Effects of human oviductal cell coculture on various functional parameters of human spermatozoa

Sperm-oviduct interaction: Differential gene expression of growth factors induced by sperm DNA fragmentation

The present study investigated the effects of DNA fragmentation of spermatozoa on the growth factors expression by a human oviduct epithelial cell line (OE-E6/E7). Two separate groups were examined in this study. The cell line was cultured in the presence of spermatozoa with normal DNA fragmentation index (DFI) or abnormal DFI. Total RNA from the cell line in each group was isolated, and relative expression of objective genes was analysed using PCR array. Also, the concentration of VEGF, BMP-2, BMP-7 and MSTN in the supernatant of cell culture was analysed by the ELISA method. The PCR array analysis revealed that most of the growth factors had been upregulated in the abnormal group. However, the differences between groups were statistically significant (p < 0.05) for five genes, including VEGF-A, BMP-2, BMP-6, BMP-7 and OSM. Furthermore, MSTN was the only gene that down-regulated significantly under the influence of the spermatozoa with abnormal DFI. Moreover, the results of ELISA analysis were in agreement with the data of the PCR array. It has been concluded that DNA fragmentation in human spermatozoa can probably change regular events throughout the oviducts. Consequently, the genes of interest may change sperm function and probably its fate in the female reproductive tract.

Assessment of Sperm Binding Capacity in the Tubal Reservoir Using a Bovine Ex Vivo Oviduct Culture and Fluorescence Microscopy

Sperm binding within the oviductal sperm reservoir plays an important role for reproductive success by enabling sperm survival and maintaining fertilizing capacity. To date, numerous in vitro technologies have been established to measure sperm binding capacity to cultured oviductal cells or oviductal explants. However, these methods do not accurately represent the microenvironment and complex multi-molecular nature of the oviduct. In this paper, we describe a novel protocol for assessing sperm binding capacity in the tubal sperm reservoir using an ex vivo oviduct culture in the bovine model. This protocol includes the staining of frozen-thawed bovine spermatozoa with the DNA-binding dye Hoechst 33342, the co-incubation of stained sperm in closed segments of the oviduct and the visualization and quantification of bound spermatozoa by fluorescence microscopy. By generating overlays of multiple Z-stacks of randomly selected regions of interest (ROIs), spermatozoa bound in the sperm reservoir can be visualized and quantified within the 3D arrangement of the oviductal folds. This method, which is applicable to multiple species, can be used to assess individual sperm binding capacity in males for prognostic purposes as well as to assess the impact of diseases and medications on the formation of the sperm reservoir in the oviduct in humans and animals.

Oviductal secretion and gamete interaction

Experimental evidence from the last 30 years supports the fact that the oviduct is involved in the modulation of the reproductive process in eutherian mammals. Oviductal secretion contains molecules that contribute to regulation of gamete function, gamete interaction, and the early stages of embryo development. The oviductal environment would act as a sperm reservoir, maintaining sperm viability, and modulating the subpopulation of spermatozoa that initiates the capacitation process. It could also contribute to prevent the premature acrosome reaction and to reduce polyspermy. Many studies have reported the beneficial effects of the oviductal environment on fertilization and on the first stages of embryo development. Some oviductal factors have been identified in different mammalian species. The effects of oviductal secretion on the reproductive process could be thought to result from the dynamic combined action (inhibitory or stimulatory) of multiple factors present in the oviductal lumen at different stages of the ovulatory cycle and in the presence of gametes or embryos. It could be hypothesized that the absence of a given molecule would not affect fertility as its action could be compensated by another factor with similar functions. However, any alteration in this balance could affect certain events of the reproductive process and could perhaps impair fertility. Thus, the complexity of the reproductive process warrants a continuous research effort to unveil the mechanisms and factors behind its regulation in the oviductal microenvironment.

Cell membrane proteins from oviductal epithelial cell line protect human spermatozoa from oxidative damage

OBJECTIVE

To study the potential protective action in vitro of oviductal epithelial cell membrane proteins against oxidative damage in human spermatozoa.

DESIGN

Prospective in vitro study.

SETTING

University research laboratory and infertility clinic.

PATIENT(S)

Semen from men attending the infertility clinic at the Queen Mary Hospital with normal semen parameters (World Health Organization, 2010).

INTERVENTION(S)

We studied the effect of oviductal epithelial cell membrane proteins on the sperm functions and endogenous antioxidant enzyme activities.

MAIN OUTCOME MEASURE(S)

Sperm motility, lipid peroxidation, DNA fragmentation, intracellular reactive oxygen species (ROS) level, superoxide dismutase, and glutathione peroxidase activities.

RESULT(S)

Oviductal epithelial cell membrane proteins bind to the human spermatozoa and protect them from ROS-induced damages in terms of sperm motility, membrane integrity, DNA integrity, and intracellular ROS level. Spermatozoa-oviduct epithelial cell interaction also enhances the antioxidant defenses in spermatozoa.

CONCLUSION(S)

Our results demonstrated the protective effects of spermatozoon-oviductal epithelial cell interaction against oxidative stress in human spermatozoa. The results enhance our understanding of the protective mechanism of oviduct on sperm functions.

Human female reproductive tract epithelial cell culture

The female reproductive system is a complex system. Epithelia of the female reproductive system including the ovaries, the oviduct, and the uterus are important sites for follicular development, ovulation, fertilization, implantation, and embryo development. They are also able to synthesize and secrete various hormones, growth factors, and cytokines, which are essential to women's health, sexuality, and reproduction. Conversely, their dysfunction has been implicated in disorders such as infertility, endometriosis, and many other gynecological diseases, as well as cancer. In this chapter, we describe detailed procedures for establishing and maintaining primary cultures of human ovarian surface epithelium, oviductal epithelium, and endometrium. We also provide protocols for cell immortalization, clonal isolation, and in coculture with stromal cells. These cultures can be useful models for investigating the molecular and cellular functions of these epithelia in both normal and pathological states.

Characterisation of an in vitro system to study maternal communication with spermatozoa

In vivo, gamete maturation, fertilisation and early embryonic development take place inside the oviduct. Several studies have indicated that local responses towards gametes and embryos are generated by the maternal reproductive tract. However, no defined in vitro model currently exists to allow detailed and systematic investigation of maternal communications with gametes and embryos. Therefore, we characterised an in vitro model based on the interaction of boar spermatozoa with an immortalised porcine oviduct epithelial cell line to evaluate different factors that may affect this model. The factors tested were sperm viability, source of spermatozoa, cell passage effect and the effect of reproductive and non-reproductive epithelial cells in the interaction with spermatozoa. After 24 h of co-incubation, RNA was extracted and used to synthesise cDNA for quantitative real-time PCR. Alteration in the expression of genes such as adrenomedullin, heat-shock 70-kDa protein 8 and prostaglandin E synthase was considered as the end point of this assay. The results showed that sperm viability and cell passage number had an effect on oviductal gene expression in response to spermatozoa. Oviductal cells showed significant alterations in gene expression when compared with non-reproductive epithelial cells. The simple in vitro system described here has potential application for further studies in our understanding of mechanisms involved in maternal interactions with spermatozoa.

The expression of activins, their type II receptors and follistatin in human Fallopian tube during the menstrual cycle and in pseudo-pregnancy

BACKGROUND

The Fallopian tube (FT) is the site of fertilization and early embryonic development. We have previously reported the expression of activins, their receptors and follistatin by the FT. Here, our aim was to study the expression of tubal activins, their type II receptors and follistatin during the menstrual cycle and following exposure to hCG in vivo.

METHOD

A set of 30 FTs were collected from cycling women (n = 12) at different stages of the cycle (n = 4 in each stage) and pseudo-pregnant women (n = 3) at the time of hysterectomy for benign disease. The pseudo-pregnant women were injected with hCG in the days leading up to hysterectomy, and pseudo-pregnancy was confirmed by the persistence of amenorrhea, the presence of corpus luteum and decidualization of the endometrium. FT specimens were examined using immunohistochemistry and quantitative RT-PCR.

RESULTS

The expression of activin βA- and βB-subunits, activin type IIA and IIB receptors, and follistatin varied throughout the menstrual cycle, being lowest in the follicular phase and highest in the luteal phase. These results were demonstrated at the mRNA and protein level by quantitative RT-PCR and immunohistochemistry (P< 0.05). HCG injection rescued the expression of the candidate molecules from falling to the follicular stage levels but the expression remained lower than in the luteal phase.

CONCLUSIONS

We suggest that activins play a role in tubal physiology and early embryonic development. Additionally, exposure of the tubal epithelium to hCG modulates the expression of tubal activins.

Proteins from human oviductal tissue-conditioned medium modulate sperm capacitation

BACKGROUND

Spermatozoa acquire the ability to fertilize an oocyte when they become capacitated. Capacitation takes place when sperm pass through the female reproductive tract, interacting with female fluids. Both tyrosine phosphorylation of sperm proteins and the ability to respond to acrosome reaction (AR) inducers have been associated with sperm capacitation. Recent data indicate that conditioned media (CM) from human oviductal tissue culture decrease sperm affinity for the zona pellucida in vitro. Since capacitation enables the sperm-oocyte interaction, the aim of the present study was to investigate the effect of CM on events related to sperm capacitation and to assess whether these effects were permanent.

METHODS

Oviductal tissue was obtained from premenopausal patients (scheduled for hysterectomies because of uterine fibromyoma). The tissues were cultured as explants and CM were collected. Explant viability was assessed as tissue DNA integrity. Normozoospermic semen samples were obtained from healthy donors. Motile spermatozoa were incubated under capacitating conditions with or without increasing protein concentrations of CM for 6 or 22 h. Human follicular fluid-induced AR was detected by the Pisum sativum technique. Tyrosine phosphorylated proteins were detected with a monoclonal anti-phosphotyrosine antibody.

RESULTS

The incubation of spermatozoa in the presence of increasing concentrations of conditioned medium (CM) proteins caused a dose-dependent decrease in both tyrosine phosphorylation of sperm proteins and in the level of AR induction. When CM was removed from the sperm incubation media, the effects were reversed. Heat-inactivated CM did not affect either tyrosine phosphorylation or the induction of AR.

CONCLUSIONS

The present data suggest that proteins secreted from human oviductal tissue are able to inhibit events associated with sperm capacitation in vitro.

Effects of glycodelins on functional competence of spermatozoa

Glycodelin is a glycoprotein with 4 known glycoforms, namely glycodelin-S, glycodelin-A, glycodelin-F and glycodelin-C. The glycoforms are present in the female reproductive tract which the spermatozoa must pass through before fertilizing the oocyte. Thus the spermatozoa interact with each of these glycoforms in succession. The glycoforms have different effects on sperm function. Glycodelin-S in the seminal plasma suppresses albumin-induced cholesterol efflux from the spermatozoa and thereby regulates the initiation of capacitation. Glycodelin-A in the oviductal fluid suppresses extracellular signal-regulated kinase making the spermatozoa more sensitive to zona pellucida-induced acrosome reaction. Follicular fluid glycodelin-F suppresses progesterone-induced acrosome reaction and prevents premature acrosome reaction. Glycodelin-A and glycodelin-F also inhibit spermatozoa-zona pellucida binding by interacting with sperm surface fucosyltransferase-5, which also binds to zona pellucida glycoproteins. The physiological implication of this phenomenon remains to be determined. The inhibitory activities of glycodelin-A and glycodelin-F on spermatozoa-zona pellucida binding is removed by glycodelin-C in the cumulus matrix. Glycodelin-C not only displaces sperm-bound glycodelin-A and glycodelin-F, it also enhances spermatozoa-zona pellucida binding. These different biological activities of the glycodelin isoforms are determined by glycosylation of the proteins. Deglycosylation abolishes the binding and therefore the action of the glycodelins on spermatozoa. Knowledge of the mechanism of actions of glycodelins may enable development of novel strategies for fertility regulation.

Roles of glycodelin in modulating sperm function

Glycodelin is a glycoprotein with three well-defined isoforms. They are named as glycodelin-S, glycodelin-A and glycodelin-F. The three isoforms have similar protein core but different carbohydrate moieties. Glycodelin-S is abundant in the human seminal plasma. It suppresses sperm capacitation and in doing so, it maintains the spermatozoa in an uncapacitated state before they enter into the uterine cavity. Glycodelin-A is abundant in the amniotic fluid. It is also secreted from endometrial glands into uterine fluid and is produced by the fallopian tube. Glycodelin-A is the first endogenous glycoprotein that was found to inhibit the binding of spermatozoa to the zona pellucida. The immunosuppressive properties of glycodelin-A suggest that the molecule may protect the spermatozoa from immune attack in the maternal reproductive tract. Glycodelin-F was first found in the follicular fluid, hence its name. It also inhibits spermatozoa-zona pellucida binding. In addition, glycodelin-F suppresses progesterone-induced acrosome reaction, and may serve to prevent premature acrosome reaction. Preliminary findings suggest possible presence of yet another glycodelin isoform in the extracellular matrix of cumulus oophorus. Unlike glycodelin-A and -F, it stimulates spermatozoa-zona pellucida binding. In summary, different isoforms of glycodelin have different biological roles on sperm function, and they act in succession to contribute to the success of fertilization.

Glycodelin-S in Human Seminal Plasma Reduces Cholesterol Efflux andInhibits Capacitation ofSpermatozoa

Tight control of sperm capacitation is important for successful fertilization. Glycodelin-S is one of the most abundant glycoproteins in the human seminal plasma. However, its function is unclear. We investigated the role of glycodelin-S on capacitation of human spermatozoa. Binding kinetics experiments demonstrated the presence of two saturable and reversible binding sites of glycodelin-S on human spermatozoa. Differently glycosylated other isoforms of glycodelin, glycodelin-A and -F, did not compete with glycodelin-S for these binding sites, suggesting that the glycodelin-S binding sites are different from those of the other isoforms. Indirect immunofluorescent staining revealed specific binding of glycodelin-S around the sperm head. This immunoreactivity was greatly reduced in spermatozoa that had migrated through the cervical mucus surrogates. Glycodelin-S at physiological concentrations significantly reduced the bovine serum albumin and cyclodextrin-induced cholesterol efflux and down-regulated the adenylyl cyclase/protein kinase A/tyrosine kinase signaling pathway, resulting in suppression of capacitation. Deglycosylation abolished glycodelin-S binding and the effect of glycodelin-S on bovine serum albumin-induced capacitation. This indicates that the carbohydrate moiety of glycodelin-S is critical for the function of the molecule. It is concluded that glycodelin-S in seminal plasma maintains the uncapacitated state of human spermatozoa.

Effects of human oviductal in vitro secretion on spermatozoa and search of sperm-oviductal proteins interactions

It has been suggested that oviductal proteins could be involved in modulating sperm function and fertilizing ability through as yet not well-known mechanisms. The objective of the study was to investigate the pattern of proteins secreted by human oviductal tissue cultures and the effects of their conditioned media (CM) on sperm function under capacitating conditions and in phosphate buffered saline (PBS). In addition, interactions between spermatozoa and oviductal proteins were examined. The oviductal tissue was obtained from pre-menopausal patients scheduled for hysterectomies because of uterine fibromyoma. Normozoospermic semen samples were obtained from healthy donors. Cultures of human fallopian tissue were carried out and CM were collected for analysis of the de novo production of [35S]-methionine-labelled proteins by SDS-PAGE. Motile spermatozoa were incubated under capacitating conditions and in PBS, with or without CM, and sperm fertilizing ability was assessed by ionophore-induced acrosome reaction (AR) and the acrosome reaction to ionophore challenge (ARIC) score. The ionophore-induced AR was evaluated by the Pisum sativum technique. Sixteen de novo produced proteins were detected in CM. One of these proteins (molecular weight 79 kDa) was detected in extracts from spermatozoa pre-incubated with CM. Sperm survival and motility were maintained in the presence of CM, although results showed a significant decrease in ARIC score (p < 0.05), with respect to controls. The presence of CM significantly decreased sperm fertilizing ability, without affecting sperm survival. These results suggest that the oviductal secretion could contribute to preserve sperm viability and motility, and to prevent a premature response of spermatozoa to AR inducers.

Biological basis for human capacitation

More than 50 years ago Austin and Chang defined mammalian sperm capacitation as a period of time that sperm must reside in the female reproductive tract before they acquire the ability to fertilize oocytes. Since then numerous investigations have attempted to more clearly define the molecules and processes that are a part of capacitation. The data that have provided a more clear definition of capacitation were primarily derived from in vitro experiments. This is particularly true for studies on human sperm capacitation. While ethical constraints have limited an equal balance of in vivo studies there are those data that when coupled with some of the in vitro data allow for the formulation of a biological framework for human sperm capacitation in vivo. This review will put forth the biological basis for human capacitation.

Identification and characterization of human VCY2-interacting protein: VCY2IP-1, a microtubule-associated protein-like protein

VCY2 is a testis-specific protein that locates in a frequently deleted azoospermia factor c region on chromosome Yq. Although its genomic structure has been characterized, the function of VCY2 is still unknown. To gain insight regarding the likely function of VCY2, we investigated the proteins that interact with VCY2 using the yeast two-hybrid system. We identified a novel VCY2 interaction partner, named VCY2IP-1, that encodes an open reading frame of 1059 amino acids. The amino acid sequence of VCY2IP-1 shows 59.3% and 41.9% homology to two human microtubule-associated proteins (MAPs), MAP1B and MAP1A, respectively. VCY2IP-1 has an extensive homology to the N-terminus and C-terminus regions of MAP1B and MAP1A, placing it within a large family of MAPs. We mapped VCY2IP-1 to chromosome 19p13.11. The VCY2IP-1 gene spans 15 kilobases (kb) and consists of seven exons. Northern blot analysis identified a single, intense band of approximately 3.2-kb VCY2IP-1 transcript, predominantly expressed in human testis. In situ hybridization of human testicular sections showed the localization of VCY2IP-1 transcripts in germ cells, and reverse transcription-polymerase chain reaction analysis demonstrated the presence of VCY2 and VCY2IP-1 transcripts in human ejaculated spermatozoa. Our expression data support the involvement of VCY2 and VCY2IP-1 in spermatogenesis. Based on the high homology of VCY2IP-1 with MAPs, we propose the involvement of VCY2 in the cytoskeletal network via interaction with VCY2IP-1.

Modulation of human sperm function by peritoneal fluid

OBJECTIVE

To examine the effect of peritoneal fluid on various parameters of sperm function in vitro.

DESIGN

Prospective study.

SETTING

Basic research laboratory.

PATIENT(S)

Semen samples were obtained from normozoospermic volunteers (n = 43). Peritoneal fluids were aspirated laparoscopically from women with unexplained infertility (n = 14). Follicular fluid and oocytes were collected from patients undergoing IVF-ET.

INTERVENTION(S)

Sperm incubated under capacitating conditions were exposed to peritoneal fluid, and functional variables were evaluated in vitro.

MAIN OUTCOME MEASURE(S)

Sperm viability and motility, follicular fluid and calcium ionophore-induced acrosome reactions, protein tyrosine phosphorylation, expression of D-mannose binding sites, and ability of sperm to interact with zona pellucida.

RESULT(S)

Exposure of sperm to peritoneal fluid for up to 6 hours did not affect sperm viability or motility. Unlike follicular fluid, peritoneal fluid did not induce the acrosome reaction. Moreover, incubation of sperm with > or =20% v/v peritoneal fluid for 1 hour prevented the follicular fluid and the ionophore-induced acrosome reaction. Although treatment with peritoneal fluid allowed protein tyrosine phosphorylation during capacitation, it resulted in a significant decrease in the expression of D-mannose binding sites and sperm-zona pellucida binding.

CONCLUSION(S)

Peritoneal fluid maintains sperm survival and decreases sperm ability to respond to inducers of the acrosome reaction and bind to the zona pellucida in vitro, indicating that this fluid might modulate sperm function in vivo.

The effects of levonorgestrel on various sperm functions

Two doses of 750-microg levonorgestrel at 12 h apart is one of the regimens for emergency contraception. The mechanism of action of this regimen is not fully known. We investigated whether levonorgestrel influences sperm functions and thereby, exerts contraceptive activity. The motility, acrosome reaction, zona binding capacity, and oocyte fusion capacity of human spermatozoa treated with 1, 10, and 100 ng/mL levonorgestrel for 3 h were evaluated. Levonorgestrel decreased the curvilinear velocity of the treated spermatozoa in a dose-dependent manner. A significant decrease in straight-line velocity, average path velocity and linearity were also found with 100 ng/mL levonorgestrel treatment. This concentration of levonorgestrel, but not others, also marginally decreased (p = 0.045) the zona binding capacity of the treated spermatozoa. The steroid had no effect on acrosome reaction but had a dose-dependent inhibition on spermatozoa-oocyte fusion. These data show that levonorgestrel affects sperm function only at high concentration and the contribution of these effects to emergency contraception is unlikely to be significant.

VCY2 protein interacts with the HECT domain of ubiquitin-protein ligase E3A

VCY2 locates in the AZFc region on chromosome Yq and is frequently deleted in infertile men with severe oligozoospermia or azoospermia. VCY2 is a testis-specific protein with unknown function. This study was to identify the protein that interacts with VCY2. We used the full-length VCY2 as bait to screen the human testis cDNA library using yeast two-hybrid approach. We identified a number of positive-interacting clones that encode ubiquitin-protein ligase E3A (UBE3A). UBE3A contains a HECT domain that binds VCY2. The specificity of the interaction was confirmed by co-immunoprecipitation and yeast mating. Northern blot analyses revealed two UBE3A transcripts 1.4 and 2kb that were abundantly expressed in human testis. We also showed that both VCY2 and UBE3A mRNAs were expressed in ejaculated human spermatozoa, indicating that both genes localize in the germ cell compartment. These data suggest that UBE3A ubiquitination may be required for VCY2 function.

Effects of human follicular fluid on the capacitation and motility of human spermatozoa

OBJECTIVE

To investigate the capacitation and motility kinetics of spermatozoa treated with human follicular fluid (FF).

DESIGN

Controlled, experimental laboratory study.

SETTING

University-based gynecology unit.

PATIENT(S)

Human FF was collected from women undergoing assisted reproductive treatment. Semen samples were obtained from men visiting subfertility clinics.

INTERVENTION(S)

Spermatozoa were incubated with human FF under various experimental conditions. Spermatozoa incubated with Earle's balanced salt solution were used as the control.

MAIN OUTCOME MEASURE(S)

Chlortetracycline staining patterns and sperm motility parameters.

RESULT(S)

The rate of capacitation in the human FF-treated spermatozoa was significantly higher than that in the control spermatozoa after 1 hour and 3 hours of treatment. The percentage of acrosome-reacted spermatozoa also was significantly higher after human FF treatment than after control treatment. These effects of human FF were dose-dependent. Human FF-treated spermatozoa maintained their velocities at the zero-hour level for 5 hours, whereas the velocities of the control spermatozoa decreased significantly after 1 hour. Human FF treatment significantly increased the beat cross-frequency above the rate at zero hour for 5 hours. The hyperactivation of the human FF-treated spermatozoa remained stable for 3 hours, whereas that of the control spermatozoa decreased significantly after 1 hour of incubation. Significantly more human FF-treated spermatozoa underwent hyperactivation than did control spermatozoa after 1 hour and 3 hours of treatment. The effects of human FF on beat cross-frequency and hyperactivation were dose-dependent.

CONCLUSION(S)

Human FF promotes capacitation and the acrosome reaction within a short period. It also stimulates or maintains various sperm motility parameters.

Effects of human follicular fluid on spermatozoa that have been cocultured with human oviductal cells

OBJECTIVE

To investigate the sequential effects of human oviductal cells and human follicular fluid (hFF) on various sperm functions.

DESIGN

Laboratory experimental study.

SETTING

University gynecology unit.

PATIENT(S)

Fallopian tubes were from patients undergoing tubal ligation or hysterectomy. Semen was from men attending the subfertility clinics.

INTERVENTION(S)

Spermatozoa were treated with [1] 6 hours in Earle's balanced salt solution (EBSS-BSA; control); [2] 5 hours in EBSS-BSA and 1 hour with hFF (hFF); [3] 5 hours with oviductal cells and 1 hour in EBSS-BSA (coculture); and [4] 5 hours with oviductal cells and 1 hour with hFF (sequential).

MAIN OUTCOME MEASURE(S)

Motility, acrosome reaction, zona binding, and oocyte fusion.

RESULT(S)

Groups II and III spermatozoa had similar motility and were better than that of group I. Group IV displayed higher motility parameters than the other groups. Human follicular fluid induced acrosome reaction. The incidence of acrosome reaction in group IV was significantly lower than that in group II. Group III did not affect the acrosome reaction. Spermatozoa in groups II-IV had lower zona binding capacity than those in group I. Human follicular fluid stimulated oocyte penetration, whereas oviductal cells suppressed this effect of hFF.

CONCLUSION(S)

Oviductal cells maintained the fertilizing capacity of spermatozoa, whereas hFF facilitated the fertilization process of oviductal spermatozoa.