Autogenous tissue-engineered cartilage -: Evaluation as an implant material

Objectives: To determine whether autogenous tissue-engineered cartilage grafts can be synthesized in predetermined shapes, to compare tissue-engineered cartilage with native cartilage with respect to histological characteristics and biomechanical properties, and to demonstrate how multiple transplantations affect tissue-engineered cartilage. Design: Controlled, prospective animal study. Subjects: Twenty New Zealand white rabbits, 3 weeks old. Interventions: Autogenous chondrocytes were seeded onto biodegradable polyglycolic acid-poly-L-lactic acid copolymer templates in 1 of 3 shapes (cross, nasal tip graft, or auricle). Grafts and controls of sculpted cartilage were divided among 3 groups: short-term implantation (4 or 8 weeks), long-term implantation (6 or 12 months), and a reimplantation group. The gross morphological features, histological findings, and tensile strength of grafts were assessed. Results: Production of tissue-engineered cartilage was confirmed in 30 of 31 implants. Histological evaluation demonstrated characteristic cartilaginous matrix, but with prominent vascular and fibrous tissue ingrowth. In longterm implantation grafts (n = 4), foci of osteoid were evident by 6 months. In the subset of transplanted grafts (n = 7), 5 of 7 demonstrated significant loss of cartilage viability. Tensile strength measurements demonstrated values 24% and 41% of those of controls at 4 and 8 weeks, respectively. Conclusions: Tissue-engineered autogenous cartilage can be reliably produced, and predetermination of graft shape is possible. Histologically, grafts represent composites of mature cartilage infiltrated by vasculature and fibrous tissue, with delayed osteoid formation. Graft viability is compromised by early transplantation, and tensile strength is less than that of native cartilage. These results demonstrate the feasibility of tissue-engineered cartilage as a future graft material.