Pulsed Magnetic Field Stimuli Can Promote Chondrogenic Differentiation of Superparamagnetic Iron Oxide Nanoparticles-Labeled Mesenchymal Stem Cells in Rats

Mesenchymal stem cells (MSCs) have potential uses for cartilage repair due to the potential of chondrogenic differentiation. However, developing effective approaches to regulate chondrogenesis in vivo remains a big challenging. To address the limitations, we propose the application of magnetic fields, which features excellent performance for tissue penetration, good biocompatibility even at high magnetic strength, and wireless remote control. To test this concept, a pulsed magnetic field (PMF) was used to enhance the chondrogenesis of SPIO-labeled MSCs in a rat model of cartilage defects. The SPIO labeling not only efficiently strengthens the responsiveness of MSCs to the externally applied PMF but also enables in vivo non-invasive monitoring of MSCs with magnetic resonance imaging (MRI). Importantly, biochemical and gene expression analysis reveal the upregulation of certain cartilage biomarkers (i.e., SOX9 and COL2A1), showing that the PMF improves the chondrogenesis of MSCs via activation of the TGF-β/SMAD signaling pathways. These results indicate a promising scheme for stem cell-based cartilage repair.