Platelet-related Diseases Research Articles

Epigenetic regulation of megakaryopoiesis and platelet formation.

Platelets, produced by megakaryocytes, play unique roles in physiological processes, such as hemostasis, coagulation, and immune regulation, while also contributing to various clinical diseases. During megakaryocyte differentiation, the morphology and function of cells undergo significant changes due to the programmed expression of a series of genes. Epigenetic changes modify gene expression without altering the DNA base sequence, effectively affecting the inner workings of the cell at different stages of growth, proliferation, differentiation, and apoptosis. These modifications also play important roles in megakaryocyte development and platelet biogenesis. However, the specific mechanisms underlying epigenetic processes and the vast epigenetic regulatory network formed by their interactions remain unclear. In this review, we systematically summarize the key roles played by epigenetics in megakaryocyte development and platelet formation, including DNA methylation, histone modification, and non-coding RNA regulation. We expect our review to provide a deeper understanding of the biological processes underlying megakaryocyte development and platelet formation and to inform the development of new clinical interventions aimed at addressing platelet-related diseases and improving patients' prognoses.

Long non-coding RNA NORAD regulates megakaryocyte differentiation and proplatelet formation via the DUSP6/ERK signaling pathway

Megakaryopoiesis and platelet production is a complex process that is underpotential regulation at multiple stages. Many long non-coding RNAs (lncRNAs) are distributed in hematopoietic stem cells and platelets. lncRNAs may play important roles as key epigenetic regulators in megakaryocyte differentiation and proplatelet formation. lncRNA NORAD can affect cell ploidy by sequestering PUMILIO proteins, although its direct effect on megakaryocyte differentiation and thrombopoiesis is still unknown. In this study, we demonstrate NORAD RNA is highly expressed in the cytoplasm during megakaryocyte differentiation. Interestingly, we identified for the first time that NORAD has a strong inhibitory effect on megakaryocyte differentiation and proplatelet formation from cultured megakaryocytes. DUSP6/ERK1/2 pathway is activated in response to NORAD knockdown during megakaryocytopoiesis, which is achieved by sequestering PUM2 proteins. Finally, compared with the wild-type control mice, NORAD knockout mice show a faster platelet recovery after severe thrombocytopenia induced by 6 Gy total body irradiation. These findings demonstrate lncRNA NORAD has a key role in regulating megakaryocyte differentiation and thrombopoiesis, which provides a promising molecular target for the treatment of platelet-related diseases such as severe thrombocytopenia.

Interleukins in Platelet Biology: Unraveling the Complex Regulatory Network.

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.

Automated Platelet Counter with Detection Using K-Means Clustering

Platelet is a blood cell type that is stored and circulated in the human body. It acts as a blood thickening agent and prevents blood from overflowing whenever bleeding occurs. An excessive or inadequate number of platelets could lead to platelet-related diseases. The current practice of platelet counting involves the manual counting process using a haemocytometer, Wright’s Stain which uses the dyes to facilitate the differentiation of blood cell types, and a tally counter. Yet, this process can be time-consuming, demanding, and exhausting for haematologists, and likely to be prone to errors. Thus, this paper presents a study on automated platelet counter and detection using image processing techniques. The K-Means Clustering was employed to count and detect the presence of platelets in microscopic blood smear images. Several processes were performed prior to the K-means clustering, including image enhancement and YCbCr image formatting. Subsequently, image masking, as well as area thresholding were applied to eliminate every unwanted entity and highlight the visibility of the platelets before the number of platelets could be detected and counted. A comparative experiment was designed in which the K-Means Clustering platelet count and detection were compared with the actual number of platelets reported by haematologists. The platelet counts and detection were categorized into three detection categories which are Less Detection (LD), Accurate Detection (AD), and Over Detection (OD). The proposed study was evaluated to 90 testing platelet images. Out of the 90 testing images, 75 platelet images were perfectly counted and detected which returned 91.67% of accuracy. This signifies that the K-Means Clustering algorithm was discovered to be efficient and dependable for automated platelet counter and detection

Liposomal Resveratrol Alleviates Platelet Storage Lesion via Antioxidation and the Physical Buffering Effect.

Platelet transfusion is essential in the treatment of platelet-related diseases and the prevention of bleeding in patients with surgical procedures. Platelet transfusion efficacy and shelf life are limited mainly by the development of platelet storage lesion (PSL). Mitigating PSL is the key to prolonging the platelet shelf life and reducing wastage. Excess intracellular reactive oxygen species (ROS) are one of the main factors causing PSL. In this study, we explored a nanomedicine strategy to improve the quality and functions of platelets in storage. Resveratrol (Res), a natural plant product, is known for its antioxidative effect. However, medical applications of Res are limited due to its low water solubility and stability. Therefore, we used a resveratrol-loaded liposomal system (Res-Lipo) to better utilize the antioxidant effect of the drug. This study aimed to evaluate the effect of Res-Lipo on platelet oxidative stress and alleviation of PSL during the storage time. Res-Lipo scavenged intracellular ROS and inhibited platelet apoptosis and activation during storage. Res-Lipo not only maintained mitochondrial function but also improved platelet aggregation in response to adenosine 5'-diphosphate. These results revealed that Res-Lipo ameliorated PSL and prolonged the platelet survival time in vivo. The strategy provides a potential method for extending the platelet storage time and might be considered a potential and safe additive to alleviate PSL.

MXRA7 is involved in megakaryocyte differentiation and platelet production.

Matrix remodeling is a critical process in hematopoiesis. The biology of MXRA7, as a matrix remodeling associated gene, has still not been reported in hematopoietic process. Public databases showed that MXRA7 expressed in hematopoietic stem cells, suggesting that it may be involved in hematopoiesis. We found that the amounts of megakaryocytes were lower in bone marrow and spleen from Mxra7-/- mice compared with that from wild-type mice. Knock-out of MXRA7 also reduced the amount of platelet in peripheral blood and affected the function of platelets. Knock-out of MXRA7 inhibited hematopoietic stem/progenitor cells differentiate to megakaryocytes possibly through down-regulating the expression of GATA-1 and FOG-1. Moreover, knockdown of MXRA7 in MEG-01 cells could inhibit the cell proliferation and cell apoptosis. Knockdown of MXRA7 inhibited the differentiation of MEG-01 cells and proplatelet formation through suppressing the ERK/MAPK signaling pathway and the expression of β-tubulin. In conclusion, the current study demonstrated the potential significance of MXRA7 in megakaryocyte differentiation and platelet production. The novel findings proposed a new target for the treatment of platelet-related diseases, and much more investigations are guaranteed to dissect the mechanisms of MXRA7 in megakaryocyte differentiation and platelet production.

Etiological Profiles of Patients With Thrombocytopenia in Central India: A Tertiary Centre Study.

Introduction Platelet-related disease may result from an abnormal platelet count, namely thrombocytopenia or thrombocythemia, or altered platelet function, and thus is associated with bleeding or with thrombotic manifestation. Thrombocytopenia is defined as a subnormal number of platelets i.e. less than 1,50,000/µL in the peripheral blood. It can lead to inadequate clot formation and increased risk of bleeding and is a common indication for bone marrow aspiration and biopsy. Methodology The study was a hospital-based prospective observational study from January 2019 to June 2020. All cases of thrombocytopenia which were diagnosed first on haematology analyser (platelet counts <150,000/µL) and confirmed subsequently by peripheral smear with/without bleeding manifestations due to thrombocytopenia were taken up for the study. The aims and objectives of this study were to find out the epidemiological spectrum and prevalence of thrombocytopenia according to age and sex along with the correlation of haematological and bone marrow findings of such patients. Result This study comprised 100 cases of thrombocytopenia, with acute leukaemia accounting for the majority (28/100), followed by dimorphic anaemia (15/100), megaloblastic anaemia (11/100), hypocellular marrow, infection, and other conditions.All cases (100%) displayed the clinical symptom of widespread weakness and pallor, which was followed by fatiguability (72%) and dyspnoea (48%). Many thrombocytopenic individuals also had lymphadenopathy and hepatomegaly, the last two least common appearances. Lymphadenopathy and hepatomegaly which were the last two least common presentations were present in a significant number of thrombocytopenic patients. Conclusion The study of bone marrow is helpful in the diagnosis of thrombocytopenia cases. Bone marrow examination is a simple, safe outpatient procedure and yields an impressive amount of diagnostically valuable data in a wide variety of disorders of thrombocytopenia.An evaluation of the patient's bone marrow unquestionably aids in the early diagnosis and treatment of their ailment.

The role of miRNAs in regulation of platelet activity and related diseases - a bioinformatic analysis

MicroRNAs (miRNAs) are small, non-coding RNAs, able to regulate cellular functions by induction of mRNA degradation and post-transcriptional repression of gene expression. Platelets are the major source of circulating miRNAs, with significant regulatory potential on cardiovascular pathophysiology and other diseases. MiRNAs have been shown to modify the expression of platelet proteins, which influence the platelets reactivity. Circulating miRNAs can be determined from plasma, serum, or whole blood, and they can be used as diagnostic and prognostic biomarkers as well as therapeutic targets including cardiovascular diseases (CVDs). Herein, we present original results from bioinformatic analyses, which identified top 22 platelet-related miRNAs including hsa-miR-320a, hsa-miR-16-5p, hsa-miR-106a-5p, hsa-miR-320b, hsa-miR-15a-5p, hsa-miR-15b-5p, hsa-miR-195-5p, hsa-miR-92a-3p as widely involved in platelet reactivity and associated diseases, including CVDs, Alzheimer’s and cerebrovascular diseases, cancer and hypertension. Analysis focused on the identification of the highly regulatory targets shared between those miRNAs identified 43 of them. Best ranked genes associated with overall platelet activity and most susceptible for noncoding regulation were PTEN, PIK3R1, CREB1, APP, and MAPK1. Top targets also strongly associated with CVDs were VEGFA, IGF1, ESR1, BDNF, and PPARG. Top targets associated with other platelet-related diseases including cancer identified in our study were TP53, KRAS, and CCND1. The most affected pathways by top miRNAs and top targets included diseases of signal transduction by Growth Factor Receptors (GDFRs) and second messengers, platelet activation, signaling, and aggregation, signaling by VEGF, MAPK family signaling cascades, and signaling by Interleukins. Terms specific only for platelet-related miRNAs included coronary artery disease, platelet degranulation, and neutrophil degranulation, while for the top platelet-related genes it was Estrogen Signaling Receptor (ESR) mediated signaling, extra-nuclear estrogen signaling, and endometriosis. Our results show the novel features of platelet physiology and may provide a basis for further clinical studies focused on platelet reactivity. They also show in which aspects miRNAs can be promising biomarkers of platelet-related pathological processes.

Study on the intervention of platelet biological activity by ultrasound

Platelets are non-nucleated blood effector cells, which plays an important role in coagulation, hemostasis, and thrombosis. However, platelets are extremely susceptible to activation by external stimuli, which in turn damages the platelet's natural biological activity and affects its biological function. Platelet biological activity has become a hotspot in the field of vascular diseases. In this study, ultrasound parameters (ultrasound intensity and duration time) were used to intervene in the biological activity of platelets. The response of platelets to ultrasound energy was explored from the aspects of platelet morphology, aggregation ability and particle release (the expression of P-selectin and the number of particles). The results showed that the ultrasound intensity of 0.25 W/cm 2 (1 MHz, 60 s) had no effect on the morphology, aggregation ability and particle release of platelets. When the ultrasonic intensity was increased to greater than 0.25 W/cm 2, the generation of platelet pseudopods, morphological changes, increase of particle release, as well as effect on aggregation were observed. When the ultrasound duration time was 60 s (1 MHz, 0.25 W/cm 2), it had no effect on the biological activity of platelets. However, when the ultrasound time was greater than 60 s, the morphology, aggregation ability and microparticles release would been induced with no effect on the secretion of CD62P and total protein components. Therefore, when the ultrasound parameters were 1 MHz and 0.25 W/cm 2 with 60 s duration time, the ultrasound energy had no effect on the biological activity of platelets. The results in this study are of great significant for ultrasound energy intervention for the treatment of platelet-related diseases.

Quantitative systems pharmacology model of thrombopoiesis and platelet life-cycle, and its application to thrombocytopenia based on chronic liver disease.

Platelets are produced by hematopoietic stem cells via megakaryocytes in the bone marrow and play a critical role in hemostasis. The aim of this study was to develop a new platelet model based on the thrombopoiesis and platelet life‐cycle by a quantitative systems pharmacology modeling approach, which could describe changes in platelet count profiles in platelet‐related diseases and drug intervention. The proposed platelet model consists of 44 components. The model was applied to thrombopoiesis of a thrombopoietin receptor agonist, lusutrombopag. It could well describe the observed platelet count profiles after administration of lusutrombopag for both healthy subjects and patients with chronic liver disease and thrombocytopenia. This model should be useful for understanding the disease progression of platelet‐related conditions, such as thrombocytopenia and for predicting platelet count profiles in various disease situations related to platelets and drug administration in drug development.

Electrochemical Detection Method Using Serotonin Oxidation inside a Single Human Platelet

An early diagnosis of platelet-related diseases is important for maintaining a healthy human life for blood clotting disorders caused by internal and/or external stimuli. Various technologies based on physics and chemistry have been developed for the detection of platelets. These methods are mainly set up in clinical laboratory and hospitals, cannot be portable, and require both complex pretreatment procedure and expensive detectors for platelet detection. Platelets are one of the human blood compositions and an important role in blood coagulation. Therefore, it is necessary to develop a method that can be adopted as a medical device capable of diagnosis in everyday life. We proposed an electrochemical collision method for direct detection of serotonin in a single platelet from human blood. This method is based on collisions of platelets with an ultramicroelectrode (UME) and observed the oxidation signal of serotonin without any modification of electrode through single-entity electrochemistry (SEE). When a platelet collides with the UME, secreted serotonin from the platelet gets oxidized at the electrode surface generating anodic currents. In our methods, the current for effective detection of platelets is very sensitive because there is no redox species. Studies on biomolecule detection through SEE can be useful for measuring the number of blood cells in our blood. Observing changes in the current that occur when platelets selectively collide with the UME, is medically useful information obtained cheaply and easily. The SEE method applied to blood analysis will be a new way to overcome the limitations of the existing sampling process, analysis time and environment. It is also expected to contribute to the development of high-performance sensors based on point-of-care-testing (POCT) devices capable of on-site and real-time diagnosis.

Rumex acetosa modulates platelet function and inhibits thrombus formation in rats

BackgroundThe Rumex acetosa has been used in medicinal treatment, food technology and phytotherapeutics in Eastern Asia and many other countries. However, its effect on cardiovascular system and antiplatelet activity remained to be known. In this study, we examined the antiplatelet activity of R. acetosa in detailed manner to understand underlying mechanism.MethodsTo study this, whole blood was obtained from male Sprague Dawley (SD) rats and aggregation of washed platelets measured using light transmission aggregometry. Intracellular calcium ion concentration ([Ca2+]i) was measured using Fura-2/AM while ATP release evaluated by luminometer. Activation of integrin αIIbβ3 analyzed by flow cytometry and clot retraction. Furthermore, we studied the signaling pathways mediated by R. acetosa extract by western blot analysis.ResultsR. acetosa extract markedly inhibited collagen-induced platelet aggregation and ATP release in a dose-dependent manner. It also suppressed [Ca2+]i mobilization, integrin αIIbβ3 activation and clot retraction. The extract significantly attenuated phosphorylation of the MAPK pathway (i.e., ERK1/2, JNK), MKK4, PI3K/Akt, and Src family kinase.ConclusionTaken together, this data suggests that R. acetosa extract exhibits anti-platelet activity via modulating MAPK, PI3K/Akt pathways, and integrin αIIbβ3-mediated inside-out and outside-in signaling, and it may protect against the development of platelet-related cardiovascular diseases.

Three-D Models for Megakaryopoiesis and Platelet Production

Access to human platelets is fundamental in the quest for understanding the mechanisms of platelet-related diseases and the clinical need for platelet transfusions for patients. Effective solutions for producing platelets ex vivo are essential to obtaining this goal. Circulating platelets are highly specialised cells produced by megakaryocytes through the extension of unique pseudopods called pro-platelets. Leading studies point to the bone marrow niche as the core of blood cell production, revealing interesting and complex environmental factors for consideration. Megakaryocytes take cues from the physic-chemical 3D environment in the bone marrow, which includes contact with extracellular matrix components, interaction with other cell types, particularly endothelial cells, and the shear stress generated by the blood circulation into the sinusoid lumen. The technical impossibility of obtaining an intact bone marrow organ prompted the investigation of potential models to extrapolate ex vivo structures and functions to gain new insight on its activity. Thus, future advancements in the study of megakaryopoiesis depend on the evolution of bioengineering techniques for developing physiologically relevant models that reproduce the conditions in the bone marrow niche environment. Silk fibroin, derived from Bombyx mori silkworm cocoons,1 is one of the most promising biomaterials for bone marrow tissue engineering due to its tunable architecture and mechanical properties. Silk is a naturally derived, biocompatible biomaterial, which can be prepared in a range of material formats and processed entirely in aqueous systems allowing the incorporation of labile compounds without loss of bioactivity (e.g., extracellular matrix components). Exploiting innovative silk biomaterials, we have developed a series of 3D scalable systems that reproduce structure and composition of the human bone marrow, supporting natural platelet release from megakaryocytes.2-4 Data demonstrate that 1) silk supports platelet production maintaining their function without premature activation; 2) silk surface topography and stiffness direct megakaryocyte behaviour by activating mechanosensors and calcium signalling; 3) bloodstream impact on megakaryocyte function can be mimicked by perfusing the silk models at different shear rate and flows; 4) silk functionalisation with fibronectin and/or endothelial cells enhances megakaryocyte function; 5) silk models can be used to reproduce and study the primary megakaryocyte related disorders such as Myeloproliferative Neoplasms and Inherited Thrombocytopenias; 6) the same silk models can be exploited to test drug efficacy and/or toxicology on a per patient basis. Our models provide valuable and unique technology to reproduce the complexity of human bone marrow and study megakaryocytes and platelet formation. The silk platform has potentially limitless applications for basic research, clinic, pharmaceutical industry and transfusion medicine. Omenetto FG and Kaplan DL. New opportunities for an ancient material. Science. 2010; 329: 528. Di Buduo CA, Wray LS, Tozzi L, et al. Programmable 3D silk bone marrow niche for platelet generation ex vivo and modeling of megakaryopoiesis pathologies. Blood. 2015; 125: 2254. Di Buduo CA, Soprano PM, Tozzi L, et al. Modular flow chamber for engineering bone marrow architecture and function. Biomaterials. 2017; 146: 60. Abbonante V, Di Buduo CA, Gruppi C, et al. A new path to platelet production through matrix sensing. Haematologica. 2017; 102: 1150. Disclosures No relevant conflicts of interest to declare.

Zinc Homeostasis in Platelet-Related Diseases.

Zn2+ deficiency in the human population is frequent in underdeveloped countries. Worldwide, approximatively 2 billion people consume Zn2+-deficient diets, accounting for 1–4% of deaths each year, mainly in infants with a compromised immune system. Depending on the severity of Zn2+ deficiency, clinical symptoms are associated with impaired wound healing, alopecia, diarrhea, poor growth, dysfunction of the immune and nervous system with congenital abnormalities and bleeding disorders. Poor nutritional Zn2+ status in patients with metastatic squamous cell carcinoma or with advanced non-Hodgkin lymphoma, was accompanied by cutaneous bleeding and platelet dysfunction. Forcing Zn2+ uptake in the gut using different nutritional supplementation of Zn2+ could ameliorate many of these pathological symptoms in humans. Feeding adult rodents with a low Zn2+ diet caused poor platelet aggregation and increased bleeding tendency, thereby attracting great scientific interest in investigating the role of Zn2+ in hemostasis. Storage protein metallothionein maintains or releases Zn2+ in the cytoplasm, and the dynamic change of this cytoplasmic Zn2+ pool is regulated by the redox status of the cell. An increase of labile Zn2+ pool can be toxic for the cells, and therefore cytoplasmic Zn2+ levels are tightly regulated by several Zn2+ transporters located on the cell surface and also on the intracellular membrane of Zn2+ storage organelles, such as secretory vesicles, endoplasmic reticulum or Golgi apparatus. Although Zn2+ is a critical cofactor for more than 2000 transcription factors and 300 enzymes, regulating cell differentiation, proliferation, and basic metabolic functions of the cells, the molecular mechanisms of Zn2+ transport and the physiological role of Zn2+ store in megakaryocyte and platelet function remain elusive. In this review, we summarize the contribution of extracellular or intracellular Zn2+ to megakaryocyte and platelet function and discuss the consequences of dysregulated Zn2+ homeostasis in platelet-related diseases by focusing on thrombosis, ischemic stroke and storage pool diseases.

Effects and Mechanisms of Vitamin C Post-Conditioning on Platelet Activation after Hypoxia/Reoxygenation

Background: Platelet activation occurs upon ischemia/reperfusion and is related to the generation of reactive oxygen species (ROS) during this process. Vitamin C (VC) is a powerful antioxidant. VC scavenges ROS, reduces platelet activation, and attenuates reperfusion injury. However, the effects of VC on platelets undergoing hypoxia/reoxygenation (H/R) remain unclear. Objectives: Herein, we evaluated the effects of VC on platelets in vitro following H/R and the related mechanisms. Method: Fresh platelets were collected from 67 volunteers at the Blood Center of Hebei Province. Platelets were diluted with saline to a concentration of 2.00 × 10¹¹/L. Aggregation and the curve slope were evaluated within 4 h with a whole-blood impedance analyzer. To determine the optimal experimental time, platelets were treated with hypoxia or reoxygenation for different times, and impedance aggregometry was carried out by measuring changes in electrical impedance induced by arachidonic acid (0.5 mM) and adenosine diphosphate (10 µM), thereby establishing the H/R model. Three antioxidants (VC, melatonin, and probucol) were used to treat platelets after H/R, and impedance aggregometry was used to determine their effects on platelet aggregation. The influence of VC on apoptosis-related indicators was detected. ROS and the mitochondrial membrane potential were observed by inverted fluorescence microscopy and flow cytometry, respectively. Related protein levels were detected by Western blotting. Results: ROS scavengers inhibited platelet activation and aggregation in a concentration-dependent manner. VC post-conditioning scavenged ROS, downregulated cytochrome C, Bax, and caspase-9 proteins, and upregulated Bcl-2 protein. These effects collectively blocked platelet apoptosis and inhibited platelet aggregation. Conclusions: VC inhibited platelet aggregation by blocking apoptosis. Thus, VC may have applications in the treatment of platelet-related diseases.

Autophagic regulation of platelet biology.

Platelets, developed from megakaryocytes, are characterized by anucleate and short-life span hemocyte in mammal vessel. Platelets are very important in the cardiovascular system. Studies indicate the occurrence of autophagy platelets and megakaryocytes. Moreover, abnormal autophagy decreases the number of platelets and suppresses platelet aggregation. In addition, mitophagy, as a kind of selective autophagy, could inhibit platelet aggregation under oxidative stress or hypoxic, whereas promote platelet aggregation after reperfusion. Finally, autophagy regulates hemorrhagic and thrombosis diseases by influencing the number and function of platelets. In this paper, the role of autophagy in platelets and megakaryocytes, as well as coupled with the promotive or inhibitory role of hemorrhagic and thrombosis diseases are elucidated. Therefore, autophagy may be a potentially therapeutic target in modulating the platelet-related diseases.

Recent advances in mechanisms of megakaryopoiesis and platelet formation

Platelets are specialized cells, which are functioned to prevent bleeding and minimize blood vessel injury, and are also the predominating factor in the processes of hemostasis and thrombosis, while implicate in other processes including inflammation, innate immunity, angiogenesis and tumor metastasis. Among current mechanisms of platelet formation, platelets are produced by megakaryocytes, which are themselves generated by a process of controlled differentiation and maturation of bone marrow hematopoietic stem cells (HSC) and progenitor cells. Megakaryocytes release platelets by extending long, branching proplatelets, into sinusoidal blood vessels. Bone marrow cavity and extracellular matrix composition together with cytokines as thrombopoietin (TPO) are key regulators of megakaryopoiesis by supporting cell differentiation and platelet formation. Understanding the mechanisms of megakaryocyte differentiation and platelet formation can provide a solid theoretical basis for the treatment of platelet-related diseases. This review summarizes the current scientific research progress in the mechanisms of megakaryopoiesis and thrombopoiesis. Key words: Megakaryocytes; Cell differentiation; Thrombopoiesis; Transcription factors; Apoptosis; Megakaryopoiesis

An acoustic strategy for gold nanoparticle loading in platelets as biomimetic multifunctional carriers.

In recent years, a wide variety of bioinspired colloidal particles with novel cell mimetic functions have been the subject of extensive research in materials science, chemistry, biology, physics, and engineering. However, most of the approaches are derived from natural cell membrane coatings, which are still too primitive compared with living cells. In this study, we have chosen gold nanoparticles (GNPs) to explore the bioactivity response of living platelets and nanoparticle loading efficiency under different ultrasonic intensity and frequency treatment conditions. The results show that GNPs with no surface modification could be easily loaded into intra-platelets by both incubation (30 min) and ultrasonic exposure (1 min) methods. The amount of GNP loading was (4.4 ± 0.9) × 10-3 and (5.8 ± 2.4) × 10-3 pg per platelet upon incubation and acoustic triggering (1 MHz, 0.25 W cm-2), respectively. Although the other US treatment intensities (0.75, 1.50 and 2.25 W cm-2) also promoted higher amounts of GNPs in the platelets, the higher US intensity might bring about partial damage of the platelet membrane. Compared with 1 MHz ultrasonic exposure, the change of the GNP loading amount was not significantly higher upon ultrasonic frequency treatment of 45, 80 or 100 kHz. Therefore, it has been found that an US intensity of 0.25 W cm-2 could facilitate the intra-platelet delivery efficacy of the GNPs without damaging the biological activity. Furthermore, two possible pathways of GNPs entering into platelets upon US treatment are presented: one is the endocytosis/open canalicular system (OCS), and the other is cell membrane permeability enhancement, which is proved by the SEM and TEM results. Finally, the GNP-loaded platelets have been demonstrated as useful probes for photoacoustic imaging (PAI) and dark-field microscopy (DFM)-based imaging, which might allow a wide range of potential applications in diagnostics and therapy of platelet-related diseases.

FUNDC2 regulates platelet activation through AKT/GSK-3β/cGMP axis.

AKT kinase is vital for regulating signal transduction in platelet aggregation. We previously found that mitochondrial protein FUNDC2 mediates phosphoinositide 3-kinase (PI3K)/phosphatidylinositol-3,4,5-trisphosphate (PIP3)-dependent AKT phosphorylation and regulates platelet apoptosis. The aim of this study was to evaluate the role of FUNDC2 in platelet activation and aggregation. We demonstrated that FUNDC2 deficiency diminished platelet aggregation in response to a variety of agonists, including adenosine 5'-diphosphate (ADP), collagen, ristocetin/VWF, and thrombin. Consistently, in vivo assays of tail bleeding and thrombus formation showed that FUNDC2-knockout mice displayed deficiency in haemostasis and thrombosis. Mechanistically, FUNDC2 deficiency impairs the phosphorylation of AKT and downstream GSK-3β in a PI3K-dependent manner. Moreover, cGMP also plays an important role in FUNDC2/AKT-mediated platelet activation. This FUNDC2/AKT/GSK-3β/cGMP axis also regulates clot retraction of platelet-rich plasma. FUNDC2 positively regulates platelet functions via AKT/GSK-3β/cGMP signalling pathways, which provides new insight for platelet-related diseases.

Regulation of the Megakaryocyte Development and the Platelet Production--Review

The main physiological function of megakaryocytes is the production of platelets, whose development, maturation and platelet production are a complex regulatory process, and are involved in many factors. In recent years it was found that the lung is also the main site of megakaryocyte-producing platelets in addition to bone marrow. Based on the findings of recent years, this review summarizes the process of megakaryocyte development, maturation and platelet production, with emphasis on the analyzing the regulatory effects of apoptotic factors, miRNA, thrombopoietin and its receptors, interleukins, transcription factors and their corresponding signal pathways on platelet production. To understand the regulatory mechanism of platelet production can help to understand the pathological mechanism of platelet-related diseases and provide new ideas for the diagnosis and treatment of platelet-related diseases.