Efficient differentiation and integration of lineage-restricted neural precursors in the traumatically injured adult cat spinal cord.

Several recent studies have shown that highly undifferentiated neural stem cells (NSCs) grafted into the intact or injured adult spinal cord of animal either remain undifferentiated or show fate restriction to a astrocytic lineage. This indicates that functionally diverse roles expected of cellular replacement cannot be performed by the transplantation of highly immature precursors; rather, more differentiated or appropriate mixtures of more restricted neural precursors may be important in replacement strategies. In this study, we investigated the ability of lineage-restricted neural progenitors derived from adult mouse periventricular subependymal zone (SEZ) to integrate and differentiate into the chronically injured adult spinal cord. To this end, NSCs were grown as adherent cultures followed by expansion in non-adhesive dishes. This allowed us to grow NSCs as colonies of restricted neural precursors, illustrated by NCAM, nestin, Sox-2, A2B5, and GFAP immunostaining. The mixture of lineage-restricted precursors was directly implanted into the chronically injured spinal cord of immunosuppressed cats. The fate of the cells was traced with GFP fluorescence and immunocytochemistry for neural markers such as beta-III-tubulin, GFAP, and Ng2. After four weeks, transplanted cells survived, giving rise to neurons and in addition to cells with an astrocytic phenotype. We conclude that a mixture of more restricted neural precursors may be better suited than highly immature NSCs for neural replacement strategies after central nervous system (CNS) injuries.