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Bioluminescence Imaging of Olig2‐Neural Stem Cells Reveals Improved Engraftment in a Demyelination Mouse Model

A major issue in the potential application of neural stem cell (NSC)‐based cell replacement therapy for demyelinating diseases is the question of the survival, functional behavior, and stability of implanted NSC‐derived oligodendrocyte precursor cells (OPCs) over an extended period. To address this issue, we employed bioluminescence imaging (BLI) as a noninvasive longitudinal in vivo monitoring technique and followed the fate of NSCs isolated from luciferase–green fluorescent protein–actin transgenic mice after stereotactic implantation in the demyelinated corpus callosum of cuprizone‐fed mice. We compared normal NSCs with NSCs that were primed to become OPCs by the induction of Olig2 overexpression (Olig2‐NSCs). BLI, validated by immunohistochemistry, revealed that, after a steep cell loss after implantation during the first 3 weeks, approximately 10% of the Olig2‐NSCs stably survived for 2 months after implantation, in contrast to <1% of the normal NSCs. Immunohistochemistry, at the light and electron microscopic levels, revealed that the majority of the surviving Olig2‐NSCs had differentiated into an oligodendrocytic cell lineage and contributed to remyelination of axons in the corpus callosum. The number of axons remyelinated by the implanted cells, however, was a small fraction of the total number of axons remyelinated by endogenous oligodendrocytes. Apparently, most of the implanted NSCs did not survive the transition into an inappropriate non‐neurogenic niche, compressed by surrounding host tissue, in hostile, inflammatory conditions created by activated microglia. Only the ones that managed to differentiate rapidly into a mature neural cell type and become functionally integrated survived. STEM CELLS 2009;27:1582–1591