To Understand Whether Estrogen Has A Certain Effect On Fibrosis Of Renal Interstitial After Renal Ischemia-reperfusion Injury

Objective:To investigate whether estrogen can improve the degree of renal interstitial fibrosis after renal ischemia reperfusion injury by regulating the expression of TGF-β_1,so as to further explore the possible mechanism of estrogen’s protective effect on renal ischemia reperfusion injury.Methods:（1）Thirty-two female SD rats had ovary removal two weeks before experiment,they were randomly divided into four groups（8 rats/group）:normal group,sham operation group,renal ischemia reperfusion injury group,and estrogen intervention group.Normal group:no treatment,routine feeding.In the sham operation group,the right kidney was completely removed and the left kidney was exposed by surgery after conventional anesthesia,left renal pedicle was untreated,and the abdominal cavity was closed after 45 min,and the incision was sutured layer by layer.Ischemia reperfusion injury group:after well anesthetized,the right kidney was removed,and the left renal pedicle was closed with non-invasive arterial clip.After continuous clipped ischemia for 45 min,the renal blood supply was restored and the abdominal cavity was closed.Estrogen intervention group:experimental animals were given daily subcutaneous injection of estrogen（100 ug/kg）for three days before surgery.And the remaining steps were same to the ischemia-reperfusion injury group.After the above operation,rats in each group were routinely fed for 14 days before sacrifice.（2）Paraffin sections of renal tissue were stained with HE.Paller score was used to quantify the degree of renal tissue damage.（3）Paraffin sections were stained with Masson staining kit.The degree of renal fibrosis in each group were observed under light microscope.（4）The change of TGF-β₁ protein levels in renal stroma of each group was detected by Western-blot.Results:（1）HE showed obvious pathological damage in the ischemia reperfusion injury group,including glomerular atrophy,renal tubules swelling,necrosis and cells shedding,significant changes in lumen size,and pathological changes in renal interstitial.Paller score was significantly higher than that in the normal group and the sham group（P<0.05）.However,in the estrogen intervention group,the glomerular structure remain intact.Renal tubular epithelial cells,renal interstitial cells and inflammatory cells were less invasive than those in the I/R group,and Paller score was lower than those in the ischemia reperfusion injury group（P<0.05）.（2）Masson staining showed obvious interstitial fibrosis in the ischemia-reperfusion injury group.Compared with the former group,interstitial fibrosis in estrogen intervention group was significantly relieved.（3）Estrogen reduce the expression of TGF-β₁ protein in the renal interstitial after renal ischemia reperfusion injury,and the expression of TGF-β1 in the renal ischemia reperfusion injury group was significantly enhanced compared with the normal group（P<0.05）.The expression of TGF-β₁protein in the kidney of the estrogen intervention group was significantly lower than that of the ischemia-reperfusion injury group（P<0.05）.Conclusion:Estrogen may improve the degree of renal interstitial fibrosis by decreases the expression of TGF-β₁ in the renal interstitial of the rats in the ischemia reperfusion injury group,so as to exert a protective effect after renal ischemia reperfusion injury.