Cell injury triggers actin polymerization to initiate epithelial restitution

The actin cytoskeleton role within the sequence of physiological epithelial repair in the intact epithelium has yet to be elucidated. We explore the role of actin in gastric repair in vivo and in vitro gastric organoids (gastroids). In response to two-photon induced cellular damage of either in vivo gastric or in vitro gastroid epithelium, actin redistribution specifically occurred in the lateral membranes neighboring the damaged cell, followed by migration inward to close the gap at the basal pole of the dead cell, in parallel with dead cell exfoliation into the lumen. The repair and focal increase of actin was significantly blocked by EDTA or the inhibition of actin polymerization. Inhibitors of myosin light chain kinase, myosin II, trefoil factor 2 signaling, or phospholipase C slowed initial actin redistribution, and the repair. While Rac1 inhibition facilitated repair, inhibition of RhoA/Rho-associated protein kinase inhibited. Inhibitors of focal adhesion kinase and Cdc42 had negligible effects. Initial actin polymerization occurs in the lateral membrane, and is primarily important to initiate dead cell exfoliation and cell migration to close the gap.