TGFβ对角质形成细胞mmp-9启动区甲基化的作用及机制研究

Overexpression of MMP-9 is an important negative factor for ulcers healing in diabetic foot. It is showed that the increase expression of MMP-9 always accompanies with low expression of TGF-β in diabetic ulcers. Local use of TGF-β in animal ulcers could promote wound healing. It implies that MMP-9 and TGF-β play important roles in wound healing. It is reported that TGF-β could promote DNA methylation in specific gene promoter and lead to gene silencing. Our studies have found that the DNA demethylation of mmp-9 gene promoter induced by AGEs upregulated the expression of MMP-9 in human epidermal keratinocytes, in which the roles of TGF-β/Smads signaling pathways is unclear. So we hypothesize that TGF-β probably reverse the DNA demethylation of mmp-9 gene promoter induced by AGEs and lead to the downregulation of MMP-9. This study aims to detect the expression and interaction of TGF-β/Smads pathway regulating factors when the DNA demethylation of mmp-9 gene promoter is induced by AGEs in keratinocytes. In addition, with the in vivo and vitro tests, we also intend to find whether the intervention or overexpression of TGF-β would reverse the DNA demethylation of mmp-9 gene promoter and downregulate the expression of MMP-9 induced by AGEs in human epidermal keratinocytes. It is intended to provide a new method for the intervention of MMP-9 overexpression.

MMP-9过度分泌是糖尿病足溃疡难以愈合的重要因素，研究显示糖尿病患者溃疡中MMP-9表达增加伴有TGF-β表达低下，局部使用TGF-β可促进动物伤口愈合，提示MMP-9和TGF-β在伤口愈合中扮演着重要角色。有研究报道TGF-β可促进特定基因启动区甲基化而沉默靶基因，本课题组研究发现AGEs诱导mmp-9启动区去甲基化上调角质细胞MMP-9表达，TGF-β/Smads通路在其中作用并不清楚。我们假设：TGF-β可逆转AGEs诱导的mmp-9启动区去甲基化而下调MMP-9表达。本课题拟通过体内外研究明确AGEs诱导的角质细胞mmp-9启动区去甲基化与TGF-β/Smads通路各调节因子的相互作用，通过TGF-β干预或过表达等方法探讨TGF-β/Smads通路激活能否逆转AGEs诱导的角质细胞mmp-9启动区去甲基化而下调MMP-9表达，为糖尿病溃疡中MMP-9过度分泌干预提供新靶点。