Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.
Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada.
J Cell Physiol. 2021 Oct;236(10):7117-7133. doi: 10.1002/jcp.30352. Epub 2021 Feb 26.
The period beginning with the signal for ovulation, when a fully-grown oocyte progresses through meiosis to become a mature egg that is fertilized and develops as a preimplantation embryo, is crucial for healthy development. The early preimplantation embryo is unusually sensitive to cell volume perturbations, with even moderate decreases in volume or dysregulation of volume-regulatory mechanisms resulting in developmental arrest. To prevent this, early embryos possess mechanisms of cell volume control that are apparently unique to them. These rely on the accumulation of glycine and betaine (N, N, N-trimethylglycine) as organic osmolytes-compounds that can provide intracellular osmotic support without the deleterious effects of inorganic ions. Preimplantation embryos also have the same mechanisms as somatic cells that mediate rapid responses to deviations in cell volume, which rely on inorganic ion transport. Both the unique, embryo-specific mechanisms that use glycine and betaine and the inorganic ion-dependent mechanisms undergo major changes during meiotic maturation and preimplantation development. The most profound changes occur immediately after ovulation is triggered. Before this, oocytes cannot regulate their volume, since they are strongly attached to their rigid extracellular matrix shell, the zona pellucida. After ovulation is triggered, the oocyte detaches from the zona pellucida and first becomes capable of independent volume regulation. A complex set of developmental changes in each cell volume-regulatory mechanism continues through egg maturation and preimplantation development. The unique cell volume-regulatory mechanisms in eggs and preimplantation embryos and the developmental changes they undergo appear critical for normal healthy embryo development.
从排卵信号开始的时期，一个成熟的卵母细胞通过减数分裂发育为一个成熟的卵子，这个卵子受精并发育为一个着床前胚胎，这对健康发育至关重要。早期着床前胚胎对细胞体积扰动异常敏感，即使体积适度减少或体积调节机制失调也会导致发育停滞。为了防止这种情况发生，早期胚胎具有显然是它们特有的细胞体积控制机制。这些机制依赖于甘氨酸和甜菜碱（N，N，N-三甲基甘氨酸）的积累作为有机渗透物-可以提供细胞内渗透支持而不会产生无机离子的有害影响的化合物。着床前胚胎还具有与体细胞相同的介导细胞体积偏差快速反应的机制，这依赖于无机离子运输。在减数分裂成熟和着床前发育过程中，使用甘氨酸和甜菜碱的独特胚胎特异性机制和依赖无机离子的机制都发生了重大变化。最深刻的变化发生在排卵触发之后。在此之前，卵母细胞不能调节它们的体积，因为它们强烈附着在其刚性细胞外基质壳，透明带。排卵触发后，卵母细胞从透明带中分离出来，并首先能够独立地调节体积。在卵母细胞成熟和着床前发育过程中，每种细胞体积调节机制都经历了一系列复杂的发育变化。卵和着床前胚胎中的独特细胞体积调节机制及其经历的发育变化似乎对正常健康胚胎发育至关重要。
