Cocultures of adult and juvenile chondrocytes compared with adult and juvenile chondral fragments: in vitro matrix production.

BACKGROUND: The use of allogenic juvenile chondrocytes or autologous chondral fragments has shown promising laboratory results for the repair of chondral lesions. HYPOTHESIS: Juvenile chondrocytes would not affect matrix production when mixed with adult chondrocytes or cartilage fragments. STUDY DESIGN: Controlled laboratory study. METHODS: Cartilage sources consisted of 3 adult and 3 juvenile (human) donors. In part 1, per each donor, juvenile chondrocytes were mixed with adult chondrocytes in 5 different proportions: 100%, 50%, 25%, 12.5%, and 0%. Three-dimensional cultures in low-melt agarose were performed. At 6 weeks, biochemical and histologic analyses were performed. In part 2, isolated adult, isolated juvenile, and mixed 3-dimensional cultures (1:1) were performed with chondral fragments (<1 mm), both with low-melt agarose and a hyaluronic acid scaffold. At 2 and 6 weeks, cultures were evaluated with biochemical and histologic analyses. RESULTS: Part 1: Biochemical and histologic analyses showed that isolated juvenile cultures performed significantly better than mixed and isolated adult cultures. No significant differences were noted between mixed cultures (1:1) and isolated adult cultures. Part 2: Biochemical and histologic results at 6 weeks showed that mixed cartilage fragment cultures performed better than isolated adult cultures in terms of proteoglycans/DNA ratio (P = .014), percentage of safranin O-positive cells (P = .012), Bern score (P = .001), and collagen type II. No statistically significant difference was noted between juvenile and mixed cultures. CONCLUSION: Extracellular matrix production of juvenile chondrocytes is inhibited by adult chondrocytes. The addition of juvenile cartilage fragments to adult fragments improves matrix production, with a positive interaction between the 2 sources. CLINICAL RELEVANCE: Even if the underlying mechanisms are still unknown, this study describes the behavior of juvenile/adult cocultures using both chondrocytes and cartilage fragments, with potential for new research and clinical applications.