Stem cell self-organization into mature neuronal tissue in subarachnoid space

Embryonic stem (ES) cells might one day be used to repair damaged organs. In the normal embryo, they have the unique ability to self-organize into spatially appropriate arrangements of cells, but this capacity has not been demonstrated outside of embryonic development. Here we report that ES cells transplanted into the subarachnoid space of the normal adult rat spinal cord self -organized into CNS-like tissue with features resembling rat cord. By 3 months after transplantation, the grafts contained primarily the three principle neural cell types: astrocytes, oligodendrocytes, and neurons. ES astrocytes had created a glial limitans resembling the layer covering the normal cord, ES oligodendrocytes had produced mature patterns of myelination, and ES neurons exhibited features of cholinergic motor neurons.