The Role Of Renal Interstitial Fibrosis In Renal Anemia And Its Intervention

Objective:Renal anemia(RA)is one of the most common complications of chronic kidney disease(CKD),whieh can accelerate renal damage,induce cardiovascular events,and significantly reduce the quality of life and prognosis of patients.However,the current understanding of the pathogenesis and intervention mechanism of renal anemia is still incomplete,especially lack of an ideal animal model of renal anemia.This study aims to analyze the clinical features and related factors of renal anemia in patients with IgA nephropathy and establish a stable animal model of renal anemia.Then use the model’s renal anemia characteristics,apply anti-fibrotic drug nintedanib to observe its effect on renal anemia,thereby elucidate the renal anemia mechanism to provide clinical and experimental research basis for better treatment of RA.Methods:1.462 adult patients who were diagnosed as IgA nephropathy by renal biopsy and met the standard of nephrectomy were divided into anemic group and non-anemic group according to hemoglobin level.The clinical and pathological features and related factors of RA in patients with IgA nephropathy were analyzed2.Adenine model(administering 50 mg/kg.d5 75 mg/kg.d adenine gavage,4 weeks),aristolochic acid model(administering mice with 3 mg/kg.2d,3mg/kg.3d intraperitoneal injection of aristolochic acid,6 weeks),observed changes of serum creatinine(SCr),urea nitrogen(BUN);hemoglobin(Hb),hematocrit(HCT);PAS staining observed renal tissue damage,lesions of renal fibrosis were detected by Masson,s and Sirius red staining,andα-SMA levels in renal tissues were determined by immunohistochemistry and Western blot.The amount and location of EPO expression in renal tissue were determined by quantitative PCR(qPCR),western blot and immunofluorescence.3.The animal experiments studied by the intervention mechanism were divided into three groups:control group,model group andnintedanibgroup.The expressions of Hb and HCT in each group were observed.The expression of EPO in serum and renal tissues of each group was changed.The pathological changes of kidney in each group were observed by PAS staining.The renal fibrosis was detected by Masson’s and Sirius red staining.The tissue a-SMA was determined by immunohistochemistry.Western blot was used to detect FGFRI,ERK1/2 and its phosphorylation level,and to detect the expression of TNFa protein.Results:1.Regression analysis suggested that the factors associated with anemia of IgA nephropathy were female,low serum albumin,decreased eGFR,and severe renal interstitial fibrosis/tubular atrophy.2.Animal model experiments showed that 50 mg/kg.d and 75 mg/kg.d adenine could not be used as animal models of renal anemia for 4 weeks.The SCr of mice treated with aristolochic acid 3mg/kg.2d(AA/2d)and 3mg/kg.3d(AA/3d)was higher than the control group after 6 weeks treatment.The Hb of the AA/2d and AA/3d group was lower than the control group.PAS staining and fibrosis staining showed obvious renal interstitial fibrosis in AA/2d group and AA/3d group.The results of qPCR and Western blot showed that the expression levels of EPO mRNA and protein in kidney tissues of AA/2d and AA/3d groups were significantly decreased.Immunofluorescence results showed that EPO expression was positive in the tubulointerstitial.3.Nintedanib can improve aristolochic acid-induced RA in mice.Improved and reduced renal interstitial fibrosis.Phosphorylation levels of FGFR1 and ERK1/2 are decreased,and levels of TNFa are decreased.Conclusion:Clinical studies have found that severe renal interstitial fibrosis/tubular atrophy is a factor in the occurrence and aggravation of renal anemia in patients with IgA nephropathy.3 mg/kg.3d of aristolochic acid for 6 weeks can successfully establish a stable mouse model of RA.The pathology is renal interstitial fibrosis.The anti-fibrotic drug nintedanib was used to improve the aristolochic acid-induced RA and reduce renal interstitial fibrosis.The mechanism may be related to the inhibition of FGFRI phosphorylation by nintedanib.It is confirmed that renal interstitial fibrosis is one of the important mechanisms for the development of renal anemia in chronic kidney disease.