%0 Journal Article %A Pierre-Louis Hollier %A Sarah Guimbal %A Pierre Mora %A Aïssata Diop %A Lauriane Cornuault %A Thierry Couffinhal %A Alain-Pierre Gadeau %A Marie-Ange Renault %A Candice Chapouly %T Genetic disruption of the Blood Brain Barrier leads to protective barrier formation at the Glia Limitans %D 2020 %R 10.1101/2020.03.13.990762 %J bioRxiv %P 2020.03.13.990762 %X Recent work demonstrated that Central Nervous System (CNS) inflammation induces endothelial Blood Brain Barrier (BBB) opening as well as the formation of a tight junction barrier between reactive astrocytes at the Glia Limitans. We hypothesized that these two barriers may be reciprocally regulated by each other state and further, that the CNS parenchyma may acquire protection from the reactive astrocytic Glia Limitans not only in neuro-inflammation but also when BBB integrity is compromised under resting condition, without pathology. Previous studies identified Sonic hedgehog (Shh) astrocytic secretion as implicated in stabilizing the BBB during neuropathology and we recently demonstrated that desert hedgehog (Dhh) is expressed at the BBB in adults.Here we unraveled the role of the morphogen Dhh in maintaining BBB tightness and, using endothelial Dhh knockdown as a model of permeable BBB, we demonstrated that a double barrier system comprising both the BBB and Glia Limitans, is implemented in the CNS and regulated by a crosstalk going from endothelial cell to astrocytes.First, we showed that, under neuro-inflammatory conditions, Dhh expression is severely down regulated at the BBB and that Dhh is necessary for endothelial intercellular junction integrity as Dhh knockdown leads to CNS vascular leakage. We then demonstrated that, in Dhh endothelial knockout (DhhECKO) mice which display an open BBB, astrocytes are reactive and express the tight junction Claudin 4 (Cldn4) and showed that astrocytes can respond to signals secreted by the permeable endothelial BBB by becoming reactive and expressing Cldn4. To examine the consequences of the above results on disease severity, we finally induced multiple sclerosis in DhhECKO mice versus control littermates and showed that the pathology is less severe in the knockout animals due to Glia Limitans tightening, in response to BBB leakage, which drives inflammatory infiltrate entrapment into the perivascular space. Altogether these results suggest that genetic disruption of the BBB generates endothelial signals capable of driving the implementation of a secondary barrier at the Glia Limitans to protect the parenchyma. The concept of a reciprocally regulated CNS double barrier system has implications for treatment strategies in both the acute and chronic phases of multiple sclerosis pathophysiology.AlbAlbuminAldh1l1Aldehyde dehydrogenase 1 family, member L1BBBBlood Brain BarrierCd4Cluster of differentiation 4Cd45Cluster of differentiation 45Cdh5Cadherin5Cldn4Claudin4Cldn5Claudin5DhhDesert hedgehogFoxO1Forkhead box O1FgbFibrinogen beta chainGfapGlial fibrillary acidic proteinIcam1Intercellular adhesion molecule 1IgGImmunoglobulin GIL-1βInterleukin-1βMbpMyelin basic proteinNeuNb Platelet derived growth factor subunit bPdgfrβPlatelet derived growth factor receptor betaPecam1Platelet/endothelial cell adhesion molecule 1PodxlPodocalyxinPVSPerivascular spaceTympThymidine phosphorylaseVcam1Vascular cell adhesion molecule 1VegfAVascular endothelial growth factor AVimVimentinZo1Zonula Occludens 1 %U https://www.biorxiv.org/content/biorxiv/early/2020/03/15/2020.03.13.990762.full.pdf