Localization patterns of the ganglioside GM1 in human sperm are indicative of male fertility and independent of traditional semen measures

Segmental differentiation of the murine epididymis: identification of segment-specific, GM1-enriched vesicles and regulation by luminal fluid factors†

The murine epididymis has 10 distinct segments that provide the opportunity to identify compartmentalized cell physiological mechanisms underlying sperm maturation. However, despite the essential role of the epididymis in reproduction, remarkably little is known about segment-specific functions of this organ. Here, we investigate the dramatic segmental localization of the ganglioside GM1, a glycosphingolipid already known to play key roles in sperm capacitation and acrosome exocytosis. Frozen tissue sections of epididymides from adult mice were treated with the binding subunit of cholera toxin conjugated to AlexaFluor 488 to label GM1. We report that GM1-enriched vesicles were found exclusively in principal and clear cells of segment 2. These vesicles were also restricted to the lumen of segment 2 and did not appear to flow with the sperm into segment 3, within the limits of detection by confocal microscopy. Interestingly, this segment-specific presence was altered in several azoospermic mouse models and in wild-type mice after efferent duct ligation. These findings indicate that a lumicrine factor, itself dependent on spermatogenesis, controls this segmental differentiation. The RNA sequencing results confirmed global de-differentiation of the proximal epididymal segments in response to efferent duct ligation. Additionally, GM1 localization on the surface of the sperm head increased as sperm transit through segment 2 and have contact with the GM1-enriched vesicles. This is the first report of segment-specific vesicles and their role in enriching sperm with GM1, a glycosphingolipid known to be critical for sperm function, providing key insights into the segment-specific physiology and function of the epididymis.

Effect of Microsurgical Varicocele Repair on Sperm Capacitation and Probability of Generating a Pregnancy as Measured by Pre and Postoperative Novel Testing With Cap-Score

OBJECTIVE

To study whether varicocele repair would improve sperm capacitation and probability of generating a pregnancy.

METHODS

Data were collected prospectively from 40 consecutive adult men who presented with infertility confirmed by semen analysis (SA) and found to have a varicocele on exam or ultrasound who underwent unilateral or bilateral subinguinal microscopic varicocelectomy. We recorded pre and postoperative SA, Cap-Score, and probability of generating a pregnancy (PGP) with a 3-month follow-up. Values were compared using paired t test and Wilcox rank-sum test.

RESULTS

Results showed a 17.4% relative increase in Cap-Score (23%-27% capacitation), 25% relative increase in PGP (24%-30%), as well as statistically significant improvements in sperm concentration, motility, and total sperm count postoperatively.

CONCLUSION

This study confirms that microsurgical varicocelectomy significantly improves sperm capacitation ability and improves the expected probability of generating a pregnancy within 3 rounds of intrauterine insemination. The improvement in sperm capacitation ability may help explain how varicocele repair may improve the chance of pregnancy, regardless of standard semen parameter improvements.

Profiling the male germline genome to unravel its reproductive potential

OBJECTIVE

To identify specific germline mutations related to sperm reproductive competence, in couples with unexplained infertility.

DESIGN

In this retrospective study, couples were divided according to whether they had successful intracytoplasmic sperm injection outcomes (fertile) or not (infertile). Ancillary sperm function tests were performed on ejaculates, and whole exome sequencing was performed on spermatozoal DNA. Sperm aneuploidy and gene mutation profiles were compared between the 2 cohorts as well as according to the specific reasons for reproductive failure.

SETTING

Center for reproductive medicine at a major academic medical center.

PATIENT(S)

Thirty-one couples with negative infertility workups and normal semen parameters.

INTERVENTION(S)

Couples with mutations on fertilization- or embryo development-related genes were subsequently treated by assisted gamete treatment or microfluidics, respectively.

MAIN OUTCOME MEASURE(S)

Intracytoplasmic sperm injection cycle outcomes including fertilization, clinical pregnancy, and delivery rates.

RESULT(S)

Sperm aneuploidy was lower in the fertile group (4.0% vs. 8.4%). Spermatozoa from both cohorts displayed mutations associated with sperm-egg fusion (ADAM3A) and acrosomal development (SPACA1), regardless of reproductive outcome. The infertile cohort was then categorized according to the reasons for reproductive failure: absent fertilization, poor early embryo development, implantation failure, or pregnancy loss. Spermatozoa from the fertilization failure subgroup (n = 4) had negligible PLCζ presence (10% ± 9%) and gene mutations (PLCZ1, PIWIL1, ADAM15) indicating a sperm-related oocyte-activating deficiency. These couples were successfully treated by assisted gamete treatment in their subsequent cycles. Spermatozoa from the poor early embryo development subgroup (n = 5) had abnormal centrosomes (45.9% ± 5%), and displayed mutations impacting centrosome integrity (HAUS1) and spindle/microtubular stabilization (KIF4A, XRN1). Microfluidic sperm processing subsequently yielded a term pregnancy. Spermatozoa from the implantation failure subgroup (n = 7) also had abnormal centrosomes (53.1% ± 13%) and carried mutations affecting embryonic implantation (IL9R) and microtubule and centrosomal integrity (MAP1S, SUPT5H, PLK4), whereas those from the pregnancy loss subgroup (n = 5) displayed mutations on genes involved in trophoblast development (NLRP7), cell cycle regulation (MARK4, TRIP13, DAB2IP, KIF1C), and recurrent miscarriage (TP53).

CONCLUSION(S)

By assessing the sperm genome, we identified specific germline mutations related to various reproductive processes. This information may clarify elusive factors underlying reproductive competence and enhance treatment for couples with unexplained infertility.

Defects in sperm capacitation/fertilizing ability are equally prevalent across ages in men seeking fertility assistance

RESEARCH QUESTION

How do capacitation ability, measured by Cap-Score™, and traditional semen analysis measures (volume, concentration, motility) change with age in men questioning their fertility (MQF)?

DESIGN

Cap-Score and semen analysis measures were obtained from MQF (n = 2652; multicentric design: 35 reproductive endocrinologist prescribers, n = 16 clinics). Morphology was not included due to differences among clinics. A Mann-Whitney test was used to compare Cap-Scores between MQF and men with known recent paternity (n = 76). The following age groups were constructed for MQF: 20-24, 25-29, 30-34, 35-39, 40-44, 45-49 and 50+. Associations between semen analysis, Cap-Score and age groups were evaluated using mixed-model analysis of variance to identify possible influence of Cap-Score collection kit type (n = 763 collected at home; n = 1889 collected at clinics).

RESULTS

MQF had reduced capacitation ability (mean ± SE; 29.25 ± 0.15 versus 35.34 ± 0.88; P < 0.001). No change in Cap-Score (P = 0.916) or concentration (P = 0.926) was detected with age group. In contrast, both volume (P = 0.008) and % motility (P < 0.001) declined with age.

CONCLUSIONS

Men presenting because of difficulties in generating pregnancy showed equivalent reductions in capacitation ability regardless of age. In contrast, motility and volume declined with age. These data suggest that capacitation ability is a more sensitive indicator of male fertility across age groups than traditional semen analysis and should not be reserved for older men. Importantly, these data do not address whether sperm fertilizing ability declines in the general population as men age. Instead, they indicate that if men are having difficulty conceiving, no matter what their age, then defects in sperm fertilizing ability are equally likely to be the cause.

New horizons in human sperm selection for assisted reproduction

Male infertility is a commonly encountered pathology that is estimated to be a contributory factor in approximately 50% of couples seeking recourse to assisted reproductive technologies. Upon clinical presentation, such males are commonly subjected to conventional diagnostic andrological practices that rely on descriptive criteria to define their fertility based on the number of morphologically normal, motile spermatozoa encountered within their ejaculate. Despite the virtual ubiquitous adoption of such diagnostic practices, they are not without their limitations and accordingly, there is now increasing awareness of the importance of assessing sperm quality in order to more accurately predict a male's fertility status. This realization raises the important question of which characteristics signify a high-quality, fertilization competent sperm cell. In this review, we reflect on recent advances in our mechanistic understanding of sperm biology and function, which are contributing to a growing armory of innovative approaches to diagnose and treat male infertility. In particular we review progress toward the implementation of precision medicine; the robust clinical adoption of which in the setting of fertility, currently lags well behind that of other fields of medicine. Despite this, research shows that the application of advanced technology platforms such as whole exome sequencing and proteomic analyses hold considerable promise in optimizing outcomes for the management of male infertility by uncovering and expanding our inventory of candidate infertility biomarkers, as well as those associated with recurrent pregnancy loss. Similarly, the development of advanced imaging technologies in tandem with machine learning artificial intelligence are poised to disrupt the fertility care paradigm by advancing our understanding of the molecular and biological causes of infertility to provide novel avenues for future diagnostics and treatments.

A genetically targeted sensor reveals spatial and temporal dynamics of acrosomal calcium and sperm acrosome exocytosis

Secretion of the acrosome, a single vesicle located rostrally in the head of a mammalian sperm, through a process known as "acrosome exocytosis" (AE), is essential for fertilization. However, the mechanisms leading to and regulating this complex process are controversial. In particular, poor understanding of Ca2+ dynamics between sperm subcellular compartments and regulation of membrane fusion mechanisms have led to competing models of AE. Here, we developed a transgenic mouse expressing an Acrosome-targeted Sensor for Exocytosis (AcroSensE) to investigate the spatial and temporal Ca2+ dynamics in AE in live sperm. AcroSensE combines a genetically encoded Ca2+ indicator (GCaMP) fused with an mCherry indicator to spatiotemporally resolve acrosomal Ca2+ rise (ACR) and membrane fusion events, enabling real-time study of AE. We found that ACR is dependent on extracellular Ca2+ and that ACR precedes AE. In addition, we show that there are intermediate steps in ACR and that AE correlates better with the ACR rate rather than absolute Ca2+ amount. Finally, we demonstrate that ACR and membrane fusion progression kinetics and spatial patterns differ with different stimuli and that sites of initiation of ACR and sites of membrane fusion do not always correspond. These findings support a model involving functionally redundant pathways that enable a highly regulated, multistep AE in heterogeneous sperm populations, unlike the previously proposed "acrosome reaction" model.

High-coverage targeted lipidomics revealed dramatic lipid compositional changes in asthenozoospermic spermatozoa and inverse correlation of ganglioside GM3 with sperm motility

BACKGROUND

It has been previously demonstrated that cholesterol content and cholesterol/phospholipid ratio were significantly higher in asthenozoospermia and oligoasthenoteratozoospermia. The majority of published studies have investigated the fatty acid composition of phospholipids rather than lipids themselves. This study evaluated the lipid composition of asthenozoospermic and normozoospermic spermatozoa, and identified the exact lipid species that correlated with sperm motility.

METHODS

A total of 12 infertile asthenozoospermia patients and 12 normozoospermia subjects with normal sperm motility values were tested for semen volume, sperm concentration, count, motility, vitality and morphology. High-coverage targeted lipidomics with 25 individual lipid classes was performed to analyze the sperm lipid components and establish the exact lipid species that correlated with sperm motility.

RESULTS

A total of 25 individual lipid classes and 479 lipid molecular species were identified and quantified. Asthenozoospermic spermatozoa showed an increase in the level of four lipid classes, including Cho, PE, LPI and GM3. A total of 48 lipid molecular species were significantly altered between normozoospermic and asthenozoospermic spermatozoa. Furthermore, the levels of total GM3 and six GM3 molecular species, which were altered in normozoospermic spermatozoa versus asthenozoospermic spermatozoa, were inversely correlated with sperm progressive and total motility.

CONCLUSIONS

Several unique lipid classes and lipid molecular species were significantly altered between asthenozoospermic and normozoospermic spermatozoa, revealing new possibilities for further mechanistic pursuits and highlighting the development needs of culture medium formulations to improve sperm motility.

Machine-learning algorithm incorporating capacitated sperm intracellular pH predicts conventional in vitro fertilization success in normospermic patients

OBJECTIVE

To measure human sperm intracellular pH (pH_i) and develop a machine-learning algorithm to predict successful conventional in vitro fertilization (IVF) in normospermic patients.

DESIGN

Spermatozoa from 76 IVF patients were capacitated in vitro. Flow cytometry was used to measure sperm pH_i, and computer-assisted semen analysis was used to measure hyperactivated motility. A gradient-boosted machine-learning algorithm was trained on clinical data and sperm pH_i and membrane potential from 58 patients to predict successful conventional IVF, defined as a fertilization ratio (number of fertilized oocytes [2 pronuclei]/number of mature oocytes) greater than 0.66. The algorithm was validated on an independent set of data from 18 patients.

SETTING

Academic medical center.

PATIENT(S)

Normospermic men undergoing IVF. Patients were excluded if they used frozen sperm, had known male factor infertility, or used intracytoplasmic sperm injection only.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Successful conventional IVF.

RESULT(S)

Sperm pH_i positively correlated with hyperactivated motility and with conventional IVF ratio (n = 76) but not with intracytoplasmic sperm injection fertilization ratio (n = 38). In receiver operating curve analysis of data from the test set (n = 58), the machine-learning algorithm predicted successful conventional IVF with a mean accuracy of 0.72 (n = 18), a mean area under the curve of 0.81, a mean sensitivity of 0.65, and a mean specificity of 0.80.

CONCLUSION(S)

Sperm pH_i correlates with conventional fertilization outcomes in normospermic patients undergoing IVF. A machine-learning algorithm can use clinical parameters and markers of capacitation to accurately predict successful fertilization in normospermic men undergoing conventional IVF.

Multicentric, prospective observational data show sperm capacitation predicts male fertility, and cohort comparison reveals a high prevalence of impaired capacitation in men questioning their fertility

RESEARCH QUESTIONS

Can a previously defined relationship between sperm capacitation and the probability of a man generating pregnancy within three cycles, prospectively predict male fertility in diverse clinical settings? A second study asked, what is the prevalence of impaired sperm fertilizing ability in men questioning their fertility (MQF), and does this relate to traditional semen analysis metrics?

DESIGN

In the multicentric, prospective observational study, data (n = 128; six clinics) were analysed to test a published relationship between the percentage of fertilization-competent, capacitated spermatozoa (Cap-Score) and probability of generating pregnancy (PGP) within three cycles of intrauterine insemination. Logistic regression of total pregnancy outcomes (n = 252) assessed fit. In the cohort comparison, Cap-Scores of MQF (n = 2155; 22 clinics) were compared with those of 76 fertile men.

RESULTS

New outcomes (n = 128) were rank-ordered by Cap-Score and divided into quintiles (25-26 per group); chi-squared testing revealed no difference between predicted and observed pregnancies (P = 0.809). Total outcomes (n = 252; 128 new + 124 previous) were pooled and the model recalculated, yielding an improved fit (P < 0.001). Applying the Akaike information criterion found that the optimal model used Cap-Score alone. Cap-Scores were performed on 2155 men (with semen analysis data available for 1948). To compare fertilizing ability, men were binned by PGP (≤19%, 20-29%, 30-39%, 40-49%, 50-59%, ≥60%). Distributions of PGP and the corresponding Cap-Scores were significantly lower in MQF versus fertile men (P < 0.001). Notably, 64% of MQF with normal volume, concentration and motility (757/1183) had PGP of 39% or less (Cap-Scores ≤31), versus 25% of fertile men.

CONCLUSIONS

Sperm capacitation prospectively predicted male fertility. Impaired capacitation affects many MQF with normal semen analysis results, informing diagnosis versus idiopathic infertility.

Male Infertility: Shining a Light on Lipids and Lipid-Modulating Enzymes in the Male Germline

Despite the prevalence of male factor infertility, most cases are defined as idiopathic, thus limiting treatment options and driving increased rates of recourse to assisted reproductive technologies (ARTs). Regrettably, our current armory of ARTs does not constitute therapeutic treatments for male infertility, thus highlighting an urgent need for novel intervention strategies. In our attempts to fill this void, we have come to appreciate that the production of pathological levels of oxygen radicals within the male germline are a defining etiology of many idiopathic infertility cases. Indeed, an imbalance of reactive oxygen species can precipitate a cascade of deleterious sequelae, beginning with the peroxidation of membrane lipids and culminating in cellular dysfunction and death. Here, we shine light on the importance of lipid homeostasis, and the impact of lipid stress in the demise of the male germ cell. We also seek to highlight the utility of emerging lipidomic technologies to enhance our understanding of the diverse roles that lipids play in sperm function, and to identify biomarkers capable of tracking infertility in patient cohorts. Such information should improve our fundamental understanding of the mechanistic causes of male infertility and find application in the development of efficacious treatment options.

The current status and future of andrology: A consensus report from the Cairo workshop group

BACKGROUND

In attempting to formulate potential WHO guidelines for the diagnosis of male infertility, the Evidence Synthesis Group noted a paucity of high-quality data on which to base key recommendations. As a result, a number of authors suggested that key areas of research/evidence gaps should be identified, so that appropriate funding and policy actions could be undertaken to help address key questions.

OBJECTIVES

The overall objective of this Consensus workshop was to clarify current knowledge and deficits in clinical laboratory andrology, so that clear paths for future development could be navigated.

MATERIALS AND METHODS

Following a detailed literature review, each author, prior to the face-to-face meeting, prepared a summary of their topic and submitted a PowerPoint presentation. The topics covered were (a) Diagnostic testing in male fertility and infertility, (b) Male fertility/infertility in the modern world, (c) Clinical management of male infertility, and (d) The overuse of ICSI. At the meeting in Cairo on February 18, 2019, the evidence was presented and discussed and a series of consensus points agreed.

RESULTS

The paper presents a background and summary of the evidence relating to these four topics and addresses key points of significance. Following discussion of the evidence, a total of 36 consensus points were agreed.

DISCUSSION

The Discussion section presents areas where there was further debate and key areas that were highlighted during the day.

CONCLUSION

The consensus points provide clear statements of evidence gaps and/or potential future research areas/topics. Appropriate funding streams addressing these can be prioritized and consequently, in the short and medium term, answers provided. By using this strategic approach, andrology can make the rapid progress necessary to address key scientific, clinical, and societal challenges that face our discipline now and in the near future.

Recent advances in understanding and managing male infertility

Infertility is a prevalent condition affecting an estimated 70 million people globally. The World Health Organization estimates that 9% of couples worldwide struggle with fertility issues and that male factor contributes to 50% of the issues. Male infertility has a variety of causes, ranging from genetic mutations to lifestyle choices to medical illnesses or medications. Recent studies examining DNA fragmentation, capacitation, and advanced paternal age have shed light on previously unknown topics. The role of conventional male reproductive surgeries aimed at improving or addressing male factor infertility, such as varicocelectomy and testicular sperm extraction, have recently been studied in an attempt to expand their narrow indications. Despite advances in the understanding of male infertility, idiopathic sperm abnormalities still account for about 30% of male infertility. With current and future efforts examining the molecular and genetic factors responsible for spermatogenesis and fertilization, we may be better able to understand etiologies of male factor infertility and thus improve outcomes for our patients.

Cap-Score™ prospectively predicts probability of pregnancy

Semen analysis (SA) poorly predicts male fertility, because it does not assess sperm fertilizing ability. The percentage of capacitated sperm determined by G_M1 localization (“Cap‐Score™”), differs between cohorts of fertile and potentially infertile men, and retrospectively, between men conceiving or failing to conceive by intrauterine insemination (IUI). Here, we prospectively tested whether Cap‐Score can predict male fertility with the outcome being clinical pregnancy within ≤3 IUI cycles. Cap‐Score and SA were performed (n = 208) with outcomes initially available for 91 men. Men were predicted to have either low (n = 47) or high (n = 44) chance of generating pregnancy using previously‐defined Cap‐Score reference ranges. Absolute and cumulative pregnancy rates were reduced in men predicted to have low pregnancy rates versus high ([absolute: 10.6% vs. 29.5%; p = 0.04]; [cumulative: 4.3% vs. 18.2%, 9.9% vs. 29.1%, and 14.0% vs. 32.8% for cycles 1–3; n = 91, 64, and 41; p = 0.02]). Only Cap‐Score, not male/female age or SA results, differed significantly between outcome groups. Logistic regression evaluated Cap‐Score and SA results relative to the probability of generating pregnancy (PGP) for men who were successful in, or completed, three IUI cycles (n = 57). Cap‐Score was significantly related to PGP (p = 0.01). The model fit was then tested with 67 additional patients (n = 124; five clinics); the equation changed minimally, but fit improved (p < 0.001; margin of error: 4%). The Akaike Information Criterion found the best model used Cap‐Score as the only predictor. These data show that Cap‐Score provides a practical, predictive assessment of male fertility, with applications in assisted reproduction and treatment of male infertility.

Molecular Basis of Human Sperm Capacitation

In the early 1950s, Austin and Chang independently described the changes that are required for the sperm to fertilize oocytes in vivo. These changes were originally grouped under name of “capacitation” and were the first step in the development of in vitro fertilization (IVF) in humans. Following these initial and fundamental findings, a remarkable number of observations led to characterization of the molecular steps behind this process. The discovery of certain sperm-specific molecules and the possibility to record ion currents through patch-clamp approaches helped to integrate the initial biochemical observation with the activity of ion channels. This is of particular importance in the male gamete due to the fact that sperm are transcriptionally inactive. Therefore, sperm must control all these changes that occur during their transit through the male and female reproductive tracts by complex signaling cascades that include post-translational modifications. This review is focused on the principal molecular mechanisms that govern human sperm capacitation with particular emphasis on comparing all the reported pieces of evidence with the mouse model.

Timing of sperm capacitation varies reproducibly among men

Sperm must mature functionally in the process of capacitation to become able to fertilize. Capacitation depends on membrane lipid changes, and can be quantitatively assessed by redistribution of the ganglioside G_M1, the basis of the Cap‐Score™ sperm function test. Here, differences in Cap‐Score were compared among and within men at two time points. Ejaculates were liquefied, washed, and incubated for 3 hr under capacitating (Cap) conditions, then fixed and analyzed immediately (Day0); after being incubated 3 hr under Cap conditions then maintained 22–24 hr in fix (Day1‐fix); or after 22–24 hr incubation under Cap conditions prior to fixation (Day1). In all cases, a light fixative previously shown to allow membrane lipid movements was used. Day1‐fix and Day1 Cap‐Scores were greater than Day0 (p < 0.001; n = 25), whereas Day1‐fix and Day1 Cap‐Scores were equivalent (p = 0.43; n = 25). In 123 samples from 52 fertile men, Cap‐Score increased more than 1SD (7.7; calculated previously from a fertile cohort) from Day0 to Day1‐fix in 44% (54/123) of the samples. To test whether timing of capacitation was consistent within an individual, 52 samples from 11 fertile men were classified into either “early” or “late” capacitation groups. The average capacitation group concordance within a donor was 81%. Median absolute deviation (MAD; in Cap‐Score units) was used to assess the tightness of clustering of the difference from Day0 to Day1‐fix within individuals. The average (2.21) and median (1.98) MAD confirmed consistency within individuals. Together, these data show that the timing of capacitation differed among men and was consistent within men.

Projecting the potential impact of the Cap-Score™ on clinical pregnancy, live births, and medical costs in couples with unexplained infertility

PURPOSE

The Cap-Score™ was developed to assess the capacitation status of men, thereby enabling personalized management of unexplained infertility by choosing timed intrauterine insemination (IUI), versus immediate in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) in individuals with a low Cap-Score™. The objective of this study was to estimate the differences in outcomes and costs comparing the use of the Cap-Score™ with timed IUI (CS-TI) and the standard of care (SOC), which was assumed to be three IUI cycles followed by three IVF-ICSI cycles.

METHODS

We developed and parameterized a decision-analytic model of management of unexplained infertility for women based on data from the published literature. We calculated the clinical pregnancy rates, live birth rates, and medical costs comparing CS-TI and SOC. We used Monte Carlo simulation to quantify uncertainty in projected estimates and performed univariate sensitivity analysis.

RESULTS

Compared to SOC, CS-TI was projected to increase the pregnancy rate by 1-26%, marginally reduce live birth rates by 1-3% in couples with women below 40 years, increase live birth rates by 3-7% in couples with women over 40 years, reduce mean medical costs by $4000-$19,200, reduce IUI costs by $600-$1370, and reduce IVF costs by $3400-$17,800, depending on the woman's age.

CONCLUSION

The Cap-Score™ is a potentially valuable clinical tool for management of unexplained infertility because it is projected to improve clinical pregnancy rates, save money, and, depending on the price of the test, increase access to treatment for infertility.

Validation of a laboratory-developed test of human sperm capacitation

Sperm must undergo capacitation to become fertilization competent. Here we validated that monosialotetrahexosylganglioside (GM1 ) localization patterns, which were assessed in the Cap-Score™ Sperm Function Test, reflect a capacitated state in human sperm. First, we defined patterns representing sperm that do or do not respond to stimuli for capacitation. Sperm with "capacitated" patterns had exposed acrosomal carbohydrates and underwent acrosome exocytosis in response to calcium ionophore (A23187). Precision was evaluated by percent change of the Cap-Score measured for 50, 100, 150, and 200 sperm. Changes of 11%, 6%, and 5% were observed (n ≥ 23); therefore, we counted ≥150 sperm per condition. Variance within and between readers was evaluated using 20 stitched image files generated from unique ejaculates. Two trained readers randomly resampled each image 20 times, reporting an average standard deviation of 3 Cap-Score units and coefficient of variation of 13% when rescoring samples, with no difference between readers. Semen liquefaction times ≤2 hr and mechanical liquefaction with Pasteur or wide-orifice transfer pipettes did not alter Cap-Score values. However, liquefaction with chymotrypsin (p = 0.002) and bromelain (p = 0.049) reduced response to capacitating stimuli and induced membrane damage, while counterintuitively improving sperm motility. Together, these data validate the Cap-Score assay for the intended purpose of providing information on sperm capacitation and male fertility. In addition to its clinical utility as a diagnostic tool, this test of sperm function can reveal the impact of common practices of semen handling on the ability of sperm to respond to capacitation stimuli.

Localization patterns of the ganglioside GM1 in human sperm are indicative of male fertility and independent of traditional semen measures

Semen analysis lacks a functional component and best identifies extreme cases of infertility. The ganglioside G_M1 is known to have functional roles during capacitation and acrosome exocytosis. Here, we assessed whether G_M1 localization patterns (Cap‐Score™) correspond with male fertility in different settings: Study 1 involved couples pursuing assisted reproduction in a tertiary care fertility clinic, while Study 2 involved men with known fertility versus those questioning their fertility at a local urology center. In Study 1, we examined various thresholds versus clinical history for 42 patients; 13 had Cap‐Scores ≥39.5%, with 12 of these (92.3%) achieving clinical pregnancy by natural conception or ≤3 intrauterine insemination cycles. Of the 29 patients scoring <39.5%, only six (20.7%) attained clinical pregnancy by natural conception or ≤3 intrauterine insemination cycles. In Study 2, Cap‐Scores were obtained from 76 fertile men (Cohort 1, pregnant partner or recent father) and compared to 122 men seeking fertility assessment (Cohort 2). Cap‐Score values were normally distributed in Cohort 1, with 13.2% having Cap‐Scores more than one standard deviation below the mean (35.3 ± 7.7%). Significantly, more men in Cohort 2 had Cap‐Scores greater than one standard deviation below the normal mean (33.6%; p = 0.001). Minimal/no relationship was found between Cap‐Score and sperm concentration, morphology, or motility. Together, these data demonstrate that Cap‐Score provides novel, clinically relevant insights into sperm function and male fertility that complement traditional semen analysis. Furthermore, the data provide normal reference ranges for fertile men that can help clinicians counsel couples toward the most appropriate fertility treatment.