EFFECTS OF RETINOIDS ON GLYCOSAMINOGLYCAN SYNTHESIS BY HUMAN SKIN FIBROBLASTS GROWN AS MONOLAYERS AND WITHIN CONTRACTED COLLAGEN LATTICES

Fibroblasts grown within contracted collagen lattices synthesize substantially less glycosaminoglycans than fibroblasts grown as monolayers on a plastic substrate, [H-3]glucosamine incorporation into hyaluronate was reduced by 70%, and incorporation into sulphated glycosaminoglycans was reduced by 40%. However, incorporation into heparan sulphate and chondroitin sulphates was reduced by 14 and 49%, respectively, resulting in a substantial change in the proportions of the individual glycosaminoglycans. On the basis of [H-3]glucosamine incorporation, hyaluronate constituted 80% of the total glycosaminoglycans synthesized in monolayer cultures, but only 67% in collagen lattice cultures. Incorporation of (SO4)-S-35 into chondroitin sulphates was reduced by 22%, whereas no change was observed in heparan sulphates following culture within collagen lattices. Exposure of the fibroblast cultures to retinoic acid (10(-6) mol/l) and retinyl propionate (2 x 10(-6) mol/l) resulted in a decrease in the incorporation of [H-3]glucosamine into hyaluronate by up to 41% in monolayer cultures, and 25% in collagen lattice cultures. The retinoids stimulated the incorporation of [H-3]glucosamine into heparan sulphate by up to 72%, and chondroitin sulphates by up to 30%, whereas (SO4)-S-35 incorporation remained essentially unaltered. Only modest changes in the incorporation of both isotopes into fibroblast sulphated glycosaminoglycans were observed following exposure to the retinoids in lattice cultures, Q-Sepharose ion-exchange chromatography at pH 2.0 revealed that there was no change in the degree of polymer sulphation of either chondroitin sulphate or heparan sulphate isolated from collagen lattice cultures compared with monolayer cultures, Retinoic acid (10(-6)mol/l) treatment did, however, reduce the degree of polymer sulphation of heparan sulphates and chondroitin sulphates in both monolayer and lattice cultures. The molecular mass of the sulphated glycosaminoglycans was unaffected by culture conditions, but hyaluronate isolated from collagen lattice cultures had a higher molecular mass than that from monolayer cultures. Retinoic acid treatment had no effect on the molecular mass of the glycosaminoglycans isolated from either culture system.