Static magnetic field-enhanced osteogenic differentiation of human umbilical cord-derived mesenchymal stem cells via matrix vesicle secretion

Background/purpose: Wharton’s jelly mesenchymal stem cells (WJMSCs) are well-known for use in nontissue-specific stem cell therapy. However, they can be a challenge for orthopedic used because they have low osteogenic differentiation ability. Several studies have found that static magnetic fields (SMFs) have positive effects on the osteogenesis of different stem cells. Nevertheless, whether SMFs have similar effects on WJMSC differentiation is unknown. Matrix vesicles are the critical characteristic of osteogenesis. Matrix vesicles serve as the initial site for physiological mineralization. Thus, the purpose of this study was to evaluate the effectiveness of a 0.4-T SMF on osteogenic differentiation and matrix vesicle secretion of WJMSCs. Methods: In methodology, WJMSCs were treated with a 0.4-T SMF. The cell viability was tested using the MTT assay. For the osteogenic analysis, the alkaline phosphatase activity assay and alizarin red S staining were performed. The osteogenic-related gene expression of ALP, BMP-2, and Runx2 was examined using real-time polymerase chain reaction. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy was used to analyze matrix vesicle secretion. Results: The cell viability showed no significant difference between the SMF-treated group and the sham-exposed cells. However, the SMF-treated group exhibited significantly more mineralized nodule formation and higher ALP activity than their control counterparts (p <.05). The expressions of osteogenic-related markers, ALP, BMP-2, and Runx2, were also significantly higher in the SMF-treated WJMSCs. The scanning electron microscopy results showed much more matrix vesicle secretion in the SMF-treated cells than in the sham-treated cells. A mineralized sheath was noted in the SMF-treated cells, along with a sporadic accumulation of spherical mineralized deposits on the cell surface. Conclusions: The results suggest that 0.4-T SMF treatment enhances the osteogenesis of WJMSCs at the early-to-middle stage of osteogenic differentiation by increasing the matrix vesicle secretion and mineralization.