Computer-aided semen analysis variables as predictors of male fertility potential

Development of a biomolecular approach to identify sperm functions and fertility using sperm RNAs

Infertility affects a significant percentage of couples worldwide, and male factors contribute significantly to this problem. Traditional assessments of male fertility rely primarily on parameters such as sperm motility, morphology, viability, and concentration. However, these metrics often do not provide a comprehensive understanding of sperm function, which is critical not only for fertilization but also for successful embryo development. Herein, we used porcine spermatozoa as a model to investigate the potential of sperm RNA markers in assessing various aspects of sperm function from motility to fertility. Using artificial insemination, we evaluated male fertility based on the litter size of sows inseminated with sperm from 20 boars. In addition, we measured parameters such as weaning rate, death births, live births, and mummy births. Sperm functional parameters, including motility and kinematics, were assessed before and after in vitro capacitation. Finally, correlations between various sperm functional parameters and sperm RNA markers were explored. Our results revealed interesting relationships between sperm functional parameters. While motility and kinematics were correlated, they were not correlated with sperm capacitation status. Surprisingly, no significant correlations were found between these parameters and male fertility. However, specific parameters of sperm capacitation status after in vitro capacitation were correlated with weaning rate and live births, highlighting their importance in predicting successful fertilization. Further analysis of sperm RNA markers identified genes related to male fertility, including IZUMO1, known for its role in sperm-egg fusion. These genes showed correlations with motility, capacitation, and fertilization parameters, shedding light on their potential roles in sperm function. In conclusion, our study demonstrates that sperm RNA markers hold promise for the diagnosis and prognosis of various aspects of sperm function, providing valuable insights into male infertility. These markers may serve as diagnostic tools to improve our understanding of male fertility problems, ultimately benefiting couples struggling with infertility.

Heat shock protein family D member 1 in boar spermatozoa is strongly related to the litter size of inseminated sows

Background

Sperm quality evaluation is the logical first step in increasing field fertility. Spermatozoa contain cytoplasmic organelles and biomolecules known as sperm-intrinsic factors, which play key roles in sperm maturation, sperm-oocyte fusion, and embryo development. In particular, sperm membrane proteins [e.g., arginine vasopressin receptor 2, beta-actin, prohibitin, and heat shock protein family D member 1 (HSPD1)] and RNA could be used as functional indicators of male fertility. We sought to clarify the effects of differential mRNA expression of selected genes on several fertilisation parameters, including sperm motility, motion kinematics, capacitation, and litter size, in a porcine model.

Results

Our results demonstrated that HSPD1 expression was significantly correlated with male fertility, as measured by the litter size of inseminated sows. The expression of HSPD1 mRNA was linked to sperm motility and other motion kinematic characteristics. Furthermore, HSPD1 had a 66.7% overall accuracy in detecting male fertility, and the high-litter size group which was selected with the HSPD1 marker had a 1.34 greater litter size than the low-litter size group.

Conclusions

Our findings indicate that HSPD1 might be a helpful biomarker for superior boar selection for artificial insemination, which could boost field fertility.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00689-0.

Inverse correlation between reactive oxygen species in unwashed semen and sperm motion parameters as measured by a computer-assisted semen analyzer

This study investigated the correlation between sperm motion parameters obtained by a computer-assisted semen analyzer and levels of reactive oxygen species in unwashed semen. In total, 847 patients, except for azoospermic patients were investigated. At the time of each patient's first consultation, semen parameters were measured using SMAS™ or CellSoft 3000™, and production of reactive oxygen species was measured using a computer-driven LKB Wallac Luminometer 1251 Analyzer. The patients were divided into two groups: reactive oxygen species - positive and negative. The semen parameters within each group were measured using one of the two computer-assisted semen analyzer systems and then compared. Correlations between reactive oxygen species levels and sperm motion parameters in semen from the reactive oxygen species - positive group were also investigated. Reactive oxygen species were detected in semen samples of 282 cases (33.3%). Sperm concentration (P < 0.01; P < 0.01), motility (P < 0.01; P < 0.05), and progressive motility (P < 0.01; P < 0.01) were markedly lower in the reactive oxygen species - positive group than in the reactive oxygen species - negative group. Among the sperm motion parameters in the reactive oxygen species - positive group, sperm concentration (P < 0.01; P < 0.01), motility (P < 0.05; P < 0.01), mALH (P < 0.05; P < 0.01), and progressive motility (P < 0.05; P < 0.01) also showed inverse correlations with the logarithmic transformed reactive oxygen species levels. Therefore, this study demonstrated that excessive reactive oxygen species in semen damage sperm concentration, motility, and other sperm motion parameters.

Clinical assessment of the male fertility

The evaluation of infertility in males consists of physical examination and semen analyses. Standardized semen analyses depend on the descriptive analysis of sperm motility, morphology, and concentration, with a threshold level that must be surpassed to be considered a fertile spermatozoon. Nonetheless, these conventional parameters are not satisfactory for clinicians since 25% of infertility cases worldwide remain unexplained. Therefore, newer tests methods have been established to investigate sperm physiology and functions by monitoring characteristics such as motility, capacitation, the acrosome reaction, reactive oxygen species, sperm DNA damage, chromatin structure, zona pellucida binding, and sperm-oocyte fusion. After the introduction of intracytoplasmic sperm injection technique, sperm maturity, morphology, and aneuploidy conditions have gotten more attention for investigating unexplained male infertility. In the present article, recent advancements in research regarding the utilization of male fertility prediction tests and their role and accuracy are reviewed.

Cryopreservation of cynomolgus macaque (Macaca fascicularis) sperm with glycerol and ethylene glycol, and its effect on sperm-specific ion channels - CatSper and Hv1

The cryoprotective agent (CPA) is one of the most important factors that affects the cryosurvival of sperm. The aim of the present study was to compare two different CPAs, glycerol (Gly) and ethylene glycol (EG), on the cryopreservation of cynomolgus macaques sperm and evaluate the effects of cryopreservation on sperm motility, acrosomal integrity, DNA integrity, mitochondrial function and the sperm membrane ion channels CatSper and Hv1. Compared to fresh sperm, cryopreservation with either 0.7 M Gly or EG decreased the sperm motility (79.8 ± 1.5% Vs. 47.3 ± 1.8% and 47.6 ± 1.4%), acrosomal integrity (89.6 ± 1.2% Vs. 80.1 ± 1.8% and 79.6 ± 1.7%), DNA integrity (91.9 ± 0.7% Vs. 82.9 ± 1.0% and 82.3 ± 1.0%) and mitochondrial membrane potential (87.9 ± 1.8% Vs. 70.6 ± 2.7% and 67.9 ± 2.5%) and the quantity of the CatSper and Hv1 channels determined by Western Blot (p < 0.05), and EG showed equal cryoprotection to cynomolgus sperm in all of the sperm parameters. Our results indicated, for the first time, that cryopreservation decreases the quantity of sperm membrane ion channels (CatSper and Hv1), which might be one of the reasons that frozen sperm have a low fertilizing ability. The study will be beneficial to understand the biological process involved in sperm cryopreservation of nonhuman primates and contribute to improving cryopreservation protocols than can maintain sperm function and fertilizing ability.

Unexplained male infertility: diagnosis and management

Unexplained male infertility is a diagnosis reserved for men in whom routine semen analyses results are within normal values and physical as well as endocrine abnormalities were ruled out. In addition to erectile problems and coital factors, immunologic causes and sperm dysfunction may contribute to such condition. New etiologies of unexplained male infertility include low level leukocytospermia and mitochondrial DNA polymerase gene polymorphism. Contemporary andrology may reveal cellular and sub-cellular sperm dysfunctions which may explain subfertility in such cases, thus aiding the clinician to direct the further work-up, diagnosis and counseling of the infertile male. The objective of this article is to highlight the concept of unexplained male infertility and focuses on the diagnosis and treatment of this condition in the era of modern andrology and assisted reproductive techniques. Extensive literature review was performed using the search engines: Pubmed, Science-direct, Ovid and Scopus.

Predictive value of sperm motility characteristics assessed by computer-assisted sperm analysis in intrauterine insemination with superovulation in couples with unexplained infertility

Objective

To determine whether characteristics of sperm motility obtained by computer-assisted sperm analysis (CASA) could predict pregnancy after intrauterine insemination (IUI) in couples with unexplained infertility.

Methods

Three hundred eighty-three cycles of intrauterine insemination with superovulation were retrospectively analyzed. Semen analysis was performed with CASA before and after swim-up and the parameters were compared between pregnant and non-pregnant women.

Results

The pregnancy rate per cycle was 14.1%. Pregnant and non-pregnant women were comparable in terms of age, infertility duration, the number of dominant follicles. While sperm concentration, motility, and parameters such as average path velocity (VAP) and percentage rapid (RAPID) before semen preparation were significantly different between the pregnancy and non-pregnancy groups, there were no differences in sperm parameters when comparing the two groups after preparation. Using a receiver operating characteristic curve to measure sensitivity and specificity, the optimal threshold value for the predictors of pregnancy was revealed to be a concentration of ≥111×10⁶/mL, a motility of ≥51.4%, and RAPID ≥30.1% before preparation for IUI.

Conclusion

Sperm parameters including concentration, motility, and RAPID before sperm preparation could have predictive value for pregnancy outcome after intrauterine insemination with superovulation in couples with unexplained infertility, and would be helpful when counseling patients before they make the decision to proceed with IVF/ICSI-ET.

Computer aided boar semen motility analysis for cereulide detection in different food matrices

Computer Aided Semen Analysis (CASA) study of the boar semen motility has been demonstrated to be an appropriate assay for detection of cereulide (Bacillus cereus emetic toxin). Application of the boar semen bio-assay to detect cereulide directly in foods requires investigation of potential interference of food components, preservatives and other microbial and chemical food contaminants with the bio-assay. Current study provides evidence that none of included Staphylococcus aureus enterotoxins A, B, C and D nor B. cereus Hemolysin BL (HBL) and non-hemolytic enterotoxin (NHE) and three mycotoxins (Sterigmatocystin, Fumonisin B1 and Patulin) exhibited a toxic impact on semen progressive motility. Aflatoxin M1, M3 and zearalenone impaired semen motility only at concentrations (0.004 mg ml(-1), 0.1 mg ml(-1) and 10 mg ml(-1), respectively) much higher than those found in foods and those permitted by legislation, in comparison to cereulide which induces motility cease at concentrations lower than 20 ng ml(-1). Ten commonly used preservatives, namely potassium sorbate, sodium benzoate, (DL) malic acid, citric acid, (L+) tartaric acid, acetic acid, (DL) lactic acid, (L+) ascorbic acid, sodium chloride and sucrose induced no cease in spermatozoa motility even at preservative concentrations higher than permitted by legislation. Dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and acrylamide had no acute effect on spermatozoa motility at concentrations of 500 and 10,000 mg ml(-1), respectively. Robustness of computer aided boar semen motility analysis, tested with 14 different foods inoculated with cereulide producing B. cereus, showed distinct cereulide production in seven samples (although B. cereus growth to counts higher than 8 log CFU g(-1) was noted in 11 samples), in amounts close to those reported in foodborne outbreaks. Test evaluation in 33 samples suspected to hold cereulide showed actual cereulide presence in ten samples and no interference of food matrix with the assay.

Comparative study of Sperm Motility Analysis System and conventional microscopic semen analysis

Background and Aim:  Conventional manual sperm analysis still shows variations in structure, process and outcome although World Health Organization (WHO) guidelines present an appropriate method for sperm analysis. In the present study a new system for sperm analysis, Sperm Motility Analysis System (SMAS), was compared with manual semen analysis based on WHO guidelines. Materials and methods:  Samples from 30 infertility patients and 21 healthy volunteers were subjected to manual microscopic analysis and SMAS analysis, simultaneously. We compared these two methods with respect to sperm concentration and percent motility. Results:  Sperm concentrations obtained by SMAS (Csmas) and manual microscopic analyses on WHO guidelines (Cwho) were strongly correlated (Cwho = 1.325 × Csmas; r = 0.95, P < 0.001). If we excluded subjects with Csmas values >30 × 10⁶ sperm/mL, the results were more similar (Cwho = 1.022 × Csmas; r = 0.81, P < 0.001). Percent motility obtained by SMAS (Msmas) and manual analysis on WHO guidelines (Mwho) were strongly correlated (Mwho = 1.214 × Msmas; r = 0.89, P < 0.001). Conclusions:  The data indicate that the results of SMAS and those of manual microscopic sperm analyses based on WHO guidelines are strongly correlated. SMAS is therefore a promising system for sperm analysis. (Reprod Med Biol 2006; 5: 195-200).

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.

Intrauterine insemination: is it an effective treatment for male factor infertility?

Results were collected from 11 studies comparing intrauterine insemination (IUI) with intracervical insemination (ICI) of frozen donor semen, 10 studies comparing IUI with timed natural intercourse (NI) or ICI in couples with semen defects and seven studies comparing ICI with NI or ICI in couples with unexplained infertility. IUI significantly increased the pregnancy rate relative to favourably timed ICI in donor insemination (DI) with frozen semen both with and without gonadotrophin stimulation of the female partner (odds ratios (95% confidence interval) 1.92 (1.02-3.61) and 2.63 (1.52-4.54) respectively). The benefit of IUI tended to be less when the pregnancy rate for ICI was high and IUI had no benefit with fresh donor semen. Overall IUI was of significant benefit in the male factor couples compared with NI-ICI (odds ratio 2.20 (1.43-3.39) and the advantage appeared to be maintained when comparison was confined to properly timed ICI although the odds ratios were not significantly greater than 1. IUI had no benefit relative to favourably timed NI-ICI for couples with unexplained infertility; an apparent advantage overall was produced by studies where NI was late. None of the studies on male factor used a sperm function test to define male subfertility and three only included couples with good mucus penetration by sperm. The range of semen defects defined was such that many couples would have had a good chance of conceiving naturally given a normal female partner but nevertheless the overall pregnancy rate (4.8%) was considerably less than in the unexplained group (11.6%), suggesting that some sperm dysfunction was present. We conclude that the available evidence suggests that IUI is valuable for DI with cryopreserved semen and for couples with mild to moderately impaired semen quality and postulate that it overcomes failure to fertilize due to impaired mucus penetration and poor survival in the female reproductive tract.

Prognostic value of objective semen parameters in an in vitro fertilization program

PURPOSE

The basic semen parameters seem to have a limited predictive value in male fertility. Could other objective sperm analyses be helpful in the choice of the most adapted assisted procreation technique?

METHODS

This study concerns 78 infertile couples with insemination failures. For each semen, 21 objective parameters are analyzed in fresh semen and after sperm selection procedure. The 78 couples are then included in an IVF protocol and classified into two groups: fertile (at least one cleaved embryo is obtained) and infertile.

RESULTS

Using multiple variant discriminant factorial analysis, we have found nine nonconventional parameters which induce us to define two classes of semen. These two classes fit with the classification into fertile and infertile groups in 74.4% of the cases.

CONCLUSIONS

So these parameters allow us to predict the chance of obtaining embryos during an IVF trial and to choose for each couple the most appropriate technique: IVF or ICSI.

Identifying environmental risk to male reproductive function by occupational sperm studies: logistics and design options

Malfunction of the male reproductive system might be a sensitive marker of environmental hazards, the effects of which may extend beyond reproductive function. The testis is more vulnerable to heat and ionising radiation than any other organ of the body and several xenobiotics are known to disrupt spermatogenesis after low level exposure. Studies of environmental impact on human health are often most informative and accurate when carried out in the workplace where exposures can be high and easy to document. Semen analysis provides readily obtainable information on testicular function. The main advantages in comparison with functional measures such as fertility rates and time taken to conceive are the possibilities to examine men independently of marriage and pregnancy, to find changes of fecundity with different exposures within the same person and to detect adverse effects when no alteration of fertility is yet taking place. In the implementation of an occupational sperm study considerable attention must be paid to logistic issues. A mobile laboratory unit for initial semen preparation and processing may in some situations increase worker compliance and the quality of sperm cell motility. The cross sectional design which has been used in almost all male reproductive studies so far has several severe limitations including selection bias because of differential participation, difficulties in defining a suitable reference group, and lack of information about the time dimension of the cause-effect relation. The longitudinal design deals adequately with most of these constraints. Semen samples are collected before, during, and possibly after exposure to the risk factor of interest and causal inferences are based upon change of semen variables within a man over time rather than upon differences between men. The logistics of the longitudinal study may benefit from pre-employment health examinations to enrol newly hired workers and require fewer participants to obtain comparable statistical power. In conclusion, andrological methods and epidemiological designs are available for the implementation of valid studies concerned with environmental impact on human testicular function. Occupational sperm studies should probably not be the first choice when the objective is initial screening of environmental impact on fertility but should be implemented when their is a need to corroborate or refuse earlier evidence that specific exposures have impact on testicular function.