Evaluation of 18f-Fluorodeoxyglucose Positron Emission Tomography/ Magnetic Resonance Imaging (18F-FDG PET/MRI) in C Protein-Induced Myositis Model in Mice

Jeong Yeon Kim^1,2, Jung Woo Byun³, Jae Hwan Shin³, Ji Soo Park^1,2, Ji Hye Lee², Shin Eui Kang^1,4, Hyun Jung Yoo^1,2, Eun Bong Lee², Do Won Hwang³, Yun Sang Lee³, Jin Chul Paeng³, Eun Young Lee⁵ and Yeong Wook Song^1,6, ¹Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea, Republic of (South), ²Division of Rheumatology, Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea, Republic of (South), ³Department of Nuclear Medicine, Seoul National University Hospital, Seoul, Korea, Republic of (South), ⁴Division of Rheumatology, Department of Internal Medicine, Seoul National University Hospital, seoul, Korea, Republic of (South), ⁵Division of Rheumatology, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea, Republic of (South), ⁶Rheumatology, Seoul National University Hospital, Seoul, Korea, Republic of (South)

Meeting: 2018 ACR/ARHP Annual Meeting

Keywords: inflammation and polymyositis

Session Information

Date: Tuesday, October 23, 2018

Title: Imaging of Rheumatic Diseases Poster III: Other Modalities

Session Type: ACR Poster Session C

Session Time: 9:00AM-11:00AM

Background/Purpose:

Polymyositis is a chronic inflammatory myopathy with proximal muscle weakness due to lymphocyte infiltration, especially CD8 + T cells to the muscle layer. C protein-induced myositis (CIM) is a murine model of polymyositis (PM), muscle injury is mediated by C protein-reactive CD8 + T cells. A recent study reported that the serum levels of muscle-derived enzymes were irrelevant to the severity of CIM. In addition, although the histological scoring is the reliable way to assess the severity of CIM, it has limitation to evaluate the inflammation due to focal involvement. The aim of this study was to evaluate the correlation of skeletal muscle inflammation and ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/magnetic resonance imaging (MRI) findings in CIM.

Methods:

To induce CIM, 8–10-week-old female mice were immunized intradermally with 200 ㎍ C protein fragments emulsified in 200 ㎍ of Freund’s complete adjuvant (CFA). Pertussis toxin (0.2 ㎍) was injected intraperitoneally at the same time.

FDG (300 mCi) was intravenously injected and simultaneous PET/MRI was obtained 60 minutes later by using a hybrid PET/MRI scanner for small animal. On PET/MRI, FDG uptake was measured in the gluteal and thigh muscle, foot pad, and the soft tissue as a background. Maximal target-to-background ratio (TBR) of the muscles was measured as the index for uptake. To monitor disease progression, ¹⁸F-FDG PET/MRI evaluation was performed on day 12, day 14 and day 19 after immunization. The next day after imaging, quadriceps, hamstrings and gastrocnemius muscle specimens were harvested. Each muscle tissues were stained with hematoxylene and eosin (H&E). Myositis was graded on a scale of 1–6 according to the histologic severity.

Results:

Histological score showed significantly increased in quadriceps, hamstrings and gastrocnemius muscle compared to control mice on day 14 (mean score =1.83; p = 0.0037, mean score =2.42; p = 0.0027 and mean score =1.583; p= 0.009, respectively). Histological scores were higher but not significant in quadriceps, hamstrings and gastrocnemius muscle of CIM on day 12 (mean score =0.58; p = 0.37, mean score =0.58; p = 0.18 and mean score =1.17; p= 0.12, respectively) and on day 19 (mean score =1.00; p = 0.16, mean score =0.33; p = 0.12 and mean score =1.67; p= 0.37, respectively). Mean of histologic summation score of skeletal muscles was 0.77, 1.94, 0.5 (p = 0.016, p = 0.0014 and p= 0.12, respectively) on day 12, 14, 19 in CIM. On PET/MRI, TBR was 1.67 ± 0.51 in control, whereas it was 4.11 ± 1.34 on day 12, 6.34 ± 1.78 on day 14, and 3.93 ± 0.75 on day 19 in CIM model. TBR was correlated with histologic summation score (Spearman’s rho= 0.954, p<0.0001).

Conclusion:

The findings of FDG PET/MRI appeared to be correlated with the histologic scoring system in CIM model. FDG PET/MRI could be an effective method for quantitative, repetitive, and serial assessment of inflammatory activity in CIM model

Disclosure: J. Y. Kim, None; J. W. Byun, None; J. H. Shin, None; J. S. Park, None; J. H. Lee, None; S. E. Kang, None; H. J. Yoo, None; E. B. Lee, None; D. W. Hwang, None; Y. S. Lee, None; J. C. Paeng, None; E. Y. Lee, None; Y. W. Song, None.

To cite this abstract in AMA style:

Kim JY, Byun JW, Shin JH, Park JS, Lee JH, Kang SE, Yoo HJ, Lee EB, Hwang DW, Lee YS, Paeng JC, Lee EY, Song YW. Evaluation of 18f-Fluorodeoxyglucose Positron Emission Tomography/ Magnetic Resonance Imaging (18F-FDG PET/MRI) in C Protein-Induced Myositis Model in Mice [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 9). https://acrabstracts.org/abstract/evaluation-of-18f-fluorodeoxyglucose-positron-emission-tomography-magnetic-resonance-imaging-18f-fdg-pet-mri-in-c-protein-induced-myositis-model-in-mice/. Accessed .

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