Predictors of Failure of Closure in Percutaneous EVAR Using the Prostar XL Percutaneous Vascular Surgery Device.

OBJECTIVE: To identify predictors of failure in percutaneous endovascular aneurysm repair (P-EVAR) using the Prostar XL Percutaneous Vascular Surgery Device (Abbot Vascular, Santa Clara, CA, USA) and the need for conversion to conventional femoral cutdown (O-EVAR). METHODS: Consecutive patients who underwent P-EVAR with the Prostar XL device between January 2009 and April 2012 were included in this series. Patients with a circular calcified common femoral artery (CFA) oncomputed tomography angiography were operated using O-EVAR and were therefore excluded. To identify predictors of success of closure in P-EVAR, artery characteristics, sheath size used, and comorbidities were analyzed in a univariate logistic regression model. RESULTS: Percutaneous access was achieved in 154 femoral access sites with conversion to O-EVAR was needed in10 (6.5%). Significant predictors of conversion included sheath size (continuous, relative risk [RR] 1.50, p < .03)and the ratio between sheath size and CFA diameter >0.75 (RR 8.93, p < .01). Variables such as calcification quantity scores, CFA diameter, body mass index, and comorbidities were not significant. CONCLUSION: The data demonstrate that sheath size, in particular, combined with CFA diameter predicts failure of closure in P-EVAR using the Prostar XL device. This ratio can be utilized to help in decision making with regard to the EVAR approach. A ratio of >0.75 would favor a primary open groin approach.

Endovascular photodynamic therapy with aminolaevulinic acid prevents balloon induced intimal hyperplasia and constrictive remodelling.

BACKGROUND AND OBJECTIVE: intimal hyperplasia (IH) and constrictive remodelling are important causes of restenosis following endovascular interventions, such as percutaneous transluminal angioplasty. Photodynamic therapy (PDT) with 5-aminolaevulinic (ALA) may prevent restenosis by cellular depletion and the elimination of cholinergic innervation. STUDY DESIGN/MATERIALS AND METHODS: rats (n=90) were subdivided into 4 main groups. In the experimental group (n=36: 3 replications x 4 doses x 3 examination time-points), ALA was administered (200mg/kg i.v.) 2-3h before balloon injury (BI) of the common iliac artery followed by endovascular illumination with 633nm at either 12.5, 25, 50 or 100J/cm diffuser length (dl BI+PDT group). As control groups served the BI+Light only (LO) group (n=36) that received no ALA, the BI only group (n=9) (BI), and a group (n=9) that received a Sham procedure (Sham group). RESULTS: planimetric analysis showed IH of 0.28+/-0.12mm(2) (BI), 0.27+/-0.12mm(2) (BI+LO at 100J/cmdl) in contrast to 0.02+/-0.02mm(2) after BI+PDT at 100J/cmdl at 16 weeks (p<0.05). In the BI+PDT groups, a light-dose increase of a factor 2 led to an IH decrease of 17% (p<0.05). In the BI and BI+LO groups constrictive remodelling was found, in contrast to BI+PDT treated groups at 16 weeks. The staining of cholinergic innervation of the tunic media of the blood vessel wall in BI+PDT showed no damage at the highest fluence. CONCLUSION: endovascular ALA-PDT prevents IH and constrictive remodelling after BI without damage of cholinergic innervation of the tunica media. The effective light fluence rate in the rat is 50-100J/cmdl.

Photodynamic therapy inhibits the injury-induced fibrotic response of vascular smooth muscle cells.

OBJECTIVES: excessive deposition of extracellular matrix (ECM) proteins plays a key role in the intervention-related vascular fibroproliferative response, resulting in intimal hyperplasia (IH). Cytokines, such as platelet-derived growth factor (PDGF), released after vascular injury and deposited in the ECM, are known to stimulate production of matrix proteins. Photodynamic therapy (PDT), the combination of light and a photosensitive dye to produce free radicals, is a novel approach to inhibit experimental IH by the local eradication of smooth-muscle cells (SMC) and alteration of ECM. This in vitro study examined whether PDT can inhibit the fibrotic response of vascular SMC. MATERIALS AND METHODS: the effect of PDT on important pro-fibrotic factors was determined by performing PDT of isolated ECM, injured SMC and pure PDGF. SMC production of collagen was monitored by cellular [3H]-proline incorporation. RESULTS: untreated SMC seeded on ECM demonstrated an increase of 50% in collagen production ( p <0.0001) as compared to SMC on an empty plate. This increase was also seen when SMC was incubated with the conditioned media of mechanically injured SMC, or pure PDGF. However, after PDT of ECM, injured SMC or PDGF, there was an inhibition of 40% ( p <0.05) in SMC-collagen production. CONCLUSIONS: these findings indicate that PDT can interfere with factors that lead to the vascular fibrotic response. In this way, PDT, with its cytotoxic and extracellular effects, can promote healing of the vessel wall without the stimulus of fibrosis that can lead to restenosis.

Significance of dosimetry in photodynamic therapy of injured arteries: classification of biological responses.

With conflicting results in the literature on the ability of photodynamic therapy (PDT) to inhibit intimal hyperplasia (IH), the present study systematically investigated the effects of drug and light dosimetry on the biologic responses in the artery wall. The rat common carotid artery was balloon-injured and pressurized with benzoporphyrin-derivative monoacid ring (BPD). Then, PDT was performed with an external laser at different fluences and the biologic responses of the artery wall were histologically examined at 24 h and at 2 weeks. Photodynamic therapy effects on injured arteries can be classified into four stages: low-dose PDT using 0.5 microgram/mL BPD at 50 J/cm2 (stage I) resulted in incomplete cell eradication and significant IH at 2 weeks. Irradiation with 100 J/cm2 at the same BPD concentration (stage II) completely eradicated the cells in the artery wall at 24 h but still led to IH at 2 weeks. However, 25 micrograms/mL BPD at 100 J/cm2 (stage III) resulted in total cell eradication at 24 h and inhibition of IH at 2 weeks. In contrast, high-dose PDT with 25 micrograms/mL BPD and 200 J/cm2 (stage IV) led to thrombus development and vascular occlusion at 24 h. These data, demonstrating the different stages of PDT effects on injured arteries, emphasize the critical importance of appropriate PDT dosimetry for the effective inhibition of IH.

Importance of the treatment field for the application of vascular photodynamic therapy to inhibit intimal hyperplasia.

Intimal hyperplasia (IH) plays a dominant role in the development of restenosis. In previous studies, photodynamic therapy (PDT) prevented IH induced by segmental balloon injury of the rat carotid. The critical elements required to control IH effectively with this technique are not fully understood. This study assessed the importance of the treatment field by studying the repair process of injured vessels, in which the PDT-treatment field did not target the entire injured area. The entire rat common carotid artery was balloon-injured to induce IH, whereas only the cervical segment below the bifurcation was subjected to PDT by external light irradiation after administration of the photosensitizer chloroaluminum sulfonated phthalocyanine. Light irradiation of injured arteries without photosensitizer served as control for PDT, and PDT of uninjured arteries was included as a control group for the balloon injury. Histologic characterization of the repair process was sequentially assessed. Balloon-injured arteries without PDT displayed rapid IH development with a peak at 2 weeks. Photodynamic therapy of balloon-injured arteries resulted in complete local depletion of medial smooth muscle cells (SMC), which was associated with a lack of IH until 2 weeks. However, at 4 and 16 weeks there was significant IH in PDT-treated arteries despite a lack of medial SMC repopulation. A wave of IH progression over the acellular media was observed in these arteries, migrating from the injured non-PDT-treated area. The PDT of uninjured arteries did not result in IH and was also associated with a persistent acellular media. Delayed IH development after PDT of injured vessels can result from IH progression from an injured site not included in the treatment field. This also indicated that the source of cells developing the intimal hyperplasia lesion can originate from an area remote from the lesion. Together with previous results and the determination that PDT itself does not induce IH, it can be reasoned that inclusion of the whole injured artery or a section of an uninjured margin in the treatment field is essential for effective PDT prevention of IH.

Photodynamic therapy with local photosensitizer delivery inhibits experimental intimal hyperplasia.

BACKGROUND: Photodynamic therapy (PDT), the light activation of photosensitizer dyes for the production of free radicals, effectively inhibits experimental intimal hyperplasia with systemic administration of the photosensitizer. The local application of the photosensitizer directly into a vascular lesion to avoid systemic side effects and tightly control dose administration has theoretical appeal. The aim of this study was to quantify serum and arterial tissue uptake after site-specific photosensitizer delivery and, following PDT, determine its effectiveness at inhibiting intimal hyperplasia. STUDY DESIGN/MATERIALS AND METHODS: The rat common carotid artery was balloon-injured, pressurized at 400 mm Hg for 2 minutes with the photosensitizer dye benzoporphyrin-derivative (BPD), and irradiated with 690 nm laser light at a fluence of 100 J/cm2. Control animals were pressurized with saline only, or received no additional treatment than balloon-injury. RESULTS: Pressurization with BPD resulted in complete penetration of the intima and media and was associated with relatively high tissue, but almost no detectable serum BPD concentrations. No skin photosensitization or other systemic side effects were observed with photosensitizer administration. After 9 days, PDT-treated arteries displayed a significantly lower number of smooth muscle cells in the arterial wall than balloon-injured (P < 0.001) or saline-pressurized arteries (P < 0.0002), and no intimal hyperplasia. At 21 days, IH after PDT was significantly reduced as compared with balloon-injured (P < 0.0004), or saline-pressurized arteries (P < 0.003) with no arterial dilatation. CONCLUSIONS: Site-specific delivery of liposomal BPD followed by PDT represents a safe method to treat arteries, and may be effectively used in vivo to inhibit the development of intimal hyperplasia.

Photodynamic therapy inactivates cell-associated basic fibroblast growth factor: a silent way of vascular smooth muscle cell eradication.

OBJECTIVE: Procedurally related vascular injury results in a smooth muscle cell (SMC) proliferative response which is in part initiated by SMC release of mitogens, including basic fibroblast growth factor (bFGF). This injury-induced proliferative response is believed to be a key event in intimal hyperplasia development. Photodynamic therapy (PDT), a novel approach found to be effective in inhibiting experimental intimal hyperplasia, produces cytotoxic free radicals resulting in localized SMC eradication. However, this form of SMC injury does not induce an inflammatory or proliferative response in the vessel wall. This study investigated whether PDT-generated free radicals could inactivate cell-associated bFGF normally released with cell injury. METHODS: PDT of bovine SMC was performed in vitro with the photosensitizer CASPc (5 micrograms/ml) and 675 nm laser light using three different fluences: 10, 50, and 100 J/cm2. After PDT, SMC viability was determined with the tetrazolium salt (MTT) assay and cell-associated bFGF was quantitated by ELISA. A SMC mitogenesis assay was utilized to detect cell-associated bFGF activity released with SMC injury. RESULTS: In a dose-dependent manner, PDT-generated free radicals reduced cell-associated bFGF levels. After PDT with 100 J/cm2, cell-associated bFGF content was reduced by 88% (P < 0.0002). Of special interest was the finding that PDT with 10 J/cm2 significantly (P < 0.0002) reduced cell viability to around 50%, without affecting cellular bFGF levels. Consequently, a higher PDT dose (100 J/cm2) was needed to significantly (P < 0.001) inhibit the SMC mitogenic response associated with SMC injury. CONCLUSION: These results provide a mechanism to explain how, unlike mechanical or other forms of SMC injury, optimal doses of PDT can locally eradicate medial vascular SMC without resulting in a bFGF-induced initiation of cell proliferation.

Photodynamic therapy inactivates extracellular matrix-basic fibroblast growth factor: insights to its effect on the vascular wall.

PURPOSE: Photodynamic therapy (PDT), the light activation of photosensitizer dyes for the production of oxygen and other free radical moieties without the generation of heat, has been shown to inhibit the development of experimentally induced intimal hyperplasia. The host response to PDT, a form of vascular injury that results in complete vascular wall cell eradication, is devoid of inflammation and proliferation and promotes favorable vascular wall healing. These effects do not result in intimal hyperplasia and are suggestive of PDT-induced changes in the extracellular matrix (ECM). As a model to better understand the biologic consequences of PDT on the vascular wall matrix proteins, the effect of PDT was studied on the powerful matrix-resident mitogen basic fibroblast factor (bFGF) in vitro. METHODS: PDT (5 to 200 J/cm2, 100 mW/cm2, 675 nm) was used with the photosensitizer chloroaluminum sulfonated phthalocyanine (5 micrograms/ml) to inactivate bFGF in vitro while 100 J/cm2 of irradiation was administered 24 hours after 5 mg/ml of the photosensitizer was used in vivo. PDT was used on bFGF in solution and on endothelial cell-derived ECM. Enzyme-linked immunosorbent assay was used to quantitate bFGF in solution after PDT treatment or after extraction from the ECM by collagenase and heparin. Functional activity of matrix-associated bFGF was assessed by smooth muscle cell mitogenesis by 3H-thymidine incorporation. To demonstrate the in vivo relevance of these observations, immunohistochemical analysis of PDT-treated rat carotid arteries was undertaken. RESULTS: PDT eliminated detectable levels of bFGF in solution. PDT of ECM significantly reduced matrix-bound bFGF (1.0 +/- 0.6 vs 27.5 +/- 1.3 pg/ml; p < 0.0001). This reduction in bFGF after PDT of the ECM was associated with a decrease in vascular smooth muscle cell mitogenesis (52.4% +/- 4.6%; p < 0.0001) when plated on PDT-treated matrix compared with nontreated matrix. Quantitative replenishment of exogenous bFGF to PDT-treated matrix restored proliferation to baseline levels. PDT of rat carotid arteries demonstrated a loss of bFGF staining compared with control nontreated arteries. CONCLUSIONS: PDT inactivation of matrix-resident bFGF and possibly other bioactive molecules can provide a mechanism by which PDT suppresses smooth muscle cell proliferation in the vessel wall. This free radical-mediated alteration of matrix may contribute to favorable vascular healing when PDT is used for the inhibition of injury-induced intimal hyperplasia.

Photodynamic therapy inhibits transforming growth factor beta activity associated with vascular smooth muscle cell injury.

PURPOSE: The multifunctional cytokine, transforming growth factor beta 1 (TGF-beta), plays an important role in the development of injury-associated intimal hyperplasia (IH). Strategies to suppress local TGF-beta activity may have a clinical potential to prevent restenosis caused by IH. Photodynamic therapy (PDT) involves the local generation of cytotoxic free radicals by light activation of photosensitizer dyes and has been shown to inhibit experimental IH. This study investigated whether PDT-generated free radicals can affect TGF-beta activity in a biologic system using vascular smooth muscle cells (SMCs). METHODS: The release and activation of TGF-beta by injured SMCs in culture was compared between mechanical injury and PDT. Mechanical injury was induced with a rubber policeman, and PDT was performed with the photosensitizer chloroaluminum sulfonated phthalocyanine (5 micrograms/ml) and 675 nm laser light at subtherapeutic 10 J/cm2 and the in vivo therapeutic dose of 100 J/cm2. Cell viability was assessed by the tetrazolium salt conversion assay, and active and total (active + latent) TGF-beta was determined by enzyme-linked immunosorbent assay in the conditioned media of SMCs 24 hours after treatment. Functional TGF-beta activity was assessed by inhibition of endothelial cell mitogenesis. RESULTS: Both forms of injury severely reduced (p < 0.0005) SMC viability to less than 15%. In untreated SMC conditioned media, only 14.5% of the total TGF-beta was active (27.7 +/- 8.7 pg per 1 x 10(5) cells). However, after mechanical injury and PDT with 10 J/cm2, there was a significant increase (p < 0.02) in active TGF-beta (60.1 +/- 10.1 pg and 48.6 +/- 21.0 pg, respectively), despite a total reduction of approximately 50%. In contrast to this result, PDT with 100 J/cm2 did not result in increased levels of active TGF-beta (8.1 +/- 3.5 pg), despite having similar levels of total TGF-beta. Consequently, the conditioned media of SMCs that had 100 J/cm2 PDT did not inhibit endothelial cell mitogenesis as compared with the conditioned media of SMCs with mechanical injury and 10 J/cm2 PDT (p < 0.0002). CONCLUSIONS: This report describes two novel findings: (1) injury to SMCs in vitro induces the conversion of biologically latent TGF-beta to active TGF-beta; and (2) the therapeutic PDT dose interferes with this injury activation process. This study substantiates the concept of local cytokine inhibition by PDT in a biologic system and provides new insights into the mechanisms of PDT-mediated inhibition of experimental IH.

Photodynamic therapy of extracellular matrix stimulates endothelial cell growth by inactivation of matrix-associated transforming growth factor-beta.

Photodynamic therapy (PDT), the production of cytotoxic free-radical moieties by light activation of photosensitizer dyes, is a novel approach to inhibit experimental intimal hyperplasia. Local eradication of vascular cells with this method in vivo is followed by expedient reendothelialization, and PDT of extracellular matrix (ECM) in vitro stimulates endothelial cell (EC) growth. This in vitro study explored one possible mechanism underlying these findings by investigating the effects of PDT on matrix-associated transforming growth factor-beta (TGF-beta), a potent inhibitor of EC growth. The ECM deposited by EC on tissue culture plates contained 85.4 +/- 10.2 pg/10 cm2 of TGF-beta, as measured by an ELISA. In contrast, after PDT of ECM, levels of TGF-beta could be barely be detected (0.2 +/- 0.5 pg/10 cm2). The functional consequence of this observation was demonstrated by the finding that PD1 of plates coated with a fibronectin-TGF-beta complex stimulated EC mitogenesis (102.3% +/- 19.3%, p < 0.0005) compared with the untreated control (44.1% +/- 13.5%). The inhibitory effect of ECM-associated TGF-beta on EC was further delineated by blocking its activity with a specific antibody. Whereas the antibody did not affect EC mitogenesis or PDT-treated matrix or matrix-free plates (101% +/- 8.8%, 105.6% +/- 9.8%), EC mitogenesis growing on ECM was significantly enhanced (125.9%, 17.5%, p < 0.05). Finally, SDS-PAGE analysis of PDT-treated TGF-beta in solution demonstrated that the PDT-mediated loss of TGF-beta activity was not associated with changes in its molecular weight. These data demonstrate that increased EC proliferation on PDT-treated matrix is, at least in part, mediated by inactivation of TGF-beta. PDT-removal of this EC growth inhibitor in the intima provides a mechanism by which PDT of the vascular wall could potentiate endothelial regrowth, a factor which may promote proper healing and result in the inhibition of intimal hyperplasia.

Differential modulation of vascular endothelial and smooth muscle cell function by photodynamic therapy of extracellular matrix: novel insights into radical-mediated prevention of intimal hyperplasia.

PURPOSE: Photodynamic therapy (PDT) has been demonstrated to inhibit experimental intimal hyperplasia and to lead to expedient reendothelialization but negligible repopulation of the vessel media. The mechanism that underlies the differential ingrowth of cells into PDT-treated vessel segments is not understood. Because the extracellular matrix (ECM) is known to modulate specific cell functions, this study was designed to determine whether PDT of isolated ECM affects the function of endothelial cells (ECs) and smooth muscle cells (SMCs). METHODS: PDT of bovine aortic EC-ECM was performed with chloroaluminum sulfonated phthalocyanine and 675-nm laser light. Control specimens included untreated ECM, ECM-free plates, and ECM exposed to either light or photosensitizer only. Cell function was characterized by attachment, proliferation, and migration of ECs or SMCs that were plated onto identically treated matrixes. RESULTS: SMC attachment (86% +/- 0.4% vs 95% +/- 0.4%), proliferation (46% +/- 0.5% vs 100% +/- 1.4%), and migration (40% +/- 1.0% vs 100% +/- 0.9%) were significantly inhibited after PDT of ECM when compared with untreated ECM (all p < 0.001). In contrast, PDT of ECM significantly enhanced EC proliferation (129% +/- 6.2% vs 100% +/- 6.2%; p < 0.03) and migration (118% +/- 2% vs 100% +/- 0.8; p < 0.01), but did not affect attachment. CONCLUSIONS: This report establishes PDT-induced changes in the ECM with a result of inhibition of SMCs and stimulation of EC functions. It provides insight into how PDT-treated arteries can develop favorable EC repopulation without SMC-derived intimal hyperplasia. These findings may help provide a better understanding of the interactions between cells and their immediate environment in vascular remodeling.