Damage-related changes in the cerebellum of juvenileOncorhynchus masou: reactivation of neurogenic niches and astrocytic response

Abstract

10In the cerebellum of juvenile Oncorhynchus masou, proliferating BrdU+ and HuCD+ cells and 11 constitutive neurogenic niches were detected in different zones; the largest number of labeled 12 cells were found in the dorsal part of the molecular layer and the dorsal matrix zone (DMZ). 13Cells labeled with glutamine synthetase (GS) and radial glia were also present in the intact O. 14 masou cerebellum. The most intensive proliferation was detected in the rostral part of 15 cerebellum. This part is assumed to contain active zones of constitutive neurogenesis. After an 16 injury inflicted to the cerebellum, the number of BrdU+ and HuCD+ cells increased 17 significantly. The number of BrdU+ cells after this type of injury was much greater than after a 18 telencephalon trauma. A quantitative analysis revealed that after the cerebellum injury the 19 proliferative activity in the caudal part of CCb is increased compared to that in the control. A 20 reactivation of neurogenic and neuroepithelial niches and their transformation into reactive 21 neurogenic domains, with an increased distribution density of intensely labeled HuCD+ cells of 22 different types, were observed. The increase in the number of HuCD+ differentiated cells in the 23 basal area suggests that the processes of neuronal differentiation are intensified in the cerebellum 24 of juvenile O. masou after injury. The number of GS positive cells (GS+) and fibers increased in 25 all the zones of cerebellum. The most intensive astrocytic response was noted in the dorsal part 2 26 of cerebellum. The data of the enzyme immunoassay confirm the multiple variations in the level 27 of GS after a traumatic injury to cerebellum in O. masou. 28

Proliferation, Adult Neuronal Stem Cells and Cells Migration in Pallium during Constitutive Neurogenesis and after Traumatic Injury of Telencephalon of Juvenile Masu Salmon, Oncorhynchus masou

“…Studies on medaka brain have also shown that in optic tectum, as a part of proliferative populations, aNSCs are actually neuroepithelial-like stem/progenitor cells and are not radial glial cells [4]. Similar results were obtained in other studies on fish brain, in particular, optic tectum [16], mesencephalic tegmentum [14], and cerebellum [13,17].…”

“…The brain of an adult fish is a site of continuous intense proliferative activity, not limited only to the telencephalon [12]. In some areas of proliferation in the brain, tissue-specific stem cells have a neuroepithelial phenotype rather than radial glial characteristics [5,13]. Studies on juvenile salmon fish showed that in the cerebellum of O. masou [13] and in the mesencephalic tegmentum of the chum salmon Oncorhynchus keta [14], most aNSCs have a neuroepithelial phenotype.…”

“…In some areas of proliferation in the brain, tissue-specific stem cells have a neuroepithelial phenotype rather than radial glial characteristics [5,13]. Studies on juvenile salmon fish showed that in the cerebellum of O. masou [13] and in the mesencephalic tegmentum of the chum salmon Oncorhynchus keta [14], most aNSCs have a neuroepithelial phenotype. Such cells divide symmetrically, constantly increasing the pool of neural precursors, which subsequently form neurons, glia-like cells, and ependymal cells that form the CNS [7].…”

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

“…Studies on the PCNA localization in the cerebellum of O. masou showed that the patterns of constitutive proliferation were local, small in size, CNNs located in the area of the DMZ, as well as in the molecular layer of all neuroanatomical zones [ 68 ]. The patterns of neurogenesis, revealed using the protein marker of neuronal differentiation HuCD, showed that in intact juveniles the HuCD+ cells are localized within the CNNs of the neuroepithelial type [ 13 ]. According to the data obtained on mammals, a high CBS concentration is necessary for the early maturation and growth of neuronal networks, which indicates the involvement of H 2 S in neuronal differentiation [ 85 ].…”

“…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 ].…”