Cardiomyocyte progenitors generated by direct reprogramming and molecular beacon selection attenuate ventricular remodelling after experimental myocardial infarction

Both naturally occurring and artificially engineered multipotent cardiac progenitor cells (CPCs) are associated with highly variable cardiomyocyte (CM) differentiation efficiencies, resulting in unpredictable and/or low CM yields. Therefore, CM-committed progenitors may be a more reliable cell product for therapeutic use. Here, we demonstrate that unipotent progenitors are part of the phenotype spectrum arising during direct reprogramming of neonatal cardiac fibroblasts towards CMs using lentiviral transduction of Gata4, Mef2c, Tbx5, and Myocd. Induced CM progenitors (iCMPs) simultaneously express CPC- and CM-specific proteins and can be selected via hairpin oligonucleotide molecular beacons targeting Myh6/7-mRNA–expressing cells. Purified iCMPs can be expanded extensively with preserved phenotype using ascorbic acid and give rise to CM-like cells in differentiation assays. When transplanted into infarcted mouse hearts, iCMPs prevent CM loss, attenuate fibrotic scarring, and preserve ventricular function. Given the clinical failure of conventional cardiac cell therapy using adult stem cells, further translational development of this iCMP approach is warranted. Overall design: Three sample groups were analyzed: (1) murine neonatal cardiac fibroblasts (CF, starting cells), (2) murine induced cardiomyocyte progenitors (iCMP, purified GMTMy-reprogrammed cells), (3) murine adult left ventricular heart tissue (AHT). Two biological replicates were included for each sample group.