Characterization of the oviductal sperm reservoir in cattle

Generation of Oviductal Glycoprotein 1 Cre Mouse Model for the Study of Secretory Epithelial Cells of the Oviduct

The epithelial cell lining of the oviduct plays an important role in oocyte pickup, sperm migration, preimplantation embryo development, and embryo transport. The oviduct epithelial cell layer comprises ciliated and nonciliated secretory cells. The ciliary function has been shown to support gamete and embryo movement in the oviduct, yet secretory cell function has not been well characterized. Therefore, our goal was to generate a secretory cell-specific Cre recombinase mouse model to study the role of the oviductal secretory cells. A knock-in mouse model, Ovgp1Cre:eGFP, was created by expressing Cre from the endogenous Ovgp1 (oviductal glycoprotein 1) locus, with enhanced green fluorescent protein (eGFP) as a reporter. EGFP signals were strongly detected in the secretory epithelial cells of the oviducts at estrus in adult Ovgp1Cre:eGFP mice. Signals were also detected in the ovarian stroma, uterine stroma, vaginal epithelial cells, epididymal epithelial cells, and elongated spermatids. To validate recombinase activity, progesterone receptor (PGR) expression was ablated using the Ovgp1Cre:eGFP; Pgrf/f mouse model. Surprisingly, the deletion was restricted to the epithelial cells of the uterotubal junction (UTJ) region of Ovgp1Cre:eGFP; Pgrf/f oviducts. Deletion of Pgr in the epithelial cells of the UTJ region had no effect on female fecundity. In summary, we found that eGFP signals were likely specific to secretory epithelial cells in all regions of the oviduct. However, due to a potential target-specific Cre activity, validation of appropriate recombination and expression of the gene(s) of interest is absolutely required to confirm efficient deletion when generating conditional knockout mice using the Ovgp1Cre:eGFP line.

Sperm-fluid-cell interplays in the bovine oviduct: glycosaminoglycans modulate sperm binding to the isthmic reservoir

When entering the oviduct for fertilisation, spermatozoa come into contact with the oviduct fluid (OF) and can bind to luminal epithelial cells in the isthmus to form a sperm reservoir. The objective of this study was to examine how the OF modulates sperm adhesion to the oviduct reservoir using an in vitro model of oviduct epithelial spheroids (OES). Bovine oviducts from a local slaughterhouse were used to collect OF and isthmic fragments for the in vitro incubation of OES. Compared to a non-capacitating control medium, the pre-ovulatory OF significantly decreased by 80-90% the density of spermatozoa bound to OES without affecting sperm motility, membrane integrity, or sperm-cilia interactions. This effect on sperm binding was reproduced with (1) OF from different cycle stages and anatomical regions of the oviduct; (2) OF fractions of more than 3 kDa; (3) modified OF in which proteins were denatured or digested and (4) heparan sulphate but not hyaluronic acid, two glycosaminoglycans present in the OF. In conclusion, the OF significantly decreased the number of spermatozoa that bind to oviduct epithelial cells without affecting sperm motility and this effect was due to macromolecules, including heparan sulphate.

Role of the bovine PRAMEY protein in sperm function during in vitro fertilization (IVF)

Preferentially expressed antigen in melanoma (PRAME) is a cancer/testis antigen (CTA) that is predominantly expressed in normal male gonad tissues and a variety of tumors. PRAME proteins are present in the acrosome and sperm tail, but their role in sperm function is unknown. The objective of this study was to examine the function of the bovine Y-linked PRAME (PRAMEY) during spermatozoal capacitation, the acrosome reaction (AR), and fertilization. Freshly ejaculated spermatozoa were induced to capacitate and undergo AR in vitro. Western blotting results revealed a decrease in the PRAMEY protein in capacitated spermatozoa, and the release of the PRAMEY protein from the acrosome during the AR, suggesting its involvement in sperm capacitation and AR. IVF was performed using in vitro matured bovine oocytes and cauda epididymal spermatozoa either treated with PRAMEY antibody, rabbit IgG, or DPBS. Sperm-egg binding and early embryos were examined at 6 and 45 h post IVF, respectively. The number of spermatozoa that bound per oocyte was nearly two-fold greater in the PRAMEY antibody treatment group (34.4) when compared to both the rabbit IgG (17.6) and DPBS (18.1) controls (P < 0.01). Polyspermy rate in the antibody-treated group (18.9%) was three-fold greater than the rabbit IgG control (6.0%) (P < 0.01). The results indicate that PRAMEY may play a role in anti-polyspermy defense. This study thus provides the initial evidence for the involvement of the PRAME protein family in sperm function and fertilization.

The sperm-interacting proteome in the bovine isthmus and ampulla during the periovulatory period

BACKGROUND

Spermatozoa interact with oviduct secretions before fertilization in vivo but the molecular players of this dialog and underlying dynamics remain largely unknown. Our objectives were to identify an exhaustive list of sperm-interacting proteins (SIPs) in the bovine oviduct fluid and to evaluate the impact of the oviduct anatomical region (isthmus vs. ampulla) and time relative to ovulation (pre-ovulatory vs. post-ovulatory) on SIPs number and abundance.

METHODS

Pools of oviduct fluid (OF) from the pre-ovulatory ampulla, pre-ovulatory isthmus, post-ovulatory ampulla, and post-ovulatory isthmus in the side of ovulation were collected from the slaughterhouse. Frozen-thawed bull sperm were incubated with OF or phosphate-buffered saline (control) for 60 min at 38.5 °C. After protein extraction and digestion, sperm and OF samples were analyzed by nanoLC-MS/MS and label-free protein quantification.

RESULTS

A quantitative comparison between proteins identified in sperm and OF samples (2333 and 2471 proteins, respectively) allowed for the identification of 245 SIPs. The highest number (187) were found in the pre-ovulatory isthmus, i.e., time and place of the sperm reservoir. In total, 41 SIPs (17%) were differentially abundant between stages in a given region or between regions at a given stage and 76 SIPs (31%) were identified in only one region × stage condition. Functional analysis of SIPs predicted roles in cell response to stress, regulation of cell motility, fertilization, and early embryo development.

CONCLUSION

This study provides a comprehensive list of SIPs in the bovine oviduct and evidences dynamic spatio-temporal changes in sperm-oviduct interactions around ovulation time. Moreover, these data provide protein candidates to improve sperm conservation and in vitro fertilization media.

Identification of key genes and biological pathways in different parts of yak oviduct based on transcriptome analysis

The oviduct consists of three parts: the infundibulum (In), ampulla (Am), and isthmus (Is). These have the same histological structure, but different physiological functions. In this study, transcriptomics was used to analyze mRNA in these three parts of yak oviduct. The results showed that there were 325 up-regulated genes and 282 down-regulated genes in the infundibulum and ampulla. Moreover, there were 234 up-regulated genes and 776 down-regulated genes in the isthmus and ampulla, as well as 873 up-regulated genes and 297 down-regulated genes in the infundibulum and isthmus. The expression of C3 in the infundibulum was significantly higher than that in the ampulla and isthmus. The expression of FAU in the isthmus was significantly lower than that in the ampulla and infundibulum, and the expression of EEF1A1 in the ampulla was significantly higher than that in the ampulla and infundibulum. When the infundibulum was compared with the ampulla and isthmus, it was found that the up-regulated genes were enriched in the lysosome, phagosome, staphylococcus aureus infection, and leishmaniasis pathway. When the isthmus was compared with the ampulla and infundibulum, the up-regulated genes were present in the apoptosis pathway, oxidative phosphorylation, and viral myocarditis pathway. When the isthmus was compared with the infundibulum and ampulla, the down-regulated pathways were protein processing in the endoplasmic reticulum and the endocytosis. The Epstein-Barr virus infection pathway was up-regulated according to a comparison of the isthmus and infundibulum and was down-regulated based on a comparison of the isthmus and ampulla. Transcriptional misregulation in the Middle East pathway was up-regulated based on a comparison of the isthmus and ampulla and was down-regulated based on a comparison of the isthmus and infundibulum. ERBB2, JUP, CTNND1, and KRT7 were defined as the hub genes of the yak oviduct. The results of this study provide sufficient omics data for yak fertilization, which is also of great significance to altitude medicine.

Heparin and Progesterone Exert Synergistic Effects to Improve the In-Vitro Fertilization Rate of Bovine Sperm Bound to Oviduct Cell Aggregates from the Isthmus

Simple Summary

After mating, sperm starts its long journey with the ultimate goal of fertilizing the oocyte. Inside the oviduct, sperm is attached to the surface of epithelial cells. The intact and good-quality sperm are elected and stored. Many infertility-related problems are related to the short life span of the sperm and/or the delay of the capacitation process of sperm attached to the oviduct. Thus, the elongation of the life span of the sperm would be very helpful in overcoming such problems. We hereby aimed to evaluate the fertilization ability of sperm that bind to cell aggregates oviduct (infundibulum-ampulla-isthmus), and assess the effect of heparin and or progesterone on the in-vitro fertilization ability of sperm co-incubated with isthmus cells aggregates. The sperm bound to isthmus aggregates improved the rate of in-vitro fertilization compared to infundibulum and ampulla. Moreover, pre-treatment of mature oocytes with heparin and progesterone plays a coactive role that improves the in-vitro fertilization of sperm bound to cell aggregates from isthmus. In conclusion, binding to isthmus aggregates improves the in-vitro fertilization of bovine sperm. Additionally, heparin together with progesterone, exerts a synergistic action that improves the in-vitro fertilizing potential of sperm attached to isthmus aggregates.

Abstract

After the copulation process, some sperm start the long journey with an ultimate goal of fertilizing the oocyte. Inside the oviduct, sperm are stored, waiting for the ovulated oocyte where they bind to the apical surface of the oviduct cells, which in turn hold sperm to form a sperm nest. The essential functions of the sperm reservoir include attaching spermatozoa to oviduct epithelial cells, selecting intact, good-quality sperm with an end result of extending sperm life expectancy. The current study aimed to evaluate the fertilization ability of sperm that bind to cell aggregates from different parts of the oviduct (infundibulum-ampulla-isthmus), and to assess the effect of heparin and or progesterone (P4) on the in-vitro fertilization ability of sperm co-incubated with cell aggregates from the isthmus. In-vitro fertilization was identified as a cleaved oocyte to two cells or more. The sperm bound to cell aggregates from the isthmus improved the rate of in-vitro fertilization (48.09%) compared to aggregates from the infundibulum (36.90%) and ampulla (37.61%). Moreover, pre-treatment of mature COCs with heparin (40 μg/mL) and P4 (80 nanomolar) play a coactive role that improves the in-vitro fertilization ability of sperm bound to cell aggregates from isthmus (63.33%), compared to 42.61% in the absence of cells aggregates. In conclusion, binding to cell aggregates from isthmus improves the in-vitro fertilization ability of Bovine sperm. Additionally, heparin, together with P4, exerts a synergistic action that improves the in-vitro fertilizing potential of sperm attached to cell aggregates from the isthmus of the bovine oviduct.

Progesterone and Inflammatory Response in the Oviduct during Physiological and Pathological Conditions

Progesterone has been shown to be a potent suppressor of several inflammatory pathways. During pregnancy, progesterone levels increase, allowing for normal pregnancy establishment and maintenance. The dysregulation of progesterone, as well as inflammation, leads to poor pregnancy outcomes. However, it is unclear how progesterone imbalance could impact inflammatory responses in the oviduct and subsequently result in early pregnancy loss. Therefore, in this review, we describe the role of progesterone signaling in regulating the inflammatory response, with a focus on the oviduct and pathological conditions in the Fallopian tubes.

Sperm migration, selection, survival, and fertilizing ability in the mammalian oviduct†

In vitro fertilization (IVF) gives rise to embryos in a number of mammalian species and is currently widely used for assisted reproduction in humans and for genetic purposes in cattle. However, the rate of polyspermy is generally higher in vitro than in vivo and IVF remains ineffective in some domestic species like pigs and horses, highlighting the importance of the female reproductive tract for gamete quality and fertilization. In this review, the way the female environment modulates sperm selective migration, survival, and acquisition of fertilizing ability in the oviduct is being considered under six aspects: (1) the utero-tubal junction that selects a sperm sub-population entering the oviduct; (2) the presence of sperm binding sites on luminal epithelial cells in the oviduct, which prolong sperm viability and plays a role in limiting polyspermic fertilization; (3) the contractions of the oviduct, which promote sperm migration toward the site of fertilization in the ampulla; (4) the regions of the oviduct, which play different roles in regulating sperm physiology and interactions with oviduct epithelial cells; (5) the time of ovulation, and (6) the steroid hormonal environment which regulates sperm release from the luminal epithelial cells and facilitates capacitation in a finely orchestrated manner.

Sperm phenotypic characteristics and oviduct binding ability are altered in breeding bulls with high sperm DNA fragmentation index

In the present study, we standardized an in vitro oviduct explants model for cattle and assessed the oviduct explants binding ability and phenotypic characteristics of spermatozoa obtained from breeding bulls with high- and low-sperm DNA fragmentation index (DFI%). Cryopreserved spermatozoa from Holstein Friesian crossbred breeding bulls (n = 45) with known field fertility were assessed for DFI% and were classified into either high DFI% or low DFI% category. Flow cytometry was used to assess sperm membrane integrity, acrosome reaction status, mitochondrial membrane potential and intracellular calcium concentrations. It was found that spermatozoa from bulls with low DFI% had significantly higher (P < 0.05) membrane integrity, acrosome intactness, and mitochondrial membrane potential. To assess the sperm oviduct binding ability, oviduct explants were prepared by incubating the oviduct cells overnight in TCM-199 medium at 38.5 °C under 5% CO₂. Different sperm concentrations and times of incubation were evaluated and found that 2 million spermatozoa and 1-h incubation yielded high binding index (BI). The BI was also significantly (P < 0.01) higher (>2 times) in the bulls with low-DFI% as compared to high DFI% bulls. The correlation between binding index and DFI% was negative and significant (r = -0.528; P < 0.05). Further, the binding index was positively correlated with conception rate (r = 0.703), intact sperm membrane (r = 0.631) and mitochondrial membrane potential (r = 0.609). It is inferred that sperm phenotypic characteristics and oviduct binding ability are impaired in breeding bulls with high sperm DFI%, which might be associated with low conception rates in these bulls.

Anatomical and cellular heterogeneity in the mouse oviduct-its potential roles in reproduction and preimplantation development†

The oviduct/fallopian tube is a tube-like structure that extends from the uterus to the ovary. It is an essential reproductive organ that provides an environment for internal fertilization and preimplantation development. However, our knowledge of its regional and cellular heterogeneity is still limited. Here, we examined the anatomical complexity of mouse oviducts using modern imaging techniques and fluorescence reporter lines. We found that there are consistent coiling patterns and turning points in the coiled mouse oviduct that serve as reliable landmarks for luminal morphological regionalities. We also found previously unrecognized anatomical structures in the isthmus and uterotubal junction, which likely play roles in reproduction. Furthermore, we demarcated the ampulla-isthmus junction as a distinct region. Taken together, the oviduct mucosal epithelium has highly diverse structures with distinct epithelial cell populations, reflecting its complex functions in reproduction.

Sperm interactions with the female reproductive tract: A key for successful fertilization in mammals

Sperm migration through the female genital tract is not a quiet journey. Uterine contractions quickly operate a drastic selection, leading to a very restrictive number of sperm reaching the top of uterine horns and finally, provided the presence of key molecules on sperm, the oviduct, where fertilization takes place. During hours and sometimes days before fertilization, subpopulations of spermatozoa interact with dynamic and region-specific maternal components, including soluble proteins, extracellular vesicles and epithelial cells lining the lumen of the female tract. Interactions with uterine and oviductal cells play important roles for sperm survival as they modulate the maternal immune response and allow a transient storage before ovulation. The body of work reported here highlights the importance of sperm interactions with proteins originated from both the uterine and oviductal fluids, as well as hormonal signals around the time of ovulation for sperm acquisition of fertilizing competence.

Toll-like receptor 2 mediates the immune response of the bovine oviductal ampulla to sperm binding

We previously reported that sperm binding to cultured bovine oviduct epithelial cells induces an anti-inflammatory immune response. Now we have developed a differentiated explant model to focus on the oviductal ampulla, where fertilization occurs, and to study the effect of sperm capacitation on the immune response. We used heparin to stimulate bovine sperm capacitation. Fluorescence imaging showed that 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide-labeled sperm pretreated with (Hep⁽⁺⁾ ) or without (Hep^{( -)} ) heparin rapidly attached to the explant ciliated epithelium in similar numbers. However, only Hep⁽⁺⁾ sperm upregulated explant messenger RNA (mRNA) transcription of TLR2, IL8, TGFB1, and PGES, without changes in TNFA and IL-10 expression, while Hep^{( -)} sperm only upregulated PGES. The responses were primarily anti-inflammatory, with a greater response produced by Hep⁽⁺⁾ sperm, which also produced a substantial increase in TLR2 protein expression in the epithelium. The addition of TLR1/2 (toll-like receptor 1/2) antagonist to the Hep⁽⁺⁾ and (Hep^{( -)} ) sperm-explant coincubations reduced sperm attachment to the epithelium and inhibited TLR2 protein expression and some of the Hep⁽⁺⁾ sperm-induced mRNA transcription. Our observations suggest that the ampullar epithelium immunologically reacts more strongly to sperm that have undergone heparin stimulation of capacitation. This anti-inflammatory response could serve to protect capacitated sperm as they approach the oocyte in the ampulla.

Sulfated Lewis A trisaccharide on oviduct membrane glycoproteins binds bovine sperm and lengthens sperm lifespan

A fraction of sperm deposited at mating or insemination reaches the oviduct isthmus, where sperm are retained and thereby form a reservoir. This reservoir delays capacitation, prevents polyspermy, selects a fertile population of sperm, and, foremost, increases sperm lifespan. The molecular interactions underlying the formation of a sperm reservoir are becoming clearer in mammals. Sperm lectins bind to oviductal glycans to form the reservoir. Herein, we found that the highest percentage of bovine sperm bound to the 3'-O-sulfated form of Lewis A (suLe^A) trisaccharide and sialylated Lewis A and that fluoresceinated versions of each localized to receptors on the anterior head of the sperm. Following capacitation, binding to suLe^A decreased significantly, a potential explanation for sperm release from the reservoir. MS and immunohistochemistry analyses indicated that suLe^A motifs were present predominantly on O-linked glycans initiated by GalNAc residues, but no sialylated Lewis A was detected. To determine whether sperm binding to isolated suLe^A in vitro could mimic in vivo sperm binding to oviduct cells and increase sperm longevity, we immobilized suLe^A and incubated it with sperm. Using free-swimming sperm and sperm bound to immobilized laminin as controls, we observed that over 96 h, the viability of free-swimming sperm decreased to 10%, and that of sperm bound to immobilized laminin decreased to about 50%, whereas viability of sperm bound to immobilized suLe^A was highest throughout the incubation and 60% at 96 h. These results indicate that bovine sperm binding to oviduct suLe^A retains sperm for reservoir formation and extends sperm lifespan.

Interaction of different Chlamydiae species with bovine spermatozoa

Background

Interaction of spermatozoa and Chlamydiae spp. might contribute to reduced fertility in cattle. To proof this hypothesis, bovine semen was incubated with viable or heat inactivated Chlamydia (C.) abortus or psittaci (Multiplicity of infection = 1) and sperm motility was monitored with a computer-assisted sperm analyzer over 24 h. Additionally, the interaction with the spermatozoa was further investigated by means of light and transmission electron microscopy (TEM).

Results

Only viable Chlamydiae of both species decreased sperm motility and this only after about 9 h. Taking binding rates into account, the loss of sperm motility after about 9 h could likely be a consequence of Chlamydiae attachment to the spermatozoa. About two thirds of the Chlamydiae elementary bodies were bound to the front third of the sperm, the acrosomal region. No inclusions of Chlamydiae in spermatozoa were observed in TEM after 2 h co-incubation.

Conclusions

As initial motility was not affected following co-incubation of viable Chlamydiae and bovine sperm, it seems likely that sperm could serve as a carrier/vehicle for Chlamydiae facilitating cervical passage of Chlamydiae spp. in cattle. Additionally, our results suggest that spermatozoa carrying Chlamydiae may have no initial disadvantage in reaching the oviduct, but are immotile at the time of ovulation what might have an impact on fertilization capacities of the individual sperm. Consequently, high concentrations of the investigated Chlamydiae in the seminal plasma or female genital tract might play a role in reduced fertility in cattle.

Sperm functional attributes and oviduct explant binding capacity differs between bulls with different fertility ratings in the water buffalo (Bubalus bubalis)

We report here the differences in sperm functional attributes and sperm–oviduct binding index in bulls with different field fertility ratings. Cryopreserved spermatozoa from Murrah buffalo bulls (n=9) with different fertility ratings were evaluated for membrane integrity, capacitation status, acrosome intactness and protein tyrosine phosphorylation status. Frozen­–thawed spermatozoa were incubated with oviduct explants for 1h under 5% CO2, 38.5°C with 95% relative humidity and the number of spermatozoa bound to the unit area of oviduct explants (binding index; BI) was assessed using 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolyl-carbocyanine iodide (JC-1) fluorescent staining. The proportion of membrane-intact and acrosome-intact spermatozoa was significantly (P&lt;0.05) higher and the proportion of capacitated spermatozoa was significantly (P&lt;0.05) lower in high-fertile bulls compared with medium- and low-fertile bulls. The relationship between BI and bull fertility was significant and positive (r=0.69; P=0.04). BI was negatively and significantly (r=−0.83; P=0.01) related to membrane-compromised spermatozoa. It was concluded that the sperm–oviduct explant binding index was positively related to (1) the proportion of membrane-intact spermatozoa in a given semen sample and (2) invivo fertility of the buffalo bull, indicating the possibility of developing a fertility prediction tool using a sperm–oviduct explant binding model, once validated on a greater number of bulls.

Progesterone induces the release of bull spermatozoa from oviductal epithelial cells

The mechanism that causes the detachment of spermatozoa from the oviductal reservoir around the time of ovulation remains to be elucidated. Because the cumulus cells of the bovine oocyte are known to secrete progesterone (P4), and P4 has been shown to act upon cation channels of spermatozoa (CatSper) in human spermatozoa, it was hypothesised that P4 could induce hyperactivation due to an influx of extracellular calcium, and this would facilitate detachment of spermatozoa from oviductal epithelial cells. Therefore, this study aimed to investigate the role and mechanism of action of P4 in the release of spermatozoa from bovine oviduct epithelial cells (BOEC). Initial dose–response assessments on sperm hyperactivation determined the optimum concentration of P4 (10 nM), mibefradil (a non-specific Ca2+ channel antagonist; 5µM), NNC 55-0396 dihydrochloride (NNC; a CatSper antagonist; 2µM), mifepristone (a classical and membrane P4 receptor antagonist; 400nM) and AG205 (a membrane P4 receptor antagonist; 10μM). BOEC explants were incubated with frozen–thawed bovine spermatozoa for 30min, following which loosely bound spermatozoa were removed. Two experiments were completed. In Experiment 1, BOECs were treated for 30min with either no treatment, P4, NNC, mibefradil, P4+mibefradil, P4+NNC, P4+mibefradil+NNC or P4+EGTA. In Experiment 2, BOECs were treated for 30min with either no treatment, P4, mifepristone, AG205, mifepristone+AG205, P4+mifepristone, P4+AG205 or P4+mifepristone+AG205. The number of spermatozoa remaining bound per millimetre squared of BOEC explant was determined. Progesterone stimulated the release of bound spermatozoa from BOEC explants, whereas NNC, mibefradil and EGTA inhibited this release. The release of spermatozoa by P4 was inhibited in the presence of both mifepristone and AG205, whereas the combination of both had the greatest inhibitory action on P4 release of spermatozoa. These findings suggest the presence of a P4 membrane receptor on bovine spermatozoa and that P4-induced release of spermatozoa from BOECs is likely mediated by extracellular Ca2+.

Can the antral follicular count modulate the gene expression of bovine oviducts in Aberdeen Angus and Nelore heifers?

The number of visible ovarian antral follicles (antral follicle count—AFC) is repeatable in bovine individuals, but highly variable between animals, and with differences between Bos taurus and Bos indicus breeds. Several studies have tried to determine the correlation between AFC and increased fertility in cattle. While the impacts of AFC on embryo production, hormonal levels, and pregnancy rates have been described, the molecular effects of AFC on bovine oviducts have not yet been investigated. Here, the aim was to investigate the impact of breeds, such as Aberdeen Angus and Nelore heifer with high or low AFC, on abundance of transcripts and protein related to oviductal transport, sperm reservoir formation, monospermy control, and gamete interaction in the oviducts. In summary, the ovulation side was the major factor that affected transcript abundance on bovine oviducts. However, a discreet effect among AFC and cattle breeds was also observed. Based on this, we concluded and reinforced here that differential microenvironments between ipsilateral and contralateral oviducts have a major effect on modulating the transcripts related to oviductal transport, sperm reservoir formation, monospermy control, and gamete interaction. However, we cannot exclude that there is minimal effect of AFC or breed on regulation of some genes (such as AGTR1, ACE1, FUCA1, and VEGFA) in bovine oviducts.

Endoscopy-mediated intratubal insemination in the cow - Development of a novel minimally invasive AI technique

Conventionally inseminated spermatozoa suffer a dramatic reduction in numbers during their long journey until fertilization. In addition sperm survival seems to be strongly affected by the reconstitution of the female reproductive tract in the post partum period. The purpose of this study was to develop a novel AI technique for cattle that allows the deposition of spermatozoa directly into the ampulla in the immediate vicinity of the fertilization site. This new reproductive biotechnique was investigated with focus on semen origin, sperm dosage, semen preparation and time of insemination. Finally, a first practical application was carried out by inseminating superovulated heifers with sex-sorted semen. In total, 49 Simmental heifers were used for 65 intratubal inseminations (ITI) with single ovulation and 8 ITIs after superovulation, respectively. Insemination into the oviduct was performed under epidural anesthesia via transvaginal endoscopy using a curved glass capillary loaded with semen. Two days later the oviduct and the adjacent uterine horn were endoscopically flushed and embryos or unfertilized oocytes were collected for determination of fertilization success. Across all experimental groups, tubal insemination successfully resulted in the collection of embryos; however, first tubal AI attempts and ITIs close to ovulation led to low recovery rates. In total, 109 complexes were flushed from ITIs in superstimulated heifers (n = 8) using sex sorted semen, of which 24 (22%) were at the embryo stage. In conclusion, it was shown that intratubal insemination can be successfully used for semen deposition, thus bypassing the lower female genital tract. Factors such as time of insemination, semen processing and semen quantity for superovulatory use should be further investigated.

Review: The epic journey of sperm through the female reproductive tract

Millions or billions of sperm are deposited by artificial insemination or natural mating into the cow reproductive tract but only a few arrive at the site of fertilization and only one fertilizes an oocyte. The remarkable journey that successful sperm take to reach an oocyte is long and tortuous, and includes movement through viscous fluid, avoiding dead ends and hostile immune cells. The privileged collection of sperm that complete this journey must pass selection steps in the vagina, cervix, uterus, utero-tubal junction and oviduct. In many locations in the female reproductive tract, sperm interact with the epithelium and the luminal fluid, which can affect sperm motility and function. Sperm must also be tolerated by the immune system of the female for an adequate time to allow fertilization to occur. This review emphasizes literature about cattle but also includes work in other species that emphasizes critical broad concepts. Although all parts of the female reproductive tract are reviewed, particular attention is given to the sperm destination, the oviduct.

Recombinant β-defensin 126 promotes bull sperm binding to bovine oviductal epithelia

Primate β-defensin 126 regulates the ability of spermatozoa to bind to oviductal epithelial cells in vitro. Bovine β-defensin 126 (BBD126) exhibits preferential expression in the cauda epididymis of the bull, but there have been few studies on its functional role in cattle. The aim of the present study was to examine the role of BBD126 in bull sperm binding to bovine oviductal epithelial cell (BOEC) explants. BBD126 has been shown to be highly resistant to the standard methods of dissociation used in other species and, as a result, corpus epididymal spermatozoa, which have not been exposed to the protein, were used to study the functional role of BBD126. Corpus epididymal spermatozoa were incubated with recombinant (r) BBD126 in the absence or presence of anti-BBD126 antibody. Addition of rBBD126 significantly enhanced the ability of epididymal spermatozoa to bind to BOEC explants (P < 0.05). Anti-BBD126 antibody blocked the BBD126-mediated increase in sperm binding capacity. Ejaculated spermatozoa, which are coated with native BBD126 protein but also a large number of seminal plasma proteins in vivo, were incubated with rBBD126 in the absence or presence of the anti-BBD126 antibody. Addition of rBBD126 significantly enhanced the ability of ejaculated spermatozoa to bind to BOEC explants (P < 0.05), whereas rBBD126 also reduced corpus sperm agglutination (P < 0.05). These results suggest that, similar to the role of its analogue in the macaque, spermatozoa with more BBD126 in their acrosome may represent spermatozoa with more oviduct binding capacity.

Steroid hormones regulate sperm-oviduct interactions in the bovine

After insemination in the cow, a sperm reservoir is formed within the oviducts, allowing the storage and then progressive release of spermatozoa toward the ovulated oocyte. In order to investigate the hormonal regulation of these events in vitro, the ovarian steroids 17β-estradiol (E2) and progesterone (P4) were added at various concentrations to monolayers of bovine oviduct epithelial cells (BOEC) before or during co-incubation with spermatozoa. Main findings demonstrate that (1) a 18-h pretreatment of BOEC with 100 pg/mL and 100 ng/mL of E2 decreased by 25% the ability of BOEC to bind spermatozoa after 10 min, and for the highest dose of E2, 60 min of co-incubation; (2) P4 at concentrations of 10, 100 and 1000 ng/mL induced the release within 60 min of 32-47% of bound spermatozoa from BOEC; this sperm-releasing effect was maintained after a 18-h pretreatment of BOEC with 100 pg/mL of E2; (3) E2 in concentrations above 100 pg/mL inhibited the releasing effect of P4 on bound sperm in a dose-dependent manner; (4) spermatozoa bound to BOEC, then released from BOEC by the action of P4-induced higher cleavage and blastocyst rates after in vitro fertilization than the control group. These results support the hypothesis that the dynamic changes in steroid hormones around the time of ovulation regulate the formation of the sperm reservoir and the timed delivery of capacitated spermatozoa to the site of fertilization.

The development and functions of multiciliated epithelia

Multiciliated cells are epithelial cells that are in contact with bodily fluids and are required for the proper function of major organs including the brain, the respiratory system and the reproductive tracts. Their multiple motile cilia beat unidirectionally to remove particles of external origin from their surface and/or drive cells or fluids into the lumen of the organs. Multiciliated cells in the brain are produced once, almost exclusively during embryonic development, whereas in respiratory tracts and oviducts they regenerate throughout life. In this Review, we provide a cell-to-organ overview of multiciliated cells and highlight recent studies that have greatly increased our understanding of the mechanisms driving the development and function of these cells in vertebrates. We discuss cell fate determination and differentiation of multiciliated cells, and provide a comprehensive account of their locations and functions in mammals.

Microfluidic devices for the study of sperm migration

Microfluidics technology offers us an opportunity to model the biophysical and biochemical environments encountered by sperm moving through the female reproductive tract and, at the same time, to study sperm swimming dynamics at a quantitative level. In humans, coitus results in the deposition of sperm in the vagina at the entrance to the cervix. Consequently, sperm must swim or be drawn through the cervix, uterus, uterotubal junction and oviductal isthmus to reach the oocyte in the oviductal ampulla. Only a very small percentage of inseminated sperm reach the ampulla in the periovulatory period, indicating that strong selection pressures act on sperm during migration. A better understanding of how sperm interact with the female tract would inspire improvements in diagnosis of fertility problems and development of novel-assisted reproductive technologies that minimize damage to sperm and mimic natural selection pressures on sperm.

Dynamics of Bovine Sperm Interaction with Epithelium Differ Between Oviductal Isthmus and Ampulla

In mammals, many sperm that reach the oviduct are held in a reservoir by binding to epithelium. To leave the reservoir, sperm detach from the epithelium; however, they may bind and detach again as they ascend into the ampulla toward oocytes. In order to elucidate the nature of binding interactions along the oviduct, we compared the effects of bursts of strong fluid flow (as would be caused by oviductal contractions), heparin, and hyperactivation on detachment of bovine sperm bound in vitro to epithelium on intact folds of isthmic and ampullar mucosa. Intact folds of oviductal mucosa were used to represent the strong attachments of epithelial cells to each other and to underlying connective tissue that exist in vivo. Effects of heparin on binding were tested because heparin binds to the Binder of SPerm (BSP) proteins that attach sperm to oviductal epithelium. Sperm bound by their heads to beating cilia on both isthmic and ampullar epithelia and could not be detached by strong bursts of fluid flow. Addition of heparin immediately detached sperm from isthmic epithelium but not ampullar epithelium. Addition of 4-aminopyridine immediately stimulated hyperactivation of sperm but did not detach them from isthmic or ampullar epithelium unless added with heparin. These observations indicate that the nature of binding of sperm to ampullar epithelium differs from that of binding to isthmic epithelium; specifically, sperm bound to isthmic epithelium can be detached by heparin alone, while sperm bound to ampullar epithelium requires both heparin and hyperactivation to detach from the epithelium.

The porcine sperm reservoir in relation to the function of hyaluronan

The oviduct plays a role in successful animal reproduction not only in spermatozoa and ova transport to the fertilization site but also by affording a microenvironment for fertilization and early embryonic development. The sperm reservoir (SR) is restricted in the uterotubal junction (UTJ) and caudal isthmus. Billions of porcine spermatozoa are distributed to the female reproductive tract during/after insemination, and small amounts of them are stored for about 36–40 hours in the SR, which maintains sperm viability in the pre-ovulation period through its surface epithelium and production of fluid. The SR regulates the release of spermatozoa so that only a small population moves towards the fertilization site (ampulla) to decrease polyspermy. This review attempts to provide information about the structure and function of the porcine SR, its intraluminal content (hyaluronan, HA), and the influences of HA on porcine spermatozoa in vivo. In pigs, the spermatozoa are stored in a mucous-like fluid within the UTJ and caudal isthmus in the pre-ovulation period. The oviduct fluid contains sulfated glycosaminoglycans (GAGs) and non-sulfated GAGs, i.e., HA. It is interesting to note that HA is synthesized by hyaluronan synthase-3 (HAS-3), and its receptor, CD44, is found in the epithelium of the porcine SR site. Additionally, sperm capacitation does not occur in vivo in the SR during the pre- and peri-ovulation periods, but spermatozoa in the SR will attempt to capacitate if exposed to bicarbonate. However, capacitation in the SR will rise in the post-ovulation period, indicating the role of HA in modulating sperm capacitation after ovulation. All data support the understanding that the porcine SR ensures the viability of fertile spermatozoa and maintains the non-capacitated status during the pre-ovulation period. This basic knowledge about the SR is believed to be useful to advance sperm preparation procedures for in vitro fertilization (IVF) and improve the preservation process of porcine semen.

Combined albumin and bicarbonate induces head-to-head sperm agglutination which physically prevents equine sperm–oviduct binding

In many species, sperm binding to oviduct epithelium is believed to be an essential step in generating a highly fertile capacitated sperm population primed for fertilization. In several mammalian species, this interaction is based on carbohydrate-lectin recognition.d-galactose has previously been characterized as a key molecule that facilitates sperm–oviduct binding in the horse. We used oviduct explant and oviduct apical plasma membrane (APM) assays to investigate the effects of various carbohydrates; glycosaminoglycans; lectins; S-S reductants; and the capacitating factors albumin, Ca2+and HCO3−on sperm–oviduct binding in the horse. Carbohydrate-specific lectin staining indicated thatN-acetylgalactosamine,N-acetylneuraminic acid (sialic acid) andd-mannose ord-glucose were the most abundant carbohydrates on equine oviduct epithelia, whereasd-galactose moieties were not detected. However, in a competitive binding assay, sperm–oviduct binding density was not influenced by any tested carbohydrates, glycosaminoglycans, lectins ord-penicillamine, nor did the glycosaminoglycans induce sperm tail-associated protein tyrosine phosphorylation. Furthermore,N-glycosidase F (PNGase) pretreatment of oviduct explants and APM did not alter sperm–oviduct binding density. By contrast, a combination of the sperm-capacitating factors albumin and HCO3−severely reduced (>10-fold) equine sperm–oviduct binding density by inducing rapid head-to-head agglutination, both of which events were independent of Ca2+and an elevated pH (7.9). Conversely, neither albumin and HCO3−nor any other capacitating factor could induce release of oviduct-bound sperm. In conclusion, a combination of albumin and HCO3−markedly induced sperm head-to-head agglutination which physically prevented stallion sperm to bind to oviduct epithelium.

Expression and function of transient receptor potential channels in the female bovine reproductive tract

The epithelium lining the oviduct is critical for early reproductive events, many of which are mediated via intracellular calcium ions. Despite this, little is known about the regulation of calcium homeostasis in the oviductal epithelium. Epithelial transient receptor potential channels (TRPCs) modulate calcium flux in other tissues, and their expression and functional regulation have therefore been examined using the bovine oviduct as a model for the human. The effects of FSH, LH, 17β-estradiol, and progesterone on TRPCs expression and intracellular calcium flux were determined. Transient receptor potential channels 1, 2, 3, 4, and 6 were expressed in the bovine reproductive tract, and their gene expression varied throughout the estrous cycle. In more detailed studies undertaken on TRPC1 and 6, we show that protein expression varied through the estrus cycle; specifically, 17β-estradiol, FSH, and LH individually and in combination upregulated TRPC1 and 6 expression in cultured bovine oviduct epithelial cells although progesterone antagonized these effects. Functional studies showed changes in calcium mobilization in bovine oviduct epithelial cells were dependent on TRPCs. In conclusion, TRPC1, 2, 3, 4, and 6 are present in the epithelium lining the bovine oviduct, and TRPC1 and 6 vary through the estrous cycle suggesting an important role in early reproductive function.

Mammalian sperm interactions with the female reproductive tract

The mammalian female reproductive tract interacts with sperm in various ways in order to facilitate sperm migration to the egg while impeding migrations of pathogens into the tract, to keep sperm alive during the time between mating and ovulation, and to select the fittest sperm for fertilization. The two main types of interactions are physical and molecular. Physical interactions include the swimming responses of sperm to the microarchitecture of walls, to fluid flows, and to fluid viscoelasticity. When sperm encounter walls, they have a strong tendency to remain swimming along them. Sperm will also orient their swimming into gentle fluid flows. The female tract seems to use these tendencies of sperm to guide them to the site of fertilization. When sperm hyperactivate, they are better able to penetrate highly viscoelastic media, such as the cumulus matrix surrounding eggs. Molecular interactions include communications of sperm surface molecules with receptors on the epithelial lining of the tract. There is evidence that specific sperm surface molecules are required to enable sperm to pass through the uterotubal junction into the oviduct. When sperm reach the oviduct, most bind to the oviductal epithelium. This interaction holds sperm in a storage reservoir until ovulation and serves to maintain the fertilization competence of stored sperm. When sperm are released from the reservoir, they detach from and re-attach to the epithelium repeatedly while ascending to the site of fertilization. We are only beginning to understand the communications that may pass between sperm and epithelium during these interactions.

LewisX-containing glycans on the porcine oviductal epithelium contribute to formation of the sperm reservoir

In many mammals, after semen deposition, a subpopulation of the sperm is transported to the lower oviduct, or isthmus, to form a functional sperm reservoir that provides sperm to fertilize oocytes. The precise molecular interactions that allow formation of this reservoir are unclear. It is proposed that binding of sperm receptors (lectins) to their oviductal cell ligands is accomplished by glycans. Previous results indicated that Lewis trisaccharides are present in glycosphingolipids and O- and N-linked glycans of the porcine isthmus and that Le(X)-containing molecules bind porcine sperm. Immunohistochemistry indicated that the Lewis structures identified by mass spectrometry were, in fact, Lewis X (Le(X)) trisaccharides. These motifs were localized to the luminal border of the isthmus. Assays using fluoresceinated glycans showed that 3-O-sulfated Le(X) (suLe(X)) bound to receptors localized on the head of nearly 60% of uncapacitated boar sperm but that the positional isomer 3-O-sulfo-Le(A) (suLe(A)) bound to <5% of sperm. Sperm also bound preferentially to suLe(X) made insoluble by coupling to beads. Capacitation reduced the ability of suLe(X) to bind sperm to <10%, perhaps helping to explain why sperm are released at capacitation. Pretreatment of oviduct cell aggregates with the Le(X) antibody blocked 57% of sperm binding to isthmic aggregates. Blocking putative receptors on sperm with soluble Le(X) and suLe(X) glycans specifically reduced sperm binding to oviduct cells up to 61%. These results demonstrate that the oviduct isthmus contains Le(X)-related moieties and that sperm binding to these oviduct glycans is necessary and sufficient for forming the sperm reservoir.

A novel subclass of bovine β-defensins links reproduction and immunology

β-defensins are effector molecules of the innate immune system, found in many diverse species. Their presence in invertebrates as well as vertebrates suggests highly conserved functional roles. Most β-defensins are believed to act as antimicrobial agents at epithelial surfaces, although additional functions have also been described, including immune regulatory activity, wound repair and a role in coat-colour determination. High expression of β-defensins have been found in testis and epididymidal epithelium as well as in the seminal fluid of humans, macaque, rat, mouse and cow. Human and macaque β-defensins have recently been shown to affect sperm motility while a mutation in β-defensin 126 is associated with reduced fertility in men. Genetic variation in bovine defensin genes may explain the increased incidence of low fertility in cattle. Here, we present a summary of the known functions of β-defensins as well as their emerging role in reproduction and their potential to improve fertility in cattle.

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.

Storage and release of spermatozoa from the pre-uterine tube reservoir

In mammals, after coitus a small number of spermatozoa enter the uterine tube and following attachment to uterine tube epithelium are arrested in a non-capacitated state until peri-ovulatory signalling induces their detachment. Whilst awaiting release low numbers of spermatozoa continually detach from the epithelium and the uterine tube reservoir risks depletion. There is evidence of attachment of spermatozoa to uterine epithelium in several species which might form a potential pre-uterine tube reservoir. In this study we demonstrate that: (1) dog spermatozoa attach to uterine epithelium and maintain flagellar activity, (2) in non-capacitating conditions spermatozoa progressively detach with a variety of motility characteristics, (3) attachment is not influenced by epithelial changes occurring around ovulation, (4) attachment to uterine epithelium slows capacitation, (5) capacitated spermatozoa have reduced ability to attach to uterine epithelium, (6) under capacitating conditions increased numbers of spermatozoa detach and exhibit transitional and hyperactive motility which differ to those seen in non-capacitating conditions, (7) detachment of spermatozoa and motility changes can be induced by post-ovulation but not pre-ovulation uterine tube flush fluid and by components of follicular fluid and solubilised zona pellucida, (8) prolonged culture does not change the nature of the progressive detachment seen in non-capacitating conditions nor the potential for increased detachment in capacitating conditions. We postulate that in some species binding of spermatozoa to uterine epithelium is an important component of the transport of spermatozoa. Before ovulation low numbers of spermatozoa continually detach, including those which are non-capacitated with fast forward progressive motility allowing the re-population of the uterine tube, whilst around the time of ovulation, signalling from as-yet unknown factors associated with follicular fluid, oocytes and uterine tube secretion promotes the detachment of large numbers of capacitated spermatozoa with hyperactive motility that may contribute to the fertilising pool.

Roles of the oviduct in mammalian fertilization

The oviduct or Fallopian tube is the anatomical region where every new life begins in mammalian species. After a long journey, the spermatozoa meet the oocyte in the specific site of the oviduct named ampulla and fertilization takes place. The successful fertilization depends on several biological processes that occur in the oviduct some hours before this rendezvous and affect both gametes. Estrogen and progesterone, released from the ovary, orchestrate a series of changes by genomic and nongenomic pathways in the oviductal epithelium affecting gene expression, proteome, and secretion of its cells into the fluid bathing the oviductal lumen. In addition, new regulatory molecules are being discovered playing important roles in oviductal physiology and fertilization. The present review tries to describe these processes, building a comprehensive map of the physiology of the oviduct, to better understand the importance of this organ in reproduction. With this purpose, gamete transport, sperm and oocyte changes in the oviductal environment, and other interactions between gametes and oviduct are discussed in light of recent publications in the field.

Expression of nuclear progesterone receptor and progesterone receptor membrane components 1 and 2 in the oviduct of cyclic and pregnant cows during the post-ovulation period

BACKGROUND

Progesterone (P4) may modulate oviductal functions to promote early embryo development in cattle. In addition to its nuclear receptor (PR), P4 may mediate its actions through P4 receptor membrane component 1 (PGRMC1) and its relative, PGRMC2. Two successive experiments were undertaken to characterise the expression of PR, PGRMC1 and PGRMC2 in the bovine oviduct during the post-ovulation period, and to relate their expression to the presence of an embryo, the proximity of the CL and to the region of the oviduct.

METHODS

In the first experiment (Exp. I), whole oviduct sections were collected from Holstein cows at Day 1.5, Day 4 and Day 5 post-ovulation (n = 2 cows per stage). The expression of PR, PGRMC1 and PGRMC2 was studied in the ampulla and isthmus by RT-PCR, western-blot and immunohistochemistry. In Exp. II, oviduct epithelial cells were collected from cyclic and pregnant Charolais cows (n = 4 cows per status) at Day 3.5 post-ovulation and mRNA expression of PR, PGRMC1 and PGRMC2 was examined in the ampulla and isthmus by real-time quantitative PCR.

RESULTS

In Exp. I, PR, PGRMC1 and PGRMC2 were expressed in all oviduct samples. PGRMC1 was mainly localised in the luminal epithelium whereas PR and PGRMC2 were localised in the epithelium as well as in the muscle and stroma layers of the oviduct. The expression was primarily nuclear for PR, primarily cytoplasmic for PGRMC1 and both nuclear and cytoplasmic for PGRMC2. In Exp. II, mRNA levels for PR, PGRMC1 and PGRMC2 were not affected by either the pregnancy status or the side relative to the CL. However, the expression of PR and PGRMC2 varied significantly with the region of the oviduct: PR was more highly expressed in the isthmus whereas PGRMC2 was more highly expressed in the ampulla.

CONCLUSIONS

This is the first evidence of PGRMC2 expression in the bovine oviduct. Our findings suggest that P4 regulates the functions of the bovine oviduct in a region-specific manner and through both classical and non classical pathways during the post-ovulation period.

In vivo and in vitro sperm interaction with oviductal epithelial cells of llama

Sperm reservoirs in South American Camelids would be crucial for successful fertilization. Since ovulation occurs approximately 36 h after mating, the maintenance of the sperm viability in the oviduct waiting for the ovum is a critical reproductive event. Our study aimed at determining whether the isthmus or the utero tubal junction (UTJ) could function as a sperm reservoir in llama by means of in vivo and in vitro experiments. For the in vivo experiments, the oviducts of adult females with a dominant follicle bigger than 7 mm were examined for the presence of sperm at 6, 18, 24, 28 and 35 h after mating. The results using scanning and transmission electron microscopy showed ultrastructural differences between isthmus and UTJ with respect to (1) predominance of secretory cells in the UTJ and ciliated cells in the isthmus epithelium and (2) cytoplasmic bulbous projection of the secretory cells in the UTJ. Sperm adhered by a mucus-like substance were seen only in the UTJ at 6, 18, 24 and 28 h postmating. Lack of sperm adhered to oviductal mucosa was observed around ovulation (35 h). In vitro experiments demonstrated higher ability of UTJ epithelial cell explants with respect to isthmus explants to bind sperm in a co-cultured system. The anatomical features and the presence of a sperm bonding agent in the UTJ together with the in vitro differential binding of sperm to UTJ explants strongly suggest that both may be feasible mechanisms that facilitate sperm storage in this oviductal region in llama.

In vitro systems for intercepting early embryo-maternal cross-talk in the bovine oviduct

A comprehensive understanding of the complex embryo-maternal interactions during the preimplantation period requires the analysis of very early stages of pregnancy. These are difficult to assess in vivo due to the small size of the embryo exerting local paracrine effects. Specifically designed experiments and holistic transcriptome and proteome analyses to address the early embryo-maternal cross-talk in the oviduct require sufficient numbers of well-defined cells in a standardized experimental environment. The pronounced estrous cycle-dependent changes in gene expression and morphology of bovine oviduct epithelial cells (BOECs) clearly show that a precise definition of the stage of estrous cycle is essential for obtaining a well-defined homogenous population of functional cells. The number of intact cells isolated from individual ampullae by solely mechanical means was 10-fold higher than previously reported cell yields after enzymatic treatment, and the purity was comparable. Bovine oviduct epithelial cells have been cultured as monolayers or in suspension. Proliferating cells grown in monolayers dedifferentiated, with a concomitant loss of important morphologic characteristics. After several days in culture, BOECs in monolayers are less likely to mimic the oviduct environment in vivo than BOEC vesicles formed of epithelial sheets in short-term suspension culture. A 24-h culture system for BOECs isolated on Day 3.5 of the estrous cycle showed excellent preservation of morphologic criteria, marker gene expression, and hormone responsiveness. The short-term BOEC culture system provides well-defined and functional BOECs in sufficient quantities for studies of early embryo-maternal interactions in experiments that mimic the environment in the oviduct in vivo.

The endocannabinoid system in bull sperm and bovine oviductal epithelium: role of anandamide in sperm–oviduct interaction

Anandamide binds to cannabinoid receptors and plays several central and peripheral functions. The aim of this work was to study the possible role for this endocannabinoid in controlling sperm–oviduct interaction in mammals. We observed that bull sperm and bovine oviductal epithelial cells express cannabinoid receptors, CB1 and CB2, and fatty acid amide hydrolase, the enzyme that controls intracellular anandamide levels. A quantitative assay to determine whether anandamide was involved in bovine sperm–oviduct interaction was developed. R(+)-methanandamide, a non-hydrolysable anandamide analog, inhibited sperm binding to and induced sperm release from oviductal epithelia. Selective CB1 antagonists (SR141716A or AM251) completely blocked R(+)-methanandamide effects. However, SR144528, a selective CB2 antagonist, did not exert any effect, indicating that only CB1 was involved in R(+)-methanandamide effect. This effect was not caused by inhibition of the sperm progressive motility or by induction of the acrosome reaction. Overall, our findings indicate for the first time that the endocannabinoid system is present in bovine sperm and oviductal epithelium and that anandamide modulates the sperm–oviduct interaction, by inhibition of sperm binding and induction of sperm release from oviductal epithelial cells, probably by activating CB1 receptors.