The membrane type 1 matrix metalloproteinase (MT1-MMP) is increased in left ventricular (LV) failure. However, the direct effects of altered MT1-MMP levels on survival, LV function, and geometry following myocardial infarction (MI) and the proteolytic substrates involved in this process remain unclear. MI was induced in mice with cardiac-restricted overexpression of MT1-MMP (MT1-MMPexp; full length human), reduced MT1-MMP expression (heterozygous; MT1-MMP+/−), and wild type. Post-MI survival was reduced with MT1-MMPexp and increased with MT1-MMP+/− compared with WT. LV ejection fraction was lower in the post-MI MT1-MMPexp mice compared with WT post-MI and was higher in the MT1-MMP+/− mice. In vivo localization of MT1-MMP using antibody-conjugated microbubbles revealed higher MT1-MMP levels post-MI, which were the highest in the MT1-MMPexp group and the lowest in the MT1-MMP+/− group. LV collagen content within the MI region was higher in the MT1-MMPexp vs. WT post-MI and reduced in the MT1-MMP+/− group. Furthermore, it was demonstrated that MT1-MMP proteolytically processed the profibrotic molecule, latency-associated transforming growth factor-1-binding protein (LTBP-1), and MT1-MMP-specific LTBP-1 proteolytic activity was increased by over fourfold in the post-MI MT1-MMPexp group and reduced in the MT1-MMP+/− group, which was directionally paralleled by phospho-Smad-3 levels, a critical signaling component of the profibrotic transforming growth factor pathway. We conclude that modulating myocardial MT1-MMP levels affected LV function and matrix structure, and a contributory mechanism for these effects is through processing of profibrotic signaling molecules. These findings underscore the diversity of biological effects of certain MMP types on the LV remodeling process.
Extracellular Matrix–Mediated Membrane-Type 1 Matrix Metalloproteinase Expression in Pancreatic Ductal Cells Is Regulated by Transforming Growth Factor-β1
