GROWTH-REGULATION IN SCLERODERMA FIBROBLASTS - INCREASED RESPONSE TO TRANSFORMING GROWTH-FACTOR-BETA-1

We investigated the responses of normal and scleroderma fibroblasts to various growth factors, especially transforming growth factor-beta 1 (TGF-beta 1). The effects of various growth factors on [H-3]thymidine incorporation in normal and scleroderma fibroblasts were examined. [I- 125]-labeled platelet-derived growth factor (PDGF)-BB binding in scler oderma and normal fibroblasts was examined both in the presence and ab sence of TGF-beta 1 (1 ng/ml), Cytoplasmic protein was isolated and an alyzed by Western blotting, Total RNA from fibroblasts was also isolat ed and analyzed by reverse transcriptase-polymerase chain reaction (RT -PCR) using specific primer sets. Mitogenic responses to TGF-beta 1 (0 .33-1 ng/ml) in seven scleroderma fibroblast strains were significantl y greater than those in normal controls, [I-125]-PDGF-BB binding to sc leroderma fibroblasts was increased after TGF-beta 1 stimulation, The increased response to TGF-beta 1 was shown to be mediated through PDGF -like protein induction; TGF-beta 1-treated scleroderma fibroblasts pr oduced greater amounts of 36-kD PDGF-like protein, which was reported previously as connective tissue growth factor (CTGF), than did TGF-bet a 1-treated normal fibroblasts. TGF-beta 1 treatment also upregulated PDGF-alpha receptor expression in scleroderma fibroblasts but not in n ormal dermal fibroblasts. mRNA expression of CTGF and PDGF-alpha recep tor was correlated with the above protein expression. These observatio ns suggest that the increased growth response to TGF-beta 1 in sclerod erma fibroblasts is mediated through the induction of CTGF and PDGF-al pha receptor.