Increased von Willebrand factor antigen and low ADAMTS13 activity are related to poor prognosis in covid-19 patients

ADAMTS13 or Caplacizumab Reduces the Accumulation of Neutrophil Extracellular Traps and Thrombus in Whole Blood of COVID-19 Patients under Flow

BACKGROUND

 Neutrophil NETosis and neutrophil extracellular traps (NETs) play a critical role in pathogenesis of coronavirus disease 2019 (COVID-19)-associated thrombosis. However, the extents and reserve of NETosis, and potential of thrombus formation under shear in whole blood of patients with COVID-19 are not fully elucidated. Neither has the role of recombinant ADAMTS13 or caplacizumab on the accumulation of NETs and thrombus in COVID-19 patients' whole blood under shear been investigated.

METHODS

 Flow cytometry and microfluidic assay, as well as immunoassays, were employed for the study.

RESULTS

 We demonstrated that the percentage of H3Cit + MPO+ neutrophils, indicative of NETosis, was dramatically increased in patients with severe but not critical COVID-19 compared with that in asymptomatic or mild disease controls. Upon stimulation with poly [I:C], a double strain DNA mimicking viral infection, or bacterial shigatoxin-2, the percentage of H3Cit + MPO+ neutrophils was not significantly increased in the whole blood of severe and critical COVID-19 patients compared with that of asymptomatic controls, suggesting the reduction in NETosis reserve in these patients. Microfluidic assay demonstrated that the accumulation of NETs and thrombus was significantly enhanced in the whole blood of severe/critical COVID-19 patients compared with that of asymptomatic controls. Like DNase I, recombinant ADAMTS13 or caplacizumab dramatically reduced the NETs accumulation and thrombus formation under arterial shear.

CONCLUSION

 Significantly increased neutrophil NETosis, reduced NETosis reserve, and enhanced thrombus formation under arterial shear may play a crucial role in the pathogenesis of COVID-19-associated coagulopathy. Recombinant ADAMTS13 or caplacizumab may be explored for the treatment of COVID-19-associated thrombosis.

Evaluating the potential mediating role of ADAMTS13 activity in the relationship between obesity and the severity of COVID-19: A retrospective cohort study

Obesity and low enzyme A disintegrin and metalloproteinase with thrombospondin type-1 motif-13 (ADAMTS13) activity have been linked to poor coronavirus disease 2019 (COVID-19). Given that obesity may influence ADAMTS13 activity, it is feasible; however, it remains unclear whether ADAMTS13 activity acts as a mediator between obesity and COVID-19 outcomes. We investigated the link between body mass index (BMI) and COVID-19 outcomes, using ADAMTS13 activity as a mediator. ADAMTS13 activity was measured in 86 hospitalized COVID-19 patients. BMI, ADAMTS13 activity, and COVID-19 outcomes were assessed. Obese patients had a high odds ratio for low ADAMTS13 levels. When different levels of ADAMTS13 activity were considered, the severity of COVID-19 in obese patients was 4.5 times that in the normal BMI group. Furthermore, increased coagulopathy indicators correlated with low ADAMTS13 activity. Patients with elevated ALT and AST levels showed a 3 to 4-fold increase in the chances of low ADAMTS13 activity (OR:3.19, 95% CI:1.22-8.90, P = .021; OR:2.17, 95% CI:0.91-5.27, P = .082, respectively). When ADAMTS13 activity was considered, obese patients had greater COVID-19 severity and slower viral clearance than those with normal BMI. Low ADAMTS13 activity and impaired liver function are associated with poor COVID-19 outcomes. These findings encourage researchers to use molecular component identification to study the effects of obesity on the von Willebrand factor (VWF)/ADAMTS13 axis, COVID-19 pathogenesis, and outcomes.

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.

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.

Status of major hemostatic components in the setting of COVID-19: the effect on endothelium, platelets, coagulation factors, fibrinolytic system, and complement

The coagulation, fibrinolytic, anticoagulation, and complement systems are in delicate balance with the vessel wall endothelium ensuring appropriate hemostasis. Coagulopathy in coronavirus disease 2019 (COVID-19) is not a simple disorder of one hemostatic component but a complicated process affecting most of the hemostasis system. COVID-19 disturbs the balance between the procoagulant systems and the regulatory mechanisms. Here, we investigate the effect of COVID-19 on key hemostatic components, including platelets, endothelial cells, coagulation factors, fibrinolytic system, anticoagulant protein system, and complement system, to improve our understanding of the pathophysiological processes underlying COVID-19 coagulopathy based on evidence.

Biomarkers of endothelial dysfunction are associated with poor outcome in COVID-19 patients: A systematic review and meta-analysis

Numerous studies have linked coronavirus disease 2019 (COVID-19) with endothelial dysfunction and reported elevated levels of endothelial biomarkers in this disease. We conducted a systematic review and meta-analysis of the published evidence in this respect. A systematic literature search of PubMed and Scopus databases was performed to find studies investigating biomarkers of endothelial dysfunction in COVID-19 patients. Pooled standardized mean differences and their 95% confidence intervals were calculated for each biomarker using random effect model. 74 studies with 7668 patients were included. In comparison to patients with good outcome, those with poor outcome had higher levels of von Willebrand factor (vWF) (SMD: 0.83, 95% CI: 0.59-1.07, p < 0.00001), vWF:ADAMTS13 (1.23, (0.77-1.7), p < 0.00001), angiopoietin-2 (Ang-2) (1.06 (0.6-1.51), p < 0.0001), E-selectin (1.09 (0.55-1.63), p < 0.0001), P-selectin (0.59 (0.24-0.94), p = 0.001), syndecan-1 (0.99 (0.6-1.37), p < 0.00001), mid-regional pro-adrenomedullin (MR-proADM) (1.52 (1.35-1.68), p < 0.00001), vascular endothelial growth factor (0.27 (0.02-0.53), p = 0.03), soluble fms-like tyrosine kinase-1 (sFLT-1) (1.93 (0.65-3.21), p = 0.03) and lower levels of ADAMTS13 antigen (-0.69 (-0.9 to -0.47) p < 0.00001) and activity (-0.84 (-1.06 to -0.61) p < 0.0000). Plasminogen activator inhibitor-1 and tissue plasminogen activator levels were not different between the two groups (p < 0.05). There were elevated levels of endothelial dysfunction biomarkers in COVID-19 patients with poor outcome, indicating their possible role in disease severity and prognosis. In particular, MR-proADM, vWF, syndecan-1 and sFLT-1 showed a significant association with poor outcome in these patients.

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.

An update on the pathogenesis and diagnosis of thrombotic thrombocytopenic purpura

INTRODUCTION

Severe ADAMTS13 deficiency defines thrombotic thrombocytopenic purpura (TTP). ADAMTS13 is responsible for VWF cleavage. In the absence of this enzyme, widespread thrombi formation occurs, causing microangiopathic anemia and thrombocytopenia and leading to ischemic organ injury. Understanding ADAMTS13 function is crucial to diagnose and manage TTP, both in the immune and hereditary forms.

AREAS COVERED

The role of ADAMTS13 in coagulation homeostasis and the consequences of its deficiency are detailed. Other factors that modulate the consequences of ADAMTS13 deficiency are explained, such as complement system activation, genetic predisposition, or the presence of an inflammatory status. Clinical suspicion of TTP is crucial to start prompt treatment and avoid mortality and sequelae. Available techniques to diagnose this deficiency and detect autoantibodies or gene mutations are presented, as they have become faster and more available in recent years.

EXPERT OPINION

A better knowledge of TTP pathophysiology is leading to an improvement in diagnosis and follow-up, as well as a customized treatment in patients with TTP. This scenario is necessary to define the role of new targeted therapies already available or coming soon and the need to better diagnose and monitor at the molecular level the evolution of the disease.

A novel mechanism underlying allosteric regulation of ADAMTS-13 revealed by hydrogen-deuterium exchange plus mass spectrometry

Background

ADAMTS-13, a plasma metalloprotease, cleaves von Willebrand factor. ADAMTS-13 activity appears to be regulated through allosteric inhibition by its distal C-terminus.

Objectives

The objective of this study was to better understand how domain-domain interactions may affect ADAMTS-13 conformations and functions.

Methods

We performed deuterium-hydrogen exchange plus mass spectrometry to assess the number and rate of deuterium incorporation into various peptides of full-length ADAMTS-13 and its truncated variants.

Results

Under physiological conditions, a bimodal distribution of deuterium incorporation was detected in the peptides from metalloprotease (217-230 and 282-304), cysteine-rich (446-482), and CUB (for complement C1r/C1s, Uegf, Bmp1) domains (1185-1214, 1313-1330, 1341-1347, 1358-1378, and 1393-1407) of full-length recombinant ADAMTS-13, but not of truncated variants. These results suggest that the full-length ADAMTS-13 undergoes conformational changes. On removal of the middle and distal C-terminal domains, the number and rate of deuterium incorporation were increased in the peptides from cysteine-rich (445-467, 467-482, and 495-503) and spacer domains (621-642 and 655-654) but decreased in the peptides from metalloprotease (115-124, 217-230, and 274-281). Moreover, most peptides, except for 217-230 and 1357-1376, exhibited a pD-dependent deuterium incorporation in the full-length ADAMTS-13, but not in the truncated variant (eg, MDTCS or T5C). These results further suggest that the bimodal deuterium incorporation observed in the peptides from the full-length ADAMTS-13 is the result of potential impact from the middle to distal C-terminal domains. Surface plasmon resonance revealed the direct binding interactions between the distal and proximal domains of ADAMTS-13.

Conclusion

Our results provide novel insight on how intramolecular interactions may affect conformations of ADAMTS-13, thus regulating its proteolytic functions.

An update on angiotensin-converting enzyme 2 structure/functions, polymorphism, and duplicitous nature in the pathophysiology of coronavirus disease 2019: Implications for vascular and coagulation disease associated with severe acute respiratory syndrome coronavirus infection

It has been known for many years that the angiotensin-converting enzyme 2 (ACE2) is a cell surface enzyme involved in the regulation of blood pressure. More recently, it was proven that the severe acute respiratory syndrome coronavirus (SARS-CoV-2) interacts with ACE2 to enter susceptible human cells. This functional duality of ACE2 tends to explain why this molecule plays such an important role in the clinical manifestations of coronavirus disease 2019 (COVID-19). At the very start of the pandemic, a publication from our Institute (entitled "ACE2 receptor polymorphism: susceptibility to SARS-CoV-2, hypertension, multi-organ failure, and COVID-19 disease outcome"), was one of the first reviews linking COVID-19 to the duplicitous nature of ACE2. However, even given that COVID-19 pathophysiology may be driven by an imbalance in the renin-angiotensin system (RAS), we were still far from understanding the complexity of the mechanisms which are controlled by ACE2 in different cell types. To gain insight into the physiopathology of SARS-CoV-2 infection, it is essential to consider the polymorphism and expression levels of the ACE2 gene (including its alternative isoforms). Over the past 2 years, an impressive amount of new results have come to shed light on the role of ACE2 in the pathophysiology of COVID-19, requiring us to update our analysis. Genetic linkage studies have been reported that highlight a relationship between ACE2 genetic variants and the risk of developing hypertension. Currently, many research efforts are being undertaken to understand the links between ACE2 polymorphism and the severity of COVID-19. In this review, we update the state of knowledge on the polymorphism of ACE2 and its consequences on the susceptibility of individuals to SARS-CoV-2. We also discuss the link between the increase of angiotensin II levels among SARS-CoV-2-infected patients and the development of a cytokine storm associated microvascular injury and obstructive thrombo-inflammatory syndrome, which represent the primary causes of severe forms of COVID-19 and lethality. Finally, we summarize the therapeutic strategies aimed at preventing the severe forms of COVID-19 that target ACE2. Changing paradigms may help improve patients' therapy.

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.

ADAMTS13 protease or lack of von Willebrand factor protects irradiation and melanoma-induced thrombotic microangiopathy in zebrafish

BACKGROUND

Severe deficiency of plasma ADAMTS13 activity may result in potentially fatal thrombotic thrombocytopenic purpura and relative deficiency of plasma ADAMTS13 activity may be associated with adverse outcomes of certain malignancies. Here, we report the role of ADAMTS13 or lack of von Willebrand factor (VWF) in reducing irradiation and melanoma-induced thrombotic microangiopathy (TMA) and mortality in zebrafish.

METHODS

Zebrafish melanoma cell line (ZMEL) was injected subcutaneously into wild-type (wt), adamts13-/- (a13-/- ), von Willebrand factor (vwf-/- ), and a13-/- vwf-/- zebrafish following total body irradiation; the tumor growth, its gene expression pattern, the resulting thrombocytopenia, and the mortality were determined.

RESULTS

Total body irradiation at 30 Gy alone resulted in a transient thrombocytopenia in both wt and a13-/- zebrafish. However, thrombocytopenia occurred earlier and more profound in a13-/- than in wt zebrafish, which was resolved 2 weeks following irradiation alone. An inoculation of ZMEL following the irradiation resulted in more severe and persistent thrombocytopenia, as well as earlier death in a13-/- than in wt zebrafish. The vwf-/- or a13-/- vwf-/- zebrafish were protected from developing severe thrombocytopenia following the same maneuvers. RNA-sequencing revealed significant differentially expressed genes associated with oxidation-reduction, metabolism, lipid, fatty acid and cholesterol metabolic processes, steroid synthesis, and phospholipid efflux in the melanoma explanted from a13-/- zebrafish compared with that from the wt controls.

CONCLUSIONS

Our results indicated that plasma ADAMTS13 or lack of VWF may offer a significant protection against the development of irradiation- and/or melanoma-induced TMA. Such a microenvironment may directly affect melanoma cell phenotypes via alternation in the oxidation-reduction and lipid metabolic pathways.

COVID-19 and thrombosis: The role of hemodynamics

Severe coronavirus disease 2019 (COVID-19) is characterized by an increased risk of thromboembolic events, a leading cause for adverse outcomes in patients afflicted by the more serious manifestation of the disease. These thromboembolic complications expressed as sepsis-induced coagulopathy, disseminated intravascular coagulation, venous and arterial thromboembolism, pulmonary embolism, microthrombosis, and thrombotic microangiopathy have been observed to affect different organs such as the lungs, heart, kidneys, and brain. Endothelial injury and dysfunction have been identified as the critical pathway towards thrombogenesis, and contributions of other mechanisms such as hypercoagulability, cytokine storm, neutrophils have been studied. However, the contribution of hemodynamic pathways towards thrombosis in severe COVID-19 cases has not been investigated. From the classical theory of Virchow's triad to the contemporary studies on the effect of shear enhanced platelet activation, it is well established that hemodynamics plays a role in the initiation and growth of thrombosis. This article reviews recent studies on COVID-19 related thrombotic events and offers hypotheses on how hemodynamics may be responsible for some of the adverse outcomes observed in severe COVID-19 cases. While thrombogenesis through endothelial injury and the effects of hypercoagulability on thrombosis are briefly addressed, the crux of the discussion is focused on hemodynamic factors such as stasis, turbulent flow, and non-physiological shear stress and their effects on thrombosis. In addition, hemodynamics-dependent venous, arterial, and microvascular thrombosis in COVID-19 cases is discussed. We also propose further investigation of diagnostic and therapeutic options that address the hemodynamics aspects of COVID-19 thrombus formation to assess their potential in patient care.

Endotheliopathy marked by high von Willebrand factor (vWF) antigen in COVID-19 is associated with poor outcome: a systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis aimed to compare the levels of von Willebrand Factor (vWF) antigen in patients with coronavirus disease 2019 (COVID-19) with a poor outcome compared with those with a good outcome, and explored factors that may affect the difference in terms of vWF antigen between the two groups.

METHODS

A comprehensive literature search of PubMed, Embase and Scopus databases was undertaken from inception until 7 April 2021. The primary outcome was poor outcome, which is a composite of mortality and severity of COVID-19.

RESULTS

Ten studies including a total of 996 patients were included in this systematic review and meta-analysis. vWF antigen was higher in patients with poor outcomes [standardized mean difference (SMD) 0.84 [0.45-1.23], P<0.001; I2=87.3, P<0.001). For subgroup analysis on studies that reported the vWF antigen level as a percentage, the mean difference was 121.6 [(53.7-189.4), P<0.001; I2=92.0, P<0.001]. Meta-regression showed that the SMD between poor outcome and good outcome was affected by the platelet count (coefficient 0.0061, P=0.001), d-dimer level (coefficient 0.0007, P=0.026) and factor VIII level (coefficient 0.0057, P=0.031), but not by age (coefficient -0.0610, P=0.440), gender (coefficient 0.0135, P=0.698), obesity (coefficient 0.0282, P=0.666), hypertension (coefficient 0.0273, P=0.423), diabetes (coefficient 0.0317, P=0.398) or malignancy (coefficient 0.0487, P=0.608).

CONCLUSION

This meta-analysis showed that the level of vWF antigen was significantly higher in patients with COVID-19 with a poor outcome, signalling marked endotheliopathy. Meta-regression showed that the differences became larger as the platelet count, d-dimer level and factor VIII level increased.

COVID-19 and the Vasculature: Current Aspects and Long-Term Consequences

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) was first identified in December 2019 as a novel respiratory pathogen and is the causative agent of Corona Virus disease 2019 (COVID-19). Early on during this pandemic, it became apparent that SARS-CoV-2 was not only restricted to infecting the respiratory tract, but the virus was also found in other tissues, including the vasculature. Individuals with underlying pre-existing co-morbidities like diabetes and hypertension have been more prone to develop severe illness and fatal outcomes during COVID-19. In addition, critical clinical observations made in COVID-19 patients include hypercoagulation, cardiomyopathy, heart arrythmia, and endothelial dysfunction, which are indicative for an involvement of the vasculature in COVID-19 pathology. Hence, this review summarizes the impact of SARS-CoV-2 infection on the vasculature and details how the virus promotes (chronic) vascular inflammation. We provide a general overview of SARS-CoV-2, its entry determinant Angiotensin-Converting Enzyme II (ACE2) and the detection of the SARS-CoV-2 in extrapulmonary tissue. Further, we describe the relation between COVID-19 and cardiovascular diseases (CVD) and their impact on the heart and vasculature. Clinical findings on endothelial changes during COVID-19 are reviewed in detail and recent evidence from in vitro studies on the susceptibility of endothelial cells to SARS-CoV-2 infection is discussed. We conclude with current notions on the contribution of cardiovascular events to long term consequences of COVID-19, also known as “Long-COVID-syndrome”. Altogether, our review provides a detailed overview of the current perspectives of COVID-19 and its influence on the vasculature.

Reduced ADAMTS13 Activity in Correlation with Pathophysiology, Severity, and Outcome of COVID-19: A Retrospective Observational Study

BACKGROUND

Low ADAMTS13 activity has been suggested to be an interplaying factor in the pathogenesis of COVID-19, considering that it is a thromboinflammatory disease with high risk of microthrombosis.

OBJECTIVES

The study aimed to explore the correlation between ADAMTS13 activity and the pathophysiological pathway of COVID-19.

METHODS

We carried out a retrospective observational study of 87 patients with COVID-19 in NMC Royal Hospital, Abu Dhabi, UAE. ADAMTS13 activity was measured and compared with patients' characteristics and clinical outcomes.

RESULTS

Low ADAMTS13 activity was associated with pneumonia (p = 0.007), severity of COVID-19 (p <0.001), and mechanical ventilation rates (p = 0.018). Death was more frequently observed among patients (5 patients) with low ADAMTS13 activity compared with normal activity (1 patient), as well as inflammatory markers. Decreased ADAMTS13 activity increased with the risk of pneumonia, severity of COVID-19, need for mechanical ventilation, and use of anticoagulants ([OR = 4.75, 95% CI 1.54-18.02, p = 0.011], [OR = 6.50, 95% CI 2.57-17.74; p <0.001], [OR = 4.10, 95% CI 1.29-15.82; p = 0.024], [OR = 8.00, 95% CI 3.13-22.16; p <0.001], respectively). The low ADAMTS13 activity group had a slightly longer time to viral clearance than the normal ADAMTS13 activity group, but it was not statistically significant (20 days, 95% CI 16-27 days vs 17 days, 95% CI 13-22 days; p = 0.08; Log rank = 3.1).

CONCLUSIONS

Low ADAMTS13 activity has been linked to pneumonia, COVID-19 severity, use of anticoagulants, and need for mechanical ventilation but not to mortality. We propose rADAMTS13 as a novel treatment for severe COVID-19.

Associations between the von Willebrand Factor-ADAMTS13 Axis, Complement Activation, and COVID-19 Severity and Mortality

Background  Endothelial and complement activation were both associated with immunothrombosis, a key determinant of COVID-19 severity, but their interrelation has not yet been investigated.

Objectives  We aimed to determine von Willebrand factor (VWF) antigen (VWF:Ag) concentration, VWF collagen binding activity (VWF:CBA), a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity (ADAMTS13:Ac), and their ratios in hospitalized COVID-19 patients, and to investigate how these parameters and their constellation with complement activation relate to disease severity and in-hospital mortality in COVID-19.

Methods  Samples of 102 hospitalized patients with polymerase chain reaction-confirmed severe acute respiratory syndrome coronavirus 2 positivity were included in our observational cohort study. Patients were stratified according to the peak severity of COVID-19 disease in agreement with the World Health Organization ordinal scale. Twenty-six convalescent plasma donors with previous COVID-19 disease formed the control group. VWF:Ag concentration and VWF:CBA were determined by enzyme-linked immunosorbent assay (ELISA); ADAMTS13:Ac was determined by fluorescence resonance energy transfer. Complement C3 and C3a were measured by turbidimetry and ELISA, respectively. Clinical covariates and markers of inflammation were extracted from hospital records.

Results  VWF:Ag and VWF:CBA were elevated in all groups of hospitalized COVID-19 patients and increased in parallel with disease severity. ADAMTS13:Ac was decreased in patients with severe COVID-19, with the lowest values in nonsurvivors. High (> 300%) VWF:Ag concentrations or decreased (< 67%) ADAMTS13:Ac were associated with higher risk of severe COVID-19 disease or in-hospital mortality. The concomitant presence of decreased ADAMTS13:Ac and increased C3a/C3 ratio—indicating complement overactivation and consumption—was a strong independent predictor of in-hospital mortality.

Conclusion  Our results suggest that an interaction between the VWF-ADAMTS13 axis and complement overactivation and consumption plays an important role in the pathogenesis of COVID-19.

Contribution of the von Willebrand factor/ADAMTS13 imbalance to COVID-19 coagulopathy

The 2019 coronavirus disease (COVID-19) is the disease caused by SARS-CoV-2 infection. Although this infection has been shown to affect the respiratory system, a high incidence of thrombotic events has been observed in severe cases of COVID-19 and in a significant portion of COVID-19 nonsurvivors. Although prior literature has reported on both the coagulopathy and hypercoagulability of COVID-19, the specifics of coagulation have not been fully investigated. Observations of microthrombosis in patients with COVID-19 have brought attention to potential inflammatory endothelial injury. Von Willebrand factor (VWF) and its protease, A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), play an important homeostatic role in responding to endothelial injury. This report provides an overview of the literature investigating the role the VWF/ADAMTS13 axis may have in COVID-19 thrombotic events and suggests potential therapeutic strategies to prevent the progression of coagulopathy in patients with COVID-19.

High levels of Von Willebrand factor markers in COVID-19: a systematic review and meta-analysis

The SARS-CoV-2 virus has spread to all corners of the world. Thrombosis is the cause of organ failure and subsequent death in COVID-19. The pathophysiology of thrombosis in COVID-19 needs to be further explored to shed light on its downside. For this reason, this meta-analysis of Von Willebrand Factor profile (VWF: Ag, VWF: activity, VWF: RCo), ADAMTS-13, and factor VIII levels in COVID-19 was performed. To obtain data on the status of the aforementioned hemostatic factors, a systematic literature review and meta-analysis were performed on COVID-19. After reviewing the evaluation of 348 papers, 28 papers included in the meta-analysis, which was performed using STATA. The analysis showed an increase in VWF: Ag levels in COVID‐19 patients. VWF: Ac was higher in all COVID-19 patients, while it was lower in the COVID‐19 ICU patients. The pooled mean of VWF: RCO in all patients with COVID-19 was 307.94%. In subgroup analysis, VWF: RCO was significantly higher in ICU patients than in all COVID-19 patients. The pooled mean of ADAMTS-13 activity was 62.47%, and 58.42% in ICU patients. The pooled mean of factor VIII level was 275.8%, which was significantly higher in ICU patients with COVID-19 than all patients with COVID-19. Levels of VWF: Ag, VWF: activity, VWF: ristocetin, and factor VIII are increased in patients with COVID-19. The elevated levels in ICU patients with COVID-19 suggest that these markers may have prognostic value in determining the severity of COVID-19. New therapeutic programs can be developed as a result.

Mechanisms of immunothrombosis in COVID-19

PURPOSE OF REVIEW

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus-2. Over the past year, COVID-19 has posed a significant threat to global health. Although the infection is associated with mild symptoms in many patients, a significant proportion of patients develop a prothrombotic state due to a combination of alterations in coagulation and immune cell function. The purpose of this review is to discuss the pathophysiological characteristics of COVID-19 that contribute to the immunothrombosis.

RECENT FINDINGS

Endotheliopathy during COVID-19 results in increased multimeric von Willebrand factor release and the potential for increased platelet adhesion to the endothelium. In addition, decreased anticoagulant proteins on the surface of endothelial cells further alters the hemostatic balance. Soluble coagulation markers are also markedly dysregulated, including plasminogen activator inhibitor-1 and tissue factor, leading to COVID-19 induced coagulopathy. Platelet hyperreactivity results in increased platelet-neutrophil and -monocyte aggregates further exacerbating the coagulopathy observed during COVID-19. Finally, the COVID-19-induced cytokine storm primes neutrophils to release neutrophil extracellular traps, which trap platelets and prothrombotic proteins contributing to pulmonary thrombotic complications.

SUMMARY

Immunothrombosis significantly contributes to the pathophysiology of COVID-19. Understanding the mechanisms behind COVID-19-induced coagulopathy will lead to future therapies for patients.

Age-Associated Increase in Thrombogenicity and Its Correlation with von Willebrand Factor

Endothelial cells that cover the lumen of all blood vessels have the inherent capacity to express both pro and anticoagulant molecules. However, under normal physiological condition, they generally function to maintain a non-thrombogenic surface for unobstructed blood flow. In response to injury, certain stimuli, or as a result of dysfunction, endothelial cells release a highly adhesive procoagulant protein, von Willebrand factor (VWF), which plays a central role in formation of platelet aggregates and thrombus generation. Since VWF expression is highly restricted to endothelial cells, regulation of its levels is among the most important functions of endothelial cells for maintaining hemostasis. However, with aging, there is a significant increase in VWF levels, which is concomitant with a significant rise in thrombotic events. It is not yet clear why and how aging results in increased VWF levels. In this review, we have aimed to discuss the age-related increase in VWF, its potential mechanisms, and associated coagulopathies as probable consequences.

Low ADAMTS-13 predicts adverse outcomes in hospitalized patients with suspected heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a life-threatening thrombotic complication after heparin exposure. However, the role of ADAMTS-13 and von Willebrand factor (VWF) in the disease process and outcomes of HIT is not known.

OBJECTIVE

To determine the potential role of ADAMTS-13 and VWF in hospitalized patients suspected with HIT.

METHODS

Associations of the HIT tests, ADAMTS-13 activity, and VWF antigen or activity with other clinical parameters and outcomes in the patients suspected with HIT were determined.

RESULTS

Of 261 patients, 87 (33.3%) were positive and 174 (66.7%) were negative for a HIT antibody determined by an enzyme immunoassay (EIA). Of these 87 EIA+ patients, 31 (35.6%) were also positive but 56 (64.4%) were negative for serotonin-releasing assay (SRA). There was no statistically significant difference among all three groups (i.e., EIA-, EIA+/SRA+, and EIA+/SRA-) as to their demographic features, reasons for admission to the hospital, type of procedures performed, and in-hospital mortality. Compared to those in the healthy controls, plasma ADAMTS-13 activity in patients suspected with HIT was significantly lower but plasma VWF antigen (VWFAg) and activity (VWFAc) in these patients were significantly higher. While there was no statistically significant difference among all three groups regarding plasma levels of ADAMTS-13 activity, VWFAg, and VWFAc, plasma levels of ADAMTS-13 activity <50% or the low ratios of ADAMTS-13 activity to VWFAg (or VWFAc) are highly predictive for a 90-day mortality rate, particularly in the EIA+SRA+ group.

CONCLUSIONS

These results demonstrate that relative deficiency of plasma ADAMTS-13 activity in hospitalized patients suspected with HIT is common, which may contribute at least in part to the adverse outcomes in this patient population, particularly in those with true HIT.

COVID-19 is a systemic vascular hemopathy: insight for mechanistic and clinical aspects

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is presenting as a systemic disease associated with vascular inflammation and endothelial injury. Severe forms of SARS-CoV-2 infection induce acute respiratory distress syndrome (ARDS) and there is still an ongoing debate on whether COVID-19 ARDS and its perfusion defect differs from ARDS induced by other causes. Beside pro-inflammatory cytokines (such as interleukin-1 β [IL-1β] or IL-6), several main pathological phenomena have been seen because of endothelial cell (EC) dysfunction: hypercoagulation reflected by fibrin degradation products called D-dimers, micro- and macrothrombosis and pathological angiogenesis. Direct endothelial infection by SARS-CoV-2 is not likely to occur and ACE-2 expression by EC is a matter of debate. Indeed, endothelial damage reported in severely ill patients with COVID-19 could be more likely secondary to infection of neighboring cells and/or a consequence of inflammation. Endotheliopathy could give rise to hypercoagulation by alteration in the levels of different factors such as von Willebrand factor. Other than thrombotic events, pathological angiogenesis is among the recent findings. Overexpression of different proangiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2) or placental growth factors (PlGF) have been found in plasma or lung biopsies of COVID-19 patients. Finally, SARS-CoV-2 infection induces an emergency myelopoiesis associated to deregulated immunity and mobilization of endothelial progenitor cells, leading to features of acquired hematological malignancies or cardiovascular disease, which are discussed in this review. Altogether, this review will try to elucidate the pathophysiology of thrombotic complications, pathological angiogenesis and EC dysfunction, allowing better insight in new targets and antithrombotic protocols to better address vascular system dysfunction. Since treating SARS-CoV-2 infection and its potential long-term effects involves targeting the vascular compartment and/or mobilization of immature immune cells, we propose to define COVID-19 and its complications as a systemic vascular acquired hemopathy.

Increased VWF and Decreased ADAMTS-13 in COVID-19: Creating a Milieu for (Micro)Thrombosis

von Willebrand factor (VWF) is a large adhesive multimeric protein involved in hemostasis. The larger the size (or number of VWF multimers), the greater the functionality of the protein. A deficiency or defect of VWF can lead to von Willebrand disease (VWD) and cause bleeding. Conversely, an increase in VWF may create an environment that promotes thrombosis. ADAMS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), sometimes called VWF-cleaving protease, is primarily responsible for controlling the size of VWF. The most severe deficiency (<10% of normal levels) of ADAMTS-13 arises in thrombotic thrombocytopenic purpura, a condition characterized by the presence of ultralarge VWF and clinically resulting in enhanced risk of thrombosis. However, ADAMTS-13 deficiency may result from other pathological processes. Of relevance is the recent finding that COVID-19 (coronavirus disease 2019) is associated with both increased levels and activity of VWF as well as generally decreased (or occasionally normal) activity levels of ADAMTS-13. Thus, in COVID-19 there is an alteration in the VWF/ADAMTS-13 axis, most often described by increased VWF/ADAMTS-13 ratio (or reduced ADAMTS-13/VWF ratio). COVID-19 is also associated with high prothrombotic risk. Thus, the imbalance of VWF and ADAMTS-13 in COVID-19 may be providing a milieu that promotes (micro)thrombosis, in a clinical picture resembling a secondary thrombotic microangiopathy in some patients. This review therefore assesses the literature on VWF, ADAMTS-13, and COVID-19. Whenever reported in COVID-19, VWF has always been identified as raised (compared with normal reference ranges or control populations). Reports have included VWF level (i.e., VWF antigen) and in some cases one or more VWF "activity" (e.g., collagen binding; platelet glycoprotein Ib [GPIb] binding, using ristocetin cofactor or more modern versions including VWF:GPIbR [recombinant] and VWF:GPIbM [mutant]). Whenever reported, ADAMTS-13 has been reported as "normal" or reduced; however, it should be recognized that "normal" levels may still identify a relative reduction in individual cases. Some reports also discuss the raised VWF/ADAMTS-13 (or reduced ADAMTS-13/VWF) ratio, but very few provide actual numerical data.