Non-invasive detection of adeno-associated viral gene transfer using a genetically encoded CEST-MRI reporter gene in the murine heart

J Anthony Brandon,Shelby Meier,Jose F Abisambra,Chenghao Qian,Erhe Gao,Moriel Vandsburger,Assaf A Gilad

doi:10.1038/s41598-018-22993-4

Abstract

Research into gene therapy for heart failure has gained renewed interest as a result of improved safety and availability of adeno-associated viral vectors (AAV). While magnetic resonance imaging (MRI) is standard for functional assessment of gene therapy outcomes, quantitation of gene transfer/expression relies upon tissue biopsy, fluorescence or nuclear imaging. Imaging of gene expression through the use of genetically encoded chemical exchange saturation transfer (CEST)-MRI reporter genes could be combined with clinical cardiac MRI methods to comprehensively probe therapeutic gene expression and subsequent outcomes. The CEST-MRI reporter gene Lysine Rich Protein (LRP) was cloned into an AAV9 vector and either administered systemically via tail vein injection or directly injected into the left ventricular free wall of mice. Longitudinal in vivo CEST-MRI performed at days 15 and 45 after direct injection or at 1, 60 and 90 days after systemic injection revealed robust CEST contrast in myocardium that was later confirmed to express LRP by immunostaining. Ventricular structure and function were not impacted by expression of LRP in either study arm. The ability to quantify and link therapeutic gene expression to functional outcomes can provide rich data for further development of gene therapy for heart failure.

Highlights

While magnetic resonance imaging (MRI) is standard for functional assessment of gene therapy outcomes, quantitation of gene transfer/expression relies upon tissue biopsy, fluorescence or nuclear imaging
In the first study arm, we sought to determine whether injection of an AAV9 vector encoding for Lysine Rich Protein (LRP) into a defined region of left ventricular myocardium would result in regionally elevated chemical exchange saturation transfer (CEST) contrast
In this study we demonstrated the ability to serially image longitudinal changes in CEST contrast generated by expression of a genetically encoded CEST-MRI reporter gene in the mouse heart following AAV9 mediated delivery

Summary

Introduction

CFolilclokwhetrheistoanledt audsdkintioownahlowwoarckcseasts:thottthpiss:/d/ouckunmoewnltebdegnee.ufiktsy.yeoduu./physiology_facpub Part of the Genetics and Genomics Commons, Physiology Commons, and the Rehabilitation and Therapy Commons. The ability to quantify and link therapeutic gene expression to functional outcomes can provide rich data for further development of gene therapy for heart failure. The ability to repeatedly quantify and correlate the degree and distribution of therapeutic gene expression to functional outcomes on an individual basis would provide a rich data set that can be used to refine the preparation, execution, and continued monitoring in cardiac gene therapy. Quantitative measurement of gene expression following viral delivery is has been performed using fluorescent/ bioluminescent whole body imaging in small animals[1,8,9]. Such techniques are not scalable to large animal models or clinical settings.

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Conclusion