Sperm Subpopulations Research Articles

Sperm population structure in high and low field fertility rams

The aim of the present study was to investigate whether differences in field fertility of rams are reflected in differences in sperm morphometric and kinematic population structures. The association between sperm morphometric and kinematic subpopulations was also investigated. Ejaculates from 8 adult rams, 4 with high and 4 with low field fertility, were collected weekly using an artificial vagina over 6 consecutive weeks. Analyses of sperm motility using computer-assisted sperm analysis (CASA) and sperm nuclear morphometry using computer-assisted sperm morphometry-fluorescence were performed. Clustering procedures using the kinematic and morphometric data from high and low field fertility rams resulted in the classification of spermatozoa in three kinematic and three morphometric sperm subpopulations. The distribution of subpopulations between rams of high and low field fertility was significantly different (P<0.05), with higher percentages of spermatozoa exhibiting fast and linear movements and those with large and long nuclei in the high fertility group. However, these subpopulations were not correlated. Logistic regression analyses were also performed to evaluate the relative utility of sperm subpopulations to classify rams in high and low field fertility. Total progressive sperm motility and the proportion of large and long spermatozoa were identified as the most consistent indicators of fertility. It was concluded that high and low fertility rams had clear differences in morphometric and kinematic sperm subpopulations, and that the most consistent indicators of fertility were the total progressive motility and the proportion of spermatozoa with large and long head present in the ejaculate.

Should single layer centrifugation of dog semen be done before or after the semen is cooled?

The aim of this study was to assess the effectiveness of sperm selection by single layer centrifugation (SLC) on canine sperm quality when SLC was performed before or after the...

Computer assisted sperm analysis - the relationship to bull field fertility, possible errors and their impact on outputs: A review

Sperm motility is one of the indicators most evaluated before and after cryopreservation, regarding quality and fertilizing ability. The present review provides complex information about the possible negative effects on the results of computer assisted sperm analysis (CASA) and also reflects a possible connection of these results to bull field fertility. Recently, there has been a growing interest in sperm motility assessment by CASA to determine sperm motion more accurately and objectively than by subjective evaluation. CASA systems have been routinely used in most research laboratories and also with increasing tendency in the case of insemination centres. However, objectivity and comparison of CASA results through laboratories can be impacted unfavourably. This is in particular due to the absence of standardization for bull sperm motility evaluation and the presence of drawbacks in the form of human and non-human factors. Investigators have recently turned to the possible association of CASA results with the prediction of bull field fertility. However, the studies suffer from discrepancies, thus a clear relationship has not yet been confirmed. Specific combinations of motility parameters with accurate determination of sperm subpopulations could represent another part in the complex system of providing the ability to predict fertility in vivo. The task of future works should be to establish standardization regarding sperm motility evaluation of specific animals, in addition to the settings and algorithms of CASA systems. Furthermore, predictive value CASA outputs to bull field fertility demand more extensive research aimed at a more precise definition of this relationship.

Management of the storage of cryopreserved sperm on dairy cattle farms

26 liquid nitrogen tanks were selected from different dairy cattle farms. Three sperm doses were introduced in a frequently used canister, while another three straws were deposited in another canister that did not contain any sperm doses, to determine whether the refilling with liquid nitrogen had been done appropriately. Then, 10 sperm doses belonging to the same freezing lot were stored in our laboratory under ideal conditions to be used as control doses. After certain time period, the doses were collected from the farms and were analysed to obtain data about their total sperm motility and the individual kinetic parameters of each sperm. Four sperm subpopulations (SP) with different patterns of motility were identified using a cluster multivariate analysis. The results show that the mean total sperm motility has hardly decreased for the doses stored in the frequently used canister (45.2 ? 6.9%) in comparison with the doses stored in the rarely used canister (46.9 ? 59.0). However, the decrease in total motility was greater when compared with the control doses (59.0%). As for the sperm SP, (SP4 rapid and progressive sperm) which contained 31% of the total of sperm (control doses), differed the most when control doses were compared to straw stored in farm tanks. The percentage of the latter was reduced to 10 % after being stored in the tanks of the farms for 7 mo. Such damage in SP 4 is progressive and cumulative and would probably reduce drastically compromising the fertility of the aforementioned sperm doses.

Comparison of Flow Cytometric Analysis and Eosin-Nigrosin Staining Methods for Determining some Morphological Characteristics of Bull Epididymal Spermatozoa

The aim of this study is to investigate necrosis and apoptosis in epididymal bull spermatozoa before freezing and after thawing using the flow cytometric method and to compare this with eosin-nigrosin dyeing, which is the conventional method used in assessing of spermatozoa. The testicles from fourteen bulls at local slaughterhouse were used for this study. The proportions of live spermatozoa, total apoptotic, necrotic and early necrotic spermatozoa levels were observed via flow cytometry. Annexin V/PI fluoruscence dyeing was used to investigate the proprotions of apoptotic, necrotic, early necrotic and live spermatozoa for flow cytometry. The proportion of dead spermatozoa and protoplasmic droplets were determined using the eosin-nigrosin conventional dyeing method in fresh and frozen-thawed spermatozoa. The average dead spermatozoa count with flow cytometry was less than with the eosin-nigrosin method (P<0.05). Some morphological characteristics such as protoplasmic droplets could be determined with the eosin-nigrosin method; however, sperm subpopulations entering the death process (apoptotic, necrotic and early necrotic) could be defined clearly only with the flow cytometric method. As a result, combination of eosin-nigrosin dyeing method and flow cytometric analysis of sperm morphological evaluation could give better results of bull epididymal semen in comparison to eosin-nigrosin dyeing method alone.

Seminal quality in the first fraction of ejaculate

Semen samples from 40 patients were collected in consecutive fractions. The variability in semen quality of each fraction was then determined. The first ejaculated fraction (FEF) primarily contained prostatic secretions, while the second ejaculate fraction (SEF) held the majority of the spermatozoa suspended in the secretions from the seminal vesicle. Differences in sperm quality were observed when the FEF was compared to the SEF and the total ejaculate fraction (TEF). These included the seminal parameters (volume, sperm concentration, motility) and sperm DNA fragmentation (SDF). When compared to TEF and SEF, the FEF presented a lower volume, higher sperm concentration, higher motility rates, and lower SDF. The data suggest that the first fraction renders an improved subpopulation of spermatozoa, with lower SDF. Spermatozoa from this fraction and hence their use for ART may have a positive effect on fertilization and embryo development.

Effects of repeated electroejaculations on kinematic sperm subpopulations and quality markers of Mexican creole goats

Here we show the effects of repeated electroejaculation (EE) on mean values of motility, mitochondrial functionality, and expression of active caspases on goat sperm obtained by EE. Evaluations were done using CASA and flow cytometry. A strategy for identification of kinematic sperm subpopulations, when individual data of sperm are not provided by the CASA system, is provided. Fifty semen samples, five of each of ten adult creole goats, were obtained by electroejaculation. Mean values of total motility, progressive motility and flow cytometry evaluations were compared among EEs. Relationships among mean values of variables were investigated using Spearman correlation and principal component analysis (PCA). For identification of kinematic sperm subpopulations, PCA followed by hierarchical clustering was applied on data of the intervals provided automatically by the CASA system. Total motility does no change after repeated EE. Mean values of motility parameters and molecular markers were unrelated in multivariate space, but bivariate correlations were found. Values in upper and lower intervals defined clearly the sperm subpopulations, which had motility parameters changing over time. Taken together, our results show that repeated EE does not affect mean values of total motility, that molecular markers are not related with motility parameters, and that it is possible to identify kinematic sperm subpopulations when individual data, of motility parameters, are not provided by the CASA system.

Ram seminal plasma proteins contribute to sperm capacitation and modulate sperm–zona pellucida interaction

Incubation of ram spermatozoa in capacitating conditions with cAMP-elevating agents promotes a progressive time-dependent increase in the capacitated sperm subpopulation. In this study, the fertilizing capacity of ram spermatozoa (ability to bind to the zona pellucida, ZBA rate) capacitated in these conditions was determined. The results showed an increase (P < 0.001) in ZBA rate related to control samples in basal medium that contained BSA, calcium, and bicarbonate (1.97 ± 0.19 vs. 1.31 ± 0.09 sperm bound/oocyte, respectively). A significant correlation between protein tyrosine phosphorylation and ZBA rate (P < 0.05, r = 0.501) corroborated that incubation in a “high-cAMP” environment improves the fertilizing ability of ram spermatozoa. Likewise, the presence of two seminal plasma (SP) proteins able to protect sperm against cold shock (RSVP14 and RSVP20) was evidenced in both SP and the ram sperm surface, and their influence in the fertilizing ability of spermatozoa capacitated in basal medium or with cAMP-elevating agents was determined. The results verified that RSVP14 and RSVP20 act as decapacitating factors given that their addition to SP-free sperm samples previously to capacitation maintained high proportions of the noncapacitated sperm pattern with no increase in protein tyrosine phosphorylation. However, the obtained ZBA rate in the high-cAMP–containing samples was increased in the presence of RSVP20 (P < 0.05). These findings would indicate that the stimulating effect exerted by this protein on the sperm–oocyte binding occurs downstream from the cAMP generation and that the mechanisms by which RSVP20 promotes the zona pellucida binding might be independent of protein tyrosine phosphorylation.

Identification of proteins involved in human sperm motility using high-throughput differential proteomics.

Mammalian sperm motility is a prerequisite for in vivo fertilization, and alterations in this parameter are commonly observed in infertile males. However, we still do not have a complete understanding of the molecular mechanisms controlling it. The aim of this study was to identify proteins involved in human sperm motility deficiency by using TMT protein labeling and LC-MS/MS. Two complementary approaches were used: comparison between sperm samples differing in motility (asthenozoospermic versus normozoospermic) and comparison between sperm subpopulations of fractionated normozoospermic samples differing in motility (non-migrated versus migrated). LC-MS/MS resulted in the identification of 1157 and 887 proteins in the first and second approaches, respectively. Remarkably, similar proteomic alterations were detected in the two experiments, with 80 proteins differentially expressed in the two groups of samples and 93 differentially expressed in the two groups of subpopulations. The differential proteins were analyzed by GO, cellular pathways, and clustering analyses and resulted in the identification of core deregulated proteins and pathways associated with sperm motility dysfunction. These included proteins associated with energetic metabolism, protein folding/degradation, vesicle trafficking, and the cytoskeleton. Contrary to what is usually accepted, the outcomes support the hypothesis that several metabolic pathways (notably, mitochondrial-related ones) contribute toward regulating sperm motility.

Mitochondrial activity and reactive oxygen species production define distinct subpopulations of human sperm with different functional properties

Mitochondrial activity and reactive oxygen species production define distinct subpopulations of human sperm with different functional properties

Oviductal secretion and gamete interaction.

Experimental evidence from the last 30 years supports the fact that the oviduct is involved in the modulation of the reproductive process in eutherian mammals. Oviductal secretion contains molecules that contribute to regulation of gamete function, gamete interaction, and the early stages of embryo development. The oviductal environment would act as a sperm reservoir, maintaining sperm viability, and modulating the subpopulation of spermatozoa that initiates the capacitation process. It could also contribute to prevent the premature acrosome reaction and to reduce polyspermy. Many studies have reported the beneficial effects of the oviductal environment on fertilization and on the first stages of embryo development. Some oviductal factors have been identified in different mammalian species. The effects of oviductal secretion on the reproductive process could be thought to result from the dynamic combined action (inhibitory or stimulatory) of multiple factors present in the oviductal lumen at different stages of the ovulatory cycle and in the presence of gametes or embryos. It could be hypothesized that the absence of a given molecule would not affect fertility as its action could be compensated by another factor with similar functions. However, any alteration in this balance could affect certain events of the reproductive process and could perhaps impair fertility. Thus, the complexity of the reproductive process warrants a continuous research effort to unveil the mechanisms and factors behind its regulation in the oviductal microenvironment.

Sorting of sperms with reverse progressive characteristic may provide another option for acquiring spermatozoa with significant improvement in fertility related quality for patients with oligospermia

Previous study had reported a sub-group from progressive motile sperm sub-population with characteristics often referred to as upstream swimming or reversed progressiveness [1]. However, only until recently this sub-group can be separated with minimum damage [2]. Therefore, through the use of a novel microfluidic biochip design, it is the purpose of current study to exam whether or not spermatozoa thus acquired could show improvements not only in sperm motility but also in DNA integrity for normal as well as oligospermia patents.

Dynamic quantification of intracellular calcium and protein tyrosine phosphorylation in cryopreserved boar spermatozoa during short-time incubation with oviductal fluid

Freshly ejaculated boar spermatozoa require several hours of exposure to capacitating conditions to undergo capacitation. We hypothesized that cryopreserved boar spermatozoa might elicit a capacitation response after a relatively shorter time of exposure to capacitating conditions. Washed, frozen-thawed boar spermatozoa were incubated separately with pre-ovulatory isthmic oviductal fluid (EODF), post-ovulatory ODF (MODF), capacitation medium (CM), and noncapacitating medium (NCM) for 60 minutes. Aliquots of spermatozoa were taken at 0, 5, 15, 30, and 60 minutes during incubation and sperm kinematics, intracellular calcium [Ca2+]i content, and protein tyrosine phosphorylation (PTP) were studied. The proportion of motile spermatozoa increased significantly after 5 minutes of incubation with EODF. A similar increase was not observed in the other groups. During the initial 5 minutes of incubation, the proportion of spermatozoa with high [Ca2+]i decreased significantly in all four groups. The proportion of tyrosine phosphorylated spermatozoa increased from 6.49 ± 1.93% to 15.42 ± 3.58% and 18.41 ± 1.57% in EODF and MODF groups, respectively, at 5 minutes of incubation. Neither CM nor NCM elicited any immediate effect on PTP in spermatozoa. There was a positive and significant correlation between [Ca2+]i and sperm motility (P = 0.009). It may be concluded that frozen-thawed boar spermatozoa undergo capacitation-associated changes after a relatively short exposure to EODF, and there are some subpopulations of spermatozoa that undergo PTP despite possessing low [Ca2+]i.

Sperm characterization and identification of sperm sub-populations in ejaculates from pampas deer (Ozotoceros bezoarticus)

Pampas deer (Ozotoceros bezoarticus) is a native endangered species. Knowledge of the basic spermiogram characteristics and the morphometric descriptors is necessary to effectively develop sperm cryopreservation. In other species, sperm sub-population is related to sperm cryo-resistance. The objective was to provide a general description of the sperm, including sperm head morphometric descriptors, its repeatability, and the existence of sperm sub-populations. Sperm were obtained from adult males by electroejaculation during the breeding season. The motility score was 3.4±0.2 (mean±SEM) and progressive motility was 59.4±3.7%. Ejaculated volume was 413.9±51.0μl, the total number of sperm ejaculated was 321.2±55.4×106. Also, 63.3±3.1% of the sperm were morphologically abnormal and 23.7±2.3% had acrosome damage. The sperm head length was 7.6±0.01μm, width 4.4±0.01μm, area 28.1±0.07μm2 and the perimeter was 21.9±0.04μm. There was a positive relationship among morphometric descriptors and the motility score, overall motility and progressive motility. Also length (P=0.011), width (P=0.003), area (P=0.006) and perimeter (P=0.009) of sperm head obtained in two different collections were positively related. Overall, the low concentration, volume, overall quality and abnormal morphology, and wide variation of these variables may be a limitation for the development of sperm cryopreserved banks. There were three sperm sub-populations with different morphometric characteristics. The morphometric descriptors are maintained similarly among different collections.

Hydroxyflutamide alters the characteristics of live boar spermatozoa

Our previous study revealed that in vitro incubation of boar ejaculates with hydroxyflutamide (OH-Flu) causes changes in sperm plasma membrane integrity and its stability and sperm mitochondrial oxidative capability. To broaden the knowledge of cellular physiology of spermatozoa, we investigated direct effects of OH-Flu administered for 2 and 24 hours at concentrations of 5, 50, and 100 μg/mL, on sperm mitochondrial membrane potential and mitochondrial superoxide anion production using JC-1 dye and MitoSOX Red fluorescent probe, respectively. We further measured phosphatidylserine membrane translocation (PST) from the inner to the outer layer of the sperm plasma membrane using an annexin-V binding assay. To provide new information of direct effects of OH-Flu on cell signaling pathway, we measured sperm intracellular calcium ion dynamics using Fluo-3. Finally, we assessed sperm motility using a computer-assisted spermatozoa analysis system. Motile sperm were highlighted using the “C-Ruch” computer program for detailed analysis of the straight line velocity distribution. For each functional test, boar spermatozoa were examined and analyzed by flow cytometry and/or confocal microscopy. The results revealed a significant decrease (P < 0.05) in sperm mitochondrial membrane potential and a concomitant increase (P < 0.05) in mitochondrial superoxide anion production after a 2-hour incubation with 50 μg OH-Flu compared with the respective controls and other doses used (P < 0.05). The adverse effects of OH-Flu become strengthened over time (P < 0.05). Notably, 50 and 100 μg OH-Flu appeared to be effective in decreasing sperm motility. Hydroxyflutamide significantly decreased (P < 0.05) the fast sperm subpopulation percentage after 15 minutes and reduced the straight line velocity distribution (P < 0.05). An assessment of PST revealed an increase in the percentage of PST-positive spermatozoa (P < 0.05) only after exposure to OH-Flu for 24 hours. Moreover, OH-Flu at all concentrations induced a rapid increase in sperm intracellular calcium ion concentration. Altogether, the altered in vitro characteristics of live boar spermatozoa provide new insight into direct effects of OH-Flu on sperm mitochondrial membrane potential, superoxide anion production, translocation of membrane phosphatidylserine, free calcium ion dynamics, and sperm motility.

Gamete cryobanks for laboratory research: Developing a rapid and easy-to-perform protocol for the cryopreservation of the sea urchin Paracentrotus lividus (Lmk, 1816) spermatozoa

Gamete cryopreservation is a biotechnology that can guarantee a continuous supply of gametes, regardless of the seasonal reproductive cycle. In this study we developed a protocol for the cryopreservation of the sea urchin Paracentrotuslividus spermatozoa, with a view to the creation of cryobanks of semen to be used as a model system in laboratory research and ecotoxicological tests. All the key phases of the procedure were separately considered and the effect on sperm motility was evaluated by means of computer assisted analysis. The best results were obtained using 7% dimethylsulfoxide in 1% NaCl plus 0.04M trehalose as the extender, at a freezing rate of −20°C/min. On thawing, in semen samples cryopreserved in accordance with this protocol the velocity parameters of the sub-population of rapid sperm (best performing spermatozoa) did not significantly differ from semen on collection; in addition also the fertilization ability was restored, and about 50% of normal developed plutei larvae were obtained by thawed semen. The developed protocol is rapid and easy-to-perform; moreover, the use of gametes from reared urchins makes it unnecessary to continuously collect specimens from natural populations, making this procedure a promising starting point for the creation of alternative and more sustainable methodologies in laboratory research on sea urchin gametes and embryos.

Membrane hyperpolarization during human sperm capacitation.

Sperm capacitation is a complex and indispensable physiological process that spermatozoa must undergo in order to acquire fertilization capability. Spermatozoa from several mammalian species, including mice, exhibit a capacitation-associated plasma membrane hyperpolarization, which is necessary for the acrosome reaction to occur. Despite its importance, this hyperpolarization event has not been adequately examined in human sperm. In this report we used flow cytometry to show that a subpopulation of human sperm indeed undergo a plasma membrane hyperpolarization upon in vitro capacitation. This hyperpolarization correlated with two other well-characterized capacitation parameters, namely an increase in intracellular pH and Ca(2+) concentration, measured also by flow cytometry. We found that sperm membrane hyperpolarization was completely abolished in the presence of a high external K(+) concentration (60 mM), indicating the participation of K(+) channels. In order to identify, which of the potential K(+) channels were involved in this hyperpolarization, we used different K(+) channel inhibitors including charybdotoxin, slotoxin and iberiotoxin (which target Slo1) and clofilium (a more specific blocker for Slo3). All these K(+) channel antagonists inhibited membrane hyperpolarization to a similar extent, suggesting that both members of the Slo family may potentially participate. Two very recent papers recorded K(+) currents in human sperm electrophysiologically, with some contradictory results. In the present work, we show through immunoblotting that Slo3 channels are present in the human sperm membrane. In addition, we found that human Slo3 channels expressed in CHO cells were sensitive to clofilium (50 μM). Considered altogether, our data indicate that Slo1 and Slo3 could share the preponderant role in the capacitation-associated hyperpolarization of human sperm in contrast to what has been previously reported for mouse sperm, where Slo3 channels are the main contributors to the hyperpolarization event.

Validation of computer-assisted sperm-motility analysis in the amphibian Silurana tropicalis

We have developed and validated a computer-assisted sperm-motility assessment (CASA) method for use with the emerging amphibian model Silurana tropicalis. The testicular sperm-activation method was validated by analysing activation replicate coefficients of variation, effects of tracking time settings on velocity distributions and the relative partitioning of differentially motile sperm subpopulations between matched right and left testes. Two major sperm subpopulations were identified using multivariate pattern analysis and their relative frequencies were consistent between samples from matched right and left testes and from randomly drawn subsets of six frogs sampled from the total set of 16 frogs. The power of this approach for detecting treatment effects targeting the hypothalamic-pituitary--gonadal axis was investigated by injecting a group of frogs with 100IU human chorionic gonadotrophin (hCG) 2h before sampling and comparing their sperm-subpopulation frequencies with non-injected controls. While parametric analysis across sperm samples failed to detect treatment effects, subpopulation analysis showed that hCG significantly increased the proportion of progressive and non-sinuous spermatozoa compared with controls (Chi square=6.40, DF=1, P=0.011). This demonstrated the potential value of analysing objectively measured sperm behaviour as an endpoint.

Influence of season and reproductive management on the morphometry of ram sperm head

The aim of the present work was to study the morphometric characteristics of apparently normal ram sperm heads of an ovine insemination centre over a year, using a computer-assisted sperm morphometric assessment system (CASMA) which is commercially available. For this, 383 ejaculates from 9 mature rams kept in non-controlled environmental conditions were used. The morphometry was analyzed in fresh sperm and each spermatozoon was measured for four primary parameters (length, L; area, A; width, W and perimeter, P) and four derived parameters (ellipticity, L/W; rugosity, 4πA/P2; elongation, L−W/L+W and regularity, πLW/4A).A clear seasonal behaviour of both morphometric and derived parameters was observed, with sperm size being larger in autumn and winter. This behaviour was also observed for ellipticity and elongation.Due to organizational reasons in the insemination centre, the rams’ reproductive activity was suspended during the month of August; this fact was reflected, in the ejaculates collected in September, in the decrease of the sperm head size, as well as in the increase of ellipticity.The procedures used in the present study did not allow for natural separation in sperm subpopulations considering the size and shape of apparently normal sperm heads, but it was possible to divide the ejaculate into two subpopulations, taking rugosity into account. These subpopulations were present in all the rams – and had a clear seasonal distribution.

Versatile Action of Picomolar Gradients of Progesterone on Different Sperm Subpopulations

High step concentrations of progesterone may stimulate various sperm physiological processes, such as priming and the acrosome reaction. However, approaching the egg, spermatozoa face increasing concentrations of the hormone, as it is secreted by the cumulus cells and then passively diffuses along the cumulus matrix and beyond. In this context, several questions arise: are spermatozoa sensitive to the steroid gradients as they undergo priming and the acrosome reaction? If so, what are the functional gradual concentrations of progesterone? Do spermatozoa in different physiological states respond differentially to steroid gradients? To answer these questions, spermatozoa were confronted with progesterone gradients generated by different hormone concentrations (1 pM to 100 µM). Brief exposure to a 10 pM progesterone gradient stimulated priming for the acrosome reaction in one sperm subpopulation, and simultaneously induced the acrosome reaction in a different sperm subpopulation. This effect was not observed in non-capacitated cells or when progesterone was homogeneously distributed. The results suggest a versatile role of the gradual distribution of very low doses of progesterone, which selectively stimulate the priming and the acrosome reaction in different sperm subpopulations.