Background

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system (CNS) and is thought to have autoimmune etiology (Thompson et al., 2018). Current therapeutic treatments mainly target lymphocytes; however, this can cause serious side effects and does not provide sufficient therapeutic efficacy for those with progressive MS. Therefore, animal models of MS are important for further elucidation of pathological mechanisms and discovery of new treatments. Available pathological mouse model of MS, including the experimental autoimmune encephalomyelitis (EAE) model, the cuprizone application model, and lysolecithin-injection models, each has its own advantages (Kipp et al., 2017). EAE is used widely to study MS (Ransohoff, 2012; Baker and Amor, 2014). All EAE models enable investigation of both the immune system and CNS, which are the targets of MS therapies (Mix et al., 2010). Although there are several animal models of EAE, two are common in MS research (Burrows et al., 2019). One is the C57BL/6 mouse, which is immunized with myelin oligodendrocyte glycoprotein (MOG) (Mendel et al., 1995), and the other is the SJL mouse, which is immunized with proteolipid protein (PLP) (Tuohy et al., 1988). The former develops chronic EAE (Mendel et al., 1995; Bittner et al., 2014) and is more popular because the C57BL/6J strain has abundant genomic resources (Gold et al., 2006). The latter model develops remitting and relapsing disease, which does not happen in the MOG-EAE model; therefore, this model is used as a model for relapsing-remitting MS (Tuohy et al., 1989).

Studies of the mechanisms underlying MS and development of suitable therapies can be conducted using EAE models; however remyelination is difficult to study in EAE model, two toxic models displaying demyelination and remyelination are widely used (Ransohoff, 2012). Cuprizone, a copper chelator, kills oligodendrocytes, resulting in demyelination and remyelination (Matsushima and Morell, 2001), whereas lysolecithin, also called lysophosphatidylcholine (LPC), is toxic to the myelin sheath (Hall, 1972). The lysolecithin-injected model has an important characteristic in that demyelination can be controlled both spatially and temporally (Keough et al., 2015). By contrast, the EAE model better reflects the autoimmune pathogenesis of MS, and represents a secondary progressive form the disease model with some modifications (Tanabe et al., 2019). Although this EAE model described in this protocol can be generated easily, disease incidence and symptoms vary according to the experimental environment. Therefore, we propose a solid method that can reliably create a C57BL/6J EAE model, which is close to human pathology and highly versatile as an animal model.