Evaluation of Apoptosis in Collagen-induced Arthritis with I-Annexin V Scintigraphy

Received 3/30/2009; revised 4/24/2009; accepted 4/30/2009. For correspondence and reprints contact: Wan-Yu Lin, M.D., Department of Nuclear Medicine, Taichung Veterans General Hospital. 160 Section 3, ChungGung Road, Taichung 407, Taiwan. Tel: (886)4-23741349, Fax: (886)4-23741348, E-mail:[email protected] Background: Rheumatoid arthritis (RA) is a chronic progressive disease and an autoimmune disorder characterized by joint inflammation due to abnormal accumulation of macrophages and autoreactive T lymphocytes in joints. Apoptosis is considered to be part of the pathogenesis of the disease. The radiolabeled annexin V has been proven effective in detecting apoptotic cells. Recently, the Institute of Nuclear Energy Research (INER) has successfully labeled annexin V with I. In this study, we used INER-produced I-Annexin V for the evaluation of apoptotic status in collagen-induced arthritis (CIA) rats. Methods: Ten Sprague-Dawley (SD) rats were divided into two groups: a control group and a CIA group (five in each group). Bovine type II collagen emulsified with complete Freund’s adjuvant was injected intradermally at the back and tail to induce arthritis in SD rats. Scintigraphy was performed 4 h and 24 h after injection of I-annexin V in both CIA rats and control rats. ROI was selected for the ankle joint and the soft tissue of the thigh of the left rear leg in all rats. Activity of ankle to muscle (A/M ratio) was calculated by computer. Afterwards, rats were sacrificed for H&E, TUNEL and DAPI (diamidino-2-phenylindole) staining. Results: Obvious swelling of the left rear legs was noted in CIA rats. Increased I-annexin V uptake in the ankles and paws was noted in the CIA rats. In contrast, no significant I-annexin V uptake was noted in the ankles of the control rats. The A/M ratios in CIA rats were significantly higher when compared to that in control rats at both 4 h and 24 h after I-annexin V injection. The P values were less than 0.05 using the MannWhitney U test. Using the TUNEL and DAPI stain, apoptotic cells were seen in the ankle joints of the left rear legs in CIA rats but not in the ankle joints of normal rats. Conclusion: I-annexin V produced by INER can be used to evaluate apoptosis in the joints of a CIA rat and may be a potential agent for the in-vivo evaluation of apoptosis in humans.