A side-by-side comparison of different capacitation media in developing mouse sperm fertilizing ability.

To acquire the ability to fertilize the egg, mammalian spermatozoa must undergo a series of changes occurring within the highly synchronized and specialized environment of the female reproductive tract, collectively known as capacitation. In an attempt to replicate this process in vitro, various culture media for mouse sperm were formulated over the past decades, sharing a similar overall composition but differing mainly in ion concentrations and metabolic substrates. The widespread use of the different media to study the mechanisms of capacitation might hinder a comprehensive understanding of this process, as the medium could become a confounding variable in the analysis. In this context, the present side-by-side study compares the influence of four commonly used culture media (FD, HTF and two TYH versions) on mouse sperm capacitation. We evaluated the induction of protein kinase A phosphorylation pathway, motility, hyperactivation and acrosome reaction. Additionally, in vitro fertilization and embryo development were also assessed. By analyzing these outcomes in two mouse colonies with different reproductive performance, our study provides critical insights to improve the global understanding of sperm function. The results obtained highlight the importance of considering variations in medium composition, and their potential implications for the future interpretation of results.

Membrane potential hyperpolarization: a critical factor in acrosomal exocytosis and fertilization in sperm within the female reproductive tract.

Hyperpolarization of the membrane potential (Em), a phenomenon regulated by SLO3 channels, stands as a central feature in sperm capacitation-a crucial process conferring upon sperm the ability to fertilize the oocyte. In vitro studies demonstrated that Em hyperpolarization plays a pivotal role in facilitating the mechanisms necessary for the development of hyperactivated motility (HA) and acrosomal exocytosis (AE) occurrence. Nevertheless, the physiological significance of sperm Em within the female reproductive tract remains unexplored. As an approach to this question, we studied sperm migration and AE incidence within the oviduct in the absence of Em hyperpolarization using a novel mouse model established by crossbreeding of SLO3 knock-out (KO) mice with EGFP/DsRed2 mice. Sperm from this model displays impaired HA and AE in vitro. Interestingly, examination of the female reproductive tract shows that SLO3 KO sperm can reach the ampulla, mirroring the quantity of sperm observed in wild-type (WT) counterparts, supporting that the HA needed to reach the fertilization site is not affected. However, a noteworthy distinction emerges-unlike WT sperm, the majority of SLO3 KO sperm arrive at the ampulla with their acrosomes still intact. Of the few SLO3 KO sperm that do manage to reach the oocytes within this location, fertilization does not occur, as indicated by the absence of sperm pronuclei in the MII-oocytes recovered post-mating. In vitro, SLO3 KO sperm fail to penetrate the ZP and fuse with the oocytes. Collectively, these results underscore the vital role of Em hyperpolarization in AE and fertilization within their physiological context, while also revealing that Em is not a prerequisite for the development of the HA motility, essential for sperm migration through the female tract to the ampulla.

Standards in semen examination: publishing reproducible and reliable data based on high-quality methodology.

Biomedical science is rapidly developing in terms of more transparency, openness and reproducibility of scientific publications. This is even more important for all studies that are based on results from basic semen examination. Recently two concordant documents have been published: the 6th edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen, and the International Standard ISO 23162:2021. With these tools, we propose that authors should be instructed to follow these laboratory methods in order to publish studies in peer-reviewed journals, preferable by using a checklist as suggested in an Appendix to this article.

Effect of ulipristal acetate on gene expression profile in endometrial cells in culture and in vivo upon post-ovulatory administration in fertile women.

PURPOSE: To analyse the effect of ulipristal acetate (UPA) as emergency contraception (EC) on the gene expression of human endometrial cell line (HEC-1A) and endometrium from fertile women treated with UPA after ovulation. MATERIALS AND METHODS: HEC-1A cells were treated with UPA, and endometrial tissue from four healthy women was collected in cycles before, during and 2 months after post-ovulation pill intake. Ovulation and luteal phase were monitored, and endometrial biopsies were obtained at day LH + 7 in each cycle. In all cases, we analysed the expression profile of 192 genes associated to endometrial receptivity. RESULTS: We observed a significant change in total transcriptomic activity of UPA-treated HEC-1A cells compared to controls. In vivo, we also observed a trend to down-regulation of genes in the UPA-treated cycle that was partially restored in the post-treatment cycle. Altogether, our results supported a partially reversible effect of UPA in gene expression associated with uterine receptivity. CONCLUSIONS: When UPA was administered after ovulation, it seems to induce a down-regulation of the main genes involved in conditioning the endometrium for implantation. This effect is partially restored two months after pill intake. The action of UPA on the endometrium for users of EC should be further investigated.

Cysteine-Rich Secretory Proteins (CRISP) are Key Players in Mammalian Fertilization and Fertility.

Mammalian fertilization is a complex process involving a series of successive sperm-egg interaction steps mediated by different molecules and mechanisms. Studies carried out during the past 30 years, using a group of proteins named CRISP (Cysteine-RIch Secretory Proteins), have significantly contributed to elucidating the molecular mechanisms underlying mammalian gamete interaction. The CRISP family is composed of four members (i.e., CRISP1-4) in mammals, mainly expressed in the male tract, present in spermatozoa and exhibiting Ca2+ channel regulatory abilities. Biochemical, molecular and genetic approaches show that each CRISP protein participates in more than one stage of gamete interaction (i.e., cumulus penetration, sperm-ZP binding, ZP penetration, gamete fusion) by either ligand-receptor interactions or the regulation of several capacitation-associated events (i.e., protein tyrosine phosphorylation, acrosome reaction, hyperactivation, etc.) likely through their ability to regulate different sperm ion channels. Moreover, deletion of different numbers and combination of Crisp genes leading to the generation of single, double, triple and quadruple knockout mice showed that CRISP proteins are essential for male fertility and are involved not only in gamete interaction but also in previous and subsequent steps such as sperm transport within the female tract and early embryo development. Collectively, these observations reveal that CRISP have evolved to perform redundant as well as specialized functions and are organized in functional modules within the family that work through independent pathways and contribute distinctly to fertility success. Redundancy and compensation mechanisms within protein families are particularly important for spermatozoa which are transcriptionally and translationally inactive cells carrying numerous protein families, emphasizing the importance of generating multiple knockout models to unmask the true functional relevance of family proteins. Considering the high sequence and functional homology between rodent and human CRISP proteins, these observations will contribute to a better understanding and diagnosis of human infertility as well as the development of new contraceptive options.

Pharmacological Inactivation of CatSper Blocks Sperm Fertilizing Ability Independently of the Capacitation Status of the Cells: Implications for Non-hormonal Contraception.

Cation channel of sperm (CatSper), the main sperm-specific Ca2+ channel, plays a key role in mammalian fertilization, and it is essential for male fertility, becoming an attractive target for contraception. Based on this, in the present work, we investigated the effects of CatSper inactivation on in vitro and in vivo sperm fertilizing ability and the mechanisms underlying such effects. Exposure of cauda epididymal mouse sperm to different concentrations (1-20 µM) of the potent CatSper inhibitor HC-056456 (HC) during in vitro capacitation showed no effects on sperm viability but significantly affected Ca2+ entry into the cells, progressive motility, protein tyrosine phosphorylation, induced acrosome reaction, and hyperactivation, as well as the sperm's ability to in vitro fertilize cumulus oocyte complexes and zona-free eggs. Whereas the presence of HC during gamete coincubation did not affect in vitro fertilization, exposure of either non-capacitating or already capacitated sperm to HC prior to gamete coincubation severely reduced fertilization, indicating that sperm function is affected by HC when the cells are incubated with the drug before sperm-egg interaction. Of note, insemination of HC-treated sperm into the uterus significantly or completely reduced the percentage of oviductal fertilized eggs showing, for the first time, the effects of a CatSper inhibitor on in vivo fertilization. These observations, together with the finding that HC affects sperm fertilizing ability independently of the sperm capacitation status, provide further insights on how CatSper regulates sperm function and represent a solid proof of concept for developing a male/female non-hormonal contraceptive based on the pharmacological blockage of CatSper activity.

Evolutionary analysis of genes coding for Cysteine-RIch Secretory Proteins (CRISPs) in mammals.

BACKGROUND: Cysteine-RIch Secretory Proteins (CRISP) are expressed in the reproductive tract of mammalian males and are involved in fertilization and related processes. Due to their important role in sperm performance and sperm-egg interaction, these genes are likely to be exposed to strong selective pressures, including postcopulatory sexual selection and/or male-female coevolution. We here perform a comparative evolutionary analysis of Crisp genes in mammals. Currently, the nomenclature of CRISP genes is confusing, as a consequence of discrepancies between assignments of orthologs, particularly due to numbering of CRISP genes. This may generate problems when performing comparative evolutionary analyses of mammalian clades and species. To avoid such problems, we first carried out a study of possible orthologous relationships and putative origins of the known CRISP gene sequences. Furthermore, and with the aim to facilitate analyses, we here propose a different nomenclature for CRISP genes (EVAC1-4, "EVolutionarily-analyzed CRISP") to be used in an evolutionary context. RESULTS: We found differing selective pressures among Crisp genes. CRISP1/4 (EVAC1) and CRISP2 (EVAC2) orthologs are found across eutherian mammals and seem to be conserved in general, but show signs of positive selection in primate CRISP1/4 (EVAC1). Rodent Crisp1 (Evac3a) seems to evolve under a comparatively more relaxed constraint with positive selection on codon sites. Finally, murine Crisp3 (Evac4), which appears to be specific to the genus Mus, shows signs of possible positive selection. We further provide evidence for sexual selection on the sequence of one of these genes (Crisp1/4) that, unlike others, is thought to be exclusively expressed in male reproductive tissues. CONCLUSIONS: We found differing selective pressures among CRISP genes and sexual selection as a contributing factor in CRISP1/4 gene sequence evolution. Our evolutionary analysis of this unique set of genes contributes to a better understanding of Crisp function in particular and the influence of sexual selection on reproductive mechanisms in general.

Mechanisms involved in the contraceptive effects of ulipristal acetate.

The use of emergency contraception (EC) methods is increasing worldwide as it constitutes an effective way to prevent unplanned pregnancy after unprotected sexual intercourse. During the last decade, ulipristal acetate (UPA), a selective progesterone receptor modulator, has emerged as the most effective EC pill, and it is now recommended as first-line hormonal treatment for EC in several countries. Its principal mechanism of action involves inhibition or delay of follicular rupture, but only when administered during the follicular phase before the luteinizing hormone (LH) peak. However, considering the high efficacy of UPA, it is possible that it also exerts contraceptive effects besides ovulation. In the present review, we summarize and discuss the existing evidence obtained on the effect of UPA on sperm function and post-ovulatory events as potential additional mechanisms to prevent pregnancy. The bulk of evidence collected so far indicates that UPA would not affect gamete function; however, it could impair embryo-uterine interaction. Thus, besides the described effects on ovarian function, UPA contraceptive effectiveness might also be attributed to post-ovulatory effects, depending on the moment of the female cycle in which the drug is administered.

Compensatory endocytosis occurs after cortical granule exocytosis in mouse eggs.

Compensatory endocytosis (CE) is one of the primary mechanisms through which cells maintain their surface area after exocytosis. Considering that in eggs massive exocytosis of cortical granules (CG) takes place after fertilization, the aim of this study was to evaluate the occurrence of CE following cortical exocytosis in mouse eggs. For this purpose, we developed a pulse-chase assay to detect CG membrane internalization. Results showed internalized labeling in SrCl2 -activated and fertilized eggs when chasing at 37°C, but not at a nonpermissive temperature (4°C). The use of kinase and calcineurin inhibitors led us to conclude that this internal labeling corresponded to CE. Further experiments showed that CE in mouse eggs is dependent on actin dynamics and dynamin activity, and could be associated with a transient exposure of phosphatidylserine. Finally, CE was impaired in A23187 ionophore-activated eggs, highlighting once again the mechanistic differences between the activation methods. Altogether, these results demonstrate for the first time that egg activation triggers CE in mouse eggs after exocytosis of CG, probably as a plasma membrane homeostasis mechanism.

A single post-ovulatory dose of ulipristal acetate impairs post-fertilization events in mice.

Ulipristal acetate (UPA) is a selective progesterone receptor modulator used for emergency contraception that has proven to be highly effective in preventing pregnancy when taken up to 120 h after unprotected sexual intercourse. Even though it may act mainly by delaying or inhibiting ovulation, additional effects of UPA on post-fertilization events cannot be excluded. Therefore, the aim of this study was to determine whether a single post-ovulatory dose of UPA could prevent pregnancy using the mouse as a pre-clinical model. Mated females received a single dose of UPA (40 mg/kg) on Day E1.5 or E2.5 (E0.5: copulatory plug detection) and post-fertilization events were evaluated. Our studies revealed that UPA administration produced a significant decrease in the number of conceptuses compared to control. Moreover, UPA-treated females exhibited a lower number of early implantation sites on Day E5.5, despite normal in vivo embryo development and transport to the uterus at E3.5. Administration of UPA produced histological and functional alterations in the uterine horns, i.e., a dyssynchronous growth between endometrial glands and stroma, with non-physiological combination of both fractions compared to controls, and a completely impaired ability to respond to an artificial decidualization stimulus. Altogether, our results show that the administration of a single post-ovulatory dose of UPA impairs mouse pregnancy probably due to an effect on embryo-uterine interaction, supporting additional effects of the drug on post-fertilization events. Although these studies cannot be performed with human samples, our results with the mouse model provide new insights into the mechanism of action of UPA as an emergency contraception method.

Impaired male fertility and abnormal epididymal epithelium differentiation in mice lacking CRISP1 and CRISP4.

Epididymal Cysteine Rich Secretory Proteins 1 and 4 (CRISP1 and CRISP4) associate with sperm during maturation and play different roles in fertilization. However, males lacking each of these molecules individually are fertile, suggesting compensatory mechanisms between these homologous proteins. Based on this, in the present work, we generated double CRISP1/CRISP4 knockout (DKO) mice and examined their reproductive phenotype. Our data showed that the simultaneous lack of the two epididymal proteins results in clear fertility defects. Interestingly, whereas most of the animals exhibited specific sperm fertilizing ability defects supportive of the role of CRISP proteins in fertilization, one third of the males showed an unexpected epididymo-orchitis phenotype with altered levels of inflammatory molecules and non-viable sperm in the epididymis. Further analysis showed that DKO mice exhibited an immature epididymal epithelium and abnormal luminal pH, supporting these defects as likely responsible for the different phenotypes observed. These observations reveal that CRISP proteins are relevant for epididymal epithelium differentiation and male fertility, contributing to a better understanding of the fine-tuning mechanisms underlying sperm maturation and immunotolerance in the epididymis with clear implications for human epididymal physiology and pathology.

Ceramide-1-phosphate has protective properties against cyclophosphamide-induced ovarian damage in a mice model of premature ovarian failure.

STUDY QUESTION: Is ceramide-1-phosphate (C1P) an ovarian protective agent during alkylating chemotherapy? SUMMARY ANSWER: Local administration of C1P drastically reduces ovarian damage induced by cyclophosphamide (Cy) via protection of follicular reserve, restoration of hormone levels, inhibition of apoptosis and improvement of stromal vasculature, while protecting fertility, oocyte quality and uterine morphology. WHAT IS KNOWN ALREADY: Cancer-directed therapies cause accelerated loss of ovarian reserve and lead to premature ovarian failure (POF). Previous studies have demonstrated that C1P regulates different cellular processes including cell proliferation, cell migration, angiogenesis and apoptosis. This sphingolipid may be capable of modulating vascular development and apoptosis in ovaries affected by chemotherapy. STUDY DESIGN, SIZE, DURATION: The 6-8-week-old mice were weighed and administered either a single intraperitoneal injection of Cy (75 mg/kg) or an equal volume of saline solution only for control mice. Control and Cy mice underwent sham surgery and received an intrabursal injection of saline solution, while Cy + C1P animal groups received 5 µl C1P, either 0.5 or 1 mM, under the bursa of both ovaries 1 h prior to Cy administration. PARTICIPANTS/MATERIALS, SETTING, METHODS: Animals were euthanized by cervical dislocation or cardiac puncture 2 weeks after surgery for collection of blood orovary and uterus samples, which were cleaned of adhering tissue in culture medium and used for subsequent assays. Ovaries were used for Western blotting or immunohistochemical and/or histological analyses or steroid extraction, as required (n = 5-8 per group). A set of mice (n = 3/group) was destined for oocyte recovery and IVF. Finally, another set (n = 5-6/group) was separated to study fertility parameters. MAIN RESULTS AND THE ROLE OF CHANCE: The number of primordial (P < 0.01), primary (P < 0.05) and preantral follicles (P < 0.05) were decreased in Cy-treated mice compared to control animals, while atretic follicles were increased (P < 0.001). In Cy + C1P mice, the ovaries recovered control numbers of these follicular structures, in both C1P doses studied. Cy affected AMH expression, while it was at least partially recovered when C1P is administered as well. Cy caused an increase in serum FSH concentration (P < 0.01), which was prevented by C1P coadministration (P < 0.01). E2 levels in Cy-treated ovaries decreased significantly compared to control ovaries (P < 0.01), whilst C1P restored E2 levels to those of control ovaries (P < 0.01). Cy increased the expression of BAX (P < 0.01) and decreased the expression of BCLX-L compared to control ovaries (P < 0.01). The ovarian BCLX-L:BAX ratio was also lower in Cy-treated mice (P < 0.05). In the Cy + C1P group, the expression levels of BAX, BCLX-L and BCLX-L:BAX ratio were no different than those in control ovaries. In addition, acid sphingomyelinase (A-SMase) expression was higher in Cy-treated ovaries, whilst remaining similar to the control in the Cy + C1P group. Cy increased the apoptotic index (TUNEL-positive follicles/total follicles) in preantral and early antral stages, compared to control ovaries (P < 0.001 and P < 0.01, respectively). C1P protected follicles from this increase. No primordial or primary follicular cells stained for either cleaved caspase-3 or TUNEL when exposed to Cy, therefore, we have found no evidence for follicular reserve depletion in response to Cy being due to apoptosis. Cy caused evident vascular injury, especially in large cortical stromal vessels, and some neovascularization. In the Cy + C1P group, the disruptions in vascular wall continuity were less evident and the number of healthy stromal blood vessels seemed to be restored. In Cy-treated ovaries α-SMA-positive cells showed a less uniform distribution around blood vessels. C1P coadministration partially prevented this Cy-induced effect, with a higher presence of α-SMA-positive cells surrounding vessels. By H&E staining, Cy-treated mice showed endometrial alterations compared to controls, affecting both epithelial and stromal compartments. However, C1P allowed that the stromal tissue to maintain its loose quality and its glandular branches. Cy-treated animals had significantly lower pregnancy rates and smaller litter sizes compared with control mice (P = 0.013 and P < 0.05, respectively), whereas cotreatment with C1P preserved normal fertility. Furthermore, a higher (P < 0.05) proportion of abnormal oocytes was recovered from Cy-treated mice compared to the control, which was prevented by C1P administration. LARGE SCALE DATA: N/A. LIMITATIONS REASONS FOR CAUTION: The results of this study were generated from an in-vivo animal experimental model, already used by several authors. Further studies on C1P functions in female reproduction in pathological conditions such as chemotherapy-induced ovarian failure and on the safety of use of this sphingolipid are required. WIDER IMPLICATIONS OF THE FINDINGS: The present findings showed that C1P administration prior to Cy might be a promising fertility preservation strategy in female patients who undergo chemotherapy. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by grants from ANPCyT (PICT 2015-1117), CONICET (PIP 380), Cancer National Institute (INC) and Roemmers Foundation, Argentina. The authors declare no conflicts of interest.

Influence of the genetic background on the reproductive phenotype of mice lacking Cysteine-Rich Secretory Protein 1 (CRISP1).

Epididymal sperm protein CRISP1 has the ability to both regulate murine CatSper, a key sperm calcium channel, and interact with egg-binding sites during fertilization. In spite of its relevance for sperm function, Crisp1-/-mice are fertile. Considering that phenotypes can be influenced by the genetic background, in the present work mice from the original mixed Crisp1-/- colony (129/SvEv*C57BL/6) were backcrossed onto the C57BL/6 strain for subsequent analysis of their reproductive phenotype. Whereas fertility and fertilization rates of C57BL/6 Crisp1-/- males did not differ from those reported for mice from the mixed background, several sperm functional parameters were clearly affected by the genetic background. Crisp1-/- sperm from the homogeneous background exhibited defects in both the progesterone-induced acrosome reaction and motility not observed in the mixed background, and normal rather than reduced protein tyrosine phosphorylation. Additional studies revealed a significant decrease in sperm hyperactivation as well as in cAMP and protein kinase A (PKA) substrate phosphorylation levels in sperm from both colonies. The finding that exposure of mutant sperm to a cAMP analog and phosphodiesterase inhibitor overcame the sperm functional defects observed in each colony indicated that a common cAMP-PKA signaling defect led to different phenotypes depending on the genetic background. Altogether, our observations indicate that the phenotype of CRISP1 null males is modulated by the genetic context and reveal new roles for the protein in both the functional events and signaling pathways associated to capacitation.

Study of the effect of ulipristal acetate on human sperm ability to interact with tubal tissue and cumulus-oocyte-complexes.

OBJECTIVE: Ulispristal acetate (UPA) is a selective progesterone receptor modulator widely used for emergency contraception (EC). The described main mechanism of action is by inhibiting or delaying ovulation; however, the postovulatory effects of the drug are still on debate. Therefore, the aim of this study was to determine whether UPA could interfere with human sperm fertilizing ability. STUDY DESIGN: Human motile spermatozoa were incubated under capacitating conditions with or without UPA, and then used to inseminate human tubal explants, mouse cumulus-oocyte complexes and zona-free hamster eggs. The ability of UPA to interact with human sperm progesterone (P)-binding sites was investigated by incubating the cells with fluorescent-labeled P and analyzing them by fluorescence microscopy. RESULTS: UPA did not affect the ability of human sperm to bind to human tubal tissue explants surface or to penetrate the mouse cumulus mass and the zona-free hamster eggs. In addition, concentrations of UPA much higher than those present in the plasma of EC pill users were required to bind to human sperm P-binding sites. CONCLUSIONS: Our study supports a lack of an agonist or antagonist action of UPA on different functional parameters associated with the fertilizing ability of human sperm. IMPLICATIONS: This study provides new functional evidence supporting that the contraceptive action of UPA is not related to effects on human sperm cells, contributing to a better understanding of the mechanism of action of UPA as EC.

Acrosome Reaction as a Preparation for Gamete Fusion.

The acrosome reaction (AR) is a universal requisite for sperm-egg fusion. However, whereas through the animal kingdom fusion of spermatozoa with the egg plasma membrane occurs via the inner acrosomal membrane exposed after the AR, in eutherian mammals, gamete fusion takes place through a specialized region of the acrosome known as the equatorial segment (ES) which becomes fusogenic only after the AR is completed. This chapter focuses on the different molecular mechanisms involved in the acquisition of the fusogenicity of the ES after the AR. We provide an update of the knowledge about the proteins proposed to have a role in this process either by modifying cytoskeletal and/or membrane molecules or by relocalizing to the ES after the AR to subsequently participate in gamete fusion.

The tyrosine kinase FER is responsible for the capacitation-associated increase in tyrosine phosphorylation in murine sperm.

Sperm capacitation is required for fertilization. At the molecular level, this process is associated with fast activation of protein kinase A. Downstream of this event, capacitating conditions lead to an increase in tyrosine phosphorylation. The identity of the tyrosine kinase(s) mediating this process has not been conclusively demonstrated. Recent experiments using stallion and human sperm have suggested a role for PYK2 based on the use of small molecule inhibitors directed against this kinase. However, crucially, loss-of-function experiments have not been reported. Here, we used both pharmacological inhibitors and genetically modified mice models to investigate the identity of the tyrosine kinase(s) mediating the increase in tyrosine phosphorylation in mouse sperm. Similar to stallion and human, PF431396 blocks the capacitation-associated increase in tyrosine phosphorylation. Yet, sperm from Pyk2(-/-) mice displayed a normal increase in tyrosine phosphorylation, implying that PYK2 is not responsible for this phosphorylation process. Here, we show that PF431396 can also inhibit FER, a tyrosine kinase known to be present in sperm. Sperm from mice targeted with a kinase-inactivating mutation in Fer failed to undergo capacitation-associated increases in tyrosine phosphorylation. Although these mice are fertile, their sperm displayed a reduced ability to fertilize metaphase II-arrested eggs in vitro.

In vitro and in vivo effects of ulipristal acetate on fertilization and early embryo development in mice.

STUDY QUESTION: Does ulipristal acetate (UPA), a selective progesterone receptor modulator used for emergency contraception (EC), interfere with fertilization or early embryo development in vitro and in vivo? SUMMARY ANSWER: At doses similar to those used for EC, UPA does not affect mouse gamete transport, fertilization or embryo development. WHAT IS KNOWN ALREADY: UPA acts as an emergency contraceptive mainly by inhibiting or delaying ovulation. However, there is little information regarding its effects on post-ovulatory events preceding implantation. STUDY DESIGN, SIZE, DURATION: This was an in vitro and in vivo experimental study involving the use of mouse gametes and embryos from at least three animals in each set of experiments. PARTICIPANTS/MATERIALS, SETTING, METHODS: For in vitro fertilization experiments, mouse epididymal spermatozoa capacitated in the presence of different concentrations of UPA (0-1000 ng/ml) were used to inseminate cumulus-intact or cumulus-free eggs in the presence or absence of UPA during gamete co-incubation, and the percentage of fertilized eggs was determined. For in vivo fertilization experiments, superovulated females caged with proven fertile males were injected with UPA (40 mg/kg) or vehicle just before or just after mating and the percentage of fertilized eggs recovered from the ampulla was determined. To investigate the effect of UPA on embryo development, zygotes were recovered from mated females, cultured in the presence of UPA (1000 ng/ml) for 4 days and the progression of embryo development was monitored daily. MAIN RESULTS AND THE ROLE OF CHANCE: In vitro studies revealed that the presence of UPA during capacitation and/or gamete co-incubation does not affect fertilization. Whereas the in vivo administration of UPA at the same time as hCG injection produced a decrease in the number of eggs ovulated compared with controls (vehicle injected animals, P < 0.05), no effects on fertilization were observed when UPA was administered shortly before or after mating. No differences were observed in either the percentage of cleaved embryos or the cleavage speed when UPA was present during in vitro embryo culture. LIMITATIONS, REASONS FOR CAUTION: Considering the ethical and technical limitations inherent to the use of human gametes for fertilization studies, the mouse model was used as an approach for exploring the potential effects of UPA on in vivo sperm transport and fertilization. Nevertheless, the extrapolation of these results to humans requires further investigation. WIDER IMPLICATIONS OF THE FINDINGS: This study presents new evidence on the lack of effect of UPA on gamete interaction and embryo development, providing new insights into the mechanism of action of UPA as an emergency contraceptive method with potential clinical implications. These new findings could contribute to increase the acceptability and proper use of UPA as an emergency contraceptive method. STUDY FUNDING/COMPETING INTERESTS: This study was partially supported by a National Agency of Scientific and Technological Promotion (ANPCyT), Argentina grants PICT 2011-061 to D.J.C. and PICT 2011-2023 to P.S.C. None of the authors has any competing interests to declare.

CRISP1 as a novel CatSper regulator that modulates sperm motility and orientation during fertilization.

Ca(2+)-dependent mechanisms are critical for successful completion of fertilization. Here, we demonstrate that CRISP1, a sperm protein involved in mammalian fertilization, is also present in the female gamete and capable of modulating key sperm Ca(2+) channels. Specifically, we show that CRISP1 is expressed by the cumulus cells that surround the egg and that fertilization of cumulus-oocyte complexes from CRISP1 knockout females is impaired because of a failure of sperm to penetrate the cumulus. We provide evidence that CRISP1 stimulates sperm orientation by modulating sperm hyperactivation, a vigorous motility required for penetration of the egg vestments. Moreover, patch clamping of sperm revealed that CRISP1 has the ability to regulate CatSper, the principal sperm Ca(2+) channel involved in hyperactivation and essential for fertility. Given the critical role of Ca(2+) for sperm motility, we propose a novel CRISP1-mediated fine-tuning mechanism to regulate sperm hyperactivation and orientation for successful penetration of the cumulus during fertilization.