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Objectives To track bone marrow stem cells (BMSCs) labeled by enhanced green fluorescent protein (EGFP) and superparamagnetic iron oxide ( SPIO ) -poly-L-lysine (PLL) compound by MRI in vitro for autotransplantation into pancreas of type 1 diabetes miniature pigs. Methods The BMSCs were isolated by density gradient centrifugation and attachment culture from type 1 diabetes minipigs' bone marrow. Expressional intensity of EGFP in BMSCs transfected lentivirus-EGFP with a multiplicity of infection Different magnetic resonance scanning protocols were carried out on various density BMSCs labeled by different concentration of SPIO in various time-point in vitro. Results When SPIO concentration was 25mg/L (count in Fe3 + ), the positive Fe3+ -labeling rate of BMSCs was 93. 1%. Most of SPIO particles in BMSCs' cytoplasm were observed in secondary lysosomes, but they were not detected in important organelle as cell nucleus. Comparing with gelatin the MRI of BMSCs labeled with SPIO in the condition with 1 ×104/ml cells density and 25 mg/L Fe3+ concentration in vitro, the signal intensity changes (△SI) after BMSCs labeled with SPIO 3 weeks and 6 weeks in TSE T1WI, TSE T2WI and FLASH T2 * WI sequences were 12%, 41%, 63% and 7%, 28%, 46% respectively (P ＜ 0.01 and P ＜ 0.05, respectively).Conclusions The data showed that the porcine BMSCs labeled with SPIO and EGFP could be traced successfully in vitro by MRI in the suitable sequences.
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In vivo imaging system(IVIS)is a new and rapidly expanding technology,which has a wide range of applications in life science such as cell tracing.By counting the number of photons emitted from a specimen,IVIS can quantify biological events such as tumor growth.We used B16F10-luc-G5 tumor cells and 20 Babl/C mice injected subcutaneously with B16F10-luc-G5 tumor cells(1×106 in 100 μL)to develop a method to quantitatively analyze cells traced by IVIS in vitro and in vivo,respectively.The results showed a strong correlation between the number of tumor cells and the intensity of bioluminescence signal(R2=0.99)under different exposure conditions in in vitro assay.The results derived from the in vivo experiments showed that tumor luminescence was observed in all mice by IVIS at all days,and there was significant difference(P<0.01)between every two days from day 3 to day 14.Moreover,tumor dynamic morphology could be monitored by IVIS when it was invisible.There was a strong correlation between tumor volume and bioluminescence signal(R2=0.97)by IVIS.In summary,we demonstrated a way to accurately carry out the quantitative analysis of cells using IVIS both in vitro and in vivo.The data indicate that IVIS can be used as an effective and quantitative method for cell tracing both in vitro and in vivo.