Platelet Extracellular Vesicles: Beyond the Blood

The emerging roles of platelet-derived extracellular vesicles in disease

INTRODUCTION

Platelet-derived extracellular vesicles (pEVs) are nanoscale, membrane-bound vesicles released by platelets during activation or apoptosis. They contain various bioactive and non-bioactive molecules and play significant roles in numerous physiological and pathological processes through intercellular communication, thus attracting growing attention in biomedical research.

METHODS

This review comprehensively overviews the biogenesis, clearance, and molecular characteristics of pEVs. It also covers current methodologies for their isolation and characterization. The therapeutic implications of pEVs in key clinical settings like tissue regeneration, hemostasis, immune modulation, and vascular repair, with a focus on cancer progression, wound healing, and hemorrhagic shock management, are explored. Their role in cellular signal transduction is examined, and their functional properties are compared with other platelet-derived products such as platelet-rich plasma.

RESULTS

pEVs show potential as both therapeutic agents and diagnostic biomarkers. They are involved in modulating inflammatory responses, promoting angiogenesis, and enhancing cellular repair mechanisms.

CONCLUSION

Future research should concentrate on optimizing their therapeutic efficacy, refining biomarker applications, and exploring targeted delivery strategies to fully utilize their potential in regenerative medicine, oncology, and hemostasis management.

Platelets and diseases: signal transduction and advances in targeted therapy

Platelets are essential anucleate blood cells that play pivotal roles in hemostasis, tissue repair, and immune modulation. Originating from megakaryocytes in the bone marrow, platelets are small in size but possess a highly specialized structure that enables them to execute a wide range of physiological functions. The platelet cytoplasm is enriched with functional proteins, organelles, and granules that facilitate their activation and participation in tissue repair processes. Platelet membranes are densely populated with a variety of receptors, which, upon activation, initiate complex intracellular signaling cascades. These signaling pathways govern platelet activation, aggregation, and the release of bioactive molecules, including growth factors, cytokines, and chemokines. Through these mechanisms, platelets are integral to critical physiological processes such as thrombosis, wound healing, and immune surveillance. However, dysregulated platelet function can contribute to pathological conditions, including cancer metastasis, atherosclerosis, and chronic inflammation. Due to their central involvement in both normal physiology and disease, platelets have become prominent targets for therapeutic intervention. Current treatments primarily aim to modulate platelet signaling to prevent thrombosis in cardiovascular diseases or to reduce excessive platelet aggregation in other pathological conditions. Antiplatelet therapies are widely employed in clinical practice to mitigate clot formation in high-risk patients. As platelet biology continues to evolve, emerging therapeutic strategies focus on refining platelet modulation to enhance clinical outcomes and prevent complications associated with platelet dysfunction. This review explores the structure, signaling pathways, biological functions, and therapeutic potential of platelets, highlighting their roles in both physiological and pathological contexts.

Platelet Extracellular Vesicles as Natural Delivery Vehicles for Mitochondrial Dysfunction Therapy?

Mitochondria are vital for energy production, metabolic regulation, and cellular signaling. Their dysfunction is strongly implicated in neurological, cardiovascular, and muscular degenerative diseases, where energy deficits and oxidative stress accelerate disease progression. Platelet extracellular vesicles (PEVs), once called "platelet dust", have emerged as promising agents for mitigating mitochondrial dysfunction. Like other extracellular vesicles (EVs), PEVs carry diverse molecular cargo and surface markers implicated in disease processes and therapeutic efficacy. Notably, they may possibly contain intact or partially functional mitochondrial components, making them tentatively attractive for targeting mitochondrial damage. Although direct research on PEVs-mediated mitochondrial rescue remains limited, current evidence suggests that PEVs can modulate diseases associated with mitochondrial dysfunction and potentially enhance mitochondrial health. This review explores the therapeutic potential of PEVs in neurodegenerative and cardiovascular disorders, highlighting their role in restoring mitochondrial health. By examining recent advancements in PEVs research, we aim to shed light on novel strategies for utilizing PEVs as therapeutic agents. Our goal is to underscore the importance of further fundamental and applied research into PEVs-based interventions, as innovative tools for combating a wide range of diseases linked to mitochondrial dysfunction.

The potential mechanisms of extracellular vesicles in transfusion-related adverse reactions: Recent advances

Blood transfusion is an irreplaceable clinical treatment. Blood components are differentiated and stored according to specific guidelines. Storage temperatures and times vary depending on the blood component, but they all release extracellular vesicles (EVs) during storage. Although blood transfusions can be life-saving, they can also cause many adverse transfusion reactions, among which the effects of EVs are of increasing interest to researchers. EVs are submicron particles that vary in size, composition, and surface biomarkers, are encapsulated by a lipid bilayer, and are not capable of self-replication. EVs released by blood cells are important contributors to pathophysiologic states through proinflammatory, coagulant, and immunosuppressive effects, which in turn promote or inhibit the associated disease phenotype. Therefore, this review explores the potential mechanisms of hematopoietic-derived EVs in transfusion-associated adverse reactions and discusses the potential of the latest proteomics tools to be applied to the analysis of EVs in the field of transfusion medicine with a view to reducing the risk of blood transfusion.

The Role of Platelet-Neutrophil Interactions in Driving Autoimmune Diseases

Platelets and neutrophils are among the most abundant cell types in peripheral blood. Beyond their traditional roles in thrombosis and haemostasis, they also play an active role in modulating immune responses. Current knowledge on the role of platelet-neutrophil interactions in the immune system has been rapidly expanding. Notably, circulating platelet-neutrophil complexes (PNCs) have been widely detected in various inflammatory diseases and infections, closely associated with inflammatory processes affecting multiple organs. These findings emphasise the critical role of platelet-neutrophil interactions in driving and sustaining inflammatory responses. In this review, we elucidate the mechanisms by which neutrophils and platelets physically interact, leading to mutual activation. Additionally, activated platelets release pro-inflammatory factors that further modulate neutrophil effector functions, enhancing their immune response capabilities. We highlight the role of platelets in promoting the formation of neutrophil extracellular traps (NETs), which, in turn, promote local platelet activation, thereby exacerbating the immune response and sustaining chronic inflammation. Furthermore, we review current evidence on the role of platelet-neutrophil interactions in common autoimmune diseases such as systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and rheumatoid arthritis (RA). Finally, we identify gaps in understanding the mechanisms of these interactions in the context of other autoimmune diseases and underscore the potential of targeting platelets and neutrophils as a therapeutic strategy for these conditions.

Platelet-derived extracellular vesicles: emerging players in hemostasis and thrombosis

Platelets, long recognized for their role in hemostasis and thrombosis, have emerged as key players in a wide array of physiological and pathological processes through the release of platelet-derived extracellular vesicles (PEVs). These nanoscale vesicles, rich in bioactive molecules such as proteins, lipids, and nucleic acids, facilitate intercellular communication and influence processes ranging from angiogenesis and inflammation to immune modulation and tissue repair. PEVs, the most abundant extracellular vesicles in circulation, display procoagulant activity 50-100 times greater than activated platelets, underscoring their pivotal role in hemostasis and thrombosis. Recent research has unveiled their dual role in health and disease, highlighting their potential as diagnostic biomarkers and therapeutic vehicles. PEVs are implicated in cancer progression, autoimmune diseases, and infectious diseases, where they modulate tumor microenvironments, immune responses, and inflammatory pathways. Moreover, their ability to deliver therapeutic agents with high specificity and biocompatibility positions them as promising tools in regenerative medicine, drug delivery, and targeted therapies. This review comprehensively explores PEV biogenesis, cargo composition, and their multifaceted roles in hemostasis and thrombosis, as well as their broader implications in disease. It also explores the potential of PEVs as diagnostic markers and innovative therapeutic strategies, offering insights into their application in treating thrombotic disorders, cancer, and inflammatory diseases. Despite significant advancements, challenges remain in standardizing isolation protocols and translating preclinical findings into clinical applications. Unlocking the full potential of PEVs promises to revolutionize diagnostics and therapeutics, paving the way for novel approaches to managing complex diseases.

Extracellular vesicles as therapeutic modulators of neuroinflammation in Alzheimer's disease: a focus on signaling mechanisms

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid-beta (Aβ) plaques and tau tangles, which contribute significantly to neuroinflammation, a central driver of disease pathogenesis. The activation of microglia and astrocytes, coupled with the complex interactions between Aβ and tau pathologies and the innate immune response, leads to a cascade of inflammatory events. This process triggers the release of pro-inflammatory cytokines and chemokines, exacerbating neuronal damage and fostering a cycle of chronic inflammation that accelerates neurodegeneration. Key signaling pathways, such as nuclear factor-kappa B (NF-κB), Janus kinase/signal transducer and activator of transcription (JAK/STAT), mitogen-activated protein kinase (MAPK), and phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), are involved in regulating the production of these inflammatory mediators, offering potential therapeutic targets for AD. Recently, extracellular vesicles (EVs) have emerged as a promising tool for AD therapy, due to their ability to cross the blood-brain barrier (BBB) and deliver therapeutic agents. Despite challenges in standardizing EV-based therapies and ensuring their safety, EVs offer a novel approach to modulating neuroinflammation and promoting neuroregeneration. This review aims to highlight the intricate relationship between neuroinflammation, signaling pathways, and the emerging role of EV-based therapeutics in advancing AD treatment strategies.

Vaccination and Platelet Biology: Unraveling the Immuno-Hemostatic Interplay

Platelets, which have been traditionally associated with hemostasis and thrombosis functions, now receive attention for their role in immune responses that may affect vaccine development and effectiveness. Through their interactions with immune cells and modulation of inflammation alongside their role in antigen presentation, platelets become integral components of both innate and adaptive immune systems. New research shows platelets can improve vaccine effectiveness while reducing adverse side effects. During vaccine administration, platelets release cytokines and chemokines, which attract and stimulate immune cells to the injection site. Platelets work together with dendritic cells and T cells to support antigen processing and presentation, which leads to strong immune activation. Platelets' pro-inflammatory mediators strengthen local immune responses to boost protective immunity generation. Significant attention has been given to platelet involvement in vaccine-related thrombotic events, including vaccine-induced immune thrombotic thrombocytopenia (VITT). The rarity and severity of these events demonstrate the need to investigate the complex interplay between vaccine mechanisms and platelet activation. Exploration of the platelet-immune axis can lead to new methods for improving both the effectiveness and safety of vaccines. Researchers are working on creating innovative approaches for treatments that target platelet receptors and thrombosis pathways without interfering with the regular hemostatic functions of platelets. New vaccine development methods and personalized immunization strategies can emerge from targeting platelets with adjuvants and immune modulators.

Platelet Content from Acute Myocardial Infarction Patients: Elevated Levels of IL-6 and IL-8 and their impact on Endothelial Nitric Oxide Production

BACKGROUND AND AIMS

Platelets and inflammation play crucial roles in the atherothrombotic process of acute myocardial infarction (AMI), particularly in ischemia/reperfusion injury. This study aims to characterize the pro-inflammatory content of the platelet secretome in AMI patients, assess its effect on nitric oxide (NO) production, and correlate these findings with clinical parameters.

METHODS

Blood samples from 20 AMI patients and 20 controls were analyzed. Platelets were isolated and stimulated with thrombin, and their secretomes were collected. Endothelial cells were exposed to these secretomes, and NO production was measured. Our results demonstrate a significant reduction in NO production in endothelial cells exposed to the AMI platelet secretome (p < 0.05), suggesting acute endothelial dysfunction.

RESULTS

Elevated levels of interleukin-6 (IL-6) (p = 0.0323) and interleukin-8 (IL-8) (p = 0.0197) were identified in the secretome of AMI patients, correlating with clinical markers of myocardial injury. Specifically, IL-6 positively correlated with CK-MB levels (p = 0.04, Pearson r = 0.53), while IL-8 levels inversely correlated with NO production (p = 0.0141, Pearson r = -0.5652).

CONCLUSIONS

These findings underscore the critical role of platelet-derived IL-6 and IL-8 in endothelial dysfunction and myocardial injury in AMI patients. Future studies should explore the interactions between these cytokines in endothelial cells to further elucidate their roles in AMI pathology.

The Relationship of Platelets With the Clinical Manifestations and Serologic Markers in Systemic Lupus Erythematosus: A Single-Center Retrospective Study

BACKGROUND

Thrombocytopenia is a common clinical manifestation of Systemic lupus erythematosus (SLE), and platelets may play a central role in the pathogenesis of immune-mediated inflammatory diseases. The study aimed to investigate the relationship between platelet count and clinical manifestations and serologic markers in systemic lupus erythematosus (SLE).

METHODS

This single-center retrospective study extracted demographic data, blood cell counts, complement (C) levels, autoantibody profiles, and clinical presentation information from the electronic medical records of patients with SLE. The SLE Disease Activity Index 2000 (SLEDAI 2000) score was calculated, and Spearman's correlation coefficient was used to evaluate the correlation between platelet count and other variables.

RESULTS

A total of 418 patients with SLE were included in the study. The platelet count was correlated with hemoglobin, complement 3 (C3), and C4 levels; leukocyte, neutrophil, and lymphocyte counts; and the SLEDAI 2000 score. In patients with SLE with thrombocytopenia, the platelet count was associated with the hemoglobin level and a positive direct Coombs' test. The platelet count in patients with SLE without thrombocytopenia was significantly lower compared with the healthy controls, and the platelet count in this group was correlated with C3 and C4 levels, as well as the leukocyte, neutrophil, and lymphocyte counts. The disease characteristics of patients with SLE with thrombocytopenia differed from those of patients with SLE without thrombocytopenia, whereas the clinical features were essentially the same between patients with mild to moderate SLE-associated thrombocytopenia and patients with severe SLE-associated thrombocytopenia.

CONCLUSION

Patients with SLE can be categorized into two groups with different clinical features based on the presence or absence of thrombocytopenia. Furthermore, the platelet count correlates with other blood cell counts and complement levels, particularly in patients with SLE without thrombocytopenia.

Integrin β3-mediated platelet extracellular vesicle adhesion facilitates vascular smooth muscle cell dysfunction in postinjury intimal hyperplasia

Vascular smooth muscle cell (VSMC) dysfunction is a critical pathological process in postinjury intima hyperplasia. This process is driven by the adherence and accumulation of platelet-derived extracellular vesicles (PEVs) released from activated platelets to VSMCs at the site of injured intima. However, the precise mechanism remains unclear. Thus, the present study aimed to investigate how PEVs adhere to VSMCs and facilitate VSMC dysfunction in postinjury intimal hyperplasia. Morphological results confirmed that PEVs led to VSMC dysfunction and intimal hyperplasia. Integrated single-cell and proteomic analysis revealed that increased secreted phosphoprotein 1 (SPP1) expression in VSMCs played a central role in this process, possibly by mediating PEV adhesion to VSMCs and activating the focal adhesion kinase (FAK)/phosphoinositide 3 kinase (PI3K)/protein kinase B (Akt) axis. In addition, integrin beta 3 (ITGβ3, CD61) on PEVs, with increased expression under pathological conditions, was predicted to interact with SPP1. Co-immunoprecipitation (Co-IP) analysis further confirmed that ITGβ3 interacted with SPP1, thereby activating the FAK/PI3K/AKT phosphorylation and promoting PEV adhesion. Of note, blocking ITGβ3 expression on PEVs reduced PEV adhesion and intimal hyperplasia. Thus, ITGβ3-SPP1-mediated PEV adhesion to VSMCs may be a novel mechanism in intimal hyperplasia, which proposed to be critical for vascular homeostasis.

Platelets tune fear memory in mice

Several lines of evidence have shown that platelet-derived factors are key molecules in brain-body communication in pathological conditions. Here, we identify platelets as key actors in the modulation of fear behaviors in mice through the control of inhibitory neurotransmission and plasticity in the hippocampus. Interfering with platelet number or activation reduces hippocampal serotonin (5-HT) and modulates fear learning and memory in mice, and this effect is reversed by serotonin replacement by serotonin precursor (5-HTP)/benserazide. In addition, we unravel that natural killer (NK) cells participate in this mechanism, regulating interleukin-13 (IL-13) levels in the gut, with effects on serotonin production by enterochromaffin cells and uptake by platelets. Both NK cells and platelet depletion reduce the activation of hippocampal inhibitory neurons and increase the long-term potentiation of synaptic transmission. Understanding the role of platelets in the modulation of neuro-immune interactions offers additional tools for the definition of the molecular and cellular elements involved in the growing field of brain-body communication.

Deciphering Platelets: Are They Cells or an Evolved Form of Extracellular Vesicles?

Platelets are abundant in blood, where they maintain the integrity of the vasculature. Megakaryocytes, the cells responsible for platelet genesis, produce membrane protrusions from which as many as 5000 anucleate platelets can be released into the bloodstream. Platelets lack genomic DNA but contain different molecules, such as RNA, as well as organelles transmitted from the parent megakaryocyte. There is no consensus in the scientific community on whether platelets are cells or not: for example, they are sometimes called cells, small cells, anucleated cells, cell fragments, or megakaryocyte fragments. Extracellular vesicles are particles delimited by a lipid bilayer that are released from cells but cannot replicate on their own. Like platelets, extracellular vesicles lack a nucleus and carry components from their donor cell. Herein, we will explore various viewpoints suggesting that platelets may be cells, albeit not conventional cells, or may be a previously unrecognized type of extracellular vesicle. Beyond a mere debate over terminology, this perspective seeks to help properly define and classify platelets, aiming for better integration into the concept of either cells or extracellular vesicles. This will foster a clearer understanding and drive advances in platelet research.

Platelet endocytosis and α-granule cargo packaging are essential for normal skin wound healing

The high prevalence of chronic wounds, i.e., 2.5-3% of the US population, causes a large social and financial burden. Physiological wound healing is a multi-step process that involves different cell types and growth factors. Platelet-rich plasma or platelet-derived factors have been used to accelerate wound repair, but their use has been controversial with mixed results. Thus, a detailed functional understanding of platelet functions in wound healing beyond hemostasis is needed. This study investigated the importance of platelet α-granule cargo packaging and endocytosis in a dorsal full-thickness excisional skin wound model using mice with defects in α-granule cargo packaging (Nbeal2 -/- mice) and endocytosis (platelet-specific Arf6 -/- and VAMP2/3 Δ mice). We found that proper kinetic and morphological healing of dorsal skin wounds in mice requires both de novo as well as endocytosed platelet α-granule cargo. Histological and morphometric analyses of cross-sectional wound sections illustrated that mice with defects in α-granule cargo packaging or platelet endocytosis had delayed (epi)dermal regeneration in both earlier and advanced healing. This was reflected by reductions in wound collagen and muscle/keratin content, delayed scab formation and/or resolution, re-epithelialization, and cell migration and proliferation. Molecular profiling analysis of wound extracts showed that the impact of platelet function extends beyond hemostasis to the inflammation, proliferation, and tissue remodeling phases via altered expression of several bioactive molecules, including IL-1β, VEGF, MMP-9, and TIMP-1. These findings provide a basis for advances in clinical wound care through a better understanding of key mechanistic processes and cellular interactions in (patho)physiological wound healing.

Key points

De novo and endocytosed platelet α-granule cargo support physiological skin wound healing Platelet function in wound healing extends to the inflammation, proliferation, and tissue remodeling phases.

Hyperactivity and Pro-inflammatory Functions of Platelets in Diabetes

Cardiovascular complications claim the lives of up to 70% of patients with diabetes mellitus (DM). The mechanisms increasing cardiovascular risk in DM remain to be fully understood and successfully addressed. Nonetheless, there is increasing evidence in the scientific literature of the participation of platelets in the cardiovascular complications of DM. Multiple reports describe the hyperactivity of platelets in DM and their participation in inflammatory responses. The understanding of the mechanisms underlying the contribution of platelets to cardiovascular pathologies in DM will help the development of targeted therapeutic strategies able to reduce cardiovascular risk in these patients. In this literature review, we summarise our current understanding of the molecular mechanisms leading to the contribution of platelets to cardiovascular risk in DM. Both platelet haemostatic activity leading to thrombus formation and their participation to inflammatory processes are stimulated by the biochemical conditions associated with DM. We also present evidence on how DM affect the efficacy of existing therapeutic treatments for thrombosis and, by converse, how antidiabetic drugs may affect platelet function and the haemostasis/thrombosis balance. Taken together, the growing evidence of the different and unexpected roles of platelets in the progression of DM provides a strong rationale for the design of cardiovascular drugs targeting specifically platelets, their pro-inflammatory activity and their activation mechanisms in this disease. Overall, this article provides an important up-to-date overview of the pathophysiological alterations of platelets in DM, which need to be taken into account for the effective management of cardiovascular health in this disease.

Platelet-derived extracellular vesicles in cardiovascular disease and treatment - from maintaining homeostasis to targeted drug delivery

PURPOSE OF REVIEW

Cardiovascular disease (CVD) remains a major global health burden. Rising incidences necessitate improved understanding of the pathophysiological processes underlying disease progression to foster the development of novel therapeutic strategies. Besides their well recognized role in CVD, platelet-derived extracellular vesicles (PEVs) mediate inter-organ cross talk and contribute to various inflammatory diseases.

RECENT FINDINGS

PEVs are readily accessible diagnostic biomarkers that mirror pathophysiological disease progression but also may confer cardioprotective properties. Monitoring the effects of modulation of PEV signatures through pharmacotherapies has also provided novel insights into treatment efficacy. Furthermore, exploiting their inherent ability to infiltrate thrombi, atherosclerotic plaques and solid tumours, PEVs as well as platelet-membrane coated nanoparticles are emerging as novel effective and targeted treatment options for CVD and cancer.

SUMMARY

Collectively, in-depth characterization of PEVs in various diseases ultimately enhances their use as diagnostic or prognostic biomarkers and potential therapeutic targets, making them clinically relevant candidates to positively impact patient outcomes.

Protein disulfide isomerase 1 (PDIA1) regulates platelet-derived extracellular vesicle release

BACKGROUND

Protein disulfide isomerase 1 (PDIA1) and 3 (PDIA3) regulate platelet activation and thrombus formation. However, their role in the formation of platelet-derived extracellular vesicles (pEVs) remains unknown.

AIM

To characterise the effects of PDIA1 and PDIA3 inhibition on pEV formation in washed murine platelets in response to platelet glycoprotein VI (GPVI) receptor or intracellular calcium signal activation.

METHODS

Washed platelets were isolated from C57BL/6 mice and activated using convulxin or the calcium ionophore A23187. Then, the resulting pEVs were analysed using nano flow cytometry (FC), platelet aggregation was measured by FC and a 96-well plate-based assay, and intracellular free calcium concentration ([Ca2+]i) was measured by indicator fluorescence. Platelet PDIs were blocked by a classic selective PDIA1 inhibitor (bepristat 2a) and sulphonamides of aziridine-2-carboxylic acid derivatives, novel PDI inhibitors relatively selective for PDIA1 or PDIA3 (C-3389 and C-3399, respectively). Clinically relevant antiplatelet drugs were used for comparison.

RESULTS

Convulxin and A23187 concentration-dependently induced pEV formation. However, unlike convulxin, platelet activation by A23187 did not stimulate their aggregation. Bepristat 2a, C-3389 and C-3399 inhibited convulxin-induced pEV release accompanied by the reduction of [Ca2+]i. In contrast, only bepristat 2a inhibited A23187-induced pEV release, but without effect on [Ca2+]i. Cangrelor and tirofiban, but not acetylsalicylic acid (ASA), inhibited convulxin-induced pEV release, but neither of them inhibited A23187-induced pEV release.

CONCLUSION

The inhibition of PDIA1 represents a novel approach to inhibit pEV formation by a mechanism independent of platelet aggregation and calcium signaling.

Assessing platelet-derived extracellular vesicles for potential as therapeutic targets in cardiovascular diseases

INTRODUCTION

Cardiovascular disease (CVD) is the leading cause of death worldwide. Platelet-derived extracellular vesicles (PEV) have attracted extensive attention in cardiovascular disease research in recent years because their cargo is involved in a variety of pathophysiological processes, such as thrombosis, immune response, promotion or inhibition of inflammatory response, promotion of angiogenesis as well as cell proliferation and migration.

AREAS COVERED

This review explores the role of PEV in various cardiovascular diseases (such as atherosclerosis, myocardial infarction, ischemia-reperfusion injury, and heart failure), with relation to its molecular cargo (nucleic acids, bioactive lipids, proteins) and aims to provide new insights in the pathophysiologic role of PEV, and methods for preventing and treating cardiovascular diseases based on PEV.

EXPERT OPINION

Studies have shown that the cargo of PEV may be dysregulated during cardiovascular disease and delivery to tissues can result in detrimental pathophysiologic effects. Counteracting this process might have the potential to inhibit inflammation, promote angiogenesis, and inhibit cardiomyocyte death. In addition, PEV have potential as biocompatible and autologous drug carriers. Therefore, better research on the mechanisms how PEV act during cardiovascular disease and could be implemented as a therapeutic will provide new perspectives for the treatment of cardiovascular disease.

Immunohaemostasis and the significance of immune reactions in the regulation of blood coagulation

Introduction

This study was conducted to determine the specific features of the mutual influence of the immune and haemostatic systems in immunohaemostasis, the role of immune reactions in the regulation of blood coagulation, and the efficacy of modern methods of treating thrombosis and bleeding.

Methods

The study analysed relevant scientific sources on immunology and haematology and identified the specific features of the blood clotting process and the role of immune reactions in it.

Results

The study found that the immune system influences the haematological system through the interaction of blood clotting factors, platelets, plasminogen, endothelial cells with immune cells. The haemostatic system influences the immune system through mechanisms to maintain immune tolerance and immune memory and the properties of clotting factors to activate the stimulation and migration of immune cells to the site of infection. Immune reactions regulate blood coagulation by activating platelets, regulating blood coagulation factors, affecting fibrinolysis, and immune tolerance. The process of platelet activation involves immune cells, immune complexes, and microbial components. The regulation of blood coagulation factors is influenced by the ability of immune cells to produce activators and inhibitors of these factors and to stimulate or slow down fibrinolysis. The immune system's maintenance of immune tolerance to blood components is regulated by mechanisms of immune response suppression, partial immune ignoring of certain blood elements, inhibition of activation of certain immune cells, apoptosis, and selection of immature T-lymphocytes. Treatment methods for patients at risk of thrombosis and bleeding include anticoagulation, antiplatelet, dual antiplatelet therapy, thrombectomy, endovascular methods, medical prophylaxis of bleeding, and coagulation monitoring.

Conclusions

The findings of this study suggest the significance of immune responses in the regulation of blood coagulation processes, and therefore they can be used in the development of immunotherapy methods for the treatment of thrombosis and bleeding.

Gelsolin controls the release of phosphatidylserine (PS)-positive microvesicles (MVs) from platelets

Upon activation by vascular injury or extracellular agonists, platelets undergo rapid change shape, a process regulated by the actin cytoskeleton and accessory proteins. Platelet shape change is accompanied by the secretion of hemostatic factors and immunomodulatory cytokines from their intracellular granules, as well as the release of microvesicles (MVs) containing pro-inflammatory cytokines and procoagulant phosphatidylserine (PS). However, the role of actin dynamics in MV generation remains unclear. In this study, we found that blocking actin polymerization with cytochalasin D attenuated the release of PS-positive MVs in human platelets stimulated by thrombin or the calcium ionophore A23187. The actin-severing protein gelsolin (Gsn) facilitates normal actin filament turnover in activated platelets. Platelets from Gsn-deficient (Gsn-/-) mice showed reduced MV release compared to platelets from control mice. These findings indicate that the proper dynamics of the actin cytoskeleton are essential for MV generation in platelets, which has implications for their pro-inflammatory and procoagulant functions.

Bioprocessing of human platelet concentrates to generate lysates and extracellular vesicles for therapeutic applications

This work describes protocols for preparing specific forms of human platelet lysates from pooled platelet concentrates (PCs) and the isolation of platelet-derived extracellular vesicles (p-EVs). Clinical-grade PCs can be sourced from blood establishments immediately following expiration for transfusion use. Here, we describe methods to process PCs into specific lysates from which p-EVs can be isolated. Each lysate type is prepared using platelet activation and processing methods which produce distinct products that may be useful in different applications. For example, serum-converted platelet lysate (SCPL)-EVs were recently shown to have powerful therapeutic properties following myocardial infarction in mice. EVs can be isolated from all products using size exclusion chromatography, producing pure and consistent p-EVs from multiple batches. Together, these methods allow isolation of p-EVs with excellent potential for clinical and preclinical applications.•Platelet concentrates (PCs) obtained from local blood establishments are reliable and sustainable sources to generate biomaterials.•We outline five distinct methods of platelet lysate generation and one method for extracellular vesicle isolation.•Each platelet lysate form has different biological properties which may be suitable for certain applications.

The potential utilization of platelet-derived extracellular vesicles in clinical treatment

Platelet-derived extracellular vesicles (PEVs) are released by platelets in the blood circulation, which carry a rich bio-molecular cargo influential in intercellular communications. PEVs can enter the lymph, bone marrow, and synovial fluid as nano-sized particles, while platelets cannot cross tissue barriers. Considering the advantages of PEVs such as low immunogenicity, high regulation of signal transduction, and easy obtainment, PEVs may be promising therapeutic tools for medical applications. The exceptional functional roles played by PEVs explain the recent interest in exploring new cell-free therapies that could address needs in angiogenesis, regenerative medicine, and targeted drug delivery. The review takes a critical look at the main advances of PEVs in the treatment of diseases by presenting the latest knowledge from the performed studies, in order to enhance the further translation of the PEVs research into feasible therapeutic applications.

Extracellular Vesicle-Inspired Therapeutic Strategies for the COVID-19

Emerging infectious diseases like coronavirus pneumonia (COVID-19) present significant challenges to global health, extensively affecting both human society and the economy. Extracellular vesicles (EVs) have demonstrated remarkable potential as crucial biomedical tools for COVID-19 diagnosis and treatment. However, due to limitations in the performance and titer of natural vesicles, their clinical use remains limited. Nonetheless, EV-inspired strategies are gaining increasing attention. Notably, biomimetic vesicles, inspired by EVs, possess specific receptors that can act as "Trojan horses," preventing the virus from infecting host cells. Genetic engineering can enhance these vesicles by enabling them to carry more receptors, significantly increasing their specificity for absorbing the novel coronavirus. Additionally, biomimetic vesicles inherit numerous cytokine receptors from parent cells, allowing them to effectively mitigate the "cytokine storm" by adsorbing pro-inflammatory cytokines. Overall, this EV-inspired strategy offers new avenues for the treatment of emerging infectious diseases. Herein, this review systematically summarizes the current applications of EV-inspired strategies in the diagnosis and treatment of COVID-19. The current status and challenges associated with the clinical implementation of EV-inspired strategies are also discussed. The goal of this review is to provide new insights into the design of EV-inspired strategies and expand their application in combating emerging infectious diseases.

Coagulation protease-induced extracellular vesicles: their potential effects on coagulation and inflammation

Coagulation proteases, in addition to playing an essential role in blood coagulation, often influence diverse cellular functions by inducing specific signaling pathways via the activation of protease-activated receptors (PARs). PAR activation-induced cellular effects are known to be cell-specific as PARs are expressed selectively in specific cell types. However, a growing body of evidence indicates that coagulation protease-induced PAR activation in a specific cell type could affect cellular responses in other cell types via communicating through extracellular vesicles (EVs) as coagulation protease-induced PAR signaling could promote the release of EVs in various cell types. EVs are membrane-enclosed nanosized vesicles that facilitate intercellular communication by transferring bioactive molecules, such as proteins, lipids, messenger RNAs, and microRNAs, etc., from donor cells to recipient cells. Our recent findings established that factor (F)VIIa promotes the release of EVs from vascular endothelium via endothelial cell protein C receptor-dependent activation of PAR1-mediated biased signaling. FVIIa-released EVs exhibit procoagulant activity and cytoprotective responses in both in vitro and in vivo model systems. This review discusses how FVIIa and other coagulation proteases trigger the release of EVs. The review specifically discusses how FVIIa-released EVs are enriched with phosphatidylserine and anti-inflammatory microRNAs and the impact of FVIIa-released EVs on hemostasis in therapeutic settings. The review also briefly highlights the therapeutic potential of FVIIa-released EVs in treating bleeding and inflammatory disorders, such as hemophilic arthropathy.

Proteomic Characterization of Transfusable Blood Components: Fresh Frozen Plasma, Cryoprecipitate, and Derived Extracellular Vesicles via Data-Independent Mass Spectrometry

Extracellular vesicles (EVs) are a heterogeneous collection of particles that play a crucial role in cell-to-cell communication, primarily due to their ability to transport molecules, such as proteins. Thus, profiling EV-associated proteins offers insight into their biological effects. EVs can be isolated from various biological fluids, including donor blood components such as cryoprecipitate and fresh frozen plasma (FFP). In this study, we conducted a proteomic analysis of five single donor units of cryoprecipitate, FFP, and EVs derived from these blood components using a quantitative mass spectrometry approach. EVs were successfully isolated from both cryoprecipitate and FFP based on community guidelines. We identified and quantified approximately 360 proteins across all sample groups. Principal component analysis and heatmaps revealed that both cryoprecipitate and FFP are similar. Similarly, EVs derived from cryoprecipitate and FFP are comparable. However, they differ between the originating fluids and their derived EVs. Using the R-package MS-DAP, differentially expressed proteins (DEPs) were identified. The DEPs for all comparisons, when submitted for gene enrichment analysis, are involved in the complement and coagulation pathways. The protein profile generated from this study will have important clinical implications in increasing our knowledge of the proteins that are associated with EVs derived from blood components.

Choice of blood collection methods influences extracellular vesicles counts and miRNA profiling

Circulating RNAs have been investigated systematically for over 20 years, both as constituents of circulating extracellular vesicles (EVs) or, more recently, non-EV RNA carriers, such as exomeres and supermeres. The high level of variability and low reproducibility rate of EV/extracellular RNA (exRNA) results generated even on the same biofluids promoted several efforts to limit pre-analytical variability by standardizing sample collection and sample preparation, along with instrument validation, setup and calibration. Anticoagulants (ACs) are often chosen based on the initial goal of the study and not necessarily for the later EV and/or exRNA analyses. We show the effects of blood collection on EV size, abundance, and antigenic composition, as well on the miRNAs. Our focus of this work was on the effect of ACs on the number and antigenic composition of circulating EVs and on a set of circulating miRNA species, which were shown to be relevant as disease markers in several cancers and Alzheimer's disease. Results show that while the number of plasma EVs, their relative size, and post-fluorescence labeling profile varied with each AC, their overall antigenic composition, with few exceptions, did not change significantly. However, the number of EVs expressing platelet and platelet-activation markers increased in serum samples. For overall miRNA expression levels, EDTA was a better AC, although this may have been associated with stimulation of cells in the blood collection tube. Citrate and serum rendered better results for a set of miRNAs that were described as circulating markers for Alzheimer's disease, colon, and papillary thyroid cancers.

Current status and future perspectives of platelet-derived extracellular vesicles in cancer diagnosis and treatment

Platelets are a significant component of the cell population in the tumour microenvironment (TME). Platelets influence other immune cells and perform cross-talk with tumour cells, playing an important role in tumour development. Extracellular vesicles (EVs) are small membrane vesicles released from the cells into the TME. They can transfer biological information, including proteins, nucleic acids, and metabolites, from secretory cells to target receptor cells. This process affects the progression of various human diseases, particularly cancer. In recent years, several studies have demonstrated that platelet-derived extracellular vesicles (PEVs) can help regulate the malignant biological behaviours of tumours, including malignant proliferation, resistance to cell death, invasion and metastasis, metabolic reprogramming, immunity, and angiogenesis. Consequently, PEVs have been identified as key regulators of tumour progression. Therefore, targeting PEVs is a potential strategy for tumour treatment. Furthermore, the extensive use of nanomaterials in medical research has indicated that engineered PEVs are ideal delivery systems for therapeutic drugs. Recent studies have demonstrated that PEV engineering technologies play a pivotal role in the treatment of tumours by combining photothermal therapy, immunotherapy, and chemotherapy. In addition, aberrant changes in PEVs are closely associated with the clinicopathological features of patients with tumours, which may serve as liquid biopsy markers for early diagnosis, monitoring disease progression, and the prognostic assessment of patients with tumours. A comprehensive investigation into the role and potential mechanisms of PEVs in tumourigenesis may provide novel diagnostic biomarkers and potential therapeutic strategies for treating human tumours.

Differential effects of physiological agonists on the proteome of platelet-derived extracellular vesicles

Arterial thrombosis contributes to some of the most frequent causes of mortality globally, such as myocardial infarction and stroke. Platelets are essential mediators of physiological haemostasis and pathological thrombosis. Platelet activation is controlled by a multitude of signalling pathways. Upon activation, platelets shed platelet-derived extracellular vesicles (pEVs). In this Special Issue: Extracellular Vesicles, Moon et al. investigate the impact of various platelet agonists (thrombin, ADP, collagen) on the proteome of pEVs. The study demonstrates that pEVs exhibit an agonist-dependent altered proteome compared to their parent cells, with significant variations in proteins related to coagulation, complement, and platelet activation. The study observes the rapid generation of pEVs following agonist stimulation with specific proteome alterations that underscore an active packaging process. This commentary highlights the implications of their findings and discusses the role of pEV cargo in cardiovascular disease with potential novel therapeutic and diagnostic opportunities.

Unleashing the biomimetic targeting potential of platelet-derived nanocarriers on atherosclerosis

Atherosclerosis, the primary mechanism underlying the development of many cardiovascular illnesses, continues to be one of the leading causes of mortality worldwide. Platelet (PLT), which are essential for maintaining body homeostasis, have been strongly linked to the onset of atherosclerosis at various stages due to their inherent tendency to bind to atherosclerotic lesions and show an affinity for plaques. Therefore, mimicking PLT's innate adhesive features may be necessary to effectively target plaques. PLT-derived nanocarriers have emerged as a promising biomimetic targeting strategy for treating atherosclerosis due to their numerous advantages. These advantages include excellent biocompatibility, minimal macrophage phagocytosis, prolonged circulation time, targeting capability for impaired vascular sites, and suitability as carriers for anti-atherosclerotic drugs. Herein, we discuss the role of PLT in atherogenesis and propose the design of nanocarriers based on PLT-membrane coating and PLT-derived vesicles. These nanocarriers can target multiple biological elements relevant to plaque development. The review also emphasizes the current challenges and future research directions for the effective utilization of PLT-derived nanocarriers in treating atherosclerosis.

Severe Allergy as a Chronic Inflammatory Condition From a Systems Biology Perspective

Persistent and unresolved inflammation is a common underlying factor observed in several and seemingly unrelated human diseases, including cardiovascular and neurodegenerative diseases. Particularly, in atopic conditions, acute inflammatory responses such as those triggered by insect venom, food or drug allergies possess also a life-threatening potential. However, respiratory allergies predominantly exhibit late immune responses associated with chronic inflammation, that can eventually progress into a severe phenotype displaying similar features as those observed in other chronic inflammatory diseases, as is the case of uncontrolled severe asthma. This review aims to explore the different facets and systems involved in chronic allergic inflammation, including processes such as tissue remodelling and immune cell dysregulation, as well as genetic, metabolic and microbiota alterations, which are common to other inflammatory conditions. Our goal here was to deepen on the understanding of an entangled disease as is chronic allergic inflammation and expose potential avenues for the development of better diagnostic and intervention strategies.

Current Advances in Nanomaterials Affecting Functions and Morphology of Platelets

Nanomaterials have been extensively used in the biomedical field due to their unique physical and chemical properties. They promise wide applications in the diagnosis, prevention, and treatment of diseases. Nanodrugs are generally transported to target tissues or organs by coupling targeting molecules or enhanced permeability and retention effect (EPR) passively. As intravenous injection is the most common means of administration of nanomedicine, the transport process inevitably involves the interactions between nanoparticles (NPs) and blood cells. Platelets are known to not only play a critical role in normal coagulation by performing adhesion, aggregation, release, and contraction functions, but also be associated with pathological thrombosis, tumor metastasis, inflammation, and immune reactions, making it necessary to investigate the effects of NPs on platelet function during transport, particularly the way in which their physical and chemical properties determine their interaction with platelets and the underlying mechanisms by which they activate and induce platelet aggregation. However, such data are lacking. This review is intended to summarize the effects of NPs on platelet activation, aggregation, release, and apoptosis, as well as their effects on membrane proteins and morphology in order to shed light on such key issues as how to reduce their adverse reactions in the blood system, which should be taken into consideration in NP engineering.

Adipose-derived extracellular vesicles - a novel cross-talk mechanism in insulin resistance, non-alcoholic fatty liver disease, and polycystic ovary syndrome

Obesity is the best described risk factor for the development of non-alcoholic fatty liver disease (NAFLD)/metabolic dysfunction associated steatotic liver disease (MASLD) and polycystic ovary syndrome (PCOS) while the major pathogenic mechanism linking these entities is insulin resistance (IR). IR is primarily caused by increased secretion of proinflammatory cytokines, adipokines, and lipids from visceral adipose tissue. Increased fatty acid mobilization results in ectopic fat deposition in the liver which causes endoplasmic reticulum stress, mitochondrial dysfunction, and oxidative stress resulting in increased cytokine production and subsequent inflammation. Similarly, IR with hyperinsulinemia cause hyperandrogenism, the hallmark of PCOS, and inflammation in the ovaries. Proinflammatory cytokines from both liver and ovaries aggravate IR thus providing a complex interaction between adipose tissue, liver, and ovaries in inducing metabolic abnormalities in obese subjects. Although many pathogenic mechanisms of IR, NAFLD/MASLD, and PCOS are known, there is still no effective therapy for these entities suggesting the need for further evaluation of their pathogenesis. Extracellular vesicles (EVs) represent a novel cross-talk mechanism between organs and include membrane-bound vesicles containing proteins, lipids, and nucleic acids that may change the phenotype and function of target cells. Adipose tissue releases EVs that promote IR, the development of all stages of NAFLD/MASLD and PCOS, while mesenchymal stem cell-derived AVs may alleviate metabolic abnormalities and may represent a novel therapeutic device in NAFLD/MASLD, and PCOS. The purpose of this review is to summarize the current knowledge on the role of adipose tissue-derived EVs in the pathogenesis of IR, NAFLD/MASLD, and PCOS.

A natural hydrogel complex improves intervertebral disc degeneration by correcting fatty acid metabolism and inhibiting nucleus pulposus cell pyroptosis

The degeneration of intervertebral discs is strongly associated with the occurrence of pyroptosis in nucleus pulposus (NP) cells. This pyroptosis is characterized by abnormal metabolism of fatty acids in the degenerative pathological state, which is further exacerbated by the inflammatory microenvironment and degradation of the extracellular matrix. In order to address this issue, we have developed a fibrin hydrogel complex (FG@PEV). This intricate formulation amalgamates the beneficial attributes of platelet extravasation vesicles, contributing to tissue repair and regeneration. Furthermore, this complex showcases exceptional stability, gradual-release capabilities, and a high degree of biocompatibility. In order to substantiate the biological significance of FG@PEV in intervertebral disc degeneration (IVDD), we conducted a comprehensive investigation into its potential mechanism of action through the integration of RNA-seq sequencing and metabolomics analysis. Furthermore, these findings were subsequently validated through experimentation in both in vivo and in vitro models. The experimental results revealed that the FG@PEV intervention possesses the capability to reshape the inflammatory microenvironment within the disc. It also addresses the irregularities in fatty acid metabolism of nucleus pulposus cells, consequently hindering cellular pyroptosis and slowing down disc degeneration through the regulation of extracellular matrix synthesis and degradation. As a result, this injectable gel system represents a promising and innovative therapeutic approach for mitigating disc degeneration.

Platelets: Orchestrators of immunity in host defense and beyond

Platelets prevent blood loss during vascular injury and contribute to thrombus formation in cardiovascular disease. Beyond these classical roles, platelets are critical for the host immune response. They guard the vasculature against pathogens via specialized receptors, intracellular signaling cascades, and effector functions. Platelets also skew inflammatory responses by instructing innate immune cells, support adaptive immunosurveillance, and influence antibody production and T cell polarization. Concomitantly, platelets contribute to tissue reconstitution and maintain vascular function after inflammatory challenges. However, dysregulated activation of these multitalented cells exacerbates immunopathology with ensuing microvascular clotting, excessive inflammation, and elevated risk of macrovascular thrombosis. This dichotomy underscores the critical importance of precisely defining and potentially modulating platelet function in immunity.

Cellular therapeutics and immunotherapies in wound healing - on the pulse of time?

Chronic, non-healing wounds represent a significant challenge for healthcare systems worldwide, often requiring significant human and financial resources. Chronic wounds arise from the complex interplay of underlying comorbidities, such as diabetes or vascular diseases, lifestyle factors, and genetic risk profiles which may predispose extremities to local ischemia. Injuries are further exacerbated by bacterial colonization and the formation of biofilms. Infection, consequently, perpetuates a chronic inflammatory microenvironment, preventing the progression and completion of normal wound healing. The current standard of care (SOC) for chronic wounds involves surgical debridement along with localized wound irrigation, which requires inpatient care under general anesthesia. This could be followed by, if necessary, defect coverage via a reconstructive ladder utilizing wound debridement along with skin graft, local, or free flap techniques once the wound conditions are stabilized and adequate blood supply is restored. To promote physiological wound healing, a variety of approaches have been subjected to translational research. Beyond conventional wound healing drugs and devices that currently supplement treatments, cellular and immunotherapies have emerged as promising therapeutics that can behave as tailored therapies with cell- or molecule-specific wound healing properties. However, in contrast to the clinical omnipresence of chronic wound healing disorders, there remains a shortage of studies condensing the current body of evidence on cellular therapies and immunotherapies for chronic wounds. This review provides a comprehensive exploration of current therapies, experimental approaches, and translational studies, offering insights into their efficacy and limitations. Ultimately, we hope this line of research may serve as an evidence-based foundation to guide further experimental and translational approaches and optimize patient care long-term.

Extracellular vesicles and endothelial dysfunction in infectious diseases

Cardiovascular diseases (CVDs) remain the leading cause of mortality and morbidity globally. Studies have shown that infections especially bacteraemia and sepsis are associated with increased risks for endothelial dysfunction and related CVDs including atherosclerosis. Extracellular vesicles (EVs) are small, sealed membrane-derived structures that are released into body fluids and blood from cells and/or microbes and are critically involved in a variety of important cell functions and disease development, including intercellular communications, immune responses and inflammation. It is known that EVs-mediated mechanism(s) is important in the development of endothelial dysfunction in infections with a diverse spectrum of microorganisms including Escherichia coli, Candida albicans, SARS-CoV-2 (the virus for COVID-19) and Helicobacter pylori. H. pylori infection is one of the most common infections globally. During H. pylori infection, EVs can carry H. pylori components, such as lipopolysaccharide, cytotoxin-associated gene A, or vacuolating cytotoxin A, and transfer these substances into endothelial cells, triggering inflammatory responses and endothelial dysfunction. This review is to illustrate the important role of EVs in the pathogenesis of infectious diseases, and the development of endothelial dysfunction in infectious diseases especially H. pylori infection, and to discuss the potential mechanisms and clinical implications.

The role of platelet P2Y12 receptors in inflammation

Inflammation is a complex pathophysiological process underlying many clinical conditions. Platelets contribute to the thrombo-inflammatory response. Platelet P2Y12 receptors amplify platelet activation, potentiating platelet aggregation, degranulation and shape change. The contents of platelet alpha granules, in particular, act directly on leucocytes, including mediating platelet-leucocyte aggregation and activation via platelet P-selectin. Much evidence for the role of platelet P2Y12 receptors in inflammation comes from studies using antagonists of these receptors, such as the thienopyridines clopidogrel and prasugrel, and the cyclopentyltriazolopyrimidine ticagrelor, in animal and human experimental models. These suggest that antagonism of P2Y12 receptors decreases markers of inflammation with some evidence that this reduces incidence of adverse clinical sequelae during inflammatory conditions. Interpretation is complicated by pleiotropic effects such as those of the thienopyridines on circulating leucocyte numbers and of ticagrelor on adenosine reuptake. The available evidence suggests that P2Y12 receptors are prominent mediators of inflammation and P2Y12 receptor antagonism as a potentially powerful strategy in a broad range of inflammatory conditions. LINKED ARTICLES: This article is part of a themed issue on Platelet purinergic receptor and non-thrombotic disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.4/issuetoc.

Extracellular vesicles in acute respiratory distress syndrome: Understanding protective and harmful signaling for the development of new therapeutics

Acute respiratory distress syndrome (ARDS) is a severe respiratory condition characterized by increased lung permeability, hyper-inflammatory state, and fluid leak into the alveolar spaces. ARDS is a heterogeneous disease, with multiple direct and indirect causes that result in a mortality of up to 40%. Due to the ongoing Covid-19 pandemic, its incidence has increased up to ten-fold. Extracellular vesicles (EVs) are small liposome-like particles that mediate intercellular communication and play a major role in ARDS pathophysiology. Indeed, they participate in endothelial barrier dysfunction and permeability, neutrophil, and macrophage activation, and also in the development of a hypercoagulable state. A more thorough understanding of the variegated and cell-specific functions of EVs may lead to the development of safe and effective therapeutics. In this review, we have collected evidence of EVs role in ARDS, revise the main mechanisms of production and internalization and summarize the current therapeutical approaches that have shown the ability to modulate EV signaling.

Hydrogel-mediated delivery of platelet-derived exosomes: Innovations in tissue engineering

In this scholarly review, we conduct a thorough examination of the significant role played by platelet-derived exosomes (Plt-Exos) and hydrogels in the fields of tissue engineering and regenerative medicine. Our detailed investigation highlights the central involvement of Plt-Exos in various physiological and pathological processes, underscoring their potential contributions to diverse areas such as wound healing, neural rejuvenation, and cancer progression. Despite the promising therapeutic aspects, the notable variability in the isolation and characterization of pEVs underscores the need for a more rigorous and standardized methodology. Shifting our focus to hydrogels, they have emerged as promising biomaterials relevant to tissue engineering and regenerative medicine. Their unique characteristics, especially their chemical and physical adaptability, along with the modifiability of their biochemical properties, make hydrogels a captivating subject. These exceptional features open avenues for numerous tissue engineering applications, facilitating the delivery of essential growth factors, cytokines, and microRNAs. This analysis explores the innovative integration of Plt-Exos with hydrogels, presenting a novel paradigm in tissue engineering. Through the incorporation of Plt-Exos into hydrogels, there exists an opportunity to enhance tissue regeneration endeavors by combining the bioactive features of Plt-Exos with the restorative capabilities of hydrogel frameworks. In conclusion, the cooperative interaction between platelet-derived exosomes and hydrogels indicates a promising path in tissue engineering and regenerative medicine. Nevertheless, the successful execution of this approach requires a deep understanding of molecular dynamics, coupled with a dedication to refining isolation techniques.

Distinct targeting and uptake of platelet and red blood cell-derived extracellular vesicles into immune cells

Blood-derived extracellular vesicles (EVs) hold great therapeutic potential. As blood contains mixed EV populations, it is challenging to study EVs originating from different cells separately. Blood cell concentrates manufactured in blood banks offer an excellent non-invasive source of blood cell-specific EV populations. To study blood cell-specific EVs, we isolated EVs from platelet (TREVs) and red blood cell (EryEVs) concentrates and characterized them using nanoparticle tracking analysis, imaging flow cytometry, electron microscopy and western blot analysis and co-cultured them with peripheral blood mononuclear cells (PBMCs). Our aim was to use imaging flow cytometry to investigate EV interaction with PBMCs as well as study their effects on T-lymphocyte populations to better understand their possible biological functions. As a conclusion, TREVs interacted with PBMCs more than EryEVs. Distinctively, TREVs were uptaken into CD11c+ monocytes rapidly and into CD19+ B-lymphocytes in 24 h. EryEVs were not uptaken into CD11c+ monocytes before the 24-h time point, and they were only seen on the surface of lymphocytes. Neither TREVs nor EryEV were uptaken into CD3+ T-lymphocytes and no effect on T-cell populations was detected. We have previously seen similar differences in targeting PC-3 cancer cells. Further studies are needed to address the functional properties of blood cell concentrate-derived EVs. This study demonstrates that imaging flow cytometry can be used to study the distinctive differences in the interaction and uptake of EVs. Considering our current and previous results, EVs present a new valuable component for the future development of blood-derived therapeutics.

Platelet-derived extracellular vesicles play an important role in platelet transfusion therapy

Extracellular vesicles (EVs) contain the characteristics of their cell of origin and mediate cell-to-cell communication. Platelet-derived extracellular vesicles (PEVs) not only have procoagulant activity but also contain platelet-derived inflammatory factors (CD40L and mtDNA) that mediate inflammatory responses. Studies have shown that platelets are activated during storage to produce large amounts of PEVs, which may have implications for platelet transfusion therapy. Compared to platelets, PEVs have a longer storage time and greater procoagulant activity, making them an ideal alternative to platelets. This review describes the reasons and mechanisms by which PEVs may have a role in blood transfusion therapy.

Cryopreservation affects platelet macromolecular composition over time after thawing and differently impacts on cancer cells behavior in vitro

Cryopreservation affects platelets' function, questioning their use for cancer patients. We aimed to investigate the biochemical events that occur over time after thawing to optimize transfusion timing and evaluate the effect of platelet supernatants on tumor cell behavior in vitro. We compared fresh (Fresh-PLT) with Cryopreserved platelets (Cryo-PLT) at 1 h, 3 h and 6 h after thawing. MCF-7 and HL-60 cells were cultured with Fresh- or 1 h Cryo-PLT supernatants to investigate cell proliferation, migration, and PLT-cell adhesion. We noticed a significant impairment of hemostatic activity accompanied by a post-thaw decrease of CD42b+ , which identifies the CD62P--population. FTIR spectroscopy revealed a decrease in the total protein content together with changes in their conformational structure, which identified two sub-groups: 1) Fresh and 1 h Cryo-PLT; 2) 3 h and 6 h cryo-PLT. Extracellular vesicle shedding and phosphatidylserine externalization (PS) increased after thawing. Cryo-PLT supernatants inhibited cell proliferation, impaired MCF-7 cell migration, and reduced ability to adhere to tumor cells. Within the first 3 hours after thawing, irreversible alterations of biomolecular structure occur in Cryo-PLT. Nevertheless, Cryo-PLT should be considered safe for the transfusion of cancer patients because of their insufficient capability to promote cancer cell proliferation, adhesion, or migration.

Comparative effect of platelet- and mesenchymal stromal cell-derived extracellular vesicles on human cartilage explants using an ex vivo inflammatory osteoarthritis model

Aims

Extracellular vesicles (EVs) are nanoparticles secreted by all cells, enriched in proteins, lipids, and nucleic acids related to cell-to-cell communication and vital components of cell-based therapies. Mesenchymal stromal cell (MSC)-derived EVs have been studied as an alternative for osteoarthritis (OA) treatment. However, their clinical translation is hindered by industrial and regulatory challenges. In contrast, platelet-derived EVs might reach clinics faster since platelet concentrates, such as platelet lysates (PL), are already used in therapeutics. Hence, we aimed to test the therapeutic potential of PL-derived extracellular vesicles (pEVs) as a new treatment for OA, which is a degenerative joint disease of articular cartilage and does not have any curative or regenerative treatment, by comparing its effects to those of human umbilical cord MSC-derived EVs (cEVs) on an ex vivo OA-induced model using human cartilage explants.

Methods

pEVs and cEVs were isolated by size exclusion chromatography (SEC) and physically characterized by nanoparticle tracking analysis (NTA), protein content, and purity. OA conditions were induced in human cartilage explants (10 ng/ml oncostatin M and 2 ng/ml tumour necrosis factor alpha (TNFα)) and treated with 1 × 109 particles of pEVs or cEVs for 14 days. Then, DNA, glycosaminoglycans (GAG), and collagen content were quantified, and a histological study was performed. EV uptake was monitored using PKH26 labelled EVs.

Results

Significantly higher content of DNA and collagen was observed for the pEV-treated group compared to control and cEV groups. No differences were found in GAG quantification nor in EVs uptake within any treated group.

Conclusion

In conclusion, pEVs showed better performance than cEVs in our in vitro OA model. Although further studies are needed, pEVs are shown as a potential alternative to cEVs for cell-free regenerative medicine.

Expanding applications of allogeneic platelets, platelet lysates, and platelet extracellular vesicles in cell therapy, regenerative medicine, and targeted drug delivery

Platelets are small anucleated blood cells primarily known for their vital hemostatic role. Allogeneic platelet concentrates (PCs) collected from healthy donors are an essential cellular product transfused by hospitals to control or prevent bleeding in patients affected by thrombocytopenia or platelet dysfunctions. Platelets fulfill additional essential functions in innate and adaptive immunity and inflammation, as well as in wound-healing and tissue-repair mechanisms. Platelets contain mitochondria, lysosomes, dense granules, and alpha-granules, which collectively are a remarkable reservoir of multiple trophic factors, enzymes, and signaling molecules. In addition, platelets are prone to release in the blood circulation a unique set of extracellular vesicles (p-EVs), which carry a rich biomolecular cargo influential in cell-cell communications. The exceptional functional roles played by platelets and p-EVs explain the recent interest in exploring the use of allogeneic PCs as source material to develop new biotherapies that could address needs in cell therapy, regenerative medicine, and targeted drug delivery. Pooled human platelet lysates (HPLs) can be produced from allogeneic PCs that have reached their expiration date and are no longer suitable for transfusion but remain valuable source materials for other applications. These HPLs can substitute for fetal bovine serum as a clinical grade xeno-free supplement of growth media used in the in vitro expansion of human cells for transplantation purposes. The use of expired allogeneic platelet concentrates has opened the way for small-pool or large-pool allogeneic HPLs and HPL-derived p-EVs as biotherapy for ocular surface disorders, wound care and, potentially, neurodegenerative diseases, osteoarthritis, and others. Additionally, allogeneic platelets are now seen as a readily available source of cells and EVs that can be exploited for targeted drug delivery vehicles. This article aims to offer an in-depth update on emerging translational applications of allogeneic platelet biotherapies while also highlighting their advantages and limitations as a clinical modality in regenerative medicine and cell therapies.

Platelet mitochondria, a potent immune mediator in neurological diseases

Dysfunction of the immune response is regarded as a prominent feature of neurological diseases, including neurodegenerative diseases, malignant tumors, acute neurotraumatic insult, and cerebral ischemic/hemorrhagic diseases. Platelets play a fundamental role in normal hemostasis and thrombosis. Beyond those normal functions, platelets are hyperactivated and contribute crucially to inflammation and immune responses in the central nervous system (CNS). Mitochondria are pivotal organelles in platelets and are responsible for generating most of the ATP that is used for platelet activation and aggregation (clumping). Notably, platelet mitochondria show marked morphological and functional alterations under heightened inflammatory/oxidative stimulation. Mitochondrial dysfunction not only leads to platelet damage and apoptosis but also further aggravates immune responses. Improving mitochondrial function is hopefully an effective strategy for treating neurological diseases. In this review, the authors discuss the immunomodulatory roles of platelet-derived mitochondria (PLT-mitos) in neurological diseases and summarize the neuroprotective effects of platelet mitochondria transplantation.

Platelet activation: a promoter for psoriasis and its comorbidity, cardiovascular disease

Psoriasis is a chronic inflammatory skin disease with a prevalence of 0.14% to 1.99%. The underlying pathology is mainly driven by the abnormal immune responses including activation of Th1, Th17, Th22 cells and secretion of cytokines. Patients with psoriasis are more likely to develop cardiovascular disease (CVD) which has been well recognized as a comorbidity of psoriasis. As mediators of hemostasis and thromboinflammation, platelets play an important part in CVD. However, less is known about their pathophysiological contribution to psoriasis and psoriasis-associated CVD. A comprehensive understanding of the role of platelet activation in psoriasis might pave the path for more accurate prediction of cardiovascular (CV) risk and provide new strategies for psoriasis management, which alleviates the increased CV burden associated with psoriasis. Here we review the available evidence about the biomarkers and mechanisms of platelet activation in psoriasis and the role of platelet activation in intriguing the common comorbidity, CVD. We further discussed the implications and efficacy of antiplatelet therapies in the treatment of psoriasis and prevention of psoriasis-associated CVD.

Platelet-derived extracellular vesicles promote endothelial dysfunction in sepsis by enhancing neutrophil extracellular traps

BACKGROUND

The role of platelet-derived extracellular vesicles (PEVs) in the development of sepsis was investigated in this study.

METHODS

After collection of blood samples from sepsis patients and normal volunteers, the extracellular vesicles (EVs) were separated, followed by the isolation of PEVs from the blood of rats. Next, a sepsis rat model was constructed by cecal ligation and puncture (CLP), and rats received tail vein injection of PEVs to explore the role of PEVs in sepsis. Subsequently, nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM) were adopted to determine the diameter of EVs and observe the morphology of PEVs, respectively; flow cytometry to detect the percentage of CD41-and CD61-positive EVs in isolated EVs; and ELISA to assess neutrophil extracellular trap (NET) formation, endothelial function injury-related markers in clinical samples or rat blood and serum inflammatory factor level.

RESULTS

Compared with normal volunteers, the percentage of CD41- and CD61-positive EVs and the number of EVs were significantly elevated in sepsis patients. Moreover, sepsis patients also presented notably increased histone H3, myeloperoxidase (MPO), angiopoietin-2 and endocan levels in the blood, and such increase was positively correlated with the number of EVs. Also, animal experiments demonstrated that PEVs significantly promoted NET formation, mainly manifested as up-regulation of histone H3, high mobility group protein B1 (HMGB1), and MPO; promoted endothelial dysfunction (up-regulation of angiopoietin-2, endocan, and syndecan-1); and stimulated inflammatory response (up-regulation of interleukin (IL) -1β, IL-6, tumor necrosis factor (TNF)-α, and monocyte chemoattractant protein (MCP) -1) in the blood of sepsis rats.

CONCLUSION

PEVs aggravate endothelial function injury and inflammatory response in sepsis by promoting NET formation.

Extracellular vesicle-based biovectors in chronic wound healing: Biogenesis and delivery approaches

Chronic wounds remain an unresolved medical issue because of major social and therapeutic repercussions that require extensive focus. Recent related theragnostic focuses only on wound management and is not effectively promoting chronic wound healing. The rising number of patients with either under-healing or over-healing wounds highlights the ineffectiveness of current wound-healing treatments, and thus, there is an unmet need to focus on alternative treatments. To cover this gap, extracellular vesicles (EVs), for targeted delivery of therapeutics, are emerging as a potential therapy to treat both acute and persistent wounds. To address these issues, we explore the core biology of EVs, associated pharmacology, comprehension of immunogenic outcomes, and potential for long-term wound treatment with improved effectiveness and their nonacceptable side effects. Additionally, the therapeutic role of EVs in severe wound infections through biogenetic moderation, in combination with biomaterials (functional in nature), as well as drug carriers that can offer opportunities for the development of new treatments for this long-term condition, are also carefully elaborated, with an emphasis on biomaterial-based drug delivery systems. It is observed that exploring difficulties and potential outcomes of clinical translation of EV-based therapeutics for wound management has the potential to be adopted as a future therapy.