Abstract 376: Microscale Mechanisms Regulating Fibrin Clearance During Fibrinolysis

Abstract

During fibrinolysis the enzyme plasmin digests fibrin fibers, the primary structural elements in blood clots. Developing a mechanistic understanding of fibrinolysis is important for understanding the pathophysiology of hemostasis, but lysis mechanisms have long been debated. Using time-resolved fluorescence microscopy, we investigated the plasmin-mediated digestion of individual fibrin fibers. We found that digestion occurs all along the fiber length, but digestion rates vary spatially. At some fiber locations, digestion accelerates over time, likely due to a previously unknown tension-dependent mechanism that pulls fibers apart during digestion. The fiber is eventually cleaved into two halves, often with the halves displaying cone-shaped ends. To determine how fibers are digested after the initial cleavage event, fiber ends were tracked, and surprisingly the cone-shaped structure persisted over for over 13 s. To understand our experimental results, we used mathematical modeling to estimate the mean first passage time of plasmin molecules arriving at the fiber surface and the number of digestion sites on a fiber. Modeling results were comparable to the experimental time evolution of digestion sites data. Taken together, these results provide a detailed understanding of fibrinolytic mechanisms, both during and after fiber cleavage, and underscore the need to consider fibrin tension when assessing fibrinolytic approaches.