| Background:Chronic kidney disease(CKD)is a chronic renal structure and dysfunction caused by various causes,with renal injury more than 3 months.Renal fibrosis is the final pathway and the main pathological basis for progression of various renal diseases to end stage of renal disease(ESRD),including glomerulosclerosis,renal tubular atrophy and interstitial fibrosis.In renal structure,as tubulointerstitial volume accounts for 90% of the total volume,chronic tubulointerstitial lesions play an important role in the development of CKD.Microvascular injury will cause hypoxia,inflammation and endothelial cell injury,eventually leading to renal fibrosis,so the protection of microvascular and vascular regeneration can alleviate renal damage and improve renal tubulointerstitial fibrosis.The angiopoietin family,activating the Ang1/Tie2 signaling system has the effects of anti-inflammation,reducing vascular permeability,stabilizing blood vessels and promoting vascular growth.Researchs about the activation of Tie2 signal to reduce tubulointerstitial fibrosis based upon the formation of renal tubulointerstitial lesions has not been reported.This study intends to explore the Tie2 signal activation effects on renal tubulointerstitial lesions in mice with folic acid induced nephropathy.The aim is to provide potential therapeutic targets for the treatment of chronic renal tubulointerstitial lesions.Methods:4 weeks,male CD1 mice are selected,and the folic acid renal injury model group(group F)is established by intraperitoneal injection of folic acid with 5%Na HCO3 of 240mg/kg.The normal group(group Con)is established by intraperitoneal injection of 5%Na HCO3.Onthe seventh day,wetake out the right kidneysof 12 group F and 6 group Con mice,then weigh the kidney and observethe appearance of kidney.The right kidney is divided into two.Take half of right kidney to do Masson staining to observe the renal pathological and do immunohistochemical to detect renal interstitial fibroblast specific protein-1(FSP-1).Take the other half of the right kidney for western blot detection of renal tubular interstitial vascular cell adhesion molecule-1(VCAM-1).On the ninth day of experiment,group Fis divided into group F+I and group F+T,group F+I and group Con areintraperitoneally injected with Ig G antibody(1mg/only),and group F+T is intraperitoneally injected with stimulating Tie2 monoclonal antibody(1mg/only).On the twenty-eighth day of the experiment,we take out the left kidney of eachmouseand observe the appearance of the kidneys.Then we weigh the body weight and the kidney weight.Half of the kidneys are taken for masson staining and detecting the expression of FSP-1 by immunohistochemical.The other half of the kidneys are used to detect the expression of VCAM-1 by western blot.We do analysis of each index before and after the treatment of each mouse.Results:1,kidney weight / body weight ratio: On theseventh day,the ratio of group F+T(0.8859 ± 0.1168)and group F+I(0.8679 ± 0.1029)are greater than that of group Con(0.6671 ± 0.708,p<0.05),suggesting renal enlargement is shown in group F+T and group F+I.On the twenty-eighth day,the ratio of group F+T(0.7883 ± 0.1248)is not statistically significant compared with that of group Con(0.9324 ± 0.0937)(p>0.05).The ratio of group F+I(0.6781 ± 0.0602)is less than that of group Con(p<0.01).In group F+I,the ratio of twenty-eighth day is less than seventh day(p<0.01),suggesting renal atrophyis shown in group F+I.Thereis no significant difference in the ratio of twenty-eighth day to seventh day in group F+T(p>0.05).2,tubulointerstitial lesion area / total area ratio: On the seventh day,the ratio of group F+T(76.61±6.81)and F+I group(74.11±8.38)are greater than that of group Con(p<0.0001),suggesting there is a wide range of renal tubulointerstitial lesions in group F+T and group F+I.On the twenty-eighth day,the ratio of tubulointerstitial lesions in group F+T(7.47±2.25)is smaller than that on the seventh day(p<0.0001),the ratio of renal tubulointerstitial lesions in group F+I(17.74±4.40)is smaller than that on the seventh day(p<0.0001).The difference between ratio of renal tubulointerstitial lesions on the seventh day and that on the twenty-eighth day in group F+T(69.14±6.45)is greater than that in group F+I(56.37±4.36,p<0.01),suggesting that the improvement of renal tubulointerstitial lesions in group F+T is better than that in group F+I.On the twenty-eighth day,the ratio of renal tubulointerstitial fibrosis in group F+T(5.43±2.25)is less than that in group F+I(15.07±4.56,p<0.01),suggesting that Tie2 signal activation can reduce the occurrence of chronicrenal tubulointerstitial fibrosis.3,Immunohistochemistry: On the seventh day,the number of FSP-1 positive cells in group F+T and group F+I arelarger than that in group Con(p<0.0001).On the twenty-eighth day,the number of FSP-1 positive cells in group F+T is less than that in group F+I(p<0.05).The number of FSP-1 positive cells on the twenty-eighth day is less than that on the seventh day of the same group in both group F+T and group F+I(p<0.001).The difference of the number of FSP-1 positive cells between twenty-eighth day and seventh day in group F+T is greater than that in group F+I(p<0.01).4,Weston blot: On the seventh day,the expression level of VCAM-1 increases in group F+T and F+I group(p<0.01).On the twenty-eighth day,the expression level of VCAM-1 in group F+T is not statistically significant compared with that in group Con(p>0.05),and the expression level of VCAM-1 in group F+T is lower than that in group F+I(p<0.05).In group F+T,the expression level of VCAM-1 on the twenty-eighth day is lower than that on the seventh day(p<0.001).In group F+I,there is no significant difference in the expression level of VCAM-1on twenty-eighth day compared with that on the seventh day(p>0.05).Conclusion:(1)On the basis of renal tubulointerstitial lesions,activation of Tie2 signaling can significantly ameliorate tubulointerstitial lesions in mice with folic acid induced nephropathy,and can reduce the occurrence of renal tubulointerstitial fibrosis.(2)The activation of Tie2 signals may ameliorate renal tubulointerstitial lesions and decrease renal tubulointerstitial fibrosis by reducing the expression of FSP-1 and VCAM-1. |
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