Gliogenesis

Abstract: Brain-derived neurotrophic factor (BDNF) is one of the most widely distributed and extensively studied neurotrophins in the mammalian brain. Among its prominent functions, one can mention control of neuronal and glial development, neuroprotection, and modulation of both short- and long-lasting synaptic interactions, which are critical for cognition and memory. A wide spectrum of processes are controlled by BDNF, and the sometimes contradictory effects of its action can be explained based on its specific pattern of synthesis, comprising several intermediate biologically active isoforms that bind to different types of receptor, triggering several signaling pathways. The functions of BDNF must be discussed in close relation to the stage of brain development, the different cellular components of nervous tissue, as well as the molecular mechanisms of signal transduction activated under physiological and pathological conditions. In this review, we briefly summarize the current state of knowledge regarding the impact of BDNF on regulation of neurophysiological processes. The importance of BDNF for future studies aimed at disclosing mechanisms of activation of signaling pathways, neuro- and gliogenesis, as well as synaptic plasticity is highlighted.

Abstract: For many years, it was assumed that neurons and glia in the central nervous system were produced from two distinct precursor pools that diverged early during embryonic development This theory was partially based on the idea that neurogenesis and gliogenesis occurred during different periods of development, and that neurogenesis ceased perinatally However, there is now abundant evidence that neural stem cells persist in the adult brain and support ongoing neurogenesis in restricted regions of the central nervous system Surprisingly, these stem cells have the characteristics of fully differentiated glia Neuroepithelial stem cells in the embryonic neural tube do not show glial characteristics, raising questions about the putative lineage from embryonic to adult stem cells In the developing brain, radial glia have long been known to produce cortical astrocytes, but recent data indicate that radial glia might also divide asymmetrically to produce cortical neurons Here we review these new developments and propose that the stem cells in the central nervous system are contained within the neuroepithelial → radial glia → astrocyte lineage

Abstract: Differentiation of human pluripotent stem cells to small brain-like structures known as brain organoids offers an unprecedented opportunity to model human brain development and disease. To provide a vascularized and functional in vivo model of brain organoids, we established a method for transplanting human brain organoids into the adult mouse brain. Organoid grafts showed progressive neuronal differentiation and maturation, gliogenesis, integration of microglia, and growth of axons to multiple regions of the host brain. In vivo two-photon imaging demonstrated functional neuronal networks and blood vessels in the grafts. Finally, in vivo extracellular recording combined with optogenetics revealed intragraft neuronal activity and suggested graft-to-host functional synaptic connectivity. This combination of human neural organoids and an in vivo physiological environment in the animal brain may facilitate disease modeling under physiological conditions.

Abstract: Progress in the field of neurogenesis is currently limited by the lack of tools enabling fast and quantitative analysis of neurogenesis in the adult brain Doublecortin (DCX) has recently been used as a marker for neurogenesis However, it was not clear whether DCX could be used to assess modulations occurring in the rate of neurogenesis in the adult mammalian central nervous system following lesioning or stimulatory factors Using two paradigms increasing neurogenesis levels (physical activity and epileptic seizures), we demonstrate that quantification of DCX-expressing cells allows for an accurate measurement of modulations in the rate of adult neurogenesis Importantly, we excluded induction of DCX expression during physiological or reactive gliogenesis and excluded also DCX re-expression during regenerative axonal growth Our data validate DCX as a reliable and specific marker that reflects levels of adult neurogenesis and its modulation We demonstrate that DCX is a valuable alternative to techniques currently used to measure the levels of neurogenesis Importantly, in contrast to conventional techniques, analysis of neurogenesis through the detection of DCX does not require in vivo labelling of proliferating cells, thereby opening new avenues for the study of human neurogenesis under normal and pathological conditions