Chemotactic selection of frozen-thawed stallion sperm improves sperm quality and heterologous binding to oocytes

The successful use of assisted reproduction techniques (ART) depends in part on the sperm physiological status. Several sperm selection procedures have been applied to improve quality of sperm population when using the ART. There has previously been development of a Sperm Selection Assay (SSA) for humans which is based on the attraction of capacitated sperm by chemotaxis towards progesterone (P), resulting in an enriched sperm population with an optimal physiological status similar to capacitated spermatozoa, with these cells having very little DNA fragmentation and optimal concentrations of reactive oxygen species (ROS). In the present study, the aim was to adapt the SSA for frozen-thawed stallion semen samples and evaluate the functional status of those sperm selected using the SSA procedure, and to determine whether this enriched sperm population has a greater capacity to bind to the zona pellucida of cattle oocytes. There were experimental conditions developed to conduct the SSA with stallion sperm. Using these conditions, the indexes of induced acrosome reaction, protein tyrosine phosphorylation, mitochondrial membrane potential, mitochondrial and cytoplasmic reactive oxygen species, and number of sperm bound to the zona pellucida of cattle were greater when the sperm population was selected using the SSA. Consistently, the DNA fragmentation and phospholipase C zeta indexes were less for the selected sperm. In conclusion, stallion sperm selected using chemotaxis utilizing the SSA provides a sperm population of greater quality, which when used may improve the outcomes with use of the ART.

Sperm preparation through Sephadex™ filtration improves in vitro fertilization rate of buffalo oocytes

Routinely, swim-up method is used to separate high-quality sperm; however, long processing time and close cell-to-cell contact during the centrifugation step are inevitable elements of oxidative stress to sperm. The objective was to evaluate Sephadex^™ and glass wool filtration to separate motile, intact and viable sperm for in vitro fertilization in buffalo. The cumulus-oocyte complexes (COCs) were collected from ovaries of slaughtered buffaloes by aspiration and matured for 24 hr in CO₂ incubator at 38.5°C and 5% CO₂ . Matured COCs were rinsed twice in fertilization TALP and placed in the pre-warmed fertilization medium without sperm. Cryopreserved buffalo semen was thawed at 37°C for 30 s and processed through Sephadex^™ , glass wool filtration and swim-up (control). Total and motile sperm recovery rates were assessed, resuspended in fertilization TALP and incubated for 15-20 min in CO₂ incubator. Samples prepared by each method were divided into two aliquots: one aliquot was studied for sperm quality (progressive motility, membrane integrity, viability, liveability), while the other was subjected to co-incubation with sets of 10-15 in vitro matured oocytes. Data on sperm quality were analysed by ANOVA, while in vitro fertilizing rates were compared by chi-squared test using SPSS-20. Least significant difference (LSD) test was used to compare treatment means. Glass wool filtration yielded higher total and motile sperm recovery rate, while Sephadex^™ filtration improved (p < .05) sperm quality (progressive motility, membrane integrity, viability, liveability). Sperm preparation through Sephadex filtration yielded higher in vitro fertilization rate in terms of cleavage rate compared to glass wool filtration and swim-up (control). In conclusion, cryopreserved Nili-Ravi buffalo sperm selected through Sephadex filtration showed improved quality and yielded better fertilization rates (cleavage rate) of in vitro matured/fertilized oocytes. Sephadex filtration could be a promising technique for use in in vitro fertilization in buffalo.

Effects of filtration through Sephadex columns improve overall quality parameters and "in vivo" fertility of subfertile refrigerated boar-semen

This study was performed to test the effects of filtration through several chromatographic resins on the semen quality parameters (percentages of viability, altered acrosomes and morphological abnormalities, motion characteristics and the response to the Osmotic Resistance Test) of boar ejaculates of poor quality. Our results indicate that filtration through a non-ionic Sephadex resin bed (Sephadex G-15), combined with a glasswool subjection bed, induced an overall improvement of semen quality parameters, especially seen in a significant (P<0.05) decrease in the percentages of morphological abnormalities and an increase of several motility parameters related to velocity and linearity. Similar results, although less intense, were observed when the filtration through G-15 resin was accompanied by an ionically neutral polypropylene disk bed instead of glasswool. On the other hand, filtration through two separate ion-exchange Sephadex resins, cationic C-50 and anionic A-50, have less beneficial, and even detrimental, effects on boar-semen quality. In all cases, filtration was accompanied by a significant (P<0.01) decrease in the final concentration of the samples. Ultrastructural and lectin studies showed that the interaction between sperm and chromatographic resins depends on the resin type utilized, and in the case of G-15 it seems that it works by trapping that sperm with not enough strength to overcome the physical resistance associated with chromatographic particles. When semen of poor quality was filtered through G-15 resin and then was utilized for "in vivo" fertility trials, a significant (P<0.05) increase in the percentage of fertility was observed, when compared with the same, but unfiltered, samples. In summary, our results strongly indicate that filtration through ionically inert, Sephadex chromatographic resins could be a very useful and practical method to improve both boar-semen quality and fertilizing ability, especially from mediocre and/or subfertile samples.

Effects of filtration of semen doses from subfertile boars through neuter Sephadex columns

This study was designed to develop a method of improving the quality of sperm obtained from subfertile Piétrain boars. Seminal doses were filtered through neuter Sephadex columns (G-25 Medium, G-50 Fine, G-50 Medium and G-75, length 10 +/- 0.5 cm, flow rate 1 ml/20 s). Doses were prepared by pooling 10 ml semen samples collected from 58 asthenoteratospermic boars and diluted the sperm-cell rich fraction 1 : 6 in Betsville thawing solution extender. Sperm quality was determined before and after the filtering process. Sperm morphology and motility were assessed using the computer program SCA 2002 production, and sperm vitality was evaluated by fluorescence multistaining. ORT and HRT tests were used to determine the osmotic resistance of spermatozoa, and metabolic performance was assessed by measuring l-lactate production. Results indicate that the filtration process rendered increased proportions of mature spermatozoa and of viable spermatozoa with an intact acrosome, nucleus and mitochondrial sheath. Sperm filtration led to decreased percentages of spermatozoa with proximal and distal droplets and of agglutinated spermatozoa, along with slightly diminished ORT values. HRT scores and L-lactate production were unaffected. Our findings indicate that filtering through a Sephadex column improves the sperm morphology and vitality of seminal doses obtained from subfertile boars, but produces no functional changes in the spermatozoa. All four column types yielded similar results.

Capacitation, acrosome function and chromatin structure in stallion sperm

In general, fertility in breeding stallions is lower and more variable than in the other farm animal species, primarily because selection is based on pedigree, looks and/or athletic performance, with little consideration of fertility or fertility potential. Moreover, because the average stallion breeds only a limited number of mares per year and in-field fertility is influenced significantly by non-stallion factors such as management and mare fertility, meaningful fertility data are hard to come-by. Unfortunately, generating usable figures would involve impractically high costs, time and numbers of mares. Instead, a breeding soundness examination (BSE), based on assessments of sperm number, motility and morphological normality and of mating ability, is often carried out with the ostensible aim of identifying animals with the "potential for good fertility". In fact, the BSE generally succeeds only in ruling out those stallions with a very clear reason for sub-fertility, and still fails to identify some seriously sub-fertile animals. Thus, the routine BSE has very limited use as a predictor of subsequent fertility. This paper reviews assays developed for identifying capacitated, acrosome-reacted and DNA-damaged sperm, and assesses their utility for improving our ability to predict a stallion's fertility prior to the onset of his breeding career.

Application of techniques for sperm selection in fresh and frozen-thawed stallion semen

The objective of this research was to improve the techniques in processing chilled and frozen-thawed horse semen. In a preliminary experiment (Exp. I), different techniques for sperm selection and preparation [Swim-up, Glass wool (GW) filtration, Glass wool Sephadex (GWS) filtration; Percoll] were tested for their suitability for equine spermatozoa and results were compared with the routine procedure by dilution (Exp. I). In the main experiment (Exp. II), two sperm preparation techniques (GWS, Leucosorb) refering to the results of Exp. I and a previous study of our group (Pferdcheilkunde 1996 12, 773) were selected for processing complete ejaculates either for cooled-storage or cryopreservation. In a third experiment (Exp. III), pregnancy rates from inseminations with semen processed according to the techniques tested in Exp. II were compared with those obtained with semen processed according to routine procedures. In Exp. I (six stallions, six ejaculates/stallion), between 48 and 92% of spermatozoa were lost following the different sperm selection procedures (p < 0.05). Preparation of sperm increased percentage of progressively motile spermatozoa (pms) [Swim-up, GW, GWS vs dilution, Percoll (p < 0.05)] and decreased percentage of sperm head abnormalities [Swim-up, GW, GWS vs dilution, Percoll (p < 0.05)] probably by not improving the quality of individual cells, but by elimination of spermatozoa of inferior quality. In Exp. II (eight stallions, three ejaculates/stallion) Leucosorb and GWS procedures allowed the filtration of large volumes (extended ejaculates) for routine laboratory practice. GWS and Leucosorb filtration resulted in increased motility, membrane integrity and sperm viability after storage of spermatozoa until 48 h at +5 degrees C when compared with control (diluted) and centrifuged semen (p < 0.05). Significantly more spermatozoa were recovered after centrifugation (87.8 +/- 15.4%) compared with GWS (63.5 +/- 18.6%) and Leucosorb filtration (53.6 +/- 22.3%). GWS or Leucosorb procedure resulted in successful cryopreservation of stallion semen without centrifugation for removal of seminal plasma. The per cycle conception rate of inseminated mares using 200 x 106 pms transferred within 8 h after collection of semen was not affected by GWS filtration or Leucosorb separation when compared with centrifugation (n.s.; Exp. III). In conclusion, GWS and Leucosorb filtration results in the improvement of semen quality and should be considered as a method for stallion semen processing. Additional studies are needed for the evaluation of potentially higher fertilizing ability of stallion spermatozoa separated by techniques for sperm selection.

Effect of column filtration upon the quality parameters of fresh dog semen

We filtered dog semen through various resin columns to obtain a quick, simple system for improving semen quality. Fresh ejaculates were filtered through columns with either glasswool or a chemically-inert polypropylene network disc. The columns were filled with Sephadex G-15 (nonionic resin), Sephadex A-50 (anionic-exchange resin), Sephadex C-50 (cationic-exchange resin) or a combination of Sephadex A-50 and C-50. Filtration through glasswool improved semen quality, with a significant (P < 0.001) increase in the percentage of viability and decrease in the percentage of altered acrosomes (P < 0.001) and total abnormalities (P < 0.001). Total motility was not modified, but curvilinear velocity or linearity of the movement were improved using the glasswool bed. The effect of the glasswool was so intense that it masked the effects of the filtration resins. Substitution of glasswool by polypropylene discs resulted in an unmasking of the effects of the resins, although the polypropylene exerted slight effects on semen. Elution of the spermatozoa through Sephadex G-15 or Sephadex C-50 resulted in a decrease of altered acrosomes. However, filtration through Sephadex A-50 increased viability and decreased the percentage of altered acrosomes and total abnormalities. Combined filtration through Sephadex A-50 and C-50 yielded the combined results observed with the resins individually. Ultrastructural imaging of the interaction between spermatozoa and the beds and resins showed that the cells were loosely deposited upon the glasswool fibers and the Sephadex G-15 particles, whereas close interaction was observed between spermatozoa and Sephadex A-50 and C-50 particles. The whole of the sperm cell bound to C-50 particles, whereas spermatozoa were specifically bonded to A-50 particles in the apical region of the head and in segments of the tail, which were periodically distributed. The data suggest that filtration through glasswool or an anionic resin-exchange can significantly improve dog semen quality.