Changes in sperm apoptotic markers as related to seminal leukocytes and elastase

Cytotoxic Oxidative Stress Effects of Neutrophil Extracellular Traps' Components on Cattle Spermatozoa

Bovine spermatozoa are highly susceptible to oxidative stress (OS), and it is known to affect their cellular functions. The main leukocyte producers of reactive oxygen species (ROS) in mammalian semen are polymorphonuclear neutrophils (PMN). PMN activation can result in the formation of neutrophil extracellular traps (NETs), which have been shown to affect the motility and function of spermatozoa. However, OS effects on bull spermatozoa derived from individual NETs components have not been investigated. The hypothesis of this study was that specific NETs components might generate OS on bull spermatozoa. Bovine sperm cells were incubated with five NETs-associated molecules, including 30 μg/mL histone 2A (H2A), neutrophil elastase (NE), 1 μg/mL myeloperoxidase (MPO), cathepsin G (Cat-G), and cathelicidin LL37 (LL-37), for a time course ranging from 15 to 240 min. Fluorescence microscopy was used to evaluate the coincubation of bovine PMN and sperm cells. Within 15 min, H2A, NE, and LL-37 caused membrane disruption, while MPO and Cat-G caused OS on bull spermatozoa after 1 h of coincubation. NET formation was observed within 15 min of coincubation in co-cultures of bovine PMN/sperm cells. This study is the first to report on the role of cytotoxic OS effects caused by NETs-derived components in bovine sperm in vitro.

Effects of leukocyte elastase in semen on sperm quality

The study analyzed the effect of leukocyte elastase (LE) in 460 semen on sperm quality, and explore the reference interval of normal level of LE in semen. The differences of LE levels between normal semen and few, weak and abnormal semen were analyzed. Referring to domestic standards, the samples were divided into normal group (LE ≤ 250 ng/mL), occult infection (250 < LE ≤ 1000 ng/mL), and infection group (LE > 1000 ng/mL), and the differences in semen quality among the groups were compared. According to European standards, the samples were divided into normal group (≤600 ng/mL) and abnormal group (>600 ng/mL), and the differences in semen quality between the 2 groups were compared. The correlation between LE levels in semen and semen quality were analyzed. The positive rates of LE in the normal semen group and abnormal semen groups were 30.7% versus 34.7%, and there was no significant difference between the two groups (P > .05). When the semen divided into 3 groups, there was no significant difference between the physicochemical parameters, kinetic parameters, movement trajectory parameters, morphological parameters, and sperm DNA fragmentation index (DFI) (P > .05). There were significant differences in sperm morphology and sperm DFI between the two groups at 600 ng/mL (P < .05). Spearman correlation analysis showed that there was no significant difference between the level of LE in semen and physicochemical parameters, sperm kinetic parameters, sperm movement trajectory parameters, sperm morphological parameters, and sperm DFI (P > .05). It is appropriate to use 600 ng/mL as the threshold for the concentration of LE in semen; the correlation between the level of LE and sperm quality is not significant.

Semen Biochemical Components in Varicocele, Leukocytospermia, and Idiopathic Infertility

The evaluation of the seminal plasma plays a relevant role in the definition of male infertility and in assisted reproduction outcomes; for this reason, it would be recommended to find biochemical markers able to characterize sperm pathology. In this study, 53 infertile patients (grouped by the presence leukocytospermia, idiopathic infertility, or varicocele) and 10 fertile men were selected. Spermiogram was performed by light microscopy, and sperm ultrastructure was evaluated by transmission electron microscopy (TEM) mathematically elaborated. Testosterone (TESTO), estradiol (E2), ferritin (FERR), iron (Fe), transferrin (TRSF), triglycerides (TRG), cholesterol (CHOL), and isoprostanes (F₂-IsoPs) were detected in seminal plasma. Sperm characteristics and biochemical components were correlated by Spearman’s rank correlation coefficient in the whole population and in each group. The levels of TESTO and E2 were positively correlated with sperm quality in particular, and E2 was correlated with fertility index expressing the number of sperm free of ultrastructural defects evaluated by TEM. On the contrary, the indices of iron metabolism (FERR, Fe, and TRSF) were positively associated with low sperm quality and sperm necrosis, particularly in leukocytospermia and varicocele groups, pathologies in which an inflammatory status and oxidative stress condition are present. The study of the seminal plasma composition deserves attention because the levels of the various components seem to be associated with specific reproductive pathologies.

Adapted methods for scanning electron microscopy (SEM) in assessment of human sperm morphology

Infertility is a widespread problem, and in some cases, the routine basic semen analysis is not sufficient to detect the cause of male infertility. The use of the scanning electron microscope (SEM) could provide a detailed insight into spermatozoa morphology, but it requires specific sample preparation techniques. The purpose of this study was to select, adjust, and optimize a method for the preparation of spermatozoa samples prior to SEM analysis, and to establish the protocol required for its use in clinical practice. We examined sperm samples of 50 men. The samples were fixed with modified iso-osmolar aldehyde solution followed by osmium post-fixation. In the first method, dehydration of the cells and subsequent critical point drying (CPD) were performed on a coverslip. In the second method, the samples were dehydrated in centrifuge tubes; hexamethyldisilazane (HMDS) was used as a drying agent instead of CPD, and the samples were air-dried. The third procedure was based on a membrane filter. The samples were dehydrated and dried with HMDS in a Gooch crucible, continuously, without centrifugation or redispersion of the sample. Our results showed that the fixation with modified iso-osmolar aldehyde solution followed by osmium post-fixation, and combined with dehydration and CPD on a coverslip, is the most convenient procedure for SEM sample preparation. In the case of small-size samples or low sperm concentration, dehydration and drying with HMDS on the membrane filter enabled the best reliability, repeatability, and comparability of the results. The presented procedures are suitable for routine use, and they can be applied to confirm as well as to correct a diagnosis.

Sperm DNA fragmentation and mitochondrial membrane potential combined are better for predicting natural conception than standard sperm parameters

OBJECTIVE

To evaluate whether DNA fragmentation and/or mitochondrial membrane potential (MMP) predict natural conception better than standard sperm parameters.

DESIGN

Prospective cross-sectional study.

SETTING

University medical center.

PATIENT(S)

Eighty-five infertile and 51 fertile men.

INTERVENTION(S)

Assessment of sperm DNA fragmentation, MMP, and standard semen parameters over a 6- to 12-month observation period.

MAIN OUTCOME MEASURE(S)

Comparison between the results of DNA fragmentation, MMP, and standard sperm parameters alone or combined and achievement of natural conception.

RESULT(S)

Twenty-six of the 85 (31%) men from infertile couples conceived naturally. The median values of DNA fragmentation and MMP in the men who conceived within the observation period were similar to those in the fertile controls. Optimal threshold values of DNA fragmentation and MMP were 25% as determined by receiver operating characteristic analysis (area under the curve [AUC], 0.70; 95% confidence interval (CI) 0.58-0.82) and 62.5% (AUC, 0.68, 95% CI 0.56-0.80), respectively. The men in the infertile group with values of DNA fragmentation ≤25% and with MMP values ≥62.5% had significantly higher odds for conception (odds ratio [OR], 5.22; 95% CI 1.82-14.93] and OR, 4.67; 95% CI 1.74-12.5, respectively). Normal semen analysis alone had no predictive value for natural conception (OR, 1.84; 95% CI 0.67-5.07]). Both sperm function tests combined had significant odds for natural conception (OR, 8.24; 95% CI 2.91-23.33]), with a probability of 0.607 (60.7%) for both normal values and 0.158 (15.8%) for abnormal values.

CONCLUSION(S)

Sperm DNA fragmentation and MMP combined may be superior to standard semen parameters for the prediction of natural conception.

Can apoptosis and necrosis coexist in ejaculated human spermatozoa during in vitro semen bacterial infection?

PURPOSE

To evaluate whether ejaculated human spermatozoa undergo complete apoptosis or necrosis during experimental semen bacterial infection in vitro.

METHODS

Apoptotic markers, including mitochondrial transmembrane potential (ΔΨm), phosphatidylserine (PS) externalization, and DNA fragmentation, have been detected simultaneously in ejaculated human sperm after their incubation with a known pathogenic (Escherichia coli), as well as with conditionally pathogenic bacterial strains (Staphylococcus haemolyticus, Bacteroides ureolyticus) and/or leukocytes. The ΔΨm and translocation of PS was evaluated using the JC-1 and Annexin V binding tests, respectively. A modified TUNEL assay with additional staining for sperm viability was used to detect the DNA fragmentation level.

RESULTS

The exposure of ejaculated spermatozoa to bacterial strains was associated with a simultaneous decrease in the percentage of sperm with normal ΔΨm and an increase in the proportion of Annexin V-positive sperm. Additionally, in the presence of S. haemolyticus, B. ureolyticus and/or leukocytes, a significant increase in the percentage of live TUNEL-positive (apoptotic) as well as dead TUNEL-positive (necrotic) sperm cells was also observed.

CONCLUSIONS

The cellular death observed in spermatozoa in the presence of inflammatory mediators may be due to both apoptosis and necrosis. Here, we demonstrate for the first time that direct contact of conditionally pathogenic bacteria with ejaculated human sperm may play an even greater role in the promotion of apoptosis than in case of some pathogenic bacterial strains. These findings suggest that significant bacteriospermia and leukocytospermia may be direct causes of subfertility or additional negative factors worsening the prognosis of fertility in natural and assisted procreation.

Low amounts of mitochondrial reactive oxygen species define human sperm quality

We have applied the mitochondria-specific superoxide fluorescent probe MitoSOX Red (MitoSOX) to detect mitochondria-specific reactive oxygen species (mROS) production in human sperm samples using flow cytometry. We show that human ejaculates are heterogeneous in terms of mROS production, with three subpopulations clearly detectable, comprising sperm that produce increasing amounts of mROS (MitoSOX−, MitoSOX+, and MitoSOX++). The sperm subpopulation producing the lowest amount of mROS represented the most functional subset of male gametes within the ejaculate, as it was correlated with the highest amount of live and non-apoptotic sperm and increased both in samples with better semen parameters and in samples processed by both density-gradient centrifugation and swim-up, both known to select for higher quality sperm. Importantly, the MitoSOX− subpopulation was clearly more prevalent in samples that gave rise to pregnancies following assisted reproduction. Our work, therefore, not only describe discreet human sperm heterogeneity at the mROS level but also suggests that mROS may represent a strategy to both evaluate sperm samples and isolate the most functional gametes for assisted reproduction.

Free Portuguese abstract

A Portuguese translation of this abstract is freely available athttp://www.reproduction-online.org/content/147/6/817/suppl/DC1

Male infertility workup needs additional testing of expressed prostatic secretion and/or post-massage urine

The male factor accounts for almost 50% of infertility cases. Inflammation may reduce semen quality via several pathways, including oxidative stress (OxS). As male infertility routinely is assessed using semen analysis only, the possible presence of non-leukocytospermic asymptomatic inflammatory prostatitis may be overlooked. We compared local and systemic OxS levels in male partners of infertile couples with different inflammation patterns in their genital tract and/or oligospermia. Subjects (n=143) were grouped according to inflammation in their semen, expressed prostatic secretion (EPS), and/or post-massage urine (post-M). Systemic (8-isoprostanes in urine) and local (diene conjugates and total antioxidant capacity in seminal plasma) OxS was measured The levels of OxS markers were significantly elevated in both severe inflammation groups--leukocytospermic men and subjects whose inflammation was limited only to EPS and/or post-M. Comparison between oligospermic and non-oligospermic men with genital tract inflammation, and oligozoospermic men with or without inflammation in the genital tract indicated that inflammation but not oligospermia status had significant impact on the measured OxS markers. Hence, a high leukocyte count in prostate-specific materials (EPS, post-M), even in absence of clear leukocytopsermia, is an important source of local and systemic OxS that may be associated with male infertility and affect general health. We suggest including the tests for detection of inflammation of the prostate into the workup of infertile men as was suggested in the WHO 1993 recommendation.

Density gradient centrifugation prior to cryopreservation and hypotaurine supplementation improve post-thaw quality of sperm from infertile men with oligoasthenoteratozoospermia

STUDY QUESTION

Can selection of spermatozoa by density gradient centrifugation prior to cryopreservation and/or hypotaurine supplementation improve the post-thaw quality of sperm from infertile men with oligoasthenoteratozoospermia?

SUMMARY ANSWER

Sperm selection by density gradient centrifugation before freezing and supplementation of the media by hypotaurine is beneficial for the cryopreservation of semen samples of patients with oligoasthenoteratozoospermia.

WHAT IS KNOWN ALREADY

Sperm from men with oligoasthenoteratozoospermia are more susceptible than normal to cryoinjury. Density gradient centrifugation before sperm freezing may allow the selection of a subpopulation of spermatozoa more resistant to cryopreservation. Hypotaurine is an antioxidant with a protective effect on sperm functions.

STUDY DESIGN, SIZE, DURATION

The experiment was carried out according to a factorial design involving two binary factors resulting in four treatment combinations which were randomly allocated in oligoasthenoteratozoospermia sperm samples from 64 patients recruited between January 2009 and June 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Semen was provided by 64 men undergoing evaluation for infertility at the Centre for Reproductive Medicine of the University Hospital in Clermont-Ferrand, France, between January 2009 and June 2010. Four treatment combinations were tested: sperm freezing before selection without (F-S/H-; n = 16) and with hypotaurine supplementation (F-S/H+; n = 16); sperm selection before freezing without (S-F/H-; n = 16) and with hypotaurine supplementation (S-F/H+; n = 16). Measurements of sperm recovery rates and markers of apoptosis (externalization of phosphatidylserine (PS), mitochondrial membrane potential and DNA fragmentation) were compared in recovered spermatozoa after each procedure.

MAIN RESULTS AND THE ROLE OF CHANCE

Higher recovery rates of progressive and total motile spermatozoa were observed when sperm selection was performed before freezing (P < 0.05). The protective effect of hypotaurine was only observed on the percentage of live spermatozoa with PS externalization among total live spermatozoa (AN+ PI-/((AN+ PI-) + (AN- PI-)) when the sperm selection by density gradient centrifugation was performed before freezing (S-F/H+ versus S-F/H-: 6.8 ± 1.09 versus 11.8 ± 2.03%, P = 0.04). The percentage of mitochondrial membrane potential (DiOC6(3) (high)) spermatozoa was higher (P = 0.001) when sperm selection was done before freezing compared with procedures in which sperm selection was done after sperm freezing with (S-F/H+ versus F-S/H+: 58.1 ± 3.50 versus 46.7 ± 5.48%) or without (S-F/H- versus F-S/H-: 57.0 ± 5.18 versus 35.4 ± 4.99%) hypotaurine supplementation. The percentages of TUNEL+ spermatozoa were significantly lower (P = 0.001) when sperm selection was done before sperm freezing compared with procedures in which sperm selection was done after sperm freezing with (S-F/H+ versus F-S/H+: 38.6 ± 9.59 versus 55.7 ± 5.88%) or without hypotaurine supplementation (S-F/H- versus F-S/H-: 37.2 ± 7.91 versus 71.0 ± 5.66%).

LIMITATIONS, REASONS FOR CAUTION

The ICSI outcomes were not assessed and the fertility of the spermatozoa remains unknown.

WIDER IMPLICATIONS OF THE FINDINGS

Sperm selection by density gradient centrifugation before freezing and hypotaurine supplementation could improve the cryopreservation of sperm from oligoasthenoteratozoospermic men and make a larger number of functional spermatozoa available for ICSI.

STUDY FUNDING/COMPETING INTERETS(S)

This work was supported by a hospital grant (Projet Hospitalier Recherche Clinique, CHU Clermont Ferrand, France). None of the authors has any conflict of interest to declare.