Differences and Compatibility between Human and Porcine Fibrinolytic Components toward Plasmin Generation and Fibrin Degradation

Fibrinolysis is the process of blood clot breakdown by the enzyme plasmin. Despite increased usage of large animals such as pigs to study fibrinolysis in human disease models, a comprehensive study comparing the human and porcine fibrinolytic factors has not been reported. To directly compare and characterize structural and functional differences between human and porcine fibrinolytic factors. Using human or porcine source of plasminogen, tissue-type plasminogen activator (tPA), and fibrinogen, we investigated how various permutations of the three fibrinolytic factors affect overall plasmin generation. Human or porcine plasmin breakdown of fibrin generated from human or porcine fibrinogen was also investigated using turbidity-based lysis assay and visualized using SDS-PAGE. Primary structures of the various proteins were also compared. All-human components had a 24-fold higher plasmin generation than all-porcine components. Species dependence on plasmin generation was the most dependent on fibrin source, where human fibrin presence led to a 2- to 34-fold higher plasmin generation than porcine fibrin. Porcine plasmin was the better enzyme for human or porcine fibrin breakdown due to a 2.7-fold and 6.7-fold higher kcat, respectively. Peptide sequence analyses show the greatest differences lie in Kringle domain 1 for plasminogen and Kringle domain 2 for tPA, both of which bind fibrin. Fibrinogen chains also show the greatest difference within the αC domain, which has known plasminogen and tPA binding sites. Although similar, there are notable and specific differences between the human and porcine fibrinolytic systems, particularly toward plasmin generation and fibrin breakdown.