Lyon Neuroscience Research Center
FORGETTING Team, Inserm U1028, CNRS UMR5292, Claude Bernard Lyon 1 University

Author Of 1 Presentation

Neuromyelitis Optica and Anti-MOG Disease Oral Presentation

FC01.04 - Ependymocyte: a new target for aquaporin4-IgG in NMO?

Speakers
Presentation Number
FC01.04
Presentation Topic
Neuromyelitis Optica and Anti-MOG Disease
Lecture Time
13:36 - 13:48

Abstract

Background

Ependyma forms the epithelial interface boarding the ventricular walls and the spinal cord’s central canal, maintaining crucial central nervous system functions such as the regulation of cerebrospinal fluid (CSF) circulation by synchronous ciliary beating and the monitoring of molecular exchanges between CSF and parenchyma. These functions are dependent of the cellular coupling via gap junction channels.

Neuromyelitis Optica (NMO) is associated with autoantibodies (NMO-IgG), directed against aquaporin 4 (AQP4). NMO-IgG are present in patient’s serum and CSF during attacks, and are known to trigger astrocyte dysfunction leading to demyelination and axonal loss. Interestingly, ependymal cells also express AQP4 and evidences of ependymal alteration have been reported in NMO. Indeed, MRI abnormalities of the ventricles have been reported, and pathological analyses showed AQP4 loss in the ventricular walls of NMO patients.

Objectives

Our aim is to evaluate if NMO-IgG target ependymal cells, and lead to ependymal morphological changes and dysfunctions.

Methods

We used purified NMO-IgG from AQP4 antibodies positive patients’ plasma (NMO-IgG AQP4+). IgG from healthy donors (CTRL-IgG) and IgG from AQP4-antibodies negative patients (NMO-IgG AQP4-) were used as controls. We evaluated ependymal cells on two models: primary ependymal cell cultures and cultured wholemount dissections (“en-face” view of the entire ependyma) of adult rat lateral ventricular walls. We first looked at the effect of different IgGs on the expression of AQP4 and Connexin43, the main gap junction channel expressed by ependymal cells. Then, we assessed the ciliary beating of ependymal cells by analyzing the diffusion of india ink deposited on wholemount preparations. Coupling of ependymal cells in culture was evaluated by measuring the diffusion of Lucifer Yellow (LY), a gap junction specific dye incorporated in cells by scrape loading.

Results

We showed that NMO-IgG AQP4+ exposure induced: 1) the delocalization of AQP4 membrane expression and morphological changes of ependymal cells from primary cultures and wholemounts, by contrast different IgG controls had no effect; 2) morphological changes of cilia in primary cultures and alteration of the ciliary dynamic; 3) the alteration of Connexin43 expression and function, demonstrated by the decrease of LY spreading after scrape loading.

Conclusions

These results suggest that NMO-IgG directly induce dysfunctions of ependymal cells, through the perturbation of AQP4 and Cx43 expression and functions.

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