Critical role of thrombospondin-1 in promoting intestinal mucosal wound repair.

Thrombospondin-1 (TSP1) is a matricellular protein associated with the regulation of cell migration through direct binding interactions with integrin proteins and by associating with other receptors known to regulate integrin function, including CD47 and CD36. We previously demonstrated that deletion of an epithelial TSP1 receptor CD47 attenuates epithelial wound repair following intestinal mucosal injury. However, the mechanisms by which TSP1 contributes to intestinal mucosal repair remains poorly understood. Our results show upregulated TSP1 expression in colonic mucosal wounds and impaired intestinal mucosal wound healing in vivo upon intestinal epithelial specific loss of TSP1 (VillinCre/+Thbs1f/f or Thbs1ΔIEC). We report that exposure to exogenous TSP1 enhanced migration of IECs in a CD47- and TGFβ1-dependent manner, and that deficiency of TSP1 in primary murine colonic epithelial cells resulted in impaired wound healing. Mechanistically, TSP1 modulated epithelial actin cytoskeletal dynamics by suppression of RhoA activity, activation of Rac1, and changes in F-actin bundling. Overall, TSP1 was found to regulate intestinal mucosal wound healing via CD47 and TGFβ1, coordinate integrin-containing cell-matrix adhesion dynamics and remodel the actin cytoskeleton in migrating epithelial cells to enhance cell motility and promote wound repair.