No abstract

Studies of the effects of transforming growth factor (TGF) β on normal human diploid gingival fibroblasts (HGF) have been carried out to determine possible physiological effects of this growth factor. Responses distinctly different from those characterized using established cell lines were observed. Whether alone, or in combination with EGF (2.5 ng/ml), human platelet‐derived TGF‐β (0.1 ng/ml or 1.0 ng/ml) did not induce anchorage‐independent growth of HGFs in soft agar assays. However, TGF‐β with EGF acted synergistically in promoting a 1.8‐fold increase in anchorage‐dependent proliferation of quiescent HGFs. At the same concentrations TGF‐β alone stimulated the incorporation of [35S]methionine into both cellular (cell‐layer) and matrix (medium) proteins by as much as 3‐fold and 1.7‐fold respectively. Densitometric analysis of fluorographs of radiolabeled media proteins separated by SDS‐PAGE revealed that the TGF‐β‐stimulated protein synthesis was selective. However, synthesis of collagen, the major protein synthesized and secreted by HGFs, was stimulated by TGF‐β to the same extent as the average secreted protein. Protein synthesis and cell proliferation were significantly greater in subconfluent cells compared to confluent and multilayered cells. These effects are likely to reflect physiological activity of platelet‐derived TGF‐β which may act to promote the wound healing response.

No abstract

Although transforming growth factor-beta (TGF-beta) has been implicated in the local regulation of bone growth and remodelling, its specific effects on different subpopulations of bone cells have not been elucidated. Cells derived from bone are known to be heterogeneous and include both cells of different lineages and osteoblastic populations with different levels of expression of osteoblast-associated properties. Consequently, we have isolated clonal populations of bone cells to examine more precisely the effects of TGF-beta on individual subpopulations. Several clonal populations were isolated by limiting dilution from cells derived from 21-day-old fetal rat calvaria. Two of these clones, RCA 11 and RCB 2, were used here. While the two clones responded similarly to parathyroid hormone (PTH) and isoproterenol (ISP) with increases in intracellular cAMP, prostaglandin E2 (PGE2) elicited a 10-fold higher response in RCB 2 cells compared with RCA 11. RCB 2 cells expressed a 10-fold higher alkaline phosphatase activity compared with RCA 11. Both clones synthesized a variety of bone matrix associated proteins, but only RCA 11 synthesized SPP-1 (osteopontin) constitutively. TGF-beta stimulated growth of RCB 2 cells after 24 and 48 h of treatment, but had no effect on growth of RCA 11. TGF-beta supported anchorage-independent growth of RCB 2 cells, but not that of RCA 11. A 24-h exposure to TGF-beta decreased cAMP responsiveness to PTH and ISP slightly in both clones, but had no effect on PGE2 responses. Significant reductions in alkaline phosphatase activity were seen in both clones after 24- and 48-h treatments with TGF-beta.(ABSTRACT TRUNCATED AT 250 WORDS)