From co-culture to defined medium: state of the art and practical considerations.

Embryo culture in domestic and laboratory animals, and also in humans has developed significantly during recent decades. It is the aim of this review to consider the historical development of different culture systems, with a special emphasis on the recent tendency to remove somatic cells and undefined proteins from the culture systems for sanitary reasons. In addition to the sanitary aspect, developing more standardized culture conditions is useful for diminishing variation between laboratories and for studying the needs of the embryo.