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Human blood vessel organoids reveal a critical role for CTGF in maintaining microvascular integrity

ABSTRACT: 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.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Xiaoke Yin

LAB HEAD: Manuel Mayr

PROVIDER: PXD041780 | Pride | 2023-09-13

REPOSITORIES: Pride

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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:Functional decline and structural alterations of the brain microvasculature are associated with cognitive impairment and development of dementias such as Alzheimer’s disease during aging. Although mechanisms of leading to microvascular changes during aging are not clear, the loss of mitochondria and reduced efficiency of remaining mitochondria appear to play a major role. While pharmacological agents which target mitochondria such as SS-31 have been shown to be effective in beneficial during aging and diseases, the full extent on mitochondrial- and non-mitochondrial proteins in the brain microvasculature has not been examined. We tested the hypothesis that attenuation of aging-associated changes in the brain microvascular proteome via targeting mitochondria represents a therapeutic option in the aging brain. We used male, aged (>18 months) C57Bl6/J mice treated with a mitochondria-targeted tetrapeptide, SS-31 or vehicle saline. Baseline cerebral blood flow (CBF) was determined using laser speckle imaging during the two-week treatment period. Then, isolated cortical microvessels (MVs), composed of end arterioles, capillaries, and venules, were used for Orbitrap Eclipse Tribrid mass spectrometry. Baseline CBF was similar between the groups, whereas bioinformatic analysis revealed substantial differences in protein abundance of cortical MVs between SS-31 and vehicle groups. Specifically, we identified 6,266 proteins in our data set from which 12% were mitochondrial or mitochondria associated. 107 of these proteins were significantly differentially expressed between the treatment and vehicle groups, and were associated with the oxidative phosphorylation, metabolism, antioxidant defense system, or mitochondrial dynamics. Administration of SS-31 also affected many non-mitochondrial proteins. Our findings suggest that mitochondria in the microvasculature represent a therapeutic target in the aging brain, and widespread changes in the proteome may underlie the mechanisms of rejuvenating actions of SS-31 in the aging phenotype.

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Human blood vessel organoids reveal a critical role for CTGF in maintaining microvascular integrity

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