A Combinatorial Approach to Promote Regeneration after Spinal Cord injury via Biomaterials, Neural stem cells, and Immunomodulation

Spinal cord injury (SCI) disrupts the blood-spinal cord barrier, allowing immune cells to infiltrate spinal cord tissue and further exacerbating the injury. This causes CNS cell death, axonal dieback, demyelination, and build-up of inhibitory factors that limit axonal and myelin regeneration. Several decades of extensive SCI research have made it clear that this complex problem requires combinatorial solutions. This dissertation investigates three therapeutic approaches for SCI: (A) implantation of multi-channel poly (lactide-co-glycolide) (PLG) biomaterial that can bridge the defect and guide axonal growth through inhibitory barriers; (B) human Neural Stem Cell (hNSC) transplantation to replenish lost CNS cells and to myelinate regenerating axons; and (C) expression of anti-inflammatory cytokines like interleukin-10 (IL-10) to modulate the SCI inflammatory milieu and offer neuroprotection. The first chapter introduces the conceptual background for these studies. The second chapter investigates the combination of acute PLG bridge implantation and chronic hNSC transplantation for SCI. Highlights of this chapter include enhancement of hNSC engraftment, hNSC migration along regenerated axons growing into the bridge, hNSC differentiation into oligodendrocytes and myelinating host axons, hNSC-derived neurons integrating into mouse neural circuitry, and improvement in motor recovery. Additionally, I show novel evidence supporting the formation of a synaptic circuit connecting corticospinal neurons in the motor cortex and the forelimb neuromuscular junction via the PLG bridge. This study highlights the significance of a guided bridge conduit in the injury site to reestablish lost connections and hNSC transplantation to myelinate the spared and regenerated circuitry and unleash the full potential of hNSC-based regenerative therapies. The third chapter investigates the effect of localized lentiviral expression of IL-10 with or without PLG bridge implantation on outcomes after spinal cord injury. Highlights of this chapter include: IL-10 modulates the inflammatory microenvironment and significantly enhances regeneration and myelination in the PLG bridge, and this combined approach resulted in a synergistic improvement in motor recovery. Additionally, using transsynaptic PRV tracing, I demonstrate the bridge supports the rewiring of spinal neuronal circuitry from the motor cortex and PVN of the hypothalamus and further enhancement in PVN circuitry with IL-10 delivery