Long-term Follow-up Study Of Immunosuppressive Therapy For IgA Nephropathy And The Protective Effect Of YAP On Podocytes

Background and objective:IgA nephropathy(IgAN)was first proposed by Berger and Hinglais in 1968,and it is currently one of the most common primary glomerular diseases in Asia,has the characteristics of heterogeneity and progression.In patients diagnosed with IgA nephropathy,20%-40%of patients will progress to end-stage renal disease(ESRD)within 20 years,and the clinical manifestations of patients are diverse.Reducing persistent proteinuria is one of the main goals of the treatment in IgAN mainly by including ACEI/ARB and immunosuppressive therapy.The benefits of immunosuppressive therapy in patients with IgAN remain controversial,especially for those with more severe renal pathology findings and reduced renal function.In comparison to previous research,the IgAN cohort in our hospital was more severe at the time of diagnosis and more active in immunosuppressive therapy.Therefore,we conducted a real-world study to observe the effect of immunosuppressive therapy on long-term prognosis in IgAN patients in CKD stage 3 and stage 4,and to explore the predictive role of whether the treatment of immunosuppressants is effect or not on long-term prognosis.We aimed to provide a new treatment strategy for IgAN patients especially for those with more sever conditions.Methods:This was a single center retrospective cohort study.A total of 496 biopsy-confirmed IgAN patients aged ?18 years old were screened for eligibility between January 2012 and December 2014.Patients were divided into four groups according to CKD stages and the treatment of immunosuppressants therapy.The patients were divided into four groups:(1)CKD stage 3 with immunosuppressive therapy(96 subjects);(2)CKD stage 3 without immunosuppressive therapy(30 subjects);(3)CKD stage 4 with immunosuppressive therapy(26 subjects);and(4)CKD stage 4 without immunosuppressive therapy(12 subjects).The primary end points were doubling of serum creatinine,progression to ESRD,or death for all causes.The secondary end point was rapid decrease in eGFR(>1ml/min/1.73m2/year).Subgroup analysis of CKD3 immunosuppressant treatment group was conducted to explore the factors affecting the prognosis of IgAN patients after treatment and whether there are short-term alternative indicators.Results:A total of 164 patients were enrolled including 98 males and 66 females,with a male-to-female ratio of 1.5:1.The median age was 43 years,and the mean follow-up time was 5.51 years.There were 126 patients in CKD 3 stage and 38 patients in CKD 4 stage and no significant differences in baseline age,gender,duration of kidney disease,history of metabolic diseases such as hypertension and diabetes mellitus among CKD patients with different stages according to whether or not they received immunosuppressive therapy.Cox single-cause and multi-cause regression analysis showed that immunosuppressive therapy significantly improved prognosis in patients with CKD stage 3 IgAN(HR 0.435[95%CI 0.200-0.944];P=0.035),but no difference for CKD stage 4 IgAN(p=0.364>0.05).Subgroup analysis showed that baseline eGFR(OR 0.909[95%CI 0.834-0.991];p=0.031),serum IgG level(OR 0.809[95%CI 0.658-0.995];p=0.045)were associated with primary outcome and loop necrosis(OR 0.189[95%CI 0.050-0.709],p=0.014),proportion of crescents(OR 0.200[95%CI 0.100-0.521],p=0.003),MEST-C score T2 relative to T0(OR 5.490[95%CI 1.323-22.727],p=0.019),C2 relative to C1(OR 0.741[95%CI 0.090-0.915],p=0.016),C2 relative to C0(OR 0.580[95%CI 0.070-0.910],p=0.009)were associated with secondary outcome.Remission within 1 year could be used as an indicator of good long-term prognosis(HR 0.555[95%CI 0.296-0.759;p=0.035]).Conclusions:For IgAN patients with CKD stage 3,immunosuppressive therapy should be actively applied under the general treatment,but for patients with CKD stage 4,immunosuppressive therapy should be used carefully.Patients with good baseline renal function,more acute lesions of renal pathology such as loop necrosis,crescents or fewer chronic lesions such as interstitial fibrosis and tubule atrophy,would have a better prognosis after immunosuppressive therapy,and can be given active treatment after diagnosis.Besides,patients who achieved complete or partial remission within 1 year would have better long-term prognosis.Background and objective:IgA nephropathy patients may have pathological manifestations such as podocyte hypertrophy,tip lesion and resorption droplets within podocytes.More than 70%of patients have focal segmental sclerosis(S1)lesion,which is an independent risk factor for poor renal prognosis.In addition,the degree of podocyte damage can also be used as an indicator of disease severity and a predictive indicator of disease progression.Reducing podocyte damage may become a potential drug treatment target and research direction for IgA nephropathy,which can reduce the degree of proteinuria and glomerular sclerosis in patients.The Hippo signaling pathway and its most important transcriptional activator Yes-associated protein(YAP)play an important role in the podocyte apoptosis and the podocyte repair after injury.In this study,we focus on podocyte damage and YAP expression in patients with IgA nephropathy.We supposed that YAP can protect podocytes in IgAN,and the level of YAP expression is related to the severity and the prognosis.We aimed to explore whether YAP could slow down glomerular sclerosis and improve the prognosis of patients in IgA nephropathy.Methods:Screening patients who were hospitalized in Peking Union Medical College Hospital for the first diagnosis of IgAN by renal biopsy from January 2012 to December 2014.According to propensity score matching of gender and age,16 patients of Lee's grade 3-4 with proteinuria ?3.5g/d,16 patients of Lee's grade 3-4 with proteinuria 1-3.5g/d and 3 patients with Lee grade 2 were matched as disease control.Besides,5 healthy control were obtained,all of which were treated with unilateral nephrectomy to obtain relatively healthy renal cortex away from the renal tumor.Immunohistochemistry and immunofluorescence staining to determine the expression of YAP in the kidney,co-staining of WT1 and YAP to determine the expressing of YAP in podocytes nucleus.The ratio of the number of podocytes positive for YAP nucleus to the total number of podocytes in the globule represents the YAP expression level.Subgroup analysis of IgAN patients with different pathological damage grades and IgAN patients with different YAP expression levels was carried out.Results:(1)The podocyte count in patients with IgAN Lee grade 3-4 was significantly lower than that in healthy controls(26.18[23.96,28.39]vs 35.37[29.40,41.75],p=0.043;16.37[13.42,19.31]vs 35.37[29.40,41.75],p=0.001).The podocyte count decreased and the injury aggravated with the increase of pathological grade.(2)The proportion of podocytes positive for YAP nucleus decreased significantly in IgAN.And as the pathological grade increases,the proportion gradually decreases.According to the scatter plot and Pearson correlation test,the expression level of YAP has a positive linear relationship with the count of podocytes(r=0.876,p<0.001).The proportion of podocytes positive for YAP nucleus increases,then the number of podocytes in the glomerulus increases.(3)The expression level of YAP in IgAN patients is correlated with the severity of the disease.The high YAP expression group has lower 24hUP[2.60(1.18,4.02)vs 3.86(3.38,3.34),p=0.038],higher eGFR[106.68±20.01 vs 64.62±19.64,p<0.001],lower proportion of spherical sclerosis[3.77%(1.30%,6.26%)vs 30.40%(21.13%,39.68%),p<0.001]and segmental sclerosis[2.33%(0.94%,3.73%)vs 13.16%(7.25%,19.08%),p<0.001]],lower proportion of crescent[6.21%(2.94%,9.48%)vs 16.59%(9.60%,23.57%),p=0.011],and the degree of tubulointerstitial fibrosis is lighter(p<0.001).According to MEST-C grouping,YAP expression level of podocytes in patients with glomerulosclerosis(S1),renal tubular atrophy or interstitial fibrosis(T1-2),severe crescent(C2)was higher.(4)After a median follow-up of 6 years,8 patients with IgAN reached the end point.According to COX univariate and multivariate regression analysis,high podocyte YAP expression can significantly improve the prognosis of patients(HR 0.106[95%CI 0.013-0.869];p=0.037).Conclusions:In this study,we found the presence of podocyte injury with IgA nephropathy patients,and YAP may have a protective effect on podocytes.The expression level of YAP in podocytes is correlated with patients' clinical laboratory indexes,histopathological scores and has predictive value for the prognosis.Blocking the Hippo pathway to increase the expression of YAP in the nucleus may become a new treatment for IgAN.