A three-step statistical procedure to identify sperm kinematic subpopulations in canine ejaculates: changes after cryopreservation

Evaluation of the testicular artery Doppler velocimetry and its correlation with sperm defects in domestic cats

Several studies have demonstrated the correlation between Doppler velocimetric parameters of testicular artery and semen quality in domestic species, but in felines data are scarce. This study aimed to correlate the Doppler velocimetry of the testicular artery with sperm kinetics and sperm defects, in sedated and non-sedated cats. Forty tomcats were divided into two groups: sedated (SG; n=20) with dexmedetomidine (10 µm/kg) and ketamine (12 mg/kg), and non-sedated (NSG; n=20). The animals were subjected to ultrasound Doppler velocimetry of the distal supratesticular and marginal region of the testicular artery and subsequently orchiectomized. Epididymal tail spermatozoa were recovered and analyzed using a CASA system for motility, and morphology took place. Animals of SG presented a significantly higher velocity in the marginal region of the cat's testicular artery [peak systolic velocity (PSV) 11.51 cm/s; end-diastolic velocity (EDV) 7.72 cm/s] compared to NSG (PSV 7.72 cm/s, P < 0.001; EDV 4.93 cm/s, P < 0.001). Sedated cats presented higher pulsatility and resistivity indexes than non-sedated cats. The supratesticular PSV of NSG was moderately correlated with major (rs = 0621; P < 0.001) and total sperm defects (rs = 0614; P < 0001). Doppler velocimetry was fairly correlated with minor, major, and total sperm defects. In conclusion, Doppler velocimetric evaluation emerges as an important possibility in the reproductive evaluation of tomcats, once the testicular artery hemodynamics were associated with sperm defects. However, it is advisable to carry out this evaluation in non-sedated animals. If sedation is necessary, peripheral vasoconstriction should be considered.

Clustering of spermatozoa examined through flow cytometry provides more information than the conventional assessment: a resilience to osmotic stress example

Context Conventional sperm quality tests may not be sufficient to predict the fertilising ability of a given ejaculate; thus, rapid, reliable and sensitive tests are necessary to measure sperm function. Aims This study sought to address whether a cluster analysis approach based on flow cytometry variables could provide more information about sperm function. Methods Spermatozoa were exposed to either isotonic (300mOsm/kg) or hypotonic (180mOsm/kg) media for 5 and 20min, and were then stained with SYBR14 and propidium iodide (PI). Based on flow cytometry dot plots, spermatozoa were classified as either viable (SYBR14+ /PI- ) or with different degrees of plasma membrane alteration (SYBR14+ /PI+ and SYBR14- /PI+ ). Moreover, individual values of electronic volume (EV), side scattering (SS), green (FL1) and red (FL3) fluorescence were recorded and used to classify sperm cells through cluster analysis. Two strategies of this approach were run. The first one was based on EV and the FL3/FL1 quotient, and the second was based on EV, SS and the FL3/FL1 quotient. Key results The two strategies led to the identification of more than three sperm populations. In the first strategy, EV did not differ between membrane-intact and membrane-damaged sperm, but it was significantly (P P P Conclusions Cluster analysis based on flow cytometry variables provides more information about sperm function than conventional assessment does. Implications Combining flow cytometry with cluster analysis is a more robust approach for sperm evaluation.

Molecular Markers: A New Paradigm in the Prediction of Sperm Freezability

For decades now, sperm cryopreservation has been a pillar of assisted reproduction in animals as well as humans. Nevertheless, the success of cryopreservation varies across species, seasons, and latitudes and even within the same individual. With the dawn of progressive analytical techniques in the field of genomics, proteomics, and metabolomics, new options for a more accurate semen quality assessment have become available. This review summarizes currently available information on specific molecular characteristics of spermatozoa that could predict their cryotolerance before the freezing process. Understanding the changes in sperm biology as a result of their exposure to low temperatures may contribute to the development and implementation of appropriate measures to assure high post-thaw sperm quality. Furthermore, an early prediction of cryotolerance or cryosensitivity may lead to the establishment of customized protocols interconnecting adequate sperm processing procedures, freezing techniques, and cryosupplements that are most feasible for the individual needs of the ejaculate.

Canine Spermatozoa—Predictability of Cryotolerance

Simple Summary

Semen freezing in dogs is a field of growing interest. The international shipment of cryoconserved semen contributes to the avoidance of long travels and long-term storage of valuable gametes. However, the collection of one semen portion on average results in one to three doses for artificial insemination, which is a poor result in comparison to the outcome in large animals. The costs for the owners are therefore rather high. In individual dogs, the semen quality of raw semen is good; however, it could be suboptimal after thawing. To avoid costly freezing of these low-quality ejaculates, markers of freezability are useful. An abundance of markers are available for large animals, but not for dogs. This review provides an overview on markers for freezability of canine semen.

Abstract

Markers of freezability allow the selection of ejaculates of good freezability. So far, most investigations were conducted in boars, bulls, rams and horses, with high economic interests triggering the efforts. The progress in dogs is comparably slow. A critical evaluation of the methods requires consideration of practicability, with most labs not even possessing a computer assisted sperm analyser (CASA); furthermore, small canine ejaculates mostly do not allow the use of large semen volumes. In dogs, modern markers of freezability no longer assess single membrane constituents or seminal plasma components but comprise tests of cell functionality and adaptability, energy metabolism, cluster analyses of kinetic and morphometric parameters, as well as DNA intactness. Identification of the most efficient combination of tests seems useful. At present, examination by CASA combined with cluster analysis of kinetic subgroups, JC-1 staining and COMET assay or staining with toluidine blue seem most appropriate; however, cell volumetry and other functional tests deserve better attention. A better understanding of spermatozoa energy metabolism might reveal new markers. This review focuses on the requirements and markers of freezability of canine semen, highlighting potential future candidates.

Effect of supplementation of freezing media with isoespintanol on functional integrity of equine semen

Adding antioxidants to semen extender has become one of the major strategies to reduce the damage caused by freezing to stallion sperm. Isoespintanol (Iso) is a natural antioxidant that is known as a good free radical scavenger. The aim of this research was to evaluate the effect of supplementation of freezing media with Iso on functional integrity of equine semen. Semen from five Colombian Creole horses was frozen with 0, 10, 20, 30, 40 and 50 µM Iso. Post-thawing motility and kinetics, structural membrane integrity (SMI), normal morphology (NM) and functional membrane integrity (FMI) of sperm were evaluated. Seminal quality (SQi) and seminal velocity (SVi) indexes were calculated. Through a flow cytometric analysis, mitochondrial membrane potential (ΔΨM), viability and DNA integrity of frozen-thawed semen were assessed. General linear models were adjusted, and means comparisons were performed using Tukey’s test. The significance level was P<0.05. No differences for post-thaw sperm quality parameters were found, except for total motility, which showed a reduction by adding 40 µM Iso (P<0.05). However, the estimation of indexes, showed that supplementation with 20 or 30 µM Iso before semen freezing, can increase post-thaw SQi and SVi values of some horses. A higher proportion of high-∆ΨM sperm for 20 µM Iso was found. It is concluded that Iso can improve the quality and mitochondrial activity of frozen-thawed equine semen, however its effect can vary according to the horse and in high concentrations it could have detrimental effects.

Impact of Cryopreservation on Motile Subpopulations and Tyrosine-Phosphorylated Regions of Ram Spermatozoa during Capacitating Conditions

Simple Summary

Spermatozoa go through diverse changes to achieve their fertilizing potential (capacitation) and develop a specific motility pattern (hyperactivation). However, to ensure a greater reproductive success, not all the spermatozoa present in an ejaculate react equally or at the same time. Therefore, a comparative analysis was performed in the present study to improve our current understanding about how cryopreservation may affect the heterogeneous nature of fresh ejaculates during these two events. Among the four motile sperm subpopulations identified in fresh and frozen-thawed ram semen, one of them developed a hyperactivated-like movement and was the main group involve in those changes associated with sperm capacitation based on the marked increase and the positive correlation with mitochondrial activity and tyrosine phosphorylation, two relevant parameters that usually increase during capacitation. In addition, cryopreservation altered the distribution of the motile sperm subpopulations. Although the subpopulation with hyperactivated-like movement increased at the beginning of incubation in frozen-thawed samples, this subpopulation together with the subpopulation of rapid and progressive spermatozoa were replaced after a prolonged incubation by the subpopulation of slow spermatozoa with the lowest mitochondrial activity, which clearly indicate the reduction in sperm quality. These findings will aid to optimize the current cryopreservation and in vitro fertilization protocols.

Abstract

The heterogeneous nature of ejaculates highlights the relevance of studying the behavior of different sperm subpopulations. Changes in sperm motility and the increase in tyrosine phosphorylation are key events that usually occur during capacitation and can be modified by the cryopreservation process. However, the relationship between both events remains poorly defined throughout capacitation in the different sperm subpopulations. Fresh and frozen-thawed spermatozoa were incubated in capacitating (CAP) and non-capacitating (NC) media up to 240 min. Sperm kinematics, tyrosine phosphorylation and mitochondrial activity were measured by the CASA system and imaging flow cytometry. Four motile sperm subpopulations (SP) were identified in fresh and frozen-thawed ram semen after the cluster analysis. Incubation under CAP conditions over time led to greater changes in the percentage of spermatozoa included in each subpopulation compared to NC conditions, being different between fresh and frozen-thawed spermatozoa. The SP1, characterized by slow spermatozoa, progressively increased after 15 min in frozen-thawed samples incubated in both media but not in fresh ones. The SP4, characterized by fast and non-linear spermatozoa, showed a marked increase during CAP, but not under NC conditions, occurring more rapidly in frozen-thawed spermatozoa. This subpopulation (SP4) was also the only one positively and strongly correlated with mitochondrial activity and all phosphorylated sperm regions during capacitation, either in fresh or frozen-thawed samples. Our results indicated that in vitro capacitation induced significant changes in the distribution of motile sperm subpopulations, being affected by cryopreservation. Notwithstanding, the subpopulation which probably represents hyperactivated-like spermatozoa (SP4) also increased in frozen-thawed samples, occurring faster and simultaneously to the increment of mitochondrial activity and tyrosine phosphorylation of different sperm regions.

Vitrification of Iberian wolf (Canis lupus signatus) sperm: A possible alternative to conventional cryopreservation

Sperm vitrification is a simple, inexpensive method that allows the cryopreservation of sperm in the field and for endangered species is a useful alternative to conventional freezing. The study, therefore, is focused on the suitability of vitrification for cryopreserving Iberian wolf sperm and utilizing plasma testosterone concentration as a marker for procedure efficacy. Sperm and blood samples were collected from 17 wolves. There were 14 samples suitable for cryopreservation (12 ejaculated and two epididymal). Immediately after collection, these samples were proportioned into two aliquots for conventional freezing using a Tris-citric acid-glucose based extender (TCG) or vitrification utilizing an animal protein free extender (HTF®). Vitrification occurred by directly plunging a sperm suspension into liquid nitrogen. Sperm were assessed for motility, membrane integrity, acrosomal status and DNA integrity before and after cryopreservation. With both techniques, there were similar post-thaw/warming results (P > 0.05) with respect to progressive motility, kinetic variables VCL, VSL, VAP and BCF, DNA fragmentation, sperm membrane functionality and morphological abnormalities. Total motile sperm, progression ratios LIN, STR, and WOB, the ALH, sperm viability and sperm with intact membrane and acrosome were greater (P < 0.05) in the conventional frozen-thawed sperm than vitrified-warmed sperm. Plasma testosterone concentrations varied from 0.0 ng/mL to 7.7 ng/mL. For epididymal sperm, sperm motility and viability following thawing were greater in vitrified-warmed samples than conventionally-frozen samples; however, small sample numbers precluded statistical analysis. When considered together, these results indicate vitrification may be a possible alternative for wolf sperm cryopreservation.

Seminal Plasma Does Not Influence Canine Semen Stored at 5°C for Long-Term Conservation

Seminal plasma has several components that protect the sperm cells and assist in the fertilization process. In contrast, the exact role carried out by seminal plasma during the cooling of canine semen remains controversial. Moreover, concerning the long estrus period, the possibility to store chilled semen at 5°C for more than 72 hours and maintain good sperm quality for additional inseminations could increase fertilization rates. Thus, this study aimed to evaluate the seminal plasma influence on quality and oxidative stress of the extended canine semen stored at 5°C for 7 days. Three ejaculate pools from eight healthy dogs were collected by digital manipulation of the penis. The sperm kinetics, sperm vitality (eosin/nigrosin stain), integrity of plasma and acrosomal membranes, morphology, superoxide and hydrogen peroxide production, mitochondrial potential, lipid peroxidation, and oxygen reactive species production (induced and spontaneous thiobarbituric acid [thiobarbituric acid reactive substances, TBARS] assay) were evaluated every 48 hours (M0, M48, M96, and M168) until 7 days (168 hours) in cooled extended (TRIS egg yolk) semen of dogs at 5°C with (+SP) or without (-SP) autologous seminal plasma. No statistical difference was found for sperm kinetics in cooled samples with +SP and -SP during the experimental time period, except for the progressive motility of +SP samples that was higher at M48 than M96 (p = 0.023). The seminal plasma did not influence any other evaluated sperm characteristics. Finally, our results demonstrated that the presence or lack of seminal plasma during cooling the semen of dogs does not influence sperm quality at 5°C. Moreover, the components of the semen extender may contribute to maintaining good sperm quality and low reactive oxygen species production during the long period of the dog's semen cooling, even after semen centrifugation.

Effects of vitamin D supplementation in extender on sperm kinematics and apoptosis following the freeze-thaw process in normozoospermic and asthenozoospermic Holstein bulls

Background

Asthenozoospermia is a usual male infertility factor, characterized by decreased semen quality. It has been revealed that antioxidants improve sperm function, enhance endogenous antioxidant activities, and protect spermatozoa against oxidative damage during cryopreservation. This aimed to evaluate the effects of vitamin D on sperm kinematics and apoptosis in the semen of bulls with normozoospermia and asthenozoospermia after the freeze-thaw process. For this purpose, 32 semen samples of four Holstein bulls (normozoospermic, progressive motility > 70 %) and 32 semen samples of four bull (asthenozoospermic progressive motility < 40 %) were collected and pooled separately (normozoospermic and asthenozoospermic). Samples were then diluted into four equal aliquots of extender containing different vitamin D concentrations (0, 5, 10, and 50 ng/mL) and aspirated into a 0.5 mL straw.

Results

The percentages of sperm progressive motility and viability were significantly higher (P < 0.05) in 50 ng/mL of vitamin D in normozoospermic group. Sperm kinematics parameters including curvilinear velocity (VCL), straight-line velocity (VSL), and average path velocity (VAP) were significantly higher in the high dose (50 ng/mL) vitamin D-treated group compared to the low dose vitamin D-treated group (5ng/mL) in normozoospermic bull semen samples. The supplementation of the semen extender with different concentrations of vitamin D could not increase the rate of acrosome integrity in normozoospermic bulls compared to the control group (P < 0.05). In the asthenozoospermic group, 10 ng/mL vitamin D-treated group could increase the rate of plasma membrane integrity compared to 5 ng/mL vitamin D-treated group (P < 0.05). The percentages of early-apoptosis (P = 0.049) and late-apoptosis (P = 0.005) were significantly higher in the asthenozoospermic than the normozoospermic group.

Conclusions

The present study revealed that a high dose (50 ng/mL) of vitamin D protected normozoospermic bulls’ sperms from the freezing procedure and lead to higher quality of frozen-thawed bull sperm.

Overview on the Antioxidants, Egg Yolk Alternatives, and Mesenchymal Stem Cells and Derivatives Used in Canine Sperm Cryopreservation

Sperm cryopreservation is a widely used assisted reproductive technology for canine species. The long-term storage of dog sperm is effective for the breeding of dogs living far apart, scheduling the time of artificial insemination that suits the female, and preventing diseases of the reproductive tract. However, spermatozoa functions are impaired during the freeze-thaw processes, which may decrease reproductive performance. Numerous attempts have been made to restore such impairments, including the use of cryoprotectants to prevent the damage caused by ice crystal formation, and supplementation of antioxidants to reduce reactive oxygen species generation due to osmotic stress during the procedure. Egg yolk derivatives, antioxidants, and, more recently, mesenchymal stem cells (MSCs) and their derivatives have been proposed in this research field. This review article will summarize the current literature available on the topic.

Sperm subpopulations influence the pregnancy rates in cattle

This study aimed to study the characteristics and subpopulations of spermatozoa from bulls with low and high reproductive performance based on pregnancy rates. Based on historical records of pregnancy rate from four farms, 24 bulls were selected. Two groups were established, with low pregnancy rates (n = 12; LOW), including bulls that presented pregnancy rates <52.27% (33.33% to 51.81%); and a group with high pregnancy rates (n = 12; HIGH), with pregnancy rates >52.27% (52.27% to 69.64%), after fixed-time artificial insemination (FTAI). The thawed sperm straws were analysed to sperm kinetics, morphology, plasma membrane integrity and sperm subpopulations. The LOW group exhibited a higher proportion of static cells (p < .05). In contrast, the HIGH group showed greater percentages for membrane integrity and total and progressive motility, and cells with fast and medium velocity (p < .05). In the cluster procedures, four sperm subpopulations were established. The low-fertility bulls presented the highest percentage of subpopulation 2 (41.46%), characterized by slow and progressive spermatozoa. The high-fertility bulls exhibited the highest percentage of subpopulation 3 (37.17%), characterized by fast and nonlinear spermatozoa. Results from this study indicated that bulls with greater percentages of fast and nonlinear spermatozoa seem to have greater fertilization capacity and the subpopulations analysis can be considered a tool to identify ejaculates with high fertility.

Correlation of testicular artery Doppler velocimetry with kinetics and morphologic characteristics of epididymal sperm in dogs

Sperm quality can be affected by a reduction in testicular blood flow, which can be measured by Doppler ultrasonography. The aim of this study was to correlate the Doppler velocimetry of the testicular artery with kinetics of the epididymal spermatozoa in dogs. Twenty-two dogs (44 testicles) were evaluated by Doppler ultrasonography in five regions of the testicular artery before orchiectomy. Spermatozoa were recovered by the epididymal tail compression technique and analysed for kinetics on a computer-assisted semen analysis (CASA system). Morphology (modified Karras) and sperm membrane integrity were analysed by eosin-nigrosine staining. Data were analysed by Pearson's correlation test (p < .01). The mean total motility was 69.0% ± 17.7, progressive motility was 43.7% ± 14.7, average path velocity (VAP) was 127.0 µm/s ± 20.7, curvilinear velocity (VCL) was 221.0 µm/s ± 31.1, and sperm velocity index (SVI) was 389.9 ± 56.1. There were positive correlations between the peak systolic velocity (PSV) in the proximal supratesticular region with the SVI (r = .529), VCL (r = .555) and VAP (r = .473), and a negative correlation with the percentage of slow spermatozoa (r = -.463). The results suggest that the testicular artery blood flow velocity can positively affect the speed of spermatozoa movement. For the first time, we have correlated sperm kinetics with the Doppler evaluation of the testicular artery in dogs.

Effects of the cryopreservation process on dog sperm integrity

Sperm cryopreservation has become an indispensable tool in reproductive biology. However, frozen/thawed semen has a short lifespan due to loss of sperm cell integrity. To better understand which sperm cell structures are compromised by the cryopreservation process and apoptosis markers, the sperm of five healthy mature dogs was analyzed in this study. Analysis was performed after collection, cooling, and thawing via computer assisted sperm analyzer (CASA) and evaluation of membrane fluidity and permeability, phosphatidylserine translocation (Annexin V), membrane integrity, mitochondrial membrane potential, membrane lipid peroxidation (LPO) and activity of the apoptotic markers caspases 3 and 7 by flow cytometry. Cryopreservation decreased total and progressive motility and the percentage of rapid sperm (P < 0.01). Damage to sperm cells was confirmed by Annexin V (P < 0.01), indicating that capacitation-like changes were induced by the cryopreservation procedures. An increase in sperm membrane fluidity was also noted in frozen/thawed samples (P < 0.01). Plasma and acrosomal cell membranes were affected (P < 0.01), with decreases in the subpopulation displaying high membrane potential (P < 0.01). Membrane LPO was increased in thawed sperm compared to cooled sperm (P < 0.05) but was not different from that in fresh sperm. No differences were observed in caspase 3 and 7 activity after cooling, freezing, or thawing. In conclusion, total and progressive motility, plasma membrane integrity and mitochondrial membrane potential suffered from the deleterious effects caused by cryopreservation, unlike the activity of caspases that remained stable during the freezing process.

Analysis of testicular variables, semen motility and kinematics-derived indexes in boar using a CASA-Mot system

The present study aimed to evaluate differences in area, volume and testicular weight among groups related to breed and age of boar and establish associations between testicular parameters and seminal characteristics. Seminal quality has been studied using computer-assisted semen analysis (CASA) systems that reduce the subjectivity of kinematic parameters. Based on the data obtained through this system, sperm quality indexes and their derived parameters have been assessed to identify a better estimator for determining movement and velocity parameters. We also established indexes of velocity and sperm movement for boar semen. To this end, we evaluated 191 ejaculate samples from 63 boars. Differences related to the effects of season and age on quality boar semen were found (p ≤ .05) in the animal groups. Indexes were established for velocity and sperm movement based on CASA-Mot, and we proposed a sperm movement index (SMI) and sperm velocity index (SVI) with the CASA-Mot variables. Correlations were found (p < .05) among sperm indexes and CASA-Mot variables. Boar characteristics were found to be associated with some CASA-Mot variables, and the estimated SMI and SVI indexes predicted a greater variation in kinematic characteristics compared to the parameters evaluated separately using the CASA-Mot system.

Membrane stability and mitochondrial activity of bovine sperm frozen with low-density lipoproteins and trehalose

Cryopreservation results in the destabilization of the sperm plasma membrane, leading to negative side effects such as premature cryocapacitation, apoptosis and the low mitochondrial activity of bovine spermatozoa. Low-density lipoproteins (LDL) and trehalose have been used in seminal freezing to protect the integrity and stability of sperm membranes. Likewise, trehalose can increase the mitochondrial activity of sperm. The objective of this study was to evaluate the membrane stability and mitochondrial activity of bovine sperm after being frozen and treated with LDL sources and trehalose. Ten ejaculates from five bulls were cryopreserved under the treatments, CEY: chicken egg yolk (20% v/v); CCEY: centrifuged CEY (20% v/v); LDL: LDL (8% v/v); T: trehalose (100 mM); and TLDL: T (100 mM) plus LDL (8% v/v). After thawing, membrane stability and mitochondrial membrane potential (ΔΨM) were assessed by flow cytometry through the M-540/Yopro-1 and DiOC6/PI probes. The structural membrane integrity (SMI) was evaluated by fluorescence microscopy using SYBR14/PI dyes. A generalized linear model was adjusted, and the means were compared using the Tukey test. Centrifuged chicken egg yolk and LDL had a higher proportion of non-cryocapacitated non-apoptotic sperm (M-Y-), while CEY and T had the largest populations of cryocapacitated non-apoptotic sperm (M+Y-) and cryocapacitated apoptotic sperm (M+Y+). Centrifuged chicken egg yolk also showed a higher proportion of sperm with high-ΔΨM. Treatments that included egg yolk or purified LDL had a positive effect on SMI. Centrifuged chicken egg yolk has a superior cryoprotective effect on membrane stability and mitochondrial activity of bovine semen over the conventional use of CEY or the individual or simultaneous use of LDL and trehalose.

Making the most of sperm activation responses: experiments with boar spermatozoa and bicarbonate

Attempting to extract useful and reliable information about semen quality and its fertility potential remains a difficult exercise, partly because the sperm heterogeneity within samples often renders simple statistical analyses rather meaningless. In fact, a mean and standard deviation may reflect neither the very fast swimming activities of the most active cells nor the slow and sluggish activities of others. Herein we propose that the information value within semen samples can be maximised if current knowledge about sperm activation mechanisms is exploited before undertaking the measurements. We explain, using boar semen as an example, that estimating and defining relative sperm subpopulation sizes, after activation by bicarbonate, provides a means of quantifying sperm quality. Although such estimates may indeed be related to in vivo fertility, the general approach also suggests potential new avenues that could be exploited for the elaboration of novel in vitro tests for the characterisation of toxic environmental chemicals and, indeed, to reduce the number of animals used in such testing programs.

CASA-Mot in mammals: an update

Sperm motility is one of the most widely used parameters of sperm quality. Computer-aided sperm motility analysis (CASA-Mot) systems were developed to reduce the subjectivity of sperm motility assessment, and have had broad scientific and practical acceptance. In this review, the sources of variation and current applications of this technology and its relationships with other sperm quality tests are described in detail. Despite remarkable advances in the technique, there is still great need for standardisation in many species, and the numerous factors that affect the results make it difficult to provide universally accepted criteria for classifying semen samples based on sperm motility characteristics. The main fields for CASA-Mot include the study of male fertility and pathologies, evaluation of the effects of physical and chemical agents, improvement of epidemiological survey studies, more precise calculation of seminal doses for farm animals, realisation of basic studies about sperm function, improvement of sperm technologies such as cryopreservation and quality control analysis. Numerous relationships have been established between CASA-Mot and other sperm quality tests, although most of these parameters are complementary. Future CASA-Mot systems will probably be able to integrate several sperm quality parameters with motility.

Current perspectives of CASA applications in diverse mammalian spermatozoa

Since the advent of computer-aided sperm analysis (CASA) some four decades ago, advances in computer technology and software algorithms have helped establish it as a research and diagnostic instrument for the analysis of spermatozoa. Despite mammalian spermatozoa being the most diverse cell type known, CASA is a great tool that has the capacity to provide rapid, reliable and objective quantitative assessment of sperm quality. This paper provides contemporary research findings illustrating the scientific and commercial applications of CASA and its ability to evaluate diverse mammalian spermatozoa (human, primates, rodents, domestic mammals, wildlife species) at both structural and functional levels. The potential of CASA to quantitatively measure essential aspects related to sperm subpopulations, hyperactivation, morphology and morphometry is also demonstrated. Furthermore, applications of CASA are provided for improved mammalian sperm quality assessment, evaluation of sperm functionality and the effect of different chemical substances or pathologies on sperm fertilising ability. It is clear that CASA has evolved significantly and is currently superior to many manual techniques in the research and clinical setting.

Use of infrared thermography to evaluate the inflammatory reaction in cat testis after intratesticular injection of 0.9% NaCl or 20% CaCl2 with 1% lidocaine

ABSTRACT Due to the doubts and questions about the inflammatory reaction caused by chemical castration, this study aimed to use infrared thermography to detect, evaluate and monitor the inflammatory reaction caused by the intratesticular injection of calcium chloride (CaCl2) 20% with lidocaine 1%. For this, thermographic measurements were taken before (M0), 10 minutes (M1), 1 and 6 hours (M2 and M3), for 7 consecutive days (M4 to M10), at 15 (M11), 30 (M12) and 60 (M13) days after intratesticular injection. Additionally, changes to testicular tissue and effects over spermatogenesis were evaluated by andrological exam before (M0) and 60 days (M13) after intratesticular injection. All cats were orchiectomized at M13, and testicles were submitted to histological analysis. CaCl2 (20%) with lidocaine (1%) administration produced testicular tissue damage and interfered with the spermatogenesis in 70% of treated cats without exacerbating the inflammatory reaction or impairing the cat’s welfare. It was concluded that thermographic evaluation is a useful, efficient, easy and quick method to diagnose and monitor cat testicular inflammatory reactions.

Swimming kinematics and temperature effects on spermatozoa from wild and captive shortnose sturgeon (Acipenser brevirostrum)

Computer-assisted semen analysis (CASA) and cluster analysis were used to compare spermatozoa swimming kinematics and milt quality between wild and captive shortnose sturgeon (Acipenser brevirostrum). Milt samples from 27 shortnose sturgeon were collected in May 2016 and June 2017. Of these, 19 were wild caught in the Saint John River, New Brunswick, Canada, and eight were from a captive population at the Mactaquac Biodiversity facility. The following kinematic variables were measured immediately following sperm activation (˜5 s), at 30, 60, and 180 s post-activation; average path velocity (VAP); straight-line velocity (VSL); curvilinear velocity (VCL); amplitude of lateral head displacement (ALH); beat cross frequency (BCF); straightness (STR); linearity (LIN); wobble (WOB); percent motility (MOT). Analyses were conducted at 7, 10, and 14 °C to determine potential effects of temperature on kinematics. Principal components analysis (PCA) of original kinematic variables yielded two main components, a speed/wobble component along with a movement pattern component. Hierarchical cluster analysis (HCPC) indicated there were distinct subpopulations, with composition of clusters the result of fish source (wild-caught or captive). Wild-caught fish had greater sperm densities (P = 0.0064) and sperm swimming speeds compared to captive fish (P < 0.05). Temperature had a significant effect only on captive spermatozoa, and this result was not consistent between time periods. There was no effect of hormonal manipulation on spermatozoa motility kinematics. Results indicate there are significant differences in measures of milt quality between wild and captive shortnose sturgeon, indicating an effect of rearing condition on reproductive potential, which may affect fertilization success.

Comparison of sperm motility subpopulation structure among wild anadromous and farmed male Atlantic salmon (Salmo salar) parr using a CASA system

Atlantic salmon (Salmo salar) is an endangered freshwater species that needs help to recover its wild stocks. However, the priority in aquaculture is to obtain successful fertilisation and genetic variability to secure the revival of the species. The aims of the present work were to study sperm subpopulation structure and motility patterns in wild anadromous males and farmed male Atlantic salmon parr. Salmon sperm samples were collected from wild anadromous salmon (WS) and two generations of farmed parr males. Sperm samples were collected from sexually mature males and sperm motility was analysed at different times after activation (5 and 35 s). Differences among the three groups were analysed using statistical techniques based on Cluster analysis the Bayesian method. Atlantic salmon were found to have three sperm subpopulations, and the spermatozoa in ejaculates of mature farmed parr males had a higher velocity and larger size than those of WS males. This could be an adaptation to high sperm competition because salmonid species are naturally adapted to this process. Motility analysis enables us to identify sperm subpopulations, and it may be useful to correlate these sperm subpopulations with fertilisation ability to test whether faster-swimming spermatozoa have a higher probability of success.

Computational flow cytometry reveals that cryopreservation induces spermptosis but subpopulations of spermatozoa may experience capacitation-like changes

The reduced lifespan of cryopreserved spermatozoa in the mare reproductive tract has been attributed to both capacitative and apoptotic changes. However, there is a lack of studies investigating both phenomena simultaneously. In order to improve our knowledge in this particular point, we studied in raw and frozen-thawed samples apoptotic and capacitative markers using a wide battery of test based in flow cytometry. Apoptotic markers evaluated were caspase 3 activity, externalization of phosphatidylserine (PS), and mitochondrial membrane potential. Markers of changes resembling capacitation were membrane fluidity, tyrosine phosphorylation, and intracellular sodium. Conventional and computational flow cytometry using nonlinear dimensionally reduction techniques (t-distributed stochastic neighbor embedding (t-SNE)) and automatic classification of cellular expression by nonlinear stochastic embedding (ACCENSE) were used. Most of the changes induced by cryopreservation were apoptotic, with increase in caspase 3 activation (P < 0.01), PS translocation to the outer membrane (P < 0.001), loss of mitochondrial membrane potential (P < 0.05), and increase in intracellular Na+ (P < 0.01). Average values of markers of capacitative changes were not affected by cryopreservation; however, the analysis of the phenotype of individual spermatozoa using computational flow cytometry revealed the presence of subpopulations of spermatozoa experiencing capacitative changes. For the first time advanced computational techniques were applied to the analysis of spermatozoa, and these techniques were able to disclose relevant information of the ejaculate that remained hidden using conventional flow cytometry.

Optimization of the cryopreservation of dromedary camel semen: Cryoprotectants and their concentration and equilibration times

Research into an optimal cryoprotectant, its concentration and equilibration time underlies the successful cryopreservation of dromedary camel spermatozoa. This study assessed the cryo-efficiency of different cryoprotectants, their concentration and equilibration time and any interactions. In experiment 1, semen samples (n = 4 males; 2 ejaculates/male) were frozen using Green Buffer containing one of four cryoprotectants (3% glycerol, ethylene glycol, methyl formamide, dimethyl sulfoxide) and using 4 equilibration times (10 min, 0.5, 1 and 2 h). Glycerol and ethylene glycol provided the best motility recovery rates and different equilibration times were not significant for any cryoprotectant nor were any interactions noted. However different equilibration times were pertinent for improved kinematic parameters BCF and VSL. In experiment 2, glycerol and ethylene glycol were evaluated at 4 concentrations (1.5, 3, 6, 9%) with 0.5 h equilibration (n = 4 males, 3 ejaculates/male). Sperm motility recoveries, kinematics and acrosome status were assessed. Higher values for LIN and STR were found with ethylene glycol. At 0 and 1 h post thaw 3 and 6% of either cryoprotectant resulted in better motility values than 1.5%. Acrosome integrity was compromised at 9% cryoprotectant. There were interactions between cryoprotectant and concentration in total motility at 0 and 1 h. For glycerol, total motility recoveries were best at 3-9%; for ethylene glycol 1.5-6% were best at 0 h and 3-6% at 1 h. In conclusion, 3-6% glycerol or ethylene glycol offered the best cryoprotection for camel sperm while different equilibration times were not critical.

Differences in preservation of canine chilled semen using simple sperm washing, single-layer centrifugation and modified swim-up preparation techniques

This study compared the efficacy of simple sperm washing (SW), single-layer centrifugation (SLC) and modified swim-up (SU) techniques in the preparation of dog spermatozoa for cooling. Eighteen ejaculates, collected from three dogs (six per dog), were pooled (three ejaculates per pool) and divided into three aliquots: (1) one aliquot was washed and cooled at 5°C for 72h, considered as control (SW-control), (2) the second aliquot was selected by SLC through Androcoll-C and subsequently cooled in the same way as the SW-control samples (SLC-AC) and (3) the last aliquot was selected by a modified SU method with Androcoll-C and cooled as mentioned above (SU-AC). Assessment of sperm motility, sperm morphology, sperm membrane integrity and acrosome integrity were performed on aliquots of fresh semen and chilled-rewarmed samples. Sperm membrane integrity and progressive motility were significantly (PPP>0.05). The recovery rates were not significantly (P>0.05) different between SW-control, SLC-AC and SU-AC samples. Our results confirm that SU-AC may be a successful method for the preparation of dog spermatozoa for cooling.

Effects of rapid cooling prior to freezing on the quality of canine cryopreserved spermatozoa

The aim of this study was to evaluate the effects of rapid cooling prior to freezing on frozen-thawed canine sperm quality. In experiment 1, centrifuged ejaculates from 6 dogs were pooled, split into 4 aliquots and cryopreserved by the Uppsala procedure using different cooling rates (control, cooling speed 18 C/90 min and average cooling rate 0.2 C/min; rapid, cooling speed 18 C/8 min and average cooling rate 2.25 C/min) in combination with 2 glycerol addition protocols (fractionated or unfractionated). In experiment 2, centrifuged ejaculates from 4 dogs were processed individually using the same cooling rates described in experiment 1 in combination with an unfractionated glycerol addition protocol. Each of the experiments was replicated 5 times. Sperm quality was evaluated after 30 and 150 min of post-thawing incubation at 38 C. Total motility (TM), progressive motility (PM) and quality of movement parameters were assessed using a computerized system, and sperm viability (spermatozoa with intact plasma and acrosome membranes) was assessed using flow cytometry (H-42/PI/FITC-PNA). Values for TM, PM, viable spermatozoa and the quality of movement parameters after thawing were not significantly affected by the cooling rate. The interaction between the cooling rate and the added glycerol protocol was not significant. There were significant differences among the males (P<0.01) in the sperm quality parameters evaluated after thawing. The interaction between the males and the cooling rate was not significant. In conclusion, canine spermatozoa can be cryopreserved using the Uppsala method at an average cooling rate of 2.25 C/min prior to freezing together with addition of fractionated or unfractionated glycerol.

Cluster analysis reveals a binary effect of storage on boar sperm motility function

Storage of liquid-preserved boar spermatozoa is associated with a loss of fertilising ability of the preserved spermatozoa, which standard semen parameters barely reflect. Monitoring responses to molecular effectors of sperm function (e.g. bicarbonate) has proven to be a more sensitive approach to investigating storage effects. Bicarbonate not only initiates capacitation in spermatozoa, but also induces motility activation. This occurs at ejaculation, but also happens throughout passage through the oviduct. In the present study we tested whether the specific response of boar sperm subpopulations to bicarbonate, as assessed by motility activation, is altered with the duration of storage in vitro. Three ejaculates from each of seven boars were diluted in Beltsville thawing solution and stored at 17°C. Only minor changes in the parameters of diluted semen were revealed over a period of 72 h storage. For assessment of bicarbonate responses, subsamples of diluted spermatozoa were centrifuged through a discontinuous Percoll gradient after 12, 24 and 72 h storage. Subsequently, spermatozoa were incubated in two Ca2+-free variants of Tyrode’s medium either without (TyrControl) or with (TyrBic) 15 mM bicarbonate, and computer-aided sperm analysis motility measurements were made. Cluster analysis of imaging data from motile spermatozoa revealed the presence of five major sperm subpopulations with distinct motility characteristics, differing between TyrBic and TyrControl at any given time (P < 0.001). Although there was an increasing loss of motility function in both media, bicarbonate induced an increase in a ‘fast linear’ cohort of spermatozoa in TyrBic regardless of storage (66.4% at 12 h and 63.9% at 72 h). These results imply a binary pattern in response of sperm motility function descriptors to storage: although the quantitative descriptor (percentage of motile spermatozoa) declines in washed semen samples, the qualitative descriptor (percentage of spermatozoa stimulated into fast linear motion by bicarbonate) is sustained independent of the duration of storage.

Relationship between conventional semen characteristics, sperm motility patterns and fertility of Andalusian donkeys (Equus asinus)

Sperm quality has an important role in determining fertility. The aims of this study were to compare the conventional sperm parameters, plus the characteristics of the motility patterns of the different sperm subpopulations, of donkey donors with different fertility level, and to determine their relationships to fertility. Thirty ejaculates from 6 Andalusian donkeys were assessed for gel-free volume, pH, sperm concentration, motility and morphology. The fertility of donkeys was classified on the basis of pregnancy rates per cycle, where donkeys with a per cycle pregnancy rate ≥60% were considered to be "fertile" (n=3) and those with a per cycle pregnancy rate <40% were categorized to be "sub-fertile" (n=3). Significant differences (P<0.001) between the "fertile" and the "sub-fertile" group were found for total and progressive motility, and for straight line velocity. Sperm variables associated (P<0.05) with an increase in percent pregnant per cycle included total motility (r=0.37), progressive motility (r=0.53), curvilinear velocity (r=0.44), straightness (r=0.39), beat cross frequency (r=0.44), and gel-free volume (r=0.53). Four sperm subpopulations (sP) were identified in fresh semen: sP1 (slow and non-progressive spermatozoa, 20%), sP2 (moderately slow but progressive spermatozoa, 71.2%), sP3 (highly active but non-progressive spermatozoa, 2.9%), and sP4 (highly active and progressive spermatozoa, 5.9%). The lowest percentage (3.1%; P<0.001) of sP4 spermatozoa was observed in the "sub-fertile" group. Three of the sperm subpopulations were related (P<0.05) to fertility (sP2, r=0.54; sP3, r=0.45; sP4, r=0.56). In conclusion, we were able to relate the fertility of donkeys with in vitro measures of sperm motility using computer-assisted sperm analysis techniques.

Computer-assisted sperm analysis in dogs and cats: an update after 20 years

In dogs and cats, computer-assisted sperm analysis (CASA) was originally described almost 20 years ago. Subsequently, numerous CASA systems were validated and used for various applications in dogs and to a lesser extent in cats. CASA systems offer an accurate, rapid, objective and simultaneous assessment of different semen parameters allowing the visualization of subtle changes in sperm characteristics, which cannot be identified by conventional semen analysis. The main problems of these computerized measuring devices are the relatively high investment costs and the need for standardization and validation before any practical use is possible. In comparison with automated motility and concentration assessment, automated morphometry and morphology assessment is more complex and time-consuming. Once validated, CASA systems can be routinely used in veterinary centres for assessment of fertility and for the improvement of sperm diluters, cooling and cryopreservation procedures in dogs and cats. Furthermore, information obtained by CASA systems could also be important when monitoring for example the effect of environmental stress on spermatozoa and for toxicity studies. In cats, CASA is less documented, and most studies describe the characteristics of epididymal sperm, which is frequently used for in vitro fertilization in cats. Implementation of the CASA technique in cat reproduction could be interesting to further optimize assisted reproductive techniques in domestic cats and endangered wild felids.

Comparison of two different extenders for cryopreservation of epididymal dog sperm

The collection of epididymal sperm is an option for preservation of germplasm of genetically superior animals that need to be orchiectomized or have died. The extender type used to freeze sperm is important to avoid spermatozoal membrane damage and to preserve semen quality after cryopreservation. The objective of this study was to verify the effects of a commercial bovine extender (Bovimix(®); Nutricell, Campinas) and a traditional TRIS-citric acid-glucose-egg yolk-7% glycerol extender on cryopreservation of canine epididymal sperm. The testes of 13 adult dogs were kept at 5 °C for 24 h in saline solution, and epididymal sperm was recovered in Ringers solution without lactate and were evaluated for motility. Samples with ≥ 80% motility were pooled and then divided before dilution and packaging in 0.5 ml plastic straws, equilibration at 4 °C for 1 h, freezing in nitrogen vapour for 20 min and storing at -196 °C. The straws were thawed at 56 °C for 10 s and were evaluated for motility by computer assisted analysis (CASA). The semen parameters, sperm movement index, linearity, total motility and rapid progressive motility were statistically higher in Bovimix(®) than TRIS. In contrast, amplitude of lateral head displacement, slow sperm and static sperm were lower in Bovimix(®). Despite the high percentage of sperm defects in epididymal cells, regardless of the extender, we concluded that Bovimix(®) is a viable alternative for the freezing of canine epididymal sperm.

Quantification and identification of sperm subpopulations using computer-aided sperm analysis and species-specific cut-off values for swimming speed

Motility is an essential characteristic of all flagellated spermatozoa and assessment of this parameter is one criterion for most semen or sperm evaluations. Computer-aided sperm analysis (CASA) can be used to measure sperm motility more objectively and accurately than manual methods, provided that analysis techniques are standardized. Previous studies have shown that evaluation of sperm subpopulations is more important than analyzing the total motile sperm population alone. We developed a quantitative method to determine cut-off values for swimming speed to identify three sperm subpopulations. We used the Sperm Class Analyzer(®) (SCA) CASA system to assess the total percentage of motile spermatozoa in a sperm preparation as well as the percentages of rapid, medium and slow swimming spermatozoa for six mammalian species. Curvilinear velocity (VCL) cut-off values were adjusted manually for each species to include 80% rapid, 15% medium and 5% slow swimming spermatozoa. Our results indicate that the same VCL intervals cannot be used for all species to classify spermatozoa according to swimming speed. After VCL intervals were adjusted for each species, three unique sperm subpopulations could be identified. The effects of medical treatments on sperm motility become apparent in changes in the distribution of spermatozoa among the three swimming speed classes.

Sperm motility patterns in Andalusian donkey (Equus asinus) semen: effects of body weight, age, and semen quality

The aims of this study were to (1) identify sperm subpopulations with specific motion characteristics in fresh Andalusian donkey ejaculates; (2) evaluate the effects of individual donkey and ejaculates within the same donkey on the distribution of the subpopulations found; and (3) explore the relationship between the age and the body weight of donkey donors, the sperm quality parameters, and the sperm subpopulations structure. Sixty ejaculates from 12 Andalusian donkeys (five ejaculates per donkey), ranging in age from 4 to 15 years, were collected. Immediately after collection, sperm characteristics (volume, sperm concentration, objective sperm motility, and sperm morphology) were assessed. Donkeys were evaluated for body weight. Significant (P < 0.05) correlations were established between the body weight of the donkeys and the pH (r = -0.52), sperm motility (percentage of motile spermatozoa: r = -0.31; percentage of progressive motile spermatozoa: r = -0.34), and total sperm abnormalities (r = 0.38). The correlations of the age with the measures of semen quality were low and not significant (P > 0.05). A multivariate clustering procedure separated 65,342 motile spermatozoa into four subpopulations: subpopulation 1, consisting of slow and nonprogressive spermatozoa (15.4%), subpopulation 2, consisting of moderately slow but progressive spermatozoa (35.9%), subpopulation 3, consisting of highly active but nonprogressive spermatozoa (18.5%), and subpopulation 4, consisting of highly active and progressive spermatozoa (30.2%). The distribution of these subpopulations varied significantly (P < 0.05) according to several parameters such as the individual donkey, the ejaculate of the same donkey, the total motility, and the overall sperm concentration. Our results show the existence of four well-defined motile sperm subpopulations in Andalusian donkey ejaculates, and suggest a high heterogeneity in the ejaculate structure in donkey. The relationship between the distribution of the sperm subpopulations and individual donkey, total motility, and sperm concentration shows that the spermatozoa of each have different motility patterns. However, the proportions of sperm subpopulations in the ejaculates did not vary with age and body weight. Finally, the study of discrete subpopulations of motile spermatozoa could lead to a substantial increase in information acquired during donkey semen analysis.

Artificial neural networks for the definition of kinetic subpopulations in electroejaculated and epididymal spermatozoa in the domestic cat

This study was designed for the identification of different sperm kinetic subpopulations in feline semen using artificial neural networks (ANNs) and for the evaluation of the effect of ejaculation on motility patterns of these subpopulations. Seven tomcats presented for routine orchiectomy were electroejaculated, and after 5 days, orchiectomized and epididymal tail sperms were collected. Sperm motility characteristics were evaluated using a computer-assisted sperm analyzer that provided individual kinetic characteristics of each spermatozoon. A total of 23 400 spermatozoa for electroejaculated and 9200 for epididymal tail samples were evaluated using a multivariate approach, comprising principal component analysis and ANN classification. The multivariate approach allowed the identification and characterization of three different and well-defined sperm subpopulations. There were significant differences before (epididymal tail spermatozoa) and after (electroejaculated sperm) ejaculation in sperm kinetic subpopulation characteristics. In both epididymal and ejaculated samples, the majority of subpopulation was characterized by high velocity and progressiveness; however, the electroejaculated samples showed significantly higher values, suggesting that the microenvironment of the epididymal tail could affect the sperm motility or, alternatively, seminal plasma could increase the kinetic characteristics of the spermatozoa, indicating that only after ejaculation, the spermatozoa express their motility potential. Nevertheless, further studies are required to clarify the functional significance of each kinetic subpopulation.