Photodynamic therapy induces apoptosis in intimal hyperplastic arteries

Photodynamic therapy of balloon-injured rat carotid arteries using indocyanine green

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.

Protoporphyrin IX-mediated sonodynamic action induces apoptosis of K562 cells

OBJECTIVES

The present study aims to investigate apoptosis of human leukemia K562 cells induced by protoporphyrin IX (PpIX)-mediated sonodynamic therapy (PpIX-SDT).

METHODS

The uptakes of intracellular PpIX in K562 cells were detected by flow cytometry. The sub-cellular localization of PpIX was imaged by confocal microscope. The cytotoxic effect of PpIX-SDT was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenylter-trazolium bromide tetrazolium) assay. Apoptosis was evaluated by chromatin condensation with DAPI (4'-6-diamidino-2-phenylindole) staining, decrease of mitochondria membrane potential (MMP), re-distribution of Bax, and the expression changes of the key apoptosis-associated protein (Caspase-3 and polypeptide poly (ADP-robose) polymerase). The possible mechanism of SDT-induced apoptosis was investigated by detecting by intracellular ROS (reactive oxygen species) generation and effect of ROS scavenger-NAC (N-acetylcysteine) on SDT induced apoptosis.

RESULTS

The intracellular PpIX increased quickly within 2 h after PpIX administration and PpIX mainly localized in the mitochondria. Compared with PpIX alone and ultrasound alone groups, the synergistic cytotoxicity of PpIX plus ultrasound was significantly boosted. In addition, the ultrasound induced some extent of chromatin condensation and MMP loss was greatly enhanced by the presence of 2 μg/ml PpIX, where PpIX alone treatment showed no or only slight effect. Time-dependent Bax translocation, caspase-3 activation and PARP cleavage were detected in SDT treatment groups. Besides, intracellular ROS production was significantly enhanced after SDT, and the general ROS scavenger NAC could obviously alleviate the SDT-caused cell viability loss, MMP loss, Bax redistribution and nuclear changes.

CONCLUSIONS

These results indicated that PpIX-mediated sonodynamic action could induce apoptosis on K562 cells, and the intracellular ROS was involved in the PpIX-SDT induced apoptosis.

Effects of vascular photodynamic therapy in a newly adapted experimental rat aortic aneurysm model

The hypothesis driving this study was that photodynamic therapy (PDT) may limit abdominal aortic aneurysm growth due to matrix changes. The aortas of 12 rats were incubated with elastase using a newly modified experimental aneurysm model (3.5 mg/ml). Rats were allocated to an elastase-only group (n = 6) to study the elastase-induced aneurysm growth and an elastase ± PDT group to evaluate if PDT limited aneurysm growth (n = 6). PDT was performed with the photosensitizer methylene blue, and thermoneutral laser light (660 nm) was applied (120 J/cm(2), 100 mW/cm(2)) using a diode laser. Four untreated rats served as controls. The arteries were analysed after 4 weeks based on histology, immunohistochemistry and morphometry. This modified rat elastase model led to reproducible aneurysm development with no elastase-induced mortality compared with control animals (circumference, controls: 2.9 ± 0.2 vs. elastase: 5.5 ± 0.9 mm; P < 0.01). PDT after elastase incubation did not inhibit inflammatory cell infiltration. No significant change in the circumference was observed between elastase incubation and PDT treatment after elastase incubation (circumference, elastase: 5.5 ± 0.9 vs. elastase and PDT: 6.1 ± 0.8 mm; P < 0.01). Despite a PDT-induced resistance to protease digestion, PDT did not reduce aortic dilatation in the elastase-treated rat aorta. These findings suggest that PDT may not be a useful modality to prevent aneurysm growth.

Hypocrellin B-mediated sonodynamic action induces apoptosis of hepatocellular carcinoma cells

OBJECTIVE

The present study aims to investigate apoptosis of hepatocellular carcinoma cells induced by hypocrellin B-mediated sonodynamic action.

METHODS

The hypocrellin B concentration was kept constant at 2.5 μM and cells from the hepatocellular carcinoma HepG2 cell line were exposed to ultrasound with an intensity of 0.46 W/cm(2) for 8s. Cell cytotoxicity was quantified using an MTT assay 24 h after sonodynamic therapy (SDT) of hypocrellin B. Apoptosis was investigated using a flow cytometry with Annexin V-FITC and propidium iodine staining. Intracellular reactive oxygen species (ROS) levels were detected using a flow cytometry with 2,7-dichlorodihydrofluorecein diacetate (DCFH-DA) staining.

RESULTS

The cytotoxicity of hypocrellin B-mediated sonodynamic action on HepG2 cells was significantly higher than those of other treatments including ultrasound alone, hypocrellin B alone and sham treatment. Flow cytometry showed that hypocrellin B-induced sonodynamic action markedly enhanced the apoptotic rate of HepG2 cells. Increased ROS was observed in HepG2 cells after being treated with hypocrellin B-mediated sonodynamic action.

CONCLUSIONS

Our data demonstrated that hypocrellin B-mediated sonodynamic action remarkably induced apoptosis of HepG2 cells, suggesting that apoptosis is an important mechanism of cell death induced by hypocrellin B-mediated SDT.

TEM observation of ultrasound-induced mitophagy in nasopharyngeal carcinoma cells in the presence of curcumin

The present study was designed to observe the initiation of mitophagy in tumor cells after ultrasound treatment in the presence of curcumin under transmission electron microscopy. Nasopharyngeal carcinoma CNE2 cells were incubated with 10 μM curcumin and then exposed to ultrasound for 8 sec at an intensity of 0.46 W/cm(2). Severely swollen mitochondria, disrupted mitochondria and mitophagy were noted in the CNE2 cells after ultrasound treatment in the presence of curcumin. Our findings demonstrated that ultrasound treatment in the presence of curcumin significantly initiated mitophagy in CNE2 cells, which suggests that mitophagy serves as an important event in the process of cell death of nasopharyngeal carcinoma cells.

Apoptosis of ovarian cancer cells induced by methylene blue-mediated sonodynamic action

OBJECTIVE

The present study aims to investigate apoptosis of ovarian cancer cells induced by methylene blue (MB)-mediated sonodynamic therapy (SDT).

METHODS

The MB concentration was kept constant at 100μM and ovarian cancer HO-8910 cells were exposed to ultrasound therapy for 5s with an intensity of 0.46W/cm(2). The cytotoxicity was investigated 24h after MB-mediated sonodynamic action. Apoptosis was analyzed using a flow cytometer with Annexin V-FITC and propidium iodine (PI) staining as well as fluorescence microscopy with Hoechst 33258 staining. Intracellular reactive oxygen species (ROS) level was measured by flow cytometer with 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) staining.

RESULTS

The cytotoxicity of MB-mediated SDT on HO-8910 cells after MB-mediated SDT was significantly higher than those of other treatments including ultrasound alone, MB alone and sham treatment. Flow cytometric analysis showed a significant increase in the early and late apoptotic cell populations by MB-mediated SDT of HO-8910 cells. Nuclear condensation and increased ROS levels were also found in HO-8910 cells treated by MB-mediated SDT.

CONCLUSIONS

Our findings demonstrated that MB-mediated sonodynamic action significantly induced apoptosis of HO-8910 cells and an increase in intracellular ROS level. This indicates that apoptosis is an important mechanism of cell death induced by MB-mediated SDT. Thus, MB-mediated SDT might be a potential therapeutic strategy for combating ovarian cancer.

Ultrasound-Induced Cell Death of Nasopharyngeal Carcinoma Cells in the Presence of Curcumin

Objectives. Curcumin, a natural pigment from a traditional Chinese herb, has been attracting extensive attention. The present study aims to investigate cell death of nasopharyngeal carcinoma (NPC) cells induced by ultrasound sonication in the presence of curcumin in vitro. Methods. The NPC cell line CNE2 was chosen as a tumor model, and curcumin concentration was kept constant at 10 µM while the cells were subjected to ultrasound exposure for 8 s at an intensity of 0.46 W/cm2. Cell death was evaluated using flow cytometry with annexinV-FITC and propidium iodine staining, and nuclear staining with Hoechst 33258. Mitochondrial membrane potential and intracellular reactive oxygen species (ROS) were analyzed using flow cytometry with rhodamine 123 and dichlorodihydrofluorecein diacetate staining. Results. Flow cytometry showed that the combination of ultrasound and curcumin significantly increased the necrotic or late apoptotic rate by up to 31.37% compared with the controls. Nuclear condensation was observed in the nuclear staining, and collapse of ΔΨm and ROS increase were found in the CNE2 cells after the treatment with curcumin and ultrasound. Conclusions. The findings demonstrate that the presence of curcumin significantly enhances the ultrasound-induced cell death and ROS level, and induces the collapse of ΔΨm, suggesting that ultrasound sonication can increase the cell death of NPC cells in the presence of curcumin and that the treatment using curcumin and ultrasound together is a potential therapeutic modality in the management of malignant tumors.

Compartmental targeting for mTHPC-based photodynamic treatment in vivo: Correlation of efficiency, pharmacokinetics, and regional distribution of apoptosis

PURPOSE

The present study investigates the efficacy of compartmental targeting in xenografted tumors treated by meta-tetra(hydroxyphenyl)chlorin (mTHPC)-mediated photodynamic therapy (PDT). The therapeutic efficacy was, furthermore, related to a regional photoinduced distribution of apoptosis and an mTHPC biodistribution profile.

METHODS AND MATERIALS

Mice bearing EMT6 tumors were subjected to a single irradiation (10 J/cm(2)) of red laser light (652 nm) at different intervals after a single- (0.3 mg/kg or 0.15 mg/kg) or double-intravenous (2 × 0.15 mg/kg) injection(s) of mTHPC. Efficiency of the treatment was evaluated by monitoring tumor regrowth. mTHPC pharmacokinetics were assessed by high-performance liquid chromatography analysis of excised organs. The regional distribution of apoptosis in tumor sections was investigated with a newly developed colabelling immunohistochemistry technique.

RESULTS

A fractionated double-injection protocol of mTHPC with 24-h and 3-h drug-light intervals (DLI) yielded 100% tumor cure, with tumors presenting a massive apoptosis of neoplastic cells along with a distortion of vessels. The best efficiency for a single injection (0.3 mg/kg) was about 54% tumor cure and corresponded to a DLI of 3 h. At this DLI, tumors showed apoptosis of endothelial cells in residual vessels. Concentrations of mTHPC observed in plasma and tumor for the fractionated injection were not statistically different and were less than the total drug dose in each compartment.

CONCLUSIONS

The present work suggests that clinical PDT protocols with mTHPC could be greatly improved by fractionation of the drug administration. Time points should be chosen based on the intratumoral spatiotemporal drug distribution.

Sonodynamic action of pyropheophorbide-a methyl ester in liver cancer cells

OBJECTIVE

This study aimed to investigate the sonodynamic action of pyropheophorbide-a methyl ester (MPPa) in liver cancer cells to explore a novel therapeutic modality.

METHODS

H22 cells were chosen as model cells to investigate the sonodynamic action of MPPa on liver cancer. The MPPa concentration was kept constant at 2 micromol/L, and the cells were subjected to ultrasound exposure at an intensity of 0.97 W/cm(2). Cytotoxicity was investigated 24 hours after ultrasound exposure. Apoptosis was evaluated using flow cytometry with annexin V-fluorescein isothiocyanate and propidium iodine staining and nuclear staining with Hoechst 33258. Reactive oxygen species (ROS) were analyzed using flow cytometry with 2,7-dichlorodihydrofluorescein diacetate staining.

RESULTS

No significant dark cytotoxicity of MPPa was shown in the H22 cells at the concentration of 2 micromol/L. The cell death rate induced by ultrasound treatment was significantly higher in the presence of MPPa than in the absence of it (P < .05). Flow cytometry showed that the sonodynamic action of MPPa significantly increased the early and late apoptotic rates of the H22 cells. Nuclear condensation and an ROS increase were found after sonodynamic treatment.

CONCLUSIONS

Our findings showed that MPPa-mediated sonodynamic action significantly enhanced death of H22 cells and the ROS level, suggesting that MPPa is a novel sonosensitizer and the sonodynamic action of MPPa might be a potential therapeutic modality in the management of liver cancer.

In vitro photodynamic therapy with chlorin e6 leads to apoptosis of human vascular smooth muscle cells

Percutaneous coronary intervention has become the most common and widely implemented method of heart revascularization. However, the development of restenosis remains the major limitation of this method. Photodynamic therapy (PDT) recently emerged as a new and promising method for the prevention of arterial restenosis. Here the efficacy of chlorin e6 in PDT was investigated in vitro using human vascular smooth muscle cells (TG/HA-VSMCs) as one of the cell types crucial in the development of restenosis. PDT-induced cell death was studied on many levels,including annexin V staining, measurement of the generation reactive oxygen species (ROS) and caspase-3 activity,and assessment of changes in mitochondrial membrane potential and fragmentation of DNA. Photosensitization of TG/HA-VSMCs with a 170 lM of chlorin e6 and subsequent illumination with the light of a 672-nm diode laser(2 J/cm2) resulted in the generation of ROS, a decrease in cell membrane polarization, caspase-3 activation, as well as DNA fragmentation. Interestingly, the latter two apoptotic events could not be observed in photosensitized and illuminated NIH3T3 fibroblasts, suggesting different outcomes of the model of PDT in various types of cells. The results obtained with human VSMCs show that chlorin e6 may be useful in the PDT of aerial restenosis, but its efficacy still needs to be established in an animal model.

Hypocrellin B enhances ultrasound-induced cell death of nasopharyngeal carcinoma cells

Hypocrellin B, a natural pigment from a traditional Chinese herb, has been attracting extensive attention. The present study aims to investigate whether hypocrellin B can enhance cell death induced by ultrasound sonification on nasopharyngeal carcinoma cells in vitro. The sonodynamic action of hypocrellin B was investigated on nasopharyngeal carcinoma cell line CNE2 cells as tumor model cells. In the experiments, the hypocrellin B concentration was kept constant at 2.5 microM and the cells were subject to ultrasound exposure for 15 s at an intensity of 0.65 W/cm(2). Cytotoxicity was investigated 24 h after ultrasound sonification. Apoptosis was evaluated using flow cytometry with annexin V-FITC and propidium iodine staining and nuclear staining with Hoechst 33258. Cell ultrastructure morphology was observed using transmission electron microscopy (TEM). No significant dark cytotoxicity of hypocrellin B in the CNE2 cells was observed at the concentration of 2.5 microM. The cell death rate induced by ultrasound sonification was significantly higher in the presence of hypocrellin B than in the absence of hypocrellin B. Flow cytometry showed that ultrasound exposure in the presence of hypocrellin B significantly increased the early and late apoptotic rate, 18.64% and 22.57%, respectively, compared with the controls. Nuclear condensation was observed in the nuclear staining and swollen mitochondria and more vacuolar and broken cell membrane were found in TEM after the treatment of hypocrellin B and ultrasound. Our findings demonstrated that the presence of hypocrellin B significantly enhanced the cytotoxicity of ultrasound radiation in CNE2 cells, suggesting that hypocrellin B is a novel sonosensitizer and hypocrellin B-mediated sonodynamic therapy is a potential therapeutic modality in the management of malignant tumors.

Apoptosis of vascular smooth muscle cells induced by photodynamic therapy with protoporphyrin IX

Photodynamic therapy (PDT) had been shown effective in the treatment of intimal hyperplasia, which contributes to restenosis, by eradicating cells in the vessel wall. This study is designed to evaluate the effects of PDT with protoporphyrin IX (PpIX) on the viability of vascular smooth muscle cells (SMCs) and to define the cell-death pathway. Fluorescence microscopy and laser-induced fluorescence spectroscopic detection showed that SMCs selectively uptake PpIX, and the intracellular PpIX concentration increases with the amount of PpIX in the incubation solution. PDT with PpIX impaired cellular viability from 93+/-3.4% to 36+/-3.9% when the light intensity increases from 2 to 9J/cm(2) and intracellular PpIX concentration increases from 0.5 to 20 microg/ml. Although PDT induced both apoptosis and necrosis, the ratio of apoptotic cells increased with light dosage or intracellular PpIX concentration. The loss of mitochondrial membrane potential coincided with the apoptotic ratio. Our results indicated that the induction of apoptosis of SMCs may be one of the mechanisms by which PDT inhibits restenosis in vivo.

Intracoronary photodynamic therapy reduces neointimal growth without suppressing re-endothelialisation in a porcine model

OBJECTIVE

To examine the effects of intracoronary PhotoPoint photodynamic therapy (PDT) with a new photosensitiser, MV0611, in the overstretch balloon and stent porcine models of restenosis.

METHODS

28 pigs were injected with 3 mg/kg of MV0611 systemically 4 h before the procedure. Animals were divided into either the balloon overstretch injury (BI) group (n = 19) or the stented group (n = 9). After BI, a centred delivery catheter was positioned in the artery to cover the injured area, and light (532 nm, 125 J/cm(2)) was applied to activate the drug (n = 10). Control arteries (n = 9) were not activated by light. In the stented group, the drug was light activated before stent deployment. Serial sections of vessels were processed 14 days after treatment in the BI group and 30 days after treatment in the stented group for histomorphometric or immunohistochemical analysis.

RESULTS

Intracoronary PDT significantly reduced intimal thickness in both BI and stented arteries (about 65%: 0.22 (SEM 0.05) mm v 0.62 (0.05) mm, p < 0.01; and about 26%: 0.40 (0.04) mm v 0.54 (0.04) mm, p < 0.01, respectively). PDT increased luminal area by

CONCLUSION

Intracoronary PhotoPoint PDT with MV0611 reduces intimal proliferation without suppressing re-endothelialisation in a porcine model of restenosis.

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Key Words Collapse

MESH Headings

• Angioplasty, Balloon
• Animals
• Cell Proliferation
• Coronary Restenosis/prevention & control
• Coronary Vessels/injuries
• Feasibility Studies
• Female
• Immunohistochemistry
• Male
• Mesoporphyrins/pharmacokinetics
• Mesoporphyrins/therapeutic use
• Photochemotherapy/methods
• Photosensitizing Agents/pharmacokinetics
• Photosensitizing Agents/therapeutic use
• Random Allocation
• Stents
• Swine
• Tunica Intima

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Grants Collapse

Affiliation(s)

R Waksman Division of Cardiology, Washington Hospital Center, Washington, DC, USA.
I M Leitch
J Roessler
H Yazdi
R Seabron
F Tio
R W Scott
R I Grove
S Rychnovsky
B Robinson
R Pakala
E Cheneau

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Long-term inhibition of intimal hyperplasia using vascular photodynamic therapy in balloon-injured carotid arteries

Flexible treatments for intimal hyperplasia after angioplasty are still needed. The aim of this study was to demonstrate the long-term effects of vascular photodynamic therapy with talaporfin sodium on intimal hyperplasia following interventional injury. Intimal hyperplasia was induced by balloon distension injury to the carotid artery in 31 rabbits. Talaporfin, 5.0 mg/kg, was delivered systemically immediately after balloon injury. The injury site was irradiated with a diode laser light of wavelength 664 nm using a fluence of 50 J/cm2 after 30 min. At day 3 and weeks 3, 6, 9, 15, and 25 after photodynamic therapy, the treated artery of each rabbit was excised and examined immunohistochemically. Thirty minutes after talaporfin administration, drug fluorescence was found only in the balloon-injured carotid artery wall. At 3 days, no smooth muscle cells were seen in the media of the photodynamic therapy-treated arterial segments. Intimal hyperplasia developed progressively in the balloon-injured and untreated segments; however, in the segments treated with photodynamic therapy, intimal hyperplasia was markedly suppressed until 25 weeks and the media was repopulated by smooth muscle cells without macrophages. Vascular photodynamic therapy with talaporfin may be used to inhibit restenosis after vascular intervention.

Inhibition of in-stent restenosis in rabbit iliac arteries with photodynamic therapy

OBJECTIVES

Photodynamic therapy (PDT, the combination of light with a photosensitising drug in the presence of oxygen) inhibits restenosis after angioplasty without stenting. This study assesses the potential of PDT for prevention of in-stent re-stenosis.

DESIGN AND METHODS

Normal rabbits were given the photosensitising agent 5-aminolaevulinic acid (ALA) 60 mg/kg, 3 h prior to endovascular illumination of the iliac artery (635 nm at 50 J/cm(2)) either immediately before or after deployment of an oversized (3 mm diameter) stent. PDT treated arteries were retrieved 3 or 28 days later and assessed for cell counts and vascular morphometry. Control arteries (stent but no PDT) were examined at 28 days.

RESULTS

There were no adverse events and all vessels were patent at the end of the study. At 3 days there was almost complete medial cell ablation when light was delivered before stent deployment (17+/-1 cells/hpf), with little effect when illumination followed stent deployment (184+/-17 cells/hpf, p<0.0001). Twenty-eight days after PDT, the neointimal areas were 1.41+/-0.52 mm(2) (stent with no PDT), 1.24+/-0.54 mm(2) (light after stent) and 0.60+/-0.21 mm(2) (light before stent) (p=0.004).

CONCLUSIONS

PDT before stent deployment caused almost complete medial cell ablation at 3 days with inhibition of in-stent restenosis at 28 days. PDT is worthy of further study as an adjuvant to percutaneous intervention in patients with vascular disease.

Vascular Access in Hemodialysis: Issues, Management, and Emerging Concepts

This article (1) identifies the types of hemodialysis access, (2) summarizes the clinical standard of care for dialysis access grafts and fistulae, (3) describes the pathology and pathogenesis of venous stenosis in dialysis access grafts and fistulae, (4) tabulates avail-able therapies for hemodialysis vascular access dysfunction and speculates on the rea-sons for the lack of effective therapies, and (5) discusses the development and application of novel therapeutic interventions for this difficult clinical problem. The possibility that dialysis access grafts and fistulae could be the ideal clinical model for testing novel local therapies to block neointimal hyperplasia is discussed.

Modulation of Human Adventitial Fibroblast Function by Photodynamic Therapy of Collagen Matrix

OBJECTIVES

Photodynamic therapy (PDT) is a promising strategy to limit restenosis. PDT depletes the resident cells from the vessel wall without adventitial cell ingrowth. This study was undertaken to further explore the mechanisms by which PDT of matrix acts on key mechanisms in the development of restenosis.

MATERIALS AND METHODS

Control and PDT-treated collagen type-I matrix gels were prepared. Thereafter, untreated human fibroblasts were seeded on matrix gels (n=12). Fibroblast proliferation and invasive migration were quantified by calibrated phase contrast microscopy. Fibroblast bFGF and TGF-beta1 mRNA expression were analyzed using a quantitative real-time reverse transcription polymerase chain reaction.

RESULTS

Fibroblast proliferation on PDT-treated matrix gels was reduced by 30 and 76% after 3 and 7 days, respectively (3 days: P</=0.01, 7 days: P< or =0.001). PDT of matrix gels led to a 47% reduction of migration after 3 days and 51% after 7 days (P< or =0.001). PDT led to a 77% reduction of fibroblast TGF-beta1 mRNA (P< or =0.02) and to a 79% reduction of bFGF mRNA (P< or =0.03).

CONCLUSIONS

PDT of matrix-induced reduction of bFGF and TGF-beta1 mRNA levels may be important mechanisms of reducing fibroblast proliferation and invasive migration and thus the development of restenosis. These newly identified mechanisms highlight PDT's pleiotropic effects on the vessel wall and its potential clinical value.

Free radical attenuation prevents thrombosis and enables photochemical inhibition of vein graft intimal hyperplasia

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

A first trial in the clinical application of photodynamic therapy for the prevention of restenosis after coronary-stent placement

BACKGROUND AND OBJECTIVES

The aim of this clinical study was to evaluate the safety of local delivery of a photosensitizer followed by photodynamic therapy (PDT), to determine its effectiveness in reducing in-stent restenosis.

STUDY DESIGN/PATIENTS AND METHODS

Porfimer sodium was administered via a local delivery catheter to five coronary-stent implanted lesions followed by irradiation with a pulse laser. Coronary angiography (CAG) was performed at the baseline, after the procedure and at a 6-month follow-up.

RESULTS

By the 18-month clinical follow-up, no adverse events such as photodermatosis, or myocardial ischemia had occurred. At the follow-up, no coronary embolization, dissection, or aneurysmal dilatation was observed in the CAG. In-stent diameter stenosis, late loss, and loss index were 19.16+/-8.20%, 0.37+/-0.18 mm, and 0.19+/-0.12, respectively. No in-stent restenosis was observed.

CONCLUSIONS

This study suggests that PDT, with local delivery of Porfimer sodium, is safe and may be a feasible technique in preventing in-stent restenosis.

Photodynamic therapy mediated induction of accelerated re-endothelialisation following injury to the arterial wall: implications for the prevention of postinterventional restenosis

OBJECTIVE

Accelerated re-endothelialisation may inhibit the development of restenosis. Basic Fibroblast Growth Factor (bFGF) plays a key role for early proliferative activity in the artery following injury. Therefore, this study was devised to examine the effect of photodynamic therapy (PDT) on post-injury re-endothelialisation in vivo, and bFGF-mRNA expression in endothelial cells (EC) in vitro.

MATERIALS AND METHODS

Rat carotid arteries were balloon-injured prior to PDT. Arteries were analysed after 1, 3, 5, 14 and 30 days. Morphometric measurements were undertaken following injection of 0.5% Evans Blue which stains non-endothelialised surfaces only. To identify EC, immunohistochemistry (CD-31) was performed. Proliferation was assessed by fluorescence cell counting. PCR quantification of bFGF-mRNA expression and proliferation were assessed in bovine aortic EC which were plated on isolated, PDT-treated EC-derived extracellular matrix at (12), 24, 48 (72 h).

RESULTS

Three days following PDT, arteries displayed significantly increased endothelial lining (p = 0.02), which was more pronounced at 5 (p = 0.03) and 14 days (p = 0.02). At 30 days no relevant differences between PDT and control were noted. EC proliferation on PDT-treated matrix was significantly increased at 24, 48, and 72 h (p = 0.0004), whereas bFGF-mRNA expression was significantly increased at 24 h only (p = 0.007).

CONCLUSION

Post-injury PDT appears to accelerate re-endothelialisation. Expression of bFGF-mRNA, however, although increased shortly after PDT, may not be responsible for a constant stimulation of EC proliferation.

Mechanisms of reduced human vascular cell migration after photodynamic therapy

Restenosis results from intimal hyperplasia and constrictive remodeling following cardiovascular interventions. Photodynamic therapy (PDT) has been shown to inhibit intimal hyperplasia in vivo by preventing neointimal repopulation of the treated vessel. This study was undertaken in an attempt to further dissect the mechanisms by which PDT acts on secreted and extracellular matrix proteins to inhibit migration of cultured human vascular cells. PDT of three-dimensional collagen gels inhibited invasive human smooth muscle cell (SMC) migration, whereas cell-derived matrix metalloproteinase production remained unaltered. Additionally, PDT generated cross-links in the collagen gels, a result substantiated in an ex vivo model whereby PDT rendered the treated vessels resistant to pepsin digestion and inhibited invasive migration of SMC and fibroblasts. These data support the premise that by inducing matrix protein cross-links, rendering the vessel resistant to degradation, in vivo PDT inhibits repopulation of the vessel and therefore intimal hyperplasia.

Mitochondrial release of apoptosis-inducing factor and cytochrome c during smooth muscle cell apoptosis

Photodynamic therapy (PDT) is under investigation for the treatment of intimal hyperplastia in conditions such as atherosclerosis and restenosis. Although smooth muscle cells (SMCs) may be a key target for treatment, the effects of PDT on these cells are poorly characterized. In the present study, apoptosis was induced in primary human aortic SMCs by the combination of the photosensitizer verteporfin and visible light. After PDT, an increase in mitochondrial cytochrome c (cyt c) and apoptosis-inducing factor (AIF) levels were detected in the cytosol immediately and their levels increased steadily up to 2 hours. Cytosolic levels of the pro-apoptotic Bcl-2 family member Bax decreased reciprocally throughout this period, but this change did not occur before cyt c release. Confocal microscopy revealed a diffuse staining pattern of cyt c within apoptotic cells as compared to a distinct mitochondrial staining in normal cells. AIF translocated from mitochondria to the nucleus during the progression of apoptosis. After cyt c release, caspase-9 and caspase-3 processing was visible by 1 hour and caspase-6, -7, and -8 processing was apparent by 2 hours after PDT. In summary, these results demonstrate for the first time the cellular redistribution of mitochondrial AIF during SMC apoptosis, as well as the early release of cyt c and the subsequent activation of multiple caspases during PDT-induced SMC apoptosis.