A Microphysiological HHT-on-a-Chip Platform Recapitulates Patient Vascular Lesions.

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare congenital disease in which fragile vascular malformations (VM) - including small telangiectasias and large arteriovenous malformations (AVMs) - focally develop in multiple organs. There are few treatment options and no cure for HHT. Most HHT patients are heterozygous for loss-of-function mutations affecting Endoglin (ENG) or Alk1 (ACVRL1); however, why loss of these genes manifests as VMs remains poorly understood. To complement ongoing work in animal models, we have developed a fully human, cell-based microphysiological model based on our Vascularized Micro-organ (VMO) platform (the HHT-VMO) that recapitulates HHT patient VMs. Using inducible ACVRL1 -knockdown, we control timing and extent of endogenous Alk1 expression in primary human endothelial cells (EC). Resulting HHT-VMO VMs develop over several days. Interestingly, in chimera experiments AVM-like lesions can be comprised of both Alk1-intact and Alk1-deficient EC, suggesting possible cell non-autonomous effects. Single cell RNA sequencing data are consistent with microvessel pruning/regression as contributing to AVM formation, while loss of PDGFB implicates mural cell recruitment. Finally, lesion formation is blocked by the VEGFR inhibitor pazopanib, mirroring positive effects of this drug in patients. In summary, we have developed a novel HHT-on-a-chip model that faithfully reproduces HHT patient lesions and that can be used to better understand HHT disease biology and identify potential new HHT drugs.

Pulmonary hypertension exacerbated by hereditary hemorrhagic telangiectasia combined with pulmonary arteriovenous fistula and pregnancy status: A case report.

Background: Hereditary hemorrhagic telangiectasia (HHT) is an uncommon autosomal dominant condition. The combination of pregnancy and HHT can exacerbate pulmonary hypertension (PH) and, in severe cases, lead to fatality. Case presentation: The case we presented is a 28-year-old multiparous woman. She developed chest tightness and dyspnea in the second trimester of pregnancy, which was not taken seriously at that time, and the symptoms worsened postpartum. Echocardiography showed elevated pulmonary artery pressure (PAP) and the computerized tomographic pulmonary angiogram revealed a significant pulmonary arteriovenous malformation. The patient's condition continued to deteriorate despite treatment to reduce pulmonary hypertension. We reviewed and updated the history of omission, recurrent epistaxis during pregnancy, and similar symptoms running in her family. Combined with the whole exon genetic testing report revealing the ACVRL1 gene mutation at chr12:52308295, the diagnosis of HHT was established. Four months later, a transcatheter closure of the pulmonary arteriovenous fistula was performed, with satisfying outcomes presenting a decrease of more than 15 mmHg in the pulmonary artery pressure. As of right now, the patient's status is stable during the outpatient follow-up. Conclusions: HHT is a rare condition that typically occurs alongside abnormal communication between pulmonary veins and arteries, leading to a high-flow state in the pulmonary circulation. A pulmonary hypertension crisis can also be triggered by the patient's pregnancy, which further increases blood volume. By reducinhttps://www.ecdc.europa.eu/sites/default/files/documents/Methods-for-the%20detection-and-characterisation-of-SARS-CoV-2-variants-first-update-WHO-20-Dec-2021.pdfg pulmonary vascular flow, catheter closure of the pulmonary arteriovenous fistula decreases pulmonary arterial pressure.

Increased Risk for Infections and Allergic Disease in Hereditary Hemorrhagic Telangiectasia.

Background/Objectives: Hereditary hemorrhagic telangiectasia (HHT) is a rare disorder characterized by dilated blood vessels. Different immunological changes have been described in these patients. In this study, the predisposition of patients with HHT to infections and allergic diseases was assessed. Methods: Patients with HHT completed an online survey in English or German. Their data were compared to non-affected partners or friends. Results: A total of 430 out of 588 respondents with HHT answered our questions about infections and allergies. Patients with HHT suffered significantly more often from various types of allergies than their partners, especially type I allergies (n = 226/276, 82%), and had a higher risk for sinusitis, urinary tract infections, pulmonary infections, and abscesses. A total of 38% of the patients took antibiotics prior to dental or surgical procedures (n = 57/152), and, in 10% of these patients, pulmonary arteriovenous malformations (PAVMs) were not detected. On the other hand, 51% of patients with PAVM did not report a prophylactic antibiotic intake (n = 40/79). The patients who needed iron supplementations suffered more often from sepsis (OR: 9.00, 95%CI: 0.92-88.16). Conclusions: Compared to their non-affected controls, patients with HHT showed an increased risk for infections in different organs and allergic diseases. There is a need for campaigns raising greater awareness recommending prophylactic antibiotic intake in patients with PAVM.

Evaluation of Aav Capsids and Delivery Approaches for Hereditary Hemorrhagic Telangiectasia Gene Therapy.

Nosebleeds and intracranial hemorrhage from brain arteriovenous malformations (bAVMs) are among the most devastating symptoms of patients with hereditary hemorrhagic telangiectasis (HHT). All available managements have limitations. We showed that intravenous delivery of soluble FMS-related tyrosine kinase 1 using an adeno-associated viral vector (AAV9-sFLT1) reduced bAVM severity of endoglin deficient mice. However, minor liver inflammation and growth arrest in young mice were observed. To identify AAV variants and delivery methods that can best transduce brain and nasal tissue with an optimal transduction profile, we compared 3 engineered AAV capsids (AAV.cc47, AAV.cc84 and AAV1RX) with AAV9. A single-stranded CBA promoter driven tdTomato transgene was packaged in these capsids and delivered intravenously (i.v.) or intranasally (i.n.) to wild-type mice. A CMV promoter driven Alk1 transgene was packaged into AAV.cc84 and delivered to PdgfbiCre;Alk1 f/f mice through i.v. injection followed by brain AVM induction. Transduced cells in different organs, vessel density and abnormal vessels in the bAVMs, and liver inflammation were analyzed histologically. Liver and kidney function were measured enzymatically. Compared to other viral vectors, AAV.cc84, after i.v. delivery, transduced a high percentage of brain ECs and few hepatocytes; whereas after i.n. delivery, AAV.cc84 transduced ECs and perivascular cells in the brain, and ECs, epithelial cells, and skeletal muscles in the nose with minimum hepatocyte transduction. No changes to liver or kidney function were detected. Delivery of AAV.cc84-Alk1 through i.v. to PdgfbiCre;Alk1 f/f mice reduced bAVM severity. In summary, we propose that AAV.cc84-Alk1 is a promising candidate for developing gene therapy in HHT patients.

Evaluation of AAV Capsids and Delivery Approaches for Hereditary Hemorrhagic Telangiectasia Gene Therapy.

Nosebleeds and intracranial hemorrhage from brain arteriovenous malformations (bAVMs) are among the most devastating symptoms of patients with hereditary hemorrhagic telangiectasis (HHT). All available managements have limitations. We showed that intravenous (i.v.) delivery of soluble Feline McDonough Sarcoma (FMS)-related tyrosine kinase 1 using an adeno-associated viral vector (AAV9-sFLT1) reduced bAVM severity of endoglin deficient mice. However, minor liver inflammation and growth arrest in young mice were observed. To identify AAV variants and delivery methods that can best transduce brain and nasal tissue with an optimal transduction profile, we compared 3 engineered AAV capsids (AAV.cc47, AAV.cc84, and AAV1RX) with AAV9. A single-stranded CBA promoter driven tdTomato transgene was packaged in these capsids and delivered i.v. or intranasally (i.n.) to wild-type mice. A CMV promoter driven Alk1 transgene was packaged into AAV.cc84 and delivered to PdgfbiCre;Alk1f/f mice through i.v. followed by bAVM induction. Transduced cells in organs, vessel density, abnormal vessels in the bAVMs, and liver inflammation were analyzed histologically. Liver and kidney function were measured enzymatically. Compared to other viral vectors, AAV.cc84, after i.v. delivery, transduced a high percentage of brain endothelial cells (ECs) and few hepatocytes; whereas after i.n. delivery, AAV.cc84 transduced ECs and perivascular cells in the brain, and ECs, epithelial cells, and muscles in the nose with minimum hepatocyte transduction. No changes to liver or kidney function were detected. The delivery of AAV.cc84-Alk1 through i.v. to PdgfbiCre;Alk1f/f mice reduced bAVM severity. In summary, we propose that AAV.cc84-Alk1 is a promising candidate for developing gene therapy in HHT patients.

Hereditary Hemorrhagic Telangiectasia with Recurrent Epistaxis, Telangiectasia, Hepatic Arteriovenous Malformation, and a Poorly Developed Middle Cerebral Artery in a Patient with a Novel Mutation in the ACVRL1 Gene.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant vascular disorder characterized by intractable epistaxis, mucocutaneous telangiectasias, and arteriovenous malformations (AVMs) in multiple organs, including the lungs, liver, gastrointestinal tract, brain, and spinal cord. We herein report a 50-year-old Japanese man with HHT who experienced recurrent epistaxis, telangiectasia in the cornea, apex of the tongue and fingers; hepatic AVM; and a poorly developed main arterial trunk in the right middle cerebral artery. A genetic analysis revealed a novel heterozygous mutation in the activin A receptor-like type 1 gene, with a frameshift mutation in NM_000020.3:c.826_836del (p.Ile276ProfsTer112).

ACR Appropriateness Criteria® Pulmonary Arteriovenous Malformation (PAVM): 2023 Update.

Pulmonary arteriovenous malformations (PAVMs) occur in 30% to 50% of patients with hereditary hemorrhagic telangiectasia. Clinical presentations vary from asymptomatic disease to complications resulting from the right to left shunting of blood through the PAVM such as paradoxical stroke, brain abscesses, hypoxemia, and cardiac failure. Radiology plays an important role both in the diagnosis and treatment of PAVM. Based on different clinical scenarios, the appropriate imaging study has been reviewed and is presented in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Endothelial-to-Mesenchymal Transition in an Hereditary Hemorrhagic Telangiectasia-like Pediatric Case of Multiple Pulmonary Arteriovenous Malformations.

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.

Surgical treatment of brain arteriovenous malformations in patients with hereditary hemorrhagic telangiectasia: a single-center experience.

OBJECTIVE: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant disorder characterized by multiple vascular malformations. Brain arteriovenous malformations (bAVMs) are a significant manifestation of HHT. The surgical management of these lesions in patients with HHT remains debated, with limited literature on postoperative outcomes. The goal of this study was to evaluate the safety and efficacy of surgical treatment for bAVMs in patients with HHT and propose a treatment rationale based on a single-center experience. METHODS: This retrospective review included 20 patients diagnosed with HHT who underwent resection of 23 bAVMs at the Stanford University Medical Center between January 2007 and September 2023. Data were also collected on bAVMs treated conservatively, with embolization, or with radiosurgery at the authors' institution, for comparison. RESULTS: There were 16 Spetzler-Martin (SM) grade I, 6 SM grade II, and 1 SM grade IV bAVM. Six of the bAVMs presented with neurological symptoms (3 with hemorrhage and 3 with focal neurological deficits), while the rest were detected on routine screening. Complete excision was angiographically confirmed in all patients, with a mean overall hospital stay of 2.1 days and a mean follow-up of 36 months. Postoperative complications were limited to transient mild weakness in 2 patients, 1 of whom also had transient speech deficits, and visual field deficits in 3 patients, 2 of whom improved on long-term follow-up. CONCLUSIONS: In this most extensive surgical series published to date, resection of bAVMs in patients with HHT showed favorable outcomes with a low complication rate, suggesting that the benefits of surgery outweigh the risks, especially considering the potential cumulative lifetime risk of hemorrhage. MR arterial spin labeling was found to be the most sensitive noninvasive measure of detecting bAVMs in patients with HHT.

Employment of diverse in vitro systems for analyzing multiple aspects of disease, hereditary hemorrhagic telangiectasia (HHT).

BACKGROUND: In vitro disease modeling enables translational research by providing insight into disease pathophysiology and molecular mechanisms, leading to the development of novel therapeutics. Nevertheless, in vitro systems have limitations for recapitulating the complexity of tissues, and a single model system is insufficient to gain a comprehensive understanding of a disease. RESULTS: Here we explored the potential of using several models in combination to provide mechanistic insight into hereditary hemorrhagic telangiectasia (HHT), a genetic vascular disorder. Genome editing was performed to establish hPSCs (H9) with ENG haploinsufficiency and several in vitro models were used to recapitulate the functional aspects of the cells that constitute blood vessels. In a 2D culture system, endothelial cells showed early senescence, reduced viability, and heightened susceptibility to apoptotic insults, and smooth muscle cells (SMCs) exhibited similar behavior to their wild-type counterparts. Features of HHT were evident in 3D blood-vessel organoid systems, including thickening of capillary structures, decreased interaction between ECs and surrounding SMCs, and reduced cell viability. Features of ENG haploinsufficiency were observed in arterial and venous EC subtypes, with arterial ECs showing significant impairments. Molecular biological approaches confirmed the significant downregulation of Notch signaling in HHT-ECs. CONCLUSIONS: Overall, we demonstrated refined research strategies to enhance our comprehension of HHT, providing valuable insights for pathogenic analysis and the exploration of innovative therapeutic interventions. Additionally, these results underscore the importance of employing diverse in vitro systems to assess multiple aspects of disease, which is challenging using a single in vitro system.

Blood flow regulates acvrl1 transcription via ligand-dependent Alk1 activity.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disease characterized by the development of arteriovenous malformations (AVMs) that can result in significant morbidity and mortality. HHT is caused primarily by mutations in bone morphogenetic protein receptors ACVRL1/ALK1, a signaling receptor, or endoglin (ENG), an accessory receptor. Because overexpression of Acvrl1 prevents AVM development in both Acvrl1 and Eng null mice, enhancing ACVRL1 expression may be a promising approach to development of targeted therapies for HHT. Therefore, we sought to understand the molecular mechanism of ACVRL1 regulation. We previously demonstrated in zebrafish embryos that acvrl1 is predominantly expressed in arterial endothelial cells and that expression requires blood flow. Here, we document that flow dependence exhibits regional heterogeneity and that acvrl1 expression is rapidly restored after reinitiation of flow. Furthermore, we find that acvrl1 expression is significantly decreased in mutants that lack the circulating Alk1 ligand, Bmp10, and that, in the absence of flow, intravascular injection of BMP10 or the related ligand, BMP9, restores acvrl1 expression in an Alk1-dependent manner. Using a transgenic acvrl1:egfp reporter line, we find that flow and Bmp10 regulate acvrl1 at the level of transcription. Finally, we observe similar ALK1 ligand-dependent increases in ACVRL1 in human endothelial cells subjected to shear stress. These data suggest that ligand-dependent Alk1 activity acts downstream of blood flow to maintain or enhance acvrl1 expression via a positive feedback mechanism, and that ALK1 activating therapeutics may have dual functionality by increasing both ALK1 signaling flux and ACVRL1 expression.

Prevalence of hereditary hemorrhagic telangiectasia in a medical care program organization in Buenos Aires, Argentina.

INTRODUCTION: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia that might affect 1/5000-10 000 individuals worldwide. It is a rare and underdiagnosed condition. Population-based epidemiological studies are crucial for comprehending and quantifying the impact of this disease. We aim to estimate the prevalence in a Prepaid Health Care System of Buenos Aires, Argentina. METHODS: A descriptive cross-sectional study was designed, which included all patients over 18 years of age affiliated with the Hospital Italiano Medical Care Program (IHMCP), a prepaid health maintenance organization (HMO) of Buenos Aires. For case inclusion, individuals were required to have a clinical diagnosis of HHT. Case detection included the search in our Institutional Registry. The prevalence was calculated by dividing the number of cases of HHT by the total number of all active affiliates at January 2023. Age and gender specific prevalence rates were estimated. RESULTS: 48 cases were reported. The prevalence was 3.2 in 10 000 (IC 95% 2.4-4.2). Specific prevalence in women was 3.9 in 10 000 (IC 95% 2.8-5.5) and in men 2.1 in 10 000 (IC 95% 1.2-3.6). The average age was 54.8 (19), 35 patients were women (72.9%) with an average age of 55 (19.9), and 55 (17.2) for men. The most common referrals were physicians (60.4%) followed by family history (18.7%). The 48 patients corresponded to 39 families. DISCUSSION: The prevalence identified in our study is higher than the one documented in other studies.

Introducción: La telangiectasia hemorrágica hereditaria (HHT) es una displasia vascular que puede afectar a 1 de 5000 a 10 000 personas en el mundo. Es una afección rara y subdiagnosticada. Los estudios epidemiológicos son fundamentales para comprender y cuantificar el impacto de esta enfermedad. Nuestro objetivo fue estimar la prevalencia en un Sistema Prepago de Atención de la Salud, en Buenos Aires, Argentina. Métodos: Estudio descriptivo transversal en pacientes mayores de 18 años afiliados al Programa de Atención Médica del Hospital Italiano en Buenos Aires (Plan de Salud). Para la inclusión de casos, se requería el diagnóstico de HHT. La detección de casos incluyó su búsqueda en nuestro Registro Institucional. La prevalencia se calculó dividiendo el número de casos por el número total de afiliados activos en enero de 2023. Se estimaron tasas específicas por edad y género. Resultados: Se reportaron 48 casos. La prevalencia fue de 3.2 por 10 000 personas (IC 95% 2.4-4.2). La específica en mujeres fue de 3.9 (IC 95% 2.8-5.5) y en hombres de 2.1 por 10 000 (IC 95% 1.2-3.6). La edad promedio fue de 55 años (19), con 35 pacientes mujeres (72.9%) con una edad promedio de 55 años (19.9) y 55 (17.2) para hombres. La derivación más común fue de médicos (60.4%), seguidas por antecedentes familiares (18.7%). Los 48 pacientes correspondían a 39 familias. Discusión: La prevalencia identificada en nuestro estudio es más alta que la documentada en otros estudios.

A case report of limitation of transcatheter hepatic arterial embolization for hereditary hemorrhagic telangiectasia type 2 with pulmonary arterial hypertension.

INTRODUCTION AND IMPORTANCE: Arteriovenous malformations (AVMs) in the liver caused by hereditary hemorrhagic telangiectasia (HHT) influence pulmonary artery hypertension (PAH). Liver transplantation (LT) is the most common treatment for HHT-induced hepatic AVMs. However, LT is contraindicated for patients with severe PAH. There is controversy regarding the ideal therapeutic approach for HHT with PAH and hepatic AVMs. CASE PRESENTATION: We present the case of a 48-year-old female with PAH and HHT. After the initiation of PAH-targeted drugs, we considered that the PAH was mainly caused by high cardiac output secondary to multiple diffuse AVMs in the liver. LT was contraindicated due to high mean pulmonary arterial pressure (mPAP), and we opted to perform transcatheter embolization as an alternative treatment for the AVM. Multiple-stage embolization sessions did not effectively improve the shunt in the liver or the pulmonary hemodynamics. The patient died of an uncontrolled gastrointestinal hemorrhage. CLINICAL DISCUSSION: LT was considered in our case; it was contraindicated because of pulmonary hypertension that was in line with the model for end-stage liver disease exception criteria. Repeated embolization did not reduce the liver shunt or improve pulmonary hemodynamics, possibly due to the diffuse distribution of AVMs in the liver and the rapid development of new collateral vessels with each embolization. Recently, pulmonary vascular resistance (PVR) has been proposed as a more appropriate index for stratifying perioperative risk. CONCLUSION: Based on previous reports and our experience, rapid decision-making regarding LT may be needed based on mPAP and PVR after the initiation of PAH-targeted drugs.

To Test or Not to Test: A Case Report on Hereditary Hemorrhagic Telangiectasia.

A 50-year-old female patient presenting with joint pains, Raynaud's phenomenon, epistaxis, and telangiectasias was posed with a diagnostic conundrum, i.e., whether to accept the diagnosis of mixed connective tissue disease (MCTD), for which she fulfilled all the criteria, or test for another probable disease, namely hereditary hemorrhagic telangiectasia (HHT), even though only some clinical features were present and all diagnostic criteria were not satisfied. Taking the patient's onset of epistaxis as an important clue, the patient was counseled for genetic testing for HHT, which was positive. Treatment for both MCTD and HHT is underway, and appropriate surveillance is planned for the patient.

De Novo Brain Vascular Malformations in Hereditary Hemorrhagic Telangiectasia.

BACKGROUND: Approximately 10% of people with hereditary hemorrhagic telangiectasia (HHT) have brain vascular malformations (VMs). Few reports describe de novo brain VM formation. International HHT Guidelines recommend initial brain VM screening upon HHT diagnosis in children but do not address rescreening. We aimed to confirm whether brain VMs can form de novo in patients with HHT. METHODS: The Brain Vascular Malformation Consortium HHT project is a 17-center longitudinal study enrolling patients since 2010. We analyzed the database for de novo VMs defined as those detected (1) on follow-up neuroimaging in a patient without previous brain VMs or (2) in a location distinct from previously identified brain VMs and reported those in whom a de novo VM could be confirmed on central neuroimaging review. RESULTS: Of 1909 patients enrolled, 409 (21%) had brain VMs. Seven patients were recorded as having de novo brain VMs, and imaging was available for central review in four. We confirmed that three (0.7% of individuals with brain VMs) had de novo brain VMs (two capillary malformations, one brain arteriovenous malformation) with intervals of six, nine, and 13 years from initial imaging. Two with de novo brain VMs were <18 years. The fourth patient, a child, did not have a de novo brain VM but had a radiologically confirmed increase in size of an existing brain arteriovenous malformation. CONCLUSIONS: Brain VMs can, albeit rarely, form de novo in patients with HHT. Given the potential risk of hemorrhage from brain VMs, regular rescreening in patients with HHT may be warranted.

Prenatal diagnosis of pulmonary arteriovenous malformations with a postnatal diagnosis of Osler-Weber-Rendu syndrome.

Hereditary Hemorrhagic Telangiectasia (HHT), commonly known as Osler-Weber-Rendu disease, is an autosomal dominant multisystemic vascular disease associated with approximately 70% of cases of pulmonary arteriovenous malformations (PAVMs). Prenatal cases of PAVMs typically present with pulmonary vein dilatation on ultrasonography. This study presents a prenatal diagnosis of PAVMs with enlarged right pulmonary vein, cardiomegaly, cystic-appearing areas in the right lung and subsequent confirmation of Osler-Weber-Rendu syndrome using autopsy and whole exom sequencing.