Characterization of a human fetal spinal cord stem cell line, NSI-566RSC, and its induction to functional motoneurons.

Specific neuronal subtypes, especially motoneurons (MNs), derived from human stem cells provide a significant therapeutic potential for spinal cord diseases, such as amyotrophic lateral sclerosis (ALS) and spinal cord injury. So far, in vitro, MNs have only been successfully induced from embryonic stem cells (hESC) and human fetal cortical progenitors. Although neural progenitors from spinal cord would be a likely source for generating MNs, there has been no study reporting successful in vitro differentiation of MNs from spinal cord progenitors. This study first characterized a polyclonal spinal cord stem cell line isolated from an 8 week-old fetus. Then a paradigm was introduced to successfully induce MNs from this cell line, which was demonstrated by immunostaining using the MN markers HB9, Islet1 and choline acetyl transferase (ChAT). The combination of HB9 and ChAT immunostainings indicated that approximately 20% of the cells were MNs after this induction protocol. The presence of other cell types in the differentiated culture was also analysed. Finally, the electrophysiological properties of these differentiated MNs were characterized to confirm their functional integrity. The majority of these MNs fired repetitive action potentials (APs), which is an indicator of functional maturation. The recordings of spontaneous excitatory postsynaptic currents (EPSCs) confirmed the formation of synapses onto these MNs. This study reports the first successful differentiation of MNs from human spinal cord stem cells in vitro, providing a novel approach for obtaining functional MNs when designing the therapeutic strategy for spinal cord diseases or injuries.