Selective upregulation of platelet-derived growth factor alpha receptors by transforming growth factor beta in scleroderma fibroblasts.
Transforming growth factor beta (TGF-beta), a multifunctional cytokine, is an indirect mitogen for human fibroblasts through platelet-derived growth factor (PDGF), particularly the A ligand-alpha receptor arm of that system. TGF-beta effects on PDGF alpha receptor expression were studied in vitro using ligand binding techniques in three human dermal fibroblast strains: newborn foreskin, adult skin, and scleroderma (systemic sclerosis, SSc). Each cell strain responded differently to TGF-beta. In newborn foreskin fibroblasts, PDGF alpha receptor number decreased in a dose-dependent manner after exposure to low concentrations of TGF-beta (0.1-1 ng/ml). Responses of normal skin fibroblasts were varied, and mean net receptor number was unchanged. Increases in PDGF alpha receptor number by TGF-beta occurred consistently with SSc fibroblasts and low concentrations of TGF-beta (0.1-1 ng/ml) were particularly stimulatory. Increased surface expression of alpha receptor subunit by TGF-beta in SSc fibroblasts correlated with increased new PDGF alpha receptor synthesis as demonstrated by radioimmunoprecipitation analysis of metabolically labeled cells and with increased steady-state levels of corresponding mRNAs. In normal adult skin fibroblasts, TGF-beta had no effect on either synthesis or mRNA expression of alpha receptor subunits. Proliferative responses to PDGF-AA after pretreatment with TGF-beta correlated positively with effects of TGF-beta on expression of alpha receptor subunit. Decreased mitogenic responses to PDGF-AA were observed in foreskin fibroblasts, small changes in responses in adult fibroblasts, and significant increases in SSc fibroblasts. Thus, costimulation with PDGF-AA and TGF-beta selectively enhanced proliferation of fibroblasts with the SSc phenotype. Immunohistochemical examination of SSc and control skin biopsies revealed the presence of PDGF-AA in SSc skin. Data obtained by ligand binding, immunoprecipitation, mRNA, and mitogenic techniques are consistent with the hypothesis that activation of the PDGF-AA ligand/alpha receptor pathway is a characteristic of the SSc fibroblast and may contribute to the expansion of fibroblasts in SSc.
Yamakage
A
A
Department of Medicine, Medical University of South Carolina, Charleston 29425.
Kikuchi
K
K
Smith
E A
EA
LeRoy
E C
EC
Trojanowska
M
M
D000328:Adult; D015152:Blotting, Northern; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D012333:RNA, Messenger; D015531:Radioimmunoprecipitation Assay; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor; D012595:Scleroderma, Systemic / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D015854:Up-Regulation
D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D016212:Transforming Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor