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

• Type of Material: Article
• Authors: In K. Cho, Emory University; Sean P. Moran, Emory University; Ramesh Paudyal, Emory University; Karolina Piotrowska-Nitsche, Emory University; Pei-Hsun Cheng, Emory University; Xiaodong Zhang, Emory University; Hui Mao, Emory University; Anthony Chan, Emory University
• Language: English
• Date: 2014-07-27
• Publisher: Ivyspring International Publisher
• Publication Version: Final Published Version
• Copyright Statement: © 2014 Ivyspring International Publisher.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.7150/thno.9436
• Title of Journal or Parent Work: Theranostics
• ISSN: 1838-7640
• Volume: 4
• Issue: 10
• Start Page: 972
• End Page: 989
• Grant/Funding Information: This study is supported by a grant awarded by the NINDS/NIH (NS064991) to AWSC.; YNPRC is supported by the National Center for Research Resources P51RR165 and is currently supported by the Office of Research and Infrastructure Program (ORIP)/OD P51OD11132.
• Keywords: reporter gene; longitudinal monitoring; intracranial graft; inducible expression; stem cell; Magnetic resonance imaging; cell tracking; regenerative medicine; MagA
• Research Categories: Biology, Molecular; Health Sciences, Radiology; Biology, Genetics

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.