Astrocytic tight junctions control inflammatory CNS lesion pathogenesis
Sam Horng, … , Candice Chapouly, Gareth R. John
Sam Horng, … , Candice Chapouly, Gareth R. John
Published July 24, 2017
Citation Information: J Clin Invest. 2017;127(8):3136-3151. https://doi.org/10.1172/JCI91301.
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Research Article Immunology Neuroscience

Astrocytic tight junctions control inflammatory CNS lesion pathogenesis

Abstract

Lesions and neurologic disability in inflammatory CNS diseases such as multiple sclerosis (MS) result from the translocation of leukocytes and humoral factors from the vasculature, first across the endothelial blood-brain barrier (BBB) and then across the astrocytic glia limitans (GL). Factors secreted by reactive astrocytes open the BBB by disrupting endothelial tight junctions (TJs), but the mechanisms that control access across the GL are unknown. Here, we report that in inflammatory lesions, a second barrier composed of reactive astrocyte TJs of claudin 1 (CLDN1), CLDN4, and junctional adhesion molecule A (JAM-A) subunits is induced at the GL. In a human coculture model, CLDN4-deficient astrocytes were unable to control lymphocyte segregation. In models of CNS inflammation and MS, mice with astrocyte-specific Cldn4 deletion displayed exacerbated leukocyte and humoral infiltration, neuropathology, motor disability, and mortality. These findings identify a second inducible barrier to CNS entry at the GL. This barrier may be therapeutically targetable in inflammatory CNS disease.

Authors

Sam Horng, Anthony Therattil, Sarah Moyon, Alexandra Gordon, Karla Kim, Azeb Tadesse Argaw, Yuko Hara, John N. Mariani, Setsu Sawai, Per Flodby, Edward D. Crandall, Zea Borok, Michael V. Sofroniew, Candice Chapouly, Gareth R. John

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Figure 6

Clinical disability and mortality in EAE are more severe in Cldn4 CKO mice than controls.

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Clinical disability and mortality in EAE are more severe in Cldn4 CKO mi...
(A) Experimental Cldn4 CKO and control mice induced with EAE were scored daily on a standard 5-point scale (29). Disability scores are significantly more severe for CKO mice at days 14–21; *P < 0.05, **P < 0.01, 2-way ANOVA with Bonferroni correction. (B) Peak score during EAE is increased in Cldn4 CKO mice compared with controls (CKO n = 18, WT n = 24, P < 0.01, 2-tailed t test). (C–E) Also increased in Cldn4 CKO are average EAE disability score from days 7 to 21 (CKO n = 18, WT n = 24, P < 0.005) (C), average score during time of disability (CKO n = 18, WT n = 23, P < 0.05) (D), and mortality or severe paralysis requiring euthanasia (score ≥4; P < 0.005) (E). There was no difference between groups in rate of EAE induction (P = 0.32, data not shown). (F–J) Spinal cord EAE lesions harvested at 21 dpi or at the time of euthanasia demonstrate increased CD4+ cell infiltration (CKO n = 3, WT n = 6, P < 0.01, 2-tailed t test) (F and H) and increased fibrinogen (CKO n = 4, WT n = 4, P < 0.05) and IgG entry (CKO n = 4, WT n = 3, P < 0.005) (G, I, and J) in Cldn4 CKO mice compared with controls. Data for CD4+ cells were confirmed using flow cytometry (Supplemental Figure 4, A and B) with no difference in counts from the spleen (Supplemental Figure 4, C and D). Infiltrating inflammatory cells in Cldn4 CKO mice showed more parenchymal access past the glia limitans superficialis and perivascular spaces compared with controls (Supplemental Figure 4, E and F). (K and M) Demyelination in EAE lesions, as measured by loss of myelin basic protein (MBP), which represents the percentage of white matter loss (% WM loss) within the dorsolateral (corticospinal motor) tracts, is strikingly increased in Cldn4 CKO mice compared with controls (CKO n = 4, WT n = 4, P < 0.005). (L and N) Oligodendrocyte numbers within EAE lesions are not significantly different between groups (CKO n = 3, WT n = 3, P = 0.25). Scale bars: 300 μm (F and G), 500 μm (K and L). See also Supplemental Figure 4, H–K. *P < 0.05, **P < 0.01.