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Intracranial hemorrhage (ICH) associated with fetal/neonatal alloimmune thrombocytopenia (FNAIT) is attributed mainly to endothelial damage caused by binding of maternal anti-HPA-1a antibodies to the αvβ3 integrin on endothelial cells (ECs). We examined the effect of anti-HPA-1a antibodies on EC function using 2 EC lines from different vascular beds, HMVEC of dermal origin and hCMEC/D3 of cerebral origin. Anti-HPA-1a sera significantly increased apoptosis in both HMVEC and hCMEC/D3 cells and permeability in hCMEC/D3 cells only. This increase in both apoptosis and permeability was significantly inhibited by a monoclonal anti-β3 antibody (SZ21) binding to the HPA-1a epitope. Our results indicate that (1) maternal anti-HPA-1a antibodies impair EC function by increasing apoptosis and permeability and (2) ECs from different vascular beds vary in their susceptibility to pathological effects elicited by maternal anti-HPA-1a antibodies on EC permeability. Examination of maternal anti-HPA-1a antibodies for their effect on EC permeability may predict potential ICH associated with FNAIT.

Hemophilia A (HA) therapy requires intravenous replacement infusions of factor (F) VIII concentrate. Inhibitors are high-affinity immunoglobulin G that are directed against FVIII and thereby render replacement therapy ineffective. This complication has significant prognostic implications. We aimed to examine the immune system involvement in inhibitor formation specifically T-cell excision circles (TRECs) and B-cell excision circles (KRECs), markers of new T and B cells, respectively, and examine them as surrogate markers for inhibitor formation.Blood samples were collected from 35 children with severe HA. Children were divided into two groups: with FVIII inhibitors and without FVIII inhibitors. TRECs and KRECs were measured in peripheral blood.A total of 11 patients with inhibitors and 24 without were evaluated. Children with inhibitors had higher levels of TRECs however not statistically significant (p = 0.085). CjKREC levels were higher in the inhibitor patients (p = 0.003). Moreover, the sj/cjKREC ratio was lower in the inhibitor patients (p = 0.015).Our findings may add to the notion that inhibitor formation is attributed to humoral immunity due to peripheral B-cell expansion and loss of peripheral tolerance. Improved knowledge regarding the involvement of the immune system in the formation of FVIII inhibitors will enable better therapy tailoring in the era of non-replacement therapies.The etiology of FVIII inhibitor formation is multifactorial, in which the immune system plays a pivotal role. Our findings may add to the notion that inhibitor formation is attributed to humoral immunity due to peripheral B-cell expansion and production of antibodies against FVIII. Improved knowledge regarding the involvement of the immune system in the development of FVIII inhibitors will enable the identification of patients prone to inhibitor development and better therapy tailoring in the new era of non-replacement therapies.

Background Air travel thrombosis continues to be a controversial topic. Exposure to hypoxia and hypobaric conditions during air travel is assumed a risk factor. The aim of this study is to explore changes in parameters of coagulation, fibrinolysis and blood flow in a rat model of exposure to hypobaric conditions that imitate commercial and combat flights. Methods Sixty Sprague-Dawley male rats, aged 10 weeks, were divided into 5 groups according to the type and duration of exposure to hypobaric conditions. The exposure conditions were 609 m and 7620 m for 2 and 12 h duration. Blood count, thrombin– antithrombin complex, D-dimer, interleukin-1 and interleukin-6 were analyzed. All rats went through flight angiography MRI at day 13-post exposure. Results No effect of the various exposure conditions was observed on coagulation, fibrinolytic system, IL-1 or IL-6. MRI angiography showed blood flow reduction in lower limb to less than 30% in 50% of the rats. The reduction in blood flow was more pronounced in the left vessel than in the right vessel (p = 0.006, Wilcoxon signed rank test). The extent of occlusion differed across exposure groups in the right, but not the left vessel (p = 0.002, p = 0.150, respectively, Kruskal-Wallis test). However, these differences did not correlate with the exposure conditions. Conclusion In the present rat model, no clear correlation between various hypobaric conditions and activation of coagulation was observed. The reduction in blood flow in the lower limb also occurred in the control group and was not related to the type of exposure.

Severe protein C deficiency due to biallelic PROC mutations is an extremely rare thrombophilia, most commonly presenting during the neonatal period as purpura fulminans. Despite treatment, severe morbidity and mortality are frequent. The current study reports 3 unrelated patients harboring novel homozygous PROC mutations and their clinical phenotypes. We discuss how the cytoprotective activity of protein C and its role in the stabilization of endothelial barriers may account for the unique symptoms of this thrombophilia.

Introduction: Hemophilia A (HA) is an X-linked bleeding disorder caused by factor VIII (FVIII) deficiency or dysfunction due to F8 gene mutations. HA carriers are usually asymptomatic because their FVIII levels correspond to approximately half of the concentration found in healthy individuals. However, in rare cases, a carrier may exhibit symptoms of moderate to severe HA primarily due to skewed inactivation of her non-hemophilic X chromosome. Aim: The aim of the study was to investigate X-chromosome inactivation (XCI) patterns in HA carriers, with special emphasis on three karyotypically normal HA carriers presenting with moderate to severe HA phenotype due to skewed XCI, in an attempt to elucidate the molecular mechanism underlying skewed XCI in these symptomatic HA carriers. The study was based on the hypothesis that the presence of a pathogenic mutation on the non-hemophilic X chromosome is the cause of extreme inactivation of that X chromosome. Methods: XCI patterns were studied by PCR analysis of the CAG repeat region in the HUMARA gene. HA carriers that demonstrated skewed XCI were further studied by whole-exome sequencing (WES) followed by X chromosome-targeted bioinformatic analysis. Results: All three HA carriers presenting with the moderate to severe HA phenotype due to skewed XCI were found to carry pathogenic mutations on their non-hemophilic X chromosomes. Patient 1 was diagnosed with a frameshift mutation in the PGK1 gene that was associated with familial XCI skewing in three generations. Patient 2 was diagnosed with a missense mutation in the SYTL4 gene that was associated with familial XCI skewing in two generations. Patient 3 was diagnosed with a nonsense mutation in the NKAP gene that was associated with familial XCI skewing in two generations. Conclusion: Our results indicate that the main reason for skewed XCI in our female HA patients was negative selection against cells with a disadvantage caused by an additional deleterious mutation on the silenced X chromosome, thus complicating the phenotype of a monogenic X-linked disease. Based on our study, we are currently offering the X inactivation test to symptomatic hemophilia carriers and plan to expand this approach to symptomatic carriers of other X-linked diseases, which can be further used in pregnancy planning.

Background Factor XI (FXI) deficiency is a rare autosomal bleeding disorder. The rarity of spontaneous bleeding and absence of optimal tools to predict the bleeding risk in FXI-deficient patients hamper the standardization of prophylactic treatment enabling them to undergo major surgeries without blood products. Objectives We explored the effectiveness of a single and very low dose of recombinant factor VIIa (rFVIIa) along with tranexamic acid (TXA) as prophylactic treatment for FXI-deficient patients undergoing various types of surgery at various sites of injury. We studied the potential use of thrombin generation (TG) as a surrogate tool for predicting thrombogenicity. Patients and Methods Our cohort consisted of 10 patients with severe FXI deficiency undergoing 12 interventions. Patients received a single dose of 10 to 15 μg/kg rFVIIa at the end of surgery in addition to TXA initiated 2 hours before surgery at the dose of 4 g/day for 3 to 5 days. TG was tested before and 30 minutes after rFVIIa administration. Results All operations were uneventful and none of the patients bled excessively or required blood products. No thrombotic event was reported, and the postoperative hospitalization duration was comparable to that of patients without bleeding disorders. TG performed at the peak of rFVIIa was below the curve of healthy controls, thus confirming that the administered dose was not thrombogenic. Conclusion A single very low dose of rFVIIa along with TXA is a simple and safe treatment to control hemostasis in severe FXI-deficient patients undergoing diverse type of surgical procedure at various sites.

Rare bleeding disorders (RBD) are inherited coagulopathies, whose hemostatic control is based upon replacement therapy. Marstacimab (PF-06741086) is a human monoclonal IgG that targets the Kunitz2 domain of tissue factor pathway inhibitor [TFPI]. Marstacimab is currently in development for bleeding prophylaxis in patients with hemophilia.To assess the potential impact of Marstacimab upon thrombin generation (TG) in RBD patients' plasma samples.Our cohort included 18 RBD patients, with severe deficiencies: 5 Von Willebrand Disease (VWD) type 3, 4 FVII, 3 FXI, 2 FXIII deficiency and 1 patient with: FX, FV + FVIII, Fibrinogen, combined vitamin K dependent factors' deficiency. Citrated samples from RBD patients were collected and spiked with Marstacimab, TG was measured by calibrated automated thrombogram. Among all patients a reduced baseline TG was observed as compared to controls. Improvement of median (lag time, peak and ETP was observed in Marstacimab spiked samples from 8 min, 99 nM, 1116 nMx min to 5.5 min, 194 nM,1614 nMx min, respectively. None of the values measured among RBD patients exceeded normal controls.These in vitro data suggest that Marstacimab may serve as a promising approach for restoring the hemostatic balance in various RBD, though potential clinical implications should be further investigated.

Introduction Glanzmann thrombasthenia (GT) is a severe inherited platelet function disorder (IPFD), presenting with bleeding diathesis and impaired platelet aggregation, is caused by mutations in the genes ITGA2B or ITGB3. Aim We aimed to study the genetic cause of IPFD mimicking GT. Methods During 2017–2019, 16 patients were referred to our tertiary center with bleeding symptoms, impaired platelet aggregation and normal platelet count and size. Results Using flow cytometry, 13/16 patients were diagnosed with GT, yet three patients displayed normal surface expression of the integrins αIIbβ3 and αvβ3, as well as normal integrin αIIbβ3 activation following incubation with the activating monoclonal antibody anti-LIBS6, while platelet activation following ADP or epinephrine was impaired. Whole exome sequencing detected 2 variants in RASGRP2 gene in all 3 patients. Discussion Both RASGRP2 mutations predicted frameshift, premature stop codon (p. I427Mfs*92 and p. R494Afs*54, respectively) and truncated calcium-sensing guanine nucleotide exchange factor [CalDAG-GEFI]- the major signaling molecule that regulates integrin-mediated aggregation and granule secretion, causing IPFD-18. Conclusion Patients who suffer from bleeding diathesis without immune dysregulation, may be mistakenly diagnosed as GT. Further studies are required to confirm the diagnosis of specific IPFD.

Background Severe von Willebrand disease (VWD) may be associated with chronic joint damage and may require prophylactic therapy. Emicizumab is a humanized bispecific antibody, which mimics the function of coagulation factor VIII (FVIII), and it has been approved for prophylaxis in hemophilia A. Methods This is the first study assessing the potential future role of emicizumab as an alternative prophylactic treatment in patients with severe VWD, based upon a thrombin generation (TG) ex vivo analysis. We report 51 weeks of successful off label emicizumab prophylaxis in a child with severe VWD and recurrent hemarthroses and progressive arthropathy despite adherence to previous prophylaxis with replacement therapy. Results and conclusions Our work demonstrated that ex vivo spiking with emicizumab increased TG in plasma from patients with type 3 VWD. Similar TG results were observed in our treated patient, whose therapy was well tolerated without any adverse events. Both in vitro and ex vivo TG data support sufficient hemostasis without exceeding the range seen in healthy volunteers. Further collaborative studies on the efficacy and safety of emicizumab prophylaxis in severe VWD is warranted.

Activated protein C (APC) exerts diverse cell signaling pathways which results in multiple distinct cytoprotective actions. These include anti-apoptotic and anti-inflammatory activities and stabilization of endothelial and epithelial barriers. We studied the ability of APC to inhibit the leakage and the growth of newly formed as well as pre-existing choroidal neovascularization (CNV) and examined the ability of APC to stabilize the Retinal Pigmented Epithelium (RPE). We explored the contribution of Tie2 receptor to the protective effects of APC. CNV was induced by laser photocoagulation in C57BL/6J mice. APC was injected intravitreally immediately or 7 days after CNV induction. Neovascularization was evaluated on RPE-choroidal flatmounts using FITC-dextran perfusion and CD31 immunofluorescence. CNV leakage was measured by fluorescein angiography (FA). The ability of APC to stabilize the RPE barrier was evaluated in-vitro by dextran permeability and zonula occludens 1 (ZO1) immunostaining. Tie2 blocking was induced in-vivo by intraperitoneal injection of Tie2 kinase inhibitor and in-vitro by incubation with anti Tie2 antibodies. APC treatment dramatically inhibited the generation of newly formed CNV leakage sites and reversed leakage in 85% of the pre-existing CNV leaking sites. In RPE cell culture, APC induced translocation of ZO1 to the cell membrane, accompanied by reduction in permeability of the monolayer. Inhibition of Tie2 significantly decreased APC protective activities in both the mouse model and the RPE cell culture. Our results show that APC treatment significantly inhibits the leakage and growth of newly formed, as well as pre-existing CNV, and its protective activities are partially mediated via the Tie2 receptor. The data suggest that APC should be further investigated as a possible effective treatment for CNV.

Hemophilia is a hereditary congenital hemorrhagic diathesis caused by mutations in blood coagulation factor VIII (FVIII) or IX (FIX) genes, causing hemophilia A and B, respectively. Most cases are familial but a significant minority is sporadic.To examine the presenting symptoms of patients with hemophilia in Israel and identify causes for delay in diagnosis.Retrospective analysis of data from medical files of newly diagnosed patients with hemophilia during the period from 1st January 2010 to 31s December 2017.During the study period 104 children had been diagnosed with hemophilia. Fifteen percent were diagnosed with hemophilia B and 85% with hemophilia A. In most familial cases the diagnosis was established by examination of aPTT and the level of the relevant clotting factor shortly after birth. Diagnosis of sporadic cases (40 cases) was performed due to suggestive clinical symptoms. Perinatal complications were observed in 6 newborns. The most common presenting symptom was disproportionate bleeding following circumcision. In 6/21 patients who experienced excessive bleeding following circumcision there was a delay in diagnosis. Severe bleeding requiring intensive care admission was observed in twelve neonates.Diagnosis of hemophilia in Israel is made at an earlier age than in Europe. This is probably due to the performance of ritual circumcision during the neonatal period. In recent years a reduction in familial cases of severe hemophilia has been noted due to genetic counseling of hemophilia carriers. In cases of excessive bleeding following circumcision aPTT and PT should be examined promptly.

Severe Von Willebrand's disease (VWD) may be associated with chronic joint damage and may require prophylactic therapy. In severe VWD, factor VIII (FVIII) levels are low due to rapid clearness. Emicizumab is a humanized bispecific antibody which mimics the function of coagulation factor VIII (FVIII). It has been approved for prophylaxis in hemophilia A. This is the first study assessing the potential role of emicizumab as an alternative prophylactic treatment in a cohort of patients with severe VWD. We present a TG model evaluating patients' hemostasis following ex vivo spiking of their plasma samples with emicizumab. We also report 24 weeks of successful emicizumab prophylaxis in a child with severe VWD and repeated hemarthroses. A cohort of twenty-four VWD patients were included in the study. Fifty-four percent of our patients were males and the cohort consisted of 14 children (≤18 years) and 10 adults. The majority of patients (96%) were of Caucasian origin. Hemarthrosis was encountered in most type 3 VWD patients, whereas none of the type 2 VWD patients had any joint bleeds. Prophylactic treatment was administered in the majority of type 3 VWD patients, whereas type 2 VWD patients largely required only intermittent on demand therapy applied for bleeding episodes or any surgical interventions. Thrombin generation analysis was carried out blindly in plasma obtained from thirteen type 3 VWD patients and eleven type 2 VWD patients. Seventeen healthy volunteers served as a control group. In plasma from type 3 VWD patients, TG was substantially lower than in plasma from type 2 VWD patients, with ETP of 765 nM×min (596-962) vs. 1954 nM×min (1483-2008) (P = 0•001) and peak height of 47 nM (36-65) vs. 262 nM (142-318) (P = 0•002) In order to examine the potential use of emicizumab as an alternative treatment option for type 3 VWD patients, an ex vivo spiking analysis comparing the effect of Haemate P and emicizumab on TG was performed. An improvement in peak height was demonstrated following spiking with both Haemate P concentrations (P = 0•001 for both) and with the higher emicizumab concentration (P = 0•011). Notably, whereas spiking with both Haemate P concentrations increased peak height to near-normal level, spiking with higher emicizumab concentration increased it to a lesser extent (the median was still lower than in normal controls (P = 0•005). Following the decision to treat our impetus patient with emicizumab prophylaxis, TG analyses were performed in the patient's plasma before and during emicizumab loading and maintenance (Figure 3). As expected, patient's initial TG was extremely low and improved following the first administration of emicizumab loading dose (at week 2 after therapy initiation), at which time emicizumab level was 21 µg/mL. Further significant improvement of TG was noted following loading period completion while emicizumab level was 62 µg/mL. Our patient has been treated with emicizumab for more than six months altogether and did not encounter any joint bleeds since the commencement of therapy. During this period, a single dose of Haemate P was administered following tooth exfoliation. Our study contributes towards a better understanding of TG as a surrogate marker of VWD patients' hemostasis. Our data suggests that some severe VWD patients could be safely and efficiently treated with emicizumab. The successful prophylaxis of our patient and our ex vivo laboratory findings should set the ground for further collaborative multicenter studies to examine the efficacy and safety of emicizumab prophylaxis in type 3 VWD patients. Disclosures Barg: roshe: Honoraria, Speakers Bureau. Kenet:PI Healthcare, CSL Behring: Honoraria; Bayer, Pfizer, Takeda, BioMarin, Novo Nordisk: Speakers Bureau; Bayer, Pfizer, Roche, Alnylam (Sanofi), Shire: Research Funding; Bayer, Pfizer, BioMarin, Takeda, Roche, Novo Nordisk, Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: The use of Emicizumab in sever Von Willebrand disease

The phenotype of bleeding in patients with severe FXI deficiency is unpredictable and unlike other bleeding disorders, it is not directly correlated with levels of FXI. In this study we analyzed whether the global coagulation assays can serve as a clinical tool in predicting bleeding tendency in patients with severe FXI deficiency undergoing surgery, taking into account the large inter-individual variability of FXI levels and genotypes. Thrombin generation (TG) was measured in 39 platelet-poor plasma with or without tissue factor (TF) and in the presence or absence of corn trypsin inhibitor (CTI). Rotation thromboelastometry (ROTEM) was performed with fresh whole blood of 26 patients applying NATEM and INTEM tests. TG induced by recalcification can distinguish between bleeding and non-bleeding patients with severe FXI deficiency particularly among those with FXI activity of 2-20IU/dl. The addition of TF or TF and CTI to the TG assay masked the ability to differentiate between XI activity, genotype as well as bleeding and non-bleeding patients. ROTEM assays failed to distinguish bleeding from non-bleeding patients but could do so between different FXI activity levels and genotypes. In conclusion, in the current study we found a sensitive tool to distinguish between bleeding and non-bleeding patients. In order to recommend TG as a predictive tool for treatment tailoring, a larger patient group is required.

A 6 months old infant, diagnosed with a rare mutation causing severe hemophilia A, presented with spinal epidural hematoma. Parents later admitted the infant had glass cupping therapy performed within 2 weeks of the onset of symptoms. The rare mutation, rare bleeding complication, and the eventual course of therapy applied in this case will be discussed in our case report.

BACKGROUND: Fetal neonatal alloimmune thrombocytopenia (FNAIT) is a life-threatening bleeding disorder in the fetus or neonate caused by maternal alloantibodies directed against fetal platelet (PLT) antigens inherited from the father. The immune-dominant antigen leading to severe FNAIT is the human PLT antigen (HPA)-1, whose polymorphism constitutes an epitope for human leukocyte antigens (HLAs), usually DRB3*0101 leading to an immune response. STUDY DESIGN AND METHODS: In this study our aims were to find whether other allele variants of the β subunit of the HLA-DR family specifically focused on the HLA residues that bind Position 33 of the HPA-1 integrin contribute to FNAIT development and affect response to treatment and whether coexistence of both anti-HPA-1a and anti-HLA Class I specific against the father's antigens leads to a more severe thrombocytopenia in the newborn. We examine the genotype of 23 mothers to newborns with FNAIT compared to a control group. RESULTS: Our results suggested that, when HPA-1 incompatibility with the husband is found, the presence of two HLA alleles (DRB3*01:01 and DRB4*01:01) in the mother increases the risk and severity of FNAIT and reduces the success of a preventive immunoglobulin G treatment. We provide a structural model for the molecular basis of the rational effects of the different HLA alleles. In addition, we found that the presence of both anti-HPA-1 and anti-HLAs did not aggravate FNAIT in comparison to mothers harboring only anti-HPA-1. CONCLUSION: Overall, we suggest that a specific genotyping of the mother in relation to HLA-DRB as well as HPA-1 can serve as an antenatal diagnostic tool, particularly in siblings of women who gave birth to neonates with FNAIT.

To investigate the mechanism of secondary degeneration of the optic nerve, and to evaluate the neuroprotective effect of minocycline in this process.A partial transection model that morphologically separates primary and secondary degeneration was applied unilaterally in 152 Wistar rat eyes. The involvement of pro-apoptotic, pro-survival and inflammatory pathways was analyzed by quantitative real-time PCR and immunohistochemistry at multiple time points. The neuroprotective effect of daily intraperitoneal injections of minocycline 22 mg/kg/day was evaluated at 7, 11 and 21 days post-injury. Retrograde labeling of retinal ganglion cells (RGCs) with fluorogold was via the superior colliculus, and surviving RGCs were counted using retinal whole mounts.Both primary and secondary degeneration led to a significant up-regulation of the pro-apoptotic genes, GADD45α, ei24 and CDK2, and the pro-survival gene, IAP-1. These processes differed, however, in their reaction to minocycline. Minocycline protected RGC death from secondary degeneration at 11 days (6 ± 8% loss compared to 37 ± 7% in the saline-treated group, n = 15, P = 0.012), and at 21 days (42 ± 7% versus 64 ± 7% respectively, n = 15, P = 0.06) after partial transection. In contrast, its effect on primary degeneration was not significant.While the genetic profile supported similarities between primary and secondary degeneration of the optic nerve, the specific effect of minocycline on secondary degeneration revealed a potential difference between the two. The mechanism underlying secondary degeneration, and its role in optic neuropathies such as glaucoma, awaits further studies.

Introduction: Age-related macular degeneration (AMD) is considered one of the main causes of severe vision loss in older adults. Wet AMD is characterized by choroidal neovascular membrane developed under or into the sensory retina, breaking the outer blood-retina barrier (oBRB) and causing leakage and bleeding. Protein C (PC) is a plasma serine protease zymogen whose active form, activated protein C (APC), exerts diverse homeostatic cell signaling pathways apart from its anticoagulant activity. APC activities are mediated mainly through endothelial PC receptor (EPCR) and protease activated receptor (PAR)-1. APC was recently shown to act as a novel ligand for Tie2, a tyrosine kinase receptor playing an important role in angiogenesis. Thus, APC may modulate pathological angiogenesis in relevant ocular conditions, such as choroidal neovascularization (CNV), via its interaction with Tie2. To the best of our knowledge, there are no studies addressing the potential use of APC as oBRB stabilizer and CNV inhibitor. Aim: To assess the protective effect of APC as a retinal barrier stabilizer and its ability to reduce CNV growth, leakage and penetration from the choroid into the sensory retina. Moreover, to study the role of Tie2 receptor upon APC mode of action in the retina. Methods: CNV development was induced in C57BL/6J mice by laser applications. Immediately following CNV induction APC (0.1-10 µg/µl) was injected intravitrealy. Seven to 14 days later, the retina was separated from the underlying tissues and the 2 segments were flattened: sclera-choroid-retinal pigment epithelium (RPE) segment and the photoreceptors-sensory retina segment. Blood vessels were stained using CD31 (an endothelial marker) or FITC-dextran and analyzed by using a confocal microscopy. Fluorescein angiography (FA) was performed to detect leakage from CNV. The ability of APC to stabilize the oBRB and prevent leakage was studied using ARPE-19 tissue culture (simulating the oBRB). FITC-Dextran leakage through the cultured cell monolayers was measured and the tight junction protein, Zonula occludens-1 (ZO1) cellular distribution was followed using immunostaining. Tie2 Kinase inhibitor and anti-Tie2 antibodies were used for Tie2 inhibition in the murine and cell culture models, respectively. Results: Quantitative analysis of the CNV area and volume revealed that 7-14 days after laser applications, APC treatment resulted in a statistically significant reduction in CNV growth, area and volume as compared to saline. Moreover, APC inhibited the penetration of CNV from the choroid throughout the RPE into the sensory retina in a dose-dependent manner. Figure 1 summarize the quantitative assessment of APC suppression of blood vessel penetration from the choroid (Fig.1A) to the sensory retina segment (Fig.1B). FA analysis showed that APC significantly suppressed the leakage of fluorescein from the laser lesion and preserved the retinal architecture. Incubation of RPE cells with APC resulted in dose dependent translocation of ZO1 to the cell membrane region, accompanied by reduction in permeability throughout the RPE monolayer. ZO1 translocation formed a typical ZO1 honeycomb pattern that is characteristic for the stabilization of tight junctions (Fig.1C). Inhibition of Tie2, in the laser induced CNV mice model and in RPE cell culture, significantly decreased APC protective activities in both models. Conclusions: Several Chorio-retinal pathologies are accompanied by damage to the oBRB and pathological growth of CNV. Our present data provide evidence that APC can protect the choroid and the retina from CNV growth, can suppress leakage from the newly formed choroidal blood vessels and may act as oBRB stabilizer. The protective function of APC in the eye provides direction for new strategies to treat chorio-retinal diseases affected by abnormal oBRB function and CNV growth. Our preliminary results warrant further investigation to extend the data regarding the potential use of APC as a novel anti-CNV treatment and oBRB protector. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Copper plays a key role in angiogenesis and in the synthesis and stabilization of extracellular matrix skin proteins, which are critical processes of skin formation. We hypothesized that introducing copper into wound dressings would enhance wound repair. Application of wound dressings containing copper oxide to wounds inflicted in genetically engineered diabetic mice (C57BL/KsOlaHsd-Lepr(db)) resulted in increased gene and in situ up-regulation of proangiogenic factors (e.g., placental growth factor, hypoxia-inducible factor-1 alpha, and vascular endothelial growth factor), increased blood vessel formation (p

Objective To discern whether plasma levels of microparticles (MPs) measured at 24 weeks of gestation predict late complications of pregnancy. Design Secondary analysis of samples obtained prospectively. Setting Large academic medical center. Patient(s) Two hundred sixty-two healthy women selected from 642 nulliparous women with singleton pregnancies. Intervention(s) Sampling for blood cell MPs and thrombophilias at 24 weeks of gestation and measurements of blood flow resistance in uterine, placental, and umbilical arteries at 24 and 31 to 33 weeks of gestation. Main Outcome Measure(s) Relationship between levels of MPs and late pregnancy complications, thrombophilias, and blood flow resistance. Result(s) Flow cytometry only detected MPs derived from endothelial cells (CD31 + ) and platelet (CD41 + ). No statistically significant correlation was found between levels of CD31 + or CD41 + MPs and subsequent occurrence of pregnancy-induced hypertension, preeclampsia, intrauterine growth restriction, or small for gestational age infants. Nor was there a statistically significant correlation with blood flow resistance parameters at 24 weeks of gestation (except for the left uterine artery) or at 31 to 33 weeks of gestation. Levels of these MPs in thrombophilic and nonthrombophilic women were similar. Conclusion(s) Levels of circulating MPs at 24 weeks of gestation had no predictive value for subsequent development of pregnancy-induced hypertension, preeclampsia, intrauterine growth restriction, or small for gestational age infants.

SummaryTissue transglutaminase was reported to act as protein disulfide isomerase (PDI). We studied whether plasma transglutaminase – coagulation factor XIII (FXIII) – has PDI activity as well. PDI activity was measured by determining the ability to renature reduced-denatured RNase (rdRNase). We found that FXIII can re-nature rdRNase, with efficiency comparable to commercial PDI. This PDI activity was inhibited by bacitracin. Like tissue transglu-taminase, FXIII-mediated PDI activity is independent of its transglutaminase activity and is located on the A subunit. Surface-associated PDI has been previously shown to catalyse two distinct functions: transnitrosation with subsequent release of intracellular nitric oxide and disulfide bond rearrangement during platelet integrin ligation. Our results imply that FXIII-PDI activity may have a role in platelet function.

Factor XIII is a plasma transglutaminase that participates in the final stage of the coagulation cascade. Thrombin-activated FXIII (FXIIIa) catalyzes the formation of covalent crosslinks between gamma-glutamyl and epsilon-lysyl residues on fibrin molecules to yield the mature clot. In addition to its role in hemostasis, FXIIIa was previously shown by us to stimulate endothelial cells to exhibit pro-angiogenic activity. In this work, we studied the effect of FXIIIa on other cells that participate in angiogenesis and tissue repair, such as monocytes and fibroblasts. FXIIIa significantly enhanced migration and proliferation, and inhibited apoptosis of monocytes and fibroblasts. Similar to our previous observations with endothelial cells, the stimulating effect of FXIIIa on monocytes and fibroblasts was elicited via its binding to alpha (v)beta (3) integrin leading to cJun upregulation and TSP-1 downregulation. Since monocytes and fibroblasts are essential components of the tissue repair process, the results of this study, together with the proangiogenic activity of FXIIIa, further substantiate a significant role of FXIII in tissue repair.

A 6 months old infant, diagnosed with a rare mutation causing severe hemophilia A, presented with spinal epidural hematoma. Parents later admitted the infant had glass cupping therapy performed within 2 weeks of the onset of symptoms. The rare mutation, rare bleeding complication, and the eventual course of therapy applied in this case will be discussed in our case report.

To determine whether polymorphisms of platelet surface glycoprotein associated with arterial thrombosis are risk factors for branch retinal vein occlusion. A case-control study in which 69 patients with branch retinal vein occlusion and 147 controls who attended the eye clinic for nonvascular complications participated. DNA was extracted from whole blood and analyzed for genotyping of platelet glycoprotein polymorphisms by polymerase chain reactions and specific restricted enzymes. No relationship was found between the four platelet glycoprotein polymorphisms i.e. GPIa C807T, VNTR and Kozak of glycoprotein Ibalpha, the HPA-1 of glycoprotein IIIa and the occurrence of branch retinal vein occlusion. The HPA-2 polymorphism was found in 18 out 60 (30%) patients with branch retinal vein occlusion in comparison with 27 out 142 (19%) of controls, with an estimated odds ratio of 1.8 (95% confidence interval, 0.91-3.65). The four platelet glycoprotein polymorphisms are not risk factors for branch retinal vein occlusion and therefore it seems unnecessary to screen those patients for it. A larger study is required, however, to determine whether HPA-2 is a novel risk factor for branch retinal vein occlusion.

Four missense mutations in the factor XIII A-subunit gene, Arg260Leu, Ala318Val, Thr398Asn and Gly210Arg, were previously reported by us in patients with severe factor XIII deficiency. The objective of our study was to discern the effect of all four mutations on the stability and intracellular localization of the factor XIII A-subunit by their expression in COS cells. In-vitro mutagenesis, transient expression of the mutants in COS cells and subsequent pulse-chase analyses were carried out. Intracellular localization of wild-type and mutant proteins was analyzed by immunohistochemistry using a monoclonal antibody against factor XIII A-subunit. Pulse-chase analyses of metabolically labeled proteins demonstrated rapid intracellular degradation of each mutant protein as compared with wild type. Immunocytochemical and immunofluorescence analyses disclosed that wild-type and all four mutant factor XIII A-subunit proteins were diffusely distributed within the cytoplasm but not in the endoplasmic reticulum of the COS-7 cells. The Arg260Leu, Ala318Val, Thr398Asn and Gly210Arg mutations in FXIII A-subunit cause rapid intracellular degradation of the corresponding mutated protein.

Objective— Factor XIII (FXIII), a plasma transglutaminase that stabilizes fibrin clots at the final stages of blood coagulation by crosslinking fibrin monomers, is essential for embryo implantation and participates in tissue remodeling and wound healing, processes that involve angiogenesis. The aim of our study was to analyze the effect of FXIII on angiogenesis using in vitro and in vivo models and to examine the role of FXIII in the basic steps of angiogenesis, ie, migration, proliferation, and apoptosis/cell survival. Methods and Results— In the Matrigel tube formation model, only FXIIIa caused a dose-dependent enhancement of array formation. This proangiogenic effect was not associated with alterations in vascular endothelial growth factor (VEGF) protein levels nor VEGF or VEGFR2 mRNA levels. FXIIIa, but not nonactivated or transglutaminase-inactivated FXIII, significantly enhanced endothelial cell migration and proliferation and inhibited apoptosis. After treatment of HUVECs with FXIIIa, almost complete disappearance of mRNA of thrombospondin 1 (TSP-1) and a marked reduction in the secretion of TSP-1 protein were observed. A reduction in TSP-1 protein synthesis, although to a lesser extent, was observed on treatment of microvascular endothelial cells with FXIIIa. In a rabbit cornea model, injection of FXIIIa caused neovascularization associated with almost complete disappearance of TSP-1 in the cornea. Conclusions— These results show that FXIIIa exhibits a novel proangiogenic activity that is associated with downregulation of TSP-1 and also involves stimulation of endothelial cell proliferation and migration and inhibition of apoptosis. These findings might shed light on the mechanism by which FXIII mediates tissue repair and remodeling.

In the present study, the adherence of Staphylococcus aureus (strain 8325-4) and its RNAIII mutant (WA400) to immobilised fibrinogen and fibronectin, and to human endothelial cells (EC), was studied. [3H]Thymidine-labelled bacteria in stationary phase were incubated on the test surfaces for 20 min under static or flow (200/s) conditions. The results showed: (a) increased adherence of the RNAIII mutant to fibrinogen under static conditions, and decreased adherence of the mutant to fibronectin and EC under both static and flow conditions compared with the parental strain; (b) stronger ability of the mutant compared with the parental strain to induce platelet aggregation in suspension; (c) greater adherence of the parental strain and the mutant to EC pre-treated with platelet-rich plasma compared with platelet-poor plasma, and to EC pre-treated with platelet-poor plasma compared with control; (d) increased adherence of S. aureus to EC pre-treated with PMA-activated platelets and decreased adherence to EC pre-treated with tirofiban, a platelet glycoprotein IIb-IIIa inhibitor, which paralleled with increased adherence of PMA-activated platelets and decreased adherence of glycoprotein IIb-IIIa-blocked platelets to EC in the absence of bacteria; and (e) adherence of the mutant was more sensitive to pre-treatment of EC with plasma and PMA-activated platelets. In conclusion, RNAIII down-regulates S. aureus adherence to fibrinogen under static condition and up-regulates S. aureus adherence to fibronectin and EC under both static and flow conditions. The potentiating role of activated platelets in the presence of plasma in S. aureus adherence to EC is down-regulated by RNAIII, probably due to down-regulation of adherence to fibrinogen, the important plasma protein bridging S. aureus, platelets and EC.

BACKGROUND: The genetic predispositions to venous thrombosis such as factor V Leiden (FVL) mutation (Arg 506 Gln), prothrombin (FII) gene mutation (G20210A), and mutation of the methylenetetrahydrofolate reductase (MTHFR) gene (C677T) have been reported to be associated with recurrent pregnancy loss. This paper examines the prevalence of markers for genetic thrombophilias in women with recurrent miscarriage. METHODS: The prevalence of FVL, FII G20210A and MTHFR C677T was compared in 108 women with three or more pregnancy losses either exclusively in the first trimester, or mixed first and second trimester losses, with the prevalence found in 82 fertile parous control women without miscarriages. Markers for the thrombophilias were assessed by PCR analysis. RESULTS: Twenty-three of the 108 patients (21.3%), had thrombophilia markers, which was similar to the proportion of patients in the control group (20.7%) with these markers. The prevalences of FVL and FII G20210A were lower in the study group than in the control group (3.7 versus 6.1% for FVL and 4.6 versus 6.1% for FII respectively); however, the difference was not statistically significant. In contrast, the prevalence of MTHFR C677T was higher in the study group than the control population (13 versus 8.5% respectively), but this difference was not statistically significant. There was no statistically significant prevalence of any particular thrombophilia in patients with previous first and second trimester pregnancy losses compared with patients with first trimester losses alone. CONCLUSION: Thrombophilia was not found to be associated with recurrent pregnancy loss.

Objectives: Infusions of aminobisphonates (ABP) activate Vγ9δ2T cells in vivo, and induce an acute inflammatory response in 30% of patients treated for osteoporosis. Following the observation of digital thrombosis in a patient with systemic sclerosis (SSc) who was treated with an intravenous ABP, zoledronate (Zol) we evaluated whether patient and control PB mononuclear cell (MC, PBMC) acquire a pro-thrombotic phenotype in response to zoledronate (Zol).Results: Vγ9δ2T cells, of both patients and healthy donors (HD), upregulated the CD69 activation antigen and secreted tumor necrosis factor (TNF)α in response to Zol in vitro. In addition, exposure to either Zol or lipopolysaccharide (LPS), or to both additively, induced expression of the highly procoagulant, tissue factor (TF)-1 on CD14+ monocytes. Importantly, only Zol-induced TF-1 was blocked by a monoclonal antibody to TNFα. Interestingly, we found that SSc but not healthy donor (HD) Vδ1+ T cells, were concurrently activated by Zol, to produce interleukin (IL)-4. Plasma of the SSc patient who developed critical digital ischemia after infusion of Zol, but neither plasma from a second patient who had no adverse clinical response to Zol infusion nor of a HD, strongly enhanced Zol induced monocyte TF-1, which could still be blocked by anti-TNFα. Conclusions: ABP induced secretion of TNFα by Vγ9δ2+T cells may lead to TNFα dependent induction of pro-coagulant TF-1 induction, on monocytes. In certain clinical settings, e.g. SSc, TF-1+monocytes could play a role in triggering clinically relevant thrombosis.

A 75 year old patient presenting with mucocutaneous bleeding was diagnosed with acquired thrombasthenia. The diagnosis was based on lack of platelet aggregation with adenosine diphosphate (ADP), arachidonic acid and collagen, and normal aggregation induced by ristocetin.To study the mechanism of platelet function inhibition in a patient with acquired thrombasthenia.Aggregation assays of platelets from the patient and healthy controls were performed. In addition, anti-glycoprotein (GP) IIbIIIa antibodies bindingto normal in the presence or absence of the patient's serum was by flow cytometry.Aggregation of normal platelets in the presence of patient's plasma was inhibited four- and 2.5-fold in the presence of ADP and arachidonic acid respectively, while collagen-induced aggregation was completely abolished. Ristocetin-induced aggregation was normal. The patient's serum inhibited binding of commercial anti-glycoprotein IIbIIIa antibodies to normal platelets twofold by flow cytometry. Treatment with anti-CD20 monoclonal antibody (rituximab) normalized the patient's platelet aggregation.These results suggest that the patient developed inhibitory anti-GPIIbIIIa autoantibodies that caused acquired thrombasthenia.

Global regulatory genes in Staphylococcus aureus , including agr and sar , are known to regulate the expression of multiple virulence factors, including cell wall adhesins. In the present study, the adherence of S. aureus RN6390 (wild type), RN6911 ( agr ), ALC136 ( sar ), and ALC135 ( agr sar ) to immobilized fibrinogen, fibronectin, von Willebrand factor (vWF), extracellular matrix (ECM), and human endothelial cells (EC) EAhy.926 was studied. Bacteria grown to postexponential phase were subjected to light oscillation (static condition) or to shear stress at 200 s −1 (flow condition) on tissue culture polystyrene plates coated with either protein ligands, ECM, or EC. Adherence of nonlabeled bacteria to immobilized ligands was measured by an image analysis system, while adherence of [ 3 H]thymidine-labeled S. aureus to ECM and EC was measured by a β-scintillation counter. The results showed increased adherence of agr and agr sar mutants to immobilized fibrinogen and higher potential of these mutants to induce platelet aggregation in suspension, decreased adherence of sar and agr sar mutants to immobilized fibronectin and vWF as well as to ECM and EC, increased adherence of both S. aureus wild type and sar mutant to EC treated with platelet-rich plasma (PRP) compared to platelet-poor plasma (PPP) and to EC treated with PPP compared to the control, and increased adherence of S. aureus wild type to EC coated with PRP in which platelets were activated with phorbol 12-myristate 13-acetate compared to intact PRP. This finding paralleled the increased adherence to EC of activated compared to intact platelets. It is suggested that platelet-mediated S. aureus adherence to EC depends on platelet activation and the number of adherent platelets and available receptors on the platelet membrane. In conclusion, the agr locus downregulates S. aureus adherence to fibrinogen, while the sar locus upregulates S. aureus adherence to fibronectin, vWF, ECM, and EC. The effect of both agr and sar on S. aureus adherence properties develops primarily under flow conditions, which suggests different adhesion mechanisms in static and flow conditions.

Exposure of whole blood (WB) to subendothelial extracellular matrix (ECM) under shear stress in the cone and plate(let) analyser (CPA) results in platelet adhesion, followed by release reaction and aggregation of circulating platelets on the adherent platelets. The properties of circulating non-adhered platelets in the CPA was studied by exposure of WB to ECM at a high shear rate (1300/s) for 2 min (1st run), followed by transfer of the suspension to a new ECM-coated well for a second run (2nd run) under similar conditions. The results of the 2nd run demonstrated transient adhesion refractoriness associated with platelet microaggregate formation in the suspension. The adhesion refractoriness was dependent on platelet activation during the 1st run and was prevented by addition of apyrase (ADP scavenger) or ADP receptor inhibitor, suggesting a role for ADP in mediating this response. Furthermore, exposure of WB samples to suboptimal concentrations of ADP (0·4–1 μmol/l) or a thrombin receptor activating peptide (TRAP) (5 μmol/l) for 2 min resulted in a similar transient platelet adhesion refractoriness to ECM under flow conditions. The transient platelet refractoriness and microaggregate formation induced by ADP was associated with a transient reduction in glycoprotein (GP)Ib, increased P-selectin expression and increased fibrinogen binding by circulating platelets. These data suggest a role for platelet agonists at suboptimal concentrations in modulating platelet function and limiting the expansion of the thrombus.

Recently, we described a method of testing platelet deposition on extracellular matrix under flow conditions. The method was used for assessment of platelet function in various platelet disorders, for monitoring of replacement and anti-platelet therapy. In the present study, we investigated platelet deposition on a polystyrene surface compared with that on extracellular matrix, under defined shear rates, using the original Cone and Plate(let) Analyzer. A correlation of adhesion rate (surface coverage) and aggregate formation (average size) of platelets from normal citrated blood between polystyrene and extracellular matrix was observed. Blocking of von Willebrand factor binding to glycoprotein Ib by a recombinant von Willebrand factor fragment substantially decreased platelet adhesion to both surfaces. Blocking of GPIIb-IIIa by Arg–Gly–Asp–Ser peptide prevented platelet adhesion to the polystyrene while an extensive adhesion of single platelets to extracellular matrix was observed. Furthermore, platelet adhesion to polystyrene but not to extracellular matrix was completely inhibited by platelet inactivation with prostaglandin E 1 . Platelets from patients with severe von Willebrand disease yielded very low adhesion to both polystyrene and extracellular matrix. The addition of von Willebrand factor to the blood of these patients or pre-coating of polystyrene surface with von Willebrand factor restored the ability of platelets to adhere and aggregate on the surface. Platelets from patients with Glanzmann's thrombasthenia and afibrinogenemia adhered to extracellular matrix (with defective aggregate formation), while they failed to adhere to the polystyrene. Fibrinogen added to afibrinogenemia blood or pre-coating of the polystyrene with fibrinogen restored the ability of platelets to adhere and aggregate on the surface. In conclusion, the polystyrene surface, like extracellular matrix, can be used to assess platelet function disorders taking in account that platelet deposition on polystyrene under flow is absolutely dependent on platelet activation and on the presence of fibrinogen, von Willebrand factor, and their receptors.

SummaryWe investigated the effects of two well established risk factors for cardiovascular disease, homocysteine and oxidized low density lipoprotein (ox-LDL), on endothelial cell thrombogenicity. For this purpose we studied platelet adhesion to human endothelial cells (EC) under flow conditions at a shear rate of 350 s−1 following EC treatment with either homocysteine or ox-LDL. Treatment of EC with either homocysteine (1 or 10 mmol/L for 16 h) or ox-LDL (100 µg/ml for 16 h) resulted in a 2-3 fold enhancement in platelet adhesion. The enhancement in platelet adhesion induced by 1 mmol/L homocysteine, but not that induced by 10 mmol/L homocysteine, was absolutely dependent on fibrin formation. Homocysteine treatment has significantly increased the cell surface tissue factor (TF) activity and slightly reduced the expression of the intercellular adhesion molecule I (ICAM-1). In contrast, ox-LDL treatment upregulated ICAM-1 expression and had no significant effect on endothelial TF activity. Neither homocysteine nor Ox-LDL affected surface expression of the αvβ3 integrin. The homocysteine-induced enhancement in platelet adhesion was almost completely abolished by blockade of the EC TF activity by a polyclonal antibody. The enhancing effect of homocysteine was also greatly reduced by inhibition of the EC αvβ3 integrin, but was not affected by blockade of EC ICAM-1. On the other hand, ox-LDL-induced enhancement in platelet – EC adhesion was greatly inhibited by blocking ICAM-1 or αvβ3, but remained unaffected by inhibition of TF activity. Preincubation of platelets with the glycoprotein IIb-IIIa (GPIIb-IIIa) antagonist Reo-Pro has virtually abolished the enhancing effect of both homocysteine and ox-LDL. Our results suggest that homocysteine and ox-LDL might increase endothelial thrombogenicity by distinct mechanisms: homocysteine – by inducing TF activity, and ox-LDL – by upregulating ICAM-1, both of which enhance GPIIb-IIIa/fibrinogen dependent platelet adhesion to EC. The αvβ3 integrin, although not affected by EC stimulation, seems to play a crucial role in platelet-EC interaction regardless of the mechanism of EC perturbation.

Recent studies emphasize the role of blood constituents in Staphylococcus aureus ( S. aureus ) adherence to subendothelial extracellular matrix. In the present study, the adherence of two strains of S. aureus (ATCC 29213 and RN 6390) grown to a postexponential phase to cultured human umbilical vein endothelial cells (EC-304) was examined. Under flow conditions (600 s -1 ), pretreatment of endothelial cells (ECs) with human α-thrombin (2 U/mL) significantly (2- to 4-fold) increased bacterial adherence to ECs. Adherence of both S. aureus strains to thrombin-treated ECs was similarly higher in the presence of whole blood, platelet-rich plasma, or platelet-poor plasma when compared with Tris-buffered saline solution (TBS). Platelet inactivation in whole blood by prostaglandin E 1 did not reduce the adherence rate. When ATCC 29213 bacteria were suspended in TBS containing increasing concentrations of fibrinogen at near-physiologic ranges (0.25 to 2 mg/mL), a dose-dependent increase in S. aureus adherence to thrombin-activated ECs was observed that reached a maximum level of about 12-fold. Fibronectin used at the above physiologic concentrations (12.5 to 100 μg/mL) enhanced bacterial adherence up to 2-fold. Von Willebrand factor (1 IU/mL) did not support bacterial adherence to ECs, either alone or in combination with fibrinogen. Inhibition of fibrin formation either by the Gly-Pro-Arg-Pro peptide or by hirudin increased bacterial adherence by 50% and 90%, respectively. Blockage of either ICAM-I, α 5 β 1 , or α v β 3 receptors on ECs by appropriate monoclonal antibodies resulted in substantial inhibition of bacterial adherence (by 42%, 65%, and 72%, respectively). Preincubation of S. aureus with a fibrinogen γ-chain binding domain peptide led to 65% inhibition of adherence to ECs in the presence of fibrinogen. In contrast, preincubation of bacteria with the Arg-Gly-Asp-Ser peptide failed to affect their adherence. The data suggest that S. aureus adherence to the EC surface was (1) significantly enhanced by thrombin treatment of ECs, (2) not mediated by platelets, and (3) mediated by plasma fibrinogen, which binds to the bacteria via the C-terminus γ-chain binding domain but not via the Arg-Gly-Asp sequence. (J Lab Clin Med 2000;135:43-51)

Several recent studies evaluated a possible effect of the prothrombotic polymorphisms such as 5,10 methylenetetrahydrofolate reductase (MTHFR) nt 677C → T, factor V (F V) nt 1691G → A (F V Leiden), and factor II (F II) nt 20210 G → A on the risk of myocardial infarction. In the present study, we analyzed the effect of these prothrombotic polymorphisms, as well as apolipoprotein (Apo) E4, smoking, hypertension, diabetes mellitus, and hypercholesterolemia, on the risk of myocardial infarction in young males. We conducted a case-control study of 112 young males with first acute myocardial infarction (AMI) before the age of 52 and 187 healthy controls of similar age. The prevalences of heterozygotes for F V G1691A and F II G20210A were not significantly different between cases and controls (6.3% v 6.4% and 5.9% v 3.4% among cases and controls, respectively). In contrast, the prevalence of MTHFR 677T homozygosity and the allele frequency of Apo E4 were significantly higher among patients (24.1% v 10.7% and 9.4% v5.3% among cases and controls, respectively). Concomitant presence of hypertension, hypercholesterolemia, or diabetes and one or more of the four examined polymorphisms increased the risk by almost ninefold (odds ratio [OR] = 8.66; 95% confidence interval [CI], 3.49 to 21.5) and concomitant smoking by almost 18-fold (OR = 17.6; 95% CI, 6.30 to 48.9). When all atherogenic risk factors were analyzed simultaneously by a logistic model, the combination of prothrombotic and Apo E4 polymorphisms with current smoking increased the risk 25-fold (OR = 24.7; 95% CI, 7.17 to 84.9).The presented data suggest a synergistic effect between atherogenic and thrombogenic risk factors in the pathogenesis of AMI, as was recently found in a similar cohort of women.

An A-->G transition in the acceptor splice site at the intron 19/exon 20 junction of the glycoprotein IIb gene was defined as a novel mutation causing Glanzmann thrombasthenia in two Iraqi-Jewish siblings. This mutant DNA was transcribed into four distinct species of mRNA, one of which resulted in a premature termination codon and the other three predicting deletions of 50, 61 or 72 amino acids, respectively.

We investigated the role of platelets in human melanoma cell (line 397) interaction with vascular endothelial cells (ECs) under flow conditions. The ability of the tumour cells to adhere to the EC monolayer was significantly reduced by application of flow at a shear rate of 250 s(-1). A 2.2-fold increase in tumour cell adhesion to ECs under flow was observed upon addition of thrombin receptor agonist peptide (TRAP)-activated platelets but not resting platelets. A similar increase (2.5-fold) in tumour cell adhesion to ECs under flow was observed when the tumour cells were incubated with resting platelets on thrombin-treated ECs. However, thrombin treatment of the ECs alone had no effect on tumour cell adhesion in the absence of platelets. The enhancement of tumour cell adhesion to ECs by TRAP-activated platelets was virtually abolished by blockade of the platelet glycoproteins P-selectin and GPIIb-IIIa by monoclonal antibodies. Blockade of P-selectin also inhibited the direct adhesion of TRAP-activated platelets to ECs, but did not affect the interaction of the tumour cells with platelets immobilized on subendothelial extracellular matrix (ECM). Blockade of GPIIb-IIIa inhibited both platelet-EC and platelet-tumor cell interactions. Our results indicate that tumour cell adhesion to the endothelium under flow is enhanced by platelets under conditions that allow platelet adhesion to ECs. Inhibition studies suggest that activated platelet adhesion to ECs is mediated by P-selectin and GPIIb-IIIA, and tumour cell adhesion to EC-bound platelets--mainly by GPIIb-IIIa. Images Figure 3 Figure 4

The aim of our study was to explore the role of platelets and their specific integrin receptors in mediating the interaction of 4 human tumor cell lines (3 melanoma and 1 carcinoma) with the extracellular matrix (ECM) under static and arterial flow conditions. Under static conditions, all 4 cell lines adhered to the ECM. The adhesion capacity of all 4 cell lines was virtually abolished by application of flow during incubation with the ECM. Under static conditions, tumor cell adhesion was not affected by adding platelets to the cell suspension and was slightly reduced by pre-coating the ECM with platelets prior to the addition of tumor cells. In contrast, under flow conditions, platelets significantly increased tumor cell adhesion to the ECM, the enhancing effect being more pronounced when platelets were pre-incubated with the ECM prior to the addition of tumor cells than when incubated simultaneously with the cells. Platelet-mediated tumor cell adhesion under flow was markedly inhibited by blockade of the platelet GPIIb-IIIa or of the tumor cell αv integrins. Platelets of a Glanzmann thrombastenia (GT) patient were unable to support tumor cell adhesion to the ECM under flow. Our results suggest that the interaction of tumor cells with subendothelium-bound platelets under flow conditions is mediated by platelet GPIIb-IIIa and by tumor cell αv integrins independently of the nature of the β subunit. Int. J. Cancer, 70:201–207, 1997. © 1997 Wiley-Liss, Inc.

A patient with a severe bleeding tendency due to acquired von Willebrand disease (VWD) is presented. Although no underlying disorder has emerged during 6 years of follow-up, an immune-mediated mechanism was responsible for acquired VWD in this patient as demonstrated by detection of von Willebrand factor (VWF)/anti-VWF complexes in the patient's plasma and their removal by protein A-sepharose beads and resumption of normal haemostasis with correction of VWF antigen, VWF activity and VWF multimeric pattern after treatment of the patient with high-dose gammaglobulin. Detection of anti-VWF antibodies in the patient's plasma had a significant impact on the choice of therapeutic intervention to control bleeding.

article i nfo Background: Factor XIII (FXIII), a plasma pro-transglutaminase, consists of two A subunits and two B subunits (FXIIIA2B2). Following activation by thrombin, it cross-links fibrin chains at the final step of coagulation. We previously reported that FXIII subunit A (FXIIIA) serves as a protein disulfide isomerase (PDI), and that PDI promotes platelet adhesion and aggregation. Objective: This study sought to examine possible mechanistic effect of FXIII on platelet adhesion to fibrinogen; specifically, the role of its PDI activity. Methods:Exvivoexperiments: Blood platelets derived from five patients with hereditary FXIIIA deficiency before and after treatment with Fibrogammin-P (FXIIIA2B2 concentrate) were washed and incubated on immobilized fibrinogen. Bound platelets were stained and counted by microscopy. In vitro experiments: Platelets derived from patients before treatment and five healthy controls were washed and analyzed for adhesion in the pres- ence or absence of Fibrogammin-P or recombinant FXIII (FXIIIA2 concentrate). Results:Inexvivoexperiments, one hour afterFibrogammin-Ptreatment, mean (±SEM) plateletadhesion to fibrin- ogen increased by 27±2.32% (pb0.001). In in vitro experiments, treatment with Fibrogammin-P or recombinant FXIII (10 IU/mL each) enhanced platelet adhesion to fibrinogen (in patients, by 29.95±6.7% and 29.05±5.3%, respectively; in controls, by 26.06±3.24% and 26.91±4.72, respectively; pb0.04 for all). Iodoacetamide-treated FXIII (I-FXIII), where transglutaminase activity is blocked, showed similar enhanced adhesion as untreated FXIII. By contrast, addition of an antibody that specifically blocks FXIIIA-PDI activity inhibited FXIII-mediated platelet adhesion to fibrinogen by 65%. Conclusion: These findings indicate that FXIII-induced enhancement of platelet adhesion is mediated by FXIII-PDI activity.

Background Unstable carotid plaques cause cerebral emboli. Leptin promotes atherosclerosis and vessel wall remodeling. We hypothesized that carotid atherosclerotic lesion instability is associated with local leptin synthesis. Methods and Results Carotid endarterectomy plaques from symptomatic (n=40) and asymptomatic patients with progressive stenosis (n=38) were analyzed for local expression of leptin, tumor necrosis factor ( TNF )‐α, and plasminogen activator inhibitor type 1. All lesions exhibited advanced atherosclerosis inclusive of thick‐ and thin‐cap fibroatheromas or lesion rupture. Symptomatic lesions exhibited more plaque ruptures and macrophage infiltration ( P =0.001 and P =0.05, respectively). Symptomatic plaques showed preferential leptin, TNF ‐α, and plasminogen activator inhibitor type 1 transcript ( P =0.03, P =0.04, and P= 0.05, respectively). Leptin mRNA and antigen in macrophages and smooth muscle cells were confirmed by in situ hybridization and immunohistochemistry. Plasma leptin levels were not significantly different between groups ( P =1.0), whereas TNF ‐α was significantly increased in symptomatic patients ( P =0.006). Human aortic smooth muscle cell culture stimulated by TNF ‐α, lipopolysaccharide, or lipoteichoic acid revealed 6‐, 6.7‐, and 6‐fold increased secreted leptin antigen, respectively, at 72 hours ( P Conclusions Neurologically symptomatic patients overexpress leptin mRNA and synthesize leptin protein in carotid plaque macrophages and smooth muscle cells. Local leptin induction, presumably by TNF ‐α, could exert paracrine or autocrine effects, thereby contributing to the pathogenesis of lesion instability. Clinical Trial Registration URL: www.Clinicaltrials.gov . Unique identifier: NCT00449306.

Fetal neonatal alloimmune thrombocytopenia (FNAIT) is a life-threatening bleeding disorder in the fetus or neonate caused by maternal alloantibodies directed against fetal platelet (PLT) antigens inherited from the father. The immune-dominant antigen leading to severe FNAIT is the human PLT antigen (HPA)-1, whose polymorphism constitutes an epitope for human leukocyte antigens (HLAs), usually DRB3*0101 leading to an immune response.In this study our aims were to find whether other allele variants of the β subunit of the HLA-DR family specifically focused on the HLA residues that bind Position 33 of the HPA-1 integrin contribute to FNAIT development and affect response to treatment and whether coexistence of both anti-HPA-1a and anti-HLA class I specific against the father's antigens leads to a more severe thrombocytopenia in the newborn. We examine the genotype of 23 mothers to newborns with FNAIT compared to a control group.Our results suggested that, when HPA-1 incompatibility with the husband is found, the presence of two HLA alleles (DRB3*01:01 and DRB4*01:01) in the mother increases the risk and severity of FNAIT and reduces the success of a preventive immunoglobulin G treatment. We provide a structural model for the molecular basis of the rational effects of the different HLA alleles. In addition, we found that the presence of both anti-HPA-1 and anti-HLAs did not aggravate FNAIT in comparison to mothers harboring only anti-HPA-1.Overall, we suggest that a specific genotyping of the mother in relation to HLA-DRB as well as HPA-1 can serve as an antenatal diagnostic tool, particularly in siblings of women who gave birth to neonates with FNAIT.