宫内生长迟缓引起大鼠肾单位数目减少的机制研究

目的 探讨宫内生长迟缓（IUGR）引起肾单位数目减少的机制。方法 采用孕期全程低蛋白（6%蛋白）营养建立IUGR大鼠模型。选取IUGR新生雄鼠作为研究对象,采用Ki-67免疫染色和TUNEL法检测肾组织细胞的增殖和凋亡;实时定量PCR测定肾组织WT1、Bcl-2、Bax及p53的mRNA表达水平;免疫组织化学法及Western印迹法检测肾组织中WT1和Bcl-2蛋白质表达。2周龄时测定肾单位数目。结果 2周龄时,IGUR大鼠肾单位数目明显少于对照组（P＜0．01）。与对照组相比,IUGR新生鼠生肾区TUNEL阳性细胞数明显增多;肾脏WT1、Bcl-2 mRNA表达减少,Bcl-2 mRNA/Bax mRNA的比例降低．而p53 mRNA的表达差异无统计学意义;肾组织中WT1和Bcl-2蛋白质的表达量及在生肾区的分布也明显减少。结论 IUGR大鼠肾单位数目减少可能与肾发生中细胞凋亡增加相关,而WT1、Bcl-2表达减少,Bcl-2/Bax比例降低可能是细胞凋亡增加的分子机制之一。

Mechanism of nephron deficit in rat model of intrauterine growth retardation

Objective To investigate the mechanism of nephron deficit in the rat model of intrauterine growth retardation (IUGR). Methods A rat model of IUGR was established by maternal low-protein (6%) diet throughout pregnancy. Newborn male mice were chosen as objects. The cell proliferation and apoptosis in kidney were detected by Ki-67 and TUNEL method. Expression levels of WT1, Bcl-2, Bax and p53 mRNA were examined by real-time PCR. Immunohistochemistry and Western blot were used to examine the expression of WT1 and Bcl-2 gene products in renal tissue. The number of glomeruli was determined at age of 2 weeks when nephrogenesis finished. Results At two weeks postnatally, IUGR offspring had fewer glomeruli per kidney than those in controls (P<0.01). Compared to the controls, more TUNEL positive cells were located in the nephrogenic zone of IUGR newborns. In IUGR newborns, renal WT1 and Bcl-2 mRNA levels were significantly reduced, the Bcl-2 mRNA/Bax mRNA ratio was decreased, whereas the expression of p53 mRNA remained unchanged. In IUGR newborns, the expression levels of WT1 and Bcl-2 protein were significantly decreased, and their immunostaining were also suppressed in the nephrogenic zone. Conclusions Reduction of nephron number in IUGR rat may be associated with enhanced apoptosis in kidney development. Decreased WT1 and Bcl-2 expression as well as reduction of the Bcl-2/Bax ratio may contribute to the molecular mechanism.