Repetitive Mild Closed Head Injury Alters Protein Expression and Dendritic Complexity in a Mouse Model.

Worldwide head injuries are a growing problem. In the United States alone, 1.7 million people suffer a head injury each year. While most of these injuries are mild, head injury sufferers still sustain symptoms that can have major medical and economical impacts. Moreover, repetitive mild head injuries, like those observed in active military personnel and athletes, have demonstrated a more severe and long-term set of consequences. In an effort to better understand the delayed pathological changes following multiple mild head injuries, we used a mouse model of mild closed head injury (with no motor deficits observed by rotarod testing) and measured dendritic complexity at 30 days after injury and potentially related factors up to 60 days post-injury. We found an increase in TDP-43 protein at 60 days post-injury in the hippocampus and a decrease in autophagy factors three days post-injury. Alterations in dendritic complexity were neuronal subtype and location specific. Measurements of neurotropic factors suggest that an increase in complexity in the cortex may be a consequence of neuronal loss of the less connected neurons.