In this study we compared the plasma distribution and arterial accumulation of a photosensitizer, benzoporphyrin derivative (BPD), in two models of atherosclerosis: the spontaneous lesions of the Watanabe heritable hyperlipidemic (WHHL) rabbit and induced lesions of the balloon-injured, cholesterol-fed New Zealand white (NZW) rabbit. Selective uptake and retention of a photosensitizer by the abnormal portion of a vessel is a necessity in order for photodynamic therapy to become a successful modality for inhibition of intimal hyperplasia, selective removal of atherosclerotic tissue or imaging of diseased arteries, Liposome-based formulations were compared to freshly isolated native low density lipoprotein (LDL) and acetylated-LDL (Ac-LDL) as delivery vehicles for BPD, Plasma distribution of the photosensitizer was analyzed by KBr density gradient ultracentrifugation, Although the delivery vehicle influenced plasma distribution immediately postinjection, BPD subsequently partitioned according to the plasma concentration of the lipoproteins. Photosensitizer level in plaque and normal artery specimens was determined by ethyl acetate extraction and spectrofluorometric measurement. The measurement of BPD in normal and atherosclerotic arterial tissue demonstrated a selective accumulation in atherosclerotic tissue, Preassociation with LDL and Ac-LDL enhanced accumulation of BPD in atherosclerotic tissue when compared with normal artery (mean ratios of 2.8 and 4.1 were achieved, respectively), These results indicate that the preferential uptake of BPD by atherosclerotic plaque can be enhanced by preassociation with plasma lipoproteins, suggesting that light activation could lead to a highly selective destruction of diseased vascular tissue.

Photodynamic therapy has been recommended as a method of preventing intimal hyperplasia. The purpose of this study was to determine the dose and timing of Photoftin porfimer sodium needed to achieve a 3:1 or higher ratio between injured and control arteries after balloon endothelial injury. New Zealand White rabbits were anesthetized and their right femoral artery surgically exposed. A 4Fr Fogarty balloon catheter was passed retrograde into the lower abdominal aorta, inflated and pulled distally into the external iliac artery six times. All rabbits received heparin 100 IU/kg. Arteriotomies were closed and the animals recovered. Rabbits (n = 5 per group) were given intravenous Photofrin at a dose and time according to the following scheme: group I, 5.0mg/kg immediately after balloon injury; group II, 2.5mg/kg immediately after injury; group III, 5.0 mg/kg after 1 week; group IV, 5.0 mg/kg after 2 weeks; or group V, 2.5 mg/kg after 2 weeks. Animals were killed 24 h after drug administration and the aortoiliac segments removed for spectrophotofluorometric determination of Photofrin levels from injured and control segments. Mean(s.d.) ratios of injured: control arteries for groups I to V were 4.8 (2.6), 2.8 (1.2), 3.0 (1.0), 1.4 (0.3) and 1.0 (0.0) respectively. This ratio was significantly higher for group I rabbits compared with groups IV and V (P< 0.01, ANOVA). Fluorescence and light microscopy showed that Photofrin was localized primarily in the tunica media, and that the drug must be administered before significant intimal hyperplasia occurs. This study suggested that the Photofrin dose of 5 mg/kg given immediately or within 7-days of injury achieved at least a 3:1 ratio between injured to control arterial segments. Ratios based on this dose were significantly higher than those from rabbits who received Photofrin 2 weeks after endothelial injury.

The purpose of this study was to determine whether the addition of Photodynamic Therapy (PDT) using the photosensitizer Photofrin* (P*) following balloon angioplasty (BA) could prevent restenosis in an atherosclerotic animal model. Bilateral iliac atherosclerosis was created in 21 Yucatan miniswine. Six weeks later, P* 2.5 mg/kg was given IV 24 hours prior to BA (4 mm X 20 mm, 1 inflation). Following BA, swine were randomly allocated to receive PDT via a fiberoptic probe with laser energy or the same probe without laser energy. The fiberoptic probe had a 1 cm cylindrical diffusing tip and was passed co-axially through a custom catheter to ensure central location of the probe. A continuous wave argon ion-pumped dye laser tuned to 630 nm was used to provide a fluence of 100 J/cm2. Four weeks later, swine were sacrificed and vessels perfusion-fixed in-situ with glutaraldehyde and analyzed by ocular micrometry. Five occlusions occurred, all in the PDT + BA group. Percentage intimal thickness (mean +/- SD) was 51.0 +/- 29.5 in the BA group and 71.2 +/- 35.2 in the BA + PDT group (p equals 0.21). These results suggest that the addition of PDT following BA does not prevent restenosis.

Objective: To determine the feasibility of treating atherosclerotic stenoses with photodynamic therapy (PDT). Design: A prospective study with a 4-week follow-up. Subjects: Twelve Yucatan miniswine, weighing between 25 and 35 kg. Interventions: Aortoiliac atherosclerosis was created by a combination of balloon endothelial injury and dietary supplementation with 2% cholesterol and 15% lard for 7 weeks. Then the miniswine were given a porphyrin-type photosensitizer (Photofrin), 2.5 mg/kg intravenously, and treated with 630 nm light through an intravascular, cylindrical, diffusing fibreoptic probe, which was coupled to an argon-pumped dye laser to supply 120 J of laser energy. Main Outcome Measures: Differences in luminal narrowing before and after PDT. Results: Seven miniswine had an increase in luminal diameter, but five had no increase. Microscopy demonstrated a broad range of features in treated vessels, including areas with re-endothelialization and regions of platelet and blood cell adherence with absent or abnormal endothelium. Conclusion: Although this study demonstrated resolution in stenoses for some miniswine, questions concerning light dosimetry, mechanism of action and long-term effects remain to be determined.

Photodynamic therapy (PDT) represents a novel method of selectively treating atherosclerosis using a combination of photosensitizer drug, low power laser light, and molecular oxygen. In this preliminary study, PDT was used to treat atherosclerotic lesions in a miniswine model. Yucatan miniswine weighing between 20-30 kg, were rendered atherosclerotic by a combination of balloon endothelial injury and dietary supplementation with 2% cholesterol and 15% lard diet for 7 weeks. Following this, miniswine were given a porphyrin-type photosensitizer, Photofrin 2.5 mg/kg IV. Twenty-four hours after receiving Photofrin, swine received a general anesthetic and the infrarenal abdominal aorta was exposed. Through a longitudinal aortotomy, the posterior aortic wall was irradiated with 630 nm laser light at one of the following light doses: 60, 120, and 240 J/cm2. Four weeks after PDT, swine were killed and perfusion- fixed with glutaraldehyde. Light microscopy showed a decrease in intimal thickness for all light doses. Decreased cellular elements were seen in the irradiated zones as the laser power was increased. Non-irradiated sites showed typical atherosclerotic lesions with foam cells, fibrosis and calcification. This study demonstrated the feasibility of using PDT for atherosclerotic lesions.

The Yucatan miniswine has been recommended as an animal model of advanced atherosclerosis. Atherosclerotic plaques developed in this model demonstrate foam cells, widespread fibrosis, and calcification, features suggestive of human atherosclerosis. We have observed the occurrence of intraluminal projections that appear peculiar to this animal model. Forty-three miniswine, weighing between 20 and 30 kg, were rendered atherosclerotic with a combination of balloon endothelial injury of the aortoiliac segments and dietary supplementation with 2% cholesterol and 15% lard. Endothelial injury was created by retrograde balloon catheter injury of the aorta and both external iliac arteries via cutdowns on the femoral arteries. Serum cholesterol prior to starting the diet and at 1, 2, and 6 weeks following initiation of the diet was 2.0 +/- 0.4, 11.6 +/- 4.0, 15.9 +/- 5.0, and 16.4 +/- 4.2 mM, respectively (p < .0001, ANOVA). Angiographically significant lesions were apparent in 33 of 37 (89%) animals (occlusion 20/37, stenosis 17/37) at 6 weeks postinjury. In three of six (50%) animals followed up to 16 weeks postinjury, trabecular areas were seen in the external iliac arteries on angiography. Light and electron microscopy demonstrated that these areas were covered with normal endothelium and projected into the lumen or bridged with the adjacent arterial wall. Foam cells and calcification were not seen in these lesions. This finding is not typical of human atherosclerosis and appears peculiar to this type of animal model.

The purpose of this study was to assess Photofrin porfimer sodium (P*) concentration in atherosclerotic plaque (ASP) using a fluorescence detector (Fluoroprobe) compared with fluorescent photography and chemical extraction of P*. ASP was created in the aortoiliac segments of Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard diet for 7 weeks. At that time, swine were given P* I.V. in one of the following single dosages: Group I, 2.5; Group II, 1.0; or Group III, 0.5 mg/kg. Swine were sacrificed 24 hours later and aortoiliac and control carotid artery segments removed. Fluorescence was determined from these segments using photographic techniques, the Fluoroprobe, and a spectrofluorometer after chemical extraction. ASP were identified in all swine using photography and the Fluoroprobe. The intensity of fluorescence measured with the Fluoroprobe for Groups I to III was 1,098 +/- 524, 471 +/- 337, and 295 +/- 173 units, respectively (P < 0.01). The tissue concentration of P* in ASP from each group was 130.4 +/- 82.7, 10.0 +/- 1.2, and 9.1 +/- 0.6 ng/g, respectively (P < 0.01). There was a linear correlation between the fluorescence intensity measured with the Fluoroprobe and the extracted tissue concentration (r = 0.88, P < 0.0001). This study showed that a fluorescent detector such as the Fluoroprobe accurately detects the uptake of P* into atherosclerotic plaque.

Abstract— Befnzoporphyrin derivative(BPD) has been demonstrated to be fnew potent photosentsitze for photodynamic therapy(PDT). Althought most of wrok on BPD has been focused on its potential applications for cancer tratment, BPD amy have potential clilnical uses in the treatment of artheros clerosis. The purposes of this study was to determine in vitro and vivo uptake of BPD into atherosclerotic plaque. Samples of atherosclerotic human femoral and popliteal arteries were incubated with BPD‐monoacid, ring A(BPD‐MA) for 1 h in the following concentrations: 1, 5, 10, 20, 30 and 40 μg/mL. fluorescence from all samplesd was determined by chemical etraction with a spectrofluorometer. the tissue concentration for human arteries was 0.37 ± 0.03, 2.78 ± 1.5, 3.6 ± 1.91, 7.15 ± 2.36, 8.06 ± 3.09 and 14.6 ± 4.81 μg/g, respectively. In aeddition, three miniswine were rendered atherosclerotic and given BPD 2.0 mg/ Kg intravenously. The concentration of BPD‐MA in miniswine aorta was93–190 ng/g and the plaque/normal ration was 1.7–3.5, for miniswine cartoid artery contained 54 ng/g. this study showed that BPD‐MA was taken up in atherosclerotic vesselsd both in vitro and in vivo and mey have potential for PDT of atherosclerosis.