Growth Factor Treatment and Genetic Manipulation Stimulate Neurogenesis and Oligodendrogenesis by Endogenous Neural Progenitors in the Injured Adult Spinal Cord

Division of Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio 45229-3039, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 12/2006; 26(46):11948-60. DOI: 10.1523/JNEUROSCI.3127-06.2006
Source: PubMed


Neurons and oligodendrocytes are highly vulnerable to various insults, and their spontaneous replacement occurs to only a limited extent after damage in the adult spinal cord. The environment of injured tissue is thus thought to restrict the regenerative capacity of endogenous neural stem/progenitor cells; strategies for overcoming such restrictions remain to be developed. Here, we combined growth factor treatment and genetic manipulation to stimulate neurogenesis and oligodendrogenesis by endogenous progenitors in vivo. The recombinant retrovirus pMXIG, which was designed to coexpress green fluorescent proteins (GFPs) and a neurogenic/gliogenic transcription factor, was directly injected into the injured spinal cord parenchyma to manipulate proliferative cells in situ. We found that cells expressing Olig2, Nkx2.2, and NG2 were enriched among virus-infected, GFP-positive (GFP+) cells. Moreover, a fraction of GFP+ cells formed neurospheres and differentiated into neurons, astrocytes, and oligodendrocytes in vitro, demonstrating that GFP retroviruses indeed infected endogenous neural progenitors in vivo. Neuronal differentiation of control virus-infected cells did not occur at a detectable level in the injured spinal cord. We found, however, that direct administration of fibroblast growth factor 2 and epidermal growth factor into lesioned tissue could induce a significant fraction of GFP-labeled cells to express immature neuronal markers. Moreover, retrovirus-mediated overexpression of the basic helix-loop-helix transcription factors Neurogenin2 and Mash1, together with growth factor treatment, enhanced the production and maturation of new neurons and oligodendrocytes, respectively. These results demonstrate that endogenous neural progenitors can be manipulated to replace neurons and oligodendrocytes lost to insults in the injured spinal cord.

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    • "In contrast to mammals (Ohori et al., 2006; Su et al., 2014), the CNS of fishes and salamanders regenerates neurons after injury. Ependymo-radial glial cells (ERGs), with a soma forming the ventricular ependyma and radial processes reaching the pial surface , are the likely progenitors (reviewed in Becker and Becker, 2015; Berg et al., 2013; Kizil et al., 2012a). "
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    ABSTRACT: In contrast to mammals, zebrafish regenerate spinal motor neurons. During regeneration, developmental signals are re-deployed. Here, we show that, during development, diffuse serotonin promotes spinal motor neuron generation from pMN progenitor cells, leaving interneuron numbers unchanged. Pharmacological manipulations and receptor knockdown indicate that serotonin acts at least in part via 5-HT1A receptors. In adults, serotonin is supplied to the spinal cord mainly (90%) by descending axons from the brain. After a spinal lesion, serotonergic axons degenerate caudal to the lesion but sprout rostral to it. Toxin-mediated ablation of serotonergic axons also rostral to the lesion impaired regeneration of motor neurons only there. Conversely, intraperitoneal serotonin injections doubled numbers of new motor neurons and proliferating pMN-like progenitors caudal to the lesion. Regeneration of spinal-intrinsic serotonergic interneurons was unaltered by these manipulations. Hence, serotonin selectively promotes the development and adult regeneration of motor neurons in zebrafish.
    Full-text · Article · Oct 2015 · Cell Reports
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    • "Indeed, soon after neurospheres could be grown from the adult SEZ and DG, several other CNS regions were probed for this capacity. Especially from rats, neurospheres can be grown from several brain regions and even the spinal cord (Grande et al., 2013; Ohori et al., 2006; Palmer et al., 1999). This seems to be rather different in the mouse where few if any neurospheres can be derived from other regions than the SEZ, DG, and the hypothalamus (see, e.g., Babu et al., 2007; Robins et al., 2013; Sirko et al., 2013). "
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    ABSTRACT: Here, we review the stem cell hallmarks of endogenous neural stem cells (NSCs) during development and in some niches of the adult mammalian brain to then compare these with reactive astrocytes acquiring stem cell hallmarks after traumatic and ischemic brain injury. Notably, even endogenous NSCs including the earliest NSCs, the neuroepithelial cells, generate in most cases only a single type of progeny and self-renew only for a rather short time in vivo. In vitro, however, especially cells cultured under neurosphere conditions reveal a larger potential and long-term self-renewal under the influence of growth factors. This is rather well comparable to reactive astrocytes in the traumatic or ischemic brain some of which acquire neurosphere-forming capacity including multipotency and long-term self-renewal in vitro, while they remain within their astrocyte lineage in vivo. Both reactive astrocytes and endogenous NSCs exhibit stem cell hallmarks largely in vitro, but their lineage differs in vivo. Both populations generate largely a single cell type in vivo, but endogenous NSCs generate neurons and reactive astrocytes remain in the astrocyte lineage. However, at some early postnatal stages or in some brain regions reactive astrocytes can be released from this fate restriction, demonstrating that they can also enact neurogenesis. Thus, reactive astrocytes and NSCs share many characteristic hallmarks, but also exhibit key differences. This conclusion is further substantiated by genome-wide expression analysis comparing NSCs at different stages with astrocytes from the intact and injured brain parenchyma. GLIA 2015. © 2015 The Authors. Glia Published by Wiley Periodicals, Inc.
    Preview · Article · May 2015 · Glia
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    • "The majority of the obtained cells expressed Sox2, nestin and Sox9, but neither glial fibrillary acidic protein (GFAP) nor oligodendrocyte transcription factor 2 (Olig2) (Fig. 3a and b). Several types of cells, oligodendrocyte precursors, astrocytes and ependymal cells, have been reported to be NSPs in the spinal cord21222526. Sox2, as well as nestin, is a common marker for those NSPs. GFAP is a marker for astrocytes. "
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    ABSTRACT: Inhibition of Nogo-66 receptor (NgR) can promote recovery following spinal cord injury. The ecto-domain of NgR can be phosphorylated by protein kinase A (PKA), which blocks activation of the receptor. Here, we found that infusion of PKA plus ATP into the damaged spinal cord can promote recovery of locomotor function. While significant elongation of cortical-spinal axons was not detectable even in the rats showing enhanced recovery, neuronal precursor cells were observed in the region where PKA plus ATP were directly applied. NgR1 was expressed in neural stem/progenitor cells (NSPs) derived from the adult spinal cord. Both an NgR1 antagonist NEP1-40 and ecto-domain phosphorylation of NgR1 promote neuronal cell production of the NSPs, in vitro. Thus, inhibition of NgR1 in NSPs can promote neuronal cell production, which could contribute to the enhanced recovery of locomotor function following infusion of PKA and ATP.
    Full-text · Article · May 2014 · Scientific Reports
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