Effect Of Glucocorticoid On Renal Interstitial Fibrosis In Mice With Obstructive Nephropathy

Objective:To investigate the effects of glucocorticoids on renal interstitial fibrosis in unilateral ureteral obstruction(UUO)mice,and to explore its possible mechanism for the first time.Methods:Unilateral Ureteral Obstruction(UUO)model was established by ligating the left ureter of C57 mice.Mice were randomly divided into a sham operation group,a model group,and a dexamethasone treatment group.Mouse blood creatinine(Scr)and urea nitrogen(BUN)were measured on the 7th day after surgery.The left kidney tissue was stained with HE and Masson to observe the pathological changes and the degree of fibrosis.Western blotting(Western-blot)was used to detect the expression of α-SMA and TGF-β1 protein in kidney tissue;real-time fluorescence quantitative PCR(qRT-PCR)was used to detect the expression of α-SMA and TGF-β1 mRNA in kidney tissue.Result:(1)The General changes of kidney: The kidneys of mice in the sham-operated group showed smooth,dark red,and no appearance of swelling.Compared with the sham operation group,the kidney volume of the left side obstruction side of the model group was significantly increased,the color was pale,the appearance was cystic swelling,and there was a lot of water,indicating that the model was successful.In contrast,the dexamethasone treatment group had less renal swelling and water retention than the model group.(2)Blood biochemical indicators: The levels of Scr and BUN in the model group were significantly higher than those in the sham operation group(p <0.01).The levels of Scr and BUN in the dexamethasone treatment group were significantly lower than those in the model group(p<0.05).(3)Renal pathological changes: HE staining results showed that no significant changes were found in the glomeruli,renal interstitium,and renal tubules in the sham-operated group.The renal cortex of the model group was significantly thinned,the tubular epithelial cells were deformed in vacuoles,and the tubular lumens were cystic.Expansion,atrophy of the glomerulus,renal interstitial fibers hyperplasia,and a large number of inflammatory cells infiltration.Compared with the model group,the degree of renal tubular epithelial cell degeneration,tubular expansion,glomerular atrophy,and fibrosis were reduced in the dexamethasone treatment group,and only a small amount of inflammatory cell infiltration was seen.Masson staining results showed that there was no obvious blue collagen fiber deposition in the renal interstitium of the sham operation group.Compared with the sham operation group,a large amount of blue collagen fibers were seen in the renal interstitium of the model group,while the dexamethasone treatment group had a blue interstitium.Collagen fiber deposition was significantly reduced compared with the model group.(4)Western-blot results showed that the expression level of a-SMA in the model group was significantly higher than that in the sham operation group(p <0.0001),and the α-SMA level in the dexamethasone treatment group was significantly lower than that in the model group(p<0.01).Compared with the sham operation group,the expression level of TGF-β1 in the model group was significantly increased(p<0.001),and the level of TGF-β1 in the dexamethasone treatment group was significantly lower than that in the model group(p<0.05).(5)qRT-PCR results showed that the expression of α-SMA mRNA in the model group was significantly higher than that in the sham operation group(p<0.01).Compared with the model group,the expression level of α-SMA mRNA in the dexamethasone treatment group was significantly reduced(p<0.001);Compared with the sham-operated group,the expression level of TGF-β1mRNA in the model group was significantly increased(p<0.01),while the expression level of TGF-β1mRNA in the dexamethasone treatment group was significantly lower than that in the model group(p<0.05).Conclusion:(1)The expression of TGF-β1 and α-SMA in renal tissue of obstructive nephropathy is up-regulated,which is related to the formation of renal interstitial fibrosis.(2)Glucocorticoids can relieve the degree of renal interstitial fibrosis in obstructive nephropathy and protect renal function.(3)Glucocorticoids alleviate the degree of renal interstitial fibrosis in obstructive nephropathy and it is related to the down-regulation of TGF-β1 and α-SMA expression and the reduction of EMT.