Recombinant human amelogenin promotes wound healing by enhancing angiogenesis

The first barrier of the human body is the skin, and more serious harm may occur when skin wound healing is delayed. One of the components of enamel matrix proteins is amelogenin, which inhibits inflammation and promotes periodontal tissue regeneration. However, its role in skin wound healing and angiogenesis is inconclusive. Thus, this study aimed to assess the therapeutic effect of recombinant human amelogenin (rhAM) on mouse skin wounds and to determine its effect on angiogenesis and its underlying mechanism. rhAM was expressed in Escherichia coli and purified using the optimized acetic acid method. A skin injury mouse model was established to explore the effects of rhAM on skin wound healing. After treatment with rhAM for 7 days, the wound healing rate was calculated, and the therapeutic effect of rhAM on skin wounds was assessed using hematoxylin & eosin (HE), Masson, and CD31 immunofluorescence staining. The expression of growth and inflammatory factors in wound tissues were detected using Western Blot. In addition, the rhAM effects on the proliferation and migration of human umbilical vein endothelial cells (HUVEC) and mouse fibroblasts (NIH 3T3) were studied in vitro using the Cell Counting Kit-8, cell scratch, cytoskeleton staining, and qPCR. The rhAM effect on HUVEC angiogenesis and its potential mechanism was studied using tube formation and Western Blot. The results showed that the purity of the obtained rhAM was more than 90 % using the optimized acetic acid method, and high-dose rhAM treatment could improve wound healing rate in mice. Additionally, more blood vessels and collagen were produced in the skin wound, and the expression of angiopoietin-related protein 2 (ANGPTL2) and transforming growth factor (TGF)-β1 was upregulated; however, that of interleukin-6 was down-regulated. We also found that rhAM promoted the proliferation and migration of HUVEC and NIH 3T3, the mRNA levels of vascular endothelial growth factor (VEGF), fibroblast growth factor, TGF-β1 and ANGPTL2 in HUVEC cells were upregulated, and expression of VEGF and phosphorylation of the p38 mitogen-activated protein kinase were activated. Therefore, rhAM could promote skin wound healing by upregulating angiogenesis and inhibiting inflammation.