The relationship between human semen characteristics and sperm apoptosis: a pilot study

The Use of Non-Apoptotic Sperm Selected by Magnetic Activated Cell Sorting (MACS) to Enhance Reproductive Outcomes: What the Evidence Says

Sperm selection of the most competent sperm is a promising way to enhance reproductive outcomes. Apoptosis is the programmed cell death process to maintain tissue homeostasis, and MACS sperm selection of non-apoptotic cells enables the removal of apoptotic sperm from an ejaculate, thus leaving the non-apoptotic available to be microinjected, but given the associated costs of adding these sperm selection steps to the routine practice, there is a need for a careful examination of the literature available to answer questions such as who can benefit from this MACS, how significant this improvement is, and how robust the evidence and data available supporting this choice are. Thus, the aim of this narrative review was to objectively evaluate the available evidence regarding the potential benefits of the use of MACS. From the literature, there are controversial results since its implementation as an in vitro fertilization add-on, and this may be explained in part by the low quality of the evidence available, wrong designs, or even inadequate statistical analyses. We concluded that the benefits of adding MACS are unclear, and further methodologically sound research on specific populations is much needed before offering it clinically.

Analyzing the Differential Impact of Semen Preparation Methods on the Outcomes of Assisted Reproductive Techniques

Sperm separation plays a critical role in assisted reproductive technology. Based on migration, density gradient centrifugation and filtration, a properly selected sperm could help in increasing assisted reproductive outcomes in teratozoospermia (TZs). The current study aimed to assess the prognostic value of four sperm selection techniques: density gradient centrifugation (DGC), swim-up (SU), DGC-SU and DGC followed by magnetic-activated cell sorting (DGC-MACS). These were evaluated using spermatozoa functional parameters. A total of 385 infertile couples underwent the procedure of intracytoplasmic sperm injection (ICSI), with an isolated teratozoospermia in the male partner. Semen samples were prepared by using one of the mentioned sperm preparation techniques. The improvements in the percentage of normal mature spermatozoa, rate of fertilization, cleavage, pregnancy and the number of live births were assessed. The normal morphology, spermatozoa DNA fragmentation (SDF) and chromatin maturity checked by using chromomycin A3 (CMA3) with DGC-MACS preparation were better compared to the other three methods. Embryo cleavage, clinical pregnancy and implantation were better improved in the DGC-MACS than in the other tested techniques. The DGC-MACS technique helped in the selection of an increased percentage of normal viable and mature sperm with intact chromatin integrity in patients with teratozoospermia.

Effects of sperm processing techniques on IVF pregnancy rates: a mini-review

Many factors associated with assisted reproductive technologies significantly influence the success of pregnancy after in vitro fertilization (IVF) either directly or indirectly. These factors include sperm processing techniques, egg retrieval, intrauterine artificial insemination, intracytoplasmic sperm injection, and embryo transfer. Among these technologies, sperm quality is one of the most critical factors for a successful IVF pregnancy. The method used for sperm processing plays a crucial role in determining the quality of sperm. Several widely used sorting techniques, such as conventional swim-up, density gradient centrifugation, magnetic activated cell sorting, and hyaluronic acid, have been extensively compared in various studies. Previous studies have shown that each sperm processing method causes varying degrees of sperm damage, particularly in sperm motility, concentration, morphological features, viability, and DNA integrity. However, sperm processing techniques have been developed slowly, and the impact of these methods on pregnancy rates is still unclear. Further exploration is needed. In this review, we aim to compare the results of different sperm processing techniques concerning sperm quality and IVF pregnancy rates. We will also discuss possible clinical approaches, such as microfluidics and integrated approaches, for testing and improving sperm quality.

The Association of Certain Seminal Phthalate Metabolites on Spermatozoa Apoptosis: An Exploratory Mediation Analysis via Sperm Protamine

Earlier studies have suggested that exposure to phthalates (PAEs) may induce spermatozoa apoptosis. Sperm protamine as a molecular biomarker during spermatozoa apoptotic processes may mediate the association between PAE exposure and spermatozoa apoptosis. This study aimed to explore whether sperm protamine mediates the association of PAE exposure with spermatozoa apoptosis. We determined sperm protamine levels, 8 PAE metabolite concentrations in seminal plasma, and 3 spermatozoa apoptosis parameters among 111 men from an infertility clinic. The associations of PAEs as individual chemicals and mixtures with sperm protamine were determined. The mediating roles of protamine in the associations between PAEs and spermatozoa apoptosis parameters were examined by mediation analysis. After adjusting for confounders, we observed positive correlations between seminal plasma concentrations of mono(2-ethylhexyl) phthalate (MEHP) and sperm protamine-1 and protamine ratio. Estimates comparing highest vs. lowest quartiles of MEHP concentration were 4.65% (95% CI: 1.47%, 7.82%) for protamine-1 and 25.86% (95% CI: 3.05%, 53.73%) for protamine ratio. The quantile g-computation models showed that the adjusted protamine-1 per quartile increase in PAE mixture was 9.42% (95% CI: 1.00, 20.92) with MEHP being the major contributor. Although the joint association between PAE mixture and protamine ratio was negligible, MEHP was still identified as the main contributor. Furthermore, we found that protamine-2 and protamine ratio levels in the highest quartiles exhibited a decrease of 43.45% (95% CI: 60.54%, -19.75%) and an increase of 122.55% (95% CI: 60.00%, 209.57%) in Annexin V⁺/PI^- spermatozoa relative to the lowest quartiles, respectively. Mediation analysis revealed that protamine ratio significantly mediated 55.6% of the association between MEHP and Annexin V⁺/PI^- spermatozoa elevation (5.13%; 95% CI: 0.04%, 10.52%). Our findings provided evidence that human exposure to PAEs was associated with increased protamine levels which may mediate the process of spermatozoa apoptosis.

Cumulative live birth rates in donor oocyte ICSI cycles are not improved by magnetic-activated cell sorting sperm selection

RESEARCH QUESTION

Does magnetic-activated cell sorting (MACS) for sperm selection increase cumulative live birth rates (CLBR) or improve clinical parameters of reproductive success in couples undergoing intracytoplasmic sperm injection (ICSI) with donor oocytes?

DESIGN

Retrospective multicentre observational study including data compiled from unselected couples who underwent ICSI cycles with donated oocytes in 15 Spanish IVIRMA fertility clinics (January 2008 to February 2020). Patients were divided into reference (standard semen processing, n = 40,157) and MACS (additional sperm selection step by MACS, n = 1,240) groups. CLBR were plotted on Kaplan-Meier curves and compared using the Mantel-Cox test. Proportions were compared with a generalized estimating equation model, and results were adjusted to clinically relevant variables.

RESULTS

The MACS group showed a 27.1% CLBR after one embryo was transferred and 81.6% after four; the reference group had CLBR of 19.6% and 78.5%, respectively. CLBR in the MACS group was 4.2% after five oocytes were used and 75.5% after 15; for the reference group, CLBR were 7.8% and 78.3%, respectively. Kaplan-Meier curves showed statistically significant differences in CLBR per number of embryos transferred and per number of donated metaphase II oocytes between the two groups (both P < 0.0001), but not for CLBR per embryo transfer. No significant differences between groups were found for classical clinical outcomes such as pregnancy and live birth rates per embryo transfer.

CONCLUSIONS

Although MACS sperm selection slightly increased the CLBR per embryo transferred compared with the reference group, this change was not clinically meaningful. MACS should not be recommended indiscriminately to all infertile patients undergoing ICSI with donated oocytes as a sperm processing add-on.

Attenuation of aquaporin-3 may be contributing to low sperm motility and is associated with activated caspase-3 in asthenozoospermic individuals

Aquaporins play a crucial in transportation of water and solutes across cell membranes but their roles in male fertility are controversial. This study aimed to determine association of the expression level of aquaporin-3 (AQP3) and caspase-3 (CASP3) activity with sperm motility in asthenozoospermic individuals. Thirty-five asthenozoospermic and 35 normozoospermic individuals, participated in this study. Sperm chromatin structure assay (SCSA) for estimating of the DNA-damaged spermatozoa and Fluorescein-labelled inhibitors of caspases for assessment of active CASP3 were used by flow cytometry. Gene and protein expressions of AQP3 and CASP3 were assessed by real-time PCR and flow cytometry respectively. The AQP3 gene expression level in asthenozoospermic individuals was significantly lower than that of normozoospermic group whereas it was higher for the CASP3 gene expression (p < .01). The SCSA data in asthenozoospermic was significantly higher than that of normozoospermic group (p < .01). There was a negative and significant correlation between attenuated AQP3 protein level with activated CASP3 and SCSA in the asthenozoospermic group. We showed that the attenuated AQP3 level may contribute to low sperm motility via reducing glycerol for energy production in sperm tails of asthenozoospermia. Increasing CASP3 activity could indirectly show the status of active apoptosis in individuals with asthenozoospermia.

Sperm Selection by Magnetic-Activated Cell Sorting before Microinjection of Autologous Oocytes Increases Cumulative Live Birth Rates with Limited Clinical Impact: A Retrospective Study in Unselected Males

Simple Summary

Many couples attending infertility clinics still need to repeat treatments and undergo several failed attempts before achieving a healthy newborn, which leaves room for improvement in the techniques we currently use in the clinic. Among the different procedures susceptible to improvement, the selection of the most adequate sperm to be injected inside the egg is crucial to the cycle’s success. Magnetic-activated cell sorting (MACS) is a technique that removes physiologically abnormal sperm that have started a programmed cell death (apoptotic) process from a semen sample. However, it is not recommended to all patients because there is no agreement between the published literature on whether it improves reproductive outcomes. This study used data from all intracytoplasmic sperm injection cycles performed using the patient’s own oocytes in our clinics from January 2008 to February 2020. Our findings support that MACS should not be recommended to all infertile couples, since there was no significant difference in results compared to treatments in which MACS was not used. This study provides clinicians and patients with more accurate information on how MACS will impact their chances of pregnancy, and it will lead to studies focused on specific populations to which the technique can be particularly helpful.

Abstract

The application of MACS non-apoptotic sperm selection in infertility clinics is controversial since the published literature does not agree on its effect on reproductive outcomes. Therefore, it is not part of the routine clinical practice. Classical measures of reproductive success (pregnancy or live birth rates per ovarian stimulation) introduce a bias in the evaluation of a technique’s effect, since only the best embryo is transferred. This retrospective, multicenter, observational study evaluated the impact of MACS on reproductive outcomes, measuring results in classical parameters and cumulative live birth rates (CLBR). Data from ICSI cycles using autologous oocyte in Spanish IVIRMA fertility clinics from January 2008 to February 2020 were divided into two groups according to their semen processing: standard practice (reference: 46,807 patients) versus an added MACS sperm selection (1779 patients). Only when measured as CLBR per embryo transferred and per MII oocyte used was the difference between groups statistically significant. There were no significant differences between MACS and reference groups on pregnancy and live birth rates. In conclusion, results suggest that non-apoptotic sperm selection by MACS on unselected males prior to ICSI with autologous oocytes has limited clinical impact, showing a subtle increase in CLBR per embryo transferred.

Spermatogonia apoptosis induction as a possible mechanism of Toxoplasma gondii-induced male infertility

Objective(s):

The protozoan Toxoplasma gondii as an intracellular protozoan is widely prevalent in humans and animals. Infection generally occurs through consuming food contaminated with oocysts and tissue cysts from undercooked meat. The parasite is carried in sexual fluids like semen but there is little information about the effect of T. gondii on the male reproductive system. In this study, we examined the effect of T. gondii tachyzoites on apoptosis induction in type B spermatogonia (GC-1) cells.

Materials and Methods:

Fresh tachyzoites taken of infected BALB/c mice, GC-1 spg cells were infected with increasing concentrations of tachyzoites of T. gondii, then apoptotic cells were identified and quantified by flow cytometry. The genes associated with apoptosis were evaluated by RT2 Profiler PCR Array.

Results:

PCR array analysis of 84 apoptosis-related genes demonstrated that 12 genes were up-regulated at least 4-fold and that one gene was down-regulated at least 2-fold in the T. gondii infection group compared with levels in the control group. The number of genes whose expression had increased during the period of infection with T. gondii was significantly higher than those whose expressions had decreased (18 versus 1) and Tnfrsf11b had the highest rate of gene expression.

Conclusion:

T. gondii induce in vitro apoptosis of GC-1 spg cells. This effect shows a trend of concentration-dependent increase so that with an increase in the ratio of parasite burden to spermatogonial cells, in addition to an increase in the number of genes whose expression has changed, the fold of these changes has increased as well.

CASA-Mot in mammals: an update

Sperm motility is one of the most widely used parameters of sperm quality. Computer-aided sperm motility analysis (CASA-Mot) systems were developed to reduce the subjectivity of sperm motility assessment, and have had broad scientific and practical acceptance. In this review, the sources of variation and current applications of this technology and its relationships with other sperm quality tests are described in detail. Despite remarkable advances in the technique, there is still great need for standardisation in many species, and the numerous factors that affect the results make it difficult to provide universally accepted criteria for classifying semen samples based on sperm motility characteristics. The main fields for CASA-Mot include the study of male fertility and pathologies, evaluation of the effects of physical and chemical agents, improvement of epidemiological survey studies, more precise calculation of seminal doses for farm animals, realisation of basic studies about sperm function, improvement of sperm technologies such as cryopreservation and quality control analysis. Numerous relationships have been established between CASA-Mot and other sperm quality tests, although most of these parameters are complementary. Future CASA-Mot systems will probably be able to integrate several sperm quality parameters with motility.

Relationship between nuclear DNA fragmentation, mitochondrial DNA damage and standard sperm parameters in spermatozoa of fertile and sub-fertile men before and after freeze-thawing procedure

The aim of this study was to assess the stability of nuclear and mitochondrial DNA (n-DNA and mt-DNA) of spermatozoa under freeze-thawing and to find out the correlation between them and their association with standard sperm parameters. Forty-three semen samples were collected from fertile (G.1; n = 29) and sub-fertile (G.2; n = 14). N-DNA fragmentation was determined by TUNEL assay and mt-DNA using caspase 3 staining. Each semen sample was frozen at -196°C by the programmed freezer. Freeze-thawing decrease vitality, total motility and membrane integrity from (43.02 ± 22.74%; 31.63 ± 18.15%; 51.5 ± 24.82%) to (22.71 ± 17.3%; 9.21 ± 6.61%; 34.64 ± 19.92% respectively [p < .001]). G.1 native spermatozoa stained positive with TUNEL and caspase 3 were (14.85 ± 17.6% and 5.8 ± 11.59%) and increased after freeze-thawing to 27.54 ± 19.74% (p = .004) and 7.3 ± 6.13% (p = .01) respectively. In G.2, TUNEL and caspase 3 were (19.84 ± 17.52% and 7.53 ± 8.56%) and increased to (29.48 ± 16.97% [p = .03] and 10.21 ± 11.73%). In conclusion, freeze-thawing process affects not only semen parameters but also n-DNA and mt-DNA. Therefore, n-DNA and mt-DNA could be used as sensitive parameters for assessment of the cryodamage of human spermatozoa.

Urinary metabolites of polycyclic aromatic hydrocarbons, sperm DNA damage and spermatozoa apoptosis

Inconsistent results between polycyclic aromatic hydrocarbons (PAHs) exposure and adverse male reproductive health have been reported in humans. To assess whether PAH exposure is associated with declined sperm function. Ten monohydroxylated PAHs (OH-PAHs) metabolites were analyzed in repeated urine samples from an infertility clinic. We used multivariable linear models to estimate the associations of urinary OH-PAH metabolites with sperm DNA damage (n=405) and spermatozoa apoptosis (n=366). The shapes of dose-dependent associations of exposure measurements with outcomes were further evaluated by restricted cubic splines. Multiple comparisons were adjusted by false discovery rate (FDR). We found that urinary 9-hydroxyfluorene (9-OHFlu) was associated with increased tail length and comet length (p for trend=0.05 and 0.01, respectively), and that urinary 9-hydroxyphenanthrene (9-OHPh) was associated with decreased percentage of Annexin V^-/PI^- spermatozoa (p for trend=0.04). Also, suggestive associations of urinary 9-OHPh and ∑OHFlu with increased comet length, and urinary 9-OHFlu and 2-OHPh with decreased percentage of Annexin V^-/PI^- spermatozoa were observed (all p for trends <0.10). Further, these dose-dependent associations were confirmed in restricted cubic splines. Our results suggest that environmental exposure to fluorene and phenanthrene are associated with declined sperm function.

Efficient isolation of sperm with high DNA integrity and stable chromatin packaging by a combination of density-gradient centrifugation and magnetic-activated cell sorting

OBJECTIVE

This study was carried out to investigate the correlations of the sperm DNA fragmentation index (DFI) with semen parameters and apoptosis, and to investigate the effects of density-gradient centrifugation (DGC) and magnetic-activated cell sorting (MACS) on reducing the proportion of sperm with DNA fragmentation and protamine deficiency.

METHODS

Semen analysis and a sperm DNA fragmentation assay were performed to assess the correlations between semen parameters and the DFI in 458 semen samples. Sperm with progressive motility or non-apoptosis were isolated by DGC or MACS, respectively, in 29 normozoospermic semen samples. The effects of DGC or MACS alone and of DGC and MACS combined on reducing the amount of sperm in the sample with DNA fragmentation and protamine deficiency were investigated.

RESULTS

The sperm DFI showed a significant correlation (r=-0.347, p<0.001) with sperm motility and morphology (r=-0.114, p<0.05) but not with other semen parameters. The DFI (11.5%±2.0%) of semen samples was significantly reduced by DGC (8.1%±4.1%) or MACS alone (7.4%±3.9%) (p<0.05). The DFI was significantly further reduced by a combination of DGC and MACS (4.1%±1.3%, p<0.05). Moreover, the combination of DGC and MACS (1.6%±1.1%, p<0.05) significantly reduced the protamine deficiency rate of semen samples compared to DGC (4.4%±3.2%) or MACS alone (3.4%±2.2%).

CONCLUSION

The combination of DGC and MACS may be an effective method to isolate high-quality sperm with progressive motility, non-apoptosis, high DNA integrity, and low protamine deficiency in clinical use.

Quality of fresh and chilled-stored raccoon dog semen and its impact on artificial insemination efficiency

Background

The aim of the study was to evaluate the quality of fresh raccoon dog semen and raccoon dog semen stored at 4 °C. The qualitative evaluation was based on apoptosis in the sperm cells, which was tested by the Annexin V/Pi assay, the TUNEL method and JC-1. In addition, the suitability of the semen for insemination and its effect on reproduction in females were determined in relation to the time of storage.

Results

During cold storage of the semen, in the samples from all groups a gradual decrease was noted in the percentage of live cells, and an increase in the percentage of cells with abnormal morphology, exhibiting changes typical of late-stage apoptosis (V⁺/PI⁺), and of necrotic cells (V⁻/PI⁺). There was a significant increase in the percentage of ApoBrDu + sperm cells, while the mitochondrial membrane potential of the sperm decreased significantly after 12 h of storage at 4 °C in the case of lower-quality semen and after 48 h in the case of semen of good quality. As the percentage of sperm with DNA and cell membrane damage increased and the mitochondrial membrane potential decreased, there was an increase in AspAT and acrosin activity. The increase in the percentage of apoptotic sperm in the raccoon dog semen stored at 4 °C resulted in a decrease in the number of females with cubs.

Conclusions

Identification of apoptotic changes in sperm by flow cytometry using the annexin assay, the TUNEL assay and evaluation of mitochondrial membrane potential can be recommended for determination of the suitability of raccoon dog semen for artificial insemination. The study shows that fresh raccoon dog semen should not be used for insemination more than 48 h after collection in the case of semen of very high quality, or after more than 24 h in the case of semen of poorer quality. Cytometric methods of semen analysis should also be used to evaluate various extenders of raccoon dog semen and methods of cryopreservation in terms of ensuring sperm viability, fertilization capacity, and suitability for insemination.

The Protective Effects of Melatonin Against Oxidative Stress and Inflammation Induced by Acute Cadmium Exposure in Mice Testis

Cadmium (Cd) is widely used in daily life and was recently recognized as a possible source of human toxicity due to its ability to accumulate in organs. Previous studies have shown that Cd exposure may cause testicular toxicity through oxidative stress and an inflammatory effect. Melatonin has been demonstrated to be an effective anti-oxidant and has an anti-inflammatory effect. The aim of the present study was to investigate the toxicological effects of Cd on reproduction in male mice and the potential protective action of melatonin against these adverse effects. Adult male mice were injected intraperitoneally with Cd at a dose of 2 mg/kg body weight per day for seven consecutive days with or without melatonin pretreatment. Sex organ weight, sperm parameters including sperm quality, apoptosis, acrosome integrity, mitochondrial membrane potential, testicular morphology, serum sex hormone, inflammatory status, and oxidative stress were evaluated. The results showed that significant adverse effects were observed in the male reproductive system after Cd exposure, including alterations in sperm parameters, increased DNA damage, and sex hormone disturbance. Acute Cd exposure also significantly increased malondialdehyde (MDA) contents, decreased glutathione (GSH) and superoxide dismutase (SOD) activities, and upregulated levels of the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-α), and interleukin-1beta (IL-1β), in the testis. In contrast, melatonin pretreatment significantly alleviated these toxic effects, and its mechanism may involve inhibiting MDA level, restoring GSH and SOD activities, and reducing the upregulation of TNF-α and IL-1β. Our data suggest that oxidative stress and inflammation are involved in Cd-induced toxicity in the male reproductive system and that co-administration of melatonin exerts a protective effect against Cd-induced male reproductive toxicity.

Magnetic activated cell sorting: an effective method for reduction of sperm DNA fragmentation in varicocele men prior to assisted reproductive techniques

Semen parameters of varicocele men have been usually suspected to exhibit higher levels of abnormalities including DNA fragmentation, reactive oxygen species (ROS) and apoptotic markers. Negative correlation between increased level of DNA fragmentation and assisted reproductive techniques (ART) outcome has been studied by several authors. In the current study, we aim to evaluate the possible value of magnetic activated cell sorting (MACs) technology in reduction of DNA fragmentation in infertile varicocele patients prior to ART. Semen samples, collected from 36 varicocele patients, were prepared by density gradient centrifugation (DGC). Every sample was subsequently divided into two aliquots. One aliquot was kept untouched as pre-MACs control while the other aliquot was subjected to MACs technique, for depletion of apoptotic spermatozoa, and serves as post-MACs test. Sperm count, motility and DNA fragmentations were evaluated for both control and test samples. Post-MACs samples showed no deleterious reduction in total sperm motility (80.64 ± 6.97%) compared with control samples (80.97 ± 7.74%) while sperm DNA fragmentations were significantly reduced in post-MACs samples (9.61 ± 5.62%) compared with pre-MACs controls (12.43 ± 6.29%) (P < 0.05). It can be concluded that MACs technique is a simple, noninvasive, technique that can efficiently reduce DNA fragmentation in infertile varicocele patients prior to ART.

The effects of honey and vitamin E administration on apoptosis in testes of rat exposed to noise stress

AIMS:

A variety of stress factors are known to inhibit male reproductive functions. So this study was conducted in order to investigate the effects of honey and vitamin E on the germinative and somatic cells of testes of rats exposed to noise stress.

MATERIALS AND METHODS:

Mature male wistar rats (n = 24) were randomly grouped as follows: Group 1 (honey + noise stress), 2 (vitamin E + noise stress), 3 (noise stress,) and 4 as the control group. In groups 1, 2, and 3, rats were exposed to noise stress. In groups 1 and 2, rats also were given honey and vitamin E, respectively, orally for 50 days. After that, the germinative and somatic cells of testes parenchyma were isolated by digesting the whole testes by a standard method. Next, viability, apoptosis, and necrosis of the cells were evaluated by TUNEL kit and flow cytometry.

RESULTS:

The rates of apoptosis and necrosis of the testicular cells were increased (P = 0.003 and P = 0.001, respectively), but viability of these cells decreased in testes of rats exposed to noise stress (P = 0.003). However, administration of honey and vitamin E were significantly helpful in keeping the cells of testis parenchyma alive, which suffers from noise pollution (P < 0.05 and P < 0.05, respectively).

CONCLUSIONS:

Noise stress has negative influences on the cells of testicular tissue by increasing apoptotic and necrotic cells. However, the associated enhancement in healthy cells suggests that honey and vitamin E have positive influences on the testis parenchyma.

Quality of human spermatozoa: relationship between high-magnification sperm morphology and DNA integrity

The aim of this work is to establish the relationship between the morphology of Intracytoplasmic Morphologically Selected Sperm Injection (IMSI)-selected spermatozoa and their DNA integrity. The 45 ejaculates were randomly distributed into three treatment groups: normozoospermic, oligoasthenozoospermic and oligoasthenotheratozoospermic samples. The evaluation of DNA integrity was performed using the sperm chromatin dispersion test. It was established that DNA integrity of spermatozoa is strongly dependent on ejaculate quality (P < 0.05). The count of spermatozoa with nonfragmented DNA in normozoospermic samples was high and independent from IMSI-morphological classes (Class 1 versus Class 3, respectively) (P > 0.1). With decreased ejaculate quality, the percentage of spermatozoa with nonfragmented DNA decreased significantly (P < 0.05) independent from morphological class. Nevertheless, the rate of IMSI-selected spermatozoa with fragmented DNA within of Class 1 in normozoospermic (Group 1), in oligoasthenozoospermic (Group 2) and in oligoasthenotheratozoospermic (Group 3) samples was 21.1%, 31.8% and 54.1%, respectively. In conclusion, there is a direct relationship between morphological parameters of spermatozoa and their DNA integrity. However, the IMSI technique alone is not enough for the selection of spermatozoa with intact nuclei.

Effects of reduced seminal enzymatic antioxidants on sperm DNA fragmentation and semen quality of Tunisian infertile men

PURPOSE

To evaluate levels of sperm DNA fragmentation and enzymatic antioxidant status in seminal plasma of Tunisian fertile and infertile men in order to assess the effects of seminal oxidative stress on sperm DNA integrity and semen quality.

METHODS

Semen samples from 100 infertile patients (40 oligoasthenoteratozoospermics, 31 teratozoospermics and 29 asthenozoospermics) and 50 fertile men (controls) were analyzed for DNA fragmentation by TUNEL assay and biochemical parameters. Seminal antioxidant activities (Superoxide dismutase, Glutathione peroxidase and Catalase) and malondialdehyde concentrations were measured spectrophotometrically.

RESULTS

Sperm DNA fragmentation and malondialdehyde levels in infertile groups were more elevated than controls. Nevertheless, the activities of the antioxidant enzymes were significantly lower in abnormal groups compared to normozoospermics. Sperm DNA fragmentation was closely and positively correlated to malondialdehyde levels (r = 0.37, P = 0.008); meanwhile, reduced seminal antioxidant profile was negatively associated to sperm DNA fragmentation. Interestingly, we noted also that sperm DNA fragmentation was negatively correlated to sperm motility (r = -0.54, P < 0.001) and positively associated to the abnormal sperm morphology (r = 0.57, P = 0.002).

CONCLUSIONS

This report revealed that increased sperm DNA fragmentation can be due to the impaired seminal enzymatic antioxidant profile and increased Lipid peroxidation. Our results sustain that the evaluation of sperm DNA fragmentation and seminal oxidative biomarkers in infertile men is recommended as a consistent prognostic tool for male infertility assessment.

A sequential methodology that allows apoptotic cell sorting and FISH analysis in human testicular cells

The objective of this study was to develop a methodology that permits the detection and separation of apoptotic cells in human testicular tissue and their subsequent cytogenetic analysis by fluorescence in situ hybridization (FISH). The sequential methodology consisted of five steps: 1) enzymatic disaggregation of testicular tissue, 2) specific staining of apoptotic cells, 3) cell sorting by flow cytometry, 4) cell fixation, and 5) FISH. Enzymatic disaggregation yielded cell counts that ranged from 1.7x10(5) to 5x10(6) cells, and viability values greater than 72%. The apoptotic (mean ± SD: 22% ± 5.3%) and viable (45.5% ± 7.3%) populations were identified and selected by flow cytometry and demonstrated purity values ranging between 62% and 100%. The paraformaldehyde fixation of the selected fractions resulted in cell loss values of less than 10%. The application of three treatments before FISH (membrane permeabilization, elimination of cytoplasmic components, and re-fixation of the sample) resulted in hybridization frequencies of greater than 98%. In both selected fractions, cells of all spermatogenic stages and Sertoli cells were identified. The methodology developed has enabled the preparation of a cellular suspension with optimal viability and counting, the efficient selection of the apoptotic population, and its analysis by cytogenetic techniques. The application of this methodology in testicular cells should help establish whether there is a direct relationship between chromosome anomalies and apoptosis.

Relationship Between Apoptotic-Like Changes in Stored Boar Semen and DNA Fragmentation in Preimplantation Embryos

The aim of this experiment was to study the relationship between apoptotic-like changes in spermatozoa and DNA fragmentation in embryos obtained after insemination with fresh and stored semen. The ejaculates collected from three boars (five ejaculates from the same boar) were extended in Biosolwens Plus extender and stored for five days at 15-17°C. Semen, both fresh (Day 0) and stored (Day 5) used for insemination was analysed to detect apoptotic-like changes using fluorescence method: an assay to assess early changes in the membrane integrity of the sperm using the YO-PRO-1 fluorophore. After 5.5 days of insemination embryos were flushed out of the uterus and DNA fragmentation using TUNEL was analysed. In the fresh semen an average of 2.7, 3.7 and 6.2% of apoptotic sperm was observed in boar nos. 1, 2 and 3, respectively. After five days of storage the percentage of apoptotic sperm significantly increased up to 8.0, 15.7 and 23.2% in each analysed boar. The TUNEL index was 7.1% in the morphologically normal expanded blastocysts obtained after insemination with stored semen, and approximately 1.7% after insemination with fresh semen. A greater number of degenerated embryos and higher incidence of DNA fragmentation in the morphologically normal blastocysts were observed after insemination with stored semen which consists of higher percentage of apoptotic sperm compared to results from insemination with fresh semen.

Phosphatidylserine membrane translocation in human spermatozoa: topography in membrane domains and relation to cell vitality

The complex structure of the human spermatozoa membrane comprises five topographic domains. Transmembrane asymmetry of the distribution of phospholipids including phosphatidylserine (PS) is considered a marker of cell activity. The objective of the study was to determine which cytomembrane domains of human spermatozoa are involved in PS membrane translocation and to identify the possible relationship of PS translocation with spermatozoa morphology and vitality. In normozoospermic semen of 35 donors, annexin-V labeling with fluorescein determined PS translocation. Propidium iodide staining distinguished between vital and dead spermatozoa. Three types of PS membrane translocation have been distinguished: (1) in the midpiece, (2) in the acrosomal part and (3) simultaneously in the midpiece and acrosomal part. In morphologically normal vital spermatozoa, PS translocation occurred in the midpiece but never in the equatorial region. In dead spermatozoa, simultaneous PS translocation in the midpiece and acrosomal part was most often observed. The difference between proportions of, respectively, vital and dead spermatozoa presenting PS translocation located in different domains was significant (P < 0.0001). In vital cells, there was no difference in PS translocation prevalence between morphologically normal and abnormal spermatozoa (P > 0.05). The strict relation of PS translocation to specific membrane domains indicates functional specificity. It seems doubtful to include this phenomenon in physiological mechanisms of elimination of abnormal spermatozoa.

Apoptotic-like changes in the spermatozoa of fresh and stored boar semen and the quality of embryos produced in vivo

The aim of this study was to determine the apoptotic-like changes in the spermatozoa of fresh and stored boar semen and to investigate the relationship between this phenomenon and the quality of embryos produced in vivo. The experiments were divided into two series. In the first series, ten ejaculates were collected from five boars, which were crossbreeds of the Polish Landrace and Large White breeds. The semen was stored as a liquid until Day A (the day on which sperm motility decreased to 30%). Three fluorescence methods were used to evaluate semen quality: an assay to assess the early changes in sperm membrane integrity using the fluorophore YO-PRO-1, an assay for phosphatidylserine (PS) translocation across the plasma membrane using fluorescein-labeled annexin-V and the mitochondrial-specific probe JC-1 (5,5',6,6'-tetrachloro-1,1',3,3' tetraethylbenzimidazolylcarbocyanine iodide) for measuring changes in mitochondrial membrane potential. Our results showed that liquid preservation of boar semen causes apoptotic-like changes in the sperm, and a significant increase in both: apoptotic sperm (YO-PRO-1(+)/PI(-)) and early apoptotic sperm (annexin-V(+)/PI(-)) were observed between Day 0 (fresh semen) and Day A only in semen from three of the five boars. In the second series of experiments, the semen from boar nos. 1, 2, and 3 was selected for insemination of superovulated gilts. The fertilizing capacity of fresh and stored semen with different levels of apoptotic spermatozoa was measured based on the morphology and the number of cells of embryos that were obtained after insemination with this semen. Our studies indicated no significant differences in the fertilization rate of gilts after insemination with fresh and stored semen with increased levels of apoptotic spermatozoa. After insemination with stored semen, a significantly greater number of degenerated embryos were observed, but the morphologically normal blastocysts obtained after insemination with either fresh or stored semen had a similar number of nuclei.

Implication of apoptosis in sperm cryoinjury

Apoptosis is an ongoing physiological phenomenon that has been documented to play a role in male infertility, if deregulated. Caspase activation, externalization of phosphatidylserine, alteration of mitochondrial membrane potential and DNA fragmentation are markers of apoptosis found in ejaculated human spermatozoa. These markers appear in excess in subfertile men and functionally incompetent spermatozoa. Sperm cryopreservation is a widely used procedure in the context of assisted reproductive techniques. Cryopreservation and thawing is a procedure that inflicts irreversible injury on human spermatozoa. The damage is manifested by a decrease in recovery of viable spermatozoa with optimum fertilization potential. This review describes the implication of apoptosis as one of the possible mechanisms involved in sperm cryoinjury. Evidence shows significant increase in some apoptosis markers following cryopreservation and thawing. On the other hand, the increase in sperm DNA fragmentation following cryopreservation and thawing requires further investigation. Specific technical measures should be applied to minimize the induction of apoptosis in human spermatozoa during cryopreservation and thawing. These include standardization of freezing protocols and cryoprotectant use. Selection of non-apoptotic spermatozoa may also prove to be of benefit.

Impact of caspase activation in human spermatozoa

Caspases are central components in the apoptosis signaling cascade. The family of cysteine proteases transduces and enhances the apoptosis signal, and activation of effector caspases results in controlled cellular degradation. Although initially the presence of caspases in spermatozoa was controversially discussed in recent years, many studies demonstrated their activation in male germ cells. Activated apoptosis signaling results in decreased fertilizing capacity of the sperm. This review presents the current knowledge on the role of caspases in human sperm. Techniques of caspase monitoring are highlighted. With regard to the high impact of caspases on the sperm fertilizing potential, physiological and pathological settings of caspase activation and inactivation are discussed. Finally, the effects of depletion of caspase-positive sperm are shown with various standard and molecular sperm preparation methods.

Correlation between DNA damage and sperm parameters: a prospective study of 1,633 patients

OBJECTIVE

To investigate DNA fragmentation by using terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling in relation to World Health Organization parameters and computer-aided sperm analysis (CASA) in sperm to determine the possibility of obtaining a correlation among CASA parameters, sperm morphology, and DNA fragmentation.

DESIGN

Sperm analysis according to World Health Organization parameters, terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) for sperm DNA fragmentation, and CASA for sperm movement. Prospective study.

SETTING

All the patients were under clinical management, consulting for hypofertility at a fertility center in France.

PATIENT(S)

One thousand six hundred thirty-three men who were referred for infertility investigation, including a complete sperm analysis.

INTERVENTION(S)

Sperm analysis and DNA damage testing.

MAIN OUTCOME MEASURE(S)

Sperm morphology, DNA fragmentation, and movement characteristics.

RESULT(S)

One third of the patients had a TUNEL rate of >30%. Analysis of the 21 semen parameters tested revealed that 7 of them were significantly correlated with the TUNEL results.

CONCLUSION(S)

World Health Organization sperm parameters and DNA damage are complementary, rather than strongly linked. This should be considered to more fully understand the paternal contribution in assisted reproductive technologies failures.

Removal of spermatozoa with externalized phosphatidylserine from sperm preparation in human assisted medical procreation: effects on viability, motility and mitochondrial membrane potential

BACKGROUND

Externalization of phosphatidylserine (EPS) occurs in apoptotic-like spermatozoa and could be used to remove them from sperm preparations to enhance sperm quality for assisted medical procreation. We first characterized EPS in sperms from infertile patients in terms of frequency of EPS spermatozoa as well as localization of phosphatidylserine (PS) on spermatozoa. Subsequently, we determined the impact of depleting EPS spermatozoa on sperm quality.

METHODS

EPS were visualized by fluorescently-labeled annexin V binding assay. Double staining with annexin V and Hoechst differentiates apoptotic from necrotic spermatozoa. We used magnetic-activated cell sorting using annexin V-conjugated microbeads (MACS-ANMB) technique to remove EPS spermatozoa from sperm prepared by density gradient centrifugation (DGC). The impact of this technique on sperm quality was evaluated by measuring progressive motility, viability, and the integrity of the mitochondrial membrane potential (MMP) by Rhodamine 123.

RESULTS

Mean percentages of EPS spermatozoa were 14% in DGC sperm. Four subpopulations of spermatozoa were identified: 70% alive, 3% early apoptotic, 16% necrotic and 11% late apoptotic or necrotic. PS were localized on head and/or midpiece or on the whole spermatozoa. MACS efficiently eliminates EPS spermatozoa. MACS combined with DGC allows a mean reduction of 70% in EPS and of 60% in MMP-disrupted spermatozoa with a mean increase of 50% in sperm survival at 24 h.

CONCLUSION

Human ejaculates contain EPS spermatozoa which can mostly be eliminated by DGC plus MACS resulting in improved sperm long term viability, motility and MMP integrity. EPS may be used as an indicator of sperm quality and removal of EPS spermatozoa may enhance fertility potential in assisted medical procreation.

[Could apoptotic markers help the exploration of male infertility?]

Apoptosis is a cell death program involved in different steps of spermatogenesis, first at puberty, at the beginning of spermatogenesis, then in adult testicles by controlling normal spermatogenesis. As a result, apoptosis deregulation can affect spermatogenesis. Many studies have provided evidence that apoptosis deregulation in germinal cells resulted in male infertility. In addition, apoptosis detection in ejaculated spermatozoa arouses a growing interest in research as a reliable marker of spermatozoon quality. The aim of this review is to summarize our knowledge on physiological apoptosis during spermatogenesis, and then analyse the possibility of using apoptotic markers as selective markers of spermatozoon quality to optimize the rate of success of in vitro fertilization.

The relationship between human sperm apoptosis, morphology and the sperm deformity index

BACKGROUND

This study aimed to assess the relationship between apoptosis in human ejaculated spermatozoa, sperm morphology and the novel sperm deformity index (SDI).

METHODS

Semen specimens from 50 healthy donors were prepared by density-gradient centrifugation followed by incubating the prepared sperm with paramagnetic annexin V-conjugated microbeads and subjecting this to magnetic cell sorting (MACS). The procedure delivers two sperm fractions: annexin-negative (non-apoptotic) and annexin-positive (apoptotic). Activated caspase-3 levels and the integrity of the sperm mitochondrial membrane potential (MMP) were assessed as markers of apoptosis in the annexin-negative and -positive aliquots following MACS. Sperm morphology and the SDI scores were assessed using the strict criteria.

RESULTS

Compared with the apoptotic sperm subpopulations, the non-apoptotic sperm subpopulations had an improved sperm morphology profile as demonstrated by significantly higher proportions of sperm with normal morphology and significantly lower SDI scores and percentages of sperm with acrosomal defects, midpiece defects, cytoplasmic droplet and tail defects. There was a significant correlation between sperm morphology attributes studied and the expressed apoptotic markers - caspase-3 activation and MMP integrity.

CONCLUSIONS

Non-apoptotic sperm fractions have morphologically superior quality sperm compared with apoptotic fractions as reflected by significantly lower SDI scores. The study results may support abortive apoptosis, where the apoptotic mechanism of sperm is already triggered prior to ejaculation.