Use of Indocyanine Green (ICG), a Medical Near Infrared Dye, for Enhanced Fluorescent Imaging-Comparison of Organic Anion Transporting Polypeptide 1B3 (OATP1B3) and Sodium-Taurocholate Cotransporting Polypeptide (NTCP) Reporter Genes.

Menq-Rong Wu,Jong-Kai Hsiao,Yi-You Huang

doi:10.3390/molecules24122295

Abstract

Molecular and cellular imaging in living organisms have ushered in an era of comprehensive understanding of intracellular and intercellular events. Currently, more efforts have been focused on the infrared fluorescent dyes that facilitate deeper tissue visualization. Both sodium taurocholate cotransporting polypeptide (NTCP) and organic-anion-transporting polypeptide 1B3 (OATP1B3) are capable of carrying indocyanine green (ICG) into the cytoplasm. We compared the feasibility of NTCP and OATP1B3 as reporter genes in combination with ICG. NTCP and OATP1B3 were transduced into HT-29 cells. Genetically modified HT-29 cells were inoculated into nude mice. ICG was administered in vitro and in vivo and the signals were observed under confocal microscopy, flow cytometry, multimode microplate reader, and an in vivo imaging system. Both NTCP- and OATP1B3-expressing cells and xenografts had higher ICG intensities. The OATP1B3-expressing xenograft has a higher ICG uptake than the NTCP-expressing xenograft. NTCP or OATP1B3 combined with ICG could serve as a noninvasive imaging modality for molecular and cellular imaging. OATP1B3 outperforms NTCP in terms of in vivo imaging.

Highlights

Molecular and cellular imaging in living organisms has ushered in an era of comprehensive understanding of intracellular and intercellular events
Numerous reporter genes are applied in molecular imaging activities, such as traditional green fluorescent protein (GFP), red fluorescent protein (RFP), and bioluminescence imaging (BLI) [3,4]
We have previously reported the efficacy of organic-anion-transporting polypeptide 1B3 (OATP1B3) combined with indocyanine green (ICG) as a reporter gene/fluorescent source imaging system that is capable of imaging OATP1B3 activity in a HT-1080 tumor-bearing nude mouse for up to 96 h, a long period compared to other methods

Summary

Introduction

Molecular and cellular imaging in living organisms has ushered in an era of comprehensive understanding of intracellular and intercellular events. Labeling fluorescent tags or nanoparticles that exhibit magnetic resonance (MR)/computed tomography (CT)/positron emission tomography (PET) signals is convenient for short-term cell tracking. A dilutional effect exists because of cell division and metabolism [1,2]. Genetic modification with reporter genes is a superior approach for long-term repeated cell tracking. Numerous reporter genes are applied in molecular imaging activities, such as traditional green fluorescent protein (GFP), red fluorescent protein (RFP), and bioluminescence imaging (BLI) [3,4]. Examples of reporter genes include herpes simplex virus type 1 thymidine kinase reporter and dopamine transporter in PET [5,6]; and transferrin receptor, Molecules 2019, 24, 2295; doi:10.3390/molecules24122295 www.mdpi.com/journal/molecules

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