PDGFRA and idiopathic pulmonary fibrosis: PDGFRa staining showed that fibroblasts in control lungs are mostly MOXD1/SMA negative, while fibroblasts in lower lobes of IPF lungs are mostly MOXD1/SMA positive, co-staining with these markers indicated that most of the MOXD1 staining cells in IPF are myofibroblasts.