Effect of Fractionated Electron Beam Irradiation on Senescence Development in Human Adipose Tissue Stromal Cells

Introduction/Objective: The proliferative capacity of adipose tissue stem cells (ATSCs) declines with aging due to the onset of senescence. This study aimed to determine whether fractionated electron irradiation can induce stable senescence in human ATSCs. Methods: Human ATSCs were exposed to electron beam irradiation using a Novac-11 accelerator. Irradiated and control ATSCs were subsequently cultured for 14 days in serum-free medium under either normoxic (5% CO₂, 21% O₂) or hypoxic (5% CO₂, 6.5% O₂) conditions. Cellular senescence was assessed by β-galactosidase staining. Expression of surface markers CD90 and CD105 was analyzed using flow cytometry. To quantify gene expression levels of IL-6, IL-8, p16, p21, and TGF-β, total RNA was extracted and subjected to qPCR. Results: Approximately 60% of irradiated ATSCs cultured under hypoxic conditions exhibited senescence. The proportion of CD90- and CD105-positive cells was significantly reduced compared to both the baseline culture and the normoxic group (p < 0.05). Expression levels of p16 and p21 did not differ significantly from controls after 14 days under either hypoxic or normoxic conditions (p > 0.05). In contrast, IL-6 and TGF-β1 expression levels were significantly elevated compared to control groups (p < 0.05). Discussion: This study demonstrates that fractionated electron irradiation can induce stable senescence in ATSCs, particularly under hypoxic conditions. The significantly higher percentage of senescent cells in the irradiated hypoxic group suggests a synergistic effect, in which irradiation combined with reduced oxygen tension enhances senescence induction. Conclusion: Fractionated electron irradiation can effectively induce a stable state of cellular senescence in ATSCs, with hypoxia further promoting this effect.