Concentrations of secreted protein acidic and rich in cysteine in serum and urine and its expression in kidney tissues of patients with IgA nephropathy

Abstract

Objective:To investigate the concentrations of secreted protein acidic and rich in cysteine(SPARC)in the serum and urine of patients with IgA nephropathy and its expression in the kidney tissues.Methods:The concentrations of SPARC, tumor necrosis factor-α(TNF-α),interleukin 1β(IL-1β),and interleukin 6(IL-6)in the serum and urine were measured with enzyme-linked immunosorbent assay(ELISA).The contents of'SPARC protein in the culture medium of human mesangial cell (HMC)and human renal tubular epithelial cell(HKC),which had been treated with IL-6,were determined by ELISA.The ex- pression and distribution of SPARC in IgA nephropathy and normal kidney tissues were observed by immunohistochemistry as- say.Results:The concentrations of SPARC in serum and urine of IgA nephropathy patients were higher than those of the normal control subjects([2.43±1.22]μg/ml vs[0.69±0.21]μg/ml,[7.73±2.81]μg/ml vs[1.17±1.03]μg/ml,P0.01).The serum levels of TNF-α,IL-1βand IL-6 in IgA nephropathy group were significantly higher than those in the control group(P0.05);the urinary levels of TNF-αand IL-6 in IgA nephropathy group were also higher than those in the controls(P0.01). SPARC protein secreted by HKC was higher than that by HMC(P0.01).SPARC was weakly positive in normal distal cortical tubules.SPARC protein expression in tubular epithelial cells of IgA nephropathy patients was obviously higher than that of the normal controls.Condusion:The secretion of SPARC by renal tubular epithelial cells is increased in patients with IgA nephropa- thy,which results in elevation of serum SPARC and may have a protective feedback inhibitory effect on HMC proliferation.