Membrane Properties of Neuron-Like Cells Generated from Adult Human Bone-Marrow-Derived Mesenchymal Stem Cells

Adult mesenchymal stem cells (MeSCs) isolated from human bone marrow are capable of generating neural stem cell (NSC)–like cells that can be subsequently differentiated into cells expressing molecular markers for neurons. Here we report that these neuron-like cells had functional properties similar to those of brain-derived neurons. Whole-cell patch-clamp recordings and calcium imaging experiments were performed on neuron-like cells differentiated from bone-marrow-derived NSC-like cells. The neuron-like cells were subjected to current pulses to determine if they were capable of generating depolarization-induced action potentials. We found that nearly all of the cells with neuron-like morphology exhibited active membrane properties in response to the depolarizing pulses. The most common response was a single spike-like event with an overshoot and brief afterhyperpolarization. Cells that did not generate overshooting spike-like events usually displayed rectifying current–voltage relationships. The prevalence of these active membrane properties in response to the depolarizing current pulses suggested that the human MeSCs (hMeSCs) were capable of converting to a neural lineage under defined culture conditions. The spike-like events were blocked by the voltage-gated sodium channel inhibitor lidocaine, but unaffected by another sodium channel inhibitor tetrodotoxin (TTX). In calcium imaging experiments, the neuron-like cells responded to potassium chloride depolarization and l -glutamate application with increases in the cytoplasmic calcium levels. Thus, the neuron-like cells appeared to express TTX-resistant voltage-gated sodium channels, voltage-gated calcium channels, and functional l -glutamate receptors. These results demonstrate that hMeSCs were capable of generating cells with characteristics typical of functional neurons that may prove useful for neuroreplacement therapies.