Novel specific cardiac homing peptides to target failing cardiomyocytes

Abstract

Heart failure (HF) is one of the most prevalent cardiovascular diseases worldwide with high mortality. Although β-blockers are now the cornerstone of HF treatment, they are ineffective in patients’ subpopulations and may cause several side effects. Thus, the development of novel drug delivery systems directly targeting the myocardium in a tissue-specific manner is a promising approach. Two ligands have been characterized to transduce cardiomyocytes (CMs) in vitro as well as cardiac tissue in vivo: the cardiac targeting peptide (CTP) and the primary cardio myocyte (PCM) peptide. However, very little is known about their uptake mechanisms, targeting efficacies, and intracellular distribution. Characterization and optimization of the CTP and PCM peptides through a structure-activity relationship study. Over 100 variants of CTP and PCM peptides have been engineered and screened. The targeting capacity of peptides was evaluated using flow cytometry on neonatal rat ventricular CMs (NRVC) cultured with 6-carboxyfluorescein conjugated peptides. Other cells lines, including human lung adenocarcinoma (A549) and human liver cancer (HepG2) cells, were used to assess the cardiospecificity of the new peptides. Peptide uptake was also monitored by confocal microscopy imaging in NRVC and adult rat ventricular CMs (ARVC), as well as in the ex vivo model. We have generated specific cardiac homing peptides-1 and 2 (i.e., SCHoP-1 and SCHoP-2) with improved properties and increased ability to target and transduce CMs specifically, compared to the parent CTP and PCM peptides. Flow cytometry assays support that SCHoP-1 and SCHoP-2 significantly increase cardiac targeting in living NRVC by 4-fold over the CTP and PCM peptides. No cellular toxicity was observed. SCHoP-1 and SCHoP-2 target preferentially CMs, over A549 and HepG2 cells. We confirmed that they internalize in NRVC and in ARVC localized in the cytosol. CMs internalization is also increased in ex vivo hearts. SCHoP-1 and SCHoP-2 open the way to explore their potential as a targeting moiety to address a therapeutic agent specifically to failing CMs for the treatment of HF.