Expression of neuronal markers in differentiated marrow stromal cells and CD133+ stem-like cells

Bone marrow stromal cells, which normally give rise to bone, cartilage, adipose tissue, and hematopoiesis-supporting cells, have been shown to differentiate in vitro and in vivo into neural-like cells. In this study, we examined the expression of neuronal and glial markers in human marrow stromal cells under culture conditions appropriate for neural stem cells, and compared the unsorted cell population to bone marrow CD133+ stem-like cells using immunofluorescence, Western blot, and functional patch-clamp analysis. Overall, the expression of the early neuronal marker beta3-tubulin was most pronounced in the presence of DMEM/F12 and neurotrophin 3 (NT3) or brain-derived neurotrophic factor (BDNF), when marrow stromal cells were cultured onto fibronectin. Electrophysiological examination, however, could not show fast sodium currents or functional neurotransmitter receptors in differentiated marrow stromal cells. CD133+ mesenchymal stem-like cells, but not CD34+/CD133- cells, generally showed a higher expression of neuronal markers than did unsorted marrow stromal cells, and differentiated CD133+ cells more resembled neuron-like cells.