Local non-viral gene delivery of apoptin delays the onset of paresis in an experimental model of intramedullary spinal cord tumor.

OBJECTIVE: The objective of this study is to evaluate the safety and efficacy of a tumor-specific apoptosis-inducing gene, apoptin, as delivered by the non-viral carrier, PAM-RG4, in an animal model of spinal cord tumor. METHODS: Male Sprague-Dawley rats were given a 2.5-µl intramedullary injection of C6 glioma (100,000) cells and randomized into three groups (day 0). On day 5, animals received a 7.5-µl intramedullary injection of Dulbecco's modified Eagle's medium (Group 1; n=7), PAM-RG4/control gene polyplex (Group 2; n=7), or PAM-RG4/apoptin gene polyplex (Group 3; n=8). Hindlimb functional strength was assessed every other day for the duration of the study. The spinal cords of killed animals were collected and hematoxylin-eosin stained. RESULTS: Following treatment, animals that received apoptin had significantly higher mean functional hindlimb scores than those of sham control animals, showing a level of preserved hindlimb function throughout the study. In addition, Group 1 (sham control) and Group 2 (control gene) animals had median survival scores lower than those of animals receiving apoptin. Histopathological analysis showed marked retardation of tumor progression in apoptin-treated animals compared with sham controls. CONCLUSION: Our study suggests that apoptin is safe for use in the mammalian spinal cord as well as effective in slowing the progression of tumor growth in the spinal cord. The significant slowing of tumor progression, as manifested by the preserved hindlimb function, coupled with the reduction in tumor volume, shows local non-viral delivery of apoptin could serve as an emerging therapy for the treatment of intramedullary spinal cord tumors.

Hypoxia-specific GM-CSF-overexpressing neural stem cells improve graft survival and functional recovery in spinal cord injury.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine that stimulates the differentiation and function of hematopoietic cells. GM-CSF has been implicated in nervous system function. The goal of the present study was to understand the effects of hypoxia-induced GM-CSF on neural stem cells (NSCs) in a model of spinal cord injury (SCI). GM-CSF-overexpressing NSCs were engineered utilizing a hypoxia-inducible gene expression plasmid, including an Epo enhancer ahead of an SV promoter (EpoSV-GM-CSF). Cells were then subjected to hypoxia (pO(2), 1%) or a hypoxia-mimicking reagent (CoCl(2)) in vitro. The progression of time of GM-CSF expression was tracked in EpoSV-GM-CSF-transfected NSCs. Overexpression of GM-CSF in undifferentiated and differentiated NSCs created resistance to H(2)O(2)-induced apoptosis in hypoxia. NSCs transfected with EpoSV-GM-CSF or SV-GM-CSF were transplanted into rats after SCI to assess the effect of GM-CSF on NSC survival and restoration of function. Moreover, a significantly higher amount of surviving NSCs and neuronal differentiation was observed in the EpoSV-GM-CSF-treated group. Significant improvement in locomotor function was also found in this group. Thus, GM-CSF overexpression by the Epo enhancer in hypoxia was beneficial to transplanted NSC survival and to behavioral improvement, pointing toward a possible role for GM-CSF in the treatment of SCI.