AIM:To evaluate tracking of magnetically labeled mesenchymal stem cells(MSCs) after intraportal transplantation.METHODS:Mononuclear cells were isolated from bone marrow aspirates of pigs by density gradient centrifugation,cultured and expanded,after which,they were incubated with super paramagnetic iron oxide(SPIO).Prussian blue staining was performed to highlight intracellular iron.To establish swine models of acute liver injury,0.5 g/kg D-galactosamine was administrated to 10 pigs,six of which were injected via their portal veins with SPIO-labeled MSCs,while the remaining four were injected with unlabeled cells.Magnetic resonance imaging(MRI) was performed with a clinical 1.5T MR scanner immediately before transplantation and 6 h,3 d,7 d and 14 d after transplantation.Prussian blue staining was again performed with the tissue slices at the endpoint.RESULTS:Prussian blue staining of SPIO-labeled MSCs had a labeling efficiency of almost 100%.Signal intensity loss in the liver by SPIO labeling on the FFE(T2*WI) sequence persisted until 14 d after transplantation.Histological analysis by Prussian blue staining confirmed homing of labeled MSCs in the liver after 14 d;primarily distributed in hepatic sinusoids and liver parenchyma.CONCLUSION:MSCs were successfully labeled with SPIO in vitro.MRI can monitor magnetically labeled MSCs transplanted into the liver. AIM: To evaluate tracking of magnetically labeled mesenchymal stem cells (MSCs) after intraportal transplantation. METHODS: Mononuclear cells were isolated from bone marrow aspirates of pigs by density gradient centrifugation, cultured and expanded, after which, they were incubated with super paramagnetic iron oxide (SPIO) .Prussian blue staining was performed to highlight intracellular iron. To establish swine models of acute liver injury, 0.5 g / kg D-galactosamine was administrated to 10 pigs, six of which were injected via their portal veins with SPIO-labeled MSCs , while the remaining four were injected with unlabeled cells. Magnetic resonance imaging (MRI) was performed with a clinical 1.5T MR scanner immediately before transplantation and 6 h, 3 d, 7 d and 14 d after transplantation. Population blue staining was again performed with the tissue slices at the endpoint .RESULTS: Prussian blue staining of SPIO-labeled MSCs had a labeling efficiency of almost 100% .Signal intensity loss in the liver by SPIO l Histological analysis by Prussian blue staining confirmed homing of labeled MSCs in the liver after 14 days; distributed in hepatic sinusoids and liver parenchyma. CONCLUSION: MSCs were successfully labeled with SPIO in vitro. MRI can monitor magnetically labeled MSCs transplanted into the liver.