Therapeutically targeting astrocytes with stem and progenitor cell transplantation following traumatic spinal cord injury

Replacement of lost and/or dysfunctional astrocytes via multipotent neural stem cell (NSC) and lineage-restricted neural progenitor cell (NPC) transplantation is a promising therapeutic approach for traumatic spinal cord injury (SCI). Cell transplantation in general offers the potential to replace central nervous system (CNS) cell types, achieve remyelination, deliver missing gene products, promote and guide axonal growth, modulate the host immune response, deliver neuroprotective factors, and provide a cellular substrate for bridging the lesion site, amongst other possible benefits. A host of cell types that differ in their developmental stage, CNS region and species of derivation, as well as in their phenotypic potential, have been tested in a variety of SCI animal models. Historically in the SCI field, most pre-clinical NSC and NPC transplantation studies have focused on neuronal and oligodendrocyte replacement. However, much less attention has been geared towards targeting astroglial dysfunction in the inured spinal cord, despite the integral roles played by astrocytes in both normal CNS function and in the diseased nervous system. Despite the relative lack of studies, cell transplantation-based targeting of astrocytes dates back to some of the earliest transplant studies in SCI animal models. In this review, we will describe the history of work involving cell transplantation for targeting astrocytes in models of SCI. We will also touch on the current state of affairs in the field, as well as on important future directions as we move forward in trying to develop this approach into a viable strategy for SCI patients. Practical issues such as timing of delivery, route of transplantation and immunesuppression needs are beyond the scope of this review. This article is part of a Special Issue entitled SI: Spinal cord injury.