Podocyte mRNA in the urinary sediment of minimal change nephropathy and focal segmental glomerulosclerosis

BACKGROUND: Podocyte depletion is a characteristic feature of progressive renal failure. We hypothesize that studying the podocyte mRNA level in urinary sediment may provide diagnostic and prognostic information in adult nephrotic syndrome. METHODS: We studied 25 patients with minimal change nephropathy (MCN), 25 with focal segmental glomerulosclerosis (FSGS), and 17 healthy controls. The mRNA levels of nephrin, podocin, and synaptopodin in urinary sediment were quantified. RESULTS: There were significant differences in the urinary sediment nephrin and podocin, but not synaptopodin, mRNA levels between diagnosis groups. Post-hoc analysis further showed that urinary nephrin mRNA levels of the MCN group were lower than those in the control and FSGS groups, although the difference between MCN and FSGS groups did not reach statistical significance. The degree of proteinuria inversely correlated with urinary nephrin mRNA levels in the MCN (r = -0.526, p = 0.007) as well as in the FSGS group (r = -0.521, p = 0.008). For the FSGS group, the rate of renal function decline significantly correlated with baseline urinary synaptopodin mRNA levels (r = -0.496, p = 0.012). CONCLUSIONS: Urinary nephrin and podocin mRNA levels were reduced in patients with MCN and probably FSGS, and the magnitude of reduction correlated with the degree of proteinuria. Urinary synaptopodin mRNA levels correlated with the subsequent rate of renal function decline in patients with FSGS. Our result indicates that urine sediment podocyte mRNA levels provide novel insights in the pathophysiology of nephrotic syndrome and could be useful for risk stratification.