Lineage restriction of neuroepithelial precursor cells from fetal human spinal cord

In the presence of epidermal growth factor (EGF) and/or fibroblast growth factor 2 (FGF2), neuroepithelial precursor cells from dissociated fetal human spinal cord are mitotically active and form free-floating spheres of undifferentiated cells. Proliferating cells were obtained in approximately 40% of preparations with each mitogen, were immunoreactive for the intermediate filament nestin, and did not express neuronal- or glial-specific markers. Early passage neuroepithelial precursor cells were pluripotent and differentiated into neurons expressing MAP2a,b, NF-M, and TuJ1, and GFAP-positive astrocytes; however, oligodendrocytes were never seen. As the cells were passaged from P0 to P4, the percentage of differentiating neurons significantly decreased and the prevalence of astrocytes significantly increased. While the majority of cell populations from individual preparations stopped proliferating between 3 and 6 passages, two expanding cell lines have been successfully expanded in EGF and FGF2 for over 25 passages and have been maintained in culture for over one year. These cells express nestin and not other cell-specific lineage markers. When differentiated, these neuroepithelial cell lines differentiate only into astrocytes, showing no expression of any neuronal marker. These data suggest that continued passage under these conditions preferentially selects for spinal cord neural precursors that are restricted to the astrocytic lineage. Despite the lineage restriction of later passage cell populations, these results provide a rationale for future investigation into the lineage potential of these cells in vivo following transplantation into the adult CNS, potentially as a therapeutic approach for traumatic injury and neurodegenerative disease.