Conventional Platinum Metal Implants Provoke Restenosis Responses in Atherogenic but Not Healthy Arteries

Platinum-containing stents are commonly used in humans with hypercholesterolemia, whereas preclinical stent evaluation has commonly been performed in healthy animal models, providing inadequate information about stent performance under hypercholesterolemic conditions. In this investigation, we used an ApoE^−/− mouse model to test the impact of hypercholesterolemia on neointima formation on platinum-containing implants. We implanted 125 μm diameter platinum wires into the abdominal aortas of ApoE^−/− and ApoE^+/+ mice for 6 months, followed by histological and immunofluorescence examination of neointimal size and composition. It was found that ApoE^−/− mice developed neointimas with four times larger area and ten times greater thickness than ApoE^+/+ counterparts. Neointimas developed in the ApoE^−/− mice also contained higher amounts of lipids quantified as having 370 times more coverage compared to ApoE^+/+, a 3-fold increase in SMCs, and a 22-fold increase in macrophages. A confluent endothelium had regenerated in both mouse strains. The ApoE^−/− mice experienced luminal reductions more closely resembling clinically relevant restenosis in humans. Overall, the response to platinum arterial implants was highly dependent upon the atherogenic environment.