Pressure-Induced Matrix Metalloproteinase-9 Contributes to Early Hypertensive Remodeling

Background—High blood pressure causes a change in vascular wall structure involving altered extracellular matrix composition, but how this process occurs is not fully understood. Methods and Results—Using mouse carotid arteries maintained in organ culture for 3 days, we detected increased gelatin zymographic activity of matrix metalloproteinase (MMP)-2 (168±13%, P <0.05) in vessels kept at low intraluminal pressure (10 mm Hg) compared with vessels at 80 mm Hg (100%), whereas in vessels maintained at high pressure (150 mm Hg), both MMP-2 and MMP-9 activity was induced (182±32%, P <0.05, and 194±21%, P <0.01, respectively). MMPs were detected in endothelial and smooth muscle cells by immunohistochemistry and in situ gelatin zymography. In vessels at 150 mm Hg, MMP activation was associated with a shift in the pressure-diameter curve toward greater distensibility (P <0.01) compared with vessels at 80 mm Hg. However, distensibility was not altered in vessels at 10 mm Hg, in which only activated MMP-2 was detected. The role of MMPs in high pressure–induced vessel distensibility was confirmed by use of the MMP inhibitor FN-439, which prevented the shift in the pressure-diameter relationship. Furthermore, in carotid arteries from MMP-9–deficient mice, the pressure-dependent increase in MMP-2 and in situ gelatinolytic activity were maintained, but the upward shift in the pressure-diameter curve was abolished. Conclusions—MMP-9 seems to play a key role in the early stages of hypertensive vascular remodeling.