Fig. 4.

ALK2, but not ALK5, promotes epithelial cell activation in PE explants. Explants were infected with adenovirus coding for GFP alone or GFP and constitutively active ALK2 (caALK2) or ALK5 (caALK5). A, Cells expressing caALK2 were less likely to be epithelial and more likely to be activated than cells expressing only GFP (*=p<0.05). B, The distribution of GFP-positive cells in PEs infected with caALK5 virus was similar to the distribution of GFP-positive cells in explants infected with virus encoding only GFP. C, GFP-positive cells were scored as epithelial (arrowheads, left panel), activated (arrowhead, middle panel), or transformed (arrowhead, right panel) as defined in “Results.” Asterisks indicate transformed (left panel) or epithelial (right panel) cells in different focal planes of the same field.