A versatile device for in vitro magnetomechanical scaffold stimulation and enhancement of osteochondral differentiation of hMSCs

Physical stimuli have received significant attention, owing to their capacity to create more biomimetic niches. While dynamic mechanical loading has shown promise in promoting osteogenic and chondrogenic differentiation, magnetic fields have recently emerged as another potential stimulus. However, the combined effect of magnetomechanical - simultaneous magnetic and mechanical-stimulation on osteochondral tissue regeneration, remains largely unexplored. Moreover, a significant discrepancy exists across systems for magnetic stimulation in vitro, hindering cross-study comparison. Addressing these challenges, we developed a versatile, high-throughput device capable of delivering controlled magnetomechanical stimulation to 3D structures in vitro. When paired with magnetoactive, 3D printed scaffolds with low (mPLC5%) or high (mPLC20%) magnetic content, this system enabled the application of oscillating magnetic fields (0-300 mT) causing a cyclic mechanical displacement (0-2 μm). Magnetomechanical stimulation increased the expression of key osteogenic markers, including a 3-fold increase of alkaline phosphatase (ALP) and a 2-fold increase in osteocalcin concentration in mPLC5% scaffolds. Additionally, stimulated mPLC5% scaffolds showed a 2-fold increase in the relative expression of mechanotransduction markers compared to the mPLC20% condition. Moreover, a 3-fold increase in the expression of Collagen II and Aggrecan was observed in the stimulated mPLC20% scaffolds compared to their static counterparts, showing that this condition could be a potentially good candidate for chondrogenic commitment. Our findings suggest the presence of an optimal window for directing osteogenic or chondrogenic commitment, driven by the degree of cyclic deformation and the presence of the external oscillating magnetic field, in the absence of other differentiation stimuli.