PDGFRA and systemic sclerosis: These results indicate that PDGF-AA binding to PDGFR-α was increased on the surface of SSc fibroblasts to take part in signal transduction via PDGF-A/PDGFR-α and to promote fibroblast trandifferentiation to myofibroblasts at RNA and protein levels, while these effects could be enhanced by TGF-β1.