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Contrast Media & Molecular Imaging
Volume 2018, Article ID 8092781, 10 pages
https://doi.org/10.1155/2018/8092781
Research Article

Imaging and Methotrexate Response Monitoring of Systemic Inflammation in Arthritic Rats Employing the Macrophage PET Tracer [18F]Fluoro-PEG-Folate

1Amsterdam Rheumatology and Immunology Center, Location VUmc, VU University Medical Center, Amsterdam, Netherlands
2Department of Chemistry, Purdue University, West Lafayette, IN, USA
3Department of Immunology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
4Department of Physiology, VU University Medical Center, Amsterdam, Netherlands
5Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, Netherlands

Correspondence should be addressed to Conny J. van der Laken; ln.cmuv@nekalrednav.j

Received 22 September 2017; Revised 22 December 2017; Accepted 24 January 2018; Published 21 February 2018

Academic Editor: Cristina Nanni

Copyright © 2018 Durga M. S. H. Chandrupatla et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background. In rheumatoid arthritis, articular inflammation is a hallmark of disease, while the involvement of extra-articular tissues is less well defined. Here, we examined the feasibility of PET imaging with the macrophage tracer [18F]fluoro-PEG-folate, targeting folate receptor (FR), to monitor systemic inflammatory disease in liver and spleen of arthritic rats before and after methotrexate (MTX) treatment. Methods. [18F]Fluoro-PEG-folate PET scans (60 min) were acquired in saline- and MTX-treated (1 mg/kg, 4x) arthritic rats, followed by tissue resection and radiotracer distribution analysis. Liver and spleen tissues were stained for ED1/ED2-macrophage markers and FR expression. Results. [18F]Fluoro-PEG-folate PET and ex vivo tissue distribution studies revealed a significant () 2-fold lower tracer uptake in both liver and spleen of MTX-treated arthritic rats. Consistently, ED1- and ED2-positive macrophages were significantly () decreased in liver (4-fold) and spleen (3-fold) of MTX-treated compared with saline-treated rats. Additionally, FR-positive macrophages were also significantly reduced in liver (5-fold, ) and spleen (3-fold, ) of MTX- versus saline-treated rats. Conclusions. MTX treatment reduced activated macrophages in liver and spleen, as markers for systemic inflammation in these organs. Macrophage PET imaging with [18F]fluoro-PEG-folate holds promise for detection of systemic inflammation in RA as well as therapy (MTX) response monitoring.