Inhibition of autophagy alleviates the senescent state of rat mesenchymal stem cells during long-term culture

s. Following a limited number of cell divisions, mesenchymal stem cells (MSCs) undergo senescence, and these senescent cells maintain metabolic modification and remain viable for long periods. Autophagy, an intracellular bulk degradation process, provides a survival effect for cells under stress. In this study, the effect of autophagy on senescent MSCs was analyzed. Following serial passaging, rat MSCs underwent replicative senescence, characterized by positive staining for senescence-associated β-galactosidase (SA-β-gal), and increased expression levels of p16 and p21. During MSC senescence, the levels of autophagic activity were increased, a greater number of autophagic vacuoles were observed in senescent MSCs by transmission electron microscopy, acridine orange staining was elevated and the expression levels of autophagy-related proteins (microtubule-associated protein 1A/1B-light chain 3-II, Atg7 and Atg12) were increased. The role of autophagy in MSC senescence was further inves- tigated through pharmacological inhibition of autophagy with bafilomycin A1 and 3-methyladenine. Inhibition of autophagy by pharmacological means reduced the rate of positive staining for SA-β-gal and the expression levels of senescence-related proteins. In conclusion, these findings suggest that autophagy is activated during senescence and the autophagic activity may be a requirement for maintaining the senescent state of MSCs.