Rôle potentiel du TFPI dans les maladies thrombotiques et hémorragiques

L'inhibiteur de la Voie du Facteur Tissulaire (TFPI) est une protéine régulatrice de la coagulation plasmatique intervenant à la phase initiale de la cascade. Il inhibe en présence de la protéine S (PS) le facteur Xa et ce complexe TFPI-Xa inactive ensuite le complexe FT-VIIa. Nous avons recherché une résistance à l'activité anticoagulante du TFPI. La sensibilité du plasma à une quantité fixe de TFPI a été évaluée sur la base d'un temps de thromboplastine diluée (TTD) réalisé avec et sans TFPI : - chez des patients ayant présenté une thrombose veineuse profonde inexpliquée ; cette résistance suspectée sur une 1ère étude n'a pas été confirmée sur la 2ème. - chez des patientes enceintes ; une résistance au TFPI acquise a été montrée et rapportée au déficit acquis en PS ; cependant le degré de résistance au TFPI ne peut pas être utilisé comme marqueur de risque de pathologie vasculaire placentaire. Chez des patients obèses l'effet inhibiteur des taux élevés de Lp(a) sur l'activité TFPI décrit in vitro n'a pas été retrouvé in vivo pas plus que l'effet de l'aspirine sur la normalisation des taux de Lp(a). Le TFPI joue un rôle dans les manifestations hémorragiques des hémophiles. Nous avons montré que les hémophiles B ont comparativement aux A des taux moindres de TFPI ce qui pourrait expliquer leur différence en terme de manifestations hémorragiques. Les taux de TFPI libre sont bien corrélés aux paramètres de la génération de thrombine surtout au temps de latence. En présence d un anti TFPI humain la génération de thrombine est corrigée chez l'hémophile. Cette correction dépend de la concentration d'anti TFPI, est saturable et doit être étudiée sur du plasma riche en plaquettesTFPI is a multivalent Kunitz-type proteinase inhibitor that directly inhibits FXa and produces FXa-dependent feedback inhibition of the FVIIa TF complex. It was recently demonstrated that Protein S (PS) plays the role of TFPI cofactor by enhancing the TFPI inhibition of factor Xa in vivo. Approximately 80% of plasma TFPI circulates as a complex with plasma lipoproteins, about 5 20% circulating as free TFPI. Under quiescent conditions, approximately 50 80% of intravascular TFPI is stored in association with the endothelium. Full-length TFPI a carried in platelets constitutes 8-10% of the total amount of TFPI in the blood, corresponding to a quantity comparable to that of soluble full-length TFPI a in the plasma. We searched for resistance to TFPI activity in patients who presented idiopathic venous thrombosis at a young age. Plasma sensitivity to TFPI was evaluated on the basis of diluted prothrombin time (dPT) measured in patients and in control plasma in the presence (W) and absence (Wo) of exogenous TFPI. At the same time, dPT was measured on a reference plasma to establish a normalized ratio termed TFPI NR and defined as (dPT wTFPI/ dPT Wo TFPI) patient or control / (dPT wTFPI/ dPT Wo TFPI) reference plasma. In an initial study, we found that TFPI resistance could be considered as a new coagulation abnormality that could be related to unexplained thrombosis. In a second study, we failed to demonstrate a role of TFPI resistance in patients with venous thrombosis, abnormal TFPI NR being more likely related to the non-respect of preanalytical conditions rather than to an inherited trait. However, in another study, we showed that inherited or acquired PS deficiency was responsible for a TFPI resistance, providing an ex vivo demonstration that PS is the cofactor of TFPI activity. We showed that this TFPI resistance existed throughout pregnancy and that it disappeared when PS returned to normal values after delivery. We evaluated this TFPI resistance as a possible marker of the risk of a gestational vascular complication (GVC) in 72 patients at risk of developing a GVC. TFPI NR did not differ between GVC+ patients (n =15) and GVC patients (n = 57). High levels of Lipoprotein(a) (Lp(a) have been shown to be an independent risk factor for cardiovascular disease, lowering of these levels not being achievable by any treatment except possibly aspirin. An in vitro study showed that TFPI activity could be inhibited by Lp(a). We did not confirm this TFPI inhibition in vivo in 20 obese patients with coronary insufficiency who had either normal Lp(a) levels (= 0.3 g/L; n = 5) . Moreover, we found no effect of aspirin treatment on Lp(a) whatever the initial level of Lp(a). Haemophilia B patients bleed less than haemophilia A patients. We showed that this difference in bleeding profile could be explained by lower free TFPI levels in haemophilia B patients compared to haemophilia A patients. In an ongoing study, we showed that in haemophilia A patients there was a strong correlation between the different parameters of thrombin generation (TG) and free TFPI. We also showed, in a TG assay performed in platelet-rich plasma (PRP) with a low TF concentration, that LT was sensitive to free TFPI levels whatever the type of haemophilia and whatever theseverity of the disease. We demonstrated that blocking TFPI by an anti-TFPI Antibody (Ab) allows complete correction of the TG profile in PRP. We showed that it is of major importance to perform a TG assay in PRP in order to evaluate the efficacy of anti-TFPI Ab in correcting TG parameters in haemophilia patientsST ETIENNE-Bib. électronique (422189901) / SudocSudocFranceF

Rôle potentiel du TFPI dans les maladies thrombotiques et hémorragiques

TFPI is a multivalent Kunitz-type proteinase inhibitor that directly inhibits FXa and produces FXa-dependent feedback inhibition of the FVIIa–TF complex. It was recently demonstrated that Protein S (PS) plays the role of TFPI cofactor by enhancing the TFPI inhibition of factor Xa in vivo. Approximately 80% of plasma TFPI circulates as a complex with plasma lipoproteins, about 5–20% circulating as free TFPI. Under quiescent conditions, approximately 50–80% of intravascular TFPI is stored in association with the endothelium. Full-length TFPI α carried in platelets constitutes 8-10% of the total amount of TFPI in the blood, corresponding to a quantity comparable to that of soluble full-length TFPI α in the plasma. We searched for resistance to TFPI activity in patients who presented idiopathic venous thrombosis at a young age. Plasma sensitivity to TFPI was evaluated on the basis of diluted prothrombin time (dPT) measured in patients and in control plasma in the presence (W) and absence (Wo) of exogenous TFPI. At the same time, dPT was measured on a reference plasma to establish a normalized ratio termed TFPI NR and defined as (dPT wTFPI/ dPT Wo TFPI) patient or control / (dPT wTFPI/ dPT Wo TFPI) reference plasma. In an initial study, we found that TFPI resistance could be considered as a new coagulation abnormality that could be related to unexplained thrombosis. In a second study, we failed to demonstrate a role of TFPI resistance in patients with venous thrombosis, abnormal TFPI NR being more likely related to the non-respect of preanalytical conditions rather than to an inherited trait. However, in another study, we showed that inherited or acquired PS deficiency was responsible for a TFPI resistance, providing an ex vivo demonstration that PS is the cofactor of TFPI activity. We showed that this TFPI resistance existed throughout pregnancy and that it disappeared when PS returned to normal values after delivery. We evaluated this TFPI resistance as a possible marker of the risk of a gestational vascular complication (GVC) in 72 patients at risk of developing a GVC. TFPI NR did not differ between GVC+ patients (n =15) and GVC– patients (n = 57). High levels of Lipoprotein(a) (Lp(a) have been shown to be an independent risk factor for cardiovascular disease, lowering of these levels not being achievable by any treatment except possibly aspirin. An in vitro study showed that TFPI activity could be inhibited by Lp(a). We did not confirm this TFPI inhibition in vivo in 20 obese patients with coronary insufficiency who had either normal Lp(a) levels (≤ 0.3 g/L; n = 15) or high Lp(a) levels (≥ 0.3 g/L; n = 5) . Moreover, we found no effect of aspirin treatment on Lp(a) whatever the initial level of Lp(a). Haemophilia B patients bleed less than haemophilia A patients. We showed that this difference in bleeding profile could be explained by lower free TFPI levels in haemophilia B patients compared to haemophilia A patients. In an ongoing study, we showed that in haemophilia A patients there was a strong correlation between the different parameters of thrombin generation (TG) and free TFPI. We also showed, in a TG assay performed in platelet-rich plasma (PRP) with a low TF concentration, that LT was sensitive to free TFPI levels whatever the type of haemophilia and whatever theseverity of the disease. We demonstrated that blocking TFPI by an anti-TFPI Antibody (Ab) allows complete correction of the TG profile in PRP. We showed that it is of major importance to perform a TG assay in PRP in order to evaluate the efficacy of anti-TFPI Ab in correcting TG parameters in haemophilia patientsL'inhibiteur de la Voie du Facteur Tissulaire (TFPI) est une protéine régulatrice de la coagulation plasmatique intervenant à la phase initiale de la cascade. Il inhibe en présence de la protéine S (PS) le facteur Xa et ce complexe TFPI-Xa inactive ensuite le complexe FT-VIIa. Nous avons recherché une résistance à l'activité anticoagulante du TFPI. La sensibilité du plasma à une quantité fixe de TFPI a été évaluée sur la base d'un temps de thromboplastine diluée (TTD) réalisé avec et sans TFPI : - chez des patients ayant présenté une thrombose veineuse profonde inexpliquée ; cette résistance suspectée sur une 1ère étude n'a pas été confirmée sur la 2ème. - chez des patientes enceintes ; une résistance au TFPI acquise a été montrée et rapportée au déficit acquis en PS ; cependant le degré de résistance au TFPI ne peut pas être utilisé comme marqueur de risque de pathologie vasculaire placentaire. Chez des patients obèses l'effet inhibiteur des taux élevés de Lp(a) sur l'activité TFPI décrit in vitro n'a pas été retrouvé in vivo pas plus que l'effet de l'aspirine sur la normalisation des taux de Lp(a). Le TFPI joue un rôle dans les manifestations hémorragiques des hémophiles. Nous avons montré que les hémophiles B ont comparativement aux A des taux moindres de TFPI ce qui pourrait expliquer leur différence en terme de manifestations hémorragiques. Les taux de TFPI libre sont bien corrélés aux paramètres de la génération de thrombine surtout au temps de latence. En présence d’un anti TFPI humain la génération de thrombine est corrigée chez l'hémophile. Cette correction dépend de la concentration d'anti TFPI, est saturable et doit être étudiée sur du plasma riche en plaquette

Clustering of Thrombin Generation Test Data Using a Reduced Mathematical Model of Blood Coagulation

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Extremely low doses of lepirudin in a patient with heparin-induced thrombocytopenia, high bleeding risk and renal insufficiency.

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Use of population PK/PD approach to model the thrombin generation assay: assessment in haemophilia A plasma samples spiked by a TFPI antibody

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PHILEOS ( haemoPHILia and ostEoporOSis ) Study: protocol of a multicentre prospective case–control study

International audienceIntroduction Two meta-analyses showed lower bone mineral density (BMD) in patients with haemophilia (haemophilia type and severity were often not specified) compared with healthy controls. This finding could be related to reduced mobility and sedentary lifestyle, and/or hepatitis C or HIV infection. The aim of this study is to determine osteoporosis prevalence in patients with haemophilia classified in function of the disease type (A or B) and severity, and to evaluate the potential role of regular prophylactic factor replacement (early vs delayed initiation) in preserving or restoring BMD. Methods and analysis The haemoPHILia and ostEoporOSis Study is a prospective, controlled, multicentre study that will include patients in France (13 haemophilia treatment centres), Belgium (1 centre) and Romania (1 centre). In total, 240 patients with haemophilia and 240 matched healthy controls will be recruited (1:1). The primary objective is to determine osteoporosis prevalence in patients with severe haemophilia A and B (HA and HB) without prophylaxis, compared with healthy controls. Secondary outcomes include: prevalence of osteoporosis and osteopenia in patients with mild, moderate and severe HA or HB with prophylaxis (grouped in function of their age at prophylaxis initiation), compared with healthy subjects; BMD in patients with HA and HB of comparable severity; correlation between BMD and basal factor VIII/IX levels and thrombin potential; and quantification of plasmatic markers of bone remodelling (formation and resorption) in patients with haemophilia. Ethics and dissemination The protocol was approved by the French Ethics Committee and by the French National Agency for Medicines and Health Products Safety (number: 2019-A03358-49). The results of this study will be actively disseminated through scientific publications and conference presentations. Trial registration number NCT04384341

Surgery with emicizumab prophylaxis for two paediatric patients with severe haemophilia A with inhibitors

International audienceAbstract Emicizumab is a prophylaxis for patients with severe haemophilia A with and without inhibitor. Despite weekly administration of emicizumab, coagulation states stay below normal value and cannot be assessed by standard haemostasis tests. In our two patients, we used the thrombin‐generation assay (endogenous thrombin potential and Peak) to monitor the patient's clotting status. Under emicizumab, it is necessary to add a bypassing agent (BPA) such as rFVIIa (Novoseven) to avoid bleeding before surgery. The BPA dosage was based on a thrombin‐generation assay and collegial consultation

Switch to pdVWF:pdFVIII concentrate for prophylaxis in a paediatric patient with Type 3 von Willebrand disease: a case report

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Patient-Specific Modelling of Blood Coagulation

International audienceBlood coagulation represents one of the most studied processes in biomedical modelling. However, clinical applications of this modelling remain limited because of the complexity of this process and because of large inter-patient variation of the concentrations of blood factors, kinetic constants and physiological conditions. Determination of some of these patients-specific parameters is experimentally possible, but it would be related to excessive time and material costs impossible in clinical practice. We propose in this work a methodological approach to patient-specific modelling of blood coagulation. It begins with conventional thrombin generation tests allowing the determination of parameters of a reduced kinetic model. Next, this model is used to study spatial distributions of blood factors and blood coagulation in flow, and to evaluate the results of medical treatment of blood coagulation disorders