Challenges in the Monitoring of Therapeutic Plasma Exchange during Acute Heparin-Induced Thrombocytopenia in Adults under ECMO.

Therapeutic plasma exchange (TPE) has been proposed to remove heparin-induced thrombocytopenia (HIT) antibodies before planned thoracic surgery in patients with acute HIT and to allow brief re-exposure to heparin during surgery. In patients on extracorporeal membrane oxygenation (ECMO), simultaneous administration of TPE and alternative nonheparin anticoagulant therapies is challenging. We report 2 patients on ECMO with acute HIT who underwent repeated TPE to enable cardiothoracic surgery with the use of heparin. In both cases, serial monitoring of HIT antibody titer and heparin-induced platelet activation assay (HIPA) was performed. The effect of adding exogenous platelet factor 4 (PF4) in the HIPA was also tested. Negative anti-PF4/H IgG levels were achieved after 5 and 3 TPE sessions, respectively and patients could beneficiate from surgery with brief heparin re-exposure without any thrombotic complication. Negative HIPA results were obtained before negative anti-PF4/H IgG in one patient but remained positive in the other despite very low antibody titers. The addition of PF4 in HIPA led to more contrasted results for the two patients. Serial HIT screening including immunological and functional assays is necessary to closely monitor TPE in acute HIT patients on ECMO who require surgery. The addition of PF4 in HIPA could help detect clinically relevant platelet-activating antibodies and guide re-exposure to heparin.

Exacerbation of thromboinflammation by JAK2V617F mutation worsens the prognosis of cerebral venous sinus thrombosis.

ABSTRACT: Cerebral venous sinus thrombosis (CVST) is an uncommon venous thromboembolic event accounting for <1% of strokes resulting in brain parenchymal injuries. JAK2V617F mutation, the most frequent driving mutation of myeloproliferative neoplasms, has been reported to be associated with worse clinical outcomes in patients with CVST. We investigated whether hematopoietic JAK2V617F expression predisposes to specific pathophysiological processes and/or worse prognosis after CVST. Using an in vivo mouse model of CVST, we analyzed clinical, biological, and imaging outcomes in mice with hematopoietic-restricted Jak2V617F expression, compared with wild-type Jak2 mice. In parallel, we studied a human cohort of JAK2V617F-positive or -negative CVST. Early after CVST, mice with hematopoietic Jak2V617F expression had increased adhesion of platelets and neutrophils in cerebral veins located in the vicinity of CVST. On day 1, Jak2V617F mice had a worse outcome characterized by significantly more frequent and severe intracranial hemorrhages (ICHs) and higher mortality rates. Peripheral neutrophil activation was enhanced, as indicated by higher circulating platelet-neutrophil aggregates, upregulated CD11b expression, and higher myeloperoxydase plasma level. Concurrently, immunohistological and brain homogenate analysis showed higher neutrophil infiltration and increased blood-brain barrier disruption. Similarly, patients with JAK2V617F-positive CVST tended to present higher thrombotic burden and had significantly higher systemic immune-inflammation index, a systemic thromboinflammatory marker, than patients who were JAK2V617F-negative. In mice with CVST, our study corroborates that Jak2V617F mutation leads to a specific pattern including increased thrombotic burden, ICH, and mortality. The exacerbated thromboinflammatory response, observed both in mice and patients positive for JAK2V617F, could contribute to hemorrhagic complications.

Hemorrhages in Polycythemia Vera and Essential Thrombocythemia: Epidemiology, Description, and Risk Factors-Learnings from a Large Cohort.

BACKGROUND: The management of myeloproliferative neoplasms (MPNs) is based on the reduction of thrombotic risk. The incidence, impact, and risk factors of bleedings have been less studied. METHODS: All patients with polycythemia vera (n=339) or essential thrombocythemia (n=528) treated in our center are included in OBENE (Observatoire BrEstois des NEoplasies myéloprolifératives) cohort (NCT02897297). Major bleeding (MB) and clinically relevant nonmajor bleeding (CRNMB) occurring after diagnosis were included, except after leukemic transformation. RESULTS: With a median follow-up of 8.3 years, incidence of hemorrhages was 1.85% patient/year, with an incidence of MB of 0.95% patient/year. The 10-year bleeding-free survival was 89%. The most frequent locations were digestive tract, "mouth, nose and throat," and muscular hematoma. The case fatality rate of MB was 25%. The proportion of potentially avoidable postoperative bleeding was remarkable (17.6%). In multivariable analysis, eight risk factors of bleeding were identified: leukocytes >20 G/L at diagnosis (hazard ratio [HR]=5.13, 95% confidence interval [CI]: 1.77-14.86), secondary hemopathies (HR=2.99, 95% CI: 1.27-7.04), aspirin use at diagnosis (HR=2.11, 95% CI: 1.24-3.6), platelet count >1,000 G/L at diagnosis (HR=1.93, 95% CI: 1.11-3.36), history of hemorrhage (HR=1.82, 95% CI: 1.03-3.24), secondary cancers (HR=1.71, 95% CI: 1.01-2.89), atrial fibrillation (HR=1.66, 95% CI: 1.01-2.72), and male sex (HR=1.54, 95% CI: 1.02-2.33). The occurrence of a CRNMB increased the risk of a secondary MB (odds ratio=6.13, 95% CI: 2.86-12.6, p<0.00001). Most patients taking hydroxyurea displayed a nonmacrocytic median corpuscular value in the months preceding bleeding (51.4%). DISCUSSION: The morbidity and mortality of bleedings in MPN should not be underestimated, and patients with platelet count >1,000 G/L and/or leukocytes >20 G/L, and possibly patients who suffered from a CRNMB could benefit from cytoreduction to reducing bleeding risk. Postoperative bleedings represent a substantial proportion of bleeding and could be better prevented.

Heparin-induced Thrombocytopenia Diagnosis: A Retrospective Study Comparing Heparin-induced Platelet Activation Test to 14 C-serotonin Release Assay.

Laboratory confirmation of heparin-induced thrombocytopenia (HIT) is of crucial importance and remains challenging and relies on platelet functional assays highlighting the presence of heparin-dependent platelet-activating antibodies in patient serum or plasma. Platelet functional assays using washed platelets include the 14 C-serotonin release assay (SRA), usually described as the gold standard, and the heparin-induced platelet activation assay (HIPA). Since its first comparison with SRA there has been no additional published study regarding HIPA diagnostic performances compared with SRA. Aim of our retrospective study was to compare the concordance between HIPA and SRA in HIT suspected-patients with positive anti-PF4/heparin antibodies between October 2010 and October 2015. Fifty-five HIT-suspected patients who beneficiated from both HIPA and SRA were included. Positive and negative percent agreements were 83.8% (95% CI 68.0-93.8%) and 66.7% (95% CI 41.0-86.7%), respectively. Overall percent agreement was 78.2% (95% CI 65.0-92.2%). Agreement was higher in patients who underwent cardiopulmonary bypass with extracorporeal circulation circuit for cardiac surgery. We also confirm that the use of a minimum of 2 platelet donors to establish positive HIT diagnosis and 4 platelet donors to exclude HIT diagnosis allows obtaining a good agreement with SRA. Although HIPA and SRA were performed with different platelet donors and in different laboratories, HIPA had a good positive agreement with SRA for HIT diagnosis, showing that HIPA is a useful functional assay that does not require radioactivity and could be developed worldwide to improve HIT diagnosis.

Outcome of SARS-CoV-2 infection is linked to MAIT cell activation and cytotoxicity.

Immune system dysfunction is paramount in coronavirus disease 2019 (COVID-19) severity and fatality rate. Mucosal-associated invariant T (MAIT) cells are innate-like T cells involved in mucosal immunity and protection against viral infections. Here, we studied the immune cell landscape, with emphasis on MAIT cells, in cohorts totaling 208 patients with various stages of disease. MAIT cell frequency is strongly reduced in blood. They display a strong activated and cytotoxic phenotype that is more pronounced in lungs. Blood MAIT cell alterations positively correlate with the activation of other innate cells, proinflammatory cytokines, notably interleukin (IL)-18, and with the severity and mortality of severe acute respiratory syndrome coronavirus 2 infection. We also identified a monocyte/macrophage interferon (IFN)-α-IL-18 cytokine shift and the ability of infected macrophages to induce the cytotoxicity of MAIT cells in an MR1-dependent manner. Together, our results suggest that altered MAIT cell functions due to IFN-α-IL-18 imbalance contribute to disease severity, and their therapeutic manipulation may prevent deleterious inflammation in COVID-19 aggravation.

Interferon Alpha Therapy Increases Pro-Thrombotic Biomarkers in Patients with Myeloproliferative Neoplasms.

Myeloproliferative neoplasms (MPN) are associated with an increased risk of arterial and venous thrombosis. Pegylated-interferon alpha (IFN) and hydroxyurea (HU) are commonly used to treat MPN, but their effect on hemostasis has not yet been studied. The aim of our study was to determine whether IFN and HU impact the biological hemostatic profile of MPN patients by studying markers of endothelial, platelet, and coagulation activation. A total of 85 patients (50 polycythemia vera and 35 essential thrombocythemia) were included: 28 treated with IFN, 35 with HU, and 22 with no cytoreductive drug (non-treated, NT). Von Willebrand factor, shear-induced platelet aggregation, factor VIII coagulant activity (FVIII:C), fibrinogen, and thrombin generation with and without exogenous thrombomodulin were significantly higher in IFN-treated patients compared to NT patients, while protein S anticoagulant activity was lower. In 10 patients in whom IFN therapy was discontinued, these hemostatic biomarkers returned to the values observed in NT patients, strongly suggesting an impact of IFN therapy on endothelial and coagulation activation. Overall, our study shows that treatment with IFN is associated with significant and reversible effects on the biological hemostatic profile of MPN patients. Whether they could be associated with an increased thrombotic risk remains to be determined in further randomized clinical studies.

The (Fab)ulous Destiny of Idarucizumab: Highlighting Its Interference with Urine Protein Immunofixation.

Idarucizumab is a humanized antigen binding fragment (Fab) of a recombinant anti-dabigatran monoclonal antibody (IgG1-kappa) that allows rapid and sustained reversal of dabigatran-induced anticoagulation in case of bleeding or urgent surgery. Herein, we report a very unusual case of dabigatran reversal by idarucizumab in a 79-year-old woman with acute kidney failure admitted to a hospital in a context of hemoptysis. Three repeated injections were necessary because of massive dabigatran overdose and high rebounds of dabigatran plasma concentration. Idarucizumab was found on urine immunofixation up to 6 days after the last injection where it reacted with anti-kappa light chain antibody, but not with anti-gamma heavy chain antibody. Physicians should be aware of the increased half-life of idarucizumab in this context of acute kidney impairment and of its interference with urine immunofixation because it could lead to false-positive results and misdiagnosis of a paraprotein.

Critical role of neutrophil extracellular traps (NETs) in patients with Behcet's disease.

OBJECTIVES: Behçet's disease (BD) is a chronic systemic vasculitis. Thrombosis is a frequent and life-threatening complication. The pathogenesis of BD is poorly understood and evidence supporting a role for primed neutrophils in BD-associated thrombotic risk is scant. To respond to inflammatory insults, neutrophils release web-like structures, known as neutrophil extracellular traps (NETs), which are prothrombotic. We evaluated the role of NETs and markers of NETs in BD. METHODS: Blood samples were collected from patients with BD, according to the International Study Group Criteria for Behçet's disease, and healthy donors (HD). NET components, including cell-free DNA (CfDNA) and neutrophil enzymes myeloperoxidase (MPO), were assessed in serum or in purified neutrophils from patients with BD and HD. RESULTS: Patients with active BD had elevated serum cfDNA levels and MPO-DNA complexes compared with patients with inactive BD and to HD. In addition, levels of cfDNA and MPO-DNA complexes were significantly higher in patients with BD with vascular involvement compared with those without vascular symptoms. Purified neutrophils from patients with BD exhibited spontaneous NETosis compared with HD. Thrombin generation in BD plasma was significantly increased and positively correlated with the levels of MPO-DNA complexes and cfDNA. Importantly, DNAse treatment significantly decreased thrombin generation in BD plasma but not in HD plasma. In addition, biopsy materials obtained from patients with BD showed NETs production in areas of vasculitic inflammation and thrombosis. CONCLUSIONS: Our data show that NETs and markers of NETS levels are elevated in patients with BD and contribute to the procoagulant state. Targeting NETs may represent a potential therapeutic target for the reduction or prevention of BD-associated thrombotic risk.

Prevalence and outcome of heparin-induced thrombocytopenia diagnosed under veno-arterial extracorporeal membrane oxygenation: a retrospective nationwide study.

PURPOSE: Thrombocytopenia is a frequent and serious adverse event in patients treated with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for refractory cardiogenic shock. Similarly to postcardiac surgery patients, heparin-induced thrombocytopenia (HIT) could represent the causative underlying mechanism. However, the epidemiology as well as related mortality regarding HIT and VA-ECMO remains largely unknown. We aimed to define the prevalence and associated 90-day mortality of HIT diagnosed under VA-ECMO. METHODS: This retrospective study included patients under VA-ECMO from 20 French centers between 2012 and 2016. Selected patients were hospitalized for more than 3 days with high clinical suspicion of HIT and positive anti-PF4/heparin antibodies. Patients were classified according to results of functional tests as having either Confirmed or Excluded HIT. RESULTS: A total of 5797 patients under VA-ECMO were screened; 39/5797 met the inclusion criteria, with HIT confirmed in 21/5797 patients (0.36% [95% CI] [0.21-0.52]). Fourteen of 39 patients (35.9% [20.8-50.9]) with suspected HIT were ultimately excluded because of negative functional assays. Drug-induced thrombocytopenia tended to be more frequent in Excluded HIT at the time of HIT suspicion (p = 0.073). The platelet course was similar between Confirmed and Excluded HIT (p = 0.65). Mortality rate was 33.3% [13.2-53.5] in Confirmed and 50% [23.8-76.2] in Excluded HIT (p = 0.48). CONCLUSIONS: Prevalence of HIT among patients under VA-ECMO is extremely low at 0.36% with an associated mortality rate of 33.3%, which appears to be in the same range as that observed in patients treated with VA-ECMO without HIT. In addition, HIT was ultimately ruled out in one-third of patients with clinical suspicion of HIT and positive anti-PF4/heparin antibodies.

Biomarkers for the risk of thrombosis in pancreatic adenocarcinoma are related to cancer process.

BACKGROUND: Venous thrombo-embolic events (VTE) frequently occur in patients with pancreatic ductal adenocarcinoma (PDAC) and contribute to high morbidity and mortality. OBJECTIVES: To determine whether VTE biomarkers are related to cancer, inflammation or precancerous states and to assess their relevance to predict VTE in PDAC. PATIENTS AND METHODS: We compared VTE biomarkers in patients with PDAC (n = 42), intraductal papillary mucinous neoplasm of the pancreas (IPMN, n = 48) or chronic pancreatitis (n = 50). PDAC patients were followed-up for 6 months. RESULTS: Factor VIII, D-dimers, von Willebrand factor, free tissue factor pathway inhibitor and microvesicle-tissue factor (MV-TF) activity were higher in PDAC patients compared to patients with IPMN or chronic pancreatitis. PDAC patients with metastasis presented higher D-dimers and MV-TF activity compared to patients with localized lesions, but elevation of D-dimers was dependent on tumor size. In multivariate analysis, elevated D-dimers (≥2.16 µg/mL) or MV-TF activity (≥2.37 pg/mL) were significant risk factors for VTE in PDAC patients, after adjustment for age and sex (HR 4.9 [1.0-23.1] or HR 10.5 [1.5-72.4], mean [interquartile range], respectively). Cumulative probability of VTE at 6 months was higher in patients with elevated D-dimers (56.3% vs 15.6%, p = 0.009) and in patients with high MV-TF activity (74.3% vs 21.7%, p = 0.01). CONCLUSIONS: VTE biomarkers including D-dimers and MV-TF activity are not related to inflammation but rather to cancer process and dissemination. D-dimers and MV-TF activity are associated to future VTE in PDAC patients and could help identify patients who could benefit from thromboprophylaxis.

Presentation, management and outcome of heparin-induced thrombocytopenia after valvular heart surgery.

OBJECTIVES: The use of heparin exposes patients to heparin-induced thrombocytopenia, which is a challenging issue for both diagnosis and patient management. We sought to describe the clinical presentation, management and outcome of a series of patients diagnosed with heparin-induced thrombocytopenia after heart valve surgery. METHODS: All consecutive patients diagnosed with heparin-induced thrombocytopenia during the postoperative period of heart valve surgery over a 6-year period were prospectively enrolled in a single-centre registry. Clinical and biological data were collected. In-hospital and mid-term outcomes were assessed. Information regarding the occurrence of all medical events including death, recurrence of thromboembolic events and/or thrombocytopenia was collected. RESULTS: We identified 93 patients (incidence proportion = 2.8%). Most patients (82%) were asymptomatic with isolated thrombocytopenia at the time of diagnosis. The other main circumstance of diagnosis was the occurrence of thromboembolic events in 17 patients (6 strokes, 10 prosthetic valve thrombosis and 1 peripheral embolic event). The in-hospital mortality rate was 1%. No thrombolysis, interventional procedure or redo surgery was performed. Danaparoid sodium was used as heparin replacement therapy in most cases (96%) and leading to complete and uneventful thrombus resolution in all cases with only one possibly related major bleeding complication. During a mean follow-up of 36 ± 20 months, no patient presented recurrence of any heparin-induced thrombocytopenia-related complication. CONCLUSIONS: In this contemporary series of patients, heparin-induced thrombocytopenia incidence was low and isolated thrombocytopenia was the most frequent presentation. Conservative management with early diagnosis and substitutive anticoagulation therapy introduction was associated with a low rate of clinical events and a remarkably good outcome with a low mortality rate.

Von Willebrand factor, a versatile player in gastrointestinal bleeding in left ventricular assist device recipients?

BACKGROUND: Bleeding originating in the gastrointestinal (GI) tract is one of the most common adverse events after left ventricular assist device (LVAD) implantation. In these patients, GI bleeding appears to be the consequence of altered hemostasis on the one hand and alterations of the GI microvasculature on the other. CASE REPORT: We report the case of a patient who suffered repeated, severe GI bleeding early after implantation of a HeartMate II continuous-flow LVAD. RESULTS: After failure of conventional treatment strategies, GI bleeding was controlled using repeated transfusions of a purified von Willebrand factor (VWF) concentrate, almost devoid of Factor VIII (Wilfactin, LFB). No episodes of pump thrombosis were noted. Subsequent to VWF transfusions, we observed a progressive normalization of circulating vascular endothelial growth factor levels. CONCLUSIONS: Our data raise the possibility that, in addition to its hemostatic properties, transfusions of VWF might have acted as an antiangiogenic factor.

Heparin-induced thrombocytopenia after cardiac surgery: an observational study of 1,722 patients.

OBJECTIVES: To assess the characteristics and prognosis of patients in whom heparin-induced thrombocytopenia (HIT) was confirmed (HIT+) among suspected HIT patients after having cardiac surgery and to assess the accuracy of two HIT scoring systems. DESIGN: An observational prospective study. SETTING: A cardiac surgery unit of a tertiary center from November 2005 to September 2007. PARTICIPANTS: Of the 1,722 patients who underwent cardiac surgery, 63 were suspected of HIT based on a platelet count <100 × 10(9)/L, a decrease in platelet count of >30%, or the occurrence of a thrombotic event. INTERVENTION: The HIT criteria were as follows: (1) the absence of another cause of thrombocytopenia, (2) positive antiplatelet factor 4 (PF4) antibodies (>0.5 optical density [OD]/mn) on enzyme-linked immunoabsorbent assay, and (3) recovery in platelet count after the discontinuation of heparin and substitution by danaparoid sodium. MEASUREMENTS AND MAIN RESULTS: HIT was confirmed in 24 patients (1.4% [0.8%-1.9%]); 23 belonged to the 984 treated by intravenous unfractionated heparin (IVUH) (2.3% IQ [1.4%-3.3%]) and 1 to the 738 treated by low-molecularweight heparin (0.14% [0.13%-0.4%]) (OD = 17.6; 95% confidence interval, 2.4-131; p < 0.0001). In the HIT+ patients compared with the unconfirmed HIT patients, thrombocytopenia occurred 7 (range, 6-9) days after surgery versus 3 (range, 3-5) days (p < 0.0001), and kinetics of platelet count showed a biphasic pattern. Six HIT+ patients (25% [7.7-42.3]) presented with an arterial thromboembolic event. Diagnosis performances of HIT scoring systems were low. CONCLUSIONS: Confirmed HIT occurred predominantly in patients treated with IVUH. The timing of thrombocytopenia and the variation pattern of the postoperative platelet count are key factors in diagnosing HIT. The overall incidence of intracardiac thrombotic events was noted to be high.

Platelet glycoprotein VI dimerization, an active process inducing receptor competence, is an indicator of platelet reactivity.

OBJECTIVE: The immune receptor homologue glycoprotein VI (GPVI)/FcR receptor γ chain complex is primarily responsible for platelet activation by collagen. There is growing evidence that optimal binding of GPVI to collagen depends on the assembly of GPVI dimers. The valence of GPVI on resting platelets needs to be clearly established because platelet avidity for collagen would be greater if GPVI is constitutively expressed as a dimer than as a monomer. METHODS AND RESULTS: Using a monoclonal antibody (9E18) that preferentially binds to GPVI dimers, we found that GPVI was maintained in a monomeric form on human resting platelets under the control of intraplatelet cAMP concentration. Activation by soluble agonists or von Willebrand factor induced a shift toward GPVI dimerization related to increased platelet adhesion to collagen. A correlation between platelet binding of 9E18 and P-selectin exposure was observed in patients experiencing coronary artery disease, and antagonists of the ADP receptor P2Y12 limited ADP-induced GPVI dimerization. CONCLUSION: The rapid assembly of highly competent dimers of GPVI at sites of vascular lesion represents an important step in the sequence of events leading to platelet activation by collagen. GPVI dimers could represent a new marker to analyze platelet reactivity.

[New oral anticoagulant drugs: dabigatran, rivaroxaban and apixaban. Present and future]. / Les nouveaux anticoagulants oraux: utilisation actuelle et avenir.

For years, prevention and treatment of thromboembolic events have been restricted to the use of heparins and vitamin K antagonists. These treatments, in spite of their unquestioned efficacy, present numerous limits (hemorrhagic risk, need for regular laboratory controls). These limits call for the development of new antithrombotic drugs. This review briefly reports on three new molecules, in very advanced phases of clinical research: dabigatran (Pradaxa®), rivaroxaban (Xarelto®) and apixaban. These molecules represent new oral anticoagulants, which directly inhibit a coagulation factor (thrombin for dabigatran, factor Xa for rivaroxaban and apixaban) and do not need regular anticoagulant monitoring or dose adjustment. The approval is still restricted in France to the prophylaxis of venous thromboembolism in orthopaedics. Dabigratran will be soon available in the prevention of stroke in atrial fibrillation. With the forthcoming phase III studies to prevent and treat venous thromboembolism, anticoagulant therapy management will be most probably improved in the coming years.

A comparison of bilateral with single internal mammary artery grafts on postoperative mediastinal drainage and transfusion requirement.

The superiority of the left internal mammary artery (LIMA) graft over autogenous saphenous vein as a bypass conduit in coronary artery bypass surgery has been well established. Early and late patency rates of bilateral internal mammary artery (BIMA) grafts exceed those of vein grafts, and patients who receive BIMA have improved long-term survival rates and more freedom from reoperations and other cardiac events. But because of other concerns, particularly the question of increased risk of postoperative bleeding, controversy still surrounds the perioperative period. In the present study we sought to determine whether BIMA grafting was an independent risk factor of postoperative bleeding and of blood product use in patients undergoing primary elective coronary artery revascularization. For this purpose, 33 consecutive patients scheduled for BIMA grafting were matched with 66 patients operated on by single LIMA grafting. Patients in the LIMA group had significantly less postoperative mediastinal drainage than those in the BIMA group (median: 722 vs 920 mL, P = 0.0001). Fifty-six patients received blood products (56% vs 51% in LIMA and BIMA groups, respectively; P = 0.67). In multivariate analysis, BIMA and operative duration were independent predictors of increased postoperative drainage. Nevertheless, in logistic regression, BIMA was not significantly associated with blood product use, unlike precardiopulmonary bypass hematocrit and duration of surgery (OR and 95% CI: 0.89 [0.80-0.96] P = 0.01; 1.009 [1.001-1.019] P = 0.04, for an increase of 1% in hematocrit and 1 min in duration of surgery, respectively). In conclusion, these data support the idea that BIMA graft slightly increases postoperative drainage but not transfusion requirement.

Association of the -92C/G and 807C/T polymorphisms of the alpha2 subunit gene with human platelets alpha2beta1 receptor density.

OBJECTIVE: Platelet adhesion to the subendothelial tissue via the collagen receptor alpha2beta1 is a crucial event in vascular biology. Although evidence has been provided that the number of platelets alpha2beta1 copies is genetically determined, the molecular change primary responsible has not been yet elucidated. The aim of our present study was to investigate the effect of combined polymorphisms within both regulatory (-52C/T and -92C/G) and coding regions (807C/T and 1648A/G) of the alpha2 subunit gene on human platelets alpha2beta1 receptor density and/or susceptibility to coronary artery disease (CAD). METHODS AND RESULTS: Among 254 cardiac surgery patients, no evidence was found for an association between the alpha2 subunit gene polymorphisms and CAD. In contrast, in a subgroup of 113 patients, we observed a significant association between all polymorphisms except -52C/T and alpha2beta1 receptor level. Furthermore, when 3 groups of patients were defined according to the tertiles of platelets alpha2beta1 copies, the -92C/807T haplotype was more frequent in the group of patients with high alpha2beta1 receptor level. CONCLUSIONS: These results suggest that an individual effect of each polymorphism located either in the coding or promoter sequence of the alpha2 gene may act in combination to modulate variations in platelets alpha2beta1 receptor density.