Modulation of bovine chondrocyte metabolism by free periosteal grafts in vitro.

PURPOSE: Autologous chondrocyte transplantation (ACT) is an established method in cartilage repair. Although long-term results show durable repair of isolated cartilage defects, some problems still remain. Since hypertrophy of the transplanted periosteum is a common problem, alternatives for periosteum are in demand. Periosteal grafts have been reported to stimulate neochondrogenesis via paracrine effects. The objective of this study was to evaluate the modulation of chondrocyte metabolism by periosteal grafts in vitro.

METHODS

Periosteal explants and articular chondrocytes obtained from slaughtered adult cattle were co-cultured in a newly established perfusion system. The experimental groups were: 1. monocultured chondrocytes; 2. chondrocytes cultured with synovial supernatants; 3. chondrocytes cultured with periosteal supernatants; 4. chondrocytes co-cultured with periosteal explants.

RESULTS

Chondrocyte proliferation, evaluated by measuring total DNA content, was prolongated by periosteal and synovial explants. Immunocytochemical staining of collagen type II was stronger in monoculture than in co-culture. Protein biosynthetic activity estimated by [³H]-proline incorporation, as well as extracellular matrix deposition for collagen type II, were reduced by periosteal and synovial explants. Additionally, co-culturing led to a decrease in aggrecan synthesis and release. The inhibiting effects were significantly stronger when cellular chondrocyte-periosteal cross-talk was made possible via paracrine effects.

CONCLUSIONS

The results of our study suggest a catabolic effect of periosteal explants on isolated chondrocytes in vitro. Further investigations are necessary whether periosteum in ACT is dispensable.