Analysis of plasmin generation and clot lysis of plasma fibrinogen purified from a heterozygous dysfibrinogenemia, BβGly15Cys (Hamamatsu II)

We found a heterozygous dysfibrinogenemia caused by the substitution of BβGly15Cys and designated it fibrinogen Hamamatsu II (H-II). Although the propositus suffered an infarction of the medulla oblongata, other thrombotic risk factors, paradoxical cerebral infarction, and arterial dissection were not found. To determine whether the delayed lysis of fibrin clots or not in the context of the BβGly15Cys substitution, we examined the clot lysis and plasmin generation of propositusʼ fibrinogen. Fibrinogen was purified from the propositusʼ and normal control plasma by immunoaffinity chromatography and was used for the following experimentssodium dodecyl sulfate-polyacrylamide gel electrophoresis, fibrin polymerization, scanning electron microscopic observation of fibrin clot and fibers, clot lysis, and tissue-type plasminogen activator-mediated plasminogen activation. The H-II plasma fibrinogen showed the presence of albumin-binding variant forms, a dimeric molecule of variant fibrinogen, and impairment of lateral aggregation during fibrin polymerization. The H-II fibrin clot showed lower density of bundles and thinner diameters of fibers than in the normal fibrin clot. In the clot lysis experiments with overlaid plasmin, H-II fibrin showed a similar lysis period and lysis rate to the normal control. Moreover, plasmin generation from a mixture of thrombin, tissue-type plasminogen activator, plasminogen, and H-II fibrinogen also showed a similar rate to normal fibrinogen. Although the propositus suffered an infarction, the present study did not observe delayed clot lysis, that is, the clot was not resistant to plasmin degradation. Therefore, we did not clarify an association between the BβGly15Cys dysfibrinogenemia and arterial thrombosis.