Abstract Background The adult heart exhibits a very limited regenerative capacity following ischemic injury, primarily due to the inability of cardiomyocytes (CMs) to re-enter the cell cycle and the reduced angiogenic activity of endothelial cells (ECs). Recent evidence indicates that the postnatal decline in CM proliferative potential parallels a reduction in angiogenic competence. However, the mechanisms that suppress angiogenesis in the adult heart remain poorly understood. We hypothesize that the terminal maturation of CMs after birth triggers paracrine signals that restrain EC proliferation. Purpose To identify membrane-bound or secreted factors produced by adult CMs that inhibit EC proliferation and vessel formation, with the aim of developing innovative therapeutic strategies to enhance cardiac revascularization and regeneration. Methods To test this hypothesis, ECs were co-cultured with CMs at different stages of maturation. Using available RNA-sequencing datasets, we constructed a ligand–receptor interactome between CM-derived factors and receptors expressed by cardiac ECs. Through gain- and loss-of-function approaches, key anti-angiogenic molecules were identified and subsequently deleted in Cas9 mice to assess whether their loss could restore angiogenic potential in the adult heart. In parallel, we investigated whether miR199a—known to induce CM de-differentiation and proliferation—could also enhance EC proliferation and angiogenesis when co-delivered with VEGF-A via adeno-associated viral vectors. Results Adult CMs markedly suppressed EC proliferation. Transcriptomic analysis identified 20 membrane or secreted factors establishing 118 potential ligand–receptor interactions between CMs and ECs. Among these, KCNJ11 and CD74 emerged as major regulators, as confirmed by gain- and loss-of-function studies. In vivo deletion of these genes in CMs resulted in a robust increase in EC proliferation and neo-vessel formation. Moreover, CM de-differentiation triggered by miR199a enhanced EC proliferation and angiogenic responses upon VEGF-A stimulation. Conclusions Our findings indicate that fully mature CMs contribute to limiting angiogenic capacity in the adult heart, potentially explaining the limited success of previous therapeutic angiogenesis attempts. Strategies aimed at modulating CM–EC cross-talk or inducing partial CM de-differentiation may open new avenues for cardiac regenerative therapies
Longo et al. (Fri,) studied this question.