TGFB1 and systemic sclerosis: SSc and control fibroblasts were stimulated with 10 ng/ml TGF-β1 (T group), 25 ng/ml PDGF-AA (P group), and 10 ng/ml TGF-β1 plus 25 ng/ml PDGF-AA (T+P group), and PDGFR-α and α-SMA mRNA and protein expression was measured by RT-PCR and WB respectively.