Effects of Cordyceps sinensis on hydroxyproline contents and expression of p21 in renal tissue of rats with obstructive nephropathy

Objective To investigate the effects of Cordyceps sinensis on hydroxylproline contents and p21 expression in renal tissue of rats with obstructive nephropathy, and to explore the mechanism underlying its prevention against renal interstitial. Methods Sixty female SD rats were randomly divided into three groups: sham-operation group (SOR) , unilateral ureteral obstruction surgery group (UUO) and Cordyceps sinensis treatment group (CST). On days 7, 14, 21 and 28 after the operation, 5 rats from each group were randomly selected, killed and measured for blood urea nitrogen and serum creatinine. Specimens of obstructed kidney tissues were obtained to determine the severity of renal interstitial fibrosis by Masson staining, level of hydroxyproline (Hyp) contents by enzyme linked immunosorbent assay (ELISA) , and expression of p21 in renal tubular epithelial cells by immunohistochemistry. Results At each time point, the levels of blood urea nitrogen and serum creatinine were not statistically different among the three groups (P>0.05). The interstitial fibrosis, p21 expression and Hyp contents in the renal tissues of SOR group did not differ across all time point (all P> 0.05). Within either the CST or UUO group, the severity of interstitial fibrosis, Hyp content and p21 expression in renal tissue increased over the time of renal obstruction (P< 0.05). Compared with the SOR group, the UUO group and CST group had more severe renal fibrosis, higher Hyp content and p21 expression in renal tissue at each time point, with statistically significant differences between groups (P<0.05). Compared with UUO group, CST group showed milder degree of renal fibrosis, lower Hyp content (1130.59 ± 33.26ng/ml, 1175.21 ± 20.58ng/ml, 1228.68 ± 10.69ng/ml, and 1138.24 ± 21.13ng/ml ) and less expression of p21 expression in renal tissue (2.42 ± 0.96, 4.80 ± 1.13, 7.50 ± 1.32, and 9.00 ± 1.41) , with statistically significant differences between groups (P<0.05). Conclusion Renal tissue Hyp content is elevated in obstructive nephropathy. p21 may be involved in the pathogenesis and progression of renal fibrosis. Cordyceps sinensis may reduce and delay renal fibrosis induced by obstructive nephropathy, possible via reduction of Hyp content and p21 expression in tissue of obstructed rat kidney. Key words: Cordyceps sinensis; Obstructive nephropathy; Renal interstitial fibrosis; Hydroxyproline