Lupus nephritis is characterized by intrarenal inflammation. To assess the extent and severity of disease activity and renal involvement, this study examined the expression of transforming growth factor β (TGFβ) and monocyte chemoattractant protein 1 (MCP‐1) in the urinary sediment of patients with systemic lupus erythematosus (SLE).

We studied 106 patients with SLE who were classified according to their disease status as those with active disease, those with disease in remission, and those with nonrenal SLE. Ten healthy subjects were used as controls. Lupus activity was assessed by the SLE Disease Activity Index (SLEDAI). If renal biopsy was performed, the histologic activity index and chronicity index were determined, and a morphometry analysis of renal scarring was performed. The urinary expresssion of TGFβ and MCP‐1 messenger RNA (mRNA) was studied by real‐time quantitative polymerase chain reaction, and the corresponding protein concentrations of TGFβ and MCP‐1 in the urine were measured by enzyme‐linked immunosorbent assay (ELISA).

Expression of TGFβ and MCP‐1 mRNA in the urinary sediment was significantly elevated in the active disease group (P < 0.001 for both). These expression levels of TGFβ and MCP‐1 mRNA correlated with the SLEDAI score (TGFβ r = 0.71, P < 0.001; MCP‐1 r = 0.72, P < 0.001), and also significantly correlated with the histologic activity index (TGFβ r = 0.487, P = 0.004; MCP‐1 r = 0.357, P = 0.038). The urinary protein concentration of MCP‐1, but not of TGFβ, correlated with the SLEDAI score (r = 0.66, P < 0.001). However, neither the protein concentration of TGFβ nor that of MCP‐1 as measured by ELISA in the urine correlated with the histologic activity index.

The measurement of urinary mRNA expression may be a noninvasive method for the assessment of lupus disease activity and the severity of renal involvement in patients with lupus nephritis.