Synovial mast cells from knee and hip osteoarthritis: histological study and clinical correlations

Abstract

Purpose The aim of this study was to investigate the presence of synovial mast cells (MCs) in hip and knee tissue from osteoarthritis (OA) patients and to correlate them with clinical and radiological data. Methods Synovial tissue was obtained during arthroplasty from 60 patients, 30 with knee OA and 30 with hip OA. Control synovial tissue was obtained from 30 patients without OA, 15 undergoing above-knee amputation and 15 receiving a hip replacement for fracture. Before surgery, the radiographic findings were graded according to the Kellgren-Lawrence system and clinical data including pain (VAS) and functional information (KOOS and HOOS) was collected. The tissue was stained with hematoxylin–eosin and toluidine blue for histochemistry and incubated with CD117 and CD31 antibodies for immunohistochemistry. MC and vessel number and synovitis score were determined in all samples. Results Mean MC number, synovitis score and vessel number were significantly higher in the OA samples (p < 0.05) than in control tissue. MC number correlated with the synovitis score and disease severity in both patient groups. Conclusions The prevalence of MCs in synovium from OA patients and their association with synovial inflammation and pain suggest a role for them in OA pathophysiology.

Typical response of CD14++CD16– monocyte to knee synovial derived mediators as a key target to overcome the onset and progression of osteoarthritis

“…There is always a significant knowledge gap in the literature concerning the selection of an appropriate control group for OA synovium and considerable ethical challenges to acquiring such samples ( 19 ). However, there are a number of approaches available to fill this gap including using synovial samples acquired from cadaveric joints ( 20 ), above-knee amputation ( 21 ), arthroscopy for the unspecified indication ( 22 ), or even from normal-appearing areas of synovium within an OA joint ( 23 ). In this study, the non-OA-diagnosed synovium was obtained from sports injury patients, mostly young athletes who have had their anterior crucial ligament reconstruction 6 months before their injury was diagnosed.…”

Increased NMUR1 Expression in Mast Cells in the Synovial Membrane of Obese Osteoarthritis Patients

“…Additionally, MCs and their degranulation products were observed in the SM and synovial fluid of KOA patients [ 26 ]. Moreover, the number of synovial MCs correlates with the KOA patients’ synovitis score [ 25 ]. As CD88 expression in MCs contributes to granulation [ 30 ], this evidence suggests that NMU/NMUR1-mediated activation of MCs, particularly CD88(+) MC subsets, may contribute to the synovial pathology in obese KOA patients.…”

“…In addition to being found in the synovial membrane (SM), MCs are elevated in patients with rheumatoid arthritis (RA) [ 19 , 20 , 21 ] and OA [ 22 , 23 , 24 ], suggesting that MCs could constitute a crucial component of the mechanism underlying both acute and chronic inflammation. More recent studies have demonstrated a potential association between MCs and knee OA (KOA) severity [ 25 , 26 ]. Given that we also previously reported increased MC marker expression in obese KOA patients [ 6 , 27 , 28 ], we hypothesized that MCs may contribute to the NMU/NMURs system in the osteoarthritic synovium of obese individuals.…”

Targeting Neuroinflammation in Osteoarthritis with Intra-Articular Adelmidrol

“…In chronically inflamed joints, the synovial membrane becomes hypertrophic and the MC density significantly increases, as a result of the recruitment of circulating progenitors, the maturation of local MC precursors, the differentiation of local mesenchymal stem cells (MSCs) into MCs, and the release of neurotrophins as NGF that stimulate further MC proliferation. Farinelli et al have recently shown, in hip and knee tissue from OA patients undergoing arthroplasty, a significant increase in the MCs and the vessel number, which significantly correlated with the synovitis score and disease severity [ 39 ]. The synovial MC infiltration has been associated with a variety of inflammatory changes which may play a role in the pathophysiology of OA [ 40 , 41 ].…”