Imaging Glycosylation In Vivo by Metabolic Labeling and Magnetic Resonance Imaging

Abstract

Glycosylation is a ubiquitous post‐translational modification, present in over 50 % of the proteins in the human genome,1 with important roles in cell–cell communication and migration. Interest in glycome profiling has increased with the realization that glycans can be used as biomarkers of many diseases,2 including cancer.3 We report here the first tomographic imaging of glycosylated tissues in live mice by using metabolic labeling and a gadolinium‐based bioorthogonal MRI probe. Significant N‐azidoacetylgalactosamine dependent T 1 contrast was observed in vivo two hours after probe administration. Tumor, kidney, and liver showed significant contrast, and several other tissues, including the pancreas, spleen, heart, and intestines, showed a very high contrast (>10‐fold). This approach has the potential to enable the rapid and non‐invasive magnetic resonance imaging of glycosylated tissues in vivo in preclinical models of disease.

Bio-orthogonal Metabolic Fluorine Labeling Enables Deep-Tissue Visualization of Tumor Cells In Vivo by 19F Magnetic Resonance Imaging

“…However, the relatively shallow penetration of fluorescence and the significant interference from autofluorescence limit the application of this method for tracking specific proteins and cells in vivo. This strategy has also been used for contrast-enhanced 1 H MRI, but it suffers from the high biological background of 1 H …”

“…40 However, the relatively shallow penetration of fluorescence and the significant interference from autofluorescence limit the application of this method for tracking specific proteins and cells in vivo. This strategy has also been used for contrast-enhanced 1 H MRI, but it suffers from the high biological background of 1 H. 41 In light of these considerations, we envisioned that the incorporation of bio-orthogonal metabolic labeling with excellent targeting capacity and 19 F MRI with negligible biological background interference could offer a promising means for in vivo visualization of specific biological targets and processes. As a proof of concept, we chose tetra-acetylated Nazidoacetyl-mannosamine (Ac 4 ManAz, see Figure 1), an azidocontaining unnatural sugar for metabolic labeling, which could be selectively taken up by many types of cancer cells and transformed into azido-containing sialic acid that is subsequently displayed on the cell surface.…”

Physiological Effects of Ac4ManNAz and Optimization of Metabolic Labeling for Cell Tracking

“…Therefore, it has many advantages that apply to in vivo studies. Additionally, to enhance the labeling efficiency and safety, many studies have developed advanced click reactions, such as the 'Diels-Alder' 14, 15 and 'Photo-click' 16, 17 reactions, and bio-orthogonal MRI probes 18. However, these studies only focused on the labeling step of the process; safety and the bio-physiological effects and biochemical modulation by modified glycosylation in the first step have been overlooked.…”

Efficient Route to Label Mesenchymal Stromal Cell-Derived Extracellular Vesicles

“…Herein, we report our results on an EV labeling procedure with fluorescent dyes based on the bio-orthogonal copper-free click chemistry approach. In recent years, the bio-orthogonal approach has attracted considerable attention for cell labeling and/or tracking because of its high specificity and low toxicity to cells. − Among the possible bio-orthogonal approaches, the rapid, biocompatible, and specific chemical reaction between the functionalized dibenzocyclooctyne and azido-sugars generated on the cell surface by metabolic glycoengineering has shown great potential. − Thus, applying this approach, cancer cells labeling strategies and targeted delivery of nanoparticles have been recently developed and validated also in vivo. − …”