Asymptote Ltd., St. John's Innovation Centre, Cambridge, UK.
Cryobiology. 2012 Apr;64(2):71-80. doi: 10.1016/j.cryobiol.2011.12.002. Epub 2011 Dec 14.
The cellular damage that spermatozoa encounter at rapid rates of cooling has often been attributed to the formation of intracellular ice although no convincing evidence of intracellular ice formation has ever been obtained. We demonstrate that the high intracellular protein content together with the osmotic shrinkage associated with extracellular ice formation leads to intracellular vitrification of spermatozoa during cooling. At rapid rates of cooling the cell damage to spermatozoa is a result of an osmotic imbalance encountered during thawing, not intracellular ice formation. The osmotic imbalance occurs at rapid cooling rates due to a diffusion limited ice crystallisation in the extracellular fluid, i.e. the amount of ice forming during the cooling is less than expected from the equilibrium phase diagram. This explanation allows insights into other aspects of the cryobiology of spermatozoa and it is anticipated that this understanding will lead to specific improved methods of conventional cryopreservation for mammalian spermatozoa. It is also likely that this model will be relevant to the development of novel technologies for sperm preservation including vitrification and freeze drying.
精子在快速冷却过程中所遭受的细胞损伤通常归因于细胞内冰的形成，尽管从未获得过细胞内冰形成的令人信服的证据。我们证明，高细胞内蛋白质含量以及与细胞外冰形成相关的渗透压收缩导致精子在冷却过程中发生细胞内玻璃化。在快速冷却速率下，精子的细胞损伤是解冻过程中渗透压失衡的结果，而不是细胞内冰的形成。由于细胞外液中冰的扩散受限结晶，在快速冷却速率下会发生渗透压失衡，即在冷却过程中形成的冰量低于平衡相图所预期的量。这种解释可以深入了解精子冷冻生物学的其他方面，预计这种理解将导致针对哺乳动物精子的传统冷冻保存的具体改进方法。该模型也可能与精子保存的新技术的发展相关，包括玻璃化和冷冻干燥。
