Enrichment of blood from embryonic stem cells in vitro

Murine embryonic stem (ES) cells are pluripotent. When injected into blastocysts they can give rise to every cell type of a derived chimeric mouse including germ cells. Embryonic stem cells also possess remarkable in vitro differentiation potential. When removed from stromal support and leukaemia inhibitory factor (LIF), ES cells differentiate into structures known as embryoid bodies (EBs), in which all three germ layers develop and interact. As ES cells from humans become available there is increasing interest in the potential for EBs to provide an unlimited supply of stem cells for somatic transplantation therapies. Realisation of this potential will require greater understanding of the molecular determinants of cell fate within EBs. Also, culture techniques for selective expansion of cell lineages of interest will reduce the risks associated with transplantation of EB-derived cells. In this paper the kinetics of expression of mRNA and protein for early mesoderm markers within EBs is reported. In addition, a three-step culture system incorporating co-cultivation on the bone marrow derived stromal cell line, MC3T3-G2/PA6 (PA6), is explored as a way to select for haematopoietic progenitor cells (HPCs) and against undifferentiated ES cells. A system like this could enhance purification of haematopoietic stem cells (HSCs) from ES cells for bone marrow transplantation.