Neural stem cells (NSCs) possess therapeutic potentials to reverse complex pathological processes following spinal cord injury (SCI), but many obstacles remain that could not be fully overcome by NSC transplantation alone. Combining complementary strategies might be required to advance NSC-based treatments to the clinical stage. The present study was undertaken to examine whether combination of NSCs, polymer scaffolds, neurotrophin-3 (NT3), and chondroitinase, which cleaves chondroitin sulfate proteoglycans at the interface between spinal cord and implanted scaffold, could provide additive therapeutic benefits. In a rat hemisection model, poly( -caprolactone) (PCL) was used as a bridging scaffold and as a vehicle for NSC delivery. The PCL scaffolds seeded with F3 NSCs or NT3 overexpressing F3 cells (F3.NT3) were implanted into hemisected cavities. F3.NT3 showed better survival and migration, and more frequently differentiated into neurons and oligodendrocytes than F3 cells. Animals with PCL scaffold containing F3.NT3 cells showed the best locomotor recovery, and motor evoked potentials (MEPs) following transcranial magnetic stimulation were recorded only in PCL-F3.NT3 group in contralateral, but not ipsilateral, hindlimbs. Implantation of PCL scaffold with F3.NT3 cells increased NT3 levels, promoted neuroplasticity, and enhanced remyelination of contralateral white matter. Combining chondroitinase treatment after PCL-F3.NT3 implantation further enhanced cell migration and promoted axonal remodeling, and this was accompanied by augmented locomotor recovery and restoration of MEPs in ipsilateral hindlimbs. We demonstrate that combining multifaceted strategies can maximize the therapeutic benefits of NSC transplantation for SCI. Our results may have important clinical implications for the design of future NSC-based strategies.

Transplantation of neural stem cells (NSCs) has shown promise for improving functional recovery after spinal cord injury (SCI). The inhospitable milieu of injured spinal cord, however, does not support survival of grafted NSCs, reducing therapeutic efficacy of transplantation. The present study sought to examine whether overexpression of antiapoptotic gene Bcl-X L in NSCs could promote graft survival and functional recovery following transplantation in rat contusive SCI model. A human NSC line (HB1.F3) was transduced with a retroviral vector encoding Bcl-X L to generate Bcl-X L -overexpressing NSCs (HB1.F3.Bcl-X L ). Overexpression of Bcl-X L conferred resistance to staurosporine-mediated apoptosis. The number of HB1.F3.Bcl-X L cells was 1.5-fold higher at 2 weeks and 10-fold higher at 7 weeks posttransplantation than that of HB1.F3 cells. There was no decline in the number of HB1.F3.Bcl-X L cells between 2 and 7 weeks, indicating that Bcl-X L overexpression completely blocked cell death occurring between these two time points. Transplantation of HB1.F3.Bcl-X L cells improved locomotor scores and enhanced accuracy of hindlimb placement in a grid walk. Approximately 10% of surviving NSCs differentiated into oligodendrocytes. Surviving NSCs produced brain-derived neurotrophic factor (BDNF), and the level of BDNF was significantly increased only in the HB1.F3.Bcl-X L group. Transplantation of HB1.F3.Bcl-X L cells reduced cavity volumes and enhanced white matter sparing. Finally, HB1.F3.Bcl-X L grafts enhanced connectivity between the red nucleus and the spinal cord below the lesion. These results suggest that enhancing graft survival with antiapoptotic gene can potentiate therapeutic benefits of NSC-based therapy for SCI. V V C 2009 Wiley-Liss, Inc.

Spontaneous remyelination after spinal cord injury