Investigation of long-term implantation of BuMA stent in a porcine coronary model

Background Stent-based delivery of sirolimus has been shown to reduce neointimal hyperplasia significantly. However, the long-term effect of the polymer is thought to initiate and sustain an inflammatory response and contribute to the occurrence of late complications. Our study aimed to evaluate the efficacy and safety of the BuMA biodegradable drug-coated sirolimus-eluting stent (BSES) for inhibiting neointimal hyperplasia in a porcine coronary model. Methods Four types of stents were implanted at random in different coronary arteries of the same pig: BSES (n=24), bare metal stent (BMS) (n=24), biodegradable polymer coated stent without drug (PCS) (n=24) and only poly (n-butyl methacrylate) base layer coated stent (EGS) (n=23). In total, 26 animals underwent successful random placement of 95 oversized stents in the coronary arteries. Coronary angiography was performed after 28 days, 90 days and 240 days of stent implantation. After 14 days, 28 days, 90 days and 240 days, 6 animals at each timepoint were sacrificed for histomorphologic analysis. Results The 28-day, 90-day and 240-day results of quantitative coronary angiography (QCA) showed reduction in luminal loss (LL) in the BSES group when compared with the BMS group; (0.20 +/- 0.35) mm vs. (0.82 +/- 0.51) mm (P=0.035), (0.20 +/- 0.30) mm vs. (0.93 +/- 0.51) mm (P=0.013), and (0.18 +/- 0.16) mm vs. (0.19 +/- 0.24) mm (P=0.889), respectively. By 28-day, 90-day and 240-day histomorphomeric analysis results, there was also a corresponding significant reduction in neointimal tissue proliferation with similar injury scores of BSES compared with the BMS control; average neointimal area (0.90 +/- 0.49) mm(2) vs. (2.16 +/- 1.29) mm(2) (P=0.049), (1.53 +/- 0.84) mm(2) vs. (3.41 +/- 1.55) mm(2) (P=0.026), and (2.43 +/- 0.95) mm(2) vs. (3.12 +/- 1.16) mm(2) (P=0.228), respectively. High magnification histomorphologic examination revealed similar inflammation scores and endothelialization scores in both the BSES and BMS groups. Conclusions The BuMA biodegradable drug-coated sirolimus-eluting stents can significantly reduce neointimal hyperplasia and in-stent restenosis. Re-endothelialization of the BuMA stent is as good as that of the BMS in the porcine coronary model due to the reduced inflammation response to the BuMA stent. Chin Med J 2012;125(22):4083-4087