RESUMO
Objective To detect the feasibility of magnetically labeled swine bone marrow mesenehymal stem cells(MSCs)with SHU 555A combined with poly-L-arginine(PLL),under MR imaging in vitro and in vivo.Methods Swine mesenehymal stem cells were isolated and culture-expanded 3 passages in vitro,then magnetically labeled by incubation with SHU 555A(25?g Fe/ml,Resovist,Schering)for 24 hours with 750 ng/mL poly-L-lysine(PLL;average MW_275 kDa)added 1 hour before incubation.Cellular iron incorporation and detention at 0 d,4 d,8 d,12 d,16 d,20 d after labeling was qualitatively assessed using Prussian blue and quantified at atomic absorption spectrometry.Cell viability was assessed by trypan-blue exclusion test.Cell suspensions underwent MR imaging with T_1-and T_2-weighted spin-echo and fast field-echo sequences on a clinical 1.5 T MR system.At last,1?10~6 SHU 555A labeled and unlabeled MSCs were transextracardially implanted into the infracted and normal myocardium approximately 2 week following the ligation of left anterior descending coronary artery in 1 swine respectively,and finally performed 1.5-T MRI within 1 week after infarction.Results①Intracytoplasmic particles stained with Prussian blue stain were detected for all cells with mean cellular iron content of(13.13?2.30)pg per cell.With division of stem cells, the stained particles decreased gradually with iron content(0.68?0.20)pg per cell.at 16 days after labeling, approximately to the prelabeled baseline values.(0.21?0.06)pg per cell(P＞0.05).The viability of the labeled cells at various time points were not significantly different with that of nonlabeled cells(P＞0.05).②MR images showed signal intensity changed most obviouly in T2*WI in vitro.The percentage change of signal intensity increased with increasing cell numbers,and decreased with the time.As few as 5?10~4-1?10~5 cells could be detected by using this approach.③Two injected sites containing MR-MSCs were detected in vivo,presentingas low signal intensity areas with the T_2*WI scanning sequence.Conclusion Swine bone marrow MSCs can be labeled with SHU555A-PLL and depicted with a standard 1.5-T MR imager in vitro and in vivo.(J lntervent Radiol,2007,16:115-121)