Clinical significance of human sperm-zona pellucida binding

Total Fertilization Failure: A Single Center Analysis

Our main objective was to identify the male and female parameters associated with total fertilization failure (TFF) in IVF with nonmasculine indications. The present work, IRB equivalent INS 63209, is a case-control study that evaluated all cases with TFF after conventional IVF at the Center for Human Reproduction from January 2010 to December 2019 (n = 154). As a control group, we analyzed all patients who did not experience fertilization failure after conventional IVF in the same period (n = 475). We evaluated various parameters, both male and female, assessed during infertility treatment, and only cases without masculine etiology (normal seminal parameters) were included. Ages (female and male) were not different between the groups. Moreover, AMH (anti-Müllerian hormone), semen volume, preprocessing concentration and preprocessing motility were not significantly different (P > 0.05). However, the number of collected oocytes (study versus control groups, median [25-75 interquartile]: 2 [1-5] and 5 [3-8]); MII (2 [1-4] and 5 [2-7]); and postprocessing motility (85 [70-90] and 90 [80-95]) were significantly different between both groups (P < 0.05). Furthermore, a logistic regression analysis including all significant data demonstrated that the number of collected oocytes was significantly related to IVF failure. Patients with fewer than 5 oocytes had an OR of - 1.37 (- 0.938 to - 1.827) for TFF after conventional IVF. Our results showed that a lower follicular response to controlled ovarian stimulation, evidenced by a decreased number of collected oocytes, was the most important parameter associated with IVF failure in nonmasculine infertility.

Sperm selection by the oviduct: perspectives for male fertility and assisted reproductive technologies†

The contribution of sperm to embryogenesis is gaining attention with up to 50% of infertility cases being attributed to a paternal factor. The traditional methods used in assisted reproductive technologies for selecting and assessing sperm quality are mainly based on motility and viability parameters. However, other sperm characteristics, including deoxyribonucleic acid integrity, have major consequences for successful live birth. In natural reproduction, sperm navigate the male and female reproductive tract to reach and fertilize the egg. During transport, sperm encounter many obstacles that dramatically reduce the number arriving at the fertilization site. In humans, the number of sperm is reduced from tens of millions in the ejaculate to hundreds in the Fallopian tube (oviduct). Whether this sperm population has higher fertilization potential is not fully understood, but several studies in animals indicate that many defective sperm do not advance to the site of fertilization. Moreover, the oviduct plays a key role in fertility by modulating sperm transport, viability, and maturation, providing sperm that are ready to fertilize at the appropriate time. Here we present evidence of sperm selection by the oviduct with emphasis on the mechanisms of selection and the sperm characteristics selected. Considering the sperm parameters that are essential for healthy embryonic development, we discuss the use of novel in vitro sperm selection methods that mimic physiological conditions. We propose that insight gained from understanding how the oviduct selects sperm can be translated to assisted reproductive technologies to yield high fertilization, embryonic development, and pregnancy rates.

Toll-like Receptor 2 is Involved in Calcium Influx and Acrosome Reaction to Facilitate Sperm Penetration to Oocytes During in vitro Fertilization in Cattle

Cumulus cells of ovulated cumulus-oocyte complexes (COCs) express Toll-like receptor 2 (TLR2), pathogen recognition receptors, to recognize and react to sperm signals during fertilization. Sperm also express TLR2, but its contribution to the sperm-oocytes crosstalk is still unclear. Here, we adapted the in vitro fertilization (IVF) model to characterize the potential relevance of sperm TLR2 in sperm-oocytes interactions during fertilization in bovine. The IVF results showed that the ligation of sperm TLR2 with its specific antagonist/agonist resulted in down/up-regulation of the cleavage and blastocyst rates either in COCs or cumulus-free oocytes, but not in zona pellucida (ZP)-free oocytes. The computer-assisted sperm analysis (CASA) system revealed that sperm motility parameters were not affected in TLR2 antagonist/agonist-treated sperm. However, fluorescence imaging of sperm-ZP interactions revealed that the blockage or activation of the TLR2 system in sperm reduced or enhanced both binding and penetration abilities of sperm to ZP compared to control, respectively. Flow cytometrical analysis of acrosome reaction (AR) demonstrated that the TLR2 system adjusted the occurrence of AR in ZP-attached sperm, suggesting that sperm TLR2 plays physiological impacts on the sperm-oocyte crosstalk via regulating ZP-triggered AR in sperm. Given that calcium (Ca²⁺) influx is a pre-requisite step for the induction of AR, we investigated the impact of the TLR2 system on the ionophore A23187-induced Ca²⁺ influx into sperm. Notably, the exposure of sperm to TLR2 antagonist/agonist reduced/increased the intracellular Ca²⁺ level in sperm. Together, these findings shed new light that the TLR2 system is involved in sperm AR induction which enables sperm to penetrate and fertilize oocytes during the fertilization, at least in vitro, in cows. This suggests that sperm possibly developed a quite flexible sensing mechanism simultaneously against pathogens as well as COCs toward fertilization with the same TLR2 of the innate immune system.

An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section I

Simple Summary

Male fertility is often estimated by simple sperm assessment, and therefore, it is crucial to establish species-specific baselines for normal sperm parameters. In this paper, sperm physiology, function, and common abnormalities in stallions will be reviewed.

Abstract

As the use of assisted reproductive technologies (ART) and in vitro embryo production (IVP) expand in the equine industry, it has become necessary to further our understanding of semen physiology as it applies to overall fertility. This segment of our two-section review will focus on normal sperm parameters, beginning with development and extending through the basic morphology of mature spermatozoa, as well as common issues with male factor infertility in IVP. Ultimately, the relevance of sperm parameters to overall male factor fertility in equine IVP will be assessed.

The importance of trace minerals copper, manganese, selenium and zinc in bovine sperm-zona pellucida binding

SummarySperm-zona pellucida (ZP) binding is a necessary event for successful fertilization. The aim of this study was to determine the effect of trace minerals such as copper (Cu), manganese (Mn), selenium (Se) and zinc (Zn) on bovine spermatozoa binding to ZP. Sperm viability, functional membrane integrity, acrosomal status (AS), total antioxidant capacity (TAC) and sperm lipid peroxidation (LPO) were also evaluated. For the present study, in vitro fertilization (IVF) medium was supplemented with Cu (0.4 µg/ml Cu), Mn (5 ng/ml Mn), Se (100 ng/ml Se), Zn (0.8 µg/ml Zn), all minerals (Cu+Mn+Se+Zn), or tested without supplement (Control). Considerably more sperm bound to ZP when Cu, Se or Zn were added to the IVF medium, but there were no difference compared with the Control, Mn and Cu+Mn+Se+Zn groups. After 1 h of incubation, viability was increased by the addition of Cu, Mn and Se with respect to the Control but, after 2 h, viability was higher only with the addition of Mn to IVF medium. Functional membrane integrity improved in sperm treated with Cu. Acrosome integrity was higher in sperm treated with Zn after 1 h of incubation. LPO was significantly higher in sperm treated with Cu or Cu+Mn+Se+Zn. The mean TACs of sperm treated with Cu, Mn, Zn or Cu+Mn+Se+Zn were lower than in the Control. In conclusion, the results obtained in the present study determined that the presence of Cu, Se and Zn in the IVF medium increased the number of spermatozoa bound to the ZP, highlighting the importance of these minerals in the fertilization process.

Effect of early cumulus cells removal and early rescue ICSI on pregnancy outcomes in high-risk patients of fertilization failure

OBJECTIVE

The objective of this retrospective study was to evaluate clinical outcomes of early cumulus cells removal and early rescue intracytoplasmic sperm injection (ICSI) in high-risk patients of fertilization failure during human in vitro fertilization (IVF).

METHODS

A total of 5,518 patients were enrolled between January 2014 to December 2016. Of which 505 couples performed short insemination with >30% fertilization rate were included in short-term IVF group, 102 patients detected total fertilization failure (TFF) were treated with early rescue ICSI (R-ICSI group), and 4911 couples underwent conventional IVF with overnight co-incubation of gametes (traditional IVF group). The clinical outcomes were analyzed among the three groups.

RESULTS

The embryo implantation rates (40.34%, 39.78% and 42.42% for traditional, short-term IVF and R-ICSI groups, respectively) were comparable in the three groups. The clinical pregnancy rates among traditional IVF group, short-term IVF group and R-ICSI group were 57.95%, 57.03% and 60.78%, respectively, and the difference among three groups didn't reach significance.

CONCLUSION

The present study indicated that short insemination had no detrimental effects on clinical outcomes in human IVF and could prevent the occurrence of TFF combined with early rescue ICSI for high-risk patients of fertilization failure, which attained acceptable pregnancy outcomes.

Oviductal epithelial cells selected boar sperm according to their functional characteristics

The interaction of oviductal epithelial cells (OECs) with the spermatozoa has beneficial effects on the sperm functions. The aim of this study is to evaluate the in vitro fertilizing capacity of incubating spermatozoa previously selected by density gradient in OEC and determinate some sperm characteristics that could explain the results obtained. In this study, we assessed in vitro fertilization (IVF), tyrosine phosphorylation, phosphatidylserine translocation, nuclear DNA fragmentation, and chromatin decondensation. Three experimental sperm groups, previously selected by Percoll gradient, were established according to the origin of the sperm used for IVF: (i) W30 group: spermatozoa were incubated with oocytes in the absence of OEC; (ii) NB group: after sperm incubation in OEC, the unbound spermatozoa were incubated with oocytes, in the absence of OEC; and (iii) B group: after sperm incubation with OEC, the bound spermatozoa were incubated with oocytes in the OEC plates. The results showed that sperm from the NB group led to a lower IVF yield, accompanied by low penetration rates (NB: 19.6%, B: 94.9%, and W30: 62.9%; P < 0.001) and problems of nuclear decondensation. Moreover, higher levels of tyrosine phosphorylation were observed in the NB group compared with the W30 and B groups (NB: 58.7%, B: 2.5%, and W30: 4.5%; P < 0.01). A similar trend was observed in phosphatidylserine translocation (NB: 93.7%, B: 5.7%, and W30: 44.2%; P < 0.01). These results demonstrate that the OEC exerts a rigorous degree of sperm selection, even within an already highly selected population of spermatozoa, and can capture the best functional spermatozoa for fertilization.

The role of the molecular chaperone heat shock protein A2 (HSPA2) in regulating human sperm-egg recognition

One of the most common lesions present in the spermatozoa of human infertility patients is an idiopathic failure of sperm-egg recognition. Although this unique cellular interaction can now be readily by-passed by assisted reproductive strategies such as intracytoplasmic sperm injection (ICSI), recent large-scale epidemiological studies have encouraged the cautious use of this technology and highlighted the need for further research into the mechanisms responsible for defective sperm-egg recognition. Previous work in this field has established that the sperm domains responsible for oocyte interaction are formed during spermatogenesis prior to being dynamically modified during epididymal maturation and capacitation in female reproductive tract. While the factors responsible for the regulation of these sequential maturational events are undoubtedly complex, emerging research has identified the molecular chaperone, heat shock protein A2 (HSPA2), as a key regulator of these events in human spermatozoa. HSPA2 is a testis-enriched member of the 70 kDa heat shock protein family that promotes the folding, transport, and assembly of protein complexes and has been positively correlated with in vitro fertilization (IVF) success. Furthermore, reduced expression of HSPA2 from the human sperm proteome leads to an impaired capacity for cumulus matrix dispersal, sperm-egg recognition and fertilization following both IVF and ICSI. In this review, we consider the evidence supporting the role of HSPA2 in sperm function and explore the potential mechanisms by which it is depleted in the spermatozoa of infertile patients. Such information offers novel insights into the molecular mechanisms governing sperm function.

Sperm selection in natural conception: what can we learn from Mother Nature to improve assisted reproduction outcomes?

BACKGROUND

In natural conception only a few sperm cells reach the ampulla or the site of fertilization. This population is a selected group of cells since only motile cells can pass through cervical mucus and gain initial entry into the female reproductive tract. In animals, some studies indicate that the sperm selected by the reproductive tract and recovered from the uterus and the oviducts have higher fertilization rates but this is not a universal finding. Some species show less discrimination in sperm selection and abnormal sperm do arrive at the oviduct. In contrast, assisted reproductive technologies (ART) utilize a more random sperm population. In this review we contrast the journey of the spermatozoon in vivo and in vitro and discuss this in the context of developing new sperm preparation and selection techniques for ART.

METHODS

A review of the literature examining characteristics of the spermatozoa selected in vivo is compared with recent developments in in vitro selection and preparation methods. Contrasts and similarities are presented.

RESULTS AND CONCLUSIONS

New technologies are being developed to aid in the diagnosis, preparation and selection of spermatozoa in ART. To date progress has been frustrating and these methods have provided variable benefits in improving outcomes after ART. It is more likely that examining the mechanisms enforced by nature will provide valuable information in regard to sperm selection and preparation techniques in vitro. Identifying the properties of those spermatozoa which do reach the oviduct will also be important for the development of more effective tests of semen quality. In this review we examine the value of sperm selection to see how much guidance for ART can be gleaned from the natural selection processes in vivo.

Traditional intracytoplasmic sperm injection provides equivalent outcomes compared with human zona pellucida-bound selected sperm injection

The capability of human zona pellucida (ZP) to bind selectively to normal functional sperm with normal chromatin has been reported widely in the literature. The aim of this study was to evaluate whether ZP–binding sperm selection may represent a method to retrieve superior spermatozoa for intracytoplasmic sperm injection (ICSI). Patients were divided into two groups: a ZP-ICSI and a conventional ICSI group. In the ZP-ICSI group, spermatozoa for injection were selected after ZP–sperm incubation and spermatozoa that were tightly bound to the ZP were used for ICSI (ZP-ICSI). Clinical outcomes of ZP-ICSI were compared with the outcomes of traditional scientist-selected sperm injection (conventional ICSI). Results did not show any significant difference in fertilization, pregnancy, implantation and take-home-baby rates between conventional ICSI and ZP-ICSI. However, when data relative to patients who received ZP-ICSI were analyzed, an interesting result was observed: higher sperm concentration and morphology correlated with higher ZP–sperm binding. Additionally, patients with higher ZP–sperm binding seem to have improved pregnancy and take-home-baby rates. In conclusion, this study shows that ZP-ICSI is not a superior method compared with conventional ICSI. However, clinical ICSI outcomes were apparently improved in the presence of good ZP–sperm binding. We therefore speculate that sperm competence to ICSI could be reduced when the sperm's ability to bind the ZP is impaired.

How accurate is sperm morphology as an indicator of sperm function?

Sperm morphology has been consistently correlated with fertilisation success or failure. The clinical relevance of the percentage normal spermatozoa has been a widely discussed topic amongst infertility specialists and scientists. This study aimed to evaluate the role of sperm morphology as an indicator of additional sperm functions among 114 andrology referrals. The sperm functions that were investigated included chromatin packaging quality (CMA3 test (n = 109), zona-induced acrosome reaction (ZIAR test; n = 36), hemizona assay (HZI; n = 36) and progressive motility (n = 47). Chromatin packaging quality had a negative and significant (P = 0.0001, r = -0.74) correlation with the percentage normal spermatozoa, while progressive motility had a significant and positive correlation (P = 0.0001, 0.59). Accurate sperm morphology scoring as described by the WHO 2010 manual can therefore be used as an indicator of specific sperm functions.

[Complete fertilization failure following conventional IVF or ICSI: is it predictable? How to manage?]

The occurrence of complete fertilization failure following conventional in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) is a rare event. Each of six physiological stages of the fertilisation can be failing. The cause of a fertilisation failure is either the spermatozoa, or the oocyte. The aim of this study was to determine if this event is predictable, and to define the later strategy. On all sperm tests available, it seems that only, tests of zona pellucida binding and acrosomique reaction are relatively predictive of a complete fertilization failure after IVF. No test allows at the moment to predict an oocyte contribution to unsuccessful fertilization. The strategy retained after a complete fertilization failure following the first attempt of IVF is to propose an ICSI; either to do an IVF if this event arises in the rank n+1, or when the number of inseminated oocytes was low. Concerning the ICSI, the low number of micro-injected oocyte is often in question; so the strategy retained following a first fertilization failure after ICSI is to perform a new ICSI attempt after optimization of the ovarian stimulation. When the cause is spermatic, it is indicated trying a modified ICSI with the use of pentoxifiline, or an intracytoplasmic morphologically selected sperm injection (IMSI), sometimes with assisted oocyte activation. In last solution, we can propose the ovum donation.

Hemizona assay and sperm penetration assay in the prediction of IVF outcome: a systematic review

The limited predictive value of semen analysis in achieving natural conception or in IVF outcome confirms the need for sperm function tests to determine optimal management. We reviewed HZA and SPA predictive power in IVF outcome, with statistical significance of diagnostic power of the assays. HZA was readily efficient in predicting IVF outcome, while evident inconsistency among the studies analysed framed the SPA's role in male fertility evaluation. Considerable variation was noted in the diagnostic accuracy values of SPA with wide sensitivity (52-100%), specificity (0-100%), and PPV (18-100%) and NPV (0-100%) together with fluctuation and notable differentiation in methodology and cutoff values employed by each group. HZA methodology was overall consistent with minor variation in cutoff values and oocyte source, while data analysis reported strong correlation between HZA results with IVF outcome, high sensitivity (75-100%), good specificity (57-100%), and high PPV (79-100%) and NPV (68-100%). HZA correlated well with IVF outcome and demonstrated better sensitivity/specificity and positive/negative predictive power. Males with normal or slightly abnormal semen profiles could benefit by this intervention and could be evaluated prior to referral to assisted reproduction. HZA should be used in a sequential fashion with semen analysis and potentially other bioassays in an IVF setting.

Body mass index is not associated with sperm-zona pellucida binding ability in subfertile males

Lifestyle factors, such as weight and nutritional status may affect male fertility, including sperm fertilization ability. The objective of this retrospective study was to evaluate the association between body mass index (BMI) and sperm-zona pellucida binding ability assessed according to the zona binding (ZB) test, which has been described to be a relevant diagnostic tool for the prediction of in vitro fertilization (IVF) ability. Three hundred and six male patients from couples diagnosed with primary idiopathic or mild male factor infertility were included. Correlations between BMI and semen parameters according to ZB test indices were assessed, together with frequencies of positive and negative tests across the BMI categories. In this selected population, BMI was not related to conventional semen parameters or sperm quality assessed according to the ability of spermatozoa to bind to the zona pellucida. The previously described poor outcomes of IVF procedures in cases of male obesity could be due to other sperm defects, such as alterations of sperm capacitation or acrosome reaction. The link between male BMI and biological outcomes during IVF procedures, such as fertilization rates, should be further evaluated.

Inhibition of ovine in vitro fertilization by anti-Prt antibody: hypothetical model for Prt/ZP interaction

BACKGROUND

The impact of prion proteins in the rules that dictate biological reproduction is still poorly understood. Likewise, the role of prnt gene, encoding the prion-like protein testis specific (Prt), in ram reproductive physiology remains largely unknown. In this study, we assessed the effect of Prt in ovine fertilization by using an anti-Prt antibody (APPA) in fertilization medium incubated with spermatozoa and oocytes. Moreover, a computational model was constructed to infer how the results obtained could be related to a hypothetical role for Prt in sperm-zona pellucida (ZP) binding.

METHODS

Mature ovine oocytes were transferred to fertilization medium alone (control) or supplemented with APPA, or pre-immune serum (CSerum). Oocytes were inseminated with ovine spermatozoa and after 18 h, presumptive zygotes (n=142) were fixed to evaluate fertilization rates or transferred (n=374) for embryo culture until D6-7. Predicted ovine Prt tertiary structure was compared with data obtained by circular dichroism spectroscopy (CD) and a protein-protein computational docking model was estimated for a hypothetical Prt/ZP interaction.

RESULTS

The fertilizing rate was lower (P=0.006) in APPA group (46.0+/-6.79%) when compared to control (78.5+/-7.47%) and CSerum (64.5+/-6.65%) groups. In addition, the cleavage rate was higher (P<0.0001) in control (44.1+/-4.15%) than in APPA group (19.7+/-4.22%). Prt CD spectroscopy showed a 22% alpha-helical structure in 30% (m/v) aqueous trifluoroethanol (TFE) and 17% alpha in 0.6% (m/v) TFE. The predominant alpha-helical secondary structure detected correlates with the predicted three dimensional structure for ovine Prt, which was subsequently used to test Prt/ZP docking. Computational analyses predicted a favorable Prt-binding activity towards ZP domains.

CONCLUSIONS

Our data indicates that the presence of APPA reduces the number of fertilized oocytes and of cleaved embryos. Moreover, the CD analysis data reinforces the predicted ovine Prt trend towards an alpha-helical structure. Predicted protein-protein docking suggests a possible interaction between Prt and ZP, thus supporting an important role for Prt in ovine fertilization.

The hemizona assay for assessment of sperm function

The hemizona assay (HZA) has been developed as a diagnostic test for the tight binding of human spermatozoa to the human zona pellucida to predict fertilization potential. In this homologous bioassay, the two matching hemizona halves are functionally equal surfaces allowing controlled comparison of binding from a fertile control versus a test sample, with reproducible measurements of sperm binding obtained from a single oocyte. Oocytes from different sources (surplus from IVF treatment or recovered from ovarian tissue) are salt-stored and used after microbisection. Extensive clinical data have demonstrated excellent predictive power of the HZA for the outcomes of intrauterine insemination and IVF, and therefore the assay has relevance in the clinical diagnostic setting in infertility.

Influence of zona pellucida thickness on fertilization, embryo implantation and birth

Defective sperm-zona pellucida binding and penetration are the main causes of IVF failure. The purpose of this study was to evaluate the effect of zona pellucida thickness in fertilization failure and test the influence of zona pellucida thickness on implantation and birth in rabbits. Embryos and oocytes were collected from 72 females on Day 2 post-insemination. A total of 559 normal embryos were recovered; 402 embryos were transferred by laparoscopy and 157 embryos were used to measure the zona pellucida thickness using the ImageJ program. Laparoscopies were also performed on all does at Day 12 of gestation to record the number of implanted embryos. Litter size at birth was recorded. The mean zona pellucida thickness of the 157 embryos and of the 64 control group oocytes (18.3 ± 0.2 and 18.5 ± 0.3 μm, respectively) was significantly less than the zona pellucida thickness of the 74 failed fertilization oocytes (19.2 ± 0.3 μm). The probabilities of the regression coefficient being positive were 0.72 and 0.74 for implantation and birth, respectively, and the subsequent means of the coefficient were 2.92 and 0.03 for implantation and birth, respectively. In conclusion, the zona pellucida thickness has an important influence on in vivo fertilization and implantation processes, but not on birth.

Analysis of clinical data of patients with different outcomes after short-time insemination

The study is to analyse the clinical data of the two groups of patients with different fertilisation outcomes after short-time insemination and probe into short-time insemination indications. A retrospective study including 558 cycles of short-time insemination in our centre during January 2009 to June 2010 which were divided into two groups by the method of fertilisation, 472 cycles by IVF and 86 cycles by Re-ICSI group according to fertilisation conditions to and compare the differences between the two groups in the indexes of average female age, average male age, duration of infertility, forward-moving sperm counts, abnormal sperm rate, proportion of primary infertility, etc. The differences between the two groups have statistical significance in duration of infertility, forward-moving sperm counts, abnormal sperm rate and proportion of primary infertility (5.02 ± 3.12 versus 5.86 ± 3.35; 83.06 ± 78.55 versus 54.02 ± 61.78; 83.56 ± 5.24% versus 86.31 ± 5.26%; 56.87% versus 74.42%; P < 0.05). The discrepancy between the two groups has no statistical significance in average female age and average male age (P > 0.05). Duration of infertility, forward-moving sperm counts, abnormal sperm rate and previous pregnancy history have great significance to predict fertilisation failure, so decisions should be made on the basis of the above indexes when evaluating whether a patient should conduct short-time insemination.

Early cumulus cell removal could reduce the available embryo rate in human IVF

PURPOSE

This study was designed to compare cumulus cell removal at different times and to evaluate their effects on embryo developmental potential and the outcomes of in vitro fertilization (IVF).

METHODS

We retrieved 606 IVF cycles with standard long down regulation protocol from January 2010 to December 2010. These cycles were divided into two groups: group A, 364 cycles with high risk of fertilization failure, whose cumulus cells were removed 4 h after short gamete coincubation; group B, 242 cycles as control, whose cumulus cells removal were performed 17 to 18 h after insemination. The epidemiological, clinical, laboratory factors and the outcomes of these cycles were analyzed.

RESULTS

The available embryo rate of group A was significantly lower (P = 0.002). There were no significant differences in other laboratory parameters and outcomes between the two groups (P > 0.05).

CONCLUSIONS

For patients with high risk of fertilization failure, there could be a risk of compromising the rate of available embryos, if fertilization is judged by the presence of 2 PB by cumulus cell removal only 4 h post-insemination. Therefore, this strategy is not recommended to all IVF cycles and future studies are needed to confirm its reliability.

Semen analysis and sperm function tests: How much to test?

Semen analysis as an integral part of infertility investigations is taken as a surrogate measure for male fecundity in clinical andrology, male fertility, and pregnancy risk assessments. Clearly, laboratory seminology is still very much in its infancy. In as much as the creation of a conventional semen profile will always represent the foundations of male fertility evaluation, the 5th edition of the World Health Organization (WHO) manual is a definitive statement on how such assessments should be carried out and how the quality should be controlled. A major advance in this new edition of the WHO manual, resolving the most salient critique of previous editions, is the development of the first well-defined reference ranges for semen analysis based on the analysis of over 1900 recent fathers. The methodology used in the assessment of the usual variables in semen analysis is described, as are many of the less common, but very valuable, sperm function tests. Sperm function testing is used to determine if the sperm have the biologic capacity to perform the tasks necessary to reach and fertilize ova and ultimately result in live births. A variety of tests are available to evaluate different aspects of these functions. To accurately use these functional assays, the clinician must understand what the tests measure, what the indications are for the assays, and how to interpret the results to direct further testing or patient management.

Clinical management of male infertility in assisted reproduction: ICSI and beyond

The advent of in vitro fertilization and its augmentation with intracytoplasmic sperm injection (ICSI) has allowed a large number of couples suffering from moderate to severe male infertility, and also presenting with female pathologies, to achieve their reproductive dreams. Notwithstanding the existence of fundamental questions about the pathophysiological mechanisms leading to sperm dysfunction, and still unanswered concerns about health risks following ICSI, it appears that overall ICSI is safe and here to stay. Although on one hand ICSI possibly hampered advances of the knowledge in some areas of gamete biology and interaction, on the other it definitely gave impulse to studies designed to unveil the sperm contributions during and beyond fertilization, including the normalcy of the DNA/chromatin as well as molecular mechanisms of genetic/epigenetic control and nuclear organization status. In all, almost entering the fourth decade of assisted reproductive technologies, we should continue monitoring the safety of the technique and long-term development of offspring, whereas at the same time prioritizing areas of research addressing these fundamental questions.

What to do when ICSI fails

The refinement of gamete micromanipulation techniques has made conception possible for couples with male factor infertility who otherwise would remain childless. Moreover, intracytoplasmic sperm injection (ICSI) has ensured that such refractory cases can now generate offspring as successfully as in couples that merely require in vitro insemination. However, despite the now sterling record of ICSI it does not assure a successful outcome for every patient. This can be due, for instance, to the inability of the spermatozoon to activate the oocyte, and applies obviously in cases where spermatozoa are absent from the ejaculate or testicular biopsy. In the present paper we describe in detail the reasons for such failure and review the options that may help overcome it. In particular, we outline the treatment protocol for the situation in which spermatozoa are unable to induce oocyte activation. Further, we report on the clinical outcome achieved with spermatozoa retrieved from the testis, and in cases of extreme oligozoospermia we also explore the option of replicating a single spermatozoon while gaining information on its genomic content. For the most extreme situation in which men have no identifiable germ cells, we will discuss the current status of efforts to accomplish neo-gametogenesis through embryonic stem cell differentiation.

Correlation of post swim-up acrosome index with in-vitro fertilization outcomes

PURPOSE

A prospective study was planned to determine the relationship between post swim-up acrosome index (AI) evaluation and fertilization outcomes in an in vitro fertilization (IVF) program.

MATERIALS AND METHODS

Infertile couples who have applied to IVF were admitted into this study when the male partner's sperm concentration was > 20 x 10(6)/mL and motility > 30%. Pre- and post swim-up semen quality parameters including concentration, motility, sperm morphology and AI were evaluated in a prospective, randomized and blinded fashion. The couples were divided prospectively into 2 groups. In group I (25 couples) 50 000 sperm per oocyte were used for insemination considering post swim-up acrosome index, and in group II (25 couples) 50 000 sperm per oocyte were used for insemination without considering post swim-up acrosome index.

RESULTS

Pre- and post swim-up AI were 30.8 +/- 3.4 and 17.8 +/- 4.5 in group I, and 31.4 +/- 3.6 and 16.3 +/- 4.7 in group II (p > 0.05) respectively. The significant improvement in morphology and motility after double wash swim-up procedure has been observed. However, double wash swim-up procedure could not eliminate head and especially acrosomal defects which would directly effect fertilization capacity in conventional IVF program. In group I, 85.3% of oocytes were fertilized, with a 48% pregnancy rate; in group II, 71.0% of oocytes were fertilized, with a pregnancy rate of 20%. Fertilization and pregnancy rates were significantly different (p < 0.05) between the two groups.

CONCLUSION

We have concluded that it could be useful to consider post swim-up AI of sperm inseminated in conventional IVF cycles, which correlates with high fertilization and pregnancy rates.

Relationship between seminal plasma zinc concentration and spermatozoa-zona pellucida binding and the ZP-induced acrosome reaction in subfertile men

The aim of this study was to determine the relationship between seminal zinc concentration and spermatozoa-zona pellucida (ZP) binding and the ZP-induced acrosome reaction (ZPIAR) in subfertile men. Semen analyses and seminal zinc concentration assessments were carried out according to the World Health Organization manual for 458 subfertile men. A spermatozoa-ZP interaction test was carried out by incubating 2 x 10(6) motile spermatozoa with a group of four unfertilized oocytes obtained from a clinical in vitro fertilization programme. After 2 h of incubation, the number of spermatozoa bound per ZP and the ZPIAR of ZP-bound spermatozoa were examined. The effect of adding 0.5 mmol L(-1) zinc to the media on the ZPIAR of spermatozoa from normozoospermic men was also tested in vitro. Seminal zinc concentration positively correlated with sperm count and duration of abstinence, but negatively correlated with semen volume. On analysis of data from all participants, both spermatozoa-ZP binding and the ZPIAR were significantly correlated with sperm motility and normal morphology, but not with seminal zinc concentration. However, in men with normozoospermic semen, the seminal zinc concentration was significantly higher in men with defective ZPIAR (< 16%) than in those with normal ZPIAR (>or= 16%) (P < 0.01). The addition of 0.5 mmol L(-1) zinc to the culture media had no effect on spermatozoa-ZP binding, but significantly reduced the ZPIAR in vitro (P < 0.001). In conclusion, seminal zinc concentration is correlated with sperm count and the duration of abstinence in subfertile men. In men with normozoospermic semen, high seminal zinc concentration may have an adverse effect on the ZPIAR.

Enhancement of sperm-zona pellucida (ZP) binding capacity by activation of protein kinase A and C pathways in certain infertile men with defective sperm-ZP binding

BACKGROUND

Defective sperm-zona pellucida (ZP) binding (DSZPB) is a common cause of failure of fertilization in vitro. This study was to determine if DSZPB is caused by defective pathways upstream of protein kinase A (PKA) and C (PKC), or reduced protein tyrosine phosphorylation (TP).

METHODS

Infertile men with DSZPB and either normal sperm morphology (NSM) > or = 14% (n = 15) or < or =5% (n = 15) were studied. Sperm-ZP binding test was performed by incubation of motile sperm with oocytes for 2 h with or without dibutyryl cyclic AMP (dbcAMP, PKA activator) or phorbol myristate acetate (PMA, PKC activator). TP of capacitated sperm in medium was assessed by immunofluorescence with an anti-phosphotyrosine monoclonal antibody.

RESULTS

For normal sperm with normal sperm-ZP binding, both PMA and dbcAMP significantly enhanced sperm-ZP binding in a dose-response manner. Only dbcAMP, but not PMA, significantly increased TP of capacitated sperm. In DSZPB men with severe teratozoospermia (NSM < or = 5%), neither PMA nor dbcAMP enhanced sperm-ZP binding, despite dbcAMP significantly increasing the TP of capacitated sperm for all samples. In contrast, for DSZPB with NSM > or = 14%, PMA caused significantly increased sperm binding up to normal levels (> or =40 sperm bound/ZP) in five men, and dbcAMP had a similar result in two men. Again TP was significantly enhanced only by dbcAMP, but not by PMA.

CONCLUSIONS

There is defective signalling in pathways upstream of PKC and PKA in some men with DSZPB and normal semen analysis. Stimulation of TP by dbcAMP does not enhance sperm-ZP binding capacity in DSZPB men with low TP, regardless of sperm morphology.

Proteomic changes in mammalian spermatozoa during epididymal maturation

Epididymal maturation is associated with the activation of a cAMP-induced tyrosine phosphorylation cascade, which is ultimately associated with the expression of capacitation-dependent sperm functions, such as hyperactivated movement and acrosomal exocytosis. As spermatozoa progress through the epididymis they first acquire the capacity to phosphorylate tyrosine on targets on the principal piece, followed by the midpiece. By the time these cells have reached the cauda epididymidis they can phosphorylate the entire tail from neck to endpiece. This particular pattern of phosphorylation is associated with the ontogeny of fully functional spermatozoa that are capable of fertilizing the oocyte. Proteomic analyses indicate that this change is associated with the phosphorylation of several mitochondrial proteins, creation of a mitochondrial membrane potential and activation of mitochondrial free radical generation. At least in rodent species, activation of sperm mitochondria appears to be a particularly important part of epididymal maturation.

The influence of homogenous zona pellucida on human spermatozoa hyperactivation, acrosome reaction and zona binding

The study aimed to evaluate the changes in sperm motion characteristics and the occurrence of hyperactivation among sperm populations after exposure to human zona pellucida. Motile spermatozoa samples were used to evaluate the sperm-zona binding capacity, zona-induced acrosome reaction and changes in sperm motion characteristics. Sperm motion characteristic changes studied included straight line velocity, curvilinear velocity, amplitude of lateral head displacement, straightness and beat cross frequency. Recordings were performed on semen immediately after liquefaction, 3 h capacitation and after exposure to solubilised human zona pellucida. The semen samples were divided into morphology categories, namely six (16 +/- 1.4% normal forms, normal patterns), 31 (8 +/- 1.7% normal forms, G-pattern) and 27 (3 +/- 1.3% normal forms, P-pattern). The Hemizona Indices for the three morphology groups namely normal, G-patterns and P-patterns, were 77 +/- 6%, 61 +/- 5% and 41 +/- 5% respectively (P <or= 0.05). The zona-induced acrosome reaction for the three groups were 25.0 +/- 2% (normal group), 18.0 +/- 2% (G-patterns) and 14.1 +/- 0.6% (P-pattern) (P <or= 0.05). The number of hyperactivated sperm showed an increase in the ejaculates (1%), after capacitation (2%) and exposure to zona pellucida (5%) (P <or= 0.05). When divided into the three morphology groups, the number of spermatozoa with hyperactivated motility was more profound in men with normal morphology compared with G- and P-pattern men. Human zona pellucida is a strong inducer of hyperactivated motility among spermatozoa and the effect is more profound among sperm populations with normal morphology.

Characterisation of a human sperm cell subpopulation marked by the presence of the TSH2B histone

During the process of mammalian spermiogenesis, a significant reorganisation of the chromatin structure occurs involving the sequential substitution of somatic histones with protamines. In the human sperm nucleus, ~15% of the basic nuclear protein complement is maintained as histones. Human testis/sperm-specific histone H2B (hTSH2B) is a variant of the histone H2B expressed exclusively in spermatogenic germline cells and present in some mature sperm cells. Thus, this protein marks a subpopulation of sperm cells in the ejaculate. Using indirect immunofluorescence, we examined the influence of hTSH2B on zona pellucida binding and sperm head decondensation in amphibian egg cell-free extract. As suggested by previous studies, we found that hTSH2B can be localised in only ~30% of sperm cells within a given ejaculate. We established that the presence of hTSH2B does not influence sperm zona pellucida binding capacity. Finally, we found that decondensation occurred more rapidly and to a greater extent in those cells containing hTSH2B. We propose that the presence or absence of hTSH2B within spermatozoa influences pronuclei formation and the activation of paternal genes following fertilisation and during early embryonic development.

Predictive value of the hemizona assay for pregnancy outcome in patients undergoing controlled ovarian hyperstimulation with intrauterine insemination

OBJECTIVE

The hemizona assay (HZA) is an established functional test that examines in vitro sperm-zona pellucida binding capacity with high predictive power for fertilization outcome in IVF. The objective of this study was to evaluate the value of the HZA as a predictor of pregnancy in patients undergoing controlled ovarian hyperstimulation (COH) and intrauterine insemination (IUI).

DESIGN

Prospective clinical study.

SETTING

Academic center.

PATIENT(S)

Eighty-two couples with unexplained or male factor infertility that underwent 313 IUI cycles.

INTERVENTION(S)

Basic semen analysis and HZA were performed within three months of starting COH/IUI therapy.

MAIN OUTCOME MEASURE(S)

Hemizona index (HZI) and clinical pregnancy.

RESULT(S)

Overall, patients with an HZI of <30 had a significantly lower pregnancy rate compared to patients with an HZI of > or =30 (11.1% vs. 40.6%, respectively; P<.05; relative risk for failure to conceive: 1.5 (confidence interval 1.2-1.9)). In all patients combined, and in the range of HZI 0-60, the duration of infertility (P=.000) and the HZI (P=.004) were significant determinants of conception (receiver operating characteristics (ROC) analysis). In couples with male infertility, the average path velocity and HZI were significant predictors of conception (P=.001 and P=.005, respectively, ROC analysis). The negative and positive predictive values of the HZA for pregnancy were 93% and 69%, respectively. Logistic regression analysis provided models of HZI (P=.021) and duration of infertility (P=.037) with highest predictability of conception in male factor and unexplained infertility groups, respectively.

CONCLUSION(S)

The HZA predicted pregnancy in the IUI setting with high sensitivity and negative predictive value in couples with male infertility. Results of this sperm function test are useful in counseling couples before allocating them into COH/IUI therapy.

Relationship between human sperm-hyaluronan binding assay and fertilization rate in conventional in vitro fertilization

BACKGROUND

Sperm-hyaluronan-binding assay (HBA) is one of the commercial kits being marketed for routine testing of sperm maturity and fertility. However, there is no report of whether the HBA can provide additional information over standard semen analysis for sperm-fertilizing ability. The objective of this study was to investigate the relationship between HBA and fertilization rate in conventional IVF.

METHODS

A total of 175 IVF patients with > or = 3 mature oocytes inseminated were included in the study. Both the standard semen analysis and the HBA were performed on the same ejaculated sperm samples used for IVF treatments. Relationships between the semen analysis and the HBA results and fertilization rate were analysed by both the Spearman test and the multivariate logistic regression analysis.

RESULTS

Both total and progressive sperm motility and normal morphology were highly correlated with HBA scores. While both normal sperm morphology and HBA scores were statistically significantly related to fertilization rates, the HBA was less significant than normal sperm morphology. The HBA does not provide additional information for identifying patients with a poor fertilization rate.

CONCLUSION

HBA is highly significantly correlated with sperm motility and morphology but is less significant than sperm morphology in relation to the fertilization rate in IVF. Thus, the clinical predictive value of HBA for sperm-fertilizing ability in vitro is limited.

Biological Effects of Recombinant Human Zona Pellucida Proteins on Sperm Function1

The initial interaction between gametes takes place at the level of the sperm surface and the zona pellucida (ZP), the extracellular matrix of the egg in mammals. Successful fertilization requires the proper molecular recognition of the ZP by the sperm. Recently, human ZP was demonstrated to be composed of four proteins: ZP1, ZP2, ZP3, and ZP4. The goals of this study were to determine the effects of recombinant human ZP2, ZP3, and ZP4 on human sperm acrosomal exocytosis and sperm motility. Exposure of sperm to ZP proteins, alone or in combination, promoted acrosomal exocytosis in a time-dependent manner. This effect occurred in parallel with a considerable decrease in progressive motility, coincident with an increase in nonprogressive sperm motility. An analysis of kinetic parameters of ZP-treated sperm demonstrated that a characteristic motility pattern could be defined by values of curvilinear velocity > 63.9 mum/s and linearity <or= 15.5%. A strong correlation between curvilinear velocity and the amplitude of lateral head displacement was also observed. The incidence of sperm having these particular kinetic parameters increased after exposure to ZP proteins. These studies of two processes involved in sperm penetration through the ZP confirm that zona glycoproteins promote acrosomal exocytosis and now establish an additional role for these components as modifiers of sperm motility.

World Health Organization grade 'a' motility and zona-binding test accurately predict IVF outcome for mild male factor and unexplained infertilities

BACKGROUND

The aim of this study was to determine the pronostic value of a sperm-zona pellucida (ZP) binding assay, combined with World Health Organization (WHO) grade 'a' sperm motility on the day of the IVF attempt, to predict sperm fertilizing ability in unexplained and moderate male factor infertilities.

METHODS

In total, 84 couples (64 unexplained infertility; 20 male factor) underwent both a sperm-ZP binding assay and an IVF attempt, irrespective of the test's result. The test was negative when grade 'a' motility was #5% and/or the ZP binding index was <0.7. Fertilization and pregnancy rates were related to the test's results.

RESULTS

Thirty-one patients had a negative test (group N) and 53 a positive test (group P). A difference was observed concerning the fertilization rate [median (range): 0 (0-75%) versus 50 (0-100%); P = 0.0001] and the number of cycles with fertilization rate <20% (65 versus 23%; P = 0.0002) between groups N and P respectively. In the group of unexplained and male factor infertilities, the test showed a sensitivity of 83 and 60%, specificity of 50 and 90%, positive predictive value of 76 and 86%, and negative predictive value of 61 and 69% respectively.

CONCLUSION

Sperm-ZP binding test, combined with WHO grade 'a' motility assessment, is relevant to prevent IVF fertilization failures in unexplained infertility and, most particularly, in moderate male factor infertility.

Should ICSI be used in non-male factor infertility?

There is general agreement that intracytoplasmic sperm injection (ICSI) should be used in male factor infertility cases, such as oligoasthenoteratozoospermia, presence of anti-sperm antibodies, or azoospermia, these cases being diagnosed through abnormal semen analysis. There are no randomized clinical trials comparing ICSI with IVF (or other interventions) where semen quality is so poor that IVF would not achieve fertilization. It is accepted that ICSI is the only treatment option in those circumstances. The role of ICSI where IVF can be expected to give a reasonable fertilization rate is the question that needs to be answered. The argument is whether or not ICSI should be used for all cases of infertility. This paper proposes and strongly supports the use of ICSI for all indications. Considerations of fertilization and embryo development, cost effectiveness and safety will be clearly discussed.

Clinical application of sperm-oocyte interaction tests in in vitro fertilization--embryo transfer and intracytoplasmic sperm injection programs

OBJECTIVE

To review the clinical value of sperm-oocyte interaction tests for the diagnosis and management of infertility by standard IVF or intracytoplasmic sperm injection (ICSI).

DESIGN

Review of recent publications on relationships among sperm-oocyte interaction tests, sperm characteristics, and results of IVF and determination of frequency of defective sperm-oocyte interaction in infertile men.

MAIN OUTCOME MEASURE(S)

Fertilization rates with IVF, sperm characteristics, sperm-zona pellucida (ZP) binding, ZP-induced acrosome reaction (AR), and sperm-ZP penetration.

RESULT(S)

Sperm defects associated with low sperm-ZP binding or impaired ZP-induced AR and sperm-ZP penetration are the major causes of failure of fertilization when all or most oocytes from a couple do not fertilize in standard IVF. There is a high frequency of defective sperm-ZP interaction in men with oligozoospermia (<20 x 10(6)/mL) and severe teratozoospermia (strict normal sperm morphology < or =5%). Sperm morphology correlates with sperm-ZP binding, and sperm concentration correlates with ZP-induced AR in infertile men with sperm concentrations >20 x 10(6)/mL. Defective ZP-induced AR may cause infertility in up to 25% men with idiopathic infertility. These patients require ICSI despite the normal standard semen analyses.

CONCLUSION(S)

Sperm-oocyte interaction tests are useful for diagnosis of subtle sperm defects that cause infertility in men without severe abnormalities of semen analysis. Pre-IVF diagnosis of these sperm defects will assist in the clinical assignment of patients to treatment with either standard IVF or ICSI.

Failed fertilization: is it predictable?

PURPOSE OF REVIEW

The purpose of this review is to critically examine the ability of screening tests to predict fertilization failure.

RECENT FINDINGS

Failed fertilization occurs in 5-10% of in-vitro fertilization cycles and 2-3% of intracytoplasmic sperm injection cycles. Failed fertilization may result from impaired spermatozoa, oocyte deficiencies or defects in the in-vitro sperm/oocyte medium. In the in-vitro fertilization setting most cases are caused by male factor deficiencies, whereas failure of oocyte activation is the most common cause of failed fertilization after intracytoplasmic sperm injection. Although the standard semen analysis has limited ability to predict fertilization failure, strict sperm morphology criteria, sperm-zona binding ratios and zona pellucida induced acrosome reaction tests provide increased capacity to avoid this outcome. The quality of the semen sample on the day of oocyte retrieval and fertilization performance in previous in-vitro fertilization cycles may also guide the appropriate use of intracytoplasmic sperm injection. However, the routine use of the latter technique in cases of non-male factor infertility is contraindicated.

SUMMARY

The ever improving techniques highlighted in this analysis offer improved ability to predict failed fertilization.

The clinical value of sperm nuclear DNA assessment

Traditional semen analysis is essential for the diagnosis of male infertility. A number of studies over the past decade have reported that a significant contributing factor to male fertility that is not revealed as part of semen analysis is sperm DNA, specifically its composition and organization. Exogenous and endogenous factors can cause damage to sperm DNA. For example, topoisomerase II activity, which is necessary for sperm DNA packaging, can adversely influence the competence of sperm DNA if the activity of the enzyme is abnormal. Germ cell apoptosis can be induced by oxygen radicals produced from environmental (for example cigarette smoke) or testicular (for example localized ischaemia) sources. Several assays have been developed that are useful for assessing sperm DNA composition and organization. To date, each of these assays has revealed that when sperm DNA has been damaged or packaged improperly there is a concomitant and often significant decline in male fertility.

Evaluation of the effect of a cervical cap device on sperm functional characteristics in vitro

Intracervical insemination continues to be employed for homologous and donor insemination in natural and stimulated cycles. Efficacy studies for potential fertility involve in vivo assessment; however, in vitro testing of particular sperm function(s) critically involved in fertilization is an important component of such evaluation. We report here on the in vitro evaluation of the effects of the silicone Veos cervical cap (Veos, London, UK) on sperm function. Donor semen was exposed to the Veos cervical cap or a sterile 15-cc centrifuge tube (control), or treated with the spermicide nonoxynol-9 (5 mg x ml(-1) in saline) for 4 h at 37 degrees C and 5% CO2 in water-saturated air. After exposure, motility characteristics, both in semen and in spermatozoa processed by standard swim-up procedure, cervical mucus penetration and sperm-zona pellucida interaction using the hemizona assay were assessed. Results indicated that exposure to the Veos cervical cap had no effect on either sperm motility characteristics or sperm-zona pellucida interaction. A small but significant difference was observed for cervical mucus penetration (P = 0.05); however, for both the control and treated groups, vanguard spermatozoa exceeded manufacturer's guidelines for a normal test, a penetration distance of > or = 30 mm. As expected, nonoxynol-9 was a potent inhibitor of sperm function. Lack of adverse effects on in vitro spermatozoa functional characteristics after exposure to the silicone Veos cervical cap supports its addition to the repertoire of fertility treatment modalities when cervical insemination is indicated.

Characterization of the biologic activities of a recombinant human zona pellucida protein 3 expressed in human ovarian teratocarcinoma (PA-1) cells

OBJECTIVE

This study was undertaken to clone and express a recombinant human zona pellucida protein 3 and to characterize its biologic activities as a sperm ligand and an inducer of the acrosome reaction.

STUDY DESIGN

Human ovarian teratocarcinoma (PA-1) cells were transfected with an expression vector containing human zona pellucida protein 3 complementary deoxyribonucleic acid with a sequence coding for a 6-histidine tail introduced into its 3' end. Purification of the secreted glycoprotein was performed by sequential affinity (lectin and nickel--nitrilotriacetic acid) and ion-exchange chromatography.

RESULTS

Western blot analysis confirmed a molecular weight of approximately 65 kd for the purified product. A cell-free translation system revealed a correctly sized protein backbone of 47 kd. The recombinant human zona pellucida protein 3 demonstrated specific, potent, and dose-dependent competitive inhibition of sperm-zona pellucida binding in vitro under hemizona assay conditions. Recombinant human zona pellucida protein 3 also stimulated the acrosome reaction of live sperm. This effect was fast, dose dependent, and capacitation time dependent. Furthermore, advance incubation with pertussis toxin, an inactivator of heterotrimeric G proteins, blocked recombinant human zona pellucida protein 3--induced acrosomal exocytosis.

CONCLUSION

The recombinant human zona pellucida protein 3 expressed in PA-1 cells manifested the full spectrum of expected biologic activities. It therefore represents a valuable tool for examination of human fertilization and the design of new strategies in diagnosis of male factor infertility and in contraception.

Incidence of aneuploid spermatozoa from subfertile men: selected with motility versus hemizona-bound

Spermatozoa-zona pellucida binding selects for human spermatozoa with progressive motility, normal morphology and functional competency. We postulated that this gamete interaction would also act to select against spermatozoa with chromosomal numerical aberrations. Spermatozoa from 41 men participating in the intracytoplasmic sperm injection (ICSI) programme were evaluated for the incidence of aneuploidy of chromosomes 18, X and Y. The hemizona assay was utilized to determine whether zona-bound spermatozoa from these patients have a reduced incidence of aneuploidy compared with those selected by motility only in a standard swim-up procedure. Using multicolour fluorescence in-situ hybridization (FISH) with DNA probes specific for chromosomes 18, X and Y, the disomy rates for chromosomes 18, X, Y and XY were found to be 0.31, 0.27, 0.29 and 0. 14% respectively in the swim-up motile fraction, and 0.31, 0.33, 0. 32 and 0.19% respectively in the pellet fraction. Analysing the zona-bound spermatozoa, the disomy rates for chromosome 18, X, Y and XY were found to be 0.02, 0.15, 0.12 and 0.07% respectively. The zona-bound spermatozoa had a significantly lower frequency of aneuploidy than the swim-up motile fraction or the pellet fraction (P < 0.0001). The incidence of chromosome 18 aneuploidy, including both chromosome 18 disomy and nullisomy, in the swim-up motile fractions was significantly increased in patients with an abnormal or borderline hemizona index compared with those with a normal hemizona index (P < 0.05). We also found that a high incidence of sperm aneuploidy was associated to a certain extent with low fertilization rate, and with failure to achieve pregnancy through ICSI. This study suggests that the human zona pellucida has the capacity to select against aneuploid spermatozoa by an as yet undetermined mechanism.

Analysis of DNA fragmentation, plasma membrane translocation of phosphatidylserine and oxidative stress in human spermatozoa

The objectives of this cross-sectional observational study were: (i) to detect DNA damage and plasma membrane translocation of phosphatidylserine in purified sperm populations of high and low motility, and (ii) to analyse their relationship with the endogenous generation of reactive oxygen species. Ejaculates from infertile men were examined following gradient centrifugation. The main outcome measures were: sperm motion parameters (assessed with a computer analyser), generation of reactive oxygen species (measured by chemiluminescence), DNA damage (detected by terminal deoxynucleotidyl transferase-mediated dUDP nick-end labelling and monoclonal antibody labelling of single-stranded DNA) and translocation of membrane phosphatidylserine (examined with annexin V staining). DNA fragmentation and membrane translocation of phosphatidyl-serine were observed in the fractions with low and high sperm motility in all patients. The fractions with low sperm motility had significantly higher proportion of cells with DNA damage and production of reactive oxygen species than the fractions with high sperm motility (P < 0.005). DNA fragmentation was significantly and positively correlated with the generation of reactive oxygen species (r = 0.42; P = 0.02).

IN CONCLUSION

(i) spermatozoa from infertile men display translocation of membrane phosphatidylserine as diagnosed by annexin V positive staining; (ii) DNA damage (fragmentation and presence of single-stranded DNA) can be detected in ejaculated spermatozoa from infertile men in fractions with low and high sperm motility, and (iii) there is a relationship between DNA damage and oxidative stress.

Defective sperm-zona pellucida interaction: a major cause of failure of fertilization in clinical in-vitro fertilization

Sperm-zona pellucida binding and penetration were assessed on the oocytes that failed to fertilize from couples with >/=3 oocytes treated by standard in-vitro fertilization (IVF). There were four groups: fertilization rate 0% (n = 369), 1-25% (n = 194), 26-50% (n = 81) and 51-95% (n = 100). Of the couples with zero fertilization rate 70% had </=5 spermatozoa bound per zona pellucida and 42% had no spermatozoa penetrating the zona pellucida of any oocyte. In contrast, in the 51-95% fertilization rate group, only 17% had </= 5 spermatozoa bound per zona pellucida and 6% had no spermatozoa penetrating the zona pellucida. There was a significantly higher frequency of poor sperm morphology (</= 5% normal) in couples with zero fertilization rate (36%) than in the fertilization rate group 51-95% (7%). Incubation of oocytes from 68 couples with zero fertilization rate and low sperm-zonae pellucidae binding with fertile donor spermatozoa resulted in normal sperm-zona pellucida binding and most zonae pellucidae being penetrated. In conclusion, defective sperm-zona pellucida interaction was the major cause for low fertilization rates in standard IVF. This was usually because of defects of the spermatozoa rather than defects of the oocytes. Sperm defects likely to cause failure of fertilization should be diagnosed before commencing IVF and the patients directed to intracytoplasmic sperm injection.

Protein tyrosine phosphorylation during hyperactivated motility of cynomolgus monkey (Macaca fascicularis) spermatozoa

Capacitation and capacitation-related hyperactivated motility do not occur spontaneously in cynomolgus monkey (Macaca fascicularis) spermatozoa; instead, both have an absolute requirement for exogenous stimulation with caffeine and dibutyryl (db)cAMP. In the present study, we 1) defined sorting criteria for automated analysis of macaque sperm exhibiting hyperactivated motility (HA) and 2) investigated protein tyrosine phosphorylation involvement in dbcAMP- and caffeine-stimulated capacitation and HA. Motion characteristics were assessed by computer-assisted motion analysis. Tyrosine phosphorylation of sperm tail proteins was determined by immunocytochemistry with PY-20 antiserum. Automated sorting criteria for HA were curvilinear velocity (VCL) >/= 150 microm/sec; amplitude of lateral head displacement (ALH) >/= 8.0 microm, and linearity (LIN) </= 60%. Using these criteria, caffeine and dbcAMP significantly stimulated HA (61 +/- 8%) compared to control conditions (12 +/- 2%), p < 0.01, with a concomitant increase in PY-20 labeling (88 +/- 12%) vs. control (13 +/- 2%), p < 0.01. PY-20 labeling significantly correlated with HA (r = 0.75, p < 0.01) and with some motion characteristics used for HA sorting including ALH (r = 0.86, p = 0.0013) and LIN (r = -0.88, p < 0.001) but not VCL (r = 0.21). Treatment with genistein (10 microM) had no effect on HA or PY-20 immunocytochemistry in the absence of caffeine and dbcAMP, but the tyrosine kinase inhibitor significantly decreased caffeine- and dbcAMP-stimulated HA and PY-20 labeling in a dose-dependent manner (p < 0.01). These results demonstrate that tyrosine phosphorylation of sperm tail proteins is an integral signaling pathway modulating some but not all of the motion characteristics associated with cAMP- and caffeine-stimulated HA in cynomolgus monkey spermatozoa.