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Blockade of MCAM/CD146 impedes CNS infiltration of T cells over the choroid plexus.

ABSTRACT: BACKGROUND:Very late antigen 4 (VLA-4; integrin α4β1) is critical for transmigration of T helper (TH) 1 cells into the central nervous system (CNS) under inflammatory conditions such as multiple sclerosis (MS). We have previously shown that VLA-4 and melanoma cell adhesion molecule (MCAM) are important for trans-endothelial migration of human TH17 cells in vitro and here investigate their contribution to pathogenic CNS inflammation. METHODS:Antibody blockade of VLA-4 and MCAM is assessed in murine models of CNS inflammation in conjunction with conditional ablation of α4-integrin expression in T cells. Effects of VLA-4 and MCAM blockade on lymphocyte migration are further investigated in the human system via in vitro T cell transmigration assays. RESULTS:Compared to the broad effects of VLA-4 blockade on encephalitogenic T cell migration over endothelial barriers, MCAM blockade impeded encephalitogenic T cell migration in murine models of MS that especially depend on CNS migration across the choroid plexus (CP). In transgenic mice lacking T cell α4-integrin expression (CD4::Itga4-/-), MCAM blockade delayed disease onset. Migration of MCAM-expressing T cells through the CP into the CNS was restricted, where laminin 411 (composed of α4, β1, γ1 chains), the proposed major ligand of MCAM, is detected in the endothelial basement membranes of murine CP tissue. This finding was translated to the human system; blockade of MCAM with a therapeutic antibody reduced in vitro transmigration of MCAM-expressing T cells across a human fibroblast-derived extracellular matrix layer and a brain-derived endothelial monolayer, both expressing laminin α4. Laminin α4 was further detected in situ in CP endothelial-basement membranes in MS patients' brain tissue. CONCLUSIONS:Our findings suggest that MCAM-laminin 411 interactions facilitate trans-endothelial migration of MCAM-expressing T cells into the CNS, which seems to be highly relevant to migration via the CP and to potential future clinical applications in neuroinflammatory disorders.

SUBMITTER: Breuer J

PROVIDER: S-EPMC6106934 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundAlthough fibroblast growth factor (Fgf) signalling plays crucial roles in several developing and mature tissues, little information is currently available on expression of Fgf2 during early choroid plexus development and whether Fgf2 directly affects the behaviour of the choroid plexus epithelium (CPe). The purpose of this study was to investigate expression of Fgf2 in rodent and human developing CPe and possible function of Fgf2, using in vitro models. The application of Fgf2 to brain in vivo can affect the whole tissue, making it difficult to assess specific responses of the CPe.MethodsExpression of Fgf2 was studied by immunohistochemistry in rodent and human embryonic choroid plexus. Effects of Fgf2 on growth, secretion, aggregation and gene expression was investigated using rodent CPe vesicles, a three-dimensional polarized culture model that closely mimics CPe properties in vivo, and rodent CPe monolayer cultures.ResultsFgf2 was present early in development of the choroid plexus both in mouse and human, suggesting the importance of this ligand in Fgf signalling in the developing choroid plexus. Parallel analysis of Fgf2 expression and cell proliferation during CP development suggests that Fgf2 is not involved in CPe proliferation in vivo. Consistent with this observation is the failure of Fgf2 to increase proliferation in the tri-dimensional vesicle culture model. The CPe however, can respond to Fgf2 treatment, as the diameter of CPe vesicles is significantly increased by treatment with this growth factor. We show that this is due to an increase in cell aggregation during vesicle formation rather than increased secretion into the vesicle lumen. Finally, Fgf2 regulates expression of the CPe-associated transcription factors, Foxj1 and E2f5, whereas transthyretin, a marker of secretory activity, is not affected by Fgf2 treatment.ConclusionFgf2 expression early in the development of both human and rodent choroid plexus, and its ability to modulate behaviour and gene expression in CPe, supports the view that Fgf signalling plays a role in the maintenance of integrity and function of this specialized epithelium, and that this role is conserved between rodents and humans.

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Blockade of MCAM/CD146 impedes CNS infiltration of T cells over the choroid plexus.

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