Microparticles Expressing Tissue Factor Research Articles

Metformin reduces total microparticles and microparticles-expressing tissue factor in women with polycystic ovary syndrome.

The objective of this study was to evaluate the levels of total microparticles (MPs) and microparticles-expressing tissue factor (TFMPs) in women with polycystic ovarian syndrome (PCOS) who use metformin comparing to those who do not take metformin. We quantified total MPs and TFMPs in the plasma of 50 patients with PCOS-13 of these women used metformin (850mg 2×/day during at least 6months) and the other 37 did not. For this purpose, the microparticles (MPs) were purified by differential centrifugation of the plasma and, subsequently, by flow cytometry, using annexin-V and CD142 as markers. Total MPs levels were lower in treated patients (59.58±28.43MPs/µL) when compared to untreated group (97.32±59.42; p=0.033). Plasma levels of TFMPs were also significantly lower in the group of patients who used metformin (1.10±0.94MPs/µL) when compared to untreated patients (2.20±1.42MPs/µL) (p=0.003). Considering that metformin reduced the levels of total MPs and TFMPs, our results suggest that this mechanism could be involved in the antithrombotic metformin effect, corroborating with the indication of this drug in the PCOS treatment.

Microparticles: Inflammatory and haemostatic biomarkers in Polycystic Ovary Syndrome

Polycystic Ovary Syndrome (PCOS) is associated with a chronic low-grade inflammation and predisposition to hemostatic and atherosclerotic complications. This case-control study evaluated the microparticles (MPs) profile in patients with the PCOS and related these MPs to clinical and biochemical parameters. MPs derived from platelets (PMPs), leuckocytes (LMPs) and endothelial cells (EMPs) were evaluated, as well as MPs expressing tissue factor (TFMPs), by flow cytometry, comparing women with PCOS (n = 50) and a healthy control group (n = 50). PCOS women presented increased total MPs, PMPs, LMPs and EMPs levels when compared to control group (all p < 0.05). TFMPs was similar between the groups (p = 0.379). In conclusion, these MPs populations could be useful biomarkers for association with thrombosis and cardiovascular disease in PCOS women.

A low balance between microparticles expressing tissue factor pathway inhibitor and tissue factor is associated with thrombosis in Behçet's Syndrome.

Thrombosis is common in Behçet’s Syndrome (BS), and there is a need for better biomarkers for risk assessment. As microparticles expressing Tissue Factor (TF) can contribute to thrombosis in preclinical models, we investigated whether plasma microparticles expressing Tissue Factor (TF) are increased in BS. We compared blood plasma from 72 healthy controls with that from 88 BS patients (21 with a history of thrombosis (Th+) and 67 without (Th−). Using flow cytometry, we found that the total plasma MP numbers were increased in BS compared to HC, as were MPs expressing TF and Tissue Factor Pathway Inhibitor (TFPI) (all p < 0.0001). Amongst BS patients, the Th+ group had increased total and TF positive MP numbers (both p ≤ 0.0002) compared to the Th- group, but had a lower proportion of TFPI positive MPs (p < 0.05). Consequently, the ratio of TFPI positive to TF positive MP counts (TFPI/TF) was significantly lower in Th+ versus Th− BS patients (p = 0.0002), and no patient with a TFPI/TF MP ratio >0.7 had a history of clinical thrombosis. We conclude that TF-expressing MP are increased in BS and that an imbalance between microparticulate TF and TFPI may predispose to thrombosis.

Cellular and Functional Characterization of Microparticles in Sepsis-Associated Coagulopathy

Background: Disseminated intravascular coagulation (DIC) is a complex pathology characterized by microvascular thrombosis, dysregulated fibrinolysis, endothelial activation, and endothelial disruption. It is the endpoint of the coagulopathy commonly associated with sepsis and is clinically associated with multi-organ failure and/or significant bleeding. Inflammatory processes mediated by chemokines and cytokines including soluble CD40 ligand (sCD40L), interleukin 6 (IL-6), vascular endothelial growth factor (VEGF), endocan, and tissue factor play an important role in DIC pathogenesis; and in turn, dysregulation of coagulation factors effects further inflammation. Cellular damage and apoptotic processes result in the generation of microparticles, a diverse population of small, cell-derived phospholipid vesicles displaying characteristic surface proteins. Microparticles are associated with inflammation and coagulation in sepsis; however, the precise role they play remains unclear.Methods: Plasma samples from 75 patients with confirmed DIC were included in this study. 50 plasma samples from normal healthy individuals were obtained from a commercial source (George King Biomedical, Overland Park, KS). Endocan, VEGF, sCD40L, and IL-6 were measured using commercially available sandwich ELISA assays (Lunginnov, Lillie, France/R&D Systems, Minneapolis, MN). Microparticles, and microparticles expressing tissue factor were measured using commercially available functional assays (Hyphen Biomedical, Paris, France).Results: All inflammatory biomarkers were significantly elevated in DIC MP-TF (DIC-1.85±1.3 pg/ml; N-0.39.6±0.2 pg/ml, p<0.001), sCD40L (DIC-618±571 pg/ml; N-177.6±221.4 pg/ml, p<0.00) VEGF (DIC->740 pg/ml; N-32.6±50.9 pg/ml, p=0.007), endocan (DIC-10.6 ng/ml±10.9; N-1.81±0.36 ng/ml, p<0.001) and IL-6 (DIC-4968±5719 pg/ml; N-59.2±118.1 pg/ml, p<0.001). Microparticles were elevated compared to normal (p<0.001) and correlated significantly with sCD40L (p=0.0005) and VEGF (0.039). sCD40L and VEGF also correlated significantly (p=0.001)Discussion: The correlation between microparticles, sCD40L and VEGF found in these patients strongly supports the widespread activation of platelets in DIC. It is possible that this process contributes to the thrombocytopenia often seen in sepsis. In addition there was an elevation in both endocan and VEGF suggesting that, while endocan may have an effect on the level of VEGF in vivo, platelets appear to be the major source. Interestingly, microparticles specifically carrying tissue factor did not show correlation with any of the other biomarkers. This may be because these microparticles may be shed from multiple sources, particularly both activated monocytes and endothelial cells, and this may have been a confounding factor. Thus, these results provide further evidence of the widespread inflammatory milieu present in patients with DIC, particularly elucidating possible cross-talk between platelets and endothelium. Profiling of these biomarkers may be helpful in the risk stratification of patients with sepsis associated coagulopathy and following their clinical progress. DisclosuresNo relevant conflicts of interest to declare.

State-of-the-Art and Current Controversies in the Detection and Quantitation of Tissue Factor-Bearing Microparticles

Abstract SCI-11 Microparticles are submicron vesicles that circulate in blood and are derived from a variety of vascular cells. Microparticles expressing tissue factor have been shown in animal thrombosis models to contribute to thrombus formation in vivo, which has led to the evaluation of tissue factor bearing microparticle populations in a variety of thrombotic disorders including malignancy, sepsis, and coronary thrombosis. Central to the evaluation of tissue factor-bearing microparticle populations in health and disease is the establishment of accurate means for qualitative or quantitative assessment of circulating microparticles. Whilst there is considerable interest in evaluating whether pathologic disturbances in tissue factor-bearing microparticles contribute to thrombosis, analytic techniques for microparticle measurement remain in the validation stage. The method most commonly employed for the detection of tissue factor-bearing microparticles is light-scatter flow cytometry, which relies on the sizing of particles based on light-scatter profile. Light scatter, however, is also influenced by variables independent of particle size, including the wavelength of incident light, particle shape, presence of surface absorptive material, and relative refractive indices of particles and suspension medium. A number of potentially more sensitive methodologies are currently under investigation such as impedance-based flow cytometry, quasi-elastic light scattering based on Brownian movement, and atomic force microscopy. Alternatively, assays have been developed that measure tissue factor antigen or activity following isolation of microparticles from plasma or whole blood but without determination of particle size. Absent a gold standard for the measurement of tissue factor-bearing microparticle populations by which these approaches can be validated, the development of accurate methodology will require inter-assay and intra-assay precision as well as validation of clinical relevance in human studies. Disclosures: No relevant conflicts of interest to declare.