Long-term beneficial effects of hematopoietic growth factors on brain repair in the chronic phase of severe traumatic brain injury.

Severe traumatic brain injury (TBI) is the major cause of long-term, even life-long disability and cognitive impairments in young adults. The lack of therapeutic approaches to improve recovery in the chronic phase of severe TBI is a big challenge to the medical research field. Using a single severe TBI model in young adult mice, this study examined the restorative efficacy of two hematopoietic growth factors, stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF), on brain repair in the chronic phase of TBI. SCF and G-CSF alone or combination (SCF + G-CSF) treatment was administered at 3 months post-TBI. Functional recovery was evaluated by neurobehavioral tests during the period of 21 weeks after treatment. Neuropathology was examined 22 weeks after treatment. We observed that severe TBI caused persistent impairments in spatial learning/memory and somatosensory-motor function, long-term and widespread neuropathology, including dendritic reduction, decrease and overgrowth of axons, over-generated excitatory synapses, and demyelination in the cortex, hippocampus and striatum. SCF, G-CSF, and SCF + G-CSF treatments ameliorated severe TBI-induced widespread neuropathology. SCF + G-CSF treatment showed superior efficacy in improving long-term functional outcome, enhancing neural plasticity, rebalancing neural structure networks disturbed by severe TBI, and promoting remyelination. These novel findings demonstrate the therapeutic potential of SCF and G-CSF in enhancing recovery in the chronic phase of severe TBI .