Manipulating Podocytes to Protect Normal Glomerular Formation

描述（由申请人提供）：尽管足月分娩时肾单位数量减少与以后生活中心血管、肾脏和代谢疾病增加有关，但肾小球（肾单位的中心结构）的发育调节仍在很大程度上未知。我们最近的研究，以评估正常发育小鼠的肾小球数量显示，新的肾小球发生停止后，肾小球显着减少，这表明通过回归过度的肾单位生成的调整。足细胞在指导肾小球形成中具有重要作用。我们假设足细胞支配肾小球的生长/退化，并决定最终的肾单位数，增加足细胞数量或足细胞来源的VEGF促进肾小球血管系统的生长，减少肾小球退化，从而增加肾小球储备。我们将检查并定量足细胞数量和成熟度、肾小球内皮面积和毛细血管分支模式、肾小球数量和大小的时间、空间和顺序变化，以及它们与血管生成/增殖和消退信号的关系。此外，我们计划研究足细胞在肾小球损伤的成熟反应中的作用，并测试这一假设，即在成熟发育过程中操纵足细胞可以挽救损伤诱导的肾小球毛细血管生长障碍，减少肾小球退化，从而保护肾小球数量和毛细血管网络。我们将进一步研究未成熟的浅表肾小球与相对成熟的深层肾小球对发育中小鼠损伤的不同反应。为了这些目的，我们将使用两种可诱导足细胞损伤模型，注射LMB 2的Nphs 2-hCD 25转基因小鼠和嘌呤霉素侧损伤模型，以及两种可诱导足细胞特异性拯救模型，其具有足细胞过度表达VEGF或通过足细胞中SV 40 T表达诱导增殖。这些转基因模型中的每一种都优先影响成熟或未成熟的足细胞和肾小球。还将研究回归抑制剂在这些损伤和拯救模型中的作用。肾小球发育变化的后期后果将被跟踪。本提案还将讨论由于发育损伤和对足细胞的干预而导致的异常与健康的肥大肾小球。 本提案涉及肾小球发育的生物学和病理学。研究结果将进一步加深我们对足细胞在肾小球发育中作用的认识。这项工作对发育过程中建立的正常肾储备、对有害刺激的有效反应以及晚年心血管和肾脏疾病的发展倾向具有重要意义。 公共卫生相关性：本申请涉及肾小球发育的生物学和病理学。通过使用转基因小鼠模型，药物干预，组织学形态学分析和分子测定，PI将建立肾小球发育过程中的成熟和数量的基础文件和方法，测试足细胞在肾小球形成中的主导作用，并研究肾脏在早期和后期生活中对有害刺激的反应和补偿能力。 本研究结果将为进一步了解肾小球形成的调控机制提供理论依据，也为保护肾小球在损伤或发育不良时的正常功能提供可能。

DESCRIPTION (provided by applicant): Although reduced nephron number at term birth has been linked to increased cardiovascular, renal and metabolic diseases later in life, the developmental regulation of glomeruli, the central structure of nephron, remains largely unknown. Our recent studies to assess the glomerular number in normal developing mice revealed a significant reduction in glomeruli occurring after the cessation of new glomerulogenesis, which suggests adjustment by regression of excess nephronogenesis. Podocytes have an important role in guiding glomerular formation. We hypothesize that podocytes govern glomerular growth/regression and determine the final nephron number, and increasing podocyte population or podocyte-derived VEGF promotes growth of the glomerular vasculature and lessens glomerular regression thereby increasing glomerular reserve. We will examine and quantitate the temporal, spatial and sequential changes of podocyte number and maturity, glomerular endothelial area and capillary branching pattern, glomerular number and size, as well as their relationships to angiogenic/proliferative and regression signals. Moreover, we plan to study the role of podocytes in the maturational responses to glomerular injury, and test the hypothesis that podocyte manipulation during maturational development rescues injury-induced impairment of glomerular capillary growth, lessens glomerular regression thereby preserves glomerular number and capillary network. We will further investigate the differential responses of immature superficial glomeruli vs. relatively mature deep glomeruli in response to the injuries in developing mice. For these purposes, we will use two inducible podocyte injury models, the Nphs2-hCD25 transgenic mice with LMB2 injection and puromycin aminonucleoside injury model, and two inducible podocyte-specific rescuing models with podocyte over-expression of VEGF or induction of proliferation by SV40T expression in podocytes. Each of these transgenic models has impacts preferentially on mature or immature podocytes and glomeruli. The effects of regression inhibitory agents in these injury and rescuing models will also be studied. Later consequences of changes in glomerular development will be followed. This proposal will also discuss the abnormal vs. healthy hypertrophied glomeruli due to developmental injuries and interventions to podocytes. This proposal addresses the biology and pathology of glomerular development. Study results will further our understanding of the role of podocytes in glomerular development. The work carries implication for the normal renal reserve established during development, the effective response to injurious stimuli, and the predisposition for development of cardiovascular and renal diseases in later life. PUBLIC HEALTH RELEVANCE: This application addresses the biology and pathology of glomerular development. By using transgenic mice models, pharmaceutical interventions, histological morphometric analyses, and molecular assays, the PI will establish a fundamental documentation and methodologies for the glomerular maturation and number during development, test the leading role of podocytes in glomerular formation, and investigate responses and compensation capabilities of the kidney to injurious stimuli in early and later life. The results will offer further understandings for the regulatory mechanisms of glomerular formation, and may also offer therapeutic possibilities of preserving normal endowment of glomeruli in response to injury or mal-development.