Sonic Hedgehog contributes to gastric mucosal restitution after injury.

Eradication of Helicobacter pylori correlates with regeneration of the gastric epithelium, ulcer healing and re-expression of the gastric morphogen Sonic Hedgehog (Shh). We sought to identify the role of Shh as a regulator of gastric epithelial regeneration during wound healing. A mouse model expressing a parietal cell-specific, tamoxifen-inducible deletion of Shh (HKCre(ERT2);Shh(flox/flox) or PC-iShhKO) was developed. Stomachs were collected and compared 7-150 days after the final vehicle or tamoxifen injection. Ulcers were induced in both controls and PC-iShhKO mice using acetic acid and ulcer size compared 1 and 7 days post induction. (1) Re-expression of Shh correlates with decreased hyperproliferation: Compared to controls, PC-iShhKO mice developed foveolar hyperplasia. Restoration of normal gastric epithelial architecture and differentiation correlated with the re-expression of Shh in PC-iShhKO mice 150 days after the final tamoxifen injection. At the tamoxifen dose used to induce Cre recombination there was no genotoxicity reported in either HKCre(ERT2) or Shh(flox/flox) control mouse stomachs. (2) Delayed wound healing in PC-iShhKO mouse stomachs: To identify the role of Shh in gastric regeneration, an acetic acid ulcer was induced in control and PC-iShhKO mice. Ulcers began to heal in control mice by 7 days after induction. Ulcer healing was documented by decreased ulcer size, angiogenesis, macrophage infiltration and formation of granulation tissue that correlated with the re-expression of Shh within the ulcerated tissue. PC-iShhKO mice did not show evidence of ulcer healing. Re-expression of Shh contributes to gastric regeneration. Our current study may have clinical implications given that eradication of H. pylori correlates with re-expression of Shh, regeneration of the gastric epithelium and ulcer healing.