Vascular Response After Stenting of the Renal Arteries in Pigs Using an Absorbable Sirolimus-Eluting Polymer Scaffold

This study aims to assess the technical feasibility and biocompatibility of interventional application of a fully absorbable stent in renal arteries (RAs) of healthy pigs.

Absorbable poly(L-lactide) (PLLA)/poly(4-hydroxybutyrate) scaffolds either loaded with sirolimus (SIR) coating or unloaded and permanent bare metal stents (BMSs) served as control were implanted interventionally into RAs of 16 female pigs via the left common iliac artery (8F-sheath). Peroral dual antiplatelet therapy was administered throughout the study. Stented RA segments were explanted after 4 weeks and assessed histomorphometrically.

The polymer scaffolds showed a decreased residual lumen area and higher stenosis after 4 weeks (unloaded PLLA-based: 6.5 ± 1.0 mm² and 44.1 ± 7.4%; SIR-PLLA-based: 8.6 ± 0.5 mm² and 32.7 ± 0.7%) compared to BMS (11.8 ± 4.3 mm² and 23.0 ± 4.5%). Incorporation of SIR reduced the significantly higher inflammation of unloaded scaffolds; however, not to a level compared to BMS (unloaded PLLA-based: 1.3 ± 0.3; SIR-PLLA-based: 0.9 ± 0.3; BMS: 0.5 ± 0.1). In contrast, BMS showed a slightly elevated vascular injury score (0.8 ± 0.1) compared to the unloaded PLLA-based (0.6 ± 0.2) and the SIR-PLLA-based (0.4 ± 0.04) groups.

Absorbable scaffolds showed sufficient mechanical stability after porcine RA stenting. By incorporation of SIR, a significant reduction of the inflammatory and neointimal response to the unloaded polymer scaffolds was seen without systemic toxicity or thrombotic complications. However, the greater strut height of the polymer scaffold is a major limitation and need to be addressed in future work on the stent design.