Messenger RNA

Enzyme

In vivo

Endonuclease

Biology

Gene

Molecular beacon

Oligonucleotide

AP site

Molecular biology

Immunology

Inflammation

Cell biology

Preclinical imaging

Genetics

Biochemistry

Nature Biomedical Engineering

The in vivo optical imaging of RNA biomarkers of inflammation is hindered by low signal-to-background ratios, owing to non-specific signal amplification in healthy tissues. Here we report the design and in vivo applicability, for the imaging of inflammation-associated messenger RNAs (mRNAs), of a molecular beacon bearing apurinic/apyrimidinic sites, whose amplification of fluorescence is triggered by human apurinic/apyrimidinic endonuclease 1 on translocation from the nucleus into the cytoplasm specifically in inflammatory cells. We assessed the sensitivity and tissue specificity of an engineered molecular beacon targeting interleukin-6 (IL-6) mRNA in live mice, by detecting acute inflammation in their paws and drug-induced inflammation in their livers. This enzymatic-amplification strategy may enable the specific and sensitive imaging of other disease-relevant RNAs in vivo. A molecular beacon engineered to be activated by the enzyme apurinic/apyrimidinic endonuclease 1 in inflammatory cells enables the specific and sensitive optical detection of inflammation in live mice.

Spatially resolved in vivo imaging of inflammation-associated mRNA via enzymatic fluorescence amplification in a molecular beacon