Sheep were tachypaced to induce HF and recovered when pacing was stopped. Serial block face Scanning Electron Microscopy and confocal imaging were used to understand t-tubule ultrastructure and function. Candidate proteins involved in atrial t-tubule recovery were identified by western blot and causality determined using expression studies.
Sheep atrial t-tubules reappeared following recovery from HF. Despite being disordered (branched, longer and longitudinally arranged) recovered t-tubules triggered Ca2+ release and were associated with restoration of systolic Ca2+. Telethonin and myotubularin abundance correlated with t-tubule density and altered the density and structure of BIN1-driven tubules in neonatal myocytes. Myotubularin had a greater effect, increasing tubule length and branching, replicating that seen in the recovery atria.
Recovery from HF restores atrial t-tubules and systolic Ca2+ and myotubularin facilitates this process. Atrial t-tubule restoration could present a new and viable therapeutic strategy.
Brief Summary: The loss of atrial transverse (t)-tubules and the associated dysfunction in heart failure is reversible and the protein myotubularin plays an important role.
Competing Interest Statement: The authors have declared no competing interest.