COMP in the Infrapatellar Fat Pad—Results of a Prospective Histological, Immunohistological, and Biochemical Case–Control Study

Abstract

Knee osteoarthritis (OA) involves several structures and molecules in the joint, which interact in a pathophysiological process. One of these molecules is the cartilage oligomeric matrix protein (COMP). Elevated COMP levels in the synovial fluid as well as in the serum have been described in OA patients. However, this has not been described in the infrapatellar fat pad (IPFP) tissue before. In this prospective trial, we collected 14 IPFPs from patients with high‐grade OA (mean age 63.8 ± 17.6 years) who underwent total knee replacement (OA group) and from 11 healthy patients (mean age 33.7 ± 14.8 years) who underwent anterior cruciate ligament reconstruction (control group). The presence of macrophages (CD68 and CD206) and proinflammatory cytokines (interleukin 1β [IL‐1β] and IL‐6) was analyzed. Histological and immunohistological examinations as well as immunoblotting analysis for COMP, leptin, and matrix‐metalloproteinase‐3 were performed. The IPFPs of both the OA and control group consisted of adipose tissue and fibrous tissue, and the fibrous tissue showed higher score values than the adipose tissue for COMP staining (intensity as well as stained area) in both groups. Although COMP could be detected in most samples, leptin expression was found only in single specimens. COMP could be detected mostly in the fibrous tissue portion of the IPFP. We speculate that it is involved in a remodeling process taking place in the IPFP during OA. Presence of leptin was irregular in immunohistology, and the control group showed higher scores in case of presence. Interestingly, immunoblotting could detect leptin in all analyzed samples. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 38:747‐758, 2020

Defining the extracellular matrix in non-cartilage soft tissues in osteoarthritis – a systematic review

“…Two studies were identified for infrapatellar fat pad [30,31]. Grevenstein et al (2020) showed no change in COMP content between OA and control fat pads [30] and Belluzzi et al (2020) showed that there was a decrease in collagen I and III expression in OA fat pads compared to controls [31].…”

Curcumin and Freshwater Clam Extracts Alleviate the Progression of Osteoarthritis by Reducing Synovial Inflammation and Allowing Cartilage Regeneration

“…The expression levels were detected using the TAlink mouse/rabbit polymer detection system (TAHC04D, BioTnA Biotech, Kaohsiung, Taiwan). A semi-quantitative method was used to score cytokine expression in all tissue sections, as previously described [27]. Briefly, Figure 2 shows the cytokines expressed in sections that were analyzed regarding staining intensity using a score from 0 to 3 (0 = no staining, 1 = weak staining, 2 = moderate staining, 3 = strong staining).…”