Three-dimensional magnetic torque stimulation enhances functional structural maturation in developing human cardiac organoids

Mechanical forces play a critical role in heart development by activating mechanotransduction pathways. However, applying forces to cardiac organoid models has significant challenges due to technical limitations. In this study, we applied mechanical forces to cardiac organoids with a magnetic torque stimulation (MTS) system using magnetized nanoparticles controlled by a magnetic levitation system. Torque was exerted on developing cardiac organoids within a uniform magnetic field generated by a rotating magnet system. Cardiac organoids exposed to torque showed spatial distribution of atrial and ventricle specific marker proteins such as MLC2v and MLC2a. Gene expression analysis revealed that torque-applied organoids exhibited upregulation of maturation-related genes such as TNNT2, GJA1, MYH7, and KCNJ2 as well as vascular specific genes such as PECAM1, VWF, PDGFRB, and ACTA2. Analysis of mechanotransduction-related genes and proteins indicated increased expression of Lamin A/C, ITGA5, ITGB3, and emerin. Elevated phosphorylation levels of FAK, cofilin, and MLC2 were also confirmed in response to the applied force. Our findings suggest that mechanical force application via MTS system can promote both maturation and vascularization of cardiac organoids by activating mechanotransduction pathways. STATEMENT OF SIGNIFICANCE: Mechanical cues are key regulators of cardiac development, yet their role in organoid maturation remains underexplored. In this study, we introduce a Magnetic Torque Stimulation (MTS) system that delivers precisely controlled rotational forces to stem cell-derived cardiac organoids via surface-bound magnetic particles. Application of MTS significantly promoted cardiac differentiation, structural maturation, and neovascularization within the organoids in vitro. These effects are attributed to mechanotransductive modulation of key developmental signaling pathways. The MTS platform offers a robust strategy for investigating biomechanical regulation of cardiac organogenesis and holds translational potential for organoid-based disease modeling, drug discovery, and regenerative medicine.