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.

Molecular and Cellular Characterization of Primary Endothelial Cells from a Familial Cavernomatosis Patient.

Cerebral cavernous malformation (CCM) or familial cavernomatosis is a rare, autosomal dominant, inherited disease characterized by the presence of vascular malformations consisting of blood vessels with an abnormal structure in the form of clusters. Based on the altered gene (CCM1/Krit1, CCM2, CCM3) and its origin (spontaneous or familial), different types of this disease can be found. In this work we have isolated and cultivated primary endothelial cells (ECs) from peripheral blood of a type 1 CCM patient. Differential functional and gene expression profiles of these cells were analyzed and compared to primary ECs from a healthy donor. The mutation of the familial index case consisted of a heterozygous point mutation in the position +1 splicing consensus between exons 15 and 16, causing failure in RNA processing and in the final protein. Furthermore, gene expression analysis by quantitative PCR revealed a decreased expression of genes involved in intercellular junction formation, angiogenesis, and vascular homeostasis. Cell biology analysis showed that CCM1 ECs were impaired in angiogenesis and cell migration. Taken together, the results obtained suggest that the alterations found in CCM1 ECs are already present in the heterozygous condition, suffering from vascular impairment and somewhat predisposed to vascular damage.

Tacrolimus as a Promising Drug for Epistaxis and Gastrointestinal Bleeding in HHT.

BACKGROUND: Hereditary Hemorrhagic Telangiectasia (HHT) is a vascular autosomically inherited rare disease. Epistaxis (nose bleeds) is the most common symptom in HHT, leading to anemia and affecting the patient's quality of life. In addition to epistaxis, gastrointestinal bleeding (GI), more often at older ages, may lead to severe anemia and the need for blood transfusions. Thus, finding drugs to control both types of bleeding is a primary necessity in HHT. METHODS: A cross-sectional observational study was conducted in a series of 11 HHT patients treated with low tacrolimus doses (0.5-2 mg/day) on an off-label prescription basis. Patients showed refractory bleeding to previous treatments. The epistaxis severity score (ESS) and hemoglobin levels were the parameters used to evaluate the impact of tacrolimus. The occurrence of side effects was also recorded. RESULTS: Tacrolimus was well tolerated in all of the patients except 2 (who stopped the treatment). The remaining patients tolerated the treatment, with a general improvement in their health condition. Epistaxis was significantly reduced when comparing the ESS before and after the treatment. Hemoglobin levels significantly increased, overcoming the anemia, during the course of the treatment. CONCLUSION: Tacrolimus at low doses should be considered as a promising treatment for epistaxis and gastrointestinal bleeding in HHT.

Mutation in Chek2 triggers von Hippel-Lindau hemangioblastoma growth.

PURPOSE: Von Hippel-Lindau (VHL) is a rare inherited disease mainly characterized by the growth of tumours, predominantly hemangioblastomas (Hbs) in the CNS and retina, and renal carcinomas. The natural history of VHL disease is variable, differing in the age of onset and its penetrance, even among relatives. Unfortunately, sometimes VHL shows more severe than average: the onset starts in adolescence, and surgeries are required almost every year. In these cases, the factor that triggers the appearance and growth of Hbs usually remains unknown, although additional mutations are suspected. METHODS: We present the case of a VHL patient whose first surgery was at 13 years of age. Then, along his next 8 years, he has undergone 5 surgeries for resection of 10 CNS Hbs. To clarify this severe VHL condition, DNA from a CNS Hb and white blood cells (WBC) was sequenced using next-generation sequencing technology. RESULTS: Massive DNA sequencing of the WBC (germ line) revealed a pathogenic mutation in CHEK2 and the complete loss of a VHL allele (both tumour suppressors). Moreover, in the tumour sample, several mutations, in BRAF1 and PTPN11 were found. Familiar segregation studies showed that CHEK2 mutation was in the maternal lineage, while VHL was inherited by paternal lineage. CONCLUSIONS: Finally, clinical history correlated to the different genotypes in the family, concluding that the severity of these VHL manifestations are due to both, VHL-and-CHEK2 mutations. This case report aims to notice the importance of deeper genetic analyses, in inherited rare diseases, to uncover non-expected mutations.

Propranolol: A "Pick and Roll" Team Player in Benign Tumors and Cancer Therapies.

Research on cancer therapies focuses on processes such as angiogenesis, cell signaling, stemness, metastasis, and drug resistance and inflammation, all of which are influenced by the cellular and molecular microenvironment of the tumor. Different strategies, such as antibodies, small chemicals, hormones, cytokines, and, recently, gene editing techniques, have been tested to reduce the malignancy and generate a harmful microenvironment for the tumor. Few therapeutic agents have shown benefits when administered alone, but a few more have demonstrated clear improvement when administered in combination with other therapeutic molecules. In 2008 (and for the first time in the clinic), the therapeutic benefits of the ß-adrenergic receptor antagonist, propranolol, were described in benign tumors, such as infantile hemangioma. Propranolol, initially prescribed for high blood pressure, irregular heart rate, essential tremor, and anxiety, has shown, in the last decade, increasing evidence of its antitumoral properties in more than a dozen different types of cancer. Moreover, the use of propranolol in combination therapies with other drugs has shown synergistic antitumor effects. This review highlights the clinical trials in which propranolol is taking part as adjuvant therapy at single administration or in combinatorial human trials, arising as a good pick and roll partner in anticancer strategies.

A Novel Splicing Mutation in the ACVRL1/ALK1 Gene as a Cause of HHT2.

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare disorder of vascular development. Common manifestations include epistaxis, telangiectasias and arteriovenous malformations in multiple organs. Different deletions or nonsense mutations have been described in the ENG (HHT1) or ACVRL1/ALK1 (HHT2) genes, all affecting endothelial homeostasis. A novel mutation in ACVRL1/ALK1 has been identified in a Peruvian family with a clinical history compatible to HHT. Subsequently, 23 DNA samples from oral exchanges (buccal swaps) of the immediate family members were analyzed together with their clinical histories. A routine cDNA PCR followed by comparative DNA sequencing between the founder and another healthy family member showed the presence of the aforementioned specific mutation. The single mutation detected (c.525 + 1G > T) affects the consensus splice junction immediately after exon 4, provokes anomalous splicing and leads to the inclusion of intron IV between exons 4 and 5 in the ACVRL1/ALK1 mRNA and, therefore, to ALK1 haploinsufficiency. Complete sequencing determined that 10 of the 25 family members analyzed were affected by the same mutation. Notably, the approach described in this report could be used as a diagnostic technique, easily incorporated in clinical practice in developing countries and easily extrapolated to other patients carrying such a mutation.

The Role of Propranolol as a Repurposed Drug in Rare Vascular Diseases.

Rare Diseases (RD) are defined by their prevalence in less than 5 in 10,000 of the general population. Considered individually, each RD may seem insignificant, but together they add up to more than 7000 different diseases. Research in RD is not attractive for pharmaceutical companies since it is unlikely to recover development costs for medicines aimed to small numbers of patients. Since most of these diseases are life threatening, this fact underscores the urgent need for treatments. Drug repurposing consists of identifying new uses for approved drugs outside the scope of the original medical indication. It is an alternative option in drug development and represents a viable and risk-managed strategy to develop for RDs. In 2008, the "off label" therapeutic benefits of propranolol were described in the benign tumor Infantile Hemangioma. Propranolol, initially prescribed for high blood pressure, irregular heart rate, essential tremor, and anxiety, has, in the last decade, shown increasing evidence of its antiangiogenic, pro-apoptotic, vasoconstrictor and anti-inflammatory properties in different RDs, including vascular or oncological pathologies. This review highlights the finished and ongoing trials in which propranolol has arisen as a good repurposing drug for improving the health condition in RDs.

Blockade of ß2-Adrenergic Receptor Reduces Inflammation and Oxidative Stress in Clear Cell Renal Cell Carcinoma.

Von Hippel-Lindau (VHL) syndrome is a rare inherited cancer disease where the lack of VHL protein triggers the development of multisystemic tumors such us retinal hemangioblastomas (HBs), CNS-HBs, and clear cell renal cell carcinoma (ccRCC). Since standard therapies in VHL have shown limited response, leaving surgery as the only possible treatment, targeting of the ß2-adrenergic receptor (ADRB2) has shown therapeutic antitumor benefits on VHL-retinal HBs (clinical trial), VHL-CNS HBs, and VHL-ccRCC (in vitro and in vivo). In the present study, we wanted to look deep into the effects of the ADRB2 blockers propranolol and ICI-118,551 on two main aspects of cancer progression: (i) the changes on the inflammatory response of ccRCC cells; and (ii) the modulation on the Warburg effect (glycolytic metabolism), concretely, on the expression of genes involved in the cell reactive oxygen species (ROS) balance and levels. Accordingly, in vitro studies with primary VHL-ccRCC and 786-O cells measuring ROS levels, ROS-expression of detoxifying enzymes, and the expression of p65/NF-κB targets by RT-PCR were carried out. Furthermore, histological analyses of ccRCC samples from heterotopic mouse xenografts were performed. The obtained results show that ADRB2 blockade in ccRCC cells reduces the level of oxidative stress and stabilizes the inflammatory response. Thus, these data further support the idea of targeting ADRB2 as a promising strategy for the treatment of VHL and other non-VHL tumors.

The Endothelial Landscape and Its Role in Von Hippel-Lindau Disease.

Von Hippel-Lindau disease (VHL) is a rare hereditary disease characterized by the predisposal to develop different types of highly vascularized tumors. VHL patients carry a VHL mutation that causes partial lack of functional VHL protein (pVHL) in all cells, and a total lack thereof in cells harboring a second hit mutation. Absence of pVHL generates a prolonged state of pseudo-hypoxia in the cell due to accumulation of hypoxia inducible factor, an important transcription factor regulating pro-tumorigenic genes. The work here presented focuses on characterizing the endothelium of VHL patients, by means of blood outgrowth endothelial cells (BOECs). Transcriptome analysis of VHL-derived BOECs, further supported by in vitro assays, shows that these cells are at a disadvantage, as evidenced by loss of cell adhesion capacity, angiogenesis defects, and immune response and oxidative metabolic gene downregulation, which induce oxidative stress. These results suggest that the endothelium of VHL patients is functionally compromised and more susceptible to tumor development. These findings contribute to shedding light on the vascular landscape of VHL patients preceding the second hit mutation in the VHL gene. This knowledge could be useful in searching for new therapies for these patients and other vascular diseases.

SARS-CoV-2 Infection in Hereditary Hemorrhagic Telangiectasia Patients Suggests Less Clinical Impact Than in the General Population.

At the moment of writing this communication, the health crisis derived from the COVID-19 pandemic has affected more than 120 million cases, with 40 million corresponding to Europe. In total, the number of deaths is almost 3 million, but continuously rising. Although COVID-19 is primarily a respiratory disease, SARS-CoV-2 infects also endothelial cells in the pulmonary capillaries. This affects the integrity of the endothelium and increases vascular permeability. In addition, there are serious indirect consequences, like disruption of endothelial cells' junctions leading to micro-bleeds and uncontrolled blood clotting. The impact of COVID-19 in people with rare chronic cardiovascular diseases is unknown so far, and interesting to assess, because the virus may cause additional complications in these patients. The aim of the present work was to study the COVID-19 infection among the patients with Hereditary Hemorrhagic Telangiectasia (HHT). A retrospective study was carried out in a 138 HHT patients' sample attending an Ear Nose and Throat (ENT) reference consult. The evaluation of the COVID-19 infection in them reveals milder symptoms; among the 25 HHT patients who were infected, only 3 cases were hospitalized, and none of them required ICU or ventilation assistance. The results are discussed in the light of macrophage immune response.

Targeting ß2-Adrenergic Receptors Shows Therapeutical Benefits in Clear Cell Renal Cell Carcinoma from Von Hippel-Lindau Disease.

Von Hippel-Lindau (VHL), is a rare autosomal dominant inherited cancer in which the lack of VHL protein triggers the development of multisystemic tumors such us retinal hemangioblastomas (HB), CNS-HB, and clear cell renal cell carcinoma (ccRCC). ccRCC ranks third in terms of incidence and first in cause of death. Standard systemic therapies for VHL-ccRCC have shown limited response, with recurrent surgeries being the only effective treatment. Targeting of ß2-adrenergic receptor (ADRB) has shown therapeutic antitumor benefits on VHL-retinal HB (clinical trial) and VHL-CNS HB (in vitro). Therefore, the in vitro and in vivo antitumor benefits of propranolol (ADRB-1,2 antagonist) and ICI-118,551 (ADRB-2 antagonist) on VHL-/- ccRCC primary cultures and 786-O tumor cell lines have been addressed. Propranolol and ICI-118,551 activated apoptosis inhibited gene and protein expression of HIF-2α, CAIX, and VEGF, and impaired partially the nuclear internalization of HIF-2α and NFĸB/p65. Moreover, propranolol and ICI-118,551 reduced tumor growth on two in vivo xenografts. Finally, ccRCC patients receiving propranolol as off-label treatment have shown a positive therapeutic response for two years on average. In summary, propranolol and ICI-118,551 have shown antitumor benefits in VHL-derived ccRCC, and since ccRCCs comprise 63% of the total RCCs, targeting ADRB2 becomes a promising drug for VHL and other non-VHL tumors.

CLN5 in heterozygosis may protect against the development of tumors in a VHL patient.

Von Hippel-Lindau syndrome (VHL) is a rare disease of dominant inheritance that increases susceptibility to tumor development, with a complete penetrance at the age of 60. In this report, we present the unprecedented case of a VHL carrier who remains healthy at 72. Under the course of this study, it was discovered that this patient carries a mutation for a second rare disease, Neuronal Ceroid Lipofuscinosis (NCL or CNL). We hypothesize that the CLN mutation she carries offers a protective effect, preventing tumor development in the cells potentially suffering a VHL second hit mutation. To test this hypothesis, we ran a series of molecular experiments and confirmed that cell viability of primary endothelial cells decreases upon CLN5 silencing. Our results further elucidate the cell biology implications of two rare diseases interacting.

Review of Pharmacological Strategies with Repurposed Drugs for Hereditary Hemorrhagic Telangiectasia Related Bleeding.

The diagnosis of hereditary hemorrhagic telangiectasia (HHT) is based on the Curaçao criteria: epistaxis, telangiectases, arteriovenous malformations in internal organs, and family history. Genetically speaking, more than 90% of HHT patients show mutations in ENG or ACVRL1/ALK1 genes, both belonging to the TGF-ß/BMP9 signaling pathway. Despite clear knowledge of the symptoms and genes of the disease, we still lack a definite cure for HHT, having just palliative measures and pharmacological trials. Among the former, two strategies are: intervention at "ground zero" to minimize by iron and blood transfusions in order to counteract anemia. Among the later, along the last 15 years, three different strategies have been tested: (1) To favor coagulation with antifibrinolytic agents (tranexamic acid); (2) to increase transcription of ENG and ALK1 with specific estrogen-receptor modulators (bazedoxifene or raloxifene), antioxidants (N-acetylcysteine, resveratrol), or immunosuppressants (tacrolimus); and (3) to impair the abnormal angiogenic process with antibodies (bevacizumab) or blocking drugs like etamsylate, and propranolol. This manuscript reviews the main strategies and sums up the clinical trials developed with drugs alleviating HHT.

Topically Applied Etamsylate: A New Orphan Drug for HHT-Derived Epistaxis (Antiangiogenesis through FGF Pathway Inhibition).

Hereditary hemorrhagic telangiectasia (HHT) is a vascular dysplasia characterized by recurrent and spontaneous epistaxis (nose bleeds), telangiectases on skin and mucosa, internal organ arteriovenous malformations, and dominant autosomal inheritance. Mutations in Endoglin and ACVRL1 / ALK1 , genes mainly expressed in endothelium, are responsible in 90% of the cases for the pathology. These genes are involved in the transforming growth factor-ß(TGF-ß) signaling pathway. Epistaxis remains as one of the most common symptoms impairing the quality of life of patients, becoming life-threatening in some cases. Different strategies have been used to decrease nose bleeds, among them is antiangiogenesis. The two main angiogenic pathways in endothelial cells depend on vascular endothelial growth factor and fibroblast growth factor (FGF). The present work has used etamsylate, the diethylamine salt of the 2,5-dihydroxybenzene sulfonate anion, also known as dobesilate, as a FGF signaling inhibitor. In endothelial cells, in vitro experiments show that etamsylate acts as an antiangiogenic factor, inhibiting wound healing and matrigel tubulogenesis. Moreover, etamsylate decreases phosphorylation of Akt and ERK1/2. A pilot clinical trial (EudraCT: 2016-003982-24) was performed with 12 HHT patients using a topical spray of etamsylate twice a day for 4 weeks. The epistaxis severity score (HHT-ESS) and other pertinent parameters were registered in the clinical trial. The significant reduction in the ESS scale, together with the lack of significant side effects, allowed the designation of topical etamsylate as a new orphan drug for epistaxis in HHT (EMA/OD/135/18).

Evaluation of the safety and effectiveness of oral propranolol in patients with von Hippel-Lindau disease and retinal hemangioblastomas: phase III clinical trial.

BACKGROUND: von Hippel-Lindau disease (VHL) is a multisystem cancer syndrome caused by mutations in the VHL gene. Retinal hemangioblastoma is one of the most common tumours, and when it appears near the optic nerve, its treatment is challenging and risky. To date, no treatment has proven effective in changing the course of the disease. This study was designed to evaluate the safety and effectiveness of propranolol in controlling these tumours. METHODS: Seven patients were included. All patients took a daily dose of 120 mg of propranolol for 1 year. Clinical variables were assessed at baseline, and at 1, 3, 6, 9 and 12 months. The primary endpoint of the study was the number and size of retinal hemangioblastomas. On every visit, retinal outcomes and blood biomarkers (such as vascular endothelial growth factor (VEGF) and miR210) were analysed. RESULTS: Number and size of retinal hemangioblastomas remained stable in all patients. All of them had initially increased levels of VEGF and miR210. There was a gradual reabsorption of retinal exudation in two patients, correlating with a progressive decrease of both biomarkers. The only adverse effect reported was hypotension in one patient. CONCLUSIONS: Propranolol could be used to treat retinal hemangioblastomas in VHL patients, although more studies are needed to determine the ideal dose and long-term effect. VEGF and miR210 should be explored as biomarkers of disease activity. As far as we know, these are the first biomarkers proposed to monitor the VHL disease activity. TRIAL REGISTRATION NUMBER: 2014-003671-30.

Repurposing propranolol as a drug for the treatment of retinal haemangioblastomas in von Hippel-Lindau disease.

BACKGROUND: Von Hippel-Lindau (VHL) disease is a rare oncological disease with an incidence of 1:36,000, and is characterized by the growth of different types of tumours. Haemangioblastomas in the central nervous system (CNS) and retina, renal carcinoma and pheochromocytomas are the most common tumours. The absence of treatment for VHL leads to the need of repeated surgeries as the only option for these patients. Targeting VHL-derived tumours with drugs with reduced side effects is urgent to avoid repeated CNS surgeries. Recent reports have demonstrated that propranolol, a ß-blocker used for the treatment of hypertension and other cardiac and neurological diseases, is the best option for infantile hemangioma (IH). Propranolol could be an efficient treatment to control haemangioblastoma growth in VHL disease given its antiangiogenic effects that were recently demonstrated by us. The main objective of the present study was the assessment of the efficacy and safety of propranolol on retinal haemangioblastoma in von Hippel-Lindau disease (VHL). METHODS: 7 VHL patients, from different regions of Spain, affected from juxtapapillary or peripheral haemangioblastomas were administered 120 mg propranolol daily. Patients were evaluated every 3 months for 12 months, at Virgen de la Salud Hospital (Toledo). The patients had juxtapapillary or peripheral haemangioblastomas but had refused standard treatments. RESULTS: Propranolol was initiated with a progressive increase up to a final dose of 120 mg daily. All tumours remained stable, and no new tumours appeared. The reabsorption of retinal exudation was noted in the two patients having exudates. No adverse effects were recorded. VEGF and miRNA 210 levels were monitored in the plasma of patients as possible biomarkers of VHL. These levels decreased in all cases from the first month of treatment. CONCLUSIONS: Although more studies are necessary, the results of this work suggest that propranolol is a drug to be considered in the treatment of VHL patients with retinal haemangioblastomas. VEGF and miRNA 210 could be used as biomarkers of the VHL disease activity. TRIAL REGISTRATION: The study has a clinical trial design and was registered at EU Clinical Trials Register and Spanish Clinical Studies Registry, EudraCT Number: 2014-003671-30 . Registered 2 September 2014.

Mutation affecting the proximal promoter of Endoglin as the origin of hereditary hemorrhagic telangiectasia type 1.

BACKGROUND: Hereditary hemorrhagic telangiectasia (HHT) is a vascular multi-organ system disorder. Its diagnostic criteria include epistaxis, telangiectases in mucocutaneous sites, arteriovenous malformations (AVMs), and familial inheritance. HHT is transmitted as an autosomal dominant condition, caused in 85% of cases by mutations in either Endoglin (ENG) or Activin receptor-like kinase (ACVRL1/ACVRL1/ALK1) genes. Pathogenic mutations have been described in exons, splice junctions and, in a few cases with ENG mutations, in the proximal promoter, which creates a new ATG start site. However, no mutations affecting transcription regulation have been described to date in HHT, and this type of mutation is rarely identified in the literature on rare diseases. METHODS: Sequencing data from a family with HHT lead to single nucleotide change, c.-58G > A. The functionality and pathogenicity of this change was analyzed by in vitro mutagenesis, quantitative PCR and Gel shift assay. Student t test was used for statistical significance. RESULTS: A single nucleotide change, c.-58G > A, in the proximal ENG promoter co-segregated with HHT clinical features in an HHT family. This mutation was present in the proband and in 2 other symptomatic members, whereas 2 asymptomatic relatives did not harbor the mutation. Analysis of RNA from activated monocytes from the probands and the healthy brother revealed reduced ENG mRNA expression in the HHT patient (p = 0.005). Site-directed mutagenesis of the ENG promoter resulted in a three-fold decrease in luciferase activity of the mutant c.-58A allele compared to wild type (p = 0.005). Finally, gel shift assay identified a DNA-protein specific complex. CONCLUSIONS: The novel ENG c.-58G > A substitution in the ENG promoter co-segregates with HHT symptoms in a family and appears to affect the transcriptional regulation of the gene, resulting in reduced ENG expression. ENG c.-58G > A may therefore be a pathogenic HHT mutation leading to haploinsufficiency of Endoglin and HHT symptoms. To the best of our knowledge, this is the first report of a pathogenic mutation in HHT involving the binding site for a transcription factor in the promoter of ENG.

Mice Lacking Endoglin in Macrophages Show an Impaired Immune Response.

Endoglin is an auxiliary receptor for members of the TGF-ß superfamily and plays an important role in the homeostasis of the vessel wall. Mutations in endoglin gene (ENG) or in the closely related TGF-ß receptor type I ACVRL1/ALK1 are responsible for a rare dominant vascular dysplasia, the Hereditary Hemorrhagic Telangiectasia (HHT), or Rendu-Osler-Weber syndrome. Endoglin is also expressed in human macrophages, but its role in macrophage function remains unknown. In this work, we show that endoglin expression is triggered during the monocyte-macrophage differentiation process, both in vitro and during the in vivo differentiation of blood monocytes recruited to foci of inflammation in wild-type C57BL/6 mice. To analyze the role of endoglin in macrophages in vivo, an endoglin myeloid lineage specific knock-out mouse line (Eng(fl/fl)LysMCre) was generated. These mice show a predisposition to develop spontaneous infections by opportunistic bacteria. Eng(fl/fl)LysMCre mice also display increased survival following LPS-induced peritonitis, suggesting a delayed immune response. Phagocytic activity is impaired in peritoneal macrophages, altering one of the main functions of macrophages which contributes to the initiation of the immune response. We also observed altered expression of TGF-ß1 target genes in endoglin deficient peritoneal macrophages. Overall, the altered immune activity of endoglin deficient macrophages could help to explain the higher rate of infectious diseases seen in HHT1 patients.

Research on potential biomarkers in hereditary hemorrhagic telangiectasia.

Hereditary hemorrhagic telangiectasia (HHT) is a genetically heterogeneous disorder, involving mutations in two predominant genes known as Endoglin (ENG; HHT1) and activin receptor-like kinase 1 (ACVRL1/ALK1; HHT2), as well as in some less frequent genes, such as MADH4/SMAD4 (JP-HHT) or BMP9/GDF2 (HHT5). The diagnosis of HHT patients currently remains at the clinical level, according to the "Curaçao criteria," whereas the molecular diagnosis is used to confirm or rule out suspected HHT cases, especially when a well characterized index case is present in the family or in an isolated population. Unfortunately, many suspected patients do not present a clear HHT diagnosis or do not show pathogenic mutations in HHT genes, prompting the need to investigate additional biomarkers of the disease. Here, several HHT biomarkers and novel methodological approaches developed during the last years will be reviewed. On one hand, products detected in plasma or serum samples: soluble proteins (vascular endothelial growth factor, transforming growth factor ß1, soluble endoglin, angiopoietin-2) and microRNA variants (miR-27a, miR-205, miR-210). On the other hand, differential HHT gene expression fingerprinting, next generation sequencing of a panel of genes involved in HHT, and infrared spectroscopy combined with artificial neural network patterns will also be reviewed. All these biomarkers might help to improve and refine HHT diagnosis by distinguishing from the non-HHT population.

Copy number variations in endoglin locus: mapping of large deletions in Spanish families with hereditary hemorrhagic telangiectasia type 1.

BACKGROUND: The hereditary hemorrhagic telangiectasia syndrome (HHT), also known as the Rendu-Osler-Weber syndrome is a multiorganic vascular disorder inherited as an autosomal dominant trait. Diagnostic clinical criteria include: epistaxis, telangiectases in mucocutaneous and gastrointestinal sites, arteriovenous malformations (AVMs) most commonly found in pulmonary, hepatic and cerebral circulations, and familial inheritance. HHT is transmitted in 90% of the cases as an autosomal dominant condition due to mutations in either endoglin (ENG), or activin receptor-like kinase 1 (ACVRL1/ALK1) genes (HHT type 1 and 2, respectively). METHODS: We have carried out a genetic analysis of four independent Spanish families with HHT clinical criteria, which has permitted the identification of new large deletions in ENG. These mutations were first detected using the MLPA technique and subsequently, the deletion breakpoints were mapped using a customized copy number variation (CNV) microarray. The array was designed to cover the ENG gene and surrounding areas. RESULTS: All tested families carried large deletions ranging from 3-kb to 100-kb, involving the ENG gene promoter, several ENG exons, and the two downstream genes FGSH and CDK9. Interestingly, common breakpoints coincident with Alu repetitive sequences were found among these families. CONCLUSIONS: The systematic hybridization of DNA from HHT families, with deletions or duplications, to custom designed microarrays, could allow the mapping of breakpoints, coincident with repetitive Alu sequences that might act as "hot spots" in the development of chromosomal anomalies.