M. G. Bartley1, E. E. Moore2, M. J. Cohen2, N. G. Vigneshwar1, J. M. Samuels1, A. Eitel1, J. Hadley1, J. Coleman1, A. Sauaia1,2, C. Silliman4, Z. Wang3, H. B. Moore3 1University Of Colorado Denver,Surgery,Aurora, CO, USA 2Denver Health Medical Center,Surgery,Aurora, CO, USA 3University Of Colorado Denver,Transplant,Aurora, CO, USA 4Children’s Hospital Colorado,Hematology,Aurora, CO, USA
Introduction:
Annexin A2 (A2) is a highly conserved multifunctional protein located at the cell surface and intracellularly. Previous studies have shown at the cell surface, A2 with the help of S100 dimerization serves as a platform for plasminogen and tissue plasminogen activator (tPA). The heterodimer of S100-A2 normally produced via endothelial cells serves as a source of plasmin leading to fibrinolysis. Currently there is limited data evaluating their individual coagulation properties. We hypothesize that exogenous cell free A2 will augment tPA thereby increasing fibrinolysis.
Methods:
Whole blood (WB) was obtained from healthy volunteers (n=10). Samples were incubated at 37 ° C with increasing concentrations of exogenous annexin A2 ranging from 1μg/mL-125μg/mL increasing by 25. The vehicle for A2 is composed of 5% glycerol and phosphate buffer saline at physiologic pH 7.4. Vehicle alone was incubated in whole blood at a volume corresponding to the largest dose (125μg/mL) of A2. tPA, a known fibrinolytic protein was added to samples at a concentration of 75ng/mL. The following TEG measurements were recorded: clot initiation (R time, fibrin polymerization (angle) and clot strength [maximum amplitude (MA) clot lysis time 30 minutes after reaching MA (LY30)]
Results:
Fibrinolysis (LY30) was significantly increased with increasing concentrations of A2 when stimulated with tPA p=0.01. LY30 with A2 alone, vehicle, whole blood and tranexamic acid was statistically distinct from that of tPA p=0.01. At maximal dose of 125μg/mL with tPA A2 increased fibrinolytic activity by 66%. Clotting time (R time) was significantly increased with increasing concentrations of A2 when stimulated with A2. Angle was significantly decreased progressively with increased A2 and tPA p=0.001. Clot strength (MA) was decreased with increasing concentrations of A2 p=0.001
Conclusion:
Cell free annexin A2 increases the fibrinolytic properties of tPA, which from a surgical perspective could be useful as a therapeutic to augment the lytic activity of endogenous tPA and reduce the use of exogenous tPA therefore limiting the risk of bleeding.
