Influence of synovial cells on cartilage in vitro: induction of breakdown and inhibition of synthesis.

Organoid or high density cultures of: (1) synovial cells from patients with rheumatoid arthritis, and (2) prechondrogenic mesenchymal cells from limb buds of 12-day-old mouse embryos, were co-cultured for 7-10 days using the Trowell culture system. Depending on the time of commencing co-cultivation, chondrogenesis was inhibited (co-cultivation from the start) or the cartilaginous matrix was partly degraded (co-cultivation after formation of embryonic cartilage, i.e. on day 4). These effects were obtained with cells from synovial fluid as well as from synovial tissue. Matrix degradation and the behaviour of the different cell types could be demonstrated well by electron microscopy under the in vitro conditions applied.