Transforming growth factor beta1, microRNAs and diabetic nephropathy

描述(申请人提供)：糖尿病肾病是糖尿病的主要并发症之一，可导致终末期肾脏疾病。糖尿病肾病的发病率正在上升，需要新的战略来对抗这种令人衰弱的状况。糖尿病肾病的主要特征包括由于细胞外基质(ECM)蛋白的积聚而增加的肾小球硬化和系膜细胞扩张。尽管转化生长因子-β1(TGFb1)和细胞外基质蛋白胶原等多种生化途径和关键促纤维化因子参与了糖尿病肾病的发病机制，但其调控的分子机制尚不清楚。在之前的资助阶段，我们发现了肾脏微RNA(MiRNAs)在糖尿病肾病发病机制中的新作用。我们证实miR-192可以介导转化生长因子b1诱导的系膜细胞(MCs)的胶原表达，并且miR-192缺乏可以保护糖尿病肾病小鼠模型的关键特征。从那时起，肾脏miRNAs在各种肾脏疾病中得到了越来越多的关注，也被认为是有希望的糖尿病肾病的临床生物标志物。然而，我们对影响糖尿病肾病进展的miRNAs的谱及其治疗潜力仍然知之甚少。我们的目标是通过确定新发现的miRNAs及其宿主基因在糖尿病肾病发病机制中的作用，并通过翻译方法来利用它们的潜力来满足对糖尿病肾病更好治疗的迫切需要，以解决这一知识差距。我们将继续跟踪大量新的初步数据，这些数据表明，在体外MCs和糖尿病小鼠肾小球中，TGFb1和高糖共同上调了一个新的miRNAs“Mega簇”。此外，我们发现这个簇嵌入到一个长的转录本中，两者都受到应激反应转录因子的调控，而多组分miRNAs的靶基因调控蛋白质翻译、肥大和细胞应激。中心假说是，糖尿病条件下miRNAs的巨簇上调抑制了其关键功能基因靶点的表达，诱导肾小球MC肥大、蛋白质合成和纤维化，从而促进糖尿病肾病的进展。这一假说将通过三个特定的目标得到验证，这将是：i)检查Mega簇中关键miRNAs调控的分子机制；ii)确定这些miRNAs和MCs中关键的共同靶基因的功能角色；iii)最终评估新的基因靶向以及在糖尿病肾病小鼠模型中下调该miRNA簇基因组区域的翻译方法。这些具有概念创新和临床意义的研究结果可以确定糖尿病肾脏中目前未知的调节因子，这些调节因子可能导致识别迫切需要的治疗糖尿病肾病的新靶点，从而对推动该领域的发展产生积极影响。

DESCRIPTION (provided by applicant): Diabetic nephropathy (DN) is one of the major complications of diabetes that can lead to end stage renal disease. The rates of DN are escalating and new strategies are needed to combat this debilitating condition. Key features of DN include increased glomerulosclerosis and mesangial cell expansion due to the accumulation of extracellular matrix (ECM) proteins. Although several biochemical pathways and key profibrotic factors, such as transforming growth factor-b1 (TGFb1) and the ECM protein collagen, have been implicated in the pathogenesis of DN, the subtle molecular mechanisms regulating them are unclear. In the previous funding period we identified new roles for renal microRNAs (miRNAs) in the pathogenesis of DN. We demonstrated that miR-192 can mediate TGF b1 induced collagen expression in mesangial cells (MCs), and that miR-192 deficiency can protect against key features of DN in mouse models. Since then, renal miRNAs have gained increased attention in various renal diseases, and are also being recognized as promising clinical biomarkers for DN. However, we still have only limited knowledge about the spectrum of miRNAs that modify DN progression and their therapeutic potential. Our objective is to address this gap in knowledge by identifying the roles of newly identified miRNAs and their host genes in the pathogenesis of DN, and translational approaches to harness their potential to meet the critical need for better therapies for DN. We will follow up on extensive new preliminary data showing that a novel "Mega Cluster" of miRNAs is collectively up-regulated by TGFb1 and high glucose in vitro in MCs, and in diabetic mice glomeruli in vivo. Furthermore, we find that this cluster is embedded within a long transcript and both are regulated by stress responsive transcription factors, whereas target genes of multiple component miRNAs regulate protein translation, hypertrophy and cellular stress. The central hypothesis is that up-regulation of the mega cluster of miRNAs diabetic conditions suppresses the expression of their key functional gene targets, inducing glomerular MC hypertrophy, protein synthesis and fibrosis, and thereby augmenting DN progression. This hypothesis will be tested via three Specific Aims which will: i) examine the molecular mechanisms of regulation of key miRNAs within the mega cluster; ii) identify the functional roles of these miRNAs and key common target genes in MCs, and iii) finally evaluate novel gene targeting as well as translational approaches to down-regulate this miRNA cluster genomic region in mouse models of DN. The results of these conceptually innovative and clinically significant studies can define currently unknown regulatory factors in the diabetic kidney that could lead to the identification of critically needed new therapeutic targets for DN and thus have a positive impact to advance the field.