[The revolution of stem cells: bone marrow cells, neural cells and muscle cells are intercovertible].

For many years, the fate of adult cells has been assumed to be limited to their tissues of origin. Upon development cells become increasingly specialized to carry out particular functions. Recently, numerous studies have shown that some stem cells possess greater plasticity than previously envisioned. Thus, a few donor bone-marrow cells when transfused into immunodeficient mice, were recovered as glial cells in the host brain, or as cells expressing neuronal antigens. Alternatively, neural stem cells could differentiate into myeloid and lymphoid cell lineages upon transplantation into the hematopoietic system of irradiated hosts.