Identification and characterization of a Fibrillin-1 derived matrikine for cardiac regeneration and repair

The development of regenerative strategies to repair the heart is of high importance. Our lab has shown that extracellular matrix derived from decellularized fetal myocardium promotes neonatal cardiomyocyte proliferation in vitro. The goal of this study was to identify specific peptide(s)/protein(s) in solubilized cardiac ECM responsible for this proliferative effect. We hypothesized that isolation and then treatment with one or more small synthetic peptide derived from this source could replicate the cellular response to whole solubilized ECM. Decellularized fetal and adult rat hearts were fractionated by molecular weight using SDS-PAGE and transferred to PVDF membranes. Analysis of cardiomyocytes cultured on the membranes revealed regions of enhanced cardiomyocyte proliferation. Subsequent isolation and proteomic analysis of the protein bands that that correlated with proliferative regions identified fibrillin-1 as the predominant ECM protein associated with these regions of cardiomyocyte proliferation. One region (residues 55-86) of fibrillin-1 was synthesized as a peptide and tested for a direct effect on cardiomyocyte proliferation. Compared to positive and negative controls, as well as scrambled and alkylated versions, this peptide led to 3-4 fold increase in cardiomyocyte proliferation. Analysis of the amino acid sequence demonstrated high homology with laent-TGF-β binding proteins and subsequent experiments showed that the matrikine could also reduce TGF-β induced activation of cardiac fibroblasts. These data suggest that individual peptides derived from soluble ECM could have utility as a novel therapeutic for cardiac tissue engineering and regeneration.