Equine spermatozoa stored in the epididymis for up to 96h at 4°C can be successfully cryopreserved and maintain their fertilization capacity.

After injury or death of a valuable male, recovery of epididymal spermatozoa may be the last chance to ensure preservation of its genetic material. The objective of this research was to study the effect of sperm storage, at 4°C up to 96h, in the epididymides obtained from castrated horses and its effect on different functional sperm parameters. Aims were to study the effect of (1) sperm storage on viability and chromatin condensation; (2) pre-incubation of recovered epididymal sperm in the freezing extender, prior cryopreservation, on viability and chromatin condensation; and (3) freezing-thawing on viability, chromatin condensation, ROS generation, protein tyrosine phosphorylation and heterologous fertilization rate (ICSI and IVF using bovine oocytes) of sperm recovered from the epididymis up to 96h post castration. The average volume (720±159µL) and the concentration (6.5±0.4×10(9) spermatozoa/mL) of sperm recovered from the epididymis were not affected by storage. Sperm viability after refrigeration at 4°C for up to72h was similar (P<0.01). The effect of sperm dilution in the freezing media showed similar values up to 48h, while viability was preserved up to 72h (P<0.01). Cryopreserved spermatozoa show similar viability between different storage times. Chromatin condensation was not affected by storage time; however, incubation for 30min in freezing medium and freezing-thawing process induced an increase in the chromatin decondensation. ROS generation was not affected by storage up to 96h. Epididymal storage did not affect sperm protein tyrosine phosphorylation patterns; although the pattern of phosphorylation changed to strong staining of the equatorial segment when the sperm where capacitated in sperm-TALP. Finally, successful and similar pronuclear formation (analyzed by ICSI) and in vitro penetration (evaluated with bovine zone free oocyte) was observed using cryopreserved sperm obtained from prolong epididymal storage at 4°C. In conclusion, cryopreservation of epididymal stallion sperm stored for up to 72h in the epididymis at 4°C, maintain both viability and ability to fertilize in vitro.

Effects of centrifugation through three different discontinuous Percoll gradients on boar sperm function.

In this study, different combinations of 2-step, discontinuous gradient centrifugation were used, consisting of three different combinations of isotonic Percoll (45/60, 60/75 and 45/90%) that allowed us to select different sperm subpopulations from fertile and normozoospermic boars. Our objective in this study is to evaluate the effects of centrifugation through three different discontinuous Percoll gradients on sperm function parameters (motility, viability, morphology, acrosome status, chromatin condensation, DNA fragmentation, ROS generation, tyrosine phosphorylation and intracellular calcium concentration) and the sperm penetrating capacity in an IVF system. All the Percoll treatments evaluated increased the percentage of spermatozoa with normal morphology, the proportion of un-damaged DNA, normal chromatin condensation, motion parameters measured by CASA and the percentage of capacitated spermatozoa with tyrosine phosphorylated proteins compared to control group. Finally, the in vitro oocyte penetrating capacity of boar spermatozoa was significantly affected by Percoll centrifugation. All the Percoll treatments increased the penetration rates and mean number of sperm per penetrated oocyte. Despite the efficiency of all three of the sperm treatments tested in selecting spermatozoa with improved sperm parameters and capacity to penetrate oocytes in vitro, the optimum performance of this system was demonstrated after preselecting spermatozoa by centrifugation on a discontinuous 45/90 Percoll gradient. The P45/90 treatment leads to obtain a higher percentage of spermatozoa which develop properly the capacitation process as it was shown measuring tyrosine phosphorylation and intracellular calcium concentration.