The breakdown of collagen by chondrocytes.

The chondrocytes of pure articular cartilage from young pigs display collagenolytic activity when the cartilage is cultivated by an organ culture method in medium containing 5--10 IU retinol/ml. Breakdown of collagen occurs in all regions of the cartilage; in the thicker explants it is greatest and most frequent in those that contain the deepest zone composed of proliferating and hypertrophic chondrocytes; it is also very drastic in thin explants composed mainly of superficial fibro-cartilage.