The quiescent endothelium: signalling pathways regulating organ-specific endothelial normalcy

Endothelial Krüppel-like factor 2/4: Regulation and function in cardiovascular diseases

This review presents an overview of the regulation, function, disease-relevance and pharmacological regulation of the critical endothelial transcription factors KLF2/4 in vasculature. The regulatory mechanisms of KLF2/4 expression and activity in vascular endothelium in response to hemodynamic forces and biochemical stimuli are depicted. The functional effects mediated by direct or indirect target genes of KLF2/4 in endothelial cells are systematically summarized. The contributory roles that dysregulated KLF2/4 play in relevant cardiovascular pathologies, such as atherosclerotic vascular lesions, pulmonary arterial hypertension and vascular complications of diabetes were reviewed. Moreover, this review also discusses the pharmacological regulation of KLF2/4 by drugs used in clinics and therapeutic possibility by directly targeting these two transcription factors for treating atherosclerotic cardiovascular diseases. Finally, prospective opinions on the gaps in disclosing novel vascular function mediated by KLF2/4 and future research needs are expressed.

Transcriptional signatures of endothelial cells shape immune responses in cardiopulmonary health and disease

The cardiopulmonary vasculature and its associated endothelial cells (ECs) play an essential role in sustaining life by ensuring the delivery of oxygen and nutrients. Beyond these foundational functions, ECs serve as key regulators of immune responses. Recent advances in single-cell RNA sequencing have revealed that the cardiopulmonary vasculature is composed of diverse EC subpopulations, some of which exhibit specialized immunomodulatory properties. Evidence for immunomodulation includes distinct expression profiles associated with antigen presentation, cytokine secretion, immune cell recruitment, translocation, and clearance - functions critical for maintaining homeostasis in the heart and lungs. In cardiopulmonary diseases, ECs undergo substantial transcriptional reprogramming, leading to a shift from homeostasis to an activated state marked by heightened immunomodulatory activity. This transformation has highlighted the critical role for ECs in disease pathogenesis and their potential as future therapy targets. This Review emphasizes the diverse functions of ECs in the heart and lungs, particularly adaptive and maladaptive immunoregulatory roles in cardiopulmonary health and disease.

DNMT3A-dependent DNA methylation shapes the endothelial enhancer landscape

DNA methylation plays a fundamental role in regulating transcription during development and differentiation. However, its functional role in the regulation of endothelial cell (EC) transcription during state transition, meaning the switch from an angiogenic to a quiescent cell state, has not been systematically studied. Here, we report the longitudinal changes of the DNA methylome over the lifetime of the murine pulmonary vasculature. We identified prominent alterations in hyper- and hypomethylation during the transition from angiogenic to quiescent ECs. Once a quiescent state was established, DNA methylation marks remained stable throughout EC aging. These longitudinal differentially methylated regions correlated with endothelial gene expression and highlighted the recruitment of de novo DNA methyltransferase 3a (DNMT3A), evidenced by its motif enrichment at transcriptional start sites of genes with methylation-dependent expression patterns. Loss-of-function studies in mice revealed that the absence of DNMT3A-dependent DNA methylation led to the loss of active enhancers, resulting in mild transcriptional changes, likely due to loss of active enhancer integrity. These results underline the importance of DNA methylation as a key epigenetic mechanism of EC function during state transition. Furthermore, we show that DNMT3A-dependent DNA methylation appears to be involved in establishing the histone landscape required for accurate transcriptome regulation.

Unprocessed BMP9 precursor is an intrinsic antagonist for its active growth factor

BMP9, a member of the TGFβ superfamily, plays a crucial role in angiogenesis, tissue development, and innate immunity. Dysregulation of BMP9 signaling is implicated in various diseases. Unlike latent TGFβs, BMP9 is produced as a precursor that is processed into an active pro-protein complex. However, the regulatory mechanisms governing the precursor's activity and its biological functions have been largely unexplored. In this study, we demonstrate that the unprocessed BMP9 precursor acts as an intrinsic antagonist to its pro-protein in angiogenesis and osteogenesis. This inhibition occurs through competitive binding to the receptors ENG and ALK1. We also identify structural requirements for the precursor's recognition by these receptors. Our findings reveal previously underappreciated functions of the BMP9 precursor and its regulatory mechanisms in growth factor signaling, with significant implications for developmental biology and clinical interventions.

Microvascularization in 3D Human Engineered Tissue and Organoids

The microvasculature, a complex network of small blood vessels, connects systemic circulation with local tissues, facilitating the nutrient and oxygen exchange that is critical for homeostasis and organ function. Engineering these structures is paramount for advancing tissue regeneration, disease modeling, and drug testing. However, replicating the intricate architecture of native vascular systems-characterized by diverse vessel diameters, cellular constituents, and dynamic perfusion capabilities-presents significant challenges. This complexity is compounded by the need to precisely integrate biomechanical, biochemical, and cellular cues. Recent breakthroughs in microfabrication, organoids, bioprinting, organ-on-a-chip platforms, and in vivo vascularization techniques have propelled the field toward faithfully replicating vascular complexity. These innovations not only enhance our understanding of vascular biology but also enable the generation of functional, perfusable tissue constructs. Here, we explore state-of-the-art technologies and strategies in microvascular engineering, emphasizing key advancements and addressing the remaining challenges to developing fully functional vascularized tissues.

Circular RNAs increase during vascular cell differentiation and are biomarkers for vascular disease

AIMS

The role of circular RNAs (circRNAs) and their regulation in health and disease are poorly understood. Here, we systematically investigated the temporally resolved transcriptomic expression of circRNAs during differentiation of human induced pluripotent stem cells (iPSCs) into vascular endothelial cells (ECs) and smooth muscle cells (SMCs) and explored their potential as biomarkers for human vascular disease.

METHODS AND RESULTS

Using high-throughput RNA sequencing and a de novo circRNA detection pipeline, we quantified the daily levels of 31 369 circRNAs in a 2-week differentiation trajectory from human stem cells to proliferating mesoderm progenitors to quiescent, differentiated EC and SMC. We detected a significant global increase in RNA circularization, with 397 and 214 circRNAs up-regulated greater than two-fold (adjusted P < 0.05) in mature EC and SMC, compared with undifferentiated progenitor cells. This global increase in circRNAs was associated with up-regulation of host genes and their promoters and a parallel down-regulation of splicing factors. Underlying this switch, the proliferation-regulating transcription factor MYC decreased as vascular cells matured, and inhibition of MYC led to down-regulation of splicing factors such as SRSF1 and SRSF2 and changes in vascular circRNA levels. Examining the identified circRNAs in arterial tissue samples and in peripheral blood mononuclear cells (PBMCs) from patients, we found that circRNA levels decreased in atherosclerotic disease, in contrast to their increase during iPSC maturation into EC and SMC. Using machine learning, we determined that a set of circRNAs derived from COL4A1, COL4A2, HSPG2, and YPEL2 discriminated atherosclerotic from healthy tissue with an area under the receiver operating characteristic curve (AUC) of 0.79. circRNAs from HSPG2 and YPEL2 in blood PBMC samples detected atherosclerosis with an AUC of 0.73.

CONCLUSION

Time-resolved transcriptional profiling of linear and circRNA species revealed that circRNAs provide granular molecular information for disease profiling. The identified circRNAs may serve as blood biomarkers for atherosclerotic vascular disease.

Optical Tweezer-Driven Mechanotransduction: Probing pN-Scale Forces and Calcium-Mediated Redox Signaling in Single Endothelial Cells

Endothelial cells (ECs) regulate vascular function by converting mechanical forces into biochemical signals; however, the molecular mechanisms of pN-scale mechanotransduction remain elusive. Here, we develop an optical tweezer-integrated confocal microscopy system that allows precise, noninvasive manipulation of the cell membrane localization with mechanical stimuli within the 0-100 pN range while monitoring Ca2+-mediated NO/ROS redox signaling in situ in single ECs under varying force parameters. We show that pN-scale mechanical stimulation regulates extracellular Ca2+ influx, triggering downstream production of NO and ROS, which subsequently affects intracellular redox homeostasis. Key mechanosensitive ion channels (e.g., Piezo1 and TRPV4) and cytoskeletal components (e.g., F-actin) facilitate force-induced redox signaling. We further delineate the roles of membrane tension-dominant versus hybrid tension-tether models in mechanotransduction, revealing their differential engagement in force transmission pathways. This mechanistic framework establishes direct connections between pN-scale mechanical input characteristics and redox-regulated vascular homeostasis.

Signaling scaffold Shoc2 regulates lymphangiogenesis by suppressing mTORC1-mediated IFN responses

An interplay of growth factors and signaling pathways governs the development and maintenance of the lymphatic vasculature, ensuring proper fluid homeostasis and immune function. Disruption of these regulatory mechanisms can lead to congenital lymphatic disorders and contribute to various pathological conditions. However, the mechanisms underlying the molecular regulation of these processes remain elusive. Here we reveal a critical and previously unappreciated role for the signaling scaffold protein Shoc2 in lymphangiogenesis. We demonstrate that loss of Shoc2 leads to nearly a complete loss of lymphatic vasculature in vivo and senescence of lymphatic endothelial cells in vitro. Mechanistically, Shoc2 is required for balancing signaling through the ERK1/2 pathway, and its loss results in increased mTORC1 signaling. This dysregulation impairs mitochondrial respiration and triggers an IRF/IFN-II response, ultimately leading to cellular senescence. Strikingly, expression of the Noonan Syndrome with Loose anagen Hair (NSLH)-causing Shoc2 variant S2G phenocopies the effects of Shoc2 loss. Together, these studies establish the critical role of Shoc2 in lymphangiogenesis and uncover a novel mechanistic link between Shoc2 signaling, mitochondrial function, innate immune response, and lymphatic development, with significant implications for Ras-pathway-related congenital disorders.

Angiogenesis: Biological Mechanisms and In Vitro Models

The translation of biomedical devices and drug research is an expensive and long process with a low probability of receiving FDA approval. Developing physiologically relevant in vitro models with human cells offers a solution to not only improving the odds of FDA approval but also to expand our ability to study complex in vivo systems in a simpler fashion. Animal models remain the standard for pre-clinical testing; however, the data from animal models is an unreliable extrapolation when anticipating a human response in clinical trials, thus contributing to the low rates of translation. In this review, we focus on in vitro vascular or angiogenic models because of the incremental role that the vascular system plays in the translation of biomedical research. The first section of this review discusses the most common angiogenic cytokines that are used in vitro to initiate angiogenesis, followed by angiogenic inhibitors where both initiators and inhibitors work to maintain vascular homeostasis. Next, we evaluate previously published in vitro models, where we evaluate capturing the physical environment for biomimetic in vitro modeling. These topics provide a foundation of parameters that must be considered to improve and achieve vascular biomimicry. Finally, we summarize these topics to suggest a path forward with the goal of engineering human in vitro models that emulate the in vivo environment and provide a platform for biomedical device and drug screening that produces data to support clinical translation.

Heterogeneity of Renal Endothelial Cells, Interact with Neighboring Cells, and Endothelial Injury in Chronic Kidney Disease: Mechanisms and Therapeutic Implications

Chronic kidney disease (CKD) is closely associated with endothelial dysfunction, leading to symptoms such as albuminuria, edema, and coagulopathy. Recent advancements in single-cell sequencing have deepened our understanding of the heterogeneity of renal endothelial cells, which is significantly influenced by their microenvironment. Understanding the influence of neighboring cells on endothelial heterogeneity is essential for elucidating the mechanisms underlying vascular dysfunction and CKD progression. This review explores the latest research on renal endothelial cell heterogeneity and their interactions with neighboring cells. We further discuss the mechanisms of endothelial injury in CKD, including alterations to the endothelial glycocalyx, inflammation, oxidative stress, and dysfunction of the glomerular filtration barrier. Renal endothelial injury contributes to complications, including cardiovascular disease, diabetic nephropathy, and impaired vascular function. Therapeutic strategies encompass antihypertensive, hypoglycemic, and lipid-lowering treatments, supplemented by emerging approaches such as anti-inflammatory therapies, gene therapy, and lifestyle modifications. Through reviewing the relationship between endothelial injury and CKD progression, we emphasize potential strategies to enhance prognosis and mitigate disease progression.

Inducing mononuclear cells of patients with CADASIL to construct a CSVD disease model

OBJECTIVE

To produce pluripotent stem cells from peripheral blood mononuclear cells (PBMCs) of a patient with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and culture and differentiate them into vascular organoids, producing a disease model for cerebral small vessel disease (CSVD).

METHODS

(1) PMBCs from patients clinically diagnosed with CADASIL (NOTCH3 p.R141C) were induced to differentiate into pluripotent stem cells (iPSCs); the quality and differentiation ability of the iPSCs were determined. (2) CADASIL-derived iPSCs and control iPSCs were cultured and differentiated into vascular organoids. The differences in the morphological structure of the two differentiated groups of vascular organoids were observed, and both were identified.

RESULTS

(1) No mycoplasma infections were detected in the iPSCs prepared from the PBMCs of patients with CADASIL. The short tandem repeat (STR) identification verified that the iPSCs originated from the patient, and the karyotype was normal. Flow cytometry and immunofluorescence detection revealed that the iPSCs expressed SSEA4, OCT4, and NANOG stem proteins. Tri-germ differentiation testing confirmed that the iPSCs expressed the endoderm markers SOX17 and FOXA2, the mesoderm markers Brachyury and α-SMA, and the ectoderm markers Pax6 and β-III Tubulin. (2) CADASIL-derived iPSCs and control iPSCs were induced to differentiate and produce endothelial networks and vascular networks, ultimately forming vascular organoids. Compared with control vascular organoids, CADASIL vascular organoids exhibited lower growth density, earlier blood vessel sprouting, longer and thinner vascular filaments, and smaller final vascular organoids. The vascular organoids from the two sources expressed the endothelial cell marker CD31, the vascular smooth muscle marker α-SMA, and the pericyte marker PDGFR-β.

CONCLUSION

Reprogramming technology can be used to induce PBMCs to become iPSCs, and a CSVD disease model can be successfully constructed by culturing and differentiating the iPSCs into CADASIL vascular organoids. The NOTCH3 p.R141C mutation suppresses the vascular differentiation process in CADASIL.

Metabolic reprogramming and interventions in angiogenesis

BACKGROUND

Endothelial cell (EC) metabolism plays a crucial role in the process of angiogenesis. Intrinsic metabolic events such as glycolysis, fatty acid oxidation, and glutamine metabolism, support secure vascular migration and proliferation, energy and biomass production, as well as redox homeostasis maintenance during vessel formation. Nevertheless, perturbation of EC metabolism instigates vascular dysregulation-associated diseases, especially cancer.

AIM OF REVIEW

In this review, we aim to discuss the metabolic regulation of angiogenesis by EC metabolites and metabolic enzymes, as well as prospect the possible therapeutic opportunities and strategies targeting EC metabolism.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we discuss various aspects of EC metabolism considering normal and diseased vasculature. Of relevance, we highlight that the implications of EC metabolism-targeted intervention (chiefly by metabolic enzymes or metabolites) could be harnessed in orchestrating a spectrum of pathological angiogenesis-associated diseases.

Glutamine synthetase accelerates re-endothelialization of vascular grafts by mitigating endothelial cell dysfunction in a rat model

Endothelial cell (EC) dysfunction within the aorta has long been recognized as a prominent contributor to the progression of atherosclerosis and the subsequent failure of vascular graft transplantation. However, the direct relationship between EC dysfunction and vascular remodeling remains to be investigated. In this study, we sought to address this knowledge gap by employing a strategy involving the release of glutamine synthetase (GS), which effectively activated endothelial metabolism and mitigates EC dysfunction. To achieve this, we developed GS-loaded small-diameter vascular grafts (GSVG) through the electrospinning technique, utilizing dual-component solutions consisting of photo-crosslinkable hyaluronic acid and polycaprolactone. Through an in vitro model of oxidized low-density lipoprotein-induced injury in human umbilical vein endothelial cells (HUVECs), we provided compelling evidence that the GSVG promoted the restoration of motility, angiogenic sprouting, and proliferation in dysfunctional HUVECs by enhancing cellular metabolism. Furthermore, the sequencing results indicated that these effects were mediated by miR-122-5p-related signaling pathways. Remarkably, the GSVG also exhibited regulatory capabilities in shifting vascular smooth muscle cells towards a contractile phenotype, mitigating inflammatory responses and thereby preventing vascular calcification. Finally, our data demonstrated that GS incorporation significantly enhanced re-endothelialization of vascular grafts in a ferric chloride-injured rat model. Collectively, our results offer insights into the promotion of re-endothelialization in vascular grafts by restoring dysfunctional ECs through the augmentation of cellular metabolism.

Extracellular vesicles in atherosclerosis: Current and forthcoming impact

Atherosclerosis is the main pathogenic substrate for cardiovascular diseases (CVDs). Initially categorized as a passive cholesterol storage disease, nowadays, it is considered an active process, identifying inflammation among the key players for its initiation and progression. Despite these advances, patients with CVDs are still at high risk of thrombotic events and death, urging to deepen into the molecular mechanisms underlying atherogenesis, and to identify novel diagnosis and prognosis biomarkers for their stratification. In this context, extracellular vesicles (EVs) have been postulated as an alternative in search of novel biomarkers in atherosclerotic diseases, as well as to investigate the crosstalk between the cells participating in the processes leading to arterial remodelling. EVs are nanosized lipidic particles released by most cell types in physiological and pathological conditions, that enclose lipids, proteins, and nucleic acids from parental cells reflecting their activation status. First considered cellular waste disposal systems, at present, EVs have been recognized as active effectors in a myriad of cellular processes, and as potential diagnosis and prognosis biomarkers also in CVDs. This review summarizes the role of EVs as potential biomarkers of CVDs, and their involvement into the processes leading to atherosclerosis.

Vascular endothelial growth factor A: friend or foe in the pathogenesis of HIV and SARS-CoV-2 infections?

This review article discusses the role of vascular endothelial growth factor A (VEGF-A) in the pathogenesis of SARS-CoV-2 and HIV infection, both conditions being renowned for their impact on the vascular endothelium. The processes involved in vascular homeostasis and angiogenesis are reviewed briefly before exploring the interplay between hypoxia, VEGF-A, neuropilin-1 (NRP-1), and inflammatory pathways. We then focus on SARS-CoV-2 infection and show how the binding of the viral pathogen to the angiotensin-converting enzyme 2 receptor, as well as to NRP-1, leads to elevated levels of VEGF-A and consequences such as coagulation, vascular dysfunction, and inflammation. HIV infection augments angiogenesis via several mechanisms, most prominently, by the trans-activator of transcription (tat) protein mimicking VEGF-A by binding to its receptor, VEGFR-2, as well as upregulation of NRP-1, which enhances the interaction between VEGF-A and VEGFR-2. We propose that the elevated levels of VEGF-A observed during HIV/SARS-CoV-2 co-infection originate predominantly from activated immune cells due to the upregulation of HIF-1α by damaged endothelial cells. In this context, a few clinical trials have described a diminished requirement for oxygen therapy during anti-VEGF treatment of SARS-CoV-2 infection. The currently available anti-VEGF therapy strategies target the binding of VEGF-A to both VEGFR-1 and VEGFR-2. The blocking of both receptors could, however, lead to a negative outcome, inhibiting not only pathological, but also physiological angiogenesis. Based on the examination of published studies, this review suggests that treatment targeting selective inhibition of VEGFR-1 may be beneficial in the context of SARS-CoV-2 infection.

Plasma from hypertensive pregnancy patients induce endothelial dysfunction even under atheroprotective shear stress

Preeclampsia (PE) is a challenge in maternal healthcare due to its complex nature, characterized by high blood pressure, protein in the urine, and damage to various organs. There is evidence linking PE to endothelial dysfunction (ED), triggered by substances released from an oxygen-deprived placenta. Previous in vitro studies have not considered the impact of in vivo elements, such as the different patterns of blood flow, and laminar (LSS) vs. oscillatory (OSS) shear stress, on the development of ED. We investigated the impact of plasma from healthy pregnant women (HP), subjects with gestational hypertension (GH), and PE patients on global gene expression of human coronary endothelial cells (HCAECs) under LSS and OSS. Our findings revealed a unique transcriptional profile of endothelial cells induced by plasma incubation in LSS. Notably, OSS resulted in similar transcriptomes irrespective of plasma treatment. Under LSS, GH plasma resulted in a proliferative profile, whereas PE plasma was linked to pro-inflammatory and antioxidant profiles compared to HP plasma. Our findings demonstrate that shear stress levels influence the endothelial cell transcriptome in response to plasma from hypertensive pregnancy patients. Both PE and GH can induce endothelial dysfunction under atheroprotective LSS, with a more significant effect observed with PE-derived plasma.

From bench to bedside: murine models of inherited and sporadic brain arteriovenous malformations

Brain arteriovenous malformations are abnormal vascular structures in which an artery shunts high pressure blood directly to a vein without an intervening capillary bed. These lesions become highly remodeled over time and are prone to rupture. Historically, brain arteriovenous malformations have been challenging to treat, using primarily surgical approaches. Over the past few decades, the genetic causes of these malformations have been uncovered. These can be divided into (1) familial forms, such as loss of function mutations in TGF-β (BMP9/10) components in hereditary hemorrhagic telangiectasia, or (2) sporadic forms, resulting from somatic gain of function mutations in genes involved in the RAS-MAPK signaling pathway. Leveraging these genetic discoveries, preclinical mouse models have been developed to uncover the mechanisms underlying abnormal vessel formation, and thus revealing potential therapeutic targets. Impressively, initial preclinical studies suggest that pharmacological treatments disrupting these aberrant pathways may ameliorate the abnormal pathologic vessel remodeling and inflammatory and hemorrhagic nature of these high-flow vascular anomalies. Intriguingly, these studies also suggest uncontrolled angiogenic signaling may be a major driver in bAVM pathogenesis. This comprehensive review describes the genetics underlying both inherited and sporadic bAVM and details the state of the field regarding murine models of bAVM, highlighting emerging therapeutic targets that may transform our approach to treating these devastating lesions.

The Role of Aryl Hydrocarbon Receptor in Skin Homeostasis: Implications for Therapeutic Strategies in Skin Disorders

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, is extensively expressed in diverse human organs and plays a pivotal role in mediating the onset, progression, and severity of numerous diseases. Recent research has explored the substantial impact of AhR on skin homeostasis and related pathologies. As a multi-layered organ, the skin comprises multiple cell populations that express AhR. In this review, we introduce the role of AhR in various skin cells and its impact on skin barrier function. Furthermore, we explore the involvement of AhR in the development of various skin diseases, highlighting its potential as a therapeutic target for skin disorders. By targeting AhR, we may open new avenues for the development of novel and efficient skin disease treatments.

Transient receptor potential melastatin 7 cation channel, magnesium and cell metabolism in vascular health and disease

Preserving the balance of metabolic processes in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), is crucial for optimal vascular function and integrity. ECs are metabolically active and depend on aerobic glycolysis to efficiently produce energy for their essential functions, which include regulating vascular tone. Impaired EC metabolism is linked to endothelial damage, increased permeability and inflammation. Metabolic alterations in VSMCs also contribute to vascular dysfunction in atherosclerosis and hypertension. Magnesium (Mg2+) is the second most abundant intracellular divalent cation and influences molecular processes that regulate vascular function, including vasodilation, vasoconstriction, and release of vasoactive substances. Mg2+ is critically involved in maintaining cellular homeostasis and metabolism since it is an essential cofactor for ATP, nucleic acids and hundreds of enzymes involved in metabolic processes. Low Mg2+ levels have been linked to endothelial dysfunction, increased vascular tone, vascular inflammation and arterial remodeling. Growing evidence indicates an important role for the transient receptor potential melastatin-subfamily member 7 (TRPM7) cation channel in the regulation of Mg2+ homeostasis in EC and VSMCs. In the vasculature, TRPM7 deficiency leads to impaired endothelial function, increased vascular contraction, phenotypic switching of VSMCs, inflammation and fibrosis, processes that characterize the vascular phenotype in hypertension. Here we provide a comprehensive overview on TRPM7/Mg2+ in the regulation of vascular function and how it influences EC and VSMC metabolism such as glucose and energy homeostasis, redox regulation, phosphoinositide signaling, and mineral metabolism. The putative role of TRPM7/Mg2+ and altered cellular metabolism in vascular dysfunction and hypertension is also discussed.

Microvascular endothelial cells display organ-specific responses to extracellular matrix stiffness

The extracellular matrix was originally thought of as simply a cellular scaffold but is now considered a key regulator of cell function and phenotype from which cells can derive biochemical and mechanical stimuli. Age-associated changes in matrix composition drive increases in matrix stiffness. Enhanced matrix stiffness promotes the progression of numerous diseases including cardiovascular disease, musculoskeletal disease, fibrosis, and cancer. Macrovascular endothelial cells undergo endothelial dysfunction in response to enhanced matrix stiffness. However, endothelial cells are highly heterogeneous, adopting structural and gene expression profiles specific to their organ of origin. Endothelial cells isolated from different vessels (i.e. arteries, veins or capillaries) respond differently to changes in substrate stiffness. It is unknown whether microvascular endothelial cells isolated from different organs also display organ-specific responses to substrate stiffness. In this study, we compare the response of microvascular endothelial cells isolated from both the mouse lung and mammary gland to a range of physiologically relevant substrate stiffnesses. We find that endothelial origin influences microvascular endothelial cell response to substrate stiffness in terms of both proliferation and migration speed. In lung-derived endothelial cells, proliferation is bimodal, where both physiologically soft and stiff substrates drive enhanced proliferation. Conversely, in mammary gland-derived endothelial cells, proliferation increases as substrate stiffness increases. Substrate stiffness also promotes enhanced endothelial migration. Enhanced stiffness drove greater increases in migration speed in mammary gland-derived than lung-derived endothelial cells. However, stiffness-induced changes in microvascular endothelial cell morphology were consistent between both cell lines, with substrate stiffness driving an increase in endothelial volume. Our research demonstrates the importance of considering endothelial origin in experimental design, especially when investigating how age-associated changes in matrix stiffness drive endothelial dysfunction and disease progression.

Transcription factor networks in cellular quiescence

Many of the cells in mammalian tissues are in a reversible quiescent state; they are not dividing, but retain the ability to proliferate in response to extracellular signals. Quiescence relies on the activities of transcription factors (TFs) that orchestrate the repression of genes that promote proliferation and establish a quiescence-specific gene expression program. Here we discuss how the coordinated activities of TFs in different quiescent stem cells and differentiated cells maintain reversible cell cycle arrest and establish cell-protective signalling pathways. We further cover the emerging mechanisms governing the dysregulation of quiescence TF networks with age. We explore how recent developments in single-cell technologies have enhanced our understanding of quiescence heterogeneity and gene regulatory networks. We further discuss how TFs and their activities are themselves regulated at the RNA, protein and chromatin levels. Finally, we summarize the challenges associated with defining TF networks in quiescent cells.

Evolucollateral dynamics in stroke: Evolutionary pathophysiology, remodelling and emerging therapeutic strategies

Leptomeningeal collaterals (LMCs) are crucial in mitigating the impact of acute ischemic stroke (AIS) by providing alternate blood flow routes when primary arteries are obstructed. This article explores the evolutionary pathophysiology of LMCs, highlighting their critical function in stroke and the genetic and molecular mechanisms governing their development and remodelling. We address the translational challenges of applying animal model findings to human clinical scenarios, emphasizing the need for further research to validate emerging therapies-such as pharmacological agents, gene therapy and mechanical interventions-in clinical settings, aimed at enhancing collateral perfusion. Computational modelling emerges as a promising method for integrating experimental data, which requires precise parameterization and empirical validation. We introduce the 'Evolucollateral Dynamics' hypothesis, proposing a novel framework that incorporates evolutionary biology principles into therapeutic strategies, offering new perspectives on enhancing collateral circulation. This hypothesis emphasizes the role of genetic predispositions and environmental influences on collateral circulation, which may impact therapeutic strategies and optimize treatment outcomes. Future research must incorporate human clinical data to create robust treatment protocols, thereby maximizing the therapeutic potential of LMCs and improving outcomes for stroke patients.

Effects of Rhaponticum carthamoides (Willd.) Iljin on endothelial dysfunction and the inflammatory response in type 2 diabetes mellitus mice

BACKGROUND

Diabetes mellitus (DM) and its complications seriously threaten human life and health. Rhaponticum carthamoides (Willd.) Iljin (RC) is widely used to treat cardiovascular diseases. Previous studies reported that RC reduces blood glucose levels in rats with type 1 DM. However, the effects of RC on type 2 diabetes and vascular complications, as well as its related active components and underlying mechanisms, remain unclear.

PURPOSE

This study aimed to investigate the effects of RC on endothelial dysfunction and the inflammatory response in type 2 DM mice and to explore its underlying mechanism and active ingredients.

STUDY DESIGN/METHODS

Male C57BL/6J mice were used to establish a type 2 DM mouse model. After 12 weeks of oral administration of RC extract (60, 120, and 240 mg/kg) to mice, blood glucose and lipid levels were assessed. The morphological structures of the liver and kidney tissues were observed using hematoxylin and eosin (HE) staining, and their functions were evaluated by detecting relevant biochemical indicators in the serum. Then, aorta morphology was observed via HE staining. In addition, serum levels of markers of endothelial function and inflammatory factors were detected, and the expression of inflammatory factors and the phosphorylation levels of key proteins in the aorta were examined. Furthermore, prediction and enrichment analyses of potential targets of RC acting on diabetic vascular lesions were performed on the basis of pharmacophore matching using various databases. Then, the expression, localization and phosphorylation levels of potential targets in the aortas of DM mice treated with RC were assessed using Western blotting, immunofluorescence, and RT‒PCR. Finally, the active components of RC were identified through virtual screening, and their ability to improve endothelial cell dysfunction was verified.

RESULTS

RC reduced blood glucose levels and serum lipid levels of total triglyceride (TG), total cholesterol (TC), and low density lipoprotein cholesterol (LDL-c), increased high density lipoprotein cholesterol (HDL-c) levels, and improved liver and kidney function in type 2 DM mice. RC decreased endothelial cell shedding in the aortas of type 2 DM mice, increased serum nitric oxide (NO) and nitric oxide synthase (NOS) levels, and reduced soluble cluster of differentiation 40 ligand (sCD40L), tumor necrosis factor α (TNF-α), and interleukin-1β (IL-1β) levels. Further findings indicated that RC reduced the expression of aortic inflammatory factors, namely, CD40, CD40L, IL-1β, and interleukin-6 (IL-6), and increased endothelial NOS (eNOS) phosphorylation levels. Sirtuin 6 (SIRT6), protein kinase B (AKT), and eNOS were predicted to be key node targets of RC acting on DM vascular lesions, and it was confirmed that RC increased SIRT6 expression and AKT phosphorylation levels in aortic endothelial cells. 20-Hydroxyecdysone (20E), daucosterol (Dau), euscaphic acid (Eus), and syringin (Syr) were identified as active components of RC. These components protect against TNF-α-induced human umbilical vein endothelial cell (HUVEC) damage and decrease the release of lactate dehydrogenase (LDH) and IL-1β and increased the release of NO in TNF-α-induced HUVECs in a dose-dependent manner.

CONCLUSION

RC reduced blood glucose and lipid levels in mice with type 2 DM and protected liver and kidney function. RC promotes SIRT6 expression in endothelial cells; upregulates the NO/NOS system by increasing AKT/eNOS phosphorylation levels to regulate vascular tone factors; and reduces the levels of inflammatory factors such as CD40, TNF-α, and IL-1β to inhibit endothelial inflammatory responses. Based on these mechanisms, RC improves endothelial dysfunction.

Molecular Pathophysiology of Chronic Thromboembolic Pulmonary Hypertension: A Clinical Update from a Basic Research Perspective

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare but severe condition characterized by persistent obstruction and vascular remodeling in the pulmonary arteries following an acute pulmonary embolism (APE). Although APE is a significant risk factor, up to 25% of CTEPH cases occur without a history of APE or deep vein thrombosis, complicating the understanding of its pathogenesis. Herein, we carried out a narrative review discussing the mechanisms involved in CTEPH development, including fibrotic thrombus formation, pulmonary vascular remodeling, and abnormal angiogenesis, leading to elevated pulmonary vascular resistance and right heart failure. We also outlined how the disease's pathophysiology reveals both proximal and distal pulmonary artery obstruction, contributing to the development of pulmonary hypertension. We depicted the risk factors predicting CTEPH, including thrombotic history, hemostatic disorders, and certain medical conditions. We finally looked at the molecular mechanisms behind the role of endothelial dysfunction, gene expression alterations, and inflammatory processes in CTEPH progression and detection. Despite these insights, there is still a need for improved diagnostic tools, biomarkers, and therapeutic strategies to enhance early detection and management of CTEPH, ultimately aiming to reduce diagnostic delay and improve patient outcomes.

The Formation of Human Arteriovenous Malformation Organoids and Their Characteristics

Arteriovenous malformations (AVMs) are characterized by direct connections between arteries and veins without intervening capillaries, with the concomitant formation of abnormal vascular networks associated with angiogenesis. However, the current understanding of the diagnosis and treatment of AVMs is limited, and no in vitro disease models exist at present for studying this condition. In this study, we produced endothelial cells (ECs) in two-dimensional cultures and three-dimensional (3D) blood vessel organoids (BVOs), comparing gene expression profiles between normal and AVM organoids. The normal and AVM organoids were examined via immunofluorescence staining using CD31 and phalloidin. The AVM organoids showed significantly higher expression levels of CD31 and phalloidin than the normal organoids. Genes such as FSTL1, associated with angiogenesis, showed significantly higher expression in the AVM organoids than in the normal organoids. In contrast, the MARCKS gene exhibited no significant difference in expression between the two types of organoids. The capillaries and related CSPG4 genes exhibited the lowest expression in the 3D AVM organoids. Furthermore, hsa-mir-135b-5p, a small RNA related to AVMs, showed elevated expression in AVM tissues and significantly higher levels in 3D AVM organoids. In our study, we were able to successfully establish AVM organoids (hBVOs) containing ECs and mural cells through advancements in stem cell and tissue engineering. These organoids serve as valuable models for investigating disease mechanisms, drug development, and screening potential therapeutic interventions in drug discovery. These findings contribute essential insights for the development of treatment strategies targeting AVMs.

CDK6-mediated endothelial cell cycle acceleration drives arteriovenous malformations in hereditary hemorrhagic telangiectasia

Increased endothelial cell proliferation is a hallmark of arteriovenous malformations (AVMs) in hereditary hemorrhagic telangiectasia (HHT). Here, we report a cyclin-dependent kinase 6 (CDK6)-driven mechanism of cell cycle deregulation involved in endothelial cell proliferation and HHT pathology. Specifically, endothelial cells from the livers of HHT mice bypassed the G1/S checkpoint and progressed through the cell cycle at an accelerated pace. Phosphorylated retinoblastoma (pRB1)-a marker of G1/S transition through the restriction point-accumulated in endothelial cells from retinal AVMs of HHT mice and endothelial cells from skin telangiectasia samples from HHT patients. Mechanistically, inhibition of activin receptor-like kinase 1 signaling increased key restriction point mediators, and treatment with the CDK4/6 inhibitors palbociclib or ribociclib blocked increases in pRB1 and retinal AVMs in HHT mice. Palbociclib also improved vascular pathology in the brain and liver, and slowed cell cycle progression in endothelial cells and endothelial cell proliferation. Endothelial cell-specific deletion of CDK6 was sufficient to protect HHT mice from AVM pathology. Thus, clinically approved CDK4/6 inhibitors might have the potential to be repurposed for HHT.

Innovative Substrate Design with Basement Membrane Components for Enhanced Endothelial Cell Function and Endothelization

Enhancing endothelial cell growth on small-diameter vascular grafts produced from decellularized tissues or synthetic substrates is pivotal for preventing thrombosis. While optimized decellularization protocols can preserve the structure and many components of the extracellular matrix (ECM), the process can still lead to the loss of crucial basement membrane proteins, such as laminin, collagen IV, and perlecan, which are pivotal for endothelial cell adherence and functional growth. This loss can result in poor endothelialization and endothelial cell activation causing thrombosis and intimal hyperplasia. To address this, the basement membrane's ECM is emulated on fiber substrates, providing a more physiological environment for endothelial cells. Thus, fibroblasts are cultured on fiber substrates to produce an ECM membrane substrate (EMMS) with basement membrane proteins. The EMMS then underwent antigen removal (AR) treatment to eliminate antigens from the membrane while preserving essential proteins and producing an AR-treated membrane substrate (AMS). Subsequently, human endothelial cells cultured on the AMS exhibited superior proliferation, nitric oxide production, and increased expression of endothelial markers of quiescence/homeostasis, along with autophagy and antithrombotic factors, compared to those on the decellularized aortic tissue. This strategy showed the potential of pre-endowing fiber substrates with a basement membrane to enable better endothelization.

The Cerebrovascular Side of Plasticity: Microvascular Architecture across Health and Neurodegenerative and Vascular Diseases

The delivery of nutrients to the brain is provided by a 600 km network of capillaries and microvessels. Indeed, the brain is highly energy demanding and, among a total amount of 100 billion neurons, each neuron is located just 10-20 μm from a capillary. This vascular network also forms part of the blood-brain barrier (BBB), which maintains the brain's stable environment by regulating chemical balance, immune cell transport, and blocking toxins. Typically, brain microvascular endothelial cells (BMECs) have low turnover, indicating a stable cerebrovascular structure. However, this structure can adapt significantly due to development, aging, injury, or disease. Temporary neural activity changes are managed by the expansion or contraction of arterioles and capillaries. Hypoxia leads to significant remodeling of the cerebrovascular architecture and pathological changes have been documented in aging and in vascular and neurodegenerative conditions. These changes often involve BMEC proliferation and the remodeling of capillary segments, often linked with local neuronal changes and cognitive function. Cerebrovascular plasticity, especially in arterioles, capillaries, and venules, varies over different time scales in development, health, aging, and diseases. Rapid changes in cerebral blood flow (CBF) occur within seconds due to increased neural activity. Prolonged changes in vascular structure, influenced by consistent environmental factors, take weeks. Development and aging bring changes over months to years, with aging-associated plasticity often improved by exercise. Injuries cause rapid damage but can be repaired over weeks to months, while neurodegenerative diseases cause slow, varied changes over months to years. In addition, if animal models may provide useful and dynamic in vivo information about vascular plasticity, humans are more complex to investigate and the hypothesis of glymphatic system together with Magnetic Resonance Imaging (MRI) techniques could provide useful clues in the future.

Dissecting the impact of differentiation stage, replicative history, and cell type composition on epigenetic clocks

Epigenetic clocks, built on DNA methylation patterns of bulk tissues, are powerful age predictors, but their biological basis remains incompletely understood. Here, we conducted a comparative analysis of epigenetic age in murine muscle, epithelial, and blood cell types across lifespan. Strikingly, our results show that cellular subpopulations within these tissues, including adult stem and progenitor cells as well as their differentiated progeny, exhibit different epigenetic ages. Accordingly, we experimentally demonstrate that clocks can be skewed by age-associated changes in tissue composition. Mechanistically, we provide evidence that the observed variation in epigenetic age among adult stem cells correlates with their proliferative state, and, fittingly, forced proliferation of stem cells leads to increases in epigenetic age. Collectively, our analyses elucidate the impact of cell type composition, differentiation state, and replicative potential on epigenetic age, which has implications for the interpretation of existing clocks and should inform the development of more sensitive clocks.

LncRNAs Are Key Regulators of Transcription Factor-Mediated Endothelial Stress Responses

The functional role of long noncoding RNAs in the endothelium is highly diverse. Among their many functions, regulation of transcription factor activity and abundance is one of the most relevant. This review summarizes the recent progress in the research on the lncRNA-transcription factor axes and their implications for the vascular endothelium under physiological and pathological conditions. The focus is on transcription factors critical for the endothelial response to external stressors, such as hypoxia, inflammation, and shear stress, and their lncRNA interactors. These regulatory interactions will be exemplified by a selected number of lncRNAs that have been identified in the endothelium under physiological and pathological conditions that are influencing the activity or protein stability of important transcription factors. Thus, lncRNAs can add a layer of cell type-specific function to transcription factors. Understanding the interaction of lncRNAs with transcription factors will contribute to elucidating cardiovascular disease pathologies and the development of novel therapeutic approaches.

A systems view of the vascular endothelium in health and disease

The dysfunction of blood-vessel-lining endothelial cells is a major cause of mortality. Although endothelial cells, being present in all organs as a single-cell layer, are often conceived as a rather inert cell population, the vascular endothelium as a whole should be considered a highly dynamic and interactive systemically disseminated organ. We present here a holistic view of the field of vascular research and review the diverse functions of blood-vessel-lining endothelial cells during the life cycle of the vasculature, namely responsive and relaying functions of the vascular endothelium and the responsive roles as instructive gatekeepers of organ function. Emerging translational perspectives in regenerative medicine, preventive medicine, and aging research are developed. Collectively, this review is aimed at promoting disciplinary coherence in the field of angioscience for a broader appreciation of the importance of the vasculature for organ function, systemic health, and healthy aging.

Immunometabolism in atherosclerosis: a new understanding of an old disease

Atherosclerosis, a chronic inflammatory condition, remains a leading cause of death globally, necessitating innovative approaches to target pro-atherogenic pathways. Recent advancements in the field of immunometabolism have highlighted the crucial interplay between metabolic pathways and immune cell function in atherogenic milieus. Macrophages and T cells undergo dynamic metabolic reprogramming to meet the demands of activation and differentiation, influencing plaque progression. Furthermore, metabolic intermediates intricately regulate immune cell responses and atherosclerosis development. Understanding the metabolic control of immune responses in atherosclerosis, known as athero-immunometabolism, offers new avenues for preventive and therapeutic interventions. This review elucidates the emerging intricate interplay between metabolism and immunity in atherosclerosis, underscoring the significance of metabolic enzymes and metabolites as key regulators of disease pathogenesis and therapeutic targets.

Disrupted BMP-9 Signaling Impairs Pulmonary Vascular Integrity in Hepatopulmonary Syndrome

Rationale: Hepatopulmonary syndrome (HPS) is a severe complication of liver diseases characterized by abnormal dilation of pulmonary vessels, resulting in impaired oxygenation. Recent research highlights the pivotal role of liver-produced BMP-9 (bone morphogenetic protein-9) in maintaining pulmonary vascular integrity. Objectives: This study aimed to investigate the involvement of BMP-9 in human and experimental HPS. Methods: Circulating BMP-9 levels were measured in 63 healthy control subjects and 203 patients with cirrhosis with or without HPS. Two animal models of portal hypertension were employed: common bile duct ligation with cirrhosis and long-term partial portal vein ligation without cirrhosis. Additionally, the therapeutic effect of low-dose BMP activator FK506 was investigated, and the pulmonary vascular phenotype of BMP-9-knockout rats was analyzed. Measurements and Main Results: Patients with HPS related to compensated cirrhosis exhibited lower levels of circulating BMP-9 compared with patients without HPS. Patients with severe cirrhosis exhibited consistently low levels of BMP-9. HPS characteristics were observed in animal models, including intrapulmonary vascular dilations and an increase in the alveolar-arterial gradient. HPS development in both rat models correlated with reduced intrahepatic BMP-9 expression, decreased circulating BMP-9 level and activity, and impaired pulmonary BMP-9 endothelial pathway. Daily treatment with FK506 for 2 weeks restored the BMP pathway in the lungs, alleviating intrapulmonary vascular dilations and improving gas exchange impairment. Furthermore, BMP-9-knockout rats displayed a pulmonary HPS phenotype, supporting its role in disease progression. Conclusions: The study findings suggest that portal hypertension-induced loss of BMP-9 signaling contributes to HPS development.

Endothelial-mesenchymal transition in skeletal muscle: Opportunities and challenges from 3D microphysiological systems

Fibrosis is a pathological condition that in the muscular context is linked to primary diseases such as dystrophies, laminopathies, neuromuscular disorders, and volumetric muscle loss following traumas, accidents, and surgeries. Although some basic mechanisms regarding the role of myofibroblasts in the progression of muscle fibrosis have been discovered, our knowledge of the complex cell-cell, and cell-matrix interactions occurring in the fibrotic microenvironment is still rudimentary. Recently, vascular dysfunction has been emerging as a key hallmark of fibrosis through a process called endothelial-mesenchymal transition (EndoMT). Nevertheless, no effective therapeutic options are currently available for the treatment of muscle fibrosis. This lack is partially due to the absence of advanced in vitro models that can recapitulate the 3D architecture and functionality of a vascularized muscle microenvironment in a human context. These models could be employed for the identification of novel targets and for the screening of potential drugs blocking the progression of the disease. In this review, we explore the potential of 3D human muscle models in studying the role of endothelial cells and EndoMT in muscle fibrotic tissues and identify limitations and opportunities for optimizing the next generation of these microphysiological systems. Starting from the biology of muscle fibrosis and EndoMT, we highlight the synergistic links between different cell populations of the fibrotic microenvironment and how to recapitulate them through microphysiological systems.

Hydrostatic pressure drives sprouting angiogenesis via adherens junction remodelling and YAP signalling

Endothelial cell physiology is governed by its unique microenvironment at the interface between blood and tissue. A major contributor to the endothelial biophysical environment is blood hydrostatic pressure, which in mechanical terms applies isotropic compressive stress on the cells. While other mechanical factors, such as shear stress and circumferential stretch, have been extensively studied, little is known about the role of hydrostatic pressure in the regulation of endothelial cell behavior. Here we show that hydrostatic pressure triggers partial and transient endothelial-to-mesenchymal transition in endothelial monolayers of different vascular beds. Values mimicking microvascular pressure environments promote proliferative and migratory behavior and impair barrier properties that are characteristic of a mesenchymal transition, resulting in increased sprouting angiogenesis in 3D organotypic model systems ex vivo and in vitro. Mechanistically, this response is linked to differential cadherin expression at the adherens junctions, and to an increased YAP expression, nuclear localization, and transcriptional activity. Inhibition of YAP transcriptional activity prevents pressure-induced sprouting angiogenesis. Together, this work establishes hydrostatic pressure as a key modulator of endothelial homeostasis and as a crucial component of the endothelial mechanical niche.

Endothelial cell diversity: the many facets of the crystal

Endothelial cells (ECs) form the inner lining of blood vessels and play crucial roles in angiogenesis. While it has been known for a long time that there are considerable differences among ECs from lymphatic and blood vessels, as well as among arteries, veins and capillaries, the full repertoire of endothelial diversity is only beginning to be elucidated. It has become apparent that the role of ECs is not just limited to their exchange functions. Indeed, a multitude of organ-specific functions, including release of growth factors, regulation of immune functions, have been linked to ECs. Recent years have seen a surge into the identification of spatiotemporal molecular and functional heterogeneity of ECs, supported by technologies such as single-cell RNA sequencing (scRNA-seq), lineage tracing and intersectional genetics. Together, these techniques have spurred the generation of epigenomic, transcriptomic and proteomic signatures of ECs. It is now clear that ECs across organs and in different vascular beds, but even within the same vessel, have unique molecular identities and employ specialized molecular mechanisms to fulfil highly specialized needs. Here, we focus on the molecular heterogeneity of the endothelium in different organs and pathological conditions.

Vitexin Suppresses High-Glucose-upregulated Adhesion Molecule Expression in Endothelial Cells through Inhibiting NF-κB Signaling Pathway

Vascular damage is one of the significant complications of diabetes mellitus (DM). Central to this damage is endothelial damage, especially under high-glucose conditions, which promotes inflammation via the NF-κB signaling pathway. Inflammatory processes in endothelial cells directly contribute to endothelial dysfunction, such as promoting inflammatory cytokine release and activation of adhesion molecules. Vitexin, a compound found in many medicinal plants, shows promise in countering oxidative stress in diabetic contexts and modulating blood glucose. However, its effect on high-glucose-induced endothelial cell activation has not yet been studied. This research explores vitexin's potential role in this process, focusing on its influence on the NF-κB pathway in endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with 30 mM glucose (high glucose, HG) with or without vitexin treatment for 24 h. Western blotting assay was conducted for the NF-κB pathway and p-p38. Adhesion molecules (ICAM-1, VCAM-1, E-selectin, and MCP-1) were studied using flow cytometry, while pro-inflammatory cytokines were investigated using ELISA. Monocyte adhesion and vascular permeability tests were conducted to confirm the protective effect of vitexin under HG exposure. This study confirms vitexin's capacity to suppress p38 MAPK and NF-κB activation under HG conditions, reducing HG-elevated adhesion molecules and pro-inflammatory cytokine secretion. Additionally, vitexin mitigates HG-stimulated vascular permeability and monocyte adhesion. In conclusion, this study shows the therapeutic potential of vitexin against hyperglycemia-related vascular complications via p38 MAPK/NF-κB inhibition.

Vascular remodelling in cardiovascular diseases: hypertension, oxidation, and inflammation

Optimal vascular structure and function are essential for maintaining the physiological functions of the cardiovascular system. Vascular remodelling involves changes in vessel structure, including its size, shape, cellular and molecular composition. These changes result from multiple risk factors and may be compensatory adaptations to sustain blood vessel function. They occur in diverse cardiovascular pathologies, from hypertension to heart failure and atherosclerosis. Dynamic changes in the endothelium, fibroblasts, smooth muscle cells, pericytes or other vascular wall cells underlie remodelling. In addition, immune cells, including macrophages and lymphocytes, may infiltrate vessels and initiate inflammatory signalling. They contribute to a dynamic interplay between cell proliferation, apoptosis, migration, inflammation, and extracellular matrix reorganisation, all critical mechanisms of vascular remodelling. Molecular pathways underlying these processes include growth factors (e.g., vascular endothelial growth factor and platelet-derived growth factor), inflammatory cytokines (e.g., interleukin-1β and tumour necrosis factor-α), reactive oxygen species, and signalling pathways, such as Rho/ROCK, MAPK, and TGF-β/Smad, related to nitric oxide and superoxide biology. MicroRNAs and long noncoding RNAs are crucial epigenetic regulators of gene expression in vascular remodelling. We evaluate these pathways for potential therapeutic targeting from a clinical translational perspective. In summary, vascular remodelling, a coordinated modification of vascular structure and function, is crucial in cardiovascular disease pathology.

Appearance of small extracellular vesicles in the mouse pregnant serum and the localization in placentas

Exosomes or small extracellular vesicles (sEVs) are present in the blood of pregnant mice and considered to be involved in pregnancy physiology. Although sEVs in pregnant periods are proposed to be derived from placentas, sEVs-producing cells are not well known in mouse placentas. We studied the dynamics and localization of sEVs in pregnant serum and placentas, and examined gestational variation of microRNA (miRNA). Serums and placentas were collected from non-pregnant (NP) and pregnant mice throughout the entire gestational day (Gd). EVs were purified from serums and total RNA was isolated from EVs. Nanoparticle-tracking assay (NTA) revealed that the rates of sEVs in EVs are 53% at NP, and increased to 80.1% at Gd 14.5 and 97.5% at Gd 18.5. Western blotting on EVs showed positive reactivity to the tetraspanin markers and clarified that the results using anti-CD63 antibody were most consistent with the sEVs appearance detected by NTA. Serum EVs also showed a positive reaction to the syncytiotrophoblast marker, syncytin-1. Immunohistostaining using anti-CD63 antibody showed positive reactions in mouse placentas at the syncytiotrophoblasts and endothelial cells of the fetal capillaries. Quantitative PCR revealed that significantly higher amounts of miRNAs were included in the sEVs of Gd 18.5. Our results suggested that sEVs are produced in the mouse placenta and transferred to maternal or fetal bloodstreams. sEVs are expected to have a miRNA-mediated physiological effect and become useful biomarkers reflecting the pregnancy status.

Reversal of atherosclerosis by restoration of vascular copper homeostasis

Atherosclerosis has traditionally been considered as a disorder characterized by the accumulation of cholesterol and thrombotic materials within the arterial wall. However, it is now understood to be a complex inflammatory disease involving multiple factors. Central to the pathogenesis of atherosclerosis are the interactions among monocytes, macrophages, and neutrophils, which play pivotal roles in the initiation, progression, and destabilization of atherosclerotic lesions. Recent advances in our understanding of atherosclerosis pathogenesis, coupled with results obtained from experimental interventions, lead us to propose the hypothesis that atherosclerosis may be reversible. This paper outlines the evolution of this hypothesis and presents corroborating evidence that supports the potential for atherosclerosis regression through the restoration of vascular copper homeostasis. We posit that these insights may pave the way for innovative therapeutic approaches aimed at the reversal of atherosclerosis.

Early Injury Landscape in Vein Harvest by Single-Cell and Spatial Transcriptomics

BACKGROUND

Vein graft failure following cardiovascular bypass surgery results in significant patient morbidity and cost to the healthcare system. Vein graft injury can occur during autogenous vein harvest and preparation, as well as after implantation into the arterial system, leading to the development of intimal hyperplasia, vein graft stenosis, and, ultimately, bypass graft failure. Although previous studies have identified maladaptive pathways that occur shortly after implantation, the specific signaling pathways that occur during vein graft preparation are not well defined and may result in a cumulative impact on vein graft failure. We, therefore, aimed to elucidate the response of the vein conduit wall during harvest and following implantation, probing the key maladaptive pathways driving graft failure with the overarching goal of identifying therapeutic targets for biologic intervention to minimize these natural responses to surgical vein graft injury.

METHODS

Employing a novel approach to investigating vascular pathologies, we harnessed both single-nuclei RNA-sequencing and spatial transcriptomics analyses to profile the genomic effects of vein grafts after harvest and distension, then compared these findings to vein grafts obtained 24 hours after carotid-carotid vein bypass implantation in a canine model (n=4).

RESULTS

Spatial transcriptomic analysis of canine cephalic vein after initial conduit harvest and distention revealed significant enrichment of pathways (P<0.05) involved in the activation of endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells, namely pathways responsible for cellular proliferation and migration and platelet activation across the intimal and medial layers, cytokine signaling within the adventitial layer, and ECM (extracellular matrix) remodeling throughout the vein wall. Subsequent single-nuclei RNA-sequencing analysis supported these findings and further unveiled distinct EC and fibroblast subpopulations with significant upregulation (P<0.05) of markers related to endothelial injury response and cellular activation of ECs, fibroblasts, and vascular smooth muscle cells. Similarly, in vein grafts obtained 24 hours after arterial bypass, there was an increase in myeloid cell, protomyofibroblast, injury response EC, and mesenchymal-transitioning EC subpopulations with a concomitant decrease in homeostatic ECs and fibroblasts. Among these markers were genes previously implicated in vein graft injury, including VCAN, FBN1, and VEGFC, in addition to novel genes of interest, such as GLIS3 and EPHA3. These genes were further noted to be driving the expression of genes implicated in vascular remodeling and graft failure, such as IL-6, TGFBR1, SMAD4, and ADAMTS9. By integrating the spatial transcriptomics and single-nuclei RNA-sequencing data sets, we highlighted the spatial architecture of the vein graft following distension, wherein activated and mesenchymal-transitioning ECs, myeloid cells, and fibroblasts were notably enriched in the intima and media of distended veins. Finally, intercellular communication network analysis unveiled the critical roles of activated ECs, mesenchymal-transitioning ECs, protomyofibroblasts, and vascular smooth muscle cells in upregulating signaling pathways associated with cellular proliferation (MDK [midkine], PDGF [platelet-derived growth factor], VEGF [vascular endothelial growth factor]), transdifferentiation (Notch), migration (ephrin, semaphorin), ECM remodeling (collagen, laminin, fibronectin), and inflammation (thrombospondin), following distension.

CONCLUSIONS

Vein conduit harvest and distension elicit a prompt genomic response facilitated by distinct cellular subpopulations heterogeneously distributed throughout the vein wall. This response was found to be further exacerbated following vein graft implantation, resulting in a cascade of maladaptive gene regulatory networks. Together, these results suggest that distension initiates the upregulation of pathological pathways that may ultimately contribute to bypass graft failure and presents potential early targets warranting investigation for targeted therapies. This work highlights the first applications of single-nuclei and spatial transcriptomic analyses to investigate venous pathologies, underscoring the utility of these methodologies and providing a foundation for future investigations.

Under pressure: integrated endothelial cell response to hydrostatic and shear stresses

Blood flow within the vasculature is a critical determinant of endothelial cell (EC) identity and functionality, yet the intricate interplay of various hemodynamic forces and their collective impact on endothelial and vascular responses are not fully understood. Specifically, the role of hydrostatic pressure in the EC flow response is understudied, despite its known significance in vascular development and disease. To address this gap, we developed in vitro models to investigate how pressure influences EC responses to flow. Our study demonstrates that elevated pressure conditions significantly modify shear-induced flow alignment and increase endothelial cell density. Bulk and single-cell RNA sequencing analyses revealed that, while shear stress remains the primary driver of flow-induced transcriptional changes, pressure modulates shear-induced signaling in a dose-dependent manner. These pressure-responsive transcriptional signatures identified in human ECs were conserved during the onset of circulation in early mouse embryonic vascular development, where pressure was notably associated with transcriptional programs essential to arterial and hemogenic EC fates. Our findings suggest that pressure plays a synergistic role with shear stress on ECs and emphasizes the need for an integrative approach to endothelial cell mechanotransduction, one that encompasses the effects induced by pressure alongside other hemodynamic forces.

BMP9 is a key player in endothelial identity and its loss is sufficient to induce arteriovenous malformations

AIMS

BMP9 is a high affinity ligand of ALK1 and endoglin receptors that are mutated in the rare genetic vascular disorder hereditary hemorrhagic telangiectasia (HHT). We have previously shown that loss of Bmp9 in the 129/Ola genetic background leads to spontaneous liver fibrosis via capillarization of liver sinusoidal endothelial cells (LSEC) and kidney lesions. We aimed to decipher the molecular mechanisms downstream of BMP9 to better characterize its role in vascular homeostasis in different organs.

METHODS AND RESULTS

For this, we performed an RNA-seq analysis on LSEC from adult WT and Bmp9-KO mice and identified over 2000 differentially expressed genes. Gene ontology analysis showed that Bmp9 deletion led to a decrease in BMP and Notch signalling, but also LSEC capillary identity while increasing their cell cycle. The gene ontology term 'glomerulus development' was also negatively enriched in Bmp9-KO mice vs. WT supporting a role for BMP9 in kidney vascularization. Through different imaging approaches (electron microscopy, immunostainings), we found that loss of Bmp9 led to vascular enlargement of the glomeruli capillaries associated with alteration of podocytes. Importantly, we also showed for the first time that the loss of Bmp9 led to spontaneous arteriovenous malformations (AVMs) in the liver, gastrointestinal tract, and uterus.

CONCLUSION

Altogether, these results demonstrate that BMP9 plays an important role in vascular quiescence both locally in the liver by regulating endothelial capillary differentiation markers and cell cycle but also at distance in many organs via its presence in the circulation. It also reveals that loss of Bmp9 is sufficient to induce spontaneous AVMs, supporting a key role for BMP9 in the pathogenesis of HHT.

Stem cell-derived vessels-on-chip for cardiovascular disease modeling

The metabolic syndrome is accompanied by vascular complications. Human in vitro disease models are hence required to better understand vascular dysfunctions and guide clinical therapies. Here, we engineered an open microfluidic vessel-on-chip platform that integrates human pluripotent stem cell-derived endothelial cells (SC-ECs). The open microfluidic design enables seamless integration with state-of-the-art analytical technologies, including single-cell RNA sequencing, proteomics by mass spectrometry, and high-resolution imaging. Beyond previous systems, we report SC-EC maturation by means of barrier formation, arterial toning, and high nitric oxide synthesis levels under gravity-driven flow. Functionally, we corroborate the hallmarks of early-onset atherosclerosis with low sample volumes and cell numbers under flow conditions by determining proteome and secretome changes in SC-ECs stimulated with oxidized low-density lipoprotein and free fatty acids. More broadly, our organ-on-chip platform enables the modeling of patient-specific human endothelial tissue and has the potential to become a general tool for animal-free vascular research.

Gene therapy targeting the blood-brain barrier

Endothelial cells are the building blocks of vessels in the central nervous system (CNS) and form the blood-brain barrier (BBB). An intact BBB limits permeation of large hydrophilic molecules into the CNS. Thus, the healthy BBB is a major obstacle for the treatment of CNS disorders with antibodies, recombinant proteins or viral vectors. Several strategies have been devised to overcome the barrier. A key principle often consists in attaching the therapeutic compound to a ligand of receptors expressed on the BBB, for example, the transferrin receptor (TfR). The fusion molecule will bind to TfR on the luminal side of brain endothelial cells, pass the endothelial layer by transcytosis and be delivered to the brain parenchyma. However, attempts to endow therapeutic compounds with the ability to cross the BBB can be difficult to implement. An alternative and possibly more straight-forward approach is to produce therapeutic proteins in the endothelial cells that form the barrier. These cells are accessible from blood circulation and have a large interface with the brain parenchyma. They may be an ideal production site for therapeutic protein and afford direct supply to the CNS.

A Nucleic Acid-Based LYTAC Plus Platform to Simultaneously Mediate Disease-Driven Protein Downregulation

Protein degradation techniques, such as proteolysis-targeting chimeras (PROTACs) and lysosome-targeting chimeras (LYTACs), have emerged as promising therapeutic strategies for the treatment of diseases. However, the efficacy of current protein degradation methods still needs to be improved to address the complex mechanisms underlying diseases. Herein, a LYTAC Plus hydrogel engineered is proposed by nucleic acid self-assembly, which integrates a gene silencing motif into a LYTAC construct to enhance its therapeutic potential. As a proof-of-concept study, vascular endothelial growth factor receptor (VEGFR)-binding peptides and mannose-6 phosphate (M6P) moieties into a self-assembled nucleic acid hydrogel are introduced, enabling its LYTAC capability. Small interference RNAs (siRNAs) is then employed that target the angiopoietin-2 (ANG-2) gene as cross-linkers for hydrogel formation, giving the final LYTAC Plus hydrogel gene silencing ability. With dual functionalities, the LYTAC Plus hydrogel demonstrated effectiveness in simultaneously reducing the levels of VEGFR-2 and ANG-2 both in vitro and in vivo, as well as in improving therapeutic outcomes in treating neovascular age-related macular degeneration in a mouse model. As a general material platform, the LYTAC Plus hydrogel may possess great potential for the treatment of various diseases and warrant further investigation.

The interaction between particles and vascular endothelium in blood flow

Particle-based drug delivery systems have shown promising application potential to treat human diseases; however, an incomplete understanding of their interactions with vascular endothelium in blood flow prevents their inclusion into mainstream clinical applications. The flow performance of nano/micro-sized particles in the blood are disturbed by many external/internal factors, including blood constituents, particle properties, and endothelium bioactivities, affecting the fate of particles in vivo and therapeutic effects for diseases. This review highlights how the blood constituents, hemodynamic environment and particle properties influence the interactions and particle activities in vivo. Moreover, we briefly summarized the structure and functions of endothelium and simulated devices for studying particle performance under blood flow conditions. Finally, based on particle-endothelium interactions, we propose future opportunities for novel therapeutic strategies and provide solutions to challenges in particle delivery systems for accelerating their clinical translation. This review helps provoke an increasing in-depth understanding of particle-endothelium interactions and inspires more strategies that may benefit the development of particle medicine.

Amino Acid Metabolism and Atherosclerotic Cardiovascular Disease

Despite significant advances in medical treatments and drug development, atherosclerotic cardiovascular disease (ASCVD) remains a leading cause of death worldwide. Dysregulated lipid metabolism is a well-established driver of ASCVD. Unfortunately, even with potent lipid-lowering therapies, ASCVD-related deaths have continued to increase over the past decade, highlighting an incomplete understanding of the underlying risk factors and mechanisms of ASCVD. Accumulating evidence over the past decades indicates a correlation between amino acids and disease state. This review explores the emerging role of amino acid metabolism in ASCVD, uncovering novel potential biomarkers, causative factors, and therapeutic targets. Specifically, the significance of arginine and its related metabolites, homoarginine and polyamines, branched-chain amino acids, glycine, and aromatic amino acids, in ASCVD are discussed. These amino acids and their metabolites have been implicated in various processes characteristic of ASCVD, including impaired lipid metabolism, endothelial dysfunction, increased inflammatory response, and necrotic core development. Understanding the complex interplay between dysregulated amino acid metabolism and ASCVD provides new insights that may lead to the development of novel diagnostic and therapeutic approaches. Although further research is needed to uncover the precise mechanisms involved, it is evident that amino acid metabolism plays a role in ASCVD.

Pulmonary vascular phenotype identified in patients with GDF2 (BMP9) or BMP10 variants: an international multicentre study

BACKGROUND

Bone morphogenetic proteins 9 and 10 (BMP9 and BMP10), encoded by GDF2 and BMP10, respectively, play a pivotal role in pulmonary vascular regulation. GDF2 variants have been reported in pulmonary arterial hypertension (PAH) and hereditary haemorrhagic telangiectasia (HHT). However, the phenotype of GDF2 and BMP10 carriers remains largely unexplored.

METHODS

We report the characteristics and outcomes of PAH patients in GDF2 and BMP10 carriers from the French and Dutch pulmonary hypertension registries. A literature review explored the phenotypic spectrum of these patients.

RESULTS

26 PAH patients were identified: 20 harbouring heterozygous GDF2 variants, one homozygous GDF2 variant, four heterozygous BMP10 variants, and one with both GDF2 and BMP10 variants. The prevalence of GDF2 and BMP10 variants was 1.3% and 0.4%, respectively. Median age at PAH diagnosis was 30 years, with a female/male ratio of 1.9. Congenital heart disease (CHD) was present in 15.4% of the patients. At diagnosis, most of the patients (61.5%) were in New York Heart Association Functional Class III or IV with severe haemodynamic compromise (median (range) pulmonary vascular resistance 9.0 (3.3-40.6) WU). Haemoptysis was reported in four patients; none met the HHT criteria. Two patients carrying BMP10 variants underwent lung transplantation, revealing typical PAH histopathology. The literature analysis showed that 7.6% of GDF2 carriers developed isolated HHT, and identified cardiomyopathy and developmental disorders in BMP10 carriers.

CONCLUSIONS

GDF2 and BMP10 pathogenic variants are rare among PAH patients, and occasionally associated with CHD. HHT cases among GDF2 carriers are limited according to the literature. BMP10 full phenotypic ramifications warrant further investigation.

Endothelial to mesenchymal transition: at the axis of cardiovascular health and disease

Endothelial cells (ECs) line the luminal surface of blood vessels and play a major role in vascular (patho)-physiology by acting as a barrier, sensing circulating factors and intrinsic/extrinsic signals. ECs have the capacity to undergo endothelial-to-mesenchymal transition (EndMT), a complex differentiation process with key roles both during embryonic development and in adulthood. EndMT can contribute to EC activation and dysfunctional alterations associated with maladaptive tissue responses in human disease. During EndMT, ECs progressively undergo changes leading to expression of mesenchymal markers while repressing EC lineage-specific traits. This phenotypic and functional switch is considered to largely exist in a continuum, being characterized by a gradation of transitioning stages. In this report, we discuss process plasticity and potential reversibility and the hypothesis that different EndMT-derived cell populations may play a different role in disease progression or resolution. In addition, we review advancements in the EndMT field, current technical challenges, as well as therapeutic options and opportunities in the context of cardiovascular biology.