Transplantation of Neural Progenitors and V2a Interneurons after Spinal Cord Injury

Abstract

There is growing interest in the use of neural precursor cells to treat spinal cord injury (SCI). Despite extensive pre-clinical research, it remains unclear as to which donor neuron phenotypes are available for transplantation, whether the same populations exist across different sources of donor tissue (e.g., developing tissue vs. cultured cells), and whether donor cells retain their phenotype once transplanted into the hostile internal milieu of the injured adult spinal cord. In addition, while functional improvements have been reported after neural precursor transplantation post-SCI, the extent of recovery is limited and variable. The present work begins to address these issues by harnessing ventrally derived excitatory pre-motor V2a spinal interneurons (SpINs) to repair the phrenic motor circuit after cervical SCI. Recent studies have demonstrated that Chx10-positive V2a SpINs contribute to anatomical plasticity within the phrenic circuitry after cervical SCI, thus identifying them as a therapeutic candidate. Building upon this discovery, the present work tests the hypothesis that transplantation of neural progenitor cells (NPCs) enriched with V2a INs can contribute to neural networks that promote repair and enhance respiratory plasticity after cervical SCI. Cultured NPCs (neuronal and glial restricted progenitor cells) isolated from E13.5 Green fluorescent protein rats were aggregated with TdTomato-mouse embryonic stem cell-derived V2a INs in vitro, then transplanted into the injured cervical (C3-4) spinal cord. Donor cells survive, differentiate and integrate with the host spinal cord. Functional diaphragm electromyography indicated recovery 1 month following treatment in transplant recipients. Animals that received donor cells enriched with V2a INs showed significantly greater functional improvement than animals that received NPCs alone. The results from this study offer insight into the neuronal phenotypes that might be effective for (re)establishing neuronal circuits in the injured adult central nervous system.

Plasticity Induced Recovery of Breathing Occurs at Chronic Stages after Cervical Contusion

“…For example, the recruitment of V2a interneurons has been shown critical in rat and mouse models of cervical SCI to the promotion of respiratory function. [66][67][68] Nonetheless, these findings demonstrate that CSPG digestion and the induction of plasticity within the PMP at both sides of the spinal cord facilitates alterations in serotonergic fibre growth (through either, or both, sprouting or sparing of pathways) which facilitate recovery of function within the damaged respiratory motor system. Through application of ChABC, respiratory motor recovery was partially mediated by pathways through the site of injury.…”

Application of stem cells and chitosan in the repair of spinal cord injury

“…Among these two stem cells, NSCs seem to be advantageous in regenerative medicine approach for curing SCI and have the potential of migrating, proliferating and differentiating into neurons and glial cells (Curtis et al, 2018;Carelli et al, 2014;Liu et al, 2019). Thus, NSCs have been chosen as the vintage stem cell source for curing SCI without serious adverse events (Zholudeva et al, 2019;Spruance et al, 2018;Bagher et al, 2018).On the other hand, MSCs have also attracted attention significantly as an another stem cell candidate to provide regenerated cells in the injury tissues than the NSCs, due to the ease of harvest, high proliferation and autologous transplantation properties (Gruber et al, 2012). Investigation on MSCs transplantation therapy has been focused on multimodal therapeutic effects in SCI, including the remyelination of axon fibers (Morita et al, 2016), axonal sprouting (Sasaki et al, 2009;Kuh et al, 2005) and neuroprotection (Morita et al, 2016;Sasaki et al, 2009).…”

Choosing the right cell for spinal cord repair

“…Like the tissue transplants, cultured neural progenitors restored tissue continuity and enhanced repair. But an important consideration is that preparing tissue in this more clinically relevant way may also alter their developing neuronal phenotype (Zholudeva, Iyer, et al, 2018a). …”

“…Ventrally derived developing spinal cord is typically considered to comprise neurons with motor functions, while dorsal tissue is more closely associated with sensory functions (Lu, Niu, & Alaynick, 2015). For this reason, and due to the potentially more limited efficacy seen with transplantation of dorsally derived donor tissues, there is growing interest in ventrally-derived phenotypes for spinal cord repair (Brock, Graham, Staufenberg, Im, & Tuszynski, 2018; Spruance et al, 2018; Zholudeva, Iyer, et al, 2018a). …”

“…They have been shown to contribute to anatomical (Zholudeva, Karliner, Dougherty, & Lane, 2017) and functional (Romer et al, 2016) plasticity in respiratory neural circuits and play a role in locomotor central pattern generator circuits (Dougherty & Kiehn, 2010; Hayashi et al, 2018). More recently, we have shown that enriching donor cells with stem cell derived V2a interneurons can enhance the extent of motor recovery within an anatomically and functionally defined spinal network—the phrenic motor system (Zholudeva, Iyer, et al, 2018a). …”