In Vitro MR Imaging Of Ultrasmall Superparamagnetic Iron Oxide Labeled Rabbit Bone Marrow Mesenchymal Stem Cells

Purpose:The aim of this study was to determine whether intravenous USPIO can be used to label rabbit BMSCs in vivo and to evaluate the labeling efficiency of rabbit BMSCs with different labeling doses of USPIO, and to detect the characteristics and signal attenuation rules by a 1. 5T MR scanner. Methods:(1)Rabbits were injected with various doses of USPIO(15mg Fe/kg,30 mg Fe/kg,60 mg Fe/kg and 120 mg Fe/kg) 48 hours prior to extraction of BMSCs from bone marrow. Femoral bone marrow in rabbits was examined by using MR imaging before and up to 30 minnutes and 48 hours postinjection(PI) of USPIO.All in vitro experiments were performed with cells at passage 3;(2) Prussian blue stain was performed to show intracellular iron nanoparticles,enhanced CCK-8 Cell Counting Kit was applied to evaluate proliferation of labeled cells, to find out a more safe and more effective appropriate labeling dose of USPIO;(3) To choosing USPIO with most appropriate labeling dose to lable rabbit BMSCs.Osteoplastic,adipogenic and chondrogenic differentiation potential of labled cells were identified using Alizarin red staining,Oil red O stain and Sarranine O staining;Eppendorf tubes containing cells underwent 1.5T MRI with FSE T2 WI.MRI Signal intensity of in vivo labeled MSCs and unlabeled control cells were compared. Results:(1)All rabbits femoral bone marrow showed marked positive signal on T2-weighted images before PI and a corresponding marked signal loss on T2-weighted images at 48 hours PI.And we can detect a great quantity of adherent cells by inverted phase contrast microscope;(2)Intracytoplasmic iron nanoparticles were stained with Prussian blue.And the higher the labeling dose of USPIO,the higher labelling rate.The labelling rate for USPIO(30mg Fe/kg)labeling cells is near 100%.CCK-8 values show that the dose of USPIO less than 60 mg Fe/kg can not influence growth activity of labeled rabbit BMSCs obviously;(3)After BMSCs labeled by USPIO(30mg Fe/kg),It showed no significant difference in effects on the differentiation of the labeled cells.USPIO labeling caused a stronger low signal attenuation effect in T2 WI than unlablede cells. Conclusion:(1)Intravenous USPIO can be used to effectively label BMSCs in vivo without significant change in cell viability and differentiation potential.BMSCs was labeled by USPIO of 30 mg Fe/kg has higher cellular labeling efficiency and cell proliferation;(2)The suspension of labeled BMSCs can be imaged with standard 1.5-T MR equipment,Low signal intensity could be observed and FSE T2 WI was sensitive sequence for detecting USPIO-labeled BMSCs.