Initiation and propagation of coagulation from tissue factor‐bearing cell monolayers to plasma: initiator cells do not regulate spatial growth rate

Abstract

To cite this article: Ovanesov MV, Ananyeva NM, Panteleev MA, Ataullakhanov FI, Saenko EL. Initiation and propagation of coagulation from tissue factor-bearing cell monolayers to plasma: initiator cells do not regulate spatial growth rate. J Thromb Haemost 2005; 3: 321-31.Summary. Exposure of tissue factor (TF)-bearing cells to blood is the initial event in coagulation and intravascular thrombus formation. However, the mechanisms which determine thrombus growth remain poorly understood. To explore whether the procoagulant activity of vessel wall-bound cells regulates thrombus expansion, we studied in vitro spatial clot growth initiated by cultured human cells of different types in contact pathway-inhibited, non-flowing human plasma. Human aortic endothelial cells, smooth muscle cells, macrophages and lung fibroblasts differed in their ability to support thrombin generation in microplate assay with peaks of generated thrombin of 60 ± 53 nmol L , 218 ± 55 nmol L )1 and 407 ± 59 nmol L )1 (mean ± SD), respectively. Real-time videomicroscopy revealed the initiation and spatial growth phases of clot formation. Different procoagulant activity of cell monolayers was manifested as up to 4-fold difference in the lag times of clot formation. In contrast, the clot growth rate, which characterized propagation of clotting from the cell surface to plasma, was largely independent of cell type (£ 30% difference). Experiments with factor VII (FVII)-, FVIII-, FX-or FXI-deficient plasmas and annexin V revealed that (i) cell surface-associated extrinsic Xase was critical for initiation of clotting; (ii) intrinsic Xase regulated only the growth phase; and (iii) the contribution of plasma phospholipid surfaces in the growth phase was predominant. We conclude that the role of TF-bearing initiator cells is limited to the initial stage of clot formation. The functioning of intrinsic Xase in plasma provides the primary mechanism of sustained and far-ranging propagation of coagulation leading to the physical expansion of a fibrin clot.

Spatial Dynamics of Contact-Activated Fibrin Clot Formationin vitroandin silicoin Haemophilia B: Effects of Severity and Ahemphil B Treatment

“…To quantitatively characterize the spatial clotting process we calculated the size of the clot as a function of time from the light scattering profiles. We assumed that the clot size at a given time, Size(t), was equal to the distance from the activator to the point where fibrin concentration (proportional to the light scattering intensity [8]) declined to 50% of the plateau value ( fig. 2 С-D).…”

“…It is shown that clotting under these experimental conditions is sensitive to congenital deficiencies of FVIII, FIX [6,7] and FXI [3,8], that are associated with abnormal clotting commonly referred as haemophilias A, B and C, respectively. Extremely low concentrations of FVIII, FIX and, to a lesser extent, FXI have been shown to disrupt clot propagation in space.…”

Thrombin generation, fibrin clot formation and hemostasis

“…68 These findings suggest that thrombin generated on the surface of platelets during the propagation phase dictates that rate of fibrin clot formation away from the initiating cells. [67][68][69][70] Fibrin formation during cell-mediated thrombin generation likely includes a complex spatial component as well. It is likely that this physical progression of procoagulant activity from the tissue factor-bearing cell (low levels of thrombin generation) to the activated platelet surface (rapid burst of thrombin generation) induces the formation of a thrombin gradient in space.…”

“…Since different tissue factor-bearing cells support different levels of procoagulant activity, they differ in their ability to initiate fibrin formation. 68,71-73 Interestingly, Ovanesov et al (2005) showed that the rate of thrombin generation on tissue factor-bearing cells does not influence the rate of propagation of fibrin into the plasma milieu. 68 Rather, propagation of fibrin away from the site of initiation depends on the plasma composition and procoagulant activity of the surrounding milieu.…”

Introduction to haemostasis from a pharmacodynamic perspective

“…The observation that information on clot properties provides better guidance for preventing bleeding and the effectiveness of treatment than clotting time Introduction to haemostasis from a pharmacodynamic perspective Br J Clin Pharmacol / 72:4 / 541 in critically ill patients with bleeding problems [44,45] may be considered a first step in this direction.This can be taken further when evaluations will also be done that study clot growth/propagation in conditions with flow/circulation because this clinically relevant condition is not mimicked in current in vitro tests [46,47].…”