Genetic regulators of vascular smooth muscle thermogenic differentiation

肥胖和代谢综合征是主要的公共卫生负担，当脂肪量增加时就会发生，导致脂肪组织功能障碍。肥胖与产热棕色脂肪组织（BAT）的存在呈负相关，在暴露于低温的人类和小鼠中，通过循环脂素12,13- dihome水平的增加可以检测到这一点。脂肪组织中的主要细胞类型是脂肪细胞，表达解偶联蛋白1 （Ucp1）的脂肪细胞被称为棕色、米色或可再生产热脂肪细胞。产热脂肪细胞可以产生于两个不同的谱系；一类是来自表达血小板衍生生长因子受体α (Pdgfa)的间充质前脂肪细胞的典型谱系，另一类是新发现的血管平滑肌（VSM）谱系，通过冷激募集，以表达瞬时受体电位离子通道亚家族V成员1 （Trpv1）为特征。重要的是，来自Trpv1+ VSM谱系的细胞比其他脂肪细胞表达更多的UCP1。12,13- dihome是Trpv1的一个假定的光，然而12,13- dihome是否通过激活脂肪生成程序来驱动产热脂肪细胞的募集尚不清楚。我们提出了一个新的假设，即12,13- dihome通过Trpv1下游的过氧化物酶体增殖体激活受体α (Ppara)激活Trpv1+ VSM热源性脂肪前体细胞，激活这些细胞中通常被抑制的脂肪生成程序。为了验证这一假设，我们的目标是：1)确定驱动Trpv1+ VSM衍生热源性脂肪生成的信号通路；2)鉴定抑制Trpv1+血管平滑肌细胞成脂分化的基因。我们将利用Trpv1谱系追踪小鼠模型来追踪Trpv1+ VSM细胞对产热脂肪细胞的贡献。在第一个目标中，我们将使用12,13 diHOME结合功能增益和功能丧失方法来处理这些小鼠，以操纵Ppara信号并量化来自Trpv1+ VSM谱系的产热脂肪细胞的频率。在第二个目标中，我们将采用无偏倚的方法来评估来自Trpv1+谱系的产热脂肪细胞的转录组学特征，并将其与来自典型脂肪细胞谱系的细胞进行比较。随后将进行体内CRISPR筛选，以系统地测量所有小鼠基因的遗传功能丧失对Trpv1+ VSM脂肪形成的影响。该项目将得到COBRE生理学核心（细胞生物能量学）、组织病理学和显微学核心（组织分析和共聚焦显微镜）以及蛋白质组学和脂质组学核心（脂质和蛋白质分析）的大力支持。这个创新的项目由一位新的初级研究员Matthew Lynes博士领导，他将得到血管周围脂肪组织（Lucy Liaw博士）、脂肪组织发育（Patrick Seale博士）和热源性脂肪（Shingo Kajiumura博士）领域的杰出专家导师的支持。确定Trpv1+ VSM热源性脂肪生成的正、负调节因子将为肥胖和代谢综合征的治疗提供新的治疗策略。

Obesity and metabolic syndrome are major public health burdens and occur when fat mass increases, leading to dysfunction in adipose tissue. Obesity is negatively associated with the presence of thermogenic brown adipose tissue (BAT), which can be detected in humans and mice exposed to cold temperatures by an increased level of the circulating lipokine 12,13-diHOME. The major cell type in adipose tissue is the adipocyte, and adipocytes that express Uncoupling protein 1 (Ucp1) are termed brown, beige, or recruitable thermogenic adipocytes. Thermogenic adipocytes can arise from two distinct lineages; the canonical lineage derived from mesenchymal preadipocytes that express platelet derived growth factor receptor alpha (Pdgfa), or a newly identified vascular smooth muscle (VSM) lineage that are recruited by cold challenge and are characterized bythe expression of Transient receptor potential cation channel subfamily V member 1 (Trpv1). Importantly, cells from the Trpv1+ VSM lineage express more UCP1 than other adipocytes. 12,13-diHOME is a putative lig and for Trpv1, however whether 12,13-diHOME drives the recruitment of thermogenic adipocytes by activating an adipogenic program is unknown. We propose the novel hypothesis that 12,13-diHOME activates Trpv1+ VSM thermogenic adipocyte precursor cells by signaling through Peroxisome proliferator-activated receptor alpha(Ppara), which has been reported to be downstream of Trpv1, to activate an adipogenic program that is normally suppressed in these cells. To test this hypothesis, we aim: 1) to determine the signaling pathway driving Trpv1+ VSM derived thermogenic adipogenesis; and 2) to identify the genes that suppress the adipogenic differentiation of Trpv1+ vascular smooth muscle cells. We will utilize a Trpv1 lineage tracing mouse model to track the contribution of Trpv1+ VSM cells to thermogenic adipocytes. In the first aim, we will treat these mice with 12,13 diHOME in combination with gain- and loss-of-function approaches to manipulate Ppara signaling and quantify the frequency of thermogenic adipocytes from the Trpv1+ VSM lineage. In the second aim, we will take an unbiased approach to assess the transcriptomic profile of thermogenic adipocytes from the Trpv1+ lineage and compare it to cells from the canonical lineage of adipocytes. This will be followed by in vivo CRISPR screening to systematically measure the effects of genetic loss-of-function for all mouse genes on Trpv1+ VSM adipogenesis. This project will be strongly supported by the COBRE Physiology Core (for cellular bioenergetics), the Histopathology and Microscopy Core (for tissue analysis and confocal microscopy) and the Proteomics and Lipidomics Core (lipid and protein profiling). This innovative project is led by a new junior investigator, Dr. Matthew Lynes, who will be supported by outstanding expert mentors in the fields of perivascular adipose tissue (Lucy Liaw PhD), adipose tissue development (Patrick Seale PhD), and thermogenic fat (Shingo Kajiumura PhD). Determining the positive and negative regulators of Trpv1+ VSM thermogenic adipogenesis will provide new therapeutic strategies to treat obesity and metabolic syndrome.