TENASCIN-C DEGRADATION IN CHRONIC WOUNDS IS DEPENDENT ON SERINE PROTEINASE ACTIVITY

Degradation of extracellular matrix (ECM) components by proteinases is part of the physiological remodelling process during normal wound hea ling, Excessive degradation of the ECM, however, is likely to create a n environment that can no longer support keratinocyte migration and is thought to play a role in the impaired healing of chronic ulcers. Ten ascin-C is an ECM component that is markedly upregulated in acute and chronic wounds. Here we report on our investigations into the degradat ion of tenascin-C in chronic venous leg ulcers. We found proteolytic f ragments of tenascin-C in leg ulcer exudate. We also detected fragment s of fibronectin in the wound fluid and in addition observed breakdown of fibronectin by wound fluid in vitro, as has previously been report ed by others. Wound fluid of four out of six chronic leg ulcers degrad ed purified human tenascin-C in vitro, and degradation of tenascin-C c orrelated with high levels of functionally active leucocyte elastase a nd metalloproteinases in the wound fluid. To identify which proteinase s were involved in tenascin-C degradation, we tested the effect of spe cific proteinase inhibitors. The addition of EDTA or E64 did not prote ct tenascin-C from degradation, suggesting that neither metalloprotein ases nor cysteine proteinases are responsible for cleavage. Tenascin-C breakdown was inhibited by PMSF and SKALP/elafin, and we therefore co nclude that leucocyte elastase and possibly other serine proteinases a re the tenascin-C-degrading enzymes in ulcer exudate. Taking into acco unt the possible effects of tenascin-C and tenascin-C fragments on cel l behaviour, we hypothesize that degradation of tenascin-C could affec t the healing process in chronic venous ulcers.