Transforming growth factor β1 is better than α smooth muscle actin for the prediction of renal fibrosis in patients with nephritic lupus

Abstract

We investigated the concentrations of transforming growth factor β1 (TGF-β1) and α smooth muscle actin (α-SMA) in the urine of a group of patients with lupus nephritis with renal fibrosis (LNF) and a group of patients with lupus nephritis without renal fibrosis (LN). Forty-five patients in the group with LNF, 13 patients in the group with LN, and 32 healthy controls took part in the study. The diagnosis of lupus nephritis was made according to the American College of Rheumatology criteria and the histopathology. A renal biopsy sample was taken from all patients with lupus to measure the chronicity index and the percentage of fibrosis. The concentrations of TGF-β1 and α-SMA were measured in urine samples by enzyme-linked immunosorbent assay. The percentage of patients with a chronicity index ≥4 was higher in the group with LNF (31.0%) than in the group with LN (0%). The percentage of patients with fibrosis ≥5% was higher in the group with LNF (44.3%). The concentration of TGF-β1 was significantly lower in patients with a chronicity index <4 than in patients with a chronicity index ≥4 (p < 0.05). In addition, the concentration of TGF-β1 in urine samples was significantly higher in the group with fibrosis ≥5% than the group with fibrosis <5% (p < 0.05). There was a significant positive correlation between the concentration of TGF-β1 in urine samples and the chronicity index (r = 0.606; p < 0.05) and the percentage of fibrosis (r = 0.602; p < 0.05). However, there was no significant difference between the concentration of α-SMA in the urine of patients with a chronicity index <4 or those with a chronicity index ≥4 (p > 0.05) or in patients with a percentage of fibrosis ≥5% and those with fibrosis <5% (p > 0.05). In addition, there was no significant correlation between α-SMA concentrations and the chronicity index (r = 0.073; p > 0.05) or the percentage of fibrosis (r = 0.091; p > 0.05). The sensitivity, specificity, and negative predictive value of TGF-β1 were higher than those of α-SMA. In conclusion, the concentration of TGF-β1 in urine samples was a better biomarker of renal fibrosis in patients in the group with LN than the concentration of α-SMA.