Metabolic Mode of Alginate-Encapsulated Human Mesenchymal Stromal Cells as a Background for Storage at Ambient Temperature

<b><i>Introduction:</i></b> Human mesenchymal stromal cells (MSCs) are attractive for both medical practice and biomedical research. Nonfreezing short-term storage may provide safe and simple transportation and promote the practical use of MSCs. <b><i>Objectives:</i></b> We aimed to determine the duration of efficient storage at ambient temperature (22°C) of human dermal MSCs in different three-dimensional organization and to investigate the role of cell metabolic mode in the resistance to the ambient storage damaging factors. <b><i>Methods:</i></b> MSCs in monolayer, suspension, and encapsulated in alginate microspheres (AMS) were stored in sealed containers at 22°С in culture medium. Viability (fluorescein diacetate /ethidium bromide) and metabolic activity (Alamar Blue assay) were assessed at 0, 3, 7, 10, and 14 days of the storage. Mitochondrial membrane potential (JC-1 test), cell cycle analysis, reactive oxygen species level, and resistance to hydrogen peroxide were analyzed under culture conditions. <b><i>Results:</i></b> Alginate encapsulation was shown to maintain viability (about 85%), metabolic activity, and adhesion ability during storage for 7 days. The storage of MSCs in both monolayer and suspension was less efficient. Culture of MSCs in AMS decreased basal metabolic activity, mitochondrial activity, and led to reversible cell cycle arrest compared to standard two-dimensional culture. MSCs in AMS have a lower basal level of reactive oxygen species and higher resistance to hydrogen peroxide compared with those in monolayer culture. <b><i>Conclusion:</i></b> Revealed shift into quiescent metabolic mode is essential for alginate-encapsulated MSCs resistance to storage at ambient temperature.