[A study of tracking the superparamagnetic iron oxide and enhanced green fluorescent protein labeled miniature porcine bone marrow stem cells by in vitro MRI].

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 (MOI) of 30:1 reached the highest level after 96 h from transfection, while the positive rate was 43.2%. 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 25 mg/L (count in Fe(3+)), the positive Fe(3+)-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 × 10(4)/ml cells density and 25 mg/L Fe(3+) concentration in vitro, the signal intensity changes (ΔSI) after BMSCs labeled with SPIO 3 weeks and 6 weeks in TSE T(1)WI, TSE T(2)WI and FLASH T(2) 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.