Adhesive Contact to a Coated Elastic Substrate

We show how the quasi-analytic method developed to solve linear elastic contacts to coated substrates (Perriot A. and Barthel E. {\em J. Mat. Res.}, {\bf 2004}, {\em 19}, 600) may be extended to adhesive contacts. Substrate inhomogeneity lifts accidental degeneracies and highlights the general structure of the adhesive contact theory. We explicit the variation of the contact variables due to substrate inhomogeneity. The relation to other approaches based on Finite Element analysis is discussed

Advancing human induced pluripotent stem cell-derived blood-brain barrier models for studying immune cell interactions.

Human induced pluripotent stem cell (hiPSC)-derived blood-brain barrier (BBB) models established to date lack expression of key adhesion molecules involved in immune cell migration across the BBB in vivo. Here, we introduce the extended endothelial cell culture method (EECM), which differentiates hiPSC-derived endothelial progenitor cells to brain microvascular endothelial cell (BMEC)-like cells with good barrier properties and mature tight junctions. Importantly, EECM-BMEC-like cells exhibited constitutive cell surface expression of ICAM-1, ICAM-2, and E-selectin. Pro-inflammatory cytokine stimulation increased the cell surface expression of ICAM-1 and induced cell surface expression of P-selectin and VCAM-1. Co-culture of EECM-BMEC-like cells with hiPSC-derived smooth muscle-like cells or their conditioned medium further increased the induction of VCAM-1. Functional expression of endothelial ICAM-1 and VCAM-1 was confirmed by T-cell interaction with EECM-BMEC-like cells. Taken together, we introduce the first hiPSC-derived BBB model that displays an adhesion molecule phenotype that is suitable for the study of immune cell interactions

Impaired T-cell migration to the CNS under fingolimod and dimethyl fumarate.

To evaluate the long-term effects of treatments used in MS on the T-cell trafficking profile. We enrolled 83 patients with MS under fingolimod (FTY), natalizumab (NTZ), dimethyl fumarate (DMF), or other disease-modifying treatments (DMTs). Blood was drawn before treatment onset and up to 36-48 months. The ex vivo expression of CNS-related integrins (α4β1 and αL subunit of LFA-1) and the gut-related integrin (α4β7) was assessed using flow cytometry on CD4(+) and CD8(+) T cells. The adhesion profiles of CD3(+) T cells to specific integrin ligands (vascular cell adhesion molecule-1 [VCAM-1], intercellular adhesion molecule-1 [ICAM-1], and mucosal vascular addressin cell adhesion molecule-1 [MAdCAM-1]) were measured in vitro before and after 12 and 36-48 months. NTZ decreased the frequency of α4β1(+) and α4β7(+) integrin expressing T cells and the binding of these cells to VCAM-1 and MAdCAM-1, respectively. After 12 months, DMF induced a decreased frequency of αL(high)CD4(+) T cells combined with reduced binding to ICAM-1. By contrast, with FTY, there was a doubling of the frequency of α4β1(+) and αL(high), but a decreased frequency of α4β7(+) T cells. Strikingly, the binding of α4β1(+), α4β7(+), and to a lesser extent of αL(high) T cells to VCAM-1, MAdCAM-1, and ICAM-1, respectively, was decreased at month 12 under FTY treatment. The presence of manganese partially restored the binding of these T cells to VCAM-1 in vitro, suggesting that FTY interferes with integrin activation. In addition to NTZ, DMF and FTY but not other tested DMTs may also decrease T-cell-mediated immune surveillance of the CNS. Whether this mechanism may contribute to the onset of CNS opportunistic infections remains to be shown

Encephalopathies Associated With Severe COVID-19 Present Neurovascular Unit Alterations Without Evidence for Strong Neuroinflammation.

Coronavirus disease (COVID-19) has been associated with a large variety of neurologic disorders. However, the mechanisms underlying these neurologic complications remain elusive. In this study, we aimed at determining whether neurologic symptoms were caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) direct infection or by either systemic or local proinflammatory mediators. In this cross-sectional study, we checked for SARS-CoV-2 RNA by quantitative reverse transcription PCR, SARS-CoV-2-specific antibodies, and 49 cytokines/chemokines/growth factors (by Luminex) in the CSF +/- sera of a cohort of 22 COVID-19 patients with neurologic presentation and 55 neurologic control patients (inflammatory neurologic disorder [IND], noninflammatory neurologic disorder, and MS). We detected anti-SARS-CoV-2 immunoglobulin G in patients with severe COVID-19 with signs of intrathecal synthesis for some of them. Of the 4 categories of tested patients, the CSF of IND exhibited the highest level of cytokines, chemokines, and growth factors. By contrast, patients with COVID-19 did not present overall upregulation of inflammatory mediators in the CSF. However, patients with severe COVID-19 (intensive care unit patients) exhibited higher concentrations of CCL2, CXCL8, and vascular endothelium growth factor A (VEGF-A) in the CSF than patients with a milder form of COVID-19. In addition, we could show that intrathecal CXCL8 synthesis was linked to an elevated albumin ratio and correlated with the increase of peripheral inflammation (serum hepatocyte growth factor [HGF] and CXCL10). Our results do not indicate active replication of SARS-CoV-2 in the CSF or signs of massive inflammation in the CSF compartment but highlight a specific impairment of the neurovascular unit linked to intrathecal production of CXCL8

Cell-binding IgM in CSF is distinctive of multiple sclerosis and targets the iron transporter SCARA5

Intrathecal IgM production in multiple sclerosis (MS) is associated with a worse disease course. To investigate pathogenic relevance of autoreactive IgM in MS, CSF from two independent cohorts, including MS patients and controls, were screened for antibody binding to induced pluripotent stem cell-derived neurons and astrocytes, and a panel of CNS- related cell lines. IgM binding to a primitive neuro-ectodermal tumour cell line discriminated 10% of MS donors from controls. Transcriptomes of single IgM producing CSF B cells from patients with cell-binding IgM were sequenced and used to produce recombinant monoclonal antibodies for characterisation and antigen identification. We produced 5 cell-binding recombinant IgM antibodies, of which one, cloned from an HLA-DR + plasma-like B cell, mediated antigen-dependent complement activation. Immunoprecipitation and mass spectrometry, and biochemical and transcriptome analysis of the target cells identified the iron transport scavenger protein SCARA5 as the antigen target of this antibody. Intrathecal injection of a SCARA5 antibody led to an increased T cell infiltration in an EAE model. CSF IgM might contribute to CNS inflammation in MS by binding to cell surface antigens like SCARA5 and activating complement, or by facilitating immune cell migration into the brain

Differentiation of functional astrocytes from human-induced pluripotent stem cells in chemically defined media.

This protocol describes how to obtain human astrocytes from human-induced pluripotent stem cells (hiPSCs) in chemically defined media, without the use of fetal bovine serum (FBS). FBS eases the differentiation of astrocytes but also deeply alters their phenotype, as compared with their in vivo counterparts. Our protocol generates hiPSC-derived astrocytes displaying a phenotype and functions similar to human primary astrocytes, including adequate response to inflammation, neurotransmitter uptake, and trophic support to neurons. For complete details on the use and execution of this protocol, please refer to Perriot et al. (2018)