Abstract: Objective To investigate the expression of bone morphogenetic protein -7 (BMP-7) in ratearly diabetic nephropathy model for the elucidation of the relationship between BMP-7 and diabetic nephropathy. Methods Forty male SD rats were randomly divided into normal control group, diabetic nephropathy for 4 weeks group, diabetic nephropathy for 8 weeks group, and diabetic nephropathy for 12 weeks group. Streptozotocin 65mg/kg was given intraperitoneally to establish the rat model of type 1 diabetic nephropathy, and citrate buffer was injected for rats in normal control group. Rats were weighed at 4 weeks, 8 weeks and 16
weeks after the injection. Metal metabolic cage was used to collect urine for 24-hour urine protein (24h-UP) and 24 hours urine output. Rats were then sacrificed. Serum creatinine (Scr), blood urea nitrogen (BUN), and glucose (BG) were assayed in a Hitachi 7600 automatic biochemical analyzer, BMP-7 in blood and urine were measured using enzyme-linked immunosorbent assay, and BMP-7 mRNA in kidney was quantified by realtime PCR, and BMP-7 protein in kidney was detected by immunohistochemistry. Results There were statistically differences in body weight (F=18.040, P＜0.001), kidney weight/body mass index (F=70.20, P＜0.01), 24 h urine volume (F=249.6, P＜0.001), blood glucose (F=41.240, P＜0.001), 24h-UP (F=18.980, P＜0.01), Scr (F=12.690, P＜0.01), and BUN (F=14.570, P＜0.001) among the groups of normal control group, diabetic nephropathy for 4 weeks, diabetic nephropathy for 8 weeks, and diabetic nephropathy for 12 weeks. BMP-7 (F=1234.380, P＜0.001), urinary BMP-7 (F=34.510, P＜0.001), renal BMP-7 expression area (F=70.24, P0.01) were also different among the 4 groups. In diabetic nephropathy for 12 weeks group, blood BMP-7 (q=75.185, P＜0.01), urinary BMP- 7 (q=13.389, P＜0.01), BMP- 7 mRNA in kidney (q=8.402, P＜0.01) and BMP- 7 protein in kidney (q=17.902, P＜0.01) were decreased as compared with those in normal control group. Conclusion The expression of BMP-7 gene decreased in type 1 diabetes nephropathy rat model. BMP-7 may be involved in the development of diabetic nephropathy. BMP-7 may become an early diagnostic marker for renal function impairment in diabetes nephropathy.

Key words: Bone Morphogenetic Protein-7, Diabetic nephropathy, Expression, rat model