Matrix Stiffening Induces Mechanical Memory and Nuclear Fragility in Cardiomyocytes via Microtubule-Lamin Coupling

Mechanical memory (MM) describes the persistent phenotypic remodeling following exposure to a transient extrinsic biomechanical cue. Short-term biomechanical stress is a feature of several etiologies of cardiomyopathy, including dysfunction of the viable myocardium following a large myocardial infarction. However, the nuclear mechanisms linking stiffness to persistent cellular remodeling remain poorly understood.

We cultured human iPSC-cardiomyocytes on a magnetorheological elastomer (MRE) with tunable stiffness (9-56 kPa) to mimic physiological and pathological myocardium. This allowed us to assess how transient increases in stiffness influence cellular responses such as nuclear structure, and DNA damage in hiPSC-cardiomyocytes. Using a combination of Immunofluorescence imaging, Western Blot and pharmacological interventions, we examined the role of microtubule detyrosination and the LINC (Linker of Nucleoskeleton and Cytoskeleton) complex in transducing mechanical signals from the cytoskeleton to the nucleus with a focus on MM induction.

Short-term (6 h) stiff priming induced reversible phenotypic changes upon resoftening. However, 48 h of stiff priming triggered persistent MM, characterized by nuclear rupture, increased lamin A/C expression, DNA damage, and cytoplasmic leakage of DNA repair factors like KU80. Disruption of either a-tubulin detyrosination or the LINC complex prevented MM and nuclear damage, indicating that these elements are essential for nuclear mechanotransduction. In contrast, depletion of lamin A/C or DNA repair components accelerated stiffness-induced phenotypes and promoted MM onset within 6 hours. Finally, inhibition of a-tubulin detyrosination using ADV-TTL reversed both MM and DNA damage.

Acceleration of MM induction by lamin knockdown suggests that hereditary laminopathies may be associated with increased cardiomyocyte vulnerability to transient mechanical stress inducing DNA damage and senescence. Conversely, the protective effects of limiting stiffness-induced α-tubulin detyrosination, or nuclear mechano-transduction suggest potential cardioprotective strategies in the setting of laminopathies and/or sustained increases in extracellular matrix stiffness.