Vascular Response Toward an Absorbable Sirolimus-eluting Polymeric Scaffold for Vascular Application in a Model of Normal Porcine Carotid Arteries.

Abstract Backround: Fully absorbable polymeric scaffolds, as a potential alternative to permanent metallic stents, are entering the clinical field. The aim of this study is to assess the in-vivo biocompatibility of a novel Sirolimus-eluting (SIR) absorbable scaffold based on poly(L-lactide) (PLLA) and poly(4-hydroxybutyrate) (P4HB) for interventional application. Methods: Absorbable PLLA/P4HB scaffolds either loaded with SIR coating or unloaded scaffolds were implanted interventionally into common carotid arteries (CCA) of 14 female. Bare metal stents (BMS) served as control. Peroral dual anti-platelet therapy was administered throughout the study. Stented CCA segments were explanted after four weeks, and assessed histomorphometrically. Results: The absorbable scaffolds showed a decreased residual lumen area and higher stenosis after four weeks (PLLA/P4HB: 6.56 ± 0.41 mm² and 37.56 ± 4.67%; SIR-PLLA/P4HB: 6.90 ± 0.58 mm² and 35.60 ± 3.15%) as compared to BMS (15.29 ± 1.86 mm² and 7.65 ± 2.27%). Incorporation of SIR reduced the significantly higher inflammation of unloaded scaffolds however not to a level compared to bare metal stent (PLLA/P4HB: 1.20 ± 0.19; SIR-PLLA/P4HB: 0.96 ± 0.24; BMS: 0.54 ± 0.12). In contrast, the BMS showed a slightly elevated vascular injury score (0.74 ± 0.15), as compared to the PLLA/P4HB (0.54 ± 0.20) and the SIR-PLLA/P4HB (0.48 ± 0.15) groups. Conclusion: In this preclinical model, the new absorbable polymeric (SIR-) scaffolds showed similar technical feasability and safety for vascular application as the permanent metal stents. The higher inflammatory propensity of the polymeric scaffolds was slightly reduced by SIR-coating. A smaller strut thickness of the polymeric scaffolds might have been a positive effect on tissue ingrowth between the struts and needs to be addressed in future work on the stent design.