Developmental changes in glycosaminoglycans, collagen and collagenase activity in embryonic chick skin

In order to study remodeling of connective tissue during development, changes in glycosaminoglycan, collagen and collagenase activity in embryonic chick skin at various stages have been studied. Collagen content in the skin increased rapidly during days 14 to 18, then leveled off until hatching. Prior to the increase of collagen deposition in the skin, a sharp decrease in chondroitin sulfate was observed between days 11 and 14, while dermatan sulfate increased almost 4 fold during days 12 to 14, then increased steadily until hatching. Hyaluronic acid decreased progressively during the stages investigated (days 11 to 20). At the same stage as the rate of collagen deposition in the tissue became maximal (day 16), the amount of dialyzable hydroxyproline showed a maximum, indicating that an increased rate of collagen deposition in the tissue was accompanied by accelerated collagenolysis. Culture of skin from various stages of embryonic development revealed that 16 day old tissue was potentially capable of secreting the highest levels of collagenase. This collagenase was mostly inactive against soluble collagen and collagen fibrils but could be activated by 3 M NaSCN treatment.