The Alk5 kinase inhibitor SB431542 impairs PGE₂-induced mouse corneal angiogenesis. In vivo angiogenesis assays were performed by implanting a pellet containing saline, PGE₂ (30 μM), or VEGF (125 ng) together with vehicle or 10 μM SB431542 into a previously created corneal pocket. The angiogenic response was assessed after 6 to 8 days. (A) The chart shows the mean percentage plus or minus SD of positive corneas per condition from 3 independent experiments. n indicates the total number of eyes per condition. *P < .01 vs saline; **P < .001 vs saline; #P < .01 vs PGE₂ alone. (B) Representative photographs of corneas from the experiments summarized in panel A; arrowheads, pellets containing PGE₂; arrow, positive angiogenic response (note the vessels emerging from the sclerocorneal limbus and reaching the pellet).