Effect of in vitro aging on the biosynthesis of glycosaminoglycans by human skin fibroblasts. Modulation by the elastin-laminin receptor

The incorporation of a radioactive precursor H-3-glucosamine in glycoconjug ates, essentially glycosaminoglycans (GAG) was evaluated in the culture med ium and cell fraction of human skin fibroblasts. Using increasing passage n umbers, we could estimate the effect of in vitro aging on these biosyntheti c activities. The incorporation in different free (hyaluronan) and protein bound (proteoglycans) GAGs was evaluated after specific enzymatic digestion . Most newly synthesized GAGs were excreted in the extracellular medium. In corporation of the tracer in hyaluronan, the major biosynthetic product, in creased with passage number but its titratable concentration decreased with in vitro aging, suggesting a rapid post-synthetic degradation. The proport ion of chondroitin sulfates 4 (A) and 6 (C) and heparan sulfate decreased a nd that of dermatan sulfate increased with increasing passage number. We ex plored the modulation of these biosynthetic activities by the elastin lamin in receptor. Using agonists (elastin peptides) and an antagonist (melibiose ) of the receptor, their action on GAG biosynthesis was evaluated. Both ela stin peptides and melibiose increased incorporation of the tracer in GAGs, but only melibiose inhibited post-synthetic degradation of hyaluronan, ther efore increasing its concentration. The effect of passage number on the rec eptor mediated modulations was also investigated. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.