Biology subjects

Arthur, H. M.

Publications and source records attributed to Arthur, H. M..

5 recordsLinked to original sources

bioRxiv2025

ALK1-BMPRII agonism by clustering bispecific antibodies treats hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is characterized by arteriovenous malformations (AVMs) and severe bleeding caused by loss-of-function mutations in the ALK1 receptor pathway. We developed clustering agonist bispecific antibodies (BsAbs) targeting ALK1 and its activating partner, the Ser/Thr receptor kinase BMPRII. These BsAbs induced ALK1-BMPRII proximity association, stimulated the downstream Smad1/5/8 signaling cascade, and treated HHT pathologies in various mouse models. BsAb treatment reduced AVM burden by up to 95% in HHT mice, preventing anemia, cardiomegaly, and premature death. The BsAbs also enhanced Smad1/5/8 signaling in endothelial cells derived from HHT patients with ALK1 mutations and prevented retinal AVMs in a newly developed knock-in mouse carrying an HHT-causing ALK1 mutation. These findings establish ALK1-BMPRII agonism as a promising therapeutic strategy for HHT.

cell biology↗

bioRxiv2024

Endoglin regulates the integrity of the bone marrow vasculature

Endoglin (Eng) is an accessory receptor for transforming growth factor-{beta} (TGF-{beta}) that is critical for maintaining vascular integrity. Mutations in Eng cause hereditary hemorrhagic telangiectasia (HHT), resulting in arteriovenous malformations (AVMs) and blood abnormalities. Despite the known association between Eng deficiency and AVMs, the underlying mechanisms are unclear. In addition, the role of the bone marrow (BM), a major source of immune and blood cells, in endothelial Eng (EC-Eng) deficiency is unexplored. We show that BM blood vessels conditionally deficient in Eng (cKO) undergo a structured remodeling process over four weeks, with distinct proliferative and resolution phases. These phases involve angiogenic set points, the involvement of integrins, and the modulation of vascular integrity. In addition, we observe changes in hematopoietic stem and progenitor cells (HSPC) and circulating granulocytes, along with reduced red blood cells and platelets due to splenic sequestration. Using a conditional heterozygous EC-Eng deficient mouse model, reflecting the genetics of HHT patients, we identify vascular changes similar to those in the cKO model. Taken together, using multiple in vivo approaches, we suggest that reduced Eng expression in the endothelium drives significant BM vascular remodeling, sharing mechanisms with early vascular processes associated with AVM formation. Explanation of NoveltyOur findings reveal that BM blood vessels deficient in endoglin undergo an orchestrated remodeling process with distinct proliferative and resolution phases over several weeks. We identify specific angiogenic set points and profound alterations in vascular integrity, along with hematopoietic changes starting at the level of hematopoietic stem and progenitor cells. These findings advance our understanding of the role of Eng in vascular remodeling and may provide novel therapeutic targets for HHT. Key PointsO_LIConditional EC-Eng deficiency leads to vascular remodeling in the BM of mice in a temporally orchestrated manner. C_LIO_LIEC-Eng facilitates vascular integrity, hematopoietic homeostasis, and immune cell mobilization. C_LI

molecular biology↗

bioRxiv2023

Exogenous TGFβ1 and its mimic HpTGM attenuate the heart's inflammatory response to ischaemic injury and improve long term cardiac outcomes

RationaleSuccessful and timely coronary reperfusion following acute ST-elevation myocardial infarction (STEMI) is standard therapy to salvage transiently ischaemic heart muscle. However, the subsequent inflammatory response within the infarct can lead to further loss of viable myocardium. Robust interventions are required in the acute MI setting to minimise cardiac injury and reduce risk of further detrimental progression. ObjectiveTGF{beta}1 is an anti-inflammatory cytokine released endogenously in response to infection or tissue injury. The goal of this study was to investigate its protective effects when given exogenously following myocardial infarction. Methods and ResultsTGF{beta}1 is found at increased levels in the blood of STEMI patients immediately following myocardial infarction. We observe a significant correlation (p=0.003) between higher circulating TGF{beta}1 levels at 24h post MI and a reduction in infarct size over the following 3 months, suggesting that an early increase in circulating TGF{beta}1 is protective in these patients. Using a mouse model of cardiac ischaemia-reperfusion we demonstrate that additional exogenous TGF{beta}1 delivered in the acute setting has multiple beneficial outcomes. At 24 hours post-reperfusion It leads to a significantly smaller infarct size (30% reduction, p=0.025), reduced inflammatory infiltrate (28% reduction, p=0.015), lower intra-cardiac expression of inflammatory cytokines IL1{beta} and CCL2 (>50 % reduction, p=0.038 and 0.0004, respectively) and reduced scar size at 4 weeks (21% reduction, p=0.015). Furthermore exogenous delivery of an equivalent dose of HpTGM, a recently described low-fibrogenic mimic of TGF{beta}1, secreted by a helminth parasite to evade immune rejection, has an almost identical protective effect on injured mouse hearts. Furthermore using a genetic approach we show the benefit is mediated by the vascular endothelium. ConclusionsThis work reveals the potential of exogenous TGF{beta}1 and HpTGM delivered in the acute MI setting to provide protective anti-inflammatory effects and reduce infarct size, leading to a smaller scar and reduced detrimental progression.

pathology↗

bioRxiv2021

Rapid fall in circulating non-classical monocytes in ST elevation myocardial infarction patients correlates with cardiac injury

ObjectiveMyocardial infarction leads to a rapid innate immune response that is ultimately required for repair of damaged heart tissue. We therefore examined circulating monocyte dynamics immediately after reperfusion of the culprit coronary vessel in STEMI patients to determine whether this correlated with level of cardiac injury. A mouse model of cardiac ischaemia/reperfusion injury was subsequently used to establish the degree of monocyte margination to the coronary vasculature that could potentially contribute to the drop in circulating monocytes. Approach and ResultsWe retrospectively analysed blood samples from 51 STEMI patients to assess the number of non-classical (NC), classical and intermediate monocytes immediately following primary percutaneous coronary intervention. Classical and intermediate monocytes showed minimal change. On the other hand circulating numbers of NC monocytes fell by approximately 50% at 90 minutes post-reperfusion. This rapid decrease in NC monocytes was greatest in patients with the largest infarct size (p<0.05) and correlated inversely with left ventricular function (r=0.41, p=0.04). The early fall in NC monocytes post reperfusion was confirmed in a second prospective study of 13 STEMI patients. Furthermore, in a mouse cardiac ischaemia model, there was significant monocyte adhesion to coronary vessel endothelium at 2 hours post-reperfusion pointing to a specific and rapid vessel margination response to cardiac injury. ConclusionsRapid depletion of NC monocytes from the circulation in STEMI patients following coronary artery reperfusion correlates with the level of acute cardiac injury and involves rapid margination to the coronary vasculature. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/428825v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@11f758eorg.highwire.dtl.DTLVardef@5eed65org.highwire.dtl.DTLVardef@33a0d9org.highwire.dtl.DTLVardef@1854643_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LI3-5 bullet points that summarize the major findings of the study. C_LI O_LICirculating non classical monocytes show a rapid fall in STEMI patients within 90 minutes of re-opening the culprit coronary artery. C_LIO_LIThe extent of the drop in non classical monocytes correlates with loss of cardiac function and increased infarct size. C_LIO_LIA mouse model of cardiac ischaemia and reperfusion shows rapid margination of monocytes to the coronary vasculature C_LI

immunology↗

bioRxiv2020

Arterial endoglin does not protect against arteriovenous malformations

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. MethodsUsing 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. ResultsActivation 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. ConclusionExpression of ENG is not required in arterial ECs to protect against AVM formation.

genetics↗