Effect of macrophage polarization on interstitial fibrosis in mouse unilateral ureteral obstruction model

Objective To investigate the effect of macrophage polarization on tubulointerstitial fibrosis of mouse unilateral ureteral obstruction(UUO) model. Methods Twelve male C57BL/6J mice were employed, each of which with an age of 8 to 10 weeks. UUO model was established with these mice with the method of unilateral ureteral ligation. Mice were then sacrificed on the 7th and 14th day respectively after operation, and renal tissue specimens were obtained. The authors detected collagen deposition by Masson staining, and alpha smooth muscle actin (alpha SMA) as well as collagen type I (Coll-1) mRNA by real-time quantitative PCR. The authors also detected the degree of renal interstitial macrophages infiltration and expression changes of polarization by immunofluorescence staining. Results Compared with the mice that were observed on the 7th day after operation, the degree of renal interstitial fibrosis in mice observed on the 14th day after operation was comparatively serious, the difference shown by semi-quantitative results was statistically significant (P＜0.05). Moreover, mice observed on the 14th day after operation have more M2 macrophages, the difference between two groups of mice was statistically significant (P＜0.05). On the contrary, there was no statistically significant difference in the degree of M1 macrophages infiltration between these two groups of mice. Conclusions In the renal interstitial fibrosis model induced by UUO, the degree of macrophage infiltration increased significantly, mainly resulted from M2 macrophage infiltration, suggesting that M2 macrophages were involved in the formation of renal fibrosis.