Abstract 11255: Collagelin Analogs Target Collagen and Identify Myocardial Fibrosis

Introduction: Myocardial fibrosis is a common adverse condition associated with heart failure and remodeling. At present, there is a need for molecular imaging methods to detect fibrosis. Hypothesis: Analogs of collagelin (a 22 amino acid peptide mimetic of glycoprotein GPVI), named CRPA monomer and collagelin dimer, provide specific molecular binding to collagen in cardiac fibrosis. Methods: Collagelin analog binding was tested by Blitz interferometry analysis, ELISA on a collagen coated well plate using luminescence detection, Cu64-CRPA autoradiography and staining of myocardial tissues with suspected fibrosis. Tissue samples were obtained from MI rats (n=15); swine with heart failure (n=15), either untreated or treated with enzyme inhibitors Saxagliptin or Tadalafil; as well as human MI tissue. In ex-vivo binding assays, 8μm sections were stained with biotin-CRPA, followed by streptavidin-horseradish peroxidase and visualized by DAB stain. Percent fibrosis was validated by picrosirius red and analyzed by ImageJ. Results: Blitz analysis was used to assess association and dissociation curves for CRPA and collagelin dimer binding to collagen. By ELISA, a concentration dependent increase in luminescence showed CRPA consistently bound collagen. A blocking study with excess unlabeled CRPA showed a decrease in biotin-CRPA binding, suggesting peptide specificity. Autoradiography and biotin-CRPA histology of rats 5 weeks post infarct identified 15-20% fibrosis at the edge of the myocardial tissue. In swine, untreated controls showed fiber disarray and increased CRPA and picrosirius red staining, while drug treated groups showed minimal staining. CRPA also showed specificity to infarcted tissue from human myocardium and picrosirius red confirmed location of fibrosis. Conclusion: CRPA monomer and collagelin dimer bind myocardial fibrosis. Collagelin analogs have potential utility as molecular probes for identifying myocardial fibrosis.