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.