Permanent and biodegradable polymer coatings in the absence of antiproliferative drugs in a porcine model of coronary artery stenting

Aims: The purpose of the present study was to examine the comparative vascular healing response to stents coated with permanent or biodegradable polymer and uncoated stents in a porcine model of coronary artery stenting. Methods and results: Juvenile pigs were randomly allocated to implantation of stents coated with permanent polymer (PP, methacrylate-based, n=10), biodegradable polymer (BP, poly-lactic acid-based, n=10) or bare metal control stents (n=10), in the absence of antiproliferative drugs. At 28 days, animals were sacrificed and specimens prepared for histopathologic assessment. Endothelialisation was complete in all treatment groups. Vascular injury at 28 days was greater in PP stents as compared with uncoated stents (p=0.05) though not as compared with BP-coated stents (p=ns). PP stents showed increased inflammatory scores compared with BP-coated (p=0.03) and uncoated stents (p=0.02). There was also greater neointimal growth with PP-coated stents compared with uncoated stents (p=0.02). Conclusions: In the absence of antiproliferative drugs, stents coated with methacrylate-based PP, but not with poly-lactic acid-based BP, provoked significant vessel wall inflammatory reactions resulting in greater vascular injury and increased neointimal growth compared with uncoated stents. Biodegradable polymer coatings may be considered preferable to facilitate drug elution with minimal vessel wall toxicity.