Laboratory of Animal Reproduction, Department of Biological Sciences, Biomaterials Research Cluster, Bernal Institute, Faculty of Science and Engineering, University of Limerick, Limerick, V94 T9PX, Ireland.
Biomedical Center, Faculty of Medicine in Pilsen, Charles University, Pilsen, 323 00, Czech Republic.
Theriogenology. 2023 Jan 1;195:115-121. doi: 10.1016/j.theriogenology.2022.10.021. Epub 2022 Oct 21.
Bulls used in artificial insemination programmes worldwide undergo quality control checks, which are typically based on the evaluation of sperm motility and morphology. Despite this, some bulls can have lower than expected field fertility and the reasons for this remain to be elucidated. Here we hypothesised that sperm from bulls of varying fertility will differ in their ability to undergo capacitation-related events including an increase in membrane fluidity, protein tyrosine phosphorylation, hyperactivation and the acrosome reaction. Firstly, we used frozen-thawed semen from 10 high-fertility (HF) and 10 low-fertility (LF) bulls, and subjected them to in vitro capacitating conditions, following which sperm viability, membrane fluidity, acrosome integrity and protein tyrosine phosphorylation were assessed using flow cytometry. We then assessed the ability of sperm to undergo hyperactivation (induced using caffeine) utilising computer-assisted sperm analysis, and the acrosome reaction (induced using calcium ionophore) using flow cytometry. When sperm were incubated in capacitating conditions, a higher percentage of viable sperm from HF bulls exhibited high membrane fluidity when compared to LF bulls (8.8 ± 0.8% and 5.8 ± 1.2%, respectively; mean ± standard error; P < 0.05). There was no difference between fertility groups in the percentage of acrosome-reacted sperm following the incubation in in vitro capacitating conditions or following the induction of the acrosome reaction using calcium ionophore. However, more sperm from HF bulls became hyperactive in response to caffeine stimulation than sperm from LF bulls (21.6 ± 2.5% versus 14.1 ± 2.4%, respectively; mean ± standard error; P < 0.05). Taken together, sperm from LF bulls had an impaired ability to undergo membrane remodulation and to hyperactivate when induced in vitro. These are key events in the journey of sperm along the female reproductive tract and in the interaction with the oocyte and thus could explain the lower field fertility exhibited by some bulls.
全世界用于人工授精计划的公牛都要经过质量控制检查，这些检查通常基于对精子活力和形态的评估。尽管如此，一些公牛的田间受胎率仍低于预期，其原因仍有待阐明。在这里，我们假设不同受胎率的公牛的精子在经历与获能相关的事件的能力上会有所不同，这些事件包括膜流动性增加、蛋白酪氨酸磷酸化、超激活和顶体反应。首先，我们使用来自 10 头高受胎率（HF）公牛和 10 头低受胎率（LF）公牛的冷冻解冻精液，将其置于体外获能条件下，然后使用流式细胞术评估精子活力、膜流动性、顶体完整性和蛋白酪氨酸磷酸化。然后，我们使用计算机辅助精子分析评估精子超激活（使用咖啡因诱导）的能力，以及使用流式细胞术评估顶体反应（使用钙离子载体诱导）的能力。当精子在获能条件下孵育时，与 LF 公牛相比，HF 公牛的活精子中表现出高膜流动性的比例更高（分别为 8.8 ± 0.8%和 5.8 ± 1.2%；平均值 ± 标准误差；P < 0.05）。在体外获能条件下孵育或使用钙离子载体诱导顶体反应后，两组间顶体反应的精子比例没有差异。然而，与 LF 公牛的精子相比，HF 公牛的精子对咖啡因刺激的超激活反应更多（分别为 21.6 ± 2.5%和 14.1 ± 2.4%；平均值 ± 标准误差；P < 0.05）。综上所述，LF 公牛的精子在体外诱导时，其经历膜重塑和超激活的能力受损。这些是精子在雌性生殖道中行进以及与卵子相互作用的关键事件，因此可以解释一些公牛的田间受胎率较低的原因。
