角质细胞微囊泡内miR-21在皮肤损伤愈合过程中对促进MMPs的表达作用及其机制研究

Chronic wounds, such as venous, diabetic foot, or pressure ulcers, resulting in severe morbidity and mortality. Throughout the whole repair process, epidermal keratinocytes can interact with dermal fibroblasts via secreted vesicles that can carry proteins and RNA to transfer information between the two cell types. Besides, keratinocyte-derived MVs contains nucleic acid (DNA, mRNA and miRNA). miR-21 has been suggested to silence three inhibitors of the MMP network. Our preliminary study found that the expression of MMPs in fibroblasts were significantly up-regulated while the expression of TIMPs were down-regulated by keratinocyte-derived microvesicles (MVs). However, the underlying mechanism was not confirmed. Based on these findings, we hypothesize that miR-21 in MVs may regulate the expression of MMPs in fibroblasts. We will investigate the miRNAs in wound keratinocyte-derived MVs compared with normal keratinocytes, explore the impact of miR-21 on the expression of MMPs in fibroblasts using anti-miR-21 and pre-miR-21, and unveil the underlying mechanism，further applied to cutaneous ulcer in SD rat with diabetes mellitus.The study will help to provide potential therapeutic target for the chronic cutaneous wound.

糖尿病足溃疡、静脉性溃疡和褥疮等慢性皮肤损伤导致了一系列高发病率和死亡率的临床问题。在皮肤损伤修复过程中，上皮角质形成细胞能与皮肤成纤维细胞相互作用，可通过含蛋白和RNA的分泌性囊泡水平传递信息。角质形成细胞microvesicles包含核酸（DNA、mRNA和miRNA）。已经有研究表明miR-21能有效沉默MMP的抑制剂（如TIMP3）。本项目前期研究表明microvesicles增加成纤维细胞MMPs而降低TIMPs的表达，但其机制尚不明确。由此我们提出假设，MVs miR-21能促进成纤维细胞MMPs的表达。本课题拟比较分析损伤角质细胞MVs中的miR-21，并利用anti-miR-21和pre-miR-21探讨miR-21在MVs促进成纤维细胞MMPs表达中的作用，并探讨其可能机制，进一步应用于糖尿病大鼠皮肤溃疡动物模型。通过本研究希望为促进慢性皮肤损伤愈合提供理论依据和潜在的治疗方法。

皮肤损伤愈合是一个维持皮肤组织完整性的复杂生理学过程，涉及到多种不同类型细胞和信号分子。然而，愈合过程中特异性的信号通路和细胞外信号仍然不清楚。微囊泡作为一种细胞交流的关键介质，是通过向靶细胞传递遗传物质来实现功能的。在我们的研究中，含有miR-21的人角质形成细胞来源微囊泡明显促进了糖尿病大鼠的皮肤损伤愈合。深入研究表明微囊泡内miR-21能促进成纤维细胞的迁移、分化和收缩，诱导内皮细胞的促学管生成过程，以及介导促进炎症反应。在机制上，微囊泡内miR-21可能作用于成纤维细胞内关键靶向效应mRNA（例如MMP-1、MMP-3、TIMP-3和TIMP-4）来增加MMPs的表达和酶活性。此外，微囊泡内miR-21通过调节α-SMA和N-cadherin来诱导成纤维细胞-肌成纤维细胞分化。微囊泡内miR-21还能上调IL-6和IL-8的表达及其分泌从而增强免疫应答。而且，微囊泡内miR-21还能下调PTEN和RECK的蛋白表达和激活MAPK/ERK信号通路，从而增强成纤维细胞的功能。因此，我们的研究首次阐明了角质形成细胞来源微囊泡和微囊泡内miR-21在损伤愈合过程中的潜在应用机制。