Philippe Amabile

Vascular endothelial growth factor enhances atherosclerotic plaque progression

Vascular endothelial growth factor (VEGF) can promote angiogenesis but may also exert certain effects to alter the rate of atherosclerotic plaque development. To evaluate this potential impact on plaque progression, we treated cholesterol-fed mice doubly deficient in apolipoprotein E/apolipoprotein B100 with low doses of VEGF (2 μg/kg) or albumin. VEGF significantly increased macrophage levels in bone marrow and peripheral blood and increased plaque area 5-, 14- and 4-fold compared with controls at weeks 1, 2 and 3, respectively. Plaque macrophage and endothelial cell content also increased disproportionately over controls. In order to confirm that the VEGF-mediated plaque progression was not species-specific, the experiment was repeated in cholesterol-fed rabbits at the three-week timepoint, which showed comparable increases in plaque progression.

High-Efficiency Endovascular Gene Delivery Via Therapeutic Ultrasound

OBJECTIVES We studied enhancement of local gene delivery to the arterial wall by using an endovascular catheter ultrasound (US). BACKGROUND Ultrasound exposure is standard for enhancement of in vitro gene delivery. We postulate that in vivo endovascular applications can be safely developed. METHODS We used a rabbit model of arterial mechanical overdilation injury. After arterial overdilation, US catheters were introduced in bilateral rabbit femoral arteries and perfused with plasmidor adenovirus-expressing blue fluorescent protein (BFP) or phosphate buffered saline. One side received endovascular US (2 MHz, 50 W/cm2, 16 min), and the contralateral artery did not. RESULTS Relative to controls, US exposure enhanced BFP expression measured via fluorescence 12-fold for plasmid (1,502.1+/-927.3 vs. 18,053.9+/-11,612 microm2, p < 0.05) and 19-fold for adenovirus (877.1+/-577.7 vs. 17,213.15+/-3,892 microm2, p < 0.05) while increasing cell death for the adenovirus group only (26+/-5.78% vs. 13+/-2.55%, p < 0.012). CONCLUSIONS Endovascular US enhanced vascular gene delivery and increased the efficiency of nonviral platforms to levels previously attained only by adenoviral strategies.

Inhibition of vascular endothelial growth factor-mediated neointima progression with angiostatin or paclitaxel.

PURPOSE Therapeutic angiogenesis represents a new paradigm for treatment of ischemic vascular syndromes. However, vascular endothelial growth factor (VEGF) enhances the rate and degree of plaque formation. This study evaluates the potential to block these effects nonspecifically with paclitaxel or specifically with angiostatin. MATERIALS AND METHODS Recombinant human VEGF(165) (rhVEGF) was administrated intramuscularly (2-microg/kg single injection) in combination with adventitial delivery of paclitaxel, angiostatin, or vehicle alone at the site of femoral arterial balloon overdilation injury in New Zealand White rabbits (n = 5 per treatment). Five additional animals with no rhVEGF and no adventitial delivery served as procedural controls. All rabbits were fed according to a 0.25% cholesterol diet beginning 28 days before angioplasty. Treated arteries were harvested after 7 days and evaluated to determine intima-to-media (I/M) ratios, macrophage infiltrate, and endothelial cell density. RESULTS On histologic analysis, the rhVEGF/gel control group exhibited a mean I/M ratio of 0.337 +/- 0.028, a 77% increase over procedural controls, which exhibited a mean I/M of 0.190 +/- 0.010. rhVEGF/paclitaxel reduced I/M ratios to 0.151 +/- 0.007. In contrast, specific antiangiogenic therapy (rhVEGF/angiostatin) reduced I/M ratios to 0.032 +/- 0.003, a 91% decrease relative to rhVEGF/gel and an 83% decrease relative to procedural controls (P =.001 for each comparison). Local macrophages and endothelial cells also decreased with treatment. CONCLUSIONS This study shows that paclitaxel and angiostatin each afford local protection against rhVEGF-mediated increases in neointima. Angiostatin further prevents progression of underlying neointima. These local therapies may allow broader use of therapeutic angiogenesis while avoiding and treating potentially undesirable effects.

Conservative Treatment of Spontaneous and Isolated Dissection of Mesenteric Arteries

BACKGROUND Isolated and spontaneous dissection of mesenteric arteries is a rare entity; a little more than 50 cases have been reported in medical literature. There is no therapeutic consensus concerning this type of lesion. METHODS In this study, we report the results of our treatment based on a conservative approach. This retrospective study concerns eight patients with dissection of the celiac trunk and/or of the upper mesenteric artery (UMA) who were treated between 2002 and 2006. Because these patients were not presenting with acute intestinal ischemia diagnosed by clinical examination or paraclinical tests (medical imaging/biology) or with vital complications, they were treated with an efficient anticoagulation (heparin followed by anti-vitamin K) for 3 to 6 months. Endovascular or surgical treatment was used as the first option in patients with obvious intestinal ischemia or likely to have an arterial rupture, and also when medical treatment had failed. Clinical and radiological follow-up was at 1 month, 3 months, 6 months, and 1 year and then every year. Seven men and one woman (mean age, 48.2; age range, 38-53 years) were treated. Six patients presented with isolated dissection (celiac trunk=4, UMA=2). One patient had a celiac trunk and a UMA dissection and one had a celiac trunk and a UMA dissection along with a dissection of his two renal arteries. On entering the hospital, a patient was operated on for mesenteric ischemia related to a stenosis of the upper mesenteric artery (upper aortomesenteric bypass); a covered stent was implanted in the celiac trunk of another patient presenting with a contained rupture. RESULTS Both patients were successfully treated. Six patients were medically treated. One of them required an aortohepatic bypass to treat an aneurysmal evolution of the celiac trunk revealed by a computed tomography scan obtained 1 month after the symptoms had begun. In one patient, the dissection remained stable on imaging. Four patients were cured, with a mean 20.1-month follow-up. CONCLUSION Conservative treatment of spontaneous dissections of mesenteric arteries is possible when there are no complications, and it gives satisfactory results provided regular clinical and radiological checking is performed.

In Vivo Vascular Engineering: Directed Migration of Smooth Muscle Cells to Limit Neointima

Pathologic neointima formation requires directional smooth muscle cell (SMC) migration from media to intima. The very direction of SMC migration thus becomes a potential therapeutic target. Here, we hypothesize that proliferating SMC after injury can be redirected using engineered chemotactic gradients of elastin degradation to limit late pathologic neointima formation. Buffered bioerodible polymeric microspheres (MS) were constructed to provide 4-week sustained release of elastase, heat-killed elastase, or polymer only. In vitro elastase function and timecourse of release at 37 degrees C, physiologic pH, and shear was determined. Curves revealed an initial bolus followed by sustained linear release for elastase MS, while controls exhibited baseline hydrolysis of substrate. We then employ controlled perivascular release of elastase after angioplasty to engineer modified in vivo gradients of elastin degradation in rabbit femoral arteries. NZW rabbits (n = 8 each) underwent balloon angioplasty of the common femoral artery followed by perivascular distribution of MS. Significant early perivascular elastin degradation resulted. Concurrently, proliferating SMC were guided peripherally (further from lumen) with treatment without significant changes in total proliferation or inflammation. At 28 days, treatment significantly reduces neointima by 42% relative to controls. These results confirm that directionally guiding SMC responses after injury achieves favorable arterial remodeling and limits development of pathologic neointima. Thus, a potential class of therapeutics and the paradigm of in vivo vascular engineering emerge from this work.

In vivo vascular engineering of vein grafts: Directed migration of smooth muscle cells by perivascular release of elastase limits neointimal proliferation

PURPOSE Saphenous vein bypass grafting for coronary revascularization procedures remains limited by accelerated neointima formation. It was hypothesized that creation of a modified chemotactic gradient in vivo could guide migration of smooth muscle cells (SMCs) peripherally instead of in a luminal direction and reduce intimal hyperplasia during vein graft arterialization. MATERIALS AND METHODS Surgical bypass vein grafting to femoral arteries was performed in adult male New Zealand White rabbits (n = 8 per treatment group; five for 7 d and three for 28 d). Controlled-release microspheres delivering elastase or buffered polymer only were administered perivascularly at the vein graft site. At 7 days, five vein grafts per group were harvested and cross-sections were immunostained with anti-proliferating cell nuclear antigen (PCNA) to determine the number and distribution of proliferating SMCs. At 28 days, three vein grafts per group were harvested and intima-to-media (I/M) ratios were calculated after staining with Verhoeff von Gieson-Masson trichrome stain. RESULTS Significant early outward-directed elastin degradation resulted from elastase treatment. Concurrently, proliferating SMCs migrated peripherally. PCNA(+) cells in the outer half of the wall increased 2.37 fold compared to procedural controls (P <.0001). Directional shifts in SMC migration underlie these results because overall SMC proliferation was not significantly different. At 28 days after vein graft surgery, a 38% reduction (P =.0008) in neointima was observed relative to procedural controls. CONCLUSION Directional guidance of SMC responses through perivascular elastase release achieves favorable vein graft remodeling characteristics, including limited neointima development. This represents practical evidence that SMC migration can be directionally guided in vivo in a vein graft model and that plaque progression can be prevented by redistributing elastin without decreasing functional vein graft wall stability.

Perivascular Release of Insulin-like Growth Factor-1 Limits Neointima Formation in the Balloon-injured Artery by Redirecting Smooth Muscle Cell Migration

PURPOSE Insulin-like growth factor-1 (IGF-1) is a potent chemoattractant to vascular smooth muscle cells (SMCs). The authors hypothesize that perivascular release of IGF-1 in vivo can direct migration of SMCs away from the lumen and reduce neointima formation in a rabbit model of arterial balloon injury. MATERIALS AND METHODS Balloon angioplasty of the common femoral arteries was performed in adult male New Zealand White rabbits (n = 8 per treatment group) and controlled release microspheres delivering either IGF-1 or blank control treatment were implanted perivascularly at the angioplasty site prior to surgical closure. At 7 days, five arteries per group were harvested and cross-sections were subjected to anti-PCNA (proliferating cell nuclear antigen) immunostaining to determine the number and distribution of proliferating SMCs. At 28 days, the remaining three arteries per group were harvested and sections were evaluated for intima-to-media (I/M) ratios by means of VVG-Masson staining. One-way analysis of variance with Fisher protected least significant difference post hoc testing was used to determine statistical significance at P < .05. RESULTS At 7 days, PCNA(+) medial SMCs assumed a significantly more peripheral (ie, further from lumen) distribution in the vessel wall with use of perivascular IGF-1 than with use of blank treatment (P < .05). Overall SMC proliferation was not significantly different, thus the change in distribution was likely due to directionally altered SMC migration. At 28 days, perivascular IGF-1 significantly decreased I/M ratios by 44% relative to control treatment (P < .05). CONCLUSIONS Perivascular release of IGF-1 can directionally guide SMC migration away from the lumen and reduce neointima in the balloon-injured artery. This novel strategy might have implications in the development of antirestenosis therapies.

Development of a Platform to Evaluate and Limit in-Stent Restenosis

The objective of this work was to develop a platform to evaluate and deliver putative therapeutic agents for in-stent restenosis. Arterial stenting is applied in more than 60% of balloon angioplasties for treating cardiovascular disease. However, stented arteries encounter accelerated rates of restenosis. No prior platform has allowed evaluation or local management of in-stent restenosis without perturbing the very system being examined. A stainless steel, balloon-expandable stent was modified to serve as an ablumenal drug delivery platform. Several combinations of bioerodible polymer microspheres and gels were evaluated for channel retention under in vitro flow and in vivo conditions. A stent-anchored hybrid system prevented material embolization under all conditions. Unlike prior platforms, these stents do not alter local inflammation or in-stent plaque formation relative to conventional Palmaz-Schatz stents after in vivo deployment. The system also proved sensitive enough to detect plaque reduction with an antirestenotic agent. We conclude that a platform to evaluate and deliver therapeutic agents for in-stent restenosis has been achieved.

Directed Migration of Smooth Muscle Cells to Engineer Plaque-Resistant Vein Grafts

Purpose: To test the hypothesis that controlled perivascular release of tissue plasminogen activator (tPA) can generate cleaved extracellular matrix (ECM) chemotactic gradients to guide the migration of vascular smooth muscle cells (SMCs) away from the lumen, thereby limiting neointima formation. Methods: This hypothesis was tested in rabbit models in which the perivascular surface of vein bypass grafts was treated with microspheres releasing tPA (MS-tPA), microspheres containing no drug (MS-blank), or phosphate buffered saline (PBS). Vein graft segments harvested after 7 days were then evaluated for elastin content, proliferating SMCs, intima-to-media (I/M) ratio, and inflammation; late impact on neointima formation was also examined. Results: The 7-day results demonstrated cleaved elastin gradients and proliferating SMCs that assumed a more peripheral distribution in the MS-tPA group than MS-blank and PBS controls (p < 0.05). At 28 days, vein grafts treated with MS-tPA showed a mean I/M ratio (0.35±0.04) that was 63.5% lower than PBS controls (0.96±0.07, p < 0.005) and 43.5% lower than MS-blank specimens (0.62±0.08, p < 0.05). Conclusions: Perivascular release of tPA modifies ECM gradients, directionally guides SMC migration away from the lumen, and limits neointima formation.

Management of an aortoesophageal fistula caused by Kirschner wire migration in a patient with arteria lusoria

From the Thoracic Surgery Department, Hopital Nord, Marseille, France; and the Vascular Surgery Department, Hopital de la Timone, Marseille, France. Disclosures: Authors have nothing to disclose with regard to commercial support. Received for publication Feb 2, 2012; revisions received April 10, 2012; accepted for publication May 9, 2012; available ahead of print June 7, 2012. Address for reprints: Philippe Amabile, MD, Aix-Marseille Univ, 13284 Marseille, France and APHM, Department of Vascular Surgery, Hopital de la Timone, 13385 Marseille, France (E-mail: philippe.amabile@ap-hm.fr). J Thorac Cardiovasc Surg 2012;144:e25-7 0022-5223/