Assessing Inflammation in the Pathology of Knee Osteoarthritis

Zachary J. Koudys, Western University

Abstract

Osteoarthritis (OA) is a joint disease that causes pain, stiffness, and loss of function. Inflammation of the synovium plays a role in the pathology of OA. Macrophages are the dominant immune cells in synovial tissue. Activated macrophages over-express the translocator protein (TSPO). [¹⁸F]FEPPA is a 2^nd generation positron emission tomography (PET) tracer that can target TSPO with high specificity. Hybrid [¹⁸F]FEPPA PET/MRI may enable accurate quantification of macrophage activity in vivo. In this work, [¹⁸F]FEPPA tracer uptake in knee synovial tissue was measured ex vivo using autoradiography and was validated to correlate to the true macrophage activity determined by immunofluorescence (IF). A clinical [¹⁸F]FEPPA PET/MRI protocol showed similar ability to quantify macrophage activation in vivo. This study suggests that [¹⁸F]FEPPA PET/MRI may be an effective tool to investigate the role of inflammation in the pathology of OA or to validate the efficacy of future anti-inflammatory OA treatments.