Tree shrew neural stem cell transplantation promotes functional recovery of tree shrews with a hemi-sectioned spinal cord injury by upregulating nerve growth factor expression

The aim of the present study was to determine the effect of implanted neural stem cells (NSCs) on the functional recovery of tree shrews (TSs) subjected to hemi-sectioned spinal cord injury (hSCI), and to investigate the possible mechanism involved. NSCs (passage 2), derived from the hippocampus of TSs (embryonic day 20), were labeled with Hoechst 33342 and transplanted intraspinally into the hSC of TSs at thoracic level 10 in the acute (immediately after injury) and chronic (day 9 post-injury) stages. The Basso-Beattie-Bresnahan (BBB) score was recorded from days 1 to 16 post-injury, and the survival, migration, differentiation and neurotrophic factor (NTF) expression in vivo were detected. In vitro and in vivo, the expanded NSCs were able to differentiate into neurons and astrocytes, and secreted a variety of NTFs, including ciliary NTF, transforming growth factor-β1, glial cell line-derived NTF, nerve growth factor (NGF), brain-derived NTF and insulin-like growth factor. Following transplantation, the BBB score in the TSs with chronic-stage transplantation exhibited a statistically significant increase, while there was no significant difference in the acute group, compared with the control group. This corresponded with the marked upregulation of NGF indicated by reverse transcription-quantitative polymerase chain reaction. In conclusion, the transplantation of NSCs into the hSC in the chronic phase, but not the acute stage, of hSCI in non-human primate TSs is effective and associated with upregulated NGF expression. These findings may provide novel strategies for the treatment of SCI in clinical patients.