The Effect of Disease and Exercise on Single Fibrin Fiber Mechanical Properties

Abstract

Fibrin fibers are the major structural component of a blood clot. Their properties affect wound healing and diseases, such as thrombosis, heart attacks and strokes. Working with purified fibrinogen, we have found that fibrin fibers have extraordinary extensibility and elasticity1,2. Recently, we have studied the more complex and more physiologically relevant fibrin fibers in plasma clots, in an effort to find relationships between single fibrin fiber mechanical properties and diseases. We determined the mechanical properties of single fibrin fiber of individuals who have cardiovascular disease (CVD), diabetes, or who have undergone an acute bout of strenuous exercise.We found that fibrin fibers from old individuals with CVD are much more stretchable (∼1.5 times), elastic (∼1.4 times) and much stiffer (higher modulus) than those from healthy people. Moreover, we found that acute exercise also has a significant effect on fibrin fiber mechanical properties; fibrin fiber extensibility decreases significantly after exercise. Diabetes does not have a significant effect on single fibrin fiber mechanical properties. However, in the diabetes data, and subsequently in all other samples, we saw a startling correlation between fiber diameter and fiber stiffness: Fibrin fiber modulus decreases as the diameter of the fiber increases. For most samples, the modulus varied as R-1.3 or R-1.4, except for older individuals with cardiovascular disease, where the modulus varied as R-1.0. We propose a model in which the density of fibrin fibers varies: fibrin fibers have a dense core, and a less dense periphery.1. Liu, W., et al. (2010) “The mechanical properties of single fibrin fibers”, J. Thrombosis and Haemostasis 8, 1030-1036.2. Liu, W., et al. (2006) “Fibrin Fibers have Extraordinary Extensibility and Elasticity” Science 313, 634.