MMI‐0100 Inhibits Cardiac Fibrosis in a Mouse Model Overexpressing Cardiac Myosin Binding Protein C

BACKGROUND Cardiac stress can trigger production of a 40-kDa peptide fragment derived from the amino terminus of the cardiac myosin-binding protein C. Cardiac stress, as well as cMyBP-C mutations, can trigger production of 1 such truncated protein fragment, a 40-kDa peptide fragment derived from the amino terminus of cMyBP-C. Genetic expression of this 40-kDa fragment in mouse cardiomyocytes (cMyBP-C40k) leads to cardiac disease, fibrosis, and death within the first year. Fibrosis can occur in many cardiovascular diseases, and mitogen-activated protein kinase--activated protein kinase-2 signaling has been implicated in a variety of fibrotic processes. Recent studies demonstrated that mitogen-activated protein kinase--activated protein kinase-2 inhibition using the cell-permeant peptide inhibitor MMI-0100 is protective in the setting of acute myocardial infarction. We hypothesized that MMI-0100 might also be protective in a chronic model of fibrosis, produced as a result of cMyBP-C40k cardiomyocyte expression. METHODS AND RESULTS Nontransgenic and cMyBP-C40k inducible transgenic mice were given MMI-0100 or PBS daily for 30 weeks. In control groups, long-term MMI-0100 was benign, with no measurable effects on cardiac anatomy, function, cell viability, hypertrophy, or probability of survival. In the inducible transgenic group, MMI-0100 treatment reduced cardiac fibrosis, decreased cardiac hypertrophy, and prolonged survival. CONCLUSIONS Pharmaceutical inhibition of mitogen-activated protein kinase--activated protein kinase-2 signaling via MMI-0100 treatment is beneficial in the context of fibrotic cMyBPC40k disease.