Gestational Programming of Nephrogenesis

描述(申请人提供)：母亲营养不良(MUN)会导致胎儿宫内生长受限(IUGR)，这会显著增加成人终生罹患心脏病、肥胖症、II型糖尿病和其他代谢综合征的风险。与IUGR相关的肾脏编程会导致成人肾小球减少(肾小球数量减少)和成人动脉血压升高。预防这种形式的程序性肾损伤的机制和策略还知之甚少。研究人员最近发现，在MUN肾脏形成过程中，胶质源性神经营养因子(GDNF)和Notch信号通路显著下调。他们假设，这些信号通路的程序性下调导致重复的输尿管芽分支、MAPK/ERK信号和肾素-血管紧张素系统基因表达减少，最终导致肾小球数量减少、肾小球异常成熟和成人高血压。在这一过程中一个被提出的早期事件，WT1上调，是由表观遗传MUN编程调制的。在研究人员的模型中，从怀孕第10天到出生后第8天，母鼠喂食50%的减量饮食。他们将确定胎儿肾脏发育的关键时间点，此时输尿管分支和肾小球形成是IUGR的易感因素。他们将通过实时RT-PCR和Western blotting检测GDNF和Notch信号通路的程序性下调、MAPK/ERK激活和肾内RAS基因的表达，以及通过免疫组织化学和原位杂交检测区域肾脏和肾小球的表达。将描述WT1的表观遗传编程。为了确定可能的信号机制，本研究将利用重组蛋白、siRNA和病毒基因表达载体在体外MFR肾脏组织中诱导GDNF和Notch信号通路的过度表达，以复制/预防IUGR对输尿管分支、肾小球形成和信号转导通路的影响。这些发现将为MUN对程序性肾发生的影响提供一个机制分析，并为治疗人类的胎儿程序化提供一个翻译框架。 相关性：低出生体重儿出生时肾脏缺乏肾单位数量，并且由于胎儿环境不适应，基因表达发生永久性变化。这些研究旨在为这种形式的胎儿编程在肾脏发育中发生的分子变化提供洞察力。研究人员的长期目标是确定胎儿肾脏发育的关键发育点，并通过治疗逆转这种情况。

DESCRIPTION (Provided by Applicant): Maternal under-nutrition (MUN) results in intrauterine growth restriction (IUGR) of the fetus, which markedly increases the lifelong adult risk of heart disease, obesity, type II diabetes, and other components of the metabolic syndrome. IUGR-related programming of the kidney gives rise to adult nephropenia (reduced glomerular number) and elevation in adult arterial blood pressure. Mechanisms for and strategies for prevention of this form of programmed renal injury are poorly understood. The investigators recently identified significant down-regulation of the Glial derived neurotrophic factor (GDNF) and Notch signaling pathways during MUN nephrogenesis. They hypothesize that programmed down-regulation of these signaling pathways leads to a reduction of iterative ureteric bud branching, MAPK/ERK signaling, and renin-angiotensin system gene expression, which ultimately results in reduced glomerular number, abnormal glomerular maturation, and adult hypertension. A proposed early event in this process, WT1 upregulation, is modulated by epigenetic MUN programming. In the investigators' model, maternal rat dams are fed a 50% reduced diet from day 10 of gestation to postnatal day 8. They will identify the key time point during fetal kidney development when ureteric branching and glomerulogenesis are susceptible to IUGR. They will examine the programmed down-regulation of the GDNF and Notch signaling pathways, MAPK/ERK activation, and intra-renal RAS gene expression by real time RT-PCR and Western blotting, as well as regional kidney and glomerular expression by immunohistochemistry and in situ hybridization. Epigenetic programming of WT1 will be characterized. To confirm the putative signaling mechanisms, the will induce over-expression of the GDNF and Notch signaling pathways using recombinant protein, siRNA, and viral gene expression vectors in ex vivo MFR kidney explants to replicate/prevent the effects of IUGR on ureteric branching, glomerular formation, and signal transduction pathways. These findings will provide a mechanistic analysis of the impact of MUN on programmed nephrogenesis, and provide a translational framework for treating fetal programming in humans. RELEVANCE: Low birth weight newborns are born with kidneys deficient in nephron number as well as permanent changes in gene expression due to the maladaptive fetal environment. These studies are designed to provide insights into the molecular changes in kidney development that occur due to this form of fetal programming. The investigators' long term goal is to identify key developmental points in fetal kidney growth and to reverse the condition through therapeutic treatments