Interactions of factor XII with platelets and endothelial cells

The design and testing of a dual fiber textile matrix for accelerating surface hemostasis

The standard treatment for severe traumatic injury is frequently compression and application of gauze dressing to the site of hemorrhage. However, while able to rapidly absorb pools of shed blood, gauze fails to provide strong surface (topical) hemostasis. The result can be excess hemorrhage-related morbidity and mortality. We hypothesized that cost-effective materials (based on widespread availability of bulk fibers for other commercial uses) could be designed based on fundamental hemostatic principles to partially emulate the wicking properties of gauze while concurrently stimulating superior hemostasis. A panel of readily available textile fibers was screened for the ability to activate platelets and the intrinsic coagulation cascade in vitro. Type E continuous filament glass and a specialty rayon fiber were identified from the material panel as accelerators of hemostatic reactions and were custom woven to produce a dual fiber textile bandage. The glass component strongly activated platelets while the specialty rayon agglutinated red blood cells. In comparison with gauze in vitro, the dual fiber textile significantly enhanced the rate of thrombin generation, clot generation as measured by thromboelastography, adhesive protein adsorption and cellular attachment and activation. These results indicate that hemostatic textiles can be designed that mimic gauze in form but surpass gauze in ability to accelerate hemostatic reactions.

Platelets promote coagulation factor XII-mediated proteolytic cascade systems in plasma

Blood coagulation factor XII (FXII, Hageman factor) is a plasma serine protease which is autoactivated following contact with negatively charged surfaces in a reaction involving plasma kallikrein and high-molecular-weight kininogen (contact phase activation). Active FXII has the ability to initiate blood clotting via the intrinsic pathway of coagulation and inflammatory reactions via the kallikrein-kinin system. Here we have determined FXII-mediated bradykinin formation and clotting in plasma. Western blotting analysis with specific antibodies against various parts of the contact factors revealed that limited activation of FXII is sufficient to promote plasma kallikrein activation, resulting in the conversion of high-molecular-weight kininogen and bradykinin generation. The presence of platelets significantly promoted FXII-initiated bradykinin formation. Similarly,in vitroclotting assays revealed that platelets critically promoted FXII-driven thrombin and fibrin formation. In summary, our data suggest that FXII-initiated protease cascades may proceed on platelet surfaces, with implications for inflammation and clotting.

Mechanisms of Poly-N-Acetyl Glucosamine Polymer–Mediated Hemostasis: Platelet Interactions

BACKGROUND

Investigations were performed to determine whether poly-N-acetyl glucosamine (p-GlcNAc) induces hemostasis by the activation of platelets.

METHODS

Platelets were isolated from human blood, fixed in the presence poly-N-acetyl glucosamine fibers, and visualized with scanning electron microscopy. Platelet activation surface markers were measured by fluorescence multiphoton microscopy. Platelet aggregation in the presence of p-GlcNAc fibers and integrin receptor blockers was measured.

RESULTS

Scanning electron microscopy indicated that contact of platelets with poly-N-acetyl glucosamine fibers resulted in platelet activation. Fluorescent microscopy showed that contact of platelets with the marine polymer increased intracellular levels of free calcium and resulted in surface exposure of platelet phosphatidylserine, P selectin, and the alphaIIbbeta3 integrin. Antibody inhibitors of the platelet alphaIIbbeta3 integrin inhibited p-GlcNAc to stimulate fibrin polymerization.

CONCLUSION

Poly-N-acetyl glucosamine fiber material promotes hemostasis by the activation of platelets.