Oocyte activation and phospholipase C zeta (PLCζ): diagnostic and therapeutic implications for assisted reproductive technology

Expression of PLCZ1 mRNA in spermatozoa of Criollo and European bulls in a low-input system

Sperm motility and kinematics analysis are important to predict bull fertility. However, there are other molecules in the sperm with the ability to improve the pregnancy rate. For example, PLCZ1 is a sperm protein that plays a unique role in the activation of the zygote and is important for the survival of the embryo. The objective of this work was to compare the expression of PLCZ1 mRNA in sperm cells of Chihuahuan Criollo and European bulls in the winter and summer seasons, under a low-input system. Six (3.33 ± 0.43 years old) bulls (three Criollo, three European) were used. Gross and individual motility were measured in semen obtained by electrostimulation. The cell pack was pelletized by centrifugation and stored in liquid nitrogen. The sperm cells were purified and total RNA was extracted. cDNA was synthesized to perform qPCR and measure the relative level of PLCZ1 transcripts in each bull. There were no differences in individual motility, however, gross motility was lower (P < 0.05) in Criollo bulls, both in the winter (71.1 ± 2.8 vs. 76.6 ± 2.8%) and in the summer season (58.9 ± 2.8 vs. 77.7 ± 2.8%). PLCZ1 expression was 5.3 times higher (P < 0.05) in winter than in summer (5.09 ± 1.09 vs 0.959 ± 1.09). No difference (P>0.05) was found in the expression levels of PLCZ1 between both breeds (4.36 ± 1.09 vs 1.69 ± 1.09), for Criollo and European, respectively. Although the animals presented seminal motility within the recommended limits for insemination, the expression levels of PLCZ1 vary depending on the time of the year and this might impact the rate of successful pregnancies. Therefore, it is important to complement conventional analysis of seminal quality with molecular characteristics.

A DNA Methylation Perspective on Infertility

Infertility affects a significant number of couples worldwide and its incidence is increasing. While assisted reproductive technologies (ART) have revolutionized the treatment landscape of infertility, a significant number of couples present with an idiopathic cause for their infertility, hindering effective management. Profiling the genome and transcriptome of infertile men and women has revealed abnormal gene expression. Epigenetic modifications, which comprise dynamic processes that can transduce environmental signals into gene expression changes, may explain these findings. Indeed, aberrant DNA methylation has been widely characterized as a cause of abnormal sperm and oocyte gene expression with potentially deleterious consequences on fertilization and pregnancy outcomes. This review aims to provide a concise overview of male and female infertility through the lens of DNA methylation alterations.

Applications of advances in mRNA-based platforms as therapeutics and diagnostics in reproductive technologies

The recent COVID-19 pandemic led to many drastic changes in not only society, law, economics, but also in science and medicine, marking for the first time when drug regulatory authorities cleared for use mRNA-based vaccines in the fight against this outbreak. However, while indeed representing a novel application of such technology in the context of vaccination medicine, introducing RNA into cells to produce resultant molecules (proteins, antibodies, etc.) is not a novel principle. It has been common practice to introduce/inject mRNA into oocytes and embryos to inhibit, induce, and identify several factors in a research context, while such aspects have also been proposed as potential therapeutic and diagnostic applications to combat infertility in humans. Herein, we describe key areas where mRNA-based platforms have thus far represented potential areas of clinical applications, describing the advantages and limitations of such applications. Finally, we also discuss how recent advances in mRNA-based platforms, driven by the recent pandemic, may stand to benefit the treatment of infertility in humans. We also present brief future directions as to how we could utilise recent and current advancements to enhance RNA therapeutics within reproductive biology, specifically with relation to oocyte and embryo delivery.

Mutations in PLCZ1 induce male infertility associated with polyspermy and fertilization failure

PURPOSE

To investigate the genetic causes of polyspermy and total fertilization failure (TFF) in two independent male patients suffering from male infertility.

METHODS

Immunofluorescence (IF) staining was used to detect the localization of the PLCζ protein in sperm and the maternal pronucleus in the zygote. Genomic DNA samples were extracted from the peripheral blood of patients and their families. The ExAC database was used to identify the frequency of corresponding mutations. The PLCZ1 mutations were validated by Sanger sequencing. The pathogenicity of the identified mutations and their possible effects on the protein were assessed using in silico tools and molecular modeling.

RESULTS

We identified a reported homozygous mutation c.588C > A (p.Cys196Ter) and a compound heterozygous mutation c.2 T > C(p.Met1Thr)/c.590G > A (p.Arg197His) with one novel mutation in PLCZ1. The IF results showed that these multipronuclear zygotes formed as a result of polyspermy. In silico analysis predicted that the mutations result in disease-causing proteins. IF staining revealed that PLCζ is abnormally localized in the sperm samples from the two affected patients. Assisted oocyte activation (AOA) successfully rescued polyspermy and TFF and achieved pregnancy in two patients with the PLCZ1 mutation.

CONCLUSION

We identified a homozygous mutation in PLCZ1 (c.588C > A [p.Cys196Ter]) in a male patient with polyspermy after in vitro fertilization (IVF) as well as a compound heterozygous mutation c.2 T > C(p.Met1Thr)/c.590G > A (p.Arg197His) with one novel mutation in a male patient with fertilization failure after intracytoplasmic sperm injection (ICSI), and we provide evidence that the homozygous mutation can cause polyspermy and the compound heterozygous mutation can cause fertilization failure.

Assisted Oocyte Activation With Calcium Ionophore Improves Pregnancy Outcomes and Offspring Safety in Infertile Patients: A Systematic Review and Meta-Analysis

This study aimed to evaluate the efficacy and safety of calcium ionophore during assisted oocyte activation (AOA). This meta-analysis contained randomized controlled trials and prospective observational and retrospective trials. The summary odds ratio (OR) with 95% confidence intervals (CIs) was calculated for clinical pregnancy rate and live birth rate. Both fixed and random effects models were applied. A total of 22 studies were included into this meta-analysis. Seventeen of the included studies showed that calcium ionophore increased the clinical pregnancy rate (OR, 2.14; 95% CI, 1.38–3.31). Similarly, 14 studies indicated that AOA with calcium ionophore during intracytoplasmic sperm injection (ICSI) improved the live birth rate considerably (OR, 2.65; 95% CI, 1.53–4.60). Moreover, fertilization, blastocyst formation, and implantation rate were higher after using AOA with calcium ionophore combined with ICSI. In addition, calcium ionophore did not increase top-quality embryo rate, cleavage rate, miscarriage rate, congenital birth defects, and neonatal sex ratio. Therefore, calcium ionophore followed by ICSI not only significantly improved live birth and overall pregnancy, but also did not affect the incidence of miscarriage, congenital birth defects, and neonatal sex ratio. This meta-analysis indicated that using calcium ionophore to activate oocytes was beneficial for couples with poor fertilization rates following ICSI.

Phospholipase C-zeta levels are not correlated with fertilisation rates in infertile couples

In mammals, 'oocyte activation' is triggered by certain proteins, one of which is phospholipase C-zeta. Recent evidence suggests that low expression of phospholipase C-zeta might be associated with male infertility, while a limited number of studies claimed the opposite. This study was designed to test whether quantity of phospholipase C-zeta and in vitro fertilisation rates are correlated or not, assessed by flow cytometry. Semen samples from 43 infertile couples were analysed for the percentage and mean fluorescent intensity (MFI) of phospholipase C-zeta protein. Results were confirmed by immunofluorescent labelling. Patients with a fertilisation rate of 40% or lower were involved in the low fertilisation group, while the high fertilization group consisted of patients with a fertilisation rate of 60% and higher. Quantitative analyses by flow cytometry showed no significant difference among the low fertilisation and high fertilisation groups when phospholipase C-zeta ratio or MFI was considered. No correlation was found between pregnancy rates and phospholipase C-zeta quantity. None of the total fertilisation failure cases were lack of phospholipase C-zeta. In fact, fertilisation was possible even when phospholipase C-zeta levels were very low. Thus, we concluded that phospholipase C-zeta quantity cannot be considered as a diagnostic tool for male infertility.

The paternal toolbox for embryo development and health

The sperm is essential for reconstitution of embryonic diploidy and highly specialized developmental functions. Immediately after gamete fusion, the sperm-borne PLC-zeta triggers activation, generating intracellular free Ca2+ oscillations. Mutations in the PLC-zeta encoding gene are associated with the absence of this factor in mature sperm and inability to achieve fertilization. Sperm play also a role in the greater game of the choreography of fertilization. In the human, the sperm centrioles are introduced into the oocyte environment with gamete fusion. They interact with the oocyte cytoskeletal apparatus to form a functional pair of centrosomes and ultimately regulate pronuclear juxtaposition in preparation for the first cleavage. As a consequence, the fidelity of chromosome segregation during the first cell divisions depends on the function of sperm centrioles. Sperm DNA integrity is essential for embryo development and health. Damaged DNA does not impact on the sperm fertilization ability following ICSI. However, detrimental effects emerge at pre- and post-implantation stages. Sperm-specific epigenetic factors also play an active role in the regulation of embryonic development, as shown by correlations between reduced embryo morphological quality and incorrect chromatin packaging during spermiogenesis or abnormal methylation of sperm CpG islands. This functional landscape demonstrates that the contribution of the sperm to development goes far beyond its well-established role in fertilization. Clinical studies confirm this view and indicate sperm function as a crucial aspect of research to increase the efficacy of assisted reproduction treatments.

Treatment with Calcium Ionophore Improves The Results in Patients with Previous Unsuccessful Attempts at The Fertilization: A Cohort Study

BACKGROUND

The objective of this study is to evaluate artificial oocyte activation (AOA) with calcium ionophore (CaI) in a subsequent attempt at fertilisation in patients after extremely low or failed fertilisation. We assessed improvements in fertilisation, implantation and pregnancy rates as well as cancellation rates in these patients. Finally, was evaluated the result testing in addition to delivery rate and obstetric outcomes in children born after AOA.

MATERIALS AND METHODS

This was a retrospective observational study conducted in an IVF laboratory of an IVI clinic (IVIRMA Valencia, Spain). One group (509 mature oocytes from 66 patients) received a first intracytoplasmic sperm injection (ICSI) without AOA, which resulted in either a failed fertilisation or very low values (<30%). This group was compared with a second group (616 mature oocytes from the same 66 patients) that used AOA. Outcome was compared by McNemar's test and the dependent t tests.

RESULTS

AOA plus CaI resulted in enhanced fertilisation (51 vs. 13.1%), ongoing pregnancy (47 vs. 21.7%), and implantation (31.1 vs. 13.1%) rates, and less chances for cancelling the cycle (22.7 vs. 69.3%). There were no observed adverse effects in obstetric and perinatal outcomes after the use of AOA.

CONCLUSION

Our findings support the use of AOA for a given population of patients where fertilisation was affected during previous attempts. After AOA, we observed a significant increase in reproductive success due to the increased number of embryos available for embryo selection and, therefore, enhanced chances for success. The use of this artificial technique is comforting after checking non-existence of detrimental effects on the offspring.

Risk of birth defects in children conceived by artificial oocyte activation and intracytoplasmic sperm injection: a meta-analysis

BACKGROUND

Whether artificial oocyte activation (ICSI-AOA) will increase the risk of birth defects remains controversial. Thus, we performed this study to evaluate the risk of birth defects and further compare the incidence of different birth defects types (chromosomal aberrations and non-chromosomal aberrations) in children conceived by ICSI-AOA and conventional intracytoplasmic sperm injection (ICSI) in an enlarged sample size.

METHOD

A comprehensive review of the literatures comparing birth defects in children conceived by ICSI-AOA and conventional ICSI by October 2020 was performed in PubMed, Embase, Cochrane Libraries, Web of Science, and Chinese databases including China National Knowledge Infrastructure, China Biology Medicine disc and Wan Fang. Risk ratios (RR) and 95% confidence intervals (CI) were calculated.

RESULTS

Five studies were included in the final analysis. Compared with conventional ICSI, ICSI-AOA did not increase the birth defects rate (RR = 1.27, 95%CI 0.70-2.28) of children. Furthermore, in a subgroup analysis, birth defects were classified into two types (chromosomal aberrations and non-chromosomal aberrations) in four studies and no statistical difference were revealed.

CONCLUSION

Our analysis indicates that ICSI-AOA represents no significant difference in the prevalence of major birth defects or types of birth defects (chromosomal aberrations and non-chromosomal aberrations) comparing with conventional ICSI. This conclusion may provide clinicians evidence-based support in patient counseling and instruction of the application and safety concern about ICSI-AOA.

Diagnosis and Treatment of Male Infertility-Related Fertilization Failure

Infertility affects approximately 15% of reproductive-aged couples worldwide, of which up to 30% of the cases are caused by male factors alone. The origin of male infertility is mostly attributed to sperm abnormalities, of which many are caused by genetic defects. The development of intracytoplasmic sperm injection (ICSI) has helped to circumvent most male infertility conditions. However, there is still a challenging group of infertile males whose sperm, although having normal sperm parameters, are unable to activate the oocyte, even after ICSI treatment. While ICSI generally allows fertilization rates of 70 to 80%, total fertilization failure (FF) still occurs in 1 to 3% of ICSI cycles. Phospholipase C zeta (PLCζ) has been demonstrated to be a critical sperm oocyte activating factor (SOAF) and the absence, reduced, or altered forms of PLCζ have been shown to cause male infertility-related FF. The purpose of this review is to (i) summarize the current knowledge on PLCζ as the critical sperm factor for successful fertilization, as well as to discuss the existence of alternative sperm-induced oocyte activation mechanisms, (ii) describe the diagnostic tests available to determine the cause of FF, and (iii) summarize the beneficial effect of assisted oocyte activation (AOA) to overcome FF.

Perfect date-the review of current research into molecular bases of mammalian fertilization

Fertilization is a multistep process during which two terminally differentiated haploid cells, an egg and a sperm, combine to produce a totipotent diploid zygote. In the early 1950s, it became possible to fertilize mammalian eggs in vitro and study the sequence of cellular and molecular events leading to embryo development. Despite all the achievements of assisted reproduction in the last four decades, remarkably little is known about the molecular aspects of human conception. Current fertility research in animal models is casting more light on the complexity of the process all our lives start with. This review article provides an update on the investigation of mammalian fertilization and highlights the practical implications of scientific discoveries in the context of human reproduction and reproductive medicine.

The functional anatomy of the human spermatozoon: relating ultrastructure and function

The Internet, magazine articles, and even biomedical journal articles, are full of cartoons of spermatozoa that bear minimal resemblance to real spermatozoa, especially human spermatozoa, and this had led to many misconceptions about what spermatozoa look like and how they are constituted. This review summarizes the historical and current state of knowledge of mammalian sperm ultrastructure, with particular emphasis on and relevance to human spermatozoa, combining information obtained from a variety of electron microscopic (EM) techniques. Available information on the composition and configuration of the various ultrastructural components of the spermatozoon has been related to their mechanistic purpose and roles in the primary aspects of sperm function and fertilization: motility, hyperactivation, capacitation, the acrosome reaction and sperm-oocyte fusion.

Effect of Artificial Oocyte Activation on Intra-Cytoplasmic Sperm Injection Outcomes in Patients with Lower Percentage of Sperm Containing Phospholipase Cζ: A Randomized Clinical Trial

BACKGROUND

Artificial oocyte activation (AOA) is a specialized method in assisted reproductive technique (ART). According to increasing concern about using AOA, it is necessary to evaluate sperm-borne oocyte activating factors (SOAFs) including phospholipase C zeta (PLCζ). In this study, PLCζ before AOA was evaluated first and then the impact of AOA on pre-implantation embryo development was investigated.

METHODS

This prospective clinical trial enrolled couples subjected to ICSI. By evaluating PLCζ, semen samples were categorized into two groups; I (Control) and II (PLCζ deficient). Retrieved oocytes from partners were put into three categories: control group (Injected with sperm from group I, n=113), group without AOA (Injected with sperm from group II and no exposure to AOA, n=106), and group AOA (Injected with sperm from group II and exposure to AOA, n=114). Finally, fertilization results were compared via Kruskal-Wallis followed by Dunn's multiple comparison test. The p<0.05 was considered statistically significant.

RESULTS

Fertilization rate was significantly lower in the group without AOA compared to control group (41.9±6.3 vs. 78.1±4.7, p<0.001). AOA improved fertilization rate in group AOA compared to the group without AOA (69.5±3.9 vs. 41.9±6.3, p<0.01); however, cleavage (91.7±2.8, 90.9±4.6, and 95.2±3.4, respectively) and embryo quality (2.5±0.1, 2.3±0.2, and 2.4±0.2, respectively) scores were not substantially different between groups of control, with and without AOA.

CONCLUSION

We showed that PLCζ can be considered as a good biomarker in evaluation of oocyte activation capability. Further studies are required to establish the best use of PLCζ as a biomarker in clinics.

Oligoasthenoteratozoospermic (OAT) men display altered phospholipase C ζ (PLCζ) localization and a lower percentage of sperm cells expressing PLCζ and post-acrosomal sheath WW domain-binding protein (PAWP)

Oligoasthenoteratozoospermia (OAT) is demonstrated to be one of the most common causes of male subfertility. Phospholipase C ζ (PLCζ), a sperm-specific protein, is considered to be one of the sperm-borne oocyte activating factors (SOAFs), which play a vital role in fertilization. The post-acrosomal sheath WW domain-binding protein (PAWP) is another candidate for SOAF. The aim of this study was to compare the PLCζ localization patterns and percentage of PLCζ- and PAWP-positive sperm cells in patients with OAT and fertile men with normozoospermia. A total of 40 men included in this study were classified into two groups: OAT (n = 25) and control group (n = 15). Semen samples were collected and analyzed using conventional semen analysis according to the World Health Organization guidelines. The percentage of PLCζ- and PAWP-positive sperm cells and localization patterns of PLCζ were evaluated using immunofluorescence staining. The mean percentage of sperm cells expressing PAWP and PLCζ was significantly lower in OAT compared to control group (52.8 ± 4.2 vs. 76.8 ± 5 and 63.4 ± 3.5 vs. 86.7 ± 2.1, respectively). In addition, statistically significant differences were found with regard to the PLCζ localization patterns, including equatorial, acrosomal + equatorial, and equatorial + post-acrosomal pattern, between the two groups (p < 0.01). The present study showed a lower percentage of sperm cells expressing PLCζ and PAWP, as well as altered localization patterns of PLCζ in men with OAT. Given the role of PLCζ and PAWP in fertilization, as two major candidates for SOAFs, our findings indicate that PLCζ and PAWP impairments may be one of the possible etiologies of decreased fertility in OAT.

Strontium fails to induce Ca2+ release and activation in human oocytes despite the presence of functional TRPV3 channels

STUDY QUESTION

Are the transient receptor potential cation channels vanilloid 3 (TRPV3) present and able to mediate strontium (Sr²⁺) induced artificial activation in human oocytes?

SUMMARY ANSWER

Sr²⁺ did not induce Ca²⁺ rises or provoke activation in human oocytes, however, mRNA for the TRPV3 channel was present in metaphase II (MII) human oocytes after IVM and TRPV3 agonists induced Ca²⁺ rises and oocyte activation, demonstrating the channels were functional.

WHAT IS KNOWN ALREADY

Selective activation of TRPV3 by agonists induces Ca²⁺ entry and promotes mouse oocyte activation, and the absence of TRPV3 channels in mouse oocytes prevents Sr²⁺ mediated artificial activation. Sr²⁺ is sometimes used to overcome fertilization failure after ICSI in the clinic, but its efficiency is still controversial and the mechanism(s) of how it mediates the Ca²⁺ flux has not been studied yet in human.

STUDY DESIGN, SIZE, DURATION

The protein distribution (n = 10) and mRNA expression level (n = 19) of the TRPV3 channels was investigated in human MII oocytes after IVM. The Sr²⁺ (10 mM) and TRPV3 agonists (200 μM 2-aminoethoxydiphenyl borate [2-APB] and 200 μM carvacrol)-induced Ca²⁺ response was analyzed in human (n = 15, n = 16 and n = 16, respectively) and mouse oocytes (n = 15, n = 19 and n = 26, respectively). The subsequent embryonic developmental potential following the parthenogenetic activation using these three agents was recorded in human (n = 10, n = 9 and n = 9, respectively) and mouse (n = 20 per agent) oocytes, by determining pronucleus, or 2-cell and blastocyst formation rates.

PARTICIPANTS/MATERIALS, SETTING, METHODS

MII oocytes from B6D2F1 mice (6–10 weeks old) as well as human IVM oocytes and IVO oocytes (from patients aged 25–38 years old) with aggregates of smooth endoplasmic reticulum clusters were used. The expression of TRPV3 channels was determined by immunofluorescence staining with confocal microscopy and RT-PCR, and the temporal evolution of intracellular Ca²⁺ concentration was measured by time-lapse imaging after exposure to Sr²⁺ and TRPV3 agonists (2-APB and carvacrol). Artificial activation efficiency was assessed using these agents.

MAIN RESULTS AND THE ROLE OF CHANCE

Sr²⁺ did not promote Ca²⁺ oscillations or provoke activation in human oocytes. Transcripts of TRPV3 channels were present in IVM MII human oocytes. TRPV3 protein was expressed and distributed throughout the ooplasm of human oocytes, rather than particularly concentrated in plasma membrane as observed in mouse MII oocytes. Both agonists of TRPV3 (2-APB and carvacrol), promoted a single Ca²⁺ transient and activated a comparable percentage of more than half of the exposed human oocytes (P > 0.05). The agonist 2-APB was also efficient in activating mouse oocytes, however, significantly fewer mouse oocytes responded to carvacrol than 2-APB in both the Ca²⁺ analysis and activation test (P < 0.001).

LIMITATIONS REASONS FOR CAUTION

The availability of fresh IVO matured oocytes in human was limited. Data from TRPV3 knockout model are not included.

WIDER IMPLICATIONS OF THE FINDINGS

The benefit of clinical application using Sr²⁺ to overcome fertilization failure after ICSI requires further validation.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by FWO-Vlaanderen, China Scholarship Council and Special Research Fund from Ghent University (Bijzonder Onderzoeksfonds, BOF). No competing interests are declared.

Artificial oocyte activation with calcium ionophore for frozen sperm cycles

Fertilization problems are the major problems that may be faced in 30-55% of the patients during an intracytoplasmic sperm injection (ICSI) cycle. A successful oocyte activation depends on factors related to both sperm and oocyte, and one of the important factors that mediates the process is Ca²⁺ concentration within the oocyte. Artificial oocyte activation (AOA) is a method used for fertilization problems that commonly involve the usage of Ca²⁺ ionophores and is usually used in problems such as total fertilization failure (TFF) and globozoospermia. The aim of the present study was to investigate possible effects of AOA for different groups of patients with fertilization failure. Four groups of patients (previous TFF, low oocyte number, severe sperm quality, and frozen sperm (FS) group) that underwent ICSI with AOA were included in the study. All groups had similar control groups with same indications except TFF, where AOA was not performed. Fertilization rates were significantly higher in the TFF group than those observed in other AOA groups. Fertilization rates and quality of embryos observed in the remaining AOA groups were higher than those of the controls, which were statistically insignificant. Prgenancy rates were higher in all AOA groups compared to the controls, although the differences were significant in FS group only. Quality of embryos and pregnancy rates were lower in the TFF group compared to the remaining AOA groups indicating possible concomitant problems. Fertilization rates, quality of embryos and pregnancy rates seemed to be increased in all indication groups suggesting that not only TFF patients but also a wide variety of patients with different indications may benefit from AOA.

ABBREVIATIONS

ICSI: Intracytoplasmic sperm injection; ARTs: Assisted reproductive techniques; Ca: Calcium; AOA: Artificial oocyte activation; TFF: Total fertilization failures; OAT: Oligoasthenoteratozoospemia; IVF: In vitro fertilization; SOAT: Severe OAT; LON: Low ooctye number; FS: Frozen sperm; hCG: human chorionic gonadotrophin; PVP: polyvinylpyrrolidone; HSA: human serum albumin.

Dehydroepiandrosterone (DHEA) and Its Sulfate (DHEA-S) in Mammalian Reproduction: Known Roles and Novel Paradigms

Steroid hormones form an integral part of normal development in mammalian organisms. Cholesterol is the parent compound from which all steroid hormones are synthesized. The product pregnenolone formed from cholesterol serves as precursor for mineralocorticoids, glucocorticoids, as well as dehydroepiandrosterone (DHEA) and its derived sexual hormones. DHEA assumes the prohormone status of a predominant endogenous precursor and a metabolic intermediate in ovarian follicular steroidogenesis. DHEA supplementation has been used to enhance ovarian reserve. Steroids like estradiol and testosterone have long been contemplated to play important roles in regulating meiotic maturation of oocytes in conjunction with gonadotropins. It is known that oocyte priming with estrogen is necessary to develop calcium (Ca²⁺) oscillations during maturation. Accruing evidence from diverse studies suggests that DHEA and its sulfate (dehydroepiandrosterone sulfate, DHEA-S) play significantly vital role not only as intermediates in androgen and estrogen formation, but may also be the probable 'oocyte factor' and behave as endogenous agonists triggering calcium oscillations for oocyte activation. DHEA/DHEA-S have been reported to regulate calcium channels for the passage of Ca²⁺ through the oocyte cytoplasm and for maintaining required threshold of Ca²⁺ oscillations. This role of DHEA/DHEA-S assumes critical significance in assisted reproductive technology and in-vitro fertilization treatment cycles where physical, chemical, and mechanical methods are employed for artificial oocyte activation to enhance fertilization rates. However, since these methods are invasive and may also cause adverse epigenetic modifications; oral or culture-media supplementation with DHEA/DHEA-S provides a noninvasive innate mechanism of in-vitro oocyte activation based on physiological metabolic pathway.

Culture conditions affect Ca2+ release in artificially activated mouse and human oocytes

Inconsistent fertilisation and pregnancy rates have been reported by different laboratories after application of ionomycin as a clinical method of assisted oocyte activation (AOA) to overcome fertilisation failure. Using both mouse and human oocytes, in the present study we investigated the effects of ionomycin and Ca2+ concentrations on the pattern of Ca2+ release and embryonic developmental potential. In the mouse, application of 5 μM ionomycin in potassium simplex optimisation medium (KSOM) or 10 µM ionomycin in Ca2+-free KSOM significantly reduced the Ca2+ flux and resulted in failure of blastocyst formation compared with 10 μM ionomycin in KSOM. Increasing the Ca2+ concentration up to three- or sixfold did not benefit mouse embryonic developmental potential. Similarly, 10 μM ionomycin-induced rise in Ca2+ in human oocytes increased with increasing total calcium concentrations in the commercial medium. Remarkably, we observed significantly reduced mouse embryo development when performing AOA over a period of 10 min in Quinn’s AdvantageTM Fertilisation medium (Cooper Surgical) and IVFTM medium (Vitrolife) compared with Sydney IVF COOK cleavage medium (Cook Ireland), using the same sequential culture system from the post-activation stage to blastocyst formation stage in different AOA groups. In conclusion, concentrations of both ionomycin and Ca2+ in culture media used during AOA can have significant effects on Ca2+ release and further embryonic developmental potential.

Male Pronuclear Formation and Embryo Development Following Intracytoplasmic Injection of Ovine Pretreated Sperm

BACKGROUND

Failure of Male Pronucleus (MPN) formation is a major concern in the success of Intracytoplasmic Sperm Injection (ICSI) in some species. Despite the conducted unsuccessful efforts to improve ICSI efficiency in ovine, the present study was aimed to improve MPN formation and embryo development in ovine ICSI procedure through accompaniment of sperm pretreatment with co-injection of some compounds.

METHODS

In experiment 1, sperm were treated with either 2-mercaptoethanol (2ME), glutathione (GSH), or DTT (dithiothreitol) in combination with Heparin (Hep). Following DNA integrity and fragmentation assessments, the best sperm pretreatment approach in induction of sperm head decondensation was applied for the second and third experiments. In experiment 2, in vitro matured oocytes were subjected to ICSI using pretreated sperm with or without GSH and Sperm Extract (SE) co-injection. In experiment 3, the procedure was followed as experiment 2 with acrosome reacted sperm.

RESULTS

The highest percentages of oocyte activation were observed in Hep+GSH and Hep+2ME groups. The greatest MPN formations were also observed in the same groups when ICSI procedure was accompanied with GSH co-injection. Despite the higher percentage of MPN formation and oocyte activation in Hep+GSH and Hep+2ME groups, none of the employed strategies could increase the cleavage and blastocyst rates compared to the control.

CONCLUSION

In our study condition, despite the lack of significant increase in embryo development in treated groups, the significant increase in MPN formation in Hep+ GSH+co.GSH and Hep+2ME+co.GSH groups indicates the lower chance of parthenote formation that means a higher chance of normal fertilization compared with control.

Phospholipase C zeta and calcium oscillations at fertilisation: The evidence, applications, and further questions

Oocyte activation is a fundamental event at mammalian fertilisation, initiated by a series of characteristic calcium (Ca²⁺) oscillations in mammals. This characteristic pattern of Ca²⁺ release is induced in a species-specific manner by a sperm-specific enzyme termed phospholipase C zeta (PLCζ). Reduction or absence of functional PLCζ within sperm underlies male factor infertility in humans, due to mutational inactivation or abrogation of PLCζ protein expression. Underlying such clinical implications, a significant body of evidence has now been accumulated that has characterised the unique biochemical and biophysical properties of this enzyme, further aiding the unique clinical opportunities presented. Herein, we present and discuss evidence accrued over the past decade and a half that serves to support the identity of PLCζ as the mammalian sperm factor. Furthermore, we also discuss the potential novel avenues that have yet to be examined regarding PLCζ mechanism of action in both the oocyte, and the sperm. Finally, we discuss the advances that have been made regarding the clinical therapeutic and diagnostic applications of PLCζ in potentially treating male infertility as a result of oocyte activation deficiency (OAD), and also possibly more general cases of male subfertility.

Phospholipase C zeta parameters in sperm from polymorphic teratozoospermic men

Teratozoospermia is a disorder associated with high abnormal sperm morphology which affects fertility in males. In recent years, it has been described that biomarker-based sperm quality evaluation can alleviate male infertility treatment. Phospholipase C zeta (PLCζ) is a sperm-specific factor which appears to be a predicting biomarker for fertilization potential of males. Following fertilization, PLCζ enters into oocyte cytoplasm and induces oocyte activation, a fundamental stage in initiation of embryo development. Currently, PLCζ parameters, including localization patterns, the proportion of PLCζ-expressing sperm and the expression level, are not defined in polymorphic teratozoospermic men. This study aimed to evaluate PLCζ parameters in polymorphic teratozoospermic men, and compare these parameters with fertile normozoospermic men. Semen samples from thirteen normozoospermic fertile men and twenty-three polymorphic teratozoospermic men were included in this study and evaluated using western blotting and immunofluorescence analyses. Our data indicated significantly lower expression of PLCζ in polymorphic teratozoospermic men, as compared with control men; however, there was no significant difference in localization patterns and the proportion of PLCζ-expressing sperm between polymorphic teratozoospermic patients and control men. Collectively, findings from the present study demonstrated that polymorphic teratozoospermic men did not show abnormal localization patterns or the absence of PLCζ, as compared to the control men; nonetheless, lower expression of PLCζ, considering its role in oocyte activation, might be one of the possible causes of infertility in these patients.

Strategies to improve fertilisation rates with assisted conception: a systematic review

Successful fertilisation is one of the key steps determining success of assisted conception. Various factors including sperm or oocyte pathology and environmental factors have a significant impact on fertilisation rates. This systematic review is aimed to evaluate the existing evidence about factors affecting fertilisation and strategies to improve fertilisation rates. A literature search was performed using Ovid MEDLINE ® (Jan 1950-April 2016), EMBASE (Jan 1950-April 2016), Ovid OLDMEDLINE ®, Pre-MEDLINE (Jan 1950-April 2016) and the Cochrane Library. Relevant key words were used to combine sets of results and a total 243 papers were screened. Only qualitative analysis was performed, as there was major heterogeneity in study design and methodology for quantitative synthesis. Factors affecting fertilisation were divided into sperm- and oocyte-related factors. The methods to improve fertilisation rates were grouped together based on the approach used to improve fertilisation rates. Optimising laboratory condition and procedural effects in techniques is associated with improved fertilisation rates. Various techniques are described to improve fertilisation rates including assisted oocyte activation, physiological intracytoplasmic sperm injection (PICSI) and intracytoplasmic morphologically selected sperm injection (IMSI). This review highlights the promising strategies under research to enhance fertilisation rates. Adequately powered multicentre randomised trials are required to evaluate these techniques before considering clinical application.

Analysis of Pelagia noctiluca proteome Reveals a Red Fluorescent Protein, a Zinc Metalloproteinase and a Peroxiredoxin

Pelagia noctiluca is the most venomous jellyfish in the Mediterranean Sea where it forms dense blooms. Although there is several published research on this species, until now none of the works has been focused on a complete protein profile of the all body constituents of this organism. Here, we have performed a detailed proteomics characterization of the major protein components expressed by P. noctiluca. With that aim, we have considered the study of jellyfish proteins involved in defense, body constituents and metabolism, and furthered explore the significance and potential application of such bioactive molecules. P. noctiluca body proteins were separated by1D SDS-PAGE and 2DE followed by characterization by nanoLC-MS/MS and MALDI-TOF/TOF techniques. Altogether, both methods revealed 68 different proteins, including a Zinc Metalloproteinase, a Red Fluorescent Protein (RFP) and a Peroxiredoxin. These three proteins were identified for the first time in P. noctiluca. Zinc Metalloproteinase was previously reported in the venom of other jellyfish species. Besides the proteins described above, the other 65 proteins found in P. noctiluca body content were identified and associated with its clinical significance. Among all the proteins identified in this work we highlight: Zinc metalloproteinase, which has a ShK toxin domain and therefore should be implicated in the sting toxicity of P. noctiluca.; the RFP which are a very important family of proteins due to its possible application as molecular markers; and last but not least the discovery of a Peroxiredoxin in this organism makes it a new natural resource of antioxidant and anti-UV radiation agents.

Relationship between phospholipase C-zeta, semen parameters, and chromatin status

The need for additional tests to complement basic sperm analysis in clinics is well appreciated. In this regard, a number of tests such as sperm DNA integrity test as a tool in diagnosis and treatment of infertility are suggested. But recent studies have focused on main sperm factors involved in oocyte activation such as phospholipase C-zeta (PLCζ) that initiate intracellular Ca²⁺ signaling and embryogenesis. Therefore, this study aimed to investigate the relationship between PLCζ, basic semen parameters, sperm DNA fragmentation (SDF), and protamine deficiency in men with normal (n=32) and abnormal (n=23) semen parameters. Unlike SDF and protamine deficiency, as negative factors related to fertility, the mean value of PLCζ as positive factor related to infertility was significantly lower in men with abnormal semen parameters compared to men with normal semen parameters. Significant correlations were also observed between sperm concentration, motility, and abnormal morphology with the percentage of PLCζ positive spermatozoa. In addition, logistic regression analysis revealed that sperm morphology is more predictive than sperm motility and concentration for PLCζ presence. In addition, a statistically significant negative relationship was observed between the percentage of PLCζ positive spermatozoa and SDF. These findings suggested during ICSI, selection of sperm based on morphology has a profound effect on its ability to induce oocyte activation based on the likelihood of PLCζ expression. Therefore, assessment of PLCζ as an index for fertilization potential of a semen sample in men with severe teratozoospermia may define individuals who are candidates for artificial oocyte activation (AOA) and may avoid failed fertilization post ICSI.

The effect of intrauterine human chorionic gonadotropin injection before embryo transfer on the implantation and pregnancy rate in infertile patients: A randomized clinical trial

BACKGROUND

Implantation is one of the essential steps for the success of assisted reproductive techniques (ART). Their success depends on three main factors: embryo quality, endometrial receptivity (ER), and synchrony between embryo and endometrium. There are various factors that regulate the complex process of implantation. In this regard, one may refer to human chorionic gonadotropin (hCG) as the most important factor.

OBJECTIVE

This study aims to investigate the effect of intrauterine hCG injection before embryo transfer (ET) on pregnancy outcome in infertile couples.

MATERIALS AND METHODS

A total of 159 patients undergone In vitro Fertilization/ Intracytoplasmic Sperm Injection (IVF/ICSI) with an antagonist protocol were evaluated. Patients were divided into three groups (n=53). Group 1 received 500 IU of hCG, group 2 received 1000 IU of hCG intrauterine injection before ET, and the control group underwent ET without hCG preceding intrauterine injection.

RESULTS

There was no significant difference among the groups. The implantation rates were 18.86%, 13.52%, and 14.37%, chemical pregnancy rates were 34%, 32.1%, and 35.3%, and clinical pregnancy rates were 34%, 32.1%, and 31.4% respectively.

CONCLUSION

The pregnancy outcome in IVF/ICSI /ET cycles cannot be improved through hCG intrauterine injections before ET.

Gamete activation: basic knowledge and clinical applications

Background

The first clues to the process of gamete activation date back to nearly 60 years ago. The mutual activation of gametes is a crucial event during fertilization. In the testis and ovaries, spermatozoa and oocytes are in a state of meiotic and metabolic quiescence and require reciprocal signals in order to undergo functional changes that lead to competence for fertilization. First, the oocyte activates sperm by triggering motility, chemoattraction, binding and the acrosome reaction, culminating with the fusion of the two plasma membranes. At the end of this cascade of events, collectively known as sperm capacitation, sperm-induced oocyte activation occurs, generating electrical, morphological and metabolic modifications in the oocyte.

Objective and rationale

The aim of this review is to provide the current state of knowledge regarding the entire process of gamete activation in selected specific animal models that have contributed to our understanding of fertilization in mammals, including humans. Here we describe in detail the reciprocal induction of the two activation processes, the molecules involved and the mechanisms of cell interaction and signal transduction that ultimately result in successful embryo development and creation of a new individual.

Search methods

We carried out a literature survey with no restrictions on publication date (from the early 1950s to March 2016) using PubMed/Medline, Google Scholar and Web of Knowledge by utilizing common keywords applied in the field of fertilization and embryo development. We also screened the complete list of references published in the most recent research articles and relevant reviews published in English (both animal and human studies) on the topics investigated.

Outcomes

Literature on the principal animal models demonstrates that gamete activation is a pre-requisite for successful fertilization, and is a process common to all species studied to date. We provide a detailed description of the dramatic changes in gamete morphology and behavior, the regulatory molecules triggering gamete activation and the intracellular ions and second messengers involved in active metabolic pathways in different species. Recent scientific advances suggest that artificial gamete activation may represent a novel technique to improve human IVF outcomes, but this approach requires caution.

Wider implications

Although controversial, manipulation of gamete activation represents a promising tool for ameliorating the fertilization rate in assisted reproductive technologies. A better knowledge of mechanisms that transform the quiescent oocyte into a pluripotent cell may also provide new insights for the clinical use of stem cells.

Molecular triggers of egg activation at fertilization in mammals

In mammals, the sperm activates the development of the egg by triggering a series of oscillations in the cytosolic-free Ca(2+) concentration (Ca(2+) i). The sperm triggers these cytosolic Ca(2+i) oscillations after sperm-egg membrane fusion, as well as after intracytoplasmic sperm injection (ICSI). These Ca(2+) i oscillations are triggered by a protein located inside the sperm. The identity of the sperm protein has been debated over many years, but all the repeatable data now suggest that it is phospholipase Czeta (PLCζ). The main downstream target of Ca(2+) i oscillations is calmodulin-dependent protein kinase II (CAMKII (CAMK2A)), which phosphorylates EMI2 and WEE1B to inactivate the M-phase promoting factor protein kinase activity (MPF) and this ultimately triggers meiotic resumption. A later decline in the activity of mitogen-activated protein kinase (MAPK) then leads to the completion of activation which is marked by the formation of pronuclei and entry into interphase of the first cell cycle. The early cytosolic Ca(2+) increases also trigger exocytosis via a mechanism that does not involve CAMKII. We discuss some recent developments in our understanding of these triggers for egg activation within the framework of cytosolic Ca(2+) signaling.

Calcium signaling and cell proliferation

Cell proliferation is orchestrated through diverse proteins related to calcium (Ca(2+)) signaling inside the cell. Cellular Ca(2+) influx that occurs first by various mechanisms at the plasma membrane, is then followed by absorption of Ca(2+) ions by mitochondria and endoplasmic reticulum, and, finally, there is a connection of calcium stores to the nucleus. Experimental evidence indicates that the fluctuation of Ca(2+) from the endoplasmic reticulum provides a pivotal and physiological role for cell proliferation. Ca(2+) depletion in the endoplasmatic reticulum triggers Ca(2+) influx across the plasma membrane in an phenomenon called store-operated calcium entries (SOCEs). SOCE is activated through a complex interplay between a Ca(2+) sensor, denominated STIM, localized in the endoplasmic reticulum and a Ca(2+) channel at the cell membrane, denominated Orai. The interplay between STIM and Orai proteins with cell membrane receptors and their role in cell proliferation is discussed in this review.

Phospholipase C-zeta deficiency as a cause for repetitive oocyte fertilization failure during ovarian stimulation for in vitro fertilization with ICSI: a case report

PURPOSE

The purpose of this study is to describe impaired oocyte fertilization from phospholipase C-zeta (PLC-ζ) deficiency in normal-appearing sperm that was successfully treated using calcium (Ca(2+)) ionophore with intracytoplasmic sperm injection (ICSI) of oocytes matured in vitro.

METHODS

An infertile couple undergoing in vitro fertilization (IVF) experienced failed oocyte fertilization following ICSI with normal-appearing sperm. A semen sample collected from the patient was used to assess the expression of sperm PLC- ζ protein by Western blot analysis and immunofluorescence and PLC-ζ bioactivity by an in vitro model of Ca(2+) release. A second IVF cycle was performed using Ca(2+) ionophore with ICSI to enhance Ca(2+)-induced oocyte activation of oocytes matured in vitro.

RESULTS

Sperm PLC-ζ protein deficiency was demonstrated by Western blot analysis and immunofluorescence and confirmed by reduced PLC-ζ bioactivity using an in vitro model of Ca(2+) release. Nevertheless, with this sperm and supplementation of Ca(2+) ionophore following ICSI, fertilization of four of six oocytes matured in vitro was obtained. In addition, four embryos underwent cleavage and two of them reached the blastocyst stage. Transfer of these blastocysts into the uterus led to a single pregnancy and live birth.

CONCLUSIONS

Deficiency of PLC-ζ in normal-appearing human sperm is associated with impaired Ca(2+)-dependent oocyte activation during ICSI. Under this condition, use of Ca(2+) ionophore following ICSI of oocytes matured in vitro improves embryo developmental competence, possibly through the activation of Ca(2+)-dependent mechanisms governing fertilization and preimplantation embryogenesis.

Total levels, localization patterns, and proportions of sperm exhibiting phospholipase C zeta are significantly correlated with fertilization rates after intracytoplasmic sperm injection

OBJECTIVE

To study the relationship of total levels, localization patterns, and proportions of sperm exhibiting phospholipase C zeta, with fertilization rates after in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).

DESIGN

Laboratory study; controls vs. patients after IVF (n = 27) or ICSI (n = 17) treatment.

SETTING

Fertility center.

PATIENT(S)

A total of 44 semen samples, subjected to either IVF or ICSI treatment. Oocyte collection, ICSI or IVF, determination of sperm concentration and motility, and immunocytochemical analyses of phospholipase C zeta (PLCζ).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Percentages of sperm exhibiting PLCζ.

RESULT(S)

Significant positive correlation between ICSI fertilization rates and total levels, localization patterns, and the proportion (percentage) of sperm exhibiting PLCζ. Total levels, localization patterns, and the proportion of sperm exhibiting PLCζ are correlated with fertilization rates for ICSI, but not for IVF.

CONCLUSION(S)

Evaluating total levels, localization patterns, and proportions of PLCζ may represent a useful diagnostic tool for clinical purposes in men for whom IVF is not advised or has previously failed. This clinical study further supports the fundamental role of PLCζ in the oocyte activation process.

Novel signalling mechanism and clinical applications of sperm-specific PLCζ

Egg activation is the first step of embryonic development and in mammals is triggered by a series of cytoplasmic calcium (Ca2+) oscillations. Sperm–egg fusion initiates these Ca2+ oscillations by introducing a sperm-specific protein factor into the egg cytoplasm. Substantial evidence indicates that this protein is a sperm-specific phospholipase C (PLC), termed PLC-zeta (PLCζ). PLCζ stimulates cytoplasmic Ca2+ oscillations matching those at fertilization triggering early embryonic development in several mammalian species. Structurally, PLCζ is comprised of four EF-hands, a C2 domain, and X and Y catalytic domains. PLCζ is an unusual PLC since it lacks a pleckstrin homology (PH) domain. It is also distinctive in that its X–Y linker is not involved in auto-inhibition of catalytic activity, but instead binds to phosphatidylinositol 4,5-bisphosphate (PIP2). Moreover, relative to other PLC isoforms, PLCζ possesses unique potency in stimulating Ca2+ oscillations in eggs, although it does not appear to bind to plasma membrane PIP2. In contrast, PLCζ appears to interact with intracellular vesicles in eggs that contain PIP2. I discuss the recent advances in our knowledge of the intriguing biochemical and physiological properties of sperm PLCζ and postulate potential roles for PLCζ in terms of clinical diagnosis and therapy for certain forms of male infertility.

Inferring the choreography of parental genomes during fertilization from ultralarge-scale whole-transcriptome analysis

The mechanisms underlying parental genome coordination upon mammalian fertilization remain elusive due to difficulties in preparing large numbers of high-quality preimplantation cells. Here, Park et al. collect an unprecedented number of mouse oocytes and establish detailed transcriptional profiles for four early embryonic stages and parthenogenetic development. Bioinformatic analysis identifies a distinctive gene regulatory network activated in embryos after fertilization compared with parthenotes. This large-scale profile of early mouse embryos yields a valuable resource for developmental biology and stem cell research.

Fertilization precisely choreographs parental genomes by using gamete-derived cellular factors and activating genome regulatory programs. However, the mechanism remains elusive owing to the technical difficulties of preparing large numbers of high-quality preimplantation cells. Here, we collected >14 × 10⁴ high-quality mouse metaphase II oocytes and used these to establish detailed transcriptional profiles for four early embryo stages and parthenogenetic development. By combining these profiles with other public resources, we found evidence that gene silencing appeared to be mediated in part by noncoding RNAs and that this was a prerequisite for post-fertilization development. Notably, we identified 817 genes that were differentially expressed in embryos after fertilization compared with parthenotes. The regulation of these genes was distinctly different from those expressed in parthenotes, suggesting functional specialization of particular transcription factors prior to first cell cleavage. We identified five transcription factors that were potentially necessary for developmental progression: Foxd1, Nkx2-5, Sox18, Myod1, and Runx1. Our very large-scale whole-transcriptome profile of early mouse embryos yielded a novel and valuable resource for studies in developmental biology and stem cell research. The database is available at http://dbtmee.hgc.jp.

Assisted oocyte activation following ICSI fertilization failure

The capacity of intracytoplasmic sperm injection (ICSI) to permit almost any type of spermatozoa to fertilize oocytes has made it the most successful treatment for male factor infertility. Despite its high success rates, fertilization failure following ICSI still occurs in 1-3% of couples. Assisted oocyte activation (AOA) is being increasingly applied in human assisted reproduction to restore fertilization and pregnancy rates in couples with a history of ICSI fertilization failure. However, controversy still exists mainly because the artificial activating agents do not mimic precisely the initial physiological processes of mammalian oocyte activation, which has led to safety concerns. This review addresses the mechanism of human oocyte activation and the relatively rare phenomenon of fertilization failure after ICSI. Next, it describes the current diagnostic approaches and focuses on the application, efficiency and safety of AOA in human assisted reproduction.

Effect of oocyte activation with calcium ionophore on ICSI outcomes in teratospermia: A randomized clinical trial

BACKGROUND

Chemical activation is the most frequently used method for artificial oocyte activation (AOA), results in high fertilization rate.

OBJECTIVE

This prospective, randomized, unblinded, clinical study aimed to evaluate the efficiency of oocyte activation with calcium ionophore on fertilization and pregnancy rate after intracytoplasmic sperm injection (ICSI) in infertile men suffer from teratoospermia.

MATERIALS AND METHODS

Thirty eight women with teratoospermic partner underwent ICSI with antagonist protocol. A total of 313 metaphase II (MII) oocytes were randomly divided into two groups: In the oocytes of the control group (n=145), routine ICSI was applied. Oocytes in the AOA group (n=168) immediately after ICSI, were entered in culture medium supplemented with 5 µΜ calcium ionophore (A23187) for 5 minutes and then washed at least five times with MOPS solution. In both groups, the fertilization was evaluated 16-18 hours after ICSI.

RESULTS

The number of fertilized oocytes and embryos obtained were significantly different between two groups (p=0.04). There was no significant difference between the two studied groups regarding the fertilization and cleavage rate (95.33% vs. 84.4%, p=0.11; and 89.56% vs. 87.74%, p=0.76, respectively). Implantation rate was higher in AOA group than in control group, but the difference was not significant (17.64% vs. 7.4%, p=0.14). No significant differences were observed in chemical and clinical pregnancy rate between groups (47.1% vs. 16.7%, p=0.07; and 41.2% vs. 16.7%; p=0.14, respectively).

CONCLUSION

We didn't find significant difference in the implantation, fertilization, cleavage and pregnancy rates between the two groups but could significantly increase the number of fertilized oocytes and embryos obtained. Finally oocyte activation with calcium ionophore may improve ICSI outcomes in infertile men suffer from teratoospermia. Further study with more cases can provide greater value.

Sperm PLCζ: from structure to Ca2+ oscillations, egg activation and therapeutic potential

Significant evidence now supports the assertion that cytosolic calcium oscillations during fertilization in mammalian eggs are mediated by a testis-specific phospholipase C (PLC), termed PLC-zeta (PLCζ) that is released into the egg following gamete fusion. Herein, we describe the current paradigm of PLCζ in this fundamental biological process, summarizing recent important advances in our knowledge of the biochemical and physiological properties of this enzyme. We describe the data suggesting that PLCζ has distinct features amongst PLCs enabling the hydrolysis of its substrate, phosphatidylinositol 4,5-bisphosphate (PIP2) at low Ca(2+) levels. PLCζ appears to be unique in its ability to target PIP2 that is present on intracellular vesicles. We also discuss evidence that PLCζ may be a significant factor in human fertility with potential therapeutic capacity.

What should it take to describe a substance or product as 'sperm-safe'

BACKGROUND

Male reproductive potential continues to be adversely affected by many environmental, industrial and pharmaceutical toxins. Pre-emptive testing for reproductive toxicological (side-)effects remains limited, or even non-existent. Many products that come into direct contact with spermatozoa lack adequate testing for the absence of adverse effects, and numerous products that are intended for exposure to spermatozoa have only a general assumption of safety based on the absence of evidence of actual harm. Such assumptions can have unfortunate adverse impacts on at-risk individuals (e.g. couples who are trying to conceive), illustrating a clear need for appropriate up-front testing to establish actual 'sperm safety'.

METHODS

After compiling a list of general areas within the review's scope, relevant literature and other information was obtained from the authors' personal professional libraries and archives, and supplemented as necessary using PubMed and Google searches. Review by co-authors identified and eliminated errors of omission or bias.

RESULTS

This review provides an overview of the broad range of substances, materials and products that can affect male fertility, especially through sperm fertilizing ability, along with a discussion of practical methods and bioassays for their evaluation. It is concluded that products can only be claimed to be 'sperm-safe' after performing objective, properly designed experimental studies; extrapolation from supposed predicate products or other assumptions cannot be trusted.

CONCLUSIONS

We call for adopting the precautionary principle, especially when exposure to a product might affect not only a couple's fertility potential but also the health of resulting offspring and perhaps future generations.

Phospholipase C zeta (PLCζ): oocyte activation and clinical links to male factor infertility

Mounting scientific and clinical evidence supports the key role played by phospholipase C zeta (PLCζ), a sperm-specific protein, in the activation of oocytes following fertilisation. Lacking a pleckstrin homology domain, PLCζ remains the smallest known mammalian PLC and was first identified in 2002. Since then, PLCζ has been the target for a multitude of studies in both mammalian and non-mammalian species focused upon its fundamental biochemical activity and crucial role as the mediator of oocyte activation. The earliest event subsequent to gamete fusion is the onset of a series of intracellular calcium oscillations within the oocyte, which are known to modulate cortical granule exocytosis, release meiotic arrest, regulate gene expression, recruit maternal mRNA, and initiate embryogenesis. Collectively these processes are known as 'oocyte activation' and together, represent a fundamental mechanism for early embryonic development. Evidence suggests that these processes are initiated and controlled by calcium release from ooplasmic sources in response to PLCζ activity via the inositol-1,4,5-triphosphate (IP3) pathway. While the biochemical action of PLCζ has been extensively studied, especially in relation to the EF-hands, X-Y linker, and C2 domain, all of which play critical roles for in vivo activity, there are still key gaps in our knowledge, particularly in terms of regulation and interaction with other proteins within the oocyte. Moreover, increasing clinical evidence has revealed a strong correlation between certain types of male infertility and the aberrant expression, localisation, structure and function of PLCζ in human sperm, particularly in cases of recurrent intracytoplasmic sperm injection (ICSI) failure, globozoospermia, and oocyte activation deficiency (OAD). In addition, two heterozygous substitution mutations have been identified in the coding sequence of PLCζ in one particular patient causing disruption to the catalytic X and Y domains and resulting in infertility. Although, such cases can be treated via the use of artificial oocyte activators (AOAs) such as calcium ionophores, significant concern remains over the use of such chemical agents, largely due to the fact that calcium release manifests as a single transient, rather than a series of oscillations as observed during normal fertilisation. Current interest in PLCζ is thus to develop a series of prognostic, diagnostic and therapeutic approaches which could first identify male patients that are deficient in PLCζ and then rescue oocyte activation ability via assisted reproductive technology (ART) and a pure, functionally-active, recombinant human PLCζ protein. While significant progress has been made in such areas over recent years, there is a clear need to translate scientific findings to clinical settings in order to maximise successful outcome for patients.