Rheumatoid Arthritis Inflammation Visualized with PET and SPECT

Use of PET and SPECT imaging allowed researchers to visualize inflamed synovial tissue in mice, as well as the uptake correlated with the severity of the inflammation, according to a study presented at the Society of Nuclear Medicine and Molecular Imaging 2014 annual meeting.

Dutch researchers performed the preclinical study using PET and SPECT to evaluate antifibroblast activation protein (FAP) antibodies, which are involved in rheumatoid arthritis (RA) inflammation. Radiotracers labeled with 89Zr and 111In for specific imaging of FAP expression in an experimental model of RA were used.

The results showed that both 89Zr-28H1 and 111In-28H1 showed high uptake in the inflamed joints. This was three to four times higher than that of the irrelevant isotype-matched control antibody DP47GS.

“Uptake of 111In-28H1 ranged from 3.3 percent ID/g in non-inflamed joints to 27.4 percent ID/g in severely inflamed joints,” the authors wrote. “DP47GS accumulation ranged from 2.5 percent ID/g in non-inflamed tissue to 11.7 percent ID/g in severely inflamed joints.” The uptake of 28H1 in inflamed joints correlated with arthritis score and increased with severity of inflammation.

The researchers concluded that the “anti-FAP antibody 28H1 labeled with 89Zr or 111In showed excellent characteristics for imaging inflamed synovial tissue, and uptake correlated with severity of the inflammation.”