Implantation of a collagen scaffold seeded with adult rat hippocampal progenitors in a rat model of penetrating brain injury.

Penetrating brain injury (PBI) is a complex central nervous system injury in which mechanical damage to brain parenchyma results in hemorrhage, ischemia, broad areas of necrosis, and eventually cavitation. The permanent loss of brain tissue affords the possibility of treatment using a biomaterial scaffold to fill the lesion site and potentially deliver pharmacological or cellular therapeutic agents. The administration of cellular therapy may be of benefit in both mitigating the secondary injury process and promoting regeneration through replacement of certain cell populations. This study investigated the survival and differentiation of adult rat hippocampal neural progenitor cells delivered by a collagen scaffold in a rat model of PBI. The cell-scaffold construct was implanted 1 week after injury and was observed to remain intact with open pores upon analysis 4 weeks later. Implanted neural progenitors were found to have survived within the scaffold, and also to have migrated into the surrounding brain. Differentiated phenotypes included astrocytes, oligodendrocytes, vascular endothelial cells, and possibly macrophages. The demonstrated multipotency of this cell population in vivo in the context of traumatic brain injury has implications for regenerative therapies, but additional stimulation appears necessary to promote neuronal differentiation outside normally neurogenic regions.