FLOW REGULATION OF 72-KD COLLAGENASE-IV (MMP-2) AFTER EXPERIMENTAL ARTERIAL INJURY

Background-MMP-2 plays a key role in basement membrane degradation and in the migration of proliferating smooth muscle cells after vascular injury. Because low flow and shear stress have been related to the loc alization and progression of intimal hyperplasia, we hypothesized that flow conditions modulate in vivo MMP-2 transcription and activity in a model of injury-induced intimal thickening. Methods and Results-The right common carotid artery (CCA) was balloon-injured in 21 New Zealan d White male rabbits. Flow was thereafter preserved (normal flow, n=7) , reduced by partial outflow occlusion (low flow, n=7), or increased b y ligation of the left CCA (high flow, n=7). In 15 other animals (cont rols without injury), flow was reduced (n=5), increased (n=5), or pres erved (n=5). Mean blood flow and pressure in the right CCA were measur ed before and after flow modulation (day 0) and before the rabbits wer e killed (day 7). Northern analysis, gelatin-gel zymography, and fluor ometric assays were performed on day 7 to determine MMP-2 mRNA levels and activity in relation to flow and intimal thickening. Mean flow was reduced from 21+/-1 to 7+/-1 mL/min (P<0.05) by outflow occlusion and increased to 31+/-2 mL/min (P<0.05) by ligation of the contralateral CCA. Blood pressure was not different between the flow groups. Hemodyn amic parameters were similar for days 0 and 7 after flow modulation. I n the injured right CCA, there was a 186% increase in MMP-2 mRNA with normal flow (P<0.05), a 366% increase with low flow (P<0.005), and onl y a 38% increase with high flow (P>0.05) compared with the uninjured C CA with normal flow. In the uninjured CCA, MMP-2 mRNA levels were incr eased by only 39% and 26% in the low- and high-flow groups, respective ly, compared with normal-flow controls. The zymographic signal and qua ntitative fluorescent activity of gelatinase were markedly increased i n both injured and uninjured CCAs subjected to low flow. Intimal thick ening was observed after 1 week only in CCA segments with low flow and injury. Conclusions-Hemodynamic forces such as low flow upregulate in jury-induced MMP-2 mRNA and appear to be more important in regulating MMP-2 activity than injury alone. This may facilitate migration of the smooth muscle cells and subsequent development of intimal thickening.