Suarez Susan S
Department of Biomedical Sciences, T5-002B Veterinary Research Tower, Cornell University Ithaca, NY 14853, USA.
Hum Reprod Update. 2008 Nov-Dec;14(6):647-57. doi: 10.1093/humupd/dmn029. Epub 2008 Jul 24.
Sperm hyperactivation is critical to fertilization, because it is required for penetration of the zona pellucida. Hyperactivation may also facilitate release of sperm from the oviductal storage reservoir and may propel sperm through mucus in the oviductal lumen and the matrix of the cumulus oophorus. Hyperactivation is characterized by high amplitude, asymmetrical flagellar bending.
This is a review of the original literature on the mechanisms that regulate hyperactivation, including physiological factors and signaling pathways.
Computer-assisted semen analysis systems can be used to identify hyperactivated sperm by setting minimum thresholds for curvilinear velocity (VSL) and lateral head movement and a maximum threshold for path linearity. Hyperactivation is triggered by a rise in flagellar Ca(2+) resulting from influx primarily through plasma membrane CatSper channels and possibly also by release of Ca(2+) from a store in the redundant nuclear envelope. It requires increased pH and ATP production. The physiological signals that trigger the rise in Ca(2+) remain elusive, but there is evidence that the increased Ca(2+) acts through a calmodulin/calmodulin kinase pathway. Hyperactivation is considered part of the capacitation process; however, the regulatory pathway that triggers hyperactivation can operate independently from that which prepares sperm to undergo the acrosome reaction. Hyperactivation may be modulated by chemotactic signals to turn sperm toward the oocyte.
Little is known about exactly what triggers hyperactivation in human sperm. This information could enable clinicians to develop reliable fertility assays to assess normal hyperactivation in human sperm samples.
精子超激活对于受精至关重要，因为穿透透明带需要精子超激活。超激活还可能有助于精子从输卵管储存库中释放出来，并推动精子穿过输卵管管腔中的黏液以及卵丘基质。精子超激活的特征是鞭毛弯曲幅度大且不对称。
这是一篇关于调节精子超激活机制的原始文献综述，包括生理因素和信号通路。
计算机辅助精液分析系统可通过设置曲线速度（VSL）和头部横向运动的最小阈值以及路径线性的最大阈值来识别超激活的精子。超激活是由鞭毛Ca²⁺浓度升高引发的，主要是通过质膜CatSper通道内流，也可能是通过多余核膜中的储存库释放Ca²⁺。这需要pH值升高和ATP生成增加。触发Ca²⁺浓度升高的生理信号仍不清楚，但有证据表明增加的Ca²⁺通过钙调蛋白/钙调蛋白激酶途径起作用。精子超激活被认为是获能过程的一部分；然而，触发超激活的调节途径可以独立于使精子准备发生顶体反应的途径运行。超激活可能受趋化信号调节，使精子转向卵母细胞。
关于究竟是什么触发人类精子超激活，人们知之甚少。这些信息可以使临床医生开发可靠的生育力检测方法，以评估人类精子样本中的正常超激活情况。
