Neural Stem Cells/Neuronal Precursor Cells and Postmitotic Neuroblasts in Constitutive Neurogenesis and After ,Traumatic Injury to the Mesencephalic Tegmentum of Juvenile Chum Salmon, Oncorhynchus keta

Abstract

The proliferation of neural stem cells (NSCs)/neuronal precursor cells (NPCs) and the occurrence of postmitotic neuroblasts in the mesencephalic tegmentum of intact juvenile chum salmon, Oncorhynchus keta, and at 3 days after a tegmental injury, were studied by immunohistochemical labeling. BrdU+ constitutive progenitor cells located both in the periventricular matrix zone and in deeper subventricular and parenchymal layers of the brain are revealed in the tegmentum of juvenile chum salmon. As a result of traumatic damage to the tegmentum, the proliferation of resident progenitor cells of the neuroepithelial type increases. Nestin-positive and vimentin-positive NPCs and granules located in the periventricular and subventricular matrix zones, as well as in the parenchymal regions of the tegmentum, are revealed in the mesencephalic tegmentum of juvenile chum salmon, which indicates a high level of constructive metabolism and constitutive neurogenesis. The expression of vimentin and nestin in the extracellular space, as well as additionally in the NSCs and NPCs of the neuroepithelial phenotype, which do not express nestin in the control animals, is enhanced during the traumatic process. As a result of the proliferation of such cells in the post-traumatic period, local Nes+ and Vim+ NPCs clusters are formed and become involved in the reparative response. Along with the primary traumatic lesion, which coincides with the injury zone, additional Nes+ and Vim+ secondary lesions are observed to form in the adjacent subventricular and parenchymal zones of the tegmentum. In the lateral tegmentum, the number of doublecortin-positive cells is higher compared to that in the medial tegmentum, which determines the different intensities and rates of neuronal differentiation in the sensory and motor regions of the tegmentum, respectively. In periventricular regions remote from the injury, the expression of doublecortin in single cells and their groups significantly increases compared to that in the damage zone.

Hydrogen Sulfide Modulates Adult and Reparative Neurogenesis in the Cerebellum of Juvenile Masu Salmon, Oncorhynchus masou

“…Their ontogenesis is characterized by such phenomena as developmental delay and retention of signs of the embryonic organization of CNS which occur at the stage of active brain growth, where the morphogenesis processes are most clearly and fully expressed [ 11 ]. This feature of salmon CNS development, referred to as embrionalization, is confirmed by the presence of a large number of embryonic neuronal stem cells (NSCs) corresponding to cells of the neuroepithelial (NE) type, as well as radial glial (RG) cells corresponding to adult progenitors [ 12 , 13 , 14 , 15 ].…”

“…It has been shown that in the proliferative zones of the telencephalon of juvenile O. masou [ 15 ] and the mesencephalic tegmentum of juvenile chum salmon O. keta [ 14 ], vimentin is present in NE cells and is not detected in the RG of intact animals. Studies of the immunolabeling of nestin in the tegmentum of juvenile O. keta have also shown its presence in NE cells located both in the periventricular zone (PVZ) and in the tegmental parenchyma, as well as the presence of widespread Nes+ granules in the mesencephalic reticular formation in intact juvenile chum salmon [ 14 ]. After a traumatic brain injury (TBI), Vim+ RG appears in the telencephalon of juvenile O. masou and O. keta and is absent in intact animals [ 14 ].…”

“…Studies of the immunolabeling of nestin in the tegmentum of juvenile O. keta have also shown its presence in NE cells located both in the periventricular zone (PVZ) and in the tegmental parenchyma, as well as the presence of widespread Nes+ granules in the mesencephalic reticular formation in intact juvenile chum salmon [ 14 ]. After a traumatic brain injury (TBI), Vim+ RG appears in the telencephalon of juvenile O. masou and O. keta and is absent in intact animals [ 14 ]. Studies on D. rerio have shown Vim expression predominantly in neurons at the initial stage of differentiation and, possibly, in glial cells found in various brain regions [ 28 ].…”

“…In D. rerio , as in mice, the nestin expression is retained in neurogenic niches containing NSCs and proliferating NPCs [ 3 , 42 , 43 , 44 ]. Studies on the localization of nestin after a tegmentum injury in juvenile chum salmon showed a significant increase in Nes+ NE cells that form local post-traumatic foci, as well as in RG fibers, which were not detected in intact juveniles [ 14 ]. After a TBI of the tegmentum in juvenile O. keta , patterns of granular localization of nestin, which form zones adjacent to the damaged area, were also revealed [ 14 ].…”

“…Studies on the localization of nestin after a tegmentum injury in juvenile chum salmon showed a significant increase in Nes+ NE cells that form local post-traumatic foci, as well as in RG fibers, which were not detected in intact juveniles [ 14 ]. After a TBI of the tegmentum in juvenile O. keta , patterns of granular localization of nestin, which form zones adjacent to the damaged area, were also revealed [ 14 ]. Thus, taking into account the heterogeneous composition of constitutive and reactive neurogenic zones in the tegmentum of juvenile salmonids, as well as the heterogeneous pattern of NSCs/NPCs labeling using nestin and vimentin, one of the objectives of this study was to determine the molecular phenotypes of NSCs/NPCs using these two markers in the cerebellum of juvenile O. masou .…”