PET imaging of retinal inflammation in mice exposed to blue light using [ 18 F]-DPA-714.

PURPOSE: Positron emission tomography (PET) is widely used in high-precision imaging, which may provide a simple and noninvasive method for the detection of pathology and therapeutic effects. [18 F]-DPA-714 is a second-generation translocator protein (TSPO) positron emission tomography radiotracer that shows great promise in a model of neuroinflammation. In this study, [18 F]-DPA-714 micro-PET imaging was used to evaluate retinal inflammation in mice exposed to blue light, a well-established model of age-related macular degeneration (AMD) for molecular mechanism research and drug screening.

METHODS: C57BL/6J melanized mice were subjected to 10,000, 15,000, and 20,000 lux blue light for 5 days (8 h/day) to develop the retinal injury model, and the structure and function of the retina were assessed using hematoxylin-eosin (HE) staining, electroretinography (ERG), and terminal-deoxynucleotidyl transferase (TdT)-mediated nick-end labeling (TUNEL) immunostaining. Then, [18 F]-DPA-714 was injected approximately 100 μCi through each tail vein, and static imaging was performed 1 h after injection. Finally, the mice eyeballs were collected for biodistribution and immune analysis.

RESULTS: The blue light exposure significantly destroyed the structure and function of the retina, and the uptake of [18 F]-DPA-714 in the retinas of the mice exposed to blue light were the most significantly upregulated, which was consistent with the biodistribution data. In addition, the immunohistochemical, western blot, and immunofluorescence data showed an increase in microglial TSPO expression.

CONCLUSIONS: [18 F]-DPA-714 micro-PET imaging might be a good method for evaluating early inflammatory status during retinal pathology.