Outgrowth of chondrocytes from human articular cartilage explants and expression of alpha-smooth muscle actin

The objectives of this study were to investigate the effect of various enzy matic treatments on the outgrowth of chondrocytes from explants of adult hu man articular cartilage and the expression of a specific contractile protei n isoform, alpha -smooth muscle actin, known to facilitate wound closure in other connective tissues. Explants of articular cartilage were prepared fr om specimens obtained from patients undergoing total joint arthroplasty. Th e time to cell outgrowth in vitro was determined and the expression of or-s mooth muscle actin shown by immunohistochemistry. Treatment of the explants with collagenase for 15 minutes reduced the time to outgrowth from more th an 30 days to 3 days. Hyaluronidase, chondroitinase ABC, and trypsin applie d for the 15-minute period had no effect on the time to cell outgrowth when compared with untreated controls. Pretreatment with hyaluronidase prior to collagenase reduced the time to outgrowth. A notable finding of this study was that the majority of chondrocytes in the adult human articular cartila ge specimens and virtually all of the outgrowing cells contained or-smooth muscle actin. We conclude that human articular chondrocytes have the capabi lity to migrate through enzymatically degraded matrix and express a contrac tile actin isoform. Collagenase treatment reduces the time required for cel l outgrowth.