Aquaporin 1 affects pregnancy outcome and regulates aquaporin 8 and 9 expressions in the placenta

Abstract

To explore the effects of aquaporin (AQP) 1 on pregnancy outcome and the association between expression of AQP1 and other AQPs in the placenta and foetal membranes, the rate of copulatory plugs and pregnancy, amniotic fluid (AF) volume, osmolality and composition were determined in AQP1-knockout (AQP1^-/-) mice at different gestational days (GD). The expression and location of AQP1 and other AQPs in the placenta and foetal membranes of AQP1^-/- mice, AQP1-siRNA transfected WISH cells and oligohydramnios patients were also detected. Compared to control mice, AQP1^-/- mice exhibited reduced copulation plug and successful pregnancy rates, but these effects were accompanied by a larger AF volume and lower AF osmolality at late gestation. AQP9 expression was significantly decreased in the placenta and foetal membranes of AQP1^-/- mice, while AQP8 level was elevated in the foetal membranes of AQP1^-/- mice. Moreover, AQP9 expression was suppressed in WISH cells after AQP1 downregulation. Furthermore, AQP9 expression was associated with AQP1 level in the placenta and foetal membranes in oligohydramnios. AQP1 may play a critical role in regulating pregnancy outcome and maternal-foetal fluid homeostasis. Changes in AQP1 expression may lead to compensatory alterations in AQP8 and AQP9 expression in the placenta.

Keywords: Amniotic fluid; Aquaporin; Foetal membrane; Placenta; Pregnancy outcome.

Fig. 1

AQP1 depletion in mice causes a decrease of AQP9 mRNA in placenta and foetal membrane and an increase of AQP8 mRNA in foetal membrane. Relative mRNA expression of AQP1, AQP3, AQP8 and AQP9 was measured by qRT-PCR in placenta at 13.5 GD (a) and 16.5GD (b). Relative mRNA expression of AQP1, AQP3, AQP8 and AQP9 was detected using qRT-PCR in foetal membrane at 13.5 GD (c) and 16.5 GD (d). *P < 0.05 vs wild type mice

Fig. 2

AQP1 knockout mice exhibit a decrease of AQP9 protein in placenta and foetal membrane and an increase of AQP8 protein in foetal membrane. Expression of AQP1, AQP3, AQP8 and AQP9 proteins was measured by western blotting in placenta at 13.5 GD (a–a′) and 16.5GD (b–b′). Expression of AQP1, AQP3, AQP8 and AQP9 proteins was determined by western blotting in foetal membrane at 13.5 GD (c–c′) and 16.5GD (d–d′). Quantitative data for each AQP protein were presented in the histogram (a′–d′)

Fig. 3

AQP9 expression is decreased in AQP1 siRNA transfected WISH cells. Relative mRNA expression of AQP1, AQP3, AQP8 and AQP9 was measured by RT-PCR in WISH cells after AQP1 siRNA transfection. P < 0.05 vs control siRNA transfection (a). Expression of AQP1, AQP3, AQP8 and AQP9 proteins was detected by western blotting in AQP1 siRNA transfected WISH cell (b). Quantitative data for control siRNA and AQP1 siRNA protein were presented in the histogram (b′)

Fig. 4

Expression of AQP1 is associated with AQP9 protein level in oligohydramnios patients. Immunohistochemical staining of AQP1, AQP3, AQP8 and AQP9 was performed in placenta in normal AF volume group and oligohydramnios group (a–h). Immunohistochemical staining of AQP1, AQP3, AQP8 and AQP9 was conducted in amnion epithelial cells and chorion in normal AF volume group and oligohydramnios group (i–p). Bar 50 μm