Platelets最新文献

Inherited thrombocytopenia (IT) is a group of hereditary disorders characterized by a reduced platelet count as the main clinical manifestation, and often with abnormal platelet function, which can subsequently lead to impaired hemostasis. In the past decades, humanized mouse models (HMMs), that are mice engrafted with human cells or genes, have been widely used in different research areas including immunology, oncology, and virology. With advances of the development of immunodeficient mice, the engraftment, and reconstitution of functional human platelets in HMM permit studies of occurrence and development of platelet disorders including IT and treatment strategies. This article mainly reviews the development of humanized mice models, the construction methods, research status, and problems of using humanized mice for the in vivo study of human thrombopoiesis.

Previous studies have demonstrated that sirolimus (SRL) is an effective agent for the treatment of refractory/relapsed (R/R) ITP. However, the therapeutic window of sirolimus in the treatment of ITP has not been established. As the toxicity of sirolimus increases with higher blood concentrations, it is crucial to determine the optimal therapeutic concentration of SRL for the treatment of ITP. Thus, in this study, we used a retrospective cohort of ITP patients treated with sirolimus to propose the therapeutic dosage window for sirolimus. A total of 275 laboratory results of SRL blood concentration from 63 ITP patients treated with SRL were analyzed retrospectively. The ITP patients were divided into five groups based on their SRL blood concentration: 0-4 ng/ml, 4-8 ng/ml, 8-12 ng/ml, 12-16 ng/ml and ≥16 ng/ml. In addition to the SRL blood concentration, platelet counts and adverse events that occurred during the first 6 weeks of SRL treatment were analyzed. These findings were then used to establish the decision matrix tables and ROC curves, which helped identify the therapeutic window of SRL. Based on the values and trends of true-positive rate (TPR) and false-positive rate (FPR) in the ROC curve, patients who achieved a SRL blood concentration of 4-12 ng/ml displayed a higher response rate compared to those with a SRL concentration of 0-4 ng/ml or ≥16ng/ml. Additionally, the response rate was better for patients with a SRL concentration of 8-12 ng/ml compared to 4-8 ng/ml. Adverse events were related to the concentration of SRL; however, there was no significant difference in the incidence of adverse events between the concentrations of 4-8 ng/ml and 8-12 ng/ml (P > .05). Regression analysis suggested that the concentration of SRL correlated with the patient's age, PLT count at the start of SRL administration, and the dose of SRL. It is suggested that the optimal blood concentration of SRL monotherapy for managing ITP is 8-12 ng/ml. This range may achieve a favorable balance between clinical efficacy and the severity of adverse events.

Arterial tonometry and vascular calcification measures are useful in cardiovascular disease (CVD) risk assessment. Prior studies found associations between tonometry measures, arterial calcium, and CVD risk. Activated platelets release angiopoietin-1 and other factors, which may connect vascular structure and platelet function. We analyzed arterial tonometry, platelet function, aortic, thoracic and coronary calcium, and thoracic and abdominal aorta diameters measured in the Framingham Heart Study Gen3/NOS/OMNI-2 cohorts (n = 3,429, 53.7% women, mean age 54.4 years ±9.3). Platelet reactivity in whole blood or platelet-rich plasma was assessed using 5 assays and 7 agonists. We analyzed linear mixed effects models with platelet reactivity phenotypes as outcomes, adjusting for CVD risk factors and family structure. Higher arterial calcium trended with higher platelet reactivity, whereas larger aortic diameters trended with lower platelet reactivity. Characteristic impedance (Zc) and central pulse pressure positively trended with various platelet traits, while pulse wave velocity and Zc negatively trended with collagen, ADP, and epinephrine traits. All results did not pass a stringent multiple test correction threshold (p < 2.22e-04). The diameter trends were consistent with lower shear environments invoking less platelet reactivity. The vessel calcium trends were consistent with subclinical atherosclerosis and platelet activation being inter-related.

BMS-986141 is a novel, oral, protease-activated, receptor 4 (PAR4)-antagonist that exhibited robust antithrombotic activity and low bleeding risk in preclinical studies. The pharmacokinetic, pharmacodynamic, and tolerability profiles of BMS-986141 in healthy participants were assessed in a randomized, double-blind, placebo-controlled, single-ascending-dose (SAD; N = 60) study; a multiple-ascending-dose (MAD; N = 32) study; and a Japanese MAD (JMAD; N = 32) study. Exposure was dose-proportional for BMS-986141 2.5 mg and 150 mg; maximum concentrations were 17.6 ng/mL and 958 ng/mL; and areas under the curve (AUC) to infinity were 183 h* × ng/mL and 9207 h* × ng/mL, respectively. Mean half-life ranged from 33.7 to 44.7 hours across dose panels. The accumulation index following once-daily administration for 7 days suggested a 1.3- to 2-fold AUC increase at steady state. In the SAD study, BMS-986141 75 and 150 mg produced ≥80% inhibition of 25-100 µM PAR4 agonist peptide (AP)-induced platelet aggregation, without affecting PAR1-AP-induced platelet aggregation, through ≥24 hours postdose. In the MAD and JMAD studies, BMS-986141 doses ≥10 mg completely inhibited 12.5 μM and 25 μM PAR4-AP-induced platelet aggregation through 24 hours. This study found BMS-986141 was safe and well tolerated, with dose-proportional pharmacokinetics and concentration-dependent pharmacodynamics in healthy participants over a wide dose range. ClinicalTrials.gov ID: NCT02341638.

The conventional dose of recombinant human thrombopoietin (rhTPO) in the treatment of immune thrombocytopenia (ITP) is 300 U/kg per day, but the clinical reaction rate is not satisfactory. Accordingly, we explored the efficacy and safety of increasing rhTPO dose in the treatment of ITP. A retrospective study was conducted to collect the clinical data of 105 ITP patients who were divided into two groups, a low-dose group (15 000 U/day) and a high-dose group (30 000 U/day) according to the dose of rhTPO. The total effective rate of the low-dose group and the high-dose group was 31/44 (70.45%) vs. 56/61 (91.80%) (P = .049), and the average time of using rhTPO in the high-dose group was shorter than that in the low-dose group (7 days vs. 10 days, P = .001). On the 7th and 14th day of treatment, the efficacy of the high-dose group was better than that of the low-dose group [45/61 (73.77%) vs. 17/44 (38.64%), P < .001; 55/60 (91.67%) vs. 30/44 (68.18%), P < .05)]. The incidence of treatment related adverse events in the low-dose group and the high-dose group was 6/44 (13.64%) vs. 6/61 (9.84%) (P > .05), which were mild and transient in nature. In our study, high-dose rhTPO had good efficacy and high safety in the treatment of ITP with the efficacy better than low-dose rhTPO especially at day 7.

Kappa-carrageenan (KCG), which is used to induce thrombosis in laboratory animals for antithrombotic drug screening, can trigger platelet aggregation. However, the cell-surface receptor and related signaling pathways remain unclear. In this study, we investigated the molecular basis of KCG-induced platelet activation using light-transmittance aggregometry, flow cytometry, western blotting, and surface plasmon resonance assays using platelets from platelet receptor-deficient mice and recombinant proteins. KCG-induced tail thrombosis was also evaluated in mice lacking the platelet receptor. We found that KCG induces platelet aggregation with α-granule secretion, activated integrin αIIbβ3, and phosphatidylserine exposure. As this aggregation was significantly inhibited by the Src family kinase inhibitor and spleen tyrosine kinase (Syk) inhibitor, a tyrosine kinase-dependent pathway is required. Platelets exposed to KCG exhibited intracellular tyrosine phosphorylation of Syk, linker activated T cells, and phospholipase C gamma 2. KCG-induced platelet aggregation was abolished in platelets from C-type lectin-like receptor-2 (CLEC-2)-deficient mice, but not in platelets pre-treated with glycoprotein VI-blocking antibody, JAQ1. Surface plasmon resonance assays showed a direct association between murine/human recombinant CLEC-2 and KCG. KCG-induced thrombosis and thrombocytopenia were significantly inhibited in CLEC-2-deficient mice. Our findings show that KCG induces platelet activation via CLEC-2.

ANKRD26-related thrombocytopenia (ANKRD26-RT or THC2, MIM 188 000), an autosomal dominant thrombocytopenia, is unresponsive to immunosuppressive therapy and susceptible to hematological malignancies. A large number of pediatric patients are diagnosed with immune thrombocytopenia (ITP) every year; however, thrombocytopenia of genetic origin is often missed. Extensive characterization of ANKRD26-RT will help prevent missed diagnosis and misdiagnosis. Furthermore, identification of ANKRD26-RT will help in the formulation of an accurate diagnosis and a treatment plan. In our study, we report cases of two Chinese pediatric patients with ANKRD26-RT and analyze their clinical characteristics, gene mutations, and treatment modalities. Both patients were 1-year-old and presented with mild bleeding (World Health Organization(WHO) score grade 1), different degrees of platelet reduction, normal mean platelet volume, and megakaryocyte maturation impairment not obvious. Genetic tests revealed that both patients had ANKRD26 gene mutations.Patient 1 had a mutation c.-140C>G of the 5' untranslated region (UTR), and patient 2 had a mutation of c.-127A>T of 5'UTR. Both patients were treated with eltrombopag, and the treatment was no response, with no adverse reactions.

Platelets contribute to COVID-19 clinical manifestations, of which microclotting in the pulmonary vasculature has been a prominent symptom. To investigate the potential diagnostic contributions of overall platelet morphology and their α-granules and mitochondria to the understanding of platelet hyperactivation and micro-clotting, we undertook a 3D ultrastructural approach. Because differences might be small, we used the high-contrast, high-resolution technique of focused ion beam scanning EM (FIB-SEM) and employed deep learning computational methods to evaluate nearly 600 individual platelets and 30 000 included organelles within three healthy controls and three severely ill COVID-19 patients. Statistical analysis reveals that the α-granule/mitochondrion-to-plateletvolume ratio is significantly greater in COVID-19 patient platelets indicating a denser packing of organelles, and a more compact platelet. The COVID-19 patient platelets were significantly smaller -by 35% in volume - with most of the difference in organelle packing density being due to decreased platelet size. There was little to no 3D ultrastructural evidence for differential activation of the platelets from COVID-19 patients. Though limited by sample size, our studies suggest that factors outside of the platelets themselves are likely responsible for COVID-19 complications. Our studies show how deep learning 3D methodology can become the gold standard for 3D ultrastructural studies of platelets.

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.

Platelet-specific collagen receptor glycoprotein (GP)VI is stable on the surface of circulating platelets but undergoes ectodomain cleavage on activated platelets. Activation-dependent GPVI metalloproteolysis is primarily mediated by A Disintegrin And Metalloproteinase (ADAM) 10. Regulation of platelet ADAMs activity is not well-defined however Tissue Inhibitors of Metalloproteinases (TIMPs) may play a role. As levels of TIMPs on platelets and the control of ADAMs-mediated shedding by TIMPs has not been evaluated, we quantified the levels of TIMPs on the surface of resting and activated platelets from healthy donors by flow cytometry and multiplex ELISA. Variable levels of all TIMPs could be detected on platelets. Plasma contained significant quantities of TIMP1 and TIMP2, but only trace amounts of TIMP3 and TIMP4. Recombinant TIMP3 strongly ablated resting and activated platelet ADAM10 activity, when monitored using a quenched fluorogenic peptide substrate with ADAM10 specificity. Whilst ADAM10-specific inhibitor GI254023X or ethylenediamine tetraacetic acid (EDTA) could modulate ligand-initiated shedding of GPVI, only recombinant TIMP2 achieved a modest (~20%) inhibition. We conclude that some platelet TIMPs are able to modulate platelet ADAM10 activity but none strongly regulate ligand-dependent shedding of GPVI. Our findings provide new insights into the regulation of platelet receptor sheddase activity.