Abstract 10747: Genetic Enhancement of Epicardial Paracrine Signalling for Cardiac Regeneration

Abstract

After myocardial infarction (MI), paracrine signalling has been shown to contribute to heart regeneration. The epicardium, as an important signalling centre, is crucial for heart development and it is re-activated after MI, indicating its involvement in the response to injury. This project aims to accomplish in situ transfection of the epicardium to stimulate the overexpression of growth factors that will enhance regenerative signalling pathways after MI, with cardiomyocyte proliferation as the primary target. Selective epicardial transfection can potentially be achieved via a surface-mediated delivery. Therefore, we developed a novel transfection approach consisting of the deposition of bioreducible cationic polymeric polyplexes onto flat and nanostructured silicon surfaces by freeze-drying. Recombinant growth factors (rGF) were used in single and combinatorial proliferation assays to select for genes to be delivered to the epicardium. The proliferative effects were assessed on cardiomyocytes, cardiac mesenchymal stromal cells, endothelial cells and cardiac fibroblasts via high-content image analysis. Neuregulin-1 led consistently to higher S-phase proliferation marker in IMR90- and H7-derived cardiomyocytes and higher cardiomyocyte cell numbers (fold increase 1.28 ± 0.12), quantified by flow cytometry. Hepatocyte Growth Factor induced proliferation of cardiac mesenchymal stromal cells (fold increase 2.75 ± 0.31) and angiogenesis (fold increase 1.47 ± 0.34). Follistatin-like 1, from animal and bacterial sources, was also tested but no proliferative effect was detected. The relevant rGF for each cell type maintained its positive effect in combination with other rGFs. Furthermore, preliminary results from in vitro transfection of epicardial cells with these GF genes indicate the proliferative advantage of enriched epicardial paracrine signalling over the incubation of cardiac cells with the rGF . This study remains to be a first-in-field potential material-based gene delivery strategy specific to the epicardium that explores a combinatorial treatment via the delivery of more than one gene for induction of cardiomyocyte proliferation and other regenerative mechanisms for MI treatment.