Evaluation of a sphere-templated polymeric scaffold as a subcutaneous implant.

OBJECTIVE: To evaluate the performance of a sphere-templated poly(2-hydroxyethyl methacrylate) (poly[HEMA]) tissue scaffold as a subcutaneous implant by comparing it with widely used high-density porous polyethylene (HDPPE) implant material. DESIGN: We implanted sphere-templated porous poly-(HEMA) and HDPPE disks into the dorsal subcutis of C57BL/6 mice for 4 and 9 weeks. Excisional biopsy specimens of the implants and surrounding tissue were assessed for host inflammatory response, tissue ingrowth, and neovascularization using trichrome, picrosirius red, and anti-endothelial cell antibody staining. RESULTS: The poly(HEMA) and HDPPE implants showed resistance to extrusion and elicited a minimal inflammatory response. Both implants supported cellular and collagen ingrowth, but ingrowth within the HDPPE implant was thicker owing to the larger porous structure (>100 µm) of HDPPE, whereas the poly(HEMA) implant had much thinner collagen fibrils within much smaller (40-µm) pores, suggestive of less scar-type reaction. Neovascularization was supported by both implants. Blood vessels were identified within the fibrous ingrowth of the HDPPE and within individual pores of the poly(HEMA). CONCLUSIONS: Sphere-templated poly(HEMA) implanted as a subcutaneous tissue scaffold stimulates a minimal inflammatory response and supports cellular infiltration, collagen formation, and neovascularization. Because of its tightly controlled porous structure, poly-(HEMA) appears to induce less scar-type ingrowth compared with HDPPE.