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Nature Reviews. Immunology Aug 2023Immune-mediated inflammatory diseases (IMIDs) are characterized by excessive and uncontrolled inflammation and thrombosis, both of which are responsible for organ... (Review)
Review
Immune-mediated inflammatory diseases (IMIDs) are characterized by excessive and uncontrolled inflammation and thrombosis, both of which are responsible for organ damage, morbidity and death. Platelets have long been known for their role in primary haemostasis, but they are now also considered to be components of the immune system and to have a central role in the pathogenesis of IMIDs. In patients with IMIDs, platelets are activated by disease-specific factors, and their activation often reflects disease activity. Here we summarize the evidence showing that activated platelets have an active role in the pathogenesis and the progression of IMIDs. Activated platelets produce soluble factors and directly interact with immune cells, thereby promoting an inflammatory phenotype. Furthermore, platelets participate in tissue injury and promote abnormal tissue healing, leading to fibrosis. Targeting platelet activation and targeting the interaction of platelets with the immune system are novel and promising therapeutic strategies in IMIDs.
Topics: Humans; Blood Platelets; Immunomodulating Agents; Platelet Activation; Inflammation; Thrombosis
PubMed: 36707719
DOI: 10.1038/s41577-023-00834-4 -
Nature Communications Aug 2023The beneficial effects of physical activity on brain ageing are well recognised, with exerkines, factors that are secreted into the circulation in response to exercise,...
The beneficial effects of physical activity on brain ageing are well recognised, with exerkines, factors that are secreted into the circulation in response to exercise, emerging as likely mediators of this response. However, the source and identity of these exerkines remain unclear. Here we provide evidence that an anti-geronic exerkine is secreted by platelets. We show that platelets are activated by exercise and are required for the exercise-induced increase in hippocampal precursor cell proliferation in aged mice. We also demonstrate that increasing the systemic levels of the platelet-derived exerkine CXCL4/platelet factor 4 (PF4) ameliorates age-related regenerative and cognitive impairments in a hippocampal neurogenesis-dependent manner. Together these findings highlight the role of platelets in mediating the rejuvenating effects of exercise during physiological brain ageing.
Topics: Animals; Mice; Blood Platelets; Cognition; Hippocampus; Immunologic Factors; Neurogenesis; Platelet Factor 4; Aging; Cognitive Dysfunction
PubMed: 37587147
DOI: 10.1038/s41467-023-39873-9 -
Circulation Research Jan 2024Single-nucleotide polymorphisms linked with the rs1474868 T allele ( [mitofusin-2] T/T) in the human mitochondrial fusion protein gene are associated with reduced...
BACKGROUND
Single-nucleotide polymorphisms linked with the rs1474868 T allele ( [mitofusin-2] T/T) in the human mitochondrial fusion protein gene are associated with reduced platelet RNA expression and platelet counts. This study investigates the impact of MFN2 on megakaryocyte and platelet biology.
METHODS
Mice with megakaryocyte/platelet deletion of ( [ conditional knockout]) were generated using Pf4-Cre crossed with floxed mice. Human megakaryocytes were generated from cord blood and platelets isolated from healthy subjects genotyped for rs1474868. Ex vivo approaches assessed mitochondrial morphology, function, and platelet activation responses. In vivo measurements included endogenous/transfused platelet life span, tail bleed time, transient middle cerebral artery occlusion, and pulmonary vascular permeability/hemorrhage following lipopolysaccharide-induced acute lung injury.
RESULTS
Mitochondria was more fragmented in megakaryocytes derived from mice and from human cord blood with T/T genotype compared with control megakaryocytes. Human resting platelets of T/T genotype had reduced MFN2 protein, diminished mitochondrial membrane potential, and an increased rate of phosphatidylserine exposure during ex vivo culture. Platelet counts and platelet life span were reduced in mice accompanied by an increased rate of phosphatidylserine exposure in resting platelets, especially aged platelets, during ex vivo culture. also decreased platelet mitochondrial membrane potential (basal) and activated mitochondrial oxygen consumption rate, reactive oxygen species generation, calcium flux, platelet-neutrophil aggregate formation, and phosphatidylserine exposure following dual agonist activation. Ultimately, mice showed prolonged tail bleed times, decreased ischemic stroke infarct size after cerebral ischemia-reperfusion, and exacerbated pulmonary inflammatory hemorrhage following lipopolysaccharide-induced acute lung injury. Analysis of SNPs in the iSPAAR study (Identification of SNPs Predisposing to Altered ALI Risk) identified a significant association between and 28-day mortality in patients with acute respiratory distress syndrome.
CONCLUSIONS
Mfn2 preserves mitochondrial phenotypes in megakaryocytes and platelets and influences platelet life span, function, and outcomes of stroke and lung injury.
Topics: Aged; Animals; Humans; Mice; Acute Lung Injury; Blood Platelets; Hemorrhage; Lipopolysaccharides; Mitochondria; Phosphatidylserines
PubMed: 38156445
DOI: 10.1161/CIRCRESAHA.123.322914 -
Nature Communications Aug 2023Human MutT Homolog 1 (MTH1) is a nucleotide pool sanitization enzyme that hydrolyzes oxidized nucleotides to prevent their mis-incorporation into DNA under oxidative...
Human MutT Homolog 1 (MTH1) is a nucleotide pool sanitization enzyme that hydrolyzes oxidized nucleotides to prevent their mis-incorporation into DNA under oxidative stress. Expression and functional roles of MTH1 in platelets are not known. Here, we show MTH1 expression in platelets and its deficiency impairs hemostasis and arterial/venous thrombosis in vivo. MTH1 deficiency reduced platelet aggregation, phosphatidylserine exposure and calcium mobilization induced by thrombin but not by collagen-related peptide (CRP) along with decreased mitochondrial ATP production. Thrombin but not CRP induced Ca-dependent mitochondria reactive oxygen species generation. Mechanistically, MTH1 deficiency caused mitochondrial DNA oxidative damage and reduced the expression of cytochrome c oxidase 1. Furthermore, MTH1 exerts a similar role in human platelet function. Our study suggests that MTH1 exerts a protective function against oxidative stress in platelets and indicates that MTH1 could be a potential therapeutic target for the prevention of thrombotic diseases.
Topics: Humans; Blood Platelets; Phosphoric Monoester Hydrolases; Thrombin; Oxidative Stress; Hemostasis; Nucleotides; Mitochondria; Thrombosis; DNA Repair Enzymes
PubMed: 37563135
DOI: 10.1038/s41467-023-40600-7 -
Arteriosclerosis, Thrombosis, and... Nov 2023Megakaryocytes are commonly known as large, polyploid, bone marrow resident cells that contribute to hemostasis through the production of platelets. Soon after their... (Review)
Review
Megakaryocytes are commonly known as large, polyploid, bone marrow resident cells that contribute to hemostasis through the production of platelets. Soon after their discovery in the 19th century, megakaryocytes were described in tissue locations other than the bone marrow, specifically in the lungs and the blood circulation. However, the localization of megakaryocytes in the lungs and the contribution of lung megakaryocytes to the general platelet pool has only recently been appreciated. Moreover, the conception of megakaryocytes as uniform cells with the sole purpose of platelet production has been challenged. Here, we review the literature on megakaryocyte cell identity and location with a special focus on recent observations of megakaryocyte subpopulations identified by transcriptomic analyses.
Topics: Megakaryocytes; Blood Platelets; Bone Marrow; Bone Marrow Cells; Thrombopoiesis
PubMed: 37675634
DOI: 10.1161/ATVBAHA.123.318782 -
Critical Care (London, England) Jul 2023Definitions for massive transfusion (MT) vary widely between studies, contributing to challenges in interpretation of research findings and practice evaluation. In this... (Review)
Review
BACKGROUND
Definitions for massive transfusion (MT) vary widely between studies, contributing to challenges in interpretation of research findings and practice evaluation. In this first systematic review, we aimed to identify all MT definitions used in randomised controlled trials (RCTs) to date to inform the development of consensus definitions for MT.
METHODS
We systematically searched the following databases for RCTs from inception until 11 August 2022: MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Cumulative Index to Nursing and Allied Health Literature, and Transfusion Evidence Library. Ongoing trials were sought from CENTRAL, ClinicalTrials.gov, and World Health Organisation International Clinical Trials Registry Platform. To be eligible for inclusion, studies had to fulfil all the following three criteria: (1) be an RCT; (2) include an adult patient population with major bleeding who had received, or were anticipated to receive, an MT in any clinical setting; and (3) specify a definition for MT as an inclusion criterion or outcome measure.
RESULTS
Of the 8,458 distinct references identified, 30 trials were included for analysis (19 published, 11 ongoing). Trauma was the most common clinical setting in published trials, while for ongoing trials, it was obstetrics. A total of 15 different definitions of MT were identified across published and ongoing trials, varying greatly in cut-offs for volume transfused and time period. Almost all definitions specified the number of red blood cells (RBCs) within a set time period, with none including plasma, platelets or other haemostatic agents that are part of contemporary transfusion resuscitation. For completed trials, the most commonly used definition was transfusion of ≥ 10 RBC units in 24 h (9/19, all in trauma), while for ongoing trials it was 3-5 RBC units (n = 7), with the timing for transfusion being poorly defined, or in some trials not provided at all (n = 5).
CONCLUSIONS
Transfusion of ≥ 10 RBC units within 24 h was the most commonly used definition in published RCTs, while lower RBC volumes are being used in ongoing RCTs. Any consensus definitions should reflect the need to incorporate different blood components/products for MT and agree on whether a 'one-size-fits-all' approach should be used across different clinical settings.
Topics: Adult; Humans; Hemorrhage; Hemostatics; Blood Transfusion; Blood Platelets; Erythrocyte Transfusion
PubMed: 37407998
DOI: 10.1186/s13054-023-04537-z -
Cell Jun 2024Platelet dysregulation is drastically increased with advanced age and contributes to making cardiovascular disorders the leading cause of death of elderly humans. Here,...
Platelet dysregulation is drastically increased with advanced age and contributes to making cardiovascular disorders the leading cause of death of elderly humans. Here, we reveal a direct differentiation pathway from hematopoietic stem cells into platelets that is progressively propagated upon aging. Remarkably, the aging-enriched platelet path is decoupled from all other hematopoietic lineages, including erythropoiesis, and operates as an additional layer in parallel with canonical platelet production. This results in two molecularly and functionally distinct populations of megakaryocyte progenitors. The age-induced megakaryocyte progenitors have a profoundly enhanced capacity to engraft, expand, restore, and reconstitute platelets in situ and upon transplantation and produce an additional platelet population in old mice. The two pools of co-existing platelets cause age-related thrombocytosis and dramatically increased thrombosis in vivo. Strikingly, aging-enriched platelets are functionally hyper-reactive compared with the canonical platelet populations. These findings reveal stem cell-based aging as a mechanism for platelet dysregulation and age-induced thrombosis.
Topics: Animals; Hematopoietic Stem Cells; Blood Platelets; Thrombosis; Mice; Cell Differentiation; Aging; Humans; Megakaryocytes; Mice, Inbred C57BL; Megakaryocyte Progenitor Cells; Male
PubMed: 38749423
DOI: 10.1016/j.cell.2024.04.018 -
Cell Reports Sep 2023Metastasis is the major cause of cancer deaths, and cancer cells evolve to adapt to various tumor microenvironments, which hinders the treatment of tumor metastasis....
Metastasis is the major cause of cancer deaths, and cancer cells evolve to adapt to various tumor microenvironments, which hinders the treatment of tumor metastasis. Platelets play critical roles in tumor development, especially during metastasis. Here, we elucidate the role of platelet mitochondria in tumor metastasis. Cancer cells are reprogrammed to a metastatic state through the acquisition of platelet mitochondria via the PINK1/Parkin-Mfn2 pathway. Furthermore, platelet mitochondria regulate the GSH/GSSG ratio and reactive oxygen species (ROS) in cancer cells to promote lung metastasis of osteosarcoma. Impairing platelet mitochondrial function has proven to be an efficient approach to impair metastasis, providing a direction for osteosarcoma therapy. Our findings demonstrate mitochondrial transfer between platelets and cancer cells and suggest a role for platelet mitochondria in tumor metastasis.
Topics: Humans; Reactive Oxygen Species; Blood Platelets; Osteosarcoma; Bone Neoplasms; Mitochondria; Tumor Microenvironment
PubMed: 37756158
DOI: 10.1016/j.celrep.2023.113147 -
Journal of Extracellular Vesicles Jul 2023The release of growth factors, cytokines and extracellular matrix modifiers by activated platelets is an important step in the process of healthy wound healing.... (Randomized Controlled Trial)
Randomized Controlled Trial
The release of growth factors, cytokines and extracellular matrix modifiers by activated platelets is an important step in the process of healthy wound healing. Extracellular vesicles (EVs) released by activated platelets carry this bioactive cargo in an enriched form, and may therefore represent a potential therapeutic for the treatment of delayed wound healing, such as chronic wounds. While EVs show great promise in regenerative medicine, their production at clinical scale remains a critical challenge and their tolerability in humans is still to be fully established. In this work, we demonstrate that Ligand-based Exosome Affinity Purification (LEAP) chromatography can successfully isolate platelet EVs (pEVs) of clinical grade from activated platelets, which retain the regenerative properties of the parent cell. LEAP-isolated pEVs display the expected biophysical features of EV populations and transport essential proteins in wound healing processes, including insulin growth factor (IGF) and transforming growth factor beta (TGF-ß). In vitro studies show that pEVs induce proliferation and migration of dermal fibroblasts and increase dermal endothelial cells' angiogenic potential, demonstrating their wound healing potential. pEV treatment activates the ERK and Akt signalling pathways within recipient cells. In a first-in-human, double-blind, placebo-controlled, phase I clinical trial of healthy volunteer adults, designed primarily to assess safety in the context of wound healing, we demonstrate that injections of LEAP-purified pEVs in formulation buffer are safe and well tolerated (Plexoval II study, ACTRN12620000944932). As a secondary objective, biological activity in the context of wound healing rate was assessed. In this cohort of healthy participants, in which the wound bed would not be expected to be deficient in the bioactive cargo that pEVs carry, all wounds healed rapidly and completely and no difference in time to wound closure of the treated and untreated wounds was observed at the single dose tested. The outcomes of this study evidence that pEVs manufactured through the LEAP process can be injected safely in humans as a potential wound healing treatment, and warrant further study in clinical trials designed expressly to assess therapeutic efficacy in patients with delayed or disrupted wound healing.
Topics: Adult; Humans; Blood Platelets; Endothelial Cells; Extracellular Vesicles; Hematopoietic Stem Cell Transplantation; Wound Healing
PubMed: 37353884
DOI: 10.1002/jev2.12332 -
Thrombosis Research Nov 2023In a healthy individual, the lifespan of most platelets is tightly regulated by intrinsic, or mitochondrial, apoptosis. This is a special form of programmed cell death... (Review)
Review
In a healthy individual, the lifespan of most platelets is tightly regulated by intrinsic, or mitochondrial, apoptosis. This is a special form of programmed cell death governed by the BCL-2 family of proteins, where the prosurvival protein BCL-X maintains platelet viability by restraining the prodeath proteins BAK and BAX. Restriction of platelet lifespan by activation of BAK and BAX mediated intrinsic apoptosis is essential to maintain a functional, haemostatically reactive platelet population. This review focuses on the molecular regulation of intrinsic apoptosis in platelets, reviews conditions linked to enhanced platelet death, discusses ex vivo storage of platelets and describes caveats associated with the assessment of platelet apoptosis.
Topics: Humans; bcl-2-Associated X Protein; Blood Platelets; Apoptosis; bcl-X Protein
PubMed: 36739256
DOI: 10.1016/j.thromres.2022.11.024