Blockade of interaction of α9 integrin with its ligands hinders the formation of granulation in cutaneous wound healing

The wound healing is a complex process consisting of inflammatory reaction, proliferation of mesenchymal cells, and formation and contraction of granulation tissue. The integrin receptors have crucial roles in this process. Recently, alpha 9 integrin has also been detected on keratinocytes within wound sites. However, its functional significance at various wound healing processes was not fully elucidated. To address the role of alpha 9 integrin in wound healing process, we made a full-thickness skin excisional wound and treated mice with anti-alpha 9 integrin antibody. It has been shown that wound healing process was divided into three distinct phases: first, the re-epithelialization phase, second, the phase of granulation tissue formation, and finally the phase of contraction of granulation tissue. We found that contraction of granulation tissue was not impaired by blocking the interaction of alpha 9 integrin with its ligands, indicating that alpha 9 integrin is not involved in myofibroblast differentiation. It is noteworthy that the formation of granulation tissue, as characterized by dense vimentin and CD31-positive area, was impaired. The hindrance of granulation tissue formation is because of the inhibition of adhesion and migration of alpha 9 integrin-positive dermal fibroblasts. In conclusion, alpha 9 integrin is involved in the formation of granulation tissue through regulating migration and adhesion of dermal fibroblasts in the full-thickness skin excisional wound model. Laboratory Investigation (2010) 90, 881-894; doi:10.1038/labinvest.2010.69; published online 22 March 2010