The Role And Significance Of Macrophage Infiltration In Tubulointerstitial Fibrosis And Epithelial-Mesenchymal Transition

Objective This study is aimed to investigate the influence and significance of macrophage infiltration in the process of tubulointerstitial fibrosis (TTF) and epithelial-mesenchymal transition (EMT) in order to provide theoretical foundation for clinical treatment of renal diseases. Methods (1) Fifty-six cases of renal biopsy specimens with primary IgA nephropathy were collected from the department of pathology of the second hospital affiliated to AnHui Medical University, and HE, PAS, Masson staining were used to determine the degree of TIF in those cases. According to interstitial fibrosis and renal tubular atrophy, the cases were divided into three groups:light, medium and high-degree TIF group. Five cases of normal renal tissues from renal tumors were taken as control group. Immunohistochemical staining was used to detect the expression of CD68, CD206, TGF-β1, Vimentin, SMA and E-Cadherin proteins in these tissues, and the detailed clinical data of the patients were collected. (2) Human proximal tubular HK-2 cells were co-cultured with different number of monocytes U937 cells. HK-2 cells were divided into five groups according to the different number of U937 cells:control group (separately cultured HK-2 cells), HK-2 cells+U937 monocytes (1×104/ml), HK-2 cells+U937 monocytes(1× 105/ml), HK-2 cells+U937 monocytes (1×106/ml) and HK-2 cells+U937 monocytes (1×107/ml) group. The phenotypic changes of HK-2 cells were observed by the inverted microscope. At the same time, Western blot was used to investigate the expression of a-SMA, Vimentin and E-cadherin protiens. Results (1) The CD68/CD206 positive macrophages in the high-degree TIF group were more than the medium-degree TIF group, and the expression in the medium-degree TIF group were higher than in the light-degree TIF group (P<0.05). The CD68/CD206 positive macrophages were positively correlated with the expression of TGF-β1, Vimentin and SMA, but negatively correlated with the expression of E-Cadherin (P<0.05).In addition, the CD68/CD206 positive macrophages were positively correlated with the 24-hour urinary protein, serum creatinine, urea nitrogen (P<0.05). At the same time, the expression of TGF-β1, Vimentin and SMA were positively correlated with the degree of tubulointerstitial fibrosis,24-hour urinary protein, serum creatinine and urea nitrogen (P<0.05). But the expression of E-Cadherin had a negative correlation with the degree of tubulointerstitial fibrosis and clinical renal function indexes (P<0.05). (2) The morphology of HK-2 cells changed from paving stones into long spindle shaped cells, and the gap between cells was significantly increased after co-culture with U937 cells, compared with the separately cultured HK-2 cells. The expression of E-cadherin proteins decreased and a-SMA, Vimentin proteins increased after co-cultured with the U937 cells (P<0.05). Conclusions Macrophages may promote the process of renal TIF and renal tubular EMT in kidney disease.