Procoagulant tissue factor activity on microparticles is associated with disease severity and bacteremia in febrile urinary tract infections

Effect of hyperbilirubinemia and phototherapy on apoptotic microparticle levels in neonates

OBJECTIVE

We aimed to evaluate the effect of hyperbilirubinemia and phototherapy on total apoptotic, platelet-derived, endothelial-derived, and tissue factor (TF)-positive apoptotic microparticle (MP) levels in neonates with nonhemolytic pathologic hyperbilirubinemia.

METHODS

Thirty-three term neonates with nonhemolytic pathologic hyperbilirubinemia and 25 healthy term neonates were included. MP levels were analyzed by flow cytometry using peripheral blood samples only once for the neonates in the control group and twice for the neonates in the study group (before and after phototherapy). Annexin V-positive MPs were defined as apoptotic MPs. Platelet-derived MPs were defined as those containing CD31. MPs containing CD144 were defined as endothelial-derived MPs, and MPs expressing TF were identified as those containing CD142.

RESULTS

The rates of total apoptotic and endothelial-derived apoptotic MPs were significantly higher in the study group than the control group before phototherapy (P = 0.012 and P = 0.003, respectively) and after phototherapy (P = 0.046 and P = 0.001, respectively). Total apoptotic, platelet-derived, endothelial-derived, and TF-positive apoptotic MPs did not show any significant differences before and after phototherapy in the study group (P = 0.908, P = 0.823, P = 0.748, and P = 0.437, respectively).

CONCLUSIONS

Our study demonstrated that total apoptotic and endothelial-derived apoptotic MPs are increased in cases of nonhemolytic pathologic hyperbilirubinemia. We showed that phototherapy does not have a significant effect on apoptotic MP levels. Further studies are needed to evaluate the risk of elevated apoptotic MPs on the development of thromboembolism in neonates with nonhemolytic pathologic hyperbilirubinemia.

Microparticle-associated tissue factor activity correlates with the inflammatory response in septic disseminated intravascular coagulation patients

Background

Sepsis is often accompanied by the formation of disseminated intravascular coagulation (DIC). Microparticles can exert their procoagulant and proinflammatory properties in a variety of ways. The purpose of this study was to investigate the relationship between microparticle-associated tissue factor activity (TF+-MP activity) and the inflammatory response.

Methods

Data from a total of 31 DIC patients with sepsis and 31 non-DIC patients with sepsis admitted to the ICU of the First Affiliated Hospital of Harbin Medical University from December 2017 to March 2019 were collected. Blood samples were collected and DIC scores were calculated on the day of enrollment. The hospital's clinical laboratory completed routine blood, procalcitonin, and C-reactive protein tests. TF+-MP activity was measured using a tissue factor-dependent FXa generation assay. Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) levels were determined using ELISA kits.

Results

Compared with the non-DIC group, the DIC group had higher levels of leukocytes, neutrophils, procalcitonin, C-reactive protein, IL-1β, and TNF-α, and more severe inflammatory reactions. TF+-MP activity in the DIC group was higher than that in the non-DIC group. In sepsis patients, TF+-MP activity was strongly correlated with inflammatory response indices and DIC scores.

Conclusion

TF+-MP activity may play a major role in promoting inflammatory response in septic DIC.

Extracellular Vesicles in Triple-Negative Breast Cancer: Immune Regulation, Biomarkers, and Immunotherapeutic Potential

Triple-negative breast cancer (TNBC) is an aggressive subtype accounting for ~10-20% of all human BC and is characterized by the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) amplification. Owing to its unique molecular profile and limited targeted therapies, TNBC treatment poses significant challenges. Unlike other BC subtypes, TNBC lacks specific molecular targets, rendering endocrine therapies and HER2-targeted treatments ineffective. The chemotherapeutic regimen is the predominant systemic treatment modality for TNBC in current clinical practice. However, the efficacy of chemotherapy in TNBC is variable, with response rates varying between a wide range of patients, and the emerging resistance further adds to the difficulties. Furthermore, TNBC exhibits a higher mutational burden and is acknowledged as the most immunogenic of all BC subtypes. Consequently, the application of immune checkpoint inhibition has been investigated in TNBC, yielding promising outcomes. Recent evidence identified extracellular vesicles (EVs) as an important contributor in the context of TNBC immunotherapy. In view of the extraordinary ability of EVs to transfer bioactive molecules, such as proteins, lipids, DNA, mRNAs, and small miRNAs, between the cells, EVs are considered a promising diagnostic biomarker and novel drug delivery system among the prospects for immunotherapy. The present review provides an in-depth understanding of how EVs influence TNBC progression, its immune regulation, and their contribution as a predictive biomarker for TNBC. The final part of the review focuses on the recent key advances in immunotherapeutic strategies for better understanding the complex interplay between EVs and the immune system in TNBC and further developing EV-based targeted immunotherapies.

Beyond Macromolecules: Extracellular Vesicles as Regulators of Inflammatory Diseases

Inflammation is the defense mechanism of the immune system against harmful stimuli such as pathogens, toxic compounds, damaged cells, radiation, etc., and is characterized by tissue redness, swelling, heat generation, pain, and loss of tissue functions. Inflammation is essential in the recruitment of immune cells at the site of infection, which not only aids in the elimination of the cause, but also initiates the healing process. However, prolonged inflammation often brings about several chronic inflammatory disorders; hence, a balance between the pro- and anti-inflammatory responses is essential in order to eliminate the cause while producing the least damage to the host. A growing body of evidence indicates that extracellular vesicles (EVs) play a major role in cell-cell communication via the transfer of bioactive molecules in the form of proteins, lipids, DNA, RNAs, miRNAs, etc., between the cells. The present review provides a brief classification of the EVs followed by a detailed description of how EVs contribute to the pathogenesis of various inflammation-associated diseases and their implications as a therapeutic measure. The latter part of the review also highlights how EVs act as a bridging entity in blood coagulation disorders and associated inflammation. The findings illustrated in the present review may open a new therapeutic window to target EV-associated inflammatory responses, thereby minimizing the negative outcomes.

COVID-19-Associated Disseminated Intravascular Coagulopathy Presenting As Inferior ST-Segment Elevation Myocardial Infarction

Disseminated intravascular coagulopathy (DIC) is infrequently associated with COVID-19 infection. COVID-19 infection can predispose to thrombotic events through inflammation and microvascular injury. DIC is rarely associated with coronary artery disease, especially myocardial infarction (MI). In this case report, we present an uncommon case of a patient with concurrent DIC and MI in the setting of COVID-19 infection. A 73-year-old male patient with no known cardiovascular risk factor presented with syncope. Assessment in the field by emergency medical service (EMS) showed the patient had a third-degree atrioventricular block and a heart rate of 40 beats per minute. He was given atropine and transcutaneously paced. Upon admission, he was found to have an inferior wall ST-elevation myocardial infarction (STEMI) and tested positive for COVID-19. Cardiac catheterization was performed urgently and revealed triple vessel disease. Attempts to revascularize the vessels were unsuccessful. He subsequently developed cardiogenic shock. He was started on multiple pressor support. Laboratory workup was suggestive of DIC, and he later developed multiorgan failure. Continuous renal replacement therapy was initiated but failed due to persistent thrombosis of the dialysis access. Despite all measures, the patient developed cardiac arrest and passed away on the third day of hospitalization. Our understanding of COVID-19 and its complications has grown exponentially since the beginning of the pandemic. The pro-inflammatory state induced by the disease creates a hypercoagulable state that may result in thrombotic complications, including MI. In severe cases, a consumptive coagulopathy may develop, leading to DIC. This unique case report seeks to highlight the importance of staying vigilant about the potential complications of MI and DIC induced by COVID-19 so that prompt diagnosis can be made to reduce morbidity and mortality in these patients.

Extracellular vesicles participate in the pathogenesis of sepsis

Sepsis is one of the leading causes of mortality worldwide and is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The early diagnosis and effective treatment of sepsis still face challenges due to its rapid progression, dynamic changes, and strong heterogeneity among different individuals. To develop novel strategies to control sepsis, a better understanding of the complex mechanisms of sepsis is vital. Extracellular vesicles (EVs) are membrane vesicles released from cells through different mechanisms. In the disease state, the number of EVs produced by activated or apoptotic cells and the cargoes they carry were altered. They regulated the function of local or distant host cells in autocrine or paracrine ways. Current studies have found that EVs are involved in the occurrence and development of sepsis through multiple pathways. In this review, we focus on changes in the cargoes of EVs in sepsis, the regulatory roles of EVs derived from host cells and bacteria, and how EVs are involved in multiple pathological processes and organ dysfunction in sepsis. Overall, EVs have great application prospects in sepsis, such as early diagnosis of sepsis, dynamic monitoring of disease, precise therapeutic targets, and prevention of sepsis as a vaccine platform.

Pathophysiology of Coagulation and Emerging Roles for Extracellular Vesicles in Coagulation Cascades and Disorders

The notion of blood coagulation dates back to the ancient Greek civilization. However, the emergence of innovative scientific discoveries that started in the seventeenth century formulated the fundamentals of blood coagulation. Our understanding of key coagulation processes continues to evolve, as novel homeostatic and pathophysiological aspects of hemostasis are revealed. Hemostasis is a dynamic physiological process, which stops bleeding at the site of injury while maintaining normal blood flow within the body. Intrinsic and extrinsic coagulation pathways culminate in the homeostatic cessation of blood loss, through the sequential activation of the coagulation factors. Recently, the cell-based theory, which combines these two pathways, along with newly discovered mechanisms, emerged to holistically describe intricate in vivo coagulation mechanisms. The complexity of these mechanisms becomes evident in coagulation diseases such as hemophilia, Von Willebrand disease, thrombophilia, and vitamin K deficiency, in which excessive bleeding, thrombosis, or unnecessary clotting, drive the development and progression of diseases. Accumulating evidence implicates cell-derived and platelet-derived extracellular vesicles (EVs), which comprise microvesicles (MVs), exosomes, and apoptotic bodies, in the modulation of the coagulation cascade in hemostasis and thrombosis. As these EVs are associated with intercellular communication, molecular recycling, and metastatic niche creation, emerging evidence explores EVs as valuable diagnostic and therapeutic approaches in thrombotic and prothrombotic diseases.

Circulating tissue factor-positive extracellular vesicles and their association with thrombosis in different diseases

Tissue factor (TF) is a procoagulant protein released from activated host cells, such as monocytes, and tumor cells on extracellular vesicles (EVs). TF + EVs are observed in the circulation of patients with various types of diseases. In this review, we will summarize the association between TF + EVs and activation of coagulation and survival in different types of diseases, including cancer, sepsis, and infections with different viruses, such as human immunodeficiency virus (HIV), influenza A virus (IAV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We will also discuss the source of TF + EVs in various diseases. EVTF activity is associated with thrombosis in pancreatic cancer patients and coronavirus disease 2019 patients (COVID-19) and with disseminated intravascular coagulation in cancer patients. EVTF activity is also associated with worse survival in patients with cancer and COVID-19. Monocytes are the major sources of TF + EVs in sepsis, and viral infections, such as HIV, Ebola virus, and SARS-CoV-2. In contrast, alveolar epithelial cells are the major source of TF + EVs in bronchoalveolar lavage fluid in COVID-19 and influenza A patients. These studies indicate that EVTF activity could be used as a biomarker to identify patients that have an increased risk of coagulopathy and mortality.

Role of extracellular vesicles in severe pneumonia and sepsis

INTRODUCTION

Extracellular vesicles (EV) released constitutively or following external stimuli from structural and immune cells are now recognized as important mediators of cell-to-cell communication. They are involved in the pathogenesis of pneumonia and sepsis, leading causes of acute respiratory distress syndrome (ARDS) where mortality rates remain up to 40%. Multiple investigators have demonstrated that one of the underlying mechanisms of the effects of EVs is through the transfer of EV content to host cells, resulting in apoptosis, inflammation, and permeability in target organs.

AREAS COVERED

The current review focuses on preclinical research examining the role of EVs released into the plasma and injured alveolus during pneumonia and sepsis.

EXPERT OPINION

Inflammation is associated with elevated levels of circulating EVs that are released by activated structural and immune cells and can have significant proinflammatory, procoagulant, and pro-permeability effects in critically ill patients with pneumonia and/or sepsis. However, clinical translation of the use of EVs as biomarkers or potential therapeutic targets may be limited by current methodologies used to identify and quantify EVs accurately (whether from host cells or infecting organisms) and lack of understanding of the role of EVs in the reparative phase during recovery from pneumonia and/or sepsis.

Cellular and molecular mechanisms in COVID-19 coagulopathy: role of inflammation and endotheliopathy

INTRODUCTION

Coronavirus 2 (CoV-2) infection or coronavirus disease 2019 (COVID-19) is frequently associated with microvascular thrombosis.The microthrombosis in COVID-19 is the result of the interplay between inflammation and endotheliopathy. Elevated interleukin-6 (IL-6) characterizes COVID-19 inflammation resulting in endotheliopathy and coagulopathy marked by elevated D-dimer (DD). Aim of this study is to identify and to describe the coagulation changes in 100 moderate COVID-19 patients having lung involvement and to determine the association of coagulopathy with the severity and prognosis.

METHODS

Inflammation, endothelial and coagulation molecules were measured in moderate and mild disease.

RESULTS

IL-6 and tumor necrosis factor-α (TNF-α) and tissue factor (TF), von Willebrand factor (VWF), and tissue factor pathway inhibitor (TFPI) significantly increased in moderate disease as well as D-dimer, thrombin antithrombin complex (TAT), Fibrinogen (Fib), platelet factor-4 (PF4), β-thromboglobulin (β-TG), P-selectin, and platelet adhesion. Shortened clotting time (CT) and clot formation time (CFT), high maximum clot firmness (MCF) and low LY at 30 min were present in 100% of moderate COVID-19 patients compared with mild COVID-19 patients.

CONCLUSIONS

These findings demonstrate that moderate COVID-19 has a profound inflammation associated with severee ndotheliopathy and intense coagulation activation uncontrolled by TFPI. Attention should be paid to coagulopathy in COVID-19. Closely monitoring of coagulation and application of appropriate anticoagulation may improve the prognosis of moderate COVID-19 and to prevent the progression to severe COVID-19 disease.

COVID-19-associated Coagulopathy and Thromboembolism: Determination of their Patterns and Risk Factors as Predictors of Mortality Among Severe COVID-19 Patients

BACKGROUND

Corona virus disease 2019 (COVID-19) is associated with coagulopathy (CAC) and venous thromboembolism (VTE). These are well-reported complications of COVID-19 infection. Earlier publications have shown that CAC and thromboembolism are predictors of mortality among COVID-19 patients with severe disease.

MATERIAL AND METHODS

A prospective study was conducted in the Intensive Care Unit (ICU) where all confirmed COVID-19 patients were enrolled and followed until death or ICU discharge. CAC, VTE, along with all comorbidities were recorded. Predictors of mortality were determined by univariate and multivariate regression.

RESULTS

Among 261 patients with COVID-19, 48.3% survived and 51.7% died. CAC was present in 53.2% and 76.3% of the survivors and non-survivors, respectively (p<0.001); 89 patients (31.4%) had VTE (p=0.36) and 11 patients (4.2%) had arterial thrombosis (p=0.76) among survivors and non-survivors. Age between 71-80 years (p=0.009), male gender (p=0.045), CAC (p<0.001), comorbidities like chronic kidney disease (CKD, p=0.013), chronic obstructive pulmonary disease (COPD, p=0.001) and asthma (p=0.046), were significant predictors of mortality.

CONCLUSION

A severe complication of COVID-19 is CAC, such as sepsis-induced coagulopathy, overt disseminated-coagulopathy and VTE. Old age, various comorbidities (e.g. COPD, CKD or asthma), CAC, VTE (pulmonary embolism) and coagulation parameters with critical severity score (D-dimers, platelets, prothrombin time) and the SOFA (Sequential Organ Failure Assessment) score were significant predictors of mortality among COVID-19 patients.

Extracellular vesicles in renal inflammatory and infectious diseases

Extracellular vesicles can mediate cell-to-cell communication, or relieve the parent cell of harmful substances, in order to maintain cellular integrity. The content of extracellular vesicles includes miRNAs, mRNAs, growth factors, complement factors, cytokines, chemokines and receptors. These may contribute to inflammatory and infectious diseases by the exposure or transfer of potent effectors that induce vascular inflammation by leukocyte recruitment and thrombosis. Furthermore, vesicles release cytokines and induce their release from cells. Extracellular vesicles possess immune modulatory and anti-microbial properties, and induce receptor signaling in the recipient cell, not least by the transfer of pro-inflammatory receptors. Additionally, the vesicles may carry virulence factors systemically. Extracellular vesicles in blood and urine can contribute to the development of kidney diseases or exhibit protective effects. In this review we will describe the role of EVs in inflammation, thrombosis, immune modulation, angiogenesis, oxidative stress, renal tubular regeneration and infection. Furthermore, we will delineate their contribution to renal ischemia/reperfusion, vasculitis, glomerulonephritis, lupus nephritis, thrombotic microangiopathies, IgA nephropathy, acute kidney injury, urinary tract infections and renal transplantation. Due to their content of miRNAs and growth factors, or when loaded with nephroprotective modulators, extracellular vesicles have the potential to be used as therapeutics for renal regeneration.

Preliminary study of microparticle coagulation properties in septic patients with disseminated intravascular coagulation

Background

Sepsis typically results in enhanced coagulation system activation and microthrombus formation. Microparticle (MP) production promotes coagulation and enhances pro-coagulation. This study investigated how circulating MP levels and tissue factor-bearing MP (TF+-MP) activity caused coagulation in patients with septic disseminated intravascular coagulation (DIC).

Methods

Thirty patients with septic DIC and 30 healthy controls were studied from December 2017 to March 2019. Patient blood samples were collected at enrolment (day 1) and on days 3 and 5; DIC scores and Sequential Organ Failure Assessment (SOFA) scores were recorded. TF+-MP activity was measured using TF-dependent factor Xa generation experiments. Circulating MP concentrations were determined by MP capture assay. Clotting factor activity, antithrombin level, soluble thrombomodulin, and serum tissue factor pathway inhibitor (TFPI) concentrations were measured.

Results

Patients with septic DIC had lower circulating MP levels than healthy control patients. Circulating MP levels in patients with septic DIC were positively correlated with DIC scores and negatively correlated with coagulation factors, but TF+-MP activity did not correlate with clotting factor levels and TFPI.

Conclusions

In patients with septic DIC, circulating MP levels are important in promoting coagulation activation and increasing clotting factor consumption. TF+-MP activity may not be the main form of active TF.

COVID-19-Associated Coagulopathy: A Case Report of Thrombosis despite Therapeutic Anticoagulation

The Coronavirus disease (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has led to tremendous morbidity and mortality. Various inflammatory markers have been monitored and considered to be associated with disease prognosis. One of the major sources of comorbidity involved has been development of thrombosis alongside the infection. This prothrombotic phenomenon considered, COVID-19-associated coagulopathy (CAC), has been the center of discussion in dealing with this infection. There still remains ambiguity regarding management guidelines for thromboprophylaxis dosing and therapeutic anticoagulation. We present a case of severe SARS-CoV-2 infection complicated by thrombosis despite therapeutic anticoagulation contributing to prolonged intensive care unit and hospital stay.

COVID-19 Associated Coagulopathy and Implications for its Treatment

The SARS-CoV-2 coronavirus (COVID-19) pandemic is due to lack of prior immunity and there is no certain management, regarding the complications of this viral illness. The target organ for COVID-19 infection are the lungs. Patients may develop acute lung injury that can be complicated by acute respiratory failure, as well as multiorgan failure. The pathophysiology of COVID-19 infection is characterized with inflammatory changes, associated with coagulopathy. Recent data suggests diffuse bilateral pulmonary inflammation observed in COVID-19 infection that is related to a novel pulmonary-specific vasculopathy, defined as pulmonary intravascular coagulopathy (PIC), distinct from disseminated intravascular coagulopathy (DIC). The coagulopathy associated with COVID-19 is distinguished by initial elevation of D-dimer and fibrin/fibrinogen degradation products. Abnormalities in prothrombin time (PT), partial thromboplastin time (APTT) and platelet counts are not common in the early stages of the infection. This suggests the early screening measurement of D-dimer and fibrinogen. The implications for COVID-19-associated-coagulopathy is the established thromboembolic prophylaxis and standard management for sepsis-induced coagulopathy or DIC. High levels of D-dimer are a marker of higher mortality risk. However, current studies do not show the common use of full therapeutical doses of anticoagulants, unless there are other clinical indications. Bleeding in COVID-19 infection is uncommon, even when a laboratory constellation for DIC is present. However, if it occurs, standard guidelines for DIC management should be followed.

COVID-19 and its implications for thrombosis and anticoagulation

Severe acute respiratory syndrome coronavirus 2, coronavirus disease 2019 (COVID-19)-induced infection can be associated with a coagulopathy, findings consistent with infection-induced inflammatory changes as observed in patients with disseminated intravascular coagulopathy (DIC). The lack of prior immunity to COVID-19 has resulted in large numbers of infected patients across the globe and uncertainty regarding management of the complications that arise in the course of this viral illness. The lungs are the target organ for COVID-19; patients develop acute lung injury that can progress to respiratory failure, although multiorgan failure can also occur. The initial coagulopathy of COVID-19 presents with prominent elevation of D-dimer and fibrin/fibrinogen-degradation products, whereas abnormalities in prothrombin time, partial thromboplastin time, and platelet counts are relatively uncommon in initial presentations. Coagulation test screening, including the measurement of D-dimer and fibrinogen levels, is suggested. COVID-19–associated coagulopathy should be managed as it would be for any critically ill patient, following the established practice of using thromboembolic prophylaxis for critically ill hospitalized patients, and standard supportive care measures for those with sepsis-induced coagulopathy or DIC. Although D-dimer, sepsis physiology, and consumptive coagulopathy are indicators of mortality, current data do not suggest the use of full-intensity anticoagulation doses unless otherwise clinically indicated. Even though there is an associated coagulopathy with COVID-19, bleeding manifestations, even in those with DIC, have not been reported. If bleeding does occur, standard guidelines for the management of DIC and bleeding should be followed.

Extracellular vesicles in renal physiology and clinical applications for renal disease

Many cells in the nephron release extracellular vesicles (EVs). EVs envelop nucleic acids, proteins, and lipids. The surfaces of EVs express donor cell-specific markers, ligands, and major histocompatibility complex molecules. They are involved in cell-to-cell communication, immune modulation, and the removal of unwanted materials from cells. EVs have been studied as biomarkers of specific diseases and have potential therapeutic applications. Recent research has emphasized the functions of EVs in the kidney. This review provides an overview of recent findings related to the roles of EVs in the nephron, and their utility as biomarkers and therapeutic factors in renal disease.

[Value of podocalyxin levels in urinary extracellular vesicles for diagnosis of diabetic nephropathy]

OBJECTIVE

To explore the value of detecting podocalyxin (PCX) level in urinary extracellular vesicles for the diagnosis of diabetic nephropathy.

METHODS

This study was conducted among 57 diabetic patients admitted during the period from March to September, 2017, including 34 with uncomplicated diabetics and 23 with diabetic nephropathy; 21 patients with other types of nephropathy and 11 healthy individuals were also included to serve as the controls. Transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA) were used to verify the separation of urinary extracellular vesicles. The molecular markers of extracellular vesicles (TSG101 and podocalyxin [PCX]) were detected using Western blotting. PCX levels in extracellular vesicles were also detected using ELISA.

RESULTS

TEM reveal the presence of numerous extracellular vesicles in the urine with intact morphology and different sizes, and most of them were below 300 nm in diameter as shown by NTA. TSG101 expression was detected in the samples from all the 4 groups. Positive expression of PCX was detected in the samples from patients with diabetic nephropathy but not in the other groups. In patients with diabetic nephropathy, the mean PCX levels (3.27±2.30 ng/μmol)was significantly higher than those in the healthy control group (1.22±0.36 ng/μmol), uncomplicated diabetes group (2.22±1.29 ng/μmol) and nephropathy group (1.24±0.45 ng/μmol).

CONCLUSIONS

PCX level in urinary extracellular vesicles is significantly increased in patients with diabetic nephropathy, suggesting the value of PCX as a potential marker for clinical diagnosis of diabetic nephropathy.

Measurement of tissue factor activity in extracellular vesicles from human plasma samples

Tissue factor (TF) is the cellular receptor for plasma factor (F) VII/FVIIa and triggers blood coagulation. Extracellular vesicles (EVs) are small membrane vesicles that are released from activated cells and tumor cells. Different cell types, including activated monocytes and tumors cells release TF-positive EVs into the circulation. We developed an assay to measure levels of TF activity in EVs isolated from human plasma samples. We and others have used this assay to demonstrate increased levels of EV TF activity in a variety of diseases associated with thrombosis, including cancer. These studies suggest that EV TF can be used as a biomarker of thrombotic risk. The strength of this laboratory assay is that it is relatively sensitive and specific. However, the limitations of the assay are that it is labor intensive and the coefficient of variation is too high for it to be used as a clinical assay.

Exosomes and microvesicles in normal physiology, pathophysiology, and renal diseases

Extracellular vesicles are cell-derived membrane particles ranging from 30 to 5,000 nm in size, including exosomes, microvesicles, and apoptotic bodies. They are released under physiological conditions, but also upon cellular activation, senescence, and apoptosis. They play an important role in intercellular communication. Their release may also maintain cellular integrity by ridding the cell of damaging substances. This review describes the biogenesis, uptake, and detection of extracellular vesicles in addition to the impact that they have on recipient cells, focusing on mechanisms important in the pathophysiology of kidney diseases, such as thrombosis, angiogenesis, tissue regeneration, immune modulation, and inflammation. In kidney diseases, extracellular vesicles may be utilized as biomarkers, as they are detected in both blood and urine. Furthermore, they may contribute to the pathophysiology of renal disease while also having beneficial effects associated with tissue repair. Because of their role in the promotion of thrombosis, inflammation, and immune-mediated disease, they could be the target of drug therapy, whereas their favorable effects could be utilized therapeutically in acute and chronic kidney injury.

Levels of circulating microparticles in septic shock and sepsis-related complications: a case-control study

BACKGROUND

Microparticles (MP) have been largely studied as potential biomarkers in septic shock (SS) though their biological and clinical relevance is still unclear. This case-control study describes the trend of various MP subtypes during SS to evaluate their possible association with severity of illness and sepsis-related complications (disseminated intravascular coagulation [DIC] and acute kidney injury [AKI]).

METHODS

Forty patients admitted to the Intensive Care Unit with SS and 40 matched healthy volunteers were recruited. AnnexinV+, E-selectin+, thrombomodulin (TM+), leukocyte-derived (CD45+, CD36+) and platelet-derived MP (PMP-expressed as PMP/platelets ratio) were measured by flow-cytometry at baseline, on day 1, 3 and 7 after diagnosis. Severity of illness was assessed by Sequential Organ Failure Assessment Score, duration of vasoactive support and mechanical ventilation. Sepsis-related complications were considered.

RESULTS

Overall, septic patients showed higher levels of all MP considered compared to controls. TM+MP were significantly lower in more severe sepsis, while CD36+MP and PMP/platelets ratio were significantly increased in patients requiring longer vasoactive support and mechanical ventilation. As for sepsis-related complications, a higher PMP/platelets ratio in patients who developed DIC and increased E-selectin+MP in subjects who developed AKI were observed. PMP/platelets ratio at baseline was significantly associated with longer vasoactive support (OR=1.59 [1.05-2.42]), longer mechanical ventilation (OR=1.6 [1.06-2.42]) and DIC occurrence (OR=1.45 [1.08-1.96]).

CONCLUSIONS

A global response through extra-vesiculation of endothelial cells, leukocytes and platelets during the early stages of SS was confirmed. The cellular activation was detected until day 3 after diagnosis. PMP/platelets ratio at diagnosis may be useful to evaluate SS severity and DIC occurrence.

Role of extracellular vesicles in the development of sepsis-induced coagulopathy

Background

The advances of research on extracellular vesicles (EVs) are of particular interest to the clinicians as well as the researchers who are studying coagulation disorder in sepsis. Here, we intend to update the latest knowledge and currently unsolved problems that should be addressed.

Main body

Secreted membrane-enclosed vesicles including apoptotic bodies, exosomes, ectosomes, microvesicles, and microparticles are generically called EVs. Though the basic structure of these vesicles is the same, i.e., originating from the plasma membrane, their characteristics differ significantly depending on their surface structures and interior components. Numerous studies have shown elevated levels of circulating EVs that exhibit proinflammatory and procoagulant properties during sepsis. These EVs are known to play important roles in the development of coagulation disorder and organ dysfunction in sepsis. Coagulation disorder in sepsis is characterized by activated coagulation, disrupted anticoagulant systems, and imbalanced fibrinolytic systems. These processes collaborate with one another and contribute to the development of disseminated intravascular coagulation (DIC), with devastating consequences. As part of this pathogenesis, the membrane-exposed tissue factor, phosphatidylserine and bioactive substances contained within the vesicles, such as histones, nucleosomes, and high-mobility group box 1, contribute to the development of DIC. EVs not only upregulate the procoagulant systems by themselves, but they also disseminate prothrombotic activities by transferring their procoagulant properties to distant target cells. Though the basic concept behind the role of procoagulant properties, EVs in the development of sepsis-induced coagulopathy has started to be unveiled, knowledge of the actual status is far from satisfactory, mainly because of the lack of standardized assay procedures. Recent advances and current problems that remain to be resolved are introduced in this review.

Conclusion

The recent studies succeeded to elucidate the important roles of EVs in the progress of coagulation disorder in sepsis. However, further harmonization in terminology, methodology, and evaluation methods is required for future studies.

Extracellular Vesicles as Markers and Mediators in Sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. It remains a highly lethal condition in which current tools for early diagnosis and therapeutic decision-making are far from ideal. Extracellular vesicles (EVs), 30 nm to several micrometers in size, are released from cells upon activation and apoptosis and express membrane epitopes specific for their parental cells. Since their discovery two decades ago, their role as biomarkers and mediators in various diseases has been intensively studied. However, their potential importance in the sepsis syndrome has gained attention only recently. Sepsis and EVs are both complex fields in which standardization has long been overdue. In this review, several topics are discussed. First, we review current studies on EVs in septic patients with emphasis on their variable quality and clinical utility. Second, we discuss the diagnostic and therapeutic potential of EVs as well as their role as facilitators of cell communication via micro RNA and the relevance of micro-organism-derived EVs. Third, we give an overview over the potential beneficial but also detrimental roles of EVs in sepsis. Finally, we focus on the role of EVs in selected intensive care scenarios such as coagulopathy, mechanical ventilation and blood transfusion. Overall, the prospect for EV use in septic patients is bright, ranging from rapid and precise (point-of-care) diagnostics, prevention of harmful iatrogenic interventions, to using EVs as guides of individualized therapy. Before the above is achieved, however, the EV research field requires reliable standardization of the current methods and development of new analytical procedures that can close the existing technological gaps.

Comparison of microvesicle tissue factor activity in non-cancer severely ill patients and cancer patients

INTRODUCTION

Increased levels of circulating tissue factor (TF)-positive microvesicles (MVs) may increase the risk of thrombosis. Indeed, TF-positive MVs are detected in plasma of patients with various types of diseases. In this study, we measured levels of MV TF activity in non-cancer severely ill patients and cancer patients.

METHODS

We used an in-house MV TF activity assay to measure MV TF activity.

RESULTS

MV TF activity was significantly increased in a population of cancer patients but not in a population of non-cancer severely ill patients compared with healthy controls. However, in the population of severely ill patients, those with infection had significantly elevated levels of MV TF activity compared with controls. Interestingly, patients with adenocarcinoma had higher levels of MV TF activity compared with patients with non-adenocarcinoma tumors. Levels of MV TF activity were not associated with venous thromboembolism in cancer patients. MV TF activity was associated with reduced survival in cancer patients.

CONCLUSION

Cancer patients as well as severely ill patients with infection have higher levels of MV TF activity compared with healthy controls. Patients with adenocarcinoma have higher levels of MV TF activity compared with patients with other types of cancer. An elevated level of MV TF activity was associated with reduced survival in cancer patients.

Microvesicle Involvement in Shiga Toxin-Associated Infection

Shiga toxin is the main virulence factor of enterohemorrhagic Escherichia coli, a non-invasive pathogen that releases virulence factors in the intestine, causing hemorrhagic colitis and, in severe cases, hemolytic uremic syndrome (HUS). HUS manifests with acute renal failure, hemolytic anemia and thrombocytopenia. Shiga toxin induces endothelial cell damage leading to platelet deposition in thrombi within the microvasculature and the development of thrombotic microangiopathy, mostly affecting the kidney. Red blood cells are destroyed in the occlusive capillary lesions. This review focuses on the importance of microvesicles shed from blood cells and their participation in the prothrombotic lesion, in hemolysis and in the transfer of toxin from the circulation into the kidney. Shiga toxin binds to blood cells and may undergo endocytosis and be released within microvesicles. Microvesicles normally contribute to intracellular communication and remove unwanted components from cells. Many microvesicles are prothrombotic as they are tissue factor- and phosphatidylserine-positive. Shiga toxin induces complement-mediated hemolysis and the release of complement-coated red blood cell-derived microvesicles. Toxin was demonstrated within blood cell-derived microvesicles that transported it to renal cells, where microvesicles were taken up and released their contents. Microvesicles are thereby involved in all cardinal aspects of Shiga toxin-associated HUS, thrombosis, hemolysis and renal failure.

Extracellular vesicles in renal disease

Extracellular vesicles, such as exosomes and microvesicles, are host cell-derived packages of information that allow cell-cell communication and enable cells to rid themselves of unwanted substances. The release and uptake of extracellular vesicles has important physiological functions and may also contribute to the development and propagation of inflammatory, vascular, malignant, infectious and neurodegenerative diseases. This Review describes the different types of extracellular vesicles, how they are detected and the mechanisms by which they communicate with cells and transfer information. We also describe their physiological functions in cellular interactions, such as in thrombosis, immune modulation, cell proliferation, tissue regeneration and matrix modulation, with an emphasis on renal processes. We discuss how the detection of extracellular vesicles could be utilized as biomarkers of renal disease and how they might contribute to disease processes in the kidney, such as in acute kidney injury, chronic kidney disease, renal transplantation, thrombotic microangiopathies, vasculitides, IgA nephropathy, nephrotic syndrome, urinary tract infection, cystic kidney disease and tubulopathies. Finally, we consider how the release or uptake of extracellular vesicles can be blocked, as well as the associated benefits and risks, and how extracellular vesicles might be used to treat renal diseases by delivering therapeutics to specific cells.

Detection of tissue factor-positive extracellular vesicles by laser scanning confocal microscopy

INTRODUCTION

Increased levels of tissue factor-positive extracellular vesicles (TF+EVs) have been detected in the plasma of patients with various diseases, including cancer and endotoxemia. Levels of TF+EVs in plasma samples can be measured by antigen and activity assays. The aim of the present study was to visualize TF+EVs by laser scanning confocal microscopy (LSCM).

METHODS

EVs were isolated from the supernatant of two cultured human pancreatic cancer cell lines (Panc-1 and BxPc-3), from untreated or lipopolysaccharide (LPS) treated whole blood, and from plasma of pancreatic cancer patients. EV-TF activity was determined using an in-house assay. The EVs were labeled with 5(6)-carboxyfluorescein diacetate N-succinimidyl ester, which is converted to the impermeant green fluorescent molecule carboxyfluorescein inside the EVs. EVs were either captured using annexin V and detected using a fluorescent-labeled anti-TF antibody, or captured using an anti-TF antibody and detected using fluorescent-labeled annexin V. EVs were visualized by LSCM.

RESULTS

TF+EVs were easily detected from high TF-expressing BxPc-3 cells using annexin V capture, whereas the addition of tyramide amplification was required to detect TF+EVs from low TF-expressing Panc-1 cells. Visualization of TF+EVs in plasma from LPS treated whole human blood and in plasma from pancreatic cancer patients required either capture with annexin V and detection with a fluorescent-labeled anti-TF antibody with tyramide signal amplification, or capture with an anti-TF antibody and detection with a fluorescent-labeled annexin V.

CONCLUSION

LSCM enables visualization of TF+EVs in the supernatant from cultured cells and in clinical samples.

Sepsis-Associated Coagulopathy

Systemic inflammatory activation in sepsis often leads to coagulation activation, but the relationship is bilateral, as coagulation also modulates the inflammatory response. This close associate has significant consequences for the pathogenesis of microvascular thrombosis and organ dysfunction in sepsis. While coagulation activation can be beneficial for immune defense, it can also be detrimental once it becomes widespread and uncontrolled. The knowledge of the pathophysiologic mechanisms involved in the interaction between infection and coagulation may lead to the better timing for the administration of targeted antithrombotic therapies in septic patients. This brief review highlights the pathophysiologic pathways leading to the prothrombotic state in sepsis and the mechanisms that play a role in the interaction between infection and coagulation.

Tissue factor-bearing microparticles and CA19.9: two players in pancreatic cancer-associated thrombosis?

Background:

Cancer-related venous thromboembolism (VTE) heralds a poor prognosis, especially in pancreatic adenocarcinoma (PAC). Tissue factor (TF) is implicated as one of the main culprits in PAC-associated VTE and disease progression.

Methods:

In a prospective cohort study of 79 PAC patients, we measured plasma CA19–9 and microparticle-associated TF activity (MP-TF activity). In addition, we enumerated TF⁺MPs and MUC1⁺MPs in plasma (n=55), and studied the expression of TF, MUC1, CD31 and CD68 in tumour tissue (n=44).

Results:

Plasma MP-TF activity was markedly elevated in PAC patients with VTE compared with those without (median: 1925 vs 113 fM Xa min⁻¹; P<0.001) and correlated with the extent of thromboembolic events, metastatic disease and short survival. Similar results were found for CA19–9. Patients with massively progressing thrombosis and cerebral embolisms despite anticoagulant therapy (n=3) had the highest MP-TF activities (12 118–40 188 fM Xa min⁻¹) and CA19–9 (40 730–197 000 kU l⁻¹). All tumours expressed MUC1 and TF. MP-TF activity did not correlate with intensity of TF expression in adenocarcinoma cells, but corresponded with numbers of TF⁺ macrophages in the surrounding stroma.

Conclusions:

Circulating TF⁺MPs and mucins may concertedly aggravate coagulopathy in PAC. Understanding of underlying mechanisms may result in new treatment strategies for VTE prevention and improvement of survival.

Measurement of microparticle tissue factor activity in clinical samples: A summary of two tissue factor-dependent FXa generation assays

Thrombosis is a leading cause of morbidity and mortality. Detection of a prothrombotic state using biomarkers would be of great benefit to identify patients at risk of thrombosis that would benefit from thromboprophylaxis. Tissue factor (TF) is a highly procoagulant protein that under normal conditions is not present in the blood. However, increased levels of TF in the blood in the form of microparticles (MPs) (also called extracellular vesicles) are observed under various pathological conditions. In this review, we will discuss studies that have measured MP-TF activity in a variety of diseases using two similar FXa generation assay. One of the most robust signals for MP-TF activity (16-26 fold higher than healthy controls) is observed in pancreatic cancer patients with venous thromboembolism. In this case, the TF+ MPs appear to be derived from the cancer cells. Surprisingly, cirrhosis and acute liver injury are associated with 17-fold and 38-fold increases in MP-TF activity, respectively. Based on mouse models, we speculate that the TF+ MPs are derived from hepatocytes. More modest increases are observed in patients with urinary tract infections (6-fold) and in a human endotoxemia model (9-fold) where monocytes are the likely source of the TF+ MPs. Finally, there is no increase in MP-TF activity in the majority of cardiovascular disease patients. These studies indicate that MP-TF activity may be a useful biomarker to identify patients with particular diseases that have an increased risk of thrombosis.

The diagnostic usefulness of capture assays for measuring global/specific extracellular micro-particles in plasma

Capture assays were developed and validated for measuring the global pro-coagulant activity of micro-particles (MPs, mainly originated from platelets), or specific extravascular cellular MPs (released from erythrocytes, leukocytes, monocytes, endothelial cells) as those exposing TF (MP-TF, mainly observed in patients with some cancers). Conversely to Flow Cytometry methods, these capture assays measure all coagulant activity associated with MPs, through thrombin generation (MP-Activity) or Factor Xa generation (MP-TF), and therefore they bring a complementary information, as they are more specific for the pro-coagulant activity associated with MPs. Small particles (<0.40 µ) exposing Phosphatidyl Serine (PS) exhibit a greater pro-coagulant surface than larger MPs (0.40 to >1.00 µ), those preferentially measured with flow cytometry. Activity associated with MPs is a consequence of disease but can also be a cause contributing to pathological processes and development of thrombo-embolic events. In many diseases, flow cytometry and capture assays do not totally correlate, and have different associations with disease evolution. Optimized capture based assays are presented and discussed, along with their performance characteristics and some applications. They can be performed in any technically skillful hemostasis laboratory, using a thermostated ELISA equipment, or an incubator. Dynamic ranges for MP-Activity assay is from <0.1 nM to >2.5 nM Phospholipids, expressed as Phosphatidyl Serine (PS) equivalent, in the tested dilution. For MP-TF the very sensitive bio-immunoassay reported allows measuring concentrations from <0.10 pg/ml (TF equivalent) to >5.00 pg/ml, in the assayed dilution. No measurable MP-TF was found in normals, although an important concentration was generated from whole blood treated with Lipo-Poly-Saccharides. Capture based assays are then highly useful in the laboratory setting for measuring the activities associated with pro-coagulant, or specific cellular MPs.

Microparticles: markers and mediators of sepsis-induced microvascular dysfunction, immunosuppression, and AKI

Sepsis is a severe and complex syndrome that lacks effective prevention or therapeutics. The effects of sepsis on the microvasculature have become an attractive area for possible new targets and therapeutics. Microparticles (MPs) are cell membrane-derived particles that can promote coagulation, inflammation, and angiogenesis, and they can participate in cell-to-cell communication. MPs retain cell membrane and cytoplasmic constituents of their parental cells, including two procoagulants: phosphatidylserine and tissue factor. We highlight the role of microparticles released by endothelial and circulating cells after sepsis-induced microvascular injury, and we discuss possible mechanisms by which microparticles can contribute to endothelial dysfunction, immunosuppression, and multiorgan dysfunction--including sepsis-AKI. Once viewed as cellular byproducts, microparticles are emerging as a new class of markers and mediators in the pathogenesis of sepsis.