Effect of cryopreservation and oviductal cell conditioned media on Ca2+ flux of equine spermatozoa.

The study is primarily focused on examining the effects of cryopreservation and a specific type of conditioning medium on the movement of calcium ions, referred to as Ca2+ flux, in horse sperm. The findings suggest that cryopreservation significantly impacts calcium control in sperm, which may have implications for insemination timing to increase pregnancy rates with cryopreserved semen.

Objective of the Research

• The main objective of the study was to analyze the influence of cryopreservation – a process of preserving cells at a very low temperature, and oviductal cell conditioned medium (OCM) on the dynamics of calcium movement in equine (horse) sperm cells. The research also aimed to establish the nature of calcium movement in fresh equine spermatozoa.

Methodology and Findings

• The researchers evaluated the ability of both fresh and cryopreserved stallion spermatozoa to regulate calcium concentration over time in a calcium-free medium (PBS).
• The results showed that the intracellular, or within cell, calcium concentrations were significantly higher in cryopreserved spermatozoa compared to fresh spermatozoa.
• However, interestingly, extracellular, or outside cell, calcium concentrations were higher in fresh spermatozoa than the cryopreserved ones.
• This indicates that cryopreservation influences calcium handling in stallion spermatozoa.

Exploration of Oviductal Cell Conditioned Media’s Effect

• To explore the impact of oviductal cell conditioned media (OCM) on spermatozoa’s calcium dynamics, epithelial cells from non-pregnant horses were grown in a specific type of medium – TCM-199.
• The OCM was collected after a two-day incubation period and the spermatozoa were exposed to this medium or the original culture medium (TCM-199) for an hour before further analysis.
• The analysis found that the cryopreserved spermatozoa had an increased intracellular calcium concentration and a lower extracellular calcium concentration than fresh spermatozoa and transitioned calcium at a slower rate.
• However, the incubation in OCM increased the relative intracellular calcium concentration in fresh spermatozoa but not in cryopreserved ones when compared with those incubated in the original TCM-199 medium.

Conclusions of the Research

• According to the research findings, the cryopreservation process significantly impacts calcium control in horse sperm, regardless of other factors.
• This could explain the higher intracellular calcium concentrations in cryopreserved horse spermatozoa and why mares need to be inseminated very close to ovulation to optimize pregnancy rates when using cryopreserved semen.
• In summary, the OCM and cryopreservation processes have demonstrated pronounced impacts on calcium flux in equine spermatozoa that may influence fertilization practices.