Inhibition of in vitro fertilization by a monoclonal antibody reacting with the zona pellucida of the oviductal egg but not with that of the ovarian egg of the golden hamster

The fluid factor OVGP1 provides a significant oviductal microenvironment for the reproductive process in golden hamster†

The mammalian oviductal lumen is a specialized chamber that provides an environment that strictly regulates fertilization and early embryogenesis, but the regulatory mechanisms to gametes and zygotes are unclear. We evaluated the oviductal regulation of early embryonic development using Ovgp1 (encoding an oviductal humoral factor, OVGP1)-knockout golden hamsters. The experimental results revealed the following: (1) female Ovgp1-knockout hamsters failed to produce litters; (2) in the oviducts of Ovgp1-knockout animals, fertilized eggs were sometimes identified, but their morphology showed abnormal features; (3) the number of implantations in the Ovgp1-knockout females was low; (4) even if implantations occurred, the embryos developed abnormally and eventually died; and (5) Ovgp1-knockout female ovaries transferred to wild-type females resulted in the production of Ovgp1-knockout egg-derived OVGP1-null litters, but the reverse experiment did not. These results suggest that OVGP1-mediated physiological events are crucial for reproductive process in vivo, from fertilization to early embryonic development. This animal model shows that the fate of the zygote is determined not only genetically, but also by the surrounding oviductal microenvironment.

New Insights into the Mammalian Egg Zona Pellucida

Mammalian oocytes are surrounded by an extracellular coat called the zona pellucida (ZP), which, from an evolutionary point of view, is the most ancient of the coats that envelope vertebrate oocytes and conceptuses. This matrix separates the oocyte from cumulus cells and is responsible for species-specific recognition between gametes, preventing polyspermy and protecting the preimplantation embryo. The ZP is a dynamic structure that shows different properties before and after fertilization. Until very recently, mammalian ZP was believed to be composed of only three glycoproteins, ZP1, ZP2 and ZP3, as first described in mouse. However, studies have revealed that this composition is not necessarily applicable to other mammals. Such differences can be explained by an analysis of the molecular evolution of the ZP gene family, during which ZP genes have suffered pseudogenization and duplication events that have resulted in differing models of ZP protein composition. The many discoveries made in recent years related to ZP composition and evolution suggest that a compilation would be useful. Moreover, this review analyses ZP biosynthesis, the role of each ZP protein in different mammalian species and how these proteins may interact among themselves and with other proteins present in the oviductal lumen.

Oviductal secretions: will they be key factors for the future ARTs?

A variety of evolutionary processes has led to the development of different organs to ensure that internal fertilization occur successfully. Fallopian tubes are a particularly interesting example of such organs. Some of the key events during fertilization and early embryo development occur in the oviduct. Knowledge of the different components described in the oviduct is extensive. Oviductal components include hormones, growth factors and their receptors that have important roles in the physiology of the oviduct and embryo development. Other oviductal factors protect the gamete and the embryos against oxidative stress and pathogens. Different proteins and enzymes are present in the oviductal fluid and have the ability to interact with the oocyte and the sperm before the fertilization occurs. Of special interest is the oviduct-specific glycoprotein (OVGP1), a glycoprotein that is conserved in different mammals, and its association with the zona pellucida (ZP). Interaction of the oocyte with oviductal secretions leads us to emphasize the concept of 'ZP maturation' within the oviduct. The ZP changes produced in the oviduct result in an increased efficiency of the in vitro fertilization technique in some animal models, contributing in particular to the control of polyspermy and suggesting that a similar role could be played by oviductal factors in human beings. Finally, attention should be given to the presence in the oviductal fluid of several embryotrophic factors and their importance in relation to the in vivo versus in vitro developmental ability of the embryos.

Effect of a null mutation of the oviduct-specific glycoprotein gene on mouse fertilization

The mammalian fertilization process takes place in a complex microenvironment within the female genital tract. A member of the chitinase protein family, oviduct-specific glycoprotein (OGP), has been identified in oviductal fluid from various mammalian species, including humans. Although OGP is widely believed to be involved in the process of mammalian fertilization, including spermatozoon function and gamete interactions, based on experimental results obtained in vitro, its physiological significance remains controversial. The present study established OGP gene-null ( ogp (-/-)) mice, and primarily characterized their reproductive properties to study the physiological function(s) of OGP. Results obtained from studies using an in vivo or in vitro system showed that the fertility of ogp (-/-) females was within normal limits. These results indicate that OGP is not essential for the process of in vivo fertilization, at least in mice.

Organization of a gene coding for an oviduct-specific glycoprotein (oviductin) in the hamster

Hamster oviductin, a high molecular weight glycoprotein secreted by the oviducts, is believed to participate in fertilization and protection of the tubal epithelium. Expression of the oviductin gene is confined strictly to nonciliated secretory cells of the oviduct and is regulated by hormones. The objective of this study was to characterize the genomic organization and to identify potential regulatory elements implicated in the control of transcription of the oviductin gene. Polymerase chain reaction was performed on hamster genomic DNA, yielding 2.2 kb of the 5' flanking region as well as 13.6 kb of genomic sequence comprising the entire coding sequence of the oviductin gene distributed in 11 exons. Sequencing of the 5' flanking region revealed, among other elements, an almost perfect estrogen-responsive element (GGTCACTGTGACT), an atypical TATA box (TATTAA), and a perfect inverted Sp1 site located between the transcription start site and the atypical TATA box. Primer extension analyses indicated that the hamster oviductin transcript possesses an unusually short 5' untranslated region of only 14 nucleotides. The distinct organization of the hamster oviductin gene in the vicinity of the transcription start site provides an interesting ground for further functional studies.

Characterization of antibodies generated against a conserved portion of oviductal glycoprotein (OGP) and endogenous hamster OGP and their ability to decrease sperm binding to the zona pellucida in vitro

PROBLEM

The effect of antibodies generated against hamster oviductal glycoprotein (OGP) on sperm binding to the zona pellucida (ZP) was evaluated.

METHOD OF STUDY

Antibodies against a 17-amino-acid sequence of the OGP core protein (amino acids 52-68) and the denatured hamster OGP protein were generated, characterized, and tested in an in vitro sperm binding assay.

RESULTS

Sperm binding was significantly decreased (P < 0.05) when oviductal oocytes were incubated for 2 hr with 4 or 8 mg/ml of immune IgG of both antibodies when compared with normal rabbit IgG. A fluorescence assay showed binding of both antibodies to the endogenous OGP associated with the ZP of ovulated hamster oocytes.

CONCLUSIONS

These results suggest that OGP may be a potential immunocontraceptive target because both antibodies significantly decreased sperm binding to the ZP of oviductal oocytes. Immunocontraception may be accomplished by attempting to generate active immunity to a recombinant OGP, to the region selected in this study (amino acids 52-68) or to some other region of the core protein.

The mammalian oviduct: biochemistry and physiology

Oviduct fluid and oviduct epithelium seem able to modulate in-time maturation and transport of gametes and embryos. They probably allow selection of spermatozoa through too early activation. Subtle changes in the composition of tubal secretion permit fertilization and embryo development in the best conditions. The mechanisms of these changes of oviduct fluid composition (induced by endocrine stimuli and/or by embryo) are under investigation. Numerous compounds isolated in oviduct fluid are now added to the synthetic media for in vitro maturation/in vitro fertilization/embryo culture (IVM/IVF/EC). The rationale is now to mimic more and more, the biochemical composition of tubal and uterine fluids even if interactions with embryo metabolism is still far from being understood.

Oviduct during early pregnancy: hormonal regulation and interactions with the fertilized ovum

The cyclic fluctuations in circulating levels of 17 beta-estradiol and progesterone that occur during the menstrual or estrous cycle are responsible for dramatic, cyclic changes in the epithelial lining and secretory status of the mammalian oviduct. The timely transition in the synthesis and release of oviduct proteins, due to the ovarian steroids, and their interactions with oocytes, sperm, and the fertilized ovum underscore key biological events during gamete interactions and early embryonic cleavage. The regulation of these secretory alterations during the first few days of pregnancy is discussed with respect to the influence of the ovarian steroids, their interactions with the embryo microenvironment, and the possible ways in which they may mediate the critical reproductive events of fertilization and embryo development.

Oviductins possess chitinase- and mucin-like domains: a lead in the search for the biological function of these oviduct-specific ZP-associating glycoproteins

Over the last 10 years considerable progress has been made in the immunological and biochemical characterization of oviduct-specific glycoproteins. It is now well established that a subclass of these secretory products, designated as oviductins, associate with the zona pellucida of the ovulated oocyte and with the early embryo. Recent reports on the cloning of cDNAs of oviductins from various species, including that of golden hamster (Mesocricetus auratus) oviductin by our laboratory, allowed us to compare their deduced amino acid sequences with those of other proteins. Optimal alignment analysis showed that oviductins contain regions of significant similarity with catalytically inactive mammalian members of the bacterial and microfilarial chitinase protein family. Most importantly, a close examination of the hamster and human deduced amino acid sequences revealed that both glycoproteins possess contiguous Ser/Thr rich repeated units, clustered in their carboxy-terminal portions. These mucin-type motifs are similar in the hamster and human glycoprotein, although hamster oviductin contains more of these complete units. This striking feature might indicate that these molecules play a similar role to mucin-type glycoproteins, e.g., in protecting the oocyte and early embryo against attacks from their environment. We propose a model whereby oviductins are targeted to the oocyte via the interaction of their chitinase-like domains with specific oligosaccharide moieties of the zona pellucida. Once localized to this structure, oviductin molecules would act as a protective shield around the oocyte and early embryo by virtue of their densely glycosylated mucin-type domains.

Stage-specific immunolabeling for oviductin in the secretory granules of the oviductal epithelium of the golden hamster during the estrous cycle

BACKGROUND

We have previously localized an antigen of oviductal origin in the zona pellucida of postovulatory hamster ova. This antigen is a high molecular weight glycoprotein secreted by the non-ciliated secretory cells of the oviduct and is later transferred to the zona pellucida of the oocyte during oviductal transit. This glycoprotein is rich in N-acetyl-D-galactosamine residues and has been designated Hamster Oviductin-1. In the present study, a monoclonal antibody (MAb) raised against this oviductin was used to detect the presence of this antigen in oviductal tissue during the estrous cycle.

METHODS

Twenty mature female golden hamsters were used and were divided into five groups of five animals each according to the five different stages of the estrous cycle. Quantitative immunocytochemistry was performed on MAb-labeled thin sections of Lowicryl-embedded ampullary region of hamster oviducts. Control experiments were also carried out to assess the specificity of the immunolabeling.

RESULTS

Quantitative analysis of the immunogold labeling indicated that maximum labeling for oviductin in the secretory granules of oviductal epithelial secretory cells was found around the time of ovulation, i.e., at estrus. The intensity of immunolabeling decreased from metestrus to diestrus 1, was at a minimum at diestrus 2, and started to increase at proestrus.

CONCLUSION

Together, these quantitative results indicate that expression of oviductin in the secretory granules of the hamster oviductal secretory cells is stage specific. Maximum labeling for the antigen coincides with the time of ovulation suggesting an important role for the oviductal epithelium in contributing its secretory product to the zona pellucida of oocytes freshly released from the ovary. Since the oviduct is the site of sperm-egg interaction and where fertilization and early embryo development take place, the maximal production of oviductin at the time of ovulation may facilitate some of these crucial steps during the intricate process of reproduction.

Immunocytochemical localization of oviduct-specific glycoproteins in the oviductal epithelium from cows at follicular and luteal phases

The immunocytochemical localization of bovine oviduct-specific glycoproteins was investigated by light and electron microscopy. Using monoclonal antibodies (MAbs) specific for bovine oviductal glycoproteins, 3 regions (fimbriae, ampulla, and isthmus) of the epithelium in the bovine oviduct we studied during the follicular and luteal phases. The MAbs reacted specifically with the oviductal epithelial cells. Intense labeling was observed in the ampullar and fimbrial epithelia of cows at the follicular phase, but the reactions were weaker at the luteal phase. In the isthmus, the immunohistochemical reaction was faint during both follicular and luteal phases. At the ultrastructural level, the MAbs bound selectively to putative secretory granules of nonciliated cells in the ampulla and fimbriae, but not in the isthmus. These results suggest that there are cyclic changes and regional differences in the production of glycoproteins in the bovine oviduct.

Immunological detection of an oviductal glycoprotein in the rat

In the golden hamster, high-molecular-weight glycoproteins are secreted by the epithelial cells of the oviduct. The present study was designed to investigate the possibility that the rat oviduct produces specific glycoproteins similar to the oviductal glycoproteins (GHOGPs) of the golden hamster. Oviductal extracts and oviductal fluids obtained from ovulatory rats were analysed by immunoblotting for the presence of glycoproteins that cross-react with a monoclonal antibody (MAb) against GHOGPs. The MAb immunoreacted with a broad band of proteins with a range of molecular weights (MWs) of above 330 kD in oviductal extracts or oviductal fluid after fractionation by electrophoresis under reducing conditions, but these proteins were not present in serum and uterine flushings. An immunohistochemical study demonstrated that the MAb bound strongly to the epithelial cells of the oviduct and, to a lesser extent, to those of the large intestine. Weak reactions were also observed with some other tissues. However, similar material of high MW was not detected in extracts of tissues from the other organs, suggesting that the glycoprotein of high MW that reacted with the MAb is specific for the oviduct. Ultrastructural immunocytochemistry revealed that the MAb reacted specifically with putative secretory granules of nonciliated cells in the oviductal epithelium. These results indicate that the oviductal epithelial cells of the rat produce a specific glycoprotein that is immunologically similar to GHOGPs.

Production and characterization of monoclonal antibodies specific for bovine oviductal glycoproteins

Four monoclonal antibodies (MAbs) were produced in rat cells against materials obtained from the bovine oviduct. The MAbs (1H10, 2A4, 2C5, and 1B12) reacted strongly with the oviductal epithelium of cows in the follicular phase. An immunohistochemical study demonstrated that each of the MAbs bound strongly to the supranuclear cytoplasm of epithelial cells of the oviduct, but not of the stromal cells. Antigens that reacted with the MAbs were characterized by immunoblotting analysis of proteins after fractionation by SDS-PAGE under reducing conditions of oviductal flushings obtained from cows at estrus. All MAbs strongly stained a band of protein with a molecular weight (MW) of 85-97 kD. MAb 1H10 also reacted with the minor band of a 55-kD protein. Similar antigens were not detected in uterine flushings, follicular fluid, and serum. No specific immunohistochemical reactivity with the MAbs was observed with other tissues from the reproductive tract and with nonreproductive tissues. The immunohistochemical reactions were completely eliminated by pretreatment of tissues with trypsin, but not with periodic acid, results that suggest that the antigenic determinants that react with the MAbs were proteinaceous rather than carbohydrate. We have thus established clones that produce 4 MAbs that are specific for oviduct-specific glycoproteins of the cow.

Immunocytochemical analysis of the association of bovine oviduct-specific glycoproteins with early embryos

The bovine oviductal epithelium synthesizes and secretes a class of oviduct-specific glycoproteins that is present in the luminal fluid when fertilization and early embryonic development occur. The objective of this study was to determine if these characterized glycoproteins become associated with oviductal embryos. Ovarian ova and oviductal embryos were recovered from super-ovulated cows at 72 h after onset of estrus. Eggs were fixed in 3% paraformaldehyde-1% glutaraldehyde and subsequently embedded in Lowicryl K4M. Sections (1 micron) were processed for peroxidase-antiperoxidase immunocytochemistry. Immunolabeling was not detected in any region of ovarian ova. Oviductal embryos, regardless of cleavage stage, exhibited immunoperoxidase staining localized within their zona pellucidae. Sections (100 nm) obtained from a 4- and an 8-cell embryo were also subjected to colloidal gold immunoelectron microscopy to determine conclusively the subcellular distribution of the oviduct-specific glycoproteins. Gold particles were distributed uniformly throughout the width of the zona pellucida. Also, immunoreactivity was observed associated with flocculent material in the perivitelline space and with the vitelline membrane. These results indicate that the bovine oviduct-specific secretory glycoproteins become associated with oviductal embryos. This association may be biologically important to the developing embryo.

Immunological characterization of oviductal glycoproteins associated with the zona pellucida of the golden hamster egg

Three monoclonal antibodies (MAbs) were produced against materials obtained from the golden hamster oviduct. The MAbs (C11E8, C8B11, and A3D5) selectively reacted with the zona pellucida (ZP) of oviductal eggs. An immunohistochemical study demonstrated that all MAbs bound strongly to the epithelial cells of the oviduct and, to a lesser extent, of the uterus, the cervix, and the vagina. Weak reactions were also observed with some other tissues. All immunohistochemical reactions were completely eliminated by treatment of tissues with periodic acid, suggesting that the antigenic determinants that react with the MAbs are carbohydrate in nature. Antigens that reacted with the MAbs were characterized by immunoblotting analyses of 1- or 2-dimensional polyacrylamide gels after electrophoresis to fractionate tissue extracts under reducing conditions. With the oviductal extract, C11E8 and A3D5 specifically bound to broad bands that corresponded to macromolecules of more than 200 and 160 kD, respectively, whereas C8B11 reacted with a broad range of macromolecules, with the strongest reactivity being detected at molecular weights (MWs) higher than 160 kD. The macromolecules that reacted with the MAbs had carbamilation trains, suggestive of extensive microheterogeneity with respect to charge and size. Similar substances of high MW were not detected in extracts of tissues from the other reproductive organs. In addition, one MAb-positive oviductal antigen bound to the ZP of ovarian eggs, but the others did not bind to the ZP of ovarian eggs. This result indicates that the binding activity is specific for the oviductal glycoproteins. We have thus established clones that produce 3 different MAbs with strong affinity for oviduct-specific glycoproteins, one of which is associated with the ZP of the golden hamster.

Enhancement of polymorphonuclear leukocyte-mediated tumor cytotoxicity by serum factor(s)

It has been reported that beta-1,3-D-glucan isolated from Alcaligenes faecalis (TAK) promoted tumor cytolysis by mouse polymorphonuclear leukocytes (PMN). We investigated the effect of serum on mouse PMN tumor cytolysis induced by TAK and other PMN stimulators. Addition of fetal calf serum (FCS) to the cytolysis assay enhanced tumor cytolysis by PMN in a dose-dependent manner. Sera obtained from horses, mice, and rats were also effective enhancers of PMN tumor cytolysis. When FCS was added after the assay was under way, the enhancing effect decreased proportionally to the time elapsed. The enhancing activity was detected over a broad range of fractions with a peak at 170 kD by fractionation on a Superose 6 column. The responsible factor(s) in serum was stable after treatment at 60 degrees C, 30 min or after lowering the pH to 2. Mouse PMN stimulated with TAK increased production of hydrogen peroxide in the presence of FCS.

Oviductal epithelium of the baboon: hormonal control and the immuno-gold localization of oviduct-specific glycoproteins

Oviducts were obtained from a series of cycling and ovariectomized steroid-treated baboons. The lining epithelium of the ampulla and isthmus was analyzed by light and electron microscopy. Both morphological and cytomorphometric analyses revealed that the morphological and functional state of the oviductal epithelium in the baboon is controlled by the ovarian steroids. Additionally, a clear cephalocaudal steroid-responsive gradient was observed when the data from the ampulla and isthmus of the same animal were compared. Within the ampulla, estradiol induced hypertrophy, hyperplasia, ciliogenesis, and secretory activity, whereas adding progesterone to the treatment regimen (+/- estradiol) resulted in atrophy, deciliation, apoptosis, and loss of the secretory activity. These cyclic processes were less evident in the isthmus. We also used an indirect electron microscopic immunogold technique and a previously characterized polyclonal antibody to determine the localization of oviduct-specific glycoproteins. These glycoproteins were present in every secretory granule observed, regardless of oviduct region, electron density, or size of the secretory granule. In summary, our data show that 1) estradiol induces and maintains the mature epithelium of the baboon oviduct, 2) steroid withdrawal or the administration of progesterone causes regression of the epithelium, and 3) the previously identified estradiol-dependent oviduct-specific glycoproteins are synthesized within and released from the secretory epithelial cells.