Soriano-Úbeda Cristina, Romero-Aguirregomezcorta Jon, Matás Carmen, Visconti Pablo E, García-Vázquez Francisco A
1Department of Physiology, Faculty of Veterinary Science, International Excellence Campus for Higher Education and Research "Campus Mare Nostrum", University of Murcia, 30100 Murcia, Spain.
2Institute for Biomedical Research of Murcia (IMIB-Arrixaca), Murcia, Spain.
J Anim Sci Biotechnol. 2019 Mar 11;10:19. doi: 10.1186/s40104-019-0324-y. eCollection 2019.
The in vivo concentration of bicarbonate (HCO ), one of the essential sperm capacitating effectors, varies greatly in the different environments sperm go through from cauda epididymis to the fertilisation site. On the contrary, porcine in vitro sperm capacitation and fertilisation media usually contains a standard concentration of 25 mmol/L, and one of the main problems presented is the unacceptable high incidence of polyspermy. This work hypothesised that by modifying the HCO concentration of the medium, the output of in vitro sperm capacitation and fertilisation could be increased.
Once exposed to the capacitation medium, the intracellular pH (pH) of spermatozoa increased immediately even at low concentrations of HCO , but only extracellular concentrations of and above 15 mmol/L increased the substrates protein kinase A phosphorylation (pPKAs). Although with a significant delay, 15 mmol/L of HCO stimulated sperm linear motility and increased other late events in capacitation such as tyrosine phosphorylation (Tyr-P) to levels similar to those obtained with 25 mmol/L. This information allowed the establishment of a new in vitro fertilisation (IVF) system based on the optimization of HCO concentration to 15 mmol/L, which led to a 25.3% increment of the viable zygotes (8.6% in the standard system vs. 33.9%).
Optimising HCO concentrations allows for establishing an IVF method that significantly reduced porcine polyspermy and increased the production of viable zygotes. A concentration of 15 mmol/L of HCO in the medium is sufficient to trigger the in vitro sperm capacitation and increase the fertilisation efficiency in porcine.
碳酸氢根（HCO ）是精子获能的关键效应因子之一，其在精子从附睾尾到受精部位所经历的不同环境中的体内浓度差异很大。相反，猪体外精子获能和受精培养基通常含有25 mmol/L的标准浓度，而出现的主要问题之一是多精入卵发生率高得令人难以接受。这项研究假设，通过改变培养基中HCO 的浓度，可以提高体外精子获能和受精的成功率。
一旦暴露于获能培养基中，即使在低浓度的HCO 条件下，精子的细胞内pH值也会立即升高，但只有细胞外浓度达到及高于15 mmol/L时，才能增加蛋白激酶A磷酸化（pPKAs）底物。虽然有显著延迟，但15 mmol/L的HCO 刺激精子直线运动，并使获能过程中的其他晚期事件（如酪氨酸磷酸化（Tyr-P））增加到与25 mmol/L时相似的水平。这些信息使得基于将HCO 浓度优化至15 mmol/L建立了一种新的体外受精（IVF）系统，这导致活受精卵增加了25.3%（标准系统中为8.6%，而新系统中为33.9%）。
优化HCO 浓度可以建立一种体外受精方法，显著降低猪的多精入卵率，并增加活受精卵的产量。培养基中15 mmol/L的HCO 浓度足以触发猪精子的体外获能并提高受精效率。
