Fibrins

Fibrins are fibrous proteins that polymerize to form the structural mesh of a blood clot. They derive from fibrinogen, a soluble plasma glycoprotein produced by the liver. In response to vascular injury, the coagulation cascade activates thrombin, which cleaves fibrinogen to form insoluble fibrin monomers. These monomers polymerize to form a fibrous network, and factor XIIIa cross-links the strands to stabilize the clot.

The fibrin network traps platelets and blood cells, providing mechanical strength and helping to seal the breach of the vessel. It also serves as a scaffold for subsequent wound healing and tissue remodeling.

Fibrinolysis degrades fibrin through plasmin, generated from plasminogen by tissue plasminogen activator or urokinase. D-dimer and other fibrin degradation products are used clinically to assess active clot breakdown.

Clinical applications include fibrin-based products such as fibrin sealants and fibrin glue, used to promote hemostasis and tissue adhesion in surgery and regenerative medicine.

Disorders related to fibrins include bleeding due to insufficient clot formation and thrombosis due to excessive or inappropriate fibrin deposition. Abnormalities in fibrinogen levels, thrombin activity, or plasminogen activation can influence clot stability and breakdown.