Deconstructing the diet-induced remodeling of adipose tissue

项目摘要 肥胖是几种代谢性疾病的主要危险因素，尤其是糖尿病和心血管疾病。 在饮食诱导的肥胖过程中，内脏白色脂肪组织(VWAT)通过 招募新的脂肪细胞(增殖)和扩大现有的白色脂肪细胞(肥大)。至 促进这种脂肪细胞的扩张，由间充质基质细胞组成的间质血管腔 骨髓间充质干细胞和免疫细胞在细胞数量和基因表达上的巨大变化导致WAT纤维化 和炎症，从而加剧代谢功能障碍。探讨其控制机制 我们应用单细胞RNA测序(ScRNAseq)来定义间质的细胞景观 并研究在饮食诱导的肥胖过程中它是如何变化的。我们观察到巨噬细胞的广泛增加 包括CD9+衰老的巨噬细胞，它分泌促纤维化因子，最明显的是骨桥蛋白。我们也 鉴定了四个不同的MSCs群体和一个表达PDGFFRα的早期脂肪细胞祖细胞群 和PDGFRβ。在肥胖状态下，这些细胞增加其细胞外基质的产生，从而促进纤维化。在……里面 在肥大的情况下，脂肪细胞随着它们吸收和储存多余的脂肪而逐渐增加它们的体积 卡路里。这种扩张与血管生成减少一起导致局部缺氧，从而导致血管沉积 细胞周围细胞外基质。骨髓间充质干细胞和脂肪细胞产生细胞外基质的结合导致僵硬的形成 和顽固的屏障，防止脂肪细胞进一步扩张和脂肪细胞功能障碍。确定机制 对于这种功能障碍，我们对分离的脂肪细胞进行了RNAseq分析，以评估 在延长的HFD期间发生的途径变化。研究表明，脂肪细胞对 通过增强编码细胞外基质、焦点黏附和细胞骨架蛋白的基因的表达来促进饮食。事实上, 形成的病理性脂肪细胞的转录特征类似于成纤维样细胞或前体细胞。 细胞。调控增殖和肥大的转录机制仍然不清楚。我们的 早期研究发现，转录辅因子Myocardin相关转录因子MRTFA 通过调节MSCs的命运促进饮食诱导的脂肪组织代谢紊乱 成纤维高于成脂。我们假设MRTFA整合了多个导致纤维化的信号 骨髓间充质干细胞对脂肪细胞施加机械应力产生细胞外基质，导致其成纤维细胞样表型 和脂肪组织功能障碍。我们提出了三个目标：1：确定条件删除MRTFA的效果 肥胖小鼠脂肪组织细胞组成和功能的成脂前体细胞研究。2：定义 调节脂肪细胞前体细胞命运的信号通路对饮食的反应。3：确定转录 调节血管祖细胞命运的机制。在完成这些目标时，我们将明确 肥胖过程中调节WAT重塑的新机制和确定的抗肥胖靶点 肥胖治疗学。

Project Summary Obesity is a major risk factor for several metabolic diseases most notably diabetes and cardiovascular disease. During diet-induced obesity, visceral white adipose tissue (vWAT) responds to caloric excess through the recruitment of new fat cells (hyperplasia) and enlargement of existing white adipocytes (hypertrophy). To facilitate this adipocyte expansion, the stromal vascular compartment consisting of mesenchymal stromal cells (MSC) and immune cells undergo dramatic changes in cell number and gene expression leading to WAT fibrosis and inflammation, thereby exacerbating metabolic dysfunction. To investigate the mechanisms controlling hyperplasia, we applied single cell RNA sequencing (scRNAseq) to define the cellular landscape of the stroma and examine how it changes during diet-induced obesity. We observed an extensive increase in macrophages including CD9+ senescent macrophages which secreted profibrogenic factors most notably osteopontin. We also identified four distinct populations of MSCs and an early adipocyte progenitor cluster expressing both PDGFRα and PDGFRβ. In an obese state, these cells enhanced their ECM production thereby contributing to fibrosis. In the case of hypertrophy, adipocytes progressively increase their volume as they take up and store excess calories. This expansion along with reduced angiogenesis causes local hypoxia that induces the deposition of pericellular ECM. The combination of ECM production from MSCs and adipocytes leads to formation of a stiff and inflexible barrier against further adipocyte expansion and adipocyte dysfunction. To identify mechanisms responsible for the dysfunction, we performed a RNAseq analysis of isolated adipocytes to assess global pathway changes occurring during a prolonged HFD. The studies revealed that adipocytes respond dramatically to the diet by enhancing expression of genes encoding ECM, focal adhesion, and cytoskeletal proteins. In fact, the transcriptional signature of the resultant pathological adipocytes was similar to fibroblastic-like or progenitor cells. The transcriptional mechanisms regulating both hyperplasia and hypertrophy are still poorly defined. Our earlier studies discovered that the transcriptional cofactor myocardin-related transcription factor, MRTFA contributes to diet-induced metabolic disruption of adipose tissue by regulating the fate of MSCs to favor fibrogenesis over adipogenesis. We hypothesize that MRTFA integrates multiple fibrogenic signals leading to ECM production by MSCs producing mechanical stress on adipocytes leading to their fibroblastic-like phenotype and adipose tissue dysfunction. We propose three aims:1: Determine the effect of conditional deletion of MRTFA in adipogenic progenitors on the cellular composition and function of adipose tissue in obese mice. 2: Define the signaling pathways regulating adipocyte progenitor cell fate in response to diet. 3: Identify transcriptional mechanisms regulating the fate of vascular progenitors. At the completion of these aims, we will have defined new mechanisms regulating WAT remodeling during obesity and identified targets for development of anti- obesity therapeutics.