Aquaporins-1 And Homeostasis Of Maternal-fetal Fluid

A successful pregnancy requires the accumulation of significant amounts of water, both to support fetal growth and to allow for maternal physiologic changes. So the homeostasis of maternal-fetal fluid exchange is critical important during pregnancy. However, the molecular and cellular mechanisms for water and solute absorption between maternal and fetal remain to be elucidated. Among the many factors that can affect the water permeability of a membrane, one family of membrane proteins known as aquaporins (AQPs) appears to be particularly important. Aquaporins are small (28-30KD) membrane proteins, named for their ability to increase the water permeability of the lipid bilayer of plasma membranes to wate. There are currently 13 known mammalian aquaporins (AQP1-12), and AQP1 is widely expressed in endothelial of blood vessel in kindney, lung, cervix et al, which suggested that AQP1 may plays an important role in those organs.Our previous study showed that AQP1 expression at vascular endothelial cell and syncytiotrophoblast of placenta, epithelial cell of amnion, and cytotrophoblasts of chorion. RT-PCR showed that the expression of AQP1 mRNA were significantly higher in oligohydramnios patients than that of normal pregnancy fetal membranes and palacenta at term.It is suggested that AQP1 plays an important role in the homeostasis of maternal-fetal fluid, and also in pregnancy. But there is no direct evidence for that. AQP1 knockout mice are very useful animal model for research AQP1 function in vivo and has confirmed that AQP1 plays an direct function in kindney, lung, cornea, et al. But rare study show the pregnant phenotype analysis of AQP1 knockout mice.This study was to investigate the role of AQP1 during pregnancy by AQP1 null mice, which may give a direct evdence that AQPs play a part in the water and solute absorption between maternal and fetal. Those may provide an target gene for treatment. ChapterⅠExpression And Distribution Of Aquaporin 1(AQP1) in Placenta and Fetal Membrances of MiceObjective:To detect expression level and distribution of aquaporin 1(AQP1)in placenta and fetal membrances and try to find out the significance of AQP1 in homeostasis of maternal-fetal fluid exchange.Method:1. Four cases of placenta and fetal membrances were acquired after surgery. The expression of AQP1 in placenta and fetal membrances were examined by reverse polymerase chain reaction(RT-PCR). 2. Four cases of placenta and fetal membrances were obtained from normal CD-1 mice. The slides were detected by immunohistochemical staining for observing the expression of AQP1 in placenta and fetal membrances tissue.Result:1. AQP1 was expressed on both placenta and fetal membrances tissues on RNA and protein level.2. AQPl was expressed at the vascular endothelial cell and trophocyte of placenta. And AQPl was expressed at the epithelial cell of amnion.Conclusion:AQP1 expressed on both placenta and fetal membrances tissues in RNA and protein level. It is suggested that AQP1 may play an important role in the homeostasis of maternal-fetal fluidChapterⅡThe pregnant phenotype analysis of AQP1 knockout miceObjective:To investigate how pregnant phenotype change without AQP1 gene and try to find out the direct evidence that AQP1 plays an important role in the homeostasis of maternal-fetal fluid.Method:Homozygous AQP1 knockout mice were mated. The day a copulation plug was found was designated as gestational day 1 (1GD). Pregnant AQP1 knockout mice and wild-type CD-1 mice (control group) were allocated to 5 experimental groups(7GD, 13 GD, 16 GD, 18 GD and full term) by gestational age, respectively. Total embryo number, atrophies embryo number, fetus weight, placenta weight and area, were recorded in each subgroup. The amniotic fluid in each sac at 13 GD, 16 GD, 18 GD was measured, and was collected to determine the composition at 16GD. Fixing 13GD placental used to make hematoxylin and eosin stain.Data analysis:Continuous data with normal distribution are given as mean±SEM. One-way analysis of variance (ANOVA) on ranks was used to determine differences in amniotic fluid volume, placenta weight and the placenta water contents. The difference incidence rate of abnormal embryo was assessed by chi-square test. Statistical significance was accepted at P<0.05.Results:1. The number of AQP1 knockout mice embryo is decrease with the gestational age; the incidence rate of atrophies embryo in AQP1 knockout mice is significant increased compared to their wild-type (CD-1 mice) at 18GD (P=0.027).2. Fetuses of wild type (CD-1 mice) are significant heavier than AQP1 knockout fetal mice at 16GD and 18GD (P=0.000, 0.000) and at birth.3. The amount of amniotic fluid by weight is increased in AQP1 knockout mice compared to CD-1 mice at 13GD, 16GD, 18GD(P=0.011, 0.000, 0.000). The level of Urea, Cr and osmolality of the amniotic fluid of AQP1 null conceptus was significantly lower than the wild-type counterparts at 16GD. In contrast, the level of chloride is significantly higher in the AQP1-null conceptus.4. The placenta area of AQP1 knockout mice is significant bigger than their wild type. And the placenta is significant heaver than their wild type at 13GD, however significance lighter at 18GD. The placenta water content of AQP1 knockout is more than of CD-1 placenta at 13GD.5. Pathology of placenta (hematoxylin and eosin stain) showed that the trophoblast of AQP1 knockout mouse in the labyrinth and trophospongium showed degeneration. The contour of the blood vessel is also abnormal in AQP1 knockout mice.Conclusions:1. The pregnant phenotype of AQP1 knock-out mice were quite differrent from CD-1 pregnant mice.2. The pregnant phenotype of AQP1 knock-out mice exhibit embryo lose, low fetal weight, amniotic fluid increase and placenta change.3. These results showed the evidences that AQP1 plays an important role in the homeostasis of maternal-fetal fluid, and also play a direct or indirect role in fetal growth.