Prostacyclin Analogues Inhibit Platelet Reactivity, Extracellular Vesicle Release and Thrombus Formation in Patients with Pulmonary Arterial Hypertension

Mechanisms of lung endothelial cell injury and survival in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive, chronic, and incurable inflammatory pulmonary vascular disease characterized by significant sex bias and largely unexplored microbial-associated molecular mechanisms that may influence its development and sex prevalence across various subgroups. PAH can be subclassified as idiopathic, heritable, or associated with conditions such as connective tissue diseases, congenital heart defects, liver disease, infections, and chronic exposure to drugs or toxins. During PAH progression, lung vascular endothelial cells (ECs) undergo dramatic morphofunctional transformations in response to acute and chronic inflammation. These transformations include the appearance and expansion of abnormal vascular cell phenotypes such as those derived from apoptosis-resistant cell growth and endothelial-to-mesenchymal transition (EndoMT). Compelling evidence indicates that these endothelial phenotypes seem to be triggered by chronic lung vascular injury and dysfunction, often characterized by reduced secretion of vasoactive molecules like nitric oxide (NO) and exacerbated response to vasoconstrictors such as Endothelin-1 (ET-1), both long-term known contributors of PAH pathogenesis. This review sheds light on the mechanisms of EC dysfunction, apoptosis, and EndoMT in PAH, aiming to unravel the intricate interactions between ECs, pathogens, and other cell types that drive the onset and progression of this devastating disease. Ultimately, we hope to provide an overview of the complex functions of lung vascular ECs in PAH, inspiring novel therapeutic strategies that target these dysfunctional cells to improve the treatment landscape for PAH, particularly in the face of current and emerging global pathogenic threats.

Complement Immune System in Pulmonary Hypertension-Cooperating Roles of Circadian Rhythmicity in Complement-Mediated Vascular Pathology

Originally discovered in the 1890s, the complement system has traditionally been viewed as a "compliment" to the body's innate and adaptive immune response. However, emerging data have shown that the complement system is a much more complex mechanism within the body involved in regulating inflammation, gene transcription, attraction of macrophages, and many more processes. Sustained complement activation contributes to autoimmunity and chronic inflammation. Pulmonary hypertension is a disease with a poor prognosis and an average life expectancy of 2-3 years that leads to vascular remodeling of the pulmonary arteries; the pulmonary arteries are essential to host homeostasis, as they divert deoxygenated blood from the right ventricle of the heart to the lungs for gas exchange. This review focuses on direct links between the complement system's involvement in pulmonary hypertension, along with autoimmune conditions, and the reliance on the complement system for vascular remodeling processes of the pulmonary artery. Furthermore, circadian rhythmicity is highlighted as the disrupted homeostatic mechanism in the inflammatory consequences in the vascular remodeling within the pulmonary arteries, which could potentially open new therapeutic cues. The current treatment options for pulmonary hypertension are discussed with clinical trials using complement inhibitors and potential therapeutic targets that impact immune cell functions and complement activation, which could alleviate symptoms and block the progression of the disease. Further research on complement's involvement in interstitial lung diseases and pulmonary hypertension could prove beneficial for our understanding of these various diseases and potential treatment options to prevent vascular remodeling of the pulmonary arteries.

Higher EpCAM-Positive Extracellular Vesicle Concentration in Ascites Is Associated with Shorter Progression-Free Survival of Patients with Advanced High-Grade Serous Carcinoma

Platinum-resistant high-grade serous carcinoma (HGSC) is an incurable disease, so biomarkers that could help with timely treatment adjustments and personalized approach are extensively being sought. Tumor-derived extracellular vesicles (EVs) that can be isolated from ascites and blood of HGSC patients are such promising biomarkers. Epithelial cell adhesion molecule (EpCAM) expression is upregulated in most epithelium-derived tumors; however, studies on prognostic value of EpCAM overexpression in ovarian carcinoma have shown contradictory results. The aim of our study was to evaluate the potential of total and EpCAM-positive EVs as prognostic and predictive biomarkers for advanced HGSC. Flow cytometry was used to determine the concentration of total and EpCAM-positive EVs in paired pretreatment ascites and plasma samples of 37 patients with advanced HGSC who underwent different first-line therapy. We found that higher EpCAM-positive EVs concentration in ascites is associated with shorter progression-free survival (PFS) regardless of treatment strategy. We also found a strong correlation of EpCAM-positive EVs concentration between ascites and plasma. Our findings indicate that EpCAM-positive EVs in ascites of patients with advanced HGSC have the potential to serve as prognostic biomarkers for predicting early recurrence and thereby likelihood of more aggressive tumor biology and development of chemoresistance.

Exploring the Utility of Circulating Endothelial Cell-Derived Extracellular Vesicles as Markers of Health and Damage of Vasal Endothelium in Systemic Sclerosis Patients Treated with Iloprost

Endothelial cell-derived extracellular vesicles (eEVs) are released from endothelial cells, signifying endothelial integrity. Systemic Sclerosis (SSc) is a rare disease causing skin and organ fibrosis with early vascular damage. Iloprost, an SSc treatment, might affect eEV release, showing long-term benefits. We aimed to study eEVs in SSc, potentially serving as disease markers and linked to Iloprost's impact on organ involvement. We included 54 SSc patients and 15 healthy donors. Using flow cytometry on platelet-poor plasma (PPP) with specific antibodies (CD144, CD146, AnnexinV), we detected endothelial extracellular vesicles. Results showed fewer eEVs from apoptotic or normal cells in SSc patients than healthy controls. Specifically, patients with diffuse cutaneous SSc and lung issues had reduced eEVs from apoptotic endothelial cells (CD146+ AnnV+). No notable differences were seen in CD144 endothelial markers between patients and controls. After 1-day Iloprost infusion, there was an increase in eEVs, but not after 5 days. These findings suggest circulating eEVs reflect endothelial health/damage, crucial in early SSc stages. A 1-day Iloprost infusion seems effective in repairing endothelial damage, critical in scleroderma vasculopathy. Differences in marker outcomes may relate to CD146's surface expression and CD144's junctional location in endothelial cells.

Multifunctional nanoparticle-mediated combining therapy for human diseases

Combining existing drug therapy is essential in developing new therapeutic agents in disease prevention and treatment. In preclinical investigations, combined effect of certain known drugs has been well established in treating extensive human diseases. Attributed to synergistic effects by targeting various disease pathways and advantages, such as reduced administration dose, decreased toxicity, and alleviated drug resistance, combinatorial treatment is now being pursued by delivering therapeutic agents to combat major clinical illnesses, such as cancer, atherosclerosis, pulmonary hypertension, myocarditis, rheumatoid arthritis, inflammatory bowel disease, metabolic disorders and neurodegenerative diseases. Combinatorial therapy involves combining or co-delivering two or more drugs for treating a specific disease. Nanoparticle (NP)-mediated drug delivery systems, i.e., liposomal NPs, polymeric NPs and nanocrystals, are of great interest in combinatorial therapy for a wide range of disorders due to targeted drug delivery, extended drug release, and higher drug stability to avoid rapid clearance at infected areas. This review summarizes various targets of diseases, preclinical or clinically approved drug combinations and the development of multifunctional NPs for combining therapy and emphasizes combinatorial therapeutic strategies based on drug delivery for treating severe clinical diseases. Ultimately, we discuss the challenging of developing NP-codelivery and translation and provide potential approaches to address the limitations. This review offers a comprehensive overview for recent cutting-edge and challenging in developing NP-mediated combination therapy for human diseases.

Extracellular Vesicles in Pulmonary Hypertension: A Dangerous Liaison?

The term pulmonary hypertension (PH) refers to different conditions, all characterized by increased pressure and resistance in the pulmonary arterial bed. PH has a wide range of causes (essentially, cardiovascular, pulmonary, or connective tissue disorders); however, idiopathic (i.e., without a clear cause) PH exists. This chronic, progressive, and sometimes devastating disease can finally lead to right heart failure and eventually death, through pulmonary vascular remodeling and dysfunction. The exact nature of PH pathophysiology is sometimes still unclear. Extracellular vesicles (EVs), previously known as apoptotic bodies, microvesicles, and exosomes, are small membrane-bound vesicles that are generated by almost all cell types and can be detected in a variety of physiological fluids. EVs are involved in intercellular communication, thus influencing immunological response, inflammation, embryogenesis, aging, and regenerative processes. Indeed, they transport chemokines, cytokines, lipids, RNA and miRNA, and other biologically active molecules. Although the precise functions of EVs are still not fully known, there is mounting evidence that they can play a significant role in the pathophysiology of PH. In this review, after briefly recapping the key stages of PH pathogenesis, we discuss the current evidence on the functions of EVs both as PH biomarkers and potential participants in the distinct pathways of disease progression.

COVID-19 Plasma Extracellular Vesicles Increase the Density of Lipid Rafts in Human Small Airway Epithelial Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is the causative agent of the COVID-19 disease. COVID-19 viral infection can affect many cell types, including epithelial cells of the lungs and airways. Extracellular vesicles (EVs) are released by virtually all cell types, and their packaged cargo allows for intercellular communication, cell differentiation, and signal transduction. Cargo from virus-infected cells may include virally derived metabolites, miRNAs, nucleic acids, and proteins. We hypothesized that COVID-19 plasma EVs can induce the formation of signaling platforms known as lipid rafts after uptake by normal human small airway epithelial cells (SAECs). Circulating EVs from patients with or without COVID-19 were characterized by nanoparticle tracking analysis, Western blotting using specific antibodies, and transmission electron microscopy. Primary cultures of normal human small airway epithelial cells were challenged with EVs from the two patient groups, and lipid raft formation was measured by fluorescence microscopy and assessed by sucrose density gradient analysis. Collectively, our data suggest that circulating EVs from COVID-19-infected patients can induce the formation of lipid rafts in normal human small airway epithelial cells. These results suggest the need for future studies aimed at investigating whether the increased density of lipid rafts in these cells promotes viral entry and alteration of specific signaling pathways in the recipient cells.

Extracellular Vesicles in Coronary Artery Disease

Coronary artery disease (CAD) is the leading cause of death and disability worldwide. Despite recent progress in the diagnosis and treatment of CAD, evidence gaps remain, including pathogenesis, the most efficient diagnostic strategy, prognosis of individual patients, monitoring of therapy, and novel therapeutic strategies. These gaps could all be filled by developing novel, minimally invasive, blood-based biomarkers. Potentially, extracellular vesicles (EVs) could fill such gaps. EVs are lipid membrane particles released from cells into blood and other body fluids. Because the concentration, composition, and functions of EVs change during disease, and because all cell types involved in the development and progression of CAD release EVs, currently available guidelines potentially enable reliable and reproducible measurements of EVs in clinical trials, offering a wide range of opportunities. In this chapter, we provide an overview of the associations reported between EVs and CAD, including (1) the role of EVs in CAD pathogenesis, (2) EVs as biomarkers to diagnose CAD, predict prognosis, and monitor therapy in individual patients, and (3) EVs as new therapeutic targets and/or drug delivery vehicles. In addition, we summarize the challenges encountered in EV isolation and detection, and the lack of standardization, which has hampered real clinical applications of EVs. Since most conclusions are based on animal models and single-center studies, the knowledge and insights into the roles and opportunities of EVs as biomarkers in CAD are still changing, and therefore, the content of this chapter should be seen as a snapshot in time rather than a final and complete compendium of knowledge on EVs in CAD.

Tumor-Derived Extracellular Vesicles Predict Clinical Outcomes in Oligometastatic Prostate Cancer and Suppress Antitumor Immunity

PURPOSE

SABR has demonstrated clinical benefit in oligometastatic prostate cancer. However, the risk of developing new distant metastatic lesions remains high, and only a minority of patients experience durable progression-free response. Therefore, there is a critical need to identify which patients will benefit from SABR alone versus combination SABR and systemic agents. Herein we provide, to our knowledge, the first proof-of-concept of circulating prostate cancer-specific extracellular vesicles (PCEVs) as a noninvasive predictor of outcomes in oligometastatic castration-resistant prostate cancer (omCRPC) treated with SABR.

METHODS AND MATERIALS

We analyzed the levels and kinetics of PCEVs in the peripheral blood of 79 patients with omCRPC at baseline and days 1, 7, and 14 after SABR using nanoscale flow cytometry and compared with baseline values from cohorts with localized and widely metastatic prostate cancer. The association of omCRPC PCEV levels with oncological outcomes was determined with Cox regression models.

RESULTS

Levels of PCEVs were highest in mCRPC followed by omCRPC and were lowest in localized prostate cancer. High PCEV levels at baseline predicted a shorter median time to distant recurrence (3.5 vs 6.6 months; P = .0087). After SABR, PCEV levels peaked on day 7, and median overall survival was significantly longer in patients with elevated PCEV levels (32.7 vs 27.6 months; P = .003). This suggests that pretreatment PCEV levels reflect tumor burden, whereas early changes in PCEV levels after treatment predict response to SABR. In contrast, radiomic features of ¹¹C-choline positron emission tomography and computed tomography before and after SABR were not predictive of clinical outcomes. Interestingly, PCEV levels and peripheral tumor-reactive CD8 T cells (T_TR; CD8⁺ CD11a^high) were correlated.

CONCLUSIONS

This original study demonstrates that circulating PCEVs can serve as prognostic and predictive markers to SABR to identify patients with "true" omCRPC. In addition, it provides novel insights into the global crosstalk, mediated by PCEVs, between tumors and immune cells that leads to systemic suppression of immunity against CRPC. This work lays the foundation for future studies to investigate the underpinnings of metastatic progression and provide new therapeutic targets (eg, PCEVs) to improve SABR efficacy and clinical outcomes in treatment-resistant CRPC.

Platelet function changes in patients undergoing endovascular aortic aneurysm repair: Review of the literature

Patients with abdominal aortic aneurysm (AAA) have a higher risk of cardiovascular (CV) events, which seems to be associated with disturbed platelet (PLT) function. Endovascular aneurysm repair (EVAR) is an emerging, less-invasive treatment alternative to surgical AAA repair. Both platelet function abnormalities in patients with AAA and the effect of EVAR on platelet function are poorly understood. In this review, we aim to fill the gap regarding the effect of EVAR on PLT function in AAA patients by discussing PLT function disturbances in patients with AAA, PLT function changes after EVAR, evidence from clinical studies regarding PLT function before and after EVAR, and antiplatelet or and antithrombotic treatment in patients undergoing EVAR. The goal of our review is to summarize the contemporary knowledge and initiate further studies to better understand PLT function changes in patients undergoing EVAR, optimize the pharmacotherapy before and after EVAR and further improve outcomes in this group of patients.

Compassionate use of Pulmonary Vasodilators in Acute Severe Hypoxic Respiratory Failure due to COVID-19

BACKGROUND

There have been over 200 million cases and 4.4 million deaths from COVID-19 worldwide. Despite the lack of robust evidence one potential treatment for COVID-19 associated severe hypoxaemia is inhaled pulmonary vasodilator (IPVD) therapy, using either nitric oxide (iNO) or prostaglandins. We describe the implementation of, and outcomes from, a protocol using IPVDs in a cohort of patients with severe COVID-19 associated respiratory failure receiving maximal conventional support.

METHODS

Prospectively collected data from adult patients with SARS-CoV-2 admitted to the intensive care unit (ICU) at a large teaching hospital were analysed for the period 14th March 2020 - 11th February 2021. An IPVD was considered if the PaO2/FiO2 (PF) ratio was less than 13.3kPa despite maximal conventional therapy. Nitric oxide was commenced at 20ppm and titrated to response. If oxygenation improved Iloprost nebulisers were commenced and iNO weaned. The primary outcome was percentage changes in PF ratio and Alveolar-arterial (A-a) gradient.

RESULTS

Fifty-nine patients received IPVD therapy during the study period. The median PF ratio before IPVD therapy was commenced was 11.33kPa (9.93-12.91). Patients receiving an IPVD had a lower PF ratio (14.37 vs. 16.37kPa, p = 0.002) and higher APACHE-II score (17 vs. 13, p = 0.028) at ICU admission. At 72 hours after initiating an IPVD the median improvement in PF ratio was 33.9% (-4.3-84.1). At 72 hours changes in PF ratio (70.8 vs. -4.1%, p < 0.001) and reduction in A-a gradient (44.7 vs. 14.8%, p < 0.001) differed significantly between survivors (n = 33) and non-survivors (n = 26).

CONCLUSIONS

The response to IPVDs in patients with COVID-19 associated acute hypoxic respiratory failure differed significantly between survivors and non-survivors. Both iNO and prostaglandins may offer therapeutic options for patients with severe refractory hypoxaemia due to COVID-19. The use of inhaled prostaglandins, and iNO where feasible, should be studied in adequately powered prospective randomised trials.

Multivisceral Transplant in a Patient With Portopulmonary Hypertension: A Case Report

Portopulmonary hypertension, a type of pulmonary arterial hypertension in the setting of cirrhotic or noncirrhotic portal hypertension, is associated with elevated morbidity and mortality during and after transplantation. Uncontrolled portopulmonary hypertension may prevent or delay listing for transplant candidates, and the prognosis without treatment and ultimately transplant is extremely poor. We present a 29-year-old White woman, who had a post-liver transplant at infancy due to biliary atresia. Later on, she developed extensive portal vein thrombosis and portopulmonary hypertension and underwent a multivisceral transplant (liver, stomach, pancreaticoduodenal complex, and small and large intestine). Preoperative mean pulmonary artery pressure was <30 mm Hg with a pulmonary vascular resistance of <300 dynes^.s/cm⁵ on oral sildenafil and intravenous epoprostenol. Intraoperatively, management required comprehensive transfusion protocols, a careful balance between correcting blood loss and preventing thrombosis. Intravenous epoprostenol, sildenafil, milrinone, and inhaled nitric oxide were used to reduce elevated mean pulmonary artery pressure and right ventricular strain associated with vascular clamping, reperfusion, and massive fluid shifts. Nitric oxide and epoprostenol use unleashed antiplatelet effects on a patient already susceptible to coagulopathy. A multimodal and multidisciplinary approach continued throughout the surgery and in the postoperative period, which led to a successful outcome.

Calibration and standardization of extracellular vesicle measurements by flow cytometry for translational prostate cancer research

Extracellular vesicles (EVs) are microscopic particles released naturally in biofluids by all cell types. Since EVs inherits genomic and proteomic patterns from the cell of origin, they are emerging as promising liquid biomarkers for human diseases. Flow cytometry is a popular method that is able to detect, characterize and determine the concentration of EVs with minimal sample preparation. However, the limited awareness of the scientific community to utilize standardization and calibration methods of flow cytometers is an important roadblock for data reproducibility and inter-laboratory comparison. A significant collaborative effort by the Extracellular Vesicle Flow Cytometry Working Group has led to the development of guidelines and best practices for using flow cytometry and reporting data in a way to improve rigor and reproducibility in EV research. At first look, standardization and calibration of flow cytometry for EV detection may seem burdensome and technically challenging for non-academic laboratories with limited technical training and knowledge in EV flow cytometry. In this study, we build on prior research efforts and provide a systematic approach to evaluate the performance of a high sensitivity flow cytometer (herein Apogee A60-Micro Plus) and fine-tune settings to improve detection sensitivity for EVs. We performed calibration of our flow cytometer to generate data with comparable units (nanometers, MESF). Finally, we applied our optimized protocol to measure the concentrations of prostate-derived EVs in healthy individuals and prostate cancer patients. In conclusion, our proof-of-feasibility study can serve as a scientific and technical framework for other groups motivated in using flow cytometry for EV research.

Hemostatic changes in patients undergoing hemodialysis: differences between central venous catheters and arterio-venous fistulas

BACKGROUND

Failure to mature the fistula in patients undergoing hemodialysis leads to prolonged use of the central venous catheter (CVC) and can compromise the patency of the catheter and the arteriovenous fistula (AVF) due to thrombus development.

OBJECTIVE

to evaluate hemostatic changes in patients undergoing hemodialysis with prolonged use of CVC or AVF.

METHOD

cross-sectional study with a total of 200 adult participants who were divided into the following groups: I:control; II: patients who had 5 to 8 months of CVC insertion; III: patients who had 9 to 36 months of insertion; IV patients who had 5 to 8 months of AVF and V: patients who had 9 to 36 months of AVF. Platelet activation was investigated by expressions of GPIIb/IIIa and p-selectin using flow cytometry. The Elisa-thrombomodulin test was used to compare groups III and V.

RESULTS

the p-selectin percentage expression of group I was 15.30 (12.30-16.80), II 23.25 (20.75-30.55) and III 54.00 (44.75 -59.29) were significant (p<0.001). Groups I, IV and V were also significant (p<0.001). The median fluorescence for GPIIb/IIIa for groups I, II and III were significant (p<0.0001). As for the Elisa test, an increased absorbance of thrombomodulin was verified in patients who used the CVC 4372 (3951-4733) when compared to those patients who used the AVF 2162 (1932-2485) (p<0.0001).

CONCLUSION

It can be concluded that CVC patients had a larger platelet expression of GPIIb/IIIa and p-selectin than AVF patients. The high concentration of thrombomodulin in CVC patients may suggest a greater stimulation of the intrinsic than extrinsic coagulation pathways.

Platelet-Leucocyte Aggregates as Novel Biomarkers in Cardiovascular Diseases

Simple Summary

Cardiovascular diseases are the most common cause of death worldwide. Hence, novel biomarkers are urgently needed to improve diagnosis and treatment. Platelet–leucocyte aggregates are conglomerates of platelets and leucocytes and are widely investigated as biomarkers in cardiovascular diseases. Platelet–leucocytes aggregates are present in health, but increase in patients with cardiovascular risk factors and acute or stable coronary syndromes, making them a potential diagnostic marker. Moreover, platelet–leucocyte aggregates predict outcomes after surgery or percutaneous treatment and could be used to monitor antiplatelet therapy. Emerging data about the participation of platelet–leucocyte aggregates in cardiovascular diseases pathogenesis make them an attractive target for novel therapies. Furthermore, simple detection with conventional flow cytometry provides accurate and reproducible results, although requires specific sample handling. The main task for the future is to determine the standardized protocol to measure blood concentrations of platelet–leucocyte aggregates and subsequently establish their normal range in health and disease.

Abstract

Platelet–leucocyte aggregates (PLA) are a formation of leucocytes and platelets bound by specific receptors. They arise in the condition of sheer stress, thrombosis, immune reaction, vessel injury, and the activation of leukocytes or platelets. PLA participate in cardiovascular diseases (CVD). Increased levels of PLA were revealed in acute and chronic coronary syndromes, carotid stenosis cardiovascular risk factors. Due to accessible, available, replicable, quick, and low-cost quantifying using flow cytometry, PLA constitute an ideal biomarker for clinical practice. PLA are promising in early diagnosing and estimating prognosis in patients with acute or chronic coronary syndromes treated by percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). PLA were also a reliable marker of platelet activity for monitoring antiplatelet therapy. PLA consist also targets potential therapies in CVD. All of the above potential clinical applications require further studies to validate methods of assay and proof clinical benefits.

Circulating Blood-Based Biomarkers in Pulmonary Hypertension

Pulmonary hypertension (PH) is a serious hemodynamic condition, characterized by increased pulmonary vascular resistance (PVR), leading to right heart failure (HF) and death when not properly treated. The prognosis of PH depends on etiology, hemodynamic and biochemical parameters, as well as on response to specific treatment. Biomarkers appear to be useful noninvasive tools, providing information about the disease severity, treatment response, and prognosis. However, given the complexity of PH, it is impossible for a single biomarker to be adequate for the broad assessment of patients with different types of PH. The search for novel emerging biomarkers is still ongoing, resulting in a few potential biomarkers mirroring numerous pathophysiological courses. In this review, markers related to HF, myocardial remodeling, inflammation, hypoxia and tissue damage, and endothelial and pulmonary smooth muscle cell dysfunction are discussed in terms of diagnosis and prognosis. Extracellular vesicles and other markers with complex backgrounds are also reviewed. In conclusion, although many promising biomarkers have been identified and studied in recent years, there are still insufficient data on the application of multimarker strategies for monitoring and risk stratification in PH patients.

Differential and targeted vesiculation: pathologic cellular responses to elevated arterial pressure

Extracellular vesicles are small membrane-enclosed particles released during cell activation or injury. They have been investigated for several decades and found to be secreted in various diseases. Their pathogenic role is further supported by the presence of several important molecules among their cargo, including proteins, lipids, and nucleic acids. Many studies have reported enhanced and targeted extracellular vesicle biogenesis in diseases that involve chronic or transient elevation of arterial pressure resulting in endothelial dysfunction, within either the general circulatory system or specific local vascular beds. In addition, several associated pathologic processes have been studied and reported. However, the role of elevated pressure as a common pathogenic trigger across vascular domains and disease chronicity has not been previously described. This review will therefore summarize our current knowledge of the differential and targeted biogenesis of extracellular vesicles in major diseases that are characterized by elevated arterial pressure leading to endothelial dysfunction and propose a unified theory of pressure-induced extracellular vesicle-mediated pathogenesis.

Pre-operative platelet reactivity is a strong, independent predictor of bleeding complications after branched endovascular thoracoabdominal aortic aneurysm repair

Endovascular aortic repair (EVAR) an alternative to open surgical repair of thoracoabdominal aortic aneurysm (TAAA). The effect of EVAR on platelet reactivity is unknown. We prospectively determined the effect of branched EVAR (bEVAR) on platelet reactivity in patients with TAAA, and evaluated the predictive value of preoperative platelet reactivity for post-operative bleeding in 50 consecutive patients undergoing elective bEVAR (mean age 70.9 ± 5.7 years, 66% male). Blood samples were collected within 24 hours before bEVAR, after bEVAR and at hospital discharge. Platelet reactivity was assessed with impedance aggregometry using ASPI, ADP and TRAP tests. Platelet reactivity decreased within 24 hours after bEVAR compared to the measurement before bEVAR in all tests (p ≤ 0.04), with a further decrease in hospital discharge in the ADP test (p = .004). Twenty-three patients experienced post-operative bleeding complications (transfusion ≥2 red blood cell [RBC] units). Preoperative platelet reactivity below the cutoff value of 30 AUC units predicted post-operative bleeding with 78% sensitivity and 59% specificity (p = .045). In the multivariable analysis, platelet reactivity was the only independent predictor of postoperative bleeding (OR 6.507, 95% CI 1.227-34.506, p = .028). We conclude that platelet reactivity decreases following bEVAR of TAAA and is a strong and independent predictor for postoperative bleeding complications.

Platelets, extracellular vesicles and coagulation in pulmonary arterial hypertension

Pulmonary arterial hypertension is a rare disease of the pulmonary vasculature, characterised pathologically by proliferation, remodelling and thrombosis in situ. Unfortunately, existing therapeutic interventions do not reverse these findings and the disease continues to result in significant morbidity and premature mortality. A number of haematological derangements have been described in pulmonary arterial hypertension which may provide insights into the pathobiology of the disease and opportunities to explore new therapeutic pathways. These include quantitative and qualitative platelet abnormalities, such as thrombocytopaenia, increased mean platelet volume and altered platelet bioenergetics. Furthermore, a hypercoagulable state and aberrant negative regulatory pathways can be observed, which could contribute to thrombosis in situ in distal pulmonary arteries and arterioles. Finally, there is increasing interest in the role of extracellular vesicle autocrine and paracrine signalling in pulmonary arterial hypertension, and their potential utility as biomarkers and novel therapeutic targets. This review focuses on the potential role of platelets, extracellular vesicles and coagulation pathways in the pathobiology of pulmonary arterial hypertension. We highlight important unanswered clinical questions and the implications of these observations for future research and pulmonary arterial hypertension-directed therapies.