Functional motoneurons develop from human neural stem cell transplants in adult rats.

We have shown previously that primed human fetal neural stem cells, after transplantation into rat spinal cords, differentiated into cholinergic motoneurons that sent axons to contact medial gastrocnemius myocytes. Here we demonstrate that (i) axons from the transplanted cells are cholinergic and myelinated, (ii) putative synapses form on transplanted somata and dendrites in the ventral horn, (iii) human fetal neural stem cells transplantation led to normal electromyograms from medial gastrocnemius muscles, and (iv) the gait of transplanted animals was much improved. Accumulatively, our data indicate that some transplanted human fetal neural stem cells in adult motoneuron-deficient ventral horns differentiate into relatively normal motoneurons that are integrated into spinal and peripheral circuitry. These findings are steps towards the long-term goal of providing stem cell transplants for motoneuron loss.