Characterization of Neuronal Progenitor Cells of the Neonatal Forebrain. In: Gage FH, Christen Y, editors. Isolation, Characterization and Utilization of CNS Stem Cells. Berlin: Springer Berlin Heidelberg; 1997. pp. 67-86. [DOI: 10.1007/978-3-642-80308-6_5]

Transplantation of motoneuron-enriched neural cells derived from mouse embryonic stem cells improves motor function of hemiplegic mice

Embryonic stem (ES) cells are expected to be a potential donor source for neural transplantation. We have obtained motoneuron-enriched neural progenitor cells by culturing mouse ES cells with retinoic acid (RA). The cells also expressed mRNA of a neurotrophic factor, neurotrophin-3 (NT-3). The left motor cortex area of mice was damaged by cryogenic brain injury, and the neural cells were transplanted underneath the injured motor cortex, neighboring to the paraventricular region. We found that the cells expressing neuronal phenotypes not only remained close to the implantation site, but also exhibited substantial migration penetrating into the damaged lesion, in a seemingly directed manner up to cortical region. We found that some of the neural cells differentiated into Islet1-positive motoneurons. It seems likely that the ability of the ES cell-derived neural progenitor cells to respond in vivo to guidance cues and signals that can direct their migration and differentiation may contribute to functional recovery of the recipient mice. We found that an "island of the mature neuronal cells" of recipient origin emerged in the damaged motor cortex. This may be associated with the neuroprotective effects of the ES cell-derived neural cells. The ES cells differentiated into CD31+ vasculoendothelial cells with the RA treatment in vitro. Furthermore, the grafted cells may provide sufficient neurotrophic factors such as NT-3 for neuroprotection and regeneration. The grafted neural cells that migrated into residual cortex and differentiated into neurons had purposefully elongated axons that were stained with anti-neurofilament middle chain (NFM) antibody. Our study suggests that motoneurons can be induced from ES cells, and ES cells become virtually an unlimited source of cells for experimental and clinical neural cell transplantation.

Insulin-like growth factor-1 is a radial cell-associated neurotrophin that promotes neuronal recruitment from the adult songbird edpendyma/subependyma

In the adult songbird forebrain, neurons continue to be produced from precursor cells in the forebrain ependymal/subependymal zone (SZ), from which they migrate upon radial guide fibers. The new neurons and their radial cell partners may coderive from a common SZ progenitor, which may be the radial cell itself. On this basis, we asked whether radial cells might provide trophic support for the migration or survival of newly generated neurons. We focused upon the insulin-like growth factors (IGFs) IGF-1 and IGF-2, which have previously been shown to support the survival and differentiation of neural progenitor cells. We found that IGF-1 immunoreactivity was expressed heavily by adult zebra finch radial cells and their fibers, with little expression otherwise. IGF-2, in contrast, was expressed by parenchymal astrocytes and exhibited little radial cell expression. Despite their distinct distributions, IGF-1 and IGF-2 exerted similar trophic effects on finch SZ cells in vitro; both greatly increased the number of neurons migrating from explants of the adult finch SZ, relative to explants raised in low-insulin, IGF-1-deficient media. However, neither factor extended neuronal survival. These results suggest that in neurogenic regions of the adult avian forebrain, IGF-1 acts as a radial cell-associated neuronal differentiation and/or departure factor, which may serve to regulate neuronal recruitment into the adult brain.