Cardiomyocyte proliferation is promoted by intracellular Gas6-mediated Yap activity during neonatal heart regeneration

Abstract

Abstract Purpose The adult mammalian heart has limited regenerative capacity after injury, mostly attributable to postnatal cardiomyocyte (CM) cell cycle arrest. The key to unlocking the regenerative potential of the adult hearts may lie within the developmental transitions occurring during neonatal life. Gas6, a secretory protein, stimulates the proliferation of various type cells through binding to TAM receptor family, such as endothelial progenitor cells, tumor cells, and hair follicle stem-cell. However, no study to date has studied the role of Gas6 during the proliferation of CMs. Herein, our study uncovers that Gas6 is transiently expressed during early postnatal heart and regenerative heart, and functions through intracellular pathway by regulating Yap activity to promote CM proliferation. Methods CM isolation was conducted to assess the change of Gas6 expression in both postnatal development and regenerated stages using the CM-specific Tdtomato mice. Cardiac deletion of Gas6 gene mice was used to evaluate the impaired heart regeneration. CM-specific Gas6 overexpression mice were generated using adeno-associated virus system to evaluate Gas6 pro-proliferate and protect effect after ischemic injury. Secreted signal peptide truncation (ΔSP-Gas6) and predicted functional region truncation (ΔCC-Gas6) were generated to identify the intracellular mechanism of Gas6 via Sav1/p-mst1/p-lats1/ p-yap axis. Results We found that Gas6 expression is enriched in CM4 and the expression profile correlates with the expression of the CM4 marker Acta2, as well as cell-cycle genes Mki67 and Aurora B, in individual CM. Gas6 was highly expressed in the neonatal heart and continued to increase during the neonatal heart regenerative process, but was nearly absent in the adult heart under physiological and ischemia conditions. CM-specific Gas6 deletion resulted in significantly reduced CM proliferation rate and increased CM size in P0 hearts, and congestive heart failure in P28 hearts. Conversely, sustained CM-specific overexpression of Gas6 in postnatal hearts increased CM division, elevated CM numbers, and reduced CM size; and reduced infarct scar area and enhanced cardiac function after ischemia injury. Pre-overexpression of Gas6 in adult CMs protected adult cardiac function against ischemia injury, indicated by the activation of mitosis, angiogenesis and reduced oxidative phosphorylation. In primary neonatal CMs, both Gas6 and ΔSP-Gas6promoted CM proliferation with sarcomere disassembly. Mechanistically, Gas6 interacted with Sav1to inhibit Mst1recruitment and Mst1/Lats1/Yap phosphorylation cascade, therefore, promoted Yap translocation into nucleus. Conclusions We demonstrate that Gas6 is an important intrinsic regulator of neonatal heart regeneration, which acts as a promoter of Yap transcriptional activity to enhance CM proliferation. Supplementing Gas6 in the adult heart represents a potential therapeutic approach for cardiac repair.