Influence of seminal plasma on fresh and post-thaw parameters of stallion epididymal spermatozoa

The Effect of Cushioned Centrifugation, with and without Enzymatic Reduction of Viscosity, on the Motility Pattern and Kinematic Parameters of Dromedary Camel Bull Spermatozoa

In order to contribute to the development of semen processing procedures in camelids, the aims of the present study were to evaluate (i) the effect of 35% seminal plasma incubation on dromedary camel epididymal sperm motility and kinematic parameters, (ii) the effects of centrifugation, with cushion fluid and enzymatic reduction of viscosity (Papain + E64) during ejaculate processing, on the motility and kinematic parameters of dromedary camel ejaculates. The incubation with seminal plasma significantly reduced the percentage of progressively motile spermatozoa as well as the proportion of medium progressive spermatozoa whilst increasing the percentage of non-progressive spermatozoa. The centrifugation procedure improved the sperms' kinematic parameters, and the highest values were observed for samples centrifugated with cushion fluid. The samples treated with Papain + E64 showed a significant increase in both total and medium progressive spermatozoa, along with a reduction of non-progressive spermatozoa (p < 0.05). The results of this investigation show that a simple, cheap, and effective procedure, such as cushioned centrifugation, could improve the motility patterns of dromedary camel spermatozoa; in combination with enzymatic reduction of viscosity, this method leads to the best results in terms of recovery rates and sperms' kinematic parameters.

Retrograde Flushing Followed by Slicing Float-Up as an Approach to Optimize Epididymal Sperm Recovery for the Purpose of Cryopreservation in Equids

This study aimed to assess the parameters of epididymal sperm harvested by retrograde flushing (RF) followed by slicing float-up (SF). Epididymides from donkeys (n = 18) and horses (n = 28) were subjected to RF with a freezing extender and then SF technique. The retrieved sperm after RF and SF was evaluated for volume, concentration, and total sperm and then cryopreserved separately. Post-thaw total motility (TM) and progressive motility (PM) were evaluated with CASA. Sperm membrane integrity (SMI) and mitochondrial membrane potential (MMP) were assessed with flow cytometry. Sperm concentration was greater in donkeys than horses (684 ± 62.9 vs. 494 ± 50.9 million sperm/mL) (p = 0.02). The total sperm harvested was lower in SF (3.6 ± 0.7 billion) than RF (10.4 ± 1.5 billion) and in horses (4.6 ± 0.8 billion) than in donkeys (10.7 ± 1.8 billion) (p < 0.05). RF followed by SF resulted in 57% and 31% more sperm per harvest in donkeys and horses. Results of TM and PM before freezing were not affected by technique or species (p > 0.05). Post-thawing SMI and MMP did not vary with technique or species (p > 0.05); TM and PM were not influenced by the technique or the species (p > 0.05) but by their interaction (p = 0.005). In conclusion, using RF followed by SF enhances sperm recovery without affecting cryopreservation in equids.

Seminal plasma components from fertile stallions involved in the epididymal sperm freezability

BACKGROUND

Seminal plasma (SP) plays a crucial role in sperm protection and functionality. However, the effect of SP on the sperm cryopreservation is dependent on the stallion and SP composition. The use of epididymal spermatozoa incubated in the presence of SP could help the identification of the components of SP that are able to confer protection upon the spermatozoa during freezing.

OBJECTIVE

The aims of this study were (i) to identify SP components involved in the potential protection of epididymal spermatozoa during the freeze-thawing process and (ii) to identify and evaluate the proteins likely related to sperm freezability, using two-dimensional difference gel electrophoresis (2D-DIGE).

MATERIALS AND METHODS

Epididymal spermatozoa from 4 stallions were incubated with SP (80%, v/v) or without SP (control) before freezing. Sperm parameters were evaluated after thawing (viability, chromatin condensation, acrosomal integrity, reactive oxygen species [ROS]) and SP composition: total antioxidant capacity (TAC), fatty acid composition, total protein concentration, and protein components by 2D-DIGE.

RESULTS

After thawing, the proportions of viable and acrosome-intact spermatozoa were higher than control when SP from two stallions was used (F and O). The SP of all stallions reduced ROS production in comparison with the control. After analyzing the SP components, it was found that total protein concentration, TAC, polyunsaturated fatty acids (PUFA), and eight specific proteins identified by 2D-DIGE were different between stallions.

DISCUSSION

These studies allow the identification of SP components that could be involved in sperm protection or cryotolerance. Use of this information could help in the selection of stallions according to their semen freezing capacity.

CONCLUSION

The composition of the SP probably contributes to semen cryotolerance capacity. Total protein, TAC, PUFA, and some proteins such as cysteine-rich secreted protein 3 could be used as biomarkers for the selection for sperm cryotolerance.

Effect of Seminal Plasma Protein Fractions on Stallion Sperm Cryopreservation

Seminal plasma (SP) is the natural environment for spermatozoa and contains a number of components, especially proteins important for successful sperm maturation and fertilization. Nevertheless, in standard frozen stallion insemination doses production, SP is completely removed and is replaced by a semen extender. In the present study, we analyzed the effects of the selected seminal plasma protein groups that might play an important role in reducing the detrimental effects on spermatozoa during the cryopreservation process. SP proteins were separated according to their ability to bind to heparin into heparin-binding (Hep+) and heparin-non-binding (Hep-) fractions. The addition of three concentrations-125, 250, and 500 µg/mL-of each protein fraction was tested. After thawing, the following parameters were assessed: sperm motility (by CASA), plasma membrane integrity (PI staining), and acrosomal membrane integrity (PNA staining) using flow cytometry, and capacitation status (anti-phosphotyrosine antibody) using imaging-based flow cytometry. Our results showed that SP protein fractions had a significant effect on the kinematic parameters of spermatozoa and on a proportion of their subpopulations. The 125 µg/mL of Hep+ protein fraction resulted in increased linearity (LIN) and straightness (STR), moreover, with the highest values of sperm velocities (VAP, VSL), also this group contained the highest proportion of the fast sperm subpopulation. In contrast, the highest percentage of slow subpopulation was in the groups with 500 µg/mL of Hep+ fraction and 250 µg/mL of Hep- fraction. Interestingly, acrosomal membrane integrity was also highest in the groups with Hep+ fraction in concentrations of 125 µg/mL. Our results showed that the addition of protein fractions did not significantly affect the plasma membrane integrity and capacitation status of stallion spermatozoa. Moreover, our results confirmed that the effect of SP proteins on the sperm functionality is concentration-dependent, as has been reported for other species. Our study significantly contributes to the lack of studies dealing with possible use of specific stallion SP fractions in the complex puzzle of the improvement of cryopreservation protocols. It is clear that improvement in this field still needs more outputs from future studies, which should be focused on the effect of individual SP proteins on other sperm functional parameters with further implication on the success of artificial insemination in in vivo conditions.

Effects of cashew gum and nanoparticles on cooled stallion semen

BACKGROUND

Cryopreservation of stallion spermatozoa tends to cause plasma membrane damage due to the low ratio of cholesterol to phospholipids. Gums have been suggested as an alternative cryoprotectant to glycerol for stallion spermatozoa. Therefore, the present experiment was designed to verify whether the effect of addition of cashew gum (CG), or nanoparticles (NP) containing CG, to the extender before cooling on sperm quality in stallion semen. Ejaculates from 6 stallions were extended and split between six treatment groups (control, a-tocopherol [TOC], CG1, CG0.5, NP1 and NP0.5), stored in cryotubes at 4 °C.

RESULTS

Aliquots were analysed by computer-assisted sperm motility analysis on the day of collection, and after 24 h and 48 h of cold storage. After 48 h, the total motility with NP1 (78.53 + 6.31%) was similar to control 85.79 + 6.31% at 0 h. The same pattern was observed for progressive motility. Membrane integrity assessed by flow cytometer was similar between control, TOC and G1 at all storage times. The DNA fragmentation in the control group increased at all time points, whereas chromatin integrity was maintained after 24 h in TOC and NP0.5 compared to 0 h. There was no increase in the proportion of live spermatozoa producing hydrogen peroxide, but there was a tendency for an increased proportion of spermatozoa in the live superoxide category in CG1 after 24 h cooled storage.

CONCLUSIONS

The addition of CG or CG-derived NP to extender for stallion semen was not harmful to the sperm cells.

Efeito da adição de plasma seminal oriundo de animais de alta e baixa fertilidade na criopreservação de espermatozoides da cauda do epidídimo e do ejaculado de garanhões subférteis

RESUMO O objetivo do presente estudo foi avaliar o efeito da adição de plasma seminal de garanhões de alta e baixa fertilidade sobre a congelabilidade e a viabilidade de espermatozoides do ejaculado (EJ) e do epidídimo (EP) de garanhões subférteis. Foram utilizados seis garanhões com histórico de subfertilidade. Após coleta, espermatozoides do ejaculado foram divididos em três alíquotas: BotuSêmen® (EJ-CT); plasma seminal de alta qualidade espermática (EJ-PS1); e plasma seminal de baixa qualidade espermática (EJ-PS2). O mesmo protocolo foi realizado com espermatozoides da cauda do epidídimo após orquiectomia (EP-CT; EP-PS1; EP-PS2). Foram realizadas avaliações da cinética espermática pelo CASA e análises de integridade de membrana, acrossoma, fragmentação de DNA, capacitação espermática e peroxidação espermática por citometria de fluxo. Não foram observadas diferenças na cinética espermática entre EJ e EP, logo após a descongelação. Porém, foi observada maior (P<0,05) porcentagem de células com membranas plasmática e acrossomal íntegras nos grupos EP (EP-CT:31,7±7,5b; EP-PS1:35,2±7,0b; EP-PS2:33,9±7,2b) em comparação aos grupos EJ (EJ-CT:15,1±4,9a; EJ-PS1:11,7±4,5a; EJ-PS2:13,1±5,2a). Adicionalmente, foram observadas diferenças no índice de fragmentação de DNA (EJ-CT:2,6±0,6a; EJ-PS1:2,4±0,8a; EJ-PS2:3,0±0,8a; EP-CT:1,4±0,4b; EP-PS1:1,2±0,3b; EP-PS2:1,3±0,2b). Concluiu-se que a adição de 20% de plasma seminal, oriundo de animais férteis ou subférteis, previamente à congelação de espermatozoides epidídimários de animais subférteis não interfere na qualidade espermática.

Effects of lidocaine on equine ejaculated sperm and epididymal sperm post-castration

In equids, it is common to inject lidocaine into the testicles at the time of routine castration to provide analgesia. The effects of lidocaine on equine sperm have not been evaluated in vitro or on epididymal sperm collected following castration. The aims of this study were to determine effects of clinically relevant doses of lidocaine on equine spermatozoa in vitro using freshly collected semen and to compare the characteristics of epididymal spermatozoa after routine castration with or without intra-testicular lidocaine administration. We hypothesized that increasing concentrations of lidocaine would decrease total motility (TM), progressive motility (PM), velocity of the average path (VAP), velocity of the curved line (VCL), linearity (LIN), normal morphology (M) and membrane integrity (MI). We also hypothesized that injection of intra-testicular lidocaine would decrease TM, PM, VAP, VCL, LIN, M, and MI following routine castration, epididymal flushing and cryopreservation. In experiment 1, sperm was collected from four stallions and mixed with lidocaine at concentrations of 1 μg/ml, 10 μg/ml, 100 μg/ml, 1,000 μg/ml and 10,000 μg/ml. M and MI were compared to the control sample at 0 and 48 h. Motility parameters were analyzed at 0, 2, 4, 6, 24, and 48 h. In experiment 2, 12 stallions were castrated under general anesthesia. One testicle was removed without the use of intra-testicular lidocaine and the other testicle was removed 10 min after injection of 10 ml of 2% lidocaine. Results: In experiment 1, fresh sperm showed no significant difference (p < 0.05) compared to control at either 1 μg/ml or 10 μg/ml concentrations of lidocaine. There were significant decreases in PM, VAP, VCL, and LIN at concentrations of 100μg/ml-10,000 μg/ml and for TM at lidocaine concentrations of 1,000-10,000 μg/ml compared to control. Morphology did not change at any lidocaine concentration. Membrane integrity decreased significantly at 10,000 μg/ml lidocaine. In the second experiment 1.03 ± 0.42 μg/ml lidocaine was detected in the epididymal flush of stallions treated with lidocaine. There were no significant differences in any measured parameters between the control and the lidocaine treated testicles. Intra-testicular lidocaine injection at the time of castration did not affect any measured parameters after epididymal flush. Lidocaine concentrations higher than 100 μg/ml in-vitro resulted in decreased motility parameters of the spermatozoa independent of exposure time.