Altered molecular signatures during kidney development after intrauterine growth restriction of different origins

Intrauterine growth restriction (IUGR) has been linked to predisposition towards an unfavorable course of glomerulopathies and early loss of kidney function. This study was performed to identify transcriptional alterations in male IUGR rats during and at the end of nephrogenesis in order to generate hypotheses which molecular mechanisms contribute to adverse kidney programming. IUGR was induced by low protein (LP) diet throughout pregnancy, bilateral uterine vessel ligation (LIG), or intrauterine stress (IUS) by sham operation. Offspring of unimpaired dams served as controls. Significant acute kidney damage was ruled out by negative results for proteins indicative of ER-stress, autophagy, apoptosis or infiltration with macrophages. Renal gene expression was examined by transcriptome microarrays, demonstrating 53 (LP, n=12; LIG, n=32; IUS, n=9) and 134 (LP, n=10; LIG, n=41; IUS, n=83) differentially expressed transcripts on postnatal days (PND) 1 and 7, respectively. Reduced Pilra (all IUGR groups, PND 7), Nupr1 (LP and LIG, PND 7) and Kap (LIG, PND 1) as well as increased Ccl20, S100a8/a9 (LIG, PND 1), Ifna4 and Ltb4r2 (IUS, PND 7) indicated that inflammation-related molecular dysregulation could be a “common” feature after IUGR of different origins. Network analyses of transcripts and predicted upstream regulators hinted at proinflammatory adaptions mainly in LIG (arachidonic acid-binding, neutrophil aggregation, toll-like-receptor, NF-kappa B and TNF signaling) and dysregulation of AMPK and PPAR signaling in LP pups. The latter may increase susceptibility towards obesity-associated kidney damage. Western blots of the most prominent predicted upstream regulators confirmed significant dysregulation of RICTOR in LP (PND 7) and LIG pups (PND 1), suggesting that mTOR-related processes could further modulate kidney programming in these groups of IUGR pups.宫内生长受限（IUGR）已被证实与肾小球疾病病程不良及肾功能早期丧失的易感性密切相关。本研究旨在探究雄性宫内生长受限（IUGR）仔鼠在肾发生过程中及肾发生结束时的转录组改变，以解析介导不良肾脏编程的分子机制并提出相关研究假说。本研究通过妊娠全程低蛋白（LP）饮食、双侧子宫血管结扎（LIG）或假手术诱导宫内应激（IUS）三种方式构建仔鼠IUGR模型，以未接受造模的孕鼠所产仔鼠作为空白对照。通过检测内质网应激、自噬、凋亡及巨噬细胞浸润相关蛋白均呈阴性，排除了仔鼠发生显著急性肾损伤的可能。通过转录组芯片检测肾脏基因表达情况，结果显示：在出生后第1天（PND 1）与第7天（PND 7）时，分别筛选得到53个（低蛋白组：n=12；结扎组：n=32；宫内应激组：n=9）与134个（低蛋白组：n=10；结扎组：n=41；宫内应激组：n=83）差异表达转录本。Pilra在所有IUGR组的PND7时表达下调、Nupr1在低蛋白组与结扎组的PND7时表达下调、Kap在结扎组的PND1时表达下调；而Ccl20、S100a8/a9在结扎组的PND1时表达上调，Ifna4与Ltb4r2在宫内应激组的PND7时表达上调。上述结果提示，炎症相关分子调控异常可能是不同诱因IUGR后肾脏的共同特征。对差异转录本及预测上游调控因子的网络分析显示：结扎组主要呈现促炎症适应性反应，涉及花生四烯酸结合、中性粒细胞聚集、Toll样受体、核因子κB（NF-κB）及肿瘤坏死因子（TNF）信号通路；低蛋白组则存在腺苷酸活化蛋白激酶（AMPK）与过氧化物酶体增殖物激活受体（PPAR）信号通路的调控异常。后者可能会增加仔鼠罹患肥胖相关性肾损伤的易感性。针对核心预测上游调控因子的蛋白质免疫印迹实验证实：低蛋白组（PND7）与结扎组（PND1）仔鼠的RICTOR表达存在显著异常，提示哺乳动物雷帕霉素靶蛋白（mTOR）相关过程可进一步调控该两类IUGR仔鼠的肾脏编程。