Evaluation of a rat knee mono-arthritis using microPET.

AIM: Assessing the activity of synovitis, which is characterized by an increase in cell metabolism, is important for the prediction of future articular destruction in clinical and preclinical studies. To evaluate the correlation between ¹⁸F-FDG accumulation and arthritis pathology during its establishment, we used microPET to evaluted ¹⁸F-FDG accumulation in vivo during rat Mycobacterium wall-induced knee arthritis.

METHODS

¹⁸F-FDG PET images of arthritic rats were acquired on days 1, 2, 3 and 7 after arthritis induction. The subjects (n=2/time) were subsequently subjected to macro-autoradiography, and ¹⁸F-FDG accumulation was compared with histological findings.

RESULTS

¹⁸F-FDG PET images depicted swollen joints, and ¹⁸F-FDG accumulation increased with the progression of arthritis. Histologically, increased ¹⁸F-FDG accumulation correlated with the pannus rather than the infiltration of inflammatory cells around the joints.

CONCLUSION

¹⁸F-FDG accumulation in arthritis reflects proliferating pannus and inflammatory activity enhanced by inflammatory cytokines. ¹⁸F-FDG microPET should be effective for quantifying the inflammatory activity of arthritis and/or its therapeutic response.