Development of mouse embryos grown in human cord serum (HCS) in vitro

Mouse embryos of the blastocyst stage (day 0 of culture) were cultured in human cord serum (HCS) for 8 days. Until day 7 in vitro, the embryos had developed to the 4-5 somite stage. Apart from the occurrence of some cell necroses in the embryonic ectoderm and vacuoles in the yolk sac entoderm and to a lesser degree even in the embryonic entoderm, the in vitro development of the embryos was indistinguishable from the in vivo development. However, between days 7 and 8 in vitro the embryonic development was heavily disturbed. The most pronounced disturbances were visible in the central nervous system (CNS) of the embryos. A great number of the neuroepithelial cells of the entire CNS were necrotic. Even mesodermal structures, mainly the axial structures in the posterior part of the embryos, were affected, leading to disorganization of somites and notochord in this region. Since in the presence of rat serum embryos develop normally between days 7 and 8 in vitro (Hsu 1981; Chen and Hsu 1982), it was stated that HCS lacks an embryonic growth and differentiation factor (EGDF-4) present in rat serum which regulates the development of the CNS and the organization of the axial structures between days 7 and 8 in vitro, i.e., during the 4-5 somite stage and the time of the turning of the embryos (8-12 somite stage).