Vessel Enlargement in Development and Pathophysiology

Mural cell dysfunction contributes to diastolic heart failure by promoting endothelial dysfunction and vessel remodelling

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is a complex cardiovascular disease associated with metabolic comorbidities. Microvascular dysfunction has been proposed to drive HFpEF, likely via endothelial cell (EC) dysfunction, yet the role of the mural cells herein has never been explored.

METHODS

We used the diabetic db/db mouse given 1% salt as a new model of HFpEF and crossed then with PDGFRβtg/tg-CreERT2-EYFPtg/tg mice to label the mural cells. We combined single-cell RNA sequencing, NichetNet analysis and histology to determine the role of mural cell dysfunction in HFpEF.

RESULTS

Db/db mice given 1% salt for 8 weeks developed diastolic dysfunction preceded by capillary density loss, pericyte loss and vessel regression. At 4 weeks of salt, hearts of db/db mice already showed EC dysfunction associated with an anti-angiogenic signature, and an increase in pericyte-EC intracellular space. Db/db + salt hearts were further characterised by increased ACTA2 expression, arteriole wall thickening and vessel enlargement. NicheNet analysis on the single cell transcriptomic data revealed little signalling from the ECs to the mural cells; instead, mural cells signalled strongly to ECs. Mechanistically, pericyte dysfunction induces an EC growth arrest via TNFα-dependent paracrine signalling and downstream signalling through STAT1.

CONCLUSION

Mural cell dysfunction contributes to HFpEF by inducing coronary vessel remodelling, at least in part by reducing EC proliferation and inducing EC inflammation through TNFα-dependent paracrine signalling.

Development and Validation of the Systemic Inflammatory Response Index-Based Nomogram for Predicting Short-Term Adverse Events in Patients With Acute Uncomplicated Type B Aortic Intramural Hematoma

Purpose

This study aims to develop and validate a nomogram based on the Systemic Inflammatory Response Index (SIRI) to predict short-term aortic-related adverse events (ARAEs) in patients with acute uncomplicated Type B intramural hematoma (IMH).

Patients and methods

We retrospectively analyzed 332 patients diagnosed with acute uncomplicated Type B IMH between April 2018 and April 2024. Patients were categorized into the stable group (N=225) and the exacerbation group (N=107) based on the occurrence of ARAEs within 30-day observation period. SIRI was calculated using neutrophil, monocyte, and lymphocyte counts. ARAEs were defined as death related to aortic disease, and the progression of IMH to aortic dissection or penetrating aortic ulcer. The nomogram was developed incorporating SIRI and other significant clinical variables. The model's performance was evaluated using the area under the curve (AUC), calibration curves, decision curve analysis (DCA), and net reclassification index (NRI).

Results

Among the 332 patients, 217 were male (65.4%), with a mean age of 64.3±9.4 years. Multivariate logistic regression and LASSO regression analyses identified SIRI, anemia, diabetes, maximum diameter of aortic diameter (MDAD), and ulcer like projection (ULP) as independent predictors of ARAEs. Two nomogram models were developed: the Clinical model, including anemia, diabetes, MDAD, and ULP; and the Clinical-SIRI model, incorporating SIRI to the Clinical model. The Clinical-SIRI model demonstrated higher predictive accuracy, with an AUC of 0.788 (95% CI: 0.740-0.831), compared to the Clinical model's AUC of 0.742 (95% CI: 0.691-0.788, P = 0.012). SIRI improved predictive accuracy, as shown by a continuous NRI of 0.521 (95% CI: 0.301-0.743). Calibration curves and DCA further supported the clinical utility of the Clinical-SIRI model.

Conclusion

The SIRI-based nomogram is a valuable prognostic tool for predicting short-term ARAEs in patients with acute uncomplicated Type B IMH.

Patterns of Dynamic Adaptability of the Circle of Willis in Response to Major Branch Artery Coverage With a Flow Diverter

BACKGROUND

The plasticity of the Circle of Willis represents an underexplored yet intriguing dimension of vascular anatomy in cerebrovascular disorders. We outline distinct patterns of change in response to aneurysm treatment using flow diversion (FD) after covering major branches.

METHODS

Retrospective analysis of digital subtraction angiographies from intracranial aneurysms treated with FD from 2013 to 2023. Vessel diameters, including those covered by the stent and adjacent arteries, were measured. Angiographic changes were evaluated at last imaging follow-up.

RESULTS

Of the 622 patients, 49 had angiographic follow-up for pattern assessment. The median age was 62 years; females represented 71.4%. The median size of the treated aneurysms was 4.7 mm. Four patterns of angiographic change were identified: 1) Patients with supraclinoid aneurysms, A1-anterior cerebral artery (ACA) caliber increased (hypoplastic: 1.05-2.00 mm; nonhypoplastic: 2.45-2.75 mm) after FD coverage of the contralateral ACA. 2) Patients with paraclinoid aneurysms and hypoplastic-fetal posterior cerebral artery (PCA), the diameter increased from 0.80 to 1.7 mm (P < 0.01) after covering the ipsilateral posterior communicating artery origin. 3) Patients with basilar-tip and proximal PCA aneurysms showed increased ipsilateral posterior communicating artery size from 1.2 to 2 mm (P < 0.01) after PCA origin coverage. 4) Patients with anterior communicating aneurysms, the diameter of the contralateral hypoplastic A1 segment increased from 1.0 to 1.35 mm (P = 0.39) or nonhypoplastic A1-ACA from 2.75 to 3.05 mm (P = 0.10) after FD coverage.

CONCLUSIONS

The circle of Willis displays both hemodynamic and anatomic plasticity after major branch coverage with a flow diverter. This phenomenon is aimed at preserving blood flow in the distal territory of the covered vessel.

Alk1/Endoglin signaling restricts vein cell size increases in response to hemodynamic cues

Hemodynamic cues are thought to control blood vessel hierarchy through a shear stress set point, where flow increases lead to blood vessel diameter expansion, while decreases in blood flow cause blood vessel narrowing. Aberrations in blood vessel diameter control can cause congenital arteriovenous malformations (AVMs). We show in zebrafish embryos that while arteries behave according to the shear stress set point model, veins do not. This behavior is dependent on distinct arterial and venous endothelial cell (EC) shapes and sizes. We show that arterial ECs enlarge more strongly when experiencing higher flow, as compared to vein cells. Through the generation of chimeric embryos, we discover that this behavior of vein cells depends on the bone morphogenetic protein (BMP) pathway components Endoglin and Alk1. Endoglin (eng) or alk1 (acvrl1) mutant vein cells enlarge when in normal hemodynamic environments, while we do not observe a phenotype in either acvrl1 or eng mutant ECs in arteries. We further show that an increase in vein diameters initiates AVMs in eng mutants, secondarily leading to higher flow to arteries. These enlarge in response to higher flow through increasing arterial EC sizes, fueling the AVM. This study thus reveals a mechanism through which BMP signaling limits vein EC size increases in response to flow and provides a framework for our understanding of how a small number of mutant vein cells via flow-mediated secondary effects on wildtype arterial ECs can precipitate larger AVMs in disease conditions, such as hereditary hemorrhagic telangiectasia (HHT).

Sequential Hemodynamic Analysis of Ruptured Posterior Communicating Artery Aneurysms Treated With Coil Embolization and Delayed Flow Diversion

BACKGROUND AND OBJECTIVES

Computational fluid dynamics has advanced our knowledge of the pathogenesis of intracranial aneurysms and the dynamic changes observed after treatment. Herein, we analyze hemodynamic changes throughout the intervention stages for ruptured posterior communicating artery (PComA) aneurysms, treated with acute coiling and delayed flow diversion (FD).

METHODS

We performed a retrospective analysis of ruptured PComA aneurysms treated with the acute coiling and delayed FD strategy between June 2013 to November 2022, using 3-dimensional reconstructions of digital subtraction angiographies. Hemodynamic simulations using ANSYS® calculated aneurysmal and adjacent arteries' wall shear stress (WSS), aneurysmal low shear areas (LSA), and mean velocities in the distal arteries.

RESULTS

Six of the 22 patients were selected for computational fluid dynamics analysis, including 4 females and 2 males with a median age of 60 years. The average aneurysm volume was 984.12 mm3, with an average surface area of 386.11 mm2; LSA was 22.90%, and the average WSS was 3.39 Pa. The 2 largest aneurysms also had the highest LSA values. After coiling, there was a reduction in the aneurysmal volume (-78.42%) and the average surface area (-55.28%), and aneurysmal WSS increased to 6.10 Pa (+79.90%). WSS values for the middle cerebral artery (MCA) increased to 10.76 Pa, while anterior cerebral artery (ACA) increased to 7.51 Pa. Complete occlusion was achieved with delayed FD at a median follow-up of 19.7 months. After FD, average WSS increased to 14.94 Pa for the MCA (+70.64%) and to 10.82 Pa for the ACA (+30.10%). The mean MCA velocity increased to 43.04 cm/s (+36.85%), and 3 cases showed an increase in ACA velocities.

CONCLUSION

LSA may have triggered rupture for the PComA aneurysms analyzed. After coiling, average WSS increased in the aneurysm wall and downstream vessels in the majority of cases analyzed. Delayed FD caused hemodynamic disturbances distal to deployment, reflected in the sequential increase in the WSS and velocities in both the ACA and MCA.

Novel mathematical approach to accurately quantify 3D endothelial cell morphology and vessel geometry based on fluorescently marked endothelial cell contours: Application to the dorsal aorta of wild-type and Endoglin-deficient zebrafish embryos

Endothelial cells, which line the lumen of blood vessels, locally sense and respond to blood flow. In response to altered blood flow dynamics during early embryonic development, these cells undergo shape changes that directly affect vessel geometry: In the dorsal aorta of zebrafish embryos, elongation of endothelial cells in the direction of flow between 48 and 72 hours post fertilization (hpf) reduces the vessel's diameter. This remodeling process requires Endoglin; excessive endothelial cell growth in the protein's absence results in vessel diameter increases. To understand how these changes in vessel geometry emerge from morphological changes of individual endothelial cells, we developed a novel mathematical approach that allows 3D reconstruction and quantification of both dorsal aorta geometry and endothelial cell surface morphology. Based on fluorescently marked endothelial cell contours, we inferred cross-sections of the dorsal aorta that accounted for dorsal flattening of the vessel. By projection of endothelial cell contours onto the estimated cross-sections and subsequent triangulation, we finally reconstructed 3D surfaces of the individual cells. By simultaneously reconstructing vessel cross-sections and cell surfaces, we found in an exploratory analysis that morphology varied between endothelial cells located in different sectors of the dorsal aorta in both wild-type and Endoglin-deficient zebrafish embryos: In wild-types, ventral endothelial cells were smaller and more elongated in flow direction than dorsal endothelial cells at both 48 hpf and 72 hpf. Although dorsal and ventral endothelial cells in Endoglin-deficient embryos had similar sizes at 48 hpf, dorsal endothelial cells were much larger at 72 hpf. In Endoglin-deficient embryos, elongation in flow direction increased between 48 hpf and 72 hpf in ventral endothelial cells but hardly changed in dorsal endothelial cells. Hereby, we provide evidence that dorsal endothelial cells contribute most to the disparate changes in dorsal aorta diameter in wild-type and Endoglin-deficient embryos between 48 hpf and 72 hpf.

A nomogram prediction model for short-term aortic-related adverse events in patients with acute Stanford type B aortic intramural hematoma: development and validation

Background

This study is to examine the factors associated with short-term aortic-related adverse events in patients with acute type B aortic intramural hematoma (IMH). Additionally, we develop a risk prediction nomogram model and evaluate its accuracy.

Methods

This study included 197 patients diagnosed with acute type B IMH. The patients were divided into stable group (n = 125) and exacerbation group (n = 72) based on the occurrence of aortic-related adverse events. Logistic regression and the Least Absolute Shrinkage and Selection Operator (LASSO) method for variables based on baseline assessments with significant differences in clinical and image characteristics were employed to identify independent predictors. A nomogram risk model was constructed based on these independent predictors. The nomogram model was evaluated using various methods such as the receiver operating characteristic curve, calibration curve, decision analysis curve, and clinical impact curve. Internal validation was performed using the Bootstrap method.

Results

A nomogram risk prediction model was established based on four variables: absence of diabetes, anemia, maximum descending aortic diameter (MDAD), and ulcer-like projection (ULP). The model demonstrated a discriminative ability with an area under the curve (AUC) of 0.813. The calibration curve indicated a good agreement between the predicted probabilities and the actual probabilities. The Hosmer-Lemeshow goodness of fit test showed no significant difference (χ 2 = 7.040, P = 0.532). The decision curve analysis (DCA) was employed to further confirm the clinical effectiveness of the nomogram.

Conclusion

This study introduces a nomogram prediction model that integrates four important risk factors: ULP, MDAD, anemia, and absence of diabetes. The model allows for personalized prediction of patients with type B IMH.

Thromboembolic Events After the Coverage of Anterior Cerebral Artery with Flow Diversion: A Single Institution Series and Systematic Review

BACKGROUND

Advances in the use of flow diversion (FD) now extend to bifurcation aneurysms; herein, we compare thromboembolic events in patients with internal carotid artery (ICA) aneurysms treated with and without exclusion of the anterior cerebral artery (ACA).

METHODS

Retrospective analysis of aneurysms in the terminal ICA treated with FD from 2013 to 2023 at a single-center study. Procedures were classified according to the coverage at the origin of the ACA and compared through bivariate-analysis. A review was also carried on PubMed, Web of Science, and EMBASE until April 2024, adhering to the PRISMA reporting guidelines.

RESULTS

Ninety-five patients harboring 113 aneurysms treated in 102 procedures were evaluated. Fifty-eight were treated covering the ACA origin. Dual antiplatelet regimens included aspirin-clopidogrel (50%), aspirin-ticagrelor (44.1%), and aspirin-prasugrel (4.9%). Thromboembolic events occurred in 6 patients (5.9%), all of which presented with large vessel occlusion of the ICA, but without reaching statistical difference in the 2 treated cohorts (P = 0.46). At a median clinical follow-up of 5.95 months, there were no differences in the functional outcomes in the 2 groups (P = 0.22). Contralateral angiographic runs post-treatment after covering the ACA origin demonstrated increase in the A1 (median: 0.45 mm; IQR = 0.4-1.2) and ICA diameter (median: 0.55 mm; IQR = 0.1-1.2). After pooling data from literature and our cohort, complete side branch occlusion after the coverage of ACA was seen in 25% of branches (95%CI = 0.16-0.36), and thromboembolic events were observed after 3% (95%CI = 0.01-0.04) of procedures.

CONCLUSIONS

Thromboembolic events can occur in distal ICA aneurysms treated with FD, but no significant association was seen with covering the ACA origin.

A robust vessel-labeling pipeline with high tissue clearing compatibility for 3D mapping of vascular networks

The combination of vessel-labeling, tissue-clearing, and light-sheet imaging techniques provides a potent tool for accurately mapping vascular networks, enabling the assessment of vascular remodeling in vascular-related disorders. However, most vascular labeling methods face challenges such as inadequate labeling efficiency or poor compatibility with current tissue clearing technology, which significantly undermines the image quality. To address this limitation, we introduce a vessel-labeling pipeline, termed Ultralabel, which relies on a specially designed dye hydrogel containing lysine-fixable dextran and gelatins for double enhancement. Ultralabel demonstrates not only excellent vessel-labeling capability but also strong compatibility with all tissue clearing methods tested, which outperforms other vessel-labeling methods. Consequently, Ultralabel enables fine mapping of vascular networks in diverse organs, as well as multi-color labeling alongside other labeling techniques. Ultralabel should provide a robust and user-friendly method for obtaining 3D vascular networks in different biomedical applications.

Time-Series Modeling and Forecasting of Cerebral Pressure-Flow Physiology: A Scoping Systematic Review of the Human and Animal Literature

The modeling and forecasting of cerebral pressure-flow dynamics in the time-frequency domain have promising implications for veterinary and human life sciences research, enhancing clinical care by predicting cerebral blood flow (CBF)/perfusion, nutrient delivery, and intracranial pressure (ICP)/compliance behavior in advance. Despite its potential, the literature lacks coherence regarding the optimal model type, structure, data streams, and performance. This systematic scoping review comprehensively examines the current landscape of cerebral physiological time-series modeling and forecasting. It focuses on temporally resolved cerebral pressure-flow and oxygen delivery data streams obtained from invasive/non-invasive cerebral sensors. A thorough search of databases identified 88 studies for evaluation, covering diverse cerebral physiologic signals from healthy volunteers, patients with various conditions, and animal subjects. Methodologies range from traditional statistical time-series analysis to innovative machine learning algorithms. A total of 30 studies in healthy cohorts and 23 studies in patient cohorts with traumatic brain injury (TBI) concentrated on modeling CBFv and predicting ICP, respectively. Animal studies exclusively analyzed CBF/CBFv. Of the 88 studies, 65 predominantly used traditional statistical time-series analysis, with transfer function analysis (TFA), wavelet analysis, and autoregressive (AR) models being prominent. Among machine learning algorithms, support vector machine (SVM) was widely utilized, and decision trees showed promise, especially in ICP prediction. Nonlinear models and multi-input models were prevalent, emphasizing the significance of multivariate modeling and forecasting. This review clarifies knowledge gaps and sets the stage for future research to advance cerebral physiologic signal analysis, benefiting neurocritical care applications.

Plxnd1-mediated mechanosensing of blood flow controls the caliber of the Dorsal Aorta via the transcription factor Klf2

The cardiovascular system generates and responds to mechanical forces. The heartbeat pumps blood through a network of vascular tubes, which adjust their caliber in response to the hemodynamic environment. However, how endothelial cells in the developing vascular system integrate inputs from circulatory forces into signaling pathways to define vessel caliber is poorly understood. Using vertebrate embryos and in vitro-assembled microvascular networks of human endothelial cells as models, flow and genetic manipulations, and custom software, we reveal that Plexin-D1, an endothelial Semaphorin receptor critical for angiogenic guidance, employs its mechanosensing activity to serve as a crucial positive regulator of the Dorsal Aorta's (DA) caliber. We also uncover that the flow-responsive transcription factor KLF2 acts as a paramount mechanosensitive effector of Plexin-D1 that enlarges endothelial cells to widen the vessel. These findings illuminate the molecular and cellular mechanisms orchestrating the interplay between cardiovascular development and hemodynamic forces.

Epsin Endocytic Adaptor Proteins in Angiogenic and Lymphangiogenic Signaling

Circulating vascular endothelial growth factor (VEGF) ligands and receptors are central regulators of vasculogenesis, angiogenesis, and lymphangiogenesis. In response to VEGF ligand binding, VEGF receptor tyrosine kinases initiate the chain of events that transduce extracellular signals into endothelial cell responses such as survival, proliferation, and migration. These events are controlled by intricate cellular processes that include the regulation of gene expression at multiple levels, interactions of numerous proteins, and intracellular trafficking of receptor-ligand complexes. Endocytic uptake and transport of macromolecular complexes through the endosome-lysosome system helps fine-tune endothelial cell responses to VEGF signals. Clathrin-dependent endocytosis remains the best understood means of macromolecular entry into cells, although the importance of non-clathrin-dependent pathways is increasingly recognized. Many of these endocytic events rely on adaptor proteins that coordinate internalization of activated cell-surface receptors. In the endothelium of both blood and lymphatic vessels, epsins 1 and 2 are functionally redundant adaptors involved in receptor endocytosis and intracellular sorting. These proteins are capable of binding both lipids and proteins and are important for promoting curvature of the plasma membrane as well as binding ubiquitinated cargo. Here, we discuss the role of epsin proteins and other endocytic adaptors in governing VEGF signaling in angiogenesis and lymphangiogenesis and discuss their therapeutic potential as molecular targets.

Somatic GJA4 mutation in intracranial extra-axial cavernous hemangiomas

OBJECTIVE

Extra-axial cavernous hemangiomas (ECHs) are sporadic and rare intracranial occupational lesions that usually occur within the cavernous sinus. The aetiology of ECHs remains unknown.

METHODS

Whole-exome sequencing was performed on ECH lesions from 12 patients (discovery cohort) and droplet digital polymerase-chain-reaction (ddPCR) was used to confirm the identified mutation in 46 additional cases (validation cohort). Laser capture microdissection (LCM) was carried out to capture and characterise subgroups of tissue cells. Mechanistic and functional investigations were carried out in human umbilical vein endothelial cells and a newly established mouse model.

RESULTS

We detected somatic GJA4 mutation (c.121G>T, p.G41C) in 5/12 patients with ECH in the discovery cohort and confirmed the finding in the validation cohort (16/46). LCM followed by ddPCR revealed that the mutation was enriched in lesional endothelium. In vitro experiments in endothelial cells demonstrated that the GJA4 mutation activated SGK-1 signalling that in turn upregulated key genes involved in cell hyperproliferation and the loss of arterial specification. Compared with wild-type littermates, mice overexpressing the GJA4 mutation developed ECH-like pathological morphological characteristics (dilated venous lumen and elevated vascular density) in the retinal superficial vascular plexus at the postnatal 3 weeks, which were reversed by an SGK1 inhibitor, EMD638683.

CONCLUSIONS

We identified a somatic GJA4 mutation that presents in over one-third of ECH lesions and proposed that ECHs are vascular malformations due to GJA4-induced activation of the SGK1 signalling pathway in brain endothelial cells.

The role of blood flow in vessel remodeling and its regulatory mechanism during developmental angiogenesis

Vessel remodeling is essential for a functional and mature vascular network. According to the difference in endothelial cell (EC) behavior, we classified vessel remodeling into vessel pruning, vessel regression and vessel fusion. Vessel remodeling has been proven in various organs and species, such as the brain vasculature, subintestinal veins (SIVs), and caudal vein (CV) in zebrafish and yolk sac vessels, retina, and hyaloid vessels in mice. ECs and periendothelial cells (such as pericytes and astrocytes) contribute to vessel remodeling. EC junction remodeling and actin cytoskeleton dynamic rearrangement are indispensable for vessel pruning. More importantly, blood flow has a vital role in vessel remodeling. In recent studies, several mechanosensors, such as integrins, platelet endothelial cell adhesion molecule-1 (PECAM-1)/vascular endothelial cell (VE-cadherin)/vascular endothelial growth factor receptor 2 (VEGFR2) complex, and notch1, have been shown to contribute to mechanotransduction and vessel remodeling. In this review, we highlight the current knowledge of vessel remodeling in mouse and zebrafish models. We further underline the contribution of cellular behavior and periendothelial cells to vessel remodeling. Finally, we discuss the mechanosensory complex in ECs and the molecular mechanisms responsible for vessel remodeling.

Intracameral Injection of AAV-DJ.COMP-ANG1 Reduces the IOP of Mice by Reshaping the Trabecular Outflow Pathway

Purpose

The angiopoietin-1 (ANG1)-TIE signaling pathway orchestrates the development and maintenance of the Schlemm's canal (SC). In this study, we investigated the impact of adeno-associated virus (AAV)-mediated gene therapy with cartilage oligomeric matrix protein-ANG1 (COMP-ANG1) on trabecular outflow pathway.

Methods

Different serotypes of AAVs were compared for transduction specificity and efficiency in the anterior segment. The selected AAVs encoding COMP-ANG1 or ZsGreen1 (control) were delivered into the anterior chambers of wild-type C57BL/6J mice. The IOP and ocular surface were monitored regularly. Ocular perfusion was performed to measure the outflow facility and label flow patterns of the trabecular drainage pathway. Structural features of SC as well as limbal, retinal, and skin vessels were visualized by immunostaining. Ultrastructural changes in the SC and trabecular meshwork were observed under transmission electron microscopy.

Results

AAV-DJ could effectively infect the anterior segment. Intracameral injection of AAV-DJ.COMP-ANG1 lowered IOP in wild-type C57BL/6J mice. No signs of inflammation or angiogenesis were noticed. Four weeks after AAV injection, the conventional outflow facility and effective filtration area were increased significantly (P = 0.005 and P = 0.04, respectively). Consistently, the area of the SC was enlarged (P < 0.001) with increased density of giant vacuoles in the inner wall (P = 0.006). In addition, the SC endothelia lay on a more discontinuous basement membrane (P = 0.046) and a more porous juxtacanalicular tissue (P = 0.005) in the COMP-ANG1 group.

Conclusions

Intracamerally injected AAV-DJ.COMP-ANG1 offers a significant IOP-lowering effect by remodeling the trabecular outflow pathway of mouse eyes.

Shear stress switches the association of endothelial enhancers from ETV/ETS to KLF transcription factor binding sites

Endothelial cells (ECs) lining blood vessels are exposed to mechanical forces, such as shear stress. These forces control many aspects of EC biology, including vascular tone, cell migration and proliferation. Despite a good understanding of the genes responding to shear stress, our insight into the transcriptional regulation of these genes is much more limited. Here, we set out to study alterations in the chromatin landscape of human umbilical vein endothelial cells (HUVEC) exposed to laminar shear stress. To do so, we performed ChIP-Seq for H3K27 acetylation, indicative of active enhancer elements and ATAC-Seq to mark regions of open chromatin in addition to RNA-Seq on HUVEC exposed to 6 h of laminar shear stress. Our results show a correlation of gained and lost enhancers with up and downregulated genes, respectively. DNA motif analysis revealed an over-representation of KLF transcription factor (TF) binding sites in gained enhancers, while lost enhancers contained more ETV/ETS motifs. We validated a subset of flow responsive enhancers using luciferase-based reporter constructs and CRISPR-Cas9 mediated genome editing. Lastly, we characterized the shear stress response in ECs of zebrafish embryos using RNA-Seq. Our results lay the groundwork for the exploration of shear stress responsive elements in controlling EC biology.

Coalescent angiogenesis-evidence for a novel concept of vascular network maturation

Angiogenesis describes the formation of new blood vessels from pre-existing vascular structures. While the most studied mode of angiogenesis is vascular sprouting, specific conditions or organs favor intussusception, i.e., the division or splitting of an existing vessel, as preferential mode of new vessel formation. In the present study, sustained (33-h) intravital microscopy of the vasculature in the chick chorioallantoic membrane (CAM) led to the hypothesis of a novel non-sprouting mode for vessel generation, which we termed "coalescent angiogenesis." In this process, preferential flow pathways evolve from isotropic capillary meshes enclosing tissue islands. These preferential flow pathways progressively enlarge by coalescence of capillaries and elimination of internal tissue pillars, in a process that is the reverse of intussusception. Concomitantly, less perfused segments regress. In this way, an initially mesh-like capillary network is remodeled into a tree structure, while conserving vascular wall components and maintaining blood flow. Coalescent angiogenesis, thus, describes the remodeling of an initial, hemodynamically inefficient mesh structure, into a hierarchical tree structure that provides efficient convective transport, allowing for the rapid expansion of the vasculature with maintained blood supply and function during development.

Newborns of Mothers with Venous Disease during Pregnancy Show Increased Levels of Lipid Peroxidation and Markers of Oxidative Stress and Hypoxia in the Umbilical Cord

Chronic venous disease (CVD) encompasses a set of disorders of the venous system that have a high prevalence in Western societies and are associated with significant sociohealth costs. Pregnancy is a period in which different hormonal and haemodynamic changes occur that lead to significant changes in the cardiovascular system, increasing the risk of developing venous problems, especially during the third trimester of gestation. In turn, CVD involves a series of local and systemic alterations that can have negative repercussions in pregnancy. In this context, the role of oxidative stress in the pathophysiology of this condition has been shown to significantly affect other vascular structures during pregnancy, such as the placenta. However, the effects of oxidative stress on the umbilical cord in women with CVD have not yet been fully elucidated. Thus, the objective of this study was to analyse the gene and protein expression of the enzymes NOX-1, NOX-2 and iNOS, which are involved in the production of reactive oxygen and nitrogen species, respectively. Similarly, the presence of hypoxia-inducible factor 1-alpha (HIF-1α) in the umbilical cord in women with CVD was compared to that of pregnant control women, and the levels of the lipid peroxidation marker malonyldialdehyde (MDA) in cord tissue and blood was also analysed. Our results support a significant increase in the enzymes NOX-1, NOX-2 and iNOS and HIF-1α and MDA in the umbilical cord tissue and blood of women with CVD. For the first time, our work demonstrates an increase in oxidative stress and cellular damage in the umbilical cords of pregnant women who develop this condition, deepening the understanding of the consequences of CVD during pregnancy.