Viability imaging of stem cell using a MRI reporter gene and MEMRI
Journal of Cardiovascular Magnetic Resonance volume 11, Article number: P181 (2009)
Embryonic stem cells have demonstrated the potential to restore the myocardium. MRI is an ideal method to evaluate myocardial cell therapy. Superparamagnetic iron oxide nanoparticle (SPIO) has been widely used to monitor stem cell therapy. However, this technique does not provide any biologic information of cell viability.
This novel reporter gene (RG) is designed to express antigenic epitopes on the surface of embryonic stem cell (ESC). Employing SPIO-conjugated monoclonal antibodies, MRI signal specific to hESC viability can be generated. Mn2+ is known to be able to enter viable cells through the voltage gated Ca2+ channel and subsequently can shorten T1 relaxation time generating bright signal on T1 weighted sequence.
MRI RG was constructed driven by EF1α promoter to express c-myc, HA epitopes and firefly luciferase (Luc) on the cell surface. This fusion protein has been designed to be anchored on the cell surface by PDGFR transmembrane domain. Both c-myc and HA epitopes are the molecular targets for MRI viability signal using SPIO conjugated monoclonal antibodies. H9 hESC female line was tranduced with this RG using a p2K7 lentiviral vector. hESC-RG incubated with anti c-myc and HA microbeads were scanned by 3 T MRI using a high array knee coil. For MEMRI, 0.5 mL of 5 mM MnCl2 was injected intraperitoneally after transplanting mESC onto mouse hindlimbs. Mice were scanned using Spin echo sequence by 3 T MRI.
Functional expression of hESC-RG was confirmed by FACS, bioluminescence and Prussian blue staining. In vitro MRI showed significant dephasing signal generated from SPIO conjugated antibody for c-myc and HA (Figure 1A). Magnetically pre-labeled hESC were injected into the lateral wall of left ventricle (LV) and the robust dephasing signal was noted on MRI (Figure 1B,C). In vivo MEMRI could show significant enhancement of viable mESC on the mouse hindlimbs using T1 weighted sequence (Figure 1D,E).
The novel MRI RG enabled viable embryonic stem cells to generate significant molecular MRI signal. In vivo molecular signal of hESC viability will be feasible using this innovative MRI RG. MEMRI enabled in vivo evaluation of viability of stem cells.
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Chung, J., Kee, K., Perra, R.R. et al. Viability imaging of stem cell using a MRI reporter gene and MEMRI. J Cardiovasc Magn Reson 11 (Suppl 1), P181 (2009). https://doi.org/10.1186/1532-429X-11-S1-P181