Subcutaneous implants coated with tissue-engineered cartilage.

OBJECTIVE: To investigate the ability to coat two alloplastic implants, porous high-density polyethylene (PHDPE) and expanded polytetrafluoroethylene (e-PTFE), with tissue-engineered cartilage (TEC) from human septal chondrocytes in a mouse model. STUDY DESIGN: Prospective study. METHODS: PHDPE and e-PTFE disks were coated with alginate impregnated with human septal chondrocytes and implanted into athymic nude mice. A control group consisting of PHDPE and e-PTFE disks coated with alginate only were implanted. Gross, histological, and biochemical characteristics of the TEC constructs were examined at 10 and 20 weeks following implantation. RESULTS: One animal in the experimental group and one animal in the control group died. Implants coated with TEC were successfully generated in 18 (94.7%) mice in the experimental group (n = 19) and in zero (0%) of the control group (n = 17). The final weight of each harvested specimen decreased in the control group and increased in the experimental group, when compared with preimplant weight. Mean decrease in weight in the control group was greater at 20 weeks than at 10 weeks (P = .017). Mean increase in weight in the experimental group was greater at 20 weeks than at 10 weeks (P = .009). The diameter of the control group decreased, while the diameter of the experimental group was maintained. The reduction in diameter was less in the experimental group than in the control group at 10 (P = .018) and 20 weeks (P = .01). Gross and histological examination confirmed the formation of neocartilage, with characteristics similar to native cartilage, in the experimental group at 10 and 20 weeks. Glycosaminoglycan content in the experimental group at 20 weeks was approximately 80% of that measured in implanted human septal cartilage. Cartilaginous and fibrovascular ingrowth into implant pores was more extensive in the PHDPE than the e-PTFE experimental group. CONCLUSIONS: Implants coated with TEC from human septal cartilage can be reliably produced in the athymic nude mouse model. Maintenance of shape, as measured by the conservation of construct diameter, is possible. Fibrovascular ingrowth and cartilage formation into the pores of the alloplastic implants was observed. This integration of a construct composed of a synthetic implant coated with TEC may improve the performance of alloplastic implants through better long-term fixation and increased resistance to infection.

Injectable cartilage: using alginate and human chondrocytes.

OBJECTIVE: To create engineered cartilage through an injectable medium that could be used as a minimally invasive implant material. METHODS: Human nasal septal chondrocytes, carried in an alginate polymer, were injected and molded percutaneously into nude mice and developed in vivo. The cartilage was harvested from 14 to 38 weeks and analyzed through gross, histological, immunohistochemical, and biochemical analysis. RESULTS: Of the 15 explants, 14 (93%) resembled native cartilage on gross analysis. The injections maintained their overall appearance with some loss of definition. On histological analysis, 6 of the explants (40%) appeared similar to native cartilage throughout the sample. Eight of the explants (53%) resembled native cartilage; however, there were some areas of fibrous tissue differentiation. The neocartilage stained positive for type II collagen. Explants harvested at week 26 or later and the samples that histologically resembled native cartilage had similar hydroxyproline content to native septal cartilage. CONCLUSIONS: Injectable, autologous cartilage may be the answer to the long search for the ideal implant in facial plastic surgery. Alginate and human chondrocytes can be used to create an injection that may be molded and maintains its overall size and shape, with some loss of definition, for at least 38 weeks after injection.