PET molecular imaging of peripheral and central inflammatory processes targeting the TSPO 18 kDa

The purpose of this study was to determine the in vivo potential of the TSPO 18 kDa as a bio-marker of inflammation, with the use of its radioligand [¹⁸F]DPA-714, to non-invasively quantify the inflammatory state within the scope of various pathologies. Multiple animal models of various inflammatory diseases, to include: inflammatory bowel disease, neuro-inflammation, and septic shock, were developed and put in place by adapted measures. The animals well-being and the subsequent inflammation was evaluated. The inflammatory state was measured using quantitative PET imaging with the TSPO radioligand [¹⁸F]DPA-714 and correlated to the expression of conventional inflammatory markers using microscopy. Based on the observed data, we were able to distinguish control groups from treated groups when using [¹⁸F]DPA-714. This TSPO radioligand permitted us to quantify the inflammatory level and to observe evolutionary changes in the inflammatory state of the disease in multiple models. The PET results, using the [¹⁸F]DPA-714 signal was correlated with an increased TSPO expression at cellular level. Results indicate that [¹⁸F]DPA-714 is a suitable tracer for studying inflammation of multiple diseases. [¹⁸F]DPA-714 could be a good molecular probe to non-invasively evaluate the level and localization of inflammation. Moreover, in vivo imaging using this TSPO ligand is potentially a powerful tool to stage and certainly to follow the evolution and therapeutic efficiency at molecular level in inflammatory diseases. (author)