Interfering with the Chronic Immune Response Rescues Chronic Degeneration After Traumatic Brain Injury.
J Neurosci. 2016 Sep 21;36(38):9962-75. doi: 10.1523/JNEUROSCI.1898-15.2016.
|Authors/Editors:||Ertürk A, Mentz S, Stout EE, Hedehus M, Dominguez SL, Neumaier L, Krammer F, Llovera G, Srinivasan K, Hansen DV, Liesz A, Scearce-Levie KA, Sheng M.|
After traumatic brain injury (TBI), neurons surviving the initial insult can undergo chronic (secondary) degeneration via poorly understood mechanisms, resulting in long-term cognitive impairment. Although a neuroinflammatory response is promptly activated after TBI, it is unknown whether it has a significant role in chronic phases of TBI (>1 year after injury). Using a closed-head injury model of TBI in mice, we showed by MRI scans that TBI caused substantial degeneration at the lesion site within a few weeks and these did not expand significantly thereafter. However, chronic alterations in neurons were observed, with reduced dendritic spine density lasting >1 year after injury. In parallel, we found a long-lasting inflammatory response throughout the entire brain. Deletion of one allele of CX3CR1, a chemokine receptor, limited infiltration of peripheral immune cells and largely prevented the chronic degeneration of the injured brain and provided a better functional recovery in female, but not male, mice. Therefore, targeting persistent neuroinflammation presents a new therapeutic option to reduce chronic neurodegeneration.