Enhanced regeneration in spinal cord injury by concomitant treatment with granulocyte colony-stimulating factor and neuronal stem cells

Granulocyte colony-stimulating factor (G-CSF) inhibits programmed cell death and stimulates neuronal progenitor differentiation. Neuronal stem cells transplanted into injured spinal cord can survive, differentiating into astroglia and oligodendroglia, and supporting axon growth and myelination. Herein, we evaluate the combined effects of G-CSF and neuronal stem cells on spinal cord injury. For 40 Sprague-Dawley rats (n=10 in each group) transverse spinal cord resections at the T8-9 level were carried out, leaving an approximately 2-mm gap between the distal and proximal ends of the cord. Neuronal stem cells embedded in fibrin glue treated with or without G-CSF (50 microg/kg x 5 days) (groups III and IV) or fibrin glue with or without G-CSF (50 microg/kg x 5 days) (groups I and II) were transplanted into the gap in the injured spinal cord. Spinal cord regeneration was assessed using a clinical locomotor rating scale scores and electrophysiological, histological and immunohistochemical analysis 3 months after injury. Regeneration was more advanced in group IV than in groups III or II according to the clinical motor score, motor evoked potential, and conduction latency. Most advanced cord regeneration across the gap was observed in group IV rats. Higher densities of bromodeoxyuridine in the injured area and higher expression levels of Neu-N and MAP-2 over the distal end of the injured spinal cord were observed in group IV compared with groups II or III, but there was no significant difference in expression of glial fibrillary acid protein. This synergy between G-CSF and neuronal stem cells may be due to increased proliferation of progenitor cells in the injured area and increased expression of neuronal stem cell markers extrinsically or intrinsically in the distal end of injured cord.