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Mitochondrial dysfunction induces ALK5-SMAD2-mediated hypovascularization and arteriovenous malformations in mouse retinas.

ABSTRACT: Although mitochondrial activity is critical for angiogenesis, its mechanism is not entirely clear. Here we show that mice with endothelial deficiency of any one of the three nuclear genes encoding for mitochondrial proteins, transcriptional factor (TFAM), respiratory complex IV component (COX10), or redox protein thioredoxin 2 (TRX2), exhibit retarded retinal vessel growth and arteriovenous malformations (AVM). Single-cell RNA-seq analyses indicate that retinal ECs from the three mutant mice have increased TGFβ signaling and altered gene expressions associated with vascular maturation and extracellular matrix, correlating with vascular malformation and increased basement membrane thickening in microvesels of mutant retinas. Mechanistic studies suggest that mitochondrial dysfunction from Tfam, Cox10, or Trx2 depletion induces a mitochondrial localization and MAPKs-mediated phosphorylation of SMAD2, leading to enhanced ALK5-SMAD2 signaling. Importantly, pharmacological blockade of ALK5 signaling or genetic deficiency of SMAD2 prevented retinal vessel growth retardation and AVM in all three mutant mice. Our studies uncover a novel mechanism whereby mitochondrial dysfunction via the ALK5-SMAD2 signaling induces retinal vascular malformations, and have therapeutic values for the alleviation of angiogenesis-associated human retinal diseases.

SUBMITTER: Zhang H

PROVIDER: S-EPMC9741628 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

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Mitochondrial dysfunction induces ALK5-SMAD2-mediated hypovascularization and arteriovenous malformations in mouse retinas.

Zhang Haifeng H Li Busu B Huang Qunhua Q López-Giráldez Francesc F Tanaka Yoshiaki Y Lin Qun Q Mehta Sameet S Wang Guilin G Graham Morven M Liu Xinran X Park In-Hyun IH Eichmann Anne A Min Wang W Zhou Jenny Huanjiao JH

Nature communications 20221210 1

Although mitochondrial activity is critical for angiogenesis, its mechanism is not entirely clear. Here we show that mice with endothelial deficiency of any one of the three nuclear genes encoding for mitochondrial proteins, transcriptional factor (TFAM), respiratory complex IV component (COX10), or redox protein thioredoxin 2 (TRX2), exhibit retarded retinal vessel growth and arteriovenous malformations (AVM). Single-cell RNA-seq analyses indicate that retinal ECs from the three mutant mice hav ...[more]

PMID: 36496409

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Project description:Although mitochondrial activity is critical for angiogenesis, its mechanism is not entirely clear. Here, we investigate the angiogenic functions of three separate nuclear genes that encode for mitochondrial proteins, including mitochondrial transcriptional factor (TFAM), respiratory complex IV component (COX10), and a mitochondrial redox protein thioredoxin 2 (TRX2), which are responsible for distinct mitochondrial functions. We aim to investigate if mitochondrial activities regulate common endothelial cell (EC) signaling pathways during angiogenesis. The silencing of Tfam, Cox10, or Trx2 in an in vitro 3D sprouting assay attenuates EC sprouting, which correlated with reduced EC proliferation but not with ROS generation or EC apoptosis. Mice with an inducible deletion of Tfam, Cox10, or Trx2 exhibit retarded retinal vessel growth without penetration into the deep plexi at early ages (P5-P12). The three mutant mice develop arteriovenous malformations (AVM) with microaneurysm formation in the microvessels at advanced ages (P12-P30); the hypovasculature and microaneurysm phenotypes resemble that of aged human retinas and human primitive retinal vascular abnormalities such as Coats’ disease, Leber’s military aneurysms and familial exudative vitreoretinopathy. Single-cell RNA-seq analyses of retinal ECs suggest that the three mutant mice have common EC clusters with reduced gene expressions in anion transporters, actin organization, extracellular matrix, and angiogenesis. These EC clusters also have increased gene expressions in endothelial-mesenchymal transition and arterial markers, correlating with enhanced TGFbR signaling in Tfam, Cox10, or Trx2-deficient mice. Importantly, pharmacological blockade by TGFbR inhibitors attenuated retinal vessel growth retardation and AVM formation in all three mutant mice. Our study demonstrates that mitochondrial dysfunction induces TGF-b receptor-mediated arteriovenous malformations and microaneurysm formation in mouse retinas, and provide a novel model and therapeutic intervention for human primitive retinal vascular abnormalities, which are characterized by retinal vascular malformations and are associated with many pathological complications such as diabetes and hypertension that can result in vision loss.

Project description:Background and purposeBrain arteriovenous malformation (bAVM) is an important risk factor for intracranial hemorrhage. Current treatments for bAVM are all associated with considerable risks. There is no safe method to prevent bAVM hemorrhage. Thalidomide reduces nose bleeding in patients with hereditary hemorrhagic telangiectasia, an inherited disorder characterized by vascular malformations. In this study, we tested whether thalidomide and its less toxic analog, lenalidomide, reduce bAVM hemorrhage using a mouse model.MethodsbAVMs were induced through induction of brain focal activin-like kinase 1 (Alk1, an AVM causative gene) gene deletion and angiogenesis in adult Alk1-floxed mice. Thalidomide was injected intraperitoneally twice per week for 6 weeks, starting either 2 or 8 weeks after AVM induction. Lenalidomide was injected intraperitoneally daily starting 8 weeks after AVM induction for 6 weeks. Brain samples were collected at the end of the treatments for morphology, mRNA, and protein analyses. The influence of Alk1 downregulation on PDGFB (platelet-derived growth factor B) expression was also studied on cultured human brain microvascular endothelial cells. The effect of PDGFB in mural cell recruitment in bAVM was explored by injection of a PDGFB overexpressing lentiviral vector to the mouse brain.ResultsThalidomide or lenalidomide treatment reduced the number of dysplastic vessels and hemorrhage and increased mural cell (vascular smooth muscle cells and pericytes) coverage in the bAVM lesion. Thalidomide reduced the burden of CD68+ cells and the expression of inflammatory cytokines in the bAVM lesions. PDGFB expression was reduced in ALK1-knockdown human brain microvascular endothelial cells and in mouse bAVM lesion. Thalidomide increased Pdgfb expression in bAVM lesion. Overexpression of PDGFB mimicked the effect of thalidomide.ConclusionsThalidomide and lenalidomide improve mural cell coverage of bAVM vessels and reduce bAVM hemorrhage, which is likely through upregulation of Pdgfb expression.

Project description:BackgroundCerebral arteriovenous malformations (cAVM) are a significant cause of intracranial hemorrhagic stroke and brain damage. The arteriovenous junctions in AVM nidus are known to have hemodynamic disturbances such as altered shear stress, which could lead to endothelial dysfunction. The molecular mechanisms coupling shear stress and endothelial dysfunction in cAVMs are poorly understood. We speculated that disturbed blood flow in artery-vein junctions activates Notch receptors and promotes endothelial mesenchymal plasticity during cAVM formation.MethodsWe investigated the expression profile of endothelial mesenchymal transition (EndMT) and cell adhesion markers, as well as activated Notch receptors, in 18 human cAVM samples and 15 control brain tissues, by quantitative real-time PCR (qRT-PCR) and immunohistochemical evaluation. Employing a combination of a microfluidic system, qRT-PCR, immunofluorescence, as well as invasion and inhibitor assays, the effects of various shear stress conditions on Notch-induced EndMT and invasive potential of human cerebral microvascular endothelial cells (hCMEC/d3) were analyzed.ResultsWe found evidence for EndMT and enhanced expression of activated Notch intracellular domain (NICD3 and NICD4) in human AVM nidus samples. The expression of transmembrane adhesion receptor integrin α9/β1 is significantly reduced in cAVM nidal vessels. Cell-cell adhesion proteins such as VE-cadherin and N-cadherin were differentially expressed in AVM nidus compared with control brain tissues. Using well-characterized hCMECs, we show that altered fluid shear stress steers Notch3 nuclear translocation and promotes SNAI1/2 expression and nuclear localization. Oscillatory flow downregulates integrin α9/β1 and VE-cadherin expression, while N-cadherin expression and endothelial cell invasiveness are augmented. Gamma-secretase inhibitor RO4929097, and to a lesser level DAPT, prevent the mesenchymal transition and invasiveness of cerebral microvascular endothelial cells exposed to oscillatory fluid flow.ConclusionsOur study provides, for the first time, evidence for the role of oscillatory shear stress in mediating the EndMT process and dysregulated expression of cell adhesion molecules, especially multifunctional integrin α9/β1 in human cAVM nidus. Concomitantly, our findings indicate the potential use of small-molecular inhibitors such as RO4929097 in the less-invasive therapeutic management of cAVMs.

Dataset Information

Mitochondrial dysfunction induces ALK5-SMAD2-mediated hypovascularization and arteriovenous malformations in mouse retinas.

Publications

Mitochondrial dysfunction induces ALK5-SMAD2-mediated hypovascularization and arteriovenous malformations in mouse retinas.

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