EBI2 Is Temporarily Upregulated in MO3.13 Oligodendrocytes during Maturation and Regulates Remyelination in the Organotypic Cerebellar Slice Model

Abstract

The EBI2 receptor regulates the immune system and is expressed in various immune cells including B and T lymphocytes. It is also expressed in astrocytes in the central nervous system (CNS) where it regulates pro-inflammatory cytokine release, cell migration and protects from chemically induced demyelination. Its signaling and expression are implicated in various diseases including multiple sclerosis, where its expression is increased in infiltrating immune cells in the white matter lesions. Here, for the first time, the EBI2 protein in the CNS cells in the human brain was examined. The function of the receptor in MO3.13 oligodendrocytes, as well as its role in remyelination in organotypic cerebellar slices, were investigated. Human brain sections were co-stained for EBI2 receptor and various markers of CNS-specific cells and the human oligodendrocyte cell line MO3.13 was used to investigate changes in EBI2 expression and cellular migration. Organotypic cerebellar slices prepared from wild-type and cholesterol 25-hydroxylase knock-out mice were used to study remyelination following lysophosphatidylcholine (LPC)-induced demyelination. The data showed that EBI2 receptor is present in OPCs but not in myelinating oligodendrocytes in the human brain and that EBI2 expression is temporarily upregulated in maturing MO3.13 oligodendrocytes. Moreover, we show that migration of MO3.13 cells is directly regulated by EBI2 and that its signaling is necessary for remyelination in cerebellar slices post-LPC-induced demyelination. The work reported here provides new information on the expression and role of EBI2 in oligodendrocytes and myelination and provides new tools for modulation of oligodendrocyte biology and therapeutic approaches for demyelinating diseases.

EBI2 is expressed in glial cells in multiple sclerosis lesions, and its knock‐out modulates remyelination in the cuprizone model

“…Some differences between the WTs and the KOs emerged after the 2-week recovery period when the WT mice appeared to recover myelin more efficiently than their EBI2 KO counterparts. A similar effect was recently reported in chemically demyelinated cerebellar slices where EBI2 signalling was persistently antagonised and resulted in significantly less remyelination after 22 days in vitro (Velasco-Estevez et al, 2021). Interestingly, the loss and then recovery of mature oligodendrocytes (CC1 + ) was more evident in the WT mice.…”

“…We demonstrated before that myelination is delayed in early postnatal days in EBI2 KO mice (Rutkowska et al, 2017). We also showed that persistent antagonism of EBI2 in chemically demyelinated cerebellar slices attenuates spontaneous remyelination (Velasco‐Estevez et al, 2021). Here, in the cuprizone model, a significant loss of lipids in the genu of the corpus callosum was found after 5 weeks of cuprizone diet in the WT and EBI2 KO mice brains (Figure 1a,b).…”

“…We reported before that, in vitro, EBI2 regulates astrocyte migration, pro‐inflammatory signalling, normal myelin development and protects from lysophosphatidylcholine‐induced demyelination in organotypic cerebellar slices (Rutkowska et al, 2015; Rutkowska et al, 2016; Rutkowska et al, 2017; Rutkowska et al, 2018). Most recently, our investigations demonstrated that persistent pharmacological antagonism of EBI2 signalling inhibits spontaneous remyelination in chemically demyelinated cerebellar slices (Velasco‐Estevez et al, 2021). Here, we continued our investigations of EBI2 function in the CNS by examining EBI2 expression in the CNS cells in the MS brain and its function in the cuprizone model of MS.…”

“…They drive demyelination and then facilitate remyelination by releasing various inflammatory mediators and further activation and recruitment of glia and other cells. Activation of astrocyte‐expressed EBI2 with its ligand oxysterol 7α,25‐OHC induces migration in vitro (Rutkowska et al, 2018; Velasco‐Estevez et al, 2021). Here, the number of GFAP + astrocytes did not increase after cuprizone treatment.…”

“…With the use of the same organotypic cerebellar slice model, we showed that long‐term downregulation or antagonism of EBI2 signalling during myelin development in the early postnatal days staggers its normal development, implicating the importance of EBI2 signalling for normal myelination (Rutkowska et al, 2017). Importantly, we recently demonstrated that uninhibited EBI2 signalling is needed for spontaneous remyelination in chemically demyelinated cerebellar slices indicating EBI2 role also in remyelination (Velasco‐Estevez et al, 2021).…”