Search Results (41)

Thrombocytopenia is a common hematological disorder characterized by reduced platelet counts and an increased risk of bleeding, for which current pharmacological treatments are often limited by adverse effects, drug resistance, or high costs. Traditional Chinese medicinal herbs such as ginseng, notoginseng, peony root, and astragalus have long been used for blood-nourishing and qi-tonifying purposes and are frequently prescribed for conditions associated with blood deficiency and hematopoietic dysfunction. This review systematically summarizes glycoside compounds derived from these herbs, focusing on their structural characteristics and pharmacological activities relevant to thrombocytopenia. Accumulating evidence indicates that glycosylation enhances the solubility, bioavailability, and stability of aglycones, thereby influencing their biological effects. Preclinical studies suggest that glycoside compounds may improve the hematopoietic microenvironment through anti-inflammatory, antioxidant, and immunomodulatory actions, potentially reducing immune-mediated platelet destruction. In addition, they may promote thrombopoiesis by modulating hematopoietic signaling pathways, such as PI3K/AKT, and by restoring immune balance, particularly via regulation of the Treg/Th17 axis. Collectively, these multi-target effects on hematopoiesis and immune regulation highlight glycoside compounds as promising lead candidates for the development of novel therapeutic approaches to thrombocytopenia. Full article

Host defense peptides (HDPs), ancestral effectors of innate immunity, have emerged as pleiotropic regulators transcending their antimicrobial origins. This review critically examines the complex interplay among HDPs, hemostasis, and tissue repair. We analyze molecular mechanisms governing interactions with platelets and endothelial cells, highlighting a fundamental paradigm shift: platelets and megakaryocytes are active synthesizers of a specific peptide repertoire rather than passive carriers. Functional dualities are elucidated, contrasting LL-37-driven platelet agonism via glycoprotein VI (GPVI) against the amyloid-like stabilization of fibrin by defensins. Based on these mechanisms, we propose a framework wherein HDPs function as concentration-dependent molecular switches between physiological repair and pathological thromboinflammation. Furthermore, the review addresses the hypothesis of “adaptive thrombopoiesis,” where systemic peptide surges act as danger signals to reprogram the function of newly formed platelets. Finally, therapeutic implications are evaluated, emphasizing the design of protease-resistant peptidomimetics to harness protective effects while mitigating vascular toxicity. Full article

Background/Objectives: Thrombotic events represent the leading cause of morbidity and mortality in patients with Philadelphia chromosome-negative myeloproliferative neoplasms (Ph⁻ MPNs), particularly in those aged > 60 years. The immature platelet fraction (IPF) reflects the proportion of newly released, reticulated, highly reactive platelets and has emerged as a marker of thrombopoietic activity in various prothrombotic conditions. Methods: We prospectively measured IPF in 45 patients with newly diagnosed Ph⁻ MPNs (24 with essential thrombocythemia, 13 with polycythemia vera, 5 with MPN-unclassified, and 3 with primary myelofibrosis) and 27 controls without MPN. Results: IPF was significantly higher in patients with Ph⁻ MPN than in controls (median 27 vs. 10.9, p < 0.0001). Within the MPN cohort, IPF values differed significantly across subtypes (p = 0.027), being highest in essential thrombocythemia and primary myelofibrosis, intermediate in unclassified MPN, and lowest in polycythemia vera. Patients older than 60 years exhibited higher IPF independently of platelet count (p = 0.021). No significant difference was observed between JAK2V617F-positive and -negative cases. Conclusions: These results indicate that IPF captures accelerated and dysregulated thrombopoiesis characteristics of Ph⁻ MPNs and may provide additional insight into subtype-specific biology and age-related prothrombotic risk beyond conventional complete blood count parameters. Full article

Background/Objectives: Dendritic cells (DCs) are key regulators of immune responses in cardiovascular disease, yet their role in platelet homeostasis and thrombopoiesis remains incompletely understood. We previously demonstrated that chronic depletion of CD11c⁺ cells accelerates atherosclerotic plaque development. The objective of this study was to determine whether sustained loss of CD11c⁺ cells alters platelet production and systemic inflammatory signaling under atherogenic conditions. Methods: CD11c-DTR bone marrow chimeric mice on ApoE⁻/⁻ background were generated and fed a high-cholesterol diet. CD11c⁺ cells were depleted by repeated diphtheria toxin administration over six weeks. Circulating platelet counts were quantified by automated hematology analysis. Systemic inflammatory changes were assessed using serum cytokine and chemokine profiling, and serum thrombopoietin (TPO) levels were measured by ELISA. Results: Chronic CD11c⁺ cell depletion resulted in a significant increase in circulating platelet counts in ApoE⁻/⁻ mice. Serum cytokine profiling revealed broad inflammatory remodeling, including increased levels of cytokines associated with megakaryopoiesis and platelet activation, such as IL-4, MCP-1, CXCL9, IL-16, and IL-1α. In parallel, serum TPO levels were significantly elevated following CD11c⁺ cell depletion. Conclusions: In the specific context of hyperlipidemic CD11c-DTR bone marrow chimeric mice, these findings demonstrate that loss of CD11c⁺ cells is associated with a pro-thrombopoietic shift, elevated platelet counts, and systemic inflammatory changes. Our data identify a CD11c⁺ cell–TPO–platelet axis linking immune regulation to platelet homeostasis and thrombo-inflammatory signaling under these specific atherogenic conditions. Full article

Background: Preeclampsia is a major obstetric disorder characterized by platelet activation and dysregulated thrombopoiesis. While conventional platelet indices reflect platelet morphology, the immature platelet fraction (IPF) provides insight into thrombopoietic activity. This study assessed IPF discrimination at presentation and its early post-treatment change in preeclampsia while controlling for potential confounding factors. Methods: In a prospective design, demographic and laboratory parameters—particularly platelet indices—were evaluated in women with preeclampsia and normotensive pregnant controls. Measurements were obtained at diagnosis and repeated 24–48 h after treatment, including initiation of medical treatment or delivery. Logistic regression and ROC analyses were performed, adjusting for age and gestational age. Results: Sixty-four women with preeclampsia and 25 normotensive controls were included; the preeclampsia group was older (31.3 ± 5 vs. 28.4 ± 4 years), and delivery occurred in 73.4%. At diagnosis, IPF, MPV, and PDW were higher, and platelet counts were lower compared with controls. After treatment, IPF decreased markedly (ΔIPF = 3.4; p < 0.001), accompanied by reductions in MPV and PDW, while platelet counts remained unchanged in the preeclampsia group. ΔIPF showed subtype-related differences, being higher in late-onset preeclampsia. Only IPF retained an independent association with preeclampsia (OR = 27.29; p = 0.006), whereas age, platelet count, MPV, PDW, BUN, and CRP were not significant. On ROC analysis, IPF demonstrated strong diagnostic performance (AUC = 0.992; cut-off ≥4%), with 98.4% sensitivity and 100% specificity. Conclusions: Easily measurable as part of a routine complete blood count, IPF may support diagnostic evaluation and clinical monitoring, consistent with its early post-treatment decline and subtype-related patterns. Full article

Megakaryocytes (MKs) are specialized hematopoietic cells long recognized for their ability to produce platelets. Increasing evidence now highlights MKs as multifunctional immune effectors that bridge hematopoiesis with host immunity. In the bone marrow (BM), MKs arise through thrombopoietin (TPO)-mediated differentiation of hematopoietic stem cells (HSCs) and show substantial heterogeneity, with discrete subsets specialized for platelet production (thrombopoiesis), HSC niche maintenance, or immune modulation. Outside the BM, MKs in the lungs and spleen perform tissue-specific immune functions, including pathogen recognition, phagocytosis, antigen presentation, and secretion of cytokines. During bacterial infections and sepsis, infectious or inflammatory cues reprogram MKs to amplify immune signaling and host responses, but can also drive coagulopathy and contribute to organ failure. Collectively, these findings redefine MKs as dynamic immunomodulatory cells positioned at the interface of thrombopoiesis and innate and adaptive immunity. In this review, we synthesize emerging literature on MK biogenesis, functional diversity, and immune modulation, with a special focus on their roles in bacterial infections and sepsis. Full article

Megakaryocytes (MKs) have traditionally been viewed as terminal hematopoietic cells responsible solely for platelet production. However, recent advances in imaging and single-cell transcriptomics have revealed substantial heterogeneity among MK populations and diverse functions beyond thrombopoiesis. MKs actively participate in innate and adaptive immunity, modulate the hematopoietic stem cell (HSC) niche, and adapt to physiological and pathological stimuli. Located in distinct anatomical sites such as bone marrow and lung, MKs exhibit compartment-specific specializations that enable them to serve as critical integrators of hemostatic, immune, and regenerative processes. Experimental models using human pluripotent stem cells and inducible MKs have enhanced mechanistic insights, while innovative bioreactor platforms and xenotransplantation strategies advance translational applications in platelet production and therapy. Furthermore, immune MK subsets derived from pluripotent stem cells show promising therapeutic potential for modulating inflammation and autoimmune diseases. Continued exploration of MK diversity, tissue-specific roles, and intercellular communication will unlock new opportunities for leveraging MK plasticity in regenerative medicine, immunotherapy, and hematologic disorders, repositioning these versatile cells as central players in systemic homeostasis and defense. Full article

Platelets play a pivotal role in coagulation, traditionally recognized for their involvement in thrombin generation via the prothrombinase complex and for regulating thrombopoietin (TPO) synthesis through platelet-mediated TPO uptake. However, recent studies suggest that TPO homeostasis involves more dynamic, feedback-driven mechanisms, though these interactions remain incompletely described and experimentally confirmed. The interplay between platelet activating factor (PAF) secretion, fibrinolysis, interleukin-6 (IL-6) signalling, hepatic TPO synthesis, as well as the complexity of platelet subpopulations, emphasises platelets’ multifaceted role in haemostasis and haematopoiesis. Our article investigates novel pathways by which fibrinogen degradation products (FgDPs) influence plasminogen and TPO synthesis, focusing on the interconnection between procoagulant platelets, platelet-derived messengers, and fibrinolytic processes. In this work several intermediary mechanisms are hypothesised, including the FgDP-IL-6-plasminogen pathway, the PAF-IL-6-TPO pathway, and the thrombin-FgDP-IL-6-TPO pathway, which may link FgDP and plasminogen biosynthesis with platelet activation, cytokine release, and thrombopoiesis regulation. The proposed mechanisms involve secretion of PAF by procoagulant platelets, inducing IL-6 synthesis in endothelial cells, fibroblasts, and vascular smooth muscle cells. Subsequently, IL-6 stimulates hepatocyte-driven TPO production, potentially serving as a feedback mechanism to restore platelet counts following coagulation. Furthermore, fibrinolysis-generated FgDPs may further enhance IL-6 release, implying alternative routes for TPO regulation. Our hypotheses challenge the prevailing view that platelet numbers alone dictate TPO homeostasis. Therefore, we propose that inflammatory and fibrinolytic signals actively regulate TPO homeostasis, challenging the platelet-count-centric paradigm. These insights provide a new perspective on haematopoiesis and suggest novel therapeutic targets for thrombocytopenia and coagulation disorders, highlighting the need for further experimental validation. Full article

Mutations in the ACTN1 gene, which encodes the cytoskeletal protein α-actinin-1, have been implicated in the etiology of autosomal dominant congenital macrothrombocytopenia. α-Actinin-1 is a member of the spectrin superfamily and is essential for key physiological processes in megakaryocytes and platelets. The pathophysiological mechanisms by which α-actinin-1 mutations lead to macrothrombocytopenia have been attributed to alterations in actin organization, increased binding affinity of α-actinin-1 to actin filaments, and modulation of integrin αIIbβ3 signaling. In previous studies, we utilized megakaryocyte-specific α-actinin-1 knockout (PF4-ACTN1^−/−) mice to explore the influence of α-actinin-1 on megakaryocyte and platelet function. Despite these efforts, the precise mechanisms remain inadequately understood. To advance our understanding and clarify the role of α-actinin-1 in thrombopoiesis, we first delineated the functions of α-actinin-1 in megakaryocytes and platelets, followed by a comprehensive overview of the proteins known to interact with α-actinin-1. As a pivotal scaffold protein, α-actinin-1 interacts with a complex network of partners, including integrin αIIbβ3, and actin filaments, to modulate cytoskeletal dynamics, megakaryocyte maturation, and proplatelet formation. In addition to its well-documented proteins that interact with α-actinin-1 within megakaryocytes and platelets, α-actinin-1 also associates with proteins outside the megakaryocytic lineage, such as cytohesin-2 and MOB1, which have been predominantly examined in other cellular contexts. These varied interactions imply that α-actinin-1 may influence megakaryocyte and platelet functions through multiple mechanisms. This review provides a comprehensive synthesis of current knowledge regarding the structure, binding partners of α-actinin-1, and essential roles of α-actinin-1 in thrombopoiesis. Full article

Megakaryocytes (MKs), which primarily develop in bone marrow (BM) from hematopoietic stem cells, are critical for platelet production. Beyond their well-established role in thrombopoiesis, MKs have been identified as important for BM niche maintenance, such as by supporting the growth and differentiation of other cell types. Recently, megakaryopoiesis has been reported as yielding divergent subpopulations of MKs, as evidenced by single-cell RNA sequencing of lung, spleen, or BM resident MKs. Interestingly, these subpopulations constitute a significant proportion of “immune MKs” expressing various classical immune markers and capable of phagocytosing pathogens and contributing to antigen presentation. As such, MKs were also found to regulate inflammation, mainly by secreting various cytokines and chemokines to crosstalk with other cell types. The level and functional signature of these “immune MKs” were found to be altered in various pathological conditions, indicative of their purposeful values in health and diseases. In this review, we survey and highlight newly reported functional immune and inflammatory properties of MKs in health and in select pathologies. Full article

Interleukin-6 (IL-6) is a pleiotropic cytokine with critical roles in immune regulation, inflammation, and haematopoiesis. While its functions in host defence and tissue repair are well established, accumulating evidence suggests that IL-6 also can directly and indirectly modulate megakaryocyte and platelet biology. This review examines the mechanistic basis supporting IL-6-mediated platelet hyper-responsiveness, in addition to its effect on megakaryopoiesis and thrombopoiesis in thromboinflammatory disease states. We discuss how IL-6-mediated trans-signalling may sensitizes platelets to activation, and that this may be exclusive to glycoprotein VI (GPVI) stimulation due to Janus kinase (JAK)–signal transducer 2 crosstalk, in addition to other mechanisms that may contribute to priming platelets. We further highlight clinical evidence linking IL-6 to thrombotic complications in cardiovascular disease and infection (e.g., COVID-19 and sepsis). Given the emerging interest in IL-6-targeting therapies as anti-inflammatory and anti-thrombotic agents, a thorough understanding of how IL-6 can drive platelet responsiveness is crucial. Full article

Understanding the correlation between genotype and phenotype remains challenging for modern genetics. Digenic network analysis may provide useful models for understanding complex phenotypes that traditional Mendelian monogenic models cannot explain. Clinical data, whole exome sequencing data, in silico, and machine learning analysis were combined to construct a digenic network that may help unveil the complex genotype–phenotype correlations in a child presenting with inherited seizures and thrombocytopenia. The proband inherited a maternal heterozygous missense variant in SCN1A (NM_001165963.4:c.2722G>A) and a paternal heterozygous missense variant in MYH9 (NM_002473.6:c.3323A>C). In silico analysis showed that these two variants may be pathogenic for inherited seizures and thrombocytopenia in the proband. Moreover, focusing on 230 epilepsy-associated genes and 35 thrombopoiesis genes, variant call format data of the proband were analyzed using machine learning tools (VarCoPP 2.0) and Digenic Effect predictor. A digenic network was constructed, and SCN1A and MYH9 were found to be core genes in the network. Further analysis showed that MYH9 might be a modifier of SCN1A, and the variant in MYH9 might not only influence the severity of SCN1A-related seizure but also lead to thrombocytopenia in the bone marrow. In addition, another eight variants might also be co-factors that account for the proband’s complex phenotypes. Our data show that as a supplement to the traditional Mendelian monogenic model, digenic network analysis may provide reasonable models for the explanation of complex genotype–phenotype correlations. Full article

A key step in platelet production is the migration of megakaryocytes to the vascular sinusoids within the bone marrow. This homing is mediated by the chemokine CXCL12 and its receptor CXCR4. CXCR4 is also a positive regulator of platelet activation and thrombosis. Pim-1 kinase has been shown to regulate CXCR4 signalling in other cell types, and we have previously described how Pim kinase inhibitors attenuate platelet aggregation to CXCL12. However, the mechanism by which Pim-1 regulates CXCR4 signalling in platelets and megakaryocytes has yet to be elucidated. Using human platelets, murine bone marrow-derived megakaryocytes, and the megakaryocyte cell line MEG-01, we demonstrate that pharmacological Pim kinase inhibition leads to reduced megakaryocyte and platelet function responses to CXCL12, including reduced megakaryocyte migration and platelet granule secretion. Attenuation of CXCL12 signalling was found to be attributed to the reduced surface expression of CXCR4. The decrease in CXCR4 surface levels was found to be mediated by rapid receptor internalisation, in the absence of agonist stimulation. We demonstrate that pharmacological Pim kinase inhibition disrupts megakaryocyte and platelet function by reducing constitutive CXCR4 surface expression, decreasing the number of receptors available for agonist stimulation and signalling. These findings have implications for the development and use of Pim kinase inhibitors for the treatment of conditions associated with elevated circulating levels of CXCL12/SDF1α and increased thrombotic risk. Full article

Platelets are the terminal progeny of megakaryocytes, primarily produced in the bone marrow, and play critical roles in blood homeostasis, clotting, and wound healing. Traditionally, megakaryocytes and platelets are thought to arise from multipotent hematopoietic stem cells (HSCs) via multiple discrete progenitor populations with successive, lineage-restricting differentiation steps. However, this view has recently been challenged by studies suggesting that (1) some HSC clones are biased and/or restricted to the platelet lineage, (2) not all platelet generation follows the “canonical” megakaryocytic differentiation path of hematopoiesis, and (3) platelet output is the default program of steady-state hematopoiesis. Here, we specifically investigate the evidence that in vivo lineage tracing studies provide for the route(s) of platelet generation and investigate the involvement of various intermediate progenitor cell populations. We further identify the challenges that need to be overcome that are required to determine the presence, role, and kinetics of these possible alternate pathways. Full article

Interleukins, a diverse family of cytokines produced by various cells, play crucial roles in immune responses, immunoregulation, and a wide range of physiological and pathological processes. In the context of megakaryopoiesis, thrombopoiesis, and platelet function, interleukins have emerged as key regulators, exerting significant influence on the development, maturation, and activity of megakaryocytes (MKs) and platelets. While the therapeutic potential of interleukins in platelet-related diseases has been recognized for decades, their clinical application has been hindered by limitations in basic research and challenges in drug development. Recent advancements in understanding the molecular mechanisms of interleukins and their interactions with MKs and platelets, coupled with breakthroughs in cytokine engineering, have revitalized the field of interleukin-based therapeutics. These breakthroughs have paved the way for the development of more effective and specific interleukin-based therapies for the treatment of platelet disorders. This review provides a comprehensive overview of the effects of interleukins on megakaryopoiesis, thrombopoiesis, and platelet function. It highlights the potential clinical applications of interleukins in regulating megakaryopoiesis and platelet function and discusses the latest bioengineering technologies that could improve the pharmacokinetic properties of interleukins. By synthesizing the current knowledge in this field, this review aims to provide valuable insights for future research into the clinical application of interleukins in platelet-related diseases. Full article