IDENTIFICATION OF THE ADULT RESTING PROGENITOR-CELL BY AUTORADIOGRAPHIC TRACKING OF OLIGODENDROCYTE PRECURSORS IN EXPERIMENTAL CNS DEMYELINATION

The new population of oligodendrocytes remyelinating an experimental d emyelinating optic nerve lesion has been tracked backwards in time. Us ing autoradiography combined with electron microscopy and immunocytoch emistry, serial sections of optic nerves from young adult cats were st udied from 42 h (2 days) post-injection to 93 h (4 days) postinjection . The remyelinating oligodendrocyte lineage tvas found to commence wit h the single division of a resting progenitor cell residing in a centr al fascicular location outside the demyelinative lesion. The division of the founding progenitor cell occurs at 2 days post-lesion and resul ts in two motile daughter cells. These cells, previously described by Ids as precursor cells, migrate to the lesion, closely appose demyelin ated axons, produce axon wrapping processes and differentiate to becom e remyelinating oligodendrocytes. This study confirms that remyelinati ng oligodendrocytes originate front resting progenitor cells outside t he lesion and not from mature oligodendrocytes, and implies that repea ted demyelinative injury could exhaust the reparative capacity of such a region.