Project description:The blood-brain barrier (BBB) consists of specific physical barriers, enzymes and transporters, which together maintain the necessary extracellular environment of the central nervous system (CNS). The main physical barrier is found in the CNS endothelial cell, and depends on continuous complexes of tight junctions combined with reduced vesicular transport. Other possible constituents of the BBB include extracellular matrix, astrocytes and pericytes, but the relative contribution of these different components to the BBB remains largely unknown. Here we demonstrate a direct role of pericytes at the BBB in vivo. Using a set of adult viable pericyte-deficient mouse mutants we show that pericyte deficiency increases the permeability of the BBB to water and a range of low-molecular-mass and high-molecular-mass tracers. The increased permeability occurs by endothelial transcytosis, a process that is rapidly arrested by the drug imatinib. Furthermore, we show that pericytes function at the BBB in at least two ways: by regulating BBB-specific gene expression patterns in endothelial cells, and by inducing polarization of astrocyte end-feet surrounding CNS blood vessels. Our results indicate a novel and critical role for pericytes in the integration of endothelial and astrocyte functions at the neurovascular unit, and in the regulation of the BBB. The brain microvascular fragments were isolated from mice with different genotypes, each represented by 3-4 biological replicates. Genotypes 1-2: Platelet derived growth factor-B (PDGF-B) retention-motif knockout (pdgfbret/ret) represent the pericyte-deficient situation, and the heterozygous mice (pdgfbret/+) are used as controls. Genotypes 3-4: Hypomorphic PDGF-B mutants that rescue pdgfb-/- null mice, in which a one copy of a conditionally silent human PDGF-B transgene targeted to the Rosa 26 locus (R26P) is turned on by endothelial-specific expression of Cre recombinase. In this data set these mice are named as Tie2Cre, R26P+/0, pdgfb-/- (representing the pericyte-deficient situation). Mice wt for pdgfb (pdgfb+/+) and carrying one silent copy of R26P (R26P+/0), are used as controls. Genotype 5: Adult Notch3+/+ wildtype (WT).
Project description:Purpose: Pericytes, the mural cells of blood microvessels, have come into focus as regulators of microvascular development and function, but due to paucity of defining markers, the identification and functional characterization of PC remain problematic, and reported data are often controversial. Here, we used a new approach for the isolation of mural cell from mouse brain in combination with RNA-sequencing (RNA-seq) and previously published vascular transcriptome data to assemble a state-of-the-art catalogue of brain mural cell-enriched gene transcripts. Methods: We isolated double positive cells from the brain of Pdgfrb-eGFP/NG2-DsRed transgenic mice using FACS. Cells were lysed, RNA extracted and sequenced with next-generation sequencing (NGS). For comparison, we also determined the transcriptome of brain microvascular fragments (containing both endothelial cells and mural cells) isolated by mechanical tissue disintegration, collagenase digestion and immune-panning using anti-CD31 antibodies coupled to magnetic beads. The reads were aligned to the Ensembl mouse gene assembly (NCBIM37) using Tophat2 software (version 2.0.4). The duplicated reads were removed using the picard tool (version 1.92). To identify the genes significantly enriched in the pericyte samples as compared with microvascular samples, statistical tests were performed using the Cufflinks tool (version 2.2.1) Results: The result showed that mRNA transcripts representing 856 different genes were enriched more than two-fold in FACS isolated Pdgfrb-eGFP/NG2-DsRed double positive cells compared with whole microvascular fragments (False Discovery Rate < 0.05) The RNA from three FACS sorted brain mural cell samples and three whole brain microvascular samples isolated from three animals were processed and sequenced on the Illumina HiSeq 2500 platform in the sequencing facility in Uppsala University.
Project description:Background: The differentiation of pericytes into myofibroblasts causes microvascular degeneration, extracellular matrix (ECM) accumulation, and tissue stiffening, characteristics of fibrotic diseases. It is unclear how pericyte-myofibroblast differentiation is regulated in the microvascular environment. Our previous study established a novel two-dimensional platform for coculturing microvascular endothelial cells (ECs) and pericytes derived from the same tissue. This study investigated how ECM stiffness regulated microvascular ECs, pericytes, and their interactions. Methods: Primary microvessels were cultured in the TGM2D medium. Stiff ECM was prepared by incubating ECM solution in regular culture dishes for one hour followed by PBS wash. Soft ECM with Young’s modulus of approximately 6 kPa was used unless otherwise noted. Bone grafts were prepared from the rat skull. Immunostaining, RNA sequencing, qRT-PCR, western blotting, and knockdown experiments were performed on the cells. Results: Primary microvascular pericytes differentiated into myofibroblasts (NG2+αSMA+) on stiff ECM, even with the TGFβ signaling inhibitor A83-01. Soft ECM and A83-01 cooperatively maintained microvascular stability while inhibiting pericyte-myofibroblast differentiation (NG2+αSMA-/low). We thus defined two pericyte subpopulations: primary (NG2+αSMA-/low) and activated (NG2+αSMA+) pericytes. Soft ECM promoted microvascular regeneration and inhibited fibrosis in bone graft transplantation in vivo. As Integrins are the major mechanosensor, we performed qRT-PCR screening of Integrin family members selected from RNA sequencing data. We found that Integrin β1 (Itgb1) was the major subunit downregulated by soft ECM and A83-01 treatment. Knocking down Itgb1 suppressed myofibroblast differentiation on stiff ECM. Interestingly, ITGB1 phosphorylation (Y783) was mainly located on microvascular ECs on stiff ECM, which promoted EC secretion of paracrine factors, including CTGF, to induce pericyte-myofibroblast differentiation. CTGF knockdown or monoclonal antibody treatment partially reduced myofibroblast differentiation, implying the participation of multiple pathways in fibrosis formation. Conclusions: Microvascular ECs mediate ECM stiffness-induced pericyte-myofibroblast differentiation through paracrine signaling.
Project description:Purpose: Pericytes, the mural cells of blood microvessels, have come into focus as regulators of microvascular development and function, but due to paucity of defining markers, the identification and functional characterization of PC remain problematic, and reported data are often controversial. Here, we used a new approach for the isolation of mural cell from mouse brain in combination with RNA-sequencing (RNA-seq) and previously published vascular transcriptome data to assemble a state-of-the-art catalogue of brain mural cell-enriched gene transcripts. Methods: We isolated double positive cells from the brain of Pdgfrb-eGFP/NG2-DsRed transgenic mice using FACS. Cells were lysed, RNA extracted and sequenced with next-generation sequencing (NGS). For comparison, we also determined the transcriptome of brain microvascular fragments (containing both endothelial cells and mural cells) isolated by mechanical tissue disintegration, collagenase digestion and immune-panning using anti-CD31 antibodies coupled to magnetic beads. The reads were aligned to the Ensembl mouse gene assembly (NCBIM37) using Tophat2 software (version 2.0.4). The duplicated reads were removed using the picard tool (version 1.92). To identify the genes significantly enriched in the pericyte samples as compared with microvascular samples, statistical tests were performed using the Cufflinks tool (version 2.2.1) Results: The result showed that mRNA transcripts representing 856 different genes were enriched more than two-fold in FACS isolated Pdgfrb-eGFP/NG2-DsRed double positive cells compared with whole microvascular fragments (False Discovery Rate < 0.05)
Project description:The microvasculature plays a key role in tissue perfusion, transport of mediators, and exchange of gases and metabolites to and from tissues. Microvascular dysfunction has emerged as an important contributor to cardiovascular diseases. In this study we used human blood vessel organoids (BVOs) as a model of the microvasculature to delineate the mechanisms of microvascular dysfunction caused by metabolic rewiring. BVOs fully recapitulated key features of the normal human microvasculature, including reliance of mature endothelial cells (ECs) on glycolytic metabolism, as concluded from metabolic flux assays using 13C-glucose labelling and mass spectrometry-based metabolomics. Pharmacological targeting of PFKFB3, a potent activator of glycolysis, with two different chemical inhibitors resulted in rapid BVO restructuring, vessel regression with reduced pericyte coverage. PFKFB3 mutant BVOs also displayed similar structural remodelling compared to control BVOs. Proteomic analysis of the BVO secretome revealed remodelling of the extracellular matrix and differential expression of paracrine mediators such as CTGF. Treatment with recombinant CTGF recovered tight junction formation and increased pericyte coverage in microvessels. Our metabolic and proteomics findings demonstrate that BVOs rapidly undergo restructuring in response to metabolic changes and identify CTGF as a critical paracrine regulator of microvascular integrity.
Project description:MCT8-deficient, healthy control and mutated/corrected isogenic iPSCs were differentiated into brain microvascular endothelial cells and neural cells. Neural cells were cultured with or without T3.