Platelet Heterogeneity in Myeloproliferative Neoplasms

The Role of Platelet Dysfunctions in the Pathogenesis of the Hemostatic-Coagulant System Imbalances

Platelet dysfunction plays a critical role in the pathogenesis of various disorders affecting the hemostatic-coagulant system. This review aims to explore the mechanisms by which platelet dysfunctions contribute to the disruption of hemostasis, leading to an increased risk of both thrombosis and bleeding. Platelets, traditionally known for their role in clot formation, can exhibit altered functionality under pathological conditions such as cardiovascular diseases, metabolic disorders, and autoimmune diseases, impacting their interaction with coagulation factors and vascular endothelium. The review discusses the molecular and cellular mechanisms underlying platelet dysfunction, including aberrations in platelet activation, aggregation, and secretion. It also highlights the interplay between platelets and other components of the coagulation cascade, such as fibrinogen and clotting factors, in maintaining vascular integrity. Moreover, the review examines clinical implications, including how platelet dysfunction can be a contributing factor in conditions like deep vein thrombosis, stroke, and disseminated intravascular coagulation (DIC). Finally, current therapeutic approaches targeting platelet dysfunctions, including antiplatelet agents and emerging therapies, are reviewed to provide insights into potential strategies for managing fluid-coagulation system imbalances. This review underscores the importance of a comprehensive understanding of platelet dysfunction to improve diagnosis and treatment of hemostatic disorders.

Management of Bleeding, Thrombotic and Pregnancy-Related Complications in Women with Myeloproliferative Neoplasms: A Case-Based Review Focusing on Sex-Specific Challenges

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal hematopoietic disorders that pose unique challenges in women, particularly regarding thrombosis, bleeding, fertility, and pregnancy. Women with MPN exhibit distinct thrombotic and sometimes contradictory bleeding profiles, including a higher prevalence of unusual thrombosis such as cerebral and splanchnic vein thrombosis and increased risk of hemorrhage from anti-thrombotic medication, acquired von Willebrand syndrome and platelet dysfunction. Estrogen-containing contraceptives should generally be avoided due to thrombotic risk. Around 10-20% of newly diagnosed MPN cases are women of childbearing age and the number is increasing annually. MPN patients when compared to controls have a lower rate of live birth rate of 71% vs. 80% with a hazard ratio of 0.78 (95% CI: 0.68-0.90), and increased preterm birth (14% vs. 4%), low birth weight (<2500 g, 10% vs. 4%), and increased cesarean section rate (32% vs. 17%). Management of MPN-related pregnancy requires specific considerations regarding the prevention of thrombosis, bleeding, and pregnancy-related complications. Management strategies during pregnancy include low-dose aspirin and consideration of low-molecular-weight heparin and interferon. Despite these challenges, most women with MPN can achieve successful pregnancies with optimized care. In this case-based review, we present two cases that illustrate key aspects of managing MPN in women, summarize the current literature, and propose a diagnostic and management framework tailored to these complexities.

Application of platelet transcriptomics for assessing treatment effectiveness and predicting long-term platelet counts recovery in aplastic anemia

BACKGROUND

Aplastic anemia (AA) is a bone marrow failure disease for which the means of assessing and predicting the therapeutic effectiveness are still relatively limited. Thrombocytopenia is often the earliest and most severe symptom in patients newly diagnosed with AA. While clinical consideration is usually given to the quantitative changes in platelets during treatment, there is little focus on the resolution of the molecular characteristics of platelets in AA.

OBJECTIVES

To investigate the changes in platelet molecular characteristics throughout the treatment process of AA, and to explore the use of transcriptomics for monitoring and predicting treatment outcomes.

METHODS

We comprehensively analyzed platelet transcriptomic changes in patients with AA at initial diagnosis and different stages of treatment effectiveness using bulk transcriptome sequencing.

RESULTS

Genes associated with cell proliferation, erythroid function, and amino acid transport were elevated in newly diagnosed AA. Conversely, genes linked to histones, thrombopoiesis, mitochondrial energy metabolism, and signaling pathways were significantly downregulated. Additionally, 60.6% of the differentially expressed genes were substantially restored following complete remission. Furthermore, through the examination of longitudinal samples, we identified recovery ascending genes that could serve as viable biomarkers for assessing treatment effectiveness in AA. Besides, we observed that higher expression levels of recovery ascending genes may predict superior long-term platelet counts recovery 6 months in advance in patients with partial response.

CONCLUSION

The platelet transcriptome undergoes profound changes and can serve as a potential indicator for assessing treatment effectiveness and predicting long-term platelet counts recovery in AA.

Using heart rate variability to evaluate the association between the autonomic nervous system and coagulation function in patients with endometrial cancer

The incidence of endometrial cancer (EC) is increasing worldwide, but the specific mechanism of coagulation dysfunction in EC is not fully understood. The objective of the present study was to explore the relationship between autonomic nervous system function and coagulation function in patients with EC using heart rate variability (HRV) analysis. The study included 100 patients with EC who were treated at the Department of Gynecological Oncology of The First Affiliated Hospital of Bengbu Medical University (Bengbu, China) from December 2021 to March 2023. A 5-min resting electrocardiogram was collected from each patient to analyze HRV parameters, including the time domain parameters standard deviation of the normal-normal intervals (SDNN) and root mean square of successive interval differences (RMSSD), and the frequency domain parameters low-frequency power and high-frequency power (HF). Blood samples were submitted to biochemistry tests to measure coagulation markers, namely prothrombin time (PT), international normalized ratio of PT (PT-INR), prothrombin activity (PTA), activated partial thromboplastin time (APTT) and fibrinogen. Bivariate Spearman correlation analyses revealed that PT, PT-INR and APTT were significantly positively correlated with SDNN, RMSSD and HF, while PTA was significantly negatively correlated with RMSSD. Following adjustments for confounding factors, namely age, body mass index, menopause, ligation of the fallopian tubes, diabetes, hypertension, adjuvant chemotherapy and mean heart rate, linear regression analysis demonstrated that SDNN, RMSSD and HF were independent factors influencing PT and PT-INR in patients with EC. The findings of the present study indicate that certain HRV parameters correlate with coagulation markers in EC and provide new insight into the occurrence of cancer-associated coagulation dysfunction.

Heterogeneity of platelets and their responses

There has been increasing recognition of heterogeneity in blood platelets and their responses, particularly in recent years, where next-generation technologies and advanced bioinformatic tools that interrogate "big data" have enabled large-scale studies of RNA and protein expression across a growing list of disease states. However, pioneering platelet biologists and clinicians were already hypothesizing upon and investigating heterogeneity in platelet (and megakaryocyte) activity and platelet metabolism and aggregation over half a century ago. Building on their foundational hypotheses, in particular Professor Marian A. Packham's pioneering work and a State of the Art lecture in her memoriam at the 2023 International Society on Thrombosis and Haemostasis Congress by Anandi Krishnan, this review outlines the key features that contribute to the heterogeneity of platelets between and within individuals. Starting with important epidemiologic factors, we move stepwise through successively smaller scales down to heterogeneity revealed by single-cell technologies in health and disease. We hope that this overview will urge future scientific and clinical studies to recognize and account for heterogeneity of platelets and aim to apply methods that capture that heterogeneity. Finally, we summarize other exciting new data presented on this topic at the 2023 International Society on Thrombosis and Haemostasis Congress.

SIRPα controls CD47-dependent platelet clearance in mice and humans

Over the last decade, more data has revealed that increased surface expression of the "don't eat me" CD47 protein on cancer cells plays a role in immune evasion and tumor progression, with CD47 blockade emerging as a new therapy in immuno-oncology. CD47 is critical in regulating cell homeostasis and clearance, as binding of CD47 to the inhibitory receptor SIRPα can prevent phagocytosis and macrophage-mediated cell clearance. The purpose of this study was to examine the role of the CD47-SIRPα signal in platelet homeostasis and clearance. Therapeutic reagents targeting the CD47-SIRPα axis are very promising for treatment of hematologic malignancies and solid tumors, but lead to transient anemia or thrombocytopenia in a subset of patients. We found that platelet homeostatic clearance is regulated through the CD47-SIRPα axis and that therapeutic blockade to disrupt this interaction in mice and in humans has a significant impact on platelet levels. Furthermore, we identified genetic variations at the SIRPA locus that impact platelet levels in humans such that higher SIRPA gene expression is associated with higher platelet levels. SIRPA expression at either end of the normal range may affect clinical outcomes of treatment with anti-CD47 therapy.

The Combination of JAK2V617F Allele Burden and WT1 Expression can Be Helpful in Distinguishing the Subtype of MPN Patients

INTRODUCTION

Classical Philadelphia-negative myeloproliferative neoplasm (MPN) includes Essential Thrombocythemia (ET), Polycythemia Vera (PV) and Primary Myelofibrosis (PMF). The JAK2V617F mutation is part of the major criteria for diagnosis of MPN. WT1 is reported to be highly overexpressed in most hematological malignancy. Our aim was to explore the combination value of JAK2V617F allele burden and WT1 expression in distinguishing the subtype of MPN patients.

METHODS

Allele specific real-time quantitative fluorescence PCR (AS-qPCR) was conducted to detect JAK2V617F allele burden. WT1 expression was assessed by RQ-PCR. Our study is a retrospective study.

RESULTS

JAK2V617F allele burden and WT1 expression were different in MPN subgroups. The expression of WT1 in PMF and PV is higher than in ET. JAK2V617F allele burden in PMF and PV is also higher than in ET. ROC analysis indicated that combination of JAK2V617F allele burden and WT1 expression to discriminate ET and PV, ET and PMF, PV and PMF is 0.956, 0.871, 0.737 respectively. Furthermore, their ability to distinguish ET patients with high Hb levels from PV patients with high platelet counts is 0.891.

CONCLUSIONS

Our data revealed that combination of JAK2V617F allele burden and WT1 expression is useful in distinguishing the subtype of MPN patients.

Mammalian STE20-like kinase-1/2 are activated in human platelets stimulated by collagen or thrombin and play a vital role in collagen-activated platelets

INTRODUCTION

Mammalian ste20-like kinases-1/2 (MST1/2), the core kinases of the Hippo pathway, play critical roles in the biology of hematopoietic cells via noncanonical mechanisms and contributes to megakaryocyte differentiation, polyploidization, and maturation to produce platelets. However, the role of MST1/2 in platelet functions remains unclear.

MATERIALS AND METHODS

In this study, we investigated this topic by determining platelet aggregation and through flow cytometry, ATP release assay, clot retraction assay, and immunoblotting analysis.

RESULTS

We found that MST1/2 were rapidly phosphorylated and activated upon platelet stimulation by thrombin and collagen. XMU-MP-1, a specific inhibitor of MST1/2, blocks the activation of MST1/2 in platelets. Inhibitor-pretreated platelets showed impaired platelet aggregation and dense-granule secretion mediated by collagen, thrombin, and U46619, whereas ristocetin or ADP mediated platelet aggregation was unaffected by XMU-MP-1. Although platelet-mediated clot retraction was not affected by MST1/2 inhibitors, integrin αIIbβ3 activation was significantly attenuated in XMU-MP-1-treated platelets. Moreover, MST1/2 inhibition significantly attenuated the mobilization of platelet calcium ions and the secretion of α-granules induced by convulxin.

CONCLUSIONS

This study is the first to demonstrate that MST1/2 play vital roles in human platelets and contributes to collagen-induced platelet activation and aggregation.

Toward platelet transcriptomics in cancer diagnosis, prognosis and therapy

Widespread adoption of next-generation techniques such as RNA-sequencing (RNA-seq) has enabled research examining the transcriptome of anucleate blood platelets in health and disease, thus revealing a rich platelet transcriptomic signature that is reprogrammed in response to disease. Platelet signatures not only capture information from parent megakaryocytes and progenitor hematopoietic stem cells but also the bone marrow microenvironment, and underlying disease states. In cancer, the substantive body of research in patients with solid tumours has identified distinct signatures in 'tumour-educated platelets', reflecting influences of the tumour, stroma and vasculature on splicing, sequestration of tumour-derived RNAs, and potentially cytokine and microvesicle influences on megakaryocytes. More recently, platelet RNA expression has emerged as a highly sensitive approach to profiling chronic progressive haematologic malignancies, where the combination of large data cohorts and machine-learning algorithms enables precise feature selection and potential prognostication. Despite these advances, however, our ability to translate platelet transcriptomics toward clinical diagnostic and prognostic efforts remains limited. In this Perspective, we present a few actionable steps for our basic, translational and clinical research communities in advancing the utility of the platelet transcriptome as a highly sensitive biomarker in cancer and collectively enable efforts toward clinical translation and patient benefit.

Role of Thioredoxin-1 and its inducers in human health and diseases

Thioredoxin-1 (Trx-1) is a small redox-active protein normally found in mammalian cells that responds to the changing redox environment by contributing electrons or regulating related proteins. There is growing evidence that Trx-1 has multiple functions, including cytoprotective, anti-apoptotic, antioxidant and anti-inflammatory effects. To date, researchers have found that Trx-1 deficiency leads to severe damage in various disease models, such as atherosclerosis, cerebral ischemia, diabetes and tumors. Conversely, activation of Trx-1 has a protective effect against these diseases. Accordingly, a variety of Trx-1 inducers have been widely used in the clinic with significant therapeutic value. In this paper, we summarize the pathogenesis of Trx-1 involvement in the above-mentioned diseases and describe the protective effects of Trx-1 inducers on them.