Effect of Sonic hedgehog on the proliferation in mouse tongue epithelial cells

Objective: To investigate Sonic hedgehog (Shh) effects on proliferation and apoptosis of tongue epithelial cells in embryonic and ageing mice.

Materials and methods: Embryonic day 13.5 (E13.5), E14.5, E16.5 and postnatal day 0.5 (PN0.5) K14-Cre;Shh^fl/fl mice, and E14.5, E16.5, PN0.5, PN90.5 and postnatal 1.5 years (PN1.5Y) wild-type (Wt) mice were employed. Scanning electron microscopy, haematoxylin-eosin and immunohistochemistry were performed. Gel beads containing exogenous Shh protein were embedded in the tongue of PN90.5 and PN1.5Y Wt mice. Three days later, 5-bromodeoxyuridine (BrdU), proliferating cell nuclear antigen (PCNA) immunohistochemical and TUNEL staining were performed.

Results: The number of fungiform papillae was decreased with age. The numbers of BrdU- and PCNA-positive cells were the highest at PN0.5 and the lowest at PN1.5Y. Compared with Wt mice, K14-Cre;Shh^fl/fl mice had decreased PCNA-positive cells in the epithelium, a smaller tongue volume, and fewer papillae at PN0.5. At E14.5, the number of BrdU-positive cells was decreased in K14-Cre;Shh ^fl/fl mice. At PN1.5Y, the number of apoptotic cells in tongue tissue exposed to Shh protein was less than that in the BSA group and the numbers of BrdU- and PCNA-positive proliferating cells were increased.

Conclusion: Shh maintains cell proliferation and reduces apoptosis during tongue development and ageing.