Culture of the Mouse Preimplantation Embryo

The first culture media designed specifically to support development of the preimplantation mouse embryo were formulated over 50 years ago and were based on balanced salt solutions, containing the carbohydrates pyruvate, lactate, and glucose as the sole energy sources. Such media used a bicarbonate-carbon dioxide buffer system to maintain the desired pH, and were typically supplemented with serum albumin, but lacked free amino acids. In contrast to the complexity of a tissue culture medium, these original formulations of mouse embryo culture media were very simplistic. Over the intervening decades, as our understanding of the physiology and metabolism of the preimplantation embryo increased, together with a greater understanding of the environment within the female reproductive tract, culture media to support mouse embryo development in vitro have become more physiological and consequently more complex. A main addition to such media has been an array of amino acids. Although the media of today contain more components than their predecessors, their preparation remains relatively easy to accomplish, made feasible through the use of stock solutions, which also readily facilitates any changes to formulations to be made, an essential prerequisite for experimentation. As well as changes in media formulations, there have been exciting developments in incubator technology and design, such as the inclusion of time-lapse capability, redefining our ability to both culture and monitor embryo development in vitro.