The role of bicarbonate in the modulation of capacitation, spontaneous acrosome reaction and motility of equine fresh and frozen spermatozoa.

In this study, we defined the composition of the culture medium that yield a significant percentage of alive and functional equine spermatozoa during enough time before artificial insemination. The effects of sodium bicarbonate were analyzed in fresh and frozen semen in respect to sperm viability, capacitation, spontaneous acrosome reaction and several kinetic parameters such as total motility, progressive motility, VCL, VSL, ALH, BCF, LIN. Moreover, employing Bayk-6844 and Nifedipine, the involvement of L-type voltage-gated calcium channels in the modulation of intracellular calcium concentrations was investigated. Results evidenced an immediate effect of sodium bicarbonate in reducing fresh sperm viability and in increasing capacitation and spontaneous acrosome reaction of fresh and frozen spermatozoa. Furthermore, it affected total and progressive motility of fresh and frozen semen. Because of the sudden effects of the compound, we think that a buffer lacking sodium bicarbonate is more suitable to preserve the viability and the functional state of equine spermatozoa required to undergo at the right time those modifications necessary for fertilization. We also demonstrated that intracellular calcium modifications induced by Bayk-8644 and Nifedipine are not involved in signals related to vitality, capacitation, spontaneous acrosome reaction and motility.

Clinical benefit for cryopreservation of single human spermatozoa for ICSI: A systematic review and meta-analysis.

BACKGROUND: Systematic reviews have focused on sperm recovery and post-thaw parameters after cryopreservation, but there is no information on the associated clinical outcomes. In recent years, an increasing number of studies have reported cryopreservation of a single sperm due to the importance of fertility preservation. OBJECTIVES: To assess whether the cryopreservation of single human spermatozoa improves clinical outcomes in patients with azoospermia or severe oligospermia. MATERIALS AND METHODS: We conducted an extensive literature search using the following databases: CENTRAL, CNKI, Cochrane Systematic Reviews, EMBASE, MEDLINE, PUBMED, and Web of Science for relevant studies published through December 31, 2019. We calculated the pooled proportions of cryopreservation of a single human spermatozoon to assess the recovery, survival, fertilization, pregnancy, miscarriage, and delivery rates. Subgroup analyses were performed for the following covariates, (a) different carriers, (b) year of publication, and (c) source of sperm. RESULTS: We included 25 studies, which included 13 carriers. The pooled proportion of recovery rate of spermatozoa cryopreserved was 92% (95% CI, 87%-96%), and the survival, fertilization, pregnancy, miscarriage, and delivery rates were 76% (95% CI, 69%-83%), 63% (95% CI, 58%-67%), 57% (95% CI, 39%-74%), 12% (95% CI, 0%-33%), and 40% (95% CI, 12%-71%), respectively. Based on the subgroup analysis, the recovery and survival rates of frozen spermatozoa in a subgroup of different carriers were statistically significant. In the past decade, frozen single human spermatozoon technology has improved the recovery rates of frozen-thawed spermatozoa. However, the differences in clinical outcomes of frozen spermatozoa in subgroups of different sources of sperm were not statistically significant. DISCUSSION AND CONCLUSION: The techniques for single human spermatozoa are feasible and efficient and may benefit patients with severe oligospermia or azoospermia.