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BACKGROUND: Molecular mechanisms targeting the miRNA/mRNA axis to regulate osteoarthritis disease process have been studied. We identified the mRNA: phospholipase C delta 3 (PLCD3) and its target miRNA(miR-34a-5p) with clinical predictive value through previous bioinformatics studies, while experiments to verify their specific roles and mechanisms in regulating osteoarthritis are still lacking. OBJECTIVE: To investigate the regulatory role and mechanism of miR-34a-5p/PLCD3 axis on osteoarthritis progression. METHODS: The synovium of 15 patients with knee osteoarthritis was selected as the osteoarthritis group, and the synovium of 15 young patients with internal fixation of patellar fracture caused by trauma during the same period was selected as the control group. The expression of PLCD3 and miR-34a-5p in the synovium was detected by real-time PCR. Human fibroblast like synovial cells-osteoarthritis (HFLS-OA) cells were treated by cell transfection and divided into miR-34a-5p mimic group, pCDH-PLCD3 group, miR-34a-5p mimic+pCDH-PLCD3 group, miR-34a-5p inhibitor group, si-PLCD3 group, and miR-34a-5p inhibitor+si-PLCD3 group. The relationship between PLCD3 and miR-34a-5p expression was detected by real-time PCR. The effects of HFLS-OA cell viability and cell migration in each group were detected by CCK-8 assay and cell scratch test. Western blot assay was used to detect the expression level of apoptosis marker protein. The expression of inflammatory factors was detected by ELISA. RESULTS AND CONCLUSION: (1) PLCD3 was a direct target of miR-34a-5p, and the expression levels of PLCD3 and miR-34a-5p were negatively correlated. (2) Upregulation of PLCD3 promoted proliferation of HFLS-OA cells and inhibited cell migration. The up-regulation of miR-34a-5p significantly inhibited the activity of HFLS-OA cells and enhanced cell migration. Overexpression of miR-34a-5p significantly increased the levels of Casp3 and Casp9 proteins in HFLS-OA cells, while overexpression of PLCD3 showed the opposite trend. (3) PLCD3 overexpression significantly increased the expression of interleukin 6 and tumor necrosis factor alpha in HFLS-OA cells, while miR-34a-5p mimics showed protective activity. (4) The miR-34a-5p/PLCD3 axis may affect the progression of osteoarthritis by regulating the inflammatory process or apoptosis of synovial cells. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) in horses often affects the metacarpal/metatarsophalangeal (MCP/MTP) joints and its detection in the early stages is crucial for effective management. I t was hypothesized that the extent of cartilage damage positively correlates with synovial membrane (SM) and synovial fluid (SF) pathological findings in the MCP/MTP joints of Serbian mountain horses that transported heavy loads but did not show signs of lameness. The study was conducted on 32 MCP/MTP joints of eight horses between seven to 12 years of age. Horse limbs were transferred from the abattoir to the necropsy room and SF was sampled. Its appearance, total nucleated cell count (TNCC), mononuclear cell count (MNC), total proteins (TP), and haptoglobin (Hp) were determined. Samples of SM were collected from the dorsal palmar/plantar pouch for histology. A macroscopic examination of gross condylar pathology of the third metacarpal/metatarsal bone was performed with Indian Ink staining. Scoring was done based on Osteoarthritis Research Society International recommendations. SF was clear, pale yellow, and mostly fairly viscous. Half of the samples had TNCC above, and all had TP within the reference range. Hp values were below the reference range and were omitted from further analyses. TNCC correlated with MNC (ρs=0.81, P<0.001), microscopic (ρs=0.62, P=0.003) and macroscopic scores (ρs=0.47, P=0.008). In addition, MNC correlated with macroscopic scores (ρs=0.40, P=0.03). All pathological findings were mild and their correlation indicated that these processes are interrelated and that could be ascribed to early OA. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis is a prototypical autoimmune disease that causes joint inflammation and destruction1. There is currently no cure for rheumatoid arthritis, and the effectiveness of treatments varies across patients, suggesting an undefined pathogenic diversity1,2. Here, to deconstruct the cell states and pathways that characterize this pathogenic heterogeneity, we profiled the full spectrum of cells in inflamed synovium from patients with rheumatoid arthritis. We used multi-modal single-cell RNA-sequencing and surface protein data coupled with histology of synovial tissue from 79 donors to build single-cell atlas of rheumatoid arthritis synovial tissue that includes more than 314,000 cells. We stratified tissues into six groups, referred to as cell-type abundance phenotypes (CTAPs), each characterized by selectively enriched cell states. These CTAPs demonstrate the diversity of synovial inflammation in rheumatoid arthritis, ranging from samples enriched for T and B cells to those largely lacking lymphocytes. Disease-relevant cell states, cytokines, risk genes, histology and serology metrics are associated with particular CTAPs. CTAPs are dynamic and can predict treatment response, highlighting the clinical utility of classifying rheumatoid arthritis synovial phenotypes. This comprehensive atlas and molecular, tissue-based stratification of rheumatoid arthritis synovial tissue reveal new insights into rheumatoid arthritis pathology and heterogeneity that could inform novel targeted treatments.

Abstract Background We aimed to investigate the development of synovial fibrosis in vitro and how the fibrosis can be halted. Synovial fibrosis causes joint stiffness in arthritic diseases. The pathway of the fibrotic growth factor, transforming growth factor-beta (TGF-β), has been associated with joint pain in osteoarthritis (OA) and with the fibroid phenotype of rheumatoid arthritis (RA). This suggests that synovial fibrosis, thus accumulation of extracellular matrix (ECM) proteins, plays a role in the clinical manifestations of the diseases. Improving our understanding of fibrotic development may aid in selecting appropriate treatments and development of drugs that can target synovial fibrosis. Methods We isolated primary fibroblast-like synoviocytes (FLS) from the synovial membrane of patients undergoing total knee replacement surgery. To investigate the development of synovial fibrosis, the FLS were cultured in a crowded in vitro model mimicking the ECM. TGF-β1 was used as the fibrotic initiator, the activin receptor-like kinase 5 inhibitor (ALK5i), the anti-fibrotic drug nintedanib, and the anti-inflammatory drug tofacitinib were used as fibrotic inhibitors. The ECM protein formation was quantified in the conditioned media using specific biomarkers of type I, III, and VI collagen formation and fibronectin turnover. Results The TGF-β stimulation inducted fibrogenesis by increasing the biomarkers of fibronectin turnover, type I, III, and VI collagen formation. ALK5i and nintedanib inhibited the TGF-β response across all biomarkers. Tofacitinib trended towards inhibiting TGF-β response with up to 78% inhibition. All the treatments preserved cell viability. Conclusion We have established an in vitro model for assessing fibrogenesis in primary FLS, which can be used to assess the anti-fibrotic effect of multiple drug types. Our study implies that synovial fibrosis can be induced by TGF-β, which additionally can be halted by both direct and indirect inhibition with anti-fibrotic substances. The anti-inflammatory drug tofacitinib also halted the fibrogenesis to some extent; thus, it may exert an anti-fibrotic effect.

Abstract Recently, we found significantly reduced total superoxide dismutase (SOD) activity in the cartilage of patients with end-stage knee osteoarthritis (OA). In this study, we aimed to evaluate the SOD activity in serum, joint fluid, cartilage, and synovial membrane samples collected from 52 patients with end-stage knee OA who underwent total knee arthroplasty. The relationship between the total SOD activity in each tissue was evaluated using Spearman’s rank correlation coefficient. The joint fluid total SOD activity was used as the objective variable, and its association with the serum, cartilage, and synovial total SOD activities was evaluated using multiple linear regression analysis. Univariate analysis revealed that joint fluid total SOD activity was positively correlated with synovial total SOD activity. Multiple linear regression analysis using joint fluid total SOD activity as the objective variable showed a positive association with synovial total SOD activity (β = 0.493, adjusted R 2 = 0.172, P

Fibroblast-like synoviocytes (FLS) are mesenchymal-derived cells that play an important role in the physiology of the synovium by producing certain components of the synovial fluid and articular cartilage. In rheumatoid arthritis (RA), however, fibroblasts become a key driver of synovial inflammation and joint damage. Because of this, there has been recent interest in FLS as a therapeutic target in RA to avoid side effects such as systemic immune suppression associated with many existing RA treatments. In this review, we describe how approved treatments for RA affect FLS signaling and function and discuss the effects of investigational FLS-targeted drugs for RA.

Recently, we found significantly reduced total superoxide dismutase (SOD) activity in the cartilage of patients with end-stage knee osteoarthritis (OA). In this study, we aimed to evaluate the SOD activity in serum, joint fluid, cartilage, and synovial membrane samples collected from 52 patients with end-stage knee OA who underwent total knee arthroplasty. The relationship between the total SOD activity in each tissue was evaluated using Spearman’s rank correlation coefficient. The joint fluid total SOD activity was used as the objective variable, and its association with the serum, cartilage, and synovial total SOD activities was evaluated using multiple linear regression analysis. Univariate analysis revealed that joint fluid total SOD activity was positively correlated with synovial total SOD activity. Multiple linear regression analysis using joint fluid total SOD activity as the objective variable showed a positive association with synovial total SOD activity (β = 0.493, adjusted R2 = 0.172, P < 0.01). In patients with end-stage knee OA, the state of the synovial total SOD activity is better reflected by the total SOD activity in the joint fluid than that in the cartilage. Joint fluid total SOD activity may serve as a biomarker for the treatment and prevention of synovitis. [ABSTRACT FROM AUTHOR]

The gradual deterioration of articular cartilage was thought to be the central event in osteoarthritis (OA), but recent studies demonstrated the importance of low-grade synovitis in the progression of OA. The Syndecan (SDC) family of membrane proteoglycans is known to be involved in the regulation of inflammation, but there is limited evidence considering the role of syndecans in OA synovitis. Our study aimed to investigate the hip OA synovial membrane expression patterns of SDC1, SDC2 and SDC4, as well as exostosins and sulfotransferases (enzymes involved in the polymerisation and modification of syndecans' heparan sulphate chains). Synovial membrane samples of patients with OA (24) were divided into two groups according to their Krenn synovitis score severity. The immunohistochemical expressions of SDC1, SDC2, SDC4, EXT1, EXT2, NDST1 and NDST2 in synovial intima and subintima were then analysed and compared with the control group (patients with femoral neck fracture). According to our study, the immunoexpression of SDC1, NDST1 and EXT2 is significantly increased in the intimal cells of OA synovial membrane in patients with lower histological synovitis scores and SDC4 in patients with higher synovitis scores, in comparison with non-OA controls. The difference in the expression of SDC2 among the OA and non-OA groups was insignificant. SDC1, SDC4, NDST1 and EXT2 seem to be involved as inflammation moderators in low-grade OA synovitis and, therefore, should be further investigated as potential markers of disease progression and therapeutic goals. [ABSTRACT FROM AUTHOR]

In this study, we investigated specific and characteristic findings of the surface layer of surgical resected disc specimens in human temporomandibular joint osteoarthritis cases by transmission electron microscopy (TEM). Specimens were surgically removed from the TMJ of 5 cases (4 female patients: 5 cases) clinically osteoarthritis. Following findings were observed by TEM. Images were photographed on a JEM1400-Flash Electron microscope (JEOL, Japan) equipped with an EM-14661FLASH high-sensitivity digital complementary metal–oxide–semiconductor camera. Following findings were observed by TEM. The surface is covered with plump fibroblastic and histiocytoid cells. Collagen fiber bundles and collagenous matrix are exposed onto the eroded disc surface. Fibrinous dense material is observed on the eroded disc surface. Bundles of collagen fibers are densely observed. Collagen bundles are rich around capillary vessels. Synovial surface cells reveal features of activated macrophages with vacuole formation. Especially, plump fibroblastic and histiocytoid cells, and activated macrophages with vacuole, which were significant findings of the surface layer. These findings might have a significant effect on the regulation of synovial fluid. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is known to be caused by autoimmune disorders and can be partially alleviated through Disease-Modifying Antirheumatic Drugs (DMARDs) therapy. However, due to significant variations in the physical environment and condition of each RA patient, the types and doses of DMARDs prescribed can differ greatly. Consequently, there is a need for a platform based on patient-derived cells to determine the effectiveness of specific DMARDs for individual patient. In this study, we established an RA three-dimensional (3D) spheroid that mimics the human body's 3D environment, enabling high-throughput assays by culturing patient-derived synovial cells on a macroscale-patterned polycaprolactone (PCL) scaffold. Fibroblast-like synoviocytes (FLSs) from patient and human umbilical vein endothelial cells (HUVECs) were co-cultured to simulate vascular delivery. Additionally, RA characteristics were identified at both the genetic and cytokine levels using real-time polymerase chain reaction (RT-qPCR) and dot blot assay. The similarities in junctions and adhesion were demonstrated in both actual RA patient tissues and 3D spheroids. The 3D RA spheroid was treated with representative DMARDs, observing changes in reactive oxygen species (ROS) levels, lactate dehydrogenase (LDH) levels, and inflammatory cytokine responses to confirm the varying cell reactions depending on the DMARDs used. This study underscores the significance of the 3D drug screening platform, which can be applied to diverse inflammatory disease treatments as a personalized drug screening system. We anticipate that this platform will become an indispensable tool for advancing and developing personalized DMARD treatment strategies.

Osteoarthritis (OA) is one of the most common joint diseases in the adult population. The role of indolent inflammation and predominance of catabolic cytokines over anabolic ones in OA has now been proven. The influence of obesity on the development of OA by releasing inflammatory mediators by fat tissue has been confirmed. Infrapatellar fat tissue (Hoffa’s fat pad) is a potential donor of proinflammatory cytokines, including specific fat tissue proinflammatory cytokines - adipokines. In a healthy person, infrapatellar fat tissue contributes to the distribution of mechanical load on the joint and metabolism of the synovial fluid. Infiltration of infrapatellar fat tissue by macrophages and lymphocytes leads not only to the production of proinflammatory cytokines with chondrolytic properties, but also to the maintenance of chronic inflammation in the synovial membrane, articular cartilage, and subchondral bone. Morphologic changes in Hoffa’s fat pad can be both an indicator of the inflammatory process in the joint cavity and a predictor of pathologic changes of the joint. Among histological changes, infiltration with macrophages and lymphocytes, fibrosis, thickening of the interlobular septa, reduction in the size of fat lobules and adipocytes, and increased vascularization are important for the course of OA. Morphologic changes can be assessed using a non-invasive method - magnetic resonance imaging, which makes it possible to evaluate the presence and severity of synovitis, thickening of the synovial membrane, edema, thickening of the interlobular septa, and a decrease in the volume of Hoffa’s fat pad. Histologic and tomographic signs can potentially be used to assess the severity of OA and develop prognostic scales. Infrapatellar fat tissue is also a source of mesenchymal stem cells phenotypically similar to chondrocytes, which can be used for regeneration of joint cartilage tissue with minimally invasive intervention to harvest them.

ObjectiveSince previous studies indicate that metabolism is altered in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS), we undertook this study to determine if changes in the genome-wide chromatin and DNA states in genes associated with nutrient transporters could help to identify activated metabolic pathways in RA FLS.MethodsData from a previous comprehensive epigenomic study in FLS were analyzed to identify differences in genome-wide states and gene transcription between RA and osteoarthritis. We utilized the single nearest genes to regions of interest for pathway analyses. Homer promoter analysis was used to identify enriched motifs for transcription factors. The role of solute carrier transporters and glutamine metabolism dependence in RA FLS was determined by small interfacing RNA knockdown, functional assays, and incubation with CB-839, a glutaminase inhibitor. We performed 1 H nuclear magnetic resonance to quantify metabolites.ResultsThe unbiased pathway analysis demonstrated that solute carrier-mediated transmembrane transport was one pathway associated with differences in at least 4 genome-wide states or gene transcription. Thirty-four transporters of amino acids and other nutrients were associated with a change in at least 4 epigenetic marks. Functional assays revealed that solute carrier family 4 member 4 (SLC4A4) was critical for invasion, and glutamine was sufficient as an alternate source of energy to glucose. Experiments with CB-839 demonstrated decreased RA FLS invasion and proliferation. Finally, we found enrichment of motifs for c-Myc in several nutrient transporters.ConclusionOur findings demonstrate that changes in the epigenetic landscape of genes are related to nutrient transporters, and metabolic pathways can be used to identify RA-specific targets, including critical solute carrier transporters, enzymes, and transcription factors, to develop novel therapeutic agents.

Simple Summary: Musculoskeletal injuries in sport horses are relatively common and quite worrisome. Tendon and ligament injuries in sport horses usually result in a long period of time out of competition. Their healing usually results in tissue fibrosis and concomitant loss of elasticity, which, depending on the severity, might prevent the horse's recovery to the same performance levels or even to athletic levels. The continuous development of regenerative medicine offers therapeutical promise. Synovial membrane mesenchymal stem/stromal cells (SM-MSCs) and umbilical cord mesenchymal stem/stromal cells (UC-MSC), as well as their growth factors, have been described as having optimal characteristics for tendon and ligament regeneration. Therefore, a therapeutical combination of SM-MSC and a conditioned medium of UC-MSC was developed, produced, and administered on a tarsal long medial collateral ligament desmitis of a show-jumping horse. The production and application of the orthobiologic therapeutical combination as well as the clinical outcome are presented herein. Horses are high-performance athletes prone to sportive injuries such as tendonitis and desmitis. The formation of fibrous tissue in tendon repair remains a challenge to overcome. This impels regenerative medicine to develop innovative therapies that enhance regeneration, retrieving original tissue properties. Multipotent Mesenchymal Stem/Stromal Cells (MSCs) have been successfully used to develop therapeutic products, as they secrete a variety of bioactive molecules that play a pivotal role in tissue regeneration. These factors are released in culture media for producing a conditioned medium (CM). The aforementioned assumptions led to the formulation of equine synovial membrane MSCs (eSM-MSCs)—the cellular pool that naturally regenerates joint tissue—combined with a medium enriched in immunomodulatory factors (among other bioactive factors) produced by umbilical cord stroma-derived MSCs (eUC-MSCs) that naturally contribute to suppressing the immune rejection in the maternal–fetal barrier. A description of an equine sport horse diagnosed with acute tarsocrural desmitis and treated with this formulation is presented. Ultrasonographic ligament recovery occurred in a reduced time frame, reducing stoppage time and allowing for the horse's return to unrestricted competition after the completion of a physical rehabilitation program. This study focused on the description of the therapeutic formulation and potential in an equine desmitis treatment using the cells themselves and their secretomes. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the analgesic impact of S(+)-ketamine on pain behavior and synovial inflammation in an osteoarthritis (OA) model. Methods: Animals were grouped as follows: OA-Saline (n = 24) and OA-Ketamine (n = 24), OA induced via intra-articular sodium monoiodoacetate (MIA); a Non-OA group (n = 24) served as the control. On the 7th day post OA induction, animals received either saline or S(+)-ketamine (0.5 mg.kg−1). Behavioral and histopathological assessments were conducted up to day 28. Results: S(+)-ketamine reduced allodynia from day 7 to 28 and hyperalgesia from day 10 to 28. It notably alleviated weight distribution deficits from day 10 until the end of the study. Significant walking improvement was observed on day 14 in S(+)-ketamine-treated rats. Starting on day 14, OA groups showed grip force decline, which was countered by S(+)-ketamine on day 21. However, S(+)-ketamine did not diminish synovial inflammation. Conclusion: Low Intra-articular (IA) doses of S(+)-ketamine reduced MIA-induced OA pain but did not reverse synovial histopathological changes. IRB approval number: 23115 012030/2009-05.

ABSTRACT: Canine leishmaniasis (CanL) is a multifaceted disease triggered by the protozoan Leishmania infantum, characterized by diverse clinical presentations, including osteoarticular complications. Immune-mediated joint diseases invariably initiate at the synovial membrane, implicating its pivotal role in arthritis pathogenesis. This study aimed to investigate the influence of natural L. infantum infection on synovial fluid characteristics and the expression of immune markers, including TLR-2, FOXP3, and COX-2, in the synovial membrane. Twenty naturally infected dogs (NID) with L. infantum were sourced from the Zoonosis Surveillance Unit (ZSU). Clinical-orthopedic assessments were conducted, encompassing lameness, joint edema, crepitus, patellar luxation, and the drawer test. Synovial fluid (SF) parameters, including volume, appearance, viscosity, total nucleated cell count (TNC), neutrophil count, and total protein (TP) content, were determined. After anesthesia and euthanasia, synovial membrane specimens were obtained. SF protein concentrations categorized dogs into three groups: GI (2 to 2.5g/dL), GII (2.5 to 6.0g/dL), and GIII (>6g/dL). Inflammatory infiltrates and synovial membrane changes were assessed, and immunohistochemistry evaluated TLR-2, FOXP3, and COX-2 marker expressions. Clinical evaluations revealed various osteoarticular abnormalities in NID dogs, including lameness (55%), joint edema (25%), crepitus (30%), patellar luxation (20%), and positive drawer test (25%). Post mortem examinations revealed bilateral subchondral bone, meniscus, and trochlea erosion in 30% of cases. Amastigotes of L. infantum were identified extracellularly and within macrophages (60%). An inflammatory infiltrate was predominant in 70% of dogs, with varying intensity among the groups. Mononuclear cells, chiefly macrophages and lymphocytes, and neutrophils comprised the infiltrate. TLR-2 and COX-2 expression levels were elevated in GIII compared to GII and GI. Conversely, FOXP3 showed moderate expression in GI and minimal expression in GII and GIII. This study underscores the contributory role of L. infantum infection in the development of joint lesions in CanL. Additionally, alterations in the expression of immune markers TLR2, FOXP3, and COX2 within the synovial membrane imply the perpetuation and exacerbation of the inflammatory processes, shedding light on the intricate pathogenesis of CanL-induced arthritis.

Osteoarthritis (OA) is a progressive degenerative disease resulting in joint deterioration. Synovial inflammation is present in the OA joint and has been associated with radiographic and pain progression. Several OA risk factors, including ageing, obesity, trauma and mechanical loading, play a role in OA pathogenesis, likely by modifying synovial biology. In addition, other factors, such as mitochondrial dysfunction, damage-associated molecular patterns, cytokines, metabolites and crystals in the synovium, activate synovial cells and mediate synovial inflammation. An understanding of the activated pathways that are involved in OA-related synovial inflammation could form the basis for the stratification of patients and the development of novel therapeutics. This Review focuses on the biology of the OA synovium, how the cells residing in or recruited to the synovium interact with each other, how they become activated, how they contribute to OA progression and their interplay with other joint structures.

Rheumatoid arthritis (RA) is a refractory autoimmune disease with chronic and systemic characteristics, however, the pathogenesis of this disease has not been fully defined. Autophagy is a metabolic process that exists in eukaryotic cells and maintains normal physiological activities and cell homeostasis. Dysregulation of autophagy is related to the occurrence and development of various diseases such as RA. The databases of CNKI, Wanfang Data, VIP, PubMed, Web of Science, Elsevier, etc. were searched for the literature related to autophagy in RA pathogenesis. The role of autophagy in the pathogenesis of RA was summarized in terms of maintaining synovial inflammation (improving anti-apoptosis rate of synovial cells and regulating the phenotype transformation of synovial cells), promoting bone destruction (participating in osteoclastogenesis and regulating chondrocyte apoptosis) and disrupting immune system homeostasis (regulating the activation and maturation of immune cells, participating in the presentation of citrullinated proteins, and inducing carbamoylation of proteins), in order to provide basis and reference for the pathogenesis research and treatment of RA.

Pigmented villonodular synovitis is a rare proliferative disease of the synovial membrane, which most often affects the knee joints. Being a benign disease, at the same time, this pathology is often aggressive, and in some cases spreads to the soft tissues outside the joint. There are two forms of monoarticular damage: localized and diffuse. The diffuse form gives frequent relapses. To date, there are no standards for the management of this disease, just as there are no early markers for the detection of pigmented villonodular synovitis. This joint lesion has a long asymptomatic course, or it has symptoms of non-specific recurrent arthritis, so the patients can later be referred for magnetic resonance imaging, which is the only non-invasive method of diagnosing this pathology. At the same time, in modern conditions, most patients with recurrent synovitis will undergo an ultrasound examination of the joint according to the diagnostic standards. Ultrasonography made for abovementioned synovitis is insufficiently described in the medical literature. The aim of our study was to highlight the current data on the diagnosis and management of patients with pigmented villonodular synovitis and to describe our own clinical case. A feature of our clinical case was the detection of characteristic symptoms using ultrasonography. Irregular thickening of the synovial membrane with nodular forma­tions and villous growths, with the length of villi up to 7 mm near the patella with single loci of blood flow, was revealed by ultrasound examination and power Doppler mapping. Shear wave elastometry of the synovial membrane was performed. It demonstrated a significant increase in the stiffness of the synovial membrane, which can be a patho­gnomonic symptom of this pathology. The diagnosis of villonodular synovitis was confirmed histologically after surgical treatment. Subsequently, the patient had a recurrence of the pigmented villonodular synovitis, which was also detected by ultrasound diagnostics. Thus, pigmented villonodular synovitis of the knee joint is a rather rare pathology that requires differential diagnosis with inflammatory joint diseases. The final diagnosis is based on histological exa­mination. MRI and ultrasound diagnostics are non-invasive methods that can detect this pathology with high accuracy. The advantage of ultrasonography is its availability and non-invasiveness. The increase in stiffness of the synovial membrane along with its proliferation, which we found, can serve as an additional criterion of villonodular synovitis, and, according to the data available to us, has not been described in the literature so far.

Rheumatoid arthritis (RA) is an immune-mediated disease affecting diarthrodial joints that remains an unmet medical need despite improved therapy. This limitation likely reflects the diversity of pathogenic pathways in RA, with individual patients demonstrating variable responses to targeted therapies. Better understanding of RA pathogenesis would be aided by a more complete characterization of the disease. To tackle this challenge, we develop and apply a systems biology approach to identify important transcription factors (TFs) in individual RA fibroblast-like synoviocyte (FLS) cell lines by integrating transcriptomic and epigenomic information. Based on the relative importance of the identified TFs, we stratify the RA FLS cell lines into two subtypes with distinct phenotypes and predicted active pathways. We biologically validate these predictions for the top subtype-specific TF RARα and demonstrate differential regulation of TGFβ signaling in the two subtypes. This study characterizes clusters of RA cell lines with distinctive TF biology by integrating transcriptomic and epigenomic data, which could pave the way towards a greater understanding of disease heterogeneity.

This study aimed to quantify the long-term progression of blunt and sharp cartilage defects and their effect on joint homeostasis and function of the equine carpus. In nine adult Shetland ponies, the cartilage in the radiocarpal and middle carpal joint of one front limb was grooved (blunt or sharp randomized). The ponies were subjected to an 8-week exercise protocol and euthanized at 39 weeks. Structural and compositional alterations in joint tissues were evaluated in vivo using serial radiographs, synovial biopsies, and synovial fluid samples. Joint function was monitored by quantitative gait analysis. Macroscopic, microscopic, and biomechanical evaluation of the cartilage and assessment of subchondral bone parameters were performed ex vivo. Grooved cartilage showed higher OARSI microscopy scores than the contra-lateral sham-operated controls (p

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by progressive cartilage degradation, synovial membrane inflammation, osteophyte formation, and subchondral bone sclerosis. Pathological changes in cartilage and subchondral bone are the main processes in OA. In recent decades, many studies have demonstrated that activin-like kinase 3 (ALK3), a bone morphogenetic protein receptor, is essential for cartilage formation, osteogenesis, and postnatal skeletal development. Although the role of bone morphogenetic protein (BMP) signalling in articular cartilage and bone has been extensively studied, many new discoveries have been made in recent years around ALK3 targets in articular cartilage, subchondral bone, and the interaction between the two, broadening the original knowledge of the relationship between ALK3 and OA. In this review, we focus on the roles of ALK3 in OA, including cartilage and subchondral bone and related cells. It may be helpful to seek more efficient drugs or treatments for OA based on ALK3 signalling in future.

BACKGROUND: Osteoarthritis is inseparable from synovitis, so it has important clinical significance to explore osteoarthritis pathogenesis based on synovial tissue. OBJECTIVE: To explore the diagnosis and therapeutic targets of osteoarthritis from the perspective of synovium through analyzing the transcriptome data of synovial tissues between patients with osteoarthritis and healthy controls based on bioinformatics methods, as well as to provide follow-up research ideas for osteoarthritis. METHODS: Datasets containing normal and osteoarthritis synovial tissues were screened from Gene Expression Omnibus (GEO) database. GSE55457 and GSE55235 were selected, both of which contained 10 synovial tissue samples of osteoarthritis and 10 synovial tissue samples of healthy controls. GEO2R was utilized to perform differential gene expression analysis of GSE55457 and GSE55235 datasets, and genes with adjusted P values (adj.P) < 0.05 were collected. The online tool Xiantao Academy was used to obtained common up-regulated and down-regulated differentially expressed genes in the two datasets. GO functional annotation and KEGG pathway enrichment analysis for differentially expressed genes were performed. The STRING database was used to perform protein-protein interaction analysis. The results were visualized in Cytoscape software through CytoHubba App by 7 algorithms (BottleNeck, Clossness, Degree, DNNC, EPC, NNC and MCC). The top 10 genes with the highest scores were picked out for each algorithm, and the intersected genes of 7 algorithms were selected as the hub genes of osteoarthritis. RESULTS AND CONCLUSION: 200 common up-regulated differential genes and 124 common down-regulated differential genes were gained from the above two datasets. The results of GO analysis for the 324 differential genes showed that these genes were mainly associated with the DNA-binding transcription factor binding, RNA polymerase II specific DNA-binding transcription factor binding, poly(A) binding, platelets-derived growth factor receptor binding, glucocorticoid receptor binding, etc. KEGG analysis showed that the differential genes were mainly enriched in MAPK signaling pathway, insulin signaling pathway, osteoclast differentiation as well as parathyroid hormone synthesis, secretion and action pathways. Protein-protein interaction network analysis screened two hub genes of osteoarthritis, namely heat shock protein 90α class A member 1 (HSP90AA1) and suppressors of cytokine signaling 3 (SOCS3). These findings confirm that HSP90AA1 and SOCS3 are differentially expressed in synovial tissue of patients with osteoarthritis and healthy subjects, and may serve as surveillance markers and therapeutic target, which provide sound ideas for further study of molecular mechanisms of osteoarthritis. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Osteoarthritis (OA) is a chronic degenerative disease of the joints, adversely affecting the quality of life for the patients. To better understand the mechanisms underlying the pathological changes in osteoarthritis and identify the key genes associated with osteoarthritis pathogenesis, we utilized a comprehensive bioinformatics approach to analyze the transcriptome between osteoarthritis synovial and control samples with public microarray datasets. MATERIALS AND METHODS: First, the GSE82107 microarray dataset containing ten osteoarthritis synovial and seven control samples were selected from the Gene Expression Omnibus (GEO) database. RESULTS: A total of 52 overlapped differentially expressed genes (DEGs) in GSE82107 and OA-associated genes in the Comparative Toxicogenomics Database were identified. These OA-associated DEGs were further incorporated into a protein-protein interaction (PPI) network. Gene proopiomelanocortin (POMC) was identified in the largest cluster of PPI network with Cytoscape. GO and KEGG analyses suggested that these genes were associated with multiple functions. Other GEO datasets of osteoarthritis synovial tissues, including GSE55235 and GSE55457, were used to validate the expression level of POMC. Quantitative polymerase chain reaction and western blot analyses were also used to test the expression levels of POMC in our osteoarthritis samples. We found POMC was positively associated with transporter complex, ion channel activity, and G protein-coupled receptor signaling pathway. CONCLUSIONS: This study highlighted the OA-associated gene POMC, and its related biological pathways, suggesting it served as a potential treatment target in osteoarthritis. [ABSTRACT FROM AUTHOR]

Introduction Post-traumatic hemarthrosis is identified as intra-articular hemorrhage accompanied by five classic signs of inflammation: hyperemia, hyperthermia, edema, pain and changes in the joint function. The objective of the study was to establish whether inflammation should be underestimated in post-traumatic hemarthrosis based on the analysis of the world scientific literature of recent years. Material and methods Internet search platform Web of Science (Clarivate Analytics, USA): databases Web of Science Core Collection (subscription access), Publons (open access), Medline (open access) were used to review scientific articles. Papers from the Scopus Elsevier database (Netherlands) were explored. The search depth was 15 years. Topics that did not receive coverage in the literature of this period were studied until the 1960s in some cases. More than 200 sources were identified on the subject. The literature published in the current year was analyzed covering 15.0 % of the materials, brought out in the last 5 years including the current year covering 56.3 %, in the last 10 years including the current year covering 73.8 %, in the last 15 years including the current year covering 81.3 %. Results and discussion The severity of injury and the accompanying inflammatory factors would characterize a rapid resolution or a more severe course of post-traumatic hemarthrosis during treatment. The combination of several variants of inflammation can lead to the development of complications including osteoarthritis in cases that show mechanisms of chronic systemic inflammation of low intensity being manifested at the time of injury; ankylosis of the joint resulting from chronic systemic inflammation of low intensity involving degenerative processes. Synovitis, as a complication of post-traumatic hemarthrosis, should be differentiated with signs of low-grade inflammation, chronic course of classical inflammation and presystemic inflammation (purulent arthritis) in view of the inflammation theory. Conclusion The analysis of modern literature has shown the complexity and versatility of aspects of inflammation in posttraumatic hemarthrosis. The lack of emphasis on the assessment of the inflammatory response in rehabilitation of patients with post‑traumatic hemarthrosis can result in complications causing preconditions for the development of osteoarthritis, ankylosis, synovitis.

The vasulature of the synovial membrane of the temporomandibular joint of 18 laboratory mature Vietnamese mini male pigs divided into 3 groups was morphologically studied. Group 1 – 6 control experimental animals, 2 – 6 pigs with a 30-day’s experimental hyperglycemia, 3 – 6 pigs with a 60-day’s hyperglycemia. Hyperglycemia was induced by a single intraperitoneal injection of streptozotocin at a dose of 50 mg/kg. Pigs were sacrificed by bloodletting under general thiopental sodium anesthesia 30 and 60 days after the start of the experiment. On the indicated days of the experiment, the concentration of glucose in the blood was determined. On the micropreparations of the synovial membrane of the temporomandibular joint in the small caliber arteries there was measured the diameter of the vessel, the diameter of the lumen, the thickness of the muscular, adventitious membranes, the Wogenworth and Kernogan indices; in the veins – the diameter of the vessel, its lumen, and the thickness of the vein. In arterial and venous vessels, morphometry of endothelial cells, their nuclei, the volume of their damage, and nuclear-cytoplasmic indices were determined. Arterial, metabolic and venous vessels of the hemomicrocirculatory bed were studied morphometrically, their number per 1 mm² of the synovial membrane was determined. Quantitative values were processed statistically. In conditions of experimental hyperglycemia, a thickening of the synovial membrane of the arteries of the tempo­romandibular joint, a narrowing of their lumen, a decrease in the Kernogan index, an increase in the Wogenvoort index, the volume of damaged endotheliocytes, a disorder of their nuclear-cytoplasmic indices were revealed, an increase in the outer and inner diameters of the veins, the volume of damaged endotheliocytes, disorders of their nuclear-cytoplasmic indexes, plethora was noted. Structural changes in the hemomicrocirculatory bed in experimental hyperglycemia were characterized by a decrease of the diameters of arterioles, precapillary arterioles, hemocapillaries, dilation of capillary venules and venules, marked decrease of microvascular density. The most pronounced degree of remodeling of the studied structures was found in the vessels of the hemomicrocirculatory bed of the synovial membrane of the temporomandibular joint in a 60-day’s experimental hyperglycemia.

Abstract Background Immune and non-immune cells contribute to the pathology of chronic arthritis, and they can contribute to tissue remodeling and repair as well as disease pathogenesis. The present research aimed to analyze inflammation and bone destruction/regeneration biomarkers in patients with psoriatic arthritis (PsA), rheumatoid arthritis (RA), osteoarthritis (OA), and ankylosing spondylitis (AS). Methods Samples were obtained from the inflamed knee of patients with knee arthritis who had been referred for undergoing arthroscopies. The synovial membrane was processed for pathological description, IHC analysis, and quantification of mRNA expression ratio by qRT-PCR. Serum levels of TGF-β1, IL-23, IL-6, IL-17 A, IL-22, Dkk1, Sclerostin, BMP2, BMP4, Wnt1, and Wnt5a were measured by ELISA. All these data were analyzed and compared with the demographic, clinical, blood tests, and radiological characteristics of the patients. Results The synovial membrane samples were obtained from 42 patients for IHC, extraction, and purification of RNA for synovial mRNA expression analysis, and serum for measuring protein levels from 38 patients. IHC reactivity for TGF-β1 in the synovial tissue was higher in patients with psoriatic arthritis (p 0.036) and was positively correlated with IL-17 A (r = 0.389, p = 0.012), and Dkk1 (r = 0.388, p = 0.012). Gene expression of the IL-17 A was higher in PsA patients (p = 0.018) and was positively correlated with Dkk1 (r = 0.424, p = 0.022) and negatively correlated with BMP2 (r = -0.396, p = 0.033) and BMP4 (r = -0.472, p = 0.010). It was observed that IHC reactivity for TGF-β1 was higher in patients with erosive PsA (p = 0.024). Conclusions The IHC reactivity of TGF-β1 in synovial tissue was higher in patients with erosive psoriatic arthritis, and TGF-β1 was in relation to higher levels of gene expression of IL-17 A and Dkk1.

There is an urgent need to identify biomarkers for diagnosis and disease activity monitoring in rheumatoid arthritis (RA). We leveraged publicly available microarray gene expression data in the NCBI GEO database for whole blood (N=1,885) and synovial (N=284) tissues from RA patients and healthy controls. We developed a robust machine learning feature selection pipeline with validation on five independent datasets culminating in 13 genes: TNFAIP6, S100A8, TNFSF10, DRAM1, LY96, QPCT, KYNU, ENTPD1, CLIC1, ATP6V0E1, HSP90AB1, NCL and CIRBP which define the RA score and demonstrate its clinical utility: the score tracks the disease activity DAS28 (p = 7e-9), distinguishes osteoarthritis (OA) from RA (OR 0.57, p = 8e-10) and polyJIA from healthy controls (OR 1.15, p = 2e-4) and monitors treatment effect in RA (p = 2e-4). Finally, the immunoblotting analysis of six proteins on an independent cohort confirmed two proteins, TNFAIP6/TSG6 and HSP90AB1/HSP90.

The gradual deterioration of articular cartilage was thought to be the central event in osteoarthritis (OA), but recent studies demonstrated the importance of low-grade synovitis in the progression of OA. The Syndecan (SDC) family of membrane proteoglycans is known to be involved in the regulation of inflammation, but there is limited evidence considering the role of syndecans in OA synovitis. Our study aimed to investigate the hip OA synovial membrane expression patterns of SDC1, SDC2 and SDC4, as well as exostosins and sulfotransferases (enzymes involved in the polymerisation and modification of syndecans’ heparan sulphate chains). Synovial membrane samples of patients with OA (24) were divided into two groups according to their Krenn synovitis score severity. The immunohistochemical expressions of SDC1, SDC2, SDC4, EXT1, EXT2, NDST1 and NDST2 in synovial intima and subintima were then analysed and compared with the control group (patients with femoral neck fracture). According to our study, the immunoexpression of SDC1, NDST1 and EXT2 is significantly increased in the intimal cells of OA synovial membrane in patients with lower histological synovitis scores and SDC4 in patients with higher synovitis scores, in comparison with non-OA controls. The difference in the expression of SDC2 among the OA and non-OA groups was insignificant. SDC1, SDC4, NDST1 and EXT2 seem to be involved as inflammation moderators in low-grade OA synovitis and, therefore, should be further investigated as potential markers of disease progression and therapeutic goals.

Background: Pigmented villonodular synovitis (PVNS) is a very rare pathology of the synovial membrane and even less common in the pediatric group. Rarity leads to misdiagnosis in pre-puberty cases, which may waste significant time for the patient before definite treatment. Reviewing such cases is useful for every pediatrician or orthopedic surgeon to avoid misdiagnosing possible cases. Case Report: We report a 15-month-old boy who suffered pain and swelling in his knee for about two years before he was eventually diagnosed with PVNS and underwent surgery. Keeping this diagnosis in mind may have saved him and his family from two years of pain, several admissions, and unnecessary prescriptions. Conclusion: PVNS in pediatrics is rare, but it can occur and be misdiagnosed for diseases such as juvenile rheumatoid arthritis (JRA) and septic arthritis which elongates the pain period. PVNS responds well to subtotal synovectomy, and symptoms are relieved after the surgery if well performed. [ABSTRACT FROM AUTHOR]

Emerging evidence suggests that fatty acids (FAs) and their lipid mediator derivatives can induce both beneficial and detrimental effects on inflammatory processes and joint degradation in osteoarthritis (OA) and autoimmune-driven rheumatoid arthritis (RA). The present study characterized the detailed FA signatures of synovial membranes collected during knee replacement surgery of age- and gender-matched OA and RA patients (n = 8/diagnosis). The FA composition of total lipids was determined by gas chromatography and analyzed with univariate and multivariate methods supplemented with hierarchical clustering (HC), random forest (RF)-based classification of FA signatures, and FA metabolism pathway analysis. RA synovium lipids were characterized by reduced proportions of shorter-chain saturated FAs (SFAs) and elevated percentages of longer-chain SFAs and monounsaturated FAs, alkenyl chains, and C20 n-6 polyunsaturated FAs compared to OA synovium lipids. In HC, FAs and FA-derived variables clustered into distinct groups, which preserved the discriminatory power of the individual variables in predicting the RA and OA inflammatory states. In RF classification, SFAs and 20:3n-6 were among the most important FAs distinguishing RA and OA. Pathway analysis suggested that elongation reactions of particular long-chain FAs would have increased relevance in RA. The present study was able to determine the individual FAs, FA groups, and pathways that distinguished the more inflammatory RA from OA. The findings suggest modifications of FA elongation and metabolism of 20:4n-6, glycerophospholipids, sphingolipids, and plasmalogens in the chronically inflamed RA synovium. These FA alterations could have implications in lipid mediator synthesis and potential as novel diagnostic and therapeutic tools. [ABSTRACT FROM AUTHOR]

Pigmented villonodular synovitis is a rare proliferative disease of the synovial membrane, which most often affects the knee joints. Being a benign disease, at the same time, this pathology is often aggressive, and in some cases spreads to the soft tissues outside the joint. There are two forms of monoarticular damage: localized and diffuse. The diffuse form gives frequent relapses. To date, there are no standards for the management of this disease, just as there are no early markers for the detection of pigmented villonodular synovitis. This joint lesion has a long asymptomatic course, or it has symptoms of non-specific recurrent arthritis, so the patients can later be referred for magnetic resonance imaging, which is the only non-invasive method of diagnosing this pathology. At the same time, in modern conditions, most patients with recurrent synovitis will undergo an ultrasound examination of the joint according to the diagnostic standards. Ultrasonography made for abovementioned synovitis is insufficiently described in the medical literature. The aim of our study was to highlight the current data on the diagnosis and management of patients with pigmented villonodular synovitis and to describe our own clinical case. A feature of our clinical case was the detection of characteristic symptoms using ultrasonography. Irregular thickening of the synovial membrane with nodular formations and villous growths, with the length of villi up to 7 mm near the patella with single loci of blood flow, was revealed by ultrasound examination and power Doppler mapping. Shear wave elastometry of the synovial membrane was performed. It demonstrated a significant increase in the stiffness of the synovial membrane, which can be a pathognomonic symptom of this pathology. The diagnosis of villonodular synovitis was confirmed histologically after surgical treatment. Subsequently, the patient had a recurrence of the pigmented villonodular synovitis, which was also detected by ultrasound diagnostics. Thus, pigmented villonodular synovitis of the knee joint is a rather rare pathology that requires differential diagnosis with inflammatory joint diseases. The final diagnosis is based on histological examination. MRI and ultrasound diagnostics are non-invasive methods that can detect this pathology with high accuracy. The advantage of ultrasonography is its availability and non-invasiveness. The increase in stiffness of the synovial membrane along with its proliferation, which we found, can serve as an additional criterion of villonodular synovitis, and, according to the data available to us, has not been described in the literature so far. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a chronic immune-mediated disease that primarily affects the synovium of diarthrodial joints. During the course of RA, the synovium transforms into a hyperplastic invasive tissue that causes destruction of cartilage and bone. Fibroblast-like synoviocytes (FLS), which form the lining of the joint, are epigenetically imprinted with an aggressive phenotype in RA and have an important role in these pathological processes. In addition to producing the extracellular matrix and joint lubricants, FLS in RA produce pathogenic mediators such as cytokines and proteases that contribute to disease pathogenesis and perpetuation. The development of multi-omics integrative analyses have enabled new ways to dissect the mechanisms that imprint FLS, have helped to identify potential FLS subsets with distinct functions and have identified differences in FLS phenotypes between joints in individual patients. This Review provides an overview of advances in understanding of FLS biology and highlights omics approaches and studies that hold promise for identifying future therapeutic targets.

BackgroundCytosolic phospholipase A2 group IVA (cPLA2α)-deficient mice are resistant to collagen-induced arthritis, suggesting that cPLA2α is an important therapeutic target. Here, the anti-inflammatory effects of the AVX001 and AVX002 cPLA2α inhibitors were investigated.MethodsIn vitro enzyme activity was assessed by a modified Dole assay. Effects on inhibiting IL-1β-induced release of arachidonic acid (AA) and prostaglandin E2 (PGE2) were measured using SW982 synoviocyte cells. In vivo effects were studied in prophylactic and therapetic murine collagen-induced arthritis models and compared to methotrexate (MTX) and Enbrel, commonly used anti-rheumatic drugs. The in vivo response to treatment was evaluated in terms of the arthritis index (AI), histopathology scores and by plasma levels of PGE2 following 14 and 21 days of treatment.ResultsBoth cPLA2α inhibitors are potent inhibitors of cPLA2α in vitro. In synoviocytes, AVX001 and AVX002 reduce, but do not block, release of AA or PGE2 synthesis. In both CIA models, the AI and progression of arthritis were significantly lower in the mice treated with AVX001, AVX002, Enbrel and MTX than in non- treated mice. Several histopathology parameters of joint damage were found to be significantly reduced by AVX001 and AVX002 in both prophylactic and therapeutic study modes; namely articular cavity and peripheral tissue inflammatory cell infiltration; capillary and synovial hyperplasia; articular cartilage surface damage; and periostal and endochondral ossification. In comparison, MTX did not significantly improve any histopathology parameters and Enbrel only improved ossification. Finally, as a biomarker of inflammation and as an indication that AVX001 and AVX002 blocked the cPLA2α target, we determined that plasma levels of PGE2 were significantly reduced in response to the AVX inhibitors and MTX, but not Enbrel.ConclusionsAVX001 and AVX002 display potent anti-inflammatory activity and disease-modifying properties in cellular and in vivo models. The in vivo effects of AVX001 and AVX002 were comparable to, or superior, to those of MTX and Enbrel. Taken together, this study suggests that cPLA2α inhibitors AVX001 and AVX002 are promising small molecule disease-modifying anti-rheumatic therapies.

Objective: to study the morphological reflection of the parenteral form of highly purified chondroitin sulfate (CS) action in patients with osteoarthritis (OA) of the knee joints (KJ) during total knee arthroplasty (TA).Patients and methods. An open, prospective, controlled, randomized study included 67 patients (24 men and 43 women aged 41—73 years) with stage III knee OA and grade 2 functional insufficiency. The 1st (control) group included 35 patients, the 2nd (main) group included 32 patients. At baseline of the study, all patients were taking non-steroidal anti-inflammatory drugs (NSAIDs) at a standard daily dose. Patients of the 2nd group 2 months before the TA of KJ, additionally received a parenteral form of CS (Honrogard®), intramuscularly every other day: the first 3 injections at a dose of 100 mg/day; and if tolerability was good starting from the 4th injection, at a dose of200 mg / day (course — 25 injections). The intensity of pain was assessed according to the visual analog scale, WOMAC index, functional status according to the KOOS (Knee and Osteoarthritis Outcome Score) scale and the Lequesne index, standard radiography and magnetic resonance imaging of the knee joint were performed with an assessment of the T2 relaxation time. TA KJ was carried out according to C. Ranawat method.Results and discussion. In contrast to patients who took only NSAIDs, in patients who received CS during 50 days within 2 months before surgery, there were signs of adaptive restructuring in all layers of the preserved volume of hyaline cartilage and a decrease in the synovial membrane inflammation at the time of TA of KJ.Conclusion. The obtained results allow us to recommend the use of the parenteral form of CS (Honrogard®) according to the described scheme within 2 months before the TA of KJ in order to improve the morphological characteristics of cartilage and synovial tissue in the joints of the contralateral lower limb, taking into account the increase in the load on it in the postoperative period.

Abstract Background Synovial membrane-derived mesenchymal progenitor cells (SM-MPCs) are a promising candidate for the cell-based treatment of osteoarthritis (OA) considering their in vitro and in vivo capacity for cartilage repair. However, the OA environment may adversely impact their regenerative capacity. There are no studies for canine (c)SM-MPCs that compare normal to OA SM-MPCs, even though dogs are considered a relevant animal model for OA. Therefore, this study compared cSM-MPCs from normal and OA synovial membrane tissue to elucidate the effect of the OA environment on MPC numbers, indicated by CD marker profile and colony-forming unit (CFU) capacity, and the impact of the OA niche on tri-lineage differentiation. Methods Normal and OA synovial membrane were collected from the knee joints of healthy dogs and dogs with rupture of the cruciate ligaments. The synovium was assessed by histopathological OARSI scoring and by RT-qPCR for inflammation/synovitis-related markers. The presence of cSM-MPCs in the native tissue was further characterized with flow cytometry, RT-qPCR, and immunohistochemistry, using the MPC markers; CD90, CD73, CD44, CD271, and CD34. Furthermore, cells isolated upon enzymatic digestion were characterized by CFU capacity, and a population doublings assay. cSM-MPCs were selected based on plastic adherence, expanded to passage 2, and evaluated for the expression of MPC-related surface markers and tri-lineage differentiation capacity. Results Synovial tissue collected from the OA joints had a significantly higher OARSI score compared to normal joints, and significantly upregulated inflammation/synovitis markers S100A8/9, IL6, IL8, and CCL2. Both normal and OA synovial membrane contained cells displaying MPC properties, including a fibroblast-like morphology, CFU capacity, and maintained MPC marker expression over time during expansion. However, OA cSM-MPCs were unable to differentiate towards the chondrogenic lineage and had low adipogenic capacity in contrast to normal cSM-MPCs, whereas they possessed a higher osteogenic capacity. Furthermore, the OA synovial membrane contained significantly lower percentages of CD90+, CD44+, CD34+, and CD271+ cells. Conclusions The OA environment had adverse effects on the regenerative potential of cSM-MPCs, corroborated by decreased CFU, population doubling, and chondrogenic capacity compared to normal cSM-MPCs. OA cSM-MPCs may be a less optimal candidate for the cell-based treatment of OA than normal cSM-MPCs.

Proliferative tenosynovitis (PT) is an inflammatory and proliferative disorder of the synovial membrane of the tendon sheath that is rare in animals. The histological alterations are characterized by multinodular neovascularization, with infiltration of histiocytic and multinucleated giant cells and haemosiderin deposition. We reviewed necropsy and biopsy records of horses submitted to the Setor de Anatomia Patológica of the Universidade Federal Rural do Rio de Janeiro from January 2017 to December 2020 to select cases of PT. We identified PT in three adult Brazilian Mangalarga Marchador horses with nodular lesions on the metacarpophalangeal, metatarsophalangeal or carpal joints. The three horses were under 6 years of age and presented with lameness and pain on palpation. There were recurrences in two horses after surgical removal. Radiographic and ultrasound examinations detected masses in the flexor or extensor tendons and subtendinous bursa. Histological study of synovial membrane and tendon sheath revealed an increased number of vessels, fibroplasia, osseous metaplasia and infiltration of lymphocytes, plasma cells and siderophages. This is the first description of PT in horses, which should be included as an orthopaedic differential diagnosis, especially in Mangalarga Marchador horses with lameness. [ABSTRACT FROM AUTHOR]

Background: Immune and non-immune cells contribute to the pathology of chronic arthritis, and they can contribute to tissue remodeling and repair as well as disease pathogenesis. The present research aimed to analyze inflammation and bone destruction/regeneration biomarkers in patients with psoriatic arthritis (PsA), rheumatoid arthritis (RA), osteoarthritis (OA), and ankylosing spondylitis (AS). Methods: Samples were obtained from the inflamed knee of patients with knee arthritis who had been referred for undergoing arthroscopies. The synovial membrane was processed for pathological description, IHC analysis, and quantification of mRNA expression ratio by qRT-PCR. Serum levels of TGF-β1, IL-23, IL-6, IL-17 A, IL-22, Dkk1, Sclerostin, BMP2, BMP4, Wnt1, and Wnt5a were measured by ELISA. All these data were analyzed and compared with the demographic, clinical, blood tests, and radiological characteristics of the patients. Results: The synovial membrane samples were obtained from 42 patients for IHC, extraction, and purification of RNA for synovial mRNA expression analysis, and serum for measuring protein levels from 38 patients. IHC reactivity for TGF-β1 in the synovial tissue was higher in patients with psoriatic arthritis (p 0.036) and was positively correlated with IL-17 A (r = 0.389, p = 0.012), and Dkk1 (r = 0.388, p = 0.012). Gene expression of the IL-17 A was higher in PsA patients (p = 0.018) and was positively correlated with Dkk1 (r = 0.424, p = 0.022) and negatively correlated with BMP2 (r = -0.396, p = 0.033) and BMP4 (r = -0.472, p = 0.010). It was observed that IHC reactivity for TGF-β1 was higher in patients with erosive PsA (p = 0.024). Conclusions: The IHC reactivity of TGF-β1 in synovial tissue was higher in patients with erosive psoriatic arthritis, and TGF-β1 was in relation to higher levels of gene expression of IL-17 A and Dkk1. [ABSTRACT FROM AUTHOR]

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Osteoarthritis (OA) is the leading cause of joint failure, yet the underlying mechanisms remain elusive, and no approved therapies that slow progression exist. Dysregulated integrin function was previously implicated in OA pathogenesis. However, the roles of integrin αVβ3 and the integrin-associated receptor CD47 in OA remain largely unknown. Here, transcriptomic and proteomic analyses of human and murine osteoarthritic tissues revealed dysregulated expression of αVβ3, CD47, and their ligands. Using genetically deficient mice and pharmacologic inhibitors, we showed that αVβ3, CD47, and the downstream signaling molecules Fyn and FAK are crucial to OA pathogenesis. MicroPET/CT imaging of a mouse model showed elevated ligand-binding capacities of integrin αVβ3 and CD47 in osteoarthritic joints. Further, our in vitro studies demonstrated that chondrocyte breakdown products, derived from articular cartilage of individuals with OA, induced αVβ3/CD47-dependent expression of inflammatory and degradative mediators, and revealed the downstream signaling network. Our findings identify a central role for dysregulated αVβ3 and CD47 signaling in OA pathogenesis and suggest that activation of αVβ3 and CD47 signaling in many articular cell types contributes to inflammation and joint destruction in OA. Thus, the data presented here provide a rationale for targeting αVβ3, CD47, and their signaling pathways as a disease-modifying therapy.

How pathogenic cluster of differentiation 4 (CD4) T cells in rheumatoid arthritis (RA) develop remains poorly understood. We used Nur77-a marker of T cell antigen receptor (TCR) signaling-to identify antigen-activated CD4 T cells in the SKG mouse model of autoimmune arthritis and in patients with RA. Using a fluorescent reporter of Nur77 expression in SKG mice, we found that higher levels of Nur77-eGFP in SKG CD4 T cells marked their autoreactivity, arthritogenic potential, and ability to more readily differentiate into interleukin-17 (IL-17)-producing cells. The T cells with increased autoreactivity, nonetheless had diminished ex vivo inducible TCR signaling, perhaps reflective of adaptive inhibitory mechanisms induced by chronic autoantigen exposure in vivo. The enhanced autoreactivity was associated with up-regulation of IL-6 cytokine signaling machinery, which might be attributable, in part, to a reduced amount of expression of suppressor of cytokine signaling 3 (SOCS3)-a key negative regulator of IL-6 signaling. As a result, the more autoreactive GFPhi CD4 T cells from SKGNur mice were hyperresponsive to IL-6 receptor signaling. Consistent with findings from SKGNur mice, SOCS3 expression was similarly down-regulated in RA synovium. This suggests that despite impaired TCR signaling, autoreactive T cells exposed to chronic antigen stimulation exhibit heightened sensitivity to IL-6, which contributes to the arthritogenicity in SKG mice, and perhaps in patients with RA.

To define the cell populations that drive joint inflammation in rheumatoid arthritis (RA), we applied single-cell RNA sequencing (scRNA-seq), mass cytometry, bulk RNA sequencing (RNA-seq) and flow cytometry to T cells, B cells, monocytes, and fibroblasts from 51 samples of synovial tissue from patients with RA or osteoarthritis (OA). Utilizing an integrated strategy based on canonical correlation analysis of 5,265 scRNA-seq profiles, we identified 18 unique cell populations. Combining mass cytometry and transcriptomics revealed cell states expanded in RA synovia: THY1(CD90)+HLA-DRAhi sublining fibroblasts, IL1B+ pro-inflammatory monocytes, ITGAX+TBX21+ autoimmune-associated B cells and PDCD1+ peripheral helper T (TPH) cells and follicular helper T (TFH) cells. We defined distinct subsets of CD8+ T cells characterized by GZMK+, GZMB+, and GNLY+ phenotypes. We mapped inflammatory mediators to their source cell populations; for example, we attributed IL6 expression to THY1+HLA-DRAhi fibroblasts and IL1B production to pro-inflammatory monocytes. These populations are potentially key mediators of RA pathogenesis.

Rheumatoid arthritis (RA) is therapeutically challenging due to patient heterogeneity and variability. Herein we describe a novel integration of RA synovial genome-scale transcriptomic profiling of different patient cohorts that can be used to provide predictive insights on drug responses. A normalized compendium consisting of 256 RA synovial samples that cover an intersection of 11,769 genes from 11 datasets was build and compared with similar datasets derived from OA patients and healthy controls. Differentially expression genes (DEGs) that were identified in three independent methods were fed into functional network analysis, with subsequent grouping of the samples based on a non-negative matrix factorization method. RA-relevant pathway activation scores and four machine learning classification techniques supported the generation of a predictive model of patient treatment response. We identified 876 up-regulated DEGs including 24 known genetic risk factors and 8 drug targets. DEG-based subgrouping revealed 3 distinct RA patient clusters with distinct activity signatures for RA-relevant pathways. In the case of infliximab, we constructed a classifier of drug response that was highly accurate with an AUC/AUPR of 0.92/0.86. The most informative pathways in achieving this performance were the NFκB-, FcεRI- TCR-, and TNF signaling pathways. Similarly, the expression of the HMMR, PRPF4B, EVI2A, RAB27A, MALT1, SNX6, and IFIH1 genes contributed in predicting the patient outcome. Construction and analysis of normalized synovial transcriptomic compendia can provide useful insights for understanding RA-related pathway involvement and drug responses for individual patients.

Osteoarthritis (OA) is a chronic, progressive, severely debilitating, and multifactorial joint disease that is recognized as the most common type of arthritis. During the last decade, it shows an incremental global rise in prevalence and incidence. The interaction between etiologic factors that mediate joint degradation has been explored in numerous studies. However, the underlying processes that induce OA remain obscure, largely due to the variety and complexity of these mechanisms. During synovial joint dysfunction, the osteochondral unit undergoes cellular phenotypic and functional alterations. At the cellular level, the synovial membrane is influenced by cartilage and subchondral bone cleavage fragments and extracellular matrix (ECM) degradation products from apoptotic and necrotic cells. These "foreign bodies" serve as danger-associated molecular patterns (DAMPs) that trigger innate immunity, eliciting and sustaining low-grade inflammation in the synovium. In this review, we explore the cellular and molecular communication networks established between the major joint compartments—the synovial membrane, cartilage, and subchondral bone of normal and OA-affected joints. [ABSTRACT FROM AUTHOR]