骨形成蛋白7在糖尿病大鼠肾组织中的表达及意义

Expression of bone morphogenetic protein 7 and its potential role in diabetic rats

目的观察糖尿病大鼠肾组织中骨形成蛋白7(BMP-7)的表达及探讨其在糖尿病肾病中的可能作用。方法将大鼠分为糖尿病组及正常对照组,分别在第30、60、90、120、150及180 d测定各组的血糖、Ser、24 h尿白蛋白、尿肌酐(Ucr)水平。以HE、PASM染色及ColⅣ蛋白表达衡量肾脏病理改变。用免疫组化及RT-PCR方法检测肾组织中BMP-7、TGF-β1的蛋白及mRNA表达水平。结果糖尿病组各时间点血糖、尿白蛋白量(24 h)均明显高于对照组(P<0．01)。糖尿病组伴随病理改变的加重和ColⅣ表达的逐渐增强,BMP-7蛋白及mRNA水平(A％,30 d 95．87±1．19;180 d 26．43±1．26)逐渐降低,与对照组(A％,30 d 98．64±0．80;180 d 98．80±0．49)相比,差异有统计学意义(P<0．01或P<0．05);相反,肾组织中TGF-β1的mRNA (A％,30 d 40．26±0．98;180 d 102．12±6．45)及蛋白水平较对照组显著增加(P<0．01)。BMP-7与TGF-β1的蛋白及mRNA表达水平均呈显著负相关(P<0．01)。结论BMP-7可能是维持肾脏功能稳定的一个重要因子。BMP-7在糖尿病肾病中具有与TGF-β1相反的作用,其水平下降可能参与了糖尿病肾病早期小管间质的损伤。

Objective To observe the expression of bone morphogenetie protein 7 （BMP-7） in different stages of diabetic rats and investigate the potential role of BMP-7 in diabetic nephropathy （DN）. Methods Wistar rats were divided into diabetes meUitus（DM） group induced by intravenous injection of streptozotocin （65 mg/kg）, and normal control group injected with citrate buffer. The rats were sacrificed at day 30,60,90,120,150 and 180 following injection, respectively. The blood glucose,Scr, urinary albumin and urinary creatinine were measured in each rat before sacrifice. The renal pathological changes were examined with hematoxy]in and eosin （HE）,periodic acid-silvermethenamine staining （PASM） and protein expression of collagen IV （Col IV ）. The mRNA and protein expression of BMP-7 and TGF-β1 in kidney were detected by reverse transeription-polymerase chain reaction （RT-RCR） and immunohistoehemical staining respectively, and were quantified by computer image analysis system. Results The levels of blood glucose and urinary albumin in diabetic group were remarkably higher than those in control group（P 〈 0.01 ）. With the aggravation of diabetic nephropathy and increasing expression of Col IV , the expression of mRNA and protein of BMP-7 was progressively down-regulated （A %, 30 d 95.87±1.19 ; 180 d 26.43±1.26） （P 〈 0.01 or P 〈 0.05）, whereas the expression of TGF-β1 mRNA （A% 30 d 40.26±0.98;180 d 102.12±6.45） and protein was significantly up-regulated in the diabetic rats as compared with that of the controls （A%,30 d 98.64±0.80; 180 d 98.80±0.49）（P〈 0.01）. The protein and mRNAlevels of BMP-7 were negatively correlated with TGF-β1 respeetively（P 〈 0.01 ）. Conclusions Endogenous BMP-7 may be an important molecule for maintenance of renal homeostasis. The decrease of BMP-7 protein and mRNA during the early phase of diabetic nephropathy is possibly involved in the occurrence of diabetic nephropathy. BMP-7 may counteract TGF-β1-mediated profibrotic effects.