flow-cytometry-analysis-of-tissue-factor-expression-in-human-platelets

Flow Cytometry Analysis of Tissue Factor Expression in Human Platelets

A subset of circulating human platelets stores Tissue Factor (TF) intracellularly, the key activator of the blood coagulation cascade and thrombus ...

Centro Cardiologico Monzino IRCCS

Letter by Brambilla et al Regarding Article, "Patients With COVID-19 Have Elevated Levels of Circulating Extracellular Vesicle Tissue Factor Activity That Is Associated With Severity and Mortality-Brief Report".

Coronavirus disease 2019 (COVID-19) is a pandemic syndrome caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. SARS-CoV-2 infection induces a process of inflammation and thrombosis supported by an altered platelet activation state. This platelet activation is peculiar being characterized by the formation of platelet-leukocytes rather than platelet-platelet aggregates and by an increased procoagulant potential supported by elevated levels of TF positive platelets and microvesicles.Therapeutic strategies targeting, beyond systemic inflammation (i.e. with tocilizumab, an anti interleukin-6 receptor), this state of platelet activation might therefore be beneficial. Among the antithrombotic drugs proposed as candidates to treat patients with SARS-CoV-2 infection, antiplatelet drugs, such as aspirin are showing promising results.

Alterations in platelets during SARS-CoV-2 infection.

The association between migraine and patent foramen ovale (PFO) has been documented. We aimed to investigate platelet activation, prothrombotic phenotype, and oxidative stress status of migraineurs with PFO on 100 mg/day aspirin, before and 6 months after PFO closure. Data show that, before PFO closure, expression of the classical platelet activation markers is comparable in patients and aspirin-treated healthy subjects. Conversely, MHA-PFO patients display an increased prothrombotic phenotype (higher tissue factor platelets and microvesicles and thrombin-generation potential), sustained by an altered oxidative stress status. This phenotype, which is more controlled by P2Y-blockade than by aspirin, reverted after PFO closure together with a complete migraine remission. (pLatelEts And MigRaine iN patEnt foRamen Ovale [LEARNER]; NCT03521193).

Migraine in Patients Undergoing PFO Closure: Characterization of a Platelet-Associated Pathophysiological Mechanism: The LEARNER Study.

Studies exploring alterations in blood coagulation and platelet activation induced by COVID-19 vaccines are not concordant. We aimed to assess the impact of four COVID-19 vaccines on platelet activation, coagulation, and inflammation considering also the immunization dose and the history of SARS-CoV-2 infection.

Head-to-head comparison of four COVID-19 vaccines on platelet activation, coagulation and inflammation. The TREASURE study.

ADP-induced platelet activation leads to cell surface expression of several proteins, including TF (tissue factor). The role of ADP receptors in platelet TF modulation is still unknown. We aimed to assess the (1) involvement of P2Y and P2Y receptors in ADP-induced TF exposure; (2) modulation of TF-platelets in anti-P2Y-treated patients with coronary artery disease. Based on the obtained results, we revisited the intracellular localization of TF in platelets.

Cell Surface Platelet Tissue Factor Expression: Regulation by P2Y and Link to Residual Platelet Reactivity.

The relative contribution of small (sEVs) and large extracellular vesicles (lEVs) to the total plasma procoagulant potential is not yet well defined. Thus, we compared total and TF-sEVs and -lEVs isolated from healthy subjects and COVID-19 patients during the acute phase of the infection and after symptom remission in terms of (1) vesicle enumeration using nanoparticle tracking assay, imaging flow cytometry, and TF immunofluorescence localization in a single-vesicle analysis using microarrays; (2) cellular origin; and (3) TF-dependent Xa generation capacity, as well as assessing the contribution of the TF inhibitor, TFPI. In healthy subjects, the plasma concentration of CD9/CD63/CD81 sEVs was 30 times greater than that of calcein lEVs, and both were mainly released by platelets. Compared to lEVs, the levels of TF-sEVs were 2-fold higher. The TF-dependent Xa generation capacity of lEVs was three times greater than that of sEVs, with the latter being hindered by TFPI. Compared to HSs, the amounts of total and TF-sEVs and -lEVs were significantly greater in acute COVID-19 patients, which reverted to the physiological values at the 6-month follow-up. Interestingly, the FXa generation of lEVs only significantly increased during acute infection, with that of sEV being similar to that of HSs. Thus, in both healthy subjects and COVID-19 patients, the TF-dependent procoagulant potential is mostly sustained by large vesicles.

Head-to-Head Comparison of Tissue Factor-Dependent Procoagulant Potential of Small and Large Extracellular Vesicles in Healthy Subjects and in Patients with SARS-CoV-2 Infection.

Article	Year
Letter by Brambilla et al Regarding Article, "Patients With COVID-19 Have Elevated Levels of Circulating Extracellular Vesicle Tissue Factor Activity That Is Associated With Severity and Mor... Arteriosclerosis, thrombosis, and vascular biology\| PubMed ID: 34038167	2021
Alterations in platelets during SARS-CoV-2 infection. Platelets\| PubMed ID: 34384321	2022
Migraine in Patients Undergoing PFO Closure: Characterization of a Platelet-Associated Pathophysiological Mechanism: The LEARNER Study. JACC. Basic to translational science\| PubMed ID: 35818509	2022
Head-to-head comparison of four COVID-19 vaccines on platelet activation, coagulation and inflammation. The TREASURE study. Thrombosis research\| PubMed ID: 36702064	2023
Cell Surface Platelet Tissue Factor Expression: Regulation by P2Y and Link to Residual Platelet Reactivity. Arteriosclerosis, thrombosis, and vascular biology\| PubMed ID: 37589138	2023
Head-to-Head Comparison of Tissue Factor-Dependent Procoagulant Potential of Small and Large Extracellular Vesicles in Healthy Subjects and in Patients with SARS-CoV-2 Infection. Biology\| PubMed ID: 37759632	2023
Letter by Brambilla et al Regarding Article, "Monocyte-Mediated Thrombosis Linked to Circulating Tissue-Factor and Immune Paralysis in COVID-19". Arteriosclerosis, thrombosis, and vascular biology\| PubMed ID: 39167674	2024

Alessia Becchetti

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