Proliferative cells in the rat developing neocortical grey matter: new insights into gliogenesis
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The postnatal brain development is characterized by a substantial gain in weight and size, ascribed to increasing neuronal size and branching, and to massive addition of glial cells. This occurs concomitantly to the shrinkage of VZ and SVZ, considered to be the main germinal zones, thus suggesting the existence of other germinative niches. The aim of this study is to characterize the cortical grey matter proliferating cells during postnatal development, providing their stereological quantification and identifying the nature of their cell lineage. We performed double immunolabeling for the proliferation marker Ki67 and three proteins which identify either astrocytes (S100β) or oligodendrocytes (Olig2 and NG2), in addition to a wider panel of markers apt to validate the former markers or to investigate other cell lineages. We found that proliferating cells increase in number during the first postnatal week until P10 and subsequently decreased until P21. Cell lineage characterization revealed that grey matter proliferating cells are prevalently oligodendrocytes and astrocytes along with endothelial and microglial cells, while no neurons have been detected. Our data showed that astrogliogenesis occurs prevalently during the first 10 days of postnatal development, whereas contrary to the expected peak of oligodendrogenesis at the second postnatal week, we found a permanent pool of proliferating oligodendrocytes enduring from birth until P21. These data support the relevance of glial proliferation within the grey matter and could be a point of departure for further investigations of this complex process.
KeywordsProliferating cells Ki67 Gliogenesis Cerebral cortex Grey matter Postnatal development
We thank Prof. S. Kaplan (Ondokuz Mayıs University: Samsun, Turkey) for advice about stereological count and Dr R. Spreafico, Dr R. Garbelli and Dr M. de Curtis for critical reading of the manuscript. Furthermore, we are grateful to Dr W. Stallcup for NG2 antibody. This work was supported by grants from the Italian Ministry of Health and ERANET-NEURON JCT 2015 ImprovVision.
Compliance with ethical standards
All the experiments were performed in accordance with the guidelines defined by the European Communities Council Directive (2010/63/EU) and the experimental protocol was approved by the Ethics Committee of the Italian Ministry of Health (authorization number 143-2016-PR). All efforts were made to limit the number of animals used and their suffering.
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