Abstract
The proliferation marker Kiβ67 labels cell nuclei in the G~1~, S, M, and G~2~ phases of the cell cycle. We used Kiβ67 immunohistochemistry to quantify proliferating glial cells in brain tissue sections from twentyβfour patients, comprised of multiple sclerosis, normal brains, and other neurological disease controls. Glial proliferation was greatly increased in MS lesions when compared with control brain white matter. Both actively demyelinating/early remyelinating plaques and chronic inactive plaques of long standing often displayed large numbers of glial cells in the proliferative cycle. The bulk of these proliferating cells were of oligodendroglial lineage in the MS plaques. Kiβ67 positive macrophage/microglial lineage cells were largely restricted to acute lesions. The finding of increased numbers of proliferating oligodendroglia in most MS plaques, regardless of disease duration or activity state, indicates that the MS brain is capable of recruiting unexpectedly large numbers of new oligodendrocytes over long periods of time. The factors within the MS plaque microenvironment that provoke new oligodendrocyte generation and their subsequent loss still need to be identified. J. Neurosci. Res. 65:308β317, 2001. Β© 2001 WileyβLiss, Inc.