Contractile Function Maintains Cardiomyocyte Differentiation and Inhibits Cell Cycle Activity

Numerous endotherm species lose cardiac regenerative capacity shortly after birth, which is in contrast to many ectotherm species who regenerate throughout life. Whether the enhanced contractile function required for endothermy contributes to the cell-cycle exit remains to be explored. Herein, we use human cardiac organoids with advanced maturation combined with direct targeting of contraction using mavacamten and aficamten to enable exquisite control of active contraction over brief time windows. We show that transient inhibition of contraction re-activates the cell cycle. Multi-omics analyses demonstrated the cell cycle response to be mediated through a dedifferentiation-like process, which was swiftly reversed upon removal of the myosin inhibitors. Together these findings reveal that active contraction maintains differentiation including cell cycle arrest in cardiomyocytes. ### Competing Interest Statement E.R.P., R.J.M. and J.E.H. are co-inventors on a patent relating to the Heart-Dyno device and human cardiac organoid maturation used in this study (WO2018035574A1 filed by the University of Queensland) which is licensed to Dynomics. E.R.P., R.J.M. and J.E.H. are co-inventors on a patent for cardiac regeneration therapeutics (WO2020186283A1 filed by QIMR Berghofer). E.R.P. and J.E.H. are co-inventors on a patent for the serum-free conditions supporting the vascular population used in this study (WO2024016058 filed by MCRI and QIMR Berghofer). J.E.H. is co-inventor on licensed patents for cardiac differentiation and engineered heart muscle, some aspects of which are used in this study (WO2015040142A1 and WO2015025030A1), which are licensed to MyriaMed and Repairon. E.R.P., R.J.M. and J.E.H. are cofounders, scientific advisors, and stockholders in Dynomics. J.E.H. and R.J.M. are co-inventors on a provisional patent filed by QIMR Berghofer on the DM-hCO conditions (2024902826). Q-D.W. is an employee of AstraZeneca. The remaining authors declare no competing interests. Snow Medical Research Foundation, SMRF2019-060 National Health and Medical Research Council of Australia, GNT2008376 Diabets Australia, Y23G-KRYJ Novo Nordisk Foundation, NNF21CC0073729