transforming-growth-factor-beta and Arteriovenous-Malformations

In this review, we discuss the role of transforming growth factor-beta (TGF-β) in the development of pulmonary vascular disease (PVD), both pulmonary arteriovenous malformations (AVM) and pulmonary hypertension (PH), in hereditary hemorrhagic telangiectasia (HHT). HHT or Rendu-Osler-Weber disease is an autosomal dominant genetic disorder with an estimated prevalence of 1 in 5000 persons and characterized by epistaxis, telangiectasia and AVMs in more than 80% of cases, HHT is caused by a mutation in the ENG gene on chromosome 9 encoding for the protein endoglin or activin receptor-like kinase 1 (ACVRL1) gene on chromosome 12 encoding for the protein ALK-1, resulting in HHT type 1 or HHT type 2, respectively. A third disease-causing mutation has been found in the SMAD-4 gene, causing a combination of HHT and juvenile polyposis coli. All three genes play a role in the TGF-β signaling pathway that is essential in angiogenesis where it plays a pivotal role in neoangiogenesis, vessel maturation and stabilization. PH is characterized by elevated mean pulmonary arterial pressure caused by a variety of different underlying pathologies. HHT carries an additional increased risk of PH because of high cardiac output as a result of anemia and shunting through hepatic AVMs, or development of pulmonary arterial hypertension due to interference of the TGF-β pathway. HHT in combination with PH is associated with a worse prognosis due to right-sided cardiac failure. The treatment of PVD in HHT includes medical or interventional therapy.

Topics: Activin Receptors, Type II; Animals; Arteriovenous Malformations; Endoglin; Humans; Hypertension, Pulmonary; Lung Diseases; Mutation; Risk; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Diseases

The formation of a hierarchical vascular network, composed of arteries, veins, and capillaries, is essential for embryogenesis and is required for the production of new functional vasculature in the adult. Elucidating the molecular mechanisms that orchestrate the differentiation of vascular endothelial cells into arterial and venous cell fates is requisite for regenerative medicine, as the directed formation of perfused vessels is desirable in a myriad of pathological settings, such as in diabetes and following myocardial infarction. Additionally, this knowledge will enhance our understanding and treatment of vascular anomalies, such as arteriovenous malformations (AVMs). From studies in vertebrate model organisms, such as mouse, zebrafish, and chick, a number of key signaling pathways have been elucidated that are required for the establishment and maintenance of arterial and venous fates. These include the Hedgehog, Vascular Endothelial Growth Factor (VEGF), Transforming Growth Factor-β (TGF-β), Wnt, and Notch signaling pathways. In addition, a variety of transcription factor families acting downstream of, or in concert with, these signaling networks play vital roles in arteriovenous (AV) specification. These include Notch and Notch-regulated transcription factors (e.g., HEY and HES), SOX factors, Forkhead factors, β-Catenin, ETS factors, and COUP-TFII. It is becoming apparent that AV specification is a highly coordinated process that involves the intersection and carefully orchestrated activity of multiple signaling cascades and transcriptional networks. This review will summarize the molecular mechanisms that are involved in the acquisition and maintenance of AV fate, and will highlight some of the limitations in our current knowledge of the molecular machinery that directs AV morphogenesis.

Topics: Animals; Arteriovenous Malformations; Disease Models, Animal; Humans; Mice; Receptors, Notch; Transforming Growth Factor beta; Wnt Proteins; Wnt Signaling Pathway

Hereditary haemorrhagic telangiectasia is a rare systemic autosomal dominantly inherited disorder of the fibrovascular tissue with a wide variety of clinical manifestations. Diagnosis is based on the clinical Curaçao criteria or molecular genetic testing. Dilated vessels can develop into telangiectases or larger vascular malformations in various organs, calling for an interdisciplinary approach. Epistaxis and gastrointestinal bleeding can result from these vascular defects. Various conservative and interventional treatments have been described for these conditions. However, no optimal therapy exists. Treatment can become especially difficult due to progressive anaemia or when anticoagulant or anti-thrombotic therapy becomes necessary. Screening for pulmonary arteriovenous malformations (PAVM) should be performed in all confirmed and suspected patients. Treatment by percutaneous transcatheter embolotherapy and antibiotic prophylaxis is normally effective for PAVM. Cerebral or hepatic vascular malformations and rare manifestations need to be evaluated on a case-by-case basis to determine the best course of action for treatment.

Topics: Anemia, Iron-Deficiency; Antibiotic Prophylaxis; Anticoagulants; Arteriovenous Malformations; Disease Management; Embolization, Therapeutic; Epistaxis; Fibrinolytic Agents; Gastrointestinal Hemorrhage; Hemostatics; Humans; Hypertension, Pulmonary; Intracranial Arteriovenous Malformations; Liver; Lung; Neovascularization, Pathologic; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Thrombophilia; Transforming Growth Factor beta

Topics: Antigens, CD; Arteriovenous Malformations; Embolization, Therapeutic; Endoglin; Genotype; Humans; Mutation; Phenotype; Protein Serine-Threonine Kinases; Pulmonary Artery; Pulmonary Veins; Receptors, Cell Surface; Receptors, Growth Factor; Receptors, Transforming Growth Factor beta; Telangiectasia, Hereditary Hemorrhagic; Tomography, X-Ray Computed; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Patients with hereditary haemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, suffer from the consequences of abnormal vessel structures. These structures can lead to haemorrhages or shunt effects in liver, lungs and brain. This inherited and rare disease is characterized by mutations affecting the transforming growth factor-β (TGF-β)/Bone Morphogenetic Protein (BMP) pathway that results in arteriovenous malformations and studies indicate an impaired immune response. The mechanism underlying this altered immune response in HHT patients is still unknown. TGF-β interacts with hypoxia inducible factors (HIF), which both orchestrate inflammatory and angiogenic processes. Therefore, we analysed the expression of HIF and related genes in whole blood samples from HHT patients. We could show significantly decreased expression of HIF-1α on the mRNA and protein level. However, commonly known upstream regulators of HIF-1α in inflammatory responses were not affected, whereas HIF-1α target genes were significantly downregulated. There was no correlation between HIF1A or HIF2A gene expression and the severity of HHT detected. Our results represent a rare case of HIF-1α downregulation in a human disease, which underlines the relevance of HIFs in HHT. The study indicates an interaction of the known mutation in HHT and the dysregulation of HIF-1α in HHT patients, which might contribute to the clinical phenotype.

Topics: Arteriovenous Malformations; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Mutation; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Extracranial arteriovenous malformations (AVMs) are characterized by anomalous arterial-to-venous connections, aberrant angiogenesis, local inflammation and hypoxia, and disorganized histological architecture; however, the precise molecular perturbations leading to this phenotype remain elusive. We hypothesized that extracranial AVM tissue would demonstrate deregulation of the TGF-β/BMP signaling pathway, which may serve as a potential target in the development of molecular-based therapies for AVMs. AVM tissue was harvested during resection from 10 patients with AVMs and compared to control tissue. Blood was collected from 14 AVM patients and 10 patients without AVMs as controls. Expression of TGF-β/BMP pathway components was analyzed using RT-PCR, western blotting, and immunohistochemistry. Circulating levels of TGF-β1 were analyzed by ELISA. Paired t tests were utilized to perform statistical analysis. The mRNA levels of TGF-β1, ALK1, Endoglin (ENG), Smad6, Smad7, and Smad8 were significantly elevated in AVM tissue when compared to controls. Protein levels of TGF-β1 and Smad3 were elevated in AVM tissue while protein levels of BMP-9, ALK1, Smad1, Smad6, and Smad8 were significantly decreased in AVMs. Immunohistochemistry demonstrated increased TGF-β1 in the perivascular cells of AVMs compared to normal controls, and circulating levels of TGF-β1 were significantly higher in AVM patients. Patients with AVMs demonstrate aberrant TGF-β/BMP expression in AVM tissue and blood compared to controls. Targeting aberrantly expressed components of the TGF-β/BMP pathway in extracranial AVMs may be a viable approach in the development of novel molecular therapies, and monitoring circulating TGF-β1 levels may be a useful indicator of treatment success.

Topics: Arteriovenous Malformations; Endoglin; Growth Differentiation Factor 2; Humans; RNA, Messenger; Transforming Growth Factor beta; Transforming Growth Factor beta1

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.

Topics: Animals; Arteriovenous Malformations; Gene Expression Regulation; Membrane Proteins; Mice; Mitochondria; Phosphorylation; Receptor, Transforming Growth Factor-beta Type I; Signal Transduction; Smad2 Protein; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disease caused by mutations in. We tested this hypothesis and investigated the therapeutic effects and potential risks of induced-ALK1 or -ENG overexpression (OE) for HHT.. We generated a novel mouse allele (ROSA26. These data support the notion that ENG and ALK1 form a linear signaling pathway for the formation of a proper arteriovenous network during angiogenesis. We suggest that ALK1 OE or activation can be an effective therapeutic strategy for HHT. Further research is required to study whether this therapy could be translated into treatment for humans.

Topics: Activin Receptors, Type II; Alleles; Animals; Apoptosis Regulatory Proteins; Arteriovenous Malformations; Disease Models, Animal; Endoglin; Endothelial Cells; Green Fluorescent Proteins; Growth Differentiation Factor 2; Mice; Mitochondrial Proteins; Receptors, Notch; Retinal Vessels; RNA, Untranslated; Signal Transduction; Skin; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia is an autosomal dominant vascular disorder caused by heterozygous, loss-of-function mutations in 4 transforming growth factor beta (TGFβ) pathway members, including the central transcriptional mediator of the TGFβ pathway, Smad4. Loss of Smad4 causes the formation of inappropriate, fragile connections between arteries and veins called arteriovenous malformations (AVMs), which can hemorrhage leading to stroke, aneurysm, or death. Unfortunately, the molecular mechanisms underlying AVM pathogenesis remain poorly understood, and the TGFβ downstream effectors responsible for hereditary hemorrhagic telangiectasia-associated AVM formation are currently unknown.. To identify potential biological targets of the TGFβ pathway involved in AVM formation, we performed RNA- and chromatin immunoprecipitation-sequencing experiments on BMP9 (bone morphogenetic protein 9)-stimulated endothelial cells (ECs) and isolated ECs from a Smad4-inducible, EC-specific knockout ( Smad4-iECKO) mouse model that develops retinal AVMs. These sequencing studies identified the angiopoietin-Tek signaling pathway as a downstream target of SMAD4. We used monoclonal blocking antibodies to target a specific component in this pathway and assess its effects on AVM development.. Sequencing studies uncovered 212 potential biological targets involved in AVM formation, including the EC surface receptor, TEK (TEK receptor tyrosine kinase) and its antagonistic ligand, ANGPT2 (angiopoietin-2). In Smad4-iECKO mice, Angpt2 expression is robustly increased, whereas Tek levels are decreased, resulting in an overall reduction in angiopoietin-Tek signaling. We provide evidence that SMAD4 directly represses Angpt2 transcription in ECs. Inhibition of ANGPT2 function in Smad4-deficient mice, either before or after AVMs form, prevents and alleviates AVM formation and normalizes vessel diameters. These rescue effects are attributed to a reversion in EC morphological changes, such as cell size and shape that are altered in the absence of Smad4.. Our studies provide a novel mechanism whereby the loss of Smad4 causes increased Angpt2 transcription in ECs leading to AVM formation, increased blood vessel calibers, and changes in EC morphology in the retina. Blockade of ANGPT2 function in an in vivo Smad4 model of hereditary hemorrhagic telangiectasia alleviated these vascular phenotypes, further implicating ANGPT2 as an important TGFβ downstream mediator of AVM formation. Therefore, alternative approaches that target ANGPT2 function may have therapeutic value for the alleviation of hereditary hemorrhagic telangiectasia symptoms, such as AVMs.

Topics: Angiopoietin-2; Animals; Arteriovenous Malformations; Cell Size; Disease Models, Animal; Endothelial Cells; Endothelium, Vascular; Gene Expression Regulation; Mice; Mice, Knockout; Receptor, TIE-2; Signal Transduction; Smad4 Protein; Telangiectasia, Hereditary Hemorrhagic; Transcription, Genetic; Transforming Growth Factor beta

Hereditary hemorrhagic telangiectasia (HHT), the most common inherited vascular disorder, is predominantly caused by mutations in ENG and ACVRL1, which are part of the transforming growth factor beta (TGF-β) signaling pathway. HHT is characterized by the presence of mucocutaneous telangiectases and arteriovenous malformations in visceral organs, primarily the lungs, brain and liver. The most common symptom in HHT is epistaxis originating from nasal telangiectasia, which can be difficult to prevent and can lead to severe anemia. The clinical manifestations of HHT are extremely variable, even within family members, and the exact mechanism of how endoglin and ALK1 haploinsufficiency leads to HHT manifestations remains to be identified.. The purpose of this study was to detect significantly differentially regulated genes in HHT, and try to elucidate the pathways and regulatory mechanisms occurring in the affected tissue of HHT patients, in order to further characterize this disorder and hypothesize on how telangiectases develop. By microarray technology (Agilent G3 Human GE 8x60), we performed global gene expression profiling of mRNA transcripts from HHT nasal telangiectasial (n = 40) and non-telangiectasial (n = 40) tissue using a paired design. Comparing HHT telangiectasial and non-telangiectasial tissue, significantly differentially expressed genes were detected using a paired t-test. Gene set analysis was performed using GSA-SNP. In the group of ENG mutation carriers, we detected 67 differentially expressed mRNAs, of which 62 were down-regulated in the telangiectasial tissue. Gene set analysis identified the gene ontology (GO) terms vasculogenesis, TGF-β signaling, and Wnt signaling as differentially expressed in HHT1. Altered Wnt signaling might be related to HHT pathogenesis and a greater understanding of this may lead to the discovery of therapeutic targets in HHT.

Topics: Activin Receptors, Type II; Antigens, CD; Arteriovenous Malformations; Biopsy; Cluster Analysis; Endoglin; Family Health; Female; Gene Expression Profiling; Genotype; Humans; Male; Mutation; Nasal Mucosa; Nucleic Acid Hybridization; Principal Component Analysis; Receptors, Cell Surface; Signal Transduction; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta

The expression of growth factors and proliferation of endotheliocytes in vascular malformations were studied by immunohistochemical methods. The detected specific features of growth factor expression in the endothelium of venous and arteriovenous malformations seem to reflect the differences in the pathogenesis of these formations. High proliferative activity of the endothelium in angiodysplasias of both types can underlie the disease relapsing.

Topics: Adult; Aged; Arteriovenous Malformations; Endothelial Cells; Endothelium, Vascular; Female; Fibroblast Growth Factors; Humans; Immunohistochemistry; In Vitro Techniques; Male; Middle Aged; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor B; Vascular Endothelial Growth Factor C; Vascular Endothelial Growth Factor D; Vascular Malformations; Young Adult

Mutations in endoglin (ENG) and activin-like kinase (ALK1) cause hereditary hemorrhagic telangiectasias, disorders characterized by pulmonary and brain arteriovenous malformations (BAVMs). We investigated whether polymorphisms in these genes are also associated with sporadic BAVM.. A total of 177 sporadic BAVM patients and 129 controls (all subjects white) were genotyped for 2 variants in ALK1 and 7 variants in ENG.. The ALK1 IVS3-35A>G polymorphism was associated with BAVM: (AnyA [AA+AG] genotype: odds ratio, 2.47; 95% CI, 1.38 to 4.44; P=0.002). Two ENG polymorphisms, ENG -1742A>G and ENG 207G>A, showed a trend toward association with BAVM that did not reach statistical significance.. A common polymorphism in ALK1 is associated with sporadic BAVM, suggesting that genetic variation in genes mutated in familial BAVM syndromes may play a role in sporadic BAVMs.

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Adult; Antigens, CD; Arteriovenous Malformations; Brain; Case-Control Studies; Cohort Studies; Endoglin; Female; Genetic Variation; Genotype; Humans; Male; Middle Aged; Models, Statistical; Odds Ratio; Polymorphism, Genetic; Receptors, Cell Surface; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Topics: Activin Receptors, Type I; Activin Receptors, Type II; Antigens, CD; Arteriovenous Malformations; Blood Coagulation; Endoglin; Epistaxis; Head; Humans; Membrane Proteins; Mutation; Receptors, Cell Surface; Telangiectasia, Hereditary Hemorrhagic; Transforming Growth Factor beta; Vascular Cell Adhesion Molecule-1

Vascular malformations are frequent in newborns, and they persist throughout life, which differentiates them from vascular tumors (eg, hemangiomas). Arteriovenous malformations are high-flow vascular malformations. They are considered nonmalignant but can expand and become a significant clinical risk when extensive. To characterize endothelial cells from arteriovenous malformations (AMEC), we cultured cells obtained from surgical specimens and studied their properties. After selection, the cells that grew out from explants had phenotypic and antigenic features (platelet endothelial cell adhesion molecule, von Willebrand factor) of human endothelial cells. Their spontaneous proliferation rate was higher (1.8 to 6.4 times) than that of human umbilical vein, arterial, or microvascular endothelial cells. The proliferation rate of AMEC was not sensitive to the inhibitory activity of various cytokines (interleukin-1beta, tumor necrosis factor-alpha, transforming growth factor-beta, Interferon-gamma). In basal conditions, intercellular adhesion molecule (ICAM-1) was detected at a higher level of expression (6- to 10-fold) on AMEC, but these cells failed to express E-selectin or the vascular cell adhesion molecule (VCAM-1) after cytokine stimulation. Expression of c-ets-1 proto-oncogene was shown by in situ hybridization. The low response to cytokines, the higher propensity to proliferate, and the ets-1 expression suggest that AMEC have a defective regulation of proliferation that may be due to a reduced apoptotic process.

Topics: Adolescent; Adult; Arteriovenous Malformations; Cell Division; Cells, Cultured; Culture Media; Culture Media, Conditioned; Cytokines; E-Selectin; Endothelium, Vascular; Female; Fibroblasts; Flow Cytometry; Humans; Interferon-gamma; Interleukin-1; Male; Organ Culture Techniques; Platelet Endothelial Cell Adhesion Molecule-1; Proto-Oncogene Mas; Recombinant Proteins; Transforming Growth Factor beta; Tumor Necrosis Factor-alpha; Umbilical Arteries; Umbilical Veins; Vascular Cell Adhesion Molecule-1; von Willebrand Factor

The factors responsible for the development of cerebral arteriovenous malformations (AVMs) are not well known. Patients with hereditary hemorrhagic telangiectasia (HHT) have cutaneous vascular dysplasia and a high propensity to develop systemic and cerebral AVMs. Transforming growth factor-beta (TGF-beta) complex has been implicated in HHT. The aim of this study was to evaluate the expression of TGF-beta 1, TGF-beta 2, TGF-beta 3, and their two receptors (R1 and R2) in AVMs and in normal brain vessels. Formalin-fixed, paraffin-embedded tissues from 20 patients with cerebral AVMs (including two patients with HHT) were sequentially sectioned into 6 microns sections. Similar sections from normal brain tissue were obtained from five patients without AVMs and no intracranial pathology, who had died from unrelated causes. The normal tissue sections included large intracranial arteries, small arteries, venous sinuses, cortical veins, and brain tissue containing arterioles, capillaries, and venules. All specimens underwent immunohistochemical analyses with polyclonal antibodies to the following antigens: TGF-beta 1, TGF-beta 2, TGF-beta 3, and R1 and R2. The immunoreactivity, when present, was consistently noted in endothelial cells and in the medial smooth muscle. The intensity of vessel wall immunostaining was graded on a scale from 0 to 3. The mean staining grades of normal vessels for TGF-beta 1, TGF-beta 2, TGF-beta 3, R1, and R2 were 0.6 (range 0-1), 3, 2.8 (range 2-3), 1.6 (range 0-2), and 3, respectively, whereas the mean staining grades of AVM vessels were 0.3 (range 0-1), 0.8 (range 0-1), 0.6 (range 0-1), 1.4 (range 0-2), and 0.9 (range 0-1), respectively. The study thus demonstrated that normal brain vessels (arteries, veins, small vessels) have strong (range 2.8-3) immunostaining for TGF-beta 2, TGF-beta 3, and R2, and that the AVM nidus vessels have a paucity (range 0.8-0.9) of staining for these factors. In AVM vessels that had zero immunoreactivity to the above three factors, the vessel wall was fibrocollagenous rather than muscular. Further studies to examine the TGF-beta complex behavior in AVMs are needed.

Topics: Antibodies; Arteriovenous Malformations; Gene Expression Regulation, Developmental; Humans; Transforming Growth Factor beta