Contribution of invariant natural killer T cells to skin wound healing

In the present study, we determined the contribution of invariant natural killer T (iNKT) cells to the skin wound healing process. In iNKT cell-deficient (Jα18KO) mice lacking iNKT cells, wound closure was significantly delayed compared with wild-type mice. Collagen deposition, expression of α-smooth muscle actin and CD31, and wound breaking strength were significantly attenuated in Jα18KO mice. The adoptive transfer of liver mononuclear cells from wild-type but not from Jα18KO or interferon (IFN)-γ gene-disrupted (IFN-γKO) mice resulted in the reversal of this impaired wound healing in Jα18KO mice. IFN-γ expression was induced in the wounded tissues, which was significantly decreased at 6, 12, and 24 hours, but increased on day 3 after wounding in Jα18KO mice. The main source of the late-phase IFN-γ production in Jα18KO mice were neutrophils rather than NK cells and T cells. Administration of α-galactosylceramide, an activator of iNKT cells, resulted in the acceleration of wound healing on day 3 in wild-type mice. This effect was not observed in IFN-γKO mice. These results indicate that iNKT cells play important roles in wound healing. The iNKT cell-induced IFN-γ production may regulate the wound healing process in the early phase.