BACKGROUND:Vascular diseases are accompanied by alterations in cellular phenotypes which underlie disease pathogenesis, with single-cell technologies aiding in the discovery of cellular heterogeneity among endothelial cell (EC) and vascular smooth muscle cell (VSMC) populations. In atherosclerotic disease, VSMCs are hypothesized to transition between contractile and synthetic states; however, the specific vascular subpopulations and intermediate cell states responsible for early vascular dysfunction remain unclear. METHODS:We integrated newly generated and published single-nuclear RNA-sequencing (snRNA-seq) datasets to analyze normal (n = 7), aneurysmal (n = 9), and atherosclerotic (n = 2) flash-frozen human ascending thoracic aortas. Cell types and subtypes were defined using both top marker genes and canonical gene markers. Disease enrichment and relevant cell types were identified using newly developed computational tools to integrate GWAS data from multiple vascular disease-relevant studies with the single nuclei aortic expression profiles. RESULTS:Nuclear dissociation and snRNA-seq identified ten distinct transcriptomic clusters from the integrated analysis representing all major vascular cell populations. Three distinct VSMC populations emerged that exhibited differential expression of extracellular matrix, contractile and pro-proliferative genes. Aneurysmal specimens were enriched for one fibroblast and one VSMC subpopulation compared to healthy tissue. RNA-trajectory analysis inferred a phenotypic continuum of gene expression between VSMC A and VSMC B or C and between two of the identified fibroblast types. VSMCs and Fibroblast C exhibited the greatest cell type-specific enrichment of genes mapped to GWAS loci for coronary artery disease (CAD), blood pressure, and migraine. Cell type-specific enrichment scores were more robust among the transcriptional profiles from non-diseased vascular tissue. CONCLUSIONS:Our use of single-cell isolation and new computational methods prioritizes the cell types that most contribute to vascular disease pathogenesis. Specifically, tissue dissociation and single-nuclear transcriptomics better represent all vascular cell types, from which we demonstrate enrichment of pro-proliferative VSMCs in TAA and further implicate phenotypic switching as a likely pathologic mechanism. Integrated analysis of cell-specific gene expression and vascular disease GWAS data implicate genes and pathways associated with fibroblast and VSMC cell-state transitions.

The discovery of genetic loci associated with complex diseases has outpaced the elucidation of mechanisms of disease pathogenesis. Here we conducted a genome-wide association study (GWAS) for coronary artery disease (CAD) comprising 181,522 cases among 1,165,690 participants of predominantly European ancestry. We detected 241 associations, including 30 new loci. Cross-ancestry meta-analysis with a Japanese GWAS yielded 38 additional new loci. We prioritized likely causal variants using functionally informed fine-mapping, yielding 42 associations with less than five variants in the 95% credible set. Similarity-based clustering suggested roles for early developmental processes, cell cycle signaling and vascular cell migration and proliferation in the pathogenesis of CAD. We prioritized 220 candidate causal genes, combining eight complementary approaches, including 123 supported by three or more approaches. Using CRISPR-Cas9, we experimentally validated the effect of an enhancer in MYO9B, which appears to mediate CAD risk by regulating vascular cell motility. Our analysis identifies and systematically characterizes >250 risk loci for CAD to inform experimental interrogation of putative causal mechanisms for CAD.

Introduction: Phenotypic switching of vascular cells is a complex process associated with vascular disorders, including thoracic aortic aneurysm (TAA). Vascular smooth muscle cells (VSMCs) appear to switch from a contractile to synthetic phenotype in TAA. Single nuclear RNA-seq (snRNA-seq) of normal human and TAA aortas may be used to characterize cell heterogeneity of normal aortas, population shifts in disease, and the transcriptional profile of VSMC phenotypic switching. Hypothesis: snRNA-seq of normal and TAA aortas will identify the cell heterogeneity and transcriptional profiles of TAA. Methods: We performed snRNA-seq of 5 aortas from 2 normal and 3 TAA patients. We used a 10X-CellBender pipeline for profiling and analysis. Results: snRNA-seq identified 6 major cell types. The majority were VSMCs, exhibiting 4 sub-populations in all specimens (a). Cell distribution comparisons showed VSMC1 (ELN, PKD1, FLNA high) and VSMC2 (PRKG1, PDE3A, PCDH7 high) to be differentially-enriched in controls and TAA samples, respectively (b,c). Gene set and trajectory analyses confirmed prior observations of phenotypic switching (d,e). Genes associated with switching in VSMCs included TAA genes (PRKG1, PKD1, FLNA) with concordance of expression and putative function of Mendelian variants (i-k). Cell junction and regulation of muscle contraction pathways drove trajectory. We further assessed cell-type heritability of vascular GWAS variants (h). These gene sets were differentially-regulated between control and TAA. The strongest association was between VSMC2 and ascending aortic size (h). Conclusions: In this study, we demonstrated a dissociation bias-free method for snRNA-Seq of human vasculature. We confirmed enrichment of synthetic VSMCs in TAA and implicate phenotypic switching as a pathologic mechanism. Our study identifies a cell type-specific transcriptional profile of aortopathy genes, which may drive TAA and represent therapeutic targets.

Pathologic immune hyperactivation is emerging as a key feature of critical illness in COVID-19, but the mechanisms involved remain poorly understood. We carried out proteomic profiling of plasma from cross-sectional and longitudinal cohorts of hospitalized patients with COVID-19 and analyzed clinical data from our health system database of over 3,300 patients. Using a machine learning algorithm, we identified a prominent signature of neutrophil activation, including resistin, lipocalin-2, HGF, IL-8, and G-CSF, as the strongest predictors of critical illness. Neutrophil activation was present on the first day of hospitalization in patients who would only later require transfer to the intensive care unit, thus preceding the onset of critical illness and predicting increased mortality. In the health system database, early elevations in developing and mature neutrophil counts also predicted higher mortality rates. Altogether, we define an essential role for neutrophil activation in the pathogenesis of severe COVID-19 and identify molecular neutrophil markers that distinguish patients at risk of future clinical decompensation.

COVID-19, which is caused by SARS-CoV-2, can result in acute respiratory distress syndrome and multiple organ failure1–4, but little is known about its pathophysiology. Here we generated single-cell atlases of 24 lung, 16 kidney, 16 liver and 19 heart autopsy tissue samples and spatial atlases of 14 lung samples from donors who died of COVID-19. Integrated computational analysis uncovered substantial remodelling in the lung epithelial, immune and stromal compartments, with evidence of multiple paths of failed tissue regeneration, including defective alveolar type 2 differentiation and expansion of fibroblasts and putative TP63+ intrapulmonary basal-like progenitor cells. Viral RNAs were enriched in mononuclear phagocytic and endothelial lung cells, which induced specific host programs. Spatial analysis in lung distinguished inflammatory host responses in lung regions with and without viral RNA. Analysis of the other tissue atlases showed transcriptional alterations in multiple cell types in heart tissue from donors with COVID-19, and mapped cell types and genes implicated with disease severity based on COVID-19 genome-wide association studies. Our foundational dataset elucidates the biological effect of severe SARS-CoV-2 infection across the body, a key step towards new treatments. Single-cell analysis of lung, heart, kidney and liver autopsy samples shows the molecular and cellular changes and immune response resulting from severe COVID-19 infection.

Genome editing of primary human cells with CRISPR-Cas9 is a powerful tool to study gene function. For many cell types, there are efficient protocols for editing with optimized plasmids for Cas9 and sgRNA expression. Vascular cells, however, remain refractory to plasmid-based delivery of CRISPR machinery for in vitro genome editing due to low transfection efficiency, poor expression of the Cas9 machinery, and toxic effects of the selection antibiotics. Here, we describe a method for high-efficiency editing of primary human vascular cells in vitro using nucleofection for direct delivery of sgRNA:Cas9-NLS ribonucleoprotein complexes. This method is more rapid and its high editing efficiency eliminates the need for additional selection steps. The edited cells can be employed in diverse applications, such as gene expression measurement or functional assays to assess various genetic perturbation effects in vitro. This method proves effective in vascular cells that are refractory to standard genome manipulation techniques using viral plasmid delivery. We anticipate that this technique will be applied to other non-vascular cell types that face similar barriers to efficient genome editing. © 2021 Wiley Periodicals LLC. Basic Protocol: CRISPR-Cas9 genome editing of primary human vascular cells in vitro.

Introduction: Multiple lines of evidence support the causal role of serum lipoprotein (a) [Lp(a)] in the pathogenesis of cardiovascular disease, including CAD/MI and ischemic stroke. Mendelian randomization studies demonstrate that genetic variation is the principal determinant of serum Lp(a) level, and that variants associated with higher Lp(a) are associated with higher vascular disease risk. Though 80-90% of variation in serum Lp(a) levels is genetically-determined, single nucleotide polymorphisms (SNPs) contribute a small fraction of this risk. SNPs, however, may be used to identify LPA alleles based on a reference panel. These LPA alleles are the primary genetic determinants of serum Lp(a). New methods that identify these alleles using extended SNP haplotypes may improve serum Lp(a) prediction and identify at-risk patients. Hypothesis: The use of reference panels of extended LPA haplotypes can identify patients with elevated Lp(a) in a genotyped, hospital-based cohort. Methods & Results: We identified all genotyped subjects in the Massachusetts General Brigham Biobank with a history of CAD or ischemic stroke for genetic prediction of serum Lp(a) (n = 3202). The majority of these patients (n = 2578, 80.5%) did not have a prior Lp(a) measurement as part of clinical care. We computed genetic predictions of Lp(a) in all patients by matching their SNP haplotypes to a reference panel of ~50,000 UK Biobank participants (and ~440,000 haplotypes) for whom LPA alleles had been matched to Lp(a) levels. The 90th percentile, 258 patients, had predicted Lp(a) of >75mg/dl (~159nM), equal to the 90th percentile of the general population. We observed strong correlation between predicted and clinically-measured Lp(a) (R2 = 0.75-0.92 across four clinical assays; p<0.0001 for all; n = 372). Conclusions: We demonstrate the validity of a serum Lp(a) genetic prediction with very high fidelity in a disease cohort using a new method of imputed SNP haplotypes. Using LPA alleles, as determined by SNPs, we identified patients who are likely to have elevated serum Lp(a) without a prior measurement. This method may be applied to biobank populations to identify patients at risk for cardiovascular disease mediated by elevated serum Lp(a).

Background Myocardial injury in patients with COVID‐19 is associated with increased mortality during index hospitalization; however, the relationship to long‐term sequelae of SARS‐CoV‐2 is unknown. This study assessed the relationship between myocardial injury (high‐sensitivity cardiac troponin T level) during index hospitalization for COVID‐19 and longer‐term outcomes. Methods and Results This is a prospective cohort of patients who were hospitalized at a single center between March and May 2020 with SARS‐CoV‐2. Cardiac biomarkers were systematically collected. Outcomes were adjudicated and stratified on the basis of myocardial injury. The study cohort includes 483 patients who had high‐sensitivity cardiac troponin T data during their index hospitalization. During index hospitalization, 91 (18.8%) died, 70 (14.4%) had thrombotic complications, and 126 (25.6%) had cardiovascular complications. By 12 months, 107 (22.2%) died. During index hospitalization, 301 (62.3%) had cardiac injury (high‐sensitivity cardiac troponin T≧14 ng/L); these patients had 28.6%, 32.2%, and 33.2% mortality during index hospitalization, at 6 months, and at 12 months, respectively, compared with 4.1%, 4.9%, and 4.9% mortality for those with low‐level positive troponin and 0%, 0%, and 0% for those with undetectable troponin. Of 392 (81.2%) patients who survived the index hospitalization, 94 (24%) had at least 1 readmission within 12 months, of whom 61 (65%) had myocardial injury during the index hospitalization. Of 377 (96%) patients who were alive and had follow‐up after the index hospitalization, 211 (56%) patients had a documented, detailed clinical assessment at 6 months. A total of 78 of 211 (37.0%) had ongoing COVID‐19–related symptoms; 34 of 211 (16.1%) had neurocognitive decline, 8 of 211 (3.8%) had increased supplemental oxygen requirements, and 42 of 211 (19.9%) had worsening functional status. Conclusions Myocardial injury during index hospitalization for COVID‐19 was associated with increased mortality and may predict who are more likely to have postacute sequelae of COVID‐19. Among patients who survived their index hospitalization, the incremental mortality through 12 months was low, even among troponin‐positive patients.

Introduction: Thoracic aortic aneurysms (TAAs) are common diseases associated with high morbidity and mortality. Although TAAs are more common in men, women have worse outcomes and dissect at smaller aortic diameters. Endothelin-1 (ET-1) is the most potent vasoconstrictor in humans, and an important mediator of vascular stiffness and tone. ET-1 levels are increased in patients with TAA, and genetic variants that affect ET-1 production and receptor expression are associated with vascular diseases. Though ET-1 levels do not differ between men and women with TAA, it is unknown if response to ET-1 mediates sex-specific differences. Hypothesis: ET-1 has different effects on vascular stiffness and aortic dissection risk in men and women. Methods: Angiotensin-II (AngII) was delivered subcutaneously at 1 ug/kg/min dose and rate using osmotic pumps for 28 days in endothelial cell-specific ET-1 transgenic (eET-1) and matched WT control mice. We measured blood pressure, aortic stiffness, and aortic size at the end of the study. Results: We observed marked sex-specific ET-1 effects on TAA. Despite elevated blood pressure in all animals that received AngII (Fig1A), we observed increased aortic stiffness in male eET-1 mice (+1.5 m/s eET-1 vs. +0.74 m/s WT) but decreased aortic stiffness in female eET-1 mice (-1.9 m/s eET-1 vs. +0.69 m/s WT), measured by pulse wave velocity (Fig1B). Consistent with these results, aortic diameter was only increased in male eET-1 mice (+0.61 mm eET-1 vs. +0.11 mm WT) but not in female eET-1 mice (+0.06 mm eET-1 vs. +0.11 mm WT) (Fig1C). Significantly, 2 of 3 male eET-1 animals died before 28 days from dissected TAAs, whereas all females survived the length of the study. Conclusions: In the AngII-TAA model, there is a sex dimorphic effect of ET-1 overexpression. Male mice have greater vascular stiffness and develop TAA in response to the same level of ET-1 as in matched female mice. This difference may explain the increased incidence of TAA in men.

The SARS-CoV-2 pandemic has caused over 1 million deaths globally, mostly due to acute lung injury and acute respiratory distress syndrome, or direct complications resulting in multiple-organ failures. Little is known about the host tissue immune and cellular responses associated with COVID-19 infection, symptoms, and lethality. To address this, we collected tissues from 11 organs during the clinical autopsy of 17 individuals who succumbed to COVID-19, resulting in a tissue bank of approximately 420 specimens. We generated comprehensive cellular maps capturing COVID-19 biology related to patients' demise through single-cell and single-nucleus RNA-Seq of lung, kidney, liver and heart tissues, and further contextualized our findings through spatial RNA profiling of distinct lung regions. We developed a computational framework that incorporates removal of ambient RNA and automated cell type annotation to facilitate comparison with other healthy and diseased tissue atlases. In the lung, we uncovered significantly altered transcriptional programs within the epithelial, immune, and stromal compartments and cell intrinsic changes in multiple cell types relative to lung tissue from healthy controls. We observed evidence of: alveolar type 2 (AT2) differentiation replacing depleted alveolar type 1 (AT1) lung epithelial cells, as previously seen in fibrosis; a concomitant increase in myofibroblasts reflective of defective tissue repair; and, putative TP63+ intrapulmonary basal-like progenitor (IPBLP) cells, similar to cells identified in H1N1 influenza, that may serve as an emergency cellular reserve for severely damaged alveoli. Together, these findings suggest the activation and failure of multiple avenues for regeneration of the epithelium in these terminal lungs. SARS-CoV-2 RNA reads were enriched in lung mononuclear phagocytic cells and endothelial cells, and these cells expressed distinct host response transcriptional programs. We corroborated the compositional and transcriptional changes in lung tissue through spatial analysis of RNA profiles in situ and distinguished unique tissue host responses between regions with and without viral RNA, and in COVID-19 donor tissues relative to healthy lung. Finally, we analyzed genetic regions implicated in COVID-19 GWAS with transcriptomic data to implicate specific cell types and genes associated with disease severity. Overall, our COVID-19 cell atlas is a foundational dataset to better understand the biological impact of SARS-CoV-2 infection across the human body and empowers the identification of new therapeutic interventions and prevention strategies.

Purpose of Review Chronic thromboembolic pulmonary hypertension (CTEPH) is an uncommon complication of acute pulmonary embolism (PE), in which the red, platelet-rich thrombus does not resolve but forms into an organized yellow, fibrotic scar-like obstruction in the pulmonary vasculature. Here we review the pathobiology of CTEPH. Recent Findings Our current knowledge has predominantly been informed by studies of human samples and animal models that are inherently limited in their ability to recapitulate all aspects of the disease. These studies have identified alterations in platelet biology and inflammation in the formation of a scar-like thrombus that comprised endothelial cells, myofibroblasts, and immune cells, along with a small vessel pulmonary arterial hypertension-like vasculopathy. The development of CTEPH-specific therapies is currently hindered by a limited knowledge of its pathobiology. The development of new CTEPH medical therapies will require new insights into its pathobiology that bridge the gap from bench to bedside.

Background: Corin is a protease expressed in cardiomyocytes that plays a key role in salt handling and intravascular volume homeostasis via activation of natriuretic peptides. It is unknown if Corin loss-of-function (LOF) is causally associated with risk of coronary artery disease (CAD). Methods: We analyzed all coding CORIN variants in an Italian case-control study of CAD. We functionally tested all 64 rare missense mutations in Western Blot and Mass Spectroscopy assays for proatrial natriuretic peptide cleavage. An expanded rare variant association analysis for Corin LOF mutations was conducted in whole exome sequencing data from 37 799 CAD cases and 212 184 controls. Results: We observed LOF variants in CORIN in 8 of 1803 (0.4%) CAD cases versus 0 of 1725 controls ( P , 0.007). Of 64 rare missense variants profiled, 21 (33%) demonstrated <30% of wild-type activity and were deemed damaging in the 2 functional assays for Corin activity. In a rare variant association study that aggregated rare LOF and functionally validated damaging missense variants from the Italian study, we observed no association with CAD—21 of 1803 CAD cases versus 12 of 1725 controls with adjusted odds ratio of 1.61 ([95% CI, 0.79–3.29]; P =0.17). In the expanded sequencing dataset, there was no relationship between rare LOF variants with CAD was also observed (odds ratio, 1.15 [95% CI, 0.89–1.49]; P =0.30). Consistent with the genetic analysis, we observed no relationship between circulating Corin concentrations with incident CAD events among 4744 participants of a prospective cohort study—sex-stratified hazard ratio per SD increment of 0.96 ([95% CI, 0.87–1.07], P =0.48). Conclusions: Functional testing of missense mutations improved the accuracy of rare variant association analysis. Despite compelling pathophysiology and a preliminary observation suggesting association, we observed no relationship between rare damaging variants in CORIN or circulating Corin concentrations with risk of CAD.

Coronavirus disease-2019 (COVID-19), a contagious disease caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), has reached pandemic status. As it spreads across the world, it has overwhelmed health care systems, strangled the global economy, and led to a devastating loss of life. Widespread efforts from regulators, clinicians, and scientists are driving a rapid expansion of knowledge of the SARS-CoV-2 virus and COVID-19. The authors review the most current data, with a focus on the basic understanding of the mechanism(s) of disease and translation to the clinical syndrome and potential therapeutics. The authors discuss the basic virology, epidemiology, clinical manifestation, multiorgan consequences, and outcomes. With a focus on cardiovascular complications, they propose several mechanisms of injury. The virology and potential mechanism of injury form the basis for a discussion of potential disease-modifying therapies.

Coronavirus disease-2019 (COVID-19), a contagious disease caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), has reached pandemic status. As it spreads across the world, it has overwhelmed health care systems, strangled the global economy, and led to a devastating loss of life. Widespread efforts from regulators, clinicians, and scientists are driving a rapid expansion of knowledge of the SARS-CoV-2 virus and COVID-19. The authors review the most current data, with a focus on the basic understanding of the mechanism(s) of disease and translation to the clinical syndrome and potential therapeutics. The authors discuss the basic virology, epidemiology, clinical manifestation, multiorgan consequences, and outcomes. With a focus on cardiovascular complications, they propose several mechanisms of injury. The virology and potential mechanism of injury form the basis for a discussion of potential disease-modifying therapies.

Cardiac tamponade is a rare cause of shock in the medical intensive care unit. This paper describes the case of a focal cardiac tamponade caused by compression of the left atrium due to an esophageal stent. Echocardiography yielded a diagnosis when other diagnostic methods did not. (Level of Difficulty: Advanced.)

The original version of this Article contained errors in Figures 1, 3 and 4. In panels b and d of Figure 1, the labels ‘Sdc4-/-’ were inadvertently replaced by ‘Sdc4+/+‘. In panels c and d of Figure 3, the labels ‘Sdc4-/-’ were replaced by ‘Sdc2-/-’. In panel f of Figure 3, the labels ‘FGF2’ were replaced by ‘VEGFA165’. In panel e of Figure 6, a ‘Sdc2-/-‘ label was inadvertently included. This has now been corrected in the PDF and HTML versions of the Article.

A 47-year-old man presented to our hospital after a syncopal event and 1 week of progressive chest pain. His medical history was pertinent for cardiac synovial sarcoma, which had previously undergone subtotal resection. He was seen at an outside hospital, where electrocardiography exhibited ST-

A 70-year-old man presented to the emergency department with a 3-month history of diarrhea, without blood or mucus. He also noted nausea, nonbloody emesis, and weight loss.

Arteriovenous malformations occur when abnormalities of vascular patterning result in the flow of blood from arteries to veins without an intervening capillary bed. Recent work has revealed the importance of the Notch and TGF-β signaling pathways in vascular patterning. Specifically, Notch signaling has an increasingly apparent role in arterial specification and suppression of branching, whereas TGF-β is implicated in vascular smooth muscle development and remodeling under angiogenic stimuli. These physiologic roles, consequently, have implicated both pathways in the pathogenesis of arteriovenous malformation. In this review, we summarize the studies of endothelial signaling that contribute to arteriovenous malformation and the roles of genes implicated in their pathogenesis. We further discuss how endothelial signaling may contribute to vascular smooth muscle development and how knowledge of signaling pathways may provide us targets for medical therapy in these vascular lesions.