Pricolo, Maria RosariaLópez-Unzu, Miguel AVicente, NataliaMorales-López, CristinaHuerta-López, CarlaPérez-Franco, WendyDumitru, Andra CPeña-Peña, JorgeEspinosa, Francisco MSanchez, Mateo IGarcia, RicardoSilva-Rojas, RobertoTorres, MiguelHerrero-Galán, ElíasAlegre-Cebollada, Jorge2026-07-092026-07-092026-05-15J Biol Chem . 2026 May 15;302(7):113167https://hdl.handle.net/20.500.12105/27582Adult 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. In this study, 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. 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 the analyses of markers of DNA synthesis and cytokinesis. We obtain equivalent results when titin is cleaved in cardiomyocytes stimulated with mitogenic factors in vitro and in the adult myocardium in vivo. These findings suggest that 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.J. A.-C. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. [101002927]). M. T. was funded by the ERC grant agreement N◦ 101142005. CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia, Innovación y Universidades (MCIU, MICIU/AEI/10.13039/ 501100011033) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (grant CEX2020-001041-S funded by MCIU). MALU is supported by grant FJC2021 047055-I from MCIU. J. A.-C. and R. G. acknowledge financial support from Comunidad de Madrid through grants Tec4Bio-CM (P2018/NMT4443) and TecNanoBio-CM (TEC-2024/TEC-158). A. C. D. acknowledges funding from La Caixa Foundation [LCF/BQ/PI22/11910029]. J. P.-P. acknowledges a fellowship from “la Caixa” Foundation (ID 100010434), fellowship code LCF/BQ/DR22/11950017. R. S.-R. acknowledges funding from the European Molecular Biology Organization (EMBO, postdoctoral fellowship EMBO ALTF 417-2022). M. I. S. gratefully acknowledge.engVoRhttp://creativecommons.org/licenses/by-nc-nd/4.0/cardiac regenerationcardiomyocytecell cycleproliferationsarcomeretitinAttribution-NonCommercial-NoDerivatives 4.0 International42142587302(7)113167Journal of Biological Chemistryopen access