Targeting the synovial angiogenesis as a novel treatment approach to osteoarthritis

Single-cell profiling uncovers synovial fibroblast subpopulations associated with chondrocyte injury in osteoarthritis

Background

Chondrocytes and synovial cells participate in the pathogenesis of osteoarthritis (OA). Nonetheless, the interactions and correlations between OA synovial cells and chondrocytes remain unclear. This study aims to elucidate the interactions and correlations between OA synovial cells and chondrocytes, so as to deepen understanding of OA pathogenesis.

Methods

Single-cell sequencing analysis was employed to analyze clusters of synovial and chondrocyte cells within the OA dataset. Through cell interaction analysis, the potential interactions between these two cell types were further explored. Differential gene expression analysis was used to examine the differences among synovial-related cell clusters.

Results

The study identified specific characteristics of synovial fibroblasts through single-cell sequencing analysis. Subsequent cell interaction analysis revealed interactions and correlations between synovial fibroblast clusters and cell clusters in both damaged and non-damaged cartilages. CILP+ fibroblasts showed significant interactions with non-damaged chondrocytes, while POSTN+ fibroblasts exhibited significant interactions with damaged chondrocytes. Furthermore, differential gene expression analysis revealed that genes such as PRELP, CLU, COMP, TNFRSF12A, INHBA, CILP, and SERPINE2, were significantly upregulated in CILP+ fibroblasts. These genes are involved in promoting cell proliferation, inhibiting inflammatory pathways, and stabilizing cell structure, thereby exerting reparative and protective effects on chondrocytes. In contrast, COL6A3, COL6A1, COL1A2, COL1A1, COL3A1, TGF-β1, MMP2, AEBP1, SPARC, FNDC1, and POSTN were upregulated in POSTN+ fibroblasts. These genes may contribute to chondrocyte damage and further degeneration by promoting chondrocyte catabolism, driving inflammation, activating inflammatory pathways, and facilitating chondrocyte apoptosis and destruction.

Conclusion

Our study elucidated the interactions and correlations between OA synovial cells and chondrocytes. CILP+ synovial fibroblasts may exert reparative and protective effects on chondrocytes of patients with OA by promoting cell proliferation, inhibiting inflammation, and stabilizing cellular structures, thereby potentially mitigating the progression of cartilage lesions in affected patients. In contrast, POSTN+ synovial fibroblasts may exacerbate chondrocyte deterioration in patients with OA by enhancing degradation, inflammation, and apoptosis, thereby exacerbating cartilage lesions. Investigating the underlying molecular mechanisms between OA synovial cells and chondrocytes refines the understanding of OA pathogenesis and provides valuable insights for the clinical diagnosis and treatment of OA.

Development of a Short-Term Embolic Agent Based on Cilastatin for Articular Microvessels

Background and Objectives: This study aimed to develop an embolic agent with short-term embolic effects using cilastatin as the basic material. Materials and Methods: The particle size distribution of 25 mg cilastatin-based short-term embolic agents was evaluated microscopically under three different mixing conditions. A total of thirty-six healthy male Sprague Dawley rats were divided into four groups. Each group of six rats was injected once into the tail artery with 0.4 mL each of (A) Cilastatin + D-Mannitol Mixture, (B) Iohexol, (C) Prepenem, and (D) embolization promoter (EGgel). Results: A visual inspection of the tail appearance of rats in each group was performed at 0, 3, 7, 15, and 21 days. At weeks 1 and 3, three rats per group were euthanized, and histopathological analyses were performed on the specimens obtained from each group. No significant differences were observed on day 7, but mild inflammation was observed in Group (D) on day 15. Histopathological inflammation scoring of tail central artery embolization was performed using a six-point scale (from 0 = absent to 5 = marked inflammation). Three groups were formed consisting of six male New Zealand white rabbits each: control, positive control, and test groups. The control group received an Iohexol injection (rabbits: 0.8 mL). The positive control and experimental groups were injected with prepenem and cilastatin/D-mannitol compound, respectively (0.8 mL), and vascular angiography was performed. The order of occlusion progression after embolization was as follows: test group, positive control group, and control group. Conclusions: We developed a cilastatin/D-mannitol compound that exhibits characteristics of short-term embolization by utilizing the pharmacokinetic properties of cilastatin and the crystalline material D-mannitol. We evaluated its particle size distribution microscopically, conducted histopathological evaluation including inflammation via animal experiments, and assessed the embolization effect.

Genicular Artery Embolization: A New Tool for the Management of Refractory Osteoarthritis-Related Knee Pain

Osteoarthritis (OA) of the knee is a prevalent cause of chronic pain and disability, particularly affecting women. While traditionally attributed to chronic wear and tear, recent evidence highlights multifactorial pathogenesis involving low-grade inflammation and neoangiogenesis. Current therapeutic options include physical therapy, pharmacotherapy, and total knee arthroplasty (TKA). However, a subset of patients remain symptomatic despite conservative measures, necessitating the development of minimally invasive interventions. Genicular artery embolization (GAE) emerges as a promising option, targeting neovascularization and inflammatory processes in OA. This paper reviews the pathophysiological basis, patient selection criteria, procedural details, and outcomes of GAE. Notably, GAE demonstrates efficacy in relieving knee pain and improving function in patients refractory to conventional therapy. While further research is warranted to elucidate its long-term outcomes and compare it with existing modalities, GAE represents a novel approach in the management of symptomatic knee OA, potentially delaying or obviating the need for surgical intervention. Here, we synthesize the relevant literature, technical details of the procedure, and future perspectives. Moreover, the success of GAE prompts the exploration of transarterial embolization in other musculoskeletal conditions, underscoring the evolving role of interventional radiology in personalized pain management strategies.

Topical Diclofenac Reduces Joint Synovitis in Hand Osteoarthritis: A Pilot Investigation Using Fluorescent Optical Imaging

Purpose

Synovitis, the inflammation of joint synovia, is a prominent feature of osteoarthritis (OA) manifested by enhanced synovial vascularity, endothelial leakage, and perivascular oedema. In this pilot study, we assessed the effect of topical diclofenac in hand OA (HOA) using the established semi-quantitative methods Magnetic Resonance Imaging (MRI) and Ultrasonography (US), and compared them with Fluorescent Optical Imaging (FOI), an emerging imaging modality.

Patients and Methods

Ten patients with symptomatic and diagnosed HOA used topical diclofenac for 14 days, with FOI, MRI, US, and subjective pain assessed at Baseline and after 7 (Day 8), and 14 (Day 15) days of treatment. Changes in synovitis were assessed for all 10 joints of the hand (via sum scores), and separately for the two joints most affected by synovitis. A new, fully quantitative approach for objective synovitis assessment based on the FOI images was also developed and applied.

Results

The semi-quantitative analysis of the sum scores showed a small decrease in synovitis throughout the treatment duration across the different imaging modalities. The effect of the treatment was more prominent on the two most affected joints, with a synovitis reduction vs Baseline of 21.1% and 34.2% on Day 8 and Day 15, respectively, in the FOI. The quantitative FOI pixel analysis further strengthened the evidence for this effect, with observed reduction of 17.8% and 42.4% for Days 8 and 15, respectively. A similar trend was observed for subjective pain perception, with a reduction of 7.2 and 13.3 mm on Days 8 and 15.

Conclusion

This pilot study evidenced the effect of topical diclofenac on reducing synovitis in hand OA in semi- and fully quantitative analyses, with the effect being stronger in the most affected joints. Further, supporting studies are needed to probe the accuracy of the quantitative pixel analysis of FOI images.

Does Chronic Pancreatitis in Growing Pigs Lead to Articular Cartilage Degradation and Alterations in Subchondral Bone?

Chronic pancreatitis (CP), a progressive inflammatory disease, poses diagnostic challenges due to its initially asymptomatic nature. While CP's impact on exocrine and endocrine functions is well-recognized, its potential influence on other body systems, particularly in young individuals, remains underexplored. This study investigates the hypothesis that CP in growing pigs leads to alterations in articular cartilage and subchondral bone, potentially contributing to osteoarthritis (OA) development. Utilizing a pig model of cerulein-induced CP, we examined the structural and compositional changes in subchondral bone, articular cartilage, and synovial fluid. Histological analyses, including Picrosirius Red and Safranin-O staining, were employed alongside immuno-histochemistry and Western blotting techniques. Our findings reveal significant changes in the subchondral bone, including reduced bone volume and alterations in collagen fiber composition. Articular cartilage in CP pigs exhibited decreased proteoglycan content and alterations in key proteins such as MMP-13 and TGF-β1, indicative of early cartilage degradation. These changes suggest a link between CP and musculoskeletal alterations, underscoring the need for further research into CP's systemic effects. Our study provides foundational insights into the relationship between CP and skeletal health, potentially guiding future pediatric healthcare strategies for early CP diagnosis and management.

Regulating Chondro-Bone Metabolism for Treatment of Osteoarthritis via High-Permeability Micro/Nano Hydrogel Microspheres

Destruction of cartilage due to the abnormal remodeling of subchondral bone (SB) leads to osteoarthritis (OA), and restoring chondro-bone metabolic homeostasis is the key to the treatment of OA. However, traditional intra-articular injections for the treatment of OA cannot directly break through the cartilage barrier to reach SB. In this study, the hydrothermal method is used to synthesize ultra-small size (≈5 nm) selenium-doped carbon quantum dots (Se-CQDs, SC), which conjugated with triphenylphosphine (TPP) to create TPP-Se-CQDs (SCT). Further, SCT is dynamically complexed with hyaluronic acid modified with aldehyde and methacrylic anhydride (AHAMA) to construct highly permeable micro/nano hydrogel microspheres (SCT@AHAMA) for restoring chondro-bone metabolic homeostasis. In vitro experiments confirmed that the selenium atoms scavenged reactive oxygen species (ROS) from the mitochondria of mononuclear macrophages, inhibited osteoclast differentiation and function, and suppressed early chondrocyte apoptosis to maintain a balance between cartilage matrix synthesis and catabolism. In vivo experiments further demonstrated that the delivery system inhibited osteoclastogenesis and H-vessel invasion, thereby regulating the initiation and process of abnormal bone remodeling and inhibiting cartilage degeneration in SB. In conclusion, the micro/nano hydrogel microspheres based on ultra-small quantum dots facilitate the efficient penetration of articular SB and regulate chondro-bone metabolism for OA treatment.

Analysis of proteins released from osteoarthritic cartilage by compressive loading

In osteoarthritis (OA), synovial pathology may be induced by proteins released from degenerated cartilage. This study was conducted to identify the proteins released from OA cartilage. OA cartilage was obtained from OA knees at macroscopically preserved areas (PRES) and degenerated areas (DEG), while control cartilage (CONT) was collected from non-arthritic knees. Released proteins were obtained from these cartilage samples by repeatedly applying compressive loading, which simulated loading on cartilage in vivo. The released proteins were analyzed comprehensively by antibody array analyses and a quantitative proteomic analysis. For several proteins, the exact amounts released were determined by Luminex assays. The amount of active TGF-β that was released was determined by an assay using genetically-engineered HEK cells. The results of the antibody array and proteomic analyses revealed that various biologically active proteins are released from OA cartilage, particularly from DEG, by loading. The Luminex assay confirmed that several alarmins, complement proteins C3a and C5a, and several angiogenic proteins including FGF-1, FGF-2 and VEGF-A were released in greater amounts from DEG than from CONT. The HEK cell assay indicated that active TGF-β was released from DEG at biologically significant levels. These findings may be helpful in understanding the pathology of OA.

Human vascularised synovium-on-a-chip: a mechanically stimulated, microfluidic model to investigate synovial inflammation and monocyte recruitment

Healthy synovium is critical for joint homeostasis. Synovial inflammation (synovitis) is implicated in the onset, progression and symptomatic presentation of arthritic joint diseases such as rheumatoid arthritis and osteoarthritis. Thus, the synovium is a promising target for the development of novel, disease-modifying therapeutics. However, target exploration is hampered by a lack of good pre-clinical models that accurately replicate human physiology and that are developed in a way that allows for widespread uptake. The current study presents a multi-channel, microfluidic, organ-on-a-chip (OOAC) model, comprising a 3D configuration of the human synovium and its associated vasculature, with biomechanical and inflammatory stimulation, built upon a commercially available OOAC platform. Healthy human fibroblast-like synoviocytes (hFLS) were co-cultured with human umbilical vein endothelial cells (HUVECs) with appropriate matrix proteins, separated by a flexible, porous membrane. The model was developed within the Emulate organ-chip platform enabling the application of physiological biomechanical stimulation in the form of fluid shear and cyclic tensile strain. The hFLS exhibited characteristic morphology, cytoskeletal architecture and matrix protein deposition. Synovial inflammation was initiated through the addition of interleukin-1β(IL-1β) into the synovium channel resulting in the increased secretion of inflammatory and catabolic mediators, interleukin-6 (IL-6), prostaglandin E2 (PGE2), matrix metalloproteinase 1 (MMP-1), as well as the synovial fluid constituent protein, hyaluronan. Enhanced expression of the inflammatory marker, intercellular adhesion molecule-1 (ICAM-1), was observed in HUVECs in the vascular channel, accompanied by increased attachment of circulating monocytes. This vascularised human synovium-on-a-chip model recapitulates a number of the functional characteristics of both healthy and inflamed human synovium. Thus, this model offers the first human synovium organ-chip suitable for widespread adoption to understand synovial joint disease mechanisms, permit the identification of novel therapeutic targets and support pre-clinical testing of therapies.

Comparative validation of the knee inflammation MRI scoring system and the MRI osteoarthritis knee score for semi-quantitative assessment of bone marrow lesions and synovitis-effusion in osteoarthritis: an international multi-reader exercise

Background

Bone marrow lesions (BMLs) and synovitis on magnetic resonance imaging (MRI) are associated with symptoms and predict degeneration of articular cartilage in osteoarthritis (OA). Validated methods for their semiquantitative assessment on MRI are available, but they all have similar scoring designs and questionable sensitivity to change. New scoring methods with completely different designs need to be developed and compared to existing methods.

Objectives

To compare the performance of new web-based versions of the Knee Inflammation MRI Scoring System (KIMRISS) with the MRI OA Knee Score (MOAKS) for quantification of BMLs and synovitis-effusion (S-E).

Design

Retrospective follow-up cohort.

Methods

We designed web-based overlays outlining regions in the knee that are scored for BML in MOAKS and KIMRISS. For KIMRISS, both BML and S-E are scored on consecutive sagittal slices. The performance of these methods was compared in an international reading exercise of 8 readers evaluating 60 pairs of scans conducted 1 year apart from cases recruited to the OA Initiative (OAI) cohort. Interobserver reliability for baseline status and baseline to 1 year change in BML and S-E was assessed by intra-class correlation coefficient (ICC) and smallest detectable change (SDC). Feasibility was assessed using the System Usability Scale (SUS).

Results

Mean change in BML and S-E was minimal over 1 year. Pre-specified targets for acceptable reliability (ICC ⩾ 0.80 and ⩾ 0.70 for status and change scores, respectively) were achieved more frequently for KIMRISS for both BML and synovitis. Mean (95% CI) ICC for change in BML was 0.88 (0.83-0.92) and 0.69 (0.60-0.78) for KIMRISS and MOAKS, respectively. KIMRISS mean SUS usability score was 85.7 and at the 95th centile of ranking for usability versus a score of 55.4 and 20th centile for MOAKS.

Conclusion

KIMRISS had superior performance metrics to MOAKS for quantification of BML and S-E. Both methods should be further compared in trials of new therapies for OA.

Matrix metalloproteinases in rheumatoid arthritis and osteoarthritis: a state of the art review

Although the pathological mechanisms involved in osteoarthritis (OA) and rheumatoid arthritis (RA) are different, the onset and progression of both diseases are associated with several analogous clinical manifestations, inflammation, and immune mechanisms. In both diseases, cartilage destruction is mediated by matrix metalloproteinases (MMPs) synthesized by chondrocytes and synovium fibroblasts. This review aims to summarize recent articles regarding the role of MMPs in OA and RA, as well as the possible methods of targeting MMPs to alleviate the degradation processes taking part in OA and RA. The novel experimental MMP-targeted treatments in OA and RA are MMP inhibitors eg. 3-B2, taraxasterol, and naringin, while other treatments aim to silence miRNAs, lncRNAs, or transcription factors. Additionally, other recent MMP-related developments include gene polymorphism of MMPs, which have been linked to OA susceptibility, and the MMP-generated neoepitope of CRP, which could serve as a biomarker of OA progression.

Sustained intra-cartilage delivery of interleukin-1 receptor antagonist using cationic peptide and protein-based carriers

OBJECTIVE

Blocking the interleukin-1 (IL-1) catabolic cascade following joint trauma can be achieved using its receptor antagonist, IL-1Ra. However, its clinical translation for osteoarthritis therapy has been unsuccessful due to its rapid joint clearance and lack of targeting and penetration into deep cartilage layers at therapeutic concentrations. Here, we target the high negative charge of cartilage aggrecan-glycosaminoglycans (GAGs) by attaching cationic carriers to IL-1Ra. IL-1Ra was conjugated to the cartilage targeting glycoprotein, Avidin, and a short length optimally charged cationic peptide carrier (CPC+14). It is hypothesized that electro-diffusive transport and binding properties of IL-1Ra-Avidin and IL-1Ra-CPC+14 will create intra-cartilage depots of IL-1Ra, resulting in long-term suppression of IL-1 catabolism with only a single administration.

DESIGN

IL-1Ra was conjugated to Avidin or CPC+14 using site specific maleimide linkers, and confirmed using gel electrophoresis, high-performance liquid chromatography (HPLC), and mass spectrometry. Intra-cartilage transport and retention of conjugates was compared with native IL-1Ra. Attenuation of IL-1 catabolic signaling with one-time dose of IL-1Ra-CPC+14 and IL-1Ra-Avidin was assessed over 16 days using IL-1α challenged bovine cartilage and compared with unmodified IL-1Ra.

RESULTS

Positively charged IL-1Ra penetrated through the full-thickness of cartilage, creating a drug depot. A single dose of unmodified IL-1Ra was not sufficient to attenuate IL-1-induced cartilage deterioration over 16 days. However, when delivered using Avidin, and to a greater extent CPC+14, IL-1Ra significantly suppressed cytokine induced GAG loss and nitrite release while improving cell metabolism and viability.

CONCLUSION

Charge-based cartilage targeting drug delivery systems hold promise as they can enable long-term therapeutic benefit with only a single dose.

Culture-expanded mesenchymal stromal cell therapy: does it work in knee osteoarthritis? A pathway to clinical success

Osteoarthritis (OA) is a degenerative multifactorial disease with concomitant structural, inflammatory, and metabolic changes that fluctuate in a temporal and patient-specific manner. This complexity has contributed to refractory responses to various treatments. MSCs have shown promise as multimodal therapeutics in mitigating OA symptoms and disease progression. Here, we evaluated 15 randomized controlled clinical trials (RCTs) and 11 nonrandomized RCTs using culture-expanded MSCs in the treatment of knee OA, and we found net positive effects of MSCs on mitigating pain and symptoms (improving function in 12/15 RCTs relative to baseline and in 11/15 RCTs relative to control groups at study endpoints) and on cartilage protection and/or repair (18/21 clinical studies). We examined MSC dose, tissue of origin, and autologous vs. allogeneic origins as well as patient clinical phenotype, endotype, age, sex and level of OA severity as key parameters in parsing MSC clinical effectiveness. The relatively small sample size of 610 patients limited the drawing of definitive conclusions. Nonetheless, we noted trends toward moderate to higher doses of MSCs in select OA patient clinical phenotypes mitigating pain and leading to structural improvements or cartilage preservation. Evidence from preclinical studies is supportive of MSC anti-inflammatory and immunomodulatory effects, but additional investigations on immunomodulatory, chondroprotective and other clinical mechanisms of action are needed. We hypothesize that MSC basal immunomodulatory "fitness" correlates with OA treatment efficacy, but this hypothesis needs to be validated in future studies. We conclude with a roadmap articulating the need to match an OA patient subset defined by molecular endotype and clinical phenotype with basally immunomodulatory "fit" or engineered-to-be-fit-for-OA MSCs in well-designed, data-intensive clinical trials to advance the field.

Brij® integrated bilosomes for improving the transdermal delivery of niflumic acid for effective treatment of osteoarthritis: In vitro characterization, ex vivo permeability assessment, and in vivo study

Bilosomes are innovative vesicular carriers containing bile salt with a non-ionic surfactant. Being highly flexible, bilosomes can squeeze themselves through the skin carrying the drug to the action site and improving its skin penetration. The objective of this research was to encapsulate niflumic acid (NA), a non-steroidal anti-inflammatory drug into Brij® integrated bilosomes (BIBs) for effective treatment of osteoarthritis through transdermal delivery. BIBs were formulated using 100 mg of Span 20 with different amounts of sodium cholate (NaC), sodium taurocholate (NaTC), or sodium glycocholate (NaGC) as bile salt, with the addition of 5 mg of Brij-93 or Brij-35. BIBs were prepared utilizing ethanol injection method with the application of (3¹×2²) complete factorial design using Design-Expert® software. The optimal BIBs formulation determined was (B5) which contains 5 mg of NaTC used as bile salt and 5 mg of Brij-93. B5 exhibited entrapment efficiency% = 95.21 ± 0.00%, particle size = 373.05 ± 0.07 nm, polydispersity index = 0.27 ± 0.01, and zeta potential = -32.00 ± 0.00 mV. It also had a high elasticity with a spherical shape. B5 gel displayed a sustained release profile with a significantly 2.3 folds' higher drug permeation percent across rat skin than that permeated from NA gel. Moreover, in vivo anti-osteoarthritic and histopathological studies assured the efficacy and safety of B5 gel and its superiority over NA gel. Generally, the outcomes confirmed the great efficacy of NA loaded BIBs for the topical treatment of osteoarthritis.

Phenotypic and functional characterisation of synovial fluid-derived neutrophils in knee osteoarthritis and knee infection

OBJECTIVE

An increase in the number of neutrophils (NEUs) has long been associated with infections in the knee joints; however, their impact on knee osteoarthritis (KOA) pathophysiology remains largely unexplored.

DESIGN

This study compared the phenotypic and functional characteristics of synovial fluid (SF)-derived NEUs in KOA and knee infection (INF).

RESULTS

KOA NEUs were characterised by a lower expression of CD11b, CD54, and CD64 and higher expression of CD62L, TLR2, and TLR4 compared with INF NEUs. Except for CCL2, lower levels of inflammatory mediators and proteases were detected in KOA SF than in INF SF. Functionally, KOA NEUs displayed increased reactive oxygen species production and phagocytic activity compared with INF NEUs. Moreover, KOA and INF NEUs differed in cell sizes, histological characteristics of the surrounding synovial tissues, and their effects on the endothelial cells assessed by human umbilical vein endothelial cells. When KOA patients were subdivided based on the SF NEU abundance, patients with high NEUs (10%-60%) were characterised by i) elevated SF protein levels of TNF-α, IL-1RA, MMP-9, sTREM-1, VILIP-1 and ii) lower CD54, CD64, TLR2 and TLR4 expression compared to patients with low NEUs (<10%). Analysis of paired SF samples suggests that low or high NEU percentages, respectively, persist throughout the course of disease.

CONCLUSIONS

Our findings suggest that NEU may play a significant role in KOA pathophysiology. Further studies should explore the mechanisms that contribute to the increased number of NEUs in SF and the clinical consequences of neutrophilic phenotype in KOA.

Expression of cannabinoid (CB1 and CB2) and cannabinoid-related receptors (TRPV1, GPR55, and PPARα) in the synovial membrane of the horse metacarpophalangeal joint

Background

The metacarpophalangeal joint undergoes enormous loading during locomotion and can therefore often become inflamed, potentially resulting in osteoarthritis (OA). There are studies indicating that the endocannabinoid system (ECS) modulates synovium homeostasis, and could be a promising target for OA therapy. Some cannabinoid receptors, which modulate proliferative and secretory responses in joint inflammation, have been functionally identified in human and animal synovial cells.

Objective

To characterize the cellular distribution of the cannabinoid receptors 1 (CB1R) and 2 (CB2R), and the cannabinoid-related receptors transient receptor potential vanilloid type 1 (TRPV1), G protein-related receptor 55 (GPR55) and peroxisome proliferator-activated receptor alpha (PPARα) in the synovial membrane of the metacarpophalangeal joint of the horse.

Animals

The dorsal synovial membranes of 14 equine metacarpophalangeal joints were collected post-mortem from an abattoir.

Materials and methods

The dorsal synovial membranes of 14 equine metacarpophalangeal joints were collected post-mortem from an abattoir. The expression of the CB1R, CB2R, TRPV1, GPR55, and PPARα in synovial tissues was studied using qualitative and quantitative immunofluorescence, and quantitative real-time reverse transcriptase PCR (qRT-PCR). Macrophage-like (MLS) and fibroblast-like (FLS) synoviocytes were identified by means of antibodies directed against IBA1 and vimentin, respectively.

Results

Both the mRNA and protein expression of the CB2R, TRPV1, GPR55, and PPARα were found in the synoviocytes and blood vessels of the metacarpophalangeal joints. The synoviocytes expressed the mRNA and protein of the CB1R in some of the horses investigated, but not in all.

Conclusions and clinical importance

Given the expression of the CB1R, CB2R, TRPV1, GPR55, and PPARα in the synovial elements of the metacarpophalangeal joint, these findings encouraged the development of new studies supporting the use of molecules acting on these receptors to reduce the inflammation during joint inflammation in the horse.

Role of GDF15/MAPK14 Axis in Chondrocyte Senescence as a Novel Senomorphic Agent in Osteoarthritis

Osteoarthritis (OA) is most prevalent in older individuals and exerts a heavy social and economic burden. However, an effective and noninvasive approach to OA treatment is currently not available. Chondrocyte senescence has recently been proposed as a key pathogenic mechanism in the etiology of OA. Furthermore, senescent chondrocytes (SnCCs) can release various proinflammatory cytokines, proteolytic enzymes, and other substances known as the senescence-associated secretory phenotype (SASP), allowing them to connect with surrounding cells and induce senesce. Studies have shown that the pharmacological elimination of SnCCs slows the progression of OA and promotes regeneration. Growth differentiation factor 15 (GDF15), a member of the tumor growth factor (TGF) superfamily, has recently been identified as a possible aging biomarker and has been linked to a variety of clinical conditions, including coronary artery disease, diabetes, and multiple cancer types. Thus, we obtained data from a publicly available single-cell sequencing RNA database and observed that GDF15, a critical protein in cellular senescence, is highly expressed in early OA. In addition, GDF15 is implicated in the senescence and modulation of MAPK14 in OA. Tissue and synovial fluid samples obtained from OA patients showed overexpression of GDF15. Next, we treated C20A4 cell lines with interleukin (IL)-1β with or without shGDF15 then removed the conditioned medium, and cultured C20A4 and HUVEC cell lines with the aforementioned media. We observed that C20A4 cells treated with IL-1β exhibited increased GDF15 secretion and that chondrocytes cultured with media derived from IL-1β–treated C20A4 exhibited senescence. HUVEC cell migration and tube formation were enhanced after culturing with IL-1β-treated chondrocyte media; however, decreased HUVEC cell migration and tube formation were noted in HUVEC cells cultured with GDF15-loss media. We tested the potential of inhibiting GDF15 by using a GDF15 neutralizing antibody, GDF15-nAb. GDF15-nAb exerted a similar effect, resulting in the molecular silencing of GDF15 in vivo and in vitro. Our results reveal that GDF15 is a driver of SnCCs and can contribute to OA progression by inducing angiogenesis.

The Systematic Analysis of Exercise Mechanism in Human Diseases

Background

As a part of a healthy lifestyle, exercise has been proven to be beneficial for the treatment of diseases and the prognosis of patients. Based on this, our research focuses on the impact of exercise on human health.

Methods

To study and analyze the samples in the GSE18966 gene expression profile, we first performed an analysis on the differential expressed genes (DEGs) through GEO2R, and then the DEGs enrichment in Gene Ontology functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways through the Database for Annotation, Visualization and Integrated Discovery database was conducted. Then, we delved into the gene set enrichment in KEGG through gene set enrichment analysis. After that, we achieved the construction of the protein-protein interaction (PPI) network of DEGs based on the Search Tool for the Retrieval of Interacting Genes online database, and the hub genes were screened and identified.

Results

We identified 433 upregulated DEGs and 186 downregulated DEGs from the samples before and after exercise in GSE18966. Through analysis, it was found that these DEGs-enriched pathways, such as the VEGF signaling pathway, the Wnt signaling pathway, and the insulin signaling pathway, were all involved in the regulation of various diseases. Then, GSEA analysis revealed that glycosaminoglycan biosynthesis chondroitin sulfate, type II diabetes mellitus, and basal cell carcinoma were related with exercise samples. The effects of these pathways on various diseases could be improved through exercise. Finally, 3 upregulated hub genes (VEGFA, POMC, and NRAS) and 3 downregulated hub genes (HRAS, NCOR1, and CAV1) were identified through the PPI network.

Conclusions

The bioinformatic analysis of samples before and after exercise provides key pathways and genes related to exercise to regulate various diseases, which confirms that exercise has an important influence on the treatment of many diseases.

Synovial membrane mesenchymal stem cells for cartilaginous tissues repair

BACKGROUND

The present review is focused on general aspects of the synovial membrane as well as specialized aspects of its cellular constituents, particularly the composition and location of synovial membrane mesenchymal stem cells (S-MSCs). S-MSC multipotency properties are currently at the center of translational medicine for the repair of multiple joint tissues, such as articular cartilage and meniscus lesions.

METHODS AND RESULTS

We reviewed the results of in vitro and in vivo research on the current clinical applications of S-MSCs, surface markers, cell culture techniques, regenerative properties, and immunomodulatory mechanisms of S-MSCs as well as the practical limitations of the last twenty-five years (1996 to 2021).

CONCLUSIONS

Despite the poor interest in the development of new clinical trials for the application of S-MSCs in joint tissue repair, we found evidence to support the clinical use of S-MSCs for cartilage repair. S-MSCs can be considered a valuable therapy for the treatment of repairing joint lesions.

In Vivo Investigation of the Ameliorating Effect of Tempol against MIA-Induced Knee Osteoarthritis in Rats: Involvement of TGF-β1/SMAD3/NOX4 Cue

Osteoarthritis (OA) is a complex disease characterized by structural, functional, and metabolic deteriorations of the whole joint and periarticular tissues. In the current study, we aimed to investigate the possible effects of tempol on knee OA induced by the chemical chondrotoxic monosodium iodoacetate (MIA) which closely mimics both the pain and structural changes associated with human OA. Rats were administrated oral tempol (100 mg/kg) one week post-MIA injection (3 mg/50 μL saline) at the right knee joints for 21 consecutive days. Tempol improved motor performance and debilitated the MIA-related radiological and histological alterations. Moreover, it subsided the knee joint swelling. Tempol decreased the cartilage degradation-related biomarkers as matrix metalloproteinase-13, bone alkaline phosphatase (bone ALP), and fibulin-3. The superoxide dismutase mimetic effect of tempol was accompanied by decreased NADPH oxidase 4 (NOX4), inflammatory mediators, nuclear factor-kappa B (NF-κB), over-released transforming growth factor-β1 (TGF-β1). Tempol decreased the expression of chemokine (C-C motif) ligand 2 (CCL2). On the molecular level, tempol reduced the phosphorylated protein levels of p38 mitogen-activated protein kinase (MAPK), and small mother against decapentaplegic 3 homologs (SMAD3). These findings suggest the promising role of tempol in ameliorating MIA-induced knee OA in rats via collateral suppression of the catabolic signaling cascades including TGF-β1/SMAD3/NOX4, and NOX4/p38MAPK/NF-κB and therefore modulation of oxidative stress, catabolic inflammatory cascades, chondrocyte metabolic homeostasis.

Cardiovascular Drugs and Osteoarthritis: Effects of Targeting Ion Channels

Osteoarthritis (OA) and cardiovascular diseases (CVD) share many similar features, including similar risk factors and molecular mechanisms. A great number of cardiovascular drugs act via different ion channels and change ion balance, thus modulating cell metabolism, osmotic responses, turnover of cartilage extracellular matrix and inflammation. These drugs are consumed by patients with CVD for many years; however, information about their effects on the joint tissues has not been fully clarified. Nevertheless, it is becoming increasingly likely that different cardiovascular drugs may have an impact on articular tissues in OA. Here, we discuss the potential effects of direct and indirect ion channel modulating drugs, including inhibitors of voltage gated calcium and sodium channels, hyperpolarization-activated cyclic nucleotide-gated channels, β-adrenoreceptor inhibitors and angiotensin-aldosterone system affecting drugs. The aim of this review was to summarize the information about activities of cardiovascular drugs on cartilage and subchondral bone and to discuss their possible consequences on the progression of OA, focusing on the modulation of ion channels in chondrocytes and other joint cells, pain control and regulation of inflammation. The implication of cardiovascular drug consumption in aetiopathogenesis of OA should be considered when prescribing ion channel modulators, particularly in long-term therapy protocols.

Prolidase expression in knee osteoarthritis and healthy controls: Observational study

Prolidase enzyme activity is important for collagen resynthesis. In late stages of osteoarthritis (OA) its activity is decreased.To evaluate prolidase expression in knees of patients undergoing total arthroplasty for OA, and compare with young people undergoing knee arthroscopy due to traumatic injuries.In this cross-sectional study we included 20 patients with OA grade IV who underwent total knee arthroplasty and 20 controls of young patients who underwent arthroscopy for another reason besides OA. All participants were evaluated by knee ultrasound before the procedure. During the procedure, synovial tissue biopsies were taken and analyzed by immunofluorescence to search inflammation. Measures of central tendency, dispersion measures and position measures were used for the case of quantitative variables. Student t test or Mann-Whitney U test, and the logistic regression of Cox, was used.Prolidase expression in the synovial biopsy was significantly lower in the OA group than in the controls (0.017 ± 0.009 vs 0.062 ± 0.094, P < .05). Power Doppler (PD) signal was present in the synovitis of all knee recesses of the OA group in grayscale and in 17 (85%) of knees. The mean of the micro-vessel count in patients with OA was significantly higher vs controls (11 + 5.3 vs 4 + 2.1, P = .001). The neovascularization correlated significantly with the presence of PD signal in patients with OA (1.16, 95% CI, 1.02-1.34, P = .02).The prolidase expression in the synovial membrane evaluated by immunofluorescence, in patients with late stages of knee OA, is low, which may be interpreted as an evidence of decreased collagen resynthesis.

Pseudolaric acid B ameliorates synovial inflammation and vessel formation by stabilizing PPARγ to inhibit NF-κB signalling pathway

Synovial macrophage polarization and inflammation are essential for osteoarthritis (OA) development, yet the molecular mechanisms and regulation responsible for the pathogenesis are still poorly understood. Here, we report that pseudolaric acid B (PAB) attenuated articular cartilage degeneration and synovitis during OA. PAB, a diterpene acid, specifically inhibited NF-κB signalling and reduced the production of pro-inflammatory cytokines, which further decreased M1 polarization and vessel formation. We further provide in vivo and in vitro evidences that PAB suppressed NF-κB signalling by stabilizing PPARγ. Using PPARγ antagonist could abolish anti-inflammatory effect of PAB and rescue the activation of NF-κB signalling during OA. Our findings identify a previously unrecognized role of PAB in the regulation of OA and provide mechanisms by which PAB regulates NF-κB signalling through PPARγ, which further suggest targeting synovial inflammation or inhibiting vessel formation at early stage could be an effective preventive strategy for OA.

A physicochemical double cross-linked multifunctional hydrogel for dynamic burn wound healing: shape adaptability, injectable self-healing property and enhanced adhesion

Burn wounds are one of the most destructive skin traumas that cause more than 180000 deaths each year. Patients with large, irregular burn wounds suffer from slow healing. Dynamic burn wounds have special requirements for hydrogel dressing due to their high frequency movement. To focus on dynamic burn wounds, we designed a novel double cross-linked hydrogel prepared by Schiff base and catechol-Fe³⁺ chelation bond. The unique double cross-linked structure of the hydrogel resulted in better physicochemical properties and enhanced efficacy. The enhanced physicochemical properties, such as faster gelation time (52 ± 2 s), stronger mechanical property (535 kPa of G'), enhanced adhesive strength (19.3 kPa) and better self-healing property, made the hydrogel suitable for dynamic wounds. The excellent shape adaptability (97.1 ± 1.3% of recovery) made the hydrogel suitable for wounds with irregular shapes. The hydrogel exhibited not only biodegradability during the wound healing process but also superior inherent antibacterial activity (100% killing ratio) and hemostatic property. The results showed that the hydrogel shortened the healing time of burn wounds to 13 days, and accelerated the reconstruction of skin structure and function. This double cross-linked multifunctional hydrogel is a promising candidate as a dynamic burn wound dressing.

Proteoglycan-4 regulates fibroblast to myofibroblast transition and expression of fibrotic genes in the synovium

Background

Synovial tissue fibrosis is common in advanced OA with features including the presence of stress fiber-positive myofibroblasts and deposition of cross-linked collagen type-I. Proteoglycan-4 (PRG4) is a mucinous glycoprotein secreted by synovial fibroblasts and is a major component of synovial fluid. PRG4 is a ligand of the CD44 receptor. Our objective was to examine the role of PRG4-CD44 interaction in regulating synovial tissue fibrosis in vitro and in vivo.

Methods

OA synoviocytes were treated with TGF-β ± PRG4 for 24 h and α-SMA content was determined using immunofluorescence. Rhodamine-labeled rhPRG4 was incubated with OA synoviocytes ± anti-CD44 or isotype control antibodies and cellular uptake of rhPRG4 was determined following a 30-min incubation and α-SMA expression following a 24-h incubation. HEK-TGF-β cells were treated with TGF-β ± rhPRG4 and Smad3 phosphorylation was determined using immunofluorescence and TGF-β/Smad pathway activation was determined colorimetrically. We probed for stress fibers and focal adhesions (FAs) in TGF-β-treated murine fibroblasts and fibroblast migration was quantified ± rhPRG4. Synovial expression of fibrotic markers: α-SMA, collagen type-I, and PLOD2 in Prg4 gene-trap (Prg4^GT) and recombined Prg4^GTR animals were studied at 2 and 9 months of age. Synovial expression of α-SMA and PLOD2 was determined in 2-month-old Prg4^GT/GT&Cd44^−/− and Prg4^GTR/GTR&Cd44^−/− animals.

Results

PRG4 reduced α-SMA content in OA synoviocytes (p < 0.001). rhPRG4 was internalized by OA synoviocytes via CD44 and CD44 neutralization attenuated rhPRG4’s antifibrotic effect (p < 0.05). rhPRG4 reduced pSmad3 signal in HEK-TGF-β cells (p < 0.001) and TGF-β/Smad pathway activation (p < 0.001). rhPRG4 reduced the number of stress fiber-positive myofibroblasts, FAs mean size, and cell migration in TGF-β-treated NIH3T3 fibroblasts (p < 0.05). rhPRG4 inhibited fibroblast migration in a macrophage and fibroblast co-culture model without altering active or total TGF-β levels. Synovial tissues of 9-month-old Prg4^GT/GT animals had higher α-SMA, collagen type-I, and PLOD2 (p < 0.001) content and Prg4 re-expression reduced these markers (p < 0.01). Prg4 re-expression also reduced α-SMA and PLOD2 staining in CD44-deficient mice.

Conclusion

PRG4 is an endogenous antifibrotic modulator in the joint and its effect on myofibroblast formation is partially mediated by CD44, but CD44 is not required to demonstrate an antifibrotic effect in vivo.

The complexity of molecular processes in osteoarthritis of the knee joint

Osteoarthritis (OA) is a common medical problem leading to chronic pain and physical disability among the world's population. Analyzing the molecular background of the degenerative arthritis creates the potential for developing novel targeted methods of treatment. Fifty samples of meniscus, anterior cruciate ligaments (ACLs) and articular surfaces were collected from patients who underwent total knee arthroplasty in 2016. Enzyme-linked immunosorbent assay was used to assess the levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF), transforming growth factor-β1 and LUMINEX for MMP-1, MMP-2, MMP-3, MMP-9 and MMP-13. The collected data were correlated with the severity of radiological OA, demographic data and clinical scales. Strong positive correlations in the concentration of metalloproteinases and proinflammatory cytokines, TNF-α (MMP-2 and MMP-13) and IL-6 (MMP-13), were identified. MMP-13 had a positive correlation with the concentration of MMP-1, MMP-2 and MMP-9. Negative correlation coefficient exists between clinical conditions measured with the Western Ontario and McMaster Universities Osteoarthritis Index scale and the level of TNF-α and MMP-1. The TNF-α concentration was lower in the cartilage of the articular surface among patients who took non-steroidal anti-inflammatory drugs periodically. The decrease in MMP-2 in the cartilage of the articular surface corresponded with the severity of radiological OA on the Kellgren-Lawrence scale. Current treatment methods for OA do not stop disease progression. Identifying signaling pathways and molecular particles engaged in OA and their correlations with the patient's clinical condition brings new therapeutic possibilities.

Apelin Affects the Progression of Osteoarthritis by Regulating VEGF-Dependent Angiogenesis and miR-150-5p Expression in Human Synovial Fibroblasts

Synovium-induced angiogenesis is central to osteoarthritis (OA) pathogenesis and thus a promising therapeutic target. The adipokine apelin (APLN) is involved in both OA pathogenesis and angiogenesis. We examined the role of APLN in synovium-induced angiogenesis by investigating the crosstalk between APLN and vascular endothelial growth factor (VEGF) expression in human OA synovial fibroblasts (OASFs). We found higher levels of APLN and VEGF expression in OA samples compared with normal samples. APLN-induced stimulation of VEGF expression and VEGF-dependent angiogenesis in OASFs was mitigated by FAK/Src/Akt signaling. APLN also inhibited levels of microRNA-150-5p (miR-150-5p), which represses VEGF production and angiogenesis. Analyses of an OA animal model showed that shAPLN transfection of OASFs rescued pathologic changes in OA cartilage and histology. Here, we found APLN enhances VEGF expression and angiogenesis via FAK/Src/Akt cascade and via downstream suppression of miR-150-5p expression. These findings help to clarify the pathogenesis of adipokine-induced angiogenesis in OA synovium.

The role and function of long non-coding RNAs in osteoarthritis

Osteoarthiritis (OA) is the most prevalent disease of articulating joints in human that frequently results in joint pain, movement limitations, inflammation, and progressive degradation of articular cartilage. The etiology of OA is not completely clear and there is no full treatment for this disease. Molecular investigations have revealed the involvement of non-coding RNAs such as Long non-coding RNAs (lncRNAs) in OA pathogenesis. LncRNAs play roles in multiple cellular and biological processes. Moreover, numerous lncRNAs are differentially expressed in human OA cartilage. In this review, we underlie the increasing evidence for the critical role of lncRNAs in OA pathogenesis reviewing the latest researches.

Heterotopic ossification and clinical results after total hip arthroplasty using the anterior minimally invasive and anterolateral approaches

INTRODUCTION

Total hip arthroplasty (THA) is considered the gold standard in the treatment of advanced osteoarthritis of the hip. The aim of this study was to compare the incidence of heterotopic ossification (HO), the quality of life and the function in two groups of patients who underwent total hip arthroplasty (THA), performed using the anterior minimally invasive (MIS) and the anterolateral approaches.

MATERIAL AND METHODS

Retrospective analysis of 597 patients who underwent THA in 2009-2013 was performed. In all 597 cohort data on medical history were retrieved. HO occurrence was recorded for 331 patients and was evaluated based on Brooker's scale in the X-ray scan. Functional and quality of life scores were obtained for 238 patients. The following scales were used for the survey: Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index, Visual Analogue Scale, and Hip and Knee Arthroplasty Satisfaction Scale.

RESULTS

Patients operated on from the MIS approach had statistically significantly (p < 0.05) better results with all the clinical scales used, except the Visual Analogue Scale (p > 0.05). HO was slightly more common after the MIS approach (52.5%) compared to the anterolateral approach (49.76%), though the difference was not statistically significant (p > 0.05).

CONCLUSIONS

The MIS approach was associated with better clinical and functional outcomes. In the aspect of HO, we were not able to show the superiority of the MIS approach in terms of incidence.

Intraarticular Ligament Degeneration Is Interrelated with Cartilage and Bone Destruction in Osteoarthritis

Osteoarthritis (OA) induces inflammation and degeneration of all joint components including cartilage, joint capsule, bone and bone marrow, and ligaments. Particularly intraarticular ligaments, which connect the articulating bones such as the anterior cruciate ligament (ACL) and meniscotibial ligaments, fixing the fibrocartilaginous menisci to the tibial bone, are prone to the inflamed joint milieu in OA. However, the pathogenesis of ligament degeneration on the cellular level, most likely triggered by OA associated inflammation, remains poorly understood. Hence, this review sheds light into the intimate interrelation between ligament degeneration, synovitis, joint cartilage degradation, and dysbalanced subchondral bone remodeling. Various features of ligament degeneration accompanying joint cartilage degradation have been reported including chondroid metaplasia, cyst formation, heterotopic ossification, and mucoid and fatty degenerations. The entheses of ligaments, fixing ligaments to the subchondral bone, possibly influence the localization of subchondral bone lesions. The transforming growth factor (TGF)β/bone morphogenetic (BMP) pathway could present a link between degeneration of the osteochondral unit and ligaments with misrouted stem cell differentiation as one likely reason for ligament degeneration, but less studied pathways such as complement activation could also contribute to inflammation. Facilitation of OA progression by changed biomechanics of degenerated ligaments should be addressed in more detail in the future.

Synovial Fluid MicroRNA-210 as a Potential Biomarker for Early Prediction of Osteoarthritis

Early detection and treatment are critical in the management of osteoarthritis (OA). OA is closely associated with angiogenesis and the inhibition of angiogenesis presents a novel therapeutic approach to reduce inflammation and pain in OA. Recent reports suggest that circulating microRNAs (miRNAs) have great potential as biomarkers for the diagnosis and prognosis in OA. In this study, we aimed to explore the clinical significance of miR-210 in synovial fluid samples from 10 healthy volunteers and 20 early-stage OA and 20 late-stage OA patients. miR-210 expression was assessed by real-time RT-PCR. VEGF protein levels were examined by ELISA. The results show that miR-210 is significantly upregulated in early-stage OA and late-stage OA patients compared with healthy individuals. Higher levels of VEGF are also found in OA compared with the control. Moreover, miR-210 levels are positively correlated with VEGF levels, suggesting that miR-210 might contribute to OA development through promoting VEGF expression and angiogenesis. In conclusion, upregulation of miR-210 in synovial fluid may occur in the early stage of OA and can be a useful biomarker for early diagnosis of OA.

Phagocytosis of monosodium urate crystals by human synoviocytes induces inflammation

IMPACT STATEMENT

Gout is distinguished by an inflammatory process that is mediated by phagocytosis of monosodium urate (MSU) crystals in synoviocytes by regulation of unknown mechanisms. Here we suggest that the synovial cells play a crucial role in gouty arthritis by activating inflammation by MSU uptake and increasing the secretion of pro-inflammatory cytokines IL-1β, IL-6, IL-8, TNF-α, MCP-1, and the growth factors NGF and HGF. We discuss some co-existing features in synoviocytes, including anomalous morphologies of the cells, and microvesicle formation, dysregulation in VEGF gene expression. We provide evidence that phagocytosis of MSU crystals triggers an inflammatory cellular state in synoviocytes in the pathogenesis of crystal-induced arthritis.

Inflammatory and fibrosis infiltration in synovium associated with the progression in developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a common musculoskeletal disorder characterized by progressive joint soreness and limited mobility. The aim of the present study was to investigate the pathological changes and inflammatory infiltration in the hypertrophic synovium of the hip joint associated with the progression of DDH. Synovial biopsies in the hip joint are obtained from patients with moderate DDH and severe DDH during surgery. These biopsies are processed for histological and immunohistochemical (IHC) analysis and investigation of the pathological processes in a synovium, including types of inflammatory cell infiltration, synovial angiogenesis and fibrosis, neuron endings and neuropeptide invasion. Correlation analysis was performed between the mean optical density (MOD) of each antibody, and Harris hip score (HHS) and visual analogue score (VAS) using the Spearman correlation test. Chronic inflammation in the synovium was observed via the positive IHC staining of inflammatory cells, such as T cells, B cells, macrophages and leukocytes. Excessive staining of vimentin and α smooth muscle actin in the synovium of severe DDH represented significant fibrosis and angiogenesis. These targets were also significantly correlated with HHS in severe DDH. The MOD levels of CD68 (indicators of macrophage) indicated apparent correlations with HHS and VAS in patients with severe DDH. The labels of nerve fibers and pain transmission indicators were as follows: Neurofilament‑200 and substance P. Calcitonin gene‑related peptide was upregulated in the synovium of severe DDH in contrast to that in the synovium of moderate DDH. The MOD levels of NF‑200, SP and CGRP were correlated with VAS in severe DDH. The pathology of DDH includes chronic inflammatory cell infiltration corresponding with nerve fibers and fibroblastic proliferation, which might contribute to arthritis progression and joint soreness in DDH.

Better understanding of acute gouty attack using CT perfusion in a rabbit model

OBJECTIVE

To assess hemodynamic changes related to acute gouty knee arthritis in a rabbit with CT perfusion (CTP) METHODS: Forty-two rabbits were randomly separated into two groups: the treated group of 30 and the control group of 12. The right knee was injected with monosodium urate solution and polymyxin in the treated group and saline and polymyxin in the control group. At 2, 16, 32, 48, 60, and 72 h after injection, five rabbits from the treated group and two rabbits from the control group were selected for CTP. At each time point, blood flow (BF), blood volume (BV), and clearance rate (CL) were measured, and microvessel density (MVD) was evaluated with a microscope.

RESULTS

In the treated group, BF, BV, CL, and MVD were significantly higher than in the control group (p < 0.001). Differences within paired comparison of BV, BF, CL, and MVD were all significant (all p < 0.001). Peak time of BV, BF, and MVD was 32 h and 48 h for CL. After multivariate stepwise linear regression analysis, BV was linearly associated with MVD and vice versa, which also applied to BF with MVD and BF with CL, separately. The ascending rate of MVD was the highest among that of all parameters; so was the descending rate of CL.

CONCLUSION

CTP in this rabbit knee model accurately detected hemodynamic changes during a gouty attack.

KEY POINTS

• Acute gouty arthritis can be evaluated with CTP in a rabbit knee model. • Following injection of MSU crystals, producing an acute gouty attack, CTP successfully assessed hemodynamic changes. • The ascending rate of MVD was the highest among that of all parameters; so was the descending rate of CL.

JNK pathway in osteoarthritis: pathological and therapeutic aspects

CONTEXT

Osteoarthritis (OA) is a common chronic degenerative joint disease resulting in physical disability and reduced quality of life. Different biochemical signaling pathways are involved in the progression of OA, including the c-Jun NH2-terminal kinase (JNK) signal transduction pathway.

OBJECTIVE

In this study, we have reviewed the recent updates on the association of JNK pathway with OA.

METHODS

In this review, we have explored the databases like PubMed, Google Scholar, Medline, Scopus, etc., and collected the most relevant papers of JNK signaling pathway involved in the pathogenesis and therapeutics of OA Results: JNK has been shown by scientific studies to be activated (phosphorylated) in OA that can play a key role in the cartilage destruction. Activation of JNK causes the phosphorylation of c-Jun that causes decreased proteoglycan synthesis and enhanced production of matrix metalloproteinase 13 (MMP-13). Overproduction of MMP-13 by chondrocytes plays a central role in cartilage degeneration in OA. Thus, targeting JNK pathway might be a promising therapeutic application for the prevention and treatment of OA. A number of JNK-inhibitors have been used in vitro and in vivo studies; however, not yet been translated into human use.

CONCLUSIONS

This review study indicates that JNK pathway plays an important role in development and progression of OA, and targeting the JNK pathway might be a potential approach for the treatment of OA in future.

Supporting shared hypothesis testing in the biomedical domain

Background

Pathogenesis of inflammatory diseases can be tracked by studying the causality relationships among the factors contributing to its development. We could, for instance, hypothesize on the connections of the pathogenesis outcomes to the observed conditions. And to prove such causal hypotheses we would need to have the full understanding of the causal relationships, and we would have to provide all the necessary evidences to support our claims. In practice, however, we might not possess all the background knowledge on the causality relationships, and we might be unable to collect all the evidence to prove our hypotheses.

Results

In this work we propose a methodology for the translation of biological knowledge on causality relationships of biological processes and their effects on conditions to a computational framework for hypothesis testing. The methodology consists of two main points: hypothesis graph construction from the formalization of the background knowledge on causality relationships, and confidence measurement in a causality hypothesis as a normalized weighted path computation in the hypothesis graph. In this framework, we can simulate collection of evidences and assess confidence in a causality hypothesis by measuring it proportionally to the amount of available knowledge and collected evidences.

Conclusions

We evaluate our methodology on a hypothesis graph that represents both contributing factors which may cause cartilage degradation and the factors which might be caused by the cartilage degradation during osteoarthritis. Hypothesis graph construction has proven to be robust to the addition of potentially contradictory information on the simultaneously positive and negative effects. The obtained confidence measures for the specific causality hypotheses have been validated by our domain experts, and, correspond closely to their subjective assessments of confidences in investigated hypotheses. Overall, our methodology for a shared hypothesis testing framework exhibits important properties that researchers will find useful in literature review for their experimental studies, planning and prioritizing evidence collection acquisition procedures, and testing their hypotheses with different depths of knowledge on causal dependencies of biological processes and their effects on the observed conditions.

Long noncoding RNAs in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis that may affect all joint tissues. Unfortunately, the pathogenesis of OA is not fully understood yet and it cannot be cured totally. Long noncoding RNA (lncRNA) is a type of RNA molecule greater than 200 nucleotides, and deregulated expression of lncRNAs plays an important role in many types of inflammation-related diseases. In this review, we have focused on the association of lncRNAs in the development and progression of OA and the possibility of lncRNAs as a therapeutic agent for the treatment of OA. Some lncRNAs are up-regulated in OA cartilage, and plays a critical role in the degradation of chondrocyte extracellular matrix, consequently weakening the integrity of the articular cartilage. Therapeutic targeting of these lncRNAs has shown significant influence on controlling OA progression. More clinical studies are in focus for OA treatment strategy by targeting lncRNAs.

Bone marrow lesions in hip osteoarthritis are characterized by increased bone turnover and enhanced angiogenesis

OBJECTIVE

Bone marrow lesions (BML), previously denoted bone marrow edema, are detected as water signals by magnetic resonance imaging (MRI). Previous histologic studies were unable to demonstrate any edematous changes at the tissue level. Therefore, our aim was to investigate the underlying biological mechanisms of the water signal in MRI scans of bone affected by BML.

METHODS

Tetracycline labeling in addition to water sensitive MRI scans of 30 patients planned for total hip replacement surgery was undertaken. Twenty-one femoral heads revealed BML on MRI, while nine were negative and used as controls (CON). Guided by the MRI images cylindrical biopsies were extracted from areas with BML in the femoral heads. Tissue sections from the biopsies were subjected to histomorphometric image analyses of the cancellous bone envelope.

RESULTS

Patients with BML exhibited an average 40- and 18-fold increase of bone formation rate and mineralizing surface, respectively. Additionally, samples with BML demonstrated 2-fold reduction of marrow fat and 28-fold increase of woven bone. Immunohistochemical analysis showed a 4-fold increase of angiogenesis markers CD31 and von Willebrand Factor (vWF) in the BML-group compared to CON.

CONCLUSION

This study indicates that BML are characterized by increased bone turnover, vascularity and angiogenesis in keeping with it being a reparatory process. Thus, the water signal, which is the hallmark of BML on MRI, is most probably reflecting increased tissue vascularity accompanying increased remodeling activity.

[Immunomorphological characteristics of the synovial membrane in rheumatic diseases]

The synovial membrane is frequently a target in rheumatic diseases. A search for diagnostic criteria and determination of changes in the pathological process necessitate standardized biopsy diagnostic techniques and quantification of morphological changes using digital imaging methods. The paper considers main methods for obtaining synovial membrane samples. It presents major morphological and immunohistochemical variations in synovitis in the presence of rheumatoid arthritis, ankylosing spondylitis, and osteoarthrosis. It shows different immunological and autoinflammatory mechanisms of these diseases. Synovial membrane inflammation in rheumatoid arthritis, ankylosing spondylitis, and osteoarthrosis is characterized by different components of morphogenesis, which is proven by the expression of different cell markers. Rheumatoid synovitis is an autoinflammatory process; synovitis in ankylosing spondylitis is characterized by autoinflammatory processes; biomechanical factors as joint inflammation triggers are leading in osteoarthrosis.

Low-grade inflammation as a key mediator of the pathogenesis of osteoarthritis

Osteoarthritis (OA) has long been viewed as a degenerative disease of cartilage, but accumulating evidence indicates that inflammation has a critical role in its pathogenesis. Furthermore, we now appreciate that OA pathogenesis involves not only breakdown of cartilage, but also remodelling of the underlying bone, formation of ectopic bone, hypertrophy of the joint capsule, and inflammation of the synovial lining. That is, OA is a disorder of the joint as a whole, with inflammation driving many pathologic changes. The inflammation in OA is distinct from that in rheumatoid arthritis and other autoimmune diseases: it is chronic, comparatively low-grade, and mediated primarily by the innate immune system. Current treatments for OA only control the symptoms, and none has been FDA-approved for the prevention or slowing of disease progression. However, increasing insight into the inflammatory underpinnings of OA holds promise for the development of new, disease-modifying therapies. Indeed, several anti-inflammatory therapies have shown promise in animal models of OA. Further work is needed to identify effective inhibitors of the low-grade inflammation in OA, and to determine whether therapies that target this inflammation can prevent or slow the development and progression of the disease.

Mutually Supportive Mechanisms of Inflammation and Vascular Remodeling

Chronic inflammation is often accompanied by angiogenesis, the development of new blood vessels from existing ones. This vascular response is a response to chronic hypoxia and/or ischemia, but is also contributory to the progression of disorders including atherosclerosis, arthritis, and tumor growth. Proinflammatory and proangiogenic mediators and signaling pathways form a complex and interrelated network in these conditions, and many factors exert multiple effects. Inflammation drives angiogenesis by direct and indirect mechanisms, promoting endothelial proliferation, migration, and vessel sprouting, but also by mediating extracellular matrix remodeling and release of sequestered growth factors, and recruitment of proangiogenic leukocyte subsets. The role of inflammation in promoting angiogenesis is well documented, but by facilitating greater infiltration of leukocytes and plasma proteins into inflamed tissues, angiogenesis can also propagate chronic inflammation. This review examines the mutually supportive relationship between angiogenesis and inflammation, and considers how these interactions might be exploited to promote resolution of chronic inflammatory or angiogenic disorders.

Identification of Targets of a New Nutritional Mixture for Osteoarthritis Management Composed by Curcuminoids Extract, Hydrolyzed Collagen and Green Tea Extract

Objective

We have previously demonstrated that a mixture of curcuminoids extract, hydrolyzed collagen and green tea extract (COT) inhibited inflammatory and catabolic mediator’s synthesis by osteoarthritic human chondrocytes. The objective of this study was to identify new targets of COT using genomic and proteomic approaches.

Design

Cartilage specimens were obtained from 12 patients with knee osteoarthritis. Primary human chondrocytes were cultured in monolayer until confluence and then incubated for 24 or 48 hours in the absence or in the presence of human interleukin(IL)-1β (10^-11M) and with or without COT, each compound at the concentration of 4 μg/ml. Microarray gene expression profiling between control, COT, IL-1β and COT IL-1β conditions was performed. Immunoassays were used to confirm the effect of COT at the protein level.

Results

More than 4000 genes were differentially expressed between conditions. The key regulated pathways were related to inflammation, cartilage metabolism and angiogenesis. The IL-1β stimulated chemokine ligand 6, matrix metalloproteinase-13, bone morphogenetic protein-2 and stanniocalcin1 gene expressions and protein productions were down-regulated by COT. COT significantly decreased stanniocalcin1 production in basal condition. Serpin E1 gene expression and protein production were down-regulated by IL-1β. COT reversed the inhibitory effect of IL-1β. Serpin E1 gene expression was up-regulated by COT in control condition.

Conclusion

The COT mixture has beneficial effect on osteoarthritis physiopathology by regulating the synthesis of key catabolic, inflammatory and angiogenesis factors. These findings give a scientific rationale for the use of these natural ingredients in the management of osteoarthritis.

Interleukin-1β induces fibroblast growth factor 2 expression and subsequently promotes endothelial progenitor cell angiogenesis in chondrocytes

Angiogenesis is an important event in the process of arthritis. Stimulating chondrocytes with IL-1β increased the expression of FGF-2, via the IL-1RI/ROS/AMPK/p38/NF-κB signalling pathway. FGF-2-neutralizing antibody abolished ATDC5-conditional medium-mediated angiogenesis both in vitro and in vivo.

Arthritis is a process of chronic inflammation that results in joint damage. IL (interleukin)-1β is an inflammatory cytokine that acts as a key mediator of cartilage degradation, and is abundantly expressed in arthritis. Neovascularization is one of the pathological characteristics of arthritis. However, the role of IL-1β in the angiogenesis of chondrocytes remains unknown. In the present study, we demonstrate that stimulating chondrocytes (ATDC5) with IL-1β increased the expression of FGF (fibroblast growth factor)-2, a potent angiogenic inducer, and then promoted EPC (endothelial progenitor cell) tube formation and migration. In addition, FGF-2-neutralizing antibody abolished ATDC5-conditional medium-mediated angiogenesis in vitro, as well as its angiogenic effects in the CAM (chick chorioallantoic membrane) assay and Matrigel plug nude mice model in vivo. IHC (immunohistochemistry) staining from a CIA (collagen-induced arthritis) mouse model also demonstrates that arthritis increased the expression of IL-1β and FGF-2, as well as EPC homing in articular cartilage. Moreover, IL-1β-induced FGF-2 expression via IL-1RI (type-1 IL-1 receptor), ROS (reactive oxygen species) generation, AMPK (AMP-activated protein kinase), p38 and NF-κB (nuclear factor κB) pathway has been demonstrated. On the basis of these findings, we conclude that IL-1β promotes FGF-2 expression in chondrocytes through the ROS/AMPK/p38/NF-κB signalling pathway and subsequently increases EPC angiogenesis. Therefore IL-1β serves as a link between inflammation and angiogenesis during arthritis.

The Long Noncoding RNA MEG3 Is Downregulated and Inversely Associated with VEGF Levels in Osteoarthritis

Osteoarthritis (OA) is becoming a major public health problem in China, especially considering the increase in average life expectancy of the population. Thus, enhanced understanding of the molecular changes associated with OA is urgently needed to develop more effective strategies for the diagnosis and treatment of this debilitating disease. LncRNAs play an important role in the processes of bone and cartilage development. Maternally expressed gene 3 (MEG3) is a maternally expressed lncRNA and may function as a tumor suppressor by inhibiting angiogenesis. OA is closely associated with angiogenesis and the inhibition of angiogenesis presents a novel therapeutic approach to reduce inflammation and pain in OA. In this study, we detected the mRNA expression of MEG3 and VEGF in articular cartilage samples from 20 OA patients and 10 healthy volunteers by real-time RT-PCR. VEGF protein is detected by ELISA in cartilage samples. The results show that human MEG3 is significantly downregulated in OA patients compared to normal cartilage samples. However, higher levels of VEGF mRNA and protein are found in OA compared to the control. Moreover, MEG3 levels are inversely associated with VEGF levels, suggesting that MEG3 may be involved in OA development through the regulation of angiogenesis.

Comparison of periprosthetic tissues in knee and hip joints: differential expression of CCL3 and DC-STAMP in total knee and hip arthroplasty and similar cytokine profiles in primary knee and hip osteoarthritis

OBJECTIVE

To identify expression profiles (EP) associated with aseptic loosening of total knee arthroplasty (TKA) and to compare them with EP observed in total hip arthroplasty (THA), and primary knee and hip osteoarthritis (OA).

DESIGN

Gene EP of TNF, IL-6, IL-8, CHIT1, BMP4, CCL3, CCL18, MMP9, RANKL, OPG, DC-STAMP and SOCS3 were assessed using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) on tissues retrieved from patients with aseptically failed TKA (n = 21), THA (n = 41) and primary knee (n = 20) and hip (n = 17) OA. Immunohistochemistry was applied to localize the proteins.

RESULTS

When compared to knee OA, the pseudosynovial tissue in TKA exhibit (1) elevation of alternative macrophage activation marker (CHIT1), chemokine (IL-8), and a proteolytic enzyme (MMP9); (2) downregulation of pro-inflammatory cytokine (TNF), osteoclastic regulator (OPG) and a stimulator of bone formation (BMP4); (3) no difference in IL-6, CCL3, CCL18, RANKL, DC-STAMP and SOCS3. The EP in TKA differed from EP in aseptically failed THA by lower CCL3 and DC-STAMP mRNA and protein expression. EP of all studied inflammatory and osteoclastogenic molecules were similar in knee and hip OA.

CONCLUSIONS

Comparing to OA, aseptic loosening of TKA is associated with upregulated expression of CHIT1, IL-8 and MMP9, dysregulated RANKL:OPG ratio and low levels of inflammatory cytokines. Similar cytokine profiles were associated with primary knee and hip OA. Further research is required to explain the differences in CCL3 and DC-STAMP expression between failed TKA and THA.

The characteristics of thrombin in osteoarthritic pathogenesis and treatment

Osteoarthritis (OA) is a mechanical abnormality associated with degradation of joints. It is characterized by chronic, progressive degeneration of articular cartilage, abnormalities of bone, and synovial change. The most common symptom of OA is local inflammation resulting from exogenous stress or endogenous abnormal cytokines. Additionally, OA is associated with local and/or systemic activation of coagulation and anticoagulation pathways. Thrombin plays an important role in the stimulation of fibrin deposition and the proinflammatory processes in OA. Thrombin mediates hemostatic and inflammatory responses and guides the immune response to tissue damage. Thrombin activates intracellular signaling pathways by interacting with transmembrane domain G protein coupled receptors (GPCRs), known as protease-activated receptors (PARs). In pathogenic mechanisms, PARs have been implicated in the development of acute and chronic inflammatory responses in OA. Therefore, discovery of thrombin signaling pathways would help us to understand the mechanism of OA pathogenesis and lead us to develop therapeutic drugs in the future.