New Technologies With Increased Precision Improve Understanding of Endothelial Cell Heterogeneity in Cardiovascular Health and Disease

Vascular endothelial cell morphology and alignment regulate VEGF-induced endothelial nitric oxide synthase activation

Nitric oxide (NO) production by endothelial nitric oxide synthase (eNOS) inhibits platelet and leukocyte adhesion while promoting vasorelaxation in smooth muscle cells. Dysfunctional regulation of eNOS is a hallmark of various vascular pathologies, notably atherosclerosis, often associated with areas of low shear stress on endothelial cells (ECs). While the link between EC morphology and local hemodynamics is acknowledged, the specific impact of EC morphology on eNOS regulation remains unclear. Morphological differences between elongated, aligned ECs and polygonal, randomly oriented ECs correspond to variations in focal adhesion and cytoskeletal organization, suggesting differing levels of cytoskeletal prestress. However, the functional outcomes of cytoskeletal prestress, particularly in the absence of shear stress, are not extensively studied in ECs. Some evidence suggests that elongated ECs exhibit decreased immunogenicity and enhanced NO production. This study aims to elucidate the signaling pathways governing VEGF-stimulated eNOS regulation in the aligned EC phenotype characterized by elongated and aligned cells within a monolayer. Using anisotropic topographic cues, bovine aortic endothelial cells (BAECs) were elongated and aligned, followed by VEGF treatment in the presence or absence of cytoskeletal tension inhibitors. Phosphorylation of eNOS ser1179, AKT ser437 and FAK Tyr397 in response to VEGF challenge were significantly heightened in aligned ECs compared to unaligned ECs. Moreover this response proved to be robustly tied to cytoskeletal tension as evinced by the abrogation of responses in the presence of the myosin II ATPase inhibitor, blebbistatin. Notably, this work demonstrates for the first time the reliance on FAK phosphorylation in VEGF-mediated eNOS activation and the comparatively greater contribution of the cytoskeletal machinery in propagating VEGF-eNOS signaling in aligned and elongated ECs. This research underscores the importance of utilizing appropriate vascular models in drug development and sheds light on potential mechanisms underlying vascular function and pathology that can help inform vascular graft design.

FOXO1 stimulates tip cell-enriched gene expression in endothelial cells

Forkhead box O (FOXO) family proteins are expressed in various cells, and play crucial roles in cellular metabolism, apoptosis, and aging. FOXO1-null mice exhibit embryonic lethality due to impaired endothelial cell (EC) maturation and vascular remodeling. However, FOXO1-mediated genome-wide regulation in ECs remains unclear. Here, we demonstrate that VEGF dynamically regulates FOXO1 cytosol-nucleus translocation. FOXO1 re-localizes to the nucleus via PP2A phosphatase. RNA-seq combined with FOXO1 overexpression/knockdown in ECs demonstrated that FOXO1 governs the VEGF-responsive tip cell-enriched genes, and further inhibits DLL4-NOTCH signaling. Endogenous FOXO1 ChIP-seq revealed that FOXO1 binds to the EC-unique tip-enriched genes with co-enrichment of EC master regulators, and the condensed chromatin region as a pioneer factor. We identified new promoter/enhancer regions of the VEGF-responsive tip cell genes regulated by FOXO1: ESM1 and ANGPT2. This is the first study to identify cell type-specific FOXO1 functions, including VEGF-mediated tip cell definition in primary cultured ECs.

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.

Pregnancy as a susceptible state for thrombotic microangiopathies

Pregnancy and the postpartum period represent phases of heightened vulnerability to thrombotic microangiopathies (TMAs), as evidenced by distinct patterns of pregnancy-specific TMAs (e.g., preeclampsia, HELLP syndrome), as well as a higher incidence of nonspecific TMAs, such as thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, during pregnancy. Significant strides have been taken in understanding the underlying mechanisms of these disorders in the past 40 years. This progress has involved the identification of pivotal factors contributing to TMAs, such as the complement system, ADAMTS13, and the soluble VEGF receptor Flt1. Regardless of the specific causal factor (which is not generally unique in relation to the usual multifactorial origin of TMAs), the endothelial cell stands as a central player in the pathophysiology of TMAs. Pregnancy has a major impact on the physiology of the endothelium. Besides to the development of placenta and its vascular consequences, pregnancy modifies the characteristics of the women's microvascular endothelium and tends to render it more prone to thrombosis. This review aims to delineate the distinct features of pregnancy-related TMAs and explore the contributing mechanisms that lead to this increased susceptibility, particularly influenced by the "gravid endothelium." Furthermore, we will discuss the potential contribution of histopathological studies in facilitating the etiological diagnosis of pregnancy-related TMAs.

Transcriptome Analysis of Choroidal Endothelium Links Androgen Receptor Role to Central Serous Chorioretinopathy

BACKGROUND

Central Serous Chorioretinopathy (CSCR) manifests as fluid accumulation between the neurosensory retina and the retinal pigment epithelium (RPE). Elevated levels of steroid hormones have been implicated in CSCR pathogenesis. This investigation aims to delineate the gene expression patterns of CSCR-associated risk and steroid receptors across human choroidal cell types and RPE cells to discern potential underlying mechanisms.

METHODS

This study utilized a comprehensive query of transcriptomic data derived from non-pathological human choroid and RPE cells.

FINDINGS

CSCR-associated genes such as PTPRB, CFH, and others are predominantly expressed in the choroidal endothelium as opposed to the RPE. The androgen receptor, encoded by the AR gene, demonstrates heightened expression in the macular endothelium compared to peripheral regions, unlike other steroid receptor genes. AR-expressing endothelial cells display an augmented responsiveness to Transforming growth factor beta (TGF-β), indicating a propensity towards endothelial to mesenchymal transition (endMT) transcriptional profiling.

INTERPRETATION

These results highlight the proclivity of CSCR to manifest primarily within the choroidal vasculature rather than the RPE, suggesting its categorization as a vascular eye disorder. This study accentuates the pivotal role of androgenic steroids, in addition to glucocorticoids. The observed linkage to TGF-β-mediated endMT provides a potential mechanistic insight into the disease's etiology.

Human placental vascular and perivascular cell heterogeneity differs between first trimester and term, and in pregnancies affected by foetal growth restriction

Growth-restricted placentae have a reduced vascular network, impairing exchange of nutrients and oxygen. However, little is known about the differentiation events and cell types that underpin normal/abnormal placental vascular formation and function. Here, we used 23-colour flow cytometry to characterize placental vascular/perivascular populations between first trimester and term, and in foetal growth restriction (FGR). First-trimester endothelial cells had an immature phenotype (CD144+/lowCD36-CD146low), while term endothelial cells expressed mature endothelial markers (CD36+CD146+). At term, a distinct population of CD31low endothelial cells co-expressed mesenchymal markers (CD90, CD26), indicating a capacity for endothelial to mesenchymal transition (EndMT). In FGR, compared with normal pregnancies, endothelial cells constituted 3-fold fewer villous core cells (P < 0.05), contributing to an increased perivascular: endothelial cell ratio (2.6-fold, P < 0.05). This suggests that abnormal EndMT may play a role in FGR. First-trimester endothelial cells underwent EndMT in culture, losing endothelial (CD31, CD34, CD144) and gaining mesenchymal (CD90, CD26) marker expression. Together this highlights how differences in villous core cell heterogeneity and phenotype may contribute to FGR pathophysiology across gestation.

Integrative single-cell meta-analysis reveals disease-relevant vascular cell states and markers in human atherosclerosis

Coronary artery disease (CAD) is characterized by atherosclerotic plaque formation in the arterial wall. CAD progression involves complex interactions and phenotypic plasticity among vascular and immune cell lineages. Single-cell RNA-seq (scRNA-seq) studies have highlighted lineage-specific transcriptomic signatures, but human cell phenotypes remain controversial. Here, we perform an integrated meta-analysis of 22 scRNA-seq libraries to generate a comprehensive map of human atherosclerosis with 118,578 cells. Besides characterizing granular cell-type diversity and communication, we leverage this atlas to provide insights into smooth muscle cell (SMC) modulation. We integrate genome-wide association study data and uncover a critical role for modulated SMC phenotypes in CAD, myocardial infarction, and coronary calcification. Finally, we identify fibromyocyte/fibrochondrogenic SMC markers (LTBP1 and CRTAC1) as proxies of atherosclerosis progression and validate these through omics and spatial imaging analyses. Altogether, we create a unified atlas of human atherosclerosis informing cell state-specific mechanistic and translational studies of cardiovascular diseases.

Decellularised spinal cord matrix manipulates glial niche into repairing phase via serglycin-mediated signalling pathway

Astrocytes are the most abundant and widespread glial cells in the central nervous system. The heterogeneity of astrocytes plays an essential role in spinal cord injury (SCI) repair. Decellularised spinal cord matrix (DSCM) is advantageous for repairing SCI, but little is known regarding the exact mechanisms and niche alterations. Here, we investigated the DSCM regulatory mechanism of glial niche in the neuro-glial-vascular unit using single-cell RNA sequencing. Our single cell sequencing, molecular and biochemical experiments validated that DSCM facilitated the differentiation of neural progenitor cells through increasing the number of immature astrocytes. Upregulation of mesenchyme-related genes, which maintained astrocyte immaturity, causing insensitivity to inflammatory stimuli. Subsequently, we identified serglycin (SRGN) as a functional component of DSCM, which involves inducing CD44-AKT signalling to trigger human spinal cord-derived primary astrocytes (hspASCs) proliferation and upregulation of genes related to epithelial-mesenchymal transition, thus impeding astrocyte maturation. Finally, we verified that SRGN-COLI and DSCM had similar functions in the human primary cell co-culture system to mimic the glia niche. In conclusion, our work revealed that DSCM reverted astrocyte maturation and altered the glia niche into the repairing phase through the SRGN-mediated signalling pathway.

Single-cell RNA sequencing to identify cellular heterogeneity and targets in cardiovascular diseases: from bench to bedside

The mechanisms of cardiovascular diseases (CVDs) remain incompletely elucidated. Single-cell RNA sequencing (scRNA-seq) has enabled the profiling of single-cell transcriptomes at unprecedented resolution and throughput, which is critical for deciphering cardiovascular cellular heterogeneity and underlying disease mechanisms, thereby facilitating the development of therapeutic strategies. In this review, we summarize cellular heterogeneity in cardiovascular homeostasis and diseases as well as the discovery of potential disease targets based on scRNA-seq, and yield new insights into the promise of scRNA-seq technology in precision medicine and clinical application.

Targeting endothelial tight junctions to predict and protect thoracic aortic aneurysm and dissection

AIMS

Whether changes in endothelial tight junctions (TJs) lead to the formation of thoracic aortic aneurysm and dissection (TAAD) and serve as an early indicator and therapeutic target remains elusive.

METHODS AND RESULTS

Single-cell RNA sequencing analysis showed aberrant endothelial TJ expressions in the thoracic aortas of patients with TAAD. In a β-aminopropionitrile (BAPN)-induced TAAD mouse model, endothelial TJ function was disrupted in the thoracic aortas at an early stage (5 and 10 days) as observed by a vascular permeability assay, while the intercellular distribution of crucial TJ components was significantly decreased by en face staining. For the non-invasive detection of endothelial TJ function, two dextrans of molecular weights 4 and 70 kDa were conjugated with the magnetic resonance imaging (MRI) contrast agent Gd-DOTA to synthesize FITC-dextran-DOTA-Gd and rhodamine B-dextran-DOTA-Gd. MRI images showed that both probes accumulated in the thoracic aortas of the BAPN-fed mice. Particularly, the mice with increased accumulated signals from 5 to 10 days developed TAAD at 14 days, whereas the mice with similar signals between the two time points did not. Furthermore, the protease-activated receptor 2 inhibitor AT-1001, which seals TJs, alleviated the BAPN-induced impairment of endothelial TJ function and expression and subsequently reduced TAAD incidence. Notably, endothelial-targeted ZO-1 conditional knockout increased TAAD incidence. Mechanistically, vascular inflammation and edema were observed in the thoracic aortas of the BAPN-fed mice, whereas these phenomena were attenuated by AT-1001.

CONCLUSION

The disruption of endothelial TJ function is an early event prior to TAAD formation, herein serving as a potential indicator and a promising target for TAAD.

The Role of Endothelial Cells in the Onset, Development and Modulation of Vein Graft Disease

Endothelial cells comprise the intimal layer of the vasculature, playing a crucial role in facilitating and regulating aspects such nutrient transport, vascular homeostasis, and inflammatory response. Given the importance of these cells in maintaining a healthy haemodynamic environment, dysfunction of the endothelium is central to a host of vascular diseases and is a key predictor of cardiovascular risk. Of note, endothelial dysfunction is believed to be a key driver for vein graft disease-a pathology in which vein grafts utilised in coronary artery bypass graft surgery develop intimal hyperplasia and accelerated atherosclerosis, resulting in poor long-term patency rates. Activation and denudation of the endothelium following surgical trauma and implantation of the graft encourage a host of immune, inflammatory, and cellular differentiation responses that risk driving the graft to failure. This review aims to provide an overview of the current working knowledge regarding the role of endothelial cells in the onset, development, and modulation of vein graft disease, as well as addressing current surgical and medical management approaches which aim to beneficially modulate endothelial function and improve patient outcomes.

Single‐cell transcriptional profiling of human carotid plaques reveals a subpopulation of endothelial cells associated with stroke incidences

The differences in plaque histology between symptomatic and asymptomatic patients have been widely accepted. Whether there is a heterogeneity of cells between symptomatic and asymptomatic plaques remains largely unclear. To reveal the potential heterogeneity within different plaques, which may contribute to different stroke incidences, we obtained the scRNA‐seq data from symptomatic and asymptomatic patients and identified eight cell types present in plaques. Further analysis of endothelial cells (ECs) revealed three distinct EC subpopulations appeared to be endowed with specific biological functions such as antigen processing and presentation, cell adhesion, and smooth muscle cell proliferation. Of note, the differentially expressed genes of the EC 2 subpopulation showed that the genes involved in cell adhesion were up‐regulated in asymptomatic plaques compared to symptomatic plaques. Integrating the data of intraplaque haemorrhage and plaque stability, the 5th top‐enriched biological process was cell adhesion in the stable or non‐haemorrhaged plaques compared to unstable plaques or haemorrhaged plaques. Among these cell adhesion‐related genes, the intersection gene AOC3 may play a vital role in plaque haemorrhage and plaque stability. Targeting cell adhesion and the specialized genes may provide potential new therapeutic directions to prevent asymptomatic patients from stroke.

Endothelial Dysfunction in the Pathogenesis of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA), defined as a focal dilation of the abdominal aorta beyond 50% of its normal diameter, is a common and potentially life-threatening vascular disease. The molecular and cellular mechanisms underlying AAA pathogenesis remain unclear. Healthy endothelial cells (ECs) play a critical role in maintaining vascular homeostasis by regulating vascular tone and maintaining an anti-inflammatory, anti-thrombotic local environment. Increasing evidence indicates that endothelial dysfunction is an early pathologic event in AAA formation, contributing to both oxidative stress and inflammation in the degenerating arterial wall. Recent studies utilizing single-cell RNA sequencing revealed heterogeneous EC sub-populations, as determined by their transcriptional profiles, in aortic aneurysm tissue. This review summarizes recent findings, including clinical evidence of endothelial dysfunction in AAA, the impact of biomechanical stress on EC in AAA, the role of endothelial nitric oxide synthase (eNOS) uncoupling in AAA, and EC heterogeneity in AAA. These studies help to improve our understanding of AAA pathogenesis and ultimately may lead to the generation of EC-targeted therapeutics to treat or prevent this deadly disease.