BACKGROUND/AIMS: Tendon stem cells (TSCs) exhibit a high self-renewal capacity, multi-differentiation potential, and low immunogenicity; thus, these cells might provide a new cell source for tendon repair and regeneration. TSCs are exposed to increased oxidative stress at tendon injury sites; however, how TSCs maintain their stemness under oxidative stress is not clear. METHODS AND RESULTS: In this study, we found that H2O2 treatment increased ROS accumulation in human TSCs (hTSCs) and resulted in loss of self-renewal capacity and stemness, as reflected in reduced colony formation and proliferation, decreased expression of the stemness markers Nanog, Oct-4, NS, and SSEA-4, and impaired differentiation capability. These H2O2-induced damages were prevented by pretreatment with starvation or rapamycin. Pretreatment with starvation or rapamycin prior to H2O2 exposure also led to decreased intracellular and mitochondrial ROS accumulation along with increased autophagic activity, as manifested in increased LC3 cleavage, Beclin-1 expression, and GFP-LC3-labeled autophagosome formation. Autophagy inhibition by 3-MA or CQ, or by shRNA silencing of Agt-7 or Beclin-1 reduced the protective effects of starvation and rapamycin on H2O2-treated hTSCs. CONCLUSION: Thus, the findings of this study suggest that autophagy prevents oxidative stress-induced loss of self-renewal capacity and stemness in hTSCs through suppression of ROS accumulation.
BACKGROUND/AIMS: Tendon stem cells (TSCs) exhibit a high self-renewal capacity, multi-differentiation potential, and low immunogenicity; thus, these cells might provide a new cell source for tendon repair and regeneration. TSCs are exposed to increased oxidative stress at tendon injury sites; however, how TSCs maintain their stemness under oxidative stress is not clear. METHODS AND RESULTS: In this study, we found that H2O2 treatment increased ROS accumulation in human TSCs (hTSCs) and resulted in loss of self-renewal capacity and stemness, as reflected in reduced colony formation and proliferation, decreased expression of the stemness markers Nanog, Oct-4, NS, and SSEA-4, and impaired differentiation capability. These H2O2-induced damages were prevented by pretreatment with starvation or rapamycin. Pretreatment with starvation or rapamycin prior to H2O2 exposure also led to decreased intracellular and mitochondrial ROS accumulation along with increased autophagic activity, as manifested in increased LC3 cleavage, Beclin-1 expression, and GFP-LC3-labeled autophagosome formation. Autophagy inhibition by 3-MA or CQ, or by shRNA silencing of Agt-7 or Beclin-1 reduced the protective effects of starvation and rapamycin on H2O2-treated hTSCs. CONCLUSION: Thus, the findings of this study suggest that autophagy prevents oxidative stress-induced loss of self-renewal capacity and stemness in hTSCs through suppression of ROS accumulation.