Mechanical and Biochemical Role of Fibrin Within a Venous Thrombus

Background: The physical properties of a venous thrombus are derived from molecular characteristics, including fibrin polymer diameter, density, branching, and cross-linking. Dense thrombi with thin, highly branched fibrin fibres and small pores in the meshwork have been observed to be more rigid, less permeable, and more resistant to lysis. The three dimensional fibrin meshwork acts as the main structure to entrap and capture erythrocytes, platelets and plasma components. Attached factors become integrated into the developing thrombus, co-localise with fibrin deposition and act in either a pro- or anticoagulant capacity. Similarly, factors including blood flow, osmolarity and pH, oxidative stress, platelet and leukocyte recruitment, and thrombin concentration alter thrombus composition, architecture, and its mechanical properties. Conclusions: Over time, an increase in thrombus cellular composition and a linear decrease in fibrin content as a function of thrombus age is observed. However, little else is known regarding the evolution of fibrin based clots. The role of fibrin in mediating cellular coordination, thrombus maturation, and changes of the venous wall also requires further research. This review discusses the current impact of fibrin on thrombus remodeling and addresses the limitations of the work done in this area.