Effects of childbirth on podocyturia in women with normotensive, uncomplicated pregnancies

Abstract

Changes in hemodynamics and blood pressure occur shortly before and after childbirth regardless of the mode of delivery. This study aimed to test the hypothesis that parturition induces a temporal increase in podocyturia monitored by podocyte-specific protein podocin mRNA expression levels (Pod-mRNA). A total of 105 urine specimens, consisting of 43 and 62 from 18 and 20 otherwise healthy women with vaginal delivery (VD) and elective cesarean delivery (ECS), respectively, were studied. Determination of urine protein and creatinine (Cr) concentrations and quantitative analyses of Pod-mRNA, nephrin mRNA (Nep-mRNA), synaptopodin mRNA (Syn-mRNA), and aquaporin 2 mRNA expression were performed using RT-PCR in pelleted urine samples. Levels of mRNA expression were corrected by urine Cr concentration. Podocyturia increased significantly, concomitant with a significantly decreased Nep:Pod-mRNA ratio (NPR) in the urine, collected immediately before or after childbirth regardless of the delivery mode compared with urine collected before commencement of labor or on postpartum day 3 or later. Podocyturia was significantly negatively correlated with NPR [correlation coefficient (r) = -0.614/-0.750 for VD/ECS women, respectively], as well as the Syn:Pod-mRNA ratio. Systolic blood pressure exceeded 140 mmHg during labor in 50% of VD women, and mean arterial pressure was significantly positively correlated with podocyturia during labor in VD women (r = 0.733). Thus parturition induces a transient increase in urine podocytes with reduced Nep- and Syn-mRNA expressions. Glomerular podocytes with reduced Nep- and Syn-mRNA levels were suggested to be likely to detach from the glomerular basement membrane around childbirth.