Key result
Titin cleavage drives progressive sarcomere disassembly but fails to induce cardiomyocyte proliferation.
Why the study?
Sarcomere disassembly is considered necessary for cardiomyocyte proliferation, but whether sarcomere disassembly alone can trigger cell cycle re-entry remained unknown.
Does titin cleavage-induced sarcomere disassembly trigger cell proliferation in murine cardiomyocytes?
Does titin cleavage-induced sarcomere disassembly trigger cell proliferation in murine cardiomyocytes?
Specific cleavage of titin induces sarcomere disassembly in living cardiomyocytes but is insufficient to trigger cell cycle re-entry and proliferation.
Sarcomere disassembly alone fails to induce cardiomyocyte proliferation; leaves open additional requirements for adult heart regeneration.
Aims Adult mammalian hearts have limited regenerative capacity due to the inability of cardiomyocytes to proliferate, a major clinical hurdle in contemporary cardiology. The presence of highly organized, contractile sarcomeres has long been considered an impediment for cardiomyocyte division. Indeed, sarcomere disassembly is a crucial step to complete the cell cycle in the few situations where cardiomyocytes have been observed to proliferate. However, whether sarcomere disassembly can per se trigger cell cycle re-entry remains unknown, a possibility that we have tested here. Methods and results We have engineered a system to induce sarcomere disassembly in living murine cardiomyocytes based on the specific cleavage of the structural protein titin by tobacco etch virus protease (TEVp). Although isolated neonatal cardiomyocytes with disassembled sarcomeres remain viable and retain low-amplitude contractile activity, our results show no evidence of increased cardiomyocyte proliferation in targeted cells, as indicated by analyses of markers of DNA synthesis and cytokinesis. We obtain equivalent results when titin is cleaved in the adult myocardium in vivo . Conclusion The removal of sarcomere structural barriers is necessary, but not sufficient, for cardiomyocyte proliferation, which implies that additional factors are required for cardiomyocytes to undergo cell division. Translational perspective There is a clinical need to identify therapeutic strategies that promote cardiac regeneration through the proliferation of cardiomyocytes that survive an injury to the heart, for instance after myocardial infarction. Based on the observation that cardiomyocytes require sarcomere disassembly for proliferation, we have examined if the sole disassembly of sarcomeres is enough to promote cell division in cardiomyocytes. Our work demonstrates a strategy to induce specific sarcomere disassembly, which, however does not result in increased proliferative capacity of cardiomyocytes. These results imply that additional factors need to be considered to promote cardiomyocyte proliferation by facilitating sarcomere disassembly.
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Pricolo et al. (2026) studied Cardiac regeneration. Titin cleavage via TEV protease vs. Wild-type cardiomyocytes or untreated TEVs-TTN cardiomyocytes was evaluated on Cardiomyocyte proliferation (EdU incorporation, Aurora B, Ki-67). Titin cleavage in living cardiomyocytes induces progressive sarcomere disassembly but does not trigger cell proliferation in vitro or in vivo.
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