Objectives: To investigate the feasibility of a noninvasive method for imaging translocator protein (18 kDa) (TSPO) in the retina of diabetic retinopathy (DR) rats using fluorine-18-DPA-714 ([18F]-DPA-714) micro-positron emission tomography (PET)/X-ray computed tomography (CT).
Methods: Sprague-Dawley (SD) rats were intraperitoneally injected with streptozocin (STZ) (65 mg kg-1, ip) to induce diabetes mellitus (DM). The TSPO in both eyes was detected by PET/CT using [18F]-DPA-714 12 weeks after the establishment of the DM model. The mean standardized uptake value (SUVmean) was analyzed. Western blot and quantitative real-time polymerase chain reaction (PCR) were performed to detect the TSPO protein and mRNA levels in the retina.
Results: PET/CT results showed that the SUV of [18F]-DPA-714 was markedly reduced in the retina of DR rats compared with that of normal controls 12 weeks after diabetes induction. The SUVmean of regions of interest (ROIs) in the retinas of DR and normal control rats was 0.883 ± 0.078 and 2.525 ± 0.213 (P < 0.001), respectively. The results of PET/CT were in line with the Western blots and quantitative real-time PCR.
Conclusions: The PET results demonstrated that TSPO was decreased in the early stage of DR. [18F]-DPA-714 PET/CT appears to be a useful noninvasive imaging method for detecting TSPO in the retina. A decrease in the TSPO level in the retina may play an important role in the development of DR.
Keywords: Diabetic retinopathy; Positron emission tomography; Translocator protein; [18F]-DPA-714.