The Therapeutic Effects of Human Adipose-Derived Stem Cells in a Rat Cervical Spinal Cord Injury Model

Spinal cord injury triggers a cascade of degenerative changes leading to cell death and cavitation. Severed axons fail to regenerate across the scar tissue and are only capable of limited sprouting. In this study, we investigated the effects of adult human adipose-derived stem cells (ASC) on axonal regeneration following transplantation into the injured rat cervical spinal cord. ASC did not induce activation of astrocytes in culture and supported neurite outgrowth from adult rat sensory dorsal root ganglia neurons. After transplantation into the lateral funiculus 1mm rostral and caudal to the cervical C3-C4 hemisection, ASC continued to express brain-derived neurotrophic factor, vascular endothelial growth factor, and fibroblast growth factor-2 for 3 weeks but only in animals treated with cyclosporine A. Transplanted ASC stimulated extensive ingrowth of 5HT-positive raphaespinal axons into the trauma zone with some terminal arborizations reaching the caudal spinal cord. In addition, ASC induced sprouting of raphaespinal terminals in C2 contralateral ventral horn and C6 ventral horn on both sides. Transplanted cells also changed the structure of the lesion scar with numerous astrocytic processes extended into the middle of the trauma zone in a chain-like pattern and in close association with regenerating axons. The density of the astrocytic network was also significantly decreased. Although the transplanted cells had no effect on the density of capillaries around the lesion site, the activity of OX42-positive microglial cells was markedly reduced. However, ASC did not support recovery of forelimb function. The results suggest that transplanted ASC can modify the structure of the glial scar and stimulate axonal sprouting.