Transplantation of bone marrow stromal cells (BMSCs) into spinal cord injury models has shown significant neural function recovery; however, the underlying mechanisms have not been fully understood. In the present study we examined the effect of BMSCs on neurite outgrowth of spinal motor neuron using an in vitro co-culture system. The ventral horn of the spinal grey matter was harvested from neonatal Sprague–Dawley rats, cultured with BMSCs, and immunostained for neurofilament-200 (NF-200). Neurite outgrowth of spinal motor neurons was measured using Image J software. ELISA was used to quantify neurotrophic factors such as brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) in culture media, and antibodies or exogenous neurotrophic factors were used to block or mimic the effect of BMSCs on neurite outgrowth, respectively. The results showed that neurite outgrowth significantly increased in spinal motor neurons after co-cultured with BMSCs, while the secretion level of BDNF, GDNF and NGF was dramatically elevated in co-culture. However, the neurite outgrowth-promoting effect of BMSCs was found to significantly reduced using antibodies to BDNF, GDNF and NGF. In addition, a fraction of BMSCs was found to exhibit NF-200 immunoreactivity. These results indicated that BMSCs could promote neurite outgrowth of motor neurons by means of neurotrophic factors. The findings of the present study provided new cues for the treatment of spinal cord injury.

In this study, a chitosan conduit loaded with bone marrow stromal cells (BMSCs) was developed to bridge the gap in the transected spinal cord of adult rats, and the nerve repair outcomes were evaluated by functional and histological techniques at 12 weeks after implantation. As compared to chitosan conduits alone, incorporation of BMSCs within chitosan conduits yielded additional improving effects on nerve regeneration and function restoration. The measurements with the Basso, Beattie and Bresnahan locomotor rating scale or of motor evoked potentials indicated that motor functional recovery was enhanced; retrograde tracing confirmed that the ascending tract was regenerated and the neural pathway was established; and histological analyses revealed that axon growth and remyelination in the regenerated nerve was promoted. The three-dimensional reconstruction showed that the chitosan conduit loaded with BMSCs significantly reduced the spinal cord cavity volume at the injured site. Taken together, the results collectively suggest that implantation with BMSCs-loaded chitosan conduits may become a promising approach to the repair of spinal cord injury.