Comparison of hMSC metabolic activity over 7 days. The graph shows the absorbance of alamarBlue™ at 590nm for the different temperatures and durations tested. A higher absorbance corresponds to a higher level of metabolic activity, which is an indication of cell number. A lag phase of cell growth is indicated between days 2 and 3 for all samples up to 48°C/150 s, for which there were no significant changes in metabolic activity over 7 days when compared to a control. hMSCs heated to 58°C all eventually died. ☆P≤0.05, heated groups vs. control kept at 37°C/5% CO2.