Effects of bone morphogenetic protein 2 signal pathway on renal artery calcification in progression of diabetic nephropathy

Abstract

Objective To explore the effects of renal artery calcification on the progression of diabetic nephropathy (DN), the activation and its role of bone morphogenetic protein 2(BMP2) signal pathway in renal artery of rats. Methods Sixty male SD rats were randomly divided into control group(CON group), DN group and DN with vascular calcification group (DN+VDN group). Rats of group DN and DN+VDN were fed with high sugar and fat diet and injected with streptozocin (STZ) into abdominal cavity to induce diabetes. After diabetic models were successfully made, rats of group DN+VDN were treated by vitamin D3 plus nicotine. The rats were sacrificed at 8th, 12th and 16th week respectively and the levels of renal function, blood glucose and 24 h urinary protein (24-h Upro) were measured. The pathologic changes to the renal artery were observed by von-Kossa staining and the calcium content was detected by calcium assay kit. The pathologic changes to the kidney were observed by HE. Immunohistochemistry was applied to detect the protein expression of BMP2/Smad1/Runx2/Osterix signal pathway in the renal artery and real-time PCR were applied to detect the mRNA expression levels of BMP2 and Runx2. Results The calcium content and the deposition of black granules in DN group were significantly higher than those in group CON and lower than DN+VDN group at each time point (P<0.05). The renal function indices in group DN and group DN+VDN were gradually increased in 8th,12th and 16th weeks, and were higher than those in group CON (P<0.05). Compared with that in DN group, although the level of BUN, Scr, Cys C and 24-h Upro in DN+VDN group rats were higher at different time point, the level of Cys C at each time point and the level of 24-h Upro in the 16th week showed significant differences (P<0.05). The pathological damages of the kidney in group DN and DN+VDN showed a continual worsening trend and the pathological changes of the kidney in group DN+VDN were more serious than those in group DN. Furthermore, the levels of BMP2/Smad1/Runx2/Osterix signal protein and BMP2, Runx2 mRNA in DN rats were higher than those in CON group, lower than DN+VDN group at each time point (P<0.05). Correlation analysis demonstrated that calcium content was positively correlated with serum BUN, Scr, Cys C, 24-h Upro and the expression of BMP2, Runx2 mRNA (r=0.835, 0.705, 0.829, 0.897, 0.641, 0.683, P<0.01, respectively). Conclusion Renal artery calcification may participate in and promote the progression of DN, and the BMP2 signal pathway may be an important regulating factor in DN with renal artery calcification. Key words: Diabetic nephropathies; Renal artery; Bone morphogenetic protein 2; Vascular calcification