Transplanted CNS stem cells form functional synapses in vivo

An understanding of developmental mechanisms and new cell therapies can be achieved by transplantation into the nervous system. Multipotential stem ce lls have been isolated from the foetal and adult central nervous system (CN S). Immortalized and primary precursor cells integrate into the developing brain generating both neurons and glia as defined by immunological and morp hological criteria. Here we show for the first time that in vitro-expanded CNS precursors, upon transplantation into the brains of rats, form electric ally active and functionally connected neurons. These neurons exhibit spont aneous and evoked postsynaptic events and respond to focal glutamate applic ation. Donor cells were grafted into the foetal hippocampus, and the amplit ude and frequency of spontaneous synaptic events were monitored in the graf ted cells in area CA1 for the first month of postnatal life. The formation of synapses onto grafted neurons indicates that grafted CNS stem cells can be used to study synaptic development in vivo and has important implication s for clinical cell replacement therapies.