YAP Drives Assembly of a Spatially Colocalized Cellular Triad Required for Heart Renewal

After myocardial infarction (MI), the heart fails to renew, and the cardiac microenvironment is irreversibly disrupted. Inactivation of the Hippo signaling pathway can rebuild the post ischemic microenvironment and improve cardiac function. We investigated spatially resolved cellular relationships of neonatal and adult renewal-competent hearts to gain insight into inefficient mammalian heart renewal. Spatial transcriptomics (ST) and single-cell sequencing of adult control hearts and hearts expressing YAP5SA, an active version of the Hippo signaling pathway effector YAP, which models heart renewal, revealed a conserved, renewal-competent cardiomyocyte (CM) population in control hearts and amplified in YAP5SA hearts. This CM population was also found in the wildtype, renewal competent neonatal heart after myocardial infarction, as well as the adult human heart. Cardiac fibroblasts (CFs), expressing complement C3, colocalized with these CMs. In YAP5SA hearts and neonatal hearts post-MI, macrophages (MPs) expressing complement receptor C3ar1 also colocalized, creating a pro-renewal niche composed of the CM, CF and MP triad. Both C3 and C3ar1 loss-of-function in YAP5SA hearts similarly suppressed heart renewal, indicating that C3-expressing CFs, C3ar1-expressing MPs, and complement system signaling play a direct role in heart renewal Overall design: Single cell RNA sequencing and spatial transcriptomics were performed to examine MCM control versus MCM YAP5SA adult murine hearts Single nucleus RNA sequencing were performed to examine wild type control and C3-/- p2 neonatal murine hearts 3 days after sham or MI surgeries.