Morphological changes and proliferative activity in the oviductal epithelium during hormonally defined stages of the oestrous cycle in the bitch

Sperm binding to oviduct epithelial spheroids varies among males and ejaculates but not among females in pigs

The elimination of ejaculates and males with low fertility despite good sperm motility and morphology is crucial to maintain high pregnancy rates after artificial insemination (AI) in farm animals. The ability of sperm to survive in the female tract is particularly crucial in pigs due to the large variation in the timing between AI and ovulation and the high number of oocytes to fertilise. The objective of this study was to characterise a new in vitro model of oviduct sperm reservoir using porcine oviduct epithelial spheroids (OES) and to assess the variability in sperm binding to OES among gilts, boars and their ejaculates. Isthmic mucosa fragments were collected from gilt oviducts at a slaughterhouse, and after 48 h of culture, the OES that had spontaneously formed were sorted according to their vesicle shape and size (150-200 μm in diameter) for characterisation and sperm binding assays. The OES contained viable, cytokeratin-positive and vimentin-negative cells, of which 36.4 ± 2.0% were multiciliated. The average proportion of multiciliated cells per OES did not change among culture replicates. After co-incubation with boar fresh semen, only sperm of normal morphology were found to bind, by their head, to cilia of OES. The density of sperm bound to the OES surface increased linearly with sperm concentration. The bound sperm density on OES was used to assess the binding capacity of fresh ejaculates collected from Pietrain boars. For a given ejaculate, the bound sperm density did not vary among pools of OES female donors. The analysis of five successive ejaculates from nine boars indicated significant differences in bound sperm densities on the OES among individual boars and their ejaculates (P < 0.01). There was no correlation between the sperm bound density and sperm parameters measured by computer-assisted sperm analysis or the initial dilution of the ejaculate. In conclusion, the OES characterised in this study offered physiological conditions to study sperm binding to the isthmic reservoir and evidenced that sperm from different ejaculates and different boars vary in their ability to bind to these oviduct spheroids despite homogeneous motility and morphology.

Advancements in Microfluidic Systems for the Study of Female Reproductive Biology

The female reproductive tract is a highly complex physiological system that consists of the ovaries, fallopian tubes, uterus, cervix, and vagina. An enhanced understanding of the molecular, cellular, and genetic mechanisms of the tract will allow for the development of more effective assisted reproductive technologies, therapeutics, and screening strategies for female specific disorders. Traditional 2-dimensional and 3-dimensional static culture systems may not always reflect the cellular and physical contexts or physicochemical microenvironment necessary to understand the dynamic exchange that is crucial for the functioning of the reproductive system. Microfluidic systems present a unique opportunity to study the female reproductive tract, as these systems recapitulate the multicellular architecture, contacts between different tissues, and microenvironmental cues that largely influence cell structure, function, behavior, and growth. This review discusses examples, challenges, and benefits of using microfluidic systems to model ovaries, fallopian tubes, endometrium, and placenta. Additionally, this review also briefly discusses the use of these systems in studying the effects of endocrine disrupting chemicals and diseases such as ovarian cancer, preeclampsia, and polycystic ovarian syndrome.

A Review on Microfluidics: An Aid to Assisted Reproductive Technology

Infertility is a state of the male or female reproductive system that is defined as the failure to achieve pregnancy even after 12 or more months of regular unprotected sexual intercourse. Assisted reproductive technology (ART) plays a crucial role in addressing infertility. Various ART are now available for infertile couples. Fertilization in vitro (IVF), intracytoplasmic sperm injection (ICSI) and intrauterine insemination (IUI) are the most common techniques in this regard. Various microfluidic technologies can incorporate various ART procedures such as embryo and gamete (sperm and oocyte) analysis, sorting, manipulation, culture and monitoring. Hence, this review intends to summarize the current knowledge about the application of this approach towards cell biology to enhance ART.

Exosomes as a Potential Tool for Supporting Canine Oocyte Development

The canine oviduct is a unique reproductive organ where the ovulated immature oocytes complete their maturation, while the other mammals ovulate matured gametes. Due to their peculiar reproductive characteristics, the in vitro maturation of dog oocytes is still not wellestablished compared with other mammals. Investigations of the microenvironment conditions in the oviductal canal are required to establish a reliable in vitro maturation system in the dog. Previous studies have suggested that the oviduct and its derivatives play a key role in improving fertilization as well as embryo development. In particular, the biological function of oviduct-derived exosomes on sperm and early embryo development has been investigated in porcine, bovine, and murine species. However, the information about their functions on canine cumulus-oocyte complexes is still elusive. Recent canine reproductive studies demonstrated how oviduct-derived extracellular vesicles such as microvesicles and exosomes interact with oocyte-cumulus complexes and how they can play roles in regulating canine cumulus/oocyte communications. In this review, we summarize the physiological characteristics of canine oviduct-derived exosomes and their potential effects on cumulus cells development as well as oocyte in vitro maturation via molecular signaling pathways.

A dog oviduct-on-a-chip model of serous tubal intraepithelial carcinoma

Ovarian cancer is the fifth cause of cancer-related mortality in women, with an expected 5-year survival rate of only 47%. High-grade serous carcinoma (HGSC), an epithelial cancer phenotype, is the most common malignant ovarian cancer. It is known that the precursors of HGSC originate from secretory epithelial cells within the Fallopian tube, which first develops as serous tubal intraepithelial carcinoma (STIC). Here, we used gene editing by CRISPR-Cas9 to knock out the oncogene p53 in dog oviductal epithelia cultured in a dynamic microfluidic chip to create an in vitro model that recapitulated human STIC. Similar to human STIC, the gene-edited oviduct-on-a-chip, exhibited loss of cell polarization and had reduced ciliation, increased cell atypia and proliferation, with multilayered epithelium, increased Ki67, PAX8 and Myc and decreased PTEN and RB1 mRNA expression. This study provides a biomimetic in vitro model to study STIC progression and to identify potential biomarkers for early detection of HGSC.

Composing the Early Embryonic Microenvironment: Physiology and Regulation of Oviductal Secretions

The oviductal fluid is the first environment experienced by mammalian embryos at the very beginning of life. However, it has long been believed that the oviductal environment was not essential for proper embryonic development. Successful establishment of in vitro embryo production techniques (which completely bypass the oviduct) have reinforced this idea. Yet, it became evident that in vitro produced embryos differ markedly from their in vivo counterparts, and these differences are associated with lower pregnancy outcomes and more health issues after birth. Nowadays, researchers consider the oviduct as the most suitable microenvironment for early embryonic development and a substantial effort is made to understand its dynamic, species-specific functions. In this review, we touch on the origin and molecular components of the oviductal fluid in mammals, where recent progress has been made thanks to the wider use of mass spectrometry techniques. Some of the factors and processes known to regulate oviductal secretions, including the embryo itself, as well as ovulation, insemination, endogenous and exogenous hormones, and metabolic and heat stress, are summarized. Special emphasis is laid on farm animals because, owing to the availability of sample material and the economic importance of fertility in livestock husbandry, a large part of the work on this topic has been carried out in domestic animals used for dairy and/or meat production.

Frozen-thawed ampullary cell monolayer improves bovine embryo in vitro development and quality

The aim of this study was to evaluate the effects of different timing for frozen-thawed bovine ampullary epithelial cell (BAEC) and bovine oviductal epithelial cell (BOEC) co-culture on the development and quality of bovine embryos produced in vitro. Embryo development was assessed by day 8 blastocyst yield, whereas embryo quality was determined using blastocyst differential cell count, cryotolerance and the expression of selected genes related to embryo quality. The results showed that the presence of BAECs during the last 6 h of in vitro maturation (IVM) increased blastocyst yield and survival of the vitrified-warmed blastocysts. In addition, embryos produced in the presence of BAECs during the last 6 h of IVM or in the presence of BOECs during the first 4 days of in vitro culture (IVC) showed a greater number of trophectoderm cells and a greater inner cell mass. In terms of gene expression, IFN-T was downregulated and PLAC8, AQP3 and ATP1A1 were upregulated in the presence of the BAECs during the last 6 h of the IVM and/or in the presence of BOECs during the first 4 days of IVC. In conclusion, co-culturing bovine oocytes with a frozen-thawed ampullary cell monolayer during the last 6 h of maturation increased blastocyst yield and quality.

Oviduct morphology and estrogen receptors ERα and ERβ expression in captive Chinchilla lanigera (Hystricomorpha: Chinchillidae)

Chinchilla lanigera is a hystricomorph rodent from South America whose reproductive biology presents particular characteristics that distinguishes it from other Rodentia species, such as low reproductive rate, seasonal breeding pattern, and long estrous cycle. Nevertheless, reproductive features in female chinchillas are still poorly investigated, with a scarce knowledge concerning the estrous cycle and the histology of reproductive organs. In this study, we investigate the morphology, histomorphometry, secretory activity, and immunolocalization of estrogen receptors ERα and ERβ in oviducts of nulliparous chinchillas, euthanized at fall season in Brazil. Follicular phase of estrous cycle of all studied animals was characterized by ovary and uterine morphology inspection, as well as vaginal cytology. Similar to other mammals, the oviduct wall of infundibulum, ampulla and isthmus was composed of mucosa, muscle, and serosa layers. Morphometric data of oviduct layers were used for identifying each oviduct segment. In the follicular phase, the oviduct was characterized by intense secretory activity, mainly in the ampulla, and expression of ERα and ERβ throughout the oviduct epithelium. Both ERα and ERβ were also detected in the connective tissue and smooth muscle cells. Our findings point out to the important role of estrogen in this female organ. Similar wide distribution of both ER proteins has been described for human Fallopian tube. Taken together, our data add to the understanding of the reproductive biology of female chinchillas, and may assist in the intensive breeding of this species and any eventual endeavor for conservation of chinchillas in the wild.

An oviduct-on-a-chip provides an enhanced in vitro environment for zygote genome reprogramming

Worldwide over 5 million children have been conceived using assisted reproductive technology, and research has concentrated on increasing the likelihood of ongoing pregnancy. However, studies using animal models have indicated undesirable effects of in vitro embryo culture on offspring development and health. In vivo, the oviduct hosts a period in which the early embryo undergoes complete reprogramming of its (epi)genome in preparation for the reacquisition of (epi)genetic marks. We designed an oviduct-on-a-chip platform to better investigate the mechanisms related to (epi)genetic reprogramming and the degree to which they differ between in vitro and in vivo embryos. The device supports more physiological (in vivo-like) zygote genetic reprogramming than conventional IVF. This approach will be instrumental in identifying and investigating factors critical to fertilization and pre-implantation development, which could improve the quality and (epi)genetic integrity of IVF zygotes with likely relevance for early embryonic and later fetal development.

In Vitro Mimicking of Estrous Cycle Stages: Dissecting the Impact of Estradiol and Progesterone on Oviduct Epithelium

We have previously mimicked the morphological and functional changes occurring in the oviduct epithelium during the estrous cycle in vitro by using an air-liquid interface (ALI) culture system and basolateral application of 17β-estradiol (E2) and progesterone (P4). In the current study we aimed to explore the transcriptomic changes elicited by E2 and P4 together during estrous cycle simulation and to dissect the individual effects of E2 and P4 on oviduct epithelium physiology. Primary porcine oviduct epithelial cells (POECs) (N = 6 animals) were cultured at the ALI. After differentiation for 11 days, we sequentially simulated diestrus (10 days) and estrus (2.5 days) by adding serum levels of E2 and P4 to the basolateral compartment either in combination (mix trial) or separately (P4 trial and E2 trial, respectively). Cell response was evaluated by microarray analysis (mix and P4 trials), quantitative RT-PCR, and histomorphometry (all trials). When we compared simulated diestrus with estrus stage in the mix trial, there were 169 (142 upregulated and 27 downregulated) differentially expressed genes (DEGs; fold change ≥1.5). In the P4 trial, 108 DEGs (83 upregulated and 25 downregulated) were detected. Gene enrichment analysis revealed that immune-related pathways were exclusively affected in the mix trial. In both mix and P4 trials, POECs exhibited in vivo-like morphological changes regarding epithelium height and portion of ciliated cells. However, E2 alone did not trigger morphological changes. We deduce that P4 mainly drives structural variations, and E2 is imperative for regulating immune function of the oviduct epithelium during estrous cycle.

Relationship between time post-ovulation and progesterone on oocyte maturation and pregnancy in canine cloning

Canine oocytes ovulated at prophase complete meiosis and continue to develop in presence of a high progesterone concentration in the oviduct. Considering that meiotic competence of canine oocyte is accomplished in the oviductal environment, we postulate that hormonal milieu resulting from the circulating progesterone concentration may affect oocyte maturation and early development of embryos. From 237 oocyte donors, 2620 oocytes were collected and their meiotic status and morphology were determined. To determine optimal characteristics of the mature oocytes subjected to nuclear transfer, a proportion of the meiotic status of the oocytes were classified in reference to time post-ovulation as well as progesterone (P4) level. A high proportion of matured oocytes were collected from >126h (55.5%) post-ovulation or 40-50ngmL^-1 (46.4%) group compared to the other groups. Of the oocyte donors that provided mature oocytes in vivo, there was no correlation between serum progesterone of donors and time post ovulation, however, time post-ovulation were significantly shorter for <30ng/mL group (P<0.05). Using mature oocytes, 1161 cloned embryos were reconstructed and transferred into 77 surrogates. In order to determine the relationship between pregnancy performance and serum progesterone level, embryos were transferred into surrogates showing various P4 serum levels. The highest pregnancy (31.8%) and live birth cloning efficacy (2.2%) rates were observed when the embryos were transferred into surrogates with circulating P4 levels were from 40 to 50ngmL^-1. In conclusion, measurement of circulating progesterone of female dog could be a suitable an indicator of the optimal time to collect quality oocyte and to select surrogates for cloning.

Histomorphometrics and quantitative unbiased stereology in canine uteri treated with medroxyprogesterone acetate

This article describes the effects of MPA use on the canine uterus using stereological methods. Entire reproductive tracts were removed from normal healthy canine bitches (Canis lupus familiaris) and grouped as: nulliparous (n = 11), multiparous (n = 11) and MPA-treated (n = 11; nulliparous; two treatments; 5 mg/kg). 1 cm samples were cut from the corpus, horn and uterine tube and fixed in 10% formaldehyde. Sections of each were mounted on slides and stained with hematoxylin-eosin. We assessed the fraction area for components of endometrium and myometrium and V_V (volume density) and S_V (surface density) of the gland and stroma using the M₃₆ test system provided by the STEPanizer Stereological Tool. No gross histological differences were observed between study groups in the uterine tube, uterine corpus and horn. The wall of the uterine corpus and horn in MPA-treated bitches was characterized as being thicker than in the other groups. A cross-section of the uterine corpus revealed no differences between components of uterine wall in the corpus and horn; however, differences were observed in the volume density [V_V; %] in variables such as: V_{V[str.vasc/uterus]} (nulliparous vs. multiparous; p = 0.0019) and V_{V[str.supravasc/uterus]} (multiparous vs. nulliparous and MPA; p = 0.0035). In the endometrial gland, differences were detected in S_{V[gland/endom]} (multiparous vs. MPA, p = 0.0442). In the uterine horn, differences were only observed in the variable V_{V[lumen.gland/endom]} (multiparous vs. MPA; p = 0.0019). This study shows quantitative changes in the architecture of the endometrium and myometrium in all the uterine segments, mainly morphological endometrial gland changes of the uterine corpus, increasing the surface area per unit of volume; however, these changes usually do not differ quantitatively from those observed in the uterus of multiparous bitches.

Periovulatory follicular fluid levels of estradiol trigger inflammatory and DNA damage responses in oviduct epithelial cells

OBJECTIVE

Ovarian steroid hormones (mainly E2 and P4) regulate oviduct physiology. Serum-E2 acts on the oviduct epithelium from the basolateral cell compartment. Upon ovulation, the apical compartment of the oviduct epithelium is temporarily exposed to follicular fluid, which contains much higher levels of E2 than serum. The aim of this study was to evaluate the effects of human periovulatory follicular fluid levels of E2 on oviduct epithelial cells using two porcine in vitro models.

METHODS

A cell line derived from the porcine oviductal epithelium (CCLV-RIE270) was characterized (lineage markers, proliferation characteristics and transformation status). Primary porcine oviduct epithelial cells (POEC) were cultured in air-liquid interface and differentiation was assessed histologically. Both cultures were exposed to E2 (10 ng/ml and 200 ng/ml). Proliferation of CCLV-RIE270 and POEC was determined by real-time impedance monitoring and immunohistochemical detection of Ki67. Furthermore, marker gene expression for DNA damage response (DDR) and inflammation was quantified.

RESULTS

CCLV-RIE270 was not transformed and exhibited properties of secretory oviduct epithelial cells. Periovulatory follicular fluid levels of E2 (200 ng/ml) upregulated the expression of inflammatory genes in CCLV-RIE270 but not in POEC (except for IL8). Expression of DDR genes was elevated in both models. A significant increase in cell proliferation could not be detected in response to E2.

CONCLUSIONS

CCLV-RIE270 and POEC are complementary models to evaluate the consequences of oviduct exposure to follicular fluid components. Single administration of periovulatory follicular fluid E2 levels trigger inflammatory and DNA damage responses, but not proliferation in oviduct epithelial cells.

The disparate origins of ovarian cancers: pathogenesis and prevention strategies

Ovarian cancer is the fifth cause of cancer-related death in women and comprises a histologically and genetically broad range of tumours, including those of epithelial, sex cord-stromal and germ cell origin. Recent evidence indicates that high-grade serous ovarian carcinoma, clear cell carcinoma and endometrioid carcinoma primarily arise from tissues that are not normally present in the ovary. These histogenetic pathways are informing risk-reduction strategies for the prevention of ovarian and ovary-associated cancers and have highlighted the importance of the seemingly unique ovarian microenvironment.

Designing 3-Dimensional In Vitro Oviduct Culture Systems to Study Mammalian Fertilization and Embryo Production

The oviduct was long considered a largely passive conduit for gametes and embryos. However, an increasing number of studies into oviduct physiology have demonstrated that it specifically and significantly influences gamete interaction, fertilization and early embryo development. While oviduct epithelial cell (OEC) function has been examined during maintenance in conventional tissue culture dishes, cells seeded into these two-dimensional (2-D) conditions suffer a rapid loss of differentiated OEC characteristics, such as ciliation and secretory activity. Recently, three-dimensional (3-D) cell culture systems have been developed that make use of cell inserts to create basolateral and apical medium compartments with a confluent epithelial cell layer at the interface. Using such 3-D culture systems, OECs can be triggered to redevelop typical differentiated cell properties and levels of tissue organization can be developed that are not possible in a 2-D culture. 3-D culture systems can be further refined using new micro-engineering techniques (including microfluidics and 3-D printing) which can be used to produce ‘organs-on-chips’, i.e. live 3-D cultures that bio-mimic the oviduct. In this review, concepts for designing bio-mimic 3-D oviduct cultures are presented. The increased possibilities and concomitant challenges when trying to more closely investigate oviduct physiology, gamete activation, fertilization and embryo production are discussed.

Remodeling of bovine oviductal epithelium by mitosis of secretory cells

Two types of oviductal epithelial cells, secretory and ciliated, play crucial roles in the first days after fertilization in mammals. Secretory cells produce various molecules promoting embryo development, while ciliated cells facilitate transport of oocytes and zygotes by ciliary beating. The proportions of the two cell types change during the estrous cycle. The proportion of ciliated cells on the oviductal luminal surface is abundant at the follicular phase, whereas the proportion of secretory cells gradually increases with the formation of the corpus luteum. In the present study, we hypothesize that the proportions of ciliated and secretory epithelial cells are regulated by mitosis. The proportion of the cells being positive for FOXJ1 (a ciliated cell marker) or Ki67 (a mitosis marker) in epithelial cells during the estrous cycle were immunohistochemically examined. Ki67 and FOXJ1 or PAX8 (a secretory cell marker), were double-stained to clarify which types of epithelial cells undergo mitosis. In the ampulla, the percentage of FOXJ1-positive cells was highest at the day of ovulation (Day 0) and decreased by about 50 % by Days 8-12, while in the isthmus it did not change during the estrous cycle. The proportion of Ki67-positive cells was highest at around the time of ovulation in both the ampulla and isthmus. All the Ki67-positive cells were PAX8-positive and FOXJ1-negative in both the ampulla and isthmus. These findings suggest that epithelial remodeling, which is regulated by differentiation and/or proliferation of secretory cells of the oviduct, provides the optimal environment for gamete transport, fertilization and embryonic development.

Levonorgestrel decreases cilia beat frequency of human fallopian tubes and rat oviducts without changing morphological structure

Levonorgestrel, a derivative of progesterone, effectively protects women against unwanted pregnancy as an emergency contraceptive. Previous studies have not been successful in determining the mechanism by which levonorgestrel acts. In the present study we analysed cilia beat action and cilia morphology following levonorgestrel exposure in vitro and in vivo using both light and electron microscopy. There was a significant decrease in the ciliary beat frequency (CBF) of human fallopian tubes between mucosal explants bathed in 5 μmol/L levonorgestrel and those bathed in medium alone (P < 0.05). There was a tendency for CBF to decrease more in the ampulla than in isthmus, but there were no differences between the proliferative and secretory phases. In rat oviducts, levonorgestrel produced a similar reduction in CBF (~ 10%) compared with the saline control group (P < 0.05). Histological and ultrastructural analysis demonstrated no changes in the percentage of ciliated cells or in the classic '9 + 2' structure of cilia following levonorgestrel treatment in either system. Thus, levonorgestrel reduces CBF without damaging cilia morphology. Decreases in CBF may indicate a pathological role for levonorgestrel in the transportation of the ovum and zygote in the fallopian tube.

Scanning and transmission electron microscopic analysis of ampullary segment of oviduct during estrous cycle in caprines

The ampullary segment of the mammalian oviduct provides suitable milieu for fertilization and development of zygote before implantation into uterus. It is, therefore, in the present study, the cyclic changes in the morphology of ampullary segment of goat oviduct were studied during follicular and luteal phases using scanning and transmission electron microscopy techniques. Topographical analysis revealed the presence of uniformly ciliated ampullary epithelia, concealing apical processes of non-ciliated cells along with bulbous secretory cells during follicular phase. The luteal phase was marked with decline in number of ciliated cells with increased occurrence of secretory cells. The ultrastructure analysis has demonstrated the presence of indented nuclear membrane, supranuclear cytoplasm, secretory granules, rough endoplasmic reticulum, large lipid droplets, apically located glycogen masses, oval shaped mitochondria in the secretory cells. The ciliated cells were characterized by the presence of elongated nuclei, abundant smooth endoplasmic reticulum, oval or spherical shaped mitochondria with crecentric cristae during follicular phase. However, in the luteal phase, secretory cells were possessing highly indented nucleus with diffused electron dense chromatin, hyaline nucleosol, increased number of lipid droplets. The ciliated cells had numerous fibrous granules and basal bodies. The parallel use of scanning and transmission electron microscopy techniques has enabled us to examine the cyclic and hormone dependent changes occurring in the topography and fine structure of epithelium of ampullary segment and its cells during different reproductive phases that will be great help in understanding major bottle neck that limits success rate in vitro fertilization and embryo transfer technology.

Microscopic and histochemical characterization of the bovine uterine tube during the follicular and luteal phases of estrous cycle

The morphometrical and morphological features of the infundibulum and ampulla of the uterine tubes of adult cattle were studied. The materials used in this study were consisted of 12 pairs of uterine tube of healthy cows at age of 16-36 months, collected from Assiut slaughterhouses. Through observations of the ovaries, follicular and luteal phases of estrous cycle of each cattle were specified. Semithin sections of ampulla and infundibulum at follicular and luteal phases were made and histochemical analysis of the ampulla by use of PAS, Alcian Blue, Sudan Black B was also done. In addition, acid phosphatase activity of the ampullar epithelium was demonstrated. Histological analysis of the epithelium of bovine oviduct revealed that it was consisted of non-ciliated secretory cells, two populations of ciliated cells (CC), basal cells and Peg cells. At the luteal phase, the secretory cells possessed many cytoplasmic protrusions that extended beyond the luminal borders of the ciliated cells and exocytosis of secretory materials was observed. While at the follicular phase, the ciliated cells were predominated. The histochemistry of the ampullar epithelium revealed increase in secretions of neutral, acidic mucopolysaccarides and lipid from the secretory cells at the luteal phase with moderate acid phosphatase activity. Histomorphometric examinations of infundibulum and ampulla indicated that the mean number and height of primary folds as well as the thickness of the epithelium were increased significantly at the follicular phase.

Expression of nuclear and membrane progesterone receptors in the canine oviduct during the periovulatory period

Important reproductive events take place in the canine oviduct in the presence of increasing concentrations of progesterone (P4). To investigate the potential effects of P4 on the canine oviduct, the expression of nuclear (PR) and membrane (PGRMC1 and 2, mPRα, β and γ) P4 receptors was studied by quantitative RT-PCR and immunohistochemistry. Oviducts were collected from Beagle bitches after the onset of pro-oestrus and before the LH peak (Pre-LH), after the LH peak and before ovulation (Pre-ov) and on Days 1, 4 and 7 post-ovulation (n=6 bitches/stage). PR mRNA concentrations decreased from Pre-LH to Day 7 in the ampulla and isthmus, whereas both PGRMC1 and 2 mRNA levels increased over the same period. The main change in mPR expression was an increase in mPRβ and γ mRNAs at Day 7 in the isthmus. Furthermore, PR proteins were expressed in the nuclei of luminal epithelial, stromal and muscular cells, whereas the expression of PGRMCs and mPRs was primarily cytoplasmic and localised in the luminal epithelium. The immunostaining for PR decreased at Day 4 in the stroma and muscle, whereas it remained strong in the epithelium from Pre-LH to Day 7. PGRMC1 staining was strong at Days 4 and 7 whereas PGRMC2 was highly expressed from Pre-ov to Day 7. The most intense immunostaining signals for all three mPRs were observed at Day 7. Our results strongly support the hypothesis that P4 is an important regulator of oviductal functions in the bitch through complementary classical and non-classical P4 pathways.

Effect of short-term scrotal hyperthermia on spermatological parameters, testicular blood flow and gonadal tissue in dogs

The objective was to assess the effect of a short-term scrotal hyperthermia in dogs on quantitative and qualitative ejaculate parameters, testicular blood flow and testicular and epididymal histology. After a control period, the scrotum of seven normospermic adult beagle dogs was insulated with a self-made suspensory for 48 h. Nine weeks later, two animals were castrated, while in five animals, scrotal hyperthermia was repeated. Dogs were castrated either 10 or 40 days thereafter. In each phase of scrotal insulation, average scrotal surface temperature increased by 3.0°C. Semen was collected twice weekly throughout the experiment. Total sperm count did not change after the first hyperthermia, but it slightly decreased after the second (p < 0.05). Profiles of sperm morphology and velocity parameters (CASA) rather indicated subtle physiological variations in sperm quality than effects of a local heat stress. Chromatin stability of ejaculated spermatozoa as indicated by SCSA remained constant throughout the experiment. Perfusion characteristics of the gonads, that is, systolic peak velocity, pulsatility and resistance index at the marginal location of the testicular artery, did not change due to hyperthermia (p > 0.05). Histological examination of excised testes and epididymides for apoptotic (TUNEL and activated caspase-3) and proliferating cells (Ki-67 antigen) indicated only marginal effects of scrotal insulation on tissue morphology. In conclusion, a mild short-term scrotal hyperthermia in dogs does not cause substantial changes in sperm quantity and quality. In contrast to other species, canine testes and epididymides may have a higher competence to compensate such thermal stress.

In vitro mimicking of estrous cycle stages in porcine oviduct epithelium cells: estradiol and progesterone regulate differentiation, gene expression, and cellular function

Throughout the estrous cycle the oviduct epithelium undergoes dramatic morphological and functional changes. To elucidate cyclic cellular events and associated regulation mechanisms of 17beta estradiol (E2) and progesterone (P4), we mimicked estrous cycle stages in vitro using a culture system of primary porcine oviduct epithelium cells (POEC). Cells were polarized in an air/liquid interface and then treated with E2 and P4 for physiological time periods: In experiment 1, high concentration of P4 with low concentration of E2 for 10 days resembled diestrus; in experiment 2, following the previous diestrus, sequential high E2 with low P4 for 2.5 days represented estrus. Histomorphometry and electron microscopy showed cyclic changes in cellular height, cell population, and cilia density under the influence of hormone stimulation. Transepithelial electrical resistance was high in simulated diestrus but reduced in estrus. Thus, E2 and P4 affect cellular polarity, transformation of ciliated and secretory cells, as well as electrical conductivity of oviduct epithelium. Simulation of diestrus led to significant decrease in expression of hormone receptors (PGR and ESR1) and other epithelial markers (MUC16, OVGP1, and HSP90B1), while sequential simulated estrus caused an increase in these markers. The hormonal regulation of some marker genes was clearly time-dependent. Furthermore, POEC showed increased sperm-binding capacity in simulated estrus. In this study, we also present a novel approach based on the AndroVision software, which can be routinely utilized as a parameter for ciliary activity, and for the first time, we showed fluid movement patterns along the epithelium lining in vitro.

Immunolocalization of progesterone receptors in the canine oviduct around ovulation

In the bitch, oocyte maturation, sperm storage, fertilization and early embryo development take place within the oviducts under high and increasing circulating progesterone concentrations. To investigate the potential effects of progesterone on the canine oviduct, nuclear progesterone receptors (PR) were localized. Oviducts were collected by ovariectomy from adult Beagle bitches during anestrus, after the onset of proestrus but prior to the Luteinizing Hormone (LH) peak (Pre-LH), after the LH peak but before ovulation (Pre-ov) and on Days 1, 4 and 7 after ovulation (n = 3 bitches per stage). The cellular distribution of PR was studied by immunohistochemistry (IHC) in the ampulla, isthmus and tubal part of the utero-tubal junction (UTJ). Plasma progesterone and 17β-oestradiol were assayed on the day of surgery. PR were specifically expressed in the nuclei of epithelial, stromal and muscular cells in the ampulla, isthmus and UTJ. The IHC scores did not vary from one oviductal region to another. However, the epithelium displayed higher scores than the stroma at anestrus, Pre-ov, Days 4 and 7, and also higher scores than muscle at Days 4 and 7 (p < 0.05). Immunohistochemistry scores in the stroma and muscle decreased at Days 4 and 7 compared with previous stages (p < 0.05). Furthermore, muscular IHC scores were positively correlated with circulating 17β-oestradiol concentrations and negatively correlated with circulating progesterone concentrations (p < 0.05). In conclusion, PR were identified in the canine oviduct, with differences in expression between tissues and times around ovulation, suggesting that progesterone may regulate tubal functions and reproductive events in this species.

Ciliary activity in the oviduct of cycling, pregnant, and muscarinic receptor knockout mice

The transport of the oocyte and the embryo in the oviduct is managed by ciliary beating and muscular contractions. Because nonneuronally produced acetylcholine influences ciliary beating in the trachea via the muscarinic receptors M2 and M3, we supposed that components of the cholinergic system may also modulate ciliary activity in the oviduct. To address this issue, we analyzed the expression profile of muscarinic receptors (CHRMs) in the murine oviduct by RT-PCR and assessed ciliary beat frequency (CBF) and cilia-driven particle transport speed (PTS) on the mucosal surface of opened oviductal segments in correlation with histomorphological investigations. RT-PCR of laser-assisted microdissected epithelium revealed expression of Chrm subtypes Chrm1 and Chrm3. In opened isthmic segments, particle transport was barely seen, correlating with a significantly lower number of ciliated cells compared to the ampulla. In the ampulla, basal PTS and CBF were high (71 μm/sec and 21 Hz, respectively) both in cycling and pregnant wild-type mice and in mice with targeted deletion of the Chrm genes Chrm1, Chrm3, Chrm4, and Chrm5. In contrast to the trachea, where basal ciliary activity was low and largely enhanced by muscarinic stimulation, muscarinic agonists and antagonists did not affect the high ampullar PTS. Our results imply that this high oviductal autonomous ciliary activity is independent from the intrinsic cholinergic system and serves to maintain optimal clearance of the tube throughout all stages of the estrous cycle and early pregnancy.

The tunica mucosa of the oviduct in case of ovarian cysts presence in sows

The unfavorable morphological changes in the oviductal mucosa may lead to infertility in females and be one of the reasons for slaughtering of farm animals. The aim of study was to investigate the morphological changes in the epithelium of oviductal mucosa of sows with ovarian cysts. The oviducts of 18 sows were obtained after slaughter. Sows were divided into three groups: 1st group - 6 sows with polycystic ovaries, 2nd group - 6 sows with single cysts, 3rd group - 6 sows without ovarian cysts. The epithelium was examined by light microscopy, SEM and TEM. Ciliated and secretory cells were count on 150 μm segments in apical and basal zone of folds both in ampulla and isthmus. We analyzed the number of cells in 5 folds in both these oviductal parts in dexter and sinister oviduct. We have noted unfavorable changes in oviductal mucosa consisting in increase of the secretory cells with simultaneous decrease of ciliated cells. The correlations between the general occurrence of ovarian cysts and the morphological state of epithelium of oviductal tunica mucosa were determined. The changes in proportion of cells occurred both in ampulla and isthmus. The excessive secretion covering epithelium promotes agglutinations and adhesions of the tubal folds and occlusion of the oviduct. These alterations may create problems in the migration of gametes and prevent the movements of the zygote towards the uterus and cause some disturbances in conceptus development in its early stages. Results suggest that COD is connected with unfavorable morphological and functional changes within epithelium of the oviductal tunica mucosa.

The role of the aryl hydrocarbon receptor in the female reproductive system

In recent years, many studies have emphasized how changes in aryl hydrocarbon receptor (AHR)-mediated gene expression result in biological effects, raising interest in this receptor as a regulator of normal biological function. This review focuses on what is known about the role of the AHR in the female reproductive system, which includes the ovaries, Fallopian tubes or oviduct, uterus and vagina. This review also focuses on the role of the AHR in reproductive outcomes such as cyclicity, senescence, and fertility. Specifically, studies using potent AHR ligands, as well as transgenic mice lacking the AHR-signaling pathway are discussed from a viewpoint of understanding the endogenous role of this ligand-activated transcription factor in the female reproductive lifespan. Based on findings highlighted in this paper, it is proposed that the AHR has a role in physiological functions including ovarian function, establishment of an optimum environment for fertilization, nourishing the embryo and maintaining pregnancy, as well as in regulating reproductive lifespan and fertility. The mechanisms by which the AHR regulates female reproduction are poorly understood, but it is anticipated that new models and the ability to generate specific gene deletions will provide powerful experimental tools for better understanding how alterations in AHR pathways result in functional changes in the female reproductive system.

Effect of steroid hormones onBufo arenarum oviduct. Ultrastructural study

The endocrine regulation of the mucosa of the oviductal pars convoluta was analyzed by ultrastructural studies demonstrating that ovariectomy, together with a decrease in ovarian steroids circulating levels, caused a marked regression in this portion of Bufo arenarum oviduct. Twenty-five days after ovariectomy, a decrease in the depth of the epithelial and glandular layers was observed due to the notable loss of secretory cells, whose number was clearly smaller than in nonovariectomized females. The remaining secretory cells showed involution signs, with few secretory granules in their cytoplasm, little endoplasmic reticulum near poorly developed Golgi complexes and a large amount of lipid droplets. Cells in an advanced autolysis state were found in the lumen. These characteristics evidence a nonfunctional state of the pars convoluta. Treatment with 5alpha-dihydrotestosterone (DHT) completely reversed the ovariectomy effect, inducing pars convoluta growths and restoring the characteristics of epithelial and glandular secretory cells in the whole pars convoluta, with micrographs similar to the control. These same effects were observed after treatment with estradiol-17beta (E2), progesterone (P) o E(2)+P in the glandular layer of the whole pars convoluta, but only in the epithelial layer of the most anterior region of this duct. In the secretory cells of other segments these treatments induced the formation of granules of high electron density and homogeneous aspect. Each steroid had a particular effect on the pars convoluta. Although E2 and DHT induced the development of the organoids involved in the proteins biosynthesis, P and DHT acted as secretagogues.

Dioxin exerts anti-estrogenic actions in a novel dioxin-responsive telomerase-immortalized epithelial cell line of the porcine oviduct (TERT-OPEC)

Oviduct epithelial cells are important for the nourishment and survival of ovulated oocytes and early embryos, and they respond to the steroid hormones estrogen and progesterone. Endocrine-disrupting polyhalogenated aromatic hydrocarbons (PHAH) are environmental toxins that act in part through the ligand-activated transcription factor arylhydrocarbon receptor (AhR; dioxin receptor), and exposure to PHAH has been shown to decrease fertility. To investigate effects of PHAHs on the oviduct epithelium as a potential target tissue of dioxin-type endocrine disruptors, we have established a novel telomerase-immortalized oviduct porcine epithelial cell line (TERT-OPEC). TERT-OPEC exhibited active telomerase and the immunoreactive epithelial marker cytokeratin but lacked the stromal marker vimentin. TERT-OPEC contained functional estrogen receptor (ER)-alpha and AhR, as determined by the detection of ER-alpha- and AhR-specific target molecules. Treatment of TERT-OPEC with the AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in a significant increase in the production of the cytochrome P-450 microsomal enzyme CYP1A1. Activated AhR caused a downregulation of ER nuclear protein fraction and significantly decreased ER-signaling in TERT-OPEC as determined by ERE-luciferase transient transfection assays. In summary, the TCDD-induced and AhR-mediated anti-estrogenic responses by TERT-OPEC suggest that PHAH affect the predominantly estrogen-dependent differentiation of the oviduct epithelium within the fallopian tube. This action then alters the local endocrine milieu, potentially resulting in a largely unexplored cause of impaired embryonic development and female infertility.