Theranostics 2014; 4(10):972-989. doi:10.7150/thno.9436

Research Paper

Longitudinal Monitoring of Stem Cell Grafts In Vivo Using Magnetic Resonance Imaging with Inducible Maga as a Genetic Reporter

In K. Cho1,2,3, Sean P. Moran3, Ramesh Paudyal4, Karolina Piotrowska-Nitsche3, Pei-Hsun Cheng3, Xiaodong Zhang4, Hui Mao5✉, Anthony W.S. Chan1,2,3✉

1. Genetics and Molecular Biology Program, Emory University, Atlanta, GA, USA;
2. Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA;
3. Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA;
4. Yerkes Imaging Center, Yerkes National Primate Research Center, Atlanta, GA, USA;
5. Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA.

Abstract

Purpose: The ability to longitudinally monitor cell grafts and assess their condition is critical for the clinical translation of stem cell therapy in regenerative medicine. Developing an inducible genetic magnetic resonance imaging (MRI) reporter will enable non-invasive and longitudinal monitoring of stem cell grafts in vivo. Methods: MagA, a bacterial gene involved in the formation of iron oxide nanocrystals, was genetically modified for in vivo monitoring of cell grafts by MRI. Inducible expression of MagA was regulated by a Tet-On (Tet) switch. A mouse embryonic stem cell-line carrying Tet-MagA (mESC-MagA) was established by lentivirus transduction. The impact of expressing MagA in mESCs was evaluated via proliferation assay, cytotoxicity assay, teratoma formation, MRI, and inductively coupled plasma atomic emission spectroscopy (ICP-OES). Mice were grafted with mESCs with and without MagA (mESC-MagA and mESC-WT). The condition of cell grafts with induced “ON” and non-induced “OFF” expression of MagA was longitudinally monitored in vivo using a 7T MRI scanner. After imaging, whole brain samples were harvested for histological assessment. Results: Expression of MagA in mESCs resulted in significant changes in the transverse relaxation rate (R2 or 1/T2) and susceptibility weighted MRI contrast. The pluripotency of mESCs carrying MagA was not affected in vitro or in vivo. Intracranial mESC-MagA grafts generated sufficient T2 and susceptibility weighted contrast at 7T. The mESC-MagA grafts can be monitored by MRI longitudinally upon induced expression of MagA by administering doxycycline (Dox) via diet. Conclusion: Our results demonstrate MagA could be used to monitor cell grafts noninvasively, longitudinally, and repetitively, enabling the assessment of cell graft conditions in vivo.

Keywords: Magnetic resonance imaging, reporter gene, MagA, longitudinal monitoring, stem cell, cell tracking, regenerative medicine, inducible expression, intracranial graft.

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How to cite this article:
Cho IK, Moran SP, Paudyal R, Piotrowska-Nitsche K, Cheng PH, Zhang X, Mao H, Chan AWS. Longitudinal Monitoring of Stem Cell Grafts In Vivo Using Magnetic Resonance Imaging with Inducible Maga as a Genetic Reporter. Theranostics 2014; 4(10):972-989. doi:10.7150/thno.9436. Available from http://www.thno.org/v04p0972.htm