Multiple Sclerosis and Other Acquired Demyelinating Diseases of the Central Nervous System

Acute TREM2 inhibition depletes MAFB-high microglia and hinders remyelination

We investigated the role of Triggering Receptor Expressed on Myeloid cells 2 (TREM2) in myelin regeneration in the brain. TREM2 is a receptor that activates microglia, which are crucial for clearing myelin debris and promoting remyelination. Previous studies in a mouse model of demyelination induced by the copper-chelating agent Cuprizone (CPZ) have shown that stimulation of TREM2 with a monoclonal antibody reduces demyelination, while deleting the Trem2 gene in mice impairs remyelination. Here, we blocked TREM2 function acutely with an antibody during both the demyelination and remyelination phases of the CPZ model and analyzed the impact of the antibody treatment on myelination and gene expression in single cells. We found that blocking TREM2 depleted a distinct population of microglia with high expression of the transcription factor MAFB during remyelination. The loss of these MAFB-high microglia was linked to impaired generation of myelinating oligodendrocytes. Importantly, we identified MAFB+ microglia in acute and acute-chronic brain lesions from individuals with multiple sclerosis (MS), but not in inactive lesions. We conclude that TREM2 is essential for maintaining a population of MAFB-high microglia that is associated with myelin repair. This finding has significant implications for understanding demyelinating diseases like MS and suggests that stimulating TREM2 could be a promising therapeutic approach for myelin repair.

Gastrodin promotes CNS myelinogenesis and alleviates demyelinating injury by activating the PI3K/AKT/mTOR signaling

Demyelination is a common feature of numerous neurological disorders including multiple sclerosis and leukodystrophies. Although myelin can be regenerated spontaneously following injury, this process is often inadequate, potentially resulting in neurodegeneration and exacerbating neurological dysfunction. Several drugs aimed at promoting the differentiation of oligodendrocyte precursor cells (OPCs) have yielded unsatisfactory clinical effects. A recent study has shifted the strategy of pro-OPC differentiation towards enhancing myelinogenesis. In this study we identified the pro-myelinating drug using a zebrafish model. Five traditional Chinese medicine monomers including gastrodin, paeoniflorin, puerarin, salidroside and scutellarin were assessed by bath-application in Tg (MBP:eGFP-CAAX) transgenic line at 1-5 dpf. Among the 5 monomers, only gastrodin exhibited significant pro-myelination activity. We showed that gastrodin (10 µM) enhanced myelin sheath formation and oligodendrocyte (OL) maturation without affecting the number of OLs. Gastrodin markedly increased the phosphorylation levels of PI3K, AKT, and mTOR in primary cultured OLs via direct interaction with PI3K. Co-treatment with the PI3K inhibitor LY294002 (5 µM) mitigated gastrodin-induced OL maturation. Furthermore, injection of gastrodin (100 mg·kg-1·d-1, i.p.) effectively facilitated remyelination in a lysophosphatidylcholine-induced demyelinating mouse model and alleviated demyelination in the experimental autoimmune encephalomyelitis mice. These results identify gastrodin as a promising therapeutic agent for demyelinating diseases and highlight the potential of the zebrafish model for screening pro-myelinogenic pharmacotherapy.