ABSTRACT
This chapter reviews the differences and similarities in the derivation and properties of human and murine embryonic stem (ES) cells. Electron microscopy demonstrates gap junctions and microvillae in both mouse and human ES cells. Cytoplasmic organelles which are associated with non-apoptotic cell death may be more prevalent in mouse ES cells than human. Typically, after the initial derivation on feeder layers and in the presence of serum, human ES cell lines can be maintained and propagated on feeder layers in medium containing serum alone, or serum replacement plus basic fibroblast growth factor. Advantages of feeder-free cultures are their simplicity, scalability, and the lack of concern of fibroblast carryover to initial differentiation cultures. Human ES cells are an important tool for understanding the identity and nature of tissue-restricted multipotent progenitor cells that could be used in human cell-based therapies. Progenitors readily respond to signals in their microenvironment enabling them to differentiate, and potentially functionally integrate into tissues in a recipient.
