Determination of Antibody Activity by Platelet Aggregation

Platelets play an important role in hemostasis by forming clots and stopping bleeding. In immune thrombotic conditions, platelets and leukocytes are aberrantly activated by pathogenic antibodies resulting in platelet aggregates and NETosis, leading to thrombosis and thrombocytopenia. A simple assay that assesses platelet function and antibody activity is light transmission aggregometry. This assay can be used to determine antibody activity in patients with disorders such as heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT). Briefly, for detection of pathogenic antibody, platelet-rich plasma (PRP) is treated with a specific agent (e.g., patient sera or purified patient antibodies) with constant stirring. Upon activation, platelets undergo a shape change and adhere to each other forming aggregates. This causes a reduction in opacity allowing more light to pass through PRP. Light transmission through the cuvette is proportional to the degree of platelet aggregation and is measured by the photocell over time. The advantage of this protocol is that it is a simple, reliable assay that can be applied to assess antibody activity in thrombotic conditions. Light transmission aggregometry does not require the use of radioactive reagents and is technically less demanding compared with 14C-serotonin release assay, another common assay for detecting antibody activity. Key features • This protocol can be used to assess platelet function and to detect platelet activating antibodies in diseases such as HIT and VITT. • Does not require radioactive reagents, requires an aggregometer; based on the light transmission aggregometry protocol, adapted for detection of VITT and other platelet-activating antibodies. • Two positive controls are required for reliable detection of antibodies in diseases such as HIT/VITT, namely a weak HIT/VITT antibody and a physiological agonist. • For detection of HIT/VITT antibodies, it is essential to use donors known to have platelets reactive to these antibodies to avoid false negative results.

NETosis and thrombosis in vaccine-induced immune thrombotic thrombocytopenia

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare yet serious adverse effect of the adenoviral vector vaccines ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Janssen) against COVID-19. The mechanisms involved in clot formation and thrombocytopenia in VITT are yet to be fully determined. Here we show neutrophils undergoing NETosis and confirm expression markers of NETs in VITT patients. VITT antibodies directly stimulate neutrophils to release NETs and induce thrombus formation containing abundant platelets, neutrophils, fibrin, extracellular DNA and citrullinated histone H3 in a flow microfluidics system and in vivo. Inhibition of NETosis prevents VITT-induced thrombosis in mice but not thrombocytopenia. In contrast, in vivo blockage of FcγRIIa abrogates both thrombosis and thrombocytopenia suggesting these are distinct processes. Our findings indicate that anti-PF4 antibodies activate blood cells via FcγRIIa and are responsible for thrombosis and thrombocytopenia in VITT. Future development of NETosis and FcγRIIa inhibitors are needed to treat VITT and similar immune thrombotic thrombocytopenia conditions more effectively, leading to better patient outcomes.

The mechanisms underlying the pathogenesis of vaccine-induced immune thrombotic thrombocytopenia (VITT) remain unclear. Here the authors show that anti-PF4 antibodies are responsible for the activation of platelets and neutrophils, and blockage of FcγRIIa or NETosis in vivo can prevent thrombosis.

Circulating platelet-neutrophil aggregates characterize the development of type 1 diabetes in humans and NOD mice

Platelet-neutrophil aggregates (PNAs) facilitate neutrophil activation and migration and could underpin the recruitment of neutrophils to the pancreas during type 1 diabetes (T1D) pathogenesis. PNAs, measured by flow cytometry, were significantly elevated in the circulation of autoantibody-positive (Aab⁺) children and new-onset T1D children, as well as in pre-T1D (at 4 weeks and 10–12 weeks) and T1D-onset NOD mice, compared with relevant controls, and PNAs were characterized by activated P-selectin⁺ platelets. PNAs were similarly increased in pre-T1D and T1D-onset NOD isolated islets/insulitis, and immunofluorescence staining revealed increased islet-associated neutrophil extracellular trap (NET) products (myeloperoxidase [MPO] and citrullinated histones [CitH3]) in NOD pancreata. In vitro, cell-free histones and NETs induced islet cell damage, which was prevented by the small polyanionic drug methyl cellobiose sulfate (mCBS) that binds to histones and neutralizes their pathological effects. Elevated circulating PNAs could, therefore, act as an innate immune and pathogenic biomarker of T1D autoimmunity. Platelet hyperreactivity within PNAs appears to represent a previously unrecognized hematological abnormality that precedes T1D onset. In summary, PNAs could contribute to the pathogenesis of T1D and potentially function as a pre-T1D diagnostic.

Clinical relevance of nitrated beta 2-glycoprotein I in antiphospholipid syndrome: Implications for thrombosis risk

Β₂-Glycoprotein I (β₂GPI) is an important anti-thrombotic protein and is the major auto-antigen in the antiphospholipid syndrome (APS). The clinical relevance of nitrosative stress in post translational modification of β₂GPI was examined.The effects of nitrated (n)β₂GPI on its anti-thrombotic properties and its plasma levels in primary and secondary APS were determined with appropriate clinical control groups. β2-glycoprotein I was nitrated at tyrosines 218, 275 and 309. β₂-glycoprotein I binds to lipid peroxidation modified products through Domains IV and V. Nitrated β₂GPI loses this binding (p < 0.05) and had diminished activity in inhibiting platelet adhesion to vWF under high shear flow (p < 0.01). Levels of nβ₂GPI were increased in patients with primary APS compared to patients with either secondary APS (p < 0.05), autoimmune disease without APS (p < 0.05) or non-autoimmune patients with arterial thrombosis (p < 0.01) and healthy individuals (p < 0.05).In conclusion tyrosine nitration of plasma β₂GPI is demonstrated and has important implications with regards to the pathophysiology of platelet mediated thrombosis in APS. Elevated plasma levels of nβ₂GPI in primary APS may be a risk factor for thrombosis warranting further investigation.

Evolving concepts of pathogenesis of heparin-induced thrombocytopenia: Diagnostic and therapeutic implications

Heparin-induced thrombocytopenia (HIT) is an immune reaction to heparin. It often causes severe thrombosis which may lead to limb gangrene and thrombosis-associated death. The concept of its pathogenesis has been evolving during the past five decades. Initially, HIT was thought to be caused by disseminated intravascular coagulation. Later it became clear that HIT was mediated by an immune mechanism whereby an IgG antibody induced platelet aggregation, release of procoagulant materials and consequently thrombus formation. The antigen comprises Platelet Factor 4 (PF4) and heparin which have a tendency to form ultralarge complexes. The HIT immune response has atypical features. IgG antibody appears early without IgM precedence and lasts transiently. One explanation is that there is prior priming by bacterial infection. Another unique characteristic is that it is processed as if it is a particulate antigen involving complement activation and B cells. Antigen-presenting cells/monocytes are also involved but the role of T cells is controversial. Recent advances have provided new insights into the underlying mechanisms of HIT-related thrombosis. Previously, platelets were believed to play a central role; their activation and consequently the induction of blood coagulation was the basis of the hypercoagulability in HIT. More recently, several studies have provided clear evidence that neutrophil and NETosis, monocytes and endothelial cells contribute significantly to the thrombosis in HIT. These new insights may result in development of better diagnostic laboratory assays and more effective treatments for HIT.

Updated international consensus report on the investigation and management of primary immune thrombocytopenia

Over the last decade, there have been numerous developments and changes in treatment practices for the management of patients with immune thrombocytopenia (ITP). This article is an update of the International Consensus Report published in 2010. A critical review was performed to identify all relevant articles published between 2009 and 2018. An expert panel screened, reviewed, and graded the studies and formulated the updated consensus recommendations based on the new data. The final document provides consensus recommendations on the diagnosis and management of ITP in adults, during pregnancy, and in children, as well as quality-of-life considerations.

CRISTAL: protocol for a cluster randomised, crossover, non-inferiority trial of aspirin compared to low molecular weight heparin for venous thromboembolism prophylaxis in hip or knee arthroplasty, a registry nested study

INTRODUCTION

Venous thromboembolism (VTE) is a serious complication following hip arthroplasty (HA) and knee arthroplasty (KA). This study aims to determine whether aspirin is non-inferior to low molecular weight heparin (LMWH) in preventing symptomatic VTE following HA and KA.

METHODS AND ANALYSIS

This is a cluster randomised, crossover, non-inferiority, trial nested within the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). The clusters will consist of Australian hospitals performing at least 250 HA and/or KA procedures per annum. All adult patients undergoing HA or KA will be included. The intervention will be aspirin, orally, 85-150 mg daily. The comparator will be LMWH (enoxaparin) 40 mg, subcutaneously, daily. Both drugs will commence within 24 hours postoperatively and continue for 35 days after HA and 14 days after KA. Each hospital will be randomised to commence with aspirin or LMWH and then crossover to the alternative treatment after meeting the recruitment target. Data will be collected through the AOANJRR via patient-reported surveys. The primary outcome is symptomatic VTE within 90 days post surgery, verified by AOANJRR staff. The primary analysis will include only patients undergoing elective primary total hip arthroplasty and total knee arthroplasty for osteoarthritis. Secondary outcomes will include symptomatic VTE for all HA and KA (including partial and revision) within 90 days, readmission, reoperation, major bleeding and death within 90 days and reoperation, death and patient-reported pain, function and health status at 6 months. If aspirin is found to be inferior, a cost-effectiveness analysis will be conducted. The study will aim to recruit 15 562 patients from 31 hospitals.

ETHICS AND DISSEMINATION

Ethics approval has been granted. Trial results will be submitted for publication. The trial is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12618001879257, pre-results) and is endorsed by the Australia and New Zealand Musculoskeletal Clinical Trials Network.

Romiplostim in adult patients with newly diagnosed or persistent immune thrombocytopenia (ITP) for up to 1 year and in those with chronic ITP for more than 1 year: a subgroup analysis of integrated data from completed romiplostim studies

The thrombopoietin receptor agonist romiplostim is approved for second-line use in chronic immune thrombocytopenia (ITP), but its effects in patients with ITP for ≤1 year are not well characterized. This analysis of pooled data from 9 studies included patients with ITP for ≤1 year (n = 311) or >1 year (n = 726) who failed first-line treatments and received romiplostim, placebo or standard of care. In subgroup analysis by ITP duration, patient incidences for platelet response at ≥75% of measurements were higher for romiplostim [ITP ≤1 year: 74% (204/277); ITP >1 year: 71% (450/634)] than for placebo/standard of care [ITP ≤1 year: 18% (6/34); ITP >1 year: 9% (8/92)]. Of patients with ≥9 months on study, 16% with ITP ≤1 year and 6% with ITP >1 year discontinued romiplostim and maintained platelet counts ≥50 × 109 /l for ≥6 months without ITP treatment (treatment-free remission). Independent of ITP duration, rates of serious adverse events and bleeding were lower with romiplostim than placebo/standard of care and thrombotic events occurred at similar rates. In this analysis, romiplostim and placebo/standard of care had similar safety profiles and romiplostim increased platelet counts in patients with either ITP ≤1 year or ITP >1 year, with more treatment-free remission in those with ITP ≤1 year.

Neutrophil activation and NETosis are the major drivers of thrombosis in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia/thrombosis (HIT) is a serious immune reaction to heparins, characterized by thrombocytopenia and often severe thrombosis with high morbidity and mortality. HIT is mediated by IgG antibodies against heparin/platelet factor 4 antigenic complexes. These complexes are thought to activate platelets leading to thrombocytopenia and thrombosis. Here we show that HIT immune complexes induce NETosis via interaction with FcγRIIa on neutrophils and through neutrophil-platelet association. HIT immune complexes induce formation of thrombi containing neutrophils, extracellular DNA, citrullinated histone H3 and platelets in a microfluidics system and in vivo, while neutrophil depletion abolishes thrombus formation. Absence of PAD4 or PAD4 inhibition with GSK484 abrogates thrombus formation but not thrombocytopenia, suggesting they are induced by separate mechanisms. NETs markers and neutrophils undergoing NETosis are present in HIT patients. Our findings demonstrating the involvement of NETosis in thrombosis will modify the current concept of HIT pathogenesis and may lead to new therapeutic strategies.

The pathogenesis of heparin-induced thrombocytopenia and thrombosis (HIT) is mediated by heparin-reactive autoantibodies binding to platelets (thrombocytes). Here the authors show neutrophil activation and NETosis are elevated in patients with HIT, and are essential for thrombosis in HIT mouse models.

Eltrombopag treatment during induction chemotherapy for acute myeloid leukaemia: a randomised, double-blind, phase 2 study

BACKGROUND

Patients with acute myeloid leukaemia frequently have thrombocytopenia during induction chemotherapy. Eltrombopag, an oral thrombopoietin receptor agonist, stimulates platelet production by a similar mechanism to endogenous thrombopoietin. This study investigated safety and efficacy of eltrombopag versus placebo during anthracycline-based induction treatment of patients with acute myeloid leukaemia.

METHODS

In this randomised, double-blind, phase 2 study, treatment-naive patients were recruited from clinical centres across 10 countries (Australia, Belgium, Canada, Greece, Hungary, Israel, South Korea, Poland, Russia, and the USA). Patients with acute myeloid leukaemia of any subtype except M3 and M7 were stratified by antecedent malignant haematological disorder (yes or no) and age (18-60 years or >60 years) and were then randomly assigned (1:1) using an automated interactive voice-response system randomisation schedule. Investigators and patients were blinded to study treatment. Starting on day 4, patients received standard induction chemotherapy (daunorubicin bolus intravenous infusion on days 1-3 [90 mg/m² for patients aged 18-60 years or 60 mg/m² for patients aged >60 years], plus cytarabine continuous intravenous infusion on days 1-7 [100 mg/m²]), with eltrombopag 200 mg (100 mg for east Asians) or placebo once daily, until platelet counts were 200 × 10⁹/L or higher, until remission, or after 42 days from the start of induction chemotherapy. The primary objective of the study was safety and tolerability assessed by adverse events, changes in left ventricular ejection fraction (LVEF), and clinical laboratory parameters in all treated patients. This study has been completed and is registered with ClinicalTrials.gov, number NCT01890746.

FINDINGS

Between Sept 7, 2013, and Jan 30, 2015, 149 patients were assessed for eligibility and 148 were then randomly assigned to receive eltrombopag (n=74) and placebo (n=74). Groups were matched in mean (SD) age (56·7 years [12·3] in the eltrombopag group vs 56·6 years [11·6] in the placebo group), mean (SD) initial platelet count (59·5 × 10⁹/L [43·3] vs 63·7 × 10⁹/L [48·0]), and poor-risk karyotype (16 [22%] of 74 patients in both groups). The most common grade 3-4 adverse events (≥10% in either group) were febrile neutropenia (31 [42%] vs 28 [39%]), decreased white blood cell count (8 [11%] vs 5 [7%]), and hypophosphataemia (3 [4%] vs 9 [13%]). Serious adverse events occurred in 24 (32%) patients in the eltrombopag group compared with 14 (20%) patients in the placebo group. 39 (53%) patients in the eltrombopag group died versus 29 (41%) patients in the placebo group. Thromboembolic events (5 [7%] vs 4 [6%]) and mean (SD) change in LVEF (-2·5% [7·8] vs -4·3% [8·5]) were similar.

INTERPRETATION

Data from this trial do not support combining eltrombopag with induction chemotherapy in patients with acute myeloid leukaemia.

FUNDING

Novartis Pharma AG.

American Society of Hematology 2018 guidelines for management of venous thromboembolism: heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction mediated by platelet-activating antibodies that target complexes of platelet factor 4 and heparin. Patients are at markedly increased risk of thromboembolism.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in their decisions about diagnosis and management of HIT.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 33 recommendations. The recommendations address screening of asymptomatic patients for HIT, diagnosis and initial management of patients with suspected HIT, treatment of acute HIT, and special situations in patients with acute HIT or a history of HIT, including cardiovascular surgery, percutaneous cardiovascular intervention, renal replacement therapy, and venous thromboembolism prophylaxis.

CONCLUSIONS

Strong recommendations include use of the 4Ts score rather than a gestalt approach for estimating the pretest probability of HIT and avoidance of HIT laboratory testing and empiric treatment of HIT in patients with a low-probability 4Ts score. Conditional recommendations include the choice among non-heparin anticoagulants (argatroban, bivalirudin, danaparoid, fondaparinux, direct oral anticoagulants) for treatment of acute HIT.

Identification of PDGF Receptors on Human Megakaryocytes and Megakaryocytic Cell Lines

Platelet-derived growth factor (PDGF) is a potent chemotactic and mitogenic factor implicated to play important roles in a variety of normal and pathophysiologic settings. We investigated PDGF receptor expression on human megakaryocytes and several megakaryocytic cell lines (CHRF, DAMI, Meg-01, M-07e) using enzyme-linked immunosorbent assay (ELISA), flow cytometry and immunocytochemical staining. Both PDGF receptor subtypes were identified on CHRF, DAMI, and Meg-01 cells by ELISA; PDGF beta-receptor levels exceeded alpha-receptor levels. Flow cytometry revealed that beta-receptor levels on CHRF and DAMI cells exceeded those on Meg-01 cells, and that M-07e expressed neither receptor. Immunocytochemical staining confirmed these findings and determined that bone marrow megakaryocytes also expressed PDGF receptors. Exposure of megakaryocytes to PDGF-BB dramatically induced the expression of the immediate-early gene, c-fos, within 30 min. Moreover, PDGF-BB significantly stimulated CHRF proliferation and colony formation. The present study demonstrates the presence of functional PDGF receptors on human megakaryocytes and their ability to mediate a mitogenic response.

Characterization of Fcγ Receptors on Human Megakaryocytes

Megakaryocyte and platelet Fcγ receptors (FcR) are of importance in the pathophysiology of immune complex-mediated thrombocytopenias such as heparin-induced thrombocytopenia. In this study, FcγR proteins and mRNAs in normal human megakaryocytes were examined. FcγR proteins were studied with immunocytochemical staining, dual colour flow cytometry and immunoprecipitation using monoclonal antibodies against FcγR I, FcγR II and FcγR III. FcγR mRNAs were measured with biotinylated cDNA or oligonucleotide probes using a novel quantitative in situ hybridization technique. Using these techniques, FcγR II protein and mRNA, but not FcγR I and FcγR III proteins and transcripts were detected in megakaryocytes. Further, transcript analysis showed that megakaryocytes contain only the transcript of FcγR IIA gene but no transcripts of FcγR IIB nor FcγR IIC genes; FcγR IIA transcripts with and without the transmembrane (TM) exon are present in approximately equal proportions. In contrast, neutrophils and macrophages also contain FcγR IIA transcript but FcγR IIA transcript with the TM exon predominates suggesting cell lineage-specific FcγR IIA expression. FcγR IIA transcript lacking the TM exon predicts the presence of a potential soluble form of FcγR in platelets and megakaryocytes which may have a physiological role as it can compete with the membrane-bound FcγR IIA for binding of IgG-containing immune complexes and thus protect these cells from excessive binding and injurious effects of immune complexes.

Plasma Macrophage Colony-Stimulating Factor and P-Selectin Levels in Malaria-Associated Thrombocytopenia

Thrombocytopenia is a common finding in malaria. In clinical trials, recombinant macrophage colony-stimulating factor (M-CSF) causes a reversible, dose-dependent thrombocytopenia, and high M-CSF has been reported in autoimmune thrombocytopenias. P-selectin, which is secreted into the plasma following platelet/endothelial activation or damage, is elevated in certain consumptive thrombocytopenic disorders. The relationships between thrombocytopenia, M-CSF and P-selectin were analysed in 63 patients with severe (n = 13) or uncomplicated (n = 26) P. falciparum (PF) or P. vivax (PV) malaria (n = 24). On admission, 69% of PF patients and 75% of PV patients were thrombocytopenic (platelets < 150 X 109/1). M-CSF was elevated in PF (3021 ± 1844 pg/ml) and PV (2602 ± 1668 pg/ml) patients, compared to controls (589 ± 200 pg/ml). The platelet count was inversely correlated with M-CSF in PF (r = -0.681), and in PV malaria (r = -0.548). Elevated P-selectin was found in severe PF malaria, but not in PV malaria. Severe PF malaria was associated with marked thrombocytopenia, very high M-CSF, elevated P-selectin and compelling evidence of disseminated intravascular coagulopathy (DIC). Platelet counts, M-CSF and P-selectin returned to control values in 7-14 days. These data suggest that elevated M-CSF in malaria, by enhancing macrophage activity, may result in increased macrophage-mediated platelet destruction. Further, platelet/endothelial activation or damage, as measured by P-selectin, or DIC could intensify thrombocytopenia in severe PF malaria, but does not appear to contribute to thrombocytopenia in uncomplicated PF or PV malaria.

The Clinical Usefulness of the Platelet Aggregation Test for the Diagnosis of Heparin-Induced Thrombocytopenia

The platelet aggregation test is widely used for the diagnosis of heparin-induced thrombocytopenia (HIT), a potentially serious complication of heparin therapy. We have evaluated its sensitivity and specificity in comparison with those of the 14C-serotonin release test. The sensitivity of the platelet aggregation test was found to vary with the heparin concentration and the donor of the platelets used in the test. The optimal heparin concentrations were between 0.1 and 1.0 U/ml. Using these heparin concentrations, the mean sensitivity varied from 39% (with the least reactive platelets) to 81% (with the most reactive platelets). In comparison, the sensitivity of the release test ranged from 65% to 94%. The specificities of the platelet aggregation test were 82%, 90% and 100% for the following control groups: (1) non-thrombocytopenic patients given heparin, (2) patients with thrombocytopenia due to other causes, and (3) normal controls not given heparin, respectively. The corresponding specificities for the release test was 94%, 90% and 100%. The specificities can be further increased to 100% for all controls with the adoption of a two-point system which defines a positive result as one in which platelet aggregation occurs with a low heparin concentration (0.5 U/ml) but not with 100 U heparin/ml. For optimal results, a two-point platelet aggregation test should be performed with heparin concentrations of 0.5 and 100 U/ml and using platelets of more reactive donors.

Anticardiolipin Antibodies Block the Inhibition by β2-Glycoprotein I of the Factor Xa Generating Activity of Platelets

Antiphospholipid antibodies, defined either by lupus anticoagulant (LA) activity or positive anticardiolipin immunoabsorbent assay (ACA) are associated with a predisposition to thromboses, recurrent fetal loss or thrombocytopenia. The mechanisms for these predispositions remain undefined. We have enriched immunoglobulin fractions from two patient plasmas to obtain antibodies with LA activity but no ACA, or conversely, with ACA positivity but no LA, in order to investigate in vitro characteristics which might explain a thrombotic propensity. β2-glycoprotein I (β2-GPI), the plasma cofactor required for ACA binding to negatively charged phospholipid, has previously been shown to inhibit prothrombinase generation in the presence of activated platelets (8). We now report that β2-GPI, at physiological concentrations, inhibits the generation of factor Xa in the presence of activated gel-filtered platelets. Further, ACA interferes with this inhibition, resulting in protracted, unopposed factor Xa generation. This interference with β2-GPI, a natural anticoagulant component of plasma, is potentially prothrombotic. LA immunoglobulins behave differently and inhibit factor Xa generation in a manner similar to β2-GPI. These findings provide the basis for a previously unsuspected mechanism for thrombosis in patients with aPL.

Quantification of NETs-associated markers by flow cytometry and serum assays in patients with thrombosis and sepsis

INTRODUCTION

Neutrophil extracellular traps (NETs) are networks of extracellular fibres produced from neutrophil DNA with a pathogenic role in infection, thrombosis and other conditions. Reliable assays for measuring NETs are desirable as novel treatments targeting NETs are being explored for the treatment of these conditions. We compare a whole blood flow cytometry method with serum assays to measure NETs-associated markers in patients with sepsis and thrombosis.

METHODS

Patients with deep venous thrombosis (n = 25), sepsis (n = 21) and healthy controls (n = 23) were included in the study. Neutrophil surface NETs markers were determined by flow cytometry on whole blood samples by gating of neutrophils stained for surface citrullinated histone (H3cit) and myeloperoxidase (MPO). Serum double-stranded (ds) DNA, MPO, myeloid-related protein, nucleosomes, DNAse, elastase, human high-mobility group box 1 and MPO-DNA complexes were quantified as circulating markers of NETs.

RESULTS

Neutrophil NETs markers by flow cytometry and serum NETs markers were significantly higher in patients with thrombosis and sepsis compared with healthy controls. Neutrophil NETs markers significantly correlated with the serum marker dsDNA.

CONCLUSION

Flow cytometry detection of neutrophil NETs markers is feasible in whole blood and correlates with serum markers of NETs. We propose the flow cytometry detection of MPO/H3cit positive neutrophils and serum dsDNA as simple methods to quantify cellular and extracellular NET markers in patients with thrombosis and sepsis.

Drug-induced immune thrombocytopenia: Mapping of the drug binding site to the membrane-proximal region of platelet GPIX

Drug-induced Immune thrombocytopenia (DIT) is a common complication of several medications, including commonly used antibiotics. The most widely studied DIT is caused by quinine. In DIT, antibodies predominantly bind to the platelet membrane glycoprotein (GP) IX in a drug-dependent fashion resulting in increased platelet clearance. Binding of the sensitizing drug, such as quinine, to GPIX has been proposed but is yet to be established. This work demonstrates that quinine is retained specifically by human GPIX. Quinine binding was first analyzed in wild-type mouse platelets and in transgenic mouse platelet expressing human GPIX using high performance liquid chromatography. Binding of quinine to GPIX was then measured in Chinese hamster ovary (CHO) cells expressing a combination of wild type, human or mouse, three human/mouse chimeric constructs and six mutant GPIX proteins. Quinine was retained by human GPIX. No detectable absorption was observed with mouse GPIX or human GPIbα. The quinine binding site was mapped to residues 110-115 of human GPIX suggesting that quinine interacts with specific residues of the GP. These findings provide further insights into the molecular mechanisms of DIT.

Megakaryocyte Differentiation and Platelet Formation from Human Cord Blood-derived CD34+ Cells

Platelet production occurs principally in the bone marrow in a process known as thrombopoiesis. During thrombopoiesis, hematopoietic progenitor cells differentiate to form platelet precursors called megakaryocytes, which terminally differentiate to release platelets from long cytoplasmic processes termed proplatelets. Megakaryocytes are rare cells confined to the bone marrow and are therefore difficult to harvest in sufficient numbers for laboratory use. Efficient production of human megakaryocytes can be achieved in vitro by culturing CD34⁺ cells under suitable conditions. The protocol detailed here describes isolation of CD34⁺ cells by magnetic cell sorting from umbilical cord blood samples. The necessary steps to produce highly pure, mature megakaryocytes under serum-free conditions are described. Details of phenotypic analysis of megakaryocyte differentiation and determination of proplatelet formation and platelet production are also provided. Effectors that influence megakaryocyte differentiation and/or proplatelet formation, such as anti-platelet antibodies or thrombopoietin mimetics, can be added to cultured cells to examine biological function.

Safety and efficacy of romiplostim in splenectomized and nonsplenectomized patients with primary immune thrombocytopenia

Primary immune thrombocytopenia is an autoimmune disorder characterized by increased platelet destruction and insufficient platelet production without another identified underlying disorder. Splenectomy may alter responsiveness to treatment and/or increase the risk of thrombosis, infection, and pulmonary hypertension. The analysis herein evaluated the safety and efficacy of the thrombopoietin receptor agonist romiplostim in splenectomized and nonsplenectomized adults with primary immune thrombocytopenia. Data were pooled across 13 completed clinical studies in adults with immune thrombocytopenia from 2002-2014. Adverse event rates were adjusted for time of exposure. Results were considered different when 95% confidence intervals were non-overlapping. Safety was analyzed for 1111 patients (395 splenectomized; 716 nonsplenectomized) who received romiplostim or control (placebo or standard of care). At baseline, splenectomized patients had a longer median duration of immune thrombocytopenia and a lower median platelet count, as well as a higher proportion with >3 prior immune thrombocytopenia treatments versus nonsplenectomized patients. In each treatment group, splenectomized patients used rescue medications more often than nonsplenectomized patients. Platelet response rates (≥50×10⁹/L) for romiplostim were 82% (310/376) for splenectomized and 91% (592/648) for nonsplenectomized patients (P<0.001 by Cochran-Mantel-Haenszel test). Platelet responses were stable over time in both subgroups. Exposure-adjusted adverse event rates were higher for control versus romiplostim for both splenectomized (1857 versus 1226 per 100 patient-years) and nonsplenectomized patients (1052 versus 852 per 100 patient-years). In conclusion, responses to romiplostim were seen in both splenectomized and nonsplenectomized patients, and romiplostim was not associated with an increase in the risk of adverse events in splenectomized patients. clinicaltrials.gov Identifier: 00111475(A)(B), 00117143, 00305435, 01143038, 00102323, 00102336, 00415532, 00603642, 00508820, 00907478, 00116688, and 00440037.

Changes in bone marrow morphology in adults receiving romiplostim for the treatment of thrombocytopenia associated with primary immune thrombocytopenia

The effects of romiplostim on bone marrow morphology were evaluated in adults with immune thrombocytopenia (ITP). Patients with platelet counts <50 × 10⁹/L, ≥1 prior ITP therapies, and no collagen at baseline received weekly subcutaneous romiplostim starting at 1 μg/kg, adjusted to maintain platelet counts between 50 and 200 × 10⁹/L. Biopsies were scheduled after 1, 2, or 3 years of romiplostim (cohorts 1, 2, and 3, respectively). Irrespective of scheduled time, biopsies were performed earlier if patients discontinued or failed to achieve/maintain a response to romiplostim. Reticulin (silver stain) and collagen (trichrome stain) were graded by two hematopathologists using the modified Bauermeister scale (0–4). Of 169 patients, 131 had evaluable biopsies; 9/131 (6.9 %) had increases of ≥2 grades on the modified Bauermeister scale (cohort 1: 0/34; cohort 2: 2/39; cohort 3: 7/58), including two with collagen. Three of the nine patients had follow-up biopsies, including one patient with collagen; changes were reversible after romiplostim discontinuation. Of the nine patients, one had neutropenia detected by laboratory test and two had adverse events of anemia, both non-serious and not treatment-related. By actual exposure (as some biopsies did not occur as scheduled), the number of patients with grade increases ≥2 were year 1: 3/41, year 2: 1/38, year 3: 5/52. Twenty-four patients sustained platelet counts ≥50 × 10⁹/L for ≥6 months with no ITP medications after discontinuing romiplostim, i.e., they entered clinical remission of their ITP. In conclusion, in patients with ITP receiving romiplostim, bone marrow changes were observed in a small proportion of patients.

ClinicalTrials.gov identifier: NCT#00907478

Expression and functional roles of estrogen receptor GPR30 in human intervertebral disc

Estrogen withdrawal, a characteristic of female aging, is associated with age-related intervertebral disc (IVD) degeneration. The function of estrogen is mediated by two classic nuclear receptors, estrogen receptor (ER)-α and -β, and a membrane bound G-protein-coupled receptor 30 (GPR30). To date, the expression and function of GPR30 in human spine is poorly understood. This study aimed to evaluate GPR30 expression in IVD, and its role in estrogen-related regulation of proliferation and apoptosis of disc nucleus pulposus (NP) cells. GPR30 expression was examined in 30 human adult NP and 9 fetal IVD. Results showed that GPR30 was expressed in NP cells at both mRNA and protein levels. In human fetal IVD, GPR30 protein was expressed in the NP at 12-14 weeks gestation, but was undetectable at 8-11 weeks. The effect of 17β-estradiol (E2) on GPR30-mediated proliferation and interleukin-1β (IL-1β)-induced apoptosis of NP cells was investigated. Cultured NP cells were treated with or without E2, GPR30 antagonist G36, and ER antagonist ICI 182,780. NP cell viability was tested by MTS assay. Apoptosis was determined by flow cytometry using fluorescence labeled annexin-V, TUNEL assay and immumnocytochemical staining of activated caspase-3. E2 enhanced cell proliferation and prevented IL-1β-induced cell death, but the effect was partially blocked by G36 and completely abrogated by a combination of ICI 182,780 and G36. This study demonstrates that GPR30 is expressed in human IVD to transmit signals triggering E2-induced NP cell proliferation and protecting against IL-1β-induced apoptosis. The effects of E2 on NP cells require both GPR30 and classic estrogen receptors.

Serotonin enhances megakaryopoiesis and proplatelet formation via p-Erk1/2 and F-actin reorganization

Our previous studies have shown that serotonin (5-hydroxytryptamine; 5-HT) is a growth factor for hematopoietic stem/progenitor cells. In this study, we proposed a possible mechanism: 5-HT may enhance megakaryopoiesis and proplatelet formation via Erk1/2 pathway and cytoskeleton reorganization. Here, 5-HT(2B)R was first identified in megakaryocytic cells. 5-HT also promoted the megakaryocytes (MKs) proliferation and reduced the cell apoptosis via the activation of 5-HT(2B)R and Akt pathway. The effects were reduced by the 5-HT2B R inhibitor ketanserin. The effect of 5-HT on proplatelet formation in bone marrow MKs were further confirmed: the 5-HT treated group had more proplatelet bearing MKs compared with the control group. To determine whether 5-HT has effects on cytoskeleton reorganization of MKs, and whether these effects could be reduced by ketanserin or Erk1/2 inhibitor PD98059, MKs were stained with the F-actin specific binder rhodamine-phalloidin. The polymerized actin level was lower in the control group than the 5-HT group and was distributed throughout the cytoplasm with occasional aggregations. Our data demonstrated that Erk1/2 was activated in MKs treated with 5-HT. This study suggests that 5-HT has a potent effect on platelet formation and this effect is likely mediated via 5HT(2B)R with subsequent activation of p-Erk1/2 and consequent F-actin reorganization and proplatelet formation. We also demonstrated that melatonin, the metabolite of 5-HT, exerts a protective effect on MK and platelet recovery in the irradiated mouse model. This study suggested that 5-HT plays an important role in platelet formation via 5HT(2B)R, p-Erk1/2, and F-actin reorganization.

Activation of tumour cell ECM degradation by thrombin-activated platelet membranes: potentially a P-selectin and GPIIb/IIIa-dependent process

The promotion of tumour metastasis by platelets may occur through several mechanisms including the induction of a more metastatic phenotype in tumour cells and assisted extravasation of circulating tumour cells. Whilst the mechanisms underlying platelet-assisted extravasation have been extensively studied, much less attention has been paid to the mechanisms underlying platelet promotion of an aggressive phenotype within a tumour cell population. Herein, we demonstrate in vitro that MDA-MB-231 breast carcinoma cells incubated with washed thrombin-activated platelet membranes adopt a Matrigel-degrading phenotype in a dose- and contact time-dependent manner. The same phenotypic change was observed with three other human tumour cell lines of diverse anatomical origin. Moreover, tumour cell lines that had been cultured with washed thrombin-activated platelet membranes had a greater metastatic capacity when injected into mice. This in vivo effect was reliant upon a co-incubation period of >2 h implying a mechanism involving more than platelet membrane binding that occurred within 5 min. Upon further investigation it was found that simultaneous blocking of the platelet-membrane proteins P-selectin and GPIIb/IIIa prevented interactions between platelet membranes and MDA-MB-231 cells but also significantly reduced the ability of tumour cells to degrade Matrigel. These results confirm that platelets induce a more aggressive phenotype in tumour cells but also identify the platelet proteins involved in this effect. P-selectin and GPIIb/IIIa also play a role in assisting tumour cell extravasation and, thus, are ideal targets for the therapeutic intervention of both stages of platelet-assisted metastasis.

Heme oxygenase-1 deficiency alters erythroblastic island formation, steady-state erythropoiesis and red blood cell lifespan in mice

Heme oxygenase-1 is critical for iron recycling during red blood cell turnover, whereas its impact on steady-state erythropoiesis and red blood cell lifespan is not known. We show here that in 8- to 14-week old mice, heme oxygenase-1 deficiency adversely affects steady-state erythropoiesis in the bone marrow. This is manifested by a decrease in Ter-119(+)-erythroid cells, abnormal adhesion molecule expression on macrophages and erythroid cells, and a greatly diminished ability to form erythroblastic islands. Compared with wild-type animals, red blood cell size and hemoglobin content are decreased, while the number of circulating red blood cells is increased in heme oxygenase-1 deficient mice, overall leading to microcytic anemia. Heme oxygenase-1 deficiency increases oxidative stress in circulating red blood cells and greatly decreases the frequency of macrophages expressing the phosphatidylserine receptor Tim4 in bone marrow, spleen and liver. Heme oxygenase-1 deficiency increases spleen weight and Ter119(+)-erythroid cells in the spleen, although α4β1-integrin expression by these cells and splenic macrophages positive for vascular cell adhesion molecule 1 are both decreased. Red blood cell lifespan is prolonged in heme oxygenase-1 deficient mice compared with wild-type mice. Our findings suggest that while macrophages and relevant receptors required for red blood cell formation and removal are substantially depleted in heme oxygenase-1 deficient mice, the extent of anemia in these mice may be ameliorated by the prolonged lifespan of their oxidatively stressed erythrocytes.

Immune thrombocytopenia: antiplatelet autoantibodies inhibit proplatelet formation by megakaryocytes and impair platelet production in vitro

Primary immune thrombocytopenia is an autoimmune disease mediated by antiplatelet autoantibodies that cause platelet destruction and suppression of platelet production. In vitro effects of autoantibodies on megakaryocyte production and maturation have been reported recently. However, the impact of these autoantibodies on crucial megakaryocyte functions, proplatelet formation and subsequent platelet release, has not been evaluated. We examined the effects of serum and IgG from 19 patients with immune thrombocytopenia using day 8 or 9 megakaryocytes (66.3 ± 10.6% CD41(+)), derived from cord blood hematopoietic stem cells (CD34(+)). The number of proplatelet-bearing megakaryocytes, the number of platelets released in the culture, total megakaryocyte numbers, ploidy pattern and caspase activation were measured at various times after treatment. After 5 days of treatment the number of proplatelet-bearing megakaryocytes was significantly decreased by 13 immune thrombocytopenia autoantibodies relative to the control group (P<0.0001) and this decrease was accompanied by a corresponding reduction of platelet release. Other features, including total megakaryocyte numbers, maturation and apoptosis, were not affected by immune thrombocytopenia antibodies. Treating the megakaryocytes with the thrombopoietin receptor agonists romiplostim and eltrombopag reversed the effect of the autoantibodies on megakaryocytes by restoring their capacity to form proplatelets. We conclude that antiplatelet antibodies in immune thrombocytopenia inhibit proplatelet formation by megakaryocytes and hence the ability of the megakaryocytes to release platelets. Treatment with either romiplostim or eltrombopag regenerates proplatelet formation from the megakaryocytes.

Art27 interacts with GATA4, FOG2 and NKX2.5 and is a novel co-repressor of cardiac genes

Transcription factors play a crucial role in regulation of cardiac biology. FOG-2 is indispensable in this setting, predominantly functioning through a physical interaction with GATA-4. This study aimed to identify novel co-regulators of FOG-2 to further elaborate on its inhibitory activity on GATA-4. The Art27 transcription factor was identified by a yeast-2-hybrid library screen to be a novel FOG-2 protein partner. Characterisation revealed that Art27 is co-expressed with FOG-2 and GATA-4 throughout cardiac myocyte differentiation and in multiple structures of the adult heart. Art27 physically interacts with GATA-4, FOG-2 and other cardiac transcription factors and by this means, down-regulates their activity on cardiac specific promoters α-myosin heavy chain, atrial natriuretic peptide and B-type natriuretic peptide. Regulation of endogenous cardiac genes by Art27 was shown using microarray analysis of P19CL6-Mlc2v-GFP cardiomyocytes. Together these results suggest that Art27 is a novel transcription factor that is involved in downregulation of cardiac specific genes by physically interacting and inhibiting the activity of crucial transcriptions factors involved in cardiac biology.

Heparin-induced thrombocytopenia

Heparin is widely used for the prevention and treatment of thrombotic and particularly cardiovascular disorders. Unfortunately, 0.5 to 3.0% of patients given heparin develop an immune reaction, commonly termed Type II heparin-induced thrombocytopenia (HIT). This is characterized by a moderate thrombocytopenia and in some patients, a venous or arterial thrombosis. This frequently leads to disastrous sequelae, such as limb amputation and death. The pathophysiological basis of this serious adverse drug reaction is the production of an immunoglobulin G antibody that reacts with an antigenic complex consisting of heparin and platelet factor 4. A significant risk factor for the development of HIT is recent surgery, and the frequency of developing an antiheparin-platelet factor 4 or HIT antibody is particularly high in cardiac surgery patients, although surprisingly, only a few of these patients actually develop the clinical syndrome of HIT. This review will discuss the frequency, pathophysiology, clinical features, diagnosis and management of HIT.

Presentation and outcome of idiopathic thrombocytopenic purpura in a single Australian centre

Immune thrombocytopenia can be a therapeutic challenge with multiple first- and second-line treatment options. A change in idiopathic thrombocytopenic purpura (ITP) definition and classification in recent consensus guidelines suggests that past descriptions of ITP presentation and outcome may be outdated. In this single centre retrospective analysis of patients with thrombocytopenia from 1 January 2005 to 1 June 2010, 139 patients met current ITP diagnostic criteria. About 54/139 were new presentations of primary ITP. Six- and 24-month response rates were 39% and 30% respectively. About 26/54 patients did not require treatment at presentation: 15 were followed up for at least 6 months and none required treatment subsequently. These results suggest that almost half of all new primary ITP do not need treatment.

Drug-induced immune thrombocytopenia

Thrombocytopenia is caused by immune reactions elicited by diverse drugs in clinical practice. The activity of the drug-dependent antibodies produces a marked decrease in blood platelets and a risk of serious bleeding. Understanding of the cellular mechanisms that drive drug-induced thrombocytopenia has advanced recently but there is still a need for improved laboratory tests and treatment options. This article provides an overview of the different types of drug-induced thrombocytopenia, discusses potential pathologic mechanisms, and considers diagnostic methods and treatment options.

EGFR and the complexity of receptor crosstalk in the cardiovascular system

Signaling pathways play a critical role in the maintenance of cellular structure and function. These pathways can act together with synergistic or antagonistic outcome. Cooperative and integrative cellular communication networks, otherwise known as crosstalk can amplify signaling cascades. Here, we focus on receptor crosstalk in the context of cardiovascular pathologies, mainly involving the epidermal growth factor receptor (EGFR), a critical mediator of multiple receptor pathways in normal physiological and pathophysiological processes. Considerable experimental evidence suggests that the uncontrolled expression of EGFR contributes to tumorigenesis through inhibition of apoptosis, angiogenesis, anchorage-independent growth and tumor-associated inflammation. Abnormal activation of the intrinsic tyrosine kinase of EGFR through mutation or overexpression is observed in various human cancer types. On the other hand, the role of EGFR in vascular biology is not well understood. In cardiovascular pathologies, such as atherosclerosis and restenosis, vascular smooth muscle cells (SMCs) migrate and proliferate, contributing to neointima formation, whilst apoptosis may cause plaque instability. EGFR can be transactivated by numerous pathologic stimuli that regulate SMC behaviour. This review describes our current understanding of the role of EGFR in SMC biology and pathology.

Platelets and P-selectin control tumor cell metastasis in an organ-specific manner and independently of NK cells

The prometastatic role of platelets has long been recognized with proposed mechanisms of action including shielding tumor cells from natural killer (NK) cell destruction and aiding endothelial attachment and extravasation of tumor cells with platelet P-selectin being implicated in these processes. However, many aspects of the prometastatic function of platelets remain unclear. In this study, we used mouse models of metastatic breast cancer and melanoma to investigate the platelet effect, focusing on organ specificity, the relationship with NK cells and the relative importance of platelet-derived versus endothelial-derived P-selectin. We found that platelets promote lung metastasis in the absence of NK cells in both acute and spontaneous metastasis models. In addition, the prometastatic action of platelets was found to be organ specific, clearly enhancing lung metastasis but not affecting B16F1 liver metastasis, in fact, liver metastasis was enhanced in the absence of platelets. Furthermore, the profound antimetastatic activity of NK cells was equally effective in the presence or absence of platelets and chronologically distinct from the prometastatic role of platelets. Finally, it was shown that endothelial-derived P-selectin is just as important as platelet-derived P-selectin in promoting lung metastasis and also plays an important role in liver metastasis. Taken together, our findings help clarify the roles of platelets, NK cells and P-selectin in metastasis, and they identify P-selectin as an attractive therapeutic target for preventing metastasis in multiple organs.

IL-1beta signals through the EGF receptor and activates Egr-1 through MMP-ADAM

The immediate-early gene Egr-1 controls the inducible expression of many genes implicated in the pathogenesis of a range of vascular disorders, yet our understanding of the mechanisms controlling the rapid expression of this prototypic zinc finger transcription factor is poor. Here we show that Egr-1 expression induced by IL-1beta is dependent on metalloproteinases (MMP) and a disintegrin and a metalloproteinase (ADAM). Pharmacologic MMP/ADAM inhibitors and siRNA knockdown prevent IL-1beta induction of Egr-1. Further, IL-1beta activates Egr-1 via the epidermal growth factor receptor (EGFR). This is blocked by EGFR tyrosine kinase inhibition and EGFR knockdown. IL-1beta induction of Egr-1 expression is reduced in murine embryonic fibroblasts (mEFs) deficient in ADAM17 despite unbiased expression of EGFR and IL-1RI in ADAM17-deficient and wild-type mEFs. Finally, we show that IL-1beta-inducible wound repair after mechanical injury requires both EGFR and MMP/ADAM. This study reports for the first time that Egr-1 induction by IL-1beta involves EGFR and MMP/ADAM-dependent EGFR phosphorylation.

Clinicians adopting evidence based guidelines: a case study with thromboprophylaxis

Background

Venous Thromboembolism (VTE) is a cause of hospital mortality and managing its morbidity is associated with significant expenditure. Uptake of evidenced based guideline recommendations intended to prevent VTE in hospital settings is sub-optimal. This study was conducted to explore clinicians' attitudes and the clinical environment in which they work to understand their reluctance to adopt VTE prophylaxis guidelines.

Methods

Between February and November 2009, 40 hospital employed doctors from 2 Australian metropolitan hospitals were interviewed in depth. Qualitative data were analysed according to thematic methodology.

Results

Analysis of interviews revealed that barriers to evidence based practice include i) the fragmented system of care delivery where multiple members of teams and multiple teams are responsible for each patient's care, and in the case of VTE, where everyone shares responsibility and no-one in particular is responsible; ii) the culture of practice where team practice is tailored to that of the team head, and where medicine is considered an 'art' in which guidelines should be adapted to each patient rather than applied universally. Interviewees recommend clear allocation of responsibility and reminders to counteract VTE risk assessment being overlooked.

Conclusions

Senior clinicians are the key enablers for practice change. They will need to be convinced that guideline compliance adds value to their patient care. Then with the support of systems in the organisation designed to minimize the effects of care fragmentation, they will drive practice changes in their teams. We believe that evidence based practice is only possible with a coordinated program that addresses individual, cultural and organisational constraints.

In vitro and in vivo proliferation, differentiation and migration of cardiac endothelial progenitor cells (SCA1+/CD31+ side-population cells)

BACKGROUND

Side-population (SP) cells are a select population identified by a capacity to efflux Hoechst dye and are enriched for stem/progenitor cell activity. Previous studies suggested that cardiac SP (CSP) cells could be divided into SCA1(+)/CD31(-) and SCA1(+)/CD31(+) CSP cells. SCA1(+)/CD31(-) CSP cells have been shown to be cardiac stem/progenitor cells. However, SCA1(+)/CD31(+) CSP cells have not been fully characterized.

OBJECTIVE

The aim of the present study was to characterize SCA1(+)/CD31(+) CSP cells in the adult mouse heart, and investigate their abilities to proliferate, differentiate, vascularize and migrate in vitro and in vivo.

RESULTS

Using fluorescence-activated cell sorting (FACS), RT-PCR, and assays of cell proliferation, differentiation and migration, and a murine model of myocardial infarction (MI), we showed that SCA1(+)/CD31(+) CSP cells express stem cell and endothelial-specific genes, and reside in the blood vessels. These cells were able to proliferate, differentiate, migrate and vascularize in vitro and in vivo. After MI, SDF-1α and CXCR4 were up-regulated in the damaged myocardium and on SCA1(+)/CD31(+) CSP cells, respectively. Our results further showed that SDF-1α induced migration of these cells in vitro. Importantly, we found that SCA1(+)/CD31(+) CSP cells could migrate into the ischemic region from the non-ischemic area within the myocardium and form a vascular tube-like structure after MI.

CONCLUSIONS

Based on the gene expression profile, localization of SCA1(+)/CD31(+) CSP cells, and their ability to proliferate, differentiate, migrate and vascularize in vitro and in vivo, we postulate that SCA1(+)/CD31(+) CSP cells may represent endothelial progenitor cells in the mouse heart.

Chronic adult primary immune thrombocytopenia (ITP) in the Asia-Pacific region

Patients with primary immune thrombocytopenia (ITP) from the Asia-Pacific region often exhibit characteristics distinct from those of patients from the West. Moreover, as the region itself is heterogeneous, the ITP landscape among individual Asia-Pacific countries can be diverse. The recently released international consensus report on ITP places new emphasis on ITP, but does not address the unique ITP landscape in the Asia-Pacific region, which is home to 60% of the world's population. In an attempt to characterize how the ITP landscape differs between the West and the Asia-Pacific region, an expert panel with representatives from Northeast Asia, Southeast Asia, and Australia was convened. Important differences were identified between the guidance provided in the international consensus report and experience in the Asia-Pacific region, namely diagnostic practices, incidence and approach to ITP secondary to H. pylori infection, systemic lupus erythematosus-related ITP, the use of bone marrow examination, initial treatment strategies, and the role of splenectomy, rituximab, and thrombopoietin receptor agonists.

Predictive and associative models to identify hospitalized medical patients at risk for VTE

BACKGROUND

Acutely ill hospitalized medical patients are at risk for VTE. We assessed the incidence of VTE in the observational International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) study and derived VTE risk assessment scores at admission and associative VTE scores during hospitalization.

METHODS

Data from 15,156 medical patients were analyzed to determine the cumulative incidence of clinically observed VTE over 3 months after admission. Multiple regression analysis identified factors associated with VTE risk.

RESULTS

Of the 184 patients who developed symptomatic VTE, 76 had pulmonary embolism, and 67 had lower-extremity DVT. Cumulative VTE incidence was 1.0%; 45% of events occurred after discharge. Factors independently associated with VTE were previous VTE, known thrombophilia, cancer, age > 60 years, lower-limb paralysis, immobilization ≥ 7 days, and admission to an ICU or coronary care unit (first four were available at admission). Points were assigned to each factor identified to give a total risk score for each patient. At admission, 67% of patients had a score ≥ 1. During hospitalization, 31% had a score ≥ 2; for a score of 2 or 3, observed VTE risk was 1.5% vs 5.7% for a score ≥ 4. Observed and predicted rates were similar for both models (C statistic, 0.65 and 0.69, respectively). During hospitalization, a score ≥ 2 was associated with higher overall and VTE-related mortality.

CONCLUSIONS

Weighted VTE risk scores derived from four clinical risk factors at hospital admission can predict VTE risk in acutely ill hospitalized medical patients. Scores derived from seven clinical factors during hospitalization may help us to further understand symptomatic VTE risk. These scores require external validation.

Polysaccharides from the root of Angelica sinensis promotes hematopoiesis and thrombopoiesis through the PI3K/AKT pathway

Background

Dozens of Traditional Chinese Medicine (TCM) formulas have been used for promotion of "blood production" for centuries, and we are interested in developing novel thrombopoietic medicines from these TCMs. Our previous studies have demonstrated the hematopoietic effects of DangGui BuXue Tong (DBT), a formula composed of Radix Angelicae Sinensis and Radix Astragali in animal and cellular models. As a step further to identify and characterize the active chemical components of DBT, we tested the hematopoietic and particularly, thrombopoietic effects of polysaccharide-enriched fractions from the root of Radix Angelicae Sinensis (APS) in this study.

Methods

A myelosuppression mouse model was treated with APS (10 mg/kg/day). Peripheral blood cells from APS, thrombopoietin and vehicle-treated samples were then counted at different time-points. Using the colony-forming unit (CFU) assays, we determined the effects of APS on the proliferation and differentiation of hematopoietic stem/progenitor cells and megakaryocytic lineages. Using a megakaryocytic cell line M-07e as model, we analyzed the cellular apoptosis progression with and without APS treatment by Annexin V, Mitochondrial Membrane Potential and Caspase 3 assays. Last, the anti-apoptotic effect of APS on cells treated with Ly294002, a Phosphatidylinositol 3-Kinse inhibitor (PI3K) was also tested.

Results

In animal models, APS significantly enhanced not only the recovery of platelets, other blood cells and their progenitor cells, but also the formation of Colony Forming Unit (CFU). In M-07e cells, we observed the anti-apoptotic effect of APS. Treatment by Ly294002 alone increased the percentage of cells undergoing apoptosis. However, addition of APS to Ly294002-treated cells significantly reduced the percentage of cells undergoing apoptosis.

Conclusions

APS promotes hematopoiesis and thrombopoiesis in the mouse model. This effect likely resulted from the anti-apoptosis activity of APS and is likely to involve the PI3K/AKT pathway.

Romiplostim or standard of care in patients with immune thrombocytopenia

BACKGROUND

Romiplostim, a thrombopoietin mimetic, increases platelet counts in patients with immune thrombocytopenia, with few adverse effects.

METHODS

In this open-label, 52-week study, we randomly assigned 234 adult patients with immune thrombocytopenia, who had not undergone splenectomy, to receive the standard of care (77 patients) or weekly subcutaneous injections of romiplostim (157 patients). Primary end points were incidences of treatment failure and splenectomy. Secondary end points included the rate of a platelet response (a platelet count >50×10(9) per liter at any scheduled visit), safety outcomes, and the quality of life.

RESULTS

The rate of a platelet response in the romiplostim group was 2.3 times that in the standard-of-care group (95% confidence interval [CI], 2.0 to 2.6; P<0.001). Patients receiving romiplostim had a significantly lower incidence of treatment failure (18 of 157 patients [11%]) than those receiving the standard of care (23 of 77 patients [30%], P<0.001) (odds ratio with romiplostim, 0.31; 95% CI, 0.15 to 0.61). Splenectomy also was performed less frequently in patients receiving romiplostim (14 of 157 patients [9%]) than in those receiving the standard of care (28 of 77 patients [36%], P<0.001) (odds ratio, 0.17; 95% CI, 0.08 to 0.35). The romiplostim group had a lower rate of bleeding events, fewer blood transfusions, and greater improvements in the quality of life than the standard-of-care group. Serious adverse events occurred in 23% of patients (35 of 154) receiving romiplostim and 37% of patients (28 of 75) receiving the standard of care.

CONCLUSIONS

Patients treated with romiplostim had a higher rate of a platelet response, lower incidence of treatment failure and splenectomy, less bleeding and fewer blood transfusions, and a higher quality of life than patients treated with the standard of care. ( ClinicalTrials.gov number, NCT00415532.).

A monopartite sequence is essential for p45 NF-E2 nuclear translocation, transcriptional activity and platelet production

BACKGROUND

p45 NF-E2 is a bZIP transcription factor crucial for thrombopoiesis, as indicated by the fact that loss of p45 NF-E2 function results in dramatic embryonic lethal thrombopoietic defects and its overexpression boosts platelet release.

OBJECTIVES

In the present study, we set out to identify the sequences responsible for p45 NF-E2 nuclear import, evaluate its transport mechanism and ascertain its functional significance.

METHODS

A series of p45 NF-E2 deletion constructs fused to green fluorescent protein (GFP) was created and their cellular localization examined in mammalian cells, with the factor responsible for nuclear import identified using an in vitro transport assay. A p45 NF-E2 derivative mutated in the nuclear targeting sequence (NLS) was generated and its biological activity compared with wild type (wt) in luciferase assays, and proplatelet and platelet production measured in murine megakaryocytes transduced with a retroviral vector.

RESULTS

Here we show that residues 271-273 are essential for nuclear import of p45 NF-E2 in COS-7 and in primary bone marrow cells. The p45 NF-E2 NLS facilitates nuclear import specifically via importin (IMP) 7. Although within the DNA-binding domain of p45 NF-E2, the NLS is not essential for DNA-binding, but is crucial for transcriptional activation and biological activity; where, in contrast to wt, a mutant derivative with a mutated NLS failed to promote proplatelet and platelet production in murine megakaryocytes.

CONCLUSIONS

The NLS is critical for p45 NF-E2 function, with the present study being the first to demonstrate the importance of NLS-dependent nuclear import of p45 NF-E2 for platelet development.

CXCR4 expression on transplanted peripheral blood CD34+ cells: relationship to engraftment after autologous transplantation in a cohort of multiple myeloma patients

Expression of the chemokine receptor CXCR4 by haematopoietic stem cells (HSCs) is believed to influence the process of these cells 'homing' back to the bone marrow post-transplantation, in response to the stromal cell-derived factor-1 gradient, followed by engraftment. The primary aim of this retrospective study was to compare reinfused CD34(+) cell dose, assessed from the fresh collection, with the post-thaw viable (v) CD34(+) and vCD34/CXCR4(+) dual positive cell dose as predictors of haematopoietic recovery in multiple myeloma patients undergoing autologous stem cell transplantation. Cryopreserved samples from stem cell collections of 27 myeloma patients were analysed for CD34 and CXCR4 expression and times to haematological engraftment measured. Dosage of transplanted vCD34(+) cells was on average 79% of the original calculation from the fresh collection bag (range 29-98%). The median percentage of vCD34+ cells co-expressing CXCR4 was 37% (3.7-97%). Surface expression of CXCR4 by thawed vCD34(+) cells was closely correlated to complementary DNA levels. The median dose of CD34/CXCR4(+) cells in the autografts was 1.2 × 10(6)/kg (0.2-3.0 × 10(6)/kg) compared with 3.3 × 10(6)/kg for transplanted vCD34(+) cells (1.2-5.5 × 10(6)/kg). Both CD34 and vCD34 doses correlated with neutrophil engraftment (p < 0.005) although vCD34/CXCR4(+) dose did not. However, patients given a higher dose of CD34/CXCR4(+) cells (≥1.75 × 10(6)/kg) showed a faster time to platelet recovery (p < 0.05) than those given a lower dose (≤0.42 × 10(6)/kg). These results warrant further study of CD34/CXCR4 expression by mobilised HSCs and the relationship to platelet recovery post-transplantation on a larger cohort of patients.