Abstract
IntroductionDespite the strong appeal of ferritin as a magnetic resonance imaging (MRI) reporter for stem cell research, no attempts have been made to apply this genetic imaging reporter in stem cells in an inducible manner, which is important for minimizing the potential risk related to the constitutive expression of an imaging reporter. The aim of the present study was to develop an inducible genetic MRI reporter system that enables the production of intracellular MRI contrast as needed.MethodsFerritin heavy chain (FTH1) was genetically modified by adding a Tet-On switch. A C3H10T1/2 cell line carrying Tet-FTH1 (C3H10T1/2-FTH1) was established via lentiviral transduction. The dose- and time-dependent expression of FTH1 in C3H10T1/2 cells was assessed by western blot and immunofluorescence staining. The induced “ON” and non-induced “OFF” expressions of FTH1 were detected using a 3.0 T MRI scanner. Iron accumulation in cells was analyzed by Prussian blue staining and transmission electron microscopy (TEM).ResultsThe expression of FTH1 was both dose- and time-dependently induced, and FTH1 expression peaked in response to induction with doxycycline (Dox) at 0.2 μg/ml for 72 h. The induced expression of FTH1 resulted in a significant increase in the transverse relaxation rate of C3H10T1/2-FTH1 cells following iron supplementation. Prussian blue staining and TEM revealed extensive iron accumulation in C3H10T1/2–FTH1 cells in the presence of Dox.ConclusionsCellular MRI contrast can be produced as needed via the expression of FTH1 under the control of a Tet-On switch. This finding could lay the groundwork for the use of FTH1 to track stem cells in vivo in an inducible manner.
Highlights
Despite the strong appeal of ferritin as a magnetic resonance imaging (MRI) reporter for stem cell research, no attempts have been made to apply this genetic imaging reporter in stem cells in an inducible manner, which is important for minimizing the potential risk related to the constitutive expression of an imaging reporter
MRI contrast generated via the induced expression of Ferritin heavy chain (FTH1) The results showed no significant changes in the MRI signal in the absence of Dox (Dox-); there was a significant decrease in the MRI signal in the presence of Dox (Dox+) and 500 μM ferric ammonium citrate (FAC)
The results demonstrated a marked increase in Transverse relaxation rate (R2) in C3H10T1/2-FTH1 cells treated with Dox and FAC (0.2 μg/ml and 500 μM, respectively) compared with that in the other cells (P < 0.05) (Fig. 4b)
Summary
Despite the strong appeal of ferritin as a magnetic resonance imaging (MRI) reporter for stem cell research, no attempts have been made to apply this genetic imaging reporter in stem cells in an inducible manner, which is important for minimizing the potential risk related to the constitutive expression of an imaging reporter. Along with the development of stem cell therapy for clinical practice, it Several imaging techniques have been investigated for monitoring grafted cells in vivo. Optical imaging techniques, such as bioluminescence imaging [9] and fluorescence imaging [10], have been used to track cell grafts in. Compared with radionuclide-based or optical imaging, magnetic resonance imaging (MRI) has been proposed as an ideal technique to monitor cells because of its high spatial resolution and soft tissue contrast [1, 6, 13]
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