In vivo magnetic resonance imaging of iron oxide–labeled, arterially‐injected mesenchymal stem cells in kidneys of rats with acute ischemic kidney injury: Detection and monitoring at 3T

Abstract Purpose To evaluate MRI for a qualitative and quantitative in vivo tracking of intraaortal injected iron oxide–labeled mesenchymal stem cells (MSC) into rats with acute kidney injury (AKI). Materials and Methods In vitro MRI and R 2 * measurement of nonlabeled and superparamagnetic iron oxide (SPIO)‐labeled MSC (MSC SPIO ) was performed in correlation to cellular iron content and cytological examination (Prussian blue, electron microscopy). In vivo MRI and R 2 * evaluation were performed before and after ischemic/reperfusion AKI ( N = 14) and intraaortal injection of 1.5 × 10 6 MSC SPIO ( N = 7), fetal calf serum (FCS) (medium, N = 6), and SPIO alone ( N = 1) up to 14 days using a clinical 3T scanner. Signal to noise ratios (SNR), R 2 * of kidneys, liver, spleen, and bone marrow, renal function (creatinine [CREA], blood urea nitrogen [BUN]), and kidney volume were measured and tested for statistical significance (Student's t ‐test, P < 0.05) in comparison histology (hematoxylin and eosin [H&E], Prussian blue, periodic acid‐Schiff [PAS], CD68). Results In vitro, MSC SPIO showed a reduction of SNR and T 2 * with R 2 * ≈ number of MSC SPIO (R 2 = 0.98). In vivo MSC SPIO administration resulted in a SNR decrease (35 ± 15%) and R 2 * increase (101 ± 18.3%) in renal cortex caused by MSC SPIO accumulation in contrast to control animals ( P < 0.01). Liver, spleen, and bone marrow (MSC SPIO ) showed a delayed SNR decline/R 2 * increase ( P < 0.05) resulting from MSC SPIO migration. The increase of kidney volume and the decrease in renal function ( P < 0.05) was reduced in MSC‐treated animals. Conclusion Qualitative and quantitative in vivo cell‐tracking and monitoring of organ distribution of intraaortal injected MSC SPIO in AKI is feasible in MRI at 3T. J. Magn. Reson. Imaging 2007;25:1179–1191. © 2007 Wiley‐Liss, Inc.