Influence of genetic background and media components on the development of mouse embryos in vitro

One-cell embryos from some inbred and random-bred mice, but not those derived from certain F1 hybrids, suffer from a block during in vitro development known as the two-cell block. This two-cell block can be overcome by removing glucose or inorganic phosphate from the culture system or by altering the ratio of other medium components such as sodium, potassium, or bicarbonate. This issue is made more complex by the fact that the rate of development is different for each strain of mouse and this rate of development is invariably slowed under in vitro culture conditions. This study investigated the role of glucose and inorganic phosphate, individually or in combination, in relation to the two-cell block, and rate of development in vitro of two random-bred strains (CF-1 and CD-1) and an F2 hybrid derived from a nonblocking F1 hybrid cross (C57Bl/6NCr x C3H/HeNCr). Results were compared with in vivo data for each strain, and between media. There was a significant difference in the rate of preimplantation development in vivo of the three strains chosen, which was mirrored in vitro, regardless of the medium. The two random-bred strains suffered from a glucose-related two-cell block which was primarily mediated by inorganic phosphate. Inorganic phosphate was detrimental to embryo development regardless of strain or the presence of glucose. Although glucose, in the absence of inorganic phosphate, resulted in some blocking in development in the inbred strains initially, its presence in media was associated with increased rates of development at later stages in embryos that did not block. Glucose, but not inorganic phosphate, was beneficial but not essential to the development of the F2 embryos. The results of this study demonstrated that mouse embryos from different strains have differential rates of development in vivo and in vitro, and different sensitivities to glucose and inorganic phosphate. The two-cell block was primarily induced in the combined presence of glucose and inorganic phosphate. Glucose was beneficial in the absence of inorganic phosphate, and inorganic phosphate was detrimental to the rate of in vitro development.