Multiple sclerosis (MS) is considered an autoimmune disease of the central nervous system (CNS) associated with demyelination and axonal loss eventually leading to neurodegeneration. As the preclinical stage, the radiologically isolated syndrome (RIS) is defined as the presence of asymptomatic, incidentally identified demyelinating-appearing white matter lesions in the CNS. About 50% of individuals with RIS will develop MS within 10 years. Blood-brain barrier (BBB) breakdown is amongst the earliest pathological hallmarks observed in MS. The mechanisms leading to BBB dysfunction are incompletely understood and are generally thought to be a consequence of the autoimmune neuroinflammatory process in MS. Investigating BBB dysfunction in MS is hampered by the limitation of MS tissue samples.

We made use of hiPSCs derived from 11HC, 2 RIS and 18 MS in Switzerland and Japan and differentiated them into BMEC-like cells using the extended endothelial cell culture method (EECM). We investigated the cell size, junctional integrity by immunofluorescence staining for VE-cadherin and claudin-5, expression of adhesion molecules with and without stimulation of TNF-α and IFN-γ by flow cytometry, and barrier properties by measuring the permeability (Pe) of sodium fluorescein (NaFl) and the transendothelial electrical resistance (TEER) of EECM-BMEC monolayers. Transcriptome analysis from the EECM-BMEC-like cells via RNA sequencing on HC, RIS and MS-derived BMEC-like cells is ongoing.

MS- and RIS-derived EECM-BMEC-like cells were larger in size. Some of EECM-BMEC-like cells derived from MS and RIS showed interrupted junctional staining for claudin-5. Barrier properties of MS- and RIS-derived EECM-BMEC-like cells were impaired as detected by enhanced Pe and lower TEER. The cell surface expression of ICAM-1 and VCAM-1 was however not significantly different between the respective groups. The differences in the transcriptional profile and phenotype between the groups will be presented.

Our preliminary observations suggest that BBB dysfunction may already be established at the RIS stage and thus could contribute to development of MS. Furthermore, our study confirms impaired barrier properties of EECM-BMEC-like cells derived from hiPSCs of MS when compared to HC. Taken together, our observations further underscore a contribution of intrinsic BBB dysfunction in MS pathogenesis.