Abstract 17559: Ultra-Early Endothelialization of Biolimus A9 With Bioresorbable Polymer Stent (Nobori ^® ) in Porcine Coronary Model: Possible Mechanism for Low Frequency of In-stent Thrombosis and Restenosis

Background: The stent with biolimus A9 coated by a bioresorbable polymer (Nobori ® ) has the potential to reduce thrombosis by degradation of polymer over the period. However, few data exist regarding the vessel response and endothelialization at ultra-early phase after its implantation. Therefore, we examined ultra-early endothelialization of Nobori ® in porcine model. Methods and Results: Fifteen Nobori ® and 14 control bare-metal stents (S-Stent TM ) were implanted in 12 swine (mean weight 31.9 kg). Histopathological evaluation of stented segments were performed at 2 and 14 days after implantation. Morphometric analysis of the inflammation (graded as score 0 to 3) and the intimal fibrin content (graded as score 1 to 3) was also assessed. At 14 days, neointimal thickness and % neointimal area, defined as 100 х neointimal area / stent area, were significantly lower in Nobori ® than in S-Stent TM (51.4 ± 5.9 μm vs 76.4 ± 9.6 μm, p < 0.05 and 11.2 ± 1.1 % vs 15.7 ± 1.3 %, p < 0.01, respectively). Importantly, there were no significant differences in these parameters between 2 groups at 2 days (17.3 ± 6.1 μm vs 26.7 ± 6.1 μm, p = NS and 3.8 ± 1.3% vs 6.9 ± 1.7%, p = NS, respectively). Under these conditions, stent surface endothelialization evaluated by scanning electron microscope at 2 days showed similar appearance of endothelial coverage above the struts in Nobori ® compared with S-Stent TM (Figure). Furthermore, there were no significant differences in inflammatory (1.3 ± 0.1 vs 1.3 ± 0.1, p = NS) and intimal fibrin content (2.5 ± 0.1 vs 2.3 ± 0.1, p = NS) scores. Conclusion: These results demonstrated that endothelialization could occur at ultra-early phase after Nobori ® implantation with similar inflammatory reaction to bare-metal stent, probably contributing to low frequency of in-stent thrombosis and restenosis. The use of Nobori ® may have a potential benefit even at early phase before the degradation of polymer as well as long-term benefit.