The aquaporins (AQPs) are a family of small integral membrane proteins that transport water and small solutes such as glycerol. Recent study has revealed the unexpected cellular roles of AQP, including the involvement in cell migration, although their classical role in facilitation of trans-epithelial fluid transport has been well understood. On the other hand, gastric epithelial cell layers serve as a physical barrier against aggressive factors such as acid, pepsin and Helicobacter pylori. During the early healing process of gastric lesions, the intact epithelial cells migrate to promptly reseal the wounded area. The regulation of cell volume through water flow has been suggested to be required for cell migration. However, there is no information concerning the relation of AQPs with cell migration in the gastrointestinal tract. In the present study, we examined the roles AQPs play in cell migration during the repair process of gastric epithelial cells after injury, using the rat gastric epithelial cell line RGM1 monolayers. A round wound with constant size was produced in the center of the confluent cell monolayer using a rotating silicon tip. Hg²⁺ (HgCl₂), an inhibitor of AQPs, suppressed cell migration during wound repair in a concentration- dependent manner. The RGM1 cells expressed AQP1 mRNA. The cell migration was also impaired in RGM1 in which AQP1 was knocked down by RNA interference, resulting in a marked delay of wound healing. The AQP1 knockdown RGM1 cells showed a decrease in the formation of membrane protrusions (lamellipodia) at the leading edge of the wound as compared with control RGM1 cells. These results suggest for the first time that AQP1 plays a crucial role in gastric epithelial cell migration during wound healing.