Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, Kumamoto, Japan.
Laboratory of Integrative Biological Science, Institute for Life and Medical Sciences, Kyoto University, Kyoto, Japan.
Biol Reprod. 2023 Apr 11;108(4):671-681. doi: 10.1093/biolre/ioad013.
Capacitation is an important event in the completion of fertilization by mammalian sperm. Cholesterol efflux is a trigger of capacitation. In general, cholesterol acceptors of albumin and β-cyclodextrins are used to induce capacitation during in vitro fertilization. Previously, we reported that methyl-β-cyclodextrin (MBCD), which is composed of seven glucoses, had a higher ability to induce capacitation than bovine serum albumin (BSA) in frozen-thawed mouse sperm. Comparison of albumin and cyclodextrins is helpful for understanding the mechanism of capacitation. In this study, we examined the effects of albumin, MBCD, and a different type of cyclodextrin, dimethyl-α-cyclodextrin (DMACD), which is composed of six glucoses, on several events of sperm capacitation. We showed that DMACD induced sperm capacitation and promoted fertilization ability. The time required to increase the fertilization rate differed among BSA, MBCD, and DMACD. BSA and MBCD enhanced cholesterol and phospholipid efflux, whereas DMACD enhanced only phospholipid efflux. BSA, MBCD, and DMACD increased sperm membrane fluidity, rearrangement of the lipid raft, and the acrosome reaction. These findings suggest that phospholipid efflux is a novel trigger of capacitation. Increasing the choice of sperm capacitation inducers may be useful for improving in vitro fertilization (IVF) techniques not only in mice, but also in various species in which it has been difficult to produce embryos by IVF.
获能是哺乳动物精子完成受精的重要事件。胆固醇外排是获能的触发因素。一般来说，白蛋白和β-环糊精的胆固醇受体被用于在体外受精过程中诱导获能。先前，我们报道了由七个葡萄糖组成的甲基-β-环糊精（MBCD）在冷冻解冻的小鼠精子中比牛血清白蛋白（BSA）具有更高的诱导获能能力。白蛋白和环糊精的比较有助于理解获能的机制。在这项研究中，我们研究了白蛋白、MBCD 和另一种环糊精二甲基-α-环糊精（DMACD）（由六个葡萄糖组成）对精子获能的几个事件的影响。我们表明 DMACD 诱导了精子获能并提高了受精能力。增加受精率所需的时间因 BSA、MBCD 和 DMACD 而异。BSA 和 MBCD 增强了胆固醇和磷脂外排，而 DMACD 仅增强了磷脂外排。BSA、MBCD 和 DMACD 增加了精子膜流动性、脂筏重排和顶体反应。这些发现表明，磷脂外排是获能的新触发因素。增加精子获能诱导剂的选择可能有助于提高体外受精（IVF）技术，不仅在小鼠中，而且在通过 IVF 难以产生胚胎的各种物种中。
