Marstacimab, a tissue factor pathway inhibitor neutralizing antibody, improves coagulation parameters of ex vivo dosed haemophilic blood and plasmas.

Introduction: Tissue factor pathway inhibitor (TFPI) is an endogenous inhibitor of the extrinsic pathway that negatively regulates thrombin production during coagulation. Under haemophilic conditions, where the intrinsic coagulation pathway is impaired, inhibition of TFPI may improve clotting.

Aim: We investigated the ex vivo effects of a human TFPI neutralizing antibody, marstacimab (previously PF-06741086), in coagulation assays including rotational thromboelastometry (ROTEM), thrombin generation assay (TGA) and the dilute prothrombin time (dPT) assay, performed in haemophilic whole blood and plasmas.

Abnormal clotting of the intrinsic/contact pathway in Alzheimer disease patients is related to cognitive ability.

Alzheimer disease (AD) is a neurodegenerative disorder characterized by extracellular β-amyloid (Aβ) deposition. Although peripheral inflammation and cerebrovascular pathology are reported in AD, there is a lack of plasma biomarkers in this field. Because the contact system is triggered in patient plasma, we hypothesized that the hemostasis profile could be a novel biomarker in AD.

Translational Pharmacokinetic/Pharmacodynamic Characterization and Target-Mediated Drug Disposition Modeling of an Anti-Tissue Factor Pathway Inhibitor Antibody, PF-06741086.

Tissue factor pathway inhibitor (TFPI) exhibits multiple isoforms, which are known to present in multiple locations such as plasma, endothelium, and platelets. TFPI is an endogenous negative modulator of the coagulation pathway, and therefore, neutralization of TFPI function can potentially increase coagulation activity. A human monoclonal antibody, PF-06741086, which interacts with all isoforms of TFPI is currently being tested in clinic for treating hemophilia patients with and without inhibitors.

Endomucin prevents leukocyte-endothelial cell adhesion and has a critical role under resting and inflammatory conditions.

Endomucin is a membrane-bound glycoprotein expressed luminally by endothelial cells that line postcapillary venules, a primary site of leukocyte recruitment during inflammation. Here we show that endomucin abrogation on quiescent endothelial cells enables neutrophils to adhere firmly, via LFA-1-mediated binding to ICAM-1 constitutively expressed by endothelial cells. Moreover, TNF-α stimulation downregulates cell surface expression of endomucin concurrent with increased expression of adhesion molecules.

Differential roles of cAMP and cGMP in megakaryocyte maturation and platelet biogenesis.

The cyclic nucleotides cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) regulate the activity of protein kinase A (PKA) 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) differentiation and platelet formation.

The origin and function of platelet glycosyltransferases.

Platelets are megakaryocyte subfragments that participate in hemostatic and host defense reactions and deliver pro- and antiangiogenic factors throughout the vascular system. Although they are anucleated cells that lack a complex secretory apparatus with distinct Golgi/endoplasmic reticulum compartments, past studies have shown that platelets have glycosyltransferase activities. In the present study, we show that members of 3 distinct glycosyltransferase families are found within and on the surface of platelets.

Signal transduction in vasculogenesis and developmental angiogenesis.

The vasculature is a highly specialized organ that functions in a number of key physiological tasks including the transport of oxygen and nutrients to tissues. Formation of the vascular system is an essential and rate-limiting step in development and occurs primarily through two main mechanisms, vasculogenesis and angiogenesis. Both vasculogenesis, the de novo formation of vessels, and angiogenesis, the growth of new vessels from pre-existing vessels by sprouting, are complex processes that are mediated by the precise coordination of multiple cell types to form and remodel the vascular system.

The spectrin-based membrane skeleton stabilizes mouse megakaryocyte membrane systems and is essential for proplatelet and platelet formation.

Megakaryocytes generate platelets by remodeling their cytoplasm first into proplatelets and then into preplatelets, which undergo fission to generate platelets. Although the functions of microtubules and actin during platelet biogenesis have been defined, the role of the spectrin cytoskeleton is unknown. We investigated the function of the spectrin-based membrane skeleton in proplatelet and platelet production in murine megakaryocytes.

Cytoskeletal mechanics of proplatelet maturation and platelet release.

Megakaryocytes generate platelets by remodeling their cytoplasm into long proplatelet extensions, which serve as assembly lines for platelet production. Although the mechanics of proplatelet elongation have been studied, the terminal steps of proplatelet maturation and platelet release remain poorly understood. To elucidate this process, released proplatelets were isolated, and their conversion into individual platelets was assessed.

Dynamin 3 participates in the growth and development of megakaryocytes.

High-density oligonucleotide microarrays were used to compare gene expression profiles from uncultured CD34+/CD38lo cells and culture-derived megakaryocytes (MKs). As previously published, three replicate microarray data sets from three different sources of organ donor marrow were analyzed using the software program Rosetta Resolver. After setting a stringent p value of View Article and Find Full Text PDF

Megakaryocyte-derived microparticles: direct visualization and distinction from platelet-derived microparticles.

Platelet microparticles are a normal constituent of circulating blood. Several studies have demonstrated positive correlations between thrombotic states and platelet microparticle levels. Yet little is known about the processes by which platelet microparticles are generated in vivo.

Direct visualization of the endomitotic cell cycle in living megakaryocytes: differential patterns in low and high ploidy cells.

Endomitosis in megakaryocytes (MKs) involves repeated DNA replication in the absence of cytokinesis and is a crucial part of MK development. However, chromosomal dynamics have never been observed in living MKs. We developed a new transgenic mouse model in which the expression of human histone H2B fused in-frame to green fluorescent protein is targeted to MKs.

Visualization of microtubule growth in living platelets reveals a dynamic marginal band with multiple microtubules.

The marginal band of microtubules maintains the discoid shape of resting blood platelets. Although studies of platelet microtubule coil structure conclude that it is composed of a single microtubule, no investigations of its dynamics exist. In contrast to previous studies, permeabilized platelets incubated with GTP-rhodamine-tubulin revealed tubulin incorporation at 7.

Angiogenesis is regulated by a novel mechanism: pro- and antiangiogenic proteins are organized into separate platelet alpha granules and differentially released.

Platelets, in addition to their function in hemostasis, play an important role in wound healing and tumor growth. Because platelets contain angiogenesis stimulators and inhibitors, the mechanisms by which platelets regulate angiogenesis remain unclear. As platelets adhere to activated endothelium, their action can enhance or inhibit local angiogenesis.