Comparison of the coagulopathies associated with COVID-19 and sepsis.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is associated with activation of coagulation that mainly presents as thrombosis. Sepsis is also associated with activation of coagulation that mainly presents as disseminated intravascular coagulation. Many studies have reported increased levels of plasma d-dimer in patients with COVID-19 that is associated with severity, thrombosis, and mortality. OBJECTIVES: The aim of this study was to compare levels of circulating extracellular vesicle tissue factor (EVTF) activity and active plasminogen activator inhibitor 1 (PAI-1) in plasma from patients with COVID-19 or sepsis. METHODS: We measured levels of d-dimer, EVTF activity, and active PAI-1 in plasma samples from patients with COVID-19 (intensive care unit [ICU], N = 15; and non-ICU, N = 20) and patients with sepsis (N = 35). RESULTS: Patients with COVID-19 had significantly higher levels of d-dimer, EVTF activity, and active PAI-1 compared with healthy controls. Patients with sepsis had significantly higher levels of d-dimer and EVTF activity compared with healthy controls. Levels of d-dimer were significantly lower in patients with COVID-19 compared with patients with sepsis. Levels of EVTF activity were significantly higher in ICU patients with COVID-19 compared with patients with sepsis. Levels of active PAI-1 were significantly higher in patients with COVID-19 compared with patients with sepsis. CONCLUSIONS: High levels of both EVTF activity and active PAI-1 may promote thrombosis in patients with COVID-19 due to simultaneous activation of coagulation and inhibition of fibrinolysis. The high levels of active PAI-1 in patients with COVID-19 may limit plasmin degradation of crosslinked fibrin and the release of d-dimer. This may explain the lower levels of D-dimer in patients with COVID-19 compared with patients with sepsis.

Endovascular mechanical thrombectomy in a child with COVID-19: Clot analysis reveals a novel pathway in the neuroinflammatory cascade resulting in large-vessel occlusion.

Large-vessel occlusion is rare in children, but its results can be devastating and may lead to recurrent strokes, persistent neurological deficits, and decreased quality of life. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has yielded extrapulmonary effects and multiorgan diseases, many of which are neurological manifestations. There is a paucity of literature in pediatric patients about large-vessel occlusion in the setting of COVID-19 infection. We discuss a nine-year-old child who presented with a left middle cerebral artery occlusion and underwent revascularization with a Thrombolysis in Cerebral Infarction grade 3 reperfusion approximately three weeks after COVID-19 diagnosis. The patient harbored concerning signs and symptoms of multisystem inflammatory syndrome in children. This case emphasizes the importance of recognizing SARS-CoV-2 and the propensity for thrombosis in a delayed fashion, which can lead to severe stroke in young people.

Harnessing Twitter to empower scientific engagement and communication: The ISTH 2020 virtual congress experience.

As a result of the coronavirus disease 2019 pandemic, the International Society on Thrombosis and Haemostasis (ISTH), like many societies around the world, canceled their in-person hematology congress planned for Milan, Italy, in July 2020. As a result, the first virtual ISTH congress in the organisation's 51-year history was delivered, inviting free registration from across the globe. As part of the social media support, marketing, and scientific dissemination efforts for the virtual congress, the ISTH assembled a group of official Twitter Ambassadors, which represented the broad and diverse ISTH community. Ambassadors were tasked to tweet daily throughout the congress and to share their commentary on the hematology research being presented with the "#ISTH2020" hashtag. Ambassadors were also supported by Twitter activities from the two official ISTH-affiliated journals: the Journal of Thrombosis and Haemostasis (JTH) and Research and Practice in Thrombosis and Haemostasis (RPTH). In this forum and through the Twitter ambassadors' lens, we present the Twitter Ambassadors' experience, reflect on the impact of social media on the ISTH 2020 congress, and share this experience with the wider scientific community. Specifically, we report on the role of Twitter communication for virtual meetings, discuss the pros and cons of the virtual congress, and offer Twitter-related recommendations for future virtual or blended congresses. We conclude that the ISTH Twitter Ambassador program broadened social media engagement and offers a novel route to improve social connectivity in the virtual research congress setting.

COVID-19 generates hyaluronan fragments that directly induce endothelial barrier dysfunction.

Vascular injury has emerged as a complication contributing to morbidity in coronavirus disease 2019 (COVID-19). The glycosaminoglycan hyaluronan (HA) is a major component of the glycocalyx, a protective layer of glycoconjugates that lines the vascular lumen and regulates key endothelial cell functions. During critical illness, as in the case of sepsis, enzymes degrade the glycocalyx, releasing fragments with pathologic activities into circulation and thereby exacerbating disease. Here, we analyzed levels of circulating glycosaminoglycans in 46 patients with COVID-19 ranging from moderate to severe clinical severity and measured activities of corresponding degradative enzymes. This report provides evidence that the glycocalyx becomes significantly damaged in patients with COVID-19 and corresponds with severity of disease. Circulating HA fragments and hyaluronidase, 2 signatures of glycocalyx injury, strongly associate with sequential organ failure assessment scores and with increased inflammatory cytokine levels in patients with COVID-19. Pulmonary microvascular endothelial cells exposed to COVID-19 milieu show dysregulated HA biosynthesis and degradation, leading to production of pathological HA fragments that are released into circulation. Finally, we show that HA fragments present at high levels in COVID-19 patient plasma can directly induce endothelial barrier dysfunction in a ROCK- and CD44-dependent manner, indicating a role for HA in the vascular pathology of COVID-19.

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.

COVID-19 and Sepsis Are Associated With Different Abnormalities in Plasma Procoagulant and Fibrinolytic Activity.

OBJECTIVE: Coronavirus disease 2019 (COVID-19) is associated with derangement in biomarkers of coagulation and endothelial function and has been likened to the coagulopathy of sepsis. However, clinical laboratory metrics suggest key differences in these pathologies. We sought to determine whether plasma coagulation and fibrinolytic potential in patients with COVID-19 differ compared with healthy donors and critically ill patients with sepsis. Approach and Results: We performed comparative studies on plasmas from a single-center, cross-sectional observational study of 99 hospitalized patients (46 with COVID-19 and 53 with sepsis) and 18 healthy donors. We measured biomarkers of endogenous coagulation and fibrinolytic activity by immunoassays, thrombin, and plasmin generation potential by fluorescence and fibrin formation and lysis by turbidity. Compared with healthy donors, patients with COVID-19 or sepsis both had elevated fibrinogen, d-dimer, soluble TM (thrombomodulin), and plasmin-antiplasmin complexes. Patients with COVID-19 had increased thrombin generation potential despite prophylactic anticoagulation, whereas patients with sepsis did not. Plasma from patients with COVID-19 also had increased endogenous plasmin potential, whereas patients with sepsis showed delayed plasmin generation. The collective perturbations in plasma thrombin and plasmin generation permitted enhanced fibrin formation in both COVID-19 and sepsis. Unexpectedly, the lag times to thrombin, plasmin, and fibrin formation were prolonged with increased disease severity in COVID-19, suggesting a loss of coagulation-initiating mechanisms accompanies severe COVID-19. CONCLUSIONS: Both COVID-19 and sepsis are associated with endogenous activation of coagulation and fibrinolysis, but these diseases differently impact plasma procoagulant and fibrinolytic potential. Dysregulation of procoagulant and fibrinolytic pathways may uniquely contribute to the pathophysiology of COVID-19 and sepsis.

COVID-19 patients exhibit reduced procoagulant platelet responses.

BACKGROUND: Emerging evidence implicates dysfunctional platelet responses in thrombotic complications in COVID-19 patients. Platelets are important players in inflammation-induced thrombosis. In particular, procoagulant platelets support thrombin generation and mediate thromboinflammation. OBJECTIVES: To examine if procoagulant platelet formation is altered in COVID-19 patients and if procoagulant platelets contribute to pulmonary thrombosis. PATIENTS/METHODS: Healthy donors and COVID-19 patients were recruited from the University of Utah Hospital System. Platelets were isolated and procoagulant platelet formation measured by annexin V binding as well as mitochondrial function were examined. We utilized mice lacking the ability to form procoagulant platelets (CypDplt-/- ) to examine the role of procoagulant platelets in pulmonary thrombosis. RESULTS AND CONCLUSIONS: We observed that platelets isolated from COVID-19 patients had a reduced ability to become procoagulant compared to those from matched healthy donors, as evidenced by reduced mitochondrial depolarization and phosphatidylserine exposure following dual stimulation with thrombin and convulxin. To understand what impact reduced procoagulant platelet responses might have in vivo, we subjected mice with a platelet-specific deletion of cyclophilin D, which are deficient in procoagulant platelet formation, to a model of pulmonary microvascular thrombosis. Mice with platelets lacking cyclophilin D died significantly faster from pulmonary microvascular thrombosis compared to littermate wild-type controls. These results suggest dysregulated procoagulant platelet responses may contribute to thrombotic complications during SARS-CoV-2 infection.

Neutrophil extracellular traps contribute to immunothrombosis in COVID-19 acute respiratory distress syndrome.

COVID-19 affects millions of patients worldwide, with clinical presentation ranging from isolated thrombosis to acute respiratory distress syndrome (ARDS) requiring ventilator support. Neutrophil extracellular traps (NETs) originate from decondensed chromatin released to immobilize pathogens, and they can trigger immunothrombosis. We studied the connection between NETs and COVID-19 severity and progression. We conducted a prospective cohort study of COVID-19 patients (n = 33) and age- and sex-matched controls (n = 17). We measured plasma myeloperoxidase (MPO)-DNA complexes (NETs), platelet factor 4, RANTES, and selected cytokines. Three COVID-19 lung autopsies were examined for NETs and platelet involvement. We assessed NET formation ex vivo in COVID-19 neutrophils and in healthy neutrophils incubated with COVID-19 plasma. We also tested the ability of neonatal NET-inhibitory factor (nNIF) to block NET formation induced by COVID-19 plasma. Plasma MPO-DNA complexes increased in COVID-19, with intubation (P < .0001) and death (P < .0005) as outcome. Illness severity correlated directly with plasma MPO-DNA complexes (P = .0360), whereas Pao2/fraction of inspired oxygen correlated inversely (P = .0340). Soluble and cellular factors triggering NETs were significantly increased in COVID-19, and pulmonary autopsies confirmed NET-containing microthrombi with neutrophil-platelet infiltration. Finally, COVID-19 neutrophils ex vivo displayed excessive NETs at baseline, and COVID-19 plasma triggered NET formation, which was blocked by nNIF. Thus, NETs triggering immunothrombosis may, in part, explain the prothrombotic clinical presentations in COVID-19, and NETs may represent targets for therapeutic intervention.

Platelet gene expression and function in patients with COVID-19.

There is an urgent need to understand the pathogenesis of coronavirus disease 2019 (COVID-19). In particular, thrombotic complications in patients with COVID-19 are common and contribute to organ failure and mortality. Patients with severe COVID-19 present with hemostatic abnormalities that mimic disseminated intravascular coagulopathy associated with sepsis, with the major difference being increased risk of thrombosis rather than bleeding. However, whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection alters platelet function to contribute to the pathophysiology of COVID-19 remains unknown. In this study, we report altered platelet gene expression and functional responses in patients infected with SARS-CoV-2. RNA sequencing demonstrated distinct changes in the gene-expression profile of circulating platelets of COVID-19 patients. Pathway analysis revealed differential gene-expression changes in pathways associated with protein ubiquitination, antigen presentation, and mitochondrial dysfunction. The receptor for SARS-CoV-2 binding, angiotensin-converting enzyme 2 (ACE2), was not detected by messenger RNA (mRNA) or protein in platelets. Surprisingly, mRNA from the SARS-CoV-2 N1 gene was detected in platelets from 2 of 25 COVID-19 patients, suggesting that platelets may take-up SARS-COV-2 mRNA independent of ACE2. Resting platelets from COVID-19 patients had increased P-selectin expression basally and upon activation. Circulating platelet-neutrophil, -monocyte, and -T-cell aggregates were all significantly elevated in COVID-19 patients compared with healthy donors. Furthermore, platelets from COVID-19 patients aggregated faster and showed increased spreading on both fibrinogen and collagen. The increase in platelet activation and aggregation could partially be attributed to increased MAPK pathway activation and thromboxane generation. These findings demonstrate that SARS-CoV-2 infection is associated with platelet hyperreactivity, which may contribute to COVID-19 pathophysiology.