Fig. 3.

Growth factors induce epithelial–mesenchymal transition (EMT) and smooth muscle actin (SMA) expression in serosal mesothelial cultures. Explants were cultured for 5 days under various conditions and analyzed for expression of Wt1 and SMA. A–C: After culture in normal medium, many peripheral cells of explants are fibroblastic and express SMA but not Wt1 (arrowheads), while Wt1-positive cells are negative for SMA (yellow open arrowhead). D–F: Under serum-free (sf) conditions, few of the epithelial sheet cells of cultured explants express SMA, whereas its majority express Wt1. SMA-positive cells can be Wt1-positive (open arrowheads) and Wt1-negative (arrowheads). G–L: Similar results were obtained for explants grown in sf-medium supplemented with basic fibroblast growth factor (bFGF) or epithelial growth factor (EGF), with few SMA-positive cells in the epithelial sheets. M–O: In explants grown in sf-medium supplemented with platelet-derived growth factor-BB (PDGF-BB), many fibroblastic peripheral cells in the epithelial sheet express SMA (arrowheads), many of which coexpress Wt1 (open arrowheads). Scale bar = 200 μm.