新生小鼠足细胞损伤对肾小球发育的影响

目的 探讨新生小鼠中足细胞损伤对肾小球发育的影响及其机制。 方法 于新生ICR小鼠出生后1 d注射嘌呤霉素(puromycin aminonucleoside，PA)，并以注射生理盐水作为对照。观察出生后第2、4、8、12、30、60、90天时肾重/体重、尿蛋白、血压及组织学的改变。应用免疫组化及定量RT-PCR方法测定肾皮质内肾母细胞瘤基因(WT-1)、CD31、血管内皮生长因子(VEGF)及其受体Flk-1、血管生成素(angiopoietin，Ang-1、Ang-2)及其受体Tie-1、Tie-2的表达水平。 结果 注射PA后，新生小鼠肾重、体重均明显低于对照组。出生后第2天(注射PA后1 d)时，肾小球足细胞出现足突广泛融合和微绒毛的脱落；第12天时，肾小球内CD31的表达明显下降，部分肾小球萎缩、发育不良，肾皮质浅层小球成熟指数明显下降；第30天时，原先发育不良的肾小球逐渐被吸收；第60天时，剩余肾小球出现系膜区的扩张和小球节段性硬化。PA鼠在第30天时出现蛋白尿；第60天时血压显著增高。定量RT-PCR显示，第2天时肾皮质Ang-1表达明显上调，Flk-1及Tie-2明显下降。 结论 PA可以在早期损伤的新生ICR小鼠足细胞，改变VEGF、血管生成素系统的表达，导致肾小球毛细血管袢发育不良及在后期产生蛋白尿、高血压和肾小球硬化。

Influence of injured podocytes on glomerular maturation in neonatal mice

Objective To study the effect of injured podocytes on glomerular maturation and its underlying mechanism in neonatal mice. Methods Single i.p.injection with puromycin aminonucleoside (PA， 0.1 mg/g BW) was given to ICR neonatal mice at day 1 after birth (1 dpp). Littermates injected with normal saline (NS) were used as control. Animals were examined for urine protein， blood pressure， kidney weight/body weight (KW/BW)， renal histology at 2， 4， 8， 12， 30， 60 and 90 dpp (n=6~9 for each group). Immunohistochemistry and quantitative RT-PCR were performed to examine the expression of WT-1， CD31， VEGF， Flk-1， Ang-1， Ang-2， Tie-1 and Tie-2. Results Mice with PA injection had lower kidney weight and body weight at all time points as well as lower KW/BW at 4， 8， 12 dpp when compared with NS controls. Electron microscopy revealed nearly complete foot process effacement and segmental microvillous transformation as early as 1 day after PA injection. PA-injected kidneys showed fewer capillary loops and decreased maturation index as well as less CD31-positive endothelium in cortical glomeruli at 12 dpp. Glomerular mesangial injury and developing glomerulosclerosis along with proteinuria were noted in PA-injected kidneys starting from 30 dpp. Significantly increased systolic blood pressure was detected at 60 dpp in PA mice. Compared with NS injection， PA injection significantly induced decreased mRNA expression of Flk-1 and Tie-2 as well as increased expression of Ang-1，without obvious changes of VEGF at 2 dpp. Conclusions Podocytes in neonatal kidney of ICR mice are susceptible to PA. Such podocyte injury can alter the expression of VEGF and angiopoietin system in glomeruli， leading to abnormal development of glomerular capillaries， and subsequent proteinuria， hypertension and glomerulosclerosis.