[Urinary fibronectin as an indicator of kidney fibrosis in nephritis]

To investigate clinicomorphological relationships between elevated urinary excretion of fibronectin (FN) and development of fibrosis in the kidney in patients with lupus nephritis (LN) and chronic glomerulonephritis (CGN).

Urinary FN excretion was measured at radial immunodiffusion in 54 LN patients. Of them, 15 patients had inactive LN, 39 patients had active LN varying in clinical forms. Urinary FN was also measured by passive hemagglutination in 36 CGN patients (11 inactive CGN and 25 active CGN cases). Biopsy specimens were obtained from 49 patients with active nephritis (43 with CGN and 6 with LN). FN deposits were studied immunohistochemically and morphometrically with determination of relative fibrosis area.

Urinary FN excretion in patients with nephritis was higher than in healthy controls. In active CGN and LN the levels of FN were significantly higher than in inactive CGN and LN. The highest FN urinary concentrations were registered in patients with severe CGN and LN, especially in the presence of renal failure and arterial hypertension. Among them, the highest individual values were observed in patients with rapidly progressive nephritis. No positive correlations were found between the degree of the urinary FN excretion increment and degree of proteinuria. This suggests local-renal origin of most urinary FN. Morphologically, FN deposits were revealed in 73% of the biopsies. In most of the patients with severe nephritis both in CGN and LN there was a diffuse distribution of FN in the glomerules and interstitium. A correlation with a morphological nephritis type was absent, but existed between FN presence in the renal biopsies and relative area of interstitium (fibrosis).

FN excreted in high amounts with urine in nephritis originates from the kidneys and reflects severity of fibrogenesis in the kidney.