Persistent increase of Nogo-A-positive cells and dynamic reduction in oligodendroglia lineage cells in white matter regions following experimental and clinical traumatic brain injury.

Abstract

White matter (WM) disruption and atrophy is a consequence of traumatic brain injury (TBI) and contributes to persisting cognitive impairment. An increased expression of the myelin-associated axonal outgrowth inhibitor Nogo-A and oligodendrocyte pathology might be negatively associated with postinjury WM changes. Here, we analyzed brain tissue from severe TBI patients, obtained by surgical decompression in the early postinjury phase and postmortem brain tissue of long-term TBI survivors and observed an increased number of Nogo-A+ cells in WM tracts such as the corpus callosum (CC). Likewise, the number of Nogo-A+ cells in the CC was increased from day 7 postinjury to 6 months postinjury (mpi) following central fluid percussion injury (cFPI) in mice. In addition, the number of Olig2+ cells in the CC and capsula externa remained constant, while the numbers of Olig2+/CC1+ and GST-π+ mature oligodendrocytes declined throughout the observation time of 18 months. A significantly lower number of Olig2+/CC1+ cells was found in cFPI mice compared to controls at 18 mpi. Persistent vulnerability of oligodendrocytes in combination with dynamic alterations of Nogo-A expression may have implications for the WM atrophy and insufficient recovery observed after TBI.