Circulating Von Willebrand factor and high molecular weight multimers as markers of endothelial injury predict COVID-19 in-hospital mortality

sST2 is a key outcome biomarker in COVID-19: insights from discovery randomized trial

We investigated whether baseline levels of biomarkers related to endotheliopathy, thromboinflammation, and fibrosis were associated with clinical outcomes in hospitalized COVID-19 patients. We analyzed the associations between baseline levels of 21 biomarkers and time to hospital discharge and change in NEWS-2 score in patients from DisCoVeRy trial. We fitted multivariate models adjusted for baseline ISARIC 4C score, disease severity, D-dimer values, and treatment regimen. Between March 22 and June 29, 2020, 603 participants were randomized; 454 had a sample collected at baseline and analyzed. The backward selection of multivariate models showed that higher baseline levels of soluble suppressor of tumorigenicity 2 (sST2) and nucleosomes were statistically associated with a lower chance of hospital discharge before day 29 (sST2: aHR 0.24, 95% CI [0.15-0.38], p < 10-9; nucleosomes: aHR 0.62, 95% CI [0.48-0.81], p < 10-3). Likewise, higher levels of baseline sST2 were statistically associated with lower changes in the NEWS-2 score between baseline and day 15 (adjusted beta 4.47, 95% CI [2.65-6.28], p < 10-5). Moreover, we evaluated sST2 involvement in a confirmation cohort (SARCODO study, 103 patients) and found that elevated baseline sST2 levels were significantly associated with lower rates of hospital discharge before day 29 and a higher model performance (AUC at day 29 of 92%) compared to models without sST2. sST2 emerged as an independent predictor of clinical outcomes in two large cohort of hospitalized COVID-19 patients, warranting further investigation to elucidate its role in disease progression and potential as a therapeutic target.

Relevance of anti-platelet factor 4/heparin antibodies and platelet activation in systemic inflammatory diseases and thrombosis disorders: insight from the COVID-19 pandemic

Background

The increased interest in anti-platelet factor 4 (PF4)-heparin complex (anti-PF4/H) antibodies following the COVID-19 pandemic has established them as crucial players in immunothrombosis.

Objectives

We aimed to investigate the involvement of anti-PF4/H antibodies during COVID-19 and after vaccination, particularly in patients with systemic inflammatory disease (SID).

Methods

This retrospective study analyzed the presence of anti-PF4/H antibodies and their ability to induce platelet activation in COVID-19 patients with and without suspected heparin-induced thrombocytopenia (HIT), vaccine-induced immune thrombotic thrombocytopenia (VITT) patients, and in controls and SID patients following COVID-19 vaccination.

Results

No significant increase in anti-PF4/H antibody levels was observed during COVID-19 regardless of disease severity. Despite a 2-fold increase in HIT suspicion observed during the pandemic, there was no corresponding increase in HIT diagnoses. Additionally, no significant increase in anti-PF4/H levels was noted after vaccination, even in SID patients. None of the positive anti-PF4/H antibodies detected in COVID-19 or vaccination cohorts induced platelet activation, measured by soluble P-selectin levels and flow cytometry-based on platelet microvesicle generation. Finally, in VITT patients, unlike in HIT patients, anti-PF4/H levels were strongly associated with platelet microvesicle assay and moderately with soluble P-selectin levels.

Conclusion

Our study found no significant increase in anti-PF4/H antibodies in COVID-19 or after vaccination, including in SID patients. However, in VITT patients, but not in HIT patients, these antibodies were correlated with platelet activation. This finding suggests that anti-PF4/H antibodies play a different role in the pathophysiology of VITT but that their interest is limited outside clear contexts of HIT/VITT suspicion.

Long COVID Syndrome: A Case-Control Study

BACKGROUND

Acute coronavirus disease 2019 (COVID-19) causes various cardiovascular complications. However, it is unknown if there are cardiovascular sequelae in the medium and long-term. The aim of this study was dual. Firstly, we wanted to investigate symptomatology and health-related quality of life (HRQoL) at medium-term follow-up (6 months post-COVID). Secondly, we wanted to assess whether history of COVID-19 and persistent shortness of breath at medium-term follow-up are associated with ongoing inflammation, endothelial dysfunction, and cardiac injury.

METHODS

A case-control study was performed. Virologically proven COVID-19 cases and age- and gender-matched controls were interviewed to assess symptoms and HRQoL. Biochemical tests were also performed.

RESULTS

The study comprised 174 cases and 75 controls. The mean age of the participants was 46.1±13.8 years. The median follow-up was 173.5 days (interquartile range 129-193.25 days). There was no significant difference in the demographics between cases and controls. At follow-up, cases had a higher frequency of shortness of breath, fatigue, arthralgia, abnormal taste of food (P <.001), and anosmia. Cases also exhibited worse scores in the general health and role physical domains of the Short Form Survey-36. High-sensitivity C-reactive protein (hsCRP) was significantly higher in the cases, and there was a positive correlation of hsCRP with time. Significant determinants of shortness of breath were age, female gender and white cell count, troponin I, and lower hemoglobin levels at follow-up.

CONCLUSION

Post-COVID-19 patients have persistent symptomatology at medium-term follow-up. Higher hsCRP in cases and the positive association of hsCRP with time suggest ongoing systemic inflammation in patients persisting for months after COVID-19.

Implications of von Willebrand Factor in Inflammatory Bowel Diseases: Beyond Bleeding and Thrombosis

Inflammatory bowel disease (IBD) displays an increased venous and arterial thrombotic risk despite the common occurrence of intestinal bleeding. While some of the mechanisms leading to these thrombotic complications have been studied, other specific changes in the hemostasis profile of IBD patients have been less explored. One such example relates to von Willebrand factor (VWF) whose plasma levels have been reported to be modulated in IBD. Von Willebrand factor is a plasma glycoprotein crucial for hemostatic functions via roles both in platelet function and coagulation. High plasma VWF is a known risk factor for venous thromboembolism. In addition to its canonical roles in hemostasis, VWF is known to be directly or indirectly involved in other vascular processes such as maintenance of endothelial barrier integrity or proliferation of vascular smooth muscle cells. The purpose of this review is to recapitulate and update the existing data about VWF biology in IBD and to highlight its role both in the existing procoagulant phenotype and in vascular alterations that may occur in IBD.

Delineating sex-specific circulating host response signatures associated with COVID-19 severity and mortality

Male SARS-CoV-2-infected patients have higher hospitalization rates, ICU admissions, and mortality compared to females, yet with unclear underlying mechanisms. We investigated the influence of biological sex on COVID-19 severity and patient outcomes. We profiled 41 circulating host response markers and identified differentially regulated proteins based on disease severity using covariates, such as sex, age, BMI, diabetes, and corticosteroid administration. IL-8, D-dimer, S100B, IL-6, Angpt-2, MMP-8, TNF-R1, u-PAR, u-PA, osteopontin, IL-13, TNF-α, pentraxin-3, P-selectin, fractalkine, and SP-D levels were elevated in critically ill COVID-19 males compared to severe cases. In contrast, IL-8, D-dimer, IL-6, Angpt-2, Tie-2, uPAR, and SP-D were higher in females with critical-COVID-19 than in severe cases. Notably, D-dimer, IL-6, pentraxin-3, and S100B were associated with male mortality, yet none of the measured plasma proteins associated with female mortality. Our study delineated distinct sex-specific plasma protein signatures linked to the severity and mortality of COVID-19 patients.

The Onset of Intussusceptive Angiogenesis in COVID-19 Patients Might Come from the Mobilization of Stem Cell Sub-Populations Expressing the Hemangioblast Marker CD143

COVID-19 and infectious diseases have been included in strategic development goals (SDG) of United Nations (UN). The SARS-CoV-2 pandemic has unveiled complex pathophysiological mechanisms underpinning COVID-19, notably inducing a systemic acquired vascular hemopathy characterized by endothelial dysfunction and intussusceptive angiogenesis, a rapid vascular remodeling process identified as a hallmark in severe COVID-19 cases affecting pulmonary and cardiac tissues. Stem cell migration have been proposed as significant regulators of this neoangiogenic process. In a monocentric cross-sectional study, through spectral flow cytometry analysis of peripheral blood mononuclear cells, we identified a distinct stem cell subpopulation mobilized in critical COVID-19. Indeed, by an unsupervised analysis generating a UMAP representation we highlighted eleven different clusters in critical and non-critical COVID-19 patients. Only one cluster was significantly associated to critical COVID-19 compared to non-critical patients. This cluster expressed the markers: CD45dim, CD34+, CD117+, CD147+, and CD143+, and were negative for CD133. Higher level of expression of hemangioblast markers CD143 were found in critical COVID-19 patients. This population, indicative of hemangioblast-like cells, suggests a key role in COVID-19-related neoangiogenesis, potentially driving the severe vascular complications observed. Our findings underscore the need for further investigation into the contributions of adult stem cells in COVID-19 pathology, offering new insights into therapeutic targets and interventions.

Endothelial biomarkers (Von willebrand factor, BDCA3, urokinase) as predictors of mortality in COVID-19 patients: cohort study

BACKGROUND

SARS-CoV-2 is a systemic disease that affects endothelial function and leads to coagulation disorders, increasing the risk of mortality. Blood levels of endothelial biomarkers such as Von Willebrand Factor (VWF), Thrombomodulin or Blood Dendritic Cell Antigen-3 (BDCA3), and uUokinase (uPA) increase in patients with severe disease and can be prognostic indicators for mortality. Therefore, the aim of this study was to determine the effect of VWF, BDCA3, and uPA levels on mortality.

METHODS

From May 2020 to January 2021, we studied a prospective cohort of hospitalized adult patients with polymerase chain reaction (PCR)-confirmed COVID-19 with a SaO2 ≤ 93% and a PaO2/FiO2 ratio < 300. In-hospital survival was evaluated from admission to death or to a maximum of 60 days of follow-up with Kaplan-Meier survival curves and Cox proportional hazard models as independent predictor measures of endothelial dysfunction.

RESULTS

We recruited a total of 165 subjects (73% men) with a median age of 57.3 ± 12.9 years. The most common comorbidities were obesity (39.7%), hypertension (35.4%) and diabetes (30.3%). Endothelial biomarkers were increased in non-survivors compared to survivors. According to the multivariate Cox proportional hazard model, those with an elevated VWF concentration ≥ 4870 pg/ml had a hazard ratio (HR) of 4.06 (95% CI: 1.32-12.5) compared to those with a lower VWF concentration adjusted for age, cerebrovascular events, enoxaparin dose, lactate dehydrogenase (LDH) level, and bilirubin level. uPA and BDCA3 also increased mortality in patients with levels ≥ 460 pg/ml and ≥ 3600 pg/ml, respectively.

CONCLUSION

The risk of mortality in those with elevated levels of endothelial biomarkers was observable in this study.

Insight into COVID-19 associated liver injury: Mechanisms, evaluation, and clinical implications

COVID-19 has affected millions worldwide, causing significant morbidity and mortality. While predominantly involving the respiratory tract, SARS-CoV-2 has also caused systemic illnesses involving other sites. Liver injury due to COVID-19 has been variably reported in observational studies. It has been postulated that liver damage may be due to direct damage by the SARS-CoV-2 virus or multifactorial secondary to hepatotoxic therapeutic options, as well as cytokine release syndrome and sepsis-induced multiorgan dysfunction. The approach to a COVID-19 patient with liver injury requires a thorough evaluation of the pattern of hepatocellular injury, along with the presence of underlying chronic liver disease and concurrent medications which may cause drug-induced liver injury. While studies have shown uneventful recovery in the majority of mildly affected patients, severe COVID-19 associated liver injury has been associated with higher mortality, prolonged hospitalization, and greater morbidity in survivors. Furthermore, its impact on long-term outcomes remains to be ascertained as recent studies report an association with metabolic-fatty liver disease. This present review provides insight into the subject by describing the postulated mechanism of liver injury, its impact in the presence of pre-existing liver disease, and its short- and long-term clinical implications.

Molecular Research on Coronavirus: Pathogenic Mechanisms, Antiviral Drugs, and New Vaccines

Since the COVID-19 outbreak in 2019, five coronaviruses have been found to infect humans, including SARS-CoV (severe acute respiratory syndrome coronavirus) [...].

Numerical study of ultra-large von Willebrand factor multimers in coagulopathy

An excessive von Willebrand factor (VWF) secretion, coupled with a moderate to severe deficiency of ADAMTS13 activity, serves as a linking mechanism between inflammation to thrombosis. The former facilitates platelet adhesion to the vessel wall and the latter is required to cleave VWF multimers. As a result, the ultra-large VWF (UL-VWF) multimers released by Weibel-Palade bodies remain uncleaved. In this study, using a computational model based on first principles, we quantitatively show how the uncleaved UL-VWF multimers interact with the blood cells to initiate microthrombosis. We observed that platelets first adhere to unfolded and stretched uncleaved UL-VWF multimers anchored to the microvessel wall. By the end of this initial adhesion phase, the UL-VWF multimers and platelets make a mesh-like trap in which the red blood cells increasingly accumulate to initiate a gradually growing microthrombosis. Although high-shear rate and blood flow velocity are required to activate platelets and unfold the UL-VWFs, during the initial adhesion phase, the blood velocity drastically drops after thrombosis, and as a result, the wall shear stress is elevated near UL-VWF roots, and the pressure drops up to 6 times of the healthy condition. As the time passes, these trends progressively continue until the microthrombosis fully develops and the effective size of the microthrombosis and these flow quantities remain almost constant. Our findings quantitatively demonstrate the potential role of UL-VWF in coagulopathy.

Endothelial dysfunction and disease severity in COVID-19: Insights from circulating Tang cell counts as a potential biomarker

BACKGROUND AND AIM

Endothelial dysfunction is a common risk factor of severe COVID-19. Angiogenic T cells (Tang cells) play a critical role in repairing endothelial injury; however, their changes and potential roles in COVID-19 remain unclear. We aimed to assess Tang cell counts in patients with COVID-19 and evaluate their association with disease severity and prognosis.

METHODS

Circulating Tang cell populations in patients with COVID-19 and healthy controls were quantified using flow cytometry. Demographic and routine laboratory data were recorded.

RESULTS

The Tang cell count decreased significantly with increasing disease severity and were lowest in fatal cases. Additionally, the Tang cell count was significantly decreased in patients with comorbid cardiovascular disease or hypertension. Tang cell counts were negatively correlated with inflammatory markers, kidney and myocardial injury markers, coagulation dysfunction indicators, and viral load and positively correlated with oxidative stress markers, nutritional markers, and lymphocytes. Receiver operating characteristic curves confirmed that Tang cell count could serve as a potential biomarker for predicting disease severity and patient mortality.

CONCLUSIONS

Circulating Tang cell count is significantly reduced in patients with COVID-19 and is correlated with disease severity and prognosis. The Tang cell count is an important potential biomarker for COVID-19 clinical management. Additionally, these findings provide insight into the pathological features of COVID-19 endothelial injury and provide new directions for treatment.

CD147 Plasma Levels in Hospitalised Patients with Covid-19 Pneumonia Predict Illness Severity and In-Hospital Mortality

COVID-19 and infectious diseases have been included in strategic development goals (SDG) of United Nations (UN). The CD147 receptor is one of several receptors for the SARS-CoV-2 spike protein that could mediate Covid-19 viral infection of host cells. It has been recently proposed to regulate viral invasion and dissemination among lymphocytes and progenitor/stem cells. A soluble by-product of CD147 (sCD147) exists in plasma and has been previously identified as a marker of diabetes and platelet activation. We examined plasma sCD147 levels in 161 Covid-19 patients at hospital admission. We demonstrated significantly higher plasma sCD147 levels in Covid-19 patients, which correlated with plasma multiorgan dysfunction biomarkers interleukin-6, creatinine and Troponin I. Importantly, sCD147 admission levels were associated with Covid-19 severity and survival, carrying potential value as a biomarker in hospitalized patients with Covid-19 infection.

VEGF-A plasma levels are associated with impaired DLCO and radiological sequelae in long COVID patients

BACKGROUND

Long COVID, also known as post-acute sequelae of COVID-19 (PASC), is characterized by persistent clinical symptoms following COVID-19.

OBJECTIVE

To correlate biomarkers of endothelial dysfunction with persistent clinical symptoms and pulmonary function defects at distance from COVID-19.

METHODS

Consecutive patients with long COVID-19 suspicion were enrolled. A panel of endothelial biomarkers was measured in each patient during clinical evaluation and pulmonary function test (PFT).

RESULTS

The study included 137 PASC patients, mostly male (68%), with a median age of 55 years. A total of 194 PFTs were performed between months 3 and 24 after an episode of SARS-CoV-2 infection. We compared biomarkers evaluated in PASC patients with 20 healthy volunteers (HVs) and acute hospitalized COVID-19 patients (n = 88). The study found that angiogenesis-related biomarkers and von Willebrand factor (VWF) levels were increased in PASC patients compared to HVs without increased inflammatory or platelet activation markers. Moreover, VEGF-A and VWF were associated with persistent lung CT scan lesions and impaired diffusing capacity of the lungs for carbon monoxide (DLCO) measurement. By employing a Cox proportional hazards model adjusted for age, sex, and body mass index, we further confirmed the accuracy of VEGF-A and VWF. Following adjustment, VEGF-A emerged as the most significant predictive factor associated with persistent lung CT scan lesions and impaired DLCO measurement.

CONCLUSION

VEGF-A is a relevant predictive factor for DLCO impairment and radiological sequelae in PASC. Beyond being a biomarker, we hypothesize that the persistence of angiogenic disorders may contribute to long COVID symptoms.

Biomarkers of coagulation, endothelial, platelet function, and fibrinolysis in patients with COVID-19: a prospective study

Prospective and sequential evaluation of homeostatic changes leading to thrombosis across COVID 19 disease severity spectrum are limited. In this prospective observational study, haemostasis was evaluated in patients with mild, moderate-severe, and critical COVID-19 infection. Markers of endothelial activation [Soluble thrombomodulin (sTM), von Willebrand Factor (VWF)], platelet activation [Soluble P-selectin, beta-thromboglobulin (BTG)] and global haemostasis [Rotational thromboelastometry (ROTEM)] were evaluated on days 1 and 5 after admission. The study cohort comprised of 100 adult patients (mild = 20, moderate-severe = 22, critical = 58). Sixty-five patients received anticoagulation for 10 (7-14) days. Thrombotic events were seen in 9 patients. In-hospital mortality was 21%. Endothelial activation markers were elevated at baseline in all subgroups, with levels in moderate-severe (sTM = 4.92 ng/ml, VWF = 295 U/dl) [reference-ranges: sTM = 2.26-4.55 ng/ml; Soluble P-selectin = 13.5-31.5 ng/ml; BTG = 0.034-1.99 ng/ml] and critical patients (sTM = 6.07 ng/ml, VWF = 294 U/dl) being significantly higher than in the mild group (sTM = 4.18 ng/ml, VWF = 206 U/dl). In contrast, platelet activation markers were elevated only in critically ill patients at baseline (Soluble P-selectin = 37.3 ng/ml, BTG = 2.51 ng/ml). The critical group had significantly lower fibrinolysis on days 1 and 5 when compared with the moderate-severe arm. COVID-19 infection was associated with graded endothelial activation and lower fibrinolysis that correlated with illness severity.

COVID-19 pathogenesis

The pathogenesis of COVID-19 involves a complex interplay between host factors and the SARS-CoV-2 virus, leading to a multitude of clinical manifestations beyond the respiratory system. This chapter provides an overview of the risk factors, genetic predisposition, and multisystem manifestations of COVID-19, shedding light on the underlying mechanisms that contribute to extrapulmonary manifestations. The chapter discusses the direct invasion of SARS-CoV-2 into various organs as well as the indirect mechanisms such as dysregulation of the renin-angiotensin-aldosterone system (RAAS), immune response dysfunctions within the innate and adaptive immune systems, endothelial damage, and immunothrombosis. Furthermore, the multisystem manifestations of COVID-19 across different organ systems, including the cardiovascular, renal, gastrointestinal, hepatobiliary, nervous, endocrine and metabolic, ophthalmic, ear-nose-throat, reproductive, hematopoietic, and immune systems are discussed in detail. Each system exhibits unique manifestations that contribute to the complexity of the disease.

COVID-19 and the Concept of Thrombo-Inflammation: Review of the Relationship between Immune Response, Endothelium and Coagulation

COVID-19, caused by the SARS-CoV-2 virus, has revealed a complex interplay between inflammation and coagulation, leading to the emergence of the concept of thrombo-inflammation. This concept recognizes that COVID-19 is not solely a respiratory illness, but a systemic disease with significant vascular and hematological components. COVID-19 is associated with an unusual prothrombotic state, with intense endothelial activation leading to vasculopathy, cytokine storm, complement system activation and a hypercoagulability state (the activation of platelets and the coagulation cascade, impaired fibrinolysis). The aim of this review is to discuss the different pathological pathways described in COVID-19 that lead to thromboembolic events. Widespread vaccination and post-COVID-19 immunization allows control over the severity of this pandemic. A better understanding of the pathophysiology of COVID-19 can improve the management of frail patients who are hospitalized in intensive care units.

The modes of angiogenesis: an updated perspective

Following the process of vasculogenesis during development, angiogenesis generates new vascular structures through a variety of different mechanisms or modes. These different modes of angiogenesis involve, for example, increasing microvasculature density by sprouting of endothelial cells, splitting of vessels to increase vascular surface area by intussusceptive angiogenesis, fusion of capillaries to increase blood flow by coalescent angiogenesis, and the recruitment of non-endothelial cells by vasculogenic mimicry. The recent reporting on coalescent angiogenesis as a new mode of vessel formation warrants a brief overview of angiogenesis mechanisms to provide a more complete picture. The journal Angiogenesis is devoted to the delineation of the different modes and mechanisms that collectively dictate blood vessel formation, inhibition, and function in health and disease.

SARS-CoV-2 infection and SLE: endothelial dysfunction, atherosclerosis, and thrombosis

An increased risk of atherosclerotic and thrombotic complications characterizes connective tissue diseases. Endothelial dysfunction is the basis for the initiation and progression of atherosclerosis and thrombosis. We present systemic lupus erythematosus (SLE) as a model rheumatic disease with endothelial dysfunction and discuss its mechanisms, factors that influence the early onset and rapid progression of atherosclerosis, and the increased risk of thromboembolic events. We focus on established methods to improve endothelium function, including statins, antiplatelet, and antithrombotic therapy. Hypercoagulable and hypofibrinolitic states and a hyperinflammatory response characterize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Several pathogenic mechanisms are typical for an acute phase of Covid-19 post-Covid syndrome and connective tissue diseases: endothelial dysfunction, elevated antiphospholipid antibody titer, activation of the complement system, and formation of extracellular neutrophil traps (NET). The current review discusses the mechanisms underlying SLE and the COVID-19 in the context of endothelial function, atherosclerosis, and thrombosis (Graphical abstract). Key Points • The pathophysiology of systemic lupus erythematosus (SLE) and Covid-19 shows some similarities, such as endothelial cell activation and dysfunction, the activation of complementary systems, the presence of antiphospholipid antibodies, and the formation of extracellular neutrophil traps. • Autoimmunity in both diseases creates the basis for hyperinflammatory, hypercoagulable, and hypofibrinolitic states and their thromboembolic complications. • This paper presents our perspective on the mechanisms behind the cardiovascular manifestations of SLE and COVID-19, with a particular emphasis on endothelial dysfunction. Covid-19 and systemic lupus erythematosus-potential similarities in pathophysiology. Figures of the panel illustrate the clinical manifestations of endothelial dysfunction, atherosclerosis, and thromboembolism, including coronary artery disease ([A] coronary angiography with left anterior descending artery stenosis and [B] scintigraphy with reduced perfusion in the myocardial apical segments), stroke ([C] carotid angiography, left carotid artery occlusion) and pulmonary embolism ([D]computed tomography with thrombus in the right pulmonary artery).

Immune thrombotic thrombocytopenic purpura: pathogenesis and novel therapies: a narrative review

Background and Objectives

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare, but potentially fatal blood disease, resulting from autoantibodies against A Disintegrin and Metalloprotease with ThromboSpondin Type 1 Repeats, 13 (ADAMTS13). While major progress has been made in past decades concerning early diagnosis and management of iTTP, the mechanisms underlying the formation and the mechanism of action of these autoantibodies against ADMATS13 are still unknown. This review will provide a narrative review of pathogenesis and novel therapeutics of iTTP.

Methods

We did PubMed literature search using a combination of thrombotic thrombocytopenic purpura and treatment or pathogenesis from 1955 to November 2022. A total of 4,767 articles with full text were found and only relevant articles in English were further reviewed and summarized.

Key Content and Findings

We found that the primary mechanism underlying severe ADAMTS13 deficiency in patients with iTTP is autoantibody-mediated inhibition and/or accelerated clearance of ADAMTS13 metalloprotease. Other factors including allosteric regulation and post-translational modifications (i.e., glycosylation and citrullination, and arginine methylation, etc.) may affect ADAMTS13 secretion and function and also contribute to the pathogenesis of iTTP. The standard of care for iTTP today consists of therapeutic plasma exchange, anti-von Willebrand factor (vWF) caplacizumab, and immunosuppressives (e.g., corticosteroids and rituximab), known as the triple therapy, which has significantly reduced exacerbation and mortality rates.

Conclusions

We hope that the information provided in the review article helps better understand the pathogenesis of iTTP, which may guide design novel and more effective therapeutics for this potentially fatal disorder.

Endothelial SARS-CoV-2 infection is not the underlying cause of COVID-19-associated vascular pathology in mice

Endothelial damage and vascular pathology have been recognized as major features of COVID-19 since the beginning of the pandemic. Two main theories regarding how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) damages endothelial cells and causes vascular pathology have been proposed: direct viral infection of endothelial cells or indirect damage mediated by circulating inflammatory molecules and immune mechanisms. However, these proposed mechanisms remain largely untested in vivo. In the present study, we utilized a set of new mouse genetic tools developed in our lab to test both the necessity and sufficiency of endothelial human angiotensin-converting enzyme 2 (hACE2) in COVID-19 pathogenesis. Our results demonstrate that endothelial ACE2 and direct infection of vascular endothelial cells do not contribute significantly to the diverse vascular pathology associated with COVID-19.

Gene silencing of endothelial von Willebrand factor reduces the susceptibility of human endothelial cells to SARS-CoV-2 infection

Mechanisms underlying vascular endothelial susceptibility to infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not fully understood. Emerging evidence indicates that patients lacking von Willebrand factor (vWF), an endothelial hallmark, are less severely affected by SARS-CoV-2 infection, yet the precise role of endothelial vWF in modulating coronavirus entry into endothelial cells is unknown. In the present study, we demonstrated that effective gene silencing by short interfering RNA (siRNA) for vWF expression in resting human umbilical vein endothelial cells (HUVECs) significantly reduced by 56% the cellular levels of SARS-CoV-2 genomic RNA. Similar reduction in intracellular SARS-CoV-2 genomic RNA levels was observed in non-activated HUVECs treated with siRNA targeting angiotensin-converting enzyme 2 (ACE2), the cellular gateway to coronavirus. By integrating quantitative information from real-time PCR and high-resolution confocal imaging, we demonstrated that ACE2 gene expression and its plasma membrane localization in HUVECs were both markedly reduced after treatment with siRNA anti-vWF or anti-ACE2. Conversely, siRNA anti-ACE2 did not reduce endothelial vWF gene expression and protein levels. Finally, SARS-CoV-2 infection of viable HUVECs was enhanced by overexpression of vWF, which increased ACE2 levels. Of note, we found a similar increase in interferon-β mRNA levels following transfection with untargeted, anti-vWF or anti-ACE2 siRNA and pcDNA3.1-WT-VWF. We envision that siRNA targeting endothelial vWF will protect against productive endothelial infection by SARS-CoV-2 through downregulation of ACE2 expression and might serve as a novel tool to induce disease resistance by modulating the regulatory role of vWF on ACE2 expression.

Pathological angiogenesis: mechanisms and therapeutic strategies

In multicellular organisms, angiogenesis, the formation of new blood vessels from pre-existing ones, is an essential process for growth and development. Different mechanisms such as vasculogenesis, sprouting, intussusceptive, and coalescent angiogenesis, as well as vessel co-option, vasculogenic mimicry and lymphangiogenesis, underlie the formation of new vasculature. In many pathological conditions, such as cancer, atherosclerosis, arthritis, psoriasis, endometriosis, obesity and SARS-CoV-2(COVID-19), developmental angiogenic processes are recapitulated, but are often done so without the normal feedback mechanisms that regulate the ordinary spatial and temporal patterns of blood vessel formation. Thus, pathological angiogenesis presents new challenges yet new opportunities for the design of vascular-directed therapies. Here, we provide an overview of recent insights into blood vessel development and highlight novel therapeutic strategies that promote or inhibit the process of angiogenesis to stabilize, reverse, or even halt disease progression. In our review, we will also explore several additional aspects (the angiogenic switch, hypoxia, angiocrine signals, endothelial plasticity, vessel normalization, and endothelial cell anergy) that operate in parallel to canonical angiogenesis mechanisms and speculate how these processes may also be targeted with anti-angiogenic or vascular-directed therapies.

von Willebrand factor binds to angiopoietin-2 within endothelial cells and after release from Weibel-Palade bodies

BACKGROUND

The von Willebrand factor (VWF) is a multimeric plasma glycoprotein essential for hemostasis, inflammation, and angiogenesis. The majority of VWF is synthesized by endothelial cells (ECs) and stored in Weibel-Palade bodies (WPB). Among the range of proteins shown to co-localize to WPB is angiopoietin-2 (Angpt-2), a ligand of the receptor tyrosine kinase Tie-2. We have previously shown that VWF itself regulates angiogenesis, raising the hypothesis that some of the angiogenic activity of VWF may be mediated by its interaction with Angpt-2.

METHODS

Static-binding assays were used to probe the interaction between Angpt-2 and VWF. Binding in media from cultured human umbilical vein ECs s and in plasma was determined by immunoprecipitation experiments. Immunofluorescence was used to detect the presence of Angpt-2 on VWF strings, and flow assays were used to investigate the effect on VWF function.

RESULTS

Static-binding assays revealed that Angpt-2 bound to VWF with high affinity (KD,app ∼3 nM) in a pH and calcium-dependent manner. The interaction was localized to the VWF A1 domain. Co-immunoprecipitation experiments demonstrated that the complex persisted following stimulated secretion from ECs and was present in plasma. Angpt-2 was also visible on VWF strings on stimulated ECs. The VWF-Angpt-2 complex did not inhibit the binding of Angpt-2 to Tie-2 and did not significantly interfere with VWF-platelet capture.

CONCLUSIONS

Together, these data demonstrate a direct binding interaction between Angpt-2 and VWF that persists after secretion. VWF may act to localize Angpt-2; further work is required to establish the functional consequences of this interaction.

Vascular risk factors for COVID-19 ARDS: endothelium, contact-kinin system

SARS-CoV-2 binds to ACE2 receptors, expressed within the lungs. Risk factors for hospitalization include hypertension, diabetes, ischaemic heart disease and obesity-conditions linked by the presence of endothelial pathology. Viral infection in this setting causes increased conversion of circulating Factor XII to its active form (FXIIa). This is the first step in the contact-kinin pathway, leading to synchronous activation of the intrinsic coagulation cascade and the plasma Kallikrein-Kinin system, resulting in clotting and inflammatory lung disease. Temporal trends are evident from blood results of hospitalized patients. In the first week of symptoms the activated partial thromboplastin time (APTT) is prolonged. This can occur when clotting factors are consumed as part of the contact (intrinsic) pathway. Platelet counts initially fall, reflecting their consumption in coagulation. Lymphopenia occurs after approximately 1 week, reflecting the emergence of a lymphocytic pneumonitis [COVID-19 acute respiratory distress syndrome (ARDS)]. Intrinsic coagulation also induces the contact-kinin pathway of inflammation. A major product of this pathway, bradykinin causes oedema with ground glass opacities (GGO) on imaging in early COVID-19. Bradykinin also causes release of the pleiotrophic cytokine IL-6, which causes lymphocyte recruitment. Thromobosis and lymphocytic pneumonitis are hallmark features of COVID-19 ARDS. In this review we examine the literature with particular reference to the contact-kinin pathway. Measurements of platelets, lymphocytes and APTT should be undertaken in severe infections to stratify for risk of developing ARDS.

Phase 2 randomised placebo-controlled trial of spironolactone and dexamethasone versus dexamethasone in COVID-19 hospitalised patients in Delhi

BACKGROUND

In this phase 2 randomised placebo-controlled clinical trial in patients with COVID-19, we hypothesised that blocking mineralocorticoid receptors using a combination of dexamethasone to suppress cortisol secretion and spironolactone is safe and may reduce illness severity.

METHODS

Hospitalised patients with confirmed COVID-19 were randomly allocated to low dose oral spironolactone (50 mg day 1, then 25 mg once daily for 21 days) or standard of care in a 2:1 ratio. Both groups received dexamethasone 6 mg daily for 10 days. Group allocation was blinded to the patient and research team. Primary outcomes were time to recovery, defined as the number of days until patients achieved WHO Ordinal Scale (OS) category ≤ 3, and the effect of spironolactone on aldosterone, D-dimer, angiotensin II and Von Willebrand Factor (VWF).

RESULTS

One hundred twenty patients with PCR confirmed COVID were recruited in Delhi from 01 February to 30 April 2021. 74 were randomly assigned to spironolactone and dexamethasone (SpiroDex), and 46 to dexamethasone alone (Dex). There was no significant difference in the time to recovery between SpiroDex and Dex groups (SpiroDex median 4.5 days, Dex median 5.5 days, p = 0.055). SpiroDex patients had significantly lower D-dimer levels on days 4 and 7 (day 7 mean D-dimer: SpiroDex 1.15 µg/mL, Dex 3.15 µg/mL, p = 0.0004) and aldosterone at day 7 (SpiroDex 6.8 ng/dL, Dex 14.52 ng/dL, p = 0.0075). There was no difference in VWF or angiotensin II levels between groups. For secondary outcomes, SpiroDex patients had a significantly greater number of oxygen free days and reached oxygen freedom sooner than the Dex group. Cough scores were no different during the acute illness, however the SpiroDex group had lower scores at day 28. There was no difference in corticosteroid levels between groups. There was no increase in adverse events in patients receiving SpiroDex.

CONCLUSION

Low dose oral spironolactone in addition to dexamethasone was safe and reduced D-dimer and aldosterone. Time to recovery was not significantly reduced. Phase 3 randomised controlled trials with spironolactone and dexamethasone should be considered.

TRIAL REGISTRATION

The trial was registered on the Clinical Trials Registry of India TRI: CTRI/2021/03/031721, reference: REF/2021/03/041472. Registered on 04/03/2021.

Inflammation and vascular remodeling in COVID-19 hearts

A wide range of cardiac symptoms have been observed in COVID-19 patients, often significantly influencing the clinical outcome. While the pathophysiology of pulmonary COVID-19 manifestation has been substantially unraveled, the underlying pathomechanisms of cardiac involvement in COVID-19 are largely unknown. In this multicentre study, we performed a comprehensive analysis of heart samples from 24 autopsies with confirmed SARS-CoV-2 infection and compared them to samples of age-matched Influenza H1N1 A (n = 16), lymphocytic non-influenza myocarditis cases (n = 8), and non-inflamed heart tissue (n = 9). We employed conventional histopathology, multiplexed immunohistochemistry (MPX), microvascular corrosion casting, scanning electron microscopy, X-ray phase-contrast tomography using synchrotron radiation, and direct multiplexed measurements of gene expression, to assess morphological and molecular changes holistically. Based on histopathology, none of the COVID-19 samples fulfilled the established diagnostic criteria of viral myocarditis. However, quantification via MPX showed a significant increase in perivascular CD11b/TIE2 + -macrophages in COVID-19 over time, which was not observed in influenza or non-SARS-CoV-2 viral myocarditis patients. Ultrastructurally, a significant increase in intussusceptive angiogenesis as well as multifocal thrombi, inapparent in conventional morphological analysis, could be demonstrated. In line with this, on a molecular level, COVID-19 hearts displayed a distinct expression pattern of genes primarily coding for factors involved in angiogenesis and epithelial-mesenchymal transition (EMT), changes not seen in any of the other patient groups. We conclude that cardiac involvement in COVID-19 is an angiocentric macrophage-driven inflammatory process, distinct from classical anti-viral inflammatory responses, and substantially underappreciated by conventional histopathologic analysis. For the first time, we have observed intussusceptive angiogenesis in cardiac tissue, which we previously identified as the linchpin of vascular remodeling in COVID-19 pneumonia, as a pathognomic sign in affected hearts. Moreover, we identified CD11b + /TIE2 + macrophages as the drivers of intussusceptive angiogenesis and set forward a putative model for the molecular regulation of vascular alterations.

Von Willebrand factor and the thrombophilia of severe COVID-19: in situ evidence from autopsies

Background

COVID-19 is accompanied by a hypercoagulable state and characterized by microvascular and macrovascular thrombotic complications. In plasma samples from patients with COVID-19, von Willebrand factor (VWF) levels are highly elevated and predictive of adverse outcomes, especially mortality. Yet, VWF is usually not included in routine coagulation analyses, and histologic evidence of its involvement in thrombus formation is lacking.

Objectives

To determine whether VWF, an acute-phase protein, is a bystander, ie, a biomarker of endothelial dysfunction, or a causal factor in the pathogenesis of COVID-19.

Methods

We compared autopsy samples from 28 patients with lethal COVID-19 to those from matched controls and systematically assessed for VWF and platelets by immunohistochemistry. The control group comprised 24 lungs, 23 lymph nodes, and 9 hearts and did not differ significantly from the COVID-19 group in age, sex, body mass index (BMI), blood group, or anticoagulant use.

Results

In lungs, assessed for platelets by immunohistochemistry for CD42b, microthrombi were more frequent in patients with COVID-19 (10/28 [36%] vs 2/24 [8%]; P = .02). A completely normal pattern of VWF was rare in both groups. Accentuated endothelial staining was found in controls, while VWF-rich thrombi were only found in patients with COVID-19 (11/28 [39%] vs 0/24 [0%], respectively; P < .01), as were NETosis thrombi enriched with VWF (7/28 [25%] vs 0/24 [0%], respectively; P < .01). Forty-six percent of the patients with COVID-19 had VWF-rich thrombi, NETosis thrombi, or both. Trends were also seen in pulmonary draining lymph nodes (7/20 [35%] vs 4/24 [17%]; P = .147), where the overall presence of VWF was very high.

Conclusion

We provide in situ evidence of VWF-rich thrombi, likely attributable to COVID-19, and suggest that VWF may be a therapeutic target in severe COVID-19.

Fibrin monomers evaluation during hospitalization for COVID-19 is a predictive marker of in-hospital mortality

Background

Coagulopathy is one of the main triggers of severity and worsening of Coronavirus disease 2019 (COVID-19) particularly in critically ill patients. D-dimer has been widely used to detect COVID-19 coagulation disorders and has been correlated with outcomes such as disease severity and in-hospital mortality. Involvement of other fibrin degradation products, particularly fibrin monomers (FM), remains an ongoing question.

Methods

We performed a monocentric study of adult patients with COVID-19, who were admitted either in the medical ward (MW) or in the intensive care unit (ICU) and who had FM measurements performed on them during the first wave of COVID-19 outbreak. We analyzed the positivity of FM levels (FM &gt; 7 µg/mL) to assess the ability of FM monitoring during the first days of hospitalization to predict COVID-19 outcomes.

Results

In our cohort, 935 FM measurements were performed in 246 patients during their first 9 days of hospitalization. During patient follow-up, the FM levels were higher in patients admitted directly to the ICU than in those admitted to the MW. Moreover, we observed significantly increased levels of FM in patients when the data were stratified for in-hospital mortality. At hospital admission, only 27 (11%) patients displayed a positive value for FM; this subgroup did not differ from other patients in terms of severity (indicated by ICU referral at admission) or in-hospital mortality. When analyzing FM positivity in the first 9 days of hospitalization, we found that 37% of patients had positive FM at least once during hospitalization and these patients had increased in-hospital mortality (p = 0.001). Thus, we used non-adjusted Kaplan–Meier curves for in-hospital mortality according to FM positivity during hospitalization and we observed a statistically significant difference for in-hospital mortality (hazard ratio = 1.48, 95% CI: 1.25–1.76, p &lt; 0.001). However, we compared the AUC of FM positivity associated with a ratio of D-dimer &gt;70% and found that this combined receiver operating characteristic (ROC) curve was superior to the FM positivity ROC curve alone.

Conclusion

Monitoring of FM positivity in hospitalized patients with COVID-19 could be a reliable and helpful tool to predict the worsening condition and mortality of COVID-19.

Cellular and molecular features of COVID-19 associated ARDS: therapeutic relevance

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection can be asymptomatic or cause a disease (COVID-19) characterized by different levels of severity. The main cause of severe COVID-19 and death is represented by acute (or acute on chronic) respiratory failure and acute respiratory distress syndrome (ARDS), often requiring hospital admission and ventilator support.The molecular pathogenesis of COVID-19-related ARDS (by now termed c-ARDS) is still poorly understood. In this review we will discuss the genetic susceptibility to COVID-19, the pathogenesis and the local and systemic biomarkers correlated with c-ARDS and the therapeutic options that target the cell signalling pathways of c-ARDS.

[Human immunodeficiency virus and venous thromboembolism: Role of direct oral anticoagulants]

Nowadays, thanks to highly active antiretroviral therapy (HAART), human immunodeficiency virus (HIV) infection is transforming into a chronic disease. The life expectancy of people living with HIV (PWH) has increased, as well as their risk of developing several co-morbidities, in particular cardiovascular diseases. In addition, the incidence of venous thromboembolism (VTE) is increased in PWH with a 2 to 10 times higher incidence when compared to the general population. Over the last decade, direct oral anticoagulants (DOACs) have been widely used in the treatment and prevention of VTE and non-valvular atrial fibrillation. DOACs are characterized by a rapid onset of activity, a predictable response and a relatively wide therapeutic window. Nevertheless, drug interactions exist between HAART and DOACs, exposing PWH to a theoretically increased bleeding or thrombotic risk. DOACs are substrates of the transport protein P-glycoprotein and/or of isoforms of cytochromes P450 pathway, which can be affected by some antiretroviral drugs. Limited guidelines are available to assist physicians with the complexity of those drug-drug interactions. The aim of this paper is to provide an updated review on the evidence of the high risk of VTE in PWH and the place of DOAC therapy in this population.

Platelet activation and coronavirus disease 2019 mortality: Insights from coagulopathy, antiplatelet therapy and inflammation

BACKGROUND

Coronavirus disease 2019 (COVID-19) is associated with an inflammatory cytokine burst and a prothrombotic coagulopathy. Platelets may contribute to microthrombosis, and constitute a therapeutic target in COVID-19 therapy.

AIM

To assess if platelet activation influences mortality in COVID-19.

METHODS

We explored two cohorts of patients with COVID-19. Cohort A included 208 ambulatory and hospitalized patients with varying clinical severities and non-COVID patients as controls, in whom plasma concentrations of the soluble platelet activation biomarkers CD40 ligand (sCD40L) and P-selectin (sP-sel) were quantified within the first 48hours following hospitalization. Cohort B was a multicentre cohort of 2878 patients initially admitted to a medical ward. In both cohorts, the primary outcome was in-hospital mortality.

RESULTS

In cohort A, median circulating concentrations of sCD40L and sP-sel were only increased in the 89 critical patients compared with non-COVID controls: sP-sel 40,059 (interquartile range 26,876-54,678)pg/mL; sCD40L 1914 (interquartile range 1410-2367)pg/mL (P<0.001 for both). A strong association existed between sP-sel concentration and in-hospital mortality (Kaplan-Meier log-rank P=0.004). However, in a Cox model considering biomarkers of immunothrombosis, sP-sel was no longer associated with mortality, in contrast to coagulopathy evaluated with D-dimer concentration (hazard ratio 4.86, 95% confidence interval 1.64-12.50). Moreover, in cohort B, a Cox model adjusted for co-morbidities suggested that prehospitalization antiplatelet agents had no significant impact on in-hospital mortality (hazard ratio 1.05, 95% CI 0.80-1.37; P=0.73).

CONCLUSIONS

Although we observed an association between excessive biomarkers of platelet activation and in-hospital mortality, our findings rather suggest that coagulopathy is more central in driving disease progression, which may explain why prehospitalization antiplatelet drugs were not a protective factor against mortality in our multicentre cohort.

Endothelial cell activation, Weibel-Palade body secretion, and enhanced angiogenesis in severe COVID-19

Background

Severe COVID-19 is associated with marked endothelial cell (EC) activation that plays a key role in immunothrombosis and pulmonary microvascular occlusion. However, the biological mechanisms through which SARS-CoV-2 causes EC activation and damage remain poorly defined.

Objectives

We investigated EC activation in patients with acute COVID-19, and specifically focused on how proteins stored within Weibel-Palade bodies may impact key aspects of disease pathogenesis.

Methods

Thirty-nine patients with confirmed COVID-19 were recruited. Weibel-Palade body biomarkers (von Willebrand factor [VWF], angiopoietin-2 [Angpt-2], and osteoprotegerin) and soluble thrombomodulin (sTM) levels were determined. In addition, EC activation and angiogenesis were assessed in the presence or absence of COVID-19 plasma incubation.

Results

Markedly elevated plasma VWF antigen, Angpt-2, osteoprotegerin, and sTM levels were observed in patients with acute COVID-19. The increased levels of both sTM and Weibel-Palade body components (VWF, osteoprotegerin, and Angpt-2) correlated with COVID-19 severity. Incubation of COVID-19 plasma with ECs triggered enhanced VWF secretion and increased Angpt-2 expression, as well as significantly enhanced in vitro EC tube formation and angiogenesis.

Conclusion

We propose that acute SARS-CoV-2 infection leads to a complex and multifactorial EC activation, progressive loss of thrombomodulin, and increased Angpt-2 expression, which collectively serve to promote a local proangiogenic state.

Increased Circulating CD62E+ Endothelial Extracellular Vesicles Predict Severity and in- Hospital Mortality of COVID-19 Patients

COVID-19 and infectious diseases have been included in strategic development goals (SDG) of United Nations (UN). Severe form of COVID-19 has been described as an endothelial disease. In order to better evaluate Covid-19 endotheliopathy, we characterized several subsets of circulating endothelial extracellular vesicles (EVs) at hospital admission among a cohort of 60 patients whose severity of COVID-19 was classified at the time of inclusion. Degree of COVID-19 severity was determined upon inclusion and categorized as moderate to severe in 40 patients and critical in 20 patients. We measured citrated plasma EVs expressing endothelial membrane markers. Endothelial EVs were defined as harboring VE-cadherin (CD144+), PECAM-1 (CD31 + CD41-) or E-selectin (CD62E+). An increase in CD62E + EV levels on admission to the hospital was significantly associated with critical disease. Moreover, Kaplan-Meier survival curves for CD62E + EV level showed that level ≥ 88,053 EVs/μL at admission was a significant predictor of in hospital mortality (p = 0.004). Moreover, CD62E + EV level ≥ 88,053 EV/μL was significantly associated with higher in-hospital mortality (OR 6.98, 95% CI 2.1-26.4, p = 0.002) in a univariate logistic regression model, while after adjustment to BMI CD62E + EV level ≥ 88,053 EV/μL was always significantly associated with higher in-hospital mortality (OR 5.1, 95% CI 1.4-20.0, p = 0.01). The present findings highlight the potential interest of detecting EVs expressing E-selectin (CD62) to discriminate Covid-19 patients at the time of hospital admission and identify individuals with higher risk of fatal outcome.

Effects of convalescent plasma infusion on the ADAMTS13-von Willebrand factor axis and endothelial integrity in patients with severe and critical COVID-19

Background

Convalescent plasma infusion (CPI) was given to patients with COVID-19 during the early pandemic with mixed therapeutic efficacy. However, the impacts of CPI on the ADAMTS13-von Willebrand factor (VWF) axis and vascular endothelial functions are not known.

Objectives

To determine the impacts of CPI on the ADAMTS13-VWF axis and vascular endothelial functions.

Methods

Sixty hospitalized patients with COVID-19 were enrolled in the study; 46 received CPI and 14 received no CPI. Plasma ADAMTS13 activity, VWF antigen, endothelial syndecan-1, and soluble thrombomodulin (sTM) were assessed before and 24 hours after treatment.

Results

Patients with severe and critical COVID-19 exhibited significantly lower plasma ADAMTS13 activity than the healthy controls. Conversely, these patients showed a significantly increased VWF antigen. This resulted in markedly reduced ratios of ADAMTS13 to VWF in these patients. The levels of plasma ADAMTS13 activity in each patient remained relatively constant throughout hospitalization. Twenty-four hours following CPI, plasma ADAMTS13 activity increased by ∼12% from the baseline in all patients and ∼21% in those who survived. In contrast, plasma levels of VWF antigen varied significantly over time. Patients who died exhibited a significant reduction of plasma VWF antigen from the baseline 24 hours following CPI, whereas those who survived did not. Furthermore, patients with severe and critical COVID-19 showed significantly elevated plasma levels of syndecan-1 and sTM, similar to those found in patients with immune thrombotic thrombocytopenic purpura. Both syndecan-1 and sTM levels were significantly reduced 24 hours following CPI.

Conclusion

Our results demonstrate the relative deficiency of plasma ADAMTS13 activity and endothelial damage in patients with severe and critical COVID-19, which could be modestly improved following CPI therapy.

Statins and Hemostasis: Therapeutic Potential Based on Clinical Evidence

Hemostasis preserves blood fluidity and prevents its loss after vessel injury. The maintenance of blood fluidity requires a delicate balance between pro-coagulant and fibrinolytic status. Endothelial cells (ECs) in the inner face of blood vessels maintain hemostasis through balancing anti-thrombotic and pro-fibrinolytic activities. Dyslipidemias are linked to hemostatic alterations. Thus, it is necessary a better understanding of the underlying mechanisms linking hemostasis with dyslipidemia. Statins are drugs that decrease cholesterol levels in the blood and are the gold standard for treating hyperlipidemias. Statins can be classified into natural and synthetic molecules, approved for the treatment of hypercholesterolemia. The classical mechanism of action of statins is by competitive inhibition of a key enzyme in the synthesis pathway of cholesterol, the HMG-CoA reductase. Statins are frequently administrated by oral ingestion and its interaction with other drugs and food supplements is associated with altered bioavailability. In this review we deeply discuss the actions of statins beyond the control of dyslipidemias, focusing on the actions in thrombotic modulation, vascular and cardiovascular-related diseases, metabolic diseases including metabolic syndrome, diabetes, hyperlipidemia, and hypertension, and chronic diseases such as cancer, chronic obstructive pulmonary disease, and chronic kidney disease. Furthermore, we were prompted to delved deeper in the molecular mechanisms by means statins regulate coagulation acting on liver, platelets, and endothelium. Clinical evidence show that statins are effective regulators of dyslipidemia with a high impact in hemostasis regulation and its deleterious consequences. However, studies are required to elucidate its underlying molecular mechanism and improving their therapeutical actions.

Preferential uptake of SARS-CoV-2 by pericytes potentiates vascular damage and permeability in an organoid model of the microvasculature

AIMS

Thrombotic complications and vasculopathy have been extensively associated with severe COVID-19 infection; however, the mechanisms inducing endotheliitis and the disruption of endothelial integrity in the microcirculation are poorly understood. We hypothesized that within the vessel wall, pericytes preferentially take up viral particles and mediate the subsequent loss of vascular integrity.

METHODS AND RESULTS

Immunofluorescence of post-mortem patient sections was used to assess pathophysiological aspects of COVID-19 infection. The effects of COVID-19 on the microvasculature were assessed using a vascular organoid model exposed to live viral particles or recombinant viral antigens. We find increased expression of the viral entry receptor angiotensin-converting enzyme 2 on pericytes when compared to vascular endothelium and a reduction in the expression of the junctional protein CD144, as well as increased cell death, upon treatment with both live virus and/or viral antigens. We observe a dysregulation of genes implicated in vascular permeability, including Notch receptor 3, angiopoietin-2, and TEK. Activation of vascular organoids with interleukin-1β did not have an additive effect on vascular permeability. Spike antigen was detected in some patients' lung pericytes, which was associated with a decrease in CD144 expression and increased platelet recruitment and von Willebrand factor (VWF) deposition in the capillaries of these patients, with thrombi in large vessels rich in VWF and fibrin.

CONCLUSION

Together, our data indicate that direct viral exposure to the microvasculature modelled by organoid infection and viral antigen treatment results in pericyte infection, detachment, damage, and cell death, disrupting pericyte-endothelial cell crosstalk and increasing microvascular endothelial permeability, which can promote thrombotic and bleeding complications in the microcirculation.

Assessment and Monitoring of Coagulation in Patients with COVID-19: A Review of Current Literature

Coagulation abnormalities are common in patients with COVID-19 and associated with high morbidity and mortality. It became a daily challenge to navigate through these abnormal laboratory findings and deliver the best possible treatment to the patients. The unique character of COVID-19-induced coagulopathy necessitates not only a dynamic follow-up of the patients in terms of hemostatic findings but also the introduction of new diagnostic methods to determine the overall function of the coagulation system in real time. After the recognition of the high risk of thromboembolism in COVID-19, several professional societies published their recommendations regarding anticoagulation in patients with COVID-19. This review summarizes common hemostatic findings in COVID-19 patients and presents the societal recommendations regarding the use of coagulation laboratory findings in clinical decision-making. Although several studies have investigated coagulation parameters in patients with COVID-19, the methodological shortcomings of published studies as well as the differences in employed anticoagulation regimens that have changed over time, depending on national and international guidelines, limit the applicability of these findings in other clinical settings. Accordingly, evidence-based recommendations for diagnostics during acute COVID-19 infection are still lacking. Future studies should verify the role of coagulation parameters as well as viscoelastic methods in the management of patients with COVID-19.

Plasma biomarkers associated with survival and thrombosis in hospitalized COVID-19 patients

Severe coronavirus disease-19 (COVID-19) has been associated with fibrin-mediated hypercoagulability and thromboembolic complications. To evaluate potential biomarkers of coagulopathy and disease severity in COVID-19, we measured plasma levels of eight biomarkers potentially associated with coagulation, fibrinolysis, and platelet function in 43 controls and 63 COVID-19 patients, including 47 patients admitted to the intensive care unit (ICU) and 16 non-ICU patients. COVID-19 patients showed significantly elevated levels of fibrinogen, tissue plasminogen activator (t-PA), and its inhibitor plasminogen activation inhibitor 1 (PAI-1), as well as ST2 (the receptor for interleukin-33) and von Willebrand factor (vWF) compared to the control group. We found that higher levels of t-PA, ST2, and vWF at the time of admission were associated with lower survival rates, and that thrombotic events were more frequent in patients with initial higher levels of vWF. These results support a predictive role of specific biomarkers such as t-PA and vWF in the pathophysiology of COVID-19. The data provide support for the case that hypercoagulability in COVID-19 is fibrin-mediated, but also highlights the important role that vWF may play in the genesis of thromboses in the pathophysiology of COVID-19. Interventions designed to enhance fibrinolysis might prove to be useful adjuncts in the treatment of coagulopathy in a subset of COVID-19 patients.

Microvascular lung injury and endoplasmic reticulum stress in systemic lupus erythematosus-associated alveolar hemorrhage and pulmonary vasculitis

Human COPA mutations affecting retrograde Golgi-to-endoplasmic reticulum (ER) protein transport cause diffuse alveolar hemorrhage (DAH) and ER stress ("COPA syndrome"). Patients with SLE also can develop DAH. C57BL/6 (B6) mice with pristane-induced lupus develop monocyte-dependent DAH indistinguishable from human DAH, whereas BALB/c mice are resistant. We examined Copa and ER stress in pristane-induced lupus. Copa expression, ER stress, vascular injury, and apoptosis were assessed in mice and COPA was quantified in blood from patients with SLE. Copa mRNA and protein expression were impaired in B6 mice with pristane-induced DAH, but not in pristane-treated BALB/c mice. An ER stress response (increased Hsp5a/BiP, Ddit3/CHOP, Eif2a, and spliced Xbp1) was seen in lungs from pristane-treated B6, but not BALB/c, mice. Resistance of BALB/c mice to DAH was overcome by treating them with low-dose thapsigargin plus pristane. CB6F1 mice did not develop DAH or ER stress, suggesting that susceptibility was recessive. Increased pulmonary expression of von Willebrand factor (Vwf), a marker of endothelial injury, and the chemokine Ccl2 in DAH suggested that pristane promotes lung microvascular injury and monocyte recruitment. Consistent with that possibility, lung endothelial cells and infiltrating bone marrow-derived cells from pristane-treated B6 mice expressed BiP and showed evidence of apoptosis (annexin-V and activated caspase-3 staining). COPA expression also was low in patients with SLE with lung involvement. Pristane-induced DAH may be initiated by endothelial injury, resulting in ER stress, apoptosis of lung endothelial cells, and recruitment of myeloid cells that propagate lung injury. The pathogenesis of DAH in SLE and COPA syndrome may overlap.

HIGH HEPARANASE LEVEL IN SURVIVORS OF COVID-19 - INDICATOR OF VASCULAR AND PULMONARY RECOVERY?

ABSTRACT

Background: Severe progression of coronavirus disease 2019 (COVID-19) causes respiratory failure and critical illness. Recently, COVID-19 has been associated with heparanase (HPSE)-induced endothelial barrier dysfunction and inflammation, so called endothelitis, and therapeutic treatment with heparin or low-molecular-weight heparin (LMWH) targeting HPSE has been postulated. Because, up to this date, clinicians are unable to measure the severity of endothelitis, which can lead to multiorgan failure and concomitant death, we investigated plasma levels of HPSE and heparin-binding protein (HBP) in COVID-19 intensive care patients to render a possible link between endothelitis and these plasma parameters. Therefore, a prospective prolonged cohort study was conducted, including 47 COVID-19 patients from the intensive care unit. Plasma levels of HPSE, and HBP were measured daily by enzyme-linked immunosorbent assay in survivors (n = 35) and nonsurvivors (n = 12) of COVID-19 from admission until discharge or death. All patients were either treated with heparin or LMWH, aiming for an activated partial thromboplastin time of ≥60 seconds or an anti-Xa level of >0.8 IU/mL using enoxaparin, depending on the clinical status of the patient (patients with extracorporeal membrane oxygenation or >0.1 μg/kg/min noradrenaline received heparin, all others enoxaparin). Results: We found significantly higher plasma levels of HPSE and HBP in survivors and nonsurvivors of COVID-19, compared with healthy controls. Still, interestingly, plasma HPSE levels were significantly higher ( P < 0.001) in survivors compared with nonsurvivors of COVID-19. In contrast, plasma HBP levels were significantly reduced ( P < 0.001) in survivors compared with nonsurvivors of COVID-19. Furthermore, when patients received heparin, they had significantly lower HPSE ( P = 2.22 e - 16) and significantly higher HBP ( P = 0.00013) plasma levels as when they received LMWH. Conclusion: Our results demonstrated that patients, who recover from COVID-19-induced vascular and pulmonary damage and were discharged from the intensive care unit, have significantly higher plasma HPSE level than patients who succumb to COVID-19. Therefore, HPSE is not suitable as marker for disease severity in COVID-19 but maybe as marker for patient's recovery. In addition, patients receiving therapeutic heparin treatment displayed significantly lower heparanse plasma level than upon therapeutic treatment with LMWH.

COVID-19-associated Lung Microvascular Endotheliopathy: A "From the Bench" Perspective

Rationale: Autopsy and biomarker studies suggest that endotheliopathy contributes to coronavirus disease (COVID-19)-associated acute respiratory distress syndrome. However, the effects of COVID-19 on the lung endothelium are not well defined. We hypothesized that the lung endotheliopathy of COVID-19 is caused by circulating host factors and direct endothelial infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Objectives: We aimed to determine the effects of SARS-CoV-2 or sera from patients with COVID-19 on the permeability and inflammatory activation of lung microvascular endothelial cells. Methods: Human lung microvascular endothelial cells were treated with live SARS-CoV-2; inactivated viral particles; or sera from patients with COVID-19, patients without COVID-19, and healthy volunteers. Permeability was determined by measuring transendothelial resistance to electrical current flow, where decreased resistance signifies increased permeability. Inflammatory mediators were quantified in culture supernatants. Endothelial biomarkers were quantified in patient sera. Measurements and Main Results: Viral PCR confirmed that SARS-CoV-2 enters and replicates in endothelial cells. Live SARS-CoV-2, but not dead virus or spike protein, induces endothelial permeability and secretion of plasminogen activator inhibitor 1 and vascular endothelial growth factor. There was substantial variability in the effects of SARS-CoV-2 on endothelial cells from different donors. Sera from patients with COVID-19 induced endothelial permeability, which correlated with disease severity. Serum levels of endothelial activation and injury biomarkers were increased in patients with COVID-19 and correlated with severity of illness. Conclusions: SARS-CoV-2 infects and dysregulates endothelial cell functions. Circulating factors in patients with COVID-19 also induce endothelial cell dysfunction. Our data point to roles for both systemic factors acting on lung endothelial cells and viral infection of endothelial cells in COVID-19-associated endotheliopathy.

Prognostic value of von Willebrand factor and ADAMTS13 in patients with COVID-19: A systematic review and meta-analysis

BACKGROUND

Endotheliopathy and coagulopathy appear to be the main causes for critical illness and death in patients with coronavirus disease 2019 (COVID-19). The adhesive ligand von Willebrand factor (VWF) has been involved in immunothrombosis responding to endothelial injury. Here, we reviewed the current literature and performed meta-analyses on the relationship between both VWF and its cleaving protease ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13) with the prognosis of COVID-19.

METHODS

We searched MEDLINE, Cochrane Library, Web of Science, and EMBASE databases from inception to 4 March 2022 for studies analyzing the relationship between VWF-related variables and composite clinical outcomes of patients with COVID-19. The VWF-related variables analyzed included VWF antigen (VWF:Ag), VWF ristocetin cofactor (VWF:Rco), ADAMTS13 activity (ADAMTS13:Ac), the ratio of VWF:Ag to ADAMTS13:Ac, and coagulation factor VIII (FVIII). The unfavorable outcomes were defined as mortality, intensive care unit (ICU) admission, and severe disease course. We used random or fixed effects models to create summary estimates of risk. Risk of bias was assessed based on the principle of the Newcastle-Ottawa Scale.

RESULTS

A total of 3764 patients from 40 studies were included. The estimated pooled means indicated increased plasma levels of VWF:Ag, VWF:Rco, and VWF:Ag/ADAMTS13:Ac ratio, and decreased plasma levels of ADAMTS13:Ac in COVID-19 patients with unfavorable outcomes when compared to those with favorable outcomes (composite outcomes or subgroup analyses of non-survivor versus survivor, ICU versus non-ICU, and severe versus non-severe). In addition, FVIII were higher in COVID-19 patients with unfavorable outcomes. Subgroup analyses indicated that FVIII was higher in patients admitting to ICU, while there was no significant difference between non-survivors and survivors.

CONCLUSIONS

The imbalance of the VWF-ADAMTS13 axis (massive quantitative and qualitative increases of VWF with relative deficiency of ADAMTS13) is associated with poor prognosis of patients with COVID-19.

COVID-19-associated liver injury: Clinical characteristics, pathophysiological mechanisms and treatment management

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has become a global epidemic and poses a major threat to public health. In addition to COVID-19 manifesting as a respiratory disease, patients with severe disease also have complications in extrapulmonary organs, including liver damage. Abnormal liver function is relatively common in COVID-19 patients; its clinical manifestations can range from an asymptomatic elevation of liver enzymes to decompensated hepatic function, and liver injury is more prevalent in severe and critical patients. Liver injury in COVID-19 patients is a comprehensive effect mediated by multiple factors, including liver damage directly caused by SARS-CoV-2, drug-induced liver damage, hypoxia reperfusion dysfunction, immune stress and inflammatory factor storms. Patients with chronic liver disease (especially alcohol-related liver disease, nonalcoholic fatty liver disease, cirrhosis and hepatocellular carcinoma) are at increased risk of severe disease and death after infection with SARS-CoV-2, and COVID-19 aggravates liver damage in patients with chronic liver disease. This article reviews the latest SARS-CoV-2 reports, focusing on the liver damage caused by COVID-19 and the underlying mechanism, and expounds on the risk, treatment and vaccine safety of SARS-CoV-2 in patients with chronic liver disease and liver transplantation.

Assessment of COVID -19 associated coagulopathy and multiple hemostatic markers: a single center study in Egypt

Background

Coagulopathy is still a serious pattern of coronavirus-19 disease. We aimed to evaluate COVID-19-associated coagulopathy and multiple hemostatic markers in Egyptian patients. In addition, to assess coagulation acute phase reactants and its effect on the outcome.

Methods

The study included 106 COVID-19 patients, and 51 controls. All patients were positive for COVID-19 infection by nasopharyngeal swab for detection of viral RNA by real-time PCR. In addition to baseline data and radiological findings, the coagulation profile was done with special attention to Fibrinogen, d-dimer, Factor VIII, von Willebrand factor (VWF), Protein C, Protein S, Antithrombin III (ATIII) and Lupus anticoagulant (LA)-1 and 2.

Results

The results showed significantly higher VWF, d-dimer, and LA1 (screening) and LA2 (confirmation) in patients than a control group. Significantly higher d-dimer FVIII, VWF and LA1-2 were detected in the severe group. ATIII had high diagnostic accuracy in severity prediction. We found a significantly higher international randomized ratio (INR) and VWF among patients with thrombotic events. For prediction of thrombosis; VWF at cutoff > 257.7 has 83.3% sensitivity and 83.3% specificity.

Conclusion

Patients with COVID-19 infection are vulnerable to different forms of coagulopathy. This could be associated with poor outcomes. d-Dimer is a chief tool in diagnosis, severity evaluation but not thrombosis prediction. Early screening for this complication and its proper management would improve the outcome.

D-dimer, BNP/NT-pro-BNP, and creatinine are reliable decision-making biomarkers in life-sustaining therapies withholding and withdrawing during COVID-19 outbreak

Background

The decision for withholding and withdrawing of life-sustaining treatments (LSTs) in COVID-19 patients is currently based on a collegial and mainly clinical assessment. In the context of a global pandemic and overwhelmed health system, the question of LST decision support for COVID-19 patients using prognostic biomarkers arises.

Methods

In a multicenter study in 24 French hospitals, 2878 COVID-19 patients hospitalized in medical departments from 26 February to 20 April 2020 were included. In a propensity-matched population, we compared the clinical, biological, and management characteristics and survival of patients with and without LST decision using Student's t-test, the chi-square test, and the Cox model, respectively.

Results

An LST was decided for 591 COVID-19 patients (20.5%). These 591 patients with LST decision were secondarily matched (1:1) based on age, sex, body mass index, and cancer history with 591 COVID-19 patients with no LST decision. The patients with LST decision had significantly more cardiovascular diseases, such as high blood pressure (72.9 vs. 66.7%, p = 0.02), stroke (19.3 vs. 11.1%, p < 0.001), renal failure (30.4 vs. 17.4%, p < 0.001), and heart disease (22.5 vs. 14.9%, p < 0.001). Upon admission, LST patients were more severely attested by a qSOFA score ≥2 (66.5 vs. 58.8%, p = 0.03). Biologically, LST patients had significantly higher values of D-dimer, markers of heart failure (BNP and NT-pro-BNP), and renal damage (creatinine) (p < 0.001). Their evolutions were more often unfavorable (in-hospital mortality) than patients with no LST decision (41.5 vs. 10.3%, p < 0.001). By combining the three biomarkers (D-dimer, BNP and/or NT-proBNP, and creatinine), the proportion of LST increased significantly with the number of abnormally high biomarkers (24, 41.3, 48.3, and 60%, respectively, for none, one, two, and three high values of biomarkers, trend p < 0.01).

Conclusion

The concomitant increase in D-dimer, BNP/NT-proBNP, and creatinine during the admission of a COVID-19 patient could represent a reliable and helpful tool for LST decision. Circulating biomarker might potentially provide additional information for LST decision in COVID-19.

Lower brachial artery flow-mediated dilation is associated with a worse prognosis and more lung parenchymal involvement in Covid-19: Prospective observational study

Severe acute respiratory syndrome coronavirus-2 is a highly infectious pathogenic coronavirus, which has appeared toward the end of 2019. The virus seen all over the world caused a pandemic of an acute respiratory disease named coronavirus disease 2019 (Covid-19). It has been shown that the virus that uses angiotensin-converting enzyme 2 receptors is causing endothelial dysfunction resulting in vascular inflammation and coagulopathy. It is possible to assess endothelial dysfunction by the flow-mediated dilatation (FMD) technique. Our study aimed to demonstrate the effect of endothelial dysfunction assessed using the FMD on prognosis and mortality in the patients hospitalized with the diagnosis of Covid-19. In this prospective observational study, endothelial functions of 94 patients hospitalized due to the Covid-19 in the ward or intensive care unit (ICU) were evaluated by FMD. The relationship among endothelial dysfunction and prognosis of disease, biochemical parameters, lung involvement, and mortality was investigated. We found that the FMD% values of the Covid-19 ICU patients compared to those followed up in the ward (2.66 ± 0.62 vs. 5.23 ± 1.46/P < .001) and those who died due to Covid-19 compared to those who were discharged alive (2.57 ± 0.22 vs. 4.66 ± 1.7/P < .001) were significantly lower. There were moderate negative correlation between FMD% and peak values of D-dimer (r = -0.52, P < .001), troponin (r = -0.45, P < .001), ferritin (r = -0.47, P < .001), lactate dehydrogenase (r = -0.49, P < .001), and white blood cells count (r = -0.23, P = .024). Lower FMD% was associated with higher lung parenchymal involvement (P < .001). The optimum cutoff point of FMD in predicting mortality was found to be 3.135% (sensitivity: 1, selectivity: 0.70). According to our results, lower FMD% was associated with higher lung parenchyma involvement, ICU admission, and mortality rate in Covid-19 patients. The best cutoff point for predicting mortality of FMD was 3.135%. Nevertheless, largescale, multicenter studies are needed to evaluate lower FMD values as a risk factor for mortality in Covid-19.

Peculiarities of hemostasis in patients with COVID-19

Aim. Analysis of the dynamics of different stages of clot formation and its lysis in patients with different COVID-19 severity. Materials and methods. We prospectively included 58 patients with COVID-19 (39 patients with moderate disease severity and 18 patients with severe disease) and 47 healthy volunteers as a control group. All participants underwent the assessment of flow-mediated dilation (FMD) of brachial artery, impedance aggregometry, rotational thromboelastometry and thrombodynamics. Von Willebrand factor antigen (vWF:Ag) quantification was also performed in patients with COVID-19. Measurements were repeated on the 3rd and 9th day of hospitalization. Results. Compared to the control group, patients with COVID-19 showed reduced values of platelet aggregation and greater values of the clot growth rate, as well as its size and density. On the first day of hospitalization, we found no differences in the activity of plasma hemostasis and endogenous fibrinolysis between subgroups of patients. With the progression of the disease, the growth rate and size of the clot were higher in the severe subgroup, even despite higher doses of anticoagulants in this subgroup. An increase in platelet aggregation was noted during the progression of the disease, especially in the severe subgroup. There were no differences in the results of the FMD test by subgroups of patients. The vWF:Ag level was significantly higher in the severe subgroup. Conclusion. Thus, plasma hemostasis followed by secondary platelet activation correlates with the severity of COVID-19. Patients with moderate to severe coronavirus infection have predominantly local rather than generalized endothelial dysfunction.

The rising impact of angiogenesis research

While inhibiting pathological angiogenesis has been long associated with the field of oncology, recent advances in angiogenesis research have impacted the progress of disease treatment for additional non-malignant diseases or chronic conditions in the fields of ophthalmology, cardiology, and gynecology. Moreover, stimulators of angiogenesis find application in ischemic diseases, while inhibitors of angiogenesis are being used to limit blood vessel formation, but in judicious ways that modify or "reprogram" the vasculature as a reinforcement for immunotherapy. We have noticed an increasing impact, as evidenced by increases in the total number of citations, in the literature surrounding the angiogenesis field suggesting that targeting angiogenesis per se is well established as a tractable approach for therapy in diverse conditions.

Vasculopathy in COVID-19

COVID-19 is a primary respiratory illness that is frequently complicated by systemic involvement of the vasculature. Vascular involvement leads to an array of complications ranging from thrombosis to pulmonary edema secondary to loss of barrier function. This review will address the vasculopathy of COVID-19 with a focus on the role of the endothelium in orchestrating the systemic response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The endothelial receptor systems and molecular pathways activated in the setting of COVID-19 and the consequences of these inflammatory and prothrombotic changes on endothelial cell function will be discussed. The sequelae of COVID-19 vascular involvement at the level of organ systems will also be addressed, with an emphasis on the pulmonary vasculature but with consideration of effects on other vascular beds. The dramatic changes in endothelial phenotypes associated with COVID-19 has enabled the identification of biomarkers that could help guide therapy and predict outcomes. Knowledge of vascular pathogenesis in COVID-19 has also informed therapeutic approaches that may control its systemic sequelae. Because our understanding of vascular response in COVID-19 continues to evolve, we will consider areas of controversy, such as the extent to which SARS-CoV-2 directly infects endothelium and the degree to which vascular responses to SARS-CoV-2 are unique or common to those of other viruses capable of causing severe respiratory disease. This conceptual framework describing how SARS-CoV-2 infection affects endothelial inflammation, prothrombotic transformation, and barrier dysfunction will provide a context for interpreting new information as it arises addressing the vascular complications of COVID-19.