Ischemic injury leeds to sequence of pathophysiological events, which are accompanied by a release of growth factors and morphogens that significantly affect cell proliferation, migration and also their differentiation. Following ischemia, besides enhanced neurogenesis and gliogenesis in subventricular zone of the lateral ventricles and gyrus dentatus of the hippocampus, neurogenesis/gliogenesis also occurs in non-neurogenic regions, such as cortex or striatum. Recently, the attention was turned to a new glial cell type, termed polydendrocytes or NG2 glia. Under physiological conditions, these cells are able to divide and differentiate into mature oligodendrocytes due to they have often been equated with oligodendrocyte precursor cells. Based on recent reports, polydendrocytes are also able to generate protoplasmic astrocytes (Zhu et al., 2008) and neurons in vitro (Belachew et al., 2003), however their ability to differentiate into astrocytes or neurons under physiological or pathological conditions is still highly debated. Therefore, we have investigated the effect of different growth factors and morphogens, specifically brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and a morphogen sonic hedgehog (Shh), on...

NG2-glia, a fourth major glial cell population, were shown to posses wide proliferation and differentiation potential in vitro and in vivo, therefore the aim of this study was to compare the rate of proliferation and differentiation potential of NG2-glia after different types of brain injuries, such as global and focal cerebral ischemia (GCI, FCI) or stab wound (SW), as well as during aging. Moreover, we aimed to determine the role of Sonic hedgehog (Shh) in NG2-glia proliferation/differentiation after FCI. We used transgenic mice, in which tamoxifen triggers the expression of red fluorescent protein (tdTomato) in NG2-glia and cells derived therefrom. Proliferation and differentiation potential of tdTomato+ cells in sham operated animals (controls) and those after injury were determined by immunohistochemistry employing antibodies against proliferating cell nuclear antigen and glial fibrillary acidic protein. FCI was induced by middle cerebral artery occlusion, GCI by carotid occlusion with hypotension and SW by sagittal cortical cut. Shh signaling in vivo was activated or inhibited by Smoothened agonist or Cyclopamine, respectively. Compared to controls, the proliferation rate of tdTomato+ cells was increased after all types of injuries, while it declined in aged mice (15-18- months-old) after...

Schizophrenia is a neurological disorder with a complex psychopathology, which is far from fully elucidated. In the patients with this disorder, changes on anatomical, cellular, and neurotransmitter level have been found. The aim of this work is to elucidate the function of specific ionotropic glutamate receptors in NG2 glia in the hippocampus of a mouse model of schizophrenia. For this purpose, a mouse model of schizophrenia was generated and validated using immunohistochemistry and behavioural testing. Mice with NG2 glia labelled by a fluorescent protein with a calcium indicator also in NG2 glia were used to observe the activity of glutamate channels and the properties of the extracellular space in these mice. Changes were found in the schizophrenic animals when compared to control animals in the numbers of hippocampal oligodendrocyte lineage cells, in prepulse inhibition and in both volume fraction and tortuosity of the extracellular space in hippocampus. Moreover, the percentage of cells responding to glutamate receptor agonists in NG2 glia in hippocampus also differed significantly between the schizophrenic and the control animals. In conclusion, it can be said that we were able to observe significant changes in the mouse model of schizophrenia that we generated in comparison to control...

Polydendrocytes, or NG2 glia, are fourth type of glial cells in mammal central nervous system. In the adult brain, NG2 glia represent important cell type with respect to their role in gliogenesis and nervous tissue regeneration following injury. Ligands from the Wingless/Int (Wnt) family play key role in proliferation and differentiation of NG2 glia and they can also influence regeneration of nervous tissue after ischemia. The aim of this thesis was to elucidate the role of NG2 glia in neurogenesis and gliogenesis following ischemic brain injury and investigate the impact of Wnt signalling on the reaction of NG2 glia to this type of injury. To fulfil these aims, transgenic mouse strains with tamoxifen-inducible recombination, that enabled simultaneous expression of red fluorescent dye and either activation or inhibition of the Wnt signalling pathway in NG2 glia, were employed. To induce ischemic injury, middle cerebral artery occlusion model was used. Changes in differentiation and electrophysiological properties of NG2 glia were analysed using patch-clamp technique. Activation of the Wnt signalling pathway under physiological conditions and 7 days after ischemic injury led to increased differentiation of NG2 glia toward astrocytes, while 3 days after ischemic injury activation of this signalling...

Glutamate is the main excitatory neurotransmitter in the mammalian brain and its transmission is responsible for higher brain functions, such as learning, memory and cognition. Glutamate action is mediated by a variety of glutamate receptors, though their properties were until now studied predominantly in neurons. Glutamate receptors are expressed also in NG2-glia, however their role under physiological conditions as well as in pathological states of the central nervous system is not fully understood. The aim of this work is to elucidate the presence, composition and function of these receptors in NG2-glia under physiological conditions and following focal cerebral ischemia. For this purpose we used transgenic mice, in which NG2-glia are labeled by a fluorescent protein for their precise identification. To analyze the expression pattern of glutamate receptors in NG2-glia we employed single-cell RT-qPCR. Furthermore, we used calcium imaging to characterize their functional properties.

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