Induction of tissue inhibitor of metalloproteinase and its mitogenic response to endothelial cells in human atherosclerotic and restenotic lesions.

INTRODUCTION

Expression of extracellular matrix (ECM), including collagens and proteoglycans, is increased following atherosclerosis and restenosis.

OBJECTIVE

To understand the Mechanism of ECM induction and accumulation, the balance among neutral matrix metalloproteinases (MMP), tissue inhibitor of metalloproteinase (TIMP) and activator (tissue plasminogen activator (tPA)) following atherosclerosis and restenosis was measured in human normal artery, and native atherosclerotic and restenotic lesions.

DESIGN AND RESULTS

Based on zymographic analysis, a correlation between the increase in latent and intrinsic MMP activity and an increase in the duration from first angioplasty to restenotic atherectomy was found, suggesting decreased MMP activity from normal tissue to restenotic tissue. ELISA was carried out to measure the level of TIMP. Inhibition of collagenase activity, against fluorescein-conjugated type I collagen degradation, by normal, de novo and restenotic extracts was determined. TIMP levels were found to be increased in restenotic lesions (0.38+/-0.04 ng/mL) compared with normal arterial tissue (0.27+/-0.05 ng/mL) and with tissue derived from de novo (0.30+/-0.02 ng/mL atherosclerotic lesions. Mitogenic activity of tissue extracts, against normal human heart endothelial (HHE) cells, was measured using acid phosphatase assay as the marker of cell number. Based on neutralizing antibody to TIMP, mitogenic activity was observed in restenotic tissue to HHE cells. Using plasminogen/gelatin zymographic analysis, no significant change was observed in the level of tPA in extracts from all three groups (i.e., 8.1+/-1.2, 8.7+/-0.6, and 8.6+/-0.3 (arbitrary unit) in normal, de novo and restenotic tissue, respectively).

CONCLUSIONS

These results suggest that accumulation of ECM in restenotic tissue following mechanical revascularization may in part be due to repression in MMP expression, and may be associated with increased level of TIMP and its mitogenic activity.