Thrombopoiesis Research Articles

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

Progress on novel agents treating childhood primary immune thrombocytopenia

The mechanisms of childhood primary immune thrombocytopenia(ITP) are the destruction of platelet by platelet antibody and cytotoxic T cells, which also influence the function of megakaryocyte and cause the reduction of platelet.Novel agents targeted to the immune abnormalities of ITP includes 4 types: (1)CD40-CD154 pathway blocker, such as humanized CD154 antibody Toralizumab, which is monoclonal antibody and modify Fc, hopefully to be used in treatment of ITP.(2)The drugs which block the binding between Fc receptor and anti-platelet antibody such as Rozrolimupab, which is the combination of 25 kinds of anti-RHD and presents 62% efficacy but has severe hemolysis as adverse effects which restricts the application on ITP.Soluble FcγRIIb(SM101) is also effective on ITP and it conquer the shortcome of activating of B cells to induce autoimmune diseases.(3)The drugs which block the key molecular Syk of activation the platelet phagocytosis by microphage such as R788, with 44% effectiveness.(4)The drugs which stimulate thrombopoiesis such as Avatrombopag et al. Key words: Thrombocytopenia; Immunity; Primary; New drugs; Child

MicroRNA regulation in platelet production

Platelets are produced through megakaryocytic lineage commitment, proliferation, maturation, and functional activation of hematopoietic stem cells (HSC). Platelets play an essential role in hemostasis and thrombosis. Megakaryocytopoiesis is regulated by many factors, including microRNA (miRNA). miRNAs are a family of 21 to 25 nucleotide small nonprotein-coding RNAs. They widely exist in various organisms and involve in transcriptional gene expression control. Recently, the roles of miRNA in regulating megakaryocytopoiesis have got more and more attention. Many new miRNAs which involve in this process have been discovered and their functioning mechanisms have been illustrated. In the future, as research continues, the new drugs or therapies based on miRNA may be applied to clinic treatment, and may benefit the patients with platelet dysgenesis. In this article, the authors will review the research progress of miRNA regulation in platelet production. Key words: MicroRNAs; Thrombopoiesis; Transcription factor; Signal transduction

The curative effect of intensive regulating lipid by atorvastatin in the treatment of unstable angina and its influence on serum hs-CRP

Objective To observe the curative effect of intensive regulating lipid by atorvastatin in the treatment of unstable angina and its influence on serum high sensitive C-reactive protein(hs-CRP).Methods 60 patients with unstable angina were randomly divided into two groups:the routine treatment group( basic treatment plus atorvastatin 10mg/d),the atorvastatin intensive treatment group( basic treatment plus atorvastatin 40mg/d.)The courses of treatment were both 8 weeks.The differences in the amount of serum hs-CRP,blood fat,the effect of electrocardiogram and the use of glyceryl trinitrate before and after the treatment were observed and compared.Results The differences in the angina curative effect and the amount of serum hs-CRP between the two groups were statistically sig nificant( all P ＜0.05 ).Conclusion Short-term intensive regulating lipid by statins was effective in treating unstable angina,and could quickly relieve the phlogosis in the vessels,prevent the unstable plaque from breaking and the thrombopoiesis,and thus prevent the occurrence of cardiovascular disease. Key words: Unstable angina; Arteria coronaria disease; C-reactive protein; Atorvastatin

Thrombosis and prevention after transcatheter occlusion of atrial septal defect

Transcatheter closure as an alternative to medical surgery has become a preferred therapeutic method to atrial septal defect (ASD).However,thrombopoiesis after occluder implantation has been reported comprehensively and causes a series of serious complications such as cerebral embolism、myocardial infarction,pulmonary embolism and so on.Reasons of device thrombopoiesis are closely associated with atrial fibrillation,persistent atrial septal aneurysm,occluder type,activated coagulation system and occluder endothelialization process.This paper summarizes correlation factors of occluder thrombopoiesis and current related prevention proposal after transcatheter closure of ASD,and provides theoretical and experimental foundation for prevenition of device thrombopoiesis after occluder implantation of ASD. Key words: Atrial septal defect; Intervention; Occlusion; Thrombosis

Measurement of immature platelet fraction using the automatic hematology analyzer and its clinical utility

Objective The immature platelet fraction (IPF) could be detected quantificationally in Sysmex XE-2100 with the software of XE-pro and IPF master.The study aimed to perform the methodological evaluation of IPF detection and investigate the clinical significance for the monitoring for bone marrow hyperplasia in cancer chemotherapy patients.Methods The high-level, middle-level and low-level whole blood samples were randomly chosen for detection repeatly 20 times to obtain interrun coefficient of variation (CV) for evaluation of the precision and reproducibility. Integrated quality controls were determined for continuous 20 days to obtain intrarun CV, and the stability and carryover was investigated.Furthermore, the correlation between results from Sysmex XE-2100 and results from flow cytometry was assessed.182 healthy subjects and 130 cancer patients undergoing chemotherapy were selected and the latter were divided into two groups according to platelet counts after therapy, one was normal PLT group, the other was decreased PLT group.The IPF of either group was measured and was compared with each other.Results The precision of IPF for high-level, middle-level and low-level were 4.71%, 4.33% and 4.95%, respectively, they were less than 5%.The interrun CV of IPF detection for middle-level and low-level were less than 5%.The interrun CV of IPF detection for high-level were less than 10%.The carryover ranged from 0.6% to 2.7%,and the average rate was 1.2%.A good correlation for IPF detection was shown between results from Sysmex XE-2100 and flow cytometry(r = 0.880 9,P ＜ 0.01).Regarding clinical utility of IPF detection in treatment monitoring for chemotherapy effect, the median of IPF levels in decreased PLT group, normal PLT group,control group were 14.45% ,7.35% and 15.68%, respectively.There was significant difference among the three groups (H =49.032,P ＜0.01 ).The IPF level was higher in decreased PLT group than normal PLT group (t = -5.681, P ＜ 0.O1 ), and was lower in normal PLT group after chemotherapy than the control group (t = -6.662 ,P ＜0.01 ).Conclusions The determination of IPF by the Sysmex XE-2100 owns high precision and good stability. IPF is an effective marker for evaluation of thrombopoietic condition in the cancer chemotherapy patients. Key words: Platelet count; Blood cell count; Flow cytometry; Thrombopoiesis

Macrophage derived signalling regulates negatively the megakaryocyte compartment.

Megakaryocytopoiesis is the process by which stem cells go through a process of commitment, proliferation and differentiation leading to the production of platelets. In the mouse, this process is accomplished within the bone marrow (BM) and spleen microenvironment and is carried out by regulatory molecules and accessory cells including macrophages, fibroblasts and endothelial-like cells. Previously, we have reported that macrophage depletion following administration of liposomal clodronate (LIP-CLOD) provokes enhancement of both, megakaryocytopoiesis and thrombocytopoiesis. In this report, we investigated the changes in the compartment of megakaryocyte progenitor cells (MK-CFU), their correlation with plasmatic thrombopoietin (TPO) and TPO transcription levels after macrophage depletion. LIP-CLOD-treated mice showed an increase of the MK-CFU in BM and spleen. Concerning TPO plasma levels, kinetic studies revealed a 1.5- and 1.3-fold increase in the TPO concentration at 12 and 24 hr of treatment. We also show evidence of regulation of TPO transcription in the liver and spleen. Although empty liposomes also enhanced TPO gene regulation in these organs, transcriptional TPO up regulation correlated with an increase of protein synthesis only in those animals where macrophages were effectively removed. Taken together, these results suggest that BM and spleen macrophages derived signalling regulates negatively the megakaryocyte compartment.

What is the optimal dose and duration of treatment with etoposide? I. Maximum tolerated duration of daily treatment with 50, 75, and 100 mg of oral etoposide.

Because etoposide is a cell-cycle phase-specific drug, its degree of cytotoxicity likely relies on duration of cell exposure to a specific concentration. We investigated the maximum tolerated duration of oral etoposide treatment at doses of 100, 75, and 50 mg/d in previously treated patients with biopsy-proven, advanced cancer. "Maximum tolerated" was defined as tumor progression or hematologic toxicity (World Health Organization [WHO] grade > or = 2). The maximum tolerated duration in 19 patients given 100 mg/d was > or = 21 days, since this was the predetermined cutoff point; 3 patients discontinued etoposide because of early tumor progression, and 6 others had developed leukopenia or thrombocytopenia (WHO grade > 2) by day 21. The maximum tolerated duration in 13 patients given 75 mg/d was a median of 11 weeks (range, 2 to 19); 6 patients developed tumor progression and 6 others leukopenia (WHO grade > or = 2) requiring discontinuation of treatment. Ten patients given 50 mg/d tolerated therapy for a median of 13 weeks (range, 3 to 26 weeks); treatment was halted in seven patients because of tumor progression, two because of leukopenia (WHO grade > or = 2), and one because of stomatitis. The data from this study and others suggest that above a certain minimal plasma level, etoposide induces concentration-dependent cumulative toxicity. What remains to be determined is the minimal plasma level per tumor type. It will also be interesting to see whether myelopoiesis, thrombocytopoiesis, and erythropoiesis have differential sensitivity to etoposide, since thrombocytopenia did not occur using daily etoposide doses of 50 and 75 mg, whereas at the same doses 10 of 23 patients required erythrocyte transfusion.

Inv (3) (q21q26) Associated with Abnormal Thrombopoiesis in a Ph-positive Chronic Myelocytic Leukemia

We report a rarely occurred paracentric inversion of the long arm of chromosome 3, i. e. inv (3) (q21q26), observed in patient of Ph-positive chronic myelocytic leukemia with abnormal thrombopoiesis. To our knowledge, this is the sixth case reported in English literature. This additional chromosome marker usually appears in the late chronic phase or blastic phase of chronic myelocytic leukemia, and indicates a poor prognosis. Its relationship to abnormal thrombopoiesis is also discussed. (J Genet Mol Biol 1990; 1: 14-21)

Platelet and fibrinogen production: relative sensitivities to endotoxin.

The relative sensitivities of platelet and fibrinogen production to endotoxin were determined in male New Zealand rabbits. E. coli endotoxin was administered in single intravenous doses of 0.1 to 50.0 mu/g/kg body mass. 75SeM was injected 5, 12, or 18 hr after endotoxin, and the percent incorporation into platelets and fibrinogen was used to measure thrombopoiesis and fibrinogen synthesis. Leukopenia occurred after the infusion of endotoxin at all dose levels; the lowest dose that caused thrombocytopenia was 0.5 microgram/kg. Endotoxin was detected with the Limulus test in plasma of animals that received 5 to 50 microgram/kg. The stimulation of fibrinogen and platelet production, as well as the postinfusion decrease in platelet count, correlated directly with the log of the dose of endotoxin infused. The lowest dose of endotoxin that stimulated platelet and fibrinogen production was 0.5 microgram/kg. In animals that received this dose of endotoxin, increased fibrinogen production was detected only when 75SeM was injected 5 hr later. In animals injected 5, 12, or 18 hr later. Increased platelet production was detected at these two doses only when 75SeM was injected 18 hr after endotoxin. The data indicate that fibrinogen and platelet production have similar sensitivities to endotoxin, although the time course of stimulation is different for these two blood components.

The effects of hemorrhage, hypoxia, and a preparation of erythropoietin on thrombopoiesis.

The effects of hemorrhage, hypoxia, or a preparation of erythropoietin on platelet production were investigated by measuring incorporation of selenomethionine-75Se (75SeM) into the platelets of rabbits or mice. Rabbits that were bled daily for 5 days had a significant increase in the platelet count, 48 hours after cessation of hemmorrhage, that coincided with a threefold increase in isotope incorporation into platelets. Mice that were bled daily for 3 days also had significantly higher platelet counts and a 38 per cent increase in incorporation of isotope into platelets, 3 days after the last hemorrhage. Normal rabbits, injected with plasma from repeatedly bled, anemic, and moderately thrombocytopenic rabbits, had a 58 per cent greater maximum incorporation of 75SeM than did control animals. Mice exposed to hypoxia for 6 days had a mean platelet count 23 per cent lower than normal controls, but no change in incorporation of 75SeM into platelets. Plasma from hypoxic mice did not stimulate platelet production when injected into normal mice. A preparation of human urinary erythropoietin (15 to 30 U. per mouse or 30 to 120 U. per rabbit) significantly increased incorporation of isotope into the platelets of normal mice and rabbits. The results demonstrated that hemorrhage, but not hypoxia, is associated with increased thrombopoietic activity in plasma. However, large doses of preparations of human erythropoietin contained detectable thrombopoietic activity.

Thrombocytopoiesis in W/Wv mice.

W/Wv mice are genetically anemic, but usually have normal numbers of circulating granulocytes and platelets. An intrinsic stem cell defect has been suggested by numerous experiments, and a reduced number of megakaryocytes has been found in the bone marrow. Platelet production in W/Wv mice and +/+ litter mate controls was studied by measurement of the incorporation of 75Se-methionine (SeM) into platelets after intravenous injection of 2 muCi of SeM. Mean incorporation of SeM into platelets of W/Wv mice was 17 per cent greater than that of +/+ controls at 66 hours. Mean platelet counts of W/Wv mice were not different from controls. Recovery from thrombocytopenia resulted in a greater proportion of labeled platelets in W/Wv mice, and a slight delay in recovery of the platelet count. These results suggest that W/Wv mice have a normal overall rate of thrombopoiesis despite having a decreased megakaryocyte mass.

Bioassay for thrombopoietin utilizing mice in rebound thrombocytosis.

A bioassay for the detection of the thrombopoietic stimulating factor (TSF or thrombopoietin) that utilizes thrombo–cythemic mice has been presented. A single injection of anti–mouse platelet serum (AMPS) to mice produced a characteristic thrombocytopenia that was followed by rebound thrombocytosis. Two to three days later (7–8 days after the AMPS injection), a significantly (p < 0.05) depressed thrombo–poiesis existed in response to the thrombocytosis. Normal and thrombocythemic mice were injected with normal sheep sera or sera from platelet–depleted sheep and Na235SO4 incorporation into platelets was measured. A greater difference in 35S uptake existed between AMPS–treated control mice (mice injected with normal sheep serum) and AMPS–treated stimulated mice (mice injected with serum from platelet–depleted sheep) than in normal mice treated with the same sera. Also, TSF in sheep sera was shown to lose activity after storage at −20°.

STUDIES ON THROMBOPOIESIS. III. THROMBOCYTOSIS-PROMOTING EFFECTS OF "THROMBOCYTHEMIC" AND "POLYCYTHEMIC" PLASMAS.

Abstract Thrombocyte responses were determined in groups of normal rats given multiple daily doses by gastric tube of the thermostable fraction of plasmas from patients with primary thrombocythemia or polycythemia vera and from normal human subjects. Control animals received water by the same route. Increases of 60 to 70 per cent in the recipients' platelet counts appear to constitute maximum responses obtainable with this assay technique. Daily doses of the "thrombocythemic" and "polycythemic" plasma extracts equal to 2 ml. of the original plasma per 100 grams body weight evoked, respectively, 71 and 73 per cent increases in the rats' platelet counts. Comparable amounts of normal plasma induced a 36 per cent increase in the recipients' circulating platelets. When the daily dose was decreased to 1 per cent of the rats' weights, thrombocytosis-promoting activity was no longer detectable in normal plasma. Recipients of lesser quantities of the "thrombocythemic" plasma manifested thrombocytosis equivalent to that brought about by twice the dose. The route of administration, dose-response relationship, and restoration of normal counts after treatment was stopped attest to the specificity of the stimulus contained in these test materials. Plasmas from 19 additional patients with polycythemia vera have exerted similar thrombocytosis-promoting effects in normal rats. These data provide further support for the thesis that a humoral regulator (or regulators) exerts physiologic and pathophysiologic control over thrombopoiesis.

A Study of the Thrombopoiesis in Various Thrombopenic States1

A Study of the Thrombopoiesis in Various Thrombopenic States¹

A Study of the Thrombopoiesis in Various Thrombopenic States1

A Study of the Thrombopoiesis in Various Thrombopenic States¹