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

Effect of estrogen and progesterone on intracellular free zinc and zinc transporter expression in bovine oviduct epithelial cells

Zinc (Zn) plays essential roles in numerous cellular processes. However, there is limited understanding of Zn homeostasis within the bovine reproductive system. This study investigated the influence of estradiol (E2) and progesterone (P4) on Zn transporter expression and intracellular free Zn levels in bovine oviduct epithelial cells (BOEC). For this purpose, cells were harvested from slaughtered cows and cultured in vitro. Intracellular Zn concentrations were measured using FluoZin-3AM staining, while real-time polymerase chain reaction assessed Zn transporter gene expression and quantification. Overall, our results confirmed the gene expression of all the evaluated Zn transporters (ZIP6, ZIP8, ZIP14, ZnT3, ZnT7 and ZnT9), denoted and the active role of E2 and P4 in intracellular Zn regulation. Our findings suggest an interaction between Zn, E2 and P4.

Expression of genes for transport of water and angiogenesis, as well as biochemical biomarkers in Holstein dairy cows during the ovsynch program

Changes in expression of genes associated with angiogenesis and transport of water by cells, as well as biomarkers of oxidative stress were determined at specific times during the ovsynch protocol to synchronize estrus and breed Holstein dairy cows. Blood samples were taken from 82 lactating Holstein cows at the time of the 1st GnRH injection (G1), 7 days later at the time of the PGF2a (PG) injection, and 48 h after the PGF2a treatment when the second injection of GnRH was administered (G2). The serum was analyzed for malondialdehyde (MDA), reduced glutathione (GSH), glutathione peroxidase (GPX), nitric oxide (NO), catalase (CAT), and total antioxidant capacity (TAC). The expression of vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR2), endothelial nitric oxide synthase (eNOS3), aquaporin 3 (AQP3), and AQP4 mRNAs in peripheral blood mononuclear cells (PBMCs) was analyzed. The number of copies of each of the mRNAs was quantified using qPCR. Pregnancy status was determining at 32 ± 3 days after insemination using an ultrasound "Sonoscape-5V″ model. Receiver operating curves (ROC) were used to assess the sensitivity and specificity of the biochemical parameters in serum to predict establishment of p The expression of MDA, GPX, and Catalase changed (P < 0·05) between G1, PG and G2 phases of the ovsynch protocol with higher levels at PG than at G1 and G2. The highest levels of NO were detected at G2. The ROC analyses identified NO, TAC and CAT as the most sensitive and specific biomarker for pregnancy with areas under the curve being 0.875 (P < 0.0001), 0.843 (P < 0.03), 0.833 (P < 0.017), sensitivity being 75.3, 42.86, and 26.27%, and specificity being 90, 90 and 85% respectively. The expression for VEGF, VEGFR2, eNOS3, AQP3, and AQP4 mRNAs was upregulated at PG compared to G1 and G2 phases of the ovsynch protocol. The results suggest that following the first injection of GnRH, there is an increase in expression of VEGF, VEGFR2, eNOS3, AQP3, and AQP4 mRNAs by the time of the PGF2a injection and then expression decreased. Further, ROC analyses identified increases in NO, TAC and CAT as the most sensitive and specific biomarkers with the greatest potential to predict establishment of pregnancy in Holstein cows.

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.

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.

Modification of Morphology and Glycan Pattern of the Oviductal Epithelium of Baboon Papio hamadryas during the Menstrual Cycle

The mammalian oviduct is a highly specialized structure where fertilization and early embryonic development occur. Its mucosal epithelium is involved in maintaining and modulating a dynamic intraluminal fluid. The oviductal epithelium consists of ciliated and non-ciliated (secretory) cells whose differentiation and activity are sex hormone-dependent. In this study, we investigated for the first time both the morphology and the glycan composition of baboon oviductal epithelium during the menstrual cycle. Oviducts were laparoscopically removed from 14 healthy adult female Papio hamadryas whose menstrual cycle phase was assessed based on the sex hormone levels and the vaginal cytology features. Histological investigations were carried out on fimbriae, infundibulum, ampulla, and isthmus separately fixed in 4% (v/v) paraformaldehyde, embedded in paraffin wax, and stained with hematoxylin-eosin for morphological analyses and using a panel of nine fluorescent lectins for glycoconjugate characterization. The histomorphological analysis revealed that in the entire oviduct (i) the ciliated and non-ciliated cells were indistinguishable during the follicular and luteal phases, whereas they were highly differentiated during the preovulatory phase when the non-ciliated cells exhibited apical protrusions, (ii) the epithelium height was significantly higher in the preovulatory phase compared to other menstrual phases, and (iii) the number of ciliated cells significantly (p ≤ 0.05) increased from the fimbriae to the infundibulum and progressively reduced in the other oviductal segments with the lower presence of ciliated cells in the isthmus. The glycan characterization revealed a complex and region-specific composition during the different phases of the menstrual cycle. It can be summarized as follows: (i) high-mannosylated N-linked glycans (Con A reactivity) were present throughout the oviductal epithelium during the entire menstrual cycle and characteristically in the apical protrusions of non-ciliated cells of the ampulla during the preovulatory phase; (ii) sialoglycans with α2,3-linked sialic acids (MAL II binding) were expressed along the entire oviductal surface only during the preovulatory phase, whereas α2,6-linked ones (SNA affinity) were also detected in the surface of the luteal phase, although during the preovulatory phase they were characteristically found in the glycocalyx of the isthmus cilia, and O-linked sialoglycans with sialic acids linked to Galβl,3GalNAc (T antigen) (KsPNA) and terminal N-acetylgalactosamine (Tn antigen) (KsSBA) were found in the entire oviductal surface during all phases of the menstrual cycle; (iii) GalNAc terminating O-linked glycans (HPA staining) were mainly expressed in the entire oviducts of the luteal and preovulatory phases, and characteristically in the apical protrusions of the isthmus non-ciliated cells of the preovulatory phase; and (iv) fucosylated glycans with α1,2-linked fucose (LTA reactivity) occurred in the apical surface of fimbriae during the luteal phase, whereas α1,3/4-linked fucose (UEA I binders) were present in the apical protrusions of the ampulla non-ciliated cells and in the apical surface of isthmus during the preovulatory phase as well as in the isthmus apical surface of follicular-phase oviducts. These results demonstrate for the first time that morphological and glycan changes occur in the baboon oviductal epithelium during the menstrual cycle. Particularly, the sex hormone fluctuation affects the glycan pattern in a region-specific manner, probably related to the function of the oviductal segments. The findings add new data concerning baboons which, due to their anatomical similarity to humans, make an excellent model for female reproduction studies.

Spatiotemporal expression of aquaporin 9 is critical for the antral growth of mouse ovarian follicles†

Although a few aquaporins (AQPs) expressed in granulosa cells have been postulated to mediate fluid passage into the antrum, the specific expression of AQPs in different follicle cell types and stages and their roles have not been evaluated extensively. The spatiotemporal expression of aquaporin (Aqp) 7, 8, and 9 and the functional roles of Aqp9 in antral growth and ovulation were examined using a superovulation model and 3-dimensional follicle culture. Aqp9 was expressed at a high level in the rapid growth phase (24-48 h post equine chorionic gonadotropin (eCG) for superovulation induction) compared to Aqp7 (after human chorionic gonadotropin (hCG)) and Aqp8 (8-24 h post eCG and 24 h post hCG). A dramatic increase in the expression and localization of Aqp9 mRNA in theca cells was observed, as evaluated using quantitative reverse transcription-polymerase (RT-PCR) coupled with laser capture microdissection and immunohistochemistry. AQP9 was located primarily on the theca cells of the tertiary and preovulatory follicles but not on the ovulated follicles. In phloretin-treated mice, the diameter of the preovulatory follicles and the number of ovulated oocytes decreased. Consistent with these findings, knocking down Aqp9 expression with an Aqp9 siRNA inhibited follicle growth (0.28:1 = siRNA:control) and decreased the number of ovulated follicles (0.36:1 = siRNA:control) during in vitro growth and ovulation induction. Based on these results, the expression of AQPs is under the control of the physiological status, and AQP9 expression in theca during folliculogenesis is required for antral growth and ovulation in a tissue-specific and stage-dependent manner.

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.

The Relevance of Aquaporins for the Physiology, Pathology, and Aging of the Female Reproductive System in Mammals

Aquaporins constitute a group of water channel proteins located in numerous cell types. These are pore-forming transmembrane proteins, which mediate the specific passage of water molecules through membranes. It is well-known that water homeostasis plays a crucial role in different reproductive processes, e.g., oocyte transport, hormonal secretion, completion of successful fertilization, blastocyst formation, pregnancy, and birth. Further, aquaporins are involved in the process of spermatogenesis, and they have been reported to be involved during the storage of spermatozoa. It is noteworthy that aquaporins are relevant for the physiological function of specific parts in the female reproductive system, which will be presented in detail in the first section of this review. Moreover, they are relevant in different pathologies in the female reproductive system. The contribution of aquaporins in selected reproductive disorders and aging will be summarized in the second section of this review, followed by a section dedicated to aquaporin-related proteins. Since the relevance of aquaporins for the male reproductive system has been reviewed several times in the recent past, this review aims to provide an update on the distribution and impact of aquaporins only in the female reproductive system. Therefore, this paper seeks to determine the physiological and patho-physiological relevance of aquaporins on female reproduction, and female reproductive aging.

Effects of Bisphenol A on expression of genes related to amino acid transporters, insulin- like growth factor, aquaporin and amino acid release by porcine trophectoderm cells

The peri-implantation period of pregnancy is critical for conceptus development, implantation, and signaling for establishment of pregnancy. This study evaluated the effects of bisphenol A (BPA) on proliferation, adhesion, and migration of porcine trophectoderm (pTr2) cells, expression of transporters of arginine and synthesis of amino acids. All concentrations of BPA decreased proliferation and adhesion of pTr2 cells after 96 h compared to the control group. Lower concentrations of BPA (1 × 10^-9, 1 × 10^-8, 10^-7M) increased (P < 0.05), but higher concentrations of BPA (1 × 10^-5, 1 × 10^-4 M) decreased migration of pTr2 cells. BPA increased expression of SLC7A1 mRNA at lower concentrations (1 × 10^-9 to 1 × 10^-6M) and SL7A6, another cationic acid transporter, at higher concentrations (1 × 10^-5, 1 × 10^-4 M). BPA also down-regulated the expression of IGF1 and IGF1 receptor at concentrations of 1 × 10^-7 to 1 × 10^-4 M compared to the control group. The expression of mRNAs for aquaporins (AQP) 3 and 4 were reduced at all concentrations of BPA, but at lower concentrations of BPA, (1 × 10^-9 to 1 × 10^-8M) expression of AQP9 mRNA increased and the expression of AQP11 was not affected by BPA (P > 0.05). There was an inhibitory effect of BPA on the release of synthesis of asparagine, threonine, taurine, tryptophan, and ornithine into the culture medium by pTr2 cells. Collectively, BPA adversely affected the expression of transporters for cationic amino acids like arginine, as well as AQPs, IGF1, and IGF1R associated with proliferation, migration, and adhesion of pTr2 cells. Those adverse effects would likely increase pregnancy losses during the peri-implantation period of pregnancy.

Changes in Aquaporin 1, 5 and 9 Gene Expression in the Porcine Oviduct According to Estrous Cycle and Early Pregnancy

Aquaporins (AQPs) are a group of small, integral membrane proteins which play an important role in fluid homeostasis in the reproductive system. In our previous study, we demonstrated AQP1, 5 and 9 protein expression and localization in the porcine oviduct. The presence of these isoforms could suggest their role in the transport of the ovum to the uterus by influencing the epithelial cells’ production of oviductal fluid. The aim of this study was to evaluate the expression of AQP1, AQP5 and AQP9 in the infundibulum, ampulla and isthmus in the porcine oviduct during the estrous cycle (early luteal phase, days 2–4, medium luteal phase, days 10–12, late luteal phase days 14–16, follicular phase days 18–20) and pregnancy (period before implantation, days 14–16 and after the implantation, days 30–32) using the Real-Time PCR technique. As clearly demonstrated for the first time, AQP1, 5, and 9 gene expression is influenced by the estrus cycle and pregnancy. Furthermore, expression of AQPs in the porcine oviduct may provide the physiological medium that sustains and enhances fertilization and early cleavage-stage embryonic development. Overall, our study provides a characterization of oviduct AQPs, increasing our understanding of fluid homeostasis in the porcine oviduct to successfully establish and maintain pregnancy.

Pituitary Hormones (FSH, LH, PRL, and GH) Differentially Regulate AQP5 Expression in Porcine Ovarian Follicular Cells

This study aimed to examine the effect of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and growth hormone (GH) on Aquaporin 5 (AQP5) expression in granulosa (Gc) and theca cells (Tc) from medium (MF) and large (LF) ovarian follicles of pigs. The results showed that GH significantly decreased the expression of AQP5 in Gc from MF in relation to the control. In the Gc of large follicles, PRL stimulated the expression of AQP5. However, the increased expression of AQP5 in the Tc of LF was indicated by GH and PRL in relation to the control. A significantly higher expression of the AQP5 protein in the Gc from MF and LF was indicated by FSH and PRL. In co-cultures, an increased expression of AQP5 was observed in the Gc from LF incubated with LH, PRL, and GH. A significantly increased expression of AQP5 was also observed in co-cultures of Tc from all type of follicles incubated with LH, whereas PRL stimulated the expression of AQP5 in Tc from MF. Moreover, AQP5 protein expression increased in the co-culture isolated from MF and LF after treatment with FSH, LH, PRL, and GH. AQP5 immunoreactivity was observed in the cytoplasm, mainly in the perinuclear region and endosomes, as well as in the cell membranes of Gc and Tc from the LF and MF.

AQP2 is regulated by estradiol in human endometrium and is associated with spheroid attachment in vitro

17β‑estradiol (E2) and aquaporin 2 (AQP2) are associated with endometrial receptivity, and E2 directly regulates AQP2 expression in endometrial cancer cells. The present study aimed to investigate the role of AQP2 in embryo implantation. Normal endometrial samples were collected at the Women's Hospital (Hangzhou, China) from women seeking in vitro fertilization and embryo transfer; women with endometrial abnormalities were excluded from the study. Samples were categorized into early‑mid proliferative, late proliferative, early secretory, mid‑secretory and late secretory phase groups, according to the menstrual cycle. The mRNA and protein expression levels of AQP2 were assessed in normal human endometrium in response to E2 via reverse transcription‑quantitative polymerase chain reaction and western blotting, respectively. The effects of AQP2 on spheroid attachment were assessed using an in vitro co‑culture assay with small interfering (si)RNA against AQP2. The highest expression levels of AQP2 were observed in the late proliferative and mid‑secretory phases, with the lowest levels detected in the early proliferative and late secretory phases. In addition, treatment with 10‑9 or 10‑7 M E2 for 24 h upregulated AQP2 in the cultured endometrium. Knockdown of AQP2 by siRNA significantly decreased JAr spheroid attachment; however, this effect was significantly reversed when AQP2 siRNA‑transfected cells were treated with 10‑7 M E2. The results of the present study suggested that AQP2 expression levels in human endometrium may be mediated by estrogen, and low AQP2 expression levels may be a potential cause of impaired uterine receptivity.

Deciphering the oviductal extracellular vesicles content across the estrous cycle: implications for the gametes-oviduct interactions and the environment of the potential embryo

Background

The success of early reproductive events depends on an appropriate communication between gametes/embryos and the oviduct. Extracellular vesicles (EVs) contained in oviductal secretions have been suggested as new players in mediating this crucial cross-talk by transferring their cargo (proteins, mRNA and small ncRNA) from cell to cell. However, little is known about the oviductal EVs (oEVS) composition and their implications in the reproductive success. The aim of the study was to determine the oEVs content at protein, mRNA and small RNA level and to examine whether the oEVs content is under the hormonal influence of the estrous cycle.

Results

We identified the presence of oEVs, exosomes and microvesicles, in the bovine oviductal fluid at different stages of the estrous cycle (postovulatory-stage, early luteal phase, late luteal phase and pre-ovulatory stage) and demonstrated that their composition is under hormonal regulation. RNA-sequencing identified 903 differentially expressed transcripts (FDR < 0.001) in oEVs across the estrous cycle. Moreover, small RNA-Seq identified the presence of different types of ncRNAs (miRNAs, rRNA fragments, tRNA fragments, snRNA, snoRNA, and other ncRNAs), which were partially also under hormonal influence. Major differences were found between post-ovulatory and the rest of the stages analyzed for mRNAs. Interesting miRNAs identified in oEVs and showing differential abundance among stages, miR-34c and miR-449a, have been associated with defective cilia in the oviduct and infertility. Furthermore, functional annotation of the differentially abundant mRNAs identified functions related to exosome/vesicles, cilia expression, embryo development and many transcripts encoding ribosomal proteins. Moreover, the analysis of oEVs protein content also revealed changes across the estrous cycle. Mass spectrometry identified 336 clusters of proteins in oEVs, of which 170 were differentially abundant across the estrous cycle (p-value< 0.05, ratio < 0.5 or ratio > 2). Our data revealed proteins related to early embryo development and gamete-oviduct interactions as well as numerous ribosomal proteins.

Conclusions

Our study provides with the first molecular signature of oEVs across the bovine estrous cycle, revealing marked differences between post- and pre-ovulatory stages. Our findings contribute to a better understanding of the potential role of oEVs as modulators of gamete/embryo-maternal interactions and their implications for the reproductive success.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4982-5) contains supplementary material, which is available to authorized users.

Expression of aquaporin 4 in the chicken oviduct following tamoxifen treatment

This study was designed to examine whether aquaporin 4 (AQP4) is present in the chicken oviduct, and if so, whether its expression changes during pause in laying induced by tamoxifen (TMX; oestrogen receptor modulator) treatment. The control chickens were injected with a vehicle (ethanol) and the experimental ones with TMX at a dose of 6 mg/kg of body weight. Birds were treated daily until complete cessation of egg laying. The oviductal parts, that is the infundibulum, magnum, isthmus, shell gland and vagina were isolated from hens on day 8 of the experiment, and subsequently, the gene and protein expressions of AQP4 in tissues were examined by real-time PCR and Western blot, respectively. Immunohistochemical localization of AQP4 in the wall of the chicken oviduct was also investigated. Both mRNA and protein of AQP4 were found in all segments of the chicken oviduct. The relative expression [RQ] of AQP4 was the highest in the infundibulum and the vagina and the lowest, less detectable, in the magnum and isthmus. The pattern of AQP4 protein expression was similar to that of mRNA. Treatment of hens with TMX decreased the mRNA and protein levels of AQP4 in the oviduct. Immunohistochemistry demonstrated tissue and cell-dependent localization of AQP4 protein in the oviductal wall. The intensity of the immunopositive reaction was as follows: the infundibulum > vagina > shell gland ≥ isthmus >˃ magnum. In the control chickens, the immunoreactivity for AQP4 in all oviductal segments was stronger compared with the TMX-treated hens. The results obtained indicate that AQP4 takes part in the regulation of water transport required for the formation of egg in the chicken oviduct. Moreover, a relationship between oestrogen action and AQP4 gene and protein expression is suggested.

Morphology and Aquaporin Immunohistochemistry of the Uterine Tube of Saanen Goats (Capra hircus): Comparison Throughout the Reproductive Cycle

The expression of six different aquaporins (AQP1, 2, 3, 4, 5 and 9), integral membrane water channels that facilitate bi-directional passive movement of water, was investigated by immunohistochemistry in the uterine tube of pre-pubertal and adult Saanen goats (Capra hircus), comparing the different phases of the oestrous cycle. Regional morphology and secretory processes were markedly different during the goat oestrous cycle. The tested AQP molecules showed different expression patterns in comparison with already studied species. AQP1-immunoreactivity was evidenced at the endothelium of blood vessels and in nerve fibres, regardless of the tubal tract and cycle period. AQP4-immunoreactivity was shown on the lateral plasmalemma in the basal third of the epithelial cells at infundibulum and ampulla level in the cycling goats, more evidently during follicular than during luteal phase. No AQP4-immunoreactivity was noticed at the level of the isthmus region, regardless of the cycle phase. AQP5-immunoreactivity, localized at the apical surface of epithelial cells, increased from pre-puberty to adulthood. Thereafter, AQP5-immunoreactivity was prominent during the follicular phase, when it strongly decorated the apical plasmalemma of all epithelial cells at ampullary level. During luteal phase, immunoreactivity was discontinuous, being weak to strong at the apex of the secretory cells protruding into the lumen. In the isthmus region, the strongest AQP5-immunoreactivity was seen during follicular phase, with a clear localization in the apical plasmalemma of all the epithelial cells and also on the lateral plasmalemma. AQP2, 3 and 9 were undetectable all along the goat uterine tube. Likely, a collaboration of different AQP molecules sustains the fluid production in the goat uterine tube. AQP1-mediated transudation from the blood capillaries, together with permeation of the epithelium by AQP4 in the basal rim of the epithelial cells and final intervening of apical AQP5, could be involved in fluid production as well as in secretory processes.

Difference in expression between AQP1 and AQP5 in porcine endometrium and myometrium in response to steroid hormones, oxytocin, arachidonic acid, forskolin and cAMP during the mid-luteal phase of the estrous cycle and luteolysis

BACKGROUND

Recently, we demonstrated in vitro that AQP1 and AQP5 in the porcine uterus are regulated by steroid hormones (P4, E2), arachidonic acid (AA), forskolin (FSK) and cAMP during the estrous cycle. However, the potential of the porcine separated uterine tissues, the endometrium and myometrium, to express these AQPs remains unknown. Thus, in this study, the responses of AQP1 and AQP5 to P4, E2 oxytocin (OT), AA, FSK and cAMP in the porcine endometrium and myometrium were examined during the mid-luteal phase of the estrous cycle and luteolysis.

METHODS

Real-time PCR and western blot analysis.

RESULTS

Progesterone up-regulated the expression of AQP1/AQP5 mRNAs and proteins in the endometrium and myometrium, especially during luteolysis. Similarly, E2 also stimulated the expression of both AQPs, but only in the endometrium. AA led to the upregulation of AQP1/AQP5 in the endometrium during luteolysis. In turn, OT increased the expression of AQP1/AQP5 mRNAs and proteins in the myometrium during mid-luteal phase. Moreover, a stimulatory effect of forskolin and cAMP on the expression of AQP1/AQP5 mRNAs and proteins in the endometrium and myometrium dominated during luteolysis, but during the mid-luteal phase their influence on the expression of these AQPs was differentiated depending on the type of tissue and the incubation duration.

CONCLUSIONS

These results seem to indicate that uterine tissues; endometrium and myometrium, exhibit their own AQP expression profiles in response to examined factors. Moreover, the responses of AQP1/AQP5 at mRNA and protein levels to the studied factors in the endometrium and myometrium are more pronounced during luteolysis. This suggests that the above effects of the studied factors are connected with morphological and physiological changes taking place in the pig uterus during the estrous cycle.

Compensation of aquaporin 3 in rats after resection of two-thirds of the colon: Effect of Pulsatilla decoction

AIM: To detect the expression of aquaporin 3 (AQP3) in rats after resection of two-thirds of the colon, and to assess the effect of Pulsatilla decoction on AQP3 expression.

METHODS: Resection of two-thirds of the colon was performed in rats. Rats were randomly divided into a normal control group, a model group, and a Chinese intervention group, with nine rats in each group. The Chinese intervention group was treated with Pulsatilla decoction. The expression of AQP3 protein and mRNA was detected by immunohistochemistry and real-time PCR, respectively.

RESULTS: At the first week, AQP3 compensation was observed in the colon of rats in the model group colon, and diarrhea was improved. At the second and fourth weeks, Pulsatilla decoction treatment significantly reduced the compensation time compared with rats in the model group, but did not alter the expression level of AQP3.

CONCLUSION: The expression of AQP3 is increased in rats after resection of two-thirds of the colon, and Pulsatilla decoction plays a positive role in promoting Aquaporin 3 compensation.

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.

Modifications of carbohydrate residues in the sheep oviductal ampulla after superovulation

Epithelium of oviductal ampulla was studied in normal and in superovulated sheep using morphologic analysis and lectin glycohistochemistry. The lining epithelium consisted of two types of cells, ciliated and nonciliated cells. Unlike superovulated samples, the nonciliated cells from control ewes showed apical protrusions indicating an apocrine secretory activity. The ciliated cells showed lectin-binding sites mainly at the level of the cilia which bound all the used lectins except Peanut agglutinin, suggesting the lack of glycans terminating with Galβ1,3GalNAc. In superovulated specimens, the ciliated cells with high mannosylated glycans Concanavalin A (Con A) and GlcNAc and GalNac termini Griffonia simplicifolia agglutinin II (GSA II) and Dolicurus biflorus agglutinin (DBA) decreased. The luminal surface of nonciliated cells showed all investigated sugar residues in controls, whereas it was lacking in high mannosylated (Con A) and terminal GalNAcα1,3(LFucα1,2)Galβ1,3/4GlcNAcβ1 sequence (DBA) in superovulated ewes. Apical protrusions from control ampullae nonciliated cells showed glycans containing mannose, GlcNac, GalNAc, galactose, and α2,3-linked sialic acid (Con A, KOH-sialidase- Wheat germ agglutnin [WGA], GSA II, SBA, Griffonia simplicifolia agglutinin-isolectin B4 [GSA I-B4], Maackia amurensis agglutinin II [MAL II]). The supranuclear cytoplasm of nonciliated cells expressed terminal GlcNAc (GSA II) in all specimens, also O-linked glycans (mucin-type glycans) with GalNAc and sialic acid termini (Helix pomatia agglutinin [HPA] and MAL II) in control animals, and also N-linked glycans with fucose, galactose, lactosamine, and α2,3-linked sialic acid termini (Ulex europaeus agglutinin I [UEA I], GSA I-B4, Ricinus communis agglutinin120 [RCA120], and Sambucus nigra agglutinin [SNA] ) in superovulated ewes. These results report for the first time that the superovulation treatment affects the secretory activity and the glycan pattern of the epithelium lining the sheep oviductal ampulla.

Rheotaxis guides mammalian sperm

BACKGROUND

In sea urchins, spermatozoan motility is altered by chemotactic peptides, giving rise to the assumption that mammalian eggs also emit chemotactic agents that guide spermatozoa through the female reproductive tract to the mature oocyte. Mammalian spermatozoa indeed undergo complex adaptations within the female (the process of capacitation) that are initiated by agents ranging from pH to progesterone, but these factors are not necessarily taxic. Currently, chemotaxis, thermotaxis, and rheotaxis have not been definitively established in mammals.

RESULTS

Here, we show that positive rheotaxis, the ability of organisms to orient and swim against the flow of surrounding fluid, is a major taxic factor for mouse and human sperm. This flow is generated within 4 hr of sexual stimulation and coitus in female mice; prolactin-triggered oviductal fluid secretion clears the oviduct of debris, lowers viscosity, and generates the stream that guides sperm migration in the oviduct. Rheotaxic movement is demonstrated in capacitated and uncapacitated spermatozoa in low- and high-viscosity media. Finally, we show that a unique sperm motion, which we quantify using the sperm head's rolling rate, reflects sperm rotation that generates essential force for positioning the sperm in the stream. Rotation requires CatSper channels, presumably by enabling Ca(2+) influx.

CONCLUSIONS

We propose that rheotaxis is a major determinant of sperm guidance over long distances in the mammalian female reproductive tract. Coitus induces fluid flow to guide sperm in the oviduct. Sperm rheotaxis requires rotational motion during CatSper channel-dependent hyperactivated motility.

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.

Components of oviduct physiology in eutherian mammals

Recalling the evolutionary sequence of development first of gonad and subsequently of oviducts, ovarian endocrine regulation of all known components of oviduct physiology is reviewed. Ovaries not only influence oviducts via the systemic blood circulation, but also locally by counter-current transfer of relatively high concentrations of steroid hormones and prostaglandins between the ovarian vein and oviduct branch of the ovarian artery. The efficiency and impact of such counter-current transfer is greatest around the time of ovulation, the transfer process receiving further inputs from hormones present in peritoneal fluid. Classical oviduct physiology is summarised, and the potential molecular consequences of temperature gradients within the duct lumen examined. At ovulation, an oocyte-cumulus complex is displaced in minutes from the follicular surface to the site of fertilisation at the ampullary-isthmic junction of the oviduct. This rapid initial phase is contrasted with the subsequent slow progression of embryos to the uterus in days, still encompassed within a zona pellucida. Regarding transport of spermatozoa, the formation of a pre-ovulatory reservoir in the caudal portion of the oviduct isthmus is noted, with suppression of motility and sperm-head binding to epithelial organelles acting to maintain fertilising ability. Completion of capacitation is prompted shortly before ovulation, predominantly by Ca(2+) influx into bound spermatozoa. A controlled release of spermatozoa coupled with their hyperactivation results in initial sperm:egg ratios at the site of fertilisation close to unity, thereby avoiding the pathological condition of polyspermy. Both the oviduct milieu and embryonic development are influenced by paracrine activity of follicular granulosa cells released at ovulation and remaining in suspension in the vicinity of the oocyte or embryo. These cells may amplify early pregnancy signals from a zygote to the endosalpinx. Beneficial effects of the oviduct on domestic animal embryos are contrasted with anomalies arising as a consequence of in vitro culture. Primate embryos do not require exposure to an oviduct for normal development, perhaps due to overlapping compositions of endosalpingeal and endometrial secretions. Additionally, primate endometrial secretions may be modified by viable gametes or an embryo in the presence of a cumulus cell suspension.