Disrupted Sarcomere Reorganization of Cardiomyopathy-Prone Human iPSC-Derived Cardiomyocytes on a Dynamic Mechanical...

Approximately 15% of dilated cardiomyopathy (DCM) cases are associated with Bcl2-associated athanogene 3 (BAG3) gene mutations, which play a crucial role in myofilament organization and contractile behavior. Previous studies have highlighted the role of dynamic mechanical stress in myofibril alignment in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSCCMs). In this study, we employed thermo-responsive shape memory polymers (SMPs) to mimic the dynamic mechanical environment of the extracellular matrix (ECM) and investigated their impact on myofibril assembly in healthy wild-type (WT) and BAG3 knockout (BAG3-/-) hiPSC-CMs.

We synthesized Tert-Butyl Acrylate (TBA) and Butyl acrylate (BA)-based SMP substrate. hiPSC-CMs were cultured on 30oC on 40% strained (dynamic) and un-strain (static) SMPs for two days before proceeding with polymer recovery at 37oC. Myofibril components of BAG3 knock-out (KO) and WT CMs were evaluated by immunocytochemistry fluorescent images at 5 hours and 24 hours after triggering the shape changes of the SMP substrate. We quantified Z-lines and M-lines of hiPSC-CMs to evaluate sarcomere remodeling on static and dynamic substrates.

Our findings revealed that BAG3-/- hiPSC-CMs exhibited persistent Z-line disruption in sarcomeres compared with WT hiPSC-CMs, but M-line structures were less sensitive to mechanical stress at 5 hours, highlighted a temporal distinction in the assembly and regulation of Z-lines over M-lines. While no significant changes were detected at 5 hours, BAG3-/- CMs exhibited similar impairments in M-line organization as seen with Z-lines. These findings suggest that M-lines in BAG3-/- CMs display heightened sensitivity to dynamic mechanical actuation, but this phenotype emerges only after prolonged culture.

This study highlights the interplay between genetic deficiency and mechanical stress to facilitate disease progression in BAG3-associated DCM.

The online version contains supplementary material available at 10.1007/s12195-025-00880-z.