RESUMO
Pulmonary arteriovenous malformations (PAVMs) are vascular anomalies resulting in abnormal connections between pulmonary arteries and veins. In 80% of cases, PAVMs are present from birth, but clinical manifestations are rarely seen in childhood. These congenital malformations are typically associated with Hereditary Hemorrhagic Telangiectasia (HHT), a rare disease that affects 1 in 5000/8000 individuals. HHT disease is frequently caused by mutations in genes involved in the TGF-ß pathway. However, approximately 15% of patients do not have a genetic diagnosis and, among the genetically diagnosed, more than 33% do not meet the Curaçao criteria. This makes clinical diagnosis even more challenging in the pediatric age group. Here, we introduce an 8-year-old patient bearing a severe phenotype of multiple diffuse PAVMs caused by an unknown mutation which ended in lung transplantation. Phenotypically, the case under study follows a molecular pattern which is HHT-like. Therefore, molecular- biological and cellular-functional analyses have been performed in primary endothelial cells (ECs) isolated from the explanted lung. The findings revealed a loss of functionality in lung endothelial tissue and a stimulation of endothelial-to-mesenchymal transition. Understanding the molecular basis of this transition could potentially offer new therapeutic strategies to delay lung transplantation in severe cases.
Assuntos
Células Endoteliais , Artéria Pulmonar , Veias Pulmonares , Telangiectasia Hemorrágica Hereditária , Humanos , Telangiectasia Hemorrágica Hereditária/genética , Telangiectasia Hemorrágica Hereditária/patologia , Criança , Artéria Pulmonar/anormalidades , Artéria Pulmonar/patologia , Veias Pulmonares/anormalidades , Veias Pulmonares/patologia , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Masculino , Mutação , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/patologia , Malformações Arteriovenosas/metabolismo , Transição Epitelial-Mesenquimal/genética , Transplante de Pulmão , Fístula Arteriovenosa/patologia , Fístula Arteriovenosa/genética , Pulmão/patologia , Pulmão/irrigação sanguínea , FemininoRESUMO
Arteriovenous malformations (AVMs) are congenital vascular anomalies with a poor prognosis. AVMs are considered intractable diseases, as there is no established approach for early diagnosis and treatment. Therefore, this study aimed to provide new evidence by analyzing microRNAs (miRNAs) associated with AVM. We present fundamental evidence for the early diagnosis and treatment of AVM by analyzing miRNAs in the endothelial cells of AVMs. This study performed sequencing and validation of miRNAs in endothelial cells from normal and AVM tissues. Five upregulated and two downregulated miRNAs were subsequently analyzed under hypoxia and vascular endothelial growth factor (VEGF) treatment by one-way analysis of variance (ANOVA). Under hypoxic conditions, miR-135b-5p was significantly upregulated in the AVM compared to that under normal conditions, corresponding to increased endothelial activity (p-value = 0.0238). VEGF treatment showed no significant increase in miR-135b-5p under normal conditions, however, a surge in AVM was observed. Under both hypoxia and VEGF treatment, comparison indicated a downregulation of miR-135b-5p in AVM. Therefore, miR-135b-5p was assumed to affect the pathophysiological process of AVM and might play a vital role as a potential biomarker of AVMs for application related to diagnosis and treatment.
Assuntos
Malformações Arteriovenosas , Biomarcadores , Células Endoteliais , MicroRNAs , Fator A de Crescimento do Endotélio Vascular , MicroRNAs/genética , MicroRNAs/metabolismo , Humanos , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/patologia , Malformações Arteriovenosas/diagnóstico , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Fator A de Crescimento do Endotélio Vascular/metabolismo , Fator A de Crescimento do Endotélio Vascular/genética , Masculino , Feminino , Adulto , Hipóxia Celular/genéticaRESUMO
AIMS: BMP9 is a high affinity ligand of ALK1 and endoglin receptors that are mutated in the rare genetic vascular disorder hereditary hemorrhagic telangiectasia (HHT). We have previously shown that loss of Bmp9 in the 129/Ola genetic background leads to spontaneous liver fibrosis via capillarization of liver sinusoidal endothelial cells (LSEC) and kidney lesions. We aimed to decipher the molecular mechanisms downstream of BMP9 to better characterize its role in vascular homeostasis in different organs. METHODS AND RESULTS: For this, we performed an RNA-seq analysis on LSEC from adult WT and Bmp9-KO mice and identified over 2000 differentially expressed genes. Gene ontology analysis showed that Bmp9 deletion led to a decrease in BMP and Notch signalling, but also LSEC capillary identity while increasing their cell cycle. The gene ontology term 'glomerulus development' was also negatively enriched in Bmp9-KO mice vs. WT supporting a role for BMP9 in kidney vascularization. Through different imaging approaches (electron microscopy, immunostainings), we found that loss of Bmp9 led to vascular enlargement of the glomeruli capillaries associated with alteration of podocytes. Importantly, we also showed for the first time that the loss of Bmp9 led to spontaneous arteriovenous malformations (AVMs) in the liver, gastrointestinal tract, and uterus. CONCLUSION: Altogether, these results demonstrate that BMP9 plays an important role in vascular quiescence both locally in the liver by regulating endothelial capillary differentiation markers and cell cycle but also at distance in many organs via its presence in the circulation. It also reveals that loss of Bmp9 is sufficient to induce spontaneous AVMs, supporting a key role for BMP9 in the pathogenesis of HHT.
Assuntos
Malformações Arteriovenosas , Células Endoteliais , Fator 2 de Diferenciação de Crescimento , Camundongos Knockout , Transdução de Sinais , Animais , Fator 2 de Diferenciação de Crescimento/metabolismo , Fator 2 de Diferenciação de Crescimento/genética , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/patologia , Modelos Animais de Doenças , Camundongos da Linhagem 129 , Fígado/metabolismo , Fígado/patologia , Fígado/irrigação sanguínea , Fenótipo , RNA-Seq , Receptores Notch/metabolismo , Receptores Notch/genética , MasculinoRESUMO
Hereditary hemorrhagic telangiectsia (HHT) is an inherited vascular disorder with highly variable expressivity, affecting up to 1 in 5,000 individuals. This disease is characterized by small arteriovenous malformations (AVMs) in mucocutaneous areas (telangiectases) and larger visceral AVMs in the lungs, liver, and brain. HHT is caused by loss-of-function mutations in the BMP9-10/ENG/ALK1/SMAD4 signaling pathway. This Review presents up-to-date insights on this mutated signaling pathway and its crosstalk with proangiogenic pathways, in particular the VEGF pathway, that has allowed the repurposing of new drugs for HHT treatment. However, despite the substantial benefits of these new treatments in terms of alleviating symptom severity, this not-so-uncommon bleeding disorder still currently lacks any FDA- or European Medicines Agency-approved (EMA-approved) therapies.
Assuntos
Malformações Arteriovenosas , Telangiectasia Hemorrágica Hereditária , Humanos , Telangiectasia Hemorrágica Hereditária/tratamento farmacológico , Telangiectasia Hemorrágica Hereditária/genética , Malformações Arteriovenosas/metabolismo , Transdução de Sinais/genéticaRESUMO
BACKGROUND: Distinct endothelial cell cycle states (early G1 versus late G1) provide different "windows of opportunity" to enable the differential expression of genes that regulate venous versus arterial specification, respectively. Endothelial cell cycle control and arteriovenous identities are disrupted in vascular malformations including arteriovenous shunts, the hallmark of hereditary hemorrhagic telangiectasia (HHT). To date, the mechanistic link between endothelial cell cycle regulation and the development of arteriovenous malformations (AVMs) in HHT is not known. METHODS: We used BMP (bone morphogenetic protein) 9/10 blocking antibodies and endothelial-specific deletion of activin A receptor like type 1 (Alk1) to induce HHT in Fucci (fluorescent ubiquitination-based cell cycle indicator) 2 mice to assess endothelial cell cycle states in AVMs. We also assessed the therapeutic potential of inducing endothelial cell cycle G1 state in HHT to prevent AVMs by repurposing the Food and Drug Administration-approved CDK (cyclin-dependent kinase) 4/6 inhibitor (CDK4/6i) palbociclib. RESULTS: We found that endothelial cell cycle state and associated gene expressions are dysregulated during the pathogenesis of vascular malformations in HHT. We also showed that palbociclib treatment prevented AVM development induced by BMP9/10 inhibition and Alk1 genetic deletion. Mechanistically, endothelial cell late G1 state induced by palbociclib modulates the expression of genes regulating arteriovenous identity, endothelial cell migration, metabolism, and VEGF-A (vascular endothelial growth factor A) and BMP9 signaling that collectively contribute to the prevention of vascular malformations. CONCLUSIONS: This study provides new insights into molecular mechanisms leading to HHT by defining how endothelial cell cycle is dysregulated in AVMs because of BMP9/10 and Alk1 signaling deficiencies, and how restoration of endothelial cell cycle control may be used to treat AVMs in patients with HHT.
Assuntos
Malformações Arteriovenosas , Telangiectasia Hemorrágica Hereditária , Humanos , Camundongos , Animais , Telangiectasia Hemorrágica Hereditária/genética , Telangiectasia Hemorrágica Hereditária/patologia , Fator A de Crescimento do Endotélio Vascular/metabolismo , Malformações Arteriovenosas/metabolismo , Células Endoteliais/metabolismo , Fator 2 de Diferenciação de Crescimento/metabolismo , Pontos de Checagem do Ciclo CelularRESUMO
BACKGROUND: Episodic growth due to microvascular proliferations (MVP) has been reported in congenital arteriovenous malformations (AVM), which are normally quiescent lesions composed of mature malformed vessels. Since AVM also may worsen under conditions of hormonal dysregulation, we hypothesized that hormonal influences may stimulate this process of vasoproliferative growth through potential interactions with hormone receptors (HR). METHODS: 13 Cases of AVM tissue with histologically documented vasoproliferative growth were analyzed quantitatively for the presence and tissue localization of estrogen receptor (ER), progesterone receptor (PGR), growth hormone receptor (GHR) and follicle-stimulating hormone receptor (FSHR) in relation to resident cells of interest (endothelial cells (EC), smooth muscle cells (SMC) and mast cells (MC)) by applying multiplex immunohistochemistry (IHC) staining. Expression patterns in lesions with MVP and mature vessels were quantified and compared. Available fresh frozen tissues of 3 AVM samples were used to confirm the presence of HR using Reverse-Transcriptase quantitative Polymerase Chain Reaction (RT-qPCR). RESULTS: All four HR studied were expressed in all cases within EC and SMC in areas of MVP and mature vessels, but not in normal skin tissue. ER, GHR, and FSHR showed more expression in EC of MVP and in SMC of mature vessels. RT-qPCR confirmed presence of all 4 HR in both areas. CONCLUSION: Expression of ER, PGR, GHR, and FSHR in vasoproliferative areas of congenital AVM could explain onset of sudden symptomatic growth, as has observed in a subpopulation of patients. These findings may have implications for eventual anti-hormonal targeted therapy in the lesions involved.
Assuntos
Malformações Arteriovenosas , Malformações Vasculares , Humanos , Células Endoteliais/metabolismo , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/patologia , Miócitos de Músculo Liso/metabolismo , Miócitos de Músculo Liso/patologia , Hormônios/metabolismoRESUMO
Vascular networks form, remodel, and mature under the influence of both fluid shear stress (FSS) and soluble factors. Physiological FSS promotes and maintains vascular stability via synergy with bone morphogenic proteins 9 and 10 (BMP9 and BMP10). Conversely, mutation of the BMP receptors activin-like kinase 1 (ALK1), endoglin (ENG), or the downstream effector, SMAD family member 4 (SMAD4) leads to hereditary hemorrhagic telangiectasia (HHT), characterized by fragile and leaky arterial-venous malformations (AVMs). How endothelial cells (ECs) integrate FSS and BMP signals in vascular development and homeostasis and how mutations give rise to vascular malformations is not well understood. Here, we aimed to elucidate the mechanism of synergy between FSS and SMAD signaling in vascular stability and how disruption of this synergy leads to AVMs. We found that loss of Smad4 increased the sensitivity of ECs to flow by lowering the FSS set point, with resulting AVMs exhibiting features of excessive flow-mediated morphological responses. Mechanistically, loss of SMAD4 disinhibits flow-mediated KLF4-TIE2-PI3K/Akt signaling, leading to cell cycle progression-mediated loss of arterial identity due to KLF4-mediated repression of cyclin dependent Kinase (CDK) inhibitors CDKN2A and CDKN2B. Thus, AVMs caused by Smad4 deletion are characterized by chronic high flow remodeling with excessive EC proliferation and loss of arterial identity as triggering events.
Assuntos
Malformações Arteriovenosas , Telangiectasia Hemorrágica Hereditária , Camundongos , Animais , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/metabolismo , Células Endoteliais/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Camundongos Knockout , Telangiectasia Hemorrágica Hereditária/genética , Proteínas Morfogenéticas Ósseas/genéticaRESUMO
BACKGROUND: Hereditary hemorrhagic telangiectasia (HHT) is a vascular disorder characterized by arteriovenous malformations and blood vessel enlargements. However, there are no effective drug therapies to combat arteriovenous malformation formation in patients with HHT. Here, we aimed to address whether elevated levels of ANG2 (angiopoietin-2) in the endothelium is a conserved feature in mouse models of the 3 major forms of HHT that could be neutralized to treat brain arteriovenous malformations and associated vascular defects. In addition, we sought to identify the angiogenic molecular signature linked to HHT. METHODS: Cerebrovascular defects, including arteriovenous malformations and increased vessel calibers, were characterized in mouse models of the 3 common forms of HHT using transcriptomic and dye injection labeling methods. RESULTS: Comparative RNA sequencing analyses of isolated brain endothelial cells revealed a common, but unique proangiogenic transcriptional program associated with HHT. This included a consistent upregulation in cerebrovascular expression of ANG2 and downregulation of its receptor Tyr kinase with Ig and EGF homology domains (TIE2/TEK) in HHT mice compared with controls. Furthermore, in vitro experiments revealed TEK signaling activity was hampered in an HHT setting. Pharmacological blockade of ANG2 improved brain vascular pathologies in all HHT models, albeit to varying degrees. Transcriptomic profiling further indicated that ANG2 inhibition normalized the brain vasculature by impacting a subset of genes involved in angiogenesis and cell migration processes. CONCLUSIONS: Elevation of ANG2 in the brain vasculature is a shared trait among the mouse models of the common forms of HHT. Inhibition of ANG2 activity can significantly limit or prevent brain arteriovenous malformation formation and blood vessel enlargement in HHT mice. Thus, ANG2-targeted therapies may represent a compelling approach to treat arteriovenous malformations and vascular pathologies related to all forms of HHT.
Assuntos
Malformações Arteriovenosas , Telangiectasia Hemorrágica Hereditária , Animais , Camundongos , Telangiectasia Hemorrágica Hereditária/tratamento farmacológico , Telangiectasia Hemorrágica Hereditária/genética , Células Endoteliais/metabolismo , Angiopoietina-2/genética , Angiopoietina-2/metabolismo , Malformações Arteriovenosas/metabolismo , FenótipoRESUMO
This study sought to identify potential mechanisms by which k-RasV12-expressing endothelial cell (EC) tubes demonstrate an increased propensity to regress compared with controls. Activated k-Ras mutations play a role in a variety of pathological conditions, including arteriovenous malformations, which are prone to bleed, causing serious hemorrhagic complications. ECs expressing active k-RasV12 demonstrate markedly excessive lumen formation with widened and shortened tubes accompanied by reduced pericyte recruitment and basement membrane deposition, leading to deficient capillary network assembly. The current study showed that active k-Ras-expressing ECs secreted greater amounts of MMP-1 proenzyme compared with control ECs, and readily converted it to increased active MMP-1 levels through the action of plasmin or plasma kallikrein (generated from their added zymogens). Active MMP-1 degraded three-dimensional collagen matrices, leading to more rapid and extensive regression of the active k-Ras-expressing EC tubes, in conjunction with matrix contraction, compared with control ECs. Under conditions where pericytes protect control EC tubes from plasminogen- and MMP-1-dependent tube regression, this failed to occur with k-RasV12 ECs, due to reduced pericyte interactions. In summary, k-RasV12-expressing EC vessels showed an increased propensity to regress in response to serine proteinases through accentuated levels of active MMP-1, a novel pathogenic mechanism that may underlie hemorrhagic events associated with arteriovenous malformation lesions.
Assuntos
Malformações Arteriovenosas , Metaloproteinase 1 da Matriz , Humanos , Metaloproteinase 1 da Matriz/metabolismo , Colágeno/metabolismo , Células Endoteliais/metabolismo , Fibrinolisina/metabolismo , Malformações Arteriovenosas/metabolismoRESUMO
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 TGFß 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.
Assuntos
Malformações Arteriovenosas , Receptor do Fator de Crescimento Transformador beta Tipo I , Proteína Smad2 , Animais , Camundongos , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/metabolismo , Regulação da Expressão Gênica , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Fosforilação , Transdução de Sinais , Proteína Smad2/genética , Proteína Smad2/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Receptor do Fator de Crescimento Transformador beta Tipo I/genética , Receptor do Fator de Crescimento Transformador beta Tipo I/metabolismoRESUMO
Brain arteriovenous malformations (AVMs) are a disorder wherein abnormal, enlarged blood vessels connect arteries directly to veins, without an intervening capillary bed. AVMs are one of the leading causes of hemorrhagic stroke in children and young adults. Most human sporadic brain AVMs are associated with genetic activating mutations in the KRAS gene. Our goal was to develop an in vitro model that would allow for simultaneous morphological and functional phenotypic data capture in real time during AVM disease progression. By generating human endothelial cells harboring a clinically relevant mutation found in most human patients (activating mutations within the small GTPase KRAS) and seeding them in a dynamic microfluidic cell culture system that enables vessel formation and perfusion, we demonstrate that vessels formed by KRAS4AG12V mutant endothelial cells (ECs) were significantly wider and more leaky than vascular beds formed by wild-type ECs, recapitulating key structural and functional hallmarks of human AVM pathogenesis. Immunofluorescence staining revealed a breakdown of adherens junctions in mutant KRAS vessels, leading to increased vascular permeability, a hallmark of hemorrhagic stroke. Finally, pharmacological blockade of MEK kinase activity, but not PI3K inhibition, improved endothelial barrier function (decreased permeability) without affecting vessel diameter. Collectively, our studies describe the creation of human KRAS-dependent AVM-like vessels in vitro in a self-assembling microvessel platform that is amenable to phenotypic observation and drug delivery.
Assuntos
Malformações Arteriovenosas , Acidente Vascular Cerebral Hemorrágico , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/patologia , Criança , Células Endoteliais/metabolismo , Humanos , Dispositivos Lab-On-A-Chip , Proteínas Proto-Oncogênicas p21(ras) , Adulto JovemRESUMO
Arteriovenous malformations (AVMs) are the most common types of cerebral vascular malformations, which are dynamic lesions with de novo growth potentials. The dysfunction of endothelial cells has been postulated to play a role in the pathogenesis of brain AVMs. mTOR-FABP4 signal enhances the angiogenic responses of endothelial cells and is not activated in the normal cerebral vasculature. Herein, we investigated the hypothesis that the mTOR-FABP4 signal may be activated in brain AVMs. The abundance of molecules in mTOR-FABP4 signal expression was detected by immunohistochemistry and Western blotting; special expressing cells were further characterized by double immunofluorescence using antibodies against various cell-specific markers. Next, several functional assays were performed to analyze the influence of the mTOR-FABP4 signal on proliferation, apoptosis, migration, and vascular tube formation of endothelial cells in human umbilical vein endothelial cells (HUVECs) using rapamycin and L-leucine. The expression of mTOR, p-mTOR, and FABP4 was increased in endothelial cells of human brain AVMs. Endothelial cell mTOR and p-mTOR expression were present in 70% and 55% of brain AVMs, respectively. Moreover, a population of FABP4-positive endothelial cells was detected in 80% of brain AVMs. The mTOR-FABP4 signal was activated and inhibited by L-leucine and rapamycin in HUVECs. The proliferation, apoptosis, migration, and vascular tube formation of endothelial cells could be inhibited by rapamycin. The mTOR-FABP4 signal was activated in human brain AVMs, and the mTOR-FABP4 signal was involved in proliferation, apoptosis, migration, and the vascular tube formation of endothelial cells. Taken together, whether rapamycin has therapeutic potential for treating human brain AVMs is worthy of further study. KEY MESSAGES : We confirmed that the mTOR- FABP4 pathway is activated in human brain arteriovenous malformations. We confirmed that mTOR signaling pathway affects endothelial cell function by regulating proliferation, migration, apoptosis, and tube formation of endothelial cell. Our study can provide theoretical support for mTOR pathway inhibitors in the treatment of human brain arteriovenous malformations.
Assuntos
Malformações Arteriovenosas , Proteínas de Ligação a Ácido Graxo , Serina-Treonina Quinases TOR , Malformações Arteriovenosas/metabolismo , Encéfalo/metabolismo , Proteínas de Ligação a Ácido Graxo/metabolismo , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos , Leucina/metabolismo , Sirolimo/metabolismo , Sirolimo/farmacologia , Serina-Treonina Quinases TOR/metabolismoRESUMO
This review highlights new concepts in vascular patterning in the last 10 years, with emphasis on its beauty and complexity. Endothelial cell signaling pathways that respond to molecular or mechanical signals are described, and examples of vascular patterning that use these pathways in brain, skin, heart, and kidney are highlighted. The pathological consequences of patterning loss are discussed in the context of arteriovenous malformations (AVMs), and prospects for the next 10 years presented.
Assuntos
Malformações Arteriovenosas , Humanos , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/patologia , Transdução de Sinais , Encéfalo/metabolismoRESUMO
[Figure: see text].
Assuntos
Malformações Arteriovenosas/genética , Transição Epitelial-Mesenquimal , Mutação em Linhagem Germinativa , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/patologia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Movimento Celular , Células Cultivadas , Endoglina/genética , Endotélio Vascular/metabolismo , Endotélio Vascular/patologia , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos , Neovascularização Fisiológica , Proteínas Proto-Oncogênicas p21(ras)/genética , Peixe-ZebraRESUMO
Brain arteriovenous malformation (BAVM) is an abnormality in the cerebral vascular system. Although the upregulation of the Notch signalling pathway is a deterministic factor in BAVM, the mechanism by which this pathway is upregulated in patients with BAVM is uncertain. The effects of serum starvation and vascular endothelial growth factor (VEGF) stimulation on the Notch signalling pathway in brain microvascular endothelial cells (MECs) and mouse embryonic stem (mES)/embryoid body (EB)-derived endothelial cells were investigated in this study. The duration of serum starvation and VEGF concentration were changed, cell viability was measured, and reasonable time and concentration gradients were selected for subsequent studies. Protein and mRNA expression levels of Notch signalling pathway components in both MECs and mES/EB-derived endothelial cells were detected using western blotting and real-time PCR, respectively. Expression levels of the Notch1, Notch4, Jagged1, delta-like ligand 4 (Dll4) and Hes1 proteins and mRNAs were upregulated by lower VEGF concentrations and shorter-term serum starvation but inhibited by higher VEGF concentrations and longer-term serum starvation. This study revealed effects of changes in the duration of serum starvation and VEGF concentration on the expression of Notch signalling pathway components in both MECs and mES/EB-derived endothelial cells, potentially contributing to BAVM formation.
Assuntos
Malformações Arteriovenosas , Fator A de Crescimento do Endotélio Vascular , Animais , Malformações Arteriovenosas/metabolismo , Células Endoteliais/metabolismo , Humanos , Camundongos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Mensageiro/farmacologia , Receptor Notch1/genética , Receptor Notch1/metabolismo , Transdução de Sinais , Fator A de Crescimento do Endotélio Vascular/genética , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
BACKGROUND: Activin receptor-like kinase 1 (ALK1) is an endothelial transmembrane serine threonine kinase receptor for BMP family ligands that plays a critical role in cardiovascular development and pathology. Loss-of-function mutations in the ALK1 gene cause type 2 hereditary hemorrhagic telangiectasia, a devastating disorder that leads to arteriovenous malformations. Here, we show that ALK1 controls endothelial cell polarization against the direction of blood flow and flow-induced endothelial migration from veins through capillaries into arterioles. METHODS: Using Cre lines that recombine in different subsets of arterial, capillary-venous, or endothelial tip cells, we show that capillary-venous Alk1 deletion was sufficient to induce arteriovenous malformation formation in the postnatal retina. RESULTS: ALK1 deletion impaired capillary-venous endothelial cell polarization against the direction of blood flow in vivo and in vitro. Mechanistically, ALK1-deficient cells exhibited increased integrin signaling interaction with vascular endothelial growth factor receptor 2, which enhanced downstream YAP/TAZ nuclear translocation. Pharmacologic inhibition of integrin or YAP/TAZ signaling rescued flow migration coupling and prevented vascular malformations in Alk1-deficient mice. CONCLUSIONS: Our study reveals ALK1 as an essential driver of flow-induced endothelial cell migration and identifies loss of flow-migration coupling as a driver of arteriovenous malformation formation in hereditary hemorrhagic telangiectasia disease. Integrin-YAP/TAZ signaling blockers are new potential targets to prevent vascular malformations in patients with hereditary hemorrhagic telangiectasia.
Assuntos
Malformações Arteriovenosas , Células Endoteliais , Telangiectasia Hemorrágica Hereditária , Fator A de Crescimento do Endotélio Vascular , Animais , Humanos , Malformações Arteriovenosas/metabolismo , Movimento Celular/fisiologia , Células Endoteliais/metabolismo , Telangiectasia Hemorrágica Hereditária/mortalidade , Fator A de Crescimento do Endotélio Vascular/metabolismo , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Malformações Vasculares/metabolismo , CamundongosRESUMO
BACKGROUND: Vascular endothelial cells (ECs) are subject to continuous shear stress due to blood circulation. Mechanical stress due to high shear flow can also cause arteriovenous malformation (AVM) when ECs respond hyper-sensitively to shear flow. This study was conducted to test the hypothesis that angiogenesis could be promoted in response to mechanical stress via regulation of pro-angiogenic factors in AVM cells. METHODS: ECs were extracted from the tissue samples from six AVM patients and six normal patients. Shear stress at 7 dynes/cm2 were applied for 24 h. Before and after application of shear stress to each group, RT-PCR was performed to access the expression levels of angiopoietin2(AGP2), aquaporin1(AQP1) and TGFßR1. Immunofluorescences was also performed to evaluate the level of protein expressions. RESULTS: In both normal and AVM tissues, AGP2 and TGFßR1 under the shear stress showed increased expression in the ECs compared to the non-sheared samples. When AVMs and normal arterial vasculature were compared, the expression levels of both AGP2 and TGFßR1 in AVMs were higher when compared to normal arterial vasculature with or without shear stress. Immunofluorescence-based protein analysis also confirmed shear-induced AGP2 and TGFßR1 in both samples of normal and AVM patients. CONCLUSIONS: AVMs exhibited higher sensitivity to shear stress by producing higher expressions of some marked genes and proteins that regulate the endothelial functions upon exposure to shear stress. While the physiological mechanism for AVMs remain elusive, our study shows the plausibility of physical stress imposed by the shearing flow can cause the occurrence of AVMs.
Assuntos
Malformações Arteriovenosas , Neovascularização Patológica , Estresse Mecânico , Adolescente , Adulto , Angiopoietina-2/genética , Angiopoietina-2/metabolismo , Aquaporina 1/genética , Aquaporina 1/metabolismo , Artérias/anormalidades , Artérias/metabolismo , Artérias/patologia , Malformações Arteriovenosas/genética , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/patologia , Criança , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Feminino , Expressão Gênica , Humanos , Masculino , Neovascularização Patológica/genética , Neovascularização Patológica/metabolismo , Receptor do Fator de Crescimento Transformador beta Tipo I/genética , Receptor do Fator de Crescimento Transformador beta Tipo I/metabolismo , Adulto JovemRESUMO
CTCFL is expressed in testis, oocytes and embryonic stem cells, and is aberrantly expressed in malignant cells, and is classified as a cancer-testis gene. We have previously shown by using a tetracycline-inducible Ctcfl transgene that inappropriate expression of Ctcfl negatively impacts fetal development and causes early postnatal lethality in the mouse. The affected pups displayed severe vascular abnormalities and localized hemorrhages in the brain evocative of cerebral cavernous malformations (CCM) and arteriovenous malformations (AVM) in humans. Thus, we aim to analyze; a) the presence of CCM-related proteins CCM1/KRIT1, CCM2/malcavernin and CCM3/PDCD10 in Ctcfl transgenic animals and, b) whether there is CTCFL expression in human CCM and AVM tissues. Ctcfl transgenic animals exhibited increased CD31 expression in vascular areas of the dermis and periadnexal regions but no difference was observed for vWF and α-SMA expressions. CCM-related proteins CCM1/KRIT1, CCM2/malcavernin and CCM3/PDCD10 were aberrantly expressed in coronal sections of the head in transgenic animals. We also observed CTCFL expression in human CCMs and AVMs. The induced expression of CTCFL resulting in vascular brain malformations in mice combined with the presence of CTCFL in human vascular malformations provide new insights into the role of this gene in vascular development in humans.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Hemangioma Cavernoso do Sistema Nervoso Central/metabolismo , Animais , Antígenos CD34/metabolismo , Malformações Arteriovenosas/metabolismo , Malformações Arteriovenosas/patologia , Vasos Sanguíneos/patologia , Proteínas de Ligação a DNA/genética , Genótipo , Hemangioma Cavernoso do Sistema Nervoso Central/patologia , Camundongos Transgênicos , Molécula-1 de Adesão Celular Endotelial a Plaquetas/metabolismo , Transgenes , Fator de von Willebrand/metabolismoRESUMO
Abnormalities in arterial versus venous endothelial cell identity and dysregulation of angiogenesis are deemed important in the pathophysiology of brain arteriovenous malformations (AVMs). The Sonic hedgehog (Shh) pathway is crucial for both angiogenesis and arterial versus venous differentiation of endothelial cells, through its dual role on the vascular endothelial growth factor/Notch signaling and the nuclear orphan receptor COUP-TFII. In this study, we show that Shh, Gli1 (the main transcription factor of the Shh pathway), and COUP-TFII (a target of the non-canonical Shh pathway) are aberrantly expressed in human brain AVMs. We also show that implantation of pellets containing Shh in the cornea of Efnb2/LacZ mice induces growth of distinct arteries and veins, interconnected by complex sets of arteriovenous shunts, without an interposed capillary bed, as seen in AVMs. We also demonstrate that injection in the rat brain of a plasmid containing the human Shh gene induces the growth of tangles of tortuous and dilated vessels, in part positive and in part negative for the arterial marker αSMA, with direct connections between αSMA-positive and -negative vessels. In summary, we show that the Shh pathway is active in human brain AVMs and that Shh-induced angiogenesis has characteristics reminiscent of those seen in AVMs in humans.
Assuntos
Malformações Arteriovenosas/metabolismo , Encéfalo/fisiopatologia , Proteínas Hedgehog/metabolismo , Animais , HumanosRESUMO
Arteriovenous malformations (AVMs) are high-flow lesions directly connecting arteries and veins. In the brain, AVM rupture can cause seizures, stroke, and death. Patients with AVMs exhibit reduced coverage of the vessels by pericytes, the mural cells of microvascular capillaries; however, the mechanism underlying this pericyte reduction and its association with AVM pathogenesis remains unknown. Notch signaling has been proposed to regulate critical pericyte functions. We hypothesized that Notch signaling in pericytes is crucial to maintain pericyte homeostasis and prevent AVM formation. We inhibited Notch signaling specifically in perivascular cells and analyzed the vasculature of these mice. The retinal vessels of mice with deficient perivascular Notch signaling developed severe AVMs, together with a significant reduction in pericytes and vascular smooth muscle cells (vSMC) in the arteries, while vSMCs were increased in the veins. Vascular malformations and pericyte loss were also observed in the forebrain of embryonic mice deficient for perivascular Notch signaling. Moreover, the loss of Notch signaling in pericytes downregulated Pdgfrb levels and increased pericyte apoptosis, pointing to a critical role for Notch in pericyte survival. Overall, our findings reveal a mechanism of AVM formation and highlight the Notch signaling pathway as an essential mediator in this process.