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Reduction of Vein Graft Disease Using Photodynamic Therapy with Motexafin Lutetium in a Rodent Isograft Model
Abstract
Motexafin lutetium (Lu-Tex) is a photosensitizer that targets atheromatous plaque. Subsequent photoactivation (photodynamic therapy [PDT]) induces local cytotoxic effects. The aim of the present study was to investigate whether Lu-Tex targets vein graft intimal hyperplasia and whether subsequent photoactivation attenuates the disease process.
The subcellular localization of Lu-Tex and postillumination viability were studied in cultured human vein graft smooth muscle cells. Inferior vena cava-grafted rats were injected with Lu-Tex (10 mg/kg) 4 or 12 weeks after grafting. Biodistribution was assessed in a subgroup 24 hours after administration. Light therapy (742 nm) was performed 24 hours after Lu-Tex injection by illuminating intraperitoneally placed isografts using a laparotomy. Animals were divided into the following 4 groups: PDT (n=15), Lu-Tex injection and laparotomy (n=13), light treatment (n=14), and laparotomy only (n=13). Grafts were harvested 14 days after treatment for histochemical analysis. Lu-Tex localized within subcellular organelles of smooth muscle cells, and subsequent photoactivation induced cell death via apoptosis. The Lu-Tex concentrations present in the vein grafts were 9.3 times higher than those in the normal inferior vena cava. Postoperative PDT at 4 weeks after surgery significantly reduced the intima/media ratio, whereas treatment at 12 weeks did not reduce the intima/media ratio. Activated macrophages were observed 4 weeks after grafting; however, a significant reduction occurred in these cells by 12 weeks. The mechanism by which PDT works may be related to the presence of activated macrophages.
PDT significantly reduces the intima/media ratio in the early phase of vein graft disease. Lu-Tex-mediated PDT may be a viable method for the attenuation of atherosclerotic disease in vein grafts.
... In addition to cancer treatment PDT is also suited to nononcologic conditions, and is being explored in experimental treatment of vascular diseases [Neave et al., 1988,Ortu et al., 1992,Gonschior et al., 1996,Yamaguchi et al., 2000,LaMuraglia et al., 2000,Rockson et al., 2000b] and viral infections [Matthews et al., 1988,Ben-Hur et al., 1996,Schagen et al., 1999, as well as in immunological disorders [Simkin et al., 2000] such as rheumatoid arthritis [Ratkay et al., 1994,Trauner and Hasan, 1996,Ratkay et al., 1998] and psoriasis [Robinson et al., 1999,Boehncke et al., 2000. However, the most successful non-cancer PDT clinical application so far has been the therapy of patients with visual loss due to age-related macular degeneration with choroidal neovascularisation disease ,Donati et al., 1999,Regillo, 2000,Schmidt-Erfurth and Hasan, 2000 where the treatment is called photothrombosis. ...
... Also for cardiovascular applications the cytotoxicity associated with the photochemical treatment seems to be well tolerated and might have beneficial effects. Thus, studies of photodynamic therapy of restenosis and atherosclerosis indicate that the photochemical treatment in itself may have substantial clinical benefit without causing serious adverse effects on the treated blood vessels [Yamaguchi et al., 2000,Rockson et al., 2000a,Rockson et al., 2000b (see also 5.1.2). ...
Numerous gene therapy vectors, both viral and non-viral, are taken into the cell by endocytosis, and for efficient gene delivery the therapeutic genes carried by such vectors have to escape from endocytic vesicles so that the genes can further be translocated to the nucleus. Since endosomal escape is often an inefficient process, release of the transgene from endosomes represents one of the most important barriers for gene transfer by many such vectors. To improve endosomal escape we have developed a new technology, named photochemical internalisation (PCI). In this technology photochemical reactions are initiated by photosensitising compounds localised in endocytic vesicles, inducing rupture of these vesicles upon light exposure. The technology constitutes an efficient light-inducible gene transfer method in vitro, where light-induced increases in transfection or viral transduction of more than 100 and 30 times can be observed, respectively. The method can potentially be developed into a site-specific method for gene delivery in vivo. This article will review the background for the PCI technology, and several aspects of PCI induced gene delivery with synthetic and viral vectors will be discussed. Among these are: (i) The efficiency of the technology with different gene therapy vectors; (ii) use of PCI with targeted vectors; (iii) the timing of DNA delivery relative to the photochemical treatment. The prospects of using the technology for site-specific gene delivery in vivo will be thoroughly discussed, with special emphasis on the possibilities for clinical use. In this context our in vivo experience with the PCI technology as well as the clinical experience with photodynamic therapy will be treated, as this is highly relevant for the clinical use of PCI-mediated gene delivery. The use of photochemical treatments as a tool for understanding the more general mechanisms of transfection will also be discussed.
... 100 Motexafin lutetium has been proved to target and significantly reduce atherosclerotic lesions of both vein graft intimal hyperplasia and graft coronary artery disease. 101,102 With pheophorbide derivative PH-1126, which is selectively deposited in AS plaque, foam cells can be expelled from the endothelium to the intimal surface of the plaque. 103 Pyropheophorbide-alpha methyl ester (MPPa)-mediated PDT generates ROS and induces apoptosis of RAW264.7 cells, while the damage level is related to the dose of light irradiation. ...
Atherosclerosis (AS) is a chronic inflammatory disease, which may lead to high morbidity and mortality. Currently, the clinical treatment strategy for AS is administering drugs and performing surgery. However, advanced therapy strategies are urgently required because of the deficient therapeutic effects of current managements. Increased number of energy conversion-based organic or inorganic materials has been used in cancer and other major disease treatments, bringing hope to patients with the development of nanomedicine and materials. These treatment strategies employ specific nanomaterials with specific own physiochemical properties (external stimuli: light or ultrasound) to promote foam cell apoptosis and cholesterol efflux. Based on the pathological characteristics of vulnerable plaques, energy conversion-based nano-therapy has attracted increasing attention in the field of anti-atherosclerosis. Therefore, this review focuses on recent advances in energy conversion-based treatments. In addition to summarizing the therapeutic effects of various techniques, the regulated pathological processes are highlighted. Finally, the challenges and prospects for further development of dynamic treatment for AS are discussed.
... Intracoronary PDT with a photosensitizer, MV0611, for the BI and stent porcine models of restenosis revealed reduced intimal proliferation without suppression of reendothelialization of porcine coronary arteries [15]. PDT in combination with other drugs, such as endogenous prodrug aminolaevulinic acid, liposome-incorporated Zn (II)-phthalocyanine, and talaporfin sodium, has been employed for the treatment of atherosclerotic plaque in rats, rabbits, and pigs [16][17][18][19][20]. PDT for the prevention and treatment of intimal hyperplasia has been further investigated in a rat vein graft model [21,22] and a porcine prosthetic vascular bypass graft model [23]. Together, this experimental evidence suggests that PDT is a safe and effective tool for preventing restenosis. ...
Photodynamic therapy (PDT) has been used to inhibit intimal hyperplasia in injured arteries. Because of the limited tissue penetration of visible light, an endovascular light source with a guided wire is often required for effective treatment. Indocyanine green (ICG), a near-infrared (NIR) photosensitizer, has been used in PDT for cancers. An extracorporeal light source may be used for shallow tissue because of the better tissue penetration of NIR light. The aim of this study was to evaluate the effect of ICG-PDT using extracorporeal NIR light on the inhibition of intimal hyperplasia in balloon-injured carotid arteries. A balloon injury (BI) model was used to induce intimal hyperplasia of carotid artery. Sprague–Dawley rats were divided into control, BI, BI + 1 × PDT, and BI + 2 × PDT groups. The control group underwent a sham procedure. PDT was performed 7 days after BI. In the BI + 1 × PDT group, ICG was administered 1 h before light irradiation. External illumination with 780-nm light-emitting diode light at a fluence of 4 J/cm² was applied. For the BI + 2 × PDT group, PDT was performed again at day 7, following the first PDT. Hematoxylin and eosin (H & E) staining was performed to assess vessel morphology. Arterial wall thickness was significantly larger in the BI group compared with the control group. ICG-PDT significantly reduced arterial wall thickness compared with the BI group. Repeated PDT further decreased arterial wall thickness to the level of the control group. These findings indicate a promising approach for the treatment of restenosis of carotid arteries.
... For example, photoangioplasty has been suggested as a potential treatment modality as it reduces or inhibits restenosis [122]. Similarly, a texaphyrin derivative has been used to target athermomatos plaque and was suggested as a means to treat vein graft disease [123]. ...
Photodynamic therapy (PDT) has both direct cell and indirect vascular effects. Both are well established and the latter has given rise to specifically target angiogenesis in PDT treatments. While the vascular effects are well understood, further advances in anti-angiogenesis require a detailed understanding of PDT effects at the microvasculature level. Although some of the earliest investigations of PDT noted effects on platelet aggregation the importance of their interaction with endothelial cells and the crucial role of various signaling pathways is only now emerging. This review aims to give a general overview of PDT related studies on platelets, vascular effects, and their interaction with endothelial cells to indicate the potential for studies in this area.
... 10 Macrophage ablation has potential benefit in atherosclerosis, as prior studies using phototoxic therapy with motexafin lutetium and other agents have shown significant destruction of macrophages in animal models, as well as safety in human studies. [11][12][13][14][15] However, there are limited data using thermal ablation of macrophages in atherosclerosis. ...
Macrophages are critical contributors to atherosclerosis. Single-walled carbon nanotubes (SWNTs) show promising properties for cellular imaging and thermal therapy, which may have application to vascular macrophages.
In vitro uptake and photothermal destruction of mouse macrophage cells (RAW264.7) were performed with SWNTs (14.7 nmol/L) exposed to an 808-nm light source. SWNTs were taken up by 94±6% of macrophages, and light exposure induced 93±3% cell death. In vivo vascular macrophage uptake and ablation were then investigated in carotid-ligated FVB mice (n=33) after induction of hyperlipidemia and diabetes. Two weeks postligation, near-infrared fluorescence (NIRF) carotid imaging (n=12) was performed with SWNT-Cy5.5 (8 nmol of Cy5.5) given via the tail vein. Photothermal heating and macrophage apoptosis were evaluated on freshly excised carotid arteries (n=21). NIRF of SWNTs showed higher signal intensity in ligated carotids compared with sham, confirmed by both in situ and ex vivo NIRF imaging (P<0.05, ligation versus sham). Immunofluorescence staining showed colocalization of SWNT-Cy5.5 and macrophages in atherosclerotic lesions. Light (808 nm) exposure of freshly excised carotids showed heating and induction of macrophage apoptosis in ligated left carotid arteries with SWNTs, but not in control groups without SWNTs or without light exposure.
Carbon nanotubes accumulate in atherosclerotic macrophages in vivo and provide a multifunctional platform for imaging and photothermal therapy of vascular inflammation.
... Also for cardiovascular applications, the cytotoxicity associated with the photochemical treatment seems to be well tolerated and might have beneficial effects. Thus, studies of photodynamic therapy of restenosis and atherosclerosis indicate that the photochemical treatment in itself may have substantial clinical benefit without causing serious adverse effects on the treated blood vessels [13,92,93]. A very important point also is that, although the photochemical treatment induces cytotoxic effects, these are generally restricted to illuminated areas of the body [9] , the photosensitisers in themselves usually have very little systemic toxicity. ...
This article reviews a novel technology, named photochemical internalisation (PCI), for light-induced delivery of genes, proteins and many other classes of therapeutic molecules. Degradation of macromolecules in endocytic vesicles after uptake by endocytosis is a major intracellular barrier for the therapeutic application of macromolecules having intracellular targets of action. PCI is based upon the light activation of a drug (a photosensitizer) specifically locating in the membrane of endocytic vesicle inducing the rupture of this membrane upon illumination. Thereby endocytosed molecules can be released to reach their target of action before being degraded in lysosomes. The fact that this effect is induced by illumination means that the biological activity of the molecules can be activated at specific sites in the body, simply by illuminating the relevant region. We have used the PCI strategy to obtain light-induced delivery of a variety of molecules, including proteins, peptides, oligonucleotides, genes and low molecular weight drugs. In several cases, a >100-fold increase in biological activity has been observed.
... A significant reduction in NIH was noted, but the effects were achieved only at 4 weeks postoperatively. At 12 weeks, the therapeutic action was absent, perhaps because the therapy depends on activated macrophages in the tissue [Yamaguchi 2000]. ...
Abstract Neointimal hyperplasia in aortocoronary vein grafts represents a significant problem that, by itself or by development of vein graft atherosclerosis, leads to the return of symptoms and to major adverse cardiac events after coronary artery bypass grafting. The main causes of neointimal hyperplasia are surgical trauma, intraoperative ischemia reperfusion injury, and implantation of a vein into the arterial circulation. All these pathogenetic factors cause a loss of protective endothelial mediators. The initiating steps lead to the induction of a significant inflammatory response and to the production of mitogenic factors in the vascular wall. DNA synthesis in vascular smooth muscle cells is markedly up-regulated, and intracellular signal transduction leads to transcription of immediate early genes, which causes an intense proliferative response. Vascular smooth muscle cells proliferate, migrate through the internal elastic lamina with the support of proteases, and transform from contractile-type into secretory-type cells. A thick layer of neointima is formed. The prevention of neointimal hyperplasia includes meticulous surgical technique, the choice of a large target vessel, and adequate intraoperative storage of the vein graft. Local intraoperative therapy of the implanted graft has been successfully tested in the experimental setting with a variety of substances that tackle different steps in the pathologic mechanism. Systemic pharmacologic therapy in clinical use primarily consists of the use of platelet inhibitors and anticoagulants. The transfer of experimental knowledge to bedside application has been slow. Gene therapy represents a promising field for the improved management of vein graft neointimal hyperplasia.
... However, PDT also has shown promising results to inhibit vein graft failure. 16,17 The role of PDT to prevent prosthetic graft failure is unknown. Since it is acknowledged, that intimal hyperplasia in prosthetic grafts is, in part, due to arterial cell ingrowth. ...
Bypass surgery has a failing frequency of 30% during the first year, mainly due to intimal hyperplasia (IH). This negative effect is most pronounced in artificial grafts. Photodynamic therapy (PDT) is a technique in which light activates photosensitizer dyes to produce free-radicals resulting in an eradication of cells in the vascular wall. The aim of this study was to determine the effectiveness of PDT to reduce IH in a preclinical porcine PTFE bypass model.
Ten pigs were used. After a pilot PDT dosimetry study (n=3) PTFE grafts were bilaterally placed into the circulation as bypasses from the common to the external iliac arteries (n=7). The right sides served as controls (C). Before implantation of the left grafts, the arterial connecting sites of the left distal anastomoses were PDT-treated. The arteries were pressurized at 180 mmHg for 5 minutes with the photosensitizer Methylene Blue (330 microg/ml), and thereafter endoluminally irradiated with laser light (lambda = 660 nm, 100 mW/cm(2), 150 J/cm(2)). After 4 weeks the specimens were retrieved and formalin fixed. Cross sections through the midportions of the distal anastomoses and the grafts were used for histology, immunohistochemistry to identify inflammatory cells and morphometric evaluation (n=7).
No systemic side effects and no graft occlusions were noted. PDT-treated anastomoses showed reduced IH in the mid-portions of the anastomoses (Area of IH: microm(2)/microm graft: C: 6970+/-1536, PDT: 2734+/-2560; P<0.005) as well as in the grafts (C: 5391+/-4031, PDT: 777+/-1331; P<0.02). The number of inflammatory cells per microscopic field was increased after PDT (C: 24+/-16, PDT: 37+/-15; P<0.009).
Adjuvant PDT, performed in an endovascular fashion, was a safe method to reduce prosthetic graftstenosis in a preclinical setting. This study underscores the clinical potential of PDT to inhibit the development of clinical bypass graftstenosis.
Despite progress in understanding the pathogenesis of atherosclerosis, the development of effective therapeutic strategies is a challenging task that requires more research to attain its full potential. This review discusses current pharmacotherapy in atherosclerosis and explores the potential of some important emerging therapies (antibody-based therapeutics, cytokine-targeting therapy, antisense oligonucleotides, photodynamic therapy and theranostics) in terms of clinical translation. A chemopreventive approach based on modern research of plant-derived products is also presented. Future perspectives on preventive and therapeutic management of atherosclerosis and the design of tailored treatments are outlined.
Acute coronary syndromeis a life-threatening condition of utmost clinical importance, which, despite recent progress in the field, is still associated with high morbidity and mortality. Acute coronary syndrome results from a rupture or erosion of vulnerable atherosclerotic plaque with secondary platelet activation and thrombus formation, which leads to partial or complete luminal obstruction of a coronary artery. During the last decade, scientific evidence demonstrated that, when an acute coronary event occurs, several non-culprit plaques are in a “vulnerable” state. Among the promising approaches, several investigations provided evidence of photodynamic therapy (PDT) induced stabilisation and regression of atherosclerotic plaque. Significant development of PDT strategies improved its therapeutic outcome. This review addresses PDT's pertinence and major problems/challenges toward its translation to a clinical reality. This article is protected by copyright. All rights reserved.
Graft coronary artery disease (GCAD) limits long-term patient survival following heart transplantation. There are few treatment options. Exploration into less invasive diagnostic techniques and attenuation of allograft coronary disease is warranted. The selectivity of Antrin® Injection (a motexafin lutetium sensitizer, Lu-Tex) and illumination with far-red light, approximately 732 nm, has been evaluated in several preclinical atherosclerosis models. Lu-Tex, using fluorescence microscopy, was found to partition into distinct punctate cytoplasmic compartments in cultured human bypass coronary smooth muscle cells (SMCs). Using specific organelle probes the chief subcellular localization sites were lysosomes and endoplasmic reticulum. The inhibitory effect of Lu-Tex-mediated photoactivation was demonstrated using SMCs; many cells died via an apoptotic pathway. Following illumination, fluorescence microscopy revealed sensitizer redistribution with fluorescence being observed in the mitochondria. The distribution of Lu-Tex was evaluated in a rat model of heterotopic cardiac allografts 60 days after transplantation. Lu-Tex was retained in the cardiac allograft, exhibiting a five-fold increase in retention between the allograft and native heart. These results encourage further exploration of Lu-Tex for diagnosis, and possible amelioration of chronic graft vascular disease using photodynamic therapy. Copyright © 2001 John Wiley & Sons, Ltd.
Photodynamic therapy (PDT) involves photosensitizing (light-sensitive) drugs, light, and tissue oxygen to treat a wide range of medical conditions primarily in the oncology field. Photosensitizing agents, many of which are porphyrins or chemicals of similar structure, are administered locally or parenterally and selectively absorbed or retained within the tissues targeted for therapy. This differential selectivity or retention promotes selective damage when the target tissue is exposed to light of an appropriate wavelength; the surrounding normal tissue, containing little or no drug, absorbs little light and is thus spared injury.1,2 PDT clinical research has historically focused primarily and successfully on cancer treatment;3-6 however, it has shown promise as a breakthrough treatment in ophthalmic, urologic, autoimmune, and cardiovascular diseases. Any disease associated with rapidly growing tissue, including the formation of abnormal blood vessels, can potentially be treated with this technology. For the cardiovascular system, selectivity renders PDT particularly appealing in treating restenosis and atherosclerotic illnesses such as coronary artery disease, in which other catheter-based approaches are relatively non-selective and carry a substantial risk of damage to the normal arterial wall.7 Recently there have been preclinical and clinical studies targeted to examine the utility of PDT for vascular applications. This chapter summarizes the mechanisms of action, PDT systems, and the results of these preclinical and clinical studies.
To test the hypothesis that vein graft intimal hyperplasia can be significantly suppressed by a single intra-operative transfection of the graft with a decoy oligonucleotide (ODN) binding the transcription factor Egr-1.
Experimental study.
Jugular vein to carotid artery interposition grafts in rabbits were treated with Egr-1 decoy, mutant decoy ODN, vehicle alone, using a non-distending pressure of 300 mm Hg for 20 min, or were left untreated. All animals were fed a 2% cholesterol diet. The animals were sacrificed after 48h, 6 weeks and 12 weeks. Paraffin-embedded vein sections were subjected to angiometric analysis.
Successful delivery of the ODN was confirmed by DAPI staining. Quantitative real-time PCR revealed a 60% decrease of the Egr-1 gene expression in the animals in which the Egr-1 decoy ODN was delivered. Cellular proliferation was also significantly decreased as indicated by the Ki-67 labelling index. An increase in intimal and medial thickness was found in all vein grafts. However, intimal thickness was significantly reduced in the grafts treated with Egr-1 decoy ODN, whereas luminal area was significantly increased.
A single intra-operative pressure-mediated transfection of vein grafts with Egr-1 decoy ODN significantly suppresses intimal hyperplasia in a rabbit hypercholesterolaemic model.
Motexafin lutetium is a photosensitizer that accumulates in atherosclerotic plaque and, after activation by far-red light, produces cytotoxic singlet oxygen. The combination of photosensitizer and illumination, known as photodynamic therapy (PDT), has been shown to reduce atheroma formation in animal models and is under clinical investigation. However, the effects of PDT with motexafin lutetium on isolated vascular cells are unknown. This study was designed to characterize the effects of PDT on vascular cell viability and to define the cell-death pathway for this agent. Fluorescence microscopy of RAW macrophages and human vascular smooth muscle cells revealed time-dependent uptake of motexafin lutetium. Illumination of motexafin lutetium-loaded cells with 732-nm light (2 J/cm(2)) impaired cellular viability and growth (IC(50) 5 to 20 micromol/L). Depletion of intracellular glutathione potentiated (P=0.035) and the addition of antioxidant N-acetylcysteine attenuated (P=0.002) cell death, suggesting that the intracellular redox state influences motexafin lutetium action. PDT was associated with the loss of mitochondrial membrane potential, mitochondrial release of cytochrome c, and caspase activation. PDT promoted phosphatidylserine externalization and induced apoptotic DNA fragmentation, with the number of apoptotic cells increasing from 7+/-2% to 34+/-3% of total cells. Reducing plaque cellularity by the induction of apoptosis may be one mechanism by which PDT reduces plaque burden, possibly modulates plaque vulnerability, and inhibits restenosis in vivo.
Motexafin lutetium (Lu-Tex) is a photodynamic therapy (PDT) agent that localizes in atheromatous plaque in which it can be activated by far-red light. Lu-Tex biolocalization was examined in graft coronary artery disease (GCAD) with a rodent allograft model. After photoactivation, the effect on intimal proliferation was assessed.
A PVG to ACI rat heterotopic heart transplantation model was used. Lu-Tex (10 mg/kg) was intravenously administered 90 days after transplantation. Photoactivation was performed 24 hr after Lu-Tex administration. A light-emitting diode, central wavelength of 742 nm, was used to illuminate the intraperitoneally placed allografts via a laparotomy (light fluence of 75 J/cm2 at a power density of 75 mW/cm2). Animals were divided into four groups according to postoperative treatments: PDT with Lu-Tex injection and light illumination (n=21), Lu-Tex injection and laparotomy (n=14), laparotomy with light only (n=14), and laparotomy only (n=16). GCAD was quantitatively assessed 14 days after treatments.
Lu-Tex localized in atherosclerotic plaque in vessels with GCAD. PDT significantly reduced both the percent of affected vessels and intimal proliferation compared to all other control study groups. alpha-Smooth muscle cell actin and anti-rat macrophage antibody-positive areas were significantly reduced within the neointima in allografts treated with PDT compared to all other study groups.
PDT significantly reduced atherosclerotic lesions of GCAD. Lu-Tex-mediated PDT may, therefore, be a potential method for treating accelerated atherosclerosis associated with transplantation.
Stenting has become standard treatment for patients undergoing percutaneous coronary intervention. Clinical impressions continue to support this as a user friendly, safe, and efficacious technology
Major advances in cardiovascular intervention for chronic disease are underway. These innovations lie at the interface of minimally invasive catheter-based technologies and biologic approaches for the management of complex cardiovascular diseases. This review highlights key areas where such 'biointerventional' cardiovascular therapies are envisioned to occur: cardiac cell transplantation, myocardial gene therapy, genetic and photodynamic endovascular interventions, and vascular tissue engineering.
Photodynamic therapy (PDT) has been approved as a tissue-specific light-activated cytotoxic therapy for many diseases. The ability of PDT to destroy target tissues selectively is especially appealing for atherosclerotic plaque. Biotechnology has developed a new generation of selective photosensitizers and catheter-based technological advances in light delivery have allowed the introduction of PDT into the vasculature. The largest experience to date is with motexafin lutetium (MLu, Antrin), an expanded porphyrin (texaphyrin) that accumulates in plaque. The combination of the motexafin lutetium and endovascular illumination, or Antrin phototherapy, has been shown to reduce plaque in animal models. Antrin phototherapy generates cytotoxic singlet oxygen that has been shown to induce apoptosis in macrophages and smooth muscle cells. The safety, tolerability, and preliminary efficacy of Antrin phototherapy has been assessed in a phase 1 dose-ranging clinical trial in subjects with peripheral artery disease and is currently being examined in a phase 1 study in subjects with lesions of the native coronary arteries undergoing stent implantation. The preliminary results suggest that Antrin phototherapy is safe, well tolerated, and nontraumatic.
Photodynamic therapy (PDT) inhibits post-interventional stenosis in balloon-injured arteries, but causes thrombosis when applied to vein grafts. This may result from added free radicals produced during the hypoxia-reperfusion injury of vein graft implantation. The purposes of this study were to determine whether a free radical scavenger could inhibit vein graft thrombosis, enabling PDT to inhibit intimal hyperplasia; and to investigate the role of neutrophils, also a source of radicals, in this setting.
Jugular vein bypass grafts of the common carotid artery were performed in rats. PDT was administered in situ to the vein graft and artery in the presence or absence of deferoxamine (DFX), an OH- scavenger.
PDT alone induced thrombosis in all untreated vein grafts. DFX administration or inhibition of neutrophil adhesion to the graft prevented PDT-induced vein graft thrombosis. Moreover, DFX given together with PDT significantly decreased vein graft intimal hyperplasia (0.010 mm2 +/- 0.005 mm2; P<.002) as compared with DFX alone (0.113 mm2 +/- 0.009 mm2) or untreated control animals (0.112 +/- 0.007 mm2).
OH- radicals and neutrophils both have key roles in PDT-induced vein graft thrombosis. By inhibiting free radical production or neutrophil adhesion to the graft, adequate PDT can be administered for successful inhibition of vein graft intimal hyperplasia.
Photodynamic therapy involves administration of a tumorlocalizing photosensitizing agent, which may require metabolic synthesis
(i.e., a prodrug), followed by activation of the agent by light of a specific wavelength. This therapy results in a sequence
of photochemical and photobiologic processes that cause irreversible photodamage to tumor tissues. Results from preclinical
and clinical studies conducted worldwide over a 25-year period have established photodynamic therapy as a useful treatment
approach for some cancers. Since 1993, regulatory approval for photodynamic therapy involving use of a partially purified,
commercially available hematoporphyrin derivative compound (Photofrin®) in patients with early and advanced stage cancer of
the lung, digestive tract, and genitourinary tract has been obtained in Canada, The Netherlands, France, Germany, Japan, and
the United States. We have attempted to conduct and present a comprehensive review of this rapidly expanding field. Mechanisms
of subcellular and tumor localization of photosensitizing agents, as well as of molecular, cellular, and tumor responses associated
with photodynamic therapy, are discussed. Technical issues regarding light dosimetry are also considered. [J Natl Cancer Inst
1998;90:889-905]
Objectives:
This study reports the multicenter registry experience evaluating the safety and efficacy of the Palmaz-Schatz stent in the treatment of saphenous vein graft disease.
Background:
Saphenous vein graft angioplasty is associated with frequent periprocedural complications and a high frequency of restenosis. Stent implantation has been shown to reduce restenosis, with improved long-term outcomes in the treatment of native coronary artery disease. Preliminary experience with stent placement in the treatment of saphenous vein graft lesions has been favorable.
Methods:
Twenty U.S. investigator sites enrolled a total of 589 symptomatic patients (624 lesions) for treatment of focal vein graft stenoses between January 1990 and April 1992. Follow-up angiography was performed at 6 months, and the clinical course of all study patients was prospectively collected at regular intervals for up to 12 months.
Results:
Stent delivery was successful in 98.8% of cases, and the procedural success rate was 97.1%. The lesion diameter stenosis decreased from 82 +/- 12% (mean +/- SD) before to 6.6 +/- 10.2% after treatment. Major in-hospital complications occurred in 17 patients (2.9%); stent thrombosis was found in 8 (1.4%); and major vascular or bleeding complications were noted in 83 (14.3%). Six-month angiographic follow-up revealed an overall restenosis rate (> or = 50% diameter stenosis) of 29.7%. Multivariate logistic regression analysis indicated that 1) restenotic lesions, 2) smaller reference vessel size, 3) history of diabetes mellitus, and 4) higher percent poststent diameter stenosis were independent predictors of restenosis. The 12-month actuarial event-free survival was 76.3%.
Conclusions:
Stent implantation in patients with focal saphenous vein graft lesions can be achieved with a high rate of procedural success, acceptable major complications, reduced angiographic restenosis and favorable late clinical outcome compared with historical balloon angioplasty control series. The rigorous anticoagulation regimen after stent placement results in more frequent vascular and other bleeding complications. Future randomized studies comparing standard balloon angioplasty with stent implantation are warranted to properly assess the full impact of stent placement in the treatment of saphenous vein graft lesions.
In bovine aortic or capillary endothelial cells (ECs) incubated under hypoxic conditions, cell growth was slowed in a dose-dependent manner at lower oxygen concentrations, as progression into S phase from G1 was inhibited, concomitant with decreased thymidine kinase activity. Monolayers grown to confluence in ambient air, wounded, and then transferred to hypoxia showed decreased ability to repair the wound, as a result of both decreased motility and cell division. Hypoxic ECs demonstrated a approximately 3-fold increase in the total number of high-affinity fibroblast growth factor receptors, and levels of endogenous FGF were suppressed. Consistent with the presence of functional FGF receptors, addition of basic FGF overcame, at least in part, hypoxia-mediated suppression of EC growth, and enhanced wound repair in hypoxia, stimulating both motility and cell division. Despite slower growth in hypoxia, ECs could achieve confluence, and the monolayers consisted of larger cells with altered assembly of the actin-based cytoskeleton and small gaps between contiguous cells. The permeability of these hypoxic EC monolayers to macromolecules and lower molecular weight solutes was increased. Cell surface coagulant properties were also perturbed: the anticoagulant cofactor thrombomodulin was suppressed, and a novel Factor X activator appeared on the EC surface. These data indicate that micro- and macrovascular ECs can grow and be maintained at low oxygen tensions, but hypoxic endothelium exhibits a range of altered functional properties which can potentially contribute to the pathogenesis of vascular lesions.
Wound repair and tumor vascularization depend upon blood vessel growth into hypoxic tissue. Although hypoxia slows endothelial cell (EC) proliferation and suppresses EC basic fibroblast growth factor (bFGF) expression, we report that macrophages (MPs) exposed to PO2 approximately 12-14 torr (1 torr = 133.3 Pa) synthesize and release in a time-dependent manner platelet-derived growth factor (PDGF) and acidic/basic FGFs (a/bFGFs), which stimulate the growth of hypoxic ECs. Chromatography of hypoxic MP-conditioned medium on immobilized heparin with an ascending NaCl gradient resolved three peaks of mitogenic activity: activity of the first peak was neutralized by antibody to PDGF; activity of the second peak was neutralized by antibody to aFGF; and activity of the third peak was neutralized by antibody to bFGF. Metabolically labeled lysates and supernatants from MPs exposed to hypoxia showed increased synthesis and release of immunoprecipitable PDGF and a/bFGF in the absence of changes in cell viability. Possible involvement of a heme-containing oxygen sensor in MP elaboration of growth factors was suggested by the induction of bFGF and PDGF by normoxic MPs exposed to nickel or cobalt, although metabolic inhibitors such as sodium azide were without effect. These results suggest a paracrine model in which hypoxia stimulates MP release of PDGF and a/bFGF, inducing EC proliferation and potentially promoting angiogenesis in hypoxic environments.
We have previously speculated that methylene blue-induced photooxidation of adventitial surface for 5 minutes can completely inhibit the intimal and medial growth of surgically prepared saphenous vein in vitro. In this study, inhibitory effect of methylene blue-induced photooxidation on intimal thickening of vein graft in vivo was investigated.
Jugular vein grafts were photooxidized in 0.01% methylene blue solution for 5 minutes, and interposed into arterial circulation for 4 weeks in rabbits. Vein grafts were studied by morphometry and immunohistochemistry.
The intimal thickening of photooxidized vein grafts were suppressed significantly compared with those in the nonphotooxidized group. Proliferated cell nuclear antigen (PCNA) index (total PCNA-positive cells/total cell count x 100%) of vein graft was significantly higher in the nonphotooxidized group than those in the photooxidized group.
Methylene blue-induced photooxidation is effective in the inhibition of intimal thickening of vein graft interposed in the arterial circulation for 4 weeks in vivo.
Photodynamic therapy (PDT) of locally recurrent breast cancer has been limited to treatment of small lesions because of non- selective necrosis of adjacent normal tissues in the treatment field. Lutetium Texaphyrin (PCI-0123, Lu-Tex) is a photosensitizer with improved tumor localization that is activated by 732 nm light, which can penetrate through larger tumors. We have evaluated Lu-Tex in a Phase I trial and in an ongoing Phase II trial in women with locally recurrent breast cancer with large tumors who have failed radiation therapy. Patients received Lu-Tex intravenously by rapid infusion 3 hours before illumination of cutaneous or subcutaneous lesions. In Phase I, Lu-Tex doses were escalated from 0.6 to 7.2 mg/kg in 7 cohorts. Sixteen patients with locally recurrent breast cancer lesions were treated. Dose limiting toxicities above 5.5 mg/kg were pain in the treatment field during therapy, and dysesthesias in light exposed areas. No necrosis of normal tissues in the treated field was noticed. Responses were observed in 60% of evaluable patients [n equals 15, 27% complete remission (CR), 33% partial remission (PR)], with 63% of lesions responding (n equals 73: 45% CR, 18% PR). In Phase II, 25 patients have been studied to date, receiving two treatments ranging from 1.0 to 3.0 mg/kg at a 21 day interval. Treatment fields up to 480 cm2 in size were treated successfully and activity has been observed. Patients have experienced pain at the treatment site but no tissue necrosis. These studies demonstrate the feasibility of Lu-Tex PDT to large chest wall areas in women who have failed radiation therapy for the treatment of locally recurrent breast cancer. Treatment conditions are currently being optimized in the ongoing Phase II trials.
The role of excimer laser angioplasty in treating complex coronary artery disease remains uncertain. A randomized trial comparing this new technology with balloon angioplasty cannot be designed until systematic analysis identifies the lesion types that are likely to benefit from treatment with excimer laser angioplasty. In a cohort of 764 patients who had 858 coronary stenoses treated with excimer laser-facilitated angioplasty, relative risk analysis was used to examine acute success, complications and restenosis rates, and the results were compared with those of balloon angioplasty to identify the lesion types that show the greatest benefit with the new treatment. Clinical success was achieved in 657 patients (86%), as indicated by ≤50% residual stenosis and no in-hospital complication. A major in-hospital complication (death, bypass surgery, or Q-wave or non-Q-wave myocardial infarction) occurred in 58 patients (7.6%). Follow-up angiography was obtained in 70% of eligible patients. Combining angiographic and noninvasive restenosis rates yielded an overall restenosis rate of 46%.
The status of the native coronary arteries at necropsy in the vicinity of the coronary anastomoses of saphenous vein aortocoronary bypass grafts in 20 patients with severe coronary heart disease is presented. Of the 37 graft systems (graft plus coronary artery into which graft inserted) analyzed, the lumina of 44% of the native coronary arteries within the first 2 cm distal to the anastomoses were greater than 75% narrowed in cross-sectional area by atherosclerotic plaques, and the native coronary artery at the site of the anastomosis was greater than 50% narrowed in cross-sectional area already by atheroclerotic plaque in 25% of the graft systems. The mean coronary arterial size distal to the site of the coronary graft anastomosis, even after correction for heart weight, was greater in the 13 men than in the seven women. The residual luminal areas squared per gram of heart weight, however, were similar in both men and women. These results suggest that 1) relative coronary vessel size is greater in men than women; 2) the luminal area squared per gram myocardial mass (a relative estimation of flow) is the same in the two groups of patients; and 3) less atherosclerotic plaque is necessary in women then in men to produce similar limitation to coronary flow. Thus, vessel size alone cannot account for the higher reported frequency of unsuccessful aortocoronary bypass procedures in women.
This report describes morphologic changes in saphenous veins used as aortocoronary bypass conduits, and discusses the relative contribution of various factors to these changes. The three primary changes are: (1) medial fibrous replacement, (2) adventitial fibrous proliferation, and (3) intimal fibrous proliferation. Medial fibrous replacement is caused by vein wall ischemia with loss of smooth muscle cells; adventitial fibrous proliferation is the result of organization of fibrin deposits and repair of ischemic injury; and intimal fibrous proliferation results from some stimulus, probably fibrin deposition on injured intima, which causes stimulation of smooth muscle cells to become fibroblasts or "myointimal cells". Although all grafts show some changes, the degree and severity of these three changes is variable along the length of the grafts and among separate grafts in the same patient.
To evaluate the initial mechanism involving atherosclerotic changes of the saphenous vein graft implanted for coronary artery revascularization in the early stage, immunocytochemical analysis was performed to determine the cell components and kinetics of saphenous vein grafts. Specimens of saphenous vein grafts were obtained from 7 necropsy patients who died at 4 days to 6 months after surgery. Monoclonal antibodies specific for smooth muscle cells (HHF35) and macrophages (HAM56) were used for analysis of the cell components. Migration of macrophages into the intima and the media was observed on the fourth postoperative day. Intimal thickening was characterized by the proliferation of smooth muscle cells, and scattered macrophages were present in the subendothelial layer 1 month after surgery. At 2 months, intimal thickening became prominent and macrophages were recognized circumferentially throughout the layer. At 5 to 6 months, some of the saphenous vein grafts were almost occluded by severe intimal thickening due to proliferation of the smooth muscle cells. Macrophages were also observed both inside and outside of the internal elastic lamina; these are rarely found in the artery. These results suggest that compared with the arterial graft, cytokinesia of the saphenous vein graft contributes to the development of early graft failure because of its rapidity in progression and severity.
The suitability of a colorimetric [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)] assay to the determination of cell viability following photoradiation therapy (PRT) of human breast and melanoma cell lines has been examined. Results have been shown to correlate with those obtained using a clonogenic assay system. Using the MTT assay system it was shown that differences occur in the susceptibility of both lines to PDT. In addition it has been demonstrated that both lines differ with respect to their ability to develop photosensitivity in the presence of hematoporphyrin derivative (HpD). In the absence of serum this difference is not as obvious. This MTT assay provides a valid, simple and semi-automatable system for assessment of PRT in vitro.
When cultured in a hypoxic environment similar to that found in the center of a wound, macrophages secreted active angiogenesis factor into the medium. Under conditions similar to those of well-oxygenated tissue, macrophages did not secrete active angiogenesis factor. Macrophages that secreted the factor at hypoxic conditions stopped secreting it when returned to room air. Thus the control of angiogenesis in wound healing may be the result of macrophages responding to tissue oxygen tension without the necessity of interacting with other cell types or biochemical signals.
There is no clinically useful therapy for the suppression of vein bypass graft intimal hyperplasia (IH). Photodynamic therapy (PDT), a technique that uses light to activate otherwise biologically inert photosensitizers to produce cytotoxic effects, has been demonstrated to successfully inhibit experimental IH in balloon-injured arteries. The purpose of this study was to investigate the efficacy of PDT as a method to reduce vein graft IH.
Reversed external jugular vein bypass grafts of the common carotid artery were performed in 28 male Sprague-Dawley rats. The animals received either chloroaluminum sulfonated phthalocyanine (2.5 mg/kg intravenously) 24 hours before the ex vivo irradiation of the vein grafts (VG) with 100 joule/cm2 at 675 nm (PDT VG) or saline solution as control (CON VG). Preharvest bromodeoxyuridine was administered to label proliferating cells. All vein grafts were perfusion fixed within 96 hours for a pilot study or at 2 and 4 weeks for the main study. Histology, immunohistochemistry, and morphometric analysis were performed.
There was no acute thrombus formation in the hypocellular PDT VG with occasional platelets but no leukocytes adherent to the luminal surface. Intimal areas of the PDT VG were 18% at 2 weeks and 53% at 4 weeks of the CON VGs (p < 0.05). Medial areas and percent of stenoses were also significantly less in PDT than in CON VG. However, intimal hyperplasia noted in the longitudinal sections within 2 mm of the anastomoses did not demonstrate a difference between PDT and CON VG. Intimal hyperplasia of both PDT and CON VG consisted of smooth muscle cells, verified by immunohistochemistry. Bromodeoxyuridine-labeled cells were more abundant in 2-week than in 4-week specimens, were found most frequently in the intimal areas of the CON VG body, and were equivalent in the anastomoses of PDT VG and CON VG.
These data suggest that PDT of vein grafts suppresses the development of IH in the body of the vein graft but does not affect IH adjacent to the anastomoses. The artery may be the source of proliferating smooth muscle cells that contribute to the anastomotic vein graft IH.
We sought to examine, angiographically, the longterm fate of a large number of mainly venous coronary bypass grafts and to correlate graft patency and disease with patient survival and reoperation.
Much is known about bypass graft patency and disease, but the precise relation between graft fate and patient outcome has not been substantiated and documented.
A total of 1,388 patients underwent a first coronary artery bypass graft procedure at a mean age of 48.9 years, 234 had a second bypass procedure at a mean age of 53.3 years, and 15 had a third bypass procedure at a mean age of 58.2 years during the 25-year period from 1969 to 1994. Most were male military personnel or veterans; 12% were < or = 39 years old. Of 5,284 grafts placed, 91% were venous and 9% arterial. Angiograms were performed on 5,065 (98% of surviving) grafts early, on 3,993 grafts at 1 year and on 1,978 grafts at 5 years after operation; other examinations were also performed up to 22.5 years after operation, and 353 grafts were examined after > or = 15 years. Grafts were graded for patency and disease. The status of all patients was known at the study's end.
The perioperative mortality rate was 1.4% for an isolated first coronary bypass procedure, 6.6% for reoperation. Vein graft patency was 88% early, 81% at 1 year, 75% at 5 years and 50% at > or = 15 years; when suboptimal grafts, graded B, were excluded from calculation, the proportion of excellent grafts, graded A, decreased to 40% after > or = 12.5 years. After the early study, the vein graft occlusion rate was 2.1%/year. Internal mammary artery graft patency was significantly better but decreased with time. Vein graft disease appeared by 1 year and the rate accelerated by > or = 2.5 years, involving 48% of grafts at 5 years and 81% at > or = 15 years; 44% of the latter grafts were narrowed > 50%. Survival of all patients was 93.6% at 5 years. 81.1% at 10 years, 62.1% at 15 years, 46.7% (150 patients) at 20 years and 38.4% (25 patients) at 23 years after operation. Survival decreased as age increased, but curves approximated "normal" life expectancy for older patients. Survival curves at all ages showed a steeper decline after 7 years. The rate of reoperation increased between 5 years and 10 to 14 years, then decreased to stable levels. Coronary atheroembolism from vein grafts was the major cause of morbidity and mortality associated with reoperation. Vein graft patency and disease were temporally and closely related to reoperation and survival.
Coronary bypass graft disease and occlusion are common after coronary artery bypass grafting and increase with time. They are major determinants of clinical prognosis, specifically measured by reoperation rate and survival. Intraoperative graft atheroembolism was a major reoperation hazard. Reoperation is definitely worthwhile but entails identifiable risks that must be dealt with.
Lutetium texaphyrin, PCI-0123, is a pure, water-soluble photosensitizer with a large broad absorption band centered at 732 nm. The compound was tested for photodynamic therapy (PDT) effectiveness in a murine mammary cancer model. The texaphyrin macrocycle as illustrated by magnetic resonance imaging and 14C-radiolabeled texaphyrin studies was shown to be tumor selective; a tumor-to-muscle ratio of 10.55 was seen after 5 h. Lutetium texaphyrin, at a drug dose of 20 mumol/kg with irradiation 5 h postinjection at 150 J/cm2 and 150 mW/cm2, had significant efficacy (P < 0.0001) in treating neoplasms of moderate size (40 +/- 14 mm3) and also had significant efficacy (P < 0.0001) in treating larger neoplasms (147 +/- 68 mm3). The PDT efficacy was correlated with the time interval between PCI-0123 administration and light exposure. A 100% cure rate was achieved when photoirradiation took place 3 h postinjection compared to 50% for 5 h using 10 mumol/kg and 150 J/cm2 at 150 mW/cm2. The PDT efficacy was attributable to the selective uptake/retention of the texaphyrin photosensitizer in addition to the depth of light penetration achievable at the 732 nm laser irradiation.
Photodynamic therapy (PDT) of pigmented melanoma has generally been unsuccessful because of insufficient light penetration in such tissues. In this study, the responsiveness of the heavily pigmented B16F10 murine melanoma to lutetium texaphyrin (PCI-0123), a water-soluble sensitizer with strong absorbance in the near infrared (700-760 nm), was examined. These studies were carried out in both normal and ApoE deficient C57BL/6 mice. The latter strain exhibits a lipoprotein profile more like humans (low density lipoprotein > high density lipoprotein) than rodents (high density lipoprotein > low density lipoprotein). Under optimal conditions of drug dose, light dose, and interval between drug administration and irradiation--the median survival time of C57BL/6 tumor bearing mice was approximately doubled (29 d) compared with tumor bearing control animals (13 d). The life-span of the ApoE knockout mice was greater (33 d) than the C57BL/6 animals (23 d) when irradiation occurred 3 h after administration of a 10 micromol per kg drug dose. The greater efficacy of PDT in the ApoE deficient mice was associated with more rapid clearance of drug from the blood, greater accumulation of sensitizer in tumor tissue, and substantially greater drug binding to the very low density lipoprotein/low density lipoprotein plasma fraction. Confocal laser scanning microscopy showed that the predominant subcellular site of photosensitizer binding was to melanosomes; costaining was performed with Mel-5. Melanosomes are susceptible to oxidative stress. Photo-oxidation, mediated by PCI-0123 PDT, could potentially overload an already highly oxidized stressed state leading to cell death. The good tissue penetration depth achieved by PCI-0213 mediated PDT and the activation of melanosomes makes PDT of pigmented melanoma, for the first time, clinically relevant.