Publications by authors named "Helen M Arthur"

55 Publications

Hereditary Haemorrhagic Telangiectasia, an Inherited Vascular Disorder in Need of Improved Evidence-Based Pharmaceutical Interventions.

Genes (Basel) 2021 Jan 27;12(2). Epub 2021 Jan 27.

Biosciences Institute, Centre for Life, Newcastle University, Newcastle NE1 3BZ, UK.

Hereditary haemorrhagic telangiectasia (HHT) is characterised by arteriovenous malformations (AVMs). These vascular abnormalities form when arteries and veins directly connect, bypassing the local capillary system. Large AVMs may occur in the lungs, liver and brain, increasing the risk of morbidity and mortality. Smaller AVMs, known as telangiectases, are prevalent on the skin and mucosal lining of the nose, mouth and gastrointestinal tract and are prone to haemorrhage. HHT is primarily associated with a reduction in endoglin (ENG) or ACVRL1 activity due to loss-of-function mutations. ENG and ACVRL1 transmembrane receptors are expressed on endothelial cells (ECs) and bind to circulating ligands BMP9 and BMP10 with high affinity. Ligand binding to the receptor complex leads to activation of the SMAD1/5/8 signalling pathway to regulate downstream gene expression. Various genetic animal models demonstrate that disruption of this pathway in ECs results in AVMs. The vascular abnormalities underlying AVM formation result from abnormal EC responses to angiogenic and haemodynamic cues, and include increased proliferation, reduced migration against the direction of blood flow and an increased EC footprint. There is growing evidence that targeting VEGF signalling has beneficial outcomes in HHT patients and in animal models of this disease. The anti-VEGF inhibitor bevacizumab reduces epistaxis and has a normalising effect on high cardiac output in HHT patients with hepatic AVMs. Blocking VEGF signalling also reduces vascular malformations in mouse models of HHT1 and HHT2. However, VEGF signalling is complex and drives numerous downstream pathways, and it is not yet clear which pathway (or combination of pathways) is critical to target. This review will consider the recent evidence gained from HHT clinical and preclinical studies that are increasing our understanding of HHT pathobiology and informing therapeutic strategies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/genes12020174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7911152PMC
January 2021

Clearance of senescent cells during cardiac ischemia-reperfusion injury improves recovery.

Aging Cell 2020 10 29;19(10):e13249. Epub 2020 Sep 29.

Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK.

A key component of cardiac ischemia-reperfusion injury (IRI) is the increased generation of reactive oxygen species, leading to enhanced inflammation and tissue dysfunction in patients following intervention for myocardial infarction. In this study, we hypothesized that oxidative stress, due to ischemia-reperfusion, induces senescence which contributes to the pathophysiology of cardiac IRI. We demonstrate that IRI induces cellular senescence in both cardiomyocytes and interstitial cell populations and treatment with the senolytic drug navitoclax after ischemia-reperfusion improves left ventricular function, increases myocardial vascularization, and decreases scar size. SWATH-MS-based proteomics revealed that biological processes associated with fibrosis and inflammation that were increased following ischemia-reperfusion were attenuated upon senescent cell clearance. Furthermore, navitoclax treatment reduced the expression of pro-inflammatory, profibrotic, and anti-angiogenic cytokines, including interferon gamma-induced protein-10, TGF-β3, interleukin-11, interleukin-16, and fractalkine. Our study provides proof-of-concept evidence that cellular senescence contributes to impaired heart function and adverse remodeling following cardiac ischemia-reperfusion. We also establish that post-IRI the SASP plays a considerable role in the inflammatory response. Subsequently, senolytic treatment, at a clinically feasible time-point, attenuates multiple components of this response and improves clinically important parameters. Thus, cellular senescence represents a potential novel therapeutic avenue to improve patient outcomes following cardiac ischemia-reperfusion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/acel.13249DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7576252PMC
October 2020

Therapeutic Potential of Senolytics in Cardiovascular Disease.

Cardiovasc Drugs Ther 2020 Sep 26. Epub 2020 Sep 26.

Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK.

Ageing is the biggest risk factor for impaired cardiovascular health, with cardiovascular disease being the leading cause of death in 40% of individuals over 65 years old. Ageing is associated with both an increased prevalence of cardiovascular disease including heart failure, coronary artery disease, and myocardial infarction. Furthermore, ageing is associated with a poorer prognosis to these diseases. Genetic models allowing the elimination of senescent cells revealed that an accumulation of senescence contributes to the pathophysiology of cardiovascular ageing and promotes the progression of cardiovascular disease through the expression of a proinflammatory and profibrotic senescence-associated secretory phenotype. These studies have resulted in an effort to identify pharmacological therapeutics that enable the specific elimination of senescent cells through apoptosis induction. These senescent cell apoptosis-inducing compounds are termed senolytics and their potential to ameliorate age-associated cardiovascular disease is the focus of this review.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10557-020-07075-wDOI Listing
September 2020

Oncogenes in Brain Arteriovenous Malformations.

Circ Res 2020 Aug 27;127(6):744-746. Epub 2020 Aug 27.

From the Karolinska Institutet, Tomtebodavägen, Solna, Sweden (L.J.).

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCRESAHA.120.317722DOI Listing
August 2020

Overexpression of Activin Receptor-Like Kinase 1 in Endothelial Cells Suppresses Development of Arteriovenous Malformations in Mouse Models of Hereditary Hemorrhagic Telangiectasia.

Circ Res 2020 Oct 31;127(9):1122-1137. Epub 2020 Jul 31.

Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville (Y.H.K., S.-w.C., S.P.O.).

Rationale: Hereditary hemorrhagic telangiectasia (HHT) is a genetic disease caused by mutations in , , or . Since proteins from all 3 HHT genes are components of signal transduction of TGF-β (transforming growth factor β) family members, it has been hypothesized that HHT is a disease caused by defects in the ENG-ALK1-SMAD4 linear signaling. However, in vivo evidence supporting this hypothesis is scarce.

Objective: We tested this hypothesis and investigated the therapeutic effects and potential risks of induced-ALK1 or -ENG overexpression (OE) for HHT.

Methods And Results: We generated a novel mouse allele (ROSA26) in which HA (human influenza hemagglutinin)-tagged ALK1 and bicistronic eGFP expression are induced by Cre activity. We examined whether ALK1-OE using the ROSA26 allele could suppress the development of arteriovenous malformations (AVMs) in wounded adult skin and developing retinas of - and -inducible knockout (iKO) mice. We also used a similar approach to investigate whether ENG-OE could rescue AVMs. Biochemical and immunofluorescence analyses confirmed the Cre-dependent OE of the ALK1-HA transgene. We could not detect any pathological signs in ALK1-OE mice up to 3 months after induction. ALK1-OE prevented the development of retinal AVMs and wound-induced skin AVMs in -iKO as well as -iKO mice. ALK1-OE normalized expression of SMAD and NOTCH target genes in ENG-deficient endothelial cells (ECs) and restored the effect of BMP9 (bone morphogenetic protein 9) on suppression of phosphor-AKT levels in these endothelial cells. On the other hand, ENG-OE could not inhibit the AVM development in -iKO models.

Conclusions: 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCRESAHA.119.316267DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7554133PMC
October 2020

Arterial endoglin does not protect against arteriovenous malformations.

Angiogenesis 2020 11 6;23(4):559-566. Epub 2020 Jun 6.

Centre for Life, Biosciences Institute, Newcastle University, Newcastle, NE1 3BZ, UK.

Introduction: Endoglin (ENG) forms a receptor complex with ALK1 in endothelial cells (ECs) to promote BMP9/10 signalling. Loss of function mutations in either ENG or ALK1 genes lead to the inherited vascular disorder hereditary haemorrhagic telangiectasia (HHT), characterised by arteriovenous malformations (AVMs). However, the vessel-specific role of ENG and ALK1 proteins in protecting against AVMs is unclear. For example, AVMs have been described to initiate in arterioles, whereas ENG is predominantly expressed in venous ECs. To investigate whether ENG has any arterial involvement in protecting against AVM formation, we specifically depleted the Eng gene in venous and capillary endothelium whilst maintaining arterial expression, and investigated how this affected the incidence and location of AVMs in comparison with pan-endothelial Eng knockdown.

Methods: Using the mouse neonatal retinal model of angiogenesis, we first established the earliest time point at which Apj-Cre-ERT2 activity was present in venous and capillary ECs but absent from arterial ECs. We then compared the incidence of AVMs following pan-endothelial or venous/capillary-specific ENG knockout.

Results: Activation of Apj-Cre-ERT2 with tamoxifen from postnatal day (P) 5 ensured preservation of arterial ENG protein expression. Specific loss of ENG expression in ECs of veins and capillaries led to retinal AVMs at a similar frequency to pan-endothelial loss of ENG. AVMs occurred in the proximal as well as the distal part of the retina consistent with a defect in vascular remodelling during maturation of the vasculature.

Conclusion: Expression of ENG is not required in arterial ECs to protect against AVM formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10456-020-09731-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7524831PMC
November 2020

Loss of Endothelial Endoglin Promotes High-Output Heart Failure Through Peripheral Arteriovenous Shunting Driven by VEGF Signaling.

Circ Res 2020 01 6;126(2):243-257. Epub 2019 Dec 6.

From the Biosciences Institute (S.T.-C., R.E.R., E.S., B.D., C.P., H.L., H.M.A.), Faculty of Medical Sciences, Newcastle University, United Kingdom.

Rationale: ENG (endoglin) is a coreceptor for BMP (bone morphogenetic protein) 9/10 and is strongly expressed in endothelial cells. Mutations in lead to the inherited vascular disorder hereditary hemorrhagic telangiectasia characterized by local telangiectases and larger arteriovenous malformations (AVMs); but how ENG functions to regulate the adult vasculature is not understood.

Objective: The goal of the work was to determine how ENG maintains vessel caliber in adult life to prevent AVM formation and thereby protect heart function.

Methods And Results: Genetic depletion of endothelial in adult mice led to a significant reduction in mean aortic blood pressure. There was no evidence of hemorrhage, anemia, or AVMs in major organs to explain the reduced aortic pressure. However, large AVMs developed in the peripheral vasculature intimately associated with the pelvic cartilaginous symphysis-a noncapsulated cartilage with a naturally high endogenous expression of VEGF (vascular endothelial growth factor). The increased blood flow through these peripheral AVMs explained the drop in aortic blood pressure and led to increased cardiac preload, and high stroke volumes, ultimately resulting in high-output heart failure. Development of pelvic AVMs in this region of high VEGF expression occurred because loss of ENG in endothelial cells leads to increased sensitivity to VEGF and a hyperproliferative response. Development of AVMs and associated progression to high-output heart failure in the absence of endothelial ENG was attenuated by targeting VEGF signaling with an anti-VEGFR2 (VEGF receptor 2) antibody.

Conclusions: ENG promotes the normal balance of VEGF signaling in quiescent endothelial cells to maintain vessel caliber-an essential function in conditions of increased VEGF expression such as local hypoxia or inflammation. In the absence of endothelial ENG, increased sensitivity to VEGF drives abnormal endothelial proliferation in local regions of high VEGF expression, leading to AVM formation and a rapid injurious impact on heart function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCRESAHA.119.315974DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6970547PMC
January 2020

Role of soluble endoglin in BMP9 signaling.

Proc Natl Acad Sci U S A 2019 09 20;116(36):17800-17808. Epub 2019 Aug 20.

Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, United Kingdom;

Endoglin (ENG) is a coreceptor of the transforming growth factor-β (TGFβ) family signaling complex, which is highly expressed on endothelial cells and plays a key role in angiogenesis. Its extracellular domain can be cleaved and released into the circulation as soluble ENG (sENG). High circulating levels of sENG contribute to the pathogenesis of preeclampsia (PE). Circulating bone morphogenetic protein 9 (BMP9), a vascular quiescence and endothelial-protective factor, binds sENG with high affinity, but how sENG participates in BMP9 signaling complexes is not fully resolved. sENG was thought to be a ligand trap for BMP9, preventing type II receptor binding and BMP9 signaling. Here we show that, despite cell-surface ENG being a dimer linked by disulfide bonds, sENG purified from human placenta and plasma from PE patients is primarily in a monomeric form. Incubating monomeric sENG with the circulating form of BMP9 (prodomain-bound form) in solution leads to the release of the prodomain and formation of a sENG:BMP9 complex. Furthermore, we demonstrate that binding of sENG to BMP9 does not inhibit BMP9 signaling. Indeed, the sENG:BMP9 complex signals with comparable potency and specificity to BMP9 on human primary endothelial cells. The full signaling activity of the sENG:BMP9 complex required transmembrane ENG. This study confirms that rather than being an inhibitory ligand trap, increased circulating sENG might preferentially direct BMP9 signaling via cell-surface ENG at the endothelium. This is important for understanding the role of sENG in the pathobiology of PE and other cardiovascular diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1816661116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6731690PMC
September 2019

Pharmacological clearance of senescent cells improves survival and recovery in aged mice following acute myocardial infarction.

Aging Cell 2019 06 28;18(3):e12945. Epub 2019 Mar 28.

Cardiovascular Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK.

Cardiovascular disease is the leading cause of death in individuals over 60 years old. Aging is associated with an increased prevalence of coronary artery disease and a poorer prognosis following acute myocardial infarction (MI). With age, senescent cells accumulate in tissues, including the heart, and contribute to age-related pathologies. However, the role of senescence in recovery following MI has not been investigated. In this study, we demonstrate that treatment of aged mice with the senolytic drug, navitoclax, eliminates senescent cardiomyocytes and attenuates profibrotic protein expression in aged mice. Importantly, clearance of senescent cells improved myocardial remodelling and diastolic function as well as overall survival following MI. These data provide proof-of-concept evidence that senescent cells are major contributors to impaired function and increased mortality following MI and that senolytics are a potential new therapeutic avenue for MI.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/acel.12945DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6516151PMC
June 2019

Disruption of embryonic ROCK signaling reproduces the sarcomeric phenotype of hypertrophic cardiomyopathy.

JCI Insight 2019 03 5;5. Epub 2019 Mar 5.

Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.

Sarcomeric disarray is a hallmark of gene mutations in patients with Hypertrophic Cardiomyopathy (HCM). However, it is unknown when detrimental sarcomeric changes first occur and whether they originate in the developing embryonic heart. Furthermore, Rho Kinase (ROCK) is a serine threonine protein kinase that is critical for regulating the function of several sarcomeric proteins and therefore, our aim was to determine if disruption of ROCK signalling during the earliest stages of heart development would disrupt the integrity of sarcomeres altering heart development and function. Using a mouse model in which the function of ROCK is specifically disrupted in embryonic cardiomyocytes we demonstrate a progressive cardiomyopathy that first appeared as sarcomeric disarray during cardiogenesis. This led to abnormalities in the structure of embryonic ventricular wall and compensatory cardiomyocyte hypertrophy during foetal development. This sarcomeric disruption and hypertrophy persisted throughout adult life, triggering left ventricular concentric hypertrophy with systolic dysfunction, and re-activation of foetal gene expression and cardiac fibrosis, all typical features of HCM. Taken together, our findings establish a novel mechanism for the developmental origin of the sarcomeric phenotype of HCM and suggest that variants in the ROCK genes or disruption of ROCK signalling could, in part, contribute to its pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1172/jci.insight.125172DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6538384PMC
March 2019

Length-independent telomere damage drives post-mitotic cardiomyocyte senescence.

EMBO J 2019 03 8;38(5). Epub 2019 Feb 8.

Ageing Research Laboratories, Institute for Ageing, Newcastle University, Newcastle upon Tyne, UK

Ageing is the biggest risk factor for cardiovascular disease. Cellular senescence, a process driven in part by telomere shortening, has been implicated in age-related tissue dysfunction. Here, we address the question of how senescence is induced in rarely dividing/post-mitotic cardiomyocytes and investigate whether clearance of senescent cells attenuates age-related cardiac dysfunction. During ageing, human and murine cardiomyocytes acquire a senescent-like phenotype characterised by persistent DNA damage at telomere regions that can be driven by mitochondrial dysfunction and crucially can occur independently of cell division and telomere length. Length-independent telomere damage in cardiomyocytes activates the classical senescence-inducing pathways, p21 and p16, and results in a non-canonical senescence-associated secretory phenotype, which is pro-fibrotic and pro-hypertrophic. Pharmacological or genetic clearance of senescent cells in mice alleviates detrimental features of cardiac ageing, including myocardial hypertrophy and fibrosis. Our data describe a mechanism by which senescence can occur and contribute to age-related myocardial dysfunction and in the wider setting to ageing in post-mitotic tissues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.15252/embj.2018100492DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6396144PMC
March 2019

Decreased Expression of Vascular Endothelial Growth Factor Receptor 1 Contributes to the Pathogenesis of Hereditary Hemorrhagic Telangiectasia Type 2.

Circulation 2018 12;138(23):2698-2712

Einthoven Laboratory for Experimental Vascular Medicine, Department of Internal Medicine (Nephrology), Leiden University Medical Center, The Netherlands (J.H.T., G.G., H.C.d.B., T.J.R., K.R., F.L.).

Background: Hereditary Hemorrhagic Telangiectasia type 2 (HHT2) is an inherited genetic disorder characterized by vascular malformations and hemorrhage. HHT2 results from ACVRL1 haploinsufficiency, the remaining wild-type allele being unable to contribute sufficient protein to sustain endothelial cell function. Blood vessels function normally but are prone to respond to angiogenic stimuli, leading to the development of telangiectasic lesions that can bleed. How ACVRL1 haploinsufficiency leads to pathological angiogenesis is unknown.

Methods: We took advantage of Acvrl1 mutant mice that exhibit HHT2 vascular lesions and focused on the neonatal retina and the airway system after Mycoplasma pulmonis infection, as physiological and pathological models of angiogenesis, respectively. We elucidated underlying disease mechanisms in vitro by generating Acvrl1 mouse embryonic stem cell lines that underwent sprouting angiogenesis and performed genetic complementation experiments. Finally, HHT2 plasma samples and skin biopsies were analyzed to determine whether the mechanisms evident in mice are conserved in humans.

Results: Acvrl1 retinas at postnatal day 7 showed excessive angiogenesis and numerous endothelial "tip cells" at the vascular front that displayed migratory defects. Vascular endothelial growth factor receptor 1 (VEGFR1; Flt-1) levels were reduced in Acvrl1 mice and HHT2 patients, suggesting similar mechanisms in humans. In sprouting angiogenesis, VEGFR1 is expressed in stalk cells to inhibit VEGFR2 (Flk-1, KDR) signaling and thus limit tip cell formation. Soluble VEGFR1 (sVEGFR1) is also secreted, creating a VEGF gradient that promotes orientated sprout migration. Acvrl1 embryonic stem cell lines recapitulated the vascular anomalies in Acvrl1 (HHT2) mice. Genetic insertion of either the membrane or soluble form of VEGFR1 into the ROSA26 locus of Acvrl1 embryonic stem cell lines prevented the vascular anomalies, suggesting that high VEGFR2 activity in Acvrl1 endothelial cells induces HHT2 vascular anomalies. To confirm our hypothesis, Acvrl1 mice were infected by Mycoplasma pulmonis to induce sustained airway inflammation. Infected Acvrl1 tracheas showed excessive angiogenesis with the formation of multiple telangiectases, vascular defects that were prevented by VEGFR2 blocking antibodies.

Conclusions: Our findings demonstrate a key role of VEGFR1 in HHT2 pathogenesis and provide mechanisms explaining why HHT2 blood vessels respond abnormally to angiogenic signals. This supports the case for using anti-VEGF therapy in HHT2.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCULATIONAHA.117.033062DOI Listing
December 2018

Soluble endoglin regulates expression of angiogenesis-related proteins and induction of arteriovenous malformations in a mouse model of hereditary hemorrhagic telangiectasia.

Dis Model Mech 2018 09 21;11(9). Epub 2018 Sep 21.

Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), 28040 Madrid, Spain

Endoglin is a transmembrane glycoprotein expressed in vascular endothelium that plays a key role in angiogenesis. Mutations in the endoglin gene () cause hereditary hemorrhagic telangiectasia type 1 (HHT1), characterized by arteriovenous malformations (AVMs) in different organs. These vascular lesions derive from abnormal processes of angiogenesis, whereby aberrant vascular remodeling leads to focal loss of capillaries. Current treatments for HHT1 include antiangiogenic therapies. Interestingly, a circulating form of endoglin (also known as soluble endoglin, sEng), proteolytically released from the membrane-bound protein and displaying antiangiogenic activity, has been described in several endothelial-related pathological conditions. Using human and mouse endothelial cells, we find that sEng downregulates several pro-angiogenic and pro-migratory proteins involved in angiogenesis. However, this effect is much reduced in endothelial cells that lack endogenous transmembrane endoglin, suggesting that the antiangiogenic activity of sEng is dependent on the presence of endogenous transmembrane endoglin protein. In fact, sEng partially restores the phenotype of endoglin-silenced endothelial cells to that of normal endothelial cells. Moreover, using an established neonatal retinal model of HHT1 with depleted endoglin in the vascular endothelium, sEng treatment decreases the number of AVMs and has a normalizing effect on the vascular phenotype with respect to vessel branching, vascular density and migration of the vascular plexus towards the retinal periphery. Taken together, these data show that circulating sEng can influence vascular development and AVMs by modulating angiogenesis, and that its effect on endothelial cells depends on the expression of endogenous endoglin.This article has an associated First Person interview with the first author of the paper.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/dmm.034397DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6176985PMC
September 2018

Inhibiting DPP4 in a mouse model of HHT1 results in a shift towards regenerative macrophages and reduces fibrosis after myocardial infarction.

PLoS One 2017 18;12(12):e0189805. Epub 2017 Dec 18.

Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, the Netherlands.

Aims: Hereditary Hemorrhagic Telangiectasia type-1 (HHT1) is a genetic vascular disorder caused by haploinsufficiency of the TGFβ co-receptor endoglin. Dysfunctional homing of HHT1 mononuclear cells (MNCs) towards the infarcted myocardium hampers cardiac recovery. HHT1-MNCs have elevated expression of dipeptidyl peptidase-4 (DPP4/CD26), which inhibits recruitment of CXCR4-expressing MNCs by inactivation of stromal cell-derived factor 1 (SDF1). We hypothesize that inhibiting DPP4 will restore homing of HHT1-MNCs to the infarcted heart and improve cardiac recovery.

Methods And Results: After inducing myocardial infarction (MI), wild type (WT) and endoglin heterozygous (Eng+/-) mice were treated for 5 days with the DPP4 inhibitor Diprotin A (DipA). DipA increased the number of CXCR4+ MNCs residing in the infarcted Eng+/- hearts (Eng+/- 73.17±12.67 vs. Eng+/- treated 157.00±11.61, P = 0.0003) and significantly reduced infarct size (Eng+/- 46.60±9.33% vs. Eng+/- treated 27.02±3.04%, P = 0.03). Echocardiography demonstrated that DipA treatment slightly deteriorated heart function in Eng+/- mice. An increased number of capillaries (Eng+/- 61.63±1.43 vs. Eng+/- treated 74.30±1.74, P = 0.001) were detected in the infarct border zone whereas the number of arteries was reduced (Eng+/- 11.88±0.63 vs. Eng+/- treated 6.38±0.97, P = 0.003). Interestingly, while less M2 regenerative macrophages were present in Eng+/- hearts prior to DipA treatment, (WT 29.88±1.52% vs. Eng+/- 12.34±1.64%, P<0.0001), DPP4 inhibition restored the number of M2 macrophages to wild type levels.

Conclusions: In this study, we demonstrate that systemic DPP4 inhibition restores the impaired MNC homing in Eng+/- animals post-MI, and enhances cardiac repair, which might be explained by restoring the balance between the inflammatory and regenerative macrophages present in the heart.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0189805PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5734765PMC
January 2018

Executive summary of the 12th HHT international scientific conference.

Angiogenesis 2018 02;21(1):169-181

Department of Pulmonology, St. Antonius Hospital, Koekoekslaan 1, 3435 CM, Nieuwegein, The Netherlands.

Hereditary hemorrhagic telangiectasia is an autosomal dominant trait affecting approximately 1 in 5000 people. A pathogenic DNA sequence variant in the ENG, ACVRL1 or SMAD4 genes, can be found in the majority of patients. The 12th International Scientific HHT Conference was held on June 8-11, 2017 in Dubrovnik, Croatia to present and discuss the latest scientific achievements, and was attended by over 200 scientific and clinical researchers. In total 174 abstracts were accepted of which 58 were selected for oral presentations. This article covers the basic science and clinical talks, and discussions from three theme-based workshops. We focus on significant emergent themes and unanswered questions. Understanding these topics and answering these questions will help to define the future of HHT research and therapeutics, and ultimately bring us closer to a cure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10456-017-9585-2DOI Listing
February 2018

The secret life of nonclassical monocytes.

Cytometry A 2017 11 27;91(11):1055-1058. Epub 2017 Oct 27.

International Centre for Life, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cyto.a.23280DOI Listing
November 2017

Endoglin prevents vascular malformation by regulating flow-induced cell migration and specification through VEGFR2 signalling.

Nat Cell Biol 2017 Jun 22;19(6):639-652. Epub 2017 May 22.

Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles väg 2, 171 77 Stockholm, Sweden.

Loss-of-function (LOF) mutations in the endothelial cell (EC)-enriched gene endoglin (ENG) cause the human disease hereditary haemorrhagic telangiectasia-1, characterized by vascular malformations promoted by vascular endothelial growth factor A (VEGFA). How ENG deficiency alters EC behaviour to trigger these anomalies is not understood. Mosaic ENG deletion in the postnatal mouse rendered Eng LOF ECs insensitive to flow-mediated venous to arterial migration. Eng LOF ECs retained within arterioles acquired venous characteristics and secondary ENG-independent proliferation resulting in arteriovenous malformation (AVM). Analysis following simultaneous Eng LOF and overexpression (OE) revealed that ENG OE ECs dominate tip-cell positions and home preferentially to arteries. ENG knockdown altered VEGFA-mediated VEGFR2 kinetics and promoted AKT signalling. Blockage of PI(3)K/AKT partly normalized flow-directed migration of ENG LOF ECs in vitro and reduced the severity of AVM in vivo. This demonstrates the requirement of ENG in flow-mediated migration and modulation of VEGFR2 signalling in vascular patterning.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncb3534DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5467724PMC
June 2017

Cardiosphere-Derived Cells Require Endoglin for Paracrine-Mediated Angiogenesis.

Stem Cell Reports 2017 05;8(5):1287-1298

Institute of Genetic Medicine, Centre for Life, Newcastle University, Newcastle NE1 3BZ, UK. Electronic address:

Clinical trials of stem cell therapy to treat ischemic heart disease primarily use heterogeneous stem cell populations. Small benefits occur via paracrine mechanisms that include stimulating angiogenesis, and increased understanding of these mechanisms would help to improve patient outcomes. Cardiosphere-derived-cells (CDCs) are an example of these heterogeneous stem cell populations, cultured from cardiac tissue. CDCs express endoglin, a co-receptor that binds specific transforming growth factor β (TGFβ) family ligands, including bone morphogenetic protein 9 (BMP9). In endothelial cells endoglin regulates angiogenic responses, and we therefore hypothesized that endoglin is required to promote the paracrine pro-angiogenic properties of CDCs. Cre/LoxP technology was used to genetically manipulate endoglin expression in CDCs, and we found that the pro-angiogenic properties of the CDC secretome are endoglin dependent both in vitro and in vivo. Importantly, BMP9 pre-treatment of endoglin-depleted CDCs restores their pro-angiogenic paracrine properties. As BMP9 signaling is normally required to maintain endoglin expression, we propose that media containing BMP9 could be critical for therapeutic CDC preparation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.stemcr.2017.04.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5425789PMC
May 2017

Microvessels of the heart: Formation, regeneration, and dysfunction.

Microcirculation 2017 01;24(1)

Institute of Genetic Medicine, Centre for Life, Newcastle University, Newcastle, UK.

This issue of microcirculation focusses on the special topic of "microvessels of the heart" and contains five state-of-the-art reviews and one expert article that reflect current efforts to address the major gaps in our understanding of these key microvessels. In the adult heart, most attention until recently (especially among the clinical cardiology community) has been given to the main coronary arteries, which are the culprit vessels in patients with coronary artery disease, including its most serious manifestation, acute MI. However, due to major advances in efficiently reopening the acutely blocked coronary arteries, MI is no longer the killer disease it once was. In contrast, there are few treatment options for patients who develop microvascular obstruction during acute MI. Indeed, we have a very poor understanding of this disease, or even how heart vessels are initially formed in development. This is surprising in light of the essential nature of the cardiac microvessels for efficient cardiac function throughout life. The articles in this issue are from six keynote speakers at the 66th annual meeting of the BMS at Newcastle University and review our understanding of these key vessels from initial development to their role in adult heart disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/micc.12338DOI Listing
January 2017

Using MRI to predict future adverse cardiac remodelling in a male mouse model of myocardial infarction.

Int J Cardiol Heart Vasc 2016 Jun 16;11:29-34. Epub 2016 Mar 16.

Institute of Genetic Medicine, Central Parkway, Newcastle University, Newcastle NE1 3BZ, UK.

Background: Mice are frequently used in research to examine outcomes of myocardial infarction (MI) and to investigate therapeutic interventions at an early pre-clinical stage. The MI model is generated by surgically occluding a major coronary artery, but natural variation in murine coronary anatomy can generate variable outcomes that will inevitably affect the accuracy of such investigations. The aim of this study was to use MRI to derive the most sensitive early variable that could be used to predict subsequent adverse cardiac remodelling in a male mouse model of MI.

Methods: Using a longitudinal study design, heart structure and function were evaluated using cardiac MRI at one week following surgical MI to generate the early measurements and again at four weeks, when the scar had matured. The primary variables measured at week one were left ventricular volumes at end systole (LV-ESV) and at end diastole (LV-EDV), infarct size, LV-cardiac mass, and ejection fraction (EF).

Results: Univariate and multiple regression analyses showed that LV-ESV at one week following MI could be used to accurately predict various parameters of adverse LV remodelling at four weeks post-MI. However, the highest correlation was between LV-ESV at one week following MI and LV-EDV at four weeks (r = 0.99; p < 0.0001), making LV-ESV at one week a valuable predictor variable of future adverse ventricular remodelling after MI.

Conclusion: Using MRI to determine LV-ESV at an early stage following MI enables a more robust analysis of potential therapeutic interventions to ameliorate adverse cardiac remodelling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijcha.2016.03.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5111480PMC
June 2016

Persistent infiltration and pro-inflammatory differentiation of monocytes cause unresolved inflammation in brain arteriovenous malformation.

Angiogenesis 2016 10 20;19(4):451-461. Epub 2016 Jun 20.

Center for Cerebrovascular Research, Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, USA.

An abnormally high number of macrophages are present in human brain arteriovenous malformations (bAVM) with or without evidence of prior hemorrhage, causing unresolved inflammation that may enhance abnormal vascular remodeling and exacerbate the bAVM phenotype. The reasons for macrophage accumulation at the bAVM sites are not known. We tested the hypothesis that persistent infiltration and pro-inflammatory differentiation of monocytes in angiogenic tissues increase the macrophage burden in bAVM using two mouse models and human monocytes. Mouse bAVM was induced through deletion of AVM causative genes, Endoglin (Eng) globally or Alk1 focally, plus brain focal angiogenic stimulation. An endothelial cell and vascular smooth muscle cell co-culture system was used to analyze monocyte differentiation in the angiogenic niche. After angiogenic stimulation, the Eng-deleted mice had fewer CD68(+) cells at 2 weeks (P = 0.02), similar numbers at 4 weeks (P = 0.97), and more at 8 weeks (P = 0.01) in the brain angiogenic region compared with wild-type (WT) mice. Alk1-deficient mice also had a trend toward more macrophages/microglia 8 weeks (P = 0.064) after angiogenic stimulation and more RFP(+) bone marrow-derived macrophages than WT mice (P = 0.01). More CD34(+) cells isolated from peripheral blood of patients with ENG or ALK1 gene mutation differentiated into macrophages than those from healthy controls (P < 0.001). These data indicate that persistent infiltration and pro-inflammatory differentiation of monocytes might contribute to macrophage accumulation in bAVM. Blocking macrophage homing to bAVM lesions should be tested as a strategy to reduce the severity of bAVM.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10456-016-9519-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029790PMC
October 2016

Mice Lacking Endoglin in Macrophages Show an Impaired Immune Response.

PLoS Genet 2016 Mar 24;12(3):e1005935. Epub 2016 Mar 24.

Centro de Investigación en Red de Enfermedades Raras (CIBERER), Valencia, Spain.

Endoglin is an auxiliary receptor for members of the TGF-β superfamily and plays an important role in the homeostasis of the vessel wall. Mutations in endoglin gene (ENG) or in the closely related TGF-β 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-β1 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1371/journal.pgen.1005935DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4806930PMC
March 2016

Interaction Between ALK1 Signaling and Connexin40 in the Development of Arteriovenous Malformations.

Arterioscler Thromb Vasc Biol 2016 Apr 28;36(4):707-17. Epub 2016 Jan 28.

From the Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, The Netherlands (K.G., C.L.M.); CNRS Unité mixte de recherche 7241/INSERM U1050, Center for Interdisciplinary Research in Biology, Collège de France, Paris cedex 05, France (J.T., D.D.-S.-L., S.M., N.L., F.L.); MEMOLIFE Laboratory of Excellence, Paris Sciences et Lettres Research University, Paris, France (J.T., D.D.-S.-L., S.M., N.L., F.L.); Department of Radiology, AP-HP, Tenon Hospital, Paris, France (M.F.C.); Sorbonne Universités, UPMC University, Paris, France (M.F.C.); St. Antonius Hospital, Nieuwegein, The Netherlands (F.D., R.J.S., C.J.W., J.J.M.); Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville (S.P.O.); Aix Marseille Université, CNRS IBDM UMR 7288, Marseille cedex 09, France (L.M.); and Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom (H.M.A.).

Objective: To determine the role of Gja5 that encodes for the gap junction protein connexin40 in the generation of arteriovenous malformations in the hereditary hemorrhagic telangiectasia type 2 (HHT2) mouse model.

Approach And Results: We identified GJA5 as a target gene of the bone morphogenetic protein-9/activin receptor-like kinase 1 signaling pathway in human aortic endothelial cells and importantly found that connexin40 levels were particularly low in a small group of patients with HHT2. We next took advantage of the Acvrl1(+/-) mutant mice that develop lesions similar to those in patients with HHT2 and generated Acvrl1(+/-); Gja5(EGFP/+) mice. Gja5 haploinsufficiency led to vasodilation of the arteries and rarefaction of the capillary bed in Acvrl1(+/-) mice. At the molecular level, we found that reduced Gja5 in Acvrl1(+/-) mice stimulated the production of reactive oxygen species, an important mediator of vessel remodeling. To normalize the altered hemodynamic forces in Acvrl1(+/-); Gja5(EGFP/+) mice, capillaries formed transient arteriovenous shunts that could develop into large malformations when exposed to environmental insults.

Conclusions: We identified GJA5 as a potential modifier gene for HHT2. Our findings demonstrate that Acvrl1 haploinsufficiency combined with the effects of modifier genes that regulate vessel caliber is responsible for the heterogeneity and severity of the disease. The mouse models of HHT have led to the proposal that 3 events-heterozygosity, loss of heterozygosity, and angiogenic stimulation-are necessary for arteriovenous malformation formation. Here, we present a novel 3-step model in which pathological vessel caliber and consequent altered blood flow are necessary events for arteriovenous malformation development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/ATVBAHA.115.306719DOI Listing
April 2016

Mouse models of hereditary hemorrhagic telangiectasia: recent advances and future challenges.

Front Genet 2015 18;6:25. Epub 2015 Feb 18.

Institute of Genetic Medicine, Newcastle University , Newcastle, UK.

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder characterized by a multi-systemic vascular dysplasia and hemorrhage. The precise factors leading to these vascular malformations are not yet understood and robust animal models of HHT are essential to gain a detailed understanding of the molecular and cellular events that lead to clinical symptoms, as well as to test new therapeutic modalities. Most cases of HHT are caused by mutations in either endoglin (ENG) or activin receptor-like kinase 1 (ACVRL1, also known as ALK1). Both genes are associated with TGFβ/BMP signaling, and loss of function mutations in the co-receptor ENG are causal in HHT1, while HHT2 is associated with mutations in the signaling receptor ACVRL1. Significant advances in mouse genetics have provided powerful ways to study the function of Eng and Acvrl1 in vivo, and to generate mouse models of HHT disease. Mice that are null for either Acvrl1 or Eng genes show embryonic lethality due to major defects in angiogenesis and heart development. However mice that are heterozygous for mutations in either of these genes develop to adulthood with no effect on survival. Although these heterozygous mice exhibit selected vascular phenotypes relevant to the clinical pathology of HHT, the phenotypes are variable and generally quite mild. An alternative approach using conditional knockout mice allows us to study the effects of specific inactivation of either Eng or Acvrl1 at different times in development and in different cell types. These conditional knockout mice provide robust and reproducible models of arteriovenous malformations, and they are currently being used to unravel the causal factors in HHT pathologies. In this review, we will summarize the strengths and limitations of current mouse models of HHT, discuss how knowledge obtained from these studies has already informed clinical care and explore the potential of these models for developing improved treatments for HHT patients in the future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fgene.2015.00025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4332371PMC
March 2015

Common and distinctive pathogenetic features of arteriovenous malformations in hereditary hemorrhagic telangiectasia 1 and hereditary hemorrhagic telangiectasia 2 animal models--brief report.

Arterioscler Thromb Vasc Biol 2014 Oct 31;34(10):2232-6. Epub 2014 Jul 31.

From the Department of Physiology and Functional Genomics (E.M.G.-M., H.-L.N., T.A.C., S.-w.C., S.P.O.) and Department of Surgery (Z.J.), University of Florida, Gainesville; Department of Biomedical Engineering, Tongmyong University, Busan, Republic of Korea (S.-w.C.); Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom (H.M.A.); and Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, Republic of Korea (Y.-J.L., S.P.O.).

Objective: Hereditary hemorrhagic telangiectasia is a genetic disorder characterized by visceral and mucocutaneous arteriovenous malformations (AVMs). Clinically indistinguishable hereditary hemorrhagic telangiectasia 1 and hereditary hemorrhagic telangiectasia 2 are caused by mutations in ENG and ALK1, respectively. In this study, we have compared the development of visceral and mucocutaneous AVMs in adult stages between Eng- and Alk1-inducible knockout (iKO) models.

Approach And Results: Eng or Alk1 were deleted from either vascular endothelial cells (ECs) or smooth muscle cells in adult stages using Scl-CreER and Myh11-CreER lines, respectively. Latex perfusion and intravital spectral imaging in a dorsal skinfold window chamber system were used to visualize remodeling vasculature during AVM formation. Global Eng deletion resulted in lethality with visceral AVMs and wound-induced skin AVMs. Deletion of Alk1 or Eng in ECs, but not in smooth muscle cells, resulted in wound-induced skin AVMs. Visceral AVMs were observed in EC-specific Alk1-iKO but not in Eng-iKO. Intravital spectral imaging revealed that Eng-iKO model exhibited more dynamic processes for AVM development when compared with Alk1-iKO model.

Conclusions: Both Alk1- and Eng-deficient models require a secondary insult, such as wounding, and ECs are the primary cell type responsible for the pathogenesis. However, Alk1 but not Eng deletion in ECs results in visceral AVMs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/ATVBAHA.114.303984DOI Listing
October 2014

Endothelial depletion of Acvrl1 in mice leads to arteriovenous malformations associated with reduced endoglin expression.

PLoS One 2014 4;9(6):e98646. Epub 2014 Jun 4.

Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom.

Rare inherited cardiovascular diseases are frequently caused by mutations in genes that are essential for the formation and/or function of the cardiovasculature. Hereditary Haemorrhagic Telangiectasia is a familial disease of this type. The majority of patients carry mutations in either Endoglin (ENG) or ACVRL1 (also known as ALK1) genes, and the disease is characterized by arteriovenous malformations and persistent haemorrhage. ENG and ACVRL1 encode receptors for the TGFβ superfamily of ligands, that are essential for angiogenesis in early development but their roles are not fully understood. Our goal was to examine the role of Acvrl1 in vascular endothelial cells during vascular development and to determine whether loss of endothelial Acvrl1 leads to arteriovenous malformations. Acvrl1 was depleted in endothelial cells either in early postnatal life or in adult mice. Using the neonatal retinal plexus to examine angiogenesis, we observed that loss of endothelial Acvrl1 led to venous enlargement, vascular hyperbranching and arteriovenous malformations. These phenotypes were associated with loss of arterial Jag1 expression, decreased pSmad1/5/8 activity and increased endothelial cell proliferation. We found that Endoglin was markedly down-regulated in Acvrl1-depleted ECs showing endoglin expression to be downstream of Acvrl1 signalling in vivo. Endothelial-specific depletion of Acvrl1 in pups also led to pulmonary haemorrhage, but in adult mice resulted in caecal haemorrhage and fatal anaemia. We conclude that during development, endothelial Acvrl1 plays an essential role to regulate endothelial cell proliferation and arterial identity during angiogenesis, whilst in adult life endothelial Acvrl1 is required to maintain vascular integrity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0098646PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4045906PMC
August 2015

Novel brain arteriovenous malformation mouse models for type 1 hereditary hemorrhagic telangiectasia.

PLoS One 2014 10;9(2):e88511. Epub 2014 Feb 10.

Center for Cerebrovascular Research, Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, California, United States of America.

Endoglin (ENG) is a causative gene of type 1 hereditary hemorrhagic telangiectasia (HHT1). HHT1 patients have a higher prevalence of brain arteriovenous malformation (AVM) than the general population and patients with other HHT subtypes. The pathogenesis of brain AVM in HHT1 patients is currently unknown and no specific medical therapy is available to treat patients. Proper animal models are crucial for identifying the underlying mechanisms for brain AVM development and for testing new therapies. However, creating HHT1 brain AVM models has been quite challenging because of difficulties related to deleting Eng-floxed sequence in Eng(2fl/2fl) mice. To create an HHT1 brain AVM mouse model, we used several Cre transgenic mouse lines to delete Eng in different cell-types in Eng(2fl/2fl) mice: R26CreER (all cell types after tamoxifen treatment), SM22α-Cre (smooth muscle and endothelial cell) and LysM-Cre (lysozyme M-positive macrophage). An adeno-associated viral vector expressing vascular endothelial growth factor (AAV-VEGF) was injected into the brain to induce focal angiogenesis. We found that SM22α-Cre-mediated Eng deletion in the embryo caused AVMs in the postnatal brain, spinal cord, and intestines. Induction of Eng deletion in adult mice using R26CreER plus local VEGF stimulation induced the brain AVM phenotype. In both models, Eng-null endothelial cells were detected in the brain AVM lesions, and formed mosaicism with wildtype endothelial cells. However, LysM-Cre-mediated Eng deletion in the embryo did not cause AVM in the postnatal brain even after VEGF stimulation. In this study, we report two novel HHT1 brain AVM models that mimic many phenotypes of human brain AVM and can thus be used for studying brain AVM pathogenesis and testing new therapies. Further, our data indicate that macrophage Eng deletion is insufficient and that endothelial Eng homozygous deletion is required for HHT1 brain AVM development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088511PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3919779PMC
October 2014

ENDOGLIN is dispensable for vasculogenesis, but required for vascular endothelial growth factor-induced angiogenesis.

PLoS One 2014 28;9(1):e86273. Epub 2014 Jan 28.

Department of Molecular Cell Biology, Cancer Genomics Centre, Centre for Biomedical Genetics, Leiden University Medical Center, Leiden, The Netherlands.

ENDOGLIN (ENG) is a co-receptor for transforming growth factor-β (TGF-β) family members that is highly expressed in endothelial cells and has a critical function in the development of the vascular system. Mutations in Eng are associated with the vascular disease known as hereditary hemorrhagic telangiectasia type l. Using mouse embryonic stem cells we observed that angiogenic factors, including vascular endothelial growth factor (VEGF), induce vasculogenesis in embryoid bodies even when Eng deficient cells or cells depleted of Eng using shRNA are used. However, ENG is required for the stem cell-derived endothelial cells to organize effectively into tubular structures. Consistent with this finding, fetal metatarsals isolated from E17.5 Eng heterozygous mouse embryos showed reduced VEGF-induced vascular network formation. Moreover, shRNA-mediated depletion and pharmacological inhibition of ENG in human umbilical vein cells mitigated VEGF-induced angiogenesis. In summary, we demonstrate that ENG is required for efficient VEGF-induced angiogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0086273PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3904881PMC
December 2014

Whole mount immunofluorescent staining of the neonatal mouse retina to investigate angiogenesis in vivo.

J Vis Exp 2013 Jul 9(77):e50546. Epub 2013 Jul 9.

Institute of Genetic Medicine, Newcastle University, Australia.

Angiogenesis is the complex process of new blood vessel formation defined by the sprouting of new blood vessels from a pre-existing vessel network. Angiogenesis plays a key role not only in normal development of organs and tissues, but also in many diseases in which blood vessel formation is dysregulated, such as cancer, blindness and ischemic diseases. In adult life, blood vessels are generally quiescent so angiogenesis is an important target for novel drug development to try and regulate new vessel formation specifically in disease. In order to better understand angiogenesis and to develop appropriate strategies to regulate it, models are required that accurately reflect the different biological steps that are involved. The mouse neonatal retina provides an excellent model of angiogenesis because arteries, veins and capillaries develop to form a vascular plexus during the first week after birth. This model also has the advantage of having a two-dimensional (2D) structure making analysis straightforward compared with the complex 3D anatomy of other vascular networks. By analyzing the retinal vascular plexus at different times after birth, it is possible to observe the various stages of angiogenesis under the microscope. This article demonstrates a straightforward procedure for analyzing the vasculature of a mouse retina using fluorescent staining with isolectin and vascular specific antibodies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3791/50546DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732076PMC
July 2013