structure of joint tissue with clinically-relevant instrumentation. The carbonate-to-phosphate ratio, a Raman spectroscopic measurement of bone mineral composition, was measured from subchondral bone under an intact layer of cartilage. Our initial work on a human proximal radius specimen indicated that an arthroscope configuration is capable of providing similar carbonate-to-phosphate values as spectra collected on a Raman microscope (0.25 vs. 0.24). In addition to cartilage and subchondral bone, the chemical structure of synovial fluid molecules is a key factor in maintaining healthy joint function. Synovial fluid from normal and diseased joints was examined using a novel drop deposition/Raman spectroscopic method. Raman spectra of synovial fluid from patients with radiographic evidence of osteoarthritis showed evidence of altered protein structure, as shown by increased Raman band intensity ratios at 1080 cm-1/1002 cm-1 (0.054 ?? 0.07 vs. 0.038 ?? 0.003, p

Dynamic Alterations in Microarchitecture, Mineralization and Mechanical Property of Subchondral Bone in Rat Medial Meniscal Tear Model of Osteoarthritis

Article

Full-text available

Jan 2015

Background: The properties of subchondral bone influence the integrity of articular cartilage in the pathogenesis of osteoarthritis (OA). However, the characteristics of subchondral bone alterations remain unresolved. The present study aimed to observe the dynamic alterations in the microarchitecture, mineralization, and mechanical properties of subchondral bone during the progression of OA. Methods: A medial meniscal tear (MMT) operation was performed in 128 adult Sprague Dawley rats to induce OA. At 2, 4, 8, and 12 weeks following the MMT operation, cartilage degeneration was evaluated using toluidine blue O staining, whereas changes in the microarchitecture indices and tissue mineral density (TMD), mineral-to-collagen ratio, and intrinsic mechanical properties of subchondral bone plates (BPs) and trabecular bones (Tbs) were measured using micro-computed tomography scanning, confocal Raman microspectroscopy and nanoindentation testing, respectively. Results: Cartilage degeneration occurred and worsened progressively from 2 to 12 weeks after OA induction. Microarchitecture analysis revealed that the subchondral bone shifted from bone resorption early (reduced trabecular BV/TV, trabecular number, connectivity density and trabecular thickness [Tb.Th], and increased trabecular spacing (Tb.Sp) at 2 and 4 weeks) to bone accretion late (increased BV/TV, Tb.Th and thickness of subchondral bone plate, and reduced Tb.Sp at 8 and 12 weeks). The TMD of both the BP and Tb displayed no significant changes at 2 and 4 weeks but decreased at 8 and 12 weeks. The mineral-to-collagen ratio showed a significant decrease from 4 weeks for the Tb and from 8 weeks for the BP after OA induction. Both the elastic modulus and hardness of the Tb showed a significant decrease from 4 weeks after OA induction. The BP showed a significant decrease in its elastic modulus from 8 weeks and its hardness from 4 weeks. Conclusion: The microarchitecture, mineralization and mechanical properties of subchondral bone changed in a time-dependent manner as OA progressed.

Fourier transform infrared spectroscopy research on subchondral bone in osteoarthritis

Article

Apr 2019
SPECTROCHIM ACTA A

Osteoarthritis (OA) is not only related to the degradation of articular cartilage, but also possibly to the changes of subchondral bone. The purpose of this study was to assess whether specific differences could be resolved from bone composition, as also contributed to OA. These differences were assessed by using Fourier transform infrared spectroscopy (FTIRS). The main parameters including mineral content, carbonate content, crystallinity, collagen cross-linking ratio (XLR) and acid phosphate content were represented with characteristic peak integration. It was found that mineral and carbonate content varied significantly with depths at different OA stages. Mineral content increased with depth in healthy samples, while carbonate content showed opposite trend. The mineral content reduced obviously with OA duration, which was different with carbonate decreasing only at early stage of OA. In addition, the content of acid phosphate, collagen maturity (XLR) and crystallinity slight varied with the OA aggravation. Therefore, the changes in subchondral bone were significantly associated with cartilage degeneration and OA, the associated parameters should be targeted for OA therapies.

Quantitative in vivo CT arthrography of the human osteoarthritic knee to estimate cartilage sulphated glycosaminoglycan content: Correlation with ex-vivo reference standards

Article

Feb 2016

Objective: Recently, computed tomography arthrography (CTa) was introduced as quantitative imaging biomarker to estimate cartilage sulphated glycosaminoglycan (sGAG) content in human cadaveric knees. Our aim was to assess the correlation between in vivo CTa in human osteoarthritis (OA) knees and ex vivo reference standards for sGAG and collagen content. Design: In this prospective observational study 11 knee OA patients underwent CTa before total knee replacement (TKR). Cartilage X-ray attenuation was determined in 6 cartilage regions. Femoral and tibial cartilage specimens harvested during TKR were re-scanned using equilibrium partitioning of an ionic contrast agent with micro-CT (EPIC-μCT), which served as reference standard for sGAG. Next, cartilage sGAG and collagen content were determined using dimethylmethylene blue (DMMB) and hydroxyproline assays. The correlation between CTa X-ray attenuation, EPIC-μCT X-ray attenuation, sGAG content and collagen content was assessed. Results: CTa X-ray attenuation correlated well with EPIC-μCT (r=0.76, 95% credibility interval (95%CI) 0.64 to 0.85). CTa correlated moderately with the DMMB assay (sGAG content) (r=-0.66, 95%CI -0.87 to -0.49) and to lesser extent with the hydroxyproline assay (collagen content) (r=-0.56, 95%CI -0.70 to -0.36). Conclusions: Outcomes of in vivo CTa in human OA knees correlate well with sGAG content. Outcomes of CTa also slightly correlate with cartilage collagen content. Since outcomes of CTa are mainly sGAG dependent and despite the fact that further validation using hyaline cartilage of other joints with different biochemical composition should be conducted, CTa may be suitable as quantitative imaging biomarker to estimate cartilage sGAG content in future clinical OA research.

Biochemical and Morphological Abnormalities of Subchondral Bone and Their Association with Cartilage Degeneration in Spontaneous Osteoarthritis

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