Inhibition of extracellular-matrix degrading proteases in pericardial-derived cardiovascular bioprostheses

Abstract

The presence of intrinsic remnant extracellular-matrix degrading proteases in glutaraldehyde-treated bovine pericardium per se and in explanted bioprosthetic heart valves has been demonstrated recently by us. These enzymes were shown to degrade type I collagen and thus could contribute to a possible in vivo slow tissue degeneration in time. We have investigated the potential use of protease inhibitors for effective control of this degenerative process. Collagenase, trypsin and chondroitinase were inhibited in vitro by 0.5% glutaraldehyde to 10–20% of initial activity; these remnant activities could be further inhibited by their specific inhibitors suggesting that a combination of glutaraldehyde and a mixture of enzyme inhibitors could be applied to bovine pericardium. Analysis of glutaraldehyde-treated tissue extracts by gelatin zymography revealed the presence of at least four distinct enzyme species which were active towards a collagen substrate and were inhibited most effectively by ethylenediaminetetraacetic acid and thus could be included in the matrix-metallo-proteinase family. Bovine pericardial fragments that were treated with a combination of protease inhibitors and glutaraldehyde showed a reduced colagenolytic activity compared to glutaraldehyde alone; furthermore, upon implantation in the rat subcutaneous model the proteolytic activities found in these preparations were further reduced.