Hypoxia-Cytokine Preconditioning Reduces Senescence and Improves Immunomodulatory and Tissue Repair Capabilities of UC-MSCs.

INTRODUCTION Mesenchymal Stem Cells (MSCs) undergo prolonged in vitro passaging, which leads to cellular senescence, and this reduces their therapeutic effectiveness. This study aimed to investigate whether priming MSCs with a defined cytokine mix under hypoxic environments could reduce senescence and augment their therapeutic potential.

METHODS Human umbilical cord-derived MSCs (UC-MSCs) at passage 4 (P4) and passage 8 (P8) were primed under hypoxic settings with three key cytokines (interferon γ, basic fibroblast growth factor, and leukemia inhibitory factor) for a duration of 24 h. We utilized flow cytometry, polymerase chain reaction, enzyme-linked immunosorbent assay, and other experimental approaches to examine the effects of passaging and priming on cellular properties, immunomodulatory capabilities, and neurotrophic qualities and angiogenic potentials.

RESULTS At passage 8, UC-MSCs showed a loss of their usual spindle-shaped morphology, accompanied by an increase in size, a decrease in proliferative capacity, and a reduction in the expression of stemness-related genes, whereas markers of cellular senescence were enhanced. Nonetheless, priming strategies effectively reduced the expression of these senescence markers, maintained stemness, and augmented the expression of immunomodulatory cytokines, neurotrophic factors, and vasculogenic factors. Both UC-MSCs and primed UC-MSCs at P4 and P8 showed similar surface markers, indicating that neither serial expansion nor priming changed the fundamental immunophenotype of the MSCs.

DISCUSSION The results show that hypoxia-cytokines priming effectively mitigates senescence caused by expansion while keeping their immunophenotype. This strategy not only maintains stem cell properties but also enhances their therapeutic potential, making it a feasible approach to obtain large numbers of highly active MSCs for clinical applications.

CONCLUSION In summary, hypoxia-cytokine priming delayed cellular senescence and possibly enhanced the immunomodulatory, neurotrophic, and vasculogenic properties of UC-MSCs.