Aquaporins during pregnancy

Unveiling the human fetal-maternal interface during the first trimester: biophysical knowledge and gaps

The intricate interplay between the developing placenta and fetal-maternal interactions is critical for pregnancy outcomes. Despite advancements, gaps persist in understanding biomechanics, transport processes, and blood circulation parameters, all of which are crucial for safe pregnancies. Moreover, the complexity of fetal-maternal interactions led to conflicting data and methodological variations. This review presents a comprehensive overview of current knowledge on fetal-maternal interface structures, with a particular focus on the first trimester. More in detail, the embryological development, structural characteristics, and physiological functions of placental chorionic plate and villi, fetal membranes and umbilical cord are discussed. Furthermore, a description of the main structures and features of maternal and fetal fluid dynamic exchanges is provided. However, ethical constraints and technological limitations pose still challenges to studying early placental development directly, which calls for sophisticated in vitro, microfluidic organotypic models for advancing our understanding. For this, knowledge about key in vivo parameters are necessary for their design. In this scenario, the integration of data from later gestational stages and mathematical/computational simulations have proven to be useful tools. Notwithstanding, further research into cellular and molecular mechanisms at the fetal-maternal interface is essential for enhancing prenatal care and improving maternal and fetal health outcomes.

Engineered models for placental toxicology: Emerging approaches based on tissue decellularization

Recent increases in prescriptions and illegal drug use as well as exposure to environmental contaminants during pregnancy have highlighted the critical importance of placental toxicology in understanding and identifying risks to both mother and fetus. Although advantageous for basic science, current in vitro models often fail to capture the complexity of placental response, likely due to their inability to recreate and monitor aspects of the microenvironment including physical properties, mechanical forces and stiffness, protein composition, cell-cell interactions, soluble and physicochemical factors, and other exogenous cues. Tissue engineering holds great promise in addressing these challenges and provides an avenue to better understand basic biology, effects of toxic compounds and potential therapeutics. The key to success lies in effectively recreating the microenvironment. One strategy to do this would be to recreate individual components and then combine them. However, this becomes challenging due to variables present according to conditions such as tissue location, age, health status and lifestyle. The extracellular matrix (ECM) is known to influence cellular fate by working as a storage of factors. Decellularized ECM (dECM) is a recent tool that allows usage of the original ECM in a refurbished form, providing a relatively reliable representation of the microenvironment. This review focuses on using dECM in modified forms such as whole organs, scaffold sheets, electrospun nanofibers, hydrogels, 3D printing, and combinations as building blocks to recreate aspects of the microenvironment to address general tissue engineering and toxicology challenges, thus illustrating their potential as tools for future placental toxicology studies.

The Implication of Aquaporin-9 in the Pathogenesis of Preterm Premature Rupture of Membranes

OBJECTIVE

This study aimed to detect aquaporin-9 (AQP9) concentrations in the serum of patients with preterm premature rupture of membranes (PPROM) and compare them with the healthy control group with intact membranes.

MATERIAL AND METHODS

We conducted this prospective case-control study from January 2020 to June 2020. Of the 80 pregnant patients included in the study, we enrolled 42 singleton pregnant patients with PPROM as the study group and 43 healthy gestational age-, and body mass index (BMI)-matched healthy pregnant women with intact fetal membranes as the control group. We compared demographic and clinical characteristics, complete blood count and biochemical parameters, and serum AQP9 concentrations of the participants. We constructed an ROC curve to illustrate the sensitivity and specificity performance characteristics of AQP9 and calculated a cutoff value by using the Youden index.

RESULTS

Maternal serum AQP-9 concentrations were significantly higher in patients with PPROM (804.46±195.63 pg/mL) compared to the healthy pregnant women in the control group (505.97±68.89 pg/mL, p<0.001). When we examine the area under the ROC curve (AUC), the AQP-9 value can be reflected as a statistically significant parameter for diagnosing PPROM. According to the Youden index, a 654.78 pg/mL cut-off value of AQP-9 can be utilized to diagnose PPROM with 80.5% sensitivity and 100% specificity.

CONCLUSION

Maternal serum AQP9 concentrations were significantly higher in PPROM patients than healthy pregnant women with an intact membrane. We suggest that AQP9 might be an essential biomarker of the inflammatory process and energy homeostasis in PPROM.

Contribution of aquaporins in the transamniotic water flux

We explored the contribution of each aquaporin (AQP) expressed in human amnion in the transcellular water flux across the human amnion. Human amnion was placed between two lucite chambers and net water transport (Jw) was recorded by applying a hydrostatic (7 cm H₂O) and an osmotic (40 mOsm PEG 8000) pressure gradients. The hydrostatic (Phydr) and osmotic (POsm) permeabilities were calculated before and after the blocking of AQPs. Phdr showed no significant difference after the blocking of AQPs, while POsm was dramatically reduced. Interestingly, we also found that the blocking of AQP1 produced the highest decrease of POsm (80 ± 1%). Our results strongly suggested that AQP1 seems to contribute more to the maintenance of AF volume homeostasis.

Increased maternal serum aquaporin-9 expression in pregnancies complicated with early-onset preeclampsia

OBJECTIVES

We aimed to evaluate maternal serum aquaporin-9 (AQP9) concentrations in patients with early-onset preeclampsia and compare them with the uncomplicated control group with normal blood pressure.

METHODS

This was a prospective case-control study including pregnant women who were diagnosed with early-onset preeclampsia between 20^0/7 -34^0/7 weeks of gestation. Demographic and clinical characteristics, complete blood count and biochemical parameters, and serum AQP9 concentrations were documented. A receiver operating characteristic (ROC) curve was constructed to illustrate the sensitivity and specificity performance characteristics of AQP9 and a cut-off value was estimated by using the Youden index.

RESULTS

The mean serum concentrations of maternal AQP9 were significantly increased in the early-onset preeclampsia group (722.22 ± 211.80 pg/mL) than the control group (499.97 ± 68.89 pg/mL, p < 0.001). When we analyze the area under the ROC curve (AUC), the serum AQP9 value can be considered a statistically significant parameter for diagnosing preeclampsia. According to the Youden index, a 587.70 ng/mL cut-off value of serum AQP9 level can be used to diagnose early-onset preeclampsia with 80.0% sensitivity and 89.7% specificity.

CONCLUSION

Maternal serum AQP9 concentrations were significantly increased in early-onset preeclampsia patients than healthy normotensive pregnant patients. We suggest that AQP9 might be a crucial biomarker of the inflammatory process in early-onset preeclampsia.

Nutritional and Physiological Regulation of Water Transport in the Conceptus

Water transport during pregnancy is essential for maintaining normal growth and development of conceptuses (embryo/fetus and associated membranes). Aquaporins (AQPs) are a family of small integral plasma membrane proteins that primarily transport water across the plasma membrane. At least 11 isoforms of AQPs (AQPs 1-9, 11, and 12) are differentially expressed in the mammalian placenta (amnion, allantois, and chorion), and organs (kidney, lung, brain, heart, and skin) of embryos/fetuses during prenatal development. Available evidence suggests that the presence of AQPs in the conceptus mediates water movement across the placenta to support the placentation, the homeostasis of amniotic and allantoic fluid volumes, as well as embryonic and fetal survival, growth and development. Abundances of AQPs in the conceptus can be modulated by nutritional status and physiological factors affecting the pregnant female. Here, we summarize the effects of maternal dietary factors (such as intakes of protein, arginine, lipids, all-trans retinoic acid, copper, zinc, and mercury) on the expression of AQPs in the conceptus. We also discuss the physiological changes in hormones (e.g., progesterone and estrogen), oxygen supply, nitric oxide, pH, and osmotic pressure associated with the regulation of fluid exchange between mother and fetus. These findings may help to improve the survival, growth, and development of embryo/fetus in livestock species and other mammals (including humans).