Degradation of fibronectin and vitronectin in chronic wound fluid: analysis by cell blotting, immunoblotting, and cell adhesion assays.
We used a combination of cell blotting, immunoblotting, and cell adhesion assays to analyze fibronectin and vitronectin in wound fluid from acute and chronic wounds. Acute wound fluid (e.g., suction blister fluid, mastectomy fluid) contained intact fibronectin and vitronectin as major cell adhesion proteins. In marked contrast, chronic wound fluid samples from three of 11 patients with venous stasis ulcers showed complete degradation of vitronectin and degradation of fibronectin into small molecular mass polypeptides less than 125 kDa. Three of these polypeptides--54, 93, and 125 kDa--were biologically active in promoting cell attachment and were recognized by monoclonal antibodies that bind fibronectin near the arg-gly-asp (RGD) domain. In wound fluid samples from the other eight of 11 patients, only slight degradation of vitronectin and fibronectin occurred, which resulted in a mixture of mostly intact molecules along with large fragments. Intact fibronectin in chronic wound fluid samples contained the ED-A domain, which showed that fibronectin synthesis occurred locally in the wound bed. Wound fluid containing extensively degraded vitronectin and fibronectin reversibly inhibited cell adhesion, and excess fetal bovine serum, but not purified fibronectin, neutralized the inhibitory effect. We suggest that protease activity in some chronic wounds may cause degradation of adhesion proteins and prevent cell adhesion necessary for normal wound closure.