The increase of NADH fluorescence lifetime is associated with the metabolic change during osteogenic differentiation of human mesenchymal stem cells (hMSCs)

Fluorescence lifetime of NADH had been used as an optical marker for monitoring cellular metabolism. In our pervious studies, we have demonstrated that NADH lifetime of hMSCs increase gradually with time of osteogenic differentiation. In this study, we measured NADH lifetime of hMSCs from a different donor as well as the corresponding metabolic indices such as ATP level, oxygen consumption and lactate release. We also measure the quantity of Complex I, III, IV and V. The results show that during differentiation more oxygen consumed, higher ATP level expressed and less lactate released, and the increase of NADH lifetime was associated with ATP level. Higher expression of the total Complex protein was observed at 3 and 4 weeks after differentiation than controls. However, Complex I expression did not show significant correlation with the increase of NADH fluorescence lifetime. In summary, we demonstrated that the change of NADH lifetime was associated with the metabolic change during osteogenic differentiation of hMSCs. The increase of NADH lifetime was in part due to the increased Complex protein interaction in mitochondria after differentiation.