EXPRESSION OF MATRIX METALLOPROTEINASES AND THEIR INHIBITOR TIMP-1 INTHE RAT CAROTID-ARTERY AFTER BALLOON INJURY

The temporal relationship of matrix metalloproteinases (MMPs) and a sp ecific tissue inhibitor (TIMP-1) has been examined by reverse transcri ption-polymerase chain reaction and substrate zymography, after balloo n catheter angioplasty of the rat carotid artery. The contralateral un injured carotid artery was used as a comparative control. Of the MMPs examined, only MMP-2 (72-kDa gelatinase) was produced constitutively b y normal uninjured arteries. After injury, MMP-2 mRNA levels fell comp ared with the uninjured arteries; by 24 hours, levels had increased 2- fold. Zymography showed that the inactive form of MMP-2 predominated i n uninjured vessels, but after injury, the level of the active form wa s increased. MMP-9 (92-kDa gelatinase) mRNA levels and activity peaked at 6 hours after injury and were still detectable al 7 days. MMP-3 (s tromelysin) expression was detectable at low levels as early as 2 hour s after injury and showed an approximate 2-fold increase of expression at 7 days. The presence of the active protein paralleled the mRNA exp ression. The inhibitor TIMP-1 mRNA was first detected 6 hours after in jury and showed a marked peak of expression at 24 hours; however, no e xpression was detected by 7 days. The presence of a constitutively exp ressed, low molecular weight caseinolytic enzyme (27 kDa) was observed , and the induction of a caseinolytic enzyme (30 kDa) was noted that w as induced as early as 2 hours after injury, peaked at 6 hours, and wa s barely detectable by 7 days. These results demonstrate that the proc ess of extracellular matrix breakdown by MMPs after balloon catheter-i nduced injury is controlled by a tightly regulated temporal response b y the genes responsible for the production of these enzymes and their inhibitor and by posttranslational activation of the proenzymes.