Effects of Low Magnitude Vibration on Mesenchymal Stem Cell Osteogenic Potential and Phenotype.

Mechanical stimulation, particularly low magnitude vibration (LMV), has been shown to increase bone mineral density (BMD) in vivo and the osteogenic potential of bone marrow-derived mesenchymal stem cells (BM-MSCs). However, much remains unknown about its mechanisms of action and effects on cell phenotype. To better understand this phenomenon, we subjected BM-MSCs cultures to in vitro LMV at 32-37 Hz, 0.3-0.4 g for 20 minutes every day. Gene and protein expression, calcium deposition, actin structure, and cytokine/growth factor secretion were assessed. Additionally, we investigated the role of PIEZO1, a mechanosensitive ion channel, alongside its chemical activation using YODA1 and PIEZO1 silencing. Based on the results from this study, we divided six BM-MSC groups derived from different donors into two categories: LMV-responsive and LMV-nonresponsive. The LMV-nonresponsive groups did not show an overall increase in osteogenic potential with LMV while the LMV-responsive groups experienced a consistent increase in calcium deposits, upregulation of COL1A1, OCN, and CYR61 genes, and a significant increase in PIEZO1 protein. Additionally, LMV-responsive BM-MSCs had a reduction in cell spreading area after 3 days of daily LMV, a significant reduction in some key pro-inflammatory cytokines including IL-1α, IL-1β, and TNFα, and no significant changes in the expression of senescence-associated proteins. By implementing PIEZO1 silencing, we found that this channel is essential to increase calcification in BM-MSC cultures following LMV treatment. Altogether, these findings show the effects of mechanical stimulation on BM-MSC phenotype and the role of PIEZO1 in this process.