OBJECTIVETo investigate the feasibility of in vivo magnetic resonance imaging (MRI) tracking of transplanted adipose-derived stem cells (ADSCs) labeled with superparamagnetic iron oxide (SPIO) in rat heart.

METHODSADSCs were labeled with poly-L-lysine (PLL)-SPIO complexes. Intracellular iron uptake was identified by Prussian blue stain and transmission electromicroscopy. Trypan blue staining was used to test the viability of the labeled cells. In vitro MRI of labeled cells was performed. SPIO-labeled ADSCs were transplanted into normal rat hearts and were in vivo imaged with MRI. Image findings on MRI were correlated with histological findings of the rat hearts.

RESULTSThe labeling efficacy of ADSCs with PLL-SPIO was nearly 100%. Light microscopy revealed the SPIO particles were located in the cytoplasm of the ADSCs by Prussian blue staining. Transmission electromicroscopy revealed that the SPIO particles were located in the endosomes in the cytoplasm. There was no significantly deference in viability between labeled and unlabeled groups demonstrated by Trypan blue test (P > 0.05). MRI showed signal loss in gel mixed with labeled cells as compared with the unlabeled cells group and blank group. Signal void on rat hearts were demonstrated on MRI and were well correlated with histological findings where Prussian-blue-stain positive cells presented.

CONCLUSIONMRI can be used to in vivo track the transplanted ADSCs labeled with SPIO into rat hearts and facilitate to understand the conditions of the labeled cells in the transplanted areas.