Intégrité de l'ADN des spermatozoïdes comme élément diagnostique et pronostique de la fertilité masculine

Tobacco consumption and benzo(a)pyrene-diol-epoxide-DNA adducts in spermatozoa: in smokers, swim-up procedure selects spermatozoa with decreased DNA damage

OBJECTIVE

To analyze the distribution of benzo(a)pyrene-diol-epoxide (BPDE)-DNA adducts in spermatozoa selected and nonselected by a swim-up procedure with relation to smoking habits.

DESIGN

Comparative study.

SETTING

Public university and public university hospital.

PATIENT(S)

Seventy-nine men (37 smokers and 42 nonsmokers) who visited an infertility clinic for diagnostic.

INTERVENTION(S)

Tobacco and environmental exposure assessment, semen sample analysis, swim-up procedure, BPDE-DNA adduct immunolabeling.

MAIN OUTCOME MEASURE(S)

BPDE-DNA adduct quantification in selected (SEL-SPZ) and nonselected (NONSEL-SPZ) spermatozoa. Data were normalized by using a normalized fluorescence value (NFV).

RESULT(S)

The mean NFV (±SD) in SEL-SPZ was significantly higher in smokers than in nonsmokers (18.9±11.5 vs. 10.5±10.4, respectively). Within smokers, a paired analysis (SEL-SPZ and NONSEL-SPZ) showed that NFV was significantly lower in SEL-SPZ than in NONSEL-SPZ (20.0±11.3 vs. 31.5±16.0, respectively). Conversely, within nonsmokers, the mean NFV was higher in SEL-SPZ than in NONSEL-SPZ (10.3±10.6 vs 4.3±7.1, respectively).

CONCLUSION(S)

Tobacco consumption is associated with BPDE-DNA adducts in spermatozoa. In smokers, semen processing by swim-up recovers potentially fertilizing spermatozoa that show a significantly lower amount of BPDE-DNA adducts compared with NONSEL-SPZ. Further study is needed to improve the spermatozoa selection in smoking patients requiring assisted reproductive technologies.

Les larges vacuoles des têtes spermatiques sont-elles associées à des altérations du noyau ou de l’acrosome du spermatozoïde ?

Objectifs

Rechercher la présence d’altérations nucléaires ou acrosomiques dans les spermatozoïdes présentant des vacuoles occupant au moins 13 % de la surface de la tête des spermatozoïdes (spermatozoïdes dits de type 3), détectées à l’aide de la technique MSOME (motile sperm organelle morphology examination).

Matériel et méthodes

Notre étude a été effectuée sur des recueils de sperme de 20 hommes infertiles. Une évaluation de l’acrosome par immunomarquage à l’aide d’un anticorps monoclonal antiproacrosine (Mab4D4) a été associée à une détection de la fragmentation de l’ADN par la technique TUNEL. La condensation de la chromatine spermatique a été évaluée par une coloration au bleu d’aniline, et le taux d’aneuploïdie a été déterminé par hybridation in situ en fluorescence (FISH). Une observation des échantillons spermatiques par microscopie électronique à transmission (MET) [sperme entier] et confocale [spermatozoïdes de type 3 isolés] a complété ces analyses. Les résultats ont été comparés entre des spermatozoïdes provenant du sperme entier et des spermatozoïdes de type 3 isolés.

Résultats

Une augmentation significative de la proportion d’acrosomes anormaux a été constatée dans les spermatozoïdes isolés de type 3 par comparaison au sperme entier (77,8 ± 2,49 % vs 70,6 ± 2,62 %). La fragmentation de l’ADN a été observée de manière comparable dans les spermatozoïdes de type 3 et le sperme entier (14,5 ± 3,45 % vs 11,5 ± 1,25%), un défaut de condensation de la chromatine ainsi qu’une augmentation significative du taux d’aneuploïdie ont été retrouvés dans les spermatozoïdes isolés par comparaison à ceux provenant du sperme entier (50,4 ± 3,10 % vs 26,5 ± 2,60 % et 7,8 ± 1,98 % vs 1,3 ± 0,18 %). Les larges vacuoles sont à localisation nucléaire exclusive (MET et microscopie confocale).

Conclusion

Les vacuoles seraient en relation directe avec un défaut de maturation nucléaire survenant au cours de la spermiogenèse.

Influence of in vitro exposure to mycotoxin zearalenone and its derivatives on swine sperm quality

Zearalenone (ZEA) is a fusariotoxin naturally occurring in crops with known estrogenic activity in swine, the most sensitive known species. The metabolism by swine of ZEA, principally into alpha-zearalenol (alpha-ZOL), is considered as a bio-activation because of its high affinity with estrogenic receptors. Discordant data on male reproductive failures induced by ZEA in vivo are described. In this study, we evaluated the effects to boar spermatozoa when they are exposed in vitro to ZEA and its derivatives (alpha-ZOL, beta-ZOL). We analyzed viability, apoptosis (terminal deoxynucleotidyltransferase dUTP nick end-labelling (TUNEL)), sperm chromatin stability (sperm chromatin structure assay (SCSA)) and motility (using computer-aided sperm analysis (CASA)). Each mycotoxin influenced a specific function of spermatic cells. alpha-Zearalenol and ZEA, at picomolar levels, negatively influenced chromatin structure stability and viability, respectively, whereas beta-ZOL negatively influenced the sperm motility at micromolar levels. This study is the first using these direct measures of sperm integrity to show the potential for an adverse effect of ZEA exposure on boar fertility.

Human sperm DNA fragmentation: correlation of TUNEL results as assessed by flow cytometry and optical microscopy

An association between DNA fragmentation in sperm determined by the terminal deoxynucleotidyl transferase [TdT]-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) assay and the incidence of reproductive failure has been reported, either using flow cytometry or optical microscopy. However, the results obtained using each of these two approaches are different. Since there is a relative lack of studies standardizing these two approaches, the direct comparison of the results described in the different articles is difficult at present. To allow the comparison of the TUNEL results obtained using flow cytometry and optical microscopy, we applied these two approaches in a total of 66 human sperm samples. A positive correlation is detected in the TUNEL results as measured by flow cytometry and optical microscopy (Spearman; r = 0.720, P < 0.001). The percentage of TUNEL-positive spermatozoa assessed by flow cytometry is 2.6 times higher than that detected in optical microscopy (39.7% +/- 23.1% versus 15.3% +/- 10.3%). Although there is a good correlation of the TUNEL results obtained by flow cytometry and optical microscopy, the percentages obtained with either technique are different. Therefore, the TUNEL results described in the present work should be valuable to compare the results described in many independent articles, using either optical microscopy or flow cytometry.

Spermatozoal sensitive biomarkers to defective protaminosis and fragmented DNA

Human sperm DNA damage may have adverse effects on reproductive outcome. Infertile men possess substantially more spermatozoa with damaged DNA compared to fertile donors. Although the extent of this abnormality is closely related to sperm function, the underlying etiology of ensuing male infertility is still largely controversial. Both intra-testicular and post-testicular events have been postulated and different mechanisms have been proposed to explain the presence of damaged DNA in human spermatozoa. Three among them, i.e. abnormal chromatin packaging, oxidative stress and apoptosis, are the most studied and discussed in the present review. Furthermore, results from numerous investigations are presented, including our own findings on these pathological conditions, as well as the techniques applied for their evaluation. The crucial points of each methodology on the successful detection of DNA damage and their validity on the appraisal of infertile patients are also discussed. Along with the conventional parameters examined in the standard semen analysis, evaluation of damaged sperm DNA seems to complement the investigation of factors affecting male fertility and may prove an efficient diagnostic tool in the prediction of pregnancy outcome.

Ten-year variation in semen parameters and sperm deoxyribonucleic acid integrity in a healthy fertile man

OBJECTIVE

To report parameters in semen samples and sperm DNA integrity in a healthy fertile volunteer over a 10-year period.

DESIGN

Case report.

SETTING

University-affiliated teaching hospital.

INTERVENTION(S)

None.

PATIENT(S)

Semen samples from a nonsmoking healthy male volunteer of proven fertility aged from 40 to 50 years were collected and analyzed over a decade.

MAIN OUTCOME MEASURE(S)

Semen parameters (sperm count, total sperm count, percentage of progressive motility grades a+b, morphology, and percentage of living spermatozoa) and sperm DNA integrity, measured by sperm chromatin structure assay (SCSA) and terminal uridine nick-end labeling (TUNEL) assay.

RESULT(S)

Median (min-max) value of total sperm count was 330 (126-511) million. Motility and vitality presented a median of 50% (40%-75%) and 78% (53%-92%), respectively. Among semen parameters, morphology and vitality showed the lowest within-subject coefficient of variation (CV(W)) and the total sperm count the highest (8.1% and 12.0% vs. 34.9%). Median values of DNA fragmentation index (DFI) and high DNA stainability (HDS) were 12.7% (7.9%-16.5%) and 6.5% (5.5%-8.2%), respectively. Sperm DNA fragmentation presented a median value of 8.9%, a minimum value of 1.4% and maximum value of 18.6%. Compared with TUNEL data, SCSA parameters (DFI and HDS) showed less variation over the data collection period (47.4% vs. 22.4% and 13.0%, respectively).

CONCLUSION(S)

Our data show that in this healthy fertile volunteer, semen parameters and sperm DNA integrity remained normal, and no trend was observed over the study period. More interestingly, in this subject aged from 40 to 50 years old, sperm nucleus status presented less than 20% of sperm DNA fragmentation over a decade.

[Epigenetics of the sperm cell]

In addition to genetic information, the spermatozoon carries another type of information, named epigenetic, which is not associated with variations of the DNA sequence. In somatic cells, it is now generally admitted that epigenetic information is not only regulated by DNA methylation but also involves modifications of the genome structure, or epigenome. During male germ cell maturation, the epigenome is globally re-organized, since most histones, which are associated to DNA in somatic cells, are removed and replaced by sperm specific nuclear proteins, the protamines, responsible for the tight compaction of the sperm DNA. However, a small proportion of histones, and probably other proteins, are retained within the sperm nucleus, and the structure of the sperm genome is actually heterogeneous. This heterogeneity of the sperm epigenome could support an epigenetic information, transmitted to the embryo, which could be crucial for its development. Although it is nowadays possible to appreciate the global structure of the sperm genome, the precise constitution of the sperm epigenome remains unknown. In particular, very recent data suggest that specific regions of the genome could be associated with particular proteins and define specific structures. This structural partitioning of the sperm genome could convey important epigenetic information, crucial for the embryo development.

Infection du tractus génital masculin : le point de vue du bactériologiste

Male genital tract infection and inflammation have been associated to 8 to 35% of male infertility cases in various studies. Their investigation is part of a multi-disciplinary process including new techniques as DNA integrity study. Bacterial seminal infection can cause transient or chronic persistent inflammation, and the microbiological investigations, as well as leukospermia, secretory chlamydial IgA and inflammatory cytokines help to approach the responsibility of inflammation in infertility or pathological condition, leading to antibiotic and anti-inflammatory treatment. In Assisted Reproductive Techniques (ART), bacteriospermia must be eradicated for a safe semen preparation to inseminate or to fertilize oocytes. Leukocytes cannot be completely eliminated by sperm preparation and the presence of antibiotics and antioxydants in the culture media is questionned.

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

Ejaculated spermatozoa, particularly in infertile men, have been shown to display numerous features that are typical of apoptosis in somatic cells including Fas expression, ROS production, activation of caspases, DNA fragmentation, reduction in mitochondrial membrane potential, plasma membrane translocation of phosphatidylserine and permeability. In this review we summarize the biological significance and the potential role of these markers in the exploration of men infertility.