Phenotypic characterization of neural stem cells from human fetal spinal cord: Synergistic effect of LIF and BMP4 to generate astrocytes

Abstract

If cell based therapy for spinal cord injury is to become a reality, greater insights into the biology of human derived spinal cord stem cells are a prerequisite. Significant species differences and regional specification of stem cells necessitates determining the effects of growth factors on human spinal cord stem cells. Fetal spinal cords were dissociated and expanded as neurospheres in medium with bone morphogenetic protein 4 (BMP4), leukemia inhibitory factor (LIF) or BMP4 and LIF. First-generation neurospheres comprised a heterogeneous population of neural cell types and after plating emergent cells included neurons, oligodendrocytes and GFAP(+) cells which coexpressed stem cells markers and those of the neuronal lineage and were thus identified as GFAP(+) neural precursor cells (NPC). When plated, neurospheres maintained in BMP4 demonstrated a reduced proportion of emergent oligodendrocytes from 13 to 4%, whereas LIF had no statistically significant effect on cell type distribution. Combining BMP4 and LIF reduced the proportion of oligodendrocytes to 3% and that of neurons from 37 to 16% while increasing the proportion of GFAP(+) NPC from 45 to 79%. After 10 passages in control media aggregates gave rise to multiple neural phenotypes and only continued passage of neurospheres in the presence of BMP4 and LIF resulted in unipotent aggregates giving rise to only astrocytes. These results provide a means of obtaining pure populations of human spinal-cord derived astrocytes, which could be utilized for further studies of cell replacement strategies or in vitro evaluation of therapeutics.