Role of pericytes in pancreatic islet fibrosis

摘要 纤维化是2型糖尿病患者(T2D)胰岛的一种非常常见的病变，并可导致进展 胰岛功能受损。事实上，胰岛微血管系统的缺陷损害了 内分泌细胞和血液，扰乱胰岛结构，最终导致内分泌细胞死亡。一个重要的 微血管系统的组成部分是周细胞，这是一种包裹着小血管的可收缩的平滑肌样细胞 船只。在不同的器官中，周细胞被证明分化为肌纤维母细胞，导致纤维化。 和器官功能障碍。周细胞是否也参与了胰岛成纤维细胞池的形成 年龄和2型糖尿病尚未确定。我研究的长期目标是理解这一角色 胰岛微血管系统在2型糖尿病发病机制中的作用。我的K01研究计划的目标 是为了描述胰岛素抵抗和高胰岛素血症状态下胰岛周细胞的表型 作为衰老和2型糖尿病，并确定这些变化的原因，使用体外和体内的组合 活体接近了。中心假设是，在衰老和早期2型糖尿病期间，过量的 暴露于胰岛素后，周细胞中通过哺乳动物雷帕霉素靶点(MTOR)传递的信号加剧。 这使它们分化为肌成纤维细胞。在我们的模型中，高胰岛素血症的发展是为了补偿 胰岛素抵抗和胰岛周细胞暴露于较高水平的胰岛素。胰岛素过度激活mTOR信号转导 在周细胞中，这有利于它们分化为肌成纤维细胞，并促进这些促纤维化细胞的增殖。 中心假说正在两个特定的目标中得到检验：1)确定年龄和糖尿病引起的 胰岛周细胞的表型；2)确定mTOR依赖的胰岛素信号在周细胞中的作用 转分化。在第一个目标下，我们研究了老年和2型糖尿病患者周细胞的表型。 来自老鼠和人类的胰岛(Almaça等人，2018年，细胞代谢)。此外，使用转基因小鼠 胰岛血管纤维化模型和谱系追踪，我们直接可视化了胰岛的表型转变 周细胞向肌成纤维细胞转化(Mateus Gonçalves等人，2020年，糖尿病)。在第二个目标下，我们是 胰岛素在体外和体内对胰岛周细胞向促纤维化转化的直接影响 肌成纤维细胞。此外，我们目前正在操纵体内周细胞中的胰岛素和mTOR信号。 测定对胰岛微血管功能和血糖稳态的影响。拟议中的研究可能会影响 我们对周细胞在胰岛生物学中的作用的了解。在成功完成这项建议后，我们将更好地 了解糖尿病发病机制中周细胞功能障碍和胰岛纤维化之间的联系。

Abstract Fibrosis is a very frequent lesion in the islets of type 2 diabetics (T2D) and can contribute to a progressive impairment of islet function. Indeed, defects in the islet microvasculature compromise exchanges between the endocrine cells and the blood, disrupt islet architecture and ultimately lead to endocrine cell death. An important component of the microvasculature is the pericyte, a contractile smooth muscle-like cell that wraps small blood vessels. In different organs, pericytes have been shown to differentiate into myofibroblasts, leading to fibrosis and organ dysfunction. Whether pericytes also contribute to the pool of profibrotic myofibroblasts in islets during aging and type 2 diabetes had not been determined. The long-term goal of my research is to understand the role of the islet microvasculature in the pathogenesis of type 2 diabetes. The objectives of my K01 research proposal were to characterize the phenotype of islet pericytes during insulin resistant and hyperinsulinemic states, such as aging and type 2 diabetes, and determine the cause of those changes, using a combination of in vitro and in vivo approaches. The central hypothesis was that, during aging and early type 2 diabetes, the excessive exposure to insulin exacerbated signaling through the mammalian target of rapamycin (mTOR) in pericytes, which made them differentiate into myofibroblasts. In our model, hyperinsulinemia develops to compensate for insulin resistance and islet pericytes are exposed to higher levels of insulin. Insulin overactivates mTOR signaling in pericytes, which favors their differentiation into myofibroblasts and proliferation of these profibrotic cells.The central hypothesis is being tested in two specific aims: 1) Identify age- and diabetes-induced changes in the phenotype of the islet pericyte; 2) Determine the role of mTOR-dependent insulin signaling in pericyte transdifferentiation. Under the first aim, we have examined the phenotype of pericytes in aged and type 2 diabetic islets from mice and humans (Almaça et al., 2018, Cell Metabolism). Furthermore, using a transgenic mouse model of islet vascular fibrosis and lineage tracing, we directly visualized the phenotypic transition of islet pericytes towards myofibroblasts (Mateus Gonçalves et al., 2020, Diabetologia). Under the second aim, we are determining the direct in vitro and in vivo effects of insulin on the conversion of islet pericytes into profibrotic myofibroblasts. In addition, we are currently manipulating insulin and mTOR signaling in pericytes in vivo and measure the effects on islet microvascular function and glucose homeostasis. The proposed research can impact our knowledge on the role of pericytes in islet biology. Upon successful completion of this proposal, we will better understand the link between pericyte dysfunction and islet fibrosis in the pathogenesis of diabetes.