Seidel George E
Animal Reproduction and Biotechnology Laboratory, ARBL Building, Foothills Campus, Colorado State University, Fort Collins, CO 80523-1683, USA.
Theriogenology. 2006 Jan 7;65(1):228-35. doi: 10.1016/j.theriogenology.2005.09.025. Epub 2005 Nov 2.
Numerous studies indicate that in vitro-produced bovine embryos do not survive cryopreservation as well as those produced in vivo. Furthermore, embryos cultured in vitro in the absence of blood serum are more cryotolerant than embryos cultured in media containing serum. Although in vivo-produced embryos are more cryotolerant, there appear to be breed differences. Most if not all of these observations are correlated with cytoplasmic lipid content of embryos; more and larger lipid droplets are associated with reduced cryotolerance. This review concerns strategies for modifying oocytes and embryos to increase cryosurvival. Reduction of cytoplasmic lipid content of embryos with phenazine ethosulfate (PES), a compound that oxidizes NADPH, even improved cryotolerance of bovine embryos cultured in the absence of serum. Whether cytoplasmic lipid content per se or associated changes in lipid composition of cell membranes are responsible for differences in cryotolerance is unknown. Increasing cholesterol content of membranes of sperm and oocytes via cholesterol-loaded cyclodextrin also appears to improve cryotolerance. While lipids have been emphasized and appear to be important, non-lipid aspects of cell composition also likely affect cryotolerance, and might be modified to improve cryotolerance. Additional research on mechanisms of variation in cryotolerance will be applicable to circumvent cryo-intolerance attributable to variation associated with the individual animal, breed, species, cell type, and factors such as nutrition and season of the year.
大量研究表明，体外生产的牛胚胎在冷冻保存后的存活率不如体内生产的胚胎。此外，在无血清条件下体外培养的胚胎比在含血清培养基中培养的胚胎更耐冷冻。尽管体内生产的胚胎更耐冷冻，但似乎存在品种差异。这些观察结果大多（如果不是全部的话）与胚胎的细胞质脂质含量相关；更多、更大的脂滴与冷冻耐受性降低有关。本综述关注修饰卵母细胞和胚胎以提高冷冻存活率的策略。用吩嗪硫酸乙酯（PES）（一种氧化NADPH的化合物）降低胚胎的细胞质脂质含量，甚至提高了无血清培养的牛胚胎的冷冻耐受性。尚不清楚是细胞质脂质含量本身还是细胞膜脂质组成的相关变化导致了冷冻耐受性的差异。通过负载胆固醇的环糊精增加精子和卵母细胞膜的胆固醇含量似乎也能提高冷冻耐受性。虽然脂质一直受到重视且似乎很重要，但细胞组成的非脂质方面也可能影响冷冻耐受性，并且可能通过修饰来提高冷冻耐受性。关于冷冻耐受性变化机制的更多研究将适用于规避因个体动物、品种、物种、细胞类型以及营养和季节等因素相关的差异而导致的冷冻不耐受。
