Abstract
In the current study, the mechanical and hypothermic damage induced by vibration and cold storage on human mesenchymal stem cells (hMSCs) stored at 2-8°C was quantified by measuring the total cell number and cell viability after exposure to vibration at 50 Hz (peak acceleration 140 m s(-2) and peak displacement 1.4 mm), 25 Hz (peak acceleration 140 m s(-2), peak displacement 5.7 mm), 10 Hz (peak acceleration 20 m s(-2), peak displacement 5.1 mm) and cold storage for several durations. To quantify the viability of the cells, in addition to the trypan blue exclusion method, the combination of annexin V-FITC and propidium iodide was applied to understand the mode of cell death. Cell granularity and a panel of cell surface markers for stemness, including CD29, CD44, CD105 and CD166, were also evaluated for each condition. It was found that hMSCs were sensitive to vibration at 25 Hz, with moderate effects at 50 Hz and no effects at 10 Hz. Vibration at 25 Hz also increased CD29 and CD44 expression. The study further showed that cold storage alone caused a decrease in cell viability, especially after 48 h, and also increased CD29 and CD44 and attenuated CD105 expressions. Cell death would most likely be the consequence of membrane rupture, owing to necrosis induced by cold storage. The sensitivity of cells to different vibrations within the mechanical system is due to a combined effect of displacement and acceleration, and hMSCs with a longer cold storage duration were more susceptible to vibration damage, indicating a coupling between the effects of vibration and cold storage.