Probes and Techniques for Sperm Evaluation by Flow Cytometry

Factors affecting the success of laparoscopic artificial insemination in sheep

Successful artificial breeding underpins rapid genetic and production gains in animal agriculture. In sheep, artificial insemination with frozen semen is performed via intrauterine laparoscopy as frozen-thawed spermatozoa do not traverse the cervix in sufficient numbers for high fertility and transcervical insemination is anatomically impossible in most ewes. Historically, laparoscopic artificial insemination has always been considered reasonably successful, but recent anecdotal reports of poor fertility place it at risk of warning adoption. Understanding the male, female and environmental factors that influence the fertility of sheep is warranted if the success of artificial insemination is to be improved and genetic progress maximised for the sheep industry. This review details the current practice of laparoscopic AI in sheep. It explores the effects of semen quantity and quality, the ewe, her preparation, and environmental conditions, on the fertility obtained following laparoscopic artificial insemination.

Spinning Disk Confocal Microscopy for Optimized and Quantified Live Imaging of 3D Mitochondrial Network

Mitochondria are the energy factories of a cell, and depending on the metabolic requirements, the mitochondrial morphology, quantity, and membrane potential in a cell change. These changes are frequently assessed using commercially available probes. In this study, we tested the suitability of three commercially available probes-namely 5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolo-carbocyanine iodide (JC-1), MitoTracker Red CMX Rox (CMXRos), and tetramethylrhodamine methyl ester (TMRM)-for assessing the mitochondrial quantity, morphology, and membrane potential in living human mesoangioblasts in 3D with confocal laser scanning microscope (CLSM) and scanning disk confocal microscope (SDCM). Using CLSM, JC-1, and CMXRos-but not TMRM-uncovered considerable background and variation. Using SDCM, the background signal only remained apparent for the JC-1 monomer. Repetitive imaging of CMXRos and JC-1-but not TMRM-demonstrated a 1.5-2-fold variation in signal intensity between cells using CLSM. The use of SDCM drastically reduced this variation. The slope of the relative signal intensity upon repetitive imaging using CLSM was lowest for TMRM (-0.03) and highest for CMXRos (0.16). Upon repetitive imaging using SDCM, the slope varied from 0 (CMXRos) to a maximum of -0.27 (JC-1 C1). Conclusively, our data show that TMRM staining outperformed JC-1 and CMXRos dyes in a (repetitive) 3D analysis of the entire mitochondrial quantity, morphology, and membrane potential in living cells.

Sperm quality variables of sex-sorted bull semen produced by magnetic-activated cell sorting coupled with recombinant antibodies targeting Y-chromosome-bearing sperm

The immunological sexing method using antibodies offers cost-effective, high-volume production but faces challenges in terms of X-sperm purity in sexed semen. This research aimed to produce sexed bull semen using highly specific recombinant antibodies in magnetic-activated cell sorting (MACS), evaluate sperm quality and kinematic parameters, and verify the sex ratio of sperm, embryos, and live calves. Fresh semen from two Angus bulls was separated into two equal groups: conventional (CONV) semen and semen sexed using MACS with Y-scFv antibody conjugation to separate two fractions, i.e., the X-enriched and Y-enriched fractions. Then, computer assisted semen analysis and imaging flow cytometry were used to evaluate sperm motility and kinematic variables, acrosomal integrity, sperm viability, and sperm sex ratios. The results showed that sperm motility and quality did not differ between X-enriched and CONV semen. However, the Y-enriched fraction showed significantly lower sperm quality than the X-enriched fraction and CONV semen. The sperm ratio revealed that X-sperm accounted for up to 79.50% of the X-enriched fraction, while Y-sperm accounted for up to 78.56% of the Y-enriched fraction. The sex ratio of embryos was examined using in vitro fertilization. The cleavage rates using CONV and X-enriched semen were significantly higher than that using Y-enriched semen. Accordingly, 88.26% female blastocysts were obtained by using X-enriched semen, and 83.58% male blastocysts were obtained by using Y-enriched semen. In farm trials, 304 cows were subjected to AI using X-enriched and CONV semen. The pregnancy rate did not differ between the X-enriched and CONV semen groups. On the other hand, X-enriched semen generated significantly more live female calves (83.64%) than CONV semen (47.00%). The MACS sexing method significantly enhanced the X-sperm purity in sexed semen, producing high-quality sperm, a high percentage of female blastocytes, and a high percentage of live female calves.

The characterization of CellROX™ probes could be a crucial factor in ram sperm quality assessment

Several authors have demonstrated that low levels of reactive oxygen species (ROS) are necessary for the physiological functions of sperm, such as capacitation, hyperactivation, acrosomal reaction and fertilization. However, high levels of ROS are associated with oxidative stress and detrimental effects on fertility. Consequently, deep characterization of ROS presence using different fluorescent probes could be crucial. In this sense, the study of intracellular ROS localization and the relationships between ROS and other conventional parameters could improve the characterization of sperm quality for semen preservation protocols in rams. In this work, a multiparametric study was carried out by analyzing four experimental groups of ram sperm with different initial qualities: fresh semen (from both breeding and nonbreeding seasons), frozen-thawed semen and, a positive control group treated with hydrogen peroxide (300 μM) as a marker of extreme damage. Sperm analyses, including viability, apoptosis, lipid peroxidation, motility and kinetic parameters, were applied to compare several experimental groups with different sperm qualities. After that, the signals from two different ROS probes: CellROX™ Deep Red (CRDR) and Green (CRG), were examined by flow cytometry (percentage of cells that express ROS) and fluorescence microscopy (intracellular ROS location). Comparing conventional parameters, fresh samples from the breeding season showed the highest sperm quality, while the positive control samples showed the worst sperm quality. Concerning the ROS probes, the CRDR levels were higher in fresh samples from the breeding season than in the positive control and cryopreserved samples. Surprisingly, CRG presented its highest level (P < 0.05) in the positive control group treated with peroxide by flow cytometry. CRDR and CRG presented opposite labeling patterns that were corroborated by fluorescence microscopy, which determined that the probes localized in different parts of sperm. CRDR was found in the sperm mitochondrial region, while CRG was observed in the cell nucleus, suggesting that ROS localization is an important factor. Finally, our study indicates that CRDR is correlated with proper viability and sperm motility, and could be associated with high mitochondrial activity, while CRG is associated with sperm damage.

Evaluation of Sperm DNA Fragmentation Using Two Different Methods: TUNEL via Fluorescence Microscopy, and Flow Cytometry

Background and Objectives: Sperm DNA fragmentation refers to any break in one or both of the strands of DNA in the head of a sperm. The most widely used methodologies for assessing sperm DNA fragmentation are the sperm chromatin structure assay (SCSA), the sperm chromatin dispersion assay (SCD), the single-cell gel electrophoresis assay (SCGE-comet), and the terminal-deoxynucleotidyl-transferase (TdT)-mediated dUTP nick end labelling (TUNEL) assay. The aim of this study was to compare the efficiency and sensitivity of the analysis of sperm DNA fragmentation using TUNEL via fluorescence microscopy, and flow cytometry. Materials and Methods: Semen samples were collected and analyzed for standard characteristics using light microscopy, and for sperm DNA fragmentation using both TUNEL via fluorescence microscopy, and flow cytometry. Results: There were no significant differences in the values of the sperm DNA fragmentation index (DFI) obtained when the analysis was performed using TUNEL or flow cytometry (p = 0.543). Spearman's correlation analysis revealed a significant negative correlation between sperm motility (%) and sperm DNA fragmentation (p < 0.01), as well as between sperm concentration and sperm DNA fragmentation (p < 0.05). The Mann-Whitney U test showed no significant difference in the DFI among couples with repeated implantation failure (RIF) and miscarriages (p = 0.352). Conclusions: Both methods (TUNEL via fluorescence microscopy, and flow cytometry) have a high efficiency and sensitivity in accurately detecting sperm DNA fragmentation, and can be effectively used to assess male fertility.

Glycerol-Free Equilibration with the Addition of Glycerol Shortly before the Freezing Procedure: A Perspective Strategy for Cryopreservation of Wallachian Ram Sperm

This study investigated the effect of glycerol added in different phases of sperm equilibration on CASA and flow cytometry parameters of thawed ram spermatozoa. Sperm was collected from adult Wallachian rams. The freezing extender was glycerol-free ANDROMED® (Minitub GmbH, Tiefenbach, Germany) supplied by 6% exogenous glycerol at different stages of the cryopreservation process. The purpose of this study was to compare two strategies of glycerol addition for sperm cryopreservation. The first strategy included the use of a glycerol-free extender for the procedure of glycerol-free equilibration and chilling, with the glycerolation of the extender by 6% glycerol shortly before sperm slow freezing (GFA). The second strategy included the use of a freezing extender already glycerolated by 6% glycerol before the equilibration and chilling of sperm and following slow freezing (GA). Sperm samples were analyzed after equilibration (but before freezing) and after thawing (at T0, T1 h, and T2 h time points). iSperm® mCASA (Aidmics Biotechnology Co., LTD., Taipei, Taiwan) was used for the evaluation of sperm kinematics. Flow cytometry was used to measure sperm viability (plasma membrane/acrosome intactness) and mitochondrial membrane potential. The obtained results significantly demonstrated that the glycerol-free equilibration with the addition of glycerol shortly before freezing is a perspective strategy for cryopreservation of Wallachian ram sperm.

Fluorescence Microscopy and Flow-Cytometry Assessment of Substructures in European Red Deer Epididymal Spermatozoa after Cryopreservation

Thawed spermatozoa, sampled post mortem from the fresh epididymides of European red deer and epididymides stored for up to 12 h at 2–4 °C, were evaluated by fluorescence microscopy (FM) and flow cytometry (FC). The sperm samples were extended and cryopreserved. The sperm motility (CASA), sperm viability (SYBR+/PI-), acrosome integrity, mitochondrial activity, apoptotic changes, and chromatin stability were assessed. Sperm were analyzed by FM before cryopreservation, and by FM and FC after thawing. Epididymal storage time (for 12 h) had no significant effect (p > 0.05) on the examined variables before cryopreservation. After thawing, the storage variants differed (p ˂ 0.05) in the percentage of apoptotic sperm (FM and FC) and DNA integrity (FC). The results of FM and FC differed (p ˂ 0.05) in all the analyzed parameters, excluding SYBR+/PI. Significant correlations (p ˂ 0.01) were observed between the sperm viability, acrosome integrity, and the percentage of non-apoptotic spermatozoa, regardless of the applied technique. In FM, the above parameters were also significantly correlated with mitochondrial activity. The study demonstrated that European red deer spermatozoa stored in the epididymides at 2–4 °C for 12 h can be used for cryopreservation. Both techniques were equally reliable, but FM was better suited for evaluating mitochondrial activity whereas FC was more useful in the evaluation of DNA fragmentation.

Deciphering sperm chromatin properties to predict stallion sperm fertility

Although previous studies have examined the relationship between the sperm DNA fragmentation index and fertility in stallions, other aspects of chromatin structure or packaging and fertility have not been explored. In the present study, relationships between fertility and DNA fragmentation index, protamine deficiency, total thiols, free thiols and disulfide bonds in stallion spermatozoa were investigated. Ejaculates (n = 36) were collected from 12 stallions and extended to prepare semen doses for insemination. One dose from each ejaculate was sent to the Swedish University of Agricultural Sciences. Aliquots of semen were stained for flow cytometry with acridine orange for the Sperm Chromatin Structure Assay (DNA fragmentation Index, %DFI), with chromomycin A3 (CMA) for protamine deficiency, and with monobromobimane (mBBr) for detection of total and free thiols and disulfide bonds. Per season pregnancy rates after insemination were obtained. Mixed linear models were used to analyze data. Negative correlations were found between pregnancy rate and %DFI (r = -0.35, P < 0.03) and pregnancy rate and free thiols (r = -0.60, P < 0.0001). Furthermore, there were positive correlations between total thiols and disulfide bonds (r = 0.95, P < 0.0001), and protamine and disulfide bonds (r = 0.4100, P < 0.01986). Since chromatin integrity, protamine deficiency and packaging were all associated with fertility, a combination of these factors could be used as a biomarker of fertility when assessing ejaculates.

Multiple flow cytometry analysis for assessing human sperm functional characteristics

Multiparametric analysis by flow cytometry solves one of the major problems in sperm evaluation, the inability to test multiple attributes simultaneously in a single cell, which would increase the precision to predict fertility potential since several sperm parameters are tested. The association of fluorochromes and compounds conjugated to fluorochromes in multiparametric sperm analysis is well-established in microscopy techniques. However, these techniques are subjective and limit the assessment in small cell numbers, thereby harming analytic accuracy. Therefore, the current study aimed to present new possibilities for assessing the integrity and stability of the sperm plasma membrane, acrosome status, mitochondrial potential, and superoxide anion production in the mitochondrial matrix in only 2 cytometric assays using cytometers equipped with 2 and 3 lasers. For this, human semen samples collected by masturbation and selected by the swim-up technique were divided into 3 treatments: T0 (flash-frozen semen), T50 (flash-frozen semen + fresh semen, V: V), and T100 (fresh semen) for the validation of the multiparametric protocols by flow cytometry. For both protocols, sperm percentage with positive stain for all fluorophores differed significantly between treatments. The determination coefficients presented values close to 1, which validated objective, sensitive, rapid, and reproducible methodologies. Therefore, we concluded that the results reflect the status of analyzed structure, enabling a more accurate diagnosis of male infertility that has become an increasingly prevalent worldwide setback due to exposure to a variety of environmental toxicants.

A method for multiple sampling mouse sperm in vivo†

Mice are the most widely used animal model to study human diseases. However, the difficulty of in vivo recovery of mouse sperm has posed a limitation with its use in reproductive biology research. Several published techniques for obtaining sperm samples in vivo have been described, but most of them have several caveats. Critical limitations include poor reliability and significant mortality (Electroejaculation and drug-induced ejaculation), or the need for a large number of animals, careful programming, and laborious work (directed mating). Here, we describe a new approach for in vivo collection of sperm in the mouse via direct puncture of the epididymis to address these limitations. In addition, the technique is easy, safe, and reliable, allowing the animal to recover and maintain its fertility. In this way, punctual experiments could be carried out, or even more so, serial sampling of the same animal over time. Therefore, our approach allows for long-term and time-course experiments to study sperm characteristics under different treatments or conditions while maintaining the spermatogenic niche in vivo. In summary, we present our original approach as a powerful research tool to facilitate the study of spermatozoa relevant to various areas of biomedical research.

The Autophagy Marker LC3 Is Processed during the Sperm Capacitation and the Acrosome Reaction and Translocates to the Acrosome Where It Colocalizes with the Acrosomal Membranes in Horse Spermatozoa

Despite its importance in somatic cells and during spermatogenesis, little is known about the role that autophagy may play in ejaculated spermatozoa. Our aim was to investigate whether the molecular components of autophagy, such as microtubule-associated protein 1 light chain 3 (LC3), are activated in stallion spermatozoa during the capacitation and acrosome reaction and if this activation could modulate these biological processes. To analyze the autophagy turnover, LC3I and LC3II proteins were assessed by western blotting, and the ratio between both proteins (LC3II/LC3I) was calculated. In somatic cells, this ratio indicates that autophagy has been activated and similar LC3 processing has been described in mammalian spermatozoa. The subcellular localization of autophagy-related proteins was assessed by immunofluorescence with specific antibodies that recognized Atg16, Beclin-1, and LC3. The colocalization of acrosomal membranes (PNA) and LC3 was studied by confocal microcopy, and the acrosome reacted cells were quantified by flow cytometry. The incubation of stallion sperm in capacitating conditions (BWW; 3 h) significantly increased LC3 processing. This increment was three to four times higher after the induction of the acrosome reaction in these cells. LC3 was mainly expressed in the head in mature ejaculated sperm showing a clear redistribution from the post-acrosomal region to the acrosome upon the incubation of sperm in capacitating conditions (BWW, 3 h). After the induction of the acrosome reaction, LC3 colocalized with the acrosome or the apical plasmalemma membranes in the head of the stallion spermatozoa. The inhibition or activation of autophagy-related pathways in the presence of autophagy activators (STF-62247) or inhibitors (E-64d, chloroquine) significantly increased LC3 processing and increased the percent of acrosome reacted cells, whereas 3-methyladenine almost completely inhibited LC3 processing and the acrosome reaction. In conclusion, we found that sperm capacitation and acrosome reaction could be regulated by autophagy components in sperm cells ex vivo by processes that might be independent of the intraluminal pH of the acrosome and dependent of LC3 lipidation. It can be speculated that, in stallion sperm, a form of noncanonical autophagy utilizes some components of autophagy machinery to facilitate the acrosome reaction.

A Pilot Study on the Uptake of Propidium Iodide and YO-PRO-1 Iodide through the Pannexin Channels in Wallachian Frozen-Thawed Ram Spermatozoa

Propidium iodide (PI) and YO-PRO-1 (YPI) dyes are routinely used to determine sperm viability in many livestock species. It is commonly accepted that these dyes penetrate only sperm cells with damaged plasma membranes. Recently, however, the mechanism of dye uptake unrelated to damaged plasma membranes, but instead related to pannexin channels in dog and stallion sperm cells was demonstrated. This pilot study aimed to evaluate the role of pannexins in the uptake of PI and YPI dyes on Wallachian frozen-thawed ram spermatozoa by flow cytometry using probenecid, a specific inhibitor of pannexin channels. Additionally, the expression of pannexins in Wallachian sperm was evaluated directly (by qRT-PCR). The results demonstrate the active role of pannexin channels in the uptake of PI and YPI dyes on frozen-thawed Wallachian ram sperm. In conclusion, when using the PI or YPI exclusion assay to determine Wallachian frozen-thawed ram sperm viability, the danger of overestimating the number of spermatozoa with the damaged plasma membrane must be considered. The observed breed-specific, and more importantly, individual differences in gene expression as well as in dye uptake indicate the need for further studies.

Determination of Ram (Ovis aries) Sperm DNA Damage Due to Oxidative Stress: 8-OHdG Immunodetection Assay vs. SCSA®

Conventional DNA analysis techniques can hardly detect DNA damage in ruminant spermatozoa due to high DNA compaction in these cells. Furthermore, these techniques cannot discriminate whether the damage is due to oxidative stress. The main purpose of this study was to evaluate the efficacy of two techniques for determining DNA damage in ovine sperm when the source of that damage is oxidative stress. Semen samples from twenty Manchega rams (Ovis aries) were collected and cryopreserved. After thawing, the samples were subjected to different levels of oxidative stress, and DNA oxidation was quantified using an 8-hydroxy-2′-deoxyguanosine (8-OHdG) immunodetection assay and Sperm Chromatin Structure Assay (SCSA®). For this purpose, we evaluated five different concentrations of an oxidation solution (H2O2/FeSO4•7H2O) on ram sperm DNA. Our study with the 8-OHdG immunodetection assay shows that there are higher values for DNA oxidation in samples that were subjected to the highest oxidative stress (8 M H2O2/800 µM FeSO4•7H2O) and those that were not exposed to high oxidative stress, but these differences were not significant (p ≥ 0.05). The two SCSA® parameters considered, DNA fragmentation index (DFI %) and high DNA stainability (HDS %), showed significant differences between samples that were subjected to high concentrations of the oxidation agent and those that were not (p < 0.05). We can conclude that the 8-OHdG immunodetection assay and SCSA® detect DNA damage caused by oxidative stress in ovine sperm under high oxidative conditions; SCSA® is a more straightforward method with more accurate results. For these reasons, an oxidative-stress-specific assay such as 8-OHdG immunodetection is not needed to measure DNA damage caused by oxidative stress in ram sperm samples.

Electrophysiology and Fluorescence Spectroscopy Approaches for Evaluating Gamete and Embryo Functionality in Animals and Humans

This review has examined two of the techniques most used by our research group for evaluating gamete and embryo functionality in animal species, ranging from marine invertebrates to humans. Electrophysiology has given access to fundamental information on some mechanisms underpinning the biology of reproduction. This technique demonstrates the involvement of ion channels in multiple physiological mechanisms, the achievement of homeostasis conditions, and the triggering of profound metabolic modifications, often functioning as amplification signals of cellular communication. Fluorescence spectrometry using fluorescent probes to mark specific cell structures allows detailed information to be obtained on the functional characteristics of the cell populations examined. The simple and rapid execution of this methodology allowed us to establish a panel helpful in elucidating functional features in living cells in a simultaneous and multi-parameter way in order to acquire overall drafting of gamete and embryo functionality.

Nuclear DNA Fragmentation in Boar Spermatozoa: Measurement Methods and Reproductive Performance Implications

The aim of this research was to compare the different techniques to measure sperm nuclear DNA fragmentation (sDF) and to check its relations to boar reproductive value, classical spermiogram parameters, and reproductive results of the doses in sows. Sperm chromatin stability assay (SCSA), terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and sperm chromatin dispersion test (SCD, Halomax^®) results were compared, finding a statistically significant correlation only between SCSA and TUNEL results. The fertility direct boar effect (DBE) index, calculated from the whole productive life of the boar, was not correlated (p > 0.05) with sDF (measured by any technique). Total or progressive sperm motility was not correlated with sDF, while it found a positive correlation between TUNEL measure and abnormal acrosomes (%) and between SCD measure and total sperm morphological abnormalities (%). No significant correlations were obtained between fertility or prolificacy results and sDF results with the different techniques. However, in the case of total born and SCSA measure, the correlation was close to significance (r partial = −0.095; p = 0.066), appointing to a tendency; as SCSA increases, the number of total piglets born decreases. In conclusion, although the different techniques for the sDF seem not to target exactly the same DNA events and the relationship between their values and the reproductive results and the classical spermiogram results is still to be elucidated, the studied sDF techniques may offer extra information that could be useful for the management of AI studs.

Molecular analysis of microorganisms in the semen and their impact on semen parameters

OBJECTIVE

Chronic genitourinary infections can alter male fertility and even promote carcinogenic processes. This study aimed to evaluate the effect of the presence in the semen of microorganisms on semen quality.

MATERIALS AND METHODS

Clinical symptoms and conventional and functional seminal parameters of eleven fertile donors and ten volunteers with prostatitis-like symptoms were evaluated. Nitric oxide, antioxidant capacity, and pro-inflammatory cytokines in semen and seminal plasma samples were also quantified. Finally, the expression of the ROR-γT, FoxP3, and T-bet genes in semen and the presence of DNA of microorganisms associated with prostatitis in urine and semen were evaluated.

RESULTS

When compared with fertile donors, volunteers with chronic prostatitis-like symptoms reported erectile dysfunction (0% vs. 10%, p = 0.2825) and premature ejaculation (0% vs. 40%; p = 0.0190). No statistically significant differences were observed in seminal parameters, cytokine measurement, antioxidant capacity, nitric oxide concentration and ROR-γT, FoxP3, T-bet. Microorganisms responsible for sexually transmitted infections and some bacteria associated with the microbiota and infections in the prostate gland were detected. In the semen from the subjects with prostatitis-like symptoms T. vaginalis DNA was detected; in addition, N. gonorrhoeae DNA was also detected in semen and urine samples. S. pyogenes was detected in the urine samples from the control group.

CONCLUSIONS

Prostatitis-like symptoms are a common finding in young men that affect sexual and reproductive health, but not always the seminal parameters or fertility. The presence of prostatitis- like symptoms does not affect seminal quality. However, it appears to be associated with an increased likelihood of erectile dysfunction and premature ejaculation. Thus, affecting the quality of life and sexual and reproductive health.

Comprehensive Flow-Cytometric Quality Assessment of Ram Sperm Intended for Gene Banking Using Standard and Novel Fertility Biomarkers

Flow cytometry becomes a common method for analysis of spermatozoa quality. Standard sperm characteristics such as viability, acrosome and chromatin integrity, oxidative damage (ROS) etc. can be easily assess in any animal semen samples. Moreover, several fertility-related markers were observed in humans and some other mammals. However, these fertility biomarkers have not been previously studied in ram. The aim of this study was to optimize the flow-cytometric analysis of these standard and novel markers in ram semen. Ram semen samples from Slovak native sheep breeds were analyzed using CASA system for motility and concentration and were subsequently stained with several fluorescent dyes or specific antibodies to evaluate sperm viability (SYBR-14), apoptosis (Annexin V, YO-PRO-1, FLICA, Caspases 3/7), acrosome status (PNA, LCA, GAPDHS), capacitation (merocyanine 540, FLUO-4 AM), mitochondrial activity (MitoTracker Green, rhodamine 123, JC-1), ROS (CM-H2DCFDA, DHE, MitoSOX Red, BODIPY), chromatin (acridine orange), leukocyte content, ubiquitination and aggresome formation, and overexpression of negative biomarkers (MKRN1, SPTRX-3, PAWP, H3K4me2). Analyzed semen samples were divided into two groups according to viability as indicators of semen quality: Group 1 (viability over 60%) and Group 2 (viability under 60%). Significant (p < 0.05) differences were found between these groups in sperm motility and concentration, apoptosis, acrosome integrity (only PNA), mitochondrial activity, ROS production (except for DHE), leukocyte and aggresome content, and high PAWP expression. In conclusion, several standard and novel fluorescent probes have been confirmed to be suitable for multiplex ram semen analysis by flow cytometry as well as several antibodies have been validated for the specific detection of ubiquitin, PAWP and H3K4me2 in ram spermatozoa.

Assessment of sperm mitochondrial activity by flow cytometry and fluorescent microscopy: a comparative study of mitochondrial fluorescent probes in bovine spermatozoa

CONTEXT

While conventional semen analysis is a simple, time-saving, and economical means to evaluate sperm quality, it leaves biochemical and metabolic characteristics of spermatozoa aside. To address this issue, the use of fluorescent probes assessing functional sperm parameters, such as JC-1, DiOC6 (3) and MitoTracker, has increased over the last decades. Apparently contradictory observations have nevertheless fostered an ongoing debate on their sensitivity and ability to evaluate the mitochondrial membrane potential (MMP) of sperm cells, thus warranting a re-examination of these probes.

AIMS

The present study aims to elucidate the suitability and sensitivity of each probe to evaluate the MMP of bovine spermatozoa by flow cytometry.

METHODS

Cryopreserved spermatozoa from ten bulls were thawed, stained with JC-1/SYTOXRed, DiOC6 (3)/propidium iodide (PI) or MitoTracker Deep Red (MTDR)/PI, and evaluated with flow cytometry and fluorescence microscopy.

KEY RESULTS

DiOC6 (3), JC-1 and MTDR can be simultaneously co-stained with a viability marker. The results of the present study support the ability of DiOC6 (3)/PI and JC-1/SYTOXRed, but not that of MTDR/PI, to monitor the MMP of spermatozoa.

CONCLUSIONS

JC-1/SYTOXRed assessed by flow cytometry was found to be the most sensitive and robust fluorescent probe to assess MMP. Moreover, DiOC6 (3)/PI could be a suitable alternative when the flow cytometer is not equipped with a red laser and/or an adequate optical filter.

IMPLICATIONS

Both DiOC6 (3) and JC-1, but not MTDR, could be used as probes to assess the mitochondrial membrane potential of bovine spermatozoa.

Probe ultrasonification of egg yolk plasma forms low-density lipoprotein (LDL) nanoparticles that efficiently protect canine semen during cryofreezing

Around the world, many couples have turned to in vitro fertilization as a viable solution to fertility issues. Low-density lipoprotein (LDL) is a protein best known for transporting fat molecules throughout the body, but it has also been shown to protect sperm cells during cryopreservation due to its micellar structure. In the present study, we aimed to evaluate different protocols for the preparation of nanoparticles from egg yolk plasma (EYP) containing LDL to improve the viability of cryopreserved canine semen. EYP was subjected to three distinct treatments: ultrasonification in an ultrasound bath at 40 kHz for 30 min (LDL-B); ultrasonification via an ultrasound probe at 50% amplitude for 30 min (LDL-P); and high-pressure homogenization at 10,000 PSI for six cycles (LDL-H). Sperm quality was assessed after thawing using computer-assisted sperm analysis and flow cytometry. The results revealed that compared to the EYP control, the LDL-P formulation presented significantly higher efficiency (p < 0.05) in maintaining total and progressive sperm motility, sperm membrane integrity and fluidity, and levels of intracellular reactive oxygen species. The LDL-P nanoparticles had an average size of approximately 250 nm, a PDI value of 0.3, and −1.15 mV of zeta potential, which are very important because it is an indicator of the stability of a colloidal dispersion. Therefore, we conclude that ultrasonication of EYP using a probe is an efficient method for the preparation of LDL nanoparticles that would enhance the cryoprotection of semen during freezing.

Characterization of the effects of triclosan on sperm and embryos of Mytilus and Perna mussel species

The Greenshell™ mussel (GSM), Perna canaliculus, is a culturally and commercially important species in New Zealand. Declines in spat settlement of GSM have been observed in important growing areas and the cause(s) have not been identified. One hypothesis is that chemical contaminants could be a contributing factor. The aim to this study was to investigate the effects of acute exposure on early life stages using the anti-microbial triclosan (TCS) as a benchmark toxicant and the blue mussel (BM), Mytilus galloprovincialis, as a reference species. Sperm and embryos of BM and GSM were exposed to TCS for 1 h and 48 h, respectively. Following exposures, a range of parameters were investigated including spermatozoa cellular characteristics via flow cytometry, fertilization success, larval mortality and size. Exposure to TCS negatively impacted functional parameters of sperm, reduced the fertilization success and larval size, and increased larval mortality in both BM and GSM with LC50_48h of 94.3 and 213 µg L^-1, respectively. Triclosan increased sperm ROS production in both species, which could cause destabilisation of mitochondrial and other cellular membranes, resulting in reduced mitochondrial membrane potential (BM) and increased sperm size (GSM), leading to apoptosis in both species. Fertilization success of GSM was only affected at the highest TCS concentration tested (391 µg L^-1), but development of larvae derived from exposed sperm was affected from the lowest concentrations tested (0.5 and 5.2 µg L^-1) in both species. This highlights the importance of assessing the sensitivity of contaminants across developmental stages. Results of this study confirm that TCS causes oxidative stress and has membranotropic effects, and that early life stages of the endemic GSM are suitable to assess ecotoxicity of contaminants such as TCS.

Measuring Reactive Oxygen Species in Semen for Male Preconception Care: A Scientist Perspective

Oxidative stress and elevated levels of seminal and sperm reactive oxygen species (ROS) may contribute to up to 80% of male infertility diagnosis, with sperm ROS concentrations at fertilization important in the development of a healthy fetus and child. The evaluation of ROS in semen seems promising as a potential diagnostic tool for male infertility and male preconception care with a number of clinically available tests on the market (MiOXSYS, luminol chemiluminescence and OxiSperm). While some of these tests show promise for clinical use, discrepancies in documented decision limits and lack of cohort studies/clinical trials assessing their benefits on fertilization rates, embryo development, pregnancy and live birth rates limit their current clinical utility. In this review, we provide an update on the current techniques used for analyzing semen ROS concentrations clinically, the potential to use of ROS research tools for improving clinical ROS detection in sperm and describe why we believe we are likely still a long way away before semen ROS concentrations might become a mainstream preconception diagnostic test in men.

Chronic Prostatitis: Impact of Lifestyle, Infection, and Inflammation on Semen Parameters

Chronic prostatitis is a widespread disease of the prostate affecting men’s sexual and reproductive health worldwide. Its leading causes are urogenital tract infections by microorganisms with a prostate tropism. This study aimed to evaluate semen parameters and the factors associated (lifestyle, urogenital infections, and inflammation) with the onset of chronic prostatitis symptoms. This case-control study included seventy-six donors: 30 volunteers with chronic prostatitis and 46 asymptomatic volunteers for urogenital infections as a control group. Sociodemographic, urinary symptoms, pain location, sexual and reproductive health and lifestyle-related variables were collected in a survey. Seminal quality, cytokine levels in semen and serum, and the presence of nineteen microorganisms in the urogenital tract were evaluated. Prostatitis was also associated with poor sperm morphology, more lipoperoxidation of the sperm membrane, and lower serum nitric oxide concentration. In addition, N. gonorrhoeae infection was detected more frequently in semen samples from volunteers with chronic prostatitis. Volunteers with chronic prostatitis report more frequently erectile dysfunction and premature ejaculation, anxiety, depression, and stress compared to the control group. Chronic prostate infections alter the microbiota from the genitourinary tract causing prostatitis, a disease that affects all life areas, including the familiar environment of patients. Chronic prostatitis affects seminal parameters, with a great impact on life quality and sexual and reproductive health. Despite being a relatively unexplored disease, much remains to be clarified regarding its diagnosis and treatment. Alterations in the genitourinary microbiota can favor sexually transmitted infections that produce chronic and systemic inflammation.

An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section II

Simple Summary

In order to improve fertilization and pregnancy rates within artificial insemination or in vitro fertilization techniques in horses, producers may choose to select the best sperm within an ejaculate. In this paper, we review conventional and novel methods of sperm selection.

Abstract

As the use of assisted reproductive technologies (ART) and in vitro embryo production (IVP) expand in the equine industry, it has become necessary to further our understanding of available semen selection techniques. This segment of our two-section review will focus on the selection of spermatozoa based on quality and sex for equine intracytoplasmic sperm injection (ICSI), as well as current and future developments in sperm sorting technologies. Ultimately, novel methods of semen selection will be assessed based on their efficacy in other species and their relevance and future application towards ARTs in the horse.

Ability of the ISAS3Fun Method to Detect Sperm Acrosome Integrity and Its Potential to Discriminate between High and Low Field Fertility Bulls

The objective of the present study was to investigate whether fertility differences in bulls are reflected in variations of sperm quality when analysing only one ejaculate per male. Two experiments were performed. In the first experiment, frozen semen samples from 20 adult bulls were tested; 10 bulls had high field fertility and 10 bulls had low field fertility. Analyses of sperm motility, membrane integrity, and membrane–acrosome integrity with the ISAS3Fun method were performed. Sperm morphometry of the fluorescence sperm subpopulations obtained with the ISAS3Fun method was also analysed. Significant differences between high- and low-fertility groups were only found with the ISAS3Fun technique, specifically in sperm acrosome integrity, the proportion of spermatozoa with an intact acrosome and damaged membrane, and in sperm head width of spermatozoa with intact structures. Discriminant analyses allowed us to correctly classify 90% of sperm samples in their fertility group using sperm quality parameters. Given that only the results obtained with the ISAS3Fun technique were related to bull fertility, we performed a second experiment aimed to validate the efficacy of this technique to detect the acrosomal integrity of bull spermatozoa, comparing them with the conventional FITC-PNA/propidium iodide (PNA/PI) combination under capacitating conditions. The results indicated that the ISAS3Fun combination provided an accurate assessment of both viability and acrosomal integrity for ejaculated spermatozoa, while the PNA/PI combination underestimated the extension of acrosomal damage due to false negatives. It was concluded that the simultaneous assessment of sperm plasma membranes and acrosome integrity with the ISAS3Fun method is precise and seems to have a greater potential to discriminate between high- and low-fertility bulls than more conventional in vitro sperm quality tests.

mRNA expression of oxidative-reductive proteins in boars with documented different fertility can identify relevant prognostic biomarkers

Oxidative stress unbalance is a major factor causing impairment of sperm function and, ultimately, sperm death. In this study, we identified transcriptomic and proteomic markers for oxidative-related protectors from the generation of reactive oxygen species (ROS) in spermatozoa from breeding boars with documented high- or low-fertility. Particular attention was paid to glutathione peroxidases, and to transcripts related to DNA stabilization and compaction, as protamine and transition proteins. mRNA cargo analysis was performed using porcine-specific micro-arrays (GeneChip® miRNA 4.0 and GeneChip® Porcine Gene 1.0 ST) and qPCR validation. Differences between fertility-classed boars were ample among biomarkers; some upregulated only at protein level (catalase (CAT), superoxide dismutase 1 (SOD1) and glutathione proteins), or only at the mRNA level (ATOX1, Antioxidant Protein 1). In addition, protamines 2 and 3, essential for sperm DNA condensation and also transition proteins 1 and 2 (TNP1 and TNP2), required during histone-to-protamine replacement, were overexpressed in spermatozoa from high-fertile boars. This up-regulation seems concerted to reduce DNA accessibility to ROS attack, protecting the DNA. The upregulated intracellular phospholipid hydroperoxide glutathione peroxidase (GPx4), in high-fertile boars at mRNA level, can be considered a most relevant biomarker for fertility disclosure during sperm evaluation.

Microbiota, Prostatitis, and Fertility: Bacterial Diversity as a Possible Health Ally

Background

In health, microorganisms have been associated with the disease, although the current knowledge shows that the microbiota present in various anatomical sites is associated with multiple benefits.

Objective

This study aimed to evaluate and compare the genitourinary microbiota of chronic prostatitis symptoms patients and fertile men.

Materials and Methods

In this preliminary study, ten volunteers have included 5 volunteers with symptoms of chronic prostatitis (prostatitis group) and five fertile volunteers, asymptomatic for urogenital infections (control group) matched by age. Bacterial diversity analysis was performed using the 16S molecular marker to compare the microbiota present in urine and semen samples from chronic prostatitis symptoms and fertile volunteers. Seminal quality, nitric oxide levels, and seminal and serum concentration of proinflammatory cytokines were quantified.

Results

Fertile men present a greater variety of operational taxonomical units-OTUs in semen (67.5%) and urine (17.6%) samples than chronic prostatitis symptoms men. Chronic prostatitis symptoms men presented a higher concentration of IL-12p70 in seminal plasma. No statistically significant differences were observed in conventional and functional seminal parameters. The species diversity in semen samples was similar in healthy men than prostatitis patients, inverted Simpson index median 5.3 (5.0–10.7) vs. 4.5 (2.1–7.8, p=0.1508). Nevertheless, the microbiota present in the semen and urine samples of fertile men presents more OTUs. Less microbial diversity could be associated with chronic prostatitis symptoms. The presence of bacteria in the genitourinary tract is not always associated with the disease. Understanding the factors that affect the microbiota can implement lifestyle habits that prevent chronic prostatitis.

Conclusion

Chronic prostatitis does not seem to affect male fertility; however, studies with a larger sample size are required. Our preliminary results strengthen the potential role; the greater bacterial diversity is a protective factor for chronic prostatitis.

Oxytocin in pig seminal plasma is positively related with in vivo fertility of inseminated sows

BACKGROUND

Identification of relevant in vivo biomarkers for fertility remains a challenge for the livestock industry. Concentrations of the small peptide hormone oxytocin (OXT), involved in male reproductive function and present in the seminal plasma (SP) of several species could be a robust one. This study characterized concentrations of SP-OXT in ejaculates from boars used in artificial insemination (AI) programs aiming to evaluate its relationship with sperm quality variables and in vivo fertility of their liquid-stored AI-semen. Seminal OXT concentrations (ng/mL) were measured in 169 ejaculates from 61 boars of the Duroc, Pietrain, Landrace and Large White breeds using a direct competitive immunoassay test based on AlphaLISA^® technology. Ejaculate (ejaculate volume, sperm concentration, total sperm count) and sperm parameters (motility, viability, intracellular generation of reactive oxygen species, plasma membrane fluidity) were assessed at 0 h and 72 h in AI-semen samples stored at 17 °C. In vivo fertility included only 18 Large White and Landrace boars whose AI-semen was used to inseminated > 100 sows and evaluated both farrowing rate and litter size of 3,167 sows.

RESULTS

The results showed that SP-OXT differed between boars and between ejaculates within boar (P < 0.05) but not between breeds (Duroc, Pietrain, Landrace and Large White). Ejaculates with higher SP-OXT concentration/mL (hierarchically grouped; P < 0.001) had larger volume and came from younger boars (P < 0.05). Ejaculates of boars showing positive farrowing rate deviation exhibited higher (P < 0.05) SP-OXT concentration/mL than those with negative farrowing rate deviation.

CONCLUSION

The SP concentrations of OXT are boar, ejaculate and age dependent, and positively related with ejaculate volume and farrowing rates of liquid-stored semen AI-doses.

Use of antioxidants and time of cold storage: effects over viability parameters and enzymatic levels in semen of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792)

The cold storage of milt implies potentials alterations in its quality because the storage generates as main process, free radicals that produce spermatozoa membrane lipids damage with the consequent motility and fertilising capacity disruptions. To decrease the damage generated by free radicals the cells have antioxidant defences (proteins, enzymes, and low molecular weight substances). The objective of the present study evaluated the time storage effect and different antioxidants prepared in spermatic diluents on sperm viability of O. mykiss milt stored at 4°C. The two-way ANOVA denoted that the time storage and antioxidant influence have significant effects separated or combined on viability parameters (sperm motility and viability, proteins concentrations and superoxide dismutase enzymatic activity in seminal plasma). In contrast, only the storage time affected the fertilising capacity and catalase enzymatic activity in seminal plasma. The resulting analysis can conclude that the antioxidant presence improves the viability of cold stored milt, especially the transport conditions and the antioxidants allow the fecundity despite motility decrease.

Dynamics of mitochondrial membrane potential and DNA damage during cryopreservation of cattle and buffalo bull spermatozoa

Understanding the changes in the spermatozoa during cryopreservation is indispensable for tailoring and increasing the efficiency of cryopreservation process success. However, the dynamics of damage to sperm organelles during different stages of cryopreservation is underexplored. This study assessed the mitochondrial membrane potential (MMP) and DNA damage during different stages of cryopreservation, viz. immediately after ejaculation, after equilibration and after freezing and thawing in cattle and buffalo spermatozoa using flow cytometry. Proportion of spermatozoa with high MMP decreased significantly after equilibration (from 66.06±4.59 to 42.58±6.30 in Holstein bulls and from 60.32±5.51 to 39.98±7.58 in buffalo bulls). Sperm DNA integrity [DNA fragmentation index (DFI %)] in Holstein Friesian (HF) bulls did not differ significantly between fresh and equilibrated samples but a significantly higher % DFI was observed in frozen-thawed semen samples as compared to both fresh and equilibrated samples. In contrast, % DFI in buffalo spermatozoa did not differ among the three stages of cryopreservation. It was concluded that mitochondrial damages occur during equilibration while chromatin damages occur during freezing and thawing of cattle bull spermatozoa; whereas buffalo bull spermatozoa were lesser susceptible to DNA damage during cryopreservation as compared to cattle spermatozoa.

Semen extenders: An evaluative overview of preservative mechanisms of semen and semen extenders

Reproduction is fundamental for all living things as it ensures the continued existence of a species and an improved economy in animal husbandry. Reproduction has developed since history, and diverse processes, such as artificial insemination and in vitro fertilization, have been developed. Semen extenders were discovered and developed to protect sperm from harmful factors, such as freeze and osmotic shock, oxidative stress, and cell injury by ice crystals. Semen extenders preserve sperm by stabilizing its properties, including sperm morphology, motility, and viability and membrane, acrosomal, and DNA integrity. Therefore, semen extenders must provide a favorable pH, adenosine triphosphate, anti-cooling and anti-freeze shock, and antioxidant activity to improve semen quality for fertilization. Hence, this review provides precise data on different semen extenders, preservative mechanisms, and essential additives for semen extenders in different animals.

Semen evaluation: methodological advancements in sperm quality-specific fertility assessment - A review

Assessment of male fertility is based on the evaluation of sperm. Semen evaluation measures various sperm quality parameters as fertility indicators. However, semen evaluation has limitations, and it requires the advancement and application of strict quality control methods to interpret the results. This article reviews the recent advances in evaluating various sperm-specific quality characteristics and methodologies, with the help of different assays to assess sperm-fertility status. Sperm evaluation methods that include conventional microscopic methods, computer-assisted sperm analyzers (CASA), and flow cytometric analysis, provide precise information related to sperm morphology and function. Moreover, profiling fertility-related biomarkers in sperm or seminal plasma can be helpful in predicting fertility. Identification of different sperm proteins and diagnosis of DNA damage has positively contributed to the existing pool of knowledge about sperm physiology and molecular anomalies associated with different infertility issues in males. Advances in methods and sperm-specific evaluation has subsequently resulted in a better understanding of sperm biology that has improved the diagnosis and clinical management of male factor infertility. Accurate sperm evaluation is of paramount importance in the application of artificial insemination and assisted reproductive technology. However, no single test can precisely determine fertility; the selection of an appropriate test or a set of tests and parameters is required to accurately determine the fertility of specific animal species. Therefore, a need to further calibrate the CASA and advance the gene expression tests is recommended for faster and field-level applications.

Effects of Selenium on Bull’s Sperm Oxidative Stress and Viability Under in Vitro Conditions

The aim of this study was to determine the effects of sodium selenite on the level of oxidative stress and viability of spermatozoa in fresh bull ejaculate in in vitro conditions at different temperatures. Samples of the bull's ejaculates with a concentration of 7 × 105 spermatozoa per ml were placed into the commercial semen extender containing 0 (control), 1 (1Se), 3 (3Se) and 5 (5Se) µg.ml–1 of sodium selenite. The following analyses were performed by flow cytometry after 1, 3, 6, 8, 24, 48 and 72 hours of incubation at 4 °C and 37 °C. All analyses were carried out in triplicate. The level of oxidative stress at both temperatures were significantly lower in the experimental groups in comparison to the control group. However, a significant decline of live sperm concentration and a rise of damaged sperm concentration were recorded, especially in groups 1Se and 3Se in comparison to the control group. Only in group 5Se was there observed a positive effect on the damaged spermatozoa level in comparison with groups C, 1Se and 3Se at 4 °C. In conclusion, the applied concentrations of sodium selenite had a positive effect on the level of oxidative stress in all experimental groups, but mainly at concentration of 5 µg.ml–1 of sodium selenite, especially at 4 °C. However, the effect of selenium was not sufficient for improving the sperm viability.

Sperm chromatin integrity and DNA methylation in Norwegian Red bulls of contrasting fertility

In this study, the complexity of chromatin integrity was investigated in frozen-thawed semen samples from 37 sires with contrasting fertility, expressed as 56-day non-return rates (NR56). Protamine deficiency, thiols, and disulfide bonds were assessed and compared with previously published data for DNA fragmentation index (DFI) and high DNA stainability (HDS). In addition, in vitro embryo development and sperm DNA methylation were assessed using semen samples from 16 of these bulls. The percentages of DFI and HDS were negatively associated with NR56 and cleavage rate and positively associated with sperm protamine deficiency (p < 0.05). Significant differences in cleavage and blastocyst rates were observed between bulls of high and low NR56. However, once fertilization occurred, further development into blastocysts was not associated with NR56. The differential methylation analysis showed that spermatozoa from bulls of low NR56 were hypermethylated compared to bulls of high NR56. Pathway analysis showed that genes annotated to differentially methylated cytosines could participate in different biological pathways and have important biological roles related to bull fertility. In conclusion, sperm cells from Norwegian Red bulls of inferior fertility have less compact chromatin structure, higher levels of DNA damage, and are hypermethylated compared with bulls of superior fertility.

Spermatological parameters of immunologically sexed bull semen assessed by imaging flow cytometry, and dairy farm trial

This study compared the quality parameters of bull semen sexed using an immunological method with those of conventional semen by imaging flow cytometry and applied this semen in dairy farm trials. Semen samples were collected from ten ejaculates from five bulls. Each sample was divided into two treatments: conventional semen (CON) and semen sexed using monoclonal male-specific antibodies combined with the complement system for cytotoxicity reaction (IC-sexed). After obtaining frozen-thawed semen, we used imaging flow cytometry to assess acrosome integrity, sperm sex ratio and viability. Sperm morphology was evaluated using eosin-nigrosin staining. The percentage acrosome integrity did not differ between IC-sexed and CON semen (P = 0.313). The sperm sex ratio showed that the percentage of live X-chromosome-bearing sperm was higher than that of live Y-chromosome-bearing sperm in IC-sexed semen (P = 0.001). IC-sexed semen showed a higher percentage of head and tail defects than did CON semen (P = 0.019). In field trials, 585 cows were subjected randomly to AI with CON or IC-sexed semen. The pregnancy rate of the IC-sexed group did not differ from that of the CON group (P = 0.535). However, IC-sexed semen produced a significantly higher percentage of female calves than did CON semen (P = 0.031). Thus, immunological sexing did not adversely affect the acrosome integrity of sperm. Furthermore, a female calf birth rate of over 74 % can potentially be achieved using IC-sexed semen. These findings could help farmers to replace heifers in their herds.

Seasonal Changes of Nuclear DNA Fragmentation in Boar Spermatozoa in Spain

Simple Summary

Artificial insemination is widely used in pig production and currently a boar performs several thousand matings per year. Traditionally sperm quality is focused on the number of spermatozoa, their motility and morphology. However, the quality of sperm DNA, which contains genetic information, is also related to fertility problems. The aim of this research was to study the effect of natural light hours and age of the boar on the status of the sperm DNA. After a powerful statistical analysis, it was found that the percentage of spermatozoa with fragmented DNA decreases within the observed age range as the boar gets older. On the other hand, the amount of spermatozoa with fragmented DNA was the lowest in autumn while it was the highest in summer. This study demonstrates the remaining seasonality of boars in Spain and highlights the importance of controlling the environmental conditions in the farms. Sperm DNA testing provides a basis for improving the selection of AI boars by excluding males with higher DNA fragmentation due to their very young reproductive age that may pose a potential subfertility.

Abstract

There are numerous cases when conventional spermiogram parameters are all within an acceptable range but boar subfertility persists. The total sperm nuclear DNA fragmentation index (tDFI) is a trait related to fertility and prolificacy problems that is not routinely evaluated in commercial AI boars. The aim of this research was to study the effect of the photoperiod, season and reproductive age of the boar on tDFI (measured by SCSA) of 1279 ejaculates from 372 different boars belonging to 6 different breeds located in 6 AI studs in Spain. tDFI data ranged from 0.018% to 20.1%. Although there was a significant single boar effect in the tDFI occurrence, a negative correlation between the tDFI and the age of the boar was found (p < 0.001). tDFI would decrease due to aging of the boar 0.66% each year old within the observed age range. After including age as a covariate in the ANCOVA, no differences were found in tDFI between photoperiods when the sperm collection date was evaluated. However, when the date of the production of semen in the testis was evaluated, the total percentage of spermatozoa with fragmented nuclear DNA was 1.46% higher in the increasing photoperiod in comparison to the decreasing photoperiod (p < 0.0001). On the other hand, for both dates, the lowest tDFI values corresponded to minimum day length for decreasing photoperiod phase (autumn), while the highest tDFI values were found in summer (maximum day length for decreasing photoperiod phase).

HVCN1 but Not Potassium Channels Are Related to Mammalian Sperm Cryotolerance

Little data exist about the physiological role of ion channels during the freeze–thaw process in mammalian sperm. Herein, we determined the relevance of potassium channels, including SLO1, and of voltage-gated proton channels (HVCN1) during mammalian sperm cryopreservation, using the pig as a model and through the addition of specific blockers (TEA: tetraethyl ammonium chloride, PAX: paxilline or 2-GBI: 2-guanidino benzimidazole) to the cryoprotective media at either 15 °C or 5 °C. Sperm quality of the control and blocked samples was performed at 30- and 240-min post-thaw, by assessing sperm motility and kinematics, plasma and acrosome membrane integrity, membrane lipid disorder, intracellular calcium levels, mitochondrial membrane potential, and intracellular O₂⁻⁻ and H₂O₂ levels. General blockade of K⁺ channels by TEA and specific blockade of SLO1 channels by PAX did not result in alterations in sperm quality after thawing as compared to control samples. In contrast, HVCN1-blocking with 2-GBI led to a significant decrease in post-thaw sperm quality as compared to the control, despite intracellular O₂⁻⁻ and H₂O₂ levels in 2-GBI blocked samples being lower than in the control and in TEA- and PAX-blocked samples. We can thus conclude that HVCN1 channels are related to mammalian sperm cryotolerance and have an essential role during cryopreservation. In contrast, potassium channels do not seem to play such an instrumental role.

L-Proline: An Effective Agent for Frozen and Post-thawed Donkey Semen Storage

The aim of this study was to evaluate the effects of L-proline on the extender quality of frozen and post-thawed jackass semen. Jackass (n = 6) semen samples were collected and cryopreserved in gradient concentrations (0-80 mM) of L-proline in extenders; post-thawed semen samples were cultured in L-proline medium for 10 hours at 37°C. For cryopreservation experiment I, the motile parameters, mitochondrial membrane potential (MMP), and plasma membrane, acrosome, and chromatin structure integrities of post-thawed semen were assessed. For culture experiment II, additional ROS contents were analyzed after incubation. For the fertility trial, jennies (n = 135) were divided into group I (30 mM L-proline in cryopreservation extender), group II (40 mM L-proline in culture medium), and the control. Pregnancy was diagnosed using an ultrasound scanner 30 days after ovulation. The results of experiment I showed that, motile parameters and acrosome and chromatin structure integrities of groups I and 40 mM were significantly higher than the control (P < .05). MMP of group I was significantly higher than the control and 40 mM groups (P < .05). In experiment II, after 4 hours of incubation, motile parameters, MMP, and DNA integrity in group II were significantly higher than the control (P < .05). Additionally, 40 and 80 mM L-proline in culture medium significantly reduced ROS accumulation after 4 and 10 hours of incubation (P < .05). Pregnancy rates of the control and groups I and II were 28.85%, 40%, and 36.84%, respectively. In conclusion, the extenders containing 30 to 40 mM L-proline improved both qualities of frozen and post-thawed semen, and it will be a beneficial agent for donkey frozen spermatozoa or post-thawed semen storage.

Tetrazolium Salt WST-8 as a Novel and Reliable Chromogenic Indicator for the Assessment of Boar Semen Quality

Simple Summary

Good semen quality is an essential factor for breeding success when artificial insemination is performed. However, semen quality can not fully be evaluated by merely sperm viability or motility. Standard semen quality evaluation requires costly automated computer-assisted sperm analysis or specific and laborious labeling procedures before particular parameters can be assessed by flow cytometry. In the current study, we examined whether the 2-[2-methoxy-4-nitrophenyl]-3-[4-nitrophenyl]-5-[2,4-disulfophenyl]-2H-tetrazolium (WST-8) assay, which is widely used in the cell biology field, can be applied to evaluate sperm viability, and moreover, whether the WST-8 reduction rate can correlate with multiple sperm parameters that are related to sperm quality. We demonstrated in this study that the WST-8 assay can be used as a rapid, affordable, and reliable method for the prediction of semen quality in boar.

Abstract

A tetrazolium salt, 2-[2-methoxy-4-nitrophenyl]-3-[4-nitrophenyl]-5-[2,4-disulfophenyl]-2H-tetrazolium (WST-8), has been used widely to determine cell viability; however, its application in the field of reproduction is still limited due to this assay merely providing information regarding cell viability. The aim of this study was to correlate the WST-8 reduction rate with various sperm quality-related parameters (i.e., sperm viability, motility, progressive motility, acrosome integrity and mitochondria integrity) in order to provide a rapid, reliable and affordable assessment for boar semen quality evaluation. Using different ratios of active/damaged sperm cells, we first validated our sample preparations by standard flow cytometry and computer-assisted sperm analysis. Further analyses demonstrated that the most efficient experimental condition for obtaining a reliable prediction model was when sperm concentration reached 300 × 10⁶ cells/mL with the semen/cell-counting kit-8 (CCK-8^®) ratio of 200/10 and incubated time of 20 min. Under this set up, the WST-8 reduction rate (differences on optic density reading value, ΔOD at 450 nm) and sperm parameters were highly correlated (p < 0.01) for all sperm parameters evaluated. In the case of limited semen samples, a minimal semen concentration at 150 × 10⁶ cells/mL with the semen/CCK-8^® ratio of 200/20 and incubation time for 30 min could still provide reliable prediction of sperm parameters using the WST-8 assay. Our data provide strong evidence for the first time that the WST-8 assay could be used to evaluate boar semen quality with great potential to be applied to different mammalian species.

Ram semen quality can be assessed by flow cytometry several hours after post-fixation

Ram spermatozoa are very sensitive to any cold shock or oxidative damage, therefore making them unsuitable for prolonged storage or distant transport to specialized laboratories for flow-cytometric analysis. The aim of this study was to stain ram semen samples with several fluorescent markers and analyse their stability during formaldehyde fixation. Briefly, freshly collected semen samples were stained for apoptosis (annexin V-FITC, YO-PRO™-1 and FLICA), acrosomal damage (PNA-AF488 and FITC-conjugated antibody against GAPDHS), mitochondrial activity (Mitotracker probes), oxidative damage [dihydroethidium (DHE) and CellROX™ Green] and cell viability (live/dead fixable viability dyes). Next, samples were fixed in buffer containing formaldehyde and then washed. Stained sample were analyzed using flow cytometer before fixation, immediately after fixation, and at 5 h and 20 h post-fixation. Fluorescent signals and the proportion of positively stained spermatozoa were compared statistically in fresh and post-fixed samples. All examined markers, except YO-PRO-1 (decreased significantly, P < 0.05), retained their fluorescence intensities after fixation. In conclusion, several tested markers were able to withstand formaldehyde fixation of ram semen samples as follows: annexin V and FLICA for apoptosis; PNA for acrosomal status; MitoTracker Red CMXRos for mitochondrial activity; and CellROX Green for oxidative status in combination with a suitable live/dead fixable viability dye. This optimized methodology could help to comprehensively analyse the quality of ram semen from local farms countrywide.

Assessment of Optimized Frozen/Thawed Semen Samples in Canines with the New A-Kinase Anchor Protein 4 Precursor Biomarker

Optimizing thawing conditions are required to maximize recovery of semen capacities after cryopreservation. This study aimed to assess the effect of thawing procedures on motility recovery and maintenance of semen capacities over time. A fractional factorial design approach was used to reduce the number of repetitions and simultaneously analyze the different interactions. Thirty canine frozen semen samples were thawed under different thawing conditions. Motility and velocity parameters were recorded using a computer-assisted semen analyzer up to 6 hours after thawing. Ten quadratic models were found to be significant, with the most significant effects observed on the velocity parameters. Second, this study allowed us to evaluate the effect of the proAKAP4 marker on frozen/thawed semen, with regard to motility recovery. ProAKAP4 is the precursor of A-kinase anchor protein 4. It has been studied in several species as a marker to assess sperm quality. In our study, the expression of proAKAP4 was determined using flow cytometry. No correlation was found between post-thaw motility parameters and proAKAP4 levels. However, the effects of thawing temperature, incubation time, and straw size were significant and similar to those observed for velocity parameters.

Effect of MnTBAP on in vitro capacitation of frozen-thawed stallion sperm

In vitro manipulation of spermatozoa leads to deleterious changes of structure and function that occur mainly due to oxidative stress, therefore, prevention or treatment is a strategy to improve the functions of processed sperm. In the present study, the aim was to evaluate the effects of MnTBAP supplementation, a compound with antioxidant activity, on in vitro capacitation conditions of thawed equine sperm. For this purpose, stallion spermatozoa (2 × 10⁶ cells/mL) were incubated in the sperm-TLP base medium for 4 h in which there were three different conditions: non-capacitating, capacitating, and capacitating plus 150 mM MnTBAP. There were incubations for 4 h at 37.5 °C in a humidified air atmosphere. Sample analysis was performed immediately after thawing (0 h), and at the end of the incubation period (4 h), unless otherwise indicated. The following variables were evaluated for spermatozoa: plasma membrane integrity and fluidity, acrosome integrity, intracellular calcium concentrations, intracellular pH, tyrosine phosphorylation, ATP concentrations, motility and heterologous zona-binding assay, using flow cytometry, fluorescent microscopy and/or chemiluminescence, depending on the most appropriate procedure for the variable being evaluated. Results indicated that capacitation-like changes were synergistically induced by the cAMP agonists, phosphodiesterase inhibitor and bicarbonate. The presence of bovine serum albumin was harmful to the plasma membrane. The MnTBAP supplementation had a positive effect on viability-related markers (plasma membrane integrity, membrane fluidity, associated with greater intracellular pH) when there were capacitating conditions. In conclusion, the activity of MnTBAP contributes to improving the in vitro incubation conditions of frozen-thawed stallion sperm.

Temporal and Concentration Effects of Methanol on Cryopreservation of Zebrafish (Danio rerio) Sperm

We evaluated the cryoprotective effects of methanol on zebrafish sperm at different concentrations, exposure times, and stages during cryopreservation. Samples were collected by crushing of dissected testes or abdominal stripping. After exposure to 0%, 2%, 5%, 8%, and 10% methanol for 0-11 min, fresh sperm (1 × 106 cells/mL) did not show changes in plasma membrane integrity (measured by flow cytometer), but cell size changes (light scatter) were observed after exposure to 8% or 10%. After exposure for 0-60 min, fresh sperm (1 × 108 cells/mL) did not show significant changes in survival or membrane integrity. Sperm cryopreserved in 5%, 8%, and 10% methanol showed high post-thaw survival, in 5% and 8% showed high post-thaw motility, and in 5% showed highest post-thaw membrane integrity compared to other concentrations between 0% and 10%. Within 0-60 min after thawing, no significant differences in cell survival and membrane integrity were found for any concentration (p ≥ 0.269). Comparison of 5% and 8% methanol for dissected testes (n = 20) revealed no difference in post-thaw motility, membrane integrity, cell survival, fertilization, or hatching, embryo viability; for stripped sperm (n = 10), no differences were observed in post-thaw membrane integrity, fertilization, and embryo viability, however, higher motility and survival were detected in 5% than in 8% methanol. Thus, a concentration of 5% methanol seems most suitable for cryopreserving zebrafish sperm based on post-thaw survival and motility.

Irradiating frozen-thawed stallion sperm with red-light increases their resilience to withstand post-thaw incubation at 38 °C

The aim of this study was to evaluate whether red-light stimulation increases the longevity and resilience of cryopreserved stallion sperm to withstand post-thaw incubation for 120 min. Sixteen frozen straws of 0.5 mL from eight stallions were used. Samples were cryopreserved, thawed through incubation at 38 °C for 30 s and divided into the control and samples exposed to red-light using a triple LED photo-activation system (wavelength: 620-630 nm). Three irradiation protocols consisting of different light-dark-light intervals (1-1-1, 2-2-2 and 3-3-3 min) were tested. Sperm quality parameters were analyzed immediately after light-stimulation (0 min) and after 120 min of incubation at 38 °C. Sperm motility was evaluated using a Computerized Semen Analysis System (CASA), and flow cytometry and different fluorochromes were used to evaluate the integrity and lipid disorder of plasma membrane, mitochondrial membrane potential and intracellular levels of peroxides and superoxides. Irradiation significantly increased the percentages of spermatozoa with high mitochondrial membrane potential (1-1-1 pattern) and the intracellular levels of peroxides (2-2-2 pattern) at 0 min. In addition, sperm kinematic parameters (2-2-2 and 3-3-3 patterns) and percentages of viable spermatozoa with low membrane lipid disorder (3-3-3 pattern) were significantly higher in irradiated samples than in the control at 120 min. Our results indicate that red-light stimulation could help increase the resilience of frozen-thawed stallion sperm to withstand post-thaw incubation at 38 °C for 120 min and that these effects rely on the irradiation pattern. Further research should evaluate whether light-stimulation could also have a positive on fertility rates after artificial insemination.

ProAKAP4 as Novel Molecular Marker of Sperm Quality in Ram: An Integrative Study in Fresh, Cooled and Cryopreserved Sperm

To improve artificial insemination protocols in ovine species it is crucial to optimize sperm quality evaluation after preservation technologies. Emerging technologies based on novel biomolecules and related to redox balance and proteins involved in sperm motility such as ProAKAP4 could be successfully applied in ram sperm evaluation. In this work, a multiparametric analysis of fresh, cooled, and cryopreserved ram sperm was performed at different complexity levels. Samples were evaluated in terms of motility (total motility, progressive motility, and curvilinear velocity), viability, apoptosis, content of reactive oxygen species, oxidation‒reduction potential, and ProAKAP4 expression and concentration. As expected, cryopreserved samples showed a significant decrease of sperm quality (p < 0.05), evidencing different freezability classes among samples that were detected by ProAKAP4 analyses. However, in cooled sperm no differences were found concerning motility, viability, apoptosis, ROS content, and redox balance compared to fresh sperm that could explain the reported decrease in fertility rates. However, although the proportion of sperm ProAKAP4 positive-cells remained unaltered in cooled sperm compared to fresh control, the concentration of this protein significantly decreased (p < 0.05) in cooled samples. This altered protein level could contribute to the decrease in fertility rates of cooled samples detected by some authors. More importantly, ProAKAP4 can be established as a promising diagnostic parameter of sperm quality allowing us to optimize sperm conservation protocols and finally improve artificial insemination in ovine species.

Boar sperm quality and oxidative status as affected by rosmarinic acid at 17 °C

Peroxidation damage induces sublethal injury to boar sperm during preservation. Rosmarinic acid (RA) has already been verified to efficiently protect cells from oxidant-induced injury and to produce significant effect on cryopreservation of semen. Through our experiments, we aim at investigating whether RA has a positive effect on the preservation of pig semen at room temperature. The semen collected from sexually mature Large White boars were preserved at 17 °C in Beltsville thawing solution (BTS) supplied. The boar sperm were exposed to 0, 25, 50, 75, 100, 125 and 150 μM RA in vitro and the sperm functions were examined. The sperm motility, the acrosome and plasma membrane integrity, the catalase activity (CAT), the total antioxidative capacity (T-AOC) activity and the malondialdehyde content (MDA) were examined at 0, 1, 3 and 5 days. The BTS diluent containing RA improved the sperm quality during the process of liquid preservation compared with the control treatment. After 5 days of liquid preservation, the addition of RA at 100 μM produced an optimal effect on the survival time as well as on the maintenance of motility, acrosome and plasma membrane integrity; T-AOC activity; CAT activity; and the MDA content. Besides, our results in the reproductive experiments showed that the addition of RA at 100 μM to the BTS diluent increased the pregnancy rate. These results suggest that the proper concentration of RA in boar semen extenders possibly improves the artificial insemination efficiency by reducing the sperm damage and the subsequent dysfunction during liquid preservation in swine production systems.

Diagnostic value of advanced semen analysis in evaluation of male infertility

Conventional semen analysis is the standard of care to initially evaluate the fertility status of a male patient. However, it has some limitations and among these are failure to correctly identify the aetiology underlying fertility problems, intra- and inter-observer variability and incomplete information about sperm function. Considering these drawbacks, advanced semen tests have been developed to assess male infertility, including sperm function tests, oxidative stress (OS) and sperm DNA fragmentation (SDF) tests. This review illustrates the commonly utilised sperm function techniques, along with the assays used to assess SDF and OS and their diagnostic value.

Different approaches for assessing sperm function

Different approaches can be used to assess sperm function in different conditions, i.e. sperm storage, freezing-thawing or activation by induction of capacitation and acrosome reaction. In this review we will focus on the assays routinely performed in our laboratories, giving a literature support to critically analyse different approaches. In fact, researchers usually tend to look for the "one shot" parameter that could explain itself a specific process; it is our conviction that a multiparametric approach is still more valid, as some changes in sperm function are very complex and could be explained only by operating in different ways. Sperm motility, the most evident sperm characteristic, should be assessed by computer-aided sperm analysers that permit an objective evaluation of the motility and its kinematic parameters. Commercial and open source instruments are available and could be profitably used together with specific statistical approaches. The use of microscopy, and particularly fluorescent microscopy, could be a very useful tool to assess different parameters in sperm cells both by fluorophores that give indication of a determined function, and by immunolocalization of proteins, that permits the discover of new features or to explain particular sperm functions. The same substrates could be used also in flow cytometry: the difference is that it permits to study wider sperm populations (and their sub-population distribution). Flow cytometry is undergoing a very wide use in spermatology and technical and experimental rigor is needed to obtain reliable results. Metabolic assessment of sperm features, particularly energetic supply, ATP formation and other enzyme activities, could represent a very important challenge to acquire new information and complete/integrate those derived from other techniques. Finally, functional assays such as oocyte binding and in vitro fertilization, represent a very strong tool to assess sperm function in vitro, as they could evidence the functional intactness of some pathways.

HVCN1 Channels Are Relevant for the Maintenance of Sperm Motility During In Vitro Capacitation of Pig Spermatozoa

The objective of the present study was to determine the physiological role of voltage-gated hydrogen channels 1 (HVCN1 channels) during in vitro capacitation of pig spermatozoa. Sperm samples from 20 boars were incubated in capacitating medium for 300 minutes (min) in the presence of 2-guanidino benzimidazole (2-GBI), a specific HVCN1-channel blocker, added either at 0 min or after 240 min of incubation. Control samples were incubated in capacitating medium without the inhibitor. In all samples, acrosomal exocytosis was triggered with progesterone after 240 min of incubation. Sperm viability, sperm motility and kinematics, acrosomal exocytosis, membrane lipid disorder, intracellular calcium levels and mitochondrial membrane potential were evaluated after 0, 60, 120, 180, 240, 250, 270 and 300 min of incubation. While HVCN1-blockage resulted in altered sperm viability, sperm motility and kinematics and reduced mitochondrial membrane potential as compared to control samples, at any blocker concentration and incubation time, it had a non-significant effect on intracellular Ca²⁺ levels determined through Fluo3-staining. The effects on acrosomal exocytosis were only significant in blocked samples at 0 min, and were associated with increased membrane lipid disorder and Ca²⁺ levels of the sperm head determined through Rhod5-staining. In conclusion, HVCN1 channels play a crucial role in the modulation of sperm motility and kinematics, and in Ca²⁺ entrance to the sperm head.