Inhibiting Fibronectin Attenuates Fibrosis and Improves Cardiac Function in a Model of Heart Failure
Background—Fibronectin (FN) polymerization is necessary for collagen matrix deposition and is a key contributor to increased abundance of cardiac myofibroblasts (MF) following cardiac injury. We hypothesized that interfering with FN polymerization or its genetic ablation in fibroblasts would attenuate MF, fibrosis and improve cardiac function following ischemia/reperfusion (I/R)-injury.
Methods—Mouse and human MF were utilized to assess the impact of the FN polymerization inhibitor (pUR4) in attenuating pathologic cellular features such as proliferation, migration, extracellular matrix (ECM) deposition and associated mechanisms. To evaluate the therapeutic potential of inhibiting FN polymerization in vivo, wildtype (WT) mice received daily intraperitoneal injections of either pUR4 or control peptide (III-11C) immediately after cardiac surgery, for seven consecutive days. Mice were analyzed seven days post-I/R to assess myofibroblast markers and inflammatory cell infiltration, or four weeks post-I/R, to evaluate long-term effects of FN inhibition on cardiac function and fibrosis. Further, inducible, fibroblast-restricted, FN gene ablated (Tcf21MerCreMer;Fnflox) mice were utilized to evaluate cell specificity of FN expression and polymerization in the heart.
Results—pUR4 administration on activated MF reduced FN and collagen deposition into the ECM and attenuated cell proliferation, likely mediated through decreased c-myc signaling. pUR4 also ameliorated fibroblast migration accompanied by increased β1 integrin internalization and reduced levels of phosphorylated focal adhesion kinase (FAK) protein. In vivo, daily administration of pUR4 for seven days post-I/R significantly reduced MF markers and neutrophil infiltration. This treatment regimen also significantly attenuated myocardial dysfunction, pathologic cardiac remodeling and fibrosis up to 4 weeks post-I/R. Finally, inducible ablation of FN in fibroblasts post-I/R resulted in significant functional cardioprotection with reduced hypertrophy and fibrosis. Interestingly, addition of pUR4 to the FN ablated mice did not confer further cardioprotection, suggesting that the salutary effects of inhibiting FN polymerization may be largely mediated through effects on FN secreted from the CF lineage.
Conclusions—Inhibiting FN polymerization or CF gene expression attenuates pathologic properties of MF in vitro and ameliorates adverse cardiac remodeling and fibrosis in an in vivo model of HF. Interfering with FN polymerization may be a new therapeutic strategy for treating cardiac fibrosis and HF.
- Received March 1, 2018.
- Revision received March 17, 2018.
- Accepted March 23, 2018.