Fibrin fragment E potentiates TGF-β-induced myofibroblast activation and recruitment
BackgroundFibrin is an essential constituent of the coagulation cascade, and the formation of hemostatic fibrin clots is central to wound healing. Fibrin clots are over time degraded into fibrin degradation products as the injured tissue is replaced by granulation tissue.\n\nObjectivesstudy the role of the fibrin degradation product fragment E (FnE) in fibroblast activation and migration.\n\nMethodsRat kidney fibroblasts (NRK-49F), human fetal lung fibroblasts (HFL1) and immortalized human foreskin fibroblasts (BJ) were exposed to FnE and TGF-{beta}. Fibroblast activation was measured via quantitative RT-PCR and western blot for -SMA and Collagen I1. A microfluidic chemotaxis assay was used to study directional migration. To investigate if FnE interacts with integrins, direct binding experiments were performed using surface plasmon resonance biosensor technology. Infusion pumps releasing FnE were implanted subcutaneously in mice and profibrotic effects of FnE were analyzed using immunohistochemical staining of the wound area.\n\nResultsWe present evidence that FnE is a chemoattractant for fibroblasts and that FnE can potentiate TGF-{beta}-induced myofibroblast formation. FnE forms a stable complex with V{beta}3 integrin, and the integrin {beta}3 subunit is required both for FnE-induced fibroblast migration and for potentiation of TGF-{beta}-induced myofibroblast formation. Finally, subcutaneous infusion of FnE in mice results in a fibrotic response in the hypodermis. These results support a model where FnE released from clots in wounded tissue promote wound healing and fibrosis by both recruitment and activation of fibroblasts. Fibrin fragment E could thus represent a therapeutic target for treatment of pathological fibrosis.\n\nEssentials- Fibrin is an essential constituent of the coagulation cascade, and fibrin clotting is central to wound healing.\n- Fibrin clots are over time degraded into fibrin degradation products, including fibrin fragment E (FnE).\n- FnE is a chemoattractant for fibroblasts and can potentiate TGF-{beta}-induced myofibroblast formation.\n- FnE released from clots in wounded tissue could promote wound healing and fibrosis.