Effects of semen processing on the generation of reactive oxygen species and mitochondrial membrane potential of human spermatozoa

Self-reported sleep quality and oligo/astheno/teratozoospermia among men attending an infertility clinic: a longitudinal study

OBJECTIVE

We aimed to examine the influence of sleep disturbances on the risk of oligo/astheno/teratozoospermia (OAT) in men attending an infertility clinic.

METHODS

We consecutively enrolled men attending an infertility clinic from July 2020 to June 2021. Semen parameters were obtained at initial presentation, and the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale score, and the STOP-BANG Questionnair were completed to assess sleep quality. Embryo outcomes were evaluated after infertility treatment.

RESULTS

Of 466 men enrolled, 119 had OAT (OAT group) and 347 had normozoospermia (NS group). There were no differences between the two groups regarding Epworth Sleepiness Scale and STOP-BANG Questionnaire scores. The prevalence of poor sleep quality (Pittsburgh Sleep Quality Index score ≥ 5) in the OAT group was significantly higher than that in the NS group (42% vs. 29%, p = 0.009). A higher rate of poor subjective sleep quality was observed in the OAT group compared with the NS group (p = 0.005) and Pearson's correlations revealed a negative relationship between subjective sleep quality and semen quality. Logistic regression found that subjective sleep quality was independently associated with an increased risk of OAT (adjusted odds ratio = 0.610, p = 0.007).

CONCLUSIONS

Men with OAT attending an infertility clinic exhibited poor subjective sleep quality. Improving sleep disturbances may be a target intervention to reduce the risk of OAT. This possibility warrants further investigation.

A microplate-based DCFH-DA assay for the evaluation of oxidative stress in whole semen

Aims

The well-documented relationship between sperm oxidation and male infertility strongly encourages the development of assays for reactive oxygen species detection in semen samples. The present study aims to apply the microplate-based 2',7'-dichlorofluorescein diacetate assay to the evaluation of oxidative stress in unprocessed whole semen, thus avoiding sample centrifugations and other manipulations that may cause significant reactive oxygen species increments.

Main methods

The fluorescence assay consisted in the quantification of both intracellular and extracellular reactive oxygen species levels in unwashed semen specimens by using the probe 2',7'-dichlorofluorescein diacetate into a 96-well plate. The method was useful for the preliminary assessment of the oxidation levels of whole semen samples from men undergoing standard sperm analysis as well as to evaluate the effect of some pro-glutathione molecules on semen oxidative status.

Key findings

The 2',7'-dichlorofluorescein diacetate assay was successfully adapted to the evaluation of oxidative stress in whole semen, effectively revealing the perturbation of the redox homeostasis of the sample. Accordingly, specimens with abnormal sperm parameters (n = 10) presented oxidation indexes significantly higher than those with normospermia (n = 10) [7729 (range 3407-12769) vs. 1356 (range 470-2711), p < 0.001]; in addition, semen oxidation indexes negatively correlated to sperm motility and morphology. Noteworthy, whole semen exposure to pro-glutathione compounds led to reduced semen oxidation levels and sperm protection against oxidative damage.

Significance

Based on our pilot experimental data, the microplate-based 2',7'-dichlorofluorescein diacetate assay appears to be a convenient method for the detection of reactive oxygen species levels in whole semen samples, avoiding artifacts due to semen centrifugation steps. At the same time, the test could be a helpful tool for the basic and quick screening of antioxidant molecules able to preserve semen quality.

Comparison of sperm preparation methods to improve the recovery of mature spermatozoa in sub-fertile males

The integrity of chromatin in the spermatozoon is essential for reproductive outcome. The aim of this study was to evaluate the most effective and cost-effective method to reduce the percentage of spermatozoa with defects in chromatin decondensation for use in assisted reproductive technologies (ART) procedures. Sperm samples from 15 sub-fertile males were examined at CFA Naples to determine the sperm decondensation index (SDI), using the aniline blue test, before and after preparation, comparing density gradients with two different swim-up approaches. All three techniques led to a reduction in decondensed spermatozoa with no statistical difference (P > 0.05) between the control and the treated sperm. In contrast, we found a highly significant decrease in SDI (P < 0.01) after the two swim-up methods in all the samples, confirming the efficacy of these methods in lowering the percentage of chromatin compaction damage. There was no statistical difference between the two swim-up methods, however swim-up from the pellet led to improved count, motility and the percentage of normal condensed spermatozoa. We suggest that swim-up from the pellet be used in ART on sub-fertile males, both to reduce cell stress by multiple centrifugation and improve the recovery rate of mature spermatozoa.

Ameliorative effect of bee products on in vitro maturation of sheep oocytes

The present study was undertaken to investigate the possible stimulating effects of Nigella sativa (N. sativa) honey, natural Saudi Sider honey, and honeybee pollen to the in vitro maturation (IVM) medium of sheep oocytes on their subsequent development. Hence, immature oocytes were exposed to various concentrations of natural Nigella sativa (N. sativa), and Saudi Sider honey (5, 10, and 20%), as well as honeybee pollen (1, 10, 50 μg/ml) during an in vitro maturation period (24 hours). After the exposure time, the maturation rate, glutathione (GSH) concentration, and candidate gene expression (GDF-9, MPF, CMOS, IGF-1, and BAX) were evaluated. Our results showed that the maturation rate was higher in the groups challenged with the lowest level of the bee products (5% and 1 μg/ml) when compared with that in the control group; where the mean number of oocytes in the metaphase II stage reached 0.360 for the honeybee pollen-treated group, 0.293 for the N. sativa-treated group, and 0.203 for the natural Saudi Sider honey-treated group. The glutathione level was significantly increased in the group exposed to N. sativa honey when compared with the other groups. Concerning the gene expression results, the Saudi Sider honey treatment showed the best results for all the genes except the CMOS gene, which was significantly higher than the GI and GII groups and lower than the GIV group and the BAX gene which did not show a significant difference when compared with the other groups. In conclusion, the addition of natural honey and honeybee pollen at a low concentration to an IVM medium improved the in vitro maturation rate, increased the glutathione level, and gene expression of the in vitro matured ovine oocytes.

Selecting motile, non-apoptotic and induced spermatozoa for capacitation without centrifuging by MACS-Up method

In newly improved MACS-Up method, magnetic field has been applied to separate non-apoptotic spermatozoa directly from the neat semen. The spermatozoa during passing through a viscous layer, located on the neat semen, contacted with progesterone and induced for the capacitation. Then, a clean population of non-apoptotic, and capacitated spermatozoa were selected in the pure culture media. Selected spermatozoa may be useful for use in ART. The 80 semen samples from normozoospermic individuals were divided separately into 4 attempts. Semen analysis, SCSA (sperm chromatin structure assay), FLICA (fluorescein-labelled inhibitors of caspase) methods, immunoassay of phosphorylation of tyrosine residues of sperm proteins, nuclear DNA integrity, caspase 3 activity and sperm capacitation rate were all performed for evaluation of sperm parameters respectively. To examine all aspects, the MACS-Up method compared with DGC (density gradient centrifuging) and MACS-DGC methods separately. This method can isolate non-apoptotic spermatozoa directly from the neat semen, which has similar performance compared to the MACS-DGC method. Movement and passing spermatozoa through the viscous layer, and contact with progesterone, significantly induced spermatozoa for capacitation compared with the control group. Also, the MACS-Up in comparison with routine DGC method could select spermatozoa with significantly higher total and progressive motility, DNA integrity, induced sperm population for capacitation and normal morphology. MACS-Up can be developed as an effective, short-time, and ease of performing method and used practically to select functional spermatozoa as novel sperm selection procedure. However, for clinical use of MACS-Up, all clinical aspects of this method should be considered and evaluated.

Cryo-banking of human spermatozoa by aseptic cryoprotectants-free vitrification in liquid air: Positive effect of elevated warming temperature

Cryoprotectant-free vitrification is a common method for spermatozoa cryopreservation by direct plunging into liquid nitrogen. However, the commercial liquid nitrogen could be potentially contaminated by microorganisms. Warming temperature plays an essential role for quality of human spermatozoa after vitrification. This study aimed to evaluate comparatively a quality spermatozoa after vitrification in liquid nitrogen and clean liquid air as well as with two warming rates: at 42 °C and 45 °C. After performing of routine swim-up of normozoospermia samples, spermatozoa from the same ejaculate were divided into two groups: vitrified in liquid nitrogen (LN) and sterile liquid air (LA). Spermatozoa of LN group were warmed at 42 °C, and spermatozoa of LA groups were divided and warmed at 42 °C (LA42) and 45 °C (LA45). Then spermatozoa motility, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), reactive nitrogen species (RNS), and viability were assessed. It was no found significant differences in quality of spermatozoa from LN and LA groups in the motility, ROS, MMP, RNS rates after warming at 42 °C. A tendency to obtain better spermatozoa quality was found with using of warming by 42 °C in comparison with 45 °C. It was concluded that cryoprotectant-free vitrification by direct dropping of human spermatozoa into clean liquid air can be used as an alternative to cooling in liquid nitrogen. Warming of spermatozoa at 42 °C allows to preserve the spermatozoa physiological parameters.

Effects of SLIRP on Sperm Motility and Oxidative Stress

Background

Deficient spermatozoon motility is one of the main causes of male infertility. However, there are still no accurate and effective treatments in a clinical setting for male asthenospermia. Exploring the genes and mechanism of asthenospermia has become one of the hot topics in reproductive medicine. Our aim is to study the effect of SLRIP on human spermatozoon motility and oxidative stress.

Methods

Sperm samples were collected including a normospermia group (60 cases) and an asthenospermia group (50 cases). SLIRP protein expression in spermatozoa was examined by western blotting, and relative mRNA expression of SLIRP in spermatozoa was quantified by reverse transcription polymerase chain reaction. Levels of reactive oxygen species (ROS), adenosine triphosphate (ATP) content, and the activity of manganese superoxide dismutase (MnSOD) in spermatozoa were also measured.

Results

The mRNA level and protein expression of SLIRP in the asthenospermia group were significantly reduced compared with those in the normospermia group. The ROS active oxygen level in the asthenospermia group significantly increased; however, the ATP content decreased significantly as well as the activity of MnSOD.

Conclusion

SLIRP regulates human male fertility, and SLIRP and sperm progressive motility are positively correlated. The expression of SLIRP is declined, oxidative damage is increased, and energy metabolism is decreased in spermatozoa of asthenospermia patients compared to normospermia participants.

A fast and safe technique for sperm preparation in ICSI treatments within a randomized controlled trial (RCT)

Recently a novel method based on horizontal sperm migration in injection dishes has been introduced as an additional tool for preparation of semen sample in assisted reproductive technology (ART) procedures. In the present study, we evaluated both timing and reproductive outcomes in a randomized controlled study including 1034 intra-cytoplasmic sperm injection (ICSI) procedures followed by fresh embryo transfer. Couples enrolled were divided into two sub-groups, namely conventional swim-up method (Group A), and horizontal sperm migration in injection dishes (Group B).No significant differences were found between groups with respect to fertilization rate, implantation success, clinical pregnancy outcomes and ongoing pregnancies. On the contrary, both cleavage and blastocyst rates were statistically higher in Group B, suggesting superior efficiency and safety of this innovative technique also including time-saving and cheaper costs as compared to the classical swim-up sperm preparation.Our data support the interpretation of the horizontal sperm migration as a promising procedure for semen preparation in ART cycles.

Curcumin improves asthenozoospermia by inhibiting reactive oxygen species reproduction through nuclear factor erythroid 2-related factor 2 activation

We conducted this study for the purpose of evaluating the protective mechanisms of curcumin against oxidative stress in asthenozoospermic individuals. Asthenozoospermic individuals were grouped into AS group, curcumin treatment group and brusatol + curcumin treatment group. The sperm motility was measured by computer-aided sperm analysis. We conducted flow cytometry and spectrophotometry to assess the levels of reactive oxygen species (ROS) and malondialdehyde (MDA). Chlortetracycline (CTC) was used to examine the acrosomal reaction of spermatozoa. Also, Western blotting was carried to measure antioxidant gene Nrf2 (nuclear factor erythroid 2-related factor) expression level. As our results shown, treatment with curcumin significantly decreased ROS formation and MDA production, compared with spermatozoa of AS group; however, Nrf2 inhibitor, Brusatol, inhibited Nrf2 expression and sperm function. Our results have shown that curcumin might protect spermatozoa by regulating Nrf2 level.

Centrifugation Force and Time Alter CASA Parameters and Oxidative Status of Cryopreserved Stallion Sperm

Conventional sperm selection techniques used in ARTs rely on centrifugation steps. To date, the different studies reported on the effects of centrifugation on stallion sperm motility provided contrasting results and do not include effects on mitochondrial functionality and different oxidative parameters. The effects of different centrifugation protocols (300 ×g for 5', 300 ×g for 10', 1500 ×g for 5' and 1500 ×g for 10' vs no centrifugation) on motility and oxidative status in cryopreserved stallion sperm, were analyzed. After centrifugation, almost all motility parameters were significantly altered, as observed by computer-assisted sperm analysis. A polarographic assay of oxygen consumption showed a progressive decrease in mitochondria respiration from the gentlest to the strongest protocol. By laser scanning confocal microscopy, significant reduction of mitochondrial membrane potential, at any tested protocol, and time-dependent effects, at the same centrifugal force, were found. Increased DNA fragmentation index at any tested protocol and time-dependent effects at the same centrifugal force were found, whereas increased protein carbonylation was observed only at the strongest centrifugal force. These results provide more comprehensive understandings on centrifugation-induced effects on cryopreserved stallion sperm and suggest that, even at a weak force for a short time, centrifugation impairs different aspects of equine sperm metabolism and functionality.

Downregulation of DJ-1 Fails to Protect Mitochondrial Complex I Subunit NDUFS3 in the Testes and Contributes to the Asthenozoospermia

Asthenozoospermia (AS), an important cause of male infertility, is characterized by reduced sperm motility. Among the aetiologies of AS, inflammation seems to be the main cause. DJ-1, a conserved protein product of the PARK7 gene, is associated with male infertility and plays a role in oxidative stress and inflammation. Although our previous studies showed that a reduction in DJ-1 was accompanied by mitochondrial dysfunction in the sperm of patients with AS, the specific mechanism underlying this association remained unclear. In this study, we found that compared to the patients without AS, the expression of mitochondrial protein nicotinamide adenine dinucleotide dehydrogenase (ubiquinone) Fe-S protein 3 (NDUFS3) was also significantly decreased in the sperm of patients with AS. Similarly, decreased expression of DJ-1 and NDUFS3 and reduced mitochondria complex I activity were evident in a rat model of AS. Moreover, we showed that the interaction between DJ-1 and NDUFS3 in rat testes was weakened by ORN treatment. These results suggest that the impaired mitochondrial activity could be due to the broken interaction between DJ-1 and NDUFS3 and that downregulation of DJ-1 in sperm and testes contributes to AS pathogenesis.

Oxidation-reduction potential as a new marker for oxidative stress: Correlation to male infertility

Male infertility affects men worldwide. Oxidative stress (OS), characterized by an overabundance of reactive oxygen species (ROS) or a deficiency of antioxidants, is one of the major causes of male infertility. OS causes damage at the molecular level, which impairs lipids, proteins, and DNA. The cyclic cascade of redox reactions weakens sperm function which leads to poor semen parameters and eventual sterility. There is a need for advanced diagnostic tests that can quickly and accurately detect OS. Most commonly used assays can only measure single constituents of OS. However, the MiOXSYS System introduces a new strategy to detect OS by measuring the oxidation-reduction potential (ORP)--a direct evaluation of the redox balance between ROS and antioxidants. The MiOXSYS System has shown promise as a diagnostic tool in the evaluation of male infertility. This review explores the concept of ORP, details the principle of the MiOXSYS System, and summarizes the findings in clinical studies that support ORP measurement in semen.

Use of the fluorescent dye tetramethylrhodamine methyl ester perchlorate for mitochondrial membrane potential assessment in human spermatozoa

Mitochondrial membrane potential (ΔΨm) is an indicator of sperm quality and its evaluation complements the standard semen analysis. The fluorescent dye JC-1 has been widely used to assess sperm ΔΨm; however, some problems have been detected under certain experimental conditions. Another fluorescent compound, tetramethylrhodamine methyl ester perchlorate (TMRM), has been used in somatic cells and bovine spermatozoa but not in human spermatozoa. TMRM accumulates in hyperpolarised mitochondria and the fluorescence intensity of this compound correlates with ΔΨm. Thus, the aim of this study was to evaluate and validate the usefulness of the fluorescent dye TMRM for measuring sperm ΔΨm. The results showed that TMRM accurately detects sperm populations displaying either high or low ΔΨm. Moreover, TMRM was able to measure sperm ΔΨm under the experimental conditions in which JC-1 had previously presented difficulties. Differences in ΔΨm according to sperm and semen quality were properly detected and a positive correlation between ΔΨm and conventional semen parameters was observed. Finally, a positive correlation was found between the ΔΨm measurement by TMRM and by the widely used JC-1. In conclusion, TMRM is a simple, time-effective method, easy to set in laboratories equipped with flow cytometry technology, and can accurately detect changes in ΔΨm with efficiency comparable to JC-1 without its limitations.

Comparison of two sperm processing techniques for low complexity assisted fertilization: sperm washing followed by swim-up and discontinuous density gradient centrifugation

Objective

This study aimed to assess and compare sperm motility, concentration, and morphology recovery rates, before and after processing through sperm washing followed by swim-up or discontinuous density gradient centrifugation in normospermic individuals.

Methods

Fifty-eight semen samples were used in double intrauterine insemination procedures; 17 samples (group 1) were prepared with sperm washing followed by swim-up, and 41 (group 2) by discontinuous density gradient centrifugation. This prospective non-randomized study assessed seminal parameters before and after semen processing. A dependent t-test was used for the same technique to analyze seminal parameters before and after semen processing; an independent t-test was used to compare the results before and after processing for both techniques.

Results

The two techniques produced decreases in sample concentration (sperm washing followed by swim-up: P<0.000006; discontinuous density gradient centrifugation: P=0.008457) and increases in motility and normal morphology sperm rates after processing. The difference in sperm motility between the two techniques was not statistically significant. Sperm washing followed by swim-up had better morphology recovery rates than discontinuous density gradient centrifugation (P=0.0095); and the density gradient group had better concentration recovery rates than the swim-up group (P=0.0027).

Conclusion

The two methods successfully recovered the minimum sperm values needed to perform intrauterine insemination. Sperm washing followed by swim-up is indicated for semen with high sperm concentration and better morphology recovery rates. Discontinuous density gradient centrifugation produced improved concentration recovery rates.

Percentage of motile spermatozoa at 22 hours after swim-up procedure: An indicator for intracytoplasmic sperm injection?

Objective

Methods

Results

Conclusion

Reactive Oxygen Species (ROS) in human semen: determination of a reference range

PURPOSE

High levels of reactive oxygen species (ROS) are a leading cause of male factor infertility. Measurement of ROS has been hampered by a lack of standardisation and confounding variables including choice of controls and sample selection. This study aimed to determine a reference range for ROS in human semen.

METHODS

Semen samples were obtained from men attending for routine semen analysis who gave informed consent for the study. Samples were assigned groups: Group 1 (N = 94) normal semen parameters, no leucocytospermia; Group 2 (N = 100) abnormal semen parameters, no leucocytospermia; Group 3 (N = 41) any semen parameters with leucocytospermia. ROS levels were assayed in fresh neat semen using a chemiluminescence assay measured in a single tube luminometer. Data are reported in relative light units (RLU)/sec/10(6) sperm

RESULTS

ROS levels were significantly different between Groups 1, 2 and 3 (19.75 ± 8.12, 95.03 ± 33.63, 890.17 ± 310.23 RLU/sec/10(6) sperm respectively; p < 0.001). Group 3 gave the highest value confirming this group as the optimum choice for positive controls. The reference range < 24.1 RLU/sec/10(6) sperm was determined by ROC analysis that differentiates a reference population (Group 1) from a positive control group (Group 3), optimising the sensitivity and specificity (80.5 and 87.2% respectively) of the test.

CONCLUSIONS

We have determined a reference range for ROS in human semen and identified a patient population that falls outside the normal range. This simple, cost effective assay can be incorporated into routine diagnostic testing to aid in the diagnosis of male infertility, especially with regard to unexplained infertility.

Improving fertilization rate in ICSI cycles by adding myoinositol to the semen preparation procedures: a prospective, bicentric, randomized trial on sibling oocytes

PURPOSE

To evaluate whether the in vitro incubation of spermatozoa with myoinositol may improve the fertilization rate in ICSI cycles.

METHODS

This is a prospective, bicentric, randomized study on 500 MII sibling oocytes injected in 78 ICSI cycles performed between March and October 2013. Randomization of the oocytes into two groups was performed at the time of the denudation. Fertilization rates (per oocyte injected with spermatozoa treated with myoinositol versus per oocyte injected with spermatozoa treated with placebo) were measured as primary outcome and embryo morphology as secondary outcome. Clinical outcomes were also documented.

RESULT (S)

Fertilization rate (78.9 ± 28.6% vs 63.2 ± 36.7, P = 0.002) and percentage of grade A embryos on day 3 (59.8 ± 35.6% vs 43.5 ± 41.5, P = 0.019) were significantly higher when spermatozoa were treated in vitro with myoinositol versus placebo. No differences were found for the expanded blastocyst formation rate.

CONCLUSION (S)

In vitro treatment of spermatozoa with myoinositol may optimize ICSI outcomes by improving the fertilization rate and embryo quality on day 3. The improvement of the number and the quality of embryos available in an ICSI cycle may have clinical utility if these findings can be confirmed.

Sperm quality after density gradient centrifugation with three commercially available media: a controlled trial

BACKGROUND

Density gradient is the preferred technique for sperm processing for ART. However, no study has examined sperm quality using different processing media simultaneously and under identical conditions. Therefore, we evaluated semen quality following sperm preparation by three commonly used commercially available density gradient media in a well-designed controlled trial.

METHODS

We obtained semen samples from 20 healthy volunteers. Percent motility, total motile sperm (TMS), % recovery and DNA damage were assessed before and after separation in three different sperm density gradient media-PureCeption, ISolate and SpermGrad-125.

RESULTS

Percent motility was higher in the ISolate (81.4% ± 6.6%) and SpermGrad-125 samples (85.7% ± 8.0%) (P < 0.0001) than in the PureCeption samples (62.5% ± 13.2%) (P = 0.07). TMS was higher in the PureCeption(TM) and ISolate samples (14.2% ± 15.9% and 15.8% ± 18.2%) than in those prepared with SpermGrad-125 (10.6% ± 19.7%) (P < 0.0001). Percent recovery was significantly higher in the PureCeption(TM) and ISolate samples (45.3% and 48.9%) than in the SpermGrad-125(TM) samples (30.8%) (P < 0.01). DNA fragmentation was comparable across the three gradients (PureCeption = 8.8% ± 4.7%; ISolate = 7.2 ± 5.2% and SpermGrad-125 = 11.2% ± 7.4%).

CONCLUSIONS

Three different density gradient processing media PureCeption, ISolate, and SpermGrad-125 were examined for their effects on sperm quality. Sperm processed by ISolate and Sperm Grad 125 had better motility and TMS after processing. The extent of DNA damage was comparable in all three gradients.

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