Joseph E Italiano

Brigham and Women's Hospital | BWH

Lipids contribute to hematopoiesis and membrane properties and dynamics, however, little is known about the role of lipids in megakaryopoiesis. Here, a lipidomic analysis of megakaryocyte progenitors, megakaryocytes, and platelets revealed a unique lipidome progressively enriched in polyunsaturated fatty acid (PUFA)-containing phospholipids. In vit...

Objective: Implantable cardiovascular therapeutic devices (CTD) including stents, percutaneous heart valves, and ventricular assist devices, while lifesaving, impart supraphysiologic shear stress to platelets resulting in thrombotic and bleeding device-related coagulopathy. We previously demonstrated that shear-mediated platelet dysfunction is asso...

Despite abundant research demonstrating that platelets can promote tumor cell metastasis, whether primary tumors affect platelet-producing megakaryocytes remains understudied. In this study, we used a spontaneous murine model of breast cancer to show that tumor burden reduced megakaryocyte number and size and disrupted polyploidization. Single-cell...

Platelets are small, circulating anuclear cells that have an important and well-defined role in hemostasis and wound healing. Known as the “band-aids of the blood,” platelets rapidly activate, aggregate, and release a plethora of growth factors, cytokines, and other biological mediators at sites of vascular damage, thereby forming a clot. Compellin...

Objective. Platelets are small, mechanosensitive blood cells responsible for maintaining vascular integrity and activatable on demand to limit bleeding and facilitate thrombosis. While circulating in the blood, platelets are exposed to a range of mechanical and chemical stimuli, with the platelet membrane being the primary interface and transducer...

Programmed death-ligand 1 (PD-L1) is an immune checkpoint protein that suppresses cytotoxic T lymphocytes and is often overexpressed in cancers. Due to favorable clinical trial results, immune checkpoint inhibition (ICI) is now part of Food and Drug Administration-approved immuno-oncology therapies; however, not all patients derive benefit from ICI...

Tyrosine phosphorylation of extracellular proteins is observed in cell cultures and in vivo, but little is known about the functional roles of tyrosine phosphorylation of extracellular proteins. Vertebrate Lonesome Kinase (VLK) is a broadly expressed secretory pathway tyrosine kinase present in platelet ɑ-granules. It is released from platelets upo...

Introduction: Programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) are important immune checkpoint proteins in cancer immunotherapy and targeted therapies against PD-L1 have significantly prolonged many patients' lives. Recently, high baseline platelet to lymphocyte ratio was reported to be associated with decreased patient...

Tyrosine phosphorylation of extracellular proteins is observed in cell cultures and in vivo, but little is known about the functional roles of tyrosine phosphorylation of extracellular proteins. Vertebrate Lonesome Kinase (VLK) is a broadly expressed secretory pathway tyrosine kinase present in platelet ɑgranules. It is released from platelets upon...

Tyrosine phosphorylation of proteins secreted into the extracellular space has been observed in cell cultures and in vivo, yet little is known about the role that phosphorylation of extracellular proteins serves in modulating cell function. An important reason for the gap in our knowledge of the functional significance of extracellular protein phos...

During inflammation, steady-state hematopoiesis switches to emergency hematopoiesis to repopulate myeloid cells, with a bias toward the megakaryocytic lineage. Soluble inflammatory cues are thought to be largely responsible for these alterations. However, how these plasma factors rapidly alter the bone marrow (BM) is not understood. Inflammation al...

Background The mechanisms that regulate platelet biogenesis remain unclear; factors that trigger megakaryocytes (MKs) to initiate platelet production are poorly understood. Platelet formation begins with proplatelets which are cellular extensions originating from the MK cell body. Objectives Proplatelet formation is an asynchronous and dynamic pro...

von Willebrand factor (vWF) is an essential hemostatic protein that is synthesized in endothelial cells and stored in Weibel-Palade bodies (WPBs). Understanding the mechanisms underlying WPB biogenesis and exocytosis could enable therapeutic modulation of endogenous vWF, yet optimal targets for modulating vWF release have not been established. Sinc...

Almost every platelet-derived protein originates from either megakaryocytes (MKs), or the endocytosis of factors within blood circulation. These endocytosed factors can be locally released upon platelet activation to regulate hemostasis, or to promote the growth and neovascularization of solid tumors. Although platelet endocytosis has long been rec...

Disclosures: Italiano: Ionis Research Funding: Research Funding; Platelet Biogenesis: Employment, Equity Ownership.

Disclosures: Italiano: Platelet Biogenesis: Employment, Equity Ownership; Ionis Research Funding: Research Funding. Flaumenhaft:PlateletDiagnostics: Consultancy, Other: Founder; Relay Therapeutics: Consultancy.

Platelets are specialized anucleate cells that circulate in the blood and serve to prevent bleeding and minimize blood vessel injury. In addition to their hemostatic functions, platelets participate in wound healing, angiogenesis, inflammation, and immunity, and are therefore central players in both maintaining normal physiology and in disease path...

Key Points Mouse megakaryocytes can differentially sort and package endocytosed fibrinogen and endostatin into distinct α-granules. Platelet progenitors contain subpopulations of α-granules.

Bone marrow megakaryocytes engulf neutrophils in a phenomenon termed emperipolesis. We show here that emperipolesis is a dynamic process mediated actively by both lineages, in part through the β2-integrin/ICAM-1/ezrin pathway. Tethered neutrophils enter in membrane-bound vesicles before penetrating into the megakaryocyte cytoplasm. Intracytoplasmic...

Apoptosis is a recognized limitation for generating large numbers of megakaryocytes in culture. The responsible apoptosis genes have been rigorously studied in vivo in mice, but are poorly characterized in human culture systems. As CD34+ cells isolated from human umbilical vein cord blood were differentiated into megakaryocytes in culture, two dist...

It is now recognized that compounds released from tumor cells can activate platelets, causing the release of platelet-derived factors into the tumor microenvironment. Several of these factors have been shown to directly promote neovascularization and metastasis, yet how the feedback between platelet releasate and the tumor cell affects metastatic p...

Megakaryocytes are highly specialized precursor cells that produce and release platelets into the circulation. Understanding mechanisms by which megakaryocytes develop and give rise to platelets has fascinated hematologists for more than a century. Megakaryocytes are descended from pluripotent stem cells and undergo multiple DNA replications withou...

Bone marrow megakaryocytes engulf neutrophils in a phenomenon termed emperipolesis. We show here that emperipolesis is a dynamic process mediated actively by both lineages, in part through the β2-integrin/ICAM-1/ezrin pathway. Tethered neutrophils enter in membrane-bound vesicles before penetrating into the megakaryocyte cytoplasm. Intracytoplasmic...

Introduction Antisense oligonucleotides (ASOs) are a new class of single-stranded DNA based drugs that hold great therapeutic promise for their disease modifying potential in a wide range of genetic diseases. Preclinical toxicology studies in monkeys, as well as late stage clinical trials in humans, have upon repeated dosing, reported events of ASO...

Significance Immune complexes (ICs) form when antibodies encounter their antigens. ICs are present in blood in multiple pathological conditions. Given the abundance of platelets in blood and that they express a receptor for ICs, called Fcγ receptor IIA (FcγRIIA), we examined the impact of ICs in blood in a mouse model. We found that circulating ICs...

Congenital amegakaryocytic thrombocytopaenia (CAMT) is a disorder caused by c-MPL mutations that impair thrombopoietin (TPO) signalling, resulting in a near absence of megakaryocytes (MKs). While this phenotype is consistent in adults, neonates with CAMT can present with severe thrombocytopaenia despite normal MK numbers. To investigate this, we ch...

Key Points Megakaryocytes process and present endogenous/exogenous antigens on MHC class I molecules to activate CD8+ T cells. Megakaryocytes can transfer MHC class I molecules loaded with foreign antigen to proplatelets in vitro.

Key Points Deletion of Arp2/3 leads to marked microthrombocytopenia due to abnormal platelet release and increased platelet clearance. Arp2/3 is critical for platelet lamellipodia formation and spreading, but plays a minor role for platelet adhesion and hemostasis.

Platelets are small, anuclear cells found in the circulation that have an important and well-defined role in hemostasis and wound healing. Known as the “band-aids of the blood,” these cells rapidly activate, aggregate, and release a potent milieu of growth factors, cytokines, and other biological mediators at the site of vascular damage, forming a...

Selinexor is the first oral selective inhibitor of nuclear export compound tested for cancer treatment. Selinexor has demonstrated a safety therapy profile with broad antitumor activity against solid and hematological malignancies in phases 2 and 3 clinical trials (#NCT03071276, #NCT02343042, #NCT02227251, #NCT03110562, and #NCT02606461). Although...

Background: Proteasome inhibitors such as bortezomib, a chemotherapeutic used to treat multiple myeloma, induce thrombocytopenia within days of initiation. The mechanism for this thrombocytopenia has been tied to data revealing that proteasome activity is essential for platelet formation. The major pathway of selective protein degradation uses ubiq...

Blood platelets are 2–3 μm anucleate fragments that are formed from the megakaryocyte cytoplasm and have a distinctive discoid shape. To generate and release platelets, megakaryocytes undergo endomitosis to become polyploid and follow a maturation program that results in the transformation of the bulk of their cytoplasm into multiple long processes...

Objective: Platelets, which are mainly known for their role in hemostasis, are now known to play a crucial role in metastasis. Tamoxifen is a selective estrogen receptor modulator that is widely used for the treatment of breast cancer. Tamoxifen and its metabolites have been shown to directly impact platelet function, suggesting that this drug has...

Objective - Platelets, which are mainly known for their role in hemostasis, are now known to play a crucial role in tumor metastasis and neovascularization. Metastatic disease is the cause of roughly 90% of all cancer-related deaths and understanding the mechanisms leading to dissemination of tumor cells to distant sites remains one of the main cha...

Key Points Platelet DREAM is required for platelet thrombus formation at the site of arteriolar injury in mice. Platelet DREAM plays an important role in cell activation by regulation of PI3K class Iβ activity.

Platelets, primarily known for their role in hemostasis, are now recognized to play an integral role in cancer progression and metastasis. Recent evidence has established that platelets are activated by tumor cells, including breast cancer cells, leading to the release of hundreds of growth factors, cytokines, chemokines and angiogenesis mediators...

Downstream regulatory element antagonist modulator (DREAM), a transcriptional repressor, is known to modulate pain. Using intravital microscopy with DREAM-null mice and their bone marrow chimeras, we demonstrated that hematopoietic and endothelial cell DREAM are required for platelet thrombus formation following arteriolar injury. DREAM deletion al...

A deeper understanding of the molecular events driving megakaryocytopoiesis and thrombopoiesis is essential to regulate in vitro and in vivo platelet production for clinical applications. We previously documented the crucial role of PKCepsilon in the regulation of human and mouse megakaryocyte maturation and platelet release. However, since several...

Key Points Proteomic analyses and polysome profiling of developing MKs identified a striking increase in the levels of a novel protein, MARCKS, during proplatelet formation. MARCKS deletion, inhibition, or phosphorylation inhibits proplatelet formation associated with activation of the actin-binding protein Arp2/3.

Blood platelets are 2–3 um anucleate fragments that are formed from the megakaryocyte cytoplasm and have a distinctive discoid shape. To generate and release platelets, megakaryocytes undergo endomitosis to become polyploid and follow a maturation program that results in the transformation of the bulk of their cytoplasm into multiple long processes...

In times of physiological stress, platelet count can transiently rise. What initiates this reactive thrombocytosis is poorly understood. Intriguingly, we found that treating megakaryocytes (MKs) with the releasate from activated platelets increased proplatelet production by 47%. Platelets store inflammatory cytokines, including the chemokine ligand...

A fundamental understanding of platelet biology requires functional assessment of megakaryocyte-platelet expressed genes and transcripts. The need for gene functional studies has recently increased with unbiased genome wide associations with platelet phenotypes. Animal models with an over-expressed or knocked-out gene have been particularly valuabl...

Platelets, primarily known for their role in hemostasis, are now recognized to play an integral role in cancer progression and metastasis. Recent evidence has established that platelets are activated by contact with breast tumor cells, leading to the release of hundreds of growth factors, cytokines, chemokines and angiogenesis mediators that could...

Background: In times of physiological stress (i.e. myocardial infarction, infection, inflammation, malignancy), platelet count can transiently elevate. What initiates this reactive thrombocytosis is poorly understood. Platelets store inflammatory cytokines that are released upon activation, including abundant amounts of chemokine ligand 5 (CCL5). A...

Transfusion of donor-derived platelets is commonly used for thrombocytopenia, which results from a variety of clinical conditions and relies on a constant donor supply due to the limited shelf life of these cells. Embryonic stem (ES) and induced pluripotent stem (iPS) cells represent a potential source of megakaryocytes and platelets for transfusio...

Platelets, which are mainly known for their role in hemostasis, are now known to play a crucial role in metastasis. Metastatic disease is the cause of roughly 90% of all cancer-related deaths and understanding the mechanisms leading to dissemination of tumor cells to distant sites remains one of the main challenges of cancer research. Tamoxifen is...

Background Selinexor (KPT-330), a selective inhibitor of nuclear export (SINE) Exportin 1 (XPO1, CRM1) antagonist, has shown potent activity against solid and hematological malignancies in phase 1 clinical trials. Inactivation of XPO1 by selinexor results in accumulation of tumor suppressor proteins in the nucleus and activation of cell cycle check...

DREAM (Downstream Regulatory Element Antagonistic Modulator) is a neuronal calcium sensor and acts as a transcriptional repressor for pain modulation. Recent studies showed that endothelial cell DREAM transcriptionally regulates NF-κB signaling during inflammation (Tiruppathi et al. Nat Immunol. 2014). However, it is unknown whether DREAM plays a r...

Congenital amegakaryocytic thrombocytopenia (CAMT) is a disorder caused by c-mpl mutations that block or severely reduce thrombopoietin (Tpo) signaling, leading to amegakaryocytic thrombocytopenia and ultimately aplastic anemia. In neonates and infants, CAMT can have different clinical manifestations than in adults, and cases have been described of...

Embryonic stem (ES) and induced pluripotent stem (iPS) cells represent potential sources of megakaryocytes and platelets for transfusion therapy. However, most current ES/iPS cell differentiation protocols are limited by low yields of hematopoietic progeny, including platelet-releasing megakaryocytes. Mutations in the mouse and human genes encoding...

Bone marrow megakaryocytes produce platelets by extending long cytoplasmic protrusions, designated proplatelets, into sinusoidal blood vessels. While microtubules are known to regulate platelet production, the underlying mechanism of proplatelet elongation has yet to be resolved. Here we report that proplatelet formation is a process that can be di...

Human induced pluripotent stem cells (iPSCs) provide a potentially replenishable source for the production of transfusable platelets. Here, we describe a method to generate megakaryocytes (MKs) and functional platelets from iPSCs in a scalable manner under serum/ feeder-free conditions. The method also permits the cryopreservation of MK progenitors...

Although tyrosine phosphorylation of extracellular proteins has been reported to occur extensively in vivo, no secreted protein tyrosine kinase has been identified. As a result, investigation of the potential role of extracellular tyrosine phosphorylation in physiological and pathological tissue regulation has not been possible. Here, we show that...

The proteasome inhibiter bortezomib has been successfully used to treat patients with relapsed multiple myeloma; however, many of these patients become thrombocytopenic, and it is not clear how the proteasome influences platelet production. Here we determined that pharmacologic inhibition of proteasome activity blocks proplatelet formation in human...

Key Points We have developed a biomimetic microfluidic platelet bioreactor that recapitulates bone marrow and blood vessel microenvironments. Application of shear stress in this bioreactor triggers physiological proplatelet production, and platelet release.

The fetal/neonatal hematopoietic system must generate enough blood cells to meet the demands of rapid growth. This unique challenge might underlie the high incidence of thrombocytopenia among preterm neonates. In this study, neonatal platelet production and turnover were investigated in newborn mice. Based on a combination of blood volume expansion...

Platelets are essential for haemostasis, and thrombocytopenia (platelet counts <150 × 10(9) /l) is a major clinical problem encountered across a number of conditions, including immune thrombocytopenic purpura, myelodysplastic syndromes, chemotherapy, aplastic anaemia, human immunodeficiency virus infection, complications during pregnancy and delive...

Platelets are a reservoir for angiogenic proteins that are secreted in a differentially regulated process. While the involvement of platelets in hematogenous tumor metastasis has long been recognized, the cause and effect relationship linking the two remains unclear. Due to the propensity for clotting, patients with malignancy are often anti-coagul...

We used exome sequencing to identify mutations in sideroflexin 4 (SFXN4) in two children with mitochondrial disease (the more severe case also presented with macrocytic anemia). SFXN4 is an uncharacterized mitochondrial protein that localizes to the mitochondrial inner membrane. sfxn4 knockdown in zebrafish recapitulated the mitochondrial respirato...

Platelets are a reservoir for angiogenic proteins that are secreted in a differentially regulated process. Because of the propensity for clotting, patients with malignancy are often anticoagulated with heparin products, which paradoxically offer a survival benefit by an unknown mechanism. We hypothesized that antithrombotic agents alter the release...

Animating complex biological processes contextualizes them within their underlying physiology, identifies gaps in our mechanistic understanding, affirms the importance of continued research, and provides a bridge between academic scientists and the general public. Here, two videos illustrate the clinical value of and translate state-of-the-art rese...

During thrombopoiesis, megakaroycytes undergo extensive cytoskeletal remodeling to form proplatelet extensions that eventually produce mature platelets. Proplatelet formation is a tightly orchestrated process that depends on dynamic regulation of both tubulin reorganization and Rho-associated, coiled-coil containing protein kinase/RhoA activity. A...

Circulating blood platelets are specialized cells that prevent bleeding and minimize blood vessel injury. Large progenitor cells in the bone marrow called megakaryocytes (MKs) are the source of platelets. MKs release platelets through a series of fascinating cell biological events. During maturation, they become polyploid and accumulate massive amo...

Objective: Platelet granule exocytosis serves a central role in hemostasis and thrombosis. Recently, single-cell amperometry has shown that platelet membrane fusion during granule exocytosis results in the formation of a fusion pore that subsequently expands to enable the extrusion of granule contents. However, the molecular mechanisms that contro...

Glioblastomas are very difficult tumors to treat because they are highly invasive and disseminate within the normal brain, resulting in newly growing tumors. We have identified netrin-1 as a molecule that promotes glioblastoma invasiveness. As evidence, netrin-1 stimulates glioblastoma cell invasion directly through Matrigel-coated transwells, prom...

1218 Platelets are essential for hemostasis, and thrombocytopenia (platelet counts < 150×109/L) is a major clinical problem encountered across a number of conditions. Megakaryocytes (MKs) generate platelets by extending long, branching processes, designated proplatelets, into sinusoidal blood vessels. While the mechanism of proplatelet production h...

2174 While the involvement of platelets in hematogenous tumor metastasis has long been recognized, the cause and effect relationship linking the two remains unclear. Platelets are a reservoir for angiogenic proteins that are both sequestered and secreted in a differentially regulated process (Italiano et al., 2009). We have previously shown that we...

79 Megaloblastic anemias are characterized by impaired DNA metabolism, often due to deficiencies in vitamin B12 or folate. Genes underlying hereditary forms of megaloblastic anemia not caused by vitamin B12 or folate deficiencies, however, remain largely unknown. Here we characterize a genetic deficiency in a patient with infantile-onset megaloblas...

SCI-35 In addition to their “classic” role in hemostasis, platelets are now known to be major contributors in wound healing, tumor growth, and angiogenesis. Stored within the α-granules is an array of angiogenic regulatory proteins, which are deposited by the secretion reaction of surface-activated platelets into the local environment of a tumor or...

We recently identified 68 genomic loci where common sequence variants are associated with platelet count and volume. Platelets are formed in the bone marrow by megakaryocytes, which are derived from hematopoietic stem cells by a process mainly controlled by transcription factors. The homeobox transcription factor MEIS1 is uniquely transcribed in me...

The cyclic nucleotides cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) regulate the activity of protein kinase A and protein kinase G (PKG), respectively. This process helps maintain circulating platelets in a resting state. Here we studied the role of cAMP and cGMP in the regulation of megakaryocyte (MK) differentia...

The crucial function of blood platelets in hemostasis is to prevent blood loss by stable thrombus formation. This process is driven by orchestrated mechanisms including several signal transduction cascades and morphologic transformations. The cytoplasmic microtubule modulator RanBP10 is a Ran and β1-tubulin binding protein that is essential for pla...

Platelets are anucleate, discoid cells, roughly 2-3 μm in diameter that function primarily as regulators of hemostasis, but also play secondary roles in angiogensis and innate immunity. Although human adults contain nearly one trillion platelets in circulation that are turned over every 8-10 days, our understanding of the mechanisms involved in pla...