Antiapoptotic effect of highly secreted GMCSF from neuronal cell-specific GMCSF overexpressing neural stem cells in spinal cord injury model

Study Design. Neuronal cell-specific gene expression system and neural stem cells (NSCs) were combined for treatment of spinal cord injury (SCI). Objective. To verify the reproducibility of the neuronal cellspecific therapeutic gene overexpression system, we develop a neuronal cell-specific granulocyte-macrophage colony-stimulating factor expression system (NSE-GMCSF), and then examine the characteristics of GMCSF overexpression and protective effect on neural cells in vitro and vivo. Summary of Background Data. The stem cell transplantation is considered a promising therapy for SCI. However, stem cell monotherapy strategy is insufficient for complete recovery after SCI. Therefore, combined treatment method based on stem cells with other therapeutic system may be effective for improving the therapeutic efficacy. In this study, we established the gene and stem cell therapy platform based on NSCs and neuronal cellspecific gene expression system. Methods. To examine the GMCSF expression pattern, we compared the amount of secreted GMCSF from the neuronal cell-specific GMCSF expressing NSCs with control GMCSF-expressing NSCs (respectively, NSE-GMCSF-NSCs vs. SVGMCSF- NSCs) by ELISA in vitro and in vivo, and then verified the neuronal protective effect of these cells in vitro and vivo. Results. The results showed that NSE-GMCSF-NSCs secreted more GMCSF compared with SV-GMCSF-NSCs in normoxia, hypoxia and cytotoxic conditions. The cell viability of NSEGMCSF- NSCs was increased depending on the amount of secreted GMCSF in cytotoxic condition. In addition, the amount of secreted GMCSF by NSE-GMCSF-NSCs transplanted into injured spinal cord was significantly higher than SV-GMCSFNSCs. Higher amount of secreted GMCSF decreased the expression of proapoptotic protein, Bax. Conclusion. In this study, we demonstrated that the neuronal cell-specific gene expression system induced overexpression of GMCSF in NSCs. These combined NSCs & gene therapy treatment protocol would be an effective therapeutic system for SCI.