TGF-β pro-oligodendrogenic effects on adult SVZ progenitor cultures and its interaction with the Notch signaling pathway

Oligodeoxynucleotide IMT504: Effects on Central Nervous System Repair Following Demyelination

Multiple sclerosis (MS) is an immune-mediated central nervous system (CNS) disease characterized by demyelination resulting from oligodendrocyte loss and inflammation. Cuprizone (CPZ) administration experimentally replicates MS pattern-III lesions, generating an inflammatory response through microgliosis and astrogliosis. Potentially remyelinating agents include oligodeoxynucleotides (ODN) with a specific immunomodulatory sequence consisting of the active motif PyNTTTTGT. In this work, the remyelinating effects of ODN IMT504 were evaluated through immunohistochemistry and qPCR analyses in a rat CPZ-induced demyelination model. Subcutaneous IMT504 administration exacerbated the pro-inflammatory response to demyelination and accelerated the transition to an anti-inflammatory state. IMT504 reduced microgliosis in general and the number of phagocytic microglia in particular and expanded the population of oligodendroglial progenitor cells (OPCs), later reflected in an increase in mature oligodendrocytes. The intracranial injection of IMT504 and intravenous inoculation of IMT504-treated B lymphocytes rendered comparable results. Altogether, these findings unveil potentially beneficial properties of IMT504 in the regulation of neuroinflammation and oligodendrogenesis, which may aid the development of therapies for demyelinating diseases such as MS.

The Effects of Cuprizone on Murine Subventricular Zone-Derived Neural Stem Cells and Progenitor Cells Grown as Neurospheres

Despite the extensive use of the cuprizone (CPZ) demyelination animal model, there is little evidence regarding the effects of CPZ on a cellular level. Initial studies have suggested that oligodendrocytes (OL) are the main cell targets for CPZ toxicity. However, recent data have revealed additional effects on neural stem cells and progenitor cells (NSC/NPC), which constitute a reservoir for OL regeneration during brain remyelination. We cultured NSC/NPC as neurospheres to investigate CPZ effects on cell mechanisms which are thought to be involved in demyelination and remyelination processes in vivo. Proliferating NSC/NPC cultures exposed to CPZ showed overproduction of intracellular reactive oxygen species and increased progenitor migration at the expense of a significant inhibition of cell proliferation. Although NSC/NPC survival was not affected by CPZ in proliferative conditions, we found that CPZ-treated cultures undergoing cell differentiation were more prone to cell death than controls. The commitment and cell differentiation towards neural lineages did not seem to be affected by CPZ, as shown by the conserved proportions of OL, astrocytes, and neurons. Nevertheless, when CPZ treatment was performed after cell differentiation, we detected a significant reduction in the number and the morphological complexity of OL, astrogliosis, and neuronal damage. We conclude that, in addition to damaging mature OL, CPZ also reduces NSC/NPC proliferation and activates progenitor migration. These results shed light on CPZ direct effects on NSC proliferation and the progression of in vitro differentiation.

The Notch Signaling Pathway Regulates Differentiation of NG2 Cells into Oligodendrocytes in Demyelinating Diseases

NG2 cells are highly proliferative glial cells that can self-renew or differentiate into oligodendrocytes, promoting remyelination. Following demyelination, the proliferative and differentiation potentials of NG2 cells increase rapidly, enhancing their differentiation into functional myelinating cells. Levels of the transcription factors Olig1 and Olig2 increase during the differentiation of NG2 cells and play important roles in the development and repair of oligodendrocytes. However, the ability to generate new oligodendrocytes is hampered by injury-related factors (e.g., myelin fragments, Wnt and Notch signaling components), leading to failed differentiation and maturation of NG2 cells into oligodendrocytes. Here, we review Notch signaling as a negative regulator of oligodendrocyte differentiation and discuss the extracellular ligands, intracellular pathways, and key transcription factors involved.

Astrocyte and Oligodendrocyte Responses From the Subventricular Zone After Injury

Under normal conditions, neural stem cells (NSCs or B cells) in the adult subventricular zone (SVZ) give rise to amplifying neural progenitor cells (NPCs or C cells), which can produce neuroblasts (or A cells) that migrate to the olfactory bulb and differentiate into new neurons. However, following brain injury, these cells migrate toward the injury site where they differentiate into astrocytes and oligodendrocytes. In this review, we will focus on recent findings that chronicle how astrocytes and oligodendrocytes derived from SVZ-NSCs respond to different types of injury. We will also discuss molecular regulators of SVZ-NSC proliferation and their differentiation into astrocytes and oligodendrocytes. Overall, the goal of this review is to highlight how SVZ-NSCs respond to injury and to summarize the regulatory mechanisms that oversee their glial response. These molecular and cellular processes will provide critical insights needed to develop strategies to promote brain repair following injury using SVZ-NSCs.

The impact of trophic and immunomodulatory factors on oligodendrocyte maturation: Potential treatments for encephalopathy of prematurity

Encephalopathy of prematurity (EoP) is a major cause of morbidity in preterm neonates, causing neurodevelopmental adversities that can lead to lifelong impairments. Preterm birth-related insults, such as cerebral oxygen fluctuations and perinatal inflammation, are believed to negatively impact brain development, leading to a range of brain abnormalities. Diffuse white matter injury is a major hallmark of EoP and characterized by widespread hypomyelination, the result of disturbances in oligodendrocyte lineage development. At present, there are no treatment options available, despite the enormous burden of EoP on patients, their families, and society. Over the years, research in the field of neonatal brain injury and other white matter pathologies has led to the identification of several promising trophic factors and cytokines that contribute to the survival and maturation of oligodendrocytes, and/or dampening neuroinflammation. In this review, we discuss the current literature on selected factors and their therapeutic potential to combat EoP, covering a wide range of in vitro, preclinical and clinical studies. Furthermore, we offer a future perspective on the translatability of these factors into clinical practice.

Demyelination-Remyelination in the Central Nervous System: Ligand-Dependent Participation of the Notch Signaling Pathway

Multiple sclerosis (MS) is an immune-mediated CNS disease mostly affecting young people. MS and other neurodegenerative and white matter disorders involve oligodendrocyte (OL) damage and demyelination. Therefore, elucidating the signaling pathways involved in the remyelination process through the maturation of OL progenitor cells (OPCs) may contribute to the development of new therapeutic approaches. In this context, this paper further characterizes toxic cuprizone (CPZ)-induced demyelination and spontaneous remyelination in rats and investigates the role of ligand-dependent Notch signaling activation along demyelination/remyelination both in vivo and in vitro. Toxic treatment generated an inflammatory response characterized by both microgliosis and astrogliosis. Interestingly, early demyelination revealed an increase in the proportion of Jagged1+/GFAP+ cells, which correlated with an increase in Jagged1 transcript and concomitant Jagged1-driven Notch signaling activation, particularly in NG2+ OPCs, in both the corpus callosum (CC) and subventricular zone (SVZ). The onset of remyelination then exhibited an increase in the proportion of F3/contactin+/NG2+ cells, which correlated with an increase in F3/contactin transcript during ongoing remyelination in the CC. Moreover, neurosphere cultures revealed that neural progenitor cells (NPCs) present in the brain SVZ of CPZ-treated rats recapitulate in vitro the mechanisms underlying the response to toxic injury observed in vivo, compensating for mature OL loss. Altogether, the present results offer strong evidence of cell-type and ligand-specific Notch signaling activation and its time- and area-dependent participation in toxic demyelination and spontaneous remyelination.