Impact of Deficiency of Intrinsic Coagulation Factors XI and XII on Ex Vivo Thrombus Formation and Clot Lysis

The contributions of coagulation factor XI (FXI) and FXII to human clot formation is not fully known. Patients with deficiency in FXI have a variable mild bleeding risk, whereas FXII deficiency is not associated with bleeding. These phenotypes make FXII and FXI attractive target proteins in anticoagulant therapy. Here, we studied the mechanisms of fibrin clot formation, stability, and fibrinolytic degradation in patients with severe FXI or FXII deficiency. Thrombin generation was triggered in platelet-poor (PPP) and platelet-rich plasma (PRP) with the biological FXII trigger sulfatides. Intrinsic and extrinsic thrombus formation and degradation in whole blood were determined with rotational thromboelastometry (ROTEM). Clot formation under flow was assessed by perfusion of whole blood over collagen microspots with(out) tissue factor (TF). Thrombin generation and clot formation were delayed in FXII- and FXI-deficient patients triggered with sulfatides. In FXI-deficient plasma, this delay was more pronounced in PRP compared to PPP. In whole blood of FXII-deficient patients, clots were smaller but resistance to fibrinolysis was normal. In whole blood of FXI-deficient patients, clot formation was normal but the time to complete fibrinolysis was prolonged. In flow chamber experiments triggered with collagen/TF, platelet coverage was reduced in severe compared with moderate FXI deficiency, and fibrin formation was impaired. We conclude that quantitative defects in FXII and FXI have a substantial impact on contact activation-triggered coagulation. Furthermore, FXI deficiency has a dose-dependent suppressing effect on flow-mediated and platelet/TF-dependent clot formation. These last data highlight the contribution of particularly FXI to hemostasis

Enzyme-inhibitory complexes after activation with dextran sulphate in samples from patients and healthy controls.

<p>Levels of enzyme-inhibitory complexes were measured by ELISA in samples from patients with HAE-C1INH and healthy controls after activation with dextran sulphate (DXS; Mr 500 000), without (black) and with (grey) addition of C1 esterase inhibitor (C1INH) after activation. Plasma was activated with DXS (0.25 mg/ml) for 15 minutes, than C1INH or Hepes-buffer (25 mM Hepes, 150 mM NaCl, pH = 7.5) was added and after 10 minutes stop buffer containing STI and polybrene was added. The volume of plasma was 50% of total volume during the activation with DXS, and diluted further in the assay. Significant differences are indicated in Table 4. The line represents the median value; A.U. = Arbitrary units.</p

Enzyme-inhibitory complexes after activation with ellagic acid in samples from patients and healthy controls.

<p>Levels of enzyme-inhibitory complexes were measured by ELISA in samples from patients with HAE-C1INH and healthy controls after activation with ellagic acid, without (black) and with (grey) addition of C1 esterase inhibitor (C1INH) after activation. Plasma was activated with ellagic acid (0.25 mg/ml) for 15 minutes, than C1INH or Hepes-buffer (25 mM Hepes, 150 mM NaCl, pH = 7.5) was added and after 10 minutes stop buffer containing STI and polybrene was added. The volume of plasma was 50% of total volume during the activation with ellagic acid, and diluted further in the assay. Significant differences are indicated in Table 3. The line represents the median value; A.U. = Arbitrary units.</p

Nomenclature of factor XI and the contact system

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152539/1/jth14595_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152539/2/jth14595.pd

Early atherosclerosis exhibits an enhanced procoagulant state

Thrombin generation in vivo may be important in regulating atherosclerotic progression. In the present study, we examined for the first time the activity and presence of relevant coagulation proteins in relation to the progression of atherosclerosis. Both early and stable advanced atherosclerotic lesions were collected pairwise from each individual (n=27) during autopsy. Tissue homogenates were prepared from both total plaques and isolated plaque layers, in which the activity of factors (F) II, X, and XII and tissue factor was determined. Microarray analysis was implemented to elucidate local messenger RNA synthesis of coagulation proteins. Part of each specimen was paraffin embedded, and histological sections were immunohistochemically stained for multiple coagulation markers with the use of commercial antibodies. Data are expressed as median (interquartile range [IQR]). Tissue factor, FII, FX, and FXII activities were significantly higher in early atherosclerotic lesions than in stable advanced atherosclerotic lesions. Endogenous thrombin potential and thrombin-antithrombin complex values consolidated a procoagulant profile of early atherosclerotic lesions (endogenous thrombin potential, 1240 nmol/L x min [IQR, 1173 to 1311]; thrombin-antithrombin complex, 1045 ng/mg [IQR, 842.6 to 1376]) versus stable advanced atherosclerotic lesions (endogenous thrombin potential, 782 nmol/L x min [IQR, 0 to 1151]; thrombin-antithrombin complex, 718.4 ng/mg [IQR, 508.6 to 1151]). Tissue factor, FVII, and FX colocalized with macrophages and smooth muscle cells. In addition, multiple procoagulant and anticoagulant proteases were immunohistochemically mapped to various locations throughout the atherosclerotic vessel wall in both early and advanced atherosclerotic stages. This study shows an enhanced procoagulant state of early-stage atherosclerotic plaques compared with advanced-stage plaques, which may provide novel insights into the role of coagulation during atherosclerotic plaque progressio