Mesenchymal stem cells (MSCs) show a high number of autophagosomes. Immortalized human MSCs grown at standard culture conditions (1 g/L glucose, 10% fetal bovine serum, or FBS) or following treatment with 5 μM rapamycin for 1 hour were subjected to transmission electron microscopy analysis at 15,000× magnification (top). A 150,000× image of a late-stage autolysosome is included with the control treatment (top left inset), as is a 40,000× magnification of residual autophagosome structures in the rapamycin treatment (top right inset). Primary human MSCs were analyzed for autophagosome formation at standard conditions (1 g/L glucose, 16.5% FBS) at 40,000× (bottom left) and following 5 μM rapamycin treatment for 1 hour at 10,000× (bottom right). ihMSC, immortalized human mesenchymal stem cell; prhMSC, primary human mesenchymal stem cell.