The Functional Mechanism Of A Disintegrin And Metalloproteinase-12 (ADAM-12) In Skin Wound Healing

The skin, as a physical barrier between human body and environment, is the first line to protect hosts against environmental stimuli. Wound healing is a complex but precise process. Misregulation of any process may delay or destroy the whole processes of wound healing. Therefore, it’s very important to explore the precise mechanisms involved in wound healing.The microarray analysis showed that a disintegrin and metalloproteinase-12 (ADAM-12) was increased in skin wounds compared to normal skin, which was further verified by determining mRNA and protein expression of ADAM-12 in skin wounds from mice and human by RT-PCR and Western blot. Immunofluorescence showed that ADAM-12 was markedly increased in epidermal keratinocytes surrounding the wounds. Moreover, the expression of ADAM-12 was increased in the early phase but decreased in the late phase of wound healing.Previous studies have shown that IL-17 and IL-33 induce the proliferation and inhibit the differentiation of keratinocytes to promote wound healing. We thereby checked whether IL-17 or IL-33 would induce the expression of ADAM-12. Luciferase assay did not show that IL-17 and IL-33 activated the promoter of ADAM-12. Further screening found that Ca2+ that regulates differentiation of keratinocytes induced the expression of ADAM-12. This induction was partially dependent on the activation of VitaminD receptor (VDR) as 1,25-vitamin D3 and overexpressed VDR could induce ADAM-12, while silencing VDR decreased the expression of ADAM-12 induced by Ca2+ in keratinocytes.Furthermore, we found that ADAM-12 was involved in the regulation of keratinocyte differentiation. Overexpressed ADAM-12 in keratinocytes inhibited the expression of terminal differential marker gene LOR expression that was induced by Ca2+. The deletion of ADAM in keratinocytes by CRISPR/cas9 decreased the proliferation of keratinocytes but increased keratinocyte differentiation compared to the WT keratinocytes. These results demonstrate that ADAM-12 is involved in the regulation of proliferation and differentiation of keratinocytes.Taken together, our results show that Ca2+ induces the expression of ADAM-12 partially dependent on VDR. The increased ADAM-12 inhibits the differentiation of keratinocytes, thus promotes wound healing. Moreover, the expression of ADAM-12 is increased in the early phase of wound healing but decreased in the late phase. These findings provide new insights into the role of ADAM-12 in tissue repair, and a potential therapeutic strategy for the treatment of skin wounds.