Altered connexin expression and wound healing in the epidermis of connexin-deficient mice

To analyze the effect of connexin loss on the repair of wounded tail skin, we have studied the following transgenic mouse mutants: connexin30-/-, connexin31-/- and connexin43Cre-ER(T)/fl (for inducible deletion of the connexin43 coding region). Connexin43 and connexin31 are expressed in the basal and spinous layers of wild-type epidermis, whereas connexin31 and small amounts of connexin30, as well as connexin26 proteins, were found in the granulous layer. Connexin43 was downregulated in connexin31-deficient mice, whereas mice with reduced connexin43 exhibited an upregulation of connexin30. During wound healing, connexin30 and connexin26 proteins were upregulated in all epidermal layers, whereas connexin43 and connexin31 protein expression were downregulated. In connexin31-/- mice, reduced levels of connexin30 protein were observed on days 1 and 2 after wounding. The closure of epidermal wounds in mice with decreased amounts of connexin43 protein occurred one day earlier. Under these conditions the expression profiles of connexin30 and connexin31 were also temporarily shifted by one day. Furthermore, dye transfer between keratinocytes in skin sections from connexin43-deficient mice was decreased by 40%. These results suggest that downregulation of connexin43 appears to be a prerequisite for the coordinated proliferation and mobilization of keratinocytes during wound healing.