Function of aquaporins in female and male reproductive systems

Adaptive Transition of Aquaporin 5 Expression and Localization during Preimplantation Embryo Development by In Vitro Culture

Adaptive development of early stage embryo is well established and recently it is explored that the mammalian embryos also have adaptive ability to the stressful environment. However, the mechanisms are largely unknown. In this study, to evaluate the possible role of aquaporin in early embryo developmental adaptation, the expression of aquaporin (AQP) 5 gene which is detected during early development were examined by the environmental condition. To compare expression patterns between in vivo and in vitro, we conducted quantitative RT-PCR and analyzed localization of the AQP5 by whole mount immunofluorescence. At in vivo condition, Aqp5 expressed in oocyte and in all the stages of preimplantation embryo. It showed peak at 2-cell stage and decreased continuously until morula stage. At in vitro condition, Aqp5 expression pattern was similar with in vivo embryos. It expressed both at embryonic genome activation phase and second midpreimplantation gene activation phase, but the fold changes were modified between in vivo embryos and in vitro embryos. During in vivo development, AQP5 was mainly localized in apical membrane of blastomeres of 4-cell and 8-cell stage embryos, and then it was localized in cytoplasm. However, the main localization area of AQP5 was dramatically shifted after 8-cell stage from cytoplasm to nucleus by in vitro development. Those results explore the modification of Aqp5 expression levels and location of its final products by in vitro culture. It suggests that expression of Aqp5 and the roles of AQP5 in homeostasis can be modulated by in vitro culture, and that early stage embryos can develop successfully by themselves adapting to their condition through modulation of the specific gene expression and localization.

Expression of Aquaporin 1, 5 and 9 in the Ovarian Follicles of Cycling and Early Pregnant Pigs

Aquaporins (AQPs) are water channel proteins responsible for water homeostasis and important for proper functioning of all body systems, including reproductive structures. This study was designed to determine their localization and quantitative changes in the pig ovary during different stages of the estrous cycle and early pregnancy. The expression of AQP 1, 5 and 9 proteins was determined by immunocytochemistry and Western blot analyses. AQP1 was found in the plasma membranes of capillary endothelium, AQP5 – in the plasma membranes of granulosa cells of developing follicles and flattened follicle cells of the primordial follicles, and AQP9 – in granulosa cells of the developing follicles. In the cyclic pigs, the expression of AQP1 and 5 proteins was the highest on Days 18-20, but did not change significantly between Days 2-4, 10-12 and 14-16 of the cycle. In pregnant pigs (Days 14-16 and 30-32), the expression of AQP1 and 5 did not change and was similar to that observed during Days 10-12 and 14-16. In turn, AQP9 expression did not change between all studied periods. In conclusion, studied AQP are localized in different cells populations, the endothelial and granulosa cells, and AQP1 and 5 seem to be crucial for follicular development in pigs.

17β-estradiol causes abnormal development in embryos of the viviparous eelpout

Elevated frequencies of malformations among the offspring of Baltic eelpout (Zoarces viviparus) have been observed in aquatic environments receiving high anthropogenic input suggesting that manmade chemicals could be the causative agent. However, causal links between exposure to chemicals and abnormal development have never been confirmed in laboratory experiments. The purpose of this study was to investigate if exposure to 17β-estradiol (E2) causes abnormal development in larvae of the viviparous eelpout. Wild female eelpout were collected immediately after fertilization and exposed to E2 concentrations ranging from 5.7 to 133 ng L(-1) for 6 weeks in a flow through test system. The experiment shows that E2 concentrations of 53.6 and 133 ng L(-1) cause severe abnormal development among eelpout embryos. Reduced amount of ovarian fluid and increased weight of the ovarian sac indicate disturbance of ovarian function. Female plasma concentrations of E2 and vitellogenin increase in a monotonic concentration-response relationship with significant induction in the low concentration range. Our findings support the plausibility that the abnormal development among eelpout embryos encountered in monitoring programs may actually be caused by exposure to chemicals in the environment.

Aquaporin-9 is expressed in rat Sertoli cells and interacts with the cystic fibrosis transmembrane conductance regulator

Men with mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are usually subfertile/infertile. Besides playing a role in Cl(-)/HCO3(-) transport, it has been proposed that CFTR interacts with water membrane transport systems, particularly aquaporins, to control seminiferous tubular secretion, which is regulated by the somatic Sertoli cells (SCs). As aquaporin-9 (AQP9) is highly expressed throughout the male reproductive tract, we hypothesized that it is also present in rat SCs and that it physically interacts with CFTR. To test this hypothesis, primary cultures of rat SCs were established, and expression of CFTR and AQP9 was assessed by RT-polymerase chain reactions (mRNA) and Western blot analysis (protein). A coimmunoprecipitation assay was used to evaluate the physical interaction between CFTR and AQP9. Our results show that CFTR and AQP9 are expressed in rat SCs. We were also able to detect a molecular interaction between CFTR and AQP9 in rat SCs. This is the first report describing the presence of AQP9, and its interaction with CFTR, in rat SCs. Moreover, our results provide evidence that CFTR is involved in water homeostasis of the seminiferous tubular secretion. These mechanisms may open new insights on therapeutic targets to counteract subfertility/infertility in men with cystic fibrosis and mutations in the CFTR gene.

Xenobiotic transporter expression along the male genital tract

The male genital tract plays an important role in protecting sperm by forming a distinct compartment separate from the body which limits exposure to potentially toxic substrates. Transporters along this tract can influence the distribution of xenobiotics into the male genital tract through efflux back into the blood or facilitating the accumulation of toxicants. The aim of this study was to quantitatively determine the constitutive mRNA expression of 30 xenobiotic transporters in caput and cauda regions of the epididymis, vas deferens, prostate, and seminal vesicles from adult Sprague-Dawley rats. The epididymis was found to express at least moderate levels of 18 transporters, vas deferens 15, seminal vesicles 23, and prostate 18. Constitutive expression of these xenobiotic transporters in the male genital tract may provide insight into the xenobiotics that can potentially be transported into these tissues and may provide the molecular mechanism for site specific toxicity of select agents.

Immunolocalization of aquaporin 5 during rat ovarian follicle development and expansion of the preovulatory cumulus oophorus

Immunofluorescent localization of aquaporin 5 (AQP5) was investigated in rat ovarian follicles during development and preovulatory cumulus oophorus expansion. Ampullary cumuli oophori complexes (COCs) were examined. Analysis revealed that AQP5 immunostaining appeared in preantral follicles and formed a characteristic ring encircling and touching the oolemma. The staining represented most likely AQP5 functioning at the ends of corona radiata cell projections, anchoring on the oocyte surface. However, several hours after the presumptive preovulatory LH surge, when the process of expansion of COCs started, the AQP5 staining appeared also on the cumulus granulosa cells and in the extracellular matrix. In the postovulatory ampullary COCs the fluorescent ring was not observed, which may be the result of the well-established preovulatory withdrawal of projections from the zona pellucida. At that time-point immunofluorescent staining of AQP5 appeared in most oocytes and was also present in the apical membrane of epithelial cells of the oviduct ampulla. The latter observation suggests that after ovulation AQP5 is involved in the transcellular movement of water in the oviduct ampulla and oocytes in rats.

Discovery of sex-related genes through high-throughput transcriptome sequencing from the salmon louse Caligus rogercresseyi

Understanding the molecular underpinnings involved in the reproduction of the salmon louse is critical for designing novel strategies of pest management for this ectoparasite. However, genomic information on sex-related genes is still limited. In the present work, sex-specific gene transcription was revealed in the salmon louse Caligus rogercresseyi using high-throughput Illumina sequencing. A total of 30,191,914 and 32,292,250 high quality reads were generated for females and males, and these were de novo assembled into 32,173 and 38,177 contigs, respectively. Gene ontology analysis showed a pattern of higher expression in the female as compared to the male transcriptome. Based on our sequence analysis and known sex-related proteins, several genes putatively involved in sex differentiation, including Dmrt3, FOXL2, VASA, and FEM1, and other potentially significant candidate genes in C. rogercresseyi, were identified for the first time. In addition, the occurrence of SNPs in several differentially expressed contigs annotating for sex-related genes was found. This transcriptome dataset provides a useful resource for future functional analyses, opening new opportunities for sea lice pest control.

Ion channels in the endometrium: regulation of endometrial receptivity and embryo implantation

BACKGROUND

Although embryo implantation is a prerequisite for human reproduction, it remains a poorly understood process. The molecular mechanisms regulating endometrial receptivity and/or embryo implantation are still largely unclear.

METHODS

Pubmed and Medline literature databases were searched for articles in English published up to December 2013 with relevant keywords including 'endometrium', 'Na(+), Cl(-), K(+), or Ca(2+) channels', 'ion channels', 'endometrial receptivity', 'blastocyst implantation' and 'embryo implantation'.

RESULTS

At the time of writing, more than 14 types of ion channels, including the cystic fibrosis transmembrane conductance regulator, epithelial sodium channel and various Ca(2+) and K(+) channels, had been reported to be expressed in the endometrium or cells of endometrial origin. In vitro and/or in vivo studies conducted on different species, including rodents, pigs and humans, demonstrated the involvement of various ion channels in the process of embryo implantation by regulating: (i) uterine luminal fluid volume; (ii) decidualization; and (iii) the expression of the genes associated with implantation. Importantly, abnormal ion channel expression was found to be associated with implantation failure in IVF patients.

CONCLUSIONS

Ion channels in the endometrium are emerging as important players in regulating endometrial receptivity and embryo implantation. Abnormal expression or function of ion channels in the endometrium may lead to impaired endometrial receptivity and/or implantation failure. Further investigation into the roles of endometrial ion channels may provide a better understanding of the complex process of embryo implantation and thus reveal novel targets for diagnosis and treatment of implantation failure.

Human aquaporins: regulators of transcellular water flow

BACKGROUND

Emerging evidence supports the view that (AQP) aquaporin water channels are regulators of transcellular water flow. Consistent with their expression in most tissues, AQPs are associated with diverse physiological and pathophysiological processes.

SCOPE OF REVIEW

AQP knockout studies suggest that the regulatory role of AQPs, rather than their action as passive channels, is their critical function. Transport through all AQPs occurs by a common passive mechanism, but their regulation and cellular distribution varies significantly depending on cell and tissue type; the role of AQPs in cell volume regulation (CVR) is particularly notable. This review examines the regulatory role of AQPs in transcellular water flow, especially in CVR. We focus on key systems of the human body, encompassing processes as diverse as urine concentration in the kidney to clearance of brain oedema.

MAJOR CONCLUSIONS

AQPs are crucial for the regulation of water homeostasis, providing selective pores for the rapid movement of water across diverse cell membranes and playing regulatory roles in CVR. Gating mechanisms have been proposed for human AQPs, but have only been reported for plant and microbial AQPs. Consequently, it is likely that the distribution and abundance of AQPs in a particular membrane is the determinant of membrane water permeability and a regulator of transcellular water flow.

GENERAL SIGNIFICANCE

Elucidating the mechanisms that regulate transcellular water flow will improve our understanding of the human body in health and disease. The central role of specific AQPs in regulating water homeostasis will provide routes to a range of novel therapies. This article is part of a Special Issue entitled Aquaporins.

Expression of aquaporins in prostate and seminal vesicles of diabetic rats

INTRODUCTION

Aquaporins (AQPs) are membrane proteins that facilitate the movement of water and many small solutes across biological membranes. Seminal fluid is primarily produced by prostate and seminal vesicles, and its production may potentially be mediated by many mechanisms related to transudation of fluid. Epidemiological data suggest that semen volume in diabetic men is significantly less than in nondiabetic men.

AIM

To investigate the change in volume of secretions of the prostate and seminal vesicles in diabetic rats and its association with the expression of AQPs 1-4.

METHODS

Twenty male Sprague Dawley rats were randomly divided among 4- and 6-week diabetic groups and 4- and 6-week control groups. Prostate and seminal vesicle secretions were collected and measured, and levels of expression of AQPs 1-4 were determined by immunohistochemical study and Western blot.

MAIN OUTCOME MEASURES

The levels of expression of AQPs 1-4 were determined in the prostate and seminal vesicles of diabetic rats by Western blot and immunohistochemical study.

RESULTS

Plasma glucose was significantly higher in diabetic model groups than in controls (P < 0.05). The weights of secretions of the prostate and seminal vesicles were significantly lower in diabetic model groups (P < 0.05). The levels of expression of AQPs 1 and 4 in seminal vesicles were significantly lower in diabetic model groups (P < 0.05). There was no difference in the level of expression of AQP3 in seminal vesicles among the groups. The levels of expression of AQPs 1, 3, and 4 in prostate were significantly lower in diabetic model groups (P < 0.05). AQP2 was not detectable in the prostate or seminal vesicles of any of the groups.

CONCLUSIONS

Decreased weight of prostate secretions in diabetic rats may be partly due to decreased levels of AQPs 1, 3, and 4 in prostatic tissue. Decreased weight of seminal vesicle secretions in diabetic rats may be partly due to decreased levels of AQP1 and AQP4 in seminal vesicles. There is no relationship between the expression of AQPs 1-4 and the duration of disease.

Subcellular localization of selectively permeable aquaporins in the male germ line of a marine teleost reveals spatial redistribution in activated spermatozoa

In oviparous vertebrates such as the marine teleost gilthead seabream, water and fluid homeostasis associated with testicular physiology and the external activation of spermatozoa is potentially mediated by multiple aquaporins. To test this hypothesis, we isolated five novel members of the aquaporin superfamily from gilthead seabream and developed paralog-specific antibodies to localize the cellular sites of protein expression in the male reproductive tract. Together with phylogenetic classification, functional characterization of four of the newly isolated paralogs, Aqp0a, -7, -8b, and -9b, demonstrated that they were water permeable, while Aqp8b was also permeable to urea, and Aqp7 and -9b were permeable to glycerol and urea. Immunolocalization experiments indicated that up to seven paralogous aquaporins are differentially expressed in the seabream testis: Aqp0a and -9b in Sertoli and Leydig cells, respectively; Aqp1ab, -7, and -10b from spermatogonia to spermatozoa; and Aqp1aa and -8b in spermatids and sperm. In the efferent duct, only Aqp10b was found in the luminal epithelium. Ejaculated spermatozoa showed a segregated spatial distribution of five aquaporins: Aqp1aa and -7 in the entire flagellum or the head, respectively, and Aqp1ab, -8b, and -10b both in the head and the anterior tail. The combination of immunofluorescence microscopy and biochemical fractionation of spermatozoa indicated that Aqp10b and phosphorylated Aqp1ab are rapidly translocated to the head plasma membrane upon activation, whereas Aqp8b accumulates in the mitochondrion of the spermatozoa. In contrast, Aqp1aa and -7 remained unchanged. These data reveal that aquaporin expression in the teleost testis shares conserved features of the mammalian system, and they suggest that the piscine channels may play different roles in water and solute transport during spermatogenesis, sperm maturation and nutrition, and the initiation and maintenance of sperm motility.

Whole-organ isolation approach as a basis for tissue-specific analyses in Schistosoma mansoni

Background

Schistosomiasis is one of the most important parasitic diseases worldwide, second only to malaria. Schistosomes exhibit an exceptional reproductive biology since the sexual maturation of the female, which includes the differentiation of the reproductive organs, is controlled by pairing. Pathogenicity originates from eggs, which cause severe inflammation in their hosts. Elucidation of processes contributing to female maturation is not only of interest to basic science but also considering novel concepts combating schistosomiasis.

Methodology/Principal Findings

To get direct access to the reproductive organs, we established a novel protocol using a combined detergent/protease-treatment removing the tegument and the musculature of adult Schistosoma mansoni. All steps were monitored by scanning electron microscopy (SEM) and bright-field microscopy (BF). We focused on the gonads of adult schistosomes and demonstrated that isolated and purified testes and ovaries can be used for morphological and structural studies as well as sources for RNA and protein of sufficient amounts for subsequent analyses such as RT-PCR and immunoblotting. To this end, first exemplary evidence was obtained for tissue-specific transcription within the gonads (axonemal dynein intermediate chain gene SmAxDynIC; aquaporin gene SmAQP) as well as for post-transcriptional regulation (SmAQP).

Conclusions/Significance

The presented method provides a new way of getting access to tissue-specific material of S. mansoni. With regard to many still unanswered questions of schistosome biology, such as elucidating the molecular processes involved in schistosome reproduction, this protocol provides opportunities for, e.g., sub-transcriptomics and sub-proteomics at the organ level. This will promote the characterisation of gene-expression profiles, or more specifically to complete knowledge of signalling pathways contributing to differentiation processes, so discovering involved molecules that may represent potential targets for novel intervention strategies. Furthermore, gonads and other tissues are a basis for cell isolation, opening new perspectives for establishing cell lines, one of the tools desperately needed in the post-genomic era.

As a neglected disease, schistosomiasis is still an enormous problem in the tropics and subtropics. Since the 1980s, Praziquantel (PZQ) has been the drug of choice but can be anticipated to lose efficacy in the future due to emerging resistance. Alternative drugs or efficient vaccines are still lacking, strengthening the need for the discovery of novel strategies and targets for combating schistosomiasis. One avenue is to understand the unique reproductive biology of this trematode in more detail. Sexual maturation of the adult female depends on a constant pairing with the male. This is a crucial prerequisite for the differentiation of the female reproductive organs such as the vitellarium and ovary, and consequently for the production of mature eggs. These are needed for life-cycle maintenance, but they also cause pathogenesis. With respect to adult males, the production of mature sperm is essential for fertilisation and life-cycle progression. In our study we present a convenient and inexpensive method to isolate reproductive tissues from adult schistosomes in high amounts and purity, representing a source for gonad-specific RNA and protein, which will serve for future sub-transcriptome and -proteome studies helping to characterise genes, or to unravel differentiation programs in schistosome gonads. Beyond that, isolated organs may be useful for approaches to establish cell cultures, desperately needed in the post-genomic era.

Aquaporin water channels in the canine gubernaculum testis

The jelly-like gubernaculum testis (GT) is a hydrated structure consisting of a concentric sheath of dense connective tissue around a loose mesenchymal core, with two cords of skeletal muscle cells asymmetrically placed alongside. Expansion of the GT occurs during the transabdominal phase of testicular descent, linked to cell proliferation together with modifications of the hydric content of the organ. The aim of this study was to detect immunohistochemically the presence of aquaporins (AQPs), integral membrane proteins permitting passive transcellular water movement, in the canine GTs. Samples (n=15) were obtained from pregnancies of 9 medium sized bitches and dissected from healthy fetuses. Five fetuses were aged 35-45 days of gestation, 10 fetuses from 46 days of gestation to delivery, thus offering us the opportunity to study the progressive maturation of the gubernacula. The presence of AQP3, 4, 7, 8 and -9 was assessed in the muscular components of the GT, some of them (AQP3, AQP4, AQP7) with increasing intensity through the second half of pregnancy up to term. AQP1 was localized in the capillary and venous endothelia in the younger fetuses, also in the artery adventitia and in the nerve perineurium in progressively older fetuses. These data demonstrate the potential importance and contribution of AQP-mediated water flux in hydration and volume modification of the growing GT in a canine model.

Hormonal regulation of ovarian bursa fluid in mice and involvement of aquaporins

In rodent species, the ovary and the end of oviduct are encapsulated by a thin membrane called ovarian bursa. The biological functions of ovarian bursa remain unexplored despite its structural arrangement in facilitating oocytes transport into oviduct. In the present study, we observed a rapid fluid accumulation and reabsorption within the ovarian bursa after ovarian stimulation (PMSG-primed hCG injection), suggesting that the ovarian bursa might play an active role in regulating local fluid homeostasis around the timing of ovulation. We hypothesized that the aquaporin proteins, which are specialized channels for water transport, might be involved in this process. By screening the expression of aquaporin family members (Aqp1-9) in the ovarian tissue and isolated ovarian bursa (0, 1, 2 and 5 h after hCG injection), we found that AQP2 and AQP5 mRNA showed dynamic changes after hCG treatment, showing upregulation at 1-2 h followed by gradually decrease at 5 h, which is closely related with the intra-bursa fluid dynamics. Further immunofluorescence examinations of AQP2 and AQP5 in the ovarian bursa revealed that AQP2 is specifically localized in the outer layer (peritoneal side) while AQP5 localized in the inner layer (ovarian side) of the bursa, such cell type specific and spatial-temporal expressions of AQP2 and 5 support our hypothesis that they might be involved in efficient water transport through ovarian bursa under ovulation related hormonal regulation. The physiological significance of aquaporin-mediated water transport in the context of ovarian bursa still awaits further clarification.

Testosterone influences water transport in porcine granulosa cells

The development of antral ovarian follicles entails fluid accumulation, but the mechanisms regulating water flux are unknown. Aquaporins are small, integral membrane proteins facilitating passive movement of water, some of which are known to be regulated by steroid hormones. The aim of this study was to determine whether testosterone (T) influences water transport in porcine granulosa cells. To assess water movement, the swelling of granulosa cells when moved from isotonic (319 mOsm) to hypotonic (95 mOsm) medium was measured after 12-hour pre-incubation in the presence of either testosterone (T), the antiandrogen 2-hydroxyflutamide (HF) or HF and T together. Pre-incubation with T increased the swelling of granulosa cells (p < 0.01) and this was abolished by HF (p < 0.001). Neither T nor HF affected cells in isotonic medium (319 mOsm). The results indicate that T acting via intracellular androgen receptors increases water permeability of porcine granulosa cells, probably through the regulation of aquaporin activity.

The expression and distribution of aquaporin 3 in mouse embryos before and after vitrification

Purpose

To determine the role of aquaporin 3 (AQP3) isoform in early embryonic development and protecting embryos subjected to freeze–thawing for assisted reproduction, we investigated the expression and distribution of AQP3 in mouse embryos at different developmental stages before and after vitrification.

Methods

Eight-cell embryos, morulae, and blastocysts were obtained from female mice that had been superovulated by controlled ovarian hyperstimulation. Immunofluorescence staining, laser confocal microscopy, and Western blot were used to determine the expression and distribution of AQP3 in preimplantation mouse embryos before and after vitrification.

Results

AQP3 was expressed at the 8-cell to blastocyst stage before and after vitrification. The expression and distribution of AQP3 was developmentally regulated at the 8-cell to blastocyst stage. The expression of AQP3 was significantly decreased in 8-cell embryos and early blastocysts after vitrification. However, at the morulae stage, the expression of AQP3 was increased after vitrification.

Conclusions

The developmental and vitrification-dependent changes in AQP3 expression and distribution suggest that this transmembrane channel might regulate mouse embryo development and contribute to the protective response during vitrification.

Expression and localization of aquaporins in benign prostate hyperplasia and prostate cancer

The aquaporin (AQP) families of water channels are intrinsic membrane proteins that facilitate selective water and small solute movement across the plasma membrane. The purposes of this study were to determine the expression and localization of AQPs in benign prostatic hyperplasia and prostate cancer. Prostatic tissue was collected from patients with benign prostatic hyperplasia or prostate cancer by transurethral resection of the prostate. The expression and cellular localization of the AQPs were determined in the human prostate by Western blot and immunohistochemistry. AQP1, 3, and 9 were expressed in the human prostate. Western blot analysis revealed bands at 28-36 kDa for the AQP1, 3, and 9 proteins. Of these proteins, AQP3 and 9 were expressed in the epithelium. Immunolabeling showed that AQP1 was mainly expressed in the capillaries and venules of the prostate, AQP9 was expressed in the cytoplasm of the epithelium, and AQP3 was mainly associated with the plasma membrane of the prostatic epithelium. Only AQP3 expression was localized in the cell membrane, and expressed AQP3 was translocated to the cytoplasm in prostate cancer. The epithelium in the human prostate expresses AQP3 and 9 proteins, and the capillaries and venules of the prostate express AQP1. Characterizing or modifying the expression of AQP3 may lead to an understanding of the role of the AQPs in human prostatic disease.

Observations on variation in the ultrastructure of the proximal testicular ducts of the Ground Skink, Scincella lateralis (Reptilia: Squamata)

The North American Ground Skink, Scincella lateralis, is a member of the most speciose family of lizards, the Scincidae. The only descriptions of the testicular ducts of skinks concern the light microscopy of 13 species in eight other genera. We combine histological observations with results from transmission electron microscopy on a sample of skinks collected throughout the active season. The single rete testis has squamous epithelium with a large, indented nucleus and no junctional complexes between cells or conspicuous organelles. Nuclei of sperm in the rete testis area are associated with cytoplasmic bodies that are lost in the ductuli efferentes. The ductuli efferentes have both ciliated and nonciliated cells and show little seasonal variation except for the narrowing of intercellular canaliculi when sperm are absent. When the ductus epididymis contains sperm, the anterior one-third lacks copious secretory material around luminal sperm, whereas in the posterior two-thirds sperm are embedded in a dense matrix of secretory material. Light and dark principal cells exist and both contain saccular, often distended rough endoplasmic reticula, and widened intercellular canaliculi that bridge intracellular spaces. Junctional complexes are lacking between principal cells except for apical tight junctions. Electron-dense secretory granules coalesce at the luminal border for apocrine release. The cranial end of the ductus deferens is similar in cytology to the posterior ductus epididymis. Each of the nine squamates in which the proximal testicular ducts have been studied with electron microscopy has some unique characters, but no synapomorphies for squamates as a group are recognized.

Uterine development and fertility are dependent on gene dosage of the nuclear receptor coregulator REA

Although the effectiveness of nuclear hormone-receptor complexes is known to depend on coregulator partner proteins, relatively little is known about the roles of coregulators in uterine development and early stages of pregnancy and implantation. Because conventional genetic deletion of the coregulator, repressor of estrogen receptor activity (REA), was embryonic lethal, we here study REA conditional knockout mice generated by cre-loxP recombination, in which REA function was abrogated only in progesterone receptor-expressing tissues, to define the roles of REA in postembryonic stages and in a tissue-specific manner. We find that REA has gene dose-dependent activity impacting uterine development and fertility. Conditional homozygous mutant (REA(d/d)) mice developed to adulthood and showed normal ovarian function, but females were infertile with severely compromised uterine development and function characterized by cell cycle arrest, apoptosis, and altered adenogenesis (endometrial gland morphogenesis), resulting in failure of implantation and decidualization. By contrast, mice heterozygous for REA (REA(f/d)) had a very different phenotype, with estradiol treatment resulting in hyperstimulated, large uteri showing increased proliferation of luminal epithelial cells, and enhanced fluid imbibition associated with altered regulation of aquaporins. These REA(f/d) female mice showed a subfertility phenotype with reduced numbers and sizes of litters. These findings highlight that uterine development and regulation of estrogen receptor activities show a bimodal dependence on the gene dosage of REA. Optimal uterine development and functional activities require the normal gene dosage of REA, with partial or complete deletion resulting in hyperresponsiveness or underresponsiveness to hormone and subfertility or infertility, respectively.

Expression of aquaporin 1 in the pig peri-ovarian vascular complex during the estrous cycle and early pregnancy

Aquaporin 1 (AQP1) is a water channel protein expressed in endothelial and epithelial cells of many tissues, including the vasculature, where it serves to increase water permeability of the cell membrane. The aim of this study was to investigate the expression and distribution of AQP1 in porcine peri-ovarian vascular complex (PVC) during the estrous cycle and early pregnancy. Immunohistochemistry and semi-quantitative immunoblotting techniques were used. We have demonstrated the presence of AQP1 protein in the endothelial cells of the lymphatic and vascular endothelium of the PVC during the pig estrous cycle and early pregnancy. The expression of AQP1 protein in the PVC did not change significantly between Days 10-12 and 14-16, but increased on Days 2-4 and 18-20 when compared with Days 10-12 and 14-16 of the estrous cycle. In pregnant gilts, the expression of AQP1 did not differ significantly during the onset and the end of the implantation process and also when compared to the mid- and late-luteal phases of the estrous cycle. In conclusion, AQP1 is expressed in the endothelial cells of PVC and may modulate hormonal regulation of reproductive organs.

The physiology of bicarbonate transporters in mammalian reproduction

HCO(3)(-) plays critically important roles during virtually the entire process of reproduction in mammals, including spermatogenesis, sperm capacitation, fertilization, and development of early stage embryos. Therefore, the acid-base balance in the male and female reproductive tracts must be finely modulated. The fluid milieu in the epididymis is acidic, containing very low concentration of HCO(3)(-). In this acidic low HCO(3)(-) environment, mature sperm are rendered quiescent in the epididymis. In contrast, the luminal fluid in the female uterus and oviduct is alkaline, with very high concentration of HCO(3)(-) that is essential for sperm to fulfill fertilization. HCO(3)(-) transporter of solute carrier 4 (SLC4) and SLC26 families represent the major carriers for HCO(3)(-) transport across the plasma membrane. These transporters play critical roles in intracellular pH regulation and transepithelial HCO(3)(-) transport. The physiological roles of these transporters in mammalian reproduction are of fundamental interest to investigators. Here we review recent progress in understanding the expression of HCO(3)(-) transporters in reproductive tract tissues as well as the physiological roles of these transporters in mammalian reproduction.

Fluctuation of aquaporin 1, 5, and 9 expression in the pig oviduct during the estrous cycle and early pregnancy

Thirteen mammalian aquaporin (AQPs) isoforms with a unique tissue-specific pattern of expression have been identified. To date, 11 isoforms of AQP have been reported to be expressed in female and male reproductive systems. The purpose of our study was to determine the localization and quantitative changes in the expression of AQP1, 5 and 9 within the pig oviduct during different stages of the estrous cycle and early pregnancy. The results demonstrated that AQP1, 5, and 9 were clearly detected in all studied stages of the estrous cycle and pregnancy. AQP1 was localized within oviductal blood vessels. In cyclic gilts, the expression of AQP1 protein did not change significantly between days 10-12 and 14-16 but increased on days 2-4 and 18-20. AQP5 was localized in smooth muscle cells and oviductal epithelial cells. The expression of AQP5 protein did not change significantly between days 10-12 and 14-16 of the estrous cycle but increased on days 2-4 and 18-20. The anti-AQP9 antibody labeled epithelial cells of the oviduct. The expression of AQP9 did not change significantly between days 10-12 and 14-16 of the estrous cycle but increased on days 2-4 and 18-20. In pregnant gilts, expression of AQP1, 5, and 9 did not change significantly in comparison with the estrous cycle. Therefore, a functional and distinctive collaboration seems to exist among diverse AQPs in water handling during the different oviductal phases in the estrous cycle and early pregnancy.

The water permeability channels aquaporins 1-4 are differentially expressed in granulosa and theca cells of the preovulatory follicle during precise stages of human ovulation

CONTEXT

Changes in vascular permeability and expansion of the fluid-filled antrum are major events in the LH-induced ovulatory process.

OBJECTIVES

Our objective was to investigate the presence and expression levels of aquaporins (AQPs) in the granulosa and theca cell compartments of the follicle during defined phases of human ovulation.

DESIGN AND SETTING

We conducted a prospective experimental study at the Department of Obstetrics and Gynaecology at a university hospital.

PARTICIPANTS

Twenty-eight women underwent laparoscopic sterilization and at the same time follicle retrieval at four periovulatory phases.

MAIN OUTCOME MEASURES

mRNA levels of AQP1-4 were measured in separated granulosa and theca cells from preovulatory phase, early ovulatory (EO) phase, late ovulatory phase, and postovulatory phase. Immunohistochemistry was done for AQP1-4 in intact human follicles.

RESULTS

All four AQPs were expressed in both the theca and granulosa cells during ovulation. In granulosa cells, AQP1 levels increased in the late ovulatory and postovulatory phases. Expression of AQP2-3 followed a similar pattern with a marked increase in the EO phase, whereas AQP4 levels decreased from preovulatory to the EO phase. The presence of AQP1-4 in the human follicle was verified by immunohistochemistry.

CONCLUSIONS

The results show for the first time the presence of AQP1-4 in human follicles during ovulation. The marked early rise in expression of AQP2 and AQP3 suggests a role during the process leading to follicular rupture, and the late rise of AQP1 suggests a role in corpus luteum formation.

The expression of aquaporin 8 and aquaporin 9 in fetal membranes and placenta in term pregnancies complicated by idiopathic polyhydramnios

BACKGROUND

Aquaporins are a family of membrane-bound water channel proteins that regulate the flow of water across a variety of biological membranes. The expression of aquaporin 8 and aquaporin 9 has been demonstrated in human chorioamniotic membrane and placenta. But their roles in the pathophysiology of polyhydramnios are unclear.

AIMS

To study the expression of aquaporin 8 and aquaporin 9 in fetal membranes and placenta in term pregnancies complicated by idiopathic polyhydramnios and to explore the association between aquaporin expressions and polyhydramnios.

SUBJECTS

The placentas were collected from 51 patients who underwent elective Cesarean sections at term, of which 21 cases had idiopathic polyhydramnios and the other 30 had normal amniotic fluid volume.

OUTCOME MEASURES

Real-time polymerase chain reaction and immunohistochemistry techniques were used to determine the expression and localization of aquaporin 8 and aquaporin 9 in the amnion, chorion and placenta.

RESULTS

Expression of aquaporin 8 and aquaporin 9 was detected in the amnion, chorion and placenta and located in amnion epithelia, chorion cytotrophoblasts and placental trophoblast. Compared to normal amniotic fluid volume group, the expression of aquaporin 8 in amnion, and aquaporin 9 in amnion and chorion, were significantly increased in idiopathic polyhydramnios group; however, their expression in the placenta was significantly decreased.

CONCLUSIONS

When polyhydramnios occurs, expression of aquaporin 8 and aquaporin 9 in fetal membranes and placenta is an adaptive change, which may be involved in the regulation of amniotic fluid volume. However, the modulation factors of the aquaporin 8 and aquaporin 9 expressions need further study.

Distribution and quantitative changes in amounts of aquaporin 1, 5 and 9 in the pig uterus during the estrous cycle and early pregnancy

BACKGROUND

Aquaporins (AQPs) are a family of membrane channel proteins that facilitate bulk water transport. To date, 11 isoforms of AQPs have been reported to be expressed in the female and male reproductive systems. The purpose of our study was to determine the localization and quantitative changes in the expression of AQP1, 5 and 9 within the pig uterus during different stages of the estrous cycle and early pregnancy.

METHODS

Immunoperoxidase and semi-quantitative immunoblotting techniques were used to examine the distribution and changes in amounts of AQP1, AQP5 and AQP9 in uteral cells of pigs at the early (Days 2-4), middle (10-12), late (14-16) stage of the luteal phase and late (18-20) stage of the follicular phase of the estrous cycle as well as on Days 14-16 and 30-32 of gestation (the onset and the end of implantation process).

RESULTS

The results demonstrated that AQP1, 5, and 9 were clearly detected in all studied stages of the estrous cycle and pregnancy. AQP1 was localized within uterine blood vessels. In cyclic gilts, endometrial and myometrial expression of AQP1 protein did not change significantly but increased during gestation. AQP5 was localized in smooth muscle cells and uterine epithelial cells. Endometrial expression of AQP5 protein did not change significantly between Days 2-4 and 10-12 of the estrous cycle but increased on Days 14-16 and 18-20 as well as during early pregnancy. Myometrial expression of AQP5 did not differ significantly during the estrous cycle but increased in the pregnancy. The anti-AQP9 antibody labeled uterine epithelial cells of uterus. Endometrial expression of AQP9 did not change significantly between Days 2-4 and 10-12 of the estrous cycle but increased on Days 14-16 and 18-20 as well as during early pregnancy.

CONCLUSIONS

The results suggest that a functional and distinctive collaboration exists among diverse AQPs in water handling during the different uterine phases in the estrous cycle and early pregnancy.

Piscine aquaporins: an overview of recent advances

Aquaporins are a superfamily of integral membrane proteins that facilitate the rapid and yet highly selective flux of water and other small solutes across biological membranes. Since their discovery, they have been documented throughout the living biota, with the majority of research focusing on mammals and plants. Here, we review available data for piscine aquaporins, including Agnatha (jawless fish), Chondrichthyes (chimaeras, sharks, and rays), Dipnoi (lungfishes), and Teleostei (ray-finned bony fishes). Recent evidence suggests that the aquaporin superfamily has specifically expanded in the chordate lineage consequent to serial rounds of whole genome duplication, with teleost genomes harboring the largest number of paralogs. The selective retention and dichotomous clustering of most duplicated paralogs in Teleostei, with differential tissue expression profiles, implies that novel or specialized physiological functions may have evolved in this clade. The recently proposed new nomenclature of the piscine aquaporin superfamily is discussed in relation to the phylogenetic signal and genomic synteny, with the teleost aquaporin-8 paralogs used as a case study to illustrate disparities between the underlying codons, molecular phylogeny, and physical locus. Structural data indicate that piscine aquaporins display similar channel restriction residues found in the tetrapod counterparts, and hence their functional properties seem to be conserved. However, emerging evidence suggests that regulation of aquaporin function in teleosts may have diverged in some cases. Cell localization and experimental studies imply that the physiological roles of piscine aquaporins extend at least to osmoregulation, reproduction, and early development, although in most cases their specific functions remain to be elucidated.

Effect of maturation on the expression of aquaporin 3 in mouse oocyte

This study aimed to investigate whether aquaporin 3 (Aqp3) mRNAs are expressed in immature oocytes and altered during in vitro maturation process. Five- to 6-week-old female ICR mice were primed by gonadotropin for 24 and 48 h. Immature oocytes obtained 48 h after priming were also matured in vitro for 17 to 18 h. In vivo matured oocytes were obtained after 48 h priming followed by hCG injection. Total RNAs were extracted from 80 to 150 oocytes in each experimental group, and the levels of Aqp3 mRNA were quantified by real-time reverse transcriptase polymerase chain reaction. The experiments were repeated twice using different oocytes. The Aqp3 mRNA was expressed in immature oocytes, as well as in in vitro and in vivo matured oocytes. The expression level was higher in immature oocytes obtained 48 h after priming (17.2 ± 8.6, mean ± SD) than those with no priming (5.7 ± 0.8) or obtained 24 h after priming (2.5 ± 0.8). The expression of Aqp3 mRNA decreased after in vitro maturation (1.2 ± 0.5), which was similar to in vivo matured oocytes (1.0 ± 0.0). Our work demonstrated that Aqp3 mRNA expression increased during the development of immature oocyte but decreased after completion of in vitro maturation. The results indicate that AQP3 is certainly needed for the acquisition of immature oocytes’ full growing potential within antral follicles.