Electron microscopic images of both C57BL/10 MSCs (A, B, D) and mdx MSCs (C, E, F, G). All cells showed similar morphological features: an elliptical nucleus (N), usually with multiple nucleoli (pentagrams); various mitochondrial profiles; and small vacuoles (D, E: arrowheads). Big vacuoles (F, G: asterisks) and lysosomes (E-G: L) were observed in the cytoplasm of mdx MSCs, and heterochromatin was observed in the nucleus of these cells (C: thin white arrows). Chromatin formed a thin and dense layer inside the perinuclear cisternae (D-G: thin black arrows). Mitochondria (M) with both round and elongated profiles (D, G: thick white arrows) were observed. Scale bar, 1 μm.