Integrin α2β1 is required for regulation of murine wound angiogenesis but is dispensable for reepithelialization

The alpha 2 beta 1 integrin functions as the major receptor for collagen type I on a large number of different cell types, including keratinocytes, fibroblasts, endothelial cells, and a variety of inflammatory cells. Recently, we demonstrated that adhesion of keratinocytes to collagen critically depends on alpha 2 beta 1, whereas fibroblasts can partly compensate for loss of alpha 2 beta 1 in simple adhesion to collagen. However, in three-dimensional collagen matrices, alpha 2 beta 1-null fibroblasts are hampered in generating mechanical forces. These data suggested a pivotal role for alpha 2 beta 1 during wound healing in vivo. Unexpectedly, reepithelialization of excisional wounds of alpha 2 beta 1-null mice was not impaired, indicating that keratinocytes do not require adhesion to or migration on collagen for wound closure. Whereas wound contraction and myofibroblast differentiation were similar, wound tensile strain was reduced in alpha 2 beta 1-null mice, suggesting subtle changes in organization of the extracellular matrix. In addition, we observed reduced influx of mast cells into the granulation tissue, whereas infiltration of other inflammatory cells was not impaired. Interestingly, ablation of alpha 2 beta 1 resulted in strong enhancement of neovascularization of granulation tissue and sponge implants. Both ultrastructurally and functionally, these new blood vessels appeared intact. In conclusion, our data show unique and overlapping functions of alpha 2 beta 1 integrin during murine cutaneous wound healing.