Neurogenic Potential of Implanted Neurospheres Is Regulated by Optogenetic Stimulation of Hippocampal Astrocytes Ex Vivo.

The protocol of optogenetic ChR2-mediated activation of astrocytes was used in a model of artificial neurogenic niche, neurospheres implanted into ex vivo organotypic cultures of mouse hippocampus. The electrophysiological characteristics of the hippocampus and expression of molecules involved in the mechanisms of activation of astrocytes and microglia (GFAP, CD38, C3/C3b, Cx43, CD11b, and CD18) were evaluated. Photoactivation of astrocytes led to activation of neurogenesis and changes in the expression of molecules (Cx43 and CD38) that determine bioavailability of NAD+ to ensure proliferative activity of cells in the neurogenic niche. Implantation of neurospheres into organotypic slices of the hippocampus caused an increase in C3/C3b expression and suppression of the synaptic plasticity of hippocampal neurons.

[Features of the in vitro expression profile of hippocampal neurogenic niche cells during optogenetic stimulation]. / Osobennosti ékspressionnogo profilia kletok v modeli neirogennoi nishi gippokampa in vitro pri optogeneticheskoi stimuliatsii.

In the central nervous system of mammals, there are specialized areas in which neurogenesis - neurogenic niches - is observed in the postnatal period. It is believed that astrocytes in the composition of neurogenic niches play a significant role in the regulation of neurogenesis, and therefore they are considered as a promising "target" for the possible control of neurogenesis, including the use of optogenetics. In the framework of this work, we formed an in vitro model of a neurogenic niche, consisting of cerebral endothelial cells, astrocytes and neurospheres. Astrocytes in the neurogenic niche model expressed canalorodopsin ChR2 and underwent photoactivation. The effect of photoactivated astrocytes on the expression profile of neurogenic niche cells was evaluated using immunocytochemical analysis methods. It was found that intact astrocytes in the composition of the neurogenic niche contribute to neuronal differentiation of stem cells, as well as the activation of astroglia expressing photosensitive proteins, changes the expression of molecules characterized by intercellular interactions of pools of resting and proliferating cells in the composition of the neurogenic niche with the participation of NAD+ (Cx43, CD38, CD157), lactate (MCT1). In particular, the registered changes reflect a violation of the paracrine intercellular interactions of two subpopulations of cells, one of which acts as a source of NAD+, and the second as a consumer of NAD+ to ensure the processes of intracellular signal transduction; a change in the mechanisms of lactate transport due to aberrant expression of the lactate transporter MCT1 in cells forming a pool of cells developing along the neuronal path of differentiation. In general, with photostimulation of niche astrocytes, the total proliferative activity increases mainly due to neural progenitor cells, but not neural stem cells. Thus, optogenetic activation of astrocytes can become a promising tool for controlling the activity of neurogenesis processes and the formation of a local proneurogenic microenvironment in an in vitro model of a neurogenic niche.

[Astroglia-mediated regulation of cell development in the model of neurogenic niche in vitro treated with Aß1-42]. / Astrotsit-oposredovannye mekhanizmy reguliatsii neirogeneza v modeli neirogennoi nishi in vitro pri deistviin Aß1-42.

Neurogenesis is a complex process which governs embryonic brain development and is importants for brain plasticity throughout the whole life. Postnatal neurogenesis occurs in neurogenic niches that regulate the processes of proliferation and differentiation of stem and progenitor cells under the action of stimuli that trigger the mechanisms of neuroplasticity. Cells of glial and endothelial origin are the key regulators of neurogenesis. It is known that physiological neurogeneses is crucial for memory formation, whereas reparative neurogenesis provides partial repair of altered brain structure and compensation of neurological deficits caused by brain injury. Dysregulation of neurogenesis is a characteristics of various neurodevelopmental and neurodegenerative diseases, particularly, Alzheimer's disease which is very important medical and social problem. In the in vitro model of the neurogenic niche using hippocampal neurospheres as a source of stem/progenitor cells and astrocytes, we studied effects of astrocyte activation on the expression of markers of different stages of cell proliferation and differentiation. We found that aberrant mechanisms of development of stem and progenitor cells, caused by the beta-amyloid (Aß1-42), can be partially restored by targeted activation of GFAP-expressing cells in the neurogenic niche.

[Early changes in hyppocampal neurogenesis induced by soluble Ab1-42 oligomers]. / Rannie izmeneniia v gippokampal'nom neirogeneze, indutsirovannye rastvorimymi formami oligomerov Ab1-42.

Alzheimer's disease is characterized by the loss of neurons, the accumulation of intracellular neurofibrillary tangles and extracellular amyloid plaques in the brain. However, there are contradicting data on differences in neurogenesis at the onset of the disease or before the formation of amyloid plaques. As awareness of the importance of the pre-symptom phase in neurodegenerative diseases grows in the context of early diagnosis and pathogenesis, we analyzed the critical periods of adult hippocampal neurogenesis at an early stage under the action of soluble Ab1-42 beta-amyloid. The proliferation, migration and neuronal cells survival were evaluated in mice with an injection of soluble amyloid beta-oligomers. It was found that the injection of Ab1-42 oligomers causes a decrease in cell proliferation in the mouse hippocampus. Despite the preservation of the neuroblast pool in animals after beta-amyloid injection, the process of radial migration is disrupted, and an increase in apoptosis in the neurogenic niche was revealed. Thus, our results demonstrate damage of neurogenesis critical stages: the progenitor cells, neuroblast migration, the integration of immature neurons, and the survival of neurons under application of soluble beta-amyloid oligomers. The obtained data indicate decline in proliferation rate in the subgranular zone, that is accompanied by ectopic differentiation and disturbed migration, producing, apparently, abnormal neurons that have lower survival rates. That could lead to a decrease in mature neurons numbers and the number of cells in the granular layer of the dentate gyrus.

[Transparent evolution of the energy/matter interactions on earth: from gas whirlwind to technogenic civilization].

The paper presents the idea of transparent evolution through the long-term reaction of the planet Earth on the external flow of radiant energy from the Sun. Due to limitations of matter on Earth, as well as on any other planet, the continuous pumping flow of radiant energy was shown to lead to cyclization and transport of substance on emerging gradients. The evolution of energy-matter interaction follows the path of capturing and transferring more energy by the fewer matter, i.e., the path of growth of the amount of energy used by each unit mass. For this indicator, the least effective mass transfer is a simple mass transfer as vortices of gases, in the gradients of temperature and pressure, which occurred on the primary surface of the planet. A long-term natural selection related to the accumulation of water on the planet has played a special role in developing the interaction of energy and matter. Phase transformations (ice, water, vapor) and mechanical transfers are the most common energy-matter processes. Based on water cycles, cyclic transports and transformations, chemical transformation of substances became possible developing over time into a biological transformation. This kind of the interaction of energy and matter is most efficient. In particular, during photosynthesis the energy of our star "is captured and utilized" in the most active part of the spectrum of its radiation. In the process of biological evolution of heterotrophs, a rise (by a factor of hundreds) in the coefficient that characterizes the intensity of energy exchange from protozoa to mammals is most illustratory. The development and the current dominance of humans as the most energy-using active species in capturing the energy and meaningful organization of its new flows especially on the basis of organic debris of former biospheres is admirable, but quite natural from the energy positions. In the course of technological evolution of humankind, the measure of the intensity of energy for homoeothermic (warm-blooded) animals has increased 20 times, based on the process energy used by the "average" inhabitant of the world. Thus, the victory of our species in planetary evolution is easy to fit into the mainstream of evolution through energy-matter interactions: multiple growth of star energy was used to transform the matter on the surface of the irradiated planet.