Abstract 14616: MicroRNA-133a Mediated Regulation of Membrane Type-1 Matrix Metalloproteinase in Myocardial Fibroblasts: Differential Effects in Dilated Cardiomyopathy
Background: Membrane-type 1 matrix metalloproteinase (MT1-MMP) abundance is increased in left ventricular (LV) fibroblasts from patients with dilated cardiomyopathy (DCM). However, the molecular basis for the elevated MT1-MMP protein in these fibroblasts remains unclear. MicroRNAs (miRs) regulate protein translation by interrupting ribonucleoprotein:mRNA complexes. Using a bioinformatics approach, MT1-MMP was identified as a putative target for miR-133a. Accordingly, this study tested the hypothesis that of miR-133a regulates MT1-MMP protein abundance in myocardial fibroblasts.
Methods and Results: Cultures of left ventricular myocardial fibroblasts were established from normal (n=4) and explanted DCM hearts (n=5). Expression of miR-133a (RT-qPCR) was lower in DCM fibroblasts (4.1±0.1 expression units) compared to normal (13.1±4.0 expression units, p<0.05). Knockdown of miR-133a (anti-miR-133a lentivirus) increased MT1-MMP protein abundance (190±12% and 284±56%, p<0.05), while overexpression of miR-133a (miR-133a lentivirus) reduced MT1-MMP protein abundance (67±11% and 67±7%), in both normal and DCM fibroblasts as compared to non-transduced cells (p<0.05). Using a reporter plasmid containing the 3’ untranslated region of the human MT1-MMP mRNA, MT1-MMP was validated as a direct target for miR-133a. Importantly, miR-133a overexpression in DCM fibroblasts was able to restore MT1-MMP protein levels to normal (Figure ). Neither miR-133a overexpression nor knockdown altered MT1-MMP mRNA expression.
Conclusion: These unique findings demonstrate that MT1-MMP protein abundance is directly regulated by miR-133a in myocardial fibroblasts, and suggest that persistent dysregulation of MT1-MMP in the context of DCM may be corrected by restoring miR-133a expression. Thus, this study identifies a novel mechanism through which MT1-MMP abundance may be modulated in a key cell type responsible for adverse and progressive remodeling with DCM.
- © 2013 by American Heart Association, Inc.