The specific interaction between fibrin(ogen) and hyaluronan: possible consequences in haemostasis, inflammation and wound healing.

We have proposed that fibrin and hyaluronan (HA) are macromolecular regulators during inflammation and wound healing. Here we extend our studies to characterize the specific interaction between fibrin(ogen) and HA. 125I-labelled HA (Mr approximately 32,000) was bound by plastic surfaces coated with human fibrinogen but not bovine serum albumin, ovalbumin, beta-lactoglobin or rabbit immunoglobulin G. 125I-labelled fibrinogen bound to a unique hexylamine derivative of HA coupled to Sepharose and was eluted specifically by HA oligosaccharides in a size-dependent manner. A dot blot assay, in which proteins are adsorbed to nitrocellulose and probed with 125I-HA, also showed specific binding to human fibrinogen. This assay was used to examine fibrinogens from other mammalian species. No specific 125I-HA binding was observed with the protein from horse, rat or cow. Significant binding was detected with human, sheep, rabbit, dog, baboon, goat and pig fibrinogens. Thrombin-induced formation of fibrin clots is also affected by HA, which decreases the lag time before clotting and increases the rate of clot formation. The rate of fibrin polymerization increased over 500% in the presence of 60 microM HA. Furthermore, the structure of the fibrin gel, as assessed by light scattering, was altered by HA or chondroitin sulphate in a concentration-dependent manner. The results support the proposed wound-healing model and indicate that an increase in circulating HA levels could adversely affect haemostasis and increase the risk of thrombosis or bleeding. The interaction between HA and fibrinogen emphasizes the importance of the liver endothelial cell HA receptor in the removal of glycosaminoglycans from the blood. Cultured cells continuously endocytosing 125I-HA for 4 h reutilized their total cellular HA receptors at least once every 50 min even in the presence of cycloheximide. This endocytotic receptor was therefore shown to be part of a recycling system.