Significance Of MiR-29a In The Diagnosis And Treatment Of IgA Nephropathy

BackgroundIgA nephropathy(IgAN)is regarded as a common glomerulonephritis with a prevalence of>50%of primary glomerulonephritis diagnosed by pathological biopsy[1].Approximate 15-40%of IgAN patients are likely to progress to the End-Stage Renal Disease(ESRD)[2,3].An aberrant O-linked glycosylation in the hinge region of IgA1 plays a central role in the development of this autoimmune disease[4]?The exact cause of primary IgAN is still unknown,but its onset is commonly associated with upper respiratory tract infections and episodes of macroscopic hematuria[5].Common genetic variants can influence the risk of IgAN across ethnically diverse populations[6].In a recent genome-wide association study of IgAN,several new genome-wide significant associationswere identified.Most loci were either directly associated with risk of inflammatory bowel disease or with the maintenance of the intestinal epithelial barrier and response to mucosal pathogens[7].At present,basic renal function and proteinuria are regarded as useful prognostic markers of IgAN.Nevertheless,these markers cannot precisely predict outcomes due to the heterogeneity of the disease.In addition,severe renal histological injury may be observed in some IgAN patients with benign clinical characteristics[8].Assessment of the degree of glomerular and tubulointerstitial can be used to predict renal outcomes[9].Actually,anatomopathological analysis of renal biopsies is required for the definitive diagnosis of IgAN[10].An early diagnosis is veryimpoitanttopreventIgANprogressiontoend-stagerenaldisease[11].Renal biopsy has potential complications,and repeated renal biopsy is technically difficult.There is an urgent need for reliable non-invasive biomarkers that might be applicable for detecting subclinical IgAN,estimatingthe degree of disease activity and assessing the efficacy of treatment[12].MicroRNAs(miRNAs)are noncoding,single-stranded RNA molecules of approximately 21 to 23 nucleotides in length,it is involved primarily in the control of gene expression at post transcriptional level and plays important roles in many physiological and pathological processes[13-15].miRNAs participate in each ring of cellular processs,and dys-regulation of miRNA has been correlated with multiple human diseases including CKD[16,17].The quantification of miRNAs might be performed from the urinary sediment or other samples as serum,plasma and renal tissue.Most of the miRNAs can be detected by real-time quantitative polymerase chain reaction(RT-PCR)and microarray methodologies[18,19].The potential of some miRNAs in urine as novel biomarkers for diagnosis and monitoring of IgAN has been documented[20-22].Although the treatment of IgAN is often symptomatic,organ and lifethreatening complications require more aggressive systemic treatments.In addition,studies have compared the efficacy of mycophenolate mofetil and cyclophosphamide in the treatment of IgA nephropathy on the basis of glucocorticoid therapy.The results show that mycophenolate mofetil treatment group has higher remission rate,lower proteinuria and better renal function and less adverse reactions[23].Urinary level of miR-29a was decreased in IgAN patients.However,serum,urinary and renal levels of miR-29a of patients with IgAN remain elusive.Glucocorticoid combined with MMF has been applied to the treatment of IgAN.The changes in serum and urinary miR-29a expression after treatment are unknown.In the present study,real-time PCR was performed to explore serum,urinary and intra-renal expression of miR-29a and its function in renal fibrosis of patients with IgAN,aiming to investigate the significance of miR-29a in the diagnosis and treatment evaluation of IgAN.Section ? Significance of miR-29a in the diagnosis of IgA nephropathyResearch ObjectiveThis study was designed to analyse the serum,urinary and renal expression of miR-29a of patients diagnosed with IgAN,aiming to elucidate the significance of miR-29a as a noninvasive biomarker in the diagnosis of IgAN.Research MethodThirty-five patients diagnosed with IgAN by biopsy and regular follow-up in ourhospital were assigned in the IgAN group,and to exclude allergic Purpura nephritis,lupus nephritis,viral hepatitis related nephritis,diabetes nephritis and other secondary IgAN;Exclusion of patients during pregnancy and those who are about to become pregnant;Exclusion of patients with other chronic underlying diseases(coronary heart disease,essential hypertension,cerebrovascular disease,etc..).Serum and urine sampling was collected from seventeen healthy volunteers as healthy control group,Seventeen patients with renal cancer were selected.The age and sex were matched with healthy volunteers.They were not accompanied by proteinuria,abnormal renal function,glomerular hematuria,coronary heart disease,essential hypertension,cerebrovascular disease and other basic diseases.The nephrectomy specimen was taken as a control group for normal renal tissue.RT-PCR was performed to comparemiR-29a level of serum,urine and kidney tissue samples between two groups and At the same time,clinical and pathological data were collected for each group(including blood pressure,serum creatinine,24-hour urine protein,hemoglobin,albumin,glomerular sclerosis,and crescent formation(determined by the ratio of hardened glomerules and crescent bodies in all glomerules),glomerular filtration rate).To investigate the significance of miR-29a as a noninvasive biomarker in the diagnosis of IgAN.Research ResultsCompared with control group,the urinary,serum and renal expression of miR-29a in IgAN group were decreased(P<0.05).Serum and intra-renal expression of miR-29a was positively correlated with urinary expression of miR-29a(r=0.713,P<0.05;r=0.322,P<0.05).Urinary and serum expression of miR-29a inversely correlated with proteinuria(r=-0.322,P<0.05;r=-0.356,P<0.05),and glomerulosclerosis(r=-0.427,P<0.05;r=-0.517,P<0.05)in IgAN group.Urinary expression of miR-29a positively correlated with evaluated Glomerular Filtration Rate(eGFR)(r=0.328,P<0.05),inversely correlated with diastolic blood pressure(r=-0.421,P<0.05)in the IgAN group.ConclusionsUrinary and serum miR-29a level were closely correlated withrenal histological injury and proteinuria,eGFRof IgAN.The expression of miR-29a in urine and serum may play an important role in reflecting the pathogenesis and development of IgAN.The expression level of miR-29a in urine and serum can be used as a biological indicator of IgAN renal fibrosis.Section II Significance of miR-29a in the treatment of IgA nephropathyResearch ObjectiveThis study was designed to analyse the urinary,serum and renal expression of miR-29a of patients diagnosed with IgAN,aiming to elucidate the significance of miR-29a in the evaluation of IgAN treatment.Research MethodThirty-five patients diagnosed with IgAN by biopsy and regular follow-up in ourhospital were assigned in the IgAN group.Forty-eight primary IgAN patientstreated with low dose glucocorticoid combined with MMF for 3 monthswere assigned in the treatment group.All selected patients excluded secondary IgAN patients such as allergic Purpura nephritis,lupus nephritis,viral hepatitis related nephritis,and diabetic nephropathy;Exclusion of patients during pregnancy and those who are about to become pregnant;Patients with other chronic basic diseases(coronary heart disease,essential hypertension,cerebrovascular disease,etc.)are excluded.Patients in treatment group were treated with low-dose corticosteroids combined with MMFand angiotensin receptor antagonist(ARB),initial dose of glucocorticoid prednisone was 0.5 mg/kg/d,appropriate reduction after six months of maintenance therapy,total treatment course for 1.5 years;MMF starting dose as 30mg/kg/d,1.5-2.0g/d,orally twice,appropriate reduction after 6 months of maintenance therapy,total treatment course for 1.5 years,All IgAN patients were treated with conventional dose of150mg/d losartan.Serum and urine sampling was collected from seventeen healthy volunteers as healthy control group.seventeenpatients with renal cancer were selected.The age and sex were matched with healthy volunteers.They were not accompanied by proteinuria,abnormal renal function,glomerular hematuria,coronary heart disease,essential hypertension,cerebrovascular disease and other basic diseases.The nephrectomy specimen was taken as a control group for normal renal tissue.RT-PCR was performed to compare miR-29a level of serum,urine and kidney tissue samples between two groups and At the same time,clinical and pathological data were collected for each group(including blood pressure,serum creatinine,24-hour urine protein,hemoglobin,albumin,glomerular sclerosis,and crescent formation(determined by the ratio of hardened glomerules and crescent bodies in all glomerules),glomerular filtration rate).To investigate the significance of miR-29a in the evaluation of IgAN treatment.Research ResultsCompared with control group,the urinary,serum and renal expression of miR-29a in IgAN group were decreased(P<0.05).The serum and urinary levels of miR-29a in the treatment group were significantly higher than those in the IgAN group(both P<0.05).ConclusionsUrinary and serum miR-29a level were closely correlated with the progression of IgAN.Low-dose corticosteroids combined with MMF could up-regulate the serum and urinary levels of miR-29a in IgAN patients.Serum and urinary miR-29a probably serve as biological markers toevaluate the effect of IgAN treatment.