Manipulating Podocytes to Protect Normal Glomerular Formation

描述(申请人提供)：尽管足月出生时肾单位数量减少与晚年心血管、肾脏和代谢性疾病的增加有关，但肾单位的中心结构--肾小球的发育调节在很大程度上仍不清楚。我们最近对正常发育小鼠的肾小球数量进行评估的研究显示，在新的肾小球生成停止后，肾小球显著减少，这表明通过回归过度的肾脏生成来进行调整。足细胞在肾小球的形成中起着重要的引导作用。我们假设足细胞控制肾小球的生长/退化，并决定最终的肾单位数量，增加足细胞数量或足细胞来源的血管内皮生长因子促进肾小球血管系统的生长，从而减少肾小球退化，从而增加肾小球储备。我们将检测和量化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/增殖和退化信号的关系。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，并验证足细胞在成熟发育过程中的操纵可以挽救损伤所致的肾小球毛细血管生长障碍，从而减轻肾小球退行性变，从而保留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层肾小球和相对成熟的深层肾小球对发育中的小鼠损伤的不同反应。为此，我们将使用两种可诱导的足细胞损伤模型，即注射LMB2的Nphs2-hCD25转基因小鼠和嘌呤霉素氨基核苷损伤模型，以及两种足细胞特异性的诱导修复模型，足细胞过度表达血管内皮生长因子或通过表达SV40T诱导足细胞的增殖。这些转基因模型中的每一个都优先影响成熟或未成熟的足细胞和肾小球。此外，还将研究回归抑制药在这些损伤和救援模型中的作用。随后将跟踪肾小球发育变化的后果。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肥大肾小球和健康肥大肾小球。这项建议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的作用的理解。这项工作对发育过程中建立的正常肾脏储备、对伤害性刺激的有效反应以及在以后的生活中发生心血管和肾脏疾病的易感性具有重要意义。

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.