Excitotoxic cell death induces delayed proliferation of endogenous neuroprogenitor cells in organotypic slice cultures of the rat spinal cord

The aim of the present report was to investigate whether, in the mammalian spinal cord, cell death induced by transient excitotoxic stress could trigger activation and proliferation of endogenous neuroprogenitor cells as a potential source of a lesion repair process and the underlying time course. Because it is difficult to address these issues in vivo, we used a validated model of spinal injury based on rat organotypic slice cultures that retain the fundamental tissue cytoarchitecture and replicate the main characteristics of experimental damage to the whole spinal cord. Excitotoxicity evoked by 1 h kainate application produced delayed neuronal death (40%) peaking after 1 day without further losses or destruction of white matter cells for up to 2 weeks. After 10 days, cultures released a significantly larger concentration of endogenous glutamate, suggesting functional network plasticity. Indeed, after 1 week the total number of cells had returned to untreated control level, indicating substantial cell proliferation. Activation of progenitor cells started early as they spread outside the central area, and persisted for 2 weeks. Although expression of the neuronal progenitor phenotype was observed at day 3, peaked at 1 week and tapered off at 2 weeks, very few cells matured to neurons. Astroglia precursors started proliferating later and matured at 2 weeks. These data show insult-related proliferation of endogenous spinal neuroprogenitors over a relatively brief time course, and delineate a narrow temporal window for future experimental attempts to drive neuronal maturation and for identifying the factors regulating this process. \ua9 2013 Macmillan Publishers Limited. All rights reserved

Multiscale 3D Genome Rewiring during Mouse Neural Development.

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Reaction of ependymal cells to spinal cord injury: a potential role for oncostatin pathway and microglial cells

Abstract Ependymal cells with stem cell properties reside in the adult spinal cord around the central canal. They rapidly activate and proliferate after spinal cord injury, constituting a source of new cells. They produce neurons and glial cells in lower vertebrates but they mainly generate glial cells in mammals. The mechanisms underlying their activation and their glial-biased differentiation in mammals remain ill-defined. This represents an obstacle to control these cells. We addressed this issue using RNA profiling of ependymal cells before and after injury. We found that these cells activate STAT3 and ERK/MAPK signaling during injury and downregulate cilia-associated genes and FOXJ1, a central transcription factor in ciliogenesis. Conversely, they upregulate 510 genes, six of them more than 20 fold, namely Crym, Ecm1, Ifi202b, Nupr1, Rbp1, Thbs2 and Osmr . OSMR is the receptor for the inflammatory cytokine oncostatin (OSM) and we studied its regulation and role using neurospheres derived from ependymal cells. We found that OSM induces strong OSMR and p-STAT3 expression together with proliferation reduction and astrocytic differentiation. Conversely, production of oligodendrocyte-lineage OLIG1 + cells was reduced. OSM is specifically expressed by microglial cells and was strongly upregulated after injury. We observed microglial cells apposed to ependymal cells in vivo and co-cultures experiments showed that these cells upregulate OSMR in neurosphere cells. Collectively, these results support the notion that microglial cells and OSMR/OSM pathway regulate ependymal cells in injury. In addition, the generated high throughput data provides a unique molecular resource to study how ependymal cell react to spinal cord lesion