Features of the In Vitro Expression Profile of Hippocampal Neurogenic Niche Cells during Optogenetic Stimulation

Abstract—

In the central nervous system of mammals, there are specialized areas, known as neurogenic niches, in which neurogenesis 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 study, we have formed an in vitro model of a neurogenic niche, consisting of cerebral endothelial cells, astrocytes, and neurospheres. Astrocytes in the neurogenic niche model expressed channelrhodopsin ChR2 and underwent photoactivation. The effect of photoactivated astrocytes on the expression profile of neurogenic niche cells was evaluated using methods of immunocytochemical analysis. It was found that intact astrocytes in the composition of the neurogenic niche promoted neuronal differentiation of stem cells, as well as the activation of astroglia expressing photosensitive proteins, changed 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). The registered changes reflect: (i) impaired paracrine interactions between two subpopulations of cells, one of which acts as a source of NAD⁺, and another one is a consumer of NAD⁺ required for processes of the intracellular signal transduction; (ii) changes 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 (but not neuronal stem cells). In general, during 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 the neurogenic niche.