Disordered zona pellucida-induced acrosome reaction and failure of in vitro fertilization in patients with unexplained infertility

Spermatozoal acrosome dysfunction and its role in stallion subfertility

Cases of stallion subfertility due to acrosome dysfunction have been recognized since the 1990s. While some of these were observed in stallions with reduced sperm motility and morphology, a more severe form has been reported in stallions with normal-to-excellent sperm quality parameters, which is also uniquely observed in individuals of the Thoroughbred registry. These stallions carry a susceptibility genotype (A/A-A/A in the gene FKBP6, exon 5) for Impaired Acrosomal Exocytosis (IAE). Current clinical observations from our group have identified a few highly subfertile stallions from other breed registries that also display a lower ability to undergo acrosomal exocytosis (AE) but do not carry the A/A-A/A genotype. This document provides a concise review of the role of acrosome dysfunction as a cause of stallion subfertility, including methods to estimate acrosome function and clinical descriptions of IAE in TB and non-TB stallions.

Live motile sperm sorting device for enhanced sperm-fertilization competency: comparative analysis with density-gradient centrifugation and microfluidic sperm sorting

PURPOSE

A live motile sperm sorting device (LensHooke® CA0) developed to prevent the deleterious effects of centrifugation was evaluated comparatively with conventional density-gradient centrifugation (DGC) and microfluidic-based device (Zymot) in sperm selection.

METHODS

Semen samples from 239 men were collected. CA0 under different incubation intervals (5, 10, 30, and 60 min) and temperatures (20, 25, and 37℃) was conducted. The sperm quality in CA0-, DGC-, and Zymot-processed samples was then comparatively evaluated. Semen parameters included concentration, motility, morphology, motion kinematics, DNA fragmentation index (DFI), and the rate of acrosome-reacted sperm (AR).

RESULTS

Total motility and motile sperm concentration increased in a time- and temperature-dependent manner and the total motility peaked for 30 min at 37℃. In paired analysis, CA0 showed significantly higher total motility (94.0%), progressive motility (90.8%), rapid progressive motility (83.6%), normal morphology (10.3%), and lower DFI (2.4%) and AR (4.7%) than the other two methods in normozoospermic samples (all p < 0.05). For non-normozoospermic samples, CA0 had significantly better results than the other two methods (total motility 89.2%, progressive motility 80.4%, rapid progressive motility 74.2%, normal morphology 8.5%, DFI 4.0%, and AR 4.0%; all p < 0.05).

CONCLUSION

CA0 yielded spermatozoa with enhanced sperm fertilization potentials; DFI was minimized in samples processed by CA0. CA0 was effective for both normal and abnormal semen samples due to its consistent selection efficiency.

The stallion sperm acrosome: Considerations from a research and clinical perspective

During the fertilization process, the interaction between the sperm and the oocyte is mediated by a process known as acrosomal exocytosis (AE). Although the role of the sperm acrosome on fertilization has been studied extensively over the last 70 years, little is known about the molecular mechanisms that govern acrosomal function, particularly in species other than mice or humans. Even though subfertility due to acrosomal dysfunction is less common in large animals than in humans, the evaluation of sperm acrosomal function should be considered not only as a complementary but a routine test when individuals are selected for breeding potential. This certainly holds true for stallions, which might display lower levels of fertility in the face of "acceptable" sperm quality parameters determined by conventional sperm assays. Nowadays, the use of high throughput technologies such as flow cytometry or mass spectrometry-based proteomic analysis is commonplace in the research arena. Such techniques can also be implemented in clinical scenarios of males with "idiopathic" subfertility. The current review focuses on the sperm acrosome, with particular emphasis on the stallion. We aim to describe the physiological events that lead to the acrosome formation within the testis, the role of very specific acrosomal proteins during AE, the methods to study the occurrence of AE under in vitro conditions, and the potential use of molecular biology techniques to discover new markers of acrosomal function and subfertility associated with acrosomal dysfunction in stallions.

Sperm aminopeptidase N identifies the potential for high-quality blastocysts and viable embryos in oocyte-donation cycles

STUDY QUESTION

Is there a relationship between human sperm aminopeptidase N (APN) and embryo development in humans?

SUMMARY ANSWER

Human sperm APN could possibly become a new molecular biomarker for identifying the potential for high-quality and usable embryos.

WHAT IS KNOWN ALREADY

The diagnosis of male fertility is one of the major concerns of reproductive medicine. Approximately 30-40% of men with otherwise normal fertility parameters are still unable to achieve pregnancy. The predictive clinical value of semen analysis to identify fertile or infertile males is limited; therefore, new diagnostic methodologies for sperm are urgently required. Sperm APN may be a relevant molecular marker due to its high concentration in sperm cells and its important roles in sperm physiology, such as its functions in motility, acrosome reaction and embryo development.

STUDY DESIGN, SIZE, DURATION

This study included 81 couples who underwent oocyte-donation cycles at Clínica IVI Bilbao (Spain), yielding 611 embryos, between September 2014 and July 2015.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was conducted in an assisted reproduction unit and an academic research laboratory. All the semen samples were examined and classified following World Health Organization guidelines. Spermatozoa were isolated from semen using the discontinuous colloidal silica gradient (45-90%) technique. Embryo quality and development were determined according to the Spanish Association of Reproduction Biology Studies (ASEBIR) criteria. Human sperm APN levels were analyzed by quantitative and semiquantitative flow cytometry.

MAIN RESULTS AND THE ROLE OF CHANCE

The most well-developed and usable blastocysts were associated with low sperm APN levels. Semen samples that had lower APN levels generated more expanded, hatched and usable blastocysts and fewer early, arrested and non-usable blastocysts. The cumulative probability of having well-developed blastocysts increased by 1.38-fold at Day 5 and 1.90-fold at Day 6 of embryo development, and the likelihood of having usable embryos increased by 1.48-fold, when semen samples with low APN levels were used during the ICSI technique.

LIMITATIONS, REASONS FOR CAUTION

The data were obtained from a single fertility clinic. A multicentre study will be required to confirm the results.

WIDER IMPLICATIONS OF THE FINDINGS

Human sperm APN has the potential to become a new molecular biomarker to help identify the potential for high-quality embryos and diagnose male infertility, especially when seminal parameters are close to the threshold values. It could be a crucial tool for couples for whom the number of usable blastocysts is critical for ART success.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Basque Government (GIC15/165) and the University of the Basque Country (UPV/EHU) (EHUA14/17). The authors declare that they have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Development a nomogram to predict fertilisation rate of infertile males with borderline semen by using semen parameters combined with AMH and INHB

The sperm quality of some males is in a critical state, making it hard for clinicians to choose the suitable fertilisation methods. This study aimed to develop an intelligent nomogram for predicting fertilisation rate of infertile males with borderline semen. 160 males underwent in vitro fertilisation (IVF), 58 of whom received rescue ICSI (R‐ICSI) due to fertilisation failure (fertilisation rate of IVF ≤30%). A least absolute shrinkage and selection operator (LASSO) regression analysis identified sperm concentration, progressively motile spermatozoa (PMS), seminal plasma anti‐Müllerian hormone (spAMH), seminal plasma inhibin (spINHB), serum AMH (serAMH) and serum INHB (serINHB) as significant predictors. The nomogram was plotted by multivariable logistic regression. This nomogram‐illustrated model showed good discrimination, calibration and clinical value. The area under the receiver operating characteristic curve (AUC) of the nomogram was 0.762 (p < .001). Calibration curve and Hosmer–Lemeshow test (p = .5261) showed good consistency between the predictions of the nomogram and the actual observations, and decision curve analysis showed that the nomogram was clinically useful. This nomogram may be useful in predicting fertilisation rate, mainly focused on new biomarkers, INHB and AMH. It could assist clinicians and laboratory technicians select appropriate fertilisation methods (IVF or ICSI) for male patients with borderline semen.

The Calcium-Sensing Receptor Is Essential for Calcium and Bicarbonate Sensitivity in Human Spermatozoa

CONTEXT

The calcium-sensing receptor (CaSR) is essential to maintain a stable calcium concentration in serum. Spermatozoa are exposed to immense changes in concentrations of CaSR ligands such as calcium, magnesium, and spermine during epididymal maturation, in the ejaculate, and in the female reproductive environment. However, the role of CaSR in human spermatozoa is unknown.

OBJECTIVE

This work aimed to investigate the role of CaSR in human spermatozoa.

METHODS

We identified CaSR in human spermatozoa and characterized the response to CaSR agonists on intracellular calcium, acrosome reaction, and 3',5'-cyclic adenosine 5'-monophosphate (cAMP) in spermatozoa from men with either loss-of-function or gain-of-function mutations in CASR and healthy donors.

RESULTS

CaSR is expressed in human spermatozoa and is essential for sensing extracellular free ionized calcium (Ca2+) and Mg2+. Activators of CaSR augmented the effect of sperm-activating signals such as the response to HCO3- and the acrosome reaction, whereas spermatozoa from men with a loss-of-function mutation in CASR had a diminished response to HCO3-, lower progesterone-mediated calcium influx, and were less likely to undergo the acrosome reaction in response to progesterone or Ca2+. CaSR activation increased cAMP through soluble adenylyl cyclase (sAC) activity and increased calcium influx through CatSper. Moreover, external Ca2+ or Mg2+ was indispensable for HCO3- activation of sAC. Two male patients with a CASR loss-of-function mutation in exon 3 presented with normal sperm counts and motility, whereas a patient with a loss-of-function mutation in exon 7 had low sperm count, motility, and morphology.

CONCLUSION

CaSR is important for the sensing of Ca2+, Mg2+, and HCO3- in spermatozoa, and loss-of-function may impair male sperm function.

(Pro)renin Receptor Is Present in Human Sperm and It Adversely Affects Sperm Fertility Ability

Sperm fertility ability may be modulated by different molecular systems, such as the renin-angiotensin system (RAS). Although renin is one of its most relevant peptides, the presence and role of the (pro)renin receptor (PRR) is completely unknown. We have proved for the first time the existence of PRR and its transcript in human sperm by western blot and RT-PCR. Immunofluorescence studies showed that this receptor is mainly located in the apical region over the acrosome and in the postacrosomal region of the sperm head and along the sperm tail. In addition, this prospective cohort study also proves that semen samples with higher percentages of PRR-positive spermatozoa are associated with poor sperm motility, worse blastocyst development and no-viable blastocysts. Our results provide insight into how PRR play a negative role in sperm physiology that it may condition human embryo quality and development. An in-depth understanding of the role of PRR in sperm fertility can help elucidate its role in male infertility, as well as establish biomarkers for the diagnosis or selection of sperm to use during assisted reproductive techniques.

ALWAYS ICSI? A SWOT analysis

PURPOSE

Intracytroplasmatic sperm injection (ICSI) is a common procedure used to improve reproductive results, even among couples without male factor infertility. However, the evidence available is still uncertain on the possible advantages and deficiencies that this procedure may have in patients with no formal indication for ICSI.

METHODS

A SWOT (strengths, weaknesses, opportunities, threats) analysis examines the possible advantages and deficiencies of performing ICSI in these patients with no formal indication.

RESULTS

The evidence suggests that ICSI is not justified for non-male factor infertile couples requiring in vitro conception. One of the major strengths associated to the procedure is the virtual elimination of cases further complicated by total fertilization failure and a combination between IVF and ICSI on sibling oocytes has been advised in the literature. Greater technical difficulties, higher costs and performing an unnecessary invasive technique in some cases represent some of the weaknesses of the procedure, and questions regarding safety issues should not be ruled out.

CONCLUSION

Despite the widespread use of ICSI in patients without a formal diagnosis of male factor infertility, evidence demonstrating its effectiveness in this population is still lacking. Additional large and well-designed randomized controlled trials are needed to clarify definitive indications for ICSI in non-male factor infertility.

In vitro Induction and Detection of Acrosomal Exocytosis in Human Spermatozoa

The acrosome reaction is a highly regulated exocytotic event that primes spermatozoa for successful fertilization. Upon induction, acrosomal exocytosis proceeds via a wave of vesiculation that radiates across the sperm head, destabilizing the acrosomal vesicle and resulting in the release of the acrosomal contents. Having shed their acrosome, spermatozoa are then capable of penetrating the outer vestments of the oocyte and initiating fertilization. Accordingly, the failure of spermatozoa to complete an acrosome reaction represents a relatively common etiology in male infertility patients, and the ability to induce acrosomal exocytosis has found clinical utility in the evaluation of sperm fertilizing capacity. Here, we firstly describe protocols for driving the capacitation of human spermatozoa in vitro using chemically defined media in order to prime the cells for completion of acrosomal exocytosis. We then describe methodology routinely used for the induction of acrosomal exocytosis incorporating either a physiological agonist (i.e., the steroidal hormone, progesterone) or pharmacological reagent (i.e., the divalent cation ionophore, A23187). Finally, we describe the application of histochemical and immunofluorescence techniques that can be applied to study the completion of the acrosome reaction. Such protocols have important diagnostic utility for sperm function testing in both clinical and andrological research laboratories.

LYPD4, mouse homolog of a human acrosome protein, is essential for sperm fertilizing ability and male fertility†

Fertilization is one of the fundamental biological processes, but so far, we still do not have a full understanding of the underlying molecular mechanism. We have identified a human acrosome protein, LY6/PLAUR domain containing 4 (LYPD4), expressed specifically in human testes and sperm, and conserved within mammals. Mouse Lypd4, also specific to the testis and sperm, is essential for male fertility. LYPD4 protein first appeared in round spermatids during acrosome biogenesis and became part of acrosomes during spermatogenesis and in mature sperm. Lypd4 knockout mice are infertile with normal sperm number and motility. Mutant sperm, however, failed to reach oviduct during sperm migration inside the female reproductive tract, leading to fertilization failure and infertility. In addition, Lypd4 mutant sperms were unable to fertilize denuded egg via IVF (in vitro fertilization) but could fertilize eggs within intact Cumulus-Oocyte Complex, supporting an additional role in sperm-zona interaction. Out of more than five thousand spermatozoa proteins identified by mass spectrometry analysis, only a small subset of proteins (26 proteins) was changed in the absence of LYPD4, revealing a whole proteome picture of mutant sperm defective in sperm migration and sperm-zona binding. ADAM3, a key component of fertilization complex, as well as other sperm ADAM proteins are significantly reduced. We hence propose that LYPD4 plays an essential role in mammalian fertilization, and further investigation of its function and its interaction with other sperm membrane complexes may yield insights into human fertilization and novel strategy to improve IVF success.

Characterization of seminal plasma proteomic alterations associated with the IVF and rescue-ICSI pregnancy in assisted reproduction

BACKGROUND

Seminal plasma is a promising diagnostic fluid for male infertility. In assisted reproduction, the seminal plasma-based characteristics of normozoospermic men achieving successful clinical pregnancy through rescue intracytoplasmic sperm injection after in vitro fertilization failure remain unclear.

OBJECTIVE

To identify potential seminal plasma proteins to contribute to a new understanding of unexplained male factor infertility.

MATERIALS AND METHODS

An approach with isobaric tags for relative and absolute quantification labeling coupled with liquid chromatography matrix-assisted laser desorption ionization mass spectrometry was applied to investigate differentially expressed proteins in the seminal plasma of a rescue intracytoplasmic sperm injection pregnancy group versus an in vitro fertilization pregnancy group of normozoospermic men.

RESULT(S)

The present work revealed seventy-three differentially expressed seminal plasma proteins between the in vitro fertilization and rescue intracytoplasmic sperm injection groups. Forty-five proteins were upregulated, and 28 proteins were downregulated in the rescue intracytoplasmic sperm injection group compared with the in vitro fertilization group. Bioinformatics analyses showed that these altered proteins were involved in various functions, including the kallikrein-related proteolytic cascade, immune response, and heparin binding. Furthermore, the validity of the proteomic results was verified by Western blot analysis of the proteins (lactoferrin [LTF], fibronectin [FN1], creatine kinase B type [CKB], kallikrein-2 [KLK2], aminopeptidase N [ANPEP], extracellular matrix protein 1 [ECM1], glycodelin [PAEP], alpha-1-antitrypsin [SERPINA1], and semenogelin-1 [SEMG1]) and immunofluorescence. Moreover, 16% of the seminal plasma proteins identified in the present work have not been reported in previous studies.

DISCUSSION

This panel of altered seminal plasma proteins associated with unexplained male factor infertility might have clinical relevance and may be useful in the diagnosis and prognosis of idiopathic infertility in in vitro fertilization.

CONCLUSIONS

Our work not only provides a new complementary high-confidence dataset of seminal plasma proteins but also shines new light onto the molecular characteristics of seminal plasma from normozoospermic men with different assisted reproductive outcomes.

The progesterone-induced sperm acrosome reaction is a good option for the prediction of fertilization in vitro compared with other sperm parameters

Progesterone (P₄ ) is crucial for the physiological function of spermatozoa. In the study, we investigated the correlation between P₄ -induced sperm acrosome reaction (AR) and parameters including sperm progressive motility, normal morphology and sperm DNA fragmentation (SDF), and compared the in vitro fertilization (IVF) predictive values of these indicators based on the multivariate regressions analysis and receiver operator characteristics (ROC) curve analyses. The results demonstrated a negative correlation between P₄ -induced sperm AR and the SDF, with the correlation -9.05 (-17.25 to -0.84), p<0.05, n = 47). No relationship was found between the sperm progressive motility, normal morphology and the induced AR. The P₄ -induced AR and SDF were both significantly correlated to the fertilization rate. ROC curve analyses indicated that P₄ -induced AR was a better prognostic predictor for the fertilization rate compared with the SDF, with the areas under the curve 0.729 (0.580-0.849), p<0.01 and 0.637 (0.484-0.772), p=0.16 respectively. The cut-off value for P₄ -induced AR to predict "50% fertilization rate" was 23.4% with sensitivity and specificity of 63.3% and 88.2% respectively. The overall results indicated that the assessment of P₄ -induced AR seemed to be a more sensitive indicator for fertilization rate in vitro compared with other sperm parameters.

Human sperm acrosome function assays are predictive of fertilization rate in vitro: a retrospective cohort study and meta-analysis

OBJECTIVE

To determine whether acrosome function scoring-including acrosomal enzyme (AE) levels and acrosome reaction (AR) results-can predict fertilization rate in vitro.

METHODS

We examined the predictive value of acrosomal enzymes (AE) determined by spectrophotometry/N-α-benzoyl-DL-arginine-p-nitroanilide for fertilization rate (FR) in vitro in a retrospective cohort study of 737 infertile couples undergoing IVF therapy. Additionally, a meta-analysis was done for prospective cohort or case-control studies; the following summary measures were reported to expand upon the findings: pooled spearman correlation coefficient (Rs), standardized mean difference (SMD), sensitivity (SEN), specificity (SPE), positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic score (DS), diagnostic odds ratio (DOR), and area under the summary receiver operating characteristic curve (AUC).

RESULTS

Lower AE levels determined by spectrophotometry with a cut-off value of <25μIU/10⁶ spermatozoa were predictive of total fertilization failure (TFF) with moderate SEN (88.23%) and low SPE (16.50%). On meta-analysis, a total of 44 unique articles were selected, but given the multiple techniques described there was a total of 67 total datasets extracted from these 44 articles, comprising 5356 infertile couples undergoing IVF therapy. The AE levels or induced AR% was positively correlated with FR (Rs = 0.38, SMD = 0.79; Rs = 0.40, SMD = 0.86, respectively). Lower AE levels or induced AR% was predictive of lower fertilization rate with moderate accuracy (AUC = 0.78, AUC = 0.84, respectively); this was accompanied by low SEN/moderate SPE (0.57/0.85), moderate SEN/moderate SPE (0.79/0.87), respectively. For AE assay, the diagnostic performance in Asia (Rs = 0.24, SMD = 0.50) was inferior to that in North America (Rs = 0.54, SMD = 0.81) and Europe (Rs = 0.46, SMD = 0.92). Cryopreserved spermatozoa (SMD = 0.20, P = 0.204) were inferior to fresh spermatozoa (SMD = 0.89, P <  0.001). Sperm preparation yielded inferior results as compared to no preparation; spermatozoa after swim up were weak relevant (Rs = 0.27, P = 0.044); and there was no correlation for spermatozoa after a discontinuous gradient (SMD = 1.07, P >  0.05). Lower AE levels determined by fluorometry or substrate assay were used for predicting lower FR with low sensitivity and high specificity; the spectrophotometry assay had an uncertain predictive value. For induced AR assay, the diagnostic performance in the other areas was inferior to that in Africa (Rs = 0.65, SMD = 1.86). No preparation or double preparation yielded inferior results as compared to one preparation (Rs = 0.41); discontinuous gradient (Rs = 0.17, SMD = 0.47) was inferior to swim up (Rs =0.65, SMD = 1.51). Nonphysiological triggers (SMD = 0.81) did not differ from physiological triggers (SMD = 0.95) in general; ZP (Rs = 0.63) or mannose (Rs = 0.59) was superior to other physiological or nonphysiological triggers; and there was no correlation for human follicle fluid, progesterone, cyclic adenosine 3'-5'-phosphate analogue and phorbol ester-BSA-GlcNAc Neoglycoproteins with N-acetylglucosamine residues. Lower induced AR% determined by indirect immunofluorescence, direct immunofluorescence with lection, or triple stain was used for predicting lower FR, with moderate sensitivity/high specificity, moderate sensitivity/high specificity, or high sensitivity/low specificity.

CONCLUSIONS

Although the correlation between acrosome function scoring and FR was significant, the assays were neither highly sensitive nor specific. Additionally, the diagnostic performance showed regional effects as well as an effect of the sperm preparation or assay method. More studies of multicenter, large-scale, careful design and synthesizing multiple sperm functional assays and oocyte quality assays are still needed in clinical settings to better predict fertilization outcome in IVF.

iTRAQ-based analysis of sperm proteome from normozoospermic men achieving the rescue-ICSI pregnancy after the IVF failure

Background

In the assisted reproduction, the infertile molecules of spermatozoa from normozoospermic men who underwent the unexplained failure of in vitro fertilization (IVF) due to the lack of sperm binding to the normal zona pellucida, and then achieved pregnancy with the rescue intracytoplasmic sperm injection (R-ICSI) remain unclear. More works are still necessary to explore this male infertile mechanism.

Methods

Normozoospermicmen with the IVF pregnancy and normozoospermic men with the R-ICSI pregnancy after the conventional IVF failure were collected. iTRAQ-based proteomic approach were performed to reveal the new infertile causes between the IVF pregnancy men and the R-ICSI pregnancy men. To validate the confidence of proteome data, the individual samples were analyzed by western blot and immunofluorescence. Further, the spontaneous acrosome reactions were measured to evaluate the sperm quality.

Results

Compared with IVF pregnancy group, 56 sperm proteins were differentially expressed in the R-ICSI pregnancy group. Bioinformatic analyses (PANTHER, DAVID, PubMed and STRING) indicated these altered sperm proteins were involved in various molecular functions: reproduction, chromosome organization, and sperm-oocyte interaction. Moreover, the confidence of proteome data was confirmed by western blot and immunofluorescence using the individual samples, which were consistent with our proteomic data. Additionally, an increased rate of the spontaneous acrosome reaction rate was found in the R-ICSI pregnancy group.

Conclusions

The sealtered sperm proteins and the increased spontaneous acrosome reaction rate might account for this unexplained male infertility in the R-ICSI pregnancy patients. The present proteomic results will throw light on the better understanding of the unexplained infertile mechanisms underlying these normozoospermic man who achieved R-ICSI pregnancy after IVF failure.

Electronic supplementary material

The online version of this article (10.1186/s12014-018-9203-3) contains supplementary material, which is available to authorized users.

Prenatal exposure to an environmentally relevant mixture of Canadian Arctic contaminants decreases male reproductive function in an aging rat model

Elevated levels of organochlorines (OC) have been reported in Inuit populations in the Arctic. We hypothesized that prenatal exposure to a Canadian Arctic OC mixture adversely affects male reproductive function and health with age. Sprague–Dawley female rats (F0) were gavaged with an environmentally relevant concentration of an Arctic OC mixture or corn oil (Control) during mating with untreated males until parturition (F1 litters). After postnatal day (PND) 90, the weights of the OC F1 males differed dramatically relative to Controls (P<0.05;n=10) and they exhibited respiratory distress. Except for possible thinning of the alveolar barrier, histological observation of the lungs revealed no apparent pathology to explain the respiratory distress. At PND 365, OC F1 males had reduced relative reproductive organ weights and lower sperm quality than Controls (P<0.05). At PND 90, OC F1 males were subfertile (P<0.05), but were infertile at PND 365. In conclusion, environmentally relevant prenatal OC exposure reduced reproductive function and health in aging male rats, providing new insight into the effects of early-life exposures to these contaminants.

Zona pellucida gene mRNA expression in human oocytes is related to oocyte maturity, zona inner layer retardance and fertilization competence

STUDY QUESTION

Do the mRNA expression levels of zona pellucida (ZP) genes, ZP1, 2, 3 and 4 in oocyte and cumulus cells (CC) reveal relevant information on the oocyte?

SUMMARY ANSWER

The ZP mRNA expression in human oocytes is related to oocyte maturity, zona inner layer (IL) retardance and fertilization capacity.

WHAT IS KNOWN ALREADY

ZP structure and birefringence provide useful information on oocyte cytoplasmic maturation, developmental competence for embryonic growth, blastocyst formation and pregnancy. In order to understand the molecular basis of morphological changes in the ZP, in the current study, the polarized light microscopy (PLM) approach was combined with analysis of the expression of the genes encoding ZP1, 2, 3 and 4, both in the oocytes and in the surrounding CC.

STUDY DESIGN, SIZE, DURATION

This is a retrospective study comprising 98 supernumerary human cumulus oocyte complexes (COC) [80 Metaphase II (MII), 10 Metaphase I (MI) and 8 germinal vesicle (GV)] obtained from 39 patients (median age 33.4 years, range 22-42) after controlled ovarian stimulation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Single oocytes and their corresponding CC were analysed. Oocytes were examined using PLM, and quantitative RT-PCR was performed for ZP1, 2, 3 and 4 in these individual oocytes and their CC. Ephrin-B2 (EFNB2) mRNA was measured in CC as a control. Presence of ZP3 protein in CC and oocytes was investigated using immunocytochemistry. Data were analysed using one-parametric and multivariate analysis and were corrected for the potential impact of patient and cycle characteristics.

MAIN RESULTS AND THE ROLE OF CHANCE

Oocytes contained ZP1/2/3 and 4 mRNA while in CC only ZP3 was quantifiable. Also ZP3 protein was detected in human CC. When comparing mature (MII) and immature oocytes (MI/GV) or their corresponding CC, ZP1/2 and 4 expression was lower in mature oocytes compared to the expression in immature oocytes (all P < 0.05) and ZP3 expression was lower in the CC of mature oocytes compared to the expression in CC of immature oocytes (P < 0.05). This coincided with a significantly smaller IL-ZP area and thickness in mature oocytes than in immature oocytes (all P < 0.05). In mature oocytes, IL-ZP retardance was significantly correlated with the expression of all four ZP mRNAs (all P < 0.05). The oocyte ZP3 expression was the main predictor of the fertilization capacity, next to IL-retardance and IL-thickness. Using stepwise regression analysis, IL-thickness combined with EFNB2 expression in CC and the patient's ovarian response resulted in a noninvasive oocyte fertilization prediction model.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

This is a retrospective study and the relation of oocyte mRNA levels to fertilization capacity is indirect as oocyte gene expression analysis required lysis of the oocyte.

WIDER IMPLICATIONS OF THE FINDINGS

Overall relations between PLM observations, mRNA expression changes and intrinsic oocyte competence were successfully documented. As such PLM and CC gene expression are confirmed as valuable noninvasive techniques to evaluate oocyte competence.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by University of Torino, Italy, WFWG UZ-Brussel and Agentschap voor Innovatie door Wetenschap en Technologie IWT 110680, Belgium. All authors declare that their participation in the study did not involve actual or potential conflicts of interests.

Chromatin Protamination and Catsper Expression in Spermatozoa Predict Clinical Outcomes after Assisted Reproduction Programs

Identification of parameters predicting assisted reproductive technologies (ARTs) success is a major goal of research in reproduction. Quality of gametes is essential to achieve good quality embryos and increase the success of ARTs. We evaluated two sperm parameters, chromatin maturity and expression of the sperm specific calcium channel CATSPER, in relation to ART outcomes in 206 couples undergoing ARTs. Chromatin maturity was evaluated by Chromomycin A3 (CMA3) for protamination and Aniline Blue (AB) for histone persistence and CATSPER expression by a flow cytometric method. CMA3 positivity and CATSPER expression significantly predicted the attainment of good quality embryos with an OR of 6.6 and 14.3 respectively, whereas AB staining was correlated with fertilization rate. In the subgroup of couples with women ≤35 years, CATSPER also predicted achievement of clinical pregnancy (OR = 4.4). Including CMA3, CATSPER and other parameters affecting ART outcomes (female age, female factor and number of MII oocytes), a model that resulted able to predict good embryo quality with high accuracy was developed. CMA3 staining and CATSPER expression may be considered two applicable tools to predict ART success and useful for couple counseling. This is the first study demonstrating a role of CATSPER expression in embryo development after ARTs programs.

Deficiency in Sperm-Egg Protein Interaction as a Major Cause of Fertilization Failure

Complete elucidation of fertilization process at molecular level is one of the unresolved challenges in sexual reproduction studies, and understanding the molecular mechanism is crucial in overcoming difficulties in infertility and unsuccessful in vitro fertilization. Sperm-oocyte interaction is one of the most remarkable events in fertilization process, and deficiency in protein-protein interactions which mediate this interaction is a major cause of unexplained infertility. Due to detection of how the various defects of sperm-oocyte interaction can affect fertilization failure, different experimental methods have been applied. This review summarizes the current understanding of sperm-egg interaction mechanism during fertilization and also accumulates the different types of sperm-egg interaction abnormalities and their association with infertility. Several detection approaches regarding sperm-egg protein interactions and the associated defects are reviewed in this paper.

Effects of Synthetic Serum Supplementation in Sperm Preparation Media on Sperm Capacitation and Function Test Results

Albumin supplementation of culture media induces sperm capacitation in assisted reproduction technique cycles. Synthetic serum supplementation is clinically used to replace albumin for preventing transmission of infectious agents. However, the effects of synthetic serum supplementation on sperm capacitation have rarely been investigated. Spermatozoa from 30 men with normal basic semen analysis results were collected, divided into five aliquots, and cultured in capacitating conditions in four combinations of two synthetic serum supplements, serum substitute supplement (SSS) and serum protein substitute (SPS), and two fertilization media, Quinns Advantage™ Fertilization (QF) and human tubular fluid (HTF) media. Reactive oxygen species (ROS) levels in spermatozoa were measured through chemiluminescence. Furthermore, acrosome reaction and western blotting for tyrosine phosphorylation were used to evaluate sperm capacitation. HTF+SSS had significantly higher ROS levels than QF+SPS did (11,725 ± 1,172 versus 6,278 ± 864 relative light units). In addition, the spermatozoa cultured in QF+SPS had lower motility, acrosome reaction rates, and tyrosine phosphorylation levels compared with those cultured in HTF+SSS. In conclusion, the effects of synthetic serum supplementation on sperm capacitation varied according to the combination of media. These differences may lead to variations in spermatozoon ROS levels, thus affecting sperm function test results.

In Vitro fertilization failure of normozoospermic men: search for a lack of testicular isozyme of angiotensin-converting enzyme

Background

Angiotensin converting enzyme (ACE) is a metalloprotease with two isoforms. The somatic isoform is a key component of the renin-angiotensin system; its main function is to hydrolyse angiotensin I into angiotensin II. The germinal or testicular isoform (tACE) located at the plasma membrane of the spermatozoa, plays a crucial role in the spermatozoa-oocyte interaction during in vivo fertilization, in rodents. Disruption of the tACE in mice has revealed that homozygous male tACE−/− sire few pups despite mating normally. Few spermatozoa from these tACE−/− mice are bound to the zona pellucida (ZP) despite normal semen parameters. Based on these findings in mice models, we hypothesized that some infertile men that have the same phenotype as the tACE−/− mice, ie normal semen parameters and a lack of sperm bind to the ZP in vitro, may have a tACE defect.

Methods

Twenty four men participated to this study. The case subjects (n = 10) had normal semen parameters according to the WHO guidelines (WHO 1999) but a total in vitro fertilization failure with absence of sperm fixation to the ZP. The control subjects (n = 14) also had normal semen parameters and a normal fertilization rate ≥65%. We investigated the tACE expression in spermatozoa by Western-Blot and performed a DNA sequencing of the tACE gene.

Results

Three case-subjects and one control-subject had no tACE expression. There were no statistic differences between the two groups. No mutation was detected in the tACE DNA sequence.

Conclusions

Our results didn’t show any involvement of tACE in human fertilization especially in ZP binding.

The molecular chaperone HSPA2 plays a key role in regulating the expression of sperm surface receptors that mediate sperm-egg recognition

A common defect encountered in the spermatozoa of male infertility patients is an idiopathic failure of sperm–egg recognition. In order to resolve the molecular basis of this condition we have compared the proteomic profiles of spermatozoa exhibiting an impaired capacity for sperm-egg recognition with normal cells using label free mass spectrometry (MS)-based quantification. This analysis indicated that impaired sperm–zona binding was associated with reduced expression of the molecular chaperone, heat shock 70 kDa protein 2 (HSPA2), from the sperm proteome. Western blot analysis confirmed this observation in independent patients and demonstrated that the defect did not extend to other members of the HSP70 family. HSPA2 was present in the acrosomal domain of human spermatozoa as a major component of 5 large molecular mass complexes, the most dominant of which was found to contain HSPA2 in close association with just two other proteins, sperm adhesion molecule 1 (SPAM1) and arylsulfatase A (ARSA), both of which that have previously been implicated in sperm-egg interaction. The interaction between SPAM1, ARSA and HSPA2 in a multimeric complex mediating sperm-egg interaction, coupled with the complete failure of this process when HSPA2 is depleted in infertile patients, provides new insights into the mechanisms by which sperm function is impaired in cases of male infertility.

Dynamin regulates specific membrane fusion events necessary for acrosomal exocytosis in mouse spermatozoa

Mammalian spermatozoa must complete an acrosome reaction prior to fertilizing an oocyte. The acrosome reaction is a unique exocytotic event involving a series of prolonged membrane fusions that ultimately result in the production of membrane vesicles and release of the acrosomal contents. This event requires the concerted action of a large number of fusion-competent signaling and scaffolding proteins. Here we show that two different members of the dynamin GTPase family localize to the developing acrosome of maturing mouse germ cells. Both dynamin 1 and 2 also remain within the periacrosomal region of mature mouse spermatozoa and are thus well positioned to regulate the acrosome reaction. Two pharmacological inhibitors of dynamin, dynasore and Dyngo-4a, blocked the in vitro induction of acrosomal exocytosis by progesterone, but not by the calcium ionophore A23187, and elicited a concomitant reduction of in vitro fertilization. In vivo treatment with these inhibitors also resulted in spermatozoa displaying reduced acrosome reaction potential. Dynamin 1 and 2 phosphorylation increased on progesterone treatment, and this was also selectively blocked by dynasore. On the basis of our collective data, we propose that dynamin could regulate specific membrane fusion events necessary for acrosomal exocytosis in mouse spermatozoa.

Sperm preparation: state-of-the-art--physiological aspects and application of advanced sperm preparation methods

For assisted reproduction technologies (ART), numerous techniques were developed to isolate spermatozoa capable of fertilizing oocytes. While early methodologies only focused on isolating viable, motile spermatozoa, with progress of ART, particularly intracytoplasmic sperm injection (ICSI), it became clear that these parameters are insufficient for the identification of the most suitable spermatozoon for fertilization. Conventional sperm preparation techniques, namely, swim-up, density gradient centrifugation and glass wool filtration, are not efficient enough to produce sperm populations free of DNA damage, because these techniques are not physiological and not modeled on the stringent sperm selection processes taking place in the female genital tract. These processes only allow one male germ cell out of tens of millions to fuse with the oocyte. Sites of sperm selection in the female genital tract are the cervix, uterus, uterotubal junction, oviduct, cumulus oophorus and the zona pellucida. Newer strategies of sperm preparation are founded on: (i) morphological assessment by means of 'motile sperm organelle morphological examination (MSOME)'; (ii) electrical charge; and (iii) molecular binding characteristics of the sperm cell. Whereas separation methods based on electrical charge take advantage of the sperm's adherence to a test tube surface or separate in an electrophoresis, molecular binding techniques use Annexin V or hyaluronic acid (HA) as substrates. Techniques in this category are magnet-activated cell sorting, Annexin V-activated glass wool filtration, flow cytometry and picked spermatozoa for ICSI (PICSI) from HA-coated dishes and HA-containing media. Future developments may include Raman microspectrometry, confocal light absorption and scattering spectroscopic microscopy and polarization microscopy.

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.

Dynamic resolution of acrosomal exocytosis in human sperm

An essential step in mammalian fertilisation is the sperm acrosome reaction (AR) – exocytosis of a single large vesicle (the acrosome) that surrounds the nucleus at the apical sperm head. The acrosomal and plasma membranes fuse, resulting in both the release of factors that might facilitate penetration of the zona pellucida (which invests the egg) and the externalisation of membrane components required for gamete fusion. Exocytosis in somatic cells is a rapid process – typically complete within milliseconds – yet acrosomal enzymes are required throughout zona penetration – a period of minutes. Here, we present the first studies of this crucial and complex event occurring in real-time in individual live sperm using time-lapse fluorescence microscopy. Simultaneous imaging of separate probes for acrosomal content and inner acrosomal membrane show that rapid membrane fusion, initiated at the cell apex, is followed by exceptionally slow dispersal of acrosomal content (up to 12 minutes). Cells that lose their acrosome prematurely (spontaneous AR), compromising their ability to penetrate the egg vestments, are those that are already subject to a loss of motility and viability. Cells undergoing stimulus-induced AR (progesterone or A23187) remain viable, with a proportion remaining motile (progesterone). These findings suggest that the AR is a highly adapted form of exocytosis.

[Ca2+]i signalling in sperm — making the most of what you've got

Thanks to a worrying decrease in male fertility, understanding how sperm 'work' is a matter both of interest and great importance. Sperm of all animals detect various environmental cues. The 'behavioural' and physiological responses of sperm must be specific, appropriate and correctly timed. Strangely, in a cell with few organelles and minimal cytoplasmic volume, internal Ca(2+) concentration, [Ca(2+)](i), regulates almost all these activities. How does such a simple cell achieve this - and is it as simple as it seems?

Phosphoinositide-dependent pathways in mouse sperm are regulated by egg ZP3 and drive the acrosome reaction

Sperm of many animals must complete an exocytotic event, the acrosome reaction, in order to fuse with eggs. In mammals, acrosome reactions are triggered during sperm contact with the egg extracellular matrix, or zona pellucida, by the matrix glycoprotein ZP3. Here, we show that ZP3 stimulates production of phosphatidylinositol-(3,4,5)-triphosphate in sperm membranes. Phosphatidylinositol-3-kinase antagonists that prevent acrosome reactions and fertilization in vitro, while generation of this phosphoinositide in the absence of ZP3 triggered acrosome reactions. Downstream effectors of phosphatidylinositol-(3,4,5)-triphosphate in sperm include the protein kinases, Akt and PKCzeta. These studies outline a signal transduction pathway that plays an essential role in the early events of mammalian fertilization.

Sperm function tests and fertility

Traditionally, the diagnosis of male infertility has depended upon a descriptive evaluation of human semen with emphasis on the number of spermatozoa that are present in the ejaculate, their motility and their morphology. The fundamental tenet underlying this approach is that male fertility can be defined by reference to a threshold concentration of motile, morphologically normal spermatozoa that must be exceeded in order to achieve conception. Many independent studies have demonstrated that this fundamental concept is flawed and, in reality, it is not so much the absolute number of spermatozoa that determines fertility, but their functional competence. In the light of this conclusion, a range of in vitro tests have been developed to monitor various aspects of sperm function including their potential for movement, cervical mucus penetration, capacitation, zona recognition, the acrosome reaction and sperm-oocyte fusion. Such functional assays have been found to predict the fertilizing capacity of human spermatozoa in vitro and in vivo with some accuracy. Recent developments in this field include the introduction of tests to assess the degree to which human spermatozoa have suffered oxidative stress as well as the integrity of their nuclear and mitochondrial DNA. Such assessments not only yield information on the fertilizing capacity of human spermatozoa but also their ability to support normal embryonic development.

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.

Sperm function and assisted reproduction technology

The evaluation of different functional sperm parameters has become a tool in andrological diagnosis. These assays determine the sperm's capability to fertilize an oocyte. It also appears that sperm functions and semen parameters are interrelated and interdependent. Therefore, the question arose whether a given laboratory test or a battery of tests can predict the outcome in in vitro fertilization (IVF). One-hundred and sixty-one patients who underwent an IVF treatment were selected from a database of 4178 patients who had been examined for male infertility 3 months before or after IVF. Sperm concentration, motility, acrosin activity, acrosome reaction, sperm morphology, maternal age, number of transferred embryos, embryo score, fertilization rate and pregnancy rate were determined. In addition, logistic regression models to describe fertilization rate and pregnancy were developed. All the parameters in the models were dichotomized and intra- and interindividual variability of the parameters were assessed. Although the sperm parameters showed good correlations with IVF when correlated separately, the only essential parameter in the multivariate model was morphology. The enormous intra- and interindividual variability of the values was striking. In conclusion, our data indicate that the andrological status at the end of the respective treatment does not necessarily represent the status at the time of IVF. Despite a relatively low correlation coefficient in the logistic regression model, it appears that among the parameters tested, the most reliable parameter to predict fertilization is normal sperm morphology. (Reprod Med Biol 2005; 4: 7-30).

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.

Normal range and variation of the zona pellucida-induced acrosome reaction in fertile men

OBJECTIVE

To investigate the normal range of the zona pellucida (ZP)-induced acrosome reaction (AR) in fertile men.

DESIGN

A study of normative data.

SETTING

Academic research and teaching tertiary hospital.None.Fertile men (n = 111) who had children or whose female partner was currently pregnant. MAIN OUTCOME MEASURE (S): Semen analysis, sperm-ZP binding, and the ZP-induced AR.

RESULT(S)

There was wide range for the ZP-induced AR: 20%-98% with a mean of 48%. The ZP-induced AR was significantly correlated with sperm concentration and normal morphology. The ZP-induced AR was significantly lower in men with sperm concentration <or=60 x 10(6)/mL than those with sperm concentration >60 x 10(6)/mL. Similarly, men with normal sperm morphology >or=15% had significantly higher ZP-induced AR than men with normal morphology <15%.

CONCLUSION(S)

There is a wide range of the ZP-induced AR in fertile men that is correlated with sperm concentration and normal morphology.

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.

Physiological and proteomic approaches to studying prefertilization events in the human

This research aims firstly to understand, in cellular and molecular terms, how a mature human spermatozoon is prepared for fertilization, and secondly, to identify what factors are involved in the initial signalling interactions between the egg and spermatozoon. In order to achieve these objectives, a combination of approaches is being used, including single-cell imaging, patch clamping and proteomics. Single-cell imaging reveals hidden complexity and heterogeneity in signalling responses in spermatozoa. Characterization of cell physiology at the single-cell level must be a future aim, including the study of ion channel expression and function by patch clamping. Proteomic experiments are aimed at identifying defects in protein expression in specific subgroups of men, e.g. those with globozoospermia. A better understanding of prefertilization events will allow the development of non-assisted reproductive therapy, drug-based treatments for male infertility.