Messenger RNA expression of podocyte-associated molecules in urinary sediment of patients with lupus nephritis

To examine urinary expression of podocyte-associated molecules in patients with lupus nephritis (LN).

We studied 32 patients with active LN (Active group) and 17 patients with inactive lupus (Silent group). Messenger RNA expression of nephrin, podocin, and synaptopodin in urinary sediment was quantified by real-time polymerase chain reaction and compared to other clinical measures.

The urinary concentrations of nephrin, podocin, and synaptopodin were significantly higher in the Active than the Silent group (p < 0.05 for all comparisons). There was no relation between urinary gene expression and the histological class of LN, but urinary nephrin expression correlated with proteinuria (r = 0.480, p < 0.01) and the score of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI; r = 0.578, p < 0.01). Urinary podocin expression also correlated with SLEDAI score (r = 0.389, p = 0.006). After initiation of immunosuppressive treatment, all patients were followed for an average of 13.7 +/- 2.4 months. The decline of the glomerular filtration rate (GFR) correlated with urinary expression of podocin (r = 0.406, p = 0.005) and synaptopodin (r = 0.337, p = 0.021). In a multiple linear regression model, urinary podocin expression and baseline GFR were independent predictors of GFR decline.

The concentration of podocyte-associated molecules in urinary sediment correlated with lupus activity and GFR decline. The clinical utility of quantifying urinary expression of podocyte-associated molecules for risk stratification of patients with LN deserves further study.