Internal support of tissue-engineered cartilage

Background: Auricles previously created by tissue engineering in nude mice used a biodegradable internal scaffold to maintain the desired shape of an ear. However, the biodegradable scaffold incited a compromising inflammator y response in subsequent experiments in immunocompetent animals. Objective: To test the hypothesis that tissue-engineered autologous cartila ge can be bioincorporated with a nonreactive, permanent endoskeletal scaffo ld. Materials and Methods: Auricular elastic cartilage was harvested from Yorks hire swine. The chondrocytes were isolated and suspended into a hydrogel (P luronic F-127) at a cell concentration of 5 x 10(7) cells/mL. Nonbiodegrada ble endoskeletal scaffolds were formed with 1 of 5 polymers: (1) high-densi ty polyethylene, (2) soft acrylic, (3) polymethylmethaclylate, (4) extrapur ified Silastic, and (5) conventional Silastic. Three groups were studied: ( 1) a control group using only the 5 polymers, (2) the 5 polymers enveloped by Pluronic F-127 only, and (3) the implants coated with Pluronic F-127 see ded with chondrocytes. All constructs were implanted subdermally; implants containing cells were implanted into the same animal from which the cells h ad been islolated. The implants were harvested after 8 weeks of in vivo cul ture and histologically analyzed. Results: Only implants coated by hydrogel plus cells generated healthy new cartilage. With 3 polymers (high-density polyethylene, acrylic, and extrapu rified Silastic), the coverage was nearly complete by elastic cartilage, wi th minimal fibrocartilage and minimal to no inflammatory reaction. The Food and Drug Administration-approved conventional Silastic implants resulted i n fragments of fibrous tissue mixed with elastic cartilage plus evidence of chronic inflammation. The polymethylmethacrylate implant was intermediate in the amount of cartilage formed and degree of inflammation. Conclusions: This pilot technique combining tissue-engineered autologous el astic cartilage with a permanent biocompatible endoskeleton demonstrated su ccess in limiting the inflammatory response to the scaffold, especially to high-density polyethylene, acrylic, and extrapurified Silastic. This model facilitates the potential to generate tissue of intricate shape, such as th e human ear, by internal support.