In vitro engineering of cartilage.

Because adult human cartilage shows poor capacity for repair and regeneration, innovative solutions are required for congenital and acquired degenerative cartilage lesions. Acquired lesions occur in young and old alike, the former being more at risk for sports-related injuries and the latter for age-related degenerative changes. Because cartilage is a relatively simple tissue with respect to its cellular homogeneity and avascularity, it has been a model for research of in vitro engineered tissues. Progress has been slow and obstructed on several levels. The adult chondrocyte has limited capacity for proliferation and has both catabolic and anabolic functions. These metabolic features must be controlled in order for engineered tissue to endure. Use of three-dimensional scaffolds can be combined with regulatory factors (cytokine, extracellular matrix [ECM], and mechanical) to optimize conditions for in vitro engineered cartilage. Cross-disciplinary interactions are likely to accelerate progress and to mediate application of advances made in other fields for consistently successful in vitro engineering of cartilage for all clinical needs.