|
|
Astrocyte volume changes in alpha-syntrophin deficient mice
Mikešová, Michaela ; Anděrová, Miroslava (advisor) ; Vargová, Lýdia (referee)
(EN) The formation of brain oedema, which accompanies ischemic or traumatic brain injuries, originates from a disruption of ionic/neurotransmitter homeostasis that leads to extracellular K+ elevation and neurotransmitter accumulation in the extracellular space. An increased uptake of these osmotically active substances, predominantly provided by astrocytes, is accompanied by intracellular water accumulation via aquaporin-4 (AQP4). Since it has been shown that the removal of perivascular AQP4 via the deletion of α- syntrophin, which is the protein responsible for anchoring AQP4 on the astrocytic membrane (Neely et al. 2001), delays oedema formation and K+ clearance (Amiry-Moghaddam et al. 2003), we aimed to elucidate how the alpha-syntrophin deletion affects astrocyte volume changes in the cortex during pathological states, such as hypoosmotic stress or oxygen- glucose deprivation (OGD), using three-dimensional (3D) confocal morphometry in situ. In order to visualize individual astrocytes that lack alpha-syntrophin, double transgenic mice (GFAP/EGFP/α-Syn-/- ) were generated by crossbreeding GFAP-EGFP mice with α- syntrophin knockout mice. 3D-confocal morphometry revealed that alpha-syntrophin deletion did not alter astrocyte swelling during hypoosmotic stress or their recovery in isotonic solution;...
|
|
|
Differentiation potential of polydendrocytes after focal cerebral ischemia
Filipová, Marcela ; Anděrová, Miroslava (advisor) ; Jendelová, Pavla (referee)
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...
|
|
|
Membrane Properties of Glial Cells after Ischemia in vivo
Pivoňková, Helena ; Anděrová, Miroslava (advisor) ; Vyklický, Ladislav (referee) ; Vlachová, Viktorie (referee)
In my PhD thesis, I aimed to characterize the membrane properties of astrocytes and NG2 glia during the acute and chronic phases of the ischemic injury in the central nervous system with a focus on the expression and activity of K+ ion channels. Two ischemia models in rats were used for the experiments - global cerebral ischemia 5 causing selective neuronal loss and astrogliosis in the CA1 region of the hippocampus, and incubation of spinal cord segments in a solution with high K+ concentration. We found that hippocampal astrocytes depolarize starting 3 days after ischemia, and demonstrate an increase in the inward rectification of their whole cell currents 1 month after ischemia. The Kir4.1 channel expression in the hippocampal tissue was downregulated starting 3 days after ischemia, while the expression of Kir2.1, Kir5.1 and TREK1 channels was strongly upregulated in reactive astrocytes 1 month after ischemia. NG2 glia displayed a significant increase in the outwardly rectifying delayed and A-type K+ (KDR and KA) currents 2 hours and 3 days after ischemia, and a decrease in the inwardly rectifying K+ currents 3 days after ischemia, a typical current pattern of proliferating cells. Complex astrocytes in the spinal cord pre-incubated in a solution with high [K+] showed the largest changes in their membrane...
|
|
|
Volume-regulated anion channels in astrocytes- in vitro and in situ analysis
Harantová, Lenka ; Anděrová, Miroslava (advisor) ; Vargová, Lýdia (referee)
Astrocytes need to preserve constant volume in the face of osmolarity perturbations to function properly. To regain their original volume after hyposmotically induced swelling, they extrude intracellular electrolytes and organic osmolytes, such as inorganic ions, excitative amino acids or polyols, accompanied by osmotically driven water. This process is termed regulatory volume decrease and is ensured by various ion channels and transporters. Recently, much attention has been focused on the ubiquitous volume-regulated anion channels activated by cell swelling. VRACs are moderately outwardly rectifying with intermediary conductance, permeable to inorganic anions and organic osmolytes and sensitive to broad-spectrum anion channels blockers. Using patch-clamp technique we aimed to characterize VRACs in cultured cortical astrocytes isolated from neonatal Wistar rats and to elucidate the effect of intracellular Na+ on VRAC activity. In addition, we also intended to characterize these channels in situ in brain slices of 10 - 12 days old rats, focusing mainly on hippocampal astrocytes. To induce astrocytic swelling, we exposed astrocytes to hypotonic solution (250 mOsm). In agreement with previous findings, we showed that cultured cortical astrocytes activate VRAC currents upon exposure to hypotonic stress, which...
|
|
| |
|
|
Vlastnosti a regulace objemově-závislých aniontových kanálů u astrocytů.
Harantová, Lenka ; Moravec, Jan (referee) ; Anděrová, Miroslava (advisor)
Animal cells need to preserve constant volume in the face of osmolarity perturbations to function properly. To regain their original volume after hyposmotically induced swelling, most cell types extrude intracellular electrolytes and organic osmolytes accompanied by osmotically driven water. This process is termed regulatory volume decrease and is ensured by various ion channels and transporters. Recently, much attention has been focused on the ubiquitous volume-regulated anion channels activated by cell swelling. VRACs are moderately outwardly rectifying with intermediary conductance, permeable to inorganic anions and organic osmolytes and sensitive to broad-spectrum anion channels blockers. Functional properties of VRACs in astrocytes are particularly interesting, because many brain pathologies, such as ischemia, traumatic brain injury or hyponatremia, are associated with marked astrocytic swelling and VRACs could thus constitute a possible target for therapy of cerebral edema. Furthermore, VRACs are thought to play a role in cell cycle progression, cell migration, apoptosis and intercellular communication. Despite intensive research, VRACs molecular identity and mechanism of their activation and regulation are still unclear. This work summarizes known facts about VRACs, accentuating their...
|
|
|
Astrocyte volume changes during brain ischemic injury
Mikešová, Michaela ; Zemková, Hana (referee) ; Anděrová, Miroslava (advisor)
Brain ischemic injury is a complex of pathophysiological events following transient or permanent reduction of brain blood flow. It results in a disruption of neuronal and astrocytic physiological functions, long-term reduction of brain blood flow leads to the cell death. Number of recent studies is focused on astrocytes, which might play key roles in surviving cells, including neurons, during ischemic injury. Astrocytes provide many important functions, such as maintenance of ionic homeostasis, prevention of excitotoxicity, scavenging free radicals and others and thus astrocytes may dramatically swell during ischemic conditions and contribute notably to the development of cytotoxic edema. This thesis summarizes mechanisms possibly contributing to the astrocytic swelling during brain ischemic injury as well as methods used for studying astrocyte volume changes and their quantification. Since the brain edema dramatically complicates both course and treatment of ischemic injury, knowledge of mechanisms leading to astrocytic swelling and their volume regulation during ischemia/reperfusion might be used for developing new therapeutic approaches for the treatment of cerebral ischemia, mainly for reduction of negative impact of edema.
|
|
|
Induction of neurogenesis and gliogenesis after ischemic injury of CNS
Filipová, Marcela ; Moravec, Jan (referee) ; Anděrová, Miroslava (advisor)
Ischemic injury (stroke) is one of the most common causes of death and disability in humans. Discovery of adult neurogenesis and possibilities to induce neurogenesis by cytokines brought new approaches and hopes in treating the ischemic lesion in future. The aim of this thesis is to describe cellular and molecular mechanisms of neurogenesis, mainly those discovered within last ten years. The first part describes generation of new neurons in the brain under physiological conditions, which is localized in the dentate gyrus of the hippocampus and in the subventricular zone of the lateral ventricles (i.e. in principal neurogenic regions). The second part describes animal models used for studying ischemic injury in rodents and moreover, it focuses on patophysiology of ischemic brain injury, which is accompanied by astrocyte and microglia activation. Further, the ischemia-induced neurogenesis is described in these two major neurogenic regions. Also the important role of NG2 glial cells in central nervous system (CNS) regeneration is pointed out. According to recent findings NG2 glia that are present in all regions of CNS might serve as a potential source of cells for directed differentiation into oligodendrocytes, astrocytes and even neurons during CNS repair/regeneration. In the last part of this work,...
|
|
| |
|
| |
guest ::
RSS feed.