Bilirubin coating attenuates the inflammatory response to everolimus-coated stents

The aim of this study was to evaluate the effects of bilirubin- and/or everolimus (EVL)-coated stents to prevent arterial neointimal hyperplasia and inflammation in vitro and in vivo. The stents were prepared by spray coating bare metal stents (BMS) with bilirubin and/or EVL. Study groups were divided into (1) BMS, (2) bilirubin-coated stents (BES), (3) commercialized stents (Synergy™; EES), and (4) bilirubin/EVL-coated stents (B-EES). The coating thickness and drug release rates were comparable to previous reports (i.e., <4 µm thickness and 50% drug release in 7 days). Smooth muscle cell migration was inhibited in both EVL-containing groups (20.5 ± 3.80% in EES and 18.4 ± 2.55% in B-EES) compared to the non-EVL-containing groups (78.0 ± 6.41% in BMS and 76.1 ± 4.88% in BES) (n = 10, p < 0.05). Stents were randomly implanted to 40 coronary arteries in 20 pigs and subjected to various analyses after 4 weeks of implantation. As results, the inflammation score was dramatically increased in the EES group (2.1 ± 0.42) compared to that of the other groups (1.5 ± 0.55, 1.3 ± 0.23, and 1.5 ± 0.27 for BMS, BES, and B-EES, respectively, n = 10, p < 0.05). Immunofluorescence analysis revealed that inflammation was prevented in the bilirubin-containing groups (BES and B-EES). However, the percent area of restenosis was decreased in the EVL-containing groups (20.5 ± 4.11% for EES and 18.4 ± 3.61% for B-EES) compared to the non-EVL-containing groups (32.3 ± 6.41% for BMS and 29.6 ± 5.95% for BES, n = 10, p < 0.05). The percent areas of restenosis determined by histopathology, optical coherence tomography, and micro-computed tomography were consistent. In addition, the stent was barely covered in the EES and B-EES groups at 4 weeks postimplantation. These dual drug-coated stents may be especially beneficial to patients who have an increased risk of inflammation. These stents have great potential for use in cardiovascular applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1486-1495, 2018.