Macroscopic examination and engraftment of SPIO-labeled cells in non-infarcted heart.

The SPIO-labeled pBM-MSCs were intrapericardially injected. At 7 days, heart samples were sliced into 1–3 cm short-axis sections and were then photographed (A). The heart slices were fixed in 4% formaldehyde. For the detection of SPIO–labeled cells, tissue sections were incubated with 8% hydrochloric acid and 4% potassium ferrocyanide and then with eosin. The blue color indicates the presence of SPIO within the tissue (B). Finally, for histological examination, tissue sections were paraffin-embedded and Prussian-blue/eosin staining demonstrated a preferential distribution of SPIO–labeled cells in the left ventricular myocardium (C). Scale bar: 100μm. Black arrows indicate the presence of SPIO-labeled cells evidenced by the potassium ferrocyanide staining.