Uterine aquaporin expression is dynamically regulated by estradiol and progesterone and ovarian stimulation disrupts embryo implantation without affecting luminal closure

Taurine is essential for mouse uterine luminal fluid resorption during implantation window via the SCNN1A and AQP8 signaling†

Uterine fluid homeostasis during peri-implantation is crucial for successful embryo implantation. Taurine (Tau) plays a crucial role in regulating osmotic pressure and ion transport. However, the precise mechanisms underlying Tau-mediated regulation of uterine fluid homeostasis during peri-implantation in mice remain unclear. In this study, we generated a Tau-deficient mouse model by administering Tau-free diet to Csad knockout (Csad-/-) mice to block endogenous Tau synthesis and exogenous Tau absorption (Csad-/--Tau free). Our findings demonstrated that Csad-/--Tau free mice with diminished level of Tau exhibited decreased rates of embryo implantation and impaired fertility. Further analysis revealed that the expression of Scnn1a was down-regulated during the implantation window, while Aqp8 was upregulated in Csad-/--Tau free mice, leading to uterine luminal fluid retention and defects in luminal closure, resulting in failed embryo implantation. Additionally, it was also found that E2 inhibited uterine Csad expression and Tau synthesis, while P4 promoted them. Therefore, our findings suggest that ovarian steroid hormones regulate Csad expression and Tau synthesis, thereby affecting release and resorption of uterine luminal fluid, ultimately impacting embryo implantation success.

Chenodeoxycholic acid fortified diet drives ovarian steroidogenesis to improve embryo implantation through enhancing uterine receptivity via progesterone receptor signaling pathway in rats

Infertility is a worldwide reproductive health problem influenced by the embryo implantation efficiency. We previously revealed that dietary chenodeoxycholic acid (CDCA) positively influence the early embryo implantation. But how CDCA regulate embryo implantation is largely unexplored. Herein, we investigated the mechanism behind CDCA's regulation on embryo implantation in rats. Results showed that CDCA promoted uterine receptivity, leading to increased number of implantation sites. Mechanistically, CDCA reshaped maternal amino acid metabolism and enhanced serum progesterone levels. CDCA enhanced ovarian progesterone synthesis by improving steroidogenesis-related protein (StAR and CYP11A1) expression via Takeda G-protein-coupled receptor 5. Elevated progesterone exaggerated uterine progesterone but weakened the estradiol signaling in the CDCA group, contributing to better uterine receptive for embryo implantation. Additionally, elevated transcription repressor Stat5b induced the down-regulation of progesterone-metabolizing enzyme 20-hydroxysteroid dehydrogenase 20α-HSD, complementally explained uterine progesterone signaling enhancement. Overall, our data revealed that CDCA drove ovarian steroidogenesis to improve embryo implantation through enhancing uterine receptivity via progesterone receptor pathway in rats. Therefore, CDCA diet may be a potential favorable nutritional strategy for infertility and pregnancy management.

Exploring Immune Cell Infiltration and Small Molecule Compounds for Ulcerative Colitis Treatment

BACKGROUND/OBJECTIVES

Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) with a relapsing nature and complex etiology. Bioinformatics analysis has been widely applied to investigate various diseases. This study aimed to identify crucial differentially expressed genes (DEGs) and explore potential therapeutic agents for UC.

METHODS

The GSE47908 and GSE55306 colon tissue transcriptome gene datasets were downloaded from the Gene Expression Omnibus-NCBI (GEO) database. GEO2R and Gene Set Enrichment Analysis (GSEA) were used to screen for DEGs in patients with UC compared to the normal population based on weighted gene co-expression network analysis (WGCNA). GO-BP analysis and KEGG enrichment analysis were performed on the intersecting differential genes via the Metascape website, while hub genes were analyzed by STRING11.0 and Cytoscape3.7.1. The expression of hub genes was verified in the dataset GSE38713 colon tissue specimens. Finally, the gene expression profiles of the validation set were analyzed by immuno-infiltration through the ImmuCellAI online tool, and the CMap database was used to screen for negatively correlated small molecule compounds.

RESULTS

A total of 595 and 926 genes were screened by analysis of GSE47908 and GSE55306 datasets, respectively. Combined WGCNA hub module intersection yielded 12 hub genes (CXCL8, IL1β, CXCL1, CCL20, CXCL2, CXCR2, LCN2, SELL, AGT, LILRB3, MMP3, IDO1) associated with the pathogenesis of UC. GSEA analysis yielded intersecting pathways for both datasets (colorectal cancer pathway, base excision repair, cell cycle, apoptosis). GO-BP and KEGG enrichment analyses were performed to obtain key biological processes (inflammatory response, response to bacteria, leukocyte activation involved in the immune response, leukocyte-cell adhesion, apoptosis, positive regulation of immune effector processes) and key signaling pathways (cytokine-cytokine receptor interactions, IBD, NOD-like receptor signaling pathways). The immune cell infiltration analysis suggested that the incidence of UC was mainly related to the increase in CD4+T cells, depletion of T cells, T follicular helper cells, natural killer cells, γδ T cells and the decrease in CD8 naive T cells, helper T cells 17 and effector T cells. The CMap database results showed that small molecule compounds such as vorinostat, roxarsone, and wortmannin may be therapeutic candidates for UC.

CONCLUSIONS

This study not only aids in early prediction and prevention but also provides novel insights into the pathogenesis and treatment of UC.

Hepatocyte aquaporin 8-mediated water transport facilitates bile dilution and prevents gallstone formation in mice

BACKGROUND & AIMS

Although water channel aquaporin-8 (AQP8) has been implicated in hepatic bile formation and liver diseases associated with abnormal bile flow in human and animal studies, direct evidence of its involvement in bile secretion is still lacking. This study aimed to determine the role of AQP8 in bile secretion and gallstone formation.

METHODS

We generated various transgenic knock-in and knockout mouse models and assessed liver AQP8 expression by immunostaining and immunoblotting, hepatic bile secretion by cannulation of the common bile duct, cholesterol gallstone formation by feeding a high-fat lithogenic diet, and identified regulatory small molecules by screening the organic fractions of cholagogic Chinese herbs and performing biochemical characterization.

RESULTS

We identified a novel expression pattern of AQP8 protein in the canalicular membrane of approximately 50% of the liver lobules. AQP8-deficient mice exhibited impaired hepatic bile formation, characterized by the secretion of concentrated bile with a lower flow rate and higher levels of bile lipids than that of wild-type littermates. Aqp8-/- mice showed accelerated gallstone formation, which was rescued by AAV-mediated hepatic expression of AQP8 or AQP1. Moreover, we identified a small molecule, scutellarin, that upregulates hepatocyte AQP8 expression in vitro and in vivo. In Aqp8+/+ mice, scutellarin significantly increased bile flow, decreased bile lipid concentrations, and prevented gallstone formation compared to Aqp8-/- mice. Molecular studies revealed that scutellarin promoted the ubiquitination and degradation of HIF-1α, a transcriptional negative regulator of AQP8, by disrupting its interactions with HSP90.

CONCLUSIONS

AQP8 plays a crucial role in facilitating water transport and bile dilution during hepatic bile formation, thereby mitigating gallstone formation in mice. Small-molecule intervention validated hepatocyte AQP8 as a promising drug target for gallstone therapy.

IMPACT AND IMPLICATIONS

The incidence of gallstone disease is high, and current drug treatments for gallstones are very limited, necessitating the identification of novel drug targets for therapeutic development with universal applicability. To our knowledge, this is the first study to provide direct evidence that the hepatic water channel AQP8 plays a key role in bile dilution and gallstone formation. Modulation of hepatic water transport may provide a universal therapeutic strategy for all types of gallstone diseases.

Loss of PRICKLE1 leads to abnormal endometrial epithelial architecture, decreased embryo implantation, and reduced fertility in mice

Successful embryo implantation requires coordinated changes in the uterine luminal epithelium, including structural adaptations, apical-basal polarity shifts, intrauterine fluid resorption, and cellular communication. Planar cell polarity (PCP) proteins, essential for cell organization, are understudied in the context of uterine physiology and implantation. PRICKLE proteins, components of PCP, are suggested to play critical roles in epithelial polarization and tissue morphogenesis. However, their function in the polarized unicellular layer of endometrial epithelium, which supports embryo implantation, is unknown. We developed an endometrial epithelial-specific knockout (cKO) of mouse Prickle1 using Lactoferrin-iCre to investigate its's role in uterine physiology. Prickle1 ablation in the endometrial epithelium of mice resulted in decreased embryo implantation by gestational day 4.5 leading to lower fertility. Three-dimensional imaging of the uterus revealed abnormal luminal folding, impaired luminal closure, and altered glandular length in mutant uteri. Additionally, we observed decreased aquaporin-2 expression, disrupted cellular architecture, and altered E-Cadherin expression and localization in the mutant uterine epithelium. Evidence of epithelial-mesenchymal transition (EMT) was found within luminal epithelial cells, further linking PRICKLE1 loss to uterine pathologies. Furthermore, altered polarity of cell division leading to incomplete cytokinesis and increase in binuclear or multinucleated cells suggests a crucial role for PRICKLE1 in the maintenance of epithelial architecture. Our findings highlight PRICKLE1's critical role in the PCP pathway within the uterus, revealing its importance in the molecular and cellular responses essential for successful pregnancy and fertility.

Significance Statement

Conservative cell division is essential to maintain apical-basal polarity and proper epithelial function in the uterus. Wnt/ Planar cell polarity signaling molecules are hypothesized to provide the spatial cues to organize unicellular, 2-dimensional sheet of epithelium in a plane orthogonal to the apical-basal polarity. Conditional ablation of Prickle1 , a crucial Wnt/ PCP gene, in mouse uterine epithelium results in aberrant expression of epithelial cadherin, altered plane of cell division, incomplete cytokinesis leading to binucleated/ multinucleated cells, epithelial - mesenchymal transition, and defective implantation. Role of Prickle1 in maintaining symmetric uterine epithelial cell division and tissue architecture is unique among Wnt/PCP genes, including previously described mouse models for Vangl2, Ror2, and Wnt5a . Classification: Biological Sciences (Major) Cell Biology (Minor), Physiology (Minor).

Transcriptome profiling reveals superovulation with the gonadotropin-releasing hormone agonist trigger impaired embryo implantation in mice

Introduction

Superovulation is a critical step in assisted reproductive technology, but the use of human chorionic gonadotropin (hCG) as a trigger for superovulation can result in ovarian hyperstimulation. Thus, the use of Gonadotropin-releasing hormone agonist (GnRHa) trigger has been increasingly adopted, although it has been associated with a higher rate of pregnancy failure compared to natural cycles. This study aimed to investigate the effect of GnRHa trigger on embryo implantation in a mouse model.

Methods

Mice in the superovulation (PG) group were administered 7.5 IU of PMSG, followed by the injection of 3.5 μg of GnRHa (Leuprorelin) 48 h later, while mice in the control group (CTR) mated naturally. We compared the number of oocytes, blastocysts, and corpus luteum between the two groups and the implantation sites after the transfer of natural blastocysts. Ovaries, uterus, and serum 2 and 4 days after mating were collected for qRT-PCR, transcriptome sequencing, and hormone assays.

Results

The PG group had more oocytes, blastocysts, and corpus luteum after superovulation than the CTR group. However, the mRNA expression of leukemia inhibitory factor (Lif) and the number of implantation sites were reduced in the PG group. The ELISA assay revealed that superovulation increased ovarian estrogen secretion. The transcriptome analysis showed that superphysiological estrogen led to a response of the uterus to a high estrogen signal, resulting in abnormal endometrium and extracellular matrix remodeling and up-regulation of ion transport and inflammation-related genes.

Conclusion

Our findings suggest that a combination of PMSG and GnRHa trigger impaired embryo implantation in mice, as the excessive uterine response to superphysiological estrogen levels can lead to the change of gene expression related to endometrial remodeling, abnormal expression of uterine ion transport genes and excessive immune-related genes.

Risks and outcomes of pregnancy in neuromyelitis optica spectrum disorder: A comprehensive review

Neuromyelitis optica spectrum disorder (NMOSD) is a rare central nervous system autoimmune disease. Aquaporin-4 antibody (AQP4-IgG) is present in over 75% of cases and criteria also exist for the diagnosis of seronegative NMOSD. AQP4-IgG NMOSD has a strong female predominance (9:1 ratio), with a median onset age of 40 years. Pregnancy in those with NMOSD is therefore an important topic. Fecundity in NMOSD is likely impaired, and for females who conceive, obstetric complications including miscarriages and pre-eclampsia are significantly higher in NMOSD compared to the general population and in related conditions such as multiple sclerosis (MS). In contrast to MS, NMOSD disease activity does not subside during pregnancy. Also, relapse risk substantially rises above pre-pregnancy rates in the early postpartum period. In view of the evolving landscape of NMOSD, we provide a contemporary update of the impacts of pregnancy in NMOSD.

Ginsenosides in endometrium-related diseases: Emerging roles and mechanisms

Ginsenosides, agents extracted from an important herb (ginseng), are expected to provide new therapies for endometrium-related diseases. Based on the molecular types of ginsenosides, we reviewed the main pharmacological effects of ginsenosides against endometrium-related diseases (e.g., endometrial cancers, endometriosis, and endometritis). The mechanism of action of ginsenosides involves inducing apoptosis of endometrium-related cells, promoting autophagy of endometrium-related cells, regulating epithelial-mesenchymal transition (EMT) in endometrium-related cells, and activating the immune system to kill cells associated with endometrial diseases. We hope to provide a theoretical foundation for the treatment of endometrium-related diseases by ginsenosides.

Integrins and their potential roles in mammalian pregnancy

Integrins are a highly complex family of receptors that, when expressed on the surface of cells, can mediate reciprocal cell-to-cell and cell-to-extracellular matrix (ECM) interactions leading to assembly of integrin adhesion complexes (IACs) that initiate many signaling functions both at the membrane and deeper within the cytoplasm to coordinate processes including cell adhesion, migration, proliferation, survival, differentiation, and metabolism. All metazoan organisms possess integrins, and it is generally agreed that integrins were associated with the evolution of multicellularity, being essential for the association of cells with their neighbors and surroundings, during embryonic development and many aspects of cellular and molecular biology. Integrins have important roles in many aspects of embryonic development, normal physiology, and disease processes with a multitude of functions discovered and elucidated for integrins that directly influence many areas of biology and medicine, including mammalian pregnancy, in particular implantation of the blastocyst to the uterine wall, subsequent placentation and conceptus (embryo/fetus and associated placental membranes) development. This review provides a succinct overview of integrin structure, ligand binding, and signaling followed with a concise overview of embryonic development, implantation, and early placentation in pigs, sheep, humans, and mice as an example for rodents. A brief timeline of the initial localization of integrin subunits to the uterine luminal epithelium (LE) and conceptus trophoblast is then presented, followed by sequential summaries of integrin expression and function during gestation in pigs, sheep, humans, and rodents. As appropriate for this journal, summaries of integrin expression and function during gestation in pigs and sheep are in depth, whereas summaries for humans and rodents are brief. Because similar models to those illustrated in Fig. 1, 2, 3, 4, 5 and 6 are present throughout the scientific literature, the illustrations in this manuscript are drafted as Viking imagery for entertainment purposes.

The PCOS puzzle: putting the pieces together for optimal care

Polycystic ovary syndrome (PCOS) is a multifaceted hormonal disorder that has significant ramifications for both women's reproductive and metabolic well-being. This analysis aims to offer a thorough comprehension of PCOS by investigating the various contributing factors that are crucial for its effective management. We delve into the topic of hormonal imbalances, such as elevated androgens and disrupted estrogen-progesterone dynamics, and their effects on reproductive and metabolic health. Furthermore, we explore the intricate connection between insulin resistance, hyperinsulinemia, and PCOS, highlighting their pivotal role in metabolic dysfunction. Additionally, we examine fertility challenges, irregular menstrual patterns, and metabolic complications while also reviewing current treatment methodologies. Moreover, we address the latest research concerning genetic, environmental, and epigenetic influences on PCOS. By piecing together these essential elements, healthcare professionals can attain a comprehensive understanding of PCOS and deliver optimal care for those affected by the condition.

Estrogen-sensitive activation of SGK1 induces M2 macrophages with anti-inflammatory properties and a Th2 response at the maternal-fetal interface

BACKGROUND

Decidual macrophages participate in immune regulation at the maternal-fetal interface. Abnormal M1/M2 polarization of decidual macrophages might predispose immune maladaptation in recurrent pregnancy loss (RPL). However, the mechanism of decidual macrophage polarization is unclear. We explored the role of Estradiol (E₂)-sensitive serum-glucocorticoid regulated kinase (SGK) 1 in promoting macrophage polarization and suppressing inflammation at the maternal-fetal interface.

METHODS

We assessed serum levels of E₂ and progesterone during first trimester of pregnancy in women with or without threatened miscarriages (ended in live birth, n = 448; or early miscarriages, n = 68). For detection of SGK1 in decidual macrophages, we performed immunofluorescence labeling and western blot analysis applying decidual samples from RPL (n = 93) and early normal pregnancy (n = 66). Human monocytic THP-1 cells were differentiated into macrophages and treated with Toll-like receptor (TLR) 4 ligand lipopolysaccharide (LPS), E₂, inhibitors or siRNA for in vitro analysis. Flow cytometry analysis were conducted to detect macrophages polarization. We also applied ovariectomized (OVX) mice with hormones exploring the mechanisms underlying the regulation of SGK1 activation by E₂ in the decidual macrophages in vivo.

RESULTS

SGK1 expression down regulation in the decidual macrophages of RPL was consistent with the lower concentration and slower increment of serum E₂ from 4 to 12 weeks of gestation seen in these compromised pregnancies. LPS reduced SGK1 activities, but induced the pro-inflammatory M1 phenotype of THP-1 monocyte-derived macrophages and T helper (Th) 1 cytokines that favored pregnancy loss. E₂ pretreatment promoted SGK1 activation in the decidual macrophages of OVX mice in vivo. E₂ pretreatment amplified SGK1 activation in TLR4-stimulated THP-1 macrophages in vitro through the estrogen receptor beta (ERβ) and PI3K pathway. E₂-sensitive activation of SGK1 increased M2 macrophages and Th2 immune responses, which were beneficial to successful pregnancy, by inducing ARG1 and IRF4 transcription, which are implicated in normal pregnancy. The experiments on OVX mice have shown that pharmacological inhibition of E₂ promoted nuclear translocation of NF-κB in the decidual macrophages. Further more, pharmacological inhibition or knockdown of SGK1 in TLR4-stimulated THP-1 macrophages activated NF-κB by promoting its nuclear translocation, leading to increased secretion of pro-inflammatory cytokines involved in pregnancy loss.

CONCLUSION

Our findings highlighted the immunomodulatory roles of E₂-activated SGK1 in Th2 immune responses by priming anti-inflammatory M2 macrophages at the maternal-fetal interface, resulting in a balanced immune microenvironment during pregnancy. Our results suggest new perspectives on future preventative strategies for RPL.

Time-restricted feeding ameliorates uterine epithelial estrogen receptor α transcriptional activity at the time of embryo implantation in mice fed a high-fat diet

BACKGROUND

More than 30% of reproductive-age women are obese or overweight. Obesity and exposure to a high-fat diet (HFD) detrimentally affect endometrial development and embryo implantation. We previously reported that time-restricted feeding (TRF) improved ovarian follicular development, but whether and how TRF modulates embryo implantation are poorly understood.

OBJECTIVE

We investigated the effect of TRF on embryo implantation.

METHODS

In TRF group, mice had 10 hours of food free access from 9 pm to 7 am, and fed a normal diet or a HFD. Tail vein injection of Chicago blue dye was used to examine embryo implantation sites at day 5.5 (D5.5) of pregnancy. Serum collected at D0.5 and D4.5 of pregnancy was used to examine the level of estradiol (E2) and progesterone. Uterine estrogen receptor (ER) and progesterone receptor levels and their targeted aquaporins (AQPs) were measured. LC-MS was used to analyze bile acid (BA) composition, and primary hepatocytes were used to test the effects of BA on the expression level of SULT1E1, a key enzyme in estrogen inactivation and elimination.

RESULTS

We found that TRF prevented HFD-induced embryo loss and alleviated the defect in luminal closure on D4.5 of pregnancy. The cyclic changes of E2 level were lost in mice fed ad libitum but not in TRF mice on the HFD. The HFD increased ERα expression and transcriptional activity, which induced AQP3 and AQP5 expression on D4.5 of pregnancy. TRF prevented the negative effect of the HFD on uterine luminal closure. Furthermore, in vitro and in vivo results showed that BA suppressed estrogen degradation by activating liver SULT1E1 expression.

CONCLUSIONS

Our findings demonstrated that TRF prevented HFD-induced defects in luminal closure, thereby improving embryonic implantation, and provide novel insights into the effects of dietary intervention on obesity and associated infertility.

Aquaporin-5 Dynamic Regulation

Aquaporin-5 (AQP5), belonging to the aquaporins (AQPs) family of transmembrane water channels, facilitates osmotically driven water flux across biological membranes and the movement of hydrogen peroxide and CO₂. Various mechanisms have been shown to dynamically regulate AQP5 expression, trafficking, and function. Besides fulfilling its primary water permeability function, AQP5 has been shown to regulate downstream effectors playing roles in various cellular processes. This review provides a comprehensive overview of the current knowledge of the upstream and downstream effectors of AQP5 to gain an in-depth understanding of the physiological and pathophysiological processes involving AQP5.

Adverse effect of assisted reproductive technology-related hyperoestrogensim on the secretion and absorption of uterine fluid in superovulating mice during the peri-implantation period

OBJECTIVES

This study aimed to investigate the potential mechanism of hyperoestrogensim elicited by ovulation induction affects endometrial receptivity and leads to embryo implantation abnormality or failure.

STUDY DESIGN

Establishment of ovulation induction mouse model. Changes in mouse body weight, ovarian weight, serum E2 level and oestrous cycle were observed. During the peri-implantation period, morphological changes in the mouse uterus and implantation sites and the localization and protein levels of oestrogen receptors ERα and ERβ, the tight junction factors CLDN3 and OCLN, the aquaporins AQP3, AQP4 and AQP8, and the sodium channel proteins SCNN1α, SCNN1β and SCNN1γ were observed. The expression and cellular localization of ERα, CLDN3, AQP8 and SCNN1 β in RL95-2 cell line were also detected by western blotting and immunofluorescence.

RESULTS

Ovarian and body weights were significantly higher in the 5 IU and 10 IU groups than in the CON group. The E2 level was significantly higher in the 10 IU group than in the CON group. The mice in the 10 IU group had a disordered oestrous cycle and were in oestrus for a long time. At 5.5 dpc, significantly fewer implantation sites were observed in the 10 IU group than in the CON (p<0.001) and 5 IU (p<0.05) groups. The probability of abnormal implantation and abortion was higher in the 10 IU group than in the CON and 5 IU groups. CLDN3, OCLN, AQP8 and SCNN1β in the mouse endometrium were localized on the luminal epithelium and glandular epithelium and expression levels were lower in the 10 IU group than in the CON group. The protein expression level of ERα was increased by 50% in the 10 IU group compared to the CON group. The expressions of CLDN3, AQP8, SCNN1β in RL95-2 cell line were significantly depressed by the superphysiological E2, ERα agonist or ERβ agonist, which could be reversed by the oestrogen receptor antagonist.

CONCLUSION

ART-induced hyperoestrogenism reduces CLDN3, AQP8 and SCNN1β expression through ERα, thereby destroying tight junctions and water and sodium channels in the endometrial cavity epithelium, which may cause abnormal implantation due to abnormal uterine fluid secretion and absorption.

Astrocytic Responses to Binge Alcohol Intake in the Mouse Hindbrain

Ethanol is the most commonly used toxic chemical in human cultures. Ethanol predominantly damages the brain causing various neurological disorders. Astrocytes are important cellular targets of ethanol in the brain and are involved in alcoholic symptoms. Recent studies have revealed the diversity of astrocyte populations in the brain. However, it is unclear how the different astrocyte populations respond to an excess of ethanol. Here we examined the effect of binge ethanol levels on astrocytes in the mouse brainstem and cerebellum. Ethanol administration for four consecutive days increased the glial fibrillary acidic protein (GFAP)-immunoreactive signals in the spinal tract of the trigeminal nerve (stTN) and reticular nucleus (RN). Another astrocyte marker, aquaporin 4 (AQP4), was also increased in the stTN with a pattern similar to that of GFAP. However, in the RN, the immunoreactive signals of AQP4 were different from that of GFAP and were not changed by ethanol administration. In the cerebellum, GFAP-positive signals were found in all four astrocytic populations, and those in the Bergmann glia were selectively eliminated by ethanol administration. We next examined the effect of estradiol on the ethanol-induced changes in astrocytic immunoreactive signals. The administration of estradiol alone increased the AQP4-immunoreactivity in the stTN with a pattern similar to that of ethanol, whereas the co-administration of estradiol and ethanol suppressed the intensity of the AQP4-positive signals. Thus, binge levels of ethanol intake selectively affect astrocyte populations in the brainstem and cerebellum. Sex hormones can affect the ethanol-induced neurotoxicity via modulation of astrocyte reactivity.

Aquaporins in Reproductive System

AQP0-12, a total of 13 aquaporins are expressed in the mammalian reproductive system. These aquaporins mediate the transport of water and small solutes across biofilms for maintaining reproductive tract water balance and germ cell water homeostasis. These aquaporins play important roles in the regulation of sperm and egg cell production, maturation, and fertilization processes. Impaired AQP function may lead to diminished male and female fertility. This review focuses on the distribution, function, and regulation of AQPs throughout the male and female reproductive organs and tracts. Their correlation with reproductive success, revealing recent advances in the physiological and pathophysiological roles of aquaporins in the reproductive system.

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).

Insights into the Regulation of Implantation and Placentation in Humans, Rodents, Sheep, and Pigs

Precise cell-specific spatio-temporal molecular signaling cascades regulate the establishment and maintenance of pregnancy. Importantly, the mechanisms regulating uterine receptivity, conceptus apposition and adhesion to the uterine luminal epithelia/superficial glandular epithelia and, in some species, invasion into the endometrial stroma and decidualization of stromal cells, are critical prerequisite events for placentation which is essential for the appropriate regulation of feto-placental growth for the remainder of pregnancy. Dysregulation of these signaling cascades during this critical stage of pregnancy can lead to pregnancy loss, impaired growth and development of the conceptus, and alterations in the transplacental exchange of gasses and nutrients. While many of these processes are conserved across species, significant variations in the molecular mechanisms governing maternal recognition of pregnancy, conceptus implantation, and placentation exist. This review addresses the complexity of key mechanisms that are critical for the establishment and maintenance of a successful pregnancy in humans, rodents, sheep, and pigs. Improving understanding of the molecular mechanisms governing these processes is critical to enhancing the fertility and reproductive health of humans and livestock species.

Uterine kisspeptin receptor critically regulates epithelial estrogen receptor α transcriptional activity at the time of embryo implantation in a mouse model

Embryo implantation failure is a major cause of infertility in women of reproductive age and a better understanding of uterine factors that regulate implantation is required for developing effective treatments for female infertility. This study investigated the role of the uterine kisspeptin receptor (KISS1R) in the molecular regulation of implantation in a mouse model. To conduct this study, a conditional uterine knockout (KO) of Kiss1r was created using the Pgr-Cre (progesterone receptor-CRE recombinase) driver. Reproductive profiling revealed that while KO females exhibited normal ovarian function and mated successfully to stud males, they exhibited significantly fewer implantation sites, reduced litter size and increased neonatal mortality demonstrating that uterine KISS1R is required for embryo implantation and a healthy pregnancy. Strikingly, in the uterus of Kiss1r KO mice on day 4 (D4) of pregnancy, the day of embryo implantation, KO females exhibited aberrantly elevated epithelial ERα (estrogen receptor α) transcriptional activity. This led to the temporal misexpression of several epithelial genes [Cftr (Cystic fibrosis transmembrane conductance regulator), Aqp5 (aquaporin 5), Aqp8 (aquaporin 8) and Cldn7 (claudin 7)] that mediate luminal fluid secretion and luminal opening. As a result, on D4 of pregnancy, the lumen remained open disrupting the final acquisition of endometrial receptivity and likely accounting for the reduction in implantation events. Our data clearly show that uterine KISS1R negatively regulates ERα signaling at the time of implantation, in part by inhibiting ERα overexpression and preventing detrimentally high ERα activity. To date, there are no reports on the regulation of ERα by KISS1R; therefore, this study has uncovered an important and powerful regulator of uterine ERα during early pregnancy.

SPP1 expression in the mouse uterus and placenta: Implications for implantation

Secreted phosphoprotein 1 [SPP1, also known as osteopontin (OPN)] binds integrins to mediate cell-cell and cell-extracellular matrix communication to promote cell adhesion, migration, and differentiation. Considerable evidence links SPP1 to pregnancy in several species. Current evidence suggests that SPP1 is involved in implantation and placentation in mice, but in vivo localization of SPP1 and in vivo mechanistic studies to substantiate these roles are incomplete and contradictory. We localized Spp1 mRNA and protein in the endometrium and placenta of mice throughout gestation, and utilized delayed implantation of mouse blastocysts to link SPP1 expression to the implantation chamber. Spp1 mRNA and protein localized to the endometrial luminal (LE), but not glandular epithelia (GE) in interimplantation regions of the uterus throughout gestation. Spp1 mRNA and protein also localized to uterine naturel killer (uNK) cells of the decidua. Within the implantation chamber, Spp1 mRNA localized only to intermittent LE cells, and to the inner cell mass. SPP1 protein localized to intermittent trophoblast cells, and to the parietal endoderm. These results suggest that SPP1: 1) is secreted by the LE at interimplantation sites for closure of the uterine lumen to form the implantation chamber; 2) is secreted by LE adjacent to the attaching trophoblast cells for attachment and invasion of the blastocyst; and 3) is not a component of histotroph secreted from the GE, but is secreted from uNK cells in the decidua to increase angiogenesis within the decidua to augment hemotrophic support of embryonic/fetal development of the conceptus.

Aquaporins and (in)fertility: More than just water transport

Aquaporins (AQPs) are a family of channel proteins that facilitate the transport of water and small solutes across biological membranes. They are widely distributed throughout the organism, having a number of key functions, some of them unexpected, both in health and disease. Among the various diseases in which AQPs are involved, infertility has been overlooked. According to the World Health Organization (WHO) infertility is a global public health problem with one third of the couples suffering from subfertility or even infertility due to male or female factors alone or combined. Thus, there is an urgent need to unveil the molecular mechanisms that control gametes production, maturation and fertilization-related events, to more specifically determine infertility causes. In addition, as more couples seek for fertility treatment through assisted reproductive technologies (ART), it is pivotal to understand how these techniques can be improved. AQPs are heterogeneously expressed throughout the male and female reproductive tracts, highlighting a possible regulatory role for these proteins in conception. In fact, their function, far beyond water transport, highlights potential intervention points to enhance ART. In this review we discuss AQPs distribution and structural organization, functions, and modulation throughout the male and female reproductive tracts and their relevance to the reproductive success. We also highlight the most recent advances and research trends regarding how the different AQPs are involved and regulated in specific mechanisms underlying (in)fertility. Finally, we discuss the involvement of AQPs in ART-related processes and how their handling can lead to improvement of infertility treatment.

Expression and Regulation of Aquaporins in Pregnancy Complications and Reproductive Dysfunctions

Aquaporins (AQPs), small hydrophobic integral membrane proteins, mediate rapid transport of water and small solutes. The abnormal expressions of AQPs are associated with pregnancy complications and reproductive dysfunctions, including preeclampsia, gestational diabetes mellitus, tubal ectopic pregnancy, intrahepatic cholestasis of pregnancy, preterm birth, chorioamnionitis, polyhydramnios, and oligohydramnios, thus resulting in adverse pregnancy outcomes. This review explains the alterations of AQPs in pregnancy complications and reproductive dysfunctions and summarizes the molecular mechanisms involved in the regulations of AQPs by drugs such as oxytocin, polychlorinated biphenyls, all-trans-retinoic acid, salvia miltiorrhiza, and insulin, or other factors such as oxygen and osmotic pressure. All the research provides evidence that AQPs could be the new therapeutic targets of pregnancy-related diseases.

Uterine Gpr83 mRNA is highly expressed during early pregnancy and GPR83 mediates the actions of PEN in endometrial and non-endometrial cells

OBJECTIVE

To characterize the expression and signaling of uterine GPR83 in vivo in the nonpregnant and pregnant mouse and in vitro in human endometrial and nonendometrial cells.

DESIGN

Controlled laboratory study.

SETTING

Not applicable.

PATIENTS

Not applicable.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Expression of uterine Gpr83 was determined by quantitative polymerase chain reaction throughout the estrous cycle and during early pregnancy in ovarian-stimulated and non-ovarian-stimulated mice and pregnant and pseudopregnant mice. Expression was also determined in ovariectomized mice after the administration of oil, E2, P4, or E2 + P4 and in stromal cells following 6 days of in vitro decidualization. GPR83 signaling was studied in human endometrial and embryonic kidney cell lines. Cells were treated by PEN, a GPR83 ligand, and PEN-induced extracellular signal-regulated kinase (ERK) phosphorylation was assayed under conditions that blocked Gα_q/11 and/or β-arrestin signaling.

RESULTS

Uterine Gpr83 is expressed throughout the estrous cycle and during early pregnancy; expression increases dramatically at the time of uterine receptivity, embryo implantation, and stromal cell decidualization. In the ovariectomized mouse, hormone add-back reveals that Gpr83 expression is highly responsive to the combined treatment of E2 and P4, and studies in the ovarian-stimulated mouse show that expression is also very sensitive to changes in E2 and P4 and is therefore tightly regulated by E2 and P4. At the implantation site, expression is elevated up to D6 of pregnancy and then declines rapidly on D7 and D8, suggesting that if there is any involvement in decidualization, it is likely associated with primary but not secondary stromal cell decidualization. This premise was supported by the observation that stromal cell decidualization in vitro progresses with a decline in Gpr83 expression. In ERα/PR-expressing endometrial Ishikawa cells, GPR83 mediates PEN signals in a Gα_q/11-dependent manner, and studies conducted in HEK 293 cells lacking β-arrestin revealed that GPR83 also signals via a β-arrestin-dependent manner. When signaling by either one or both pathways is downregulated, cells exhibit a major reduction in responsiveness to PEN treatment, demonstrating that signaling by both pathways is significant.

CONCLUSION

We hypothesize that PEN/GPR83 signaling regulates uterine receptivity, embryo implantation, and primary stromal cell decidualization by coupling to Gα_q/11- and β-arrestin-dependent pathways.