miR-18a靶向Smad2、Smad4调控TGF-β1/Smads通路在增生性瘢痕中的作用及机制

Hypertrophic scar often occurs after surgery, injury and burn. During the development of hypertrophic scar, the most important aspects include abnormal proliferation of fibroblasts, disturbed balance of collagen synthesis and degradation. TGF-β1/Smads signaling pathway plays the key role in the development of hypertrophic scar. Smad2 and Smad4 are both very important factor for TGF-β1/Smads signaling pathway. It was reported that miRNAs were also involved in the cellular and molecular mechanism of hypertrophic scar. Our previous study has indicated that fractional CO2 laser changed the expression levels of procollagens, TGF-βs and miR-18a genes. More and more studies also proved that miR-18a usually performed its function through TGF-β1/Smads signaling pathway. Base on these results, the proposed study aims to elucidate the role of miR-18a in the development of hypertrophic scar through targeting Smad2 and Smad4. For this, we will investigate the role of miR-18a in hypertrophic scar development using cultured human hypertrophic scar fibroblasts in vitro, rabbit ear hypertrophic scar model in vivo and fractional CO2 laser treatment for hypertrophic scar patients. This study will reveal the mechanism of miR-18a underlying TGF-β1/Smads signaling pathway through targeting Smad2 and Smad4 in hypertrophic scar. It will be helpful for us to further understand the pathogenesis of hypertrophic scar. More over, it may offer us the new ideas to develop novel biotherapy for hypertrophic scar.

增生性瘢痕（Hypertrophic Scar, HS）是手术、外伤及烧伤后常见的并发症。其形成过程中，成纤维细胞增生异常、胶原蛋白合成及降解失衡。TGF-β1/Smads通路在HS的发病机制中起着关键性的作用。Smad2和Smad4是该通路上两个非常重要的调控因子。据报道MicroRNAs也参与了HS的发生和发展。本课题组前期研究表明点阵CO2激光治疗HS过程中改变了胶原蛋白、TGF-βs和miR-18a等基因的表达水平。越来越多的研究表明miR-18a可调控TGF-β1/Smads通路进而在不同疾病中发挥着重要的作用。本项目拟通过人HS成纤维细胞、兔耳HS动物模型以及点阵CO2激光治疗人HS等方面研究miR-18a能否靶向Smad2和Smad4调控TGF-β1/Smads通路，进而影响成纤维细胞的增生，Ⅰ和Ⅲ型胶原蛋白的生成，以进一步揭示HS的发病机制，为寻找新的治疗靶点提供理论依据。

病理性瘢痕可分为增生性瘢痕和瘢痕疙瘩，主要表现为真皮成纤维细胞异常增生、细胞外基质过度沉积。本研究首先证实miR-18a能够靶向Smad4参与增生性瘢痕的发病机制。本研究同时也证实组蛋白酶抑制剂曲古抑菌素A（TSA）可通过调控miR-30a-5p和Bcl-2基因进而影响成纤维细胞的增殖、凋亡，在瘢痕疙瘩的发生和发展起到重要作用。研究初步明确了TSA和miRNA在瘢痕疙瘩成纤维细胞中存在一定的关联作用，本研究为寻找瘢痕疙瘩的新临床治疗靶点提供理论支持。具体研究内容如下TSA抑制瘢痕疙瘩成纤维细胞增殖，呈TSA诱导的时间和浓度依赖方式，并可上调成纤维细胞凋亡比例及影响细胞周期分布变化，如G2/M期阻滞。TSA抑制TGF-β/Smads信号通路的两个关键蛋白TGF-β1、Smad4的表达，并抑制抗凋亡蛋白Bcl-2的表达，抑制细胞外基质的主要成分I型胶原蛋白基因的表达。TSA可影响瘢痕疙瘩成纤维细胞增殖的miRNA表达谱，差异表达的miRNA与细胞增殖、细胞外基质的合成以及细胞凋亡密切相关。差异表达的miRNA的功能与TSA刺激瘢痕疙瘩成纤维细胞引起的细胞表型变化一致。在瘢痕疙瘩成纤维细胞中miR-30a-5p通过靶向抑制BCL2基因的表达，诱导瘢痕疙瘩成纤维细胞发生凋亡，可最终抑制瘢痕疙瘩成纤维细胞的生长以及I型胶原蛋白的合成。过表达miR-146a-5p抑制瘢痕疙瘩成纤维细胞的增殖，其可能是通过抑制SMAD4基因表达阻滞TGF-β/Smads信号通路的传递，并最终抑制瘢痕疙瘩成纤维细胞增殖及I型胶原蛋白的合成。综上所诉，本研究初步探讨了miRNA在增生性瘢痕及瘢痕疙瘩中的作用，为进一步揭示病理性瘢痕的分子机制提供了新的视点。