Increased podocyturia in pregnant women compared to non-pregnant women

Aim: Hyperfiltration is a cause of podocyturia and occurs physiologically in the kidney of pregnant women. Podocyturia is increased in preeclamptic pregnancies, but it is unclear whether there is also any increase in uncomplicated pregnancies. This study was performed to examine whether podocyturia and urine aquaporin 2 mRNA expression are increased in healthy pregnant women (PW) compared to healthy non-pregnant women (NPW). Methods: Eleven urines obtained from 11 NPW and longitudinal 76 urines from 40 PW with uncomplicated pregnancies (median number [range] of urine samples/person, 2 [1 - 3]) were studied. Determination of protein and creatinine concentrations and number of cells in urine other than blood cells, and quantitative analyses of the mRNA expression of aquaporin 2 (AQP2-mRNA), podocin (Pod-mRNA), and nephrin (Nep-mRNA) were performed using RT-PCR in pelleted urine samples. Podocyturia was monitored with urine Pod- and Nep-mRNA expression levels normalized relative to creatinine. Results: Urine cell density and urine AQP2-, Pod-, and Nep-mRNA expression normalized relative to creatinine were significantly higher in PW than NPW. The number of cells per milligram of creatinine was significantly positively correlated with expression of all three mRNAs with correlation coefficients (R-value) of 0.442, 0.481, and 0.561 for Pod-, Nep-, and AQP2-mRNA, respectively. AQP2-mRNA expression was strongly (R > 0.8) positively correlated with both Pod- and Nep-mRNA expression. Conclusion: Podocyturia monitored by Pod- and Nep-mRNA expression and urine cells expressing AQP2-mRNA were increased in uncomplicated pregnancies compared to healthy non-pregnant women. Urine cells expressing AQP2-mRNA increased with increasing podocyturia in healthy women.