Tissue engineered cartilage "bioshell" protective layer for subcutaneous implants

One current technique to reconstruct an ear for microtia involves the use of a high density polyethylene auricular implant; however, the implant can extrude if not covered in a temporoparietal fascia flap. Theoretically, an autologous tissue engineered cartilage "bioshell" protective coating around a permanent biocompatible implant might reduce potential extrusion to avoid the flap requirement. We hypothesized that if subjected to intentional exposure, a bioshell coating over an implant would provide enhanced wound healing.

Six sheets of high density polyethylene and six sheets of 24 carat pure gold wire-mesh measuring 19 mm x 25 mm were implanted subcutaneously in an immunocompetent swine model. Half of each implant group were coated with chondrocytes (50-70 million cells/cm(3)) which were suspended in Pluronic F-127 30% hydrogel; the remaining implants without chondrocytes were used as controls. At 10 weeks post-implantation, partial implant exposure via excision of overlying skin was performed to simulate extrusion and the sites were allowed to heal secondarily.

All (6/6) of bioshell implants achieved wound closure after exposure by the seventh post-operative day; controls achieved closure at approximately 10 days. Bioshell neocartilage was evaluated and confirmed histologically using hematoxylin and eosin and safranin O stains. Histochemically, neocartilage approximated native cartilage with 60% glycosaminoglycans content.

A 'proof-of-principle' tissue engineered bioshell around subcutaneous high density polyethylene and gold implants generated an elastic neocartilage coating, elicited a low inflammatory reaction, and was associated with 30% faster wound healing.