Antirestenotic effects of a locally delivered caspase inhibitor in a balloon injury model

Background - The precise role of arterial barotrauma-mediated apoptosis in causing restenosis is unclear. The purpose of this study was to determine if a link exists between angioplasty-mediated medial smooth muscle cell apoptosis and subsequent neointimal hyperplasia. Methods and Results - Bilateral iliac artery angioplasty was performed in 25 male New Zealand White rabbits. Simultaneous with balloon injury, each artery was treated locally with either the caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp(Ome)fluoromethylketone (ZVAD-fmk) or control. In the acute cohort that was survived to 4 hours (n = 10, 7 high dose and 3 low dose), an apoptotic index was calculated using the terminal deoxynucleotidyl TUNEL method. In the intermediate cohort that was survived to 2 weeks ( n = 5), luminal reendothelialization was measured via CD-31 staining. In the chronic cohort that was survived to 4 weeks ( n = 10), neointimal area was measured. In the acute cohort, there was a 40% reduction in the apoptotic index with high-dose ZVAD-fmk ( P = 0.008) and a 33% reduction with low-dose ZVAD-fmk ( P = 0.08). At 2 weeks, there was no significant difference in the degree of luminal reendothelialization. However, at 4 weeks, there was a 33% ( 0.33 +/- 0.23 versus 0.22 +/- 0.20 mm(2)) (P < 0.005) reduction in neointimal area in ZVAD-fmk-treated arteries. Conclusions - The local delivery of ZVAD-fmk during balloon injury inhibits smooth muscle cell apoptosis. This corresponds to a significant reduction in neointimal proliferation seen at 4 weeks without a significant change in the degree of reendothelialization at 2 weeks.