Temporal changes in synovial fluid composition and elastoviscous lubrication in the equine carpal fracture model.

The objective of this study was to examine temporal variations in synovial fluid composition and lubrication following articular fracture. Post-traumatic osteoarthritis (PTOA) was induced by creating an osteochondral fracture in the middle carpal joint of four horses while the contralateral limb served as a sham-operated control. Horses were exercised on a high-speed treadmill, and synovial fluid was collected pre-operatively and at serial timepoints until 75 days post-operatively. Lubricin and hyaluronic acid (HA) concentrations were measured using sandwich ELISAs, and the molecular weight distribution of HA was analyzed via gel electrophoresis. Synovial fluid viscosity and cartilage friction coefficients across all modes of lubrication were measured on days 0, 19, 33, and 61 using a commercial rheometer and a custom tribometer, respectively. HA concentrations were significantly decreased post-operatively, and high molecular weight HA (>6.1MDa) did not recover to pre-operative values by the study termination at day 75. Lubricin concentrations increased after surgery to a greater extent in the OA as compared to sham-operated limbs. Viscosity was significantly reduced after surgery. While boundary and elastoviscous mode friction coefficients did not vary, the transition number, representing the shift between these modes, was lower. Although more pronounced in the OA limbs, similar derangements in HA, HA molecular weight distribution, viscosity, and transition number were observed in the sham-operated limbs, which may be explained by synovial fluid washout during arthroscopy. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Disease-Modifying Osteoarthritis Treatment With Interleukin-1 Receptor Antagonist Gene Therapy in Small and Large Animal Models.

OBJECTIVE: Gene therapy holds great promise for the treatment of osteoarthritis (OA) because a single intraarticular injection can lead to long-term expression of therapeutic proteins within the joint. This study was undertaken to investigate the use of a helper-dependent adenovirus (HDAd)-mediated intraarticular gene therapy approach for long-term expression of interleukin-1 receptor antagonist (IL-1Ra) as sustained symptomatic and disease-modifying therapy for OA. METHODS: In mouse models of OA, efficacy of HDAd-IL-1Ra was evaluated by histologic analysis, micro-computed tomography (micro-CT), and hot plate analysis. In a horse OA model, safety and efficacy of HDAd-IL-1Ra were evaluated by blood chemistry, analyses of synovial fluid, synovial membrane, and cartilage, and gross pathology and lameness assessments. RESULTS: In skeletally immature mice, HDAd-IL-1Ra prevented development of cartilage damage, osteophytes, and synovitis. In skeletally immature and mature mice, treatment with HDAd-interleukin-1 receptor antagonist post-OA induction resulted in improved-albeit not significantly-cartilage status assessed histologically and significantly increased cartilage volume, cartilage surface, and bone surface covered by cartilage as assessed by micro-CT. Fewer osteophytes were observed in HDAd-IL-1Ra-treated skeletally immature mice. Synovitis was not affected in skeletally immature or mature mice. HDAd-IL-1Ra protected against disease-induced thermal hyperalgesia in skeletally mature mice. In the horse OA model, HDAd-IL-1Ra therapy significantly improved lameness parameters, indicating efficient symptomatic treatment. Moreover, macroscopically and histologically assessed cartilage and synovial membrane parameters were significantly improved, suggesting disease-modifying efficacy. CONCLUSION: These data from OA models in small and large animals demonstrated safe symptomatic and disease-modifying treatment with an HDAd-expressing IL-1Ra. Furthermore, this study establishes HDAd as a vector for joint gene therapy.

Upregulation of articular synovial membrane µ-opioid-like receptors in an acute equine synovitis model.

Intra-articular injection of opioids provides analgesia in painful equine joints and µ-opioid receptors (MORs) have been demonstrated in equine synovial membranes. The aim of this study was to determine whether acute inflammatory conditions will lead to up-regulation of MOR in equine synovial membranes and whether anti-inflammatory treatment can prevent any such upregulation. In a two-period, blinded, placebo-controlled randomised cross-over design, lipopolysaccharide (LPS, 1.0 ng) was injected into the left or right middle carpal joint of seven healthy ponies. Arthroscopy and synovial membrane biopsy was performed under general anaesthesia at baseline, 48 h (T48) and 672 h (T672) after LPS injection, with ponies assigned to receive either phenylbutazone (PBZ 2.2mg/kg PO BID) or placebo from 2h post-LPS. Ponies were scored for pain and lameness. Repeated synovial fluid samples were obtained and the degree of synovitis scored both macroscopically and microscopically. The density and staining pattern of MOR-like protein in synovial membrane biopsies over the course of the synovitis with or without PBZ treatment was evaluated using immunohistochemical techniques. LPS injection consistently induced a severe transient synovitis. Pain and lameness were significantly attenuated by treatment with PBZ. Up-regulation of MOR-like protein in the inflamed equine synovial membrane could be demonstrated in the placebo treated animals, but not in the PBZ-treated animals overall, although there were no significant differences at any individual time-point between the two groups. It was concluded that acute inflammation will up-regulate MOR, while anti-inflammatory treatment will attenuate this response.

Interleukin-6 and tumour necrosis factor in synovial fluid from horses with carpal joint pathology.

The carpal joints are common sites of traumatic arthritis and osteoarthritis (OA) in athletic horses. The pro-inflammatory cytokines interleukin (IL)-6 and tumour necrosis factor (TNF) may be of great importance in the development of intra-articular lesions. The aim of the present study was to investigate possible associations between synovial fluid levels of bioactive IL-6 and TNF and different types of joint lesions seen in traumatic arthritis and OA. Synovial fluid was collected from horses with carpal lameness immediately before arthroscopic surgery. Articular cartilage, synovial membranes and intra-articular ligaments were assessed macroscopically at arthroscopy. Synovial fluid levels of IL-6 and TNF were determined by bioassays, and the cytokine levels between different grades of morphologic changes in each type of assessed tissue were compared. The highest levels of IL-6 were detected in joints with chip fractures. All joints with chip fractures also showed some degree of synovitis. Tumour necrosis factor bioactivity was low and not associated with any joint lesion. Hence, TNF is not useful as a biomarker indicating a specific joint lesion in equine traumatic arthritis or OA. We conclude that a dramatic increase of IL-6 in synovial fluid indicates the presence of osteochondral fragmentation, although low or undetectable levels of IL-6 do not exclude chip fractures. The role of IL-6 in the disease process of osteochondral fragmentation needs further investigation.

Role of canonical Wnt-signalling in joint formation.

The individual elements of the vertebrate skeleton are separated by three different types of joints, fibrous, cartilaginous and synovial joints. Synovial joint formation in the limbs is coupled to the formation of the prechondrogenic condensations, which precede the formation of the joint interzone. We are beginning to understand the signals involved in the formation of prechondrogenic condensations and the subsequent differentiation of cells within the condensations into chondrocytes. However, relatively little is known about the molecules and molecular pathways involved in induction of the early joint interzone and the subsequent formation of the synovial joints. Based on gain-of function studies Wnt-signalling, in particular the canonical pathway, has been implicated in the joint induction process. Here we provide genetic evidence from loss-of function analysis of embryos lacking either the central player of the canonical Wnt-pathway, beta-catenin, in the limb mesenchyme or the two ligands, Wnt9a and Wnt4, demonstrating that canonical Wnt-signalling plays an important role in suppressing the chondrogenic potential of cells in the joint thereby actively allowing joint formation. Furthermore our data show that the beta-catenin activity is not essential for the induction of molecular markers expressed in the joint interzone. Thus, suggesting that canonical Wnt-signalling is not required for the induction, but for the subsequent maintenance of the fate of the joint interzone cells.