How does polyspermy happen in mammalian oocytes?

Embryology with precision: effective quality control in the in vitro fertilization laboratory

The purpose of this review is to address the critical need for standardization and clarity in the use of key performance indicators (KPIs) within the realm of in vitro fertilization (IVF), particularly emphasizing the integration of preimplantation genetic testing (PGT) processes. This review is timely and relevant given the persistently modest success rates of IVF treatments, which stand at approximately 30%, and the growing complexity of IVF procedures, including PGT practices. The review synthesizes recent findings across studies focusing on technical and clinical KPIs in embryology and genetic laboratories, identifying gaps in current research and practice, particularly the lack of standardized KPIs and terminology. Recent findings highlighted include the critical evaluation of technical KPIs such as Intracytoplasmic Sperm Injection (ICSI) fertilization rates, embryo development rates, and laboratory performance metrics, alongside clinical KPIs like the proportion of mature oocytes and clinical pregnancy rates. Notably, the review uncovers a significant gap in integrating and standardizing KPIs for PGT applications, which is essential for improving IVF outcomes and genetic diagnostic accuracy. The implications of these findings are profound for both clinical practice and research. For clinical practice, establishing a standardized set of KPIs, especially for PGT, could significantly enhance the success rates of IVF treatments by providing clearer benchmarks for quality and performance. For research, this review underscores the necessity for further studies to close the identified gaps, promoting a more integrated and standardized approach to KPIs in IVF and PGT processes. This comprehensive approach will not only aid in improving clinical outcomes but also in advancing the field of reproductive medicine.

Pre-fertilization approach using α-l-fucosidase modulates zona pellucida hardening during bovine in vitro embryo production

The polyspermy occurrence is considerably lower under in vivo compared to in vitro embryo culture conditions, suggesting that the presence of some factors in the maternal environment is responsible for this. The α-L-fucosidase (FUCA) is a natural glycosidase present in the oviductal fluid, therefore, this study aimed at investigating the effect of adding FUCA to the hardening of the zona pellucida (ZP), polyspermy control, and embryonic yield and quality of bovine blastocysts produced in vitro. In the first experiment, the effect of FUCA (0.125 U/mL) was evaluated during the entire in vitro fertilization (IVF). However, it was demonstrated to be embryotoxic by completely inhibiting the blastocyst formation. In the second experiment, the FUCA (0.125 U/mL) was tested as short-term incubation before IVF (pre-fertilization step) for 30 min or 2 h, which demonstrated that FUCA treatment for 30 min resulted in ZP hardening. In the third experiment, a pre-fertilization FUCA treatment (1 h) at different concentrations (0, 0.0625, and 0.125 U/mL) showed that FUCA (0.0625 U/mL) improved pre-fertilization ZP hardening and tended to increase monospermic fertilization rates but did not improve embryo yield and quality. Together, it has been demonstrated that FUCA can induce oocyte pre-fertilization ZP hardening and might improve monospermic fertilization performance, and this effect is dependent on both variables (protein concentration and incubation time).

Sperm intrusion into the implantation-stage blastocyst and its potential biological significance

The human embryo derives from fusion of oocyte and sperm, undergoes growth and differentiation, resulting in a blastocyst. To initiate implantation, the blastocyst hatches from the zona pellucida, allowing access from external inputs. Modelling of uterine sperm distribution indicates that 200-5000 sperm cells may reach the implantation-stage blastocyst following natural coitus. We show ultrastructural evidence of sperm cells intruding into trophectoderm cells of zona-free blastocysts obtained from the uterus of rhesus monkeys. Interaction between additional sperm and zona-free blastocyst could be an evolutionary feature yielding adaptive processes influencing the developmental fate of embryos. This process bears potential implications in pregnancy success, sperm competition and human health.

Novel biallelic ASTL variants are associated with polyspermy and female infertility: A successful live birth following ICSI treatment

Fertilization of the egg by the sperm is the first vital stage of embryogenesis. In mammals, only one sperm is incorporated into the oocyte. Polyspermy is a key anomaly of fertilization that is generally lethal to the embryo. To date, only a few causative genes for polyspermy have been reported. In a recent study, a homozygous variant in astacin-like metalloendopeptidase (ASTL), which encodes the ovastacin enzyme that cleaves ZP2 to prevent polyspermy, was found to be associated with female infertility characterized by polyspermy in vitro. Herein, we identified two ASTL variants in a Chinese woman likely responsible for her primary infertility and polyspermy in in vitro fertilization. Both variants were located within the key catalytic domain and predicted to alter hydrogen bonds, potentially impairing protein stability. Moreover, expression and immunoblot analyses in CHO-K1 cells indicated abnormal ovastacin zymogen activation or decreased enzyme stability. Intracytoplasmic sperm injection treatment successfully bypassed the defect in polyspermy blocking and resulted in a live birth. Our study associates ASTL variants with human infertility and further supports the contribution of this gene to blocking polyspermy in humans. Our findings expand the spectrum of ASTL mutations and should facilitate the diagnosis of oocyte-borne polyspermy.

Comparative transcriptome analysis identifies important maternal molecules and associated biological pathways for pig and human mature oocytes

Recent researches reveal that during oocyte maturation, species-specific molecular profile exists, and has important functional roles. However, molecular differences between pig (a larger animal model for human reproduction) and human mature oocytes remain unknown. Here, by comparative transcriptome analyses of single cell RNA-seq data, we aimed to identify the common and unique maternal factors and associated biological processes between in vivo and in vitro matured pig oocytes, and between in vitro matured human and pig oocytes. Annotated protein coding mRNAs were identified in pig in vivo (11147) and in vitro (11997), and human in vitro (14491) MII oocytes, respectively. For in vivo and in vitro derived pig MII oocytes, 10551 annotated maternal mRNAs were common, mainly enriched in signaling pathways such as cell cycle, oocyte meiosis, microtubule cytoskeleton, MAPK, RNA processing/binding. Besides, in vivo (596) and in vitro (1446) pig MII-specific mRNAs and their involved signaling pathways (in vivo: Bmp, calcium-mediated signaling, PI3K-Akt; in vitro: growth factor activity, JAK-STAT, cytokine-cytokine receptor interaction, calcium signaling pathway) were also found. As for in vitro derived human and pig MII oocytes, 10285 annotated mRNAs were common, enriched in a variety of signaling pathways (cell cycle, oocyte meiosis, microtubule, AMPK, RNA splicing, protein serine/threonine kinase activity, etc). In vitro MII-specific mRNAs were found for humans (4206) and pigs (1712), which were also enriched in species-specific signaling pathways (humans: golgi related terms, transcription repressor and hormone activity; pigs: ATP biosynthetic process, G protein-coupled peptide receptor activity, animoacyl-tRNA biosynthesis), respectively. These findings improve our understanding on oocyte maturation, and also the limitations of pig model for human oocyte maturation and fertilization.

Evaluation of Semen Quality of Jeju Black Cattle (JBC) to Select Bulls Optimal for Breeding and Establish Freezing Conditions Suitable for JBC Sperm

Simple Summary

Jeju black cattle, a type of native Korean cattle characterized by black fur covering the entire body, inhabit Jeju Special Self-Governing Province, a World Natural Heritage Site. Although this breed was state designated as a natural monument in 2013 due to its characteristics and genetic traits, it is on the verge of extinction and thus there is a need to preserve this breed and further improve its traits. Therefore, we evaluated sperm motility, vitality, and morphology, which have long been considered good predictors of fertility in the absence of female infertility factors. Our findings showed that the semen of the JBC-A bull was superior to the semen of four other JBC bulls. Due to the aging of the population of JBC breeding bulls, strategies should be devised to improve sperm production in vivo.

Abstract

To optimize the reproduction of Jeju black cattle (JBC), freezing conditions for sperm were established and sperm motility, vitality, morphology, and fertility were evaluated to select the optimal bull for breeding. Semen samples from five JBC bulls were individually mixed with freezing medium at a final concentration of 1 × 108 sperm/mL and frozen in liquid nitrogen vapor at a height of 3 or 7 cm (referred to as 3 cm sperm and 7 cm sperm, respectively). When the freezing conditions were compared, the motility of 7 cm sperm was significantly higher than that of 3 cm sperm for the JBC-A bull. The motility, curvilinear velocity, straight-line velocity, and average path velocity of fresh and frozen–thawed sperm were the highest for the JBC-A bull. The vitalities of fresh and frozen–thawed sperm were the highest for the JBC-A/E and JBC-A bulls, respectively. The percentage of normal cells in fresh sperm was the highest for the JBC-D bull. The rates of the normal formation of two pronuclei and total sperm penetration were the highest in zygotes fertilized with sperm from the JBC-A bull. The sperm from the JBC-A bull had superior qualities and are thus the most appropriate choice for the preservation and reproduction of these endangered cattle.

Comparison of embryonic competence and clinical outcomes between early and late cumulus cell removal for in vitro fertilization

Objective

The impact of early mechanical removal of cumulus cells on fertilization and embryonic development is not yet precisely known. This study aimed to investigate the effects of early and late cumulus cell removal on fertilization, polyspermy, embryonic development potential, blastocyst development, and clinical outcomes.

Methods

A prospective study was conducted of patients who underwent in vitro fertilization between September 2019 and October 2020. Sibling oocytes were randomly allocated after insemination to early cumulus cell removal at 6 hours (group I) and late cumulus cell removal at 16–18 hours (group II). If total fertilization failure (TFF) was determined to have occurred at early cumulus cell removal, rescue intracytoplasmic sperm injection (ICSI) was performed. Fertilization, embryonic development, and pregnancy outcomes were compared.

Results

A total of 912 oocytes were assigned to group I (458 oocytes) and group II (454 oocytes). Fertilization, polyspermy, embryo quality, and pregnancy outcomes were not significantly different between both groups. Rescue ICSI enabled fertilization of 79.2% of the TFF oocytes.

Conclusion

Early cumulus cell removal at 6 hours had no significant difference in fertilization, polyspermy, embryo development, or obstetric and perinatal outcomes compared to late removal. Early cumulus cell removal combined with early rescue ICSI may have the potential to help couples with TFF.

Follicle-stimulating hormone mediates the consumption of serum-derived glycogen by bovine cumulus-oocyte complexes during in vitro maturation

Background and Aim:

Oocyte in vitro maturation (IVM) is an appealing approach for several assisted reproductive technologies and dissecting oocyte maturation. Nonetheless, IVM leads to lower developmental competence and usually relies on undefined, serum-containing media. Therefore, biochemical profiling aimed to explore fluctuations in IVM media content during the acquisition of oocyte developmental competence.

Materials and Methods:

Bovine cumulus-oocyte complexes (COCs) underwent IVM in TCM199 medium with Earle’s salts, supplemented with 2.0 mM L-glutamine, 10% fetal bovine serum, antibiotics, and 0.05 IU/mL porcine follicle-stimulating hormone (FSH+) or vehicle control (CTL) medium for 22 h.

Results:

FSH withdrawal (CTL) diminished several processes associated with the acquisition of oocyte developmental competence, such as reduced cumulus cell expansion, diminished estradiol synthesis (FSH+: 116.0±0.0 pg/mL vs. CTL: 97.6±18.0 pg/mL), and lower oocyte nuclear maturation rate (FSH+: 96.47% vs. CTL: 88.76%). Fresh media formulations (i.e., TCM199 with FSH or vehicle) were indistinguishable under biochemical profiling threshold conditions. Biochemical profiling showed similar total protein and lipid concentrations between groups. Further, total sugar concentrations diminished from fresh media to their post-IVM counterparts, albeit in an FSH-independent manner. Glycogen concentrations remained unaltered after IVM within CTL media, albeit were substantially lower after IVM under FSH+ conditions.

Conclusion:

FSH mediates the consumption of serum-derived glycogen by bovine COCs during IVM and implies that serum-free media should contain increased glucose concentrations to facilitate the acquisition of oocyte developmental competence.

Controlled spermatozoa-oocyte interaction improves embryo quality in sheep

The current protocols of in vitro fertilization and culture in sheep rely on paradigms established more than 25 years ago, where Metaphase II oocytes are co-incubated with capacitated spermatozoa overnight. While this approach maximizes the number of fertilized oocytes, on the other side it exposes them to high concentration of reactive oxygen species (ROS) generated by active and degenerating spermatozoa, and positively correlates with polyspermy. Here we set up to precisely define the time frame during which spermatozoa effectively penetrates and fertilizes the oocyte, in order to drastically reduce spermatozoa-oocyte interaction. To do that, in vitro matured sheep oocytes co-incubated with spermatozoa in IVF medium were sampled every 30 min (start of incubation time 0) to verify the presence of a fertilizing spermatozoon. Having defined the fertilization time frame (4 h, data from 105 oocytes), we next compared the standard IVF procedures overnight (about 16 h spermatozoa/oocyte exposure, group o/nIVF) with a short one (4 h, group shIVF). A lower polyspermic fertilization (> 2PN) was detected in shIVF (6.5%) compared to o/nIVF (17.8%), P < 0.05. The o/nIVF group resulted in a significantly lower 2-cell stage embryos, than shIVF [34.6% (81/234) vs 50.6% (122/241) respectively, P < 0.001]. Likewise, the development to blastocyst stage confirmed a better quality [29% (70/241) vs 23.5% (55/234), shIVF vs o/nIVF respectively] and an increased Total Cell Number (TCN) in shIVF embryos, compared with o/n ones. The data on ROS have confirmed that its generation is IVF time-dependent, with high levels in the o/nIVF group. Overall, the data suggest that a shorter oocyte-spermatozoa incubation results in an improved embryo production and a better embryo quality, very likely as a consequence of a shorter exposure to the free oxygen radicals and the ensuing oxidative stress imposed by overnight culture.

Melatonin improves rate of monospermic fertilization and early embryo development in a bovine IVF system

The developmental competence of male and female gametes is frequently reduced under in vitro conditions, mainly due to oxidative stress during handling. The amino-acid derived hormone melatonin has emerged as a potent non-enzymatic antioxidant in many biological systems. The goal of the present study was to evaluate the effects of melatonin on post-thaw sperm quality, fertilizing ability, and embryo development and competence in vitro after in vitro fertilization. Frozen-thawed bovine spermatozoa were incubated either in the presence of 10⁻¹¹ M melatonin (MT), or its solvent (ethanol; Sham-Control), or plain Tyrode’s Albumin Lactate Pyruvate medium (TALP, Control). Computer-Assisted Sperm Analysis (CASA) and flow cytometry data after 30 min, 120 min, and 180 min incubation did not reveal any significant effects of melatonin on average motility parameters, sperm subpopulation structure as determined by hierarchical cluster, or on the percentage of viable, acrosome intact sperm, or viable sperm with active mitochondria. Nevertheless, in vitro matured cumulus-oocyte-complexes fertilized with spermatozoa which had been preincubated with 10⁻¹¹ M melatonin (MT-Sperm) showed higher (P < 0.01) rates of monospermic fertilization, reduced (P < 0.05) polyspermy and enhanced (P < 0.05) embryo development compared to the Control group. Moreover, the relative abundance of MAPK13 in the in vitro-derived blastocysts was greater (P < 0.05) than observed in the Control group. In conclusion, adding melatonin to the sperm-preparation protocol for bovine IVF improved proper fertilization and enhanced embryonic development and competence in vitro.

Glutathione ethyl ester improved the age-induced decline in the developmental competence of bovine oocytes

The aberrant redox regulation and anti-oxidative defense is one of the main causes of age-induced decline in oocytes quality and embryo development in mammals. The present study aimed to elucidate the effect of glutathione ethyl ester (GSH-OEt), a cell-permeable glutathione (GSH) donor, on the developmental competence of oocytes in cows with advanced reproductive age. Oocytes were collected from cows aged 30-50 months or >120 months, which were defined as young or aged, respectively, and subjected to in vitro maturation (IVM) in the presence of 5 mM of GSH-OEt. In aged cows, the GSH level in follicular fluid was lower, and the intracellular levels of reactive oxygen species (ROS) in post-IVM oocytes was higher than those in young cows. GSH-OEt supplementation during IVM reduced the ROS contents of oocyte in aged cows but not in young cows. GSH-OEt treatment promoted the meiotic progression and increased the proportion of oocytes with mature cytoplasm containing evenly dispersed cortical granules in aged cows. After in vitro fertilization, the normal fertilization and development to the blastocyst stage were enhanced by GSH-OEt in aged cows to levels comparable to those in young cows. Further, oocyte maturation in the presence of GSH-OEt increased the proportion of diploid blastocyst in aged cows. In contrast, GSH-OEt failed to enhance the oocyte maturation, fertilization, and embryo development in young cows. Taken together, the exogenous supplementation of GSH-OEt during IVM modulated the age-related oxidative damage of bovine oocytes and improved the developmental competence of oocytes in aged cows. Oocytes presented a distinct response to GSH-OEt treatment depending on the donor age. GSH-OEt supplementation during IVM could be of practical value through the efficiency improvement of chromosomally normal embryo production in aged cows.

The influence of processed total non-forward and non-motile sperm count on the outcome of artificial insemination with the husband's semen

Background

Artificial insemination with the husband’s semen (AIH) is an economical and noninvasive method of infertility treatment. However, AIH’s pregnancy rate is much lower than in vitro fertilization (IVF) as its multiple and complex uncertainty factors. Semen quality has been one of the main factors which affect the pregnancy outcome of AIH.

Methods

The relevant parameters of 1,142 AIH cycles were retrospectively studied, including the general parameters and the semen quality parameters among clinical pregnancy, biochemical pregnancy, non-pregnancy group, age, infertility duration, infertility type, body mass index (BMI), cycle count, morphology in previously semen examination, and semen quality parameters on the day of AIH.

Results

The statistically significant difference was only found on processed total non-forward and non-motile sperm count (N-TFMSC). The mean processed N-TFMSC in the biochemical pregnancy group was 6.37±4.27 million, significantly higher than the other two groups (vs. 4.40±3.15 million or vs. 4.48±3.60 million, P<0.05). The study was then divided into two groups according to processed N-TFMSC, Group 1 ≤5.0 million, and Group 2 >5.0 million. A statistical increase in biochemical pregnancy rate was observed when the processed N-TFMSC was >5.0 million (2.72% vs. 0.90%).

Conclusions

Processed N-TFMSC may be one of the independent factors on AIH’s outcome; it should be given equal attention the same as processed total forward motile sperm count (TFMSC).

Preventing polyspermy in mammalian eggs-Contributions of the membrane block and other mechanisms

The egg's blocks to polyspermy (fertilization of an egg by more than one sperm) were originally identified in marine and aquatic species with external fertilization, but polyspermy matters in mammalian reproduction too. Embryonic triploidy is a noteworthy event associated with pregnancy complications and loss. Polyspermy is a major cause of triploidy with up to 80% of triploid conceptuses being the result of dispermic fertilization. The mammalian female reproductive tract regulates the number of sperm that reach the site of fertilization, but mammals also utilize egg-based blocks to polyspermy. The egg-based blocks occur on the mammalian egg coat (the zona pellucida) and the egg plasma membrane, with apparent variation between different mammalian species regarding the extent to which one or both are used. The zona pellucida block to polyspermy has some similarities to the slow block in water-dwelling species, but the mammalian membrane block to polyspermy differs substantially from the fast electrical block that has been characterized in marine and aquatic species. This review discusses what is known about the incidence of polyspermy in mammals and about the mammalian membrane block to polyspermy, as well as notes some lesser-characterized potential mechanisms contributing to polyspermy prevention in mammals.

Polyspermy produces viable haploid/diploid mosaics in sturgeon

Most of sturgeon species (Acipenseridae) are currently critically endangered. Attempts to revive these populations include artificial breeding in hatcheries. However, under artificial reproduction, sturgeon embryos occasionally develop atypically, showing 3, 5, 6, 7, 9, or 10 cells at the 2- to 4-cell stage. This study was undertaken with the objective of understanding the mechanism of the atypical division (AD) in embryos during artificial breeding. Using several sturgeon species, we tested two hypotheses: (1) polyspermy and (2) retention of the second polar body. We found that (1) AD embryos survive similar to controls, (2) the ratio of AD embryos is positively correlated with the amount of sperm used for fertilization, (3) the number of micropyles and the area covered by them in AD embryos is significantly greater when compared to controls, (4) numerous spermatozoa nuclei are in the cytoplasm after fertilization, (5) all AD embryos are mosaics, and (6) AD fishes with n/2n ploidy contain diploid cells from maternal and paternal genetic markers, while the haploid cells contained only paternal ones. These results clearly indicate that AD embryos arise from plasmogamy where the accessory spermatozoon/spermatozoa entry the egg and develop jointly with zygotic cells. This suggests that a well-controlled fertilization procedure is needed to prevent the production of sturgeon with irregular ploidy, which can have detrimental genetic effects on sturgeon populations. On the other hand, if AD fish can produce haploid-derived clonal gametes, induction of multiple-sperm mosaicism might be a useful tool for the rapid production of isogenic strains of sturgeons.

Resveratrol addition to in vitro maturation and in vitro culture media enhances developmental competence of sheep embryos

The present study aimed to examine the effects of adding different concentrations of resveratrol during in vitro culture (IVC) alone and during both in vitro maturation (IVM) and IVC on ovine blastocyst yield and quality. Therefore, this study was conducted in two separate experiments. The first experiment was carried out to test the effect of different concentrations of resveratrol (0, 0.1, 0.25, 0.5, 2.0, and 5.0 μM) in the IVC medium on cleavage, morula, developmental potential of blastocyst, and total cell number (TCN) of the embryos. Addition of 0.25 and 0.5 μM of resveratrol during IVC significantly enhanced morula and blastocyst rates as compared with other groups (P < 0.05). Also, supplementation of the IVC medium with 0.5 μM of resveratrol had beneficial effects on trophectoderm cells (TE), inner cell mass (ICM), and TCN of blastocysts. In the second experiment, the same concentrations of resveratrol (0, 0.1, 0.25, 0.5, 2.0, and 5.0 μM) were applied during IVM and IVC. Therefore, oocytes were matured in vitro in the presence of different concentrations of resveratrol for 22-24 h. After in vitro fertilization, presumptive zygotes were cultured in media containing 0, 0.1, 0.25, 0.5, 2.0, and 5.0 μM of resveratrol for 8 d. No significant difference was found in the percentage of oocytes developed to MII (0, 0.1, 0.25, 0.5, and 2.0 μM of resveratrol), but the percentage of oocytes developed to MII were significantly lower in 5.0 μM of resveratrol in comparison with other groups. Addition of 0.5 μM of resveratrol to the maturation and culture media significantly increased morula and blastocyst rates compared with other groups (P < 0.05). However, a too high concentration of resveratrol (5.0 μM) during IVM and IVC decreased cleavage, morula, and blastocyst rates compared with low concentrations (P < 0.05). Treatment with 0.5/0.5 μM of resveratrol during IVM/IVC significantly improved the TE, ICM, and TCN of blastocysts. In conclusion, sequential treatment with 0.5 μM of resveratrol during IVM and IVC and during IVC alone improved the developmental competence of oocytes, which was reflected in higher blastocyst rates and TCN of blastocysts.

First evidence of viable progeny from three interspecific parents in sturgeon

Polyspermy is the most commonly observed cause of embryonic abnormalities in fertilization, often resulting in death. In sterlet (Acipenser ruthenus), however, polyspermic embryos have high survival (similar to a control group) and morphological development is similar to monospermic larvae. Ploidy of these individuals is n/2n mosaic (whereas the normal state for A. ruthenus is a functional diploid). This study was undertaken to test whether sturgeon eggs can be fertilized by several spermatozoa from different species to produce viable offspring from three interspecific parents: A. ruthenus (2n), A. gueldenstaedtii (4n), and A. baerii (4n). Four trials were performed: (1) and (2) A. baerii eggs were fertilized with a mixture of A. ruthenus and A. gueldenstaedtii sperm; (3) A. gueldenstaedtii eggs were fertilized with a mixture of A. baerii and A. ruthenus sperm; and (4) A. gueldenstaedtii eggs were fertilized with a mixture of A. gueldenstaedtii and A. ruthenus sperm. Fertilized embryos with abnormal cleavage (3, 5, 6, 7, 9, and 10 cells) were collected and kept separately until 14 days post-fertilization. Ploidy level of 25 larvae (hatched from abnormal cleaved embryos) was evaluated by flow cytometry. Forty-four percent of observed hybrids had a mosaic 2n/3n ploidy. Five larva were processed further with microsatellite analysis and demonstrated that three specimens were heterospecific polyspermic larvae, containing alleles from three parents, and two specimens were conspesific polyspermic larvae from two parents. This astonishing phenomenon was emphasized by the fact that it was generated without any significant intervention.

Application of intracytoplasmic sperm injection to the embryo production in aged cows

Reduction in oocyte quality is a major factor responsible for declining fertility associated with maternal aging in cows. The objective of the present study was to determine whether intracytoplasmic sperm injection (ICSI) could increase the efficiency of embryo production in older cows. We used cows aged 30 to 50 months or >120 months, which were defined as young or aged, respectively. The distribution of cortical granules in oocytes was affected by age as older cows had lower proportion of oocytes with mature cytoplasm containing evenly dispersed cortical granules compared to young cows. Although fertilization rates did not differ significantly between the two groups after in vitro fertilization (IVF), the rate of abnormal fertilization was higher, and the numbers of total and diploid blastocysts were lower for aged cows compared to young cows. However, in the embryos produced by ICSI, there was no significant difference in these parameters between young and aged cows. Although ICSI did not improve the blastocyst development rate, ICSI increased the proportion of diploid blastocysts in aged cows compared to IVF. In conclusion, maternal aging may negatively affect cytoplasmic maturation of bovine oocytes, which could be associated with abnormal fertilization or low developmental competence of oocytes. Our data also suggests beneficial effects of ICSI on the production of chromosomally normal embryos in aged cows.

Melatonin and tannic acid supplementation in vitro improve fertilization and embryonic development in pigs

The objective of this study was to determine the effects of melatonin supplementation during maturation and tannic acid supplementation during IVF on fertilization kinetics and early embryonic development. Experiment 1 determined the optimum concentration of melatonin supplemented to the oocytes for subsequent embryonic development. Oocytes (n = 400) were supplemented at 22 h of maturation with 0, 75, 100, or 150 nm melatonin and then subjected to IVF and embryo culture. After IVF, a portion of the embryos were evaluated for penetration, polyspermy, and male pronuclear (MPN) formation rates. Embryos were evaluated 48 h after IVF for cleavage and 144 h for blastocyst formation. There were no significant differences between treatment groups with respect to penetration and polyspermy. Supplementation of 150 nm melatonin produced a significantly greater (P < 0.05) percent of embryos with MPN compared to those supplemented with 75 nm or 100 nm. Supplementation of 150 nm melatonin produced significantly less (P < 0.05) embryos cleaved by 48 h after IVF while 75 nm melatonin supplementation had a significantly higher (P < 0.05) percentage of blastocyst formation by 144 h after IVF. Based on the optimal concentration of melatonin observed in experiment 1, experiment 2 determined the effects of supplementing 75 nm melatonin to the maturation media and 5.0 μg/ml tannic acid supplementation during IVF on oxidative stress, fertilization kinetics, and embryonic development. Oocytes (n = 720) were supplemented at 22 h of maturation with or without 75 nm melatonin and then fertilized with frozen-thawed sperm supplemented with or without 5 μg/ml tannic acid. Reactive oxygen species levels were measured in matured oocytes using 2’,7’-dichlorodihydrofluorescein diacetate. Oocytes supplemented with 75 nm melatonin had significantly less (P < 0.05) reactive oxygen species generation and oocytes fertilized with sperm incubated with tannic acid had a significantly less (P < 0.05) incidence of polyspermic penetration compared to no supplementation. All treatment groups had significantly greater (P < 0.05) incidence of male pronuclear formation compared to oocytes not supplemented with melatonin and fertilized without tannic acid. Oocytes that were supplemented with melatonin and fertilized with sperm incubated with tannic acid had a significantly higher (P < 0.05) percentage of blastocyst formation by 144 h post-IVF compared all other treatment groups. Results indicate that supplementation of 75 nm melatonin during oocyte maturation and 5 μg/ml tannic acid during IVF leads to a decrease in oxidative stress, increase in IVF success and subsequent embryo development in pigs.

The Vienna consensus: report of an expert meeting on the development of ART laboratory performance indicators

This proceedings report presents the outcomes from an international workshop supported by the European Society of Human Reproduction and Embryology (ESHRE) and Alpha Scientists in Reproductive Medicine, designed to establish consensus on definitions and recommended values for Indicators for the assisted reproductive technology (ART) laboratory. Minimum performance-level values ('competency') and aspirational ('benchmark') values were recommended for a total of 19 Indicators, including 12 Key Performance Indicators (KPIs), five Performance Indicators (PIs), and two Reference Indicators (RIs).

The Vienna consensus: report of an expert meeting on the development of art laboratory performance indicators

STUDY QUESTION

What are appropriate performance indicators (PIs) for ART laboratories for use in monitoring 'fresh' IVF and ICSI cycles?

SUMMARY ANSWER

Minimum performance (competence) levels and aspirational (benchmark) values were recommended for a total of 19 indicators, including 12 key PIs (KPIs), five PIs and two reference indicators (RIs).

WHAT IS ALREADY KNOWN

PIs are necessary for systematic monitoring of the laboratory and an important element within the Quality Management System. However, there are no established PIs for ART laboratories and there is very little evidence on the topic.

STUDY DESIGN SIZE DURATION

This is the report of a 2-day consensus meeting of expert professionals. As a starting point for the discussion, two surveys were organized to collect information on indicators used in IVF laboratories. During the meeting, the results of the surveys, scientific evidence (where available), and personal clinical experience where integrated into presentations by experts on specific topics. After presentation, each proposed indicator was discussed until consensus was reached within the panel.

PARTICIPANTS/MATERIALS SETTING METHODS

Expert professionals representing different countries and settings convened in the consensus meeting.

MAIN RESULTS AND THE ROLE OF CHANCE

The paper is divided in two parts: the workshop report and the recommendations of the expert panel. The second part reflects the discussion on each of the indicators, with the agreed definition, competence level and benchmark value for each of the 19 indicators, including 12 KPIs, 5 PIs and 2 RIs.

LIMITATIONS REASONS FOR CAUTION

The KPIs are mainly based on expert opinion. Future research may warrant an update of the recommended KPIs, their definition and the competence level and benchmark values.

WIDER IMPLICATIONS OF THE FINDINGS

Based on the information presented, each ART laboratory should select its own set of KPIs founded on laboratory organization, and processes.

STUDY FUNDING/COMPETING INTERESTS

The consensus meeting and writing of the paper was supported by funds from ESHRE and Alpha. Alpha gratefully acknowledges the following organizations for their financial support, through the provision of unrestricted educational grants: Global Fertility Alliance, Merck, Origio and Vitrolife. There are no conflicts of interest to disclose.

Fourier Transform Infrared Spectroscopic Analysis of the Intact Zona Pellucida of the Mammalian Egg: Changes in the Secondary Structure of Bovine Zona Pellucida Proteins During Fertilization

The zona pellucida is the acellular transparent envelope surrounding the mammalian oocyte. An analysis of the changes in the structures of zona pellucida proteins is essential for understanding the molecular mechanisms underlying the important physiological roles of the zona during fertilization and prelmplantatlon. The hardening of the zona caused by the structural changes during fertilization is generally accepted to be responsible for blocking polyspermy. In this study, we analyzed changes in the secondary structure of the zona during fertilization by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy. The predominance of β-sheet structure in porcine ovarian egg zona proteins in water was ascertained using FTIR spectra. α-Helix structure was also present. The attenuated total reflection (ATR)-FTIR spectrum of intact, unsolubilized porcine zonae pellucidae from ovarian eggs Indicated that the zona proteins in the native zona pellucida also have β-structure as the main constituent. Attenuated total reflectlon-FTIR spectroscopy of intact bovine zona pellucida obtained from ovarian and fertilized eggs at the blastocyst stage revealed that the β-structure content Increased during fertilization. Furthermore, a reduction of the thickness of the zona during fertilization was observed using transmission electron microscopy. Therefore, the change in the zona architecture that causes hardening of the zona during fertilization is accompanied by changes in the secondary structure of the zona proteins.

Polyspermy in birds: sperm numbers and embryo survival

Polyspermy is a major puzzle in reproductive biology. In some taxa, multiple sperm enter the ovum as part of the normal fertilization process, whereas in others, penetration of the ovum by more than one sperm is lethal. In birds, several sperm typically enter the germinal disc, yet only one fuses with the female pronucleus. It is unclear whether supernumerary sperm play an essential role in the avian fertilization process and, if they do, how females regulate the progression of sperm through the oviduct to ensure an appropriate number reach the ovum. Here, we show that when very few sperm penetrate the avian ovum, embryos are unlikely to survive beyond the earliest stages of development. We also show that when the number of inseminated sperm is limited, a greater proportion than expected reach and penetrate the ovum, indicating that females compensate for low sperm numbers in the oviduct. Our results suggest a functional role for supernumerary sperm in the processes of fertilization and early embryogenesis, providing an exciting expansion of our understanding of sperm function in birds.

Expressão gênica em ovócitos suínos de diferentes classificações morfológicas

A produção in vitro de embriões suínos tem alcançado resultados insatisfatórios: ovócitos maturados in vivo produzem uma porcentagem maior de embriões em relação aos maturados in vitro. O sucesso da maturação in vitro está diretamente relacionado com a competência ovocitária. Somente ovócitos competentes são capazes de serem fecundados e terem desenvolvimento embrionário normal. A competência ovocitária pode ser avaliada por vários parâmetros. Recentemente têm sido utilizados como parâmetro os estudos da expressão de genes associados com a competência. O presente trabalho teve por objetivo avaliar diferenças na expressão dos genes BMP15, RYBP, MATER e ZAR1 em ovócitos imaturos de diferentes classes morfológicas, sendo elas: 1, 2, 3 e 4, com a finalidade de proporcionar importantes marcadores moleculares relacionados com a capacidade ovocitária. O RNA total dos ovócitos foi extraído e utilizado como molde para a síntese da primeira fita de cDNA. Os resultados da expressão gênica foram analisados utilizando-se modelo misto, considerando os dados de expressão gênica variável dependente e as classes ovocitárias variáveis independentes. Os genes BMP15, ZAR1 e RYBP apresentaram expressão semelhante nas classes ovocitárias 1, 2 e 3; somente a categoria 4 diferiu na expressão desses genes (P<0,05). O gene MATER foi expresso de forma semelhante em todas as classes ovocitárias estudadas (P>0,05). A técnica de RT-qPCR foi eficiente para detecção desses transcritos em ovócitos de diferentes classes. No entanto, para melhor entendimento do envolvimento desses transcritos na aquisição da competência ovocitária, são necessários mais estudos avaliando ovócitos de diferentes classes morfológicas, em diferentes fases de desenvolvimento, e implicação de outros genes envolvidos com a competência ovocitária.

Influence of sperm fertilising concentration, sperm selection method and sperm capacitation procedure on the incidence of numerical chromosomal abnormalities in IVF early bovine embryos

The occurrence of numerical chromosomal aberrations, widely described as a major cause of mortality in in vitro-produced (IVP) embryos, has been linked to several factors. In the present study we investigated the effect of sperm fertilising concentration and semen handling (sperm selection and capacitation) before IVF on the rate of numerical chromosomal abnormalities in bovine embryos. In all, 466 IVP cattle embryos were karyotyped throughout three sequential experiments, analysing the effects of sperm fertilising concentration (0.1, 1.0 or 10×10(6) spermatozoa mL(-1)), selection method (unselected or Percoll-selected spermatozoa) and capacitation medium (bovine serum albumin (BSA), heparin or their combination). The percentage of normal (diploid) and aberrant (haploid, polyploid or aneuploid) embryos was noted in each experiment. The rate of numerical chromosomal abnormalities was mainly affected by sperm fertilising concentration (P<0.01) and, to a lesser extent, by the sperm capacitation medium (P<0.05). Polyploidy and haploidy rates were only affected by sperm fertilising concentration (P<0.05). Interestingly, the sperm selection technique used in the present study did not reduce the incidence of chromosome abnormalities in IVP cattle embryos (P>0.05). Finally, aneuploidy rates were not affected during the experiments (P>0.05), which suggests that they are not related to sperm-related factors. On the basis of these results, we conclude that sperm fertilising concentration is the 'paternal' key factor that affects the rate of numerical chromosomal abnormalities in IVP bovine embryos. By making small adjustments to fertilising protocols, the rate of cytogenetically aberrant embryos can be markedly reduced.

Effects of triploidy incidence on clinical outcomes for IVF-ET cycles in different ovarian stimulation protocols

PURPOSE

To discuss the relationship between triploidy incidence and clinical outcomes of embryos derived from normally fertilized oocytes from the same cohort for in vitro fertilization-embryo transfer (IVF-ET) cycles in different ovarian stimulation protocol.

METHODS

This study included 2070 in vitro fertilization (IVF) cycles with long-term protocol, 802 IVF cycles with ultra short-term protocol and 508 IVF-D (in vitro fertilization by donor semen) cycles with long-term protocol from January 2013 to September 2014. According to the different 3PN rate, patients were divided into three groups as follows: Group 1 included patients with 0% 3PN zygotes, Group 2 included patients with 1-25% 3PN zygotes and Group 3 included patients with >25% 3PN zygotes.

MAIN OUTCOME MEASURE

female age, no. of retrieved oocytes, normal fertilization rate, day-3 grade I + II embryos rate, day-3 grade I + II + III embryos rate, implantation rate, pregnancy rate and early abortion rate.

RESULTS

Triploidy cycle incidence rate in IVF and IVF-D cycles with long-term protocol were significantly higher than in IVF cycles with ultra short-term protocol (p < 0.001). Triploidy fertilization rate found no significant difference between the three groups (p > 0.05). In three protocols, normal fertilization rate in 3PN = 0% and 3PN = 1-25% groups were significantly higher compared to 3PN > 25% group (p < 0.001). In IVF cycles with long-term protocol, the day-3 grade I + II embryos, implantation and pregnancy rate in 3PN > 25% group were significantly lower than other two groups (p < 0.05). The day-3 grade I + II + III embryos and early abortion rate found no significant difference between the three groups (p > 0.05). In IVF cycles with ultra short-term protocol, there were no significant differences found in day-3 grade I + II embryos, day-3 grade I + II + III embryos, implantation, pregnancy and early abortion rate (p > 0.05). In IVF-D cycles with long-term protocol, the day-3 grade I + II embryos, day-3 grade I + II + III embryos and implantation rate in 3PN > 25% group were significantly lower than other two groups (p < 0.05). The pregnancy and early abortion rates found no significant difference in the three groups (p > 0.05).

CONCLUSION

We observed that high proportion of triploid zygotes made a negative effect on clinical outcomes for IVF-ET cycles with long-term protocol.

The effect of temperature during liquid storage of in vitro-matured bovine oocytes on subsequent embryo development

The aim of the present study was to optimize the temperature for the temporal storage of matured bovine oocytes. In vitro-matured bovine oocytes were preserved in HEPES-buffered TCM199 medium supplemented with 10% newborn calf serum at different temperatures (4 °C, 15 °C, 25 °C, and 38.5 °C) for 20 hours. Embryo development and blastocyst quality after in vitro fertilization, cytoplasmic ATP and glutathione levels in oocytes, and the frequency of apoptotic oocytes were compared among storage groups and a control group without storage. Among the storage groups, those at 25 °C and 38.5 °C showed the highest rates of blastocyst development (19.3% and 24.5%, respectively) compared with those stored at 4 °C and 15 °C (8.5% and 14.9%, respectively); however, blastocyst formation rates in all storage groups were lower than that in the control group (39.8%; P < 0.05). Storage at 38.5 °C and 15 °C was associated with reduced cell numbers in resultant blastocysts compared with the control and the 25 °C storage groups. Storage at 4 °C reduced metabolic activity of oocytes characterized by their lower ATP levels compared with the other groups. Storage for 20 hours significantly reduced the glutathione content in oocytes in all groups in a similar manner, irrespective of the temperature. Storage at 4 °C or 15 °C but not at 25 °C and 38.5 °C significantly increased the percentage of apoptotic oocytes compared with the control group. In conclusion, 25 °C was found to be the most suitable temperature for the temporal storage of matured bovine oocytes regarding both the developmental competence of oocytes and the quality of resultant blastocysts.

The effects of glucuronic acid and N-acetyl-D-glucosamine on in vitro fertilisation of porcine oocytes

High incidences of polyspermic penetration continue to challenge researchers during porcine in vitro fertilisation (IVF). The aim of this study was to reduce the incidence of polyspermy by increasing the perivitelline space thickness with glucuronic acid and N-acetyl-D-glucosamine (GlcNAc) supplementation during oocyte maturation. After maturation, zona pellucida and perivitelline space thicknesses, intracellular glutathione concentrations and fertilisation kinetics were measured, in addition to embryonic cleavage and blastocyst formation at 48h and 144h after IVF, respectively. There were no significant differences between the treatments for zona pellucida thickness, penetration rates, male pronuclear formation or cortical granule exocytosis. Glucuronic acid supplementation significantly increased (PPPP<0.05) of cleavage and blastocyst formation by 48 and 144h after IVF compared with all other groups. These results indicate that supplementing with 0.005mM glucuronic acid and 0.005mM GlcNAc during oocyte maturation decreases the incidence of polyspermic penetration by increasing perivitelline space thickness and improving embryo development in pigs.

A new rolling culture-based in vitro fertilization system capable of reducing polyspermy in porcine oocytes

The high incidence of polyspermy is one of the major obstacles during in vitro fertilization (IVF) in pigs. To overcome this, we developed a novel IVF method, which involves constant rotation. Oocytes matured in vitro were mixed with spermatozoa (0.2 × 10(5) sperm/mL) in an IVF medium (200 μL) using a 200 μL PCR tube. This tube was then rotated at 1 rpm for 6 h at 38.5°C in a rotation mixer (experimental group). A second PCR tube was simultaneously cultured without rotation (control group). The rate of polyspermy was evaluated 12 h after insemination and was significantly (P < 0.05; 21.0% vs. 48.3%) lower in the experimental group than in the control group. Sperm penetration rate was similar in oocytes from the experimental and control groups (75.2% vs. 83.1%). However, monospermic fertilization rate of the oocytes was significantly (P < 0.05; 44.8% vs. 21.2%) higher in the experimental group than in the control group. Furthermore, the rate of blastocyst formation (30.1% vs. 20.8%) increased in the experimental group, as compared to the control group. This present system will contribute to increase the efficacy of blastocyst production through reduction of polyspermic penetration.

The value of second polar body detection 4 hours after insemination and early rescue ICSI in preventing complete fertilisation failure in patients with borderline semen

In this study we evaluated the value of short-time insemination and early rescue intra-cytoplasmic sperm injection (ICSI) in preventing the occurrence of complete fertilisation failure for mild or moderate male infertility patients. A total of 866 couples with borderline semen who underwent in vitro fertilisation treatment in 2010 were included. Regular insemination was performed between January and June of 2010 and short-term insemination was performed from July through December 2010, where, as early as 4h after insemination, oocytes were denuded from cumulus cells and extrusion of the second polar body was evaluated. Of the 4153 mature oocytes with a detectable second polar body 4 h after insemination, 3874 (93.3%) showed signs of fertilisation on Day 1. Where no second polar body was present in any of the retrieved oocytes for a given patient, rescue ICSI was performed immediately. Similar rates of normal fertilisation and percentage of good-quality embryos were obtained between early rescue ICSI and regular ICSI. Clinical pregnancy occurred in 16 of 43 patients (37.2%) receiving early rescue ICSI. Our results showed early rescue ICSI in combination with evaluation of the second polar body 4 h following insemination is an effective method to prevent complete fertilisation failure for patients with mild or moderate male infertility.

Female extra-pair mating: adaptation or genetic constraint?

Why do females of so many socially monogamous species regularly engage in matings outside the pair bond? This question has puzzled behavioural ecologists for more than two decades. Until recently, an adaptionist's point of view prevailed: if females actively seek extra-pair copulations, as has been observed in several species, they must somehow benefit from this behaviour. However, do they? In this review, we argue that adaptive scenarios have received disproportionate research attention, whereas nonadaptive phenomena, such as pathological polyspermy, de novo mutations, and genetic constraints, have been neglected by empiricists and theoreticians alike. We suggest that these topics deserve to be taken seriously and that future work would benefit from combining classical behavioural ecology with reproductive physiology and evolutionary genetics.

Deubiquitinating enzymes in oocyte maturation, fertilization and preimplantation embryo development

Post-translational modifications of cellular proteins by ubiquitin and ubiquitin-like protein modifiers are important regulatory events involved in diverse aspects of gamete and embryo physiology including oocyte maturation, fertilization and development of embryos to term. Deubiquitinating enzymes (DUBs) regulate proteolysis by reversing ubiquitination, which targets proteins to the 26S proteasome. The ubiquitin C-terminal hydrolases (UCHs) comprise are DUBs that play a role in the removal of multi-ubiquitin chains. We review here the roles of UCHs in oocytes maturation, fertilization and development in mouse, bovine, porcine and rhesus monkeys. Oocyte UCHs contributes to fertilization and embryogenesis by regulating the physiology of the oocyte and blastomere cortex as well as oocyte spindle. Lack of UCHs in embryos reduces fertilization, while mutant embryos fail to undergo compaction and blastocyst formation. In addition to advancing our understanding of reproductive process, research on the role of deubiquitinating enzymes will allow us to better understand and treat human infertility, and to optimize reproductive performance in agriculturally important livestock species.

Resveratrol improves the mitochondrial function and fertilization outcome of bovine oocytes

The aim of the present study was to address the effect of resveratrol-mediated upregulation of sirtuin 1 (SIRT1) during oocyte maturation on mitochondrial function, the developmental ability of oocytes and on mechanisms responsible for blockage of polyspermic fertilization. Oocytes collected from slaughterhouse-derived ovaries were cultured in TCM-199 medium supplemented with 10% FCS and 0 or 20 µM resveratrol (Res). We examined the effect of Res on SIRT1 expression in in vitro-matured oocytes (Exp 1); fertilization and developmental ability (Exp 2); mitochondrial DNA copy number (Mt number), ATP content and mitochondrial membrane potential in matured oocytes (Exp 3); and the time required for proteinase to dissolve the zona pellucida following in vitro fertilization (as a marker of zona pellucida hardening), as well as on the distribution of cortical granules before and after fertilization (Exp 4). In Exp 1, the 20 µM Res treatment upregulated protein expression of SIRT1 in oocytes. In Exp 2, Res treatment improved the ratio of normal fertilization and the total cell number of blastocysts. In Exp 3, Res treatment significantly increased the ATP content in matured oocytes. Additionally, Res increased the overall Mt number and mitochondrial membrane potential, but the effect was donor-dependent. In Exp 4, Res-induced zona hardening improved the distribution and exocytosis of cortical granules after in vitro fertilization. In conclusion, Res improved the quality of oocytes by improving mitochondrial quantity and quality. In addition, Res added to the maturation medium enhanced SIRT1 protein expression in oocytes and improved fertilization via reinforcement of the mechanisms responsible for blockage of polyspermic fertilization.

Sperm-egg interaction and functional assessment of springbok, impala and blesbok cauda epididymal spermatozoa using a domestic cattle in vitro fertilization system

The study assesses the possibility to estimate the potential fertility of post-thawed antelope (Antidorcas marsupialis), impala (Aepyceros melampus) and blesbok (Damaliscus dorcus phillipsi) epididymal sperm using homologous and heterologous IVF and the functioning of cattle IVF system to produce antelope embryos. Cauda epididymal sperm were collected from the antelope and cryopreserved under field conditions. In vitro matured domestic cow, blesbok and springbok oocytes were co-incubated in modified-Tyrode Lactate (m-TL) IVF media with springbok, impala and blesbok sperm for heterologous IVF and springbok and blesbok sperm for homologous IVF. A group of presumptive zygotes from each treatment were examined for sperm penetration and male pronuclear formation after 18h and the remainder were cultured and evaluated for embryo cleavage 22h later. The study shows that Modified Tyrode Lactate in vitro fertilization media supports survivability, capacitation and hyperactivation of springbok, impala and blesbok sperm. Springbok, impala and blesbok post-thawed epididymal spermatozoa are capable of fertilizing domestic cow oocytes under conditions that support domestic cattle IVF. Penetration, male pronuclear formation and embryo cleavage did not differ (p>0.05) between cow oocytes inseminated with sperm from springbok, impala or blesbok however these parameters were higher (p<0.05) for oocytes inseminated with bull sperm. Modified Tyrode Lactate IVF media supported homologous fertilization and embryo development in springbok and blesbok however did not support blastocyst development. These findings suggest that cattle provide a useful model for evaluating springbok, impala and blesbok post-thawed cauda epididymal sperm functionality. Domestic cattle embryo culture conditions need to be modified to promote blastosyst development in these antelope species. Such research provides an important tool in assisted reproductive technology development when high biological value material is utilized for wild species recovery plans.

Evaluation of zona pellucida function for sperm penetration during in vitro fertilization in pigs

In porcine oocytes, the function of the zona pellucida (ZP) with regard to sperm penetration or prevention of polyspermy is not well understood. In the present study, we investigated the effects of the ZP on sperm penetration during in vitro fertilization (IVF). We collected in vitro-matured oocytes with a first polar body (ZP+ oocytes). Some of them were freed from the ZP (ZP− oocytes) by two treatments (pronase and mechanical pipetting), and the effects of these treatments on sperm penetration parameters (sperm penetration rate and numbers of penetrated sperm per oocyte) were evaluated. There was no evident difference in the parameters between the two groups. Secondly, we compared the sperm penetration parameters of ZP+ and ZP− oocytes using frozen-thawed epididymal spermatozoa from four boars. Sperm penetration into ZP+ oocytes was found to be accelerated relative to ZP− oocytes. Thirdly, we evaluated the sperm penetration of ZP+ and ZP− oocytes at 1−10 h after IVF (3 h gamete co-incubation). The proportions of oocytes penetrated by sperm increased significantly with time in both groups; however, the number of penetrated sperm per oocyte did not increase in ZP− oocytes. Finally, we performed IVF using ZP− oocytes divided into control (3 h) and prolonged gamete co-incubation (5 h) groups. Greater numbers of sperm penetrated in the 5 h group than in the control group. These results suggest that the ZP and oolemma are not competent factors for prevention of polyspermy in our present porcine IVF system. However, it appears that ZP removal is one of the possibilities for reducing polyspermic penetration in vitro in pigs.

Brief co-incubation of sperm and oocytes for in vitro fertilization techniques

BACKGROUND

The in vitro fertilization (IVF) technique is commonly used and is the only treatment option for a proportion of infertile couples. To obtain better outcomes of IVF, it is important to enhance embryo quality by optimizing IVF techniques. In IVF procedures, oocytes and sperm are routinely co-incubated overnight, which may expose oocytes and zygotes to suboptimal culture conditions with increased reactive oxygen species (ROS) produced by sperm in this long term culture. As an attempt to avoid possible detrimental effects on the oocytes from long exposure to sperm, the brief co-incubation insemination protocol was developed. However, despite a number of studies in this area, it is unclear whether brief co-incubation improves the IVF outcomes compared with the standard overnight insemination protocol.

OBJECTIVES

This Cochrane review aimed to determine whether brief co-incubation of sperm and oocytes improves outcomes compared with the standard overnight insemination protocol for women undergoing IVF.

SEARCH METHODS

We searched the Cochrane Menstrual Disorders and Subfertility Group Register (14 June 2012), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, 1st quarter), MEDLINE (1948 to 14 June 2012), EMBASE (1989 to 14 June 2012), PsycINFO (1806 to 14 June 2012) and CINAHL (1980 to 26 July 2012). In addition, we searched trials registers, reference lists of articles, conference proceedings (American Society for Reproductive Medicine (ASRM), European Society of Human Reproduction and Embryology (ESHRE)) and contacted experts in the field.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) comparing brief co-incubation of gametes with the standard overnight insemination protocol.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion and trial quality, and extracted data. Disagreements were resolved by discussion with a third author. Statistical analysis was performed using RevMan software.

MAIN RESULTS

Eight RCTs with 733 women in total that compared brief co-incubation and the standard insemination protocol were included. Live birth was not reported in the included studies. For ongoing pregnancy rate, there were 127 ongoing pregnancies in two trials including 426 women. The low quality evidence showed that brief co-incubation was associated with an increased ongoing pregnancy rate compared to the standard insemination protocol (pooled odds ratio (OR) 2.42, 95% confidence interval (CI) 1.55 to 3.77; P < 0.0001, I(2) = 0%). Measuring clinical pregnancy rate, there were 93 clinical pregnancies in three trials including 372 women. The low quality evidence showed that brief co-incubation was associated with a significantly higher clinical pregnancy rate than the overnight insemination protocol (pooled OR 2.36, 95% CI 1.45 to 3.85; P = 0.0006, I(2) = 0%). For the miscarriage rate, there were six miscarriages in one trial including 167 women. This low quality evidence suggested no significant difference in the odds of miscarriage between brief co-incubation and standard insemination (OR 1.98, 95% CI 0.35 to 11.09; P = 0.44).

AUTHORS' CONCLUSIONS

This review has provided evidence that brief co-incubation of sperm and oocytes may improve the ongoing pregnancy and clinical pregnancy rates for infertile women undergoing IVF cycles. More RCTs are required to assess whether brief co-incubation would contribute to a higher live birth rate and a lower miscarriage rate compared to the standard overnight insemination protocol.

Single layer centrifugation-selected boar spermatozoa are capable of fertilization in vitro

Background

Good quality spermatozoa are important to achieve fertilization, viable embryos and offspring. Single Layer Centrifugation (SLC) through a colloid (Androcoll-P) selects good quality spermatozoa. However, it has not been established previously whether porcine spermatozoa selected by this method maintain their fertility.

Methods

The semen was prepared either by SLC or by standard centrifugation (control) and used for in vitro fertilization (IVF) at oocyte:spermatozoa ratios of 1:50; 1:100 and 1:300 (or 4 x 10³, 8 x 10³ and 24 x 10³ spermatozoa/ml) to evaluate their subsequent ability to generate blastocysts. In addition, sperm motility was assessed by computer assisted sperm motility analysis.

Results

Total and progressive motility were significantly higher in sperm samples prepared by SLC compared to uncentrifuged samples. Sperm binding ability, polyspermy, cleavage and blastocyst rates were affected by the oocyte:sperm ratio, but not by sperm treatment.

Conclusion

The use of SLC does not adversely affect the in vitro fertilizing and embryo-generating ability of the selected spermatozoa compared to their unselected counterparts, but further modifications in the IVF conditions would be needed to improve the monospermy in IVF systems. Since SLC did not appear to have a negative effect on sperm fertilizing ability, and may in fact select for spermatozoa with a greater potential for fertilization, an in vivo trial to determine the usefulness of this sperm preparation technique prior to artificial insemination is warranted.

Comparison of intrafollicular sperm injection and intrauterine insemination in the treatment of subfertility

PURPOSE

To compare the efficacy of intrafollicular sperm injection (IFI) versus intrauterine insemination (IUI) in the treatment of subfertility.

METHODS

38 couples suffering primary or secondary subfertility contributed a total of 47 IUI or IFI cycles, 26 by IUI and 21 by IFI. Folliculogenesis, ovulation triggering, and IUI or IFI were performed. Motile spermatozoa were inseminated into the uterine cavity for IUI or injected into pre-ovulatory follicles for IFI. The rate of biochemical and clinical pregnancy was assessed.

RESULTS

The rate of biochemical pregnancy/cycle for IUI was 11 % as compared to 38 % for IFI (p = 0.04). The rate of clinical pregnancy/cycle for IUI was 11 % as compared to 29 % for IFI (p = 0.26). The rate of twin pregnancy and miscarriage was low and no high order multiple gestation was observed. The rate of ectopic tubal pregnancy/cycle for IUI was 0 % as compared to 9 % for IFI (p = 0.19); no ovarian pregnancy was observed. When the analysis was confined to IFI cycles in which 2.68-6.65 million motile spermatozoa were injected/follicle (n = 10), a rate of 60 % clinical pregnancy/cycle was observed, of which 2 were ectopic.

CONCLUSION

Under the conditions described herein, IFI was more effective than IUI at achieving pregnancy.

Identification of the inorganic pyrophosphate metabolizing, ATP substituting pathway in mammalian spermatozoa

Inorganic pyrophosphate (PPi) is generated by ATP hydrolysis in the cells and also present in extracellular matrix, cartilage and bodily fluids. Fueling an alternative pathway for energy production in cells, PPi is hydrolyzed by inorganic pyrophosphatase (PPA1) in a highly exergonic reaction that can under certain conditions substitute for ATP-derived energy. Recombinant PPA1 is used for energy-regeneration in the cell-free systems used to study the zymology of ATP-dependent ubiquitin-proteasome system, including the role of sperm-borne proteasomes in mammalian fertilization. Inspired by an observation of reduced in vitro fertilization (IVF) rates in the presence of external, recombinant PPA1, this study reveals, for the first time, the presence of PPi, PPA1 and PPi transporter, progressive ankylosis protein ANKH in mammalian spermatozoa. Addition of PPi during porcine IVF increased fertilization rates significantly and in a dose-dependent manner. Fluorometric assay detected high levels of PPi in porcine seminal plasma, oviductal fluid and spermatozoa. Immunofluorescence detected PPA1 in the postacrosomal sheath (PAS) and connecting piece of boar spermatozoa; ANKH was present in the sperm head PAS and equatorial segment. Both ANKH and PPA1 were also detected in human and mouse spermatozoa, and in porcine spermatids. Higher proteasomal-proteolytic activity, indispensable for fertilization, was measured in spermatozoa preserved with PPi. The identification of an alternative, PPi dependent pathway for ATP production in spermatozoa elevates our understanding of sperm physiology and sets the stage for the improvement of semen extenders, storage media and IVF media for animal biotechnology and human assisted reproductive therapies.

Degradation of actin nucleators affects cortical polarity of aged mouse oocytes

OBJECTIVE

To investigate the molecular mechanism of mouse oocyte polarity loss during aging.

DESIGN

Experimental study.

SETTING

Academic basic research laboratory.

ANIMAL(S)

Mice.

INTERVENTION(S)

Oocytes were collected 16 hours after injection of hCG and cultured in M16 medium for an additional 14 hours with or without caffeine.

MAIN OUTCOME MEASURE(S)

Expression and localizations of actin nucleators actin-related protein 2/3 complex, JMY, and WAVE2 were examined by immunofluorescence staining, and their messenger RNA levels were examined by real-time reverse transcription-polymerase chain reaction.

RESULT(S)

The protein and messenger RNA levels of actin-related protein 2/3 complex, JMY, and WAVE2 were decreased in aged oocytes, but the levels were normal in caffeine-treated aged oocytes.

CONCLUSION(S)

Our data indicated that the loss of oocyte polarity may be due to the degradation of actin nucleators in aged oocytes.

The biology and evolution of polyspermy: insights from cellular and functional studies of sperm and centrosomal behavior in the fertilized egg

Recent studies of centrosome biogenesis, microtubule dynamics, and their management point to their role in mediating conditions such as aging and cancer. Centrosome dysfunction is also a hallmark of pathological polyspermy. Polyspermy occurs when the oocyte is penetrated by more than one sperm and can be pathological because an excess of centrosomes compromises development. However, in some taxa, multiple sperm enter the egg with no apparent adverse effect on zygote viability. Thus, some taxa can manage excess centrosomes and represent cases of non-pathological polyspermy. While these two forms of polyspermy have long been known, we argue that there is limited understanding of the proximate and ultimate processes that underlie this taxonomic variation in the outcome of polyspermy and that studying this variation could help uncover the control and role(s) of centrosomes during fertilization in particular, but also mitosis in general. To encourage such studies we: 1) describe taxonomic differences in the outcome of polyspermy, 2) discuss mechanistic aspects of reproductive biology that may contribute to the different consequences of polyspermy, and 3) outline the potential selective events that could lead to the evolution of variation in polyspermy outcomes. We suggest that novel insights into centrosome biology may occur by cooperative studies between reproductive and evolutionary biologists focusing on the mechanisms generating variation in the fitness consequences of polyspermy, and in the taxonomic distribution of all these events. The consequent discoveries of these studies may lead to informative insights into cancer and aging along with other centrosome-related diseases and syndromes.

In vitro fertilization using non-sexed and sexed bovine sperm: sperm concentration, sorter pressure, and bull effects

The objective of these experiments was to study bovine in vitro fertilization (IVF) conditions for blastocyst production using non-sexed sperm (Experiment 1) and sexed sperm (Experiment 2). For Experiment 1, in vitro-matured oocytes (N=707) were allocated to a 2 × 3 × 4 factorial design: time of co-incubation of gametes for fertilization (4 and 18 h), sperm dose (1, 0.33, and 0.11 × 10(6) frozen-thawed sperm/ml, and sperm source (four bulls). Pronuclear status was evaluated for a subset. Experiment 2 (N=2155 oocytes) was a 2 × 3 × 2 × 6 factorial design: sex of sperm (X and Y), sperm dose (1, 0.33, and 0.11 × 10(6) frozen-thawed sperm/ml), and sperm-sorting pressures (40 and 50 psi), replicated with sperm of six bulls. Presumptive zygotes were cultured 60 h in chemically defined medium-1 (CDM-1), and for 114 h in CDM-2. For Experiment 1, pronuclear formation, cleavage and blastocysts rates were greater for 1, and 0.33 × 10(6) than 0.11 × 10(6) sperm/ml (72 and 62 vs 42%; 89 and 81 vs 58%; and 21 and 17 vs 9%, respectively; all p<0.01); polyspermy was greater for 1, than 0.33 and 0.11 × 10(6) sperm concentrations (24 vs 2 and 0%; p<0.01). There were greater main effects (p<0.01) of pronuclear formation (69 vs 48%), polyspermy (13 vs 4%), and cleavage (63 vs 54%), at 18 than at 4 h of co-incubation of gametes (all p<0.01). For Experiment 2, cleavage and blastocyst rates were greater for 1 × 10(6) sperm/ml vs 0.33 and 0.11 (69%, 47%, and 30% cleavage and 30%, 14%, and 8% blastocysts) and 40 vs 50 psi (54% and 44% cleavage and 18% and 15% blastocysts) (p<0.01). A marked bull by fertilization sperm dose interaction was found for cleavage (p<0.05). The main conclusion was that the optimal sperm concentration for cleavage and producing blastocysts via IVF with sexed sperm was considerably higher and more variable among bulls than for unsexed sperm.

Pre-fertilization zona pellucida hardening by different cross-linkers affects IVF in pigs and cattle and improves embryo production in pigs

Zona pellucida (ZP) hardening (resistance to proteolysis) has been classically identified as a post-fertilization event that contributes to the block to polyspermy. Di-(N-succinimidyl)-3,3′-dithiodipropionate (DSP), a permeable amine-reactive cross-linker, was recently shown to induce pre-fertilization ZP hardening and to improve porcine IVF productivity. The objectives of this study were to investigate i) how DSP affects pre-fertilization ZP hardening and IVF in cattle, ii) if a non-permeable amine-reactive cross-linker such as bis(sulfosuccinimidyl) suberate (BS3) affects ZP hardening and IVF in cattle and pigs, and iii) whether DSP or BS3, if improvement in IVF productivity was demonstrated in either species, affectsin vitroembryo development. Bovine and porcinein vitromatured oocytes were incubated with the cross-linkers (0.06, 0.3, and 0.6 mg/ml) for 30 min. Then they were subjected to ZP digestion or IVF. In cattle, both DSP and BS3 induced ZP hardening and decreased the penetration rate, although monospermy, penetration, or male pronuclear formation was not affected. In pigs, BS3 treatment induced ZP hardening, decreased penetration and male pronuclear formation, and increased monospermy. IVF productivity only improved when porcine oocytes were exposed to DSP. When porcine zygotes derived from this treatment were further culturedin vitro, the cleavage and blastocyst formation rates increased. These results support the idea that mechanisms involved in the prevention of polyspermic fertilization in cattle and pigs have different efficiencies, and ZP hardening induced by DSP cross-linker may be useful for improving porcine embryo production.

Biofluid mechanics of the human reproductive process: modelling of the complex interaction and pathway to the oocytes

Recent revelations in the human reproductive process have fuelled much interest in this field of study. In particular, the once prevailing view of large numbers of ejaculated sperms racing towards the egg has been refuted recently. This is opposed to the current views derived from numerous clinical findings that state that only a very small number of sperms will ever enter the oviduct. It is believed that these few sperms must have been guided to make the long, tedious and obstructed journey to the egg. For a mature spermatozoon, its hyperactivated swimming motility upon capacitation plays an important role in the fertilization of a mature egg. Likewise, the female genital tract also provides guiding mechanisms to complement the survival of normal hydrodynamic profile sperms and thus promotes an eventual sperm–egg interaction. Understanding these mechanisms can be essential for the derivation of assisted conception techniques especially those in vitro. With the aid of computational models and simulation, suitability and effectiveness of novel assisted conception methodology can be assessed, particularly for those yet to be ready for clinical trials. This review discusses the possible bioengineering models and the mechanisms by which human spermatozoa are guided to the egg.

Kinetics of fertilization and development, and sex ratio of bovine embryos produced using the semen of different bulls

The between bulls variation in in vitro fertility and the shift of sex ratio towards male embryos are two problems affecting the in vitro production (IVP) of bovine embryos. Our objective was to evaluate the kinetics of fertilization, embryo development and the sex ratio of the resulting embryos using the frozen/thawed semen of four different bulls. In a first experiment, the kinetics of pronucleus (PN) formation was evaluated at 8, 12 and 18 h post-insemination (hpi). Based upon the pronuclei sizes and the distance between the two pronuclei, inseminated oocytes were classified in three PN stages. Differences between bulls were observed at each time point, but were more important at 12 hpi. At 8 and 12 hpi bull III showed a significantly faster PN evolution by comparison with the three other bulls (P<0.05), while at 18 hpi, the proportion of the three PN stages was similar to those of bulls I and IV, bull II being delayed. In a second experiment, the kinetics of in vitro embryo development was compared using time-lapse cinematography. The analysis of embryos reaching the blastocyst stage revealed significant differences in the mean time of first cleavage (range of 22.7-25.6h, P<0.05), while the lengths of the subsequent three cell cycles did not differ between bulls. The early mean time of first cleavage with bull III was associated with an early blastulation and a high blastocyst rate at Day 7, in opposition to what was observed with bull II showing a later timing of first cleavage (first cleavage 22.1 hpi versus 25.5 hpi; blastulation 140.4 hpi versus 152.5 hpi; D7 blastocyst rates: 31.3% versus 21.9%; P<0.05). In a third experiment, 65-76 Day 8 blastocysts per bull were sexed by PCR. Only blastocysts obtained with bull III showed a shift in sex ratio towards male embryos (76% male embryos; P<0.05). Such shift was already observed at the 2-cell and morula stages. In conclusion, the bull influences the kinetics of PN formation, of embryo development and the sex ratio of the embryos. Moreover, those parameters might be related.