Place des marqueurs de l'apoptose dans l'exploration de l'infertilité masculine

Magnetic-activated cell sorting is not completely effective at reducing sperm DNA fragmentation

PURPOSE

To determine whether there is a homogeneous reduction of sperm DNA fragmentation (SDF) in sperm samples recovered from the MACS procedure, compared to spermatozoa in the initial ejaculate (NEAT) and those retained in the column.

METHODS

This study investigated the relative change in sperm DNA quality (SDF) of neat ejaculates (10 idiopathic infertile and 10 normozoospermic patients) to subpopulations of spermatozoa that had passed through the column (MACS-) and those retained (MACS+) by the annexin-V conjugated microbeads.

RESULTS

While the MACS protocol was capable of reducing the mean proportion of SDF (59.2%; P = 0.000) and sperm with highly degraded DNA (SDD; 65.7%, P = 0.000) in all patients, the reduction was not homogeneous across the patient cohort. A significant positive correlation (r = 0.772, P = 0.000) was apparent between the level of SDF in the NEAT ejaculate and the efficacy of SDF reduction observed in the MACS- fraction.

CONCLUSION

MACS is capable of reducing the proportion of SDF, especially spermatozoa with a highly degraded DNA molecule. However, this reduction did not preclude the presence of a small subpopulation of spermatozoa with damaged DNA in the MACS- fraction. The MACS protocol was two- to threefold more efficient when the SDF in NEAT ejaculate was equal to or greater than 30%. In 4 of 20 individuals, the level of SDF after MACS resulted in semen for ICSI with a higher or non-significant reduction when compared to SDF observed in the NEAT ejaculate.

Melatonin protects human spermatozoa from apoptosis via melatonin receptor- and extracellular signal-regulated kinase-mediated pathways

OBJECTIVE

To evaluate whether the protective effect of melatonin on H2O2-induced caspase activation and DNA fragmentation depends on the interaction between melatonin and its surface receptors.

DESIGN

Laboratory study.

SETTING

Center for assisted human reproduction at a Spanish hospital.

PATIENT(S)

Twenty-one healthy donors.

INTERVENTION(S)

Human spermatozoa were treated with increasing concentrations of hydrogen peroxide (H2O2; 1 μM, 10 μM, 100 μM, 1 mM) and preincubated with 1 mM melatonin.

MAIN OUTCOMES MEASURE(S)

Activation of caspase-3 and -9 as well as DNA fragmentation were examined by fluorescence methods.

RESULT(S)

Our findings showed that H2O2 induced a significant increase in caspase-9 and caspase-3, which was dose independent. Conversely, pretreatment with melatonin reduced H2O2-mediated caspase activation in a dose-dependent way. Moreover, the antiapoptotic effects of melatonin in ejaculated human spermatozoa may involve membrane melatonin receptor MT1. In addition, we found that the survival-promoting pathway extracellular signal-regulated kinase (ERK) is likely to have a role in the protective actions of melatonin in ejaculated human spermatozoa. Finally, we confirmed these results further by demonstrating that melatonin prevention of H2O2-induced DNA fragmentation is dependent on both MT1 receptor and ERK signaling.

CONCLUSION(S)

These results indicate that the stimulation with melatonin triggers a set of events culminating in cell death prevention in ejaculated human spermatozoa.

[Sperm apoptosis: myth or reality?]

Apoptosis has become a popular biologic concept, for many reasons. From embryonic development to adult tissues, apoptosis is necessary to maintain tissues homeostasis in most organ systems during organogenesis and in the adult. Human spermatogenetic epithelium is also concerned. Dysregulations of this process are involved in many pathologies (leukaemia, auto-immune diseases, etc...), and some forms of male infertility also. Apoptotic features have been found in human semen from infertile patients, and could become useful in order to appreciate semen quality, especially in Assisted Reproductive Technology (ART). Despite numerous studies, some questions remain, especially about meaning of apoptotic damages of spermatozoa.

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.

A new multiparameter flow cytometric method for human semen analysis

BACKGROUND

The objectives of this study were (i) to evaluate whether the combined use of Syto 16 and 7-amino-actinomycin-D (7-AAD) allows the detection of sperm apoptosis and (ii) to describe a new multiparameter flow cytometric method to assess simultaneously sperm concentration (SC), viability and apoptosis as well as leukocyte concentration.

METHODS

Semen samples from 68 patients were evaluated according to World Health Organization (WHO) criteria (normal, n=26; abnormal, n=42). The detection of activated caspases before and after betulinic acid (BA) incubation was carried out in 13 semen samples by flow cytometry using fluorescein-labelled inhibitors of caspases (FLICA). A multiparameter flow cytometric analysis was performed in 55 semen samples. Fluorescent microspheres were used to assess SC. Sperm apoptosis was detected by staining sperm with Syto 16 and 7-AAD. Leukocytes were counted using monoclonal anti-CD45.

RESULTS

A significant correlation between the percentage of the spermatozoa with low Syto 16 fluorescence and the percentage of spermatozoa containing activated caspases was found (r=0.68, P=0.0106; n=13). After incubation with BA, an increase of the percentage of apoptotic cells was observed in all samples, using both the Syto 16/7-AAD and the caspase activation methods. There was a good correlation between flow cytometry and optical microscopy for sperm (r=0.98, P < 0.0001) and leukocyte counting (r=0.64, P <0.0001). The percentage of apoptotic sperm was inversely correlated with both SC (r=-0.303, P=0.0246) and morphology (r=-0.384, P=0.0050) but not with motility.

CONCLUSIONS

The combination of Syto 16/7-AAD provides a sensitive assay to detect sperm apoptosis. The multiparameter flow cytometric method described offers the possibility of a simultaneous, simple, rapid and accurate assessment of several semen parameters.