Maternal-fetal fluid balance and aquaporins: from molecule to physiology.

Maternal-fetal fluid balance is critical during pregnancy, and amniotic fluid is essential for fetal growth and development. The placenta plays a key role in a successful pregnancy as the interface between the mother and her fetus. Aquaporins (AQPs) form specific water channels that allow the rapid transcellular movement of water in response to osmotic/hydrostatic pressure gradients. AQPs expression in the placenta and fetal membranes may play important roles in the maternal-fetal fluid balance.

Pregnant phenotype in aquaporin 8-deficient mice.

AIM: Aquaporin 8 (AQP8) is expressed within the female reproductive system but its physiological function reminds to be elucidated. This study investigates the role of AQP8 during pregnancy using AQP8-knockout (AQP8-KO) mice. METHODS: Homozygous AQP8-KO mice were mated, and the conception rate was recorded. AQP8-KO pregnant mice or their offspring were divided into 5 subgroups according to fetal gestational day (7, 13, 16, 18 GD) and newborn. Wild type C57 pregnant mice served as the control group. The number of pregnant mice, total embryos and atrophic embryos, as well as fetal weight, placental weight and placental area were recorded for each subgroup. The amount of amniotic fluid in each sac at 13, 16, and 18 GD was calculated. Statistical significance was determined by analysis of variance of factorial design and chi-square tests. RESULTS: Conception rates did not differ significantly between AQP8-KO and wild type mice. AQP8-KO pregnant mice had a significantly higher number of embryos compared to wild type controls. Fetal/neonatal weight was also significantly greater in the AQP8-KO group compared to age-matched wild type controls. The amount of amniotic fluid was greater in AQP8-KO pregnant mice than wild type controls, although the FM/AFA (fetal weight/amniotic fluid amount) did not differ. While AQP8-KO placental weight was significantly larger than wild type controls, there was no evidence of placental pathology in either group. CONCLUSION: The results suggest that AQP8 deficiency plays an important role in pregnancy outcome.

[Expression of aquaporin-1 in human oligohydramnios placenta and fetal membranes].

OBJECTIVE: To detect aquaporin-1 mRNA (AQP1) expression in human oligohydramnios placenta and fetal membranes. METHODS: Placenta and fetal membranes samples were obtained from 5 women with oligohydramnios and 5 with normal amniotic fluid volume. AQP-1 mRNA expression in the tissue samples was detected by semi-quantitative RT-PCR. RESULTS: The expression of AQP1 mRNA was significantly lower in oligohydramnios placenta than in normal pregnancy placenta at term (P<0.05), and also significantly lower in oligohydramnios fetal membranes than in normal fetal membranes at term (P<0.05). CONCLUSION: Alterations in AQP1 mRNA expressions in human placenta and fetal membranes may play an important role in the disorder of maternal-fetal fluid exchange and amniotic fluid volume.