[Application of stem cell technology and nuclear transfer in animal models]

Pluripotent embryonic stem (ES) cells established from undifferentiated cells of early embryos together with embryonic germ (EG) cells derived from primordial germ cells are used for gene transfer into the germ lines of mice. ES cells are also capable of in vitro differentiation into embryo-like aggregates (embryoid bodies) consisting of meso-, ecto- and endodermal cells. Except in chicken in no other vertebrate species pluripotent cell lines equivalent to murine ES cells are established. Recently, isolated human pluripotent cells originating from spare IVF embryos or aborted human foetuses have successfully been differentiated into somatic cells and may at some point serve as cellular grafts for transplantation. In therapeutic cloning somatic cells can be reprogrammed by fusion with an enucleated oocyte. Later the established autologous ES cells from the resulting nuclear transfer embryo can be differentiated into the specific cell type needed for tissue therapy.