Figure 1. Exogenous Sonic hedgehog NH₂-terminal peptide (rmShh-N) improves healing of wounded Pax6^+/+ but not Pax6^+/− corneal epithelia. A: Representative views of wounded Pax6^+/+ and Pax6^+/− eyes, following roughly circular corneal epithelial debridement, the wound visualized by topical application of sodium fluorescein after 0, 12, and 24 h of healing ex vivo. B: Mean±S.E.M. rate of epithelial wound closure for 8 wild-type and 5 Pax6^+/− corneas with (gray bars) and without (white bars) application of 5 μg/ml rmShh-N. C: Representative image of a cluster of BrdU-positive nuclei (brown) in the basal layer of a wild-type control corneal epithelium. D: Mean±SEM percentage of BrdU-positive cells in the basal layer of the cornea epithelium of 3 Pax6^+/+ and Pax6^+/− eyes, with (gray bars) or without (white bars) topical application of rmShh-N. Pax6^+/− corneas increase their mitotic rate in response to Shh, but this does not translate to increased wound healing rate. ** represents p<0.01. Scale bars: A, 1 mm; C, 50 μm.