Relationship between frame rates and subpopulation structure of bovine sperm divided by their motility analyzed by a computer-assisted sperm analysis system

The authors investigated the relationship between frame rates and subpopulation structure of bovine sperm divided by their motility analyzed by a computer-assisted sperm analysis (CASA). Kinematic parameters of bovine sperm incubated in Brackett & Oliphant medium with and without calcium ionophore for 0, 1, 5, 10, 15, 20, 25, and 30 min were evaluated by a CASA at 150 frames per second (fps) and analyzed structure of sperm motility subpopulation by cluster analysis. Then, we converted CASA data at 150 fps to 75, 50, and 30 fps and evaluated the structures of sperm motility subpopulation at different fps in each sperm by a discriminant analysis. As the results, the structure of sperm motility subpopulation was affected by frame rate. Sperm were divided into six clusters at 150, 75, and 50 fps; on the other hand, there were five clusters at 30 fps. Straight-line velocity was similar at all frame rates. However, as the frame rate became higher, curvilinear velocity and beat cross frequency of sperm head increased significantly, whereas lateral sperm head displacement decreased significantly. In conclusion, higher frame rate at 150 fps is recommended to capture the trajectory of sperm accurately by CASA in the present study.

Plasminogen activator inhibitor 1 and Antipain preserve acrosome integrity of bovine spermatozoa during cryopreservation

ABSTRACT Seminal plasma contains serine proteases and serine protease inhibitor, which are involved in mammalian fertilization, and the inhibitors can be applied to prevent cold-induced sperm capacitation. The effects of different concentrations of two serine protease inhibitors were analyzed, Plasminogen activator inhibitor 1 - PAI-1 (70ƞg, 140ƞg and 210 ƞg) and Antipain (10µg, 50µg and 100µg) as supplementation to bovine semen cryopreservation extender. The effects of the inhibitors on the sperm parameters (sperm kinetics - CASA, acrosome integrity, plasma membrane integrity, mitochondrial membrane potential, sperm defects and acrosome reaction rate) were evaluated in the post-thaw semen. Cryopreservation of sperm with Antipain decreased post-thaw kinetic parameters of MP, VSL, LIN, SRT and the percentage of hyper-activated sperm while PAI-1 (210 ƞg) decreased VSL and LIN. Antipain and PAI-1 had no effect on the integrity parameters of the plasma membrane, mitochondrial membrane potential and sperm defects. Sperm cryopreserved in the presence of Antipain and PAI-1 (70 and 140 ƞg) preserved acrosome integrity, as they were able to complete the in vitro acrosome reaction. In conclusion, the serine protease inhibitors, Antipain and PAI-1 (70 and 140ƞg) are able to preserve the acrosome integrity of cryopreserved bovine sperm.

Protein biomarkers for male artificial insemination subfertility in bovine spermatozoa

Background

Although artificial insemination (AI) technique is an established biotechnology for bovine reproduction, the results of AI (conception rates) have a tendency to decline gradually. To our annoyance, moreover, AI‐subfertile bulls have been occasionally found in the AI centers. To resolve these serious problems, it is necessary to control the sperm quality more strictly by the examinations of sperm molecules.

Methods

We reviewed a number of recent articles regarding potentials of bovine sperm proteins as the biomarkers for bull AI‐subfertility and also showed our unpublished supplemental data on the bull AI‐subfertility associated proteins.

Main findings

Bull AI‐subfertility is caused by the deficiency or dysfunctions of various molecules including regulatory proteins of ATP synthesis, acrosomal proteins, nuclear proteins, capacitation‐related proteins and seminal plasma proteins.

Conclusion

In order to control the bovine sperm quality more strictly by the molecular examinations, it is necessary to select suitable sperm protein biomarkers for the male reproductive problems which happen in the AI centers.

Effects of acrosomal conditions of frozen-thawed spermatozoa on the results of artificial insemination in Japanese Black cattle

The purposes of this study were to examine the relationship between male artificial insemination (AI) fertility and sperm acrosomal conditions assessed by new and conventional staining techniques and to identify possible reproductive dysfunctions causing low conception rates in AI using frozen-thawed spermatozoa with poor acrosomal conditions in Japanese Black bulls. We investigated individual differences among bulls in the results concerning (1) acrosomal conditions of frozen-thawed spermatozoa as assessed by not merely peanut agglutinin-lectin staining (a conventional staining technique) but also immunostaining of acrosomal tyrosine-phosphorylated proteins (a new staining technique), (2) routine AI using frozen-thawed spermatozoa as assessed by pregnancy diagnosis, (3) in vivo fertilization of frozen-thawed spermatozoa and early development of fertilized eggs as assessed by superovulation/AI-embryo collection tests and (4) in vitro fertilization of frozen-thawed spermatozoa with oocytes. The percentages of frozen-thawed spermatozoa with normal acrosomal conditions assessed by the abovementioned staining techniques were significantly correlated with the conception rates of routine AI, rates of transferable embryos in superovulation/AI-embryo collection tests and in vitro fertilization rates. These results are consistent with new suggestions that the distribution of acrosomal tyrosine-phosphorylated proteins as well as the acrosomal morphology of frozen-thawed spermatozoa are AI fertility-associated markers that are valid for the prediction of AI results and that low conception rates in AI using frozen-thawed spermatozoa with poor acrosomal conditions result from reproductive dysfunctions in the processes between sperm insemination into females and early embryo development, probably failed fertilization of frozen-thawed spermatozoa with oocytes.

Ram spermatozoa migrating through artificial mucus in vitro have reduced mitochondrial membrane potential but retain their viability

Sperm motility in vitro is one of the most common predictors of fertility in male screening. We propose that a mucus-penetration assay can isolate a cellular subpopulation critical to reproductive success. To this end, a device was designed with three modules (sample, test and collection) and its conditions of use evaluated (length of mucus, incubation time, mucus medium, sperm concentration and position in relation to the horizontal). The number of spermatozoa migrating and the viability and acrosomal status of the spermatozoa not migrating were calculated. The second objective was to evaluate the qualitative parameters of the spermatozoa migrating in 1.6% polyacrylamide for 30 min. The number of spermatozoa migrating and the sperm motility, viability and the acrosomal and mitochondrial status of three sperm populations (fresh, not migrating and migrating) were determined. A higher number of migrating spermatozoa were observed after 60 min of incubation, but this situation adversely affected sperm quality. The methylcellulose-based test showed a significantly lower number of migrating spermatozoa than the polyacrylamide test. The position at an angle of 45° resulted in a higher number of migrating spermatozoa in the polyacrylamide-based test. The sperm counts for three consecutive assays indicated an acceptable repeatability of the method. The viability and acrosomal status of the migrating spermatozoa showed no significant changes with regard to the control when the device was placed at 45°, whereas these parameters showed lower values at 0°. The percentage of high mitochondrial membrane potential spermatozoa was significantly reduced in the population of migrating spermatozoa.

Hyperactivated motility of frozen-thawed spermatozoa from fertile and subfertile Japanese black bulls induced by cyclic adenosine 3',5'-monophosphate analogue, cBiMPS

This study investigated whether a cyclic adenosine 3',5'-monophosphate (cAMP) analogue, cBiMPS, could induce hyperactivated motility in frozen-thawed Japanese Black bull spermatozoa and compared the ability of spermatozoa to undergo hyperactivation between fertile and subfertile bulls. Frozen-thawed spermatozoa from 3 fertile and 2 subfertile bulls were washed, suspended in BO-Hepes medium and incubated in the presence of 0.1 mM cBiMPS for up to 4 h. At 1-h intervals, the spermatozoa were examined for hyperactivated motility. The proportions of spermatozoa showing a circular swimming pattern with asymmetrical flagellar beating and those showing whiplash beating of flagella to the total number of motile spermatozoa were expressed as C% and W%, respectively. The motile spermatozoa % was barely affected by treatment with cBiMPS or the fertility status of the sperm donor, although it gradually decreased in all sperm samples during the 4-h incubation. In the fertile bulls, the C% was 0% at 0 h of incubation but rapidly increased during the 1-h incubation with cBiMPS. It then decreased slightly towards 4 h concomitantly with a gradual increase in W% towards 4 h. In the subfertile bulls, however, the cBiMPS-induced increase of C% was delayed for 1-3 h, although the incubation time-related changes in mean W% were similar between the fertile and subfertile bulls. In the vehicle controls for cBiMPS, the C% and W% were 0% throughout incubation for all the samples examined. The results suggest that hyperactivation of the flagellum can be induced by the cAMP analogue, cBiMPS, in frozen-thawed Japanese Black bull spermatozoa and that induction of hyperactivation may serve as a useful tool for detection of functional abnormality of spermatozoa from subfertile Japanese Black bulls.

Seasonal changes in semen characteristics, composition of seminal plasma and frequency of acrosome reaction induced by calcium and calcium ionophore A23187 in Large White boars

This study attempted to explain the mechanisms regulating boar fertility by examining seasonal changes in semen characteristics, the composition of seminal plasma and responsiveness of sperm acrosomes to Ca(2+) and the Ca(2+) ionophore A23187 (Ca(2+)/A23187). Sperm-rich and sperm-poor fractions were separately collected from 3 mature fertile Large White boars once a month over a one-year period. During the period of study, ambient temperature and relative humidity were recorded for within the stall in which the boars were kept and the semen characteristics, composition of the seminal plasma of sperm-rich fractions, and occurrence of the acrosome reaction in response to Ca(2+) (3 mM)/A23187 (0.3 microM) were examined. The highest mean maximum and minimum ambient temperatures were recorded in August-September, whereas the lowest mean maximum and minimum ambient temperatures were recorded in December and January, respectively. There was a moderate peak in relative humidity from July to October. The lowest percentages of motile spermatozoa and of spermatozoa with intact acrosomes and highest percentage of spermatozoa with abnormal morphology and strongest agglutination were seen in August-September. The total protein and albumin concentrations were lowest in August-September. Testosterone levels increased gradually as day length decreased after the summer solstice (June) and peaked in October-November. The percentage of acrosome reactions in response to Ca(2+)/A23187 was highest with the quickest response in August-September, as shown by the shortest time required for 50% of relative acrosome reactions. The farrowing rates were lowest in these same 2 months. These results suggest that seasonal infertility in Large White boars may be due, at least in part, to a combination of low motility, abnormal morphology including acrosomal abnormality, and early occurrence of the acrosome reaction in response to stimulus, possibly resulting from a decrease in acrosomal stabilizing proteins in the seminal plasma during summer. These changes may be modulated by heat/humidity stress and/or photoperiod-regulated testosterone.

Premature Capacitation of Frozen-Thawed Spermatozoa from Subfertile Japanese Black Cattle

Artificial insemination (AI) subfertility is an indication of failure of AI with frozen-thawed sperm classified as normal by conventional semen examination. Recently, 8 AI-subfertile Japanese Black cattle (S1-S8) were identified using the routine AI test or in vivo fertilization test, which included AI with frozen-thawed sperm of superovulated females and subsequent non-surgical recovery of presumptive zygotes. In the present study, we assessed capacitation states and in vitro oocyte penetration of frozen-thawed sperm from these bulls to estimate causal factors of AI subfertility. Frozen-thawed sperm from 8 AI-subfertile (S1-S8) and 9 fertile (F1-F9, control) bulls were washed and then used for a chlortetracycline (CTC) staining assay and in vitro fertilization test. The CTC staining assay revealed that approximately 50% of the sperm from 4 of the AI-subfertile bulls (S5-S8) were prematurely progressing into the capacitation state immediately after washing and resuspension in a CaCl(2)-lacking medium. In contrast, most of the sperm from the fertile bulls and other AI-subfertile bulls (S1-S4) remained uncapacitated. Addition of CaCl(2) to the medium effectively promoted a spontaneous acrosome reaction in the sperm samples from the AI-subfertile bulls (S5-S8). Moreover, the in vitro fertilization test showed that rates of sperm penetration into oocytes were significantly lower in sperm samples from the AI-subfertile bulls (S5-S8) than in the control sperm samples from the fertile bulls (F2-F4 and F7-F9). It has previously been suggested that prematurely capacitated sperm undergo a spontaneous acrosome reaction possibly due to uncontrolled influx of calcium ion, and consequently they possess relatively lower in vitro fertilizing ability. It is therefore possible that premature capacitation of sperm used for AI is a causal factor of subfertility of male Japanese Black cattle and a potentially good marker for identification of subfertile bulls for removal from AI programs.