Defective VWF secretion due to expression of MYH9-RD E1841K mutant in endothelial cells disrupts hemostasis.

Mutations in MYH9, the gene encoding the heavy chain of nonmuscle myosin IIa (NMII-A), cause MYH9-related disease (MYH9-RD), which is an autosomal-dominant thrombocytopenia with bleeding tendency. Previously, we showed that NMII-A in endothelial cells (ECs) is critical for hemostasis via regulating von Willebrand factor (VWF) release from Weibel-Palade bodies (WPBs). The aim of this study was to determine the role of the expression of MYH9 mutants in ECs in the pathogenesis of the MYH9-RD bleeding symptom. First, we expressed the 5 most common NMII-A mutants in ECs and found that E1841K mutant-expressing ECs secreted less VWF than the controls in response to a cyclic adenosine monophosphate (cAMP) signaling agonist. Then, we generated 2 knockin mouse lines, 1 with Myh9 E1841K in ECs and the other in megakaryocytes. Endothelium-specific E1841K mice exhibited impaired cAMP-induced VWF release and a prolonged bleeding time with normal platelets, whereas megakaryocyte-specific E1841K mice exhibited macrothrombocytopenia and a prolonged bleeding time with normal VWF release. Finally, we presented mechanistic findings that E1841K mutation not only interferes with S1943 phosphorylation and impairs the peripheral distribution of Rab27a-positive WPBs in Ecs under quiescent condition but also interferes with S1916 phosphorylation by disrupting the interaction with zyxin and CKIIα and reduces actin framework formation around WPBs and subsequent VWF secretion under the stimulation by a cAMP agonist. Altogether, our results suggest that impaired cAMP-induced endothelial VWF secretion by E1841K mutant expression may contribute to the MYH9-RD bleeding phenotype.

Hypofibrinogenemia with preserved hemostasis and protection from thrombosis in mice with an Fga truncation mutation.

Genetic variants within the fibrinogen Aα chain encoding the αC-region commonly result in hypodysfibrinogenemia in patients. However, the (patho)physiological consequences and underlying mechanisms of such mutations remain undefined. Here, we generated Fga270 mice carrying a premature termination codon within the Fga gene at residue 271. The Fga270 mutation was compatible with Mendelian inheritance for offspring of heterozygous crosses. Adult Fga270/270 mice were hypofibrinogenemic with ∼10% plasma fibrinogen levels relative to FgaWT/WT mice, linked to 90% reduction in hepatic Fga messenger RNA (mRNA) because of nonsense-mediated decay of the mutant mRNA. Fga270/270 mice had preserved hemostatic potential in vitro and in vivo in models of tail bleeding and laser-induced saphenous vein injury, whereas Fga-/- mice had continuous bleeding. Platelets from FgaWT/WT and Fga270/270 mice displayed comparable initial aggregation following adenosine 5'-diphosphate stimulation, but Fga270/270 platelets quickly disaggregated. Despite ∼10% plasma fibrinogen, the fibrinogen level in Fga270/270 platelets was ∼30% of FgaWT/WT platelets with a compensatory increase in fibronectin. Notably, Fga270/270 mice showed complete protection from thrombosis in the inferior vena cava stasis model. In a model of Staphylococcus aureus peritonitis, Fga270/270 mice supported local, fibrinogen-mediated bacterial clearance and host survival comparable to FgaWT/WT, unlike Fga-/- mice. Decreasing the normal fibrinogen levels to ∼10% with small interfering RNA in mice also provided significant protection from venous thrombosis without compromising hemostatic potential and antimicrobial function. These findings both reveal novel molecular mechanisms underpinning fibrinogen αC-region truncation mutations and highlight the concept that selective fibrinogen reduction may be efficacious for limiting thrombosis while preserving hemostatic and immune protective functions.

Annexin A2 in Fibrinolysis, Inflammation and Fibrosis.

As a cell surface tissue plasminogen activator (tPA)-plasminogen receptor, the annexin A2 (A2) complex facilitates plasmin generation on the endothelial cell surface, and is an established regulator of hemostasis. Whereas A2 is overexpressed in hemorrhagic disease such as acute promyelocytic leukemia, its underexpression or impairment may result in thrombosis, as in antiphospholipid syndrome, venous thromboembolism, or atherosclerosis. Within immune response cells, A2 orchestrates membrane repair, vesicle fusion, and cytoskeletal organization, thus playing a critical role in inflammatory response and tissue injury. Dysregulation of A2 is evident in multiple human disorders, and may contribute to the pathogenesis of various inflammatory disorders. The fibrinolytic system, moreover, is central to wound healing through its ability to remodel the provisional matrix and promote angiogenesis. A2 dysfunction may also promote tissue fibrogenesis and end-organ fibrosis.

Marmoset angiography just by percutaneous puncture of the caudal ventral artery.

Surgery in humans is continuously evolving and promoted minimally invasive treatment. On the other hand, despite the importance of the 3Rs principles for experimental animals is well documented, no reports describe specific methodologies for implementing "refinement" in practice. Here, we describe a new technique, the "Ohta Method" for caudal arthrocentesis in the pursuit of the 3Rs for animal experiments and the development of innovative methods for investigating systemic organ arteries through minimally invasive procedures. This procedure requires only a percutaneous puncture of the caudal artery without any injury to the limb or body trunk. In addition, it does not cut down the artery, making hemostasis easier and recovering arterial damage easier. We will show multiple organ artery angiographies in marmoset for the first time in the world. The principle described in this paper could also be applied to many other small animals, such as rats. Moreover, using this method, multiple doses of the drug or cells can be administered to the target organ at the time of therapeutic intervention, thereby enabling the establishment of more sophisticated and complex therapeutic intervention studies as translational research.

Systems Biology Analysis of the Radiation-Attenuated Schistosome Vaccine Reveals a Role for Growth Factors in Protection and Hemostasis Inhibition in Parasite Survival.

In spite of several decades of research, an effective vaccine against schistosomiasis remains elusive. The radiation-attenuated (RA) cercarial vaccine is still the best model eliciting high protection levels, although the immune mechanisms have not yet been fully characterized. In order to identify genes and pathways underlying protection we investigated patterns of gene expression in PBMC and skin draining Lymph Nodes (LN) from mice using two exposure comparisons: vaccination with 500 attenuated cercariae versus infection with 500 normal cercariae; one versus three doses. Vaccinated mice were challenged with 120 normal parasites. Integration of PBMC and LN data from the infected group revealed early up-regulation of pathways associated with Th2 skewing and polarization of IgG antibody profiles. Additionally, hemostasis pathways were downregulated in infected mice, correlating with platelet reduction, potentially a mechanism to assist parasite migration through capillary beds. Conversely, up regulation of such mechanisms after vaccination may explain parasite blockade in the lungs. In contrast, a single exposure to attenuated parasites revealed early establishment of a Th1 bias (signaling of IL-1, IFN-γ; and Leishmania infection). Genes encoding chemokines and their receptors were more prominent in vaccinated mice, indicating an enhanced capacity for inflammation, potentially augmenting the inhibition of intravascular migration. Increasing the vaccinations from one to three did not dramatically elevate protection, but there was a clear shift towards antibody-mediated effectors. However, elements of the Th1 bias were still evident. Notable features after three vaccinations were markers of cytotoxicity (including IL-6 and NK cells) together with growth factors and their receptors (FGFR/VEGF/EGF) and the apoptosis pathway. Indeed, there is evidence for the development of anergy after three vaccinations, borne out by the limited responses detected in samples after challenge. We infer that persistence of a Th1 response puts a limit on expression of antibody-mediated mechanisms. This feature may explain the failure of multiple doses to drive protection towards sterile immunity. We suggest that the secretions of lung stage parasites would make a novel cohort of antigens for testing in protection experiments.

Trastornos plaquetarios hereditarios poco frecuentes: patología molecular y aspectos diagnósticos / Infrequent hereditary platelets disorders: molecular pathology and diagnostic aspects

Introducción: Las plaquetas tienen una función clave en la hemostasia primaria a través de cuatro mecanismos fundamentales: adhesión, agregación, secreción y actividad procoagulante, todos controlados genéticamente por más de 50 genes asociados que han sido identificados. Las manifestaciones clínicas en las alteraciones hereditarias de las plaquetas suelen ser variables; aunque estas alteraciones de la coagulación suelen presentarse con una trombocitopenia notoria, también pueden exhibir trombocitopatías, en las cuales la capacidad hemostática de las plaquetas resulta afectada sin variar su número. Por tanto, existen gran variedad de manifestaciones fenotípicas y mutaciones en relación con la función plaquetaria, algunas de las cuales se explicarán más adelante. Objetivo: Realizar revisión práctica sobre mutaciones plaquetarias hereditarias de baja incidencia y destacar la importancia de su conocimiento, correcto diagnóstico, y tratamiento precoz. Métodos: Se realizó revisión literaria en inglés y españolen MEDLINE, EMBASE, Lilacs y ScienceDirect desde mayo 2019 hasta abril 2020, con el uso de combinación de palabras clave y términos MeSH relacionados con trombastenia, genética médica, hemostasis, agregación plaquetaria, trombopoyesis. Se efectuó análisis y resumen de la bibliografía revisada. Conclusión: Entre las alteraciones hereditarias de las plaquetas se pueden encontrar defectos en todos los mecanismos en que participan; sin embargo, la confirmación diagnóstica sigue siendo complicada por el tiempo y el costo que representa lo que ocasiona diagnósticos inadecuados que impactan en el manejo clínico y la evolución(AU)

Introduction: Platelets have a key role in primary hemostasis through four main mechanisms: adhesion, aggregation, secretion and procoagulant activity, all of these controlled by over 50 associated genes that have been identified. Clinical signs of hereditary platelets alterations are usually variable; even though these disorders of hemostasis generally course with a notorious thrombocytopenia, they also might have thrombocytopathies, in which the hemostatic capacity of platelets is affected without altering its number. According to this, there's a great variety of phenotypic manifestations and mutations that affect platelet function, some of these will be explained later on. Objective: To make a practical review of hereditary platelets mutations that have low incidence in population and to highlight the importance of knowing about them, how to diagnose them and early treatment. Methods: A review of literature in both Spanish and English, was done based on MEDLINE, EMBASE, Lilacs and ScienceDirect, during May 2019 and April 2020 using key words and MeSH terms such as thrombasthenia, medical genetics, hemostasis, platelets aggregation, thromopoiesis. Then, an analysis and summary of the reviewed bibliography was carried out. Conclusion: Among the hereditary alterations of platelets, many defects can be found in every mechanism involved; however, diagnostic confirmation is still complicated due to time and cost, causing inaccurate diagnoses that impact on clinic management and evolution(AU)

A Translational Model for Venous Thromboembolism: MicroRNA Expression in Hibernating Black Bears.

BACKGROUND: Hibernating American black bears have significantly different clotting parameters than their summer active counterparts, affording them protection against venous thromboembolism during prolonged periods of immobility. We sought to evaluate if significant differences exist between the expression of microRNAs in the plasma of hibernating black bears compared with their summer active counterparts, potentially contributing to differences in hemostasis during hibernation. MATERIALS AND METHODS: MicroRNA sequencing was assessed in plasma from 21 American black bears in summer active (n = 11) and hibernating states (n = 10), and microRNA signatures during hibernating and active state were established using both bear and human genome. MicroRNA targets were predicted using messenger RNA (mRNA) transcripts from black bear kidney cells. In vitro studies were performed to confirm the relationship between identified microRNAs and mRNA expression, using artificial microRNA and human liver cells. RESULTS: Using the bear genome, we identified 15 microRNAs differentially expressed in the plasma of hibernating black bears. Of these microRNAs, three were significantly downregulated (miR-141-3p, miR-200a-3p, and miR-200c-3p), were predicted to target SERPINC1, the gene for antithrombin, and demonstrated regulatory control of the gene mRNA expression in cell studies. CONCLUSIONS: Our findings suggest that the hibernating black bears' ability to maintain hemostasis and achieve protection from venous thromboembolism during prolonged periods of immobility may be due to changes in microRNA signatures and possible upregulation of antithrombin expression.

Comparison of DNA Methylation Profiles of Hemostatic Genes between Liver Tissue and Peripheral Blood within Individuals.

DNA methylation has become increasingly recognized in the etiology of complex diseases, including thrombotic disorders. Blood is often collected in epidemiological studies for genotyping and has recently also been used to examine DNA methylation in epigenome-wide association studies. DNA methylation patterns are often tissue-specific, thus, peripheral blood may not accurately reflect the methylation pattern in the tissue of relevance. Here, we collected paired liver and blood samples concurrently from 27 individuals undergoing liver surgery. We performed targeted bisulfite sequencing for a set of 35 hemostatic genes primarily expressed in liver to analyze DNA methylation levels of >10,000 cytosine-phosphate-guanine (CpG) dinucleotides. We evaluated whether DNA methylation in blood could serve as a proxy for DNA methylation in liver at individual CpGs. Approximately 30% of CpGs were nonvariable and were predominantly hypo- (<25%) or hypermethylated (>70%) in both tissues. While blood can serve as a proxy for liver at these CpGs, the low variability renders these unlikely to explain phenotypic differences. We therefore focused on CpG sites with variable methylation levels in liver. The level of blood-liver tissue correlation varied widely across these variable CpGs; moderate correlations (0.5 ≤ r < 0.75) were detected for 6% and strong correlations (r ≥ 0.75) for a further 4%. Our findings indicate that it is essential to study the concordance of DNA methylation between blood and liver at individual CpGs. This paired blood-liver dataset is intended as a resource to aid interpretation of blood-based DNA methylation results.

Effective hemostasis in children with Von Willebrand factor defects undergoing adenotonsillar procedures.

INTRODUCTION: Children with low von Willebrand factor (VWF) activity or type 1 von Willebrand disease (VWD) have increased risk of bleeding after adenotonsillar procedures and the optimal perioperative management to minimize bleeding is unknown. AIM: To report the effectiveness and safety of an institutional protocol in minimizing postoperative bleeding in children with type 1 VWD or low VWF activity. METHODS: We conducted a retrospective chart review in children with type 1 VWD or low VWF activity treated via an institutional protocol that utilizes repeated doses of Desmopressin acetate (DDAVP, 1-deamino 8-D arginine- vasopressin) or VWF concentrate, brief hospitalization for observation and extended use of oral epsilon aminocaproic acid (EACA). RESULTS: From 2010 to 2017, 13 children underwent an adenotonsillar procedure and were treated with this protocol. Although 7.6% had minor immediate bleeding and 23% had minor delayed bleeding, no patients experienced major bleeding or required transfusion, additional surgery or other measures not specified by the protocol. Mild hyponatremia was observed in 80% of patients who received DDAVP. CONCLUSION: Our institutional protocol specifying repeated dosing of DDAVP or VWF concentrate to sustain elevated VWF levels during periods of highest bleeding risk and extended use of EACA is effective at preventing major bleeding episodes after adenotonsillar procedures. However, this analysis raised safety concerns that prompted changes in the institutional protocol and highlight the need for further prospective studies to determine the optimal strategy for safely reducing bleeding complications in these patients.

C3G contributes to platelet activation and aggregation by regulating major signaling pathways.

C3G is a GEF (guanine nucleotide exchange factor) for Rap GTPases, among which the isoform Rap1b is an essential protein in platelet biology. Using transgenic mouse models with platelet-specific overexpression of C3G or mutant C3GΔCat, we have unveiled a new function of C3G in regulating the hemostatic function of platelets through its participation in the thrombin-PKC-Rap1b pathway. C3G also plays important roles in angiogenesis, tumor growth, and metastasis through its regulation of the platelet secretome. In addition, C3G contributes to megakaryopoiesis and thrombopoiesis. Here, we used a platelet-specific C3G-KO mouse model to further support the role of C3G in hemostasis. C3G-KO platelets showed a significant delay in platelet activation and aggregation as a consequence of the defective activation of Rap1, which resulted in decreased thrombus formation in vivo. Additionally, we explored the contribution of C3G-Rap1b to platelet signaling pathways triggered by thrombin, PMA or ADP, in the referenced transgenic mouse model, through the use of a battery of specific inhibitors. We found that platelet C3G is phosphorylated at Tyr504 by a mechanism involving PKC-Src. This phosphorylation was shown to be positively regulated by ERKs through their inhibition of the tyrosine phosphatase Shp2. Moreover, C3G participates in the ADP-P2Y12-PI3K-Rap1b pathway and is a mediator of thrombin-TXA2 activities. However, it inhibits the synthesis of TXA2 through cPLA2 regulation. Taken together, our data reveal the critical role of C3G in the main pathways leading to platelet activation and aggregation through the regulation of Rap1b.

High-Risk Pregnancies and Their Impact on Neonatal Primary Hemostasis.

Primary hemostasis, similar to other systems in the adjusting and transitioning neonate, undergoes developmental adaptations in the first days of life. Although platelets of neonates do not differ quantitatively compared with those of adults, they functionally present with major differences, thus supporting the theory of a "hypofunctional" phenotype that is counterbalanced by high hematocrit and more potent von Willebrand factor multimers. No clinical effect of bleeding tendency has hence been established so far for healthy term neonates. However, discrepancies in functionality have been noted, associated with gestational age, with more pronounced platelet hyporesponsiveness in preterm neonates. Multiple methods of in vitro platelet function evaluation such as PFA-100/200, platelet aggregometry, flow cytometry, and cone and platelet analyzer have been used for assessment of neonatal primary hemostasis. Several pregnancies are characterized as "high-risk" when risk factors preexist in maternal history or evolve during pregnancy. These pregnancies require specialized observation as they may have unpredictable outcome. High-risk pregnancies include clinical entities such as preeclampsia, pregnancy-induced smoking during pregnancy, gestational diabetes mellitus (GDM), autoimmune diseases, and other maternal hematological conditions. In some cases, like systemic lupus erythematosus, antiphospholipid antibody syndrome, and maternal immunologically based thrombocytopenia, neonatal thrombocytopenia is regarded as a prominent hemostasis defect, while in others, like pregnancy-induced hypertension and preeclampsia, both quantitative and qualitative disorders of neonatal platelets have been reported. In other pathologies, like GDM, neonatal primary hemostasis remains vastly unexplored, which raises the need for further investigation. The extent to which primary hemostasis is affected in neonates of high-risk pregnancies is the main objective of this narrative review.

Metabolomic, transcriptomic and genetic integrative analysis reveals important roles of adenosine diphosphate in haemostasis and platelet activation in non-small-cell lung cancer.

Lung cancer is the leading cause of cancer-related deaths in the world. The most prevalent subtype, accounting for 85% of cases, is non-small-cell lung cancer (NSCLC). Lung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD) are the most common subtypes. Despite recent advances in treatment, the low 5-year survival rate of NSCLC patients (approximately 13%) reflects the lack of early diagnostic biomarkers and incomplete understanding of the underlying disease mechanisms. We hypothesized that integration of metabolomic, transcriptomic and genetic profiles of tumours and matched normal tissues could help to identify important factors and potential therapeutic targets that contribute to tumorigenesis. We integrated omics profiles in tumours and matched adjacent normal tissues of patients with LUSC (N = 20) and LUAD (N = 17) using multiple system biology approaches. We confirmed the presence of previously described metabolic pathways in NSCLC, particularly those mediating the Warburg effect. In addition, through our combined omics analyses we found that metabolites and genes that contribute to haemostasis, angiogenesis, platelet activation and cell proliferation were predominant in both subtypes of NSCLC. The important roles of adenosine diphosphate in promoting cancer metastasis through platelet activation and angiogenesis suggest this metabolite could be a potential therapeutic target.

Innovative Molecular Testing Strategies for Adjunctive Investigations in Hemostasis and Thrombosis.

Clinicians and scientists in the fields of hemostasis and thrombosis have been among those first to integrate new molecular strategies for the purpose of enhancing disease diagnosis and treatment. The molecular diagnosis and introduction of gene therapy approaches for hemophilia are obvious examples of this tendency. In this review, the authors summarize information concerning three molecular technologies that have reached various stages of translational potential for their incorporation into the clinical management of disorders of hemostasis. Chromatin conformation assays are now being used to capture structural knowledge of long-range genomic interactions that can alter patterns of gene expression and contribute to quantitative trait pathogenesis. Liquid biopsies in various forms are providing opportunities for early cancer detection, and in the context of tumor-educated platelets, as described here, can also characterize tumor type and the extent of tumor progression. This technology is already being trialed in patients with unprovoked venous thrombosis to assess the potential for occult malignancies. Lastly, advances in single cell transcriptome analysis, provide opportunities to definitively determine molecular events in rare cells, such as antigen-specific regulatory T cells, within the context of heterogeneous cell populations.

CRISPR/Cas9-mediated in vivo gene targeting corrects hemostasis in newborn and adult factor IX-knockout mice.

Many genetic diseases, including hemophilia, require long-term therapeutic effects. Despite the initial success of liver-directed adeno-associated virus (AAV) gene therapy for hemophilia in clinical trials, long-term sustained therapeutic effects have yet to be seen. One explanation for the gradual decline of efficacy over time is that the nonintegrating AAV vector genome could be lost during cell division during hepatocyte turnover, albeit at a slow pace in adults. Readministering the same vector is challenging as a result of the AAV-neutralizing antibodies elicited by the initial treatment. Here, we investigated the use of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated homology-directed gene targeting for sustained treatment of hemophilia B. We developed a donor vector containing a promoterless partial human factor IX (FIX) complementary DNA carrying the hyperactive FIX Padua mutation. A single injection of dual AAV vectors in newborn and adult FIX-knockout (FIX-KO) mice led to stable expression of FIX at or above the normal levels for 8 months. Eight weeks after the vector treatment, we subjected a subgroup of newborn and adult treated FIX-KO mice to a two-thirds partial hepatectomy; all of these animals survived the procedure without any complications or interventions. FIX levels persisted at similar levels for 24 weeks after partial hepatectomy, indicating stable genomic targeting. Our results lend support for the use of a CRISPR/Cas9 approach to achieve lifelong expression of therapeutic proteins.

Hemophilia in a Changing Treatment Landscape.

The mainstay of hemophilia management has been the regular, prophylactic infusion of missing coagulation factors VIII/IX. This approach is limited by the need for frequent intravenous infusions, high cost, limited availability, and the development of inhibitory antibodies to factors VIII/IX. Numerous recent breakthroughs are addressing many of these limitations. These include the development of extended half-life factors that require less frequent infusions and the development of various novel agents that can be given subcutaneously and infrequently, including FVIII-mimetic antibody and downregulators of natural anticoagulants. Finally, gene therapy is set to offer patients a possibility for a cure.

Hemostatic Genes Exhibit a High Degree of Allele-Specific Regulation in Liver.

OBJECTIVE: Elucidating the genetic basis underlying hepatic hemostatic gene expression variability may contribute to unraveling genetic factors contributing to thrombotic or bleeding disorders. We aimed to identify novel cis-regulatory variants involved in regulating hemostatic genes by analyzing allele-specific expression (ASE) in human liver samples. STUDY DESIGN: Biopsies of human liver tissue and blood were collected from adults undergoing liver surgery at the Sahlgrenska University Hospital (n = 20). Genomic deoxyribonucleic acid (gDNA) and total ribonucleic acid (RNA) were isolated. A targeted approach was used to enrich and sequence 35 hemostatic genes for single nucleotide polymorphism (SNP) analysis (gDNAseq) and construct individualized genomes for transcript alignment. The allelic ratio of transcripts from targeted RNAseq was determined via ASE analysis. Public expression quantitative trait loci (eQTL) and genome-wide association study (GWAS) data were used to assess novelty and importance of the ASE SNPs (and proxies, r 2 ≥ 0.8) for relevant traits/diseases. RESULTS: Sixty percent of the genes studied showed allelic imbalance across 53 SNPs. Of these, 7 SNPs were previously validated in liver eQTL studies. For 32 with eQTLs in other cell/tissue types, this is the first time genotype-specific expression is demonstrated in liver, and for 14 ASE SNPs, this is the first ever reported genotype-expression association. A total of 29 ASE SNPs were previously associated with the respective plasma protein levels and 17 ASE SNPs to other relevant GWAS traits including venous thromboembolism, coronary artery disease, and stroke. CONCLUSION: Our study provides a comprehensive ASE analysis of hemostatic genes and insights into the regulation of hemostatic genes in human liver.

Factor XIII Subunit A in the Skin: Applications in Diagnosis and Treatment.

The role of factor XIII subunit A (FXIII-A) is not restricted to hemostasis. FXIII-A is also present intracellularly in several human cells and serves as a diagnostic marker in a wide range of dermatological diseases from inflammatory conditions to malignancies. In this review, we provide a guide on the still controversial interpretation of dermal cell types expressing FXIII-A and assess the previously described mechanisms behind their accumulation under physiological and pathological conditions of the human skin. We summarize the intracellular functions of FXIII-A as well as its possible sources in the extracellular space of the dermis with a focus on its relevance to skin homeostasis and disease pathogenesis. Finally, the potential role of FXIII-A in wound healing, as a field with long-term therapeutic implications, is also discussed.

Receptor-interacting protein kinase 3 promotes platelet activation and thrombosis.

Previous studies have shown that receptor-interacting protein kinase 3 (RIP3) is involved in many important biological processes, including necroptosis, apoptosis, and inflammation. Here we show that RIP3 plays a critical role in regulating platelet functions and in vivo thrombosis and hemostasis. Tail bleeding times were significantly longer in RIP3-knockout (RIP3-/-) mice compared with their wild-type (WT) littermates. In an in vivo model of arteriole thrombosis, mice lacking RIP3 exhibited prolonged occlusion times. WT mice repopulated with RIP3-/- bone marrow-derived cells had longer occlusion times than RIP3-/- mice repopulated with WT bone marrow-derived cells, suggesting a role for RIP3-deficient platelets in arterial thrombosis. Consistent with these findings, we observed that RIP3 was expressed in both human and mice platelets. Deletion of RIP3 in mouse platelets caused a marked defect in aggregation and attenuated dense granule secretion in response to low doses of thrombin or a thromboxane A2 analog, U46619. Phosphorylation of Akt induced by U46619 or thrombin was diminished in RIP3-/- platelets. Moreover, RIP3 interacted with Gα13 Platelet spreading on fibrinogen and clot retraction were impaired in the absence of RIP3. RIP3 inhibitor dose-dependently inhibited platelet aggregation in vitro and prevented arterial thrombus formation in vivo. These data demonstrate a role for RIP3 in promoting in vivo thrombosis and hemostasis by amplifying platelet activation. RIP3 may represent a novel promising therapeutic target for thrombotic diseases.

[Thrombosis of the portal, upper mesenteric, and splenic veins in a patient with thrombophilia (a clinical case report)]. / Tromboz vorotnoi, verkhnei bryzheechnoi i selezenochnoi ven u bol'nogo s trombofiliei.

Currently there are several dozens of hereditarily associated thrombophilias and acquired states known to condition the development of a thrombus. Thrombosis of visceral veins appears to be a considerably less often encountered event than thrombosis in the system of visceral arteries. Presented herein in the article is a clinical case report concerning subacute thrombosis of the portal, upper mesenteric and splenic veins, having developed on the background of mutations of 7 genes of the system of haemostasis in a young adult patient. Timely comprehensive examination with determining polymorphism of the haemostasis system genes made it possible to verify the aetiology of the disease in the patient, while multispiral computed tomography contributed favourably to specifying the extension of thrombosis. Due to the developed segmental necrosis of the small intestine the patient was subjected to resection of the necrotised portion of the small intestine followed by establishing an entero-enteric anastomosis. In the postoperative period adequate anticoagulant therapy was adjusted in order to prevent relapse of thrombogenesis.

RGS10 Negatively Regulates Platelet Activation and Thrombogenesis.

Regulators of G protein signaling (RGS) proteins act as GTPase activating proteins to negatively regulate G protein-coupled receptor (GPCR) signaling. Although several RGS proteins including RGS2, RGS16, RGS10, and RGS18 are expressed in human and mouse platelets, the respective unique function(s) of each have not been fully delineated. RGS10 is a member of the D/R12 subfamily of RGS proteins and is expressed in microglia, macrophages, megakaryocytes, and platelets. We used a genetic approach to examine the role(s) of RGS10 in platelet activation in vitro and hemostasis and thrombosis in vivo. GPCR-induced aggregation, secretion, and integrin activation was much more pronounced in platelets from Rgs10-/- mice relative to wild type (WT). Accordingly, these mice had markedly reduced bleeding times and were more susceptible to vascular injury-associated thrombus formation than control mice. These findings suggest a unique, non-redundant role of RGS10 in modulating the hemostatic and thrombotic functions of platelets in mice. RGS10 thus represents a potential therapeutic target to control platelet activity and/or hypercoagulable states.