The degradation of collagen in pig synovium in vitro and the effect of colchicine.

Colchicine induced a rapid destruction of the collagenous matrix of pig synovial explants in culture in the presence of serum. The most efficacious doses were 0.01-0.1 micrograms/ml (2.5 x 10(-8) M - 2.5 x 10(-7) M). The histological progression of the tissue breakdown induced by colchicine was very similar, although faster, to that described for other agents (Fell et al., 1986), with cells having basophilic nuclei accumulating in areas of fibril degradation. The loss of collagen correlated with an increase in collagenase production and at the peak of resorption (6 to 8 days) active collagenase was present in the culture media. Immunocytochemical methods demonstrated active collagenase bound to collagen fibrils after only 4 days in culture, before significant collagen degradation could be observed histologically. Collagen breakdown was completely inhibited by cortisol, and partially inhibited by indomethacin: only the inhibition by indomethacin could be reversed by exogenous prostaglandin E2. Vinblastine at a higher dose was as effective as colchicine but the lumicolchicines, which do not disrupt microtubules, were ineffective. Although the precise mechanism of action of colchicine is unknown, this culture system provides a useful in vitro model for increasing our understanding of the cellular mechanisms of tissue breakdown and for elucidating the roles of active collagenase and related metalloproteinases.