α3β1 integrin-controlled Smad7 regulates reepithelialization during wound healing in mice

Effective reepithelialization after injury is essential for correct wound healing. The upregulation of keratinocyte alpha 3 beta 1 integrin during reepithelialization suggests that this adhesion molecule is involved in wound healing; however, its precise role in this process is unknown. We have shown here that retarded reepithelialization in Itga3(-/-) mouse skin wounds is due predominantly to repressed TGF-beta 1-mediated responses. Specifically, expression of the inhibitor of TGF-beta 1-signaling Smad7 was elevated in Itga3(-/-) keratinocytes. Indeed, in vivo blockade of SmaA7 increased the rate of reepithelialization in Itga3(-/-) and WT wounds to similar levels. Our data therefore indicate that the function of alpha 3 beta 1 integrin as a mediator of keratinocyte migration is not essential for reepithelialization but suggest instead that alpha 3 beta 1 integrin has a major new in vivo role as an inhibitor of Smad7 during wound healing. Moreover, our study may identify a previously undocumented function for Smad7 as a regulator of reepithelialization in vivo and implicates Smad7 as a potential novel target for the treatment of cutaneous wounds.