The Contribution of Stem Cell Factor and Granulocyte Colony-Stimulating Factor in Reducing Neurodegeneration and Promoting Neural Network Reorganization after Traumatic Brain Injury

Abstract

Background Traumatic brain injury (TBI) is a major cause of death and disability in young adults worldwide. TBI-induced long-term cognitive deficits represent a growing clinical problem. Stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF) are involved in neuroprotection and neuronal plasticity. However, the knowledge concerning reparative efficacy of SCF+G-CSF treatment in post-acute TBI recovery remains incomplete. This study aims to determine the efficacy of SCF+G-CSF on post-acute TBI recovery in young adult mice. The controlled cortical impact model of TBI was used for inducing a severe damage in the motor cortex of the right hemisphere in 8-week-old male C57BL mice. SCF+G-CSF treatment was initiated 3 weeks after induction of TBI. Results Severe TBI led to persistent motor functional deficits (Rota-Rod test) and impaired spatial learning and memory (Morris water maze test). SCF+G-CSF treatment significantly improved the severe TBI-impaired spatial learning and memory 6 weeks after treatment. TBI also caused significant increases of Fluoro-Jade C positive degenerating neurons in bilateral frontal cortex, striatum and hippocampus, and significant reductions in MAP2 + apical dendrites and overgrowth of SMI312 + axons in peri-TBI cavity frontal cortex and in the ipsilateral hippocampal CA1 at 24 weeks post-TBI. SCF+G-CSF treatment significantly reduced TBI-induced neurodegeneration in the contralateral frontal cortex and hippocampal CA1, increased MAP2 + apical dendrites in the peri-TBI cavity frontal cortex, and prevented TBI-induced axonal overgrowth in both the peri-TBI cavity frontal cortex and ipsilateral hippocampal CA1. Conclusions These findings reveal a novel pathology of axonal overgrowth after TBI and demonstrate a therapeutic potential of SCF+G-CSF in ameliorating TBI-induced long-term neuronal pathology, neural network malformation, and impairments in spatial learning and memory.