EFFECT OF GROWTH-FACTORS ON HYALURONAN AND PROTEOGLYCAN SYNTHESIS BY RETROOCULAR TISSUE FIBROBLASTS OF GRAVES OPHTHALMOPATHY IN CULTURE

One of the pathological changes seen in Graves' ophthalmopathy is the deposition of glycosaminoglycans such as hyaluronan and proteoglycan in retroocular connective tissue. We analyzed glycosaminoglycans synthesized by retroocular tissue fibroblasts in culture derived from an individual not suffering from thyroid disease and from three patients with Graves' ophthalmopathy. Retroocular tissue fibroblasts synthesized both hyaluronan and proteoglycan, the latter composed mainly of chondroitin sulfate. This contrasts with the proteoglycan synthesized by adult skin fibroblasts which was composed of dermatan sulfate and heparan sulfate proteoglycan. Chondroitin sulfate proteoglycan secreted by retroocular tissue fibroblasts consisted of large and small chondroitin sulfate proteoglycans (CS-PG), their size being determined by the Sepharose CL-6B column. The effects of IGF-1 and PDGF on hyaluronan and proteoglycan synthesis were studied separately and in combination. Both IGF-1 and PDGF increased the synthesis of hyaluronan and proteoglycan in a dose-dependent manner. IGF-1 predominantly stimulated secretion of small CS-PG, while PDGF increased large CS-PG markedly when studied in retroocular tissue fibroblasts. In contrast, IGF-1 stimulated secretion of small proteoglycan while PDGF had little effect on proteoglycan synthesis in skin fibroblasts. Thus, glycosaminoglycan synthesized by retroocular tissue fibroblasts has a unique composition and each component is regulated independently, at least in part.