Therapeutic effect of ADC human bone marrow-derived mesenchymal stem cells transplantation in spinal cord injury model

Abstract

A spinal cord injury (SCI) usually results in long-lasting deficits, involving the loss of motor and sensory function. The stem cell transplantation therapy is promising to treat SCI. In significance, mesenchymal stem cells (MSCs) have properties of self-renewal and multi-lineage differentiation. Due to these properties, MSCs receive lots of attention in the field of cell transplantation therapy. However, MSCs has low capability to survive at the transplanted site and has low potential to differentiate after being transplanted in variuos neuronal injury models including SCI. Therefore it is very important to promote survival of MSCs upon oxidative injury for the treatment of neuronal diseases by MSCs transplantation.Agmatine, synthesized by arginine decarboxylase (ADC) gene, is reported to posesses neuroprotective properties both in in vitro and in vivo injury models. Earlier, it has been reported retroviral vector system carrying human arginine decarboxylase (hADC) gene infection to neural stem cells and NIH3T3 cell line which can synthesize amatine endogenously confered cytoprotection against H2O2 toxicity. Considering the low survival efficiency of hMSCs during transplantion, this study investigated whether hADC genes infection to hMSCs (hADC-hMSCs) promote the survival rate during stress insults in vitro and their transplantaion could favour the increase in baseline antioxidant capacity and differentiation potential at the pathological microenvironment during SCI in vivo. Induced expression of hADC gene conferred cytoprotection in hMSCs against H2O2 insult which is evident by MTT assay and Hoechst/PI staining. The survival events of hADC-hMSCs were executed through suppressed caspase-3 activation and increased expression of AKT, CREB, and BDNF thus, suggesting that hADC overexpression contributes to the survival of hMSCs against oxidative stress in vitro. In the in vivo study, mice transplanted with hMSCs overexpressed with hADC genes recorded better BBB scores, compared to other experimental groups. Immunostaining and western results showed significant increase in the expression of Tuj-1 and Olig-2 positive cells around the lesion site in hADC-hMSCs transplantation group. Moreover, the BDNF and VEGF (neurotrophic factors) expression were also elevated in hADC-hMSCs transplantation group suggesting that hADC genes could trigger the neurotrophic factors and stimulate neurogenesis and oligogenesis following SCI.This study demonstrates that the overexpression of hADC gene increased the tuj-1 positive cells and improved survival of hMSCs against H2O2 toxicity in vitro. Transplantation of hMSCs overexpressing hADC gene improved motor function following SCI. Taken together, the present findings support the idea that hADC gene can be one of the unique target for improving the survival of hMSCs and as a potent transplantable material in various CNS injury models including SCI.