Human Neural Stem Cells Differentiate and Promote Locomotor Recovery in an Early Chronic Spinal coRd Injury NOD-scid Mouse Model

Abstract

BackgroundTraumatic spinal cord injury (SCI) results in partial or complete paralysis and is characterized by a loss of neurons and oligodendrocytes, axonal injury, and demyelination/dysmyelination of spared axons. Approximately 1,250,000 individuals have chronic SCI in the U.S.; therefore treatment in the chronic stages is highly clinically relevant. Human neural stem cells (hCNS-SCns) were prospectively isolated based on fluorescence-activated cell sorting for a CD133+ and CD24−/lo population from fetal brain, grown as neurospheres, and lineage restricted to generate neurons, oligodendrocytes and astrocytes. hCNS-SCns have recently been transplanted sub-acutely following spinal cord injury and found to promote improved locomotor recovery. We tested the ability of hCNS-SCns transplanted 30 days post SCI to survive, differentiate, migrate, and promote improved locomotor recovery.Methods and FindingshCNS-SCns were transplanted into immunodeficient NOD-scid mice 30 days post spinal cord contusion injury. hCNS-SCns transplanted mice demonstrated significantly improved locomotor recovery compared to vehicle controls using open field locomotor testing and CatWalk gait analysis. Transplanted hCNS-SCns exhibited long-term engraftment, migration, limited proliferation, and differentiation predominantly to oligodendrocytes and neurons. Astrocytic differentiation was rare and mice did not exhibit mechanical allodynia. Furthermore, differentiated hCNS-SCns integrated with the host as demonstrated by co-localization of human cytoplasm with discrete staining for the paranodal marker contactin-associated protein.ConclusionsThe results suggest that hCNS-SCns are capable of surviving, differentiating, and promoting improved locomotor recovery when transplanted into an early chronic injury microenvironment. These data suggest that hCNS-SCns transplantation has efficacy in an early chronic SCI setting and thus expands the “window of opportunity” for intervention.

Part I: Minicircle vector technology limits DNA size restrictions on ex vivo gene delivery using nanoparticle vectors: Overcoming a translational barrier in neural stem cell therapy

“…In our study, gene expression was assessed in differentiated NSCs, as differentiation is the natural fate of NSCs post-transplantation therefore we consider the analysis to be of greater relevance for engineered cell therapy, than studying long term expression in NSCs [43,44].…”

“…It should be noted that a previous report where equal copy numbers of both DNA vectors were microporated into cells also suggested higher mC number within nuclei versus the parental counterpart (63.7% vs 18.3%) [32]. It has been reasoned that low molecular weight DNA has a 'higher survival rate', making it more likely to enter the nucleus for two reasons: (i) higher mobility, therefore it is less likely to be degraded by host nucleases due to lower time of residence in the cytoplasm [43,44] and (ii) improved release of smaller DNA molecules from nanoparticles allowing for quicker transportation to the nucleus [27]. Together these data indicate that mC use can enhance the level of protein expression per cell, of high relevance to release of therapeutic proteins to promote regeneration.…”

Therapeutic Activities of Engrafted Neural Stem/Precursor Cells Are Not Dormant in the Chronically Injured Spinal Cord

“…In addition to neural replacement, NSPCs promote neurological recovery by providing trophic support and modifying the host environment to create a permissive environment for endogenous regeneration and repair [4,5,9]. Based on considerable experimental evidences, clinical trials for SCI have been performed or initiated [5,6,10], and stem cell-based therapies using NSPCs are now being translated to patients with chronic SCI [6,11,12]. However, while emerging evidence supports the therapeutic potential of NSPC transplantation for the acute and subacute phases of SCI [4,5,13], few studies have investigated NSPC transplantation for the chronic phase of SCI [14] and its therapeutic efficacy for chronic SCI thus remains controversial [3,14,15].…”

Stem cells: A time to heal

“…A few patients with the most severe injuries have already received the treatment, a shot of 20 million cells. Mouse data suggest that the cells differentiate to form neurons and glia, and that the therapy can restore some function 3 . In February 2013, StemCells announced that two out of three subjects showed improved function a year after treatment.…”

“…"There's a little bit of a dogma that one would have to transplant within the first couple of weeks in order to see a functional effect, " Anderson says. But Anderson's research on rodents suggests that it might be possible to have an impact on chronic injuries as well 3 . StemCells is enrolling patients who are 3 months to 12 months post-injury.…”