Platelets最新文献

Dual antithrombotic therapy (DAT) without aspirin reduces bleeding compared with triple antithrombotic therapy (TAT) in patients with atrial fibrillation who have undergone percutaneous coronary intervention, without apparently increasing ischemic events. A prospective pharmacodynamic study was performed to investigate the impact of aspirin on bleeding time, platelet function and fibrin clot analysis in this population. Patients receiving TAT (n = 16), comprising aspirin, ticagrelor/prasugrel and a direct-acting oral anticoagulant (DOAC), were compared with those receiving DAT without aspirin (n = 18). Bleeding time was reduced with DAT compared with TAT (median 27.8 vs 30.0 minutes, p = .005). Assessed by light transmission aggregometry, median platelet aggregation was significantly increased with DAT compared with TAT in response to arachidonic acid (63 vs 3%, p = .002) and collagen (72 vs 37%, p < .001) but not 5-μmol/L adenosine diphosphate (25 vs 27%, p = .966) or thrombin-receptor-activating peptide (37 vs 24%, p = .086). VerifyNow P2Y₁₂ assay showed > 70% inhibition in all patients. Fibrin clot lysis time and maximum turbidity were similar between groups. Using P2Y₁₂ inhibitors of consistent potency, DAT improves hemostasis through sparing cyclooxygenase-1-mediated platelet activation but has a comparable effect to TAT on other pathways and fibrin clot properties. DAT with ticagrelor/prasugrel and DOAC may provide sufficient antithrombotic effect without excessive anti-hemostatic effect.

Platelets are anucleate cells that primarily facilitate thrombosis and hemostasis but can also act as mediators of vascular inflammation in disease. Platelets are typically understood to do this through the release of pre-formed chemokines coupled with direct heterotypic interactions with a variety of immune cells. However, an alternative mode of action has been described where platelets are able to undertake de novo synthesis of the cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18). The primary mechanism to produce these inflammatory mediators is the activation of the NACHT leucine-rich repeat pyrin domain-containing protein 3 (NLRP3) inflammasome, a multi-protein complex that processes IL-1β and IL-18 through caspase activation. The presence and characteristics of the NLRP3 inflammasome have been widely described in a variety of nucleated cells, although its role in anucleate platelets is less clear. In the last decade, the presence of the inflammasome has been reported in platelets and linked to several diseased states including sickle cell disease, acute coronary syndrome, sepsis, and viral hemorrhagic fever. This emerging new biology of platelets, its role in platelet function, vascular inflammation, and other related areas of exploration are critically reviewed here.

Background: Whole mount (WM) platelet transmission electron microscopy (PTEM) is a standard method for evaluating platelet dense granules (DG). However, because of the lack of a pediatric/adolescent mean DG/platelet reference range (RR), the prevalence of platelet DG deficiency in patients with suspected inherited platelet disorders (IPD) is mostly unknown in our practice. This study aimed to establish a local pediatric/adolescent RR for mean DG/platelet in a cohort of pediatric patients with clinical suspicion of IPD, which was used to determine the prevalence and clinical and laboratory features of platelet DG deficiency.

Methods: WM-PTEM was performed on healthy donors. The mean DG/platelet RR was calculated by averaging the DG of 100 platelets per donor. Patients who underwent laboratory evaluation of suspected IPD were evaluated. PTEM results, clinical histories, other laboratory testing results, and pediatric ISTH BAT scores (normal < 3; abnormal ≥3) were collected and analyzed.

Results: Healthy donors (n = 77, 41.6% female), ages 3-18 years, had a mean of 2.7 DG/platelet (±0.5), ranging from 1.9 to 3.8 per platelet. The mean DG/platelet did not correlate with age or gender. The tentative RR was calculated to be 1.9 to 3.8 DG/platelet. Of the 72 patients with suspected IPD (age 3-18 years, 69.4% female), 31 patients had BAT scores < 3 and 41 patients had BAT scores ≥3 (range 0-11). Eighteen patients (25%) were diagnosed with DG deficiency. The mean DG/platelet in patients with bleeding scores ≥3 vs. those with bleeding scores < 3 was similar. There was no difference in the number of patients with normal or abnormal bleeding scores in groups with normal vs decreased mean DG/platelet (p = .42) based on the pediatric DG/platelet RR. Platelet DG deficiency was also not correlated with abnormal platelet function testing results.

Conclusions: Approximately 25% of pediatric patients with suspected IPD were found to have platelet DG deficiency. However, the mean DG/platelet did not correlate with the ISTH BAT scores or platelet function testing results.

Hematopoietic stem and progenitor cells (HSPCs) hold significant promise for various diseases and gene therapy, highlighting the need for improved in vitro expansion while maintaining their properties. Efficient HSPC expansion requires an environment that preserves self-renewal and homing capabilities. Human Platelet Lysates (HPL) contain bioactive molecules and growth factors that may enhance HSPC functionality. This study investigates the effects of HPL on peripheral blood HSPC proliferation, self-renewal capacity, and homing. We observed that HPL significantly promoted HSPC proliferation, resulting in a 1.7-fold increase in final cell count and reduced doubling time, without affecting colony-forming capacity. Flow cytometry analysis revealed no significant changes in the percentages of CD34⁺, CD34^-CD38⁺, CD34⁺CD38⁺, and CD34⁺CD38^- cells, though CXCR4 marker expression was notably higher in the HPL-treated group. Furthermore, real-time analysis of self-renewal genes (GFI1, HOXB4, and TAL1) indicated a significant increase in GFI1 expression, while HOXB4 and TAL1 remained unchanged. Among homing-related genes (CXCR4, VLA-4, and LFA-1), CXCR4 expression increased significantly, while VLA-4 and LFA-1 levels showed no significant alterations. These findings suggest that HPL enhances HSPC proliferation while preserving their self-renewal and homing abilities, providing a promising approach for optimizing HSPC culture conditions for both research and clinical use.

The integrin family of extracellular matrix (ECM) adhesion receptors plays a central role in platelet function, including adhesion and aggregation. In resting platelets, integrins exist in a low-affinity state for their ligands, and are activated upon ligand binding to the extracellular domain or binding of cytoplasmic proteins such as talin to the intracellular β-tail. Talin function is regulated through autoinhibition, which reduces its integrin-activating function. A point mutation that blocks talin autoinhibition, Tln1^E1770A, therefore increases integrin activation and disrupts cell migration in fibroblasts. Here, we show that talin autoinhibition also plays an important role during hemostasis. Tln1^E1770A mutant mice display defective hemostasis when examined using a tail bleeding assay. Furthermore, platelets isolated from Tln1^E1770A mice exhibit disrupted aggregation and delayed clot retraction, indicating a defect in integrin signaling. However, integrin activation was not increased in platelets with defective talin autoinhibition, suggesting a different role for talin in platelets, distinct from inside-out integrin signaling. Taken together, our data shows that talin autoinhibition is an important regulatory mechanism in platelets during hemostasis.

Due to platelet storage lesions (PSL), transfused platelets are unable to function properly in the prevention and treatment of bleeding in critically ill patients. It is a traditional assumption that PSL is closely related to platelet activation during storage because of the exposure of CD62P, phosphatidylserine (PS), etc. In this standpoint, activated platelets in vitro cannot be reactivated in vivo to exert their hemostatic function and exposed PS accelerates platelet clearance. Therefore, reducing platelet activation is helpful to alleviate PSL. Diannexin is the dimer of annexin that has a higher affinity for PS. CD39 is an ADP hydrolase produced by the vascular endothelium. As a result, we construct CD39-Diannexin (CD39-DA) fusion protein and hypothesize that CD39-DA can reduce platelet activation during storage to alleviate PSL. CD39-DA can bind to the exposed PS on the surface of stored platelets by immunofluorescence. Compared to the control groups, CD39-DA reserves part of stored platelets' aggregation function confirmed by platelet aggregation assay, induced by AA, ADP and collagen. Additionally, CD39-DA reduces lactic dehydrogenase (LDH) levels and CD62P-positive events after three-day storage. Interestingly, we preliminarily discover that CD39-DA may reduce stored platelets' apoptosis and increase aggregatory platelets after activation by thrombin, collagen and calcium, which is marked by GSAO. In conclusion, we confirm that CD39-DA can alleviate PSL by reducing platelet activation.

Background: A high activation level is a normal characteristic of lyophilized platelets (LPs); however, the effects of this activation level on the efficacy and safety of LPs after transfusion are debated.

Objectives: We aimed to test the efficacy and safety of pre-activated LPs (PLPs) in rabbits with traumatic bleeding and shock.

Methods: In vitro characteristics of PLPs, including activation level, aggregation, migration, and thromboelastography parameters, were evaluated. Limb soft tissue injury accompanied by seawater immersion and controlled hemorrhagic shock was induced in 50 rabbits, which were then divided into five groups: A (no resuscitation), B (resuscitation with Lactated Ringer's solution, LR), C (resuscitation with LR and fresh platelets), D (resuscitation with LR and LPs), and E (resuscitation with LR and PLPs pre-activated by thrombin). Blood loss, platelet count, blood urea nitrogen and lactic acid concentrations, and in vivo thromboelastography R value and maximum amplitude were recorded. Biotin-X-N-hydroxysuccinimide labeling and flow cytometry were used to measure the number of infused platelets left in circulation. Histology was used to assess whether aberrant thrombi were formed in the kidney, lung, or liver.

Results: PLPs exhibited an increased P-selectin level, enhanced aggregation, and shortened R values, with no obvious changes in migration ability or maximum amplitude. PLPs transfusion had a non-inferior effect on all in vivo parameters compared with fresh platelet transfusion, and the circulation time of PLPs was much shorter than that of fresh platelets. No obvious thrombi were found.

Conclusions: PLPs transfusion demonstrated non-inferior efficacy and safety compared with fresh platelet transfusion.

Sticky Platelet Syndrome (SPS) is an inherited platelet hyperreactivity disorder associated with recurrent arterial and venous thrombosis. However, its diagnosis remains controversial due to substantial variability in light transmission aggregometry (LTA), the reference method. To map current diagnostic practices, we conducted a scoping review following PRISMA-ScR and JBI methodology, systematically searching Scopus, MEDLINE, Embase, and Google Scholar. We included 27 studies that collectively demonstrate considerable heterogeneity in patient preparation, sample handling, agonist usage, and data interpretation. These differences span pre-analytical and analytical variables such as washout periods, citrate concentration, centrifugation conditions, and threshold derivation methods. While detailed synthesis is ongoing, our preliminary observations highlight critical inconsistencies that may limit comparability across laboratories. This review underscores the need for standardized diagnostic approaches. Establishing harmonized protocols and validating them across centers could improve diagnostic accuracy and support better platelet function testing in SPS and related disorders.

Recent studies have shown that anti-ERp5 antibodies inhibit platelet activation and thrombus formation; Moreover, ERp5-deficient platelets exhibit enhanced platelet reactivity via regulation of endoplasmic reticulum (ER) stress. In this study, we used a new ERp5-knockout mouse model as well as recombinant ERp5 (rERp5) protein, to examine the role of ERp5 in platelet function and thrombosis. Although platelet-specific ERp5-deficient mice had decreased platelet count, the mice had shortened tail-bleeding times and enhanced platelet accumulation in FeCl₃-induced mesenteric artery injury, compared with wild-type mice. Using platelet-specific ERp5-deficient mice, we found that ERp5 deficiency increased platelet aggregation, granule secretion, and integrin αIIbβ3 activation. Wild-type recombinant ERp5 protein (rERp5-wt) and inactive mutant ERp5 protein (rERp5-mut) both inhibited human platelet aggregation and the binding of fibrinogen to human platelets, indicating that ERp5 protein interferes with the interaction between integrin αIIbβ3 and its ligand fibrinogen, and its enzymatic activity is not required for this process. Consistently, wild-type mice injected with rERp5-wt or rERp5-mut protein had prolonged tail-bleeding times. Our results provide important evidence that platelet ERp5 negatively regulates platelet activation and thrombus formation, via steric hindrance interfering with integrin αIIbβ3 ligation.

Platelet-like particles (PLPs), derived from megakaryocytic cell lines MEG-01 and K-562, are widely used as a surrogate to study platelet formation and function. We demonstrate by RNA-Seq that PLPs are transcriptionally distinct from platelets. Expression of key genes in signaling pathways promoting platelet activation/aggregation, such as the PI3K/AKT, protein kinase A, phospholipase C, and α-adrenergic and GP6 receptor pathways, was missing or under-expressed in PLPs. Functionally, PLPs do not aggregate following epinephrine, collagen, or ADP stimulation. While PLPs aggregated in response to thrombin, they did not display enhanced expression of surface markers P-selectin and activated α_2bβ₃, in contrast to platelets. We have previously demonstrated that platelets physically couple to MDA-PCa-2b and RC77T/E prostate cancer (PCa) cells via specific ligand-receptor interactions, leading to platelet-stimulated cell invasiveness and apoptotic resistance, and reciprocal cell-induced platelet aggregation. In contrast, PLP interactions with PCa cells inhibited both cell invasion and apoptotic resistance while failing to promote PLP aggregation. Moreover, PLPs reduced platelet-PCa cell interactions and antagonized platelet-stimulated oncogenic effects in PCa cells. RNA-Seq analysis identified candidate ligand-transmembrane protein combinations involved in anti-tumorigenic signaling of PLPs to PCa cells. Antibody neutralization of the TIMP3-MMP15 and VEGFB-FGFR1 signaling axes reversed PLP-mediated anti-invasion and apoptotic sensitization, respectively. In summary, PLPs lack many transcriptomic, molecular and functional features of platelets and possess novel anti-tumorigenic properties. These findings indicate that PLPs may have a potential therapeutic role in targeting and disrupting the oncogenic signaling between platelets and cancer cells, offering a new avenue for anti-cancer strategies.