Project description:The blood-brain barrier (BBB) dynamically controls and maintains a precisely balanced brain microenvironment necessary for reliable functioning. It is made up of highly specialized endothelial cells (ECs) in the lining of the vascular wall. These ECs are surrounded by the basal lamina, astrocytic perivascular endfeet, pericytes, microglia and neuronal processes that have been shown to contribute to barrier function1. In essence, the brain endothelium limits both transcellular and paracellular passage of cells and molecules into the central nervous system (CNS). Transcellular passage of hydrophilic molecules is limited due to a low rate of transcytotic vesicles, an extremely low pinocytotic activity, expression of active efflux transporters, and high metabolic activity. Paracellular diffusion of hydrophilic molecules and trafficking of immune cells is restricted by a network of tight junctions (TJs)2-5. Due to these characteristics, the BBB is able to protect the CNS from sudden changes in blood composition and uncontrolled influx of immune cells. In a large number of neuro-inflammatory diseases, an impaired function and an opening of the BBB are observed. In diseases of the CNS like multiple sclerosis or stroke or after brain trauma, the BBB becomes inflamed (mediated by for example reactive oxygen species (ROS) and hypoxia) and its function severely impaired which gives rise to enhanced cellular infiltration, thus contributing to tissue damage and neurological deficits. Due to the specialized nature of brain ECs, transmigration of leukocytes through cerebrovascular endothelium is likely to differ from that in other vascular beds. Generally, the transmigration process is closely controlled by the interaction of leukocytes with the endothelial surface followed by low velocity rolling, arrest, firm adhesion, and finally transmigration. For the diapedesis of immune cells across the cerebral vasculature a re-arrangement of the cytoskeleton and opening of the TJ complexes is required to allow cells to pass into the sub endothelial space. In the initial step of the adhesive cascade leukocytes adhere to the endothelium with low affinity. This adhesion is mediated by several members of the selectin family and their corresponding ligands. Despite the low affinity of these interactions, resulting contact of leukocytes with the endothelium leads to further activation of both cell types and finally transmigration of the leukocytes through the BBB6,7. The glycosylation of endothelial cells of different vascular bed origins To date it is unknown which specific carbohydrate structures on the BBB endothelium mediate leukocyte capture and rolling, and whether these structures are differentially expressed onto inflamed brain EC compared to normal brain ECs and vascular beds of other organs. Initial studies using qPCR and FACS analysis within our group reveal that brain endothelial cells have a different profile in their glycosylation-related genes compared to microvascular ECs upon inflammation, which may result in a different glycosylation profile of adhesive structures and may underlie rolling, adhesion and diapedesis of leukocytes. In this project we wish to identify specific, glycosylated structures on brain endothelial cells that mediate capture, rolling and diapedesis of leukocytes in the brain. To investigate the expression of glycosyltransferases in dendritic cells and the changes in expression associated with maturation. RNA preparations from stimulated and non-stimulated hcMEC/D3 (human brain endothelial cells line) and FMVEC (human promary microvascular endothelial cells isolated from foreskins) were sent to both Microarray Core (E) and Core(C). The RNA was put on an RNeasy Column, amplified, labeled, and hybridized to the Glycov3 microarrays. Data was sent to Dr. van Kooyk's lab for analysis.

Project description:The blood-brain barrier (BBB) dynamically controls and maintains a precisely balanced brain microenvironment necessary for reliable functioning. It is made up of highly specialized endothelial cells (ECs) in the lining of the vascular wall. These ECs are surrounded by the basal lamina, astrocytic perivascular endfeet, pericytes, microglia and neuronal processes that have been shown to contribute to barrier function1. In essence, the brain endothelium limits both transcellular and paracellular passage of cells and molecules into the central nervous system (CNS). Transcellular passage of hydrophilic molecules is limited due to a low rate of transcytotic vesicles, an extremely low pinocytotic activity, expression of active efflux transporters, and high metabolic activity. Paracellular diffusion of hydrophilic molecules and trafficking of immune cells is restricted by a network of tight junctions (TJs)2-5. Due to these characteristics, the BBB is able to protect the CNS from sudden changes in blood composition and uncontrolled influx of immune cells. In a large number of neuro-inflammatory diseases, an impaired function and an opening of the BBB are observed. In diseases of the CNS like multiple sclerosis or stroke or after brain trauma, the BBB becomes inflamed (mediated by for example reactive oxygen species (ROS) and hypoxia) and its function severely impaired which gives rise to enhanced cellular infiltration, thus contributing to tissue damage and neurological deficits. Due to the specialized nature of brain ECs, transmigration of leukocytes through cerebrovascular endothelium is likely to differ from that in other vascular beds. Generally, the transmigration process is closely controlled by the interaction of leukocytes with the endothelial surface followed by low velocity rolling, arrest, firm adhesion, and finally transmigration. For the diapedesis of immune cells across the cerebral vasculature a re-arrangement of the cytoskeleton and opening of the TJ complexes is required to allow cells to pass into the sub endothelial space. In the initial step of the adhesive cascade leukocytes adhere to the endothelium with low affinity. This adhesion is mediated by several members of the selectin family and their corresponding ligands. Despite the low affinity of these interactions, resulting contact of leukocytes with the endothelium leads to further activation of both cell types and finally transmigration of the leukocytes through the BBB6,7.

Project description:Background: Brain activity governing cognition and behaviour depends on the fine-tuned microenvironment provided by a tightly controlled blood-brain barrier (BBB). Brain endothelium dysfunction is a hallmark of BBB breakdown in most neurodegenerative/neuroinflammatory disorders. Therefore, the identification of new endogenous molecules involved in endothelial cell disruption is essential to better understand BBB dynamics. Cortistatin is a neuroimmune mediator with anti-inflammatory and neuroprotective properties that exerts beneficial effects on the peripheral endothelium. However, its role in the healthy and injured brain endothelium remains to be evaluated. Herein, this study aimed to investigate the potential function of endogenous and therapeutic cortistatin in regulating brain endothelium dysfunction in a neuroinflammatory/neurodegenerative environment. Methods: Wild-type and cortistatin-deficient murine brain endothelium and human cells were used for an in vitro barrier model, where a simulated ischemia-like environment was mimicked. Endothelial permeability, junction integrity, and immune response in the presence and absence of cortistatin were evaluated using different size tracers, immunofluorescence labelling, qPCR, and ELISA. Cortistatin molecular mechanisms underlying brain endothelium dynamics were assessed by RNA-sequencing analysis. Cortistatin role in BBB leakage was evaluated in adult mice injected with LPS. Results: The endogenous lack of cortistatin predisposes endothelium weakening with increased permeability, tight-junctions breakdown, and dysregulated immune activity. We demonstrated that both damaged and uninjured brain endothelial cells isolated from cortistatin-deficient mice, present a dysregulated and/or deactivated genetic programming. These pathways, related to basic physiology but also crucial for the repair after damage (e.g., extracellular matrix remodelling, angiogenesis, response to oxygen, signalling, and metabolites transport), are dysfunctional and make brain endothelial barrier lacking cortistatin non-responsive to any further injury. Treatment with cortistatin reversed in vitro hyperpermeability, tight-junctions disruption, inflammatory response, and reduced in vivo BBB leakage. Conclusions: The neuropeptide cortistatin has a key role in the physiology of the cerebral microvasculature and its presence is crucial to develop a canonical balanced response to damage. The reparative effects of cortistatin in the brain endothelium were accompanied by the modulation of the immune function and the rescue of barrier integrity. Cortistatin-based therapies could emerge as a novel pleiotropic strategy to ameliorate neuroinflammatory/neurodegenerative disorders with disrupted BBB.

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Non-human primate blood-brain barrier and in vitro brain endothelium: from transcriptome to the establishment of a new model

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