Oxidative status predicts quality in human mesenchymal stem cells

Alessandro Bertolo, Simona Capossela, Gion Fränkl, Martin Baur, Tobias Pötzel, Jivko Stoyanov

Human bone marrow-derived mesenchymal stem cells (MSC) are adult progenitor cells with great potential for application in cell-based therapies. From a cell-based therapy perspective, there are two limitations to MSC use: (1) these therapies require large numbers of cells, and long-term expansion of MSC in vitro promotes replicative senescence; and (2) patient variability is a challenge for defining MSC quality standards for transplantation. This study aimed to determine whether low or high oxidative status of MSC correlate with changes in cell expansion and differentiation potentials. We investigated functional aspects of mitochondria, such as cell metabolic activity indicators and expression of antioxidant enzymes. Furthermore, we tested if senescence-induced changes in oxidative status of MSC could be counteracted by methylene blue (MB), an alternative mitochondrial electron transfer known to enhance cell bioenergetics. MSC isolated from donors of the same age showed distinctive behavior in culture and were grouped as weak (low colony-forming units (CFU) and a short life in vitro) and vigorous MSC (high CFU and a long life in vitro). In comparison to weak MSC, vigorous MSC had oxidative status characterized by lower mitochondrial membrane potential, lower mitochondrial activity, and fewer reactive oxygen species production, as well as reduced mitochondrial biogenesis. Vigorous MSC had a significantly higher expansion potential compared to weak MSC, while no differences were observed during differentiation. MB treatment significantly improved expansion and differentiation potential, however only in vigorous MSC. Together, these results demonstrate the importance of mitochondrial function in MSC in vitro, and that cells with low oxidative status levels are better candidates for cell-based therapies.