Project #1: Chronic stimulation of renin cells and transformation of the kidney vasculature

项目概要/摘要 球旁 (JG) 细胞是传感器，在整个进化过程中得到完善，可以解释和响应环境变化 血压以及细胞外液的成分和体积。正常情况下，JG 细胞释放肾素 足以维持体内平衡。然而，在激烈和长期的生理挑战（脱水、 钠消耗、低血压）肾小动脉的平滑肌细胞（SMC）重新获得肾素 表型并恢复体内平衡。一旦体内平衡重新建立，转化的细胞就会停止制造 肾素并再次成为 SMC。相反，如果煽动威胁没有被消除或克服[如自发的威胁] 或小鼠体内肾素-血管紧张素系统（RAS）基因的实验性突变或 RAS 的慢性抑制， 大鼠和人类]肾素细胞的持续慢性刺激导致肾内向心肥大 动脉和小动脉。大量肥大的肾素细胞围绕并杂乱地插入小动脉内 墙壁。 SMCs向内集中聚集，使血管腔变窄并限制血流， 导致缺血、纤维化和肾衰竭。尽管 RAS 具有医学重要性并且广泛使用 儿童和青少年的抑制剂，这种严重的、尽管无声无息的发展的潜在机制 疾病未知。我们的肾素细胞消融研究表明，肾素细胞负责血管 疾病的发生不仅通过物理参与血管壁的增厚，而且还通过它们的直接细胞间作用 与 SMC 的相互作用。我们实验室的大量初步数据表明 cAMP 和 Notch 途径负责肾素细胞的转化和动脉疾病。我们假设 在长期不受限制的刺激下，p300 重塑肾素细胞的染色质，使它们产生双重作用 胚胎衰老表型。此外，转化的肾素细胞通过Notch激活诱导同心 邻近 SMC 的血管肥大。目标 1 将检验特定印记染色质的假设 结构域决定了导致同心动脉肥大的细胞命运的渐进变化。目标 图1A将定义构成患病小动脉的细胞的身份和命运。目标 1B 将测试是否 来自患病小动脉的细胞保留（或恢复）胚胎/祖细胞状态。目标2 将检验组蛋白乙酰转移酶 p300 负责这些染色质生成的假设 决定肾素细胞病理转化和同心动脉肥大的领域。 目标 3 将检验以下假设：相邻 SMC 的同心积累是由 Notch 信号传导介导的 通过肾素细胞中的 Jagged1 配体与 SMC 中的 Notch2 受体结合。使用小说 概念和技术方法，拟议的工作将揭示基本机制，染色质 负责导致这种严重动脉疾病的细胞命运变化的结构域和转录驱动因素。 这项工作有可能为合理确定目标提供新的转化机会。 设计保护患有肾脏疾病和高血压的儿童和成人肾脏的具体疗法。

PROJECT SUMMARY/ABSTRACT Juxtaglomerular (JG) cells are sensors, perfected throughout evolution to interpret and respond to changes in blood pressure and the composition and volume of the extracellular fluid. Normally, renin release from JG cells suffice to maintain homeostasis. However, under intense and prolonged physiological challenges (dehydration, sodium depletion, hypotension) smooth muscle cells (SMCs) along the kidney arterioles reacquire the renin phenotype and restore homeostasis. Once homeostasis is reestablished, the transformed cells stop making renin and become SMCs again. Conversely, if the inciting threat is not removed or overcome [as in spontaneous or experimental mutations of the renin-angiotensin system (RAS) genes or chronic inhibition of the RAS in mice, rats and humans] the relentless chronic stimulation of renin cells leads to the concentric hypertrophy of intrarenal arteries and arterioles. Numerous hypertrophic renin cells surround -and insert chaotically within- the arteriolar walls. SMCs accumulate concentrically and inwardly, narrowing the vessel lumens and restricting blood flow, resulting in ischemia, fibrosis and renal failure. In spite of its medical importance, and the prevalent use of RAS inhibitors in children and adolescents, the mechanisms underlying the development of this severe, albeit silent, disease are not known. Our renin cell ablation studies indicated that renin cells are responsible for the vascular disease not only by physically participating in the thickening of the vessel wall but also by their direct cell-to-cell interaction with SMCs. Abundant preliminary data from our laboratory suggest that the cAMP and Notch pathways are responsible for the transformation of renin cells and the arterial disease. We hypothesize that under chronic unrestrained stimulation, p300 remodels the chromatin of renin cells leading them to a dual embryonic-senescent phenotype. Further, the transformed renin cells, via Notch activation induce the concentric vascular hypertrophy of the adjacent SMCs. Aim 1 will test the hypothesis that specific imprinted chromatin domains determine the progressive changes in cell fate responsible for the concentric arterial hypertrophy. Aim 1A will define the identity and fate of the cells that compose the diseased arterioles. Aim 1B will test whether cells derived from the diseased arterioles are retained in (or reverted to) an embryonic/progenitor state. Aim 2 will test the hypothesis that Histone acetyltransferase p300 is responsible for the generation of those chromatin domains that determine the pathological transformation of renin cells and the concentric arterial hypertrophy. Aim 3 will test the hypothesis that the concentric accumulation of adjacent SMCs is mediated by Notch signaling via the engagement of the Jagged1 ligand in renin cells with the Notch2 receptor in SMCs. Using novel conceptual and technical approaches, the proposed work will uncover the fundamental mechanisms, chromatin domains and transcriptional drivers responsible for the changes in cell fate leading to this severe arterial disease. The work has the potential to open new translational opportunities for the rational identification of targets for the design of specific therapies that protect the kidneys of children and adults with kidney diseases and hypertension.