| Traumatic spinal cord injury (SCI) is characterized by a loss of neurons and oligodendrocytes, axonal injury, and demyelination/dysmyelination of spared axons. Transplantation to replace lost cells or create a more growth permissive environment may be a potential therapeutic for SCI. Human neural stem cells (hCNS-SCns) were isolated from fetal brain, grown as neurospheres, and lineage restricted to generate neurons, oligodendrocytes and astrocytes. hCNS-SCns transplanted sub-acutely following SCI survived, differentiated predominantly to oligodendrocytes, and promoted improved recovery in NOD- scid mice. The goal of this dissertation was to investigate how various aspects of the SCI microenvironment including; timing, different rodent species, immunological environments, and location can influence transplanted hCNS-SCns engraftment, differentiation, and promotion of locomotor recovery.;The first aim investigated hCNS-SCns transplantation into early chronic SCI, 30-days post-injury (dpi), in NOD-scid mice. Transplanted hCNS-SCns engrafted, differentiated predominantly to oligodendrocytes and neurons, and promoted improved recovery, suggesting that NSC transplantation can be successful beyond the sub-acute time window.;The second aim investigated sub-acute hCNS-SCns transplantation into the injury epicenter of immunosuppressed rats. 66% of transplanted animals engrafted, differentiating predominantly into astrocytes or remaining undifferentiated. Transplanted hCNS-SCns did not promote improved recovery, suggesting that transplanted hCNS-SCns that differentiate predominantly to astrocytes neither exert beneficial nor detrimental effects on locomotor recovery.;The third aim compared sub-acute hCNS-SCns transplantation parenchymally (r/c) vs. directly into the injury epicenter (epi) in immunodeficient rats. 95% of animals engrafted, ∼500% of r/c and ∼250% of epi hCNS-SCns initially transplanted were quantified revealing significantly more in r/c transplanted animals. hCNS-SCns differentiated predominantly to oligodendrocytes (∼50%), astrocytes (∼40%), and fewer than 10% to neurons. Surprisingly, the site of transplantation did not affect differentiation.;The fourth aim investigated chronic transplantation (60-dpi) in immunodeficient rats. 73% of hCNS-SCns transplanted animals engrafted, differentiating into oligodendrocytes and astrocytes. hCNS-SCns transplanted animals exhibited improved recovery suggesting that chronic transplantation can be successful.;Transplanted hCNS-SCns survived, differentiated, and promoted improved locomotor recovery in different injury microenvironments including chronic time-points post-injury expanding the "window of opportunity" for intervention. Furthermore, the injury microenvironment influences transplanted hCNS-SCns survival, fate, and ability to promote locomotor recovery. |
