Postnatal astrocytes promote neural induction from adult human bone marrow-derived stem cells

Neural stem cells (NSCs) have generated considerable interest because of their potential as a source of defined cells for drug screening or cell-based therapies for neurodegenerative diseases. Ethical and practical considerations limit the availability of human fetal-derived neural tissue and highlight the need to consider alternative sources of human NSCs. Because of their ready availability, their ability to be easily expanded, and reports of neural potential, bone marrow-derived populations have become the focus of intense study with regard to their potential clinical utility. However, recent identification of spontaneous cell fusion and limited neuronal differentiation has tempered initial optimism. In this study, we demonstrate the monoclonal neural and mesodermal potential of adult human bone marrow mesenchymal cells. Critically, we show that sequential treatment with the mitogens epidermal growth factor (EGF) and fibroblast growth factor-2 (FGF-2) followed by postnatal hippocampal astrocyte conditioned medium significantly promotes the generation of neurofilament(+)/beta-tubulin(+) cells from bone marrow precursors. The ability to generate almost limitless numbers of neural precursors from a readily accessible autologous adult human source provides a platform for further studies and potentially has important therapeutic implications.