BACKGROUND: Recent trials and clinical studies have shown that intracoronary transplantation of bone marrow-derived mesenchymal stem cells (MSCs) improves cardiac function following acute myocardial infarction (AMI). However, whether homing of MSCs into the infarcted myocardium or not is still unknown.OBJECTIVE: To study the homing of MSCs intracoronary administration in porcine myocardial infarction model using in vivo magnetic resonance imaging tracking.METHODS: Porcine MSCs were isolated and cultured by the whole bone marrow method. Following labeling by superparamagnetic iron oxide (SPIO), MSCs were treated with trypsinization to adjust the concentration at 10~(10)/L. Myocardial infarction was induced in all 10 pigs. At one week after modeling, the labeled MSCs were delivered via intracoronary infusion with standard over-the-wire (OTW) balloon angioplasty catheters. Prussian blue staining was used to evaluate labeling efficiency, and double echo steady state was used to scan four-chamber and cor biloculare at long axis view, which was considered as locating phase to obtain image of left ventricle at short axis view. RESULTS AND CONCLUSION: MSCs could be efficiently and safely labeled with SPIO. Intracoronary transplantation of MSCs is able to home the sites of myocardial injury and the border between infarcted and normal tissue. MRI can track SPIO-labeled MSCs delivered through intracoronary and were confirmed on pathology. After 5 weeks the injected labeled cells could still be detected with MRI.