Session: 321. Coagulation and Fibrinolysis: Basic and Translational: Poster I
Hematology Disease Topics & Pathways:
Fundamental Science, Research, Translational Research, Biological Processes
Citrated plasma was obtained from healthy donors (n=60). Plasma levels of PK, FXII, FXI, FIX, FVIII and C1INH antigen were measured by commercial enzyme linked immunosorbent assays validated using congenitally deficient or immunodepleted plasmas. TG was measured in the healthy donor plasma by CAT using a submaximal concentration of silica nanospheres as a trigger. aPTT was measured using an automated hematology analyzer. In additional experiments, plasma levels of individual contact and intrinsic pathway factors were varied by reconstituting congenitally deficient plasmas with increasing levels of purified zymogen (0-400% of normal) with contact pathway-initiated TG measured as described above.
In healthy donor plasmas, significant associations between aPTT and zymogen levels of PK (r = -0.35, P<0.01), FXII (r = -0.27, P<0.05), and FXI (r = -0.34, P<0.01) but not FVIII, FIX or C1INH were observed. Interestingly, significant associations between contact pathway-initiated TG parameters and levels of all zymogens analyzed, except for PK, were observed. In particular, C1INH was significantly associated with peak TG (r = -0.32, P<0.05) and endogenous thrombin potential (ETP) (r = -0.4 P<0.01). Significant associations were also observed between TG and zymogens for C1INH targets FXIIa and FXIa. In particular, FXII was correlated with peak (r=0.42, p<0.001), velocity (r=0.44, p<0.001) and ETP (r=0.3, p<0.01). FXI was correlated with lag time (r=-0.25, p<0.05), peak (r=0.35, p<0.01), time to peak (r=-0.27, p<0.05), and velocity (r=0.4, p<0.01). To further evaluate the impact of variation in a single zymogen, additional reconstitution experiments were conducted. As observed in the healthy donor plasmas, varying levels of PK had no significant effect on contact pathway-initiated TG. In contrast, a strong dose-dependent relationship between plasma levels of FXII, FXI, FIX, and FVIII and contact pathway-initiated TG were observed. Half maximal effective concentration (EC50) values for ETP were 22.5% for FXII, 5.5% for FXI, 12.4% for FIX, and 25.7% for FVIII. EC50 values for velocity were 25.3% for FXII, 9.3% for FXI, 30.9% for FIX, and 68.2% for FVIII.
Our findings indicate that CAT-based measurements of TG have improved sensitivity over the aPTT when evaluating associations with coagulation factor zymogen levels in healthy individuals. Notably, this is the first study to report a significant association between levels of FXII, FXI and their endogenous inhibitor C1INH and TG in the general population. Further, from the CAT-based measurements it is apparent that variation in individual zymogen levels differentially affects contact pathway-initiated TG.
Disclosures: No relevant conflicts of interest to declare.
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