Urinary podocyte excretion as a marker for preeclampsia

The proteinuria of preeclampsia is associated with glomerular endotheliosis, and a role for damaged and lost podocytes (glomerular epithelial cells) in the development of proteinuria has received support from studies of patients with glomerular diseases. This study asked whether urinary excretion of viable podocytes, quantified by the expression of podocin and other podocyte-specific proteins, is observed in pregnant women with clinically confirmed preeclampsia. In addition, levels of angiogenic factors implicated in the pathogenesis of preeclampsia were estimated. They included soluble receptor for vascular endothelial growth factor, also called fms-like tyrosine kinase receptor-1 (sFlt-1); placental growth factor (PIGF); and serum soluble endoglin. The cross-sectional study recruited 33 pregnant women with preeclampsia, 11 with HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome, and 23 normotensive pregnant women. All of the 15 preeclamptic women evaluated and also those with HELLP syndrome, but not normotensive control subjects, had podocin-positive cells in their urine. Podocyturia was 100% sensitive and 100% specific for the diagnosis of preeclampsia, and the degree of proteinuria correlated positively with podocyturia. The positive predictive value of urinary podocyte excretion for the presence of preeclampsia was greater than that of sFlt-1, PIGF, or endoglin. Nevertheless, serum levels of sFlt-1 were significantly higher in women with preeclampsia or HELLP syndrome than in normotensive control women, and the same was the case for serum levels of soluble endoglin. Women with preeclampsia or HELLP syndrome had lower serum levels of free PlGF than did normotensive pregnant women. Urine levels of PlGF did not differ from those in normal women. Podocyturia is a very sensitive and specific marker for preeclampsia, and it may contribute to the development of proteinuria in affected women. Further studies may clarify the effects of dysregulated vascular endothelial growth factor on mechanisms regulating podocyte attachment.