Mature oligodendrocytes. Division following experimental demyelination in adult animals.

Primary demyelination can be caused by injury to oligodendrocytes or to the myelin sheaths that these cells maintain. Although remyelination does take place in multiple sclerosis (MS), its possible role in the recovery from MS attacks has been inadequately considered, partly because of the belief that oligodendrocytes, once destroyed, cannot be replaced in the adult. The injection of lysolecithin into the mouse spinal cord causes primary demyelination, followed by the generation of new oligodendrocytes and remyelination. By using a pulse label of tritiated thymidine, this electron-microscopic autoradiographic study demonstrated a source of these regenerated oligodendrocytes. The replacement of oligodendrocytes can occur through the division of preexisting oligodendrocytes. This is the first demonstration that mature oligodendrocytes are capable of dividing in older animals. These results lend support to recent observations of an apparent proliferation of these cells in an active MS lesion. We believe that the ability of mature oligodendrocytes to divide and to remyelinate axons in the adult may play an important role in the recovery from MS attacks.