TGF-beta modulates the synthesis of proteoglycans by myocardial fibroblasts in culture.

In this study we examined the production of proteoglycans by fibroblasts cultured from the left ventricular myocardium of normal adult rats. Various molecular species of proteoglycan were detected, either by labeling glycosaminoglycan chains with 35SO4 or by labeling the proteoglycan core protein with [35S]methionine. The medium of the cell cultures, which contained quantitatively most of the proteoglycans, appeared to consist mainly of biglycan, lesser amounts of decorin and proteoglycans of higher molecular weight. Biglycan and decorin were identified not only by the characteristic mobility of the intact protein and the core protein but also by immunolocation on Western blots. TGF-beta upregulated the synthesis of all these proteoglycans, coincident with elongation of glycosaminoglycan side chains observed for biglycan and decorin. The apparent molecular weight of the core protein of the two proteoglycans remained unaffected by TGF-beta. The results of these experiments suggest that with regard to proteoglycan synthesis and its regulation by TGF-beta, cultured fibroblasts originating from the myocardium share to a large extent the properties of cultured fibroblasts of other organs.