Tumor necrosis factor-alpha (TNF-alpha) in canine osteoarthritis: Immunolocalization of TNF-alpha, stromelysin and TNF receptors in canine osteoarthritic cartilage

Association Between Sleep Apnea Syndrome and Osteoarthritis: Insights from Bidirectional Mendelian Randomization and Bioinformatics Analysis

Background

Sleep apnea syndrome(SAS) and osteoarthritis (OA) are two prevalent diseases that often coexist, but the causal relationship between them remains unclear. In light of this, our team utilizes Mendelian Randomization and bioinformatics analysis methods to investigate the potential association between the two diseases.

Methods

In this study, we utilized GWAS data pertaining to SAS and OA to assess the causal relationship between the two diseases through Mendelian randomization (MR) analysis. We then employed transcriptomic data to perform differential gene identification, WGCNA, shared gene determination, functional enrichment analysis, and colocalization analysis, all designed to further elucidate the mechanisms underlying the association between the two diseases. In the end, we utilized Mendelian randomization (MR) analysis again to delve deeper into the relationship between the two diseases and immune cells.

Results

Our research findings indicate that SAS is a risk factor for OA (p = 0.000004), knee OA (p = 0.0000001) and hip OA(p = 0.001). Furthermore, OA (p = 0.000195), knee OA (p = 0.001) are significant risk factors for SAS. However, there is no clear evidence that hip OA (p = 0.892) is a risk factor for SAS. Interestingly, the genes shared between OA and SAS are significantly enriched in leukocyte migration, leukocyte chemotaxis. Moreover, colocalization analysis suggests that the genes JUNB, COL8A1, FOSB, and IER2 may be key genes associated with both diseases. Furthermore, 57 immune cell phenotypes are associated with SAS, 95 with OA, and 6 shared between both diseases.

Conclusion

This research confirmed the bidirectional causal relationship between SAS and OA. Notably, the 4 genes (JUNB, COL8A1, FOSB, IER2) and 6 immune phenotypes are crucial for both diseases, these provide hopeful targets for future interventions against these two diseases.

Structure-based development of a canine TNF-α-specific antibody using adalimumab as a template

The canine anti-tumor necrosis factor-alpha (TNF-α) monoclonal antibody is a potential therapeutic option for treating canine arthritis. The current treatments for arthritis in dogs have limitations due to side effects, emphasizing the need for safer and more effective therapies. The crystal structure of canine TNF-α (cTNF-α) was successfully determined at a resolution of 1.85 Å, and the protein was shown to assemble as a trimer, with high similarity to the functional quaternary structure of human TNF-α (hTNF-α). Adalimumab (Humira), a known TNF-α inhibitor, effectively targets and neutralizes TNF-α to reduce inflammation and has been used to manage autoimmune conditions such as rheumatoid arthritis. By comparing the structure of cTNF-α with the complex structure of hTNF-α and adalimumab-Fab, the epitope of adalimumab on cTNF-α was identified. The significant structural similarities of epitopes in cTNF-α and hTNF-α indicate the potential of using adalimumab to target cTNF-α. Therefore, a canine/human chimeric antibody, Humivet-R1, was created by grafting the variable domain of adalimumab onto a canine antibody framework derived from ranevetmab. Humivet-R1 exhibits potent neutralizing ability (IC50  = 0.05 nM) and high binding affinity (EC50  = 0.416 nM) to cTNF-α, comparable to that of adalimumab for both hTNF-α and cTNF-α. These results strongly suggest that Humivet-R1 has the potential to provide effective treatment for canine arthritis with reduced side effects. Here, we propose a structure-guided antibody design for the use of a chimeric antibody to treat canine inflammatory disease. Our successful development strategy can speed up therapeutic antibody discovery for animals and has the potential to revolutionize veterinary medicine.

Harpagide inhibits the TNF-α-induced inflammatory response in rat articular chondrocytes by the glycolytic pathways for alleviating osteoarthritis

Osteoarthritis (OA) causes severe and functional dysfunction due to abnormal inflammation. The objective of this study was to evaluate the effect of Harpagide (HPG) on TNF-α-induced inflammation in vitro and in vivo. The effect of HPG on the proliferation of rat chondrocytes was studied. The anti-inflammatory effect of HPG and its molecular mechanisms were elucidated by qPCR, Western blotting, flow cytometry, metabolome analysis in vitro. In addition, the OA rat model was established, and the effect of HPG on OA was verified in vivo. We revealed 10 μM HPG demonstrated biocompatibility. The results demonstrated that HPG restored the upregulation of MMP-13, COX2, IL-1β and IL-6 induced by TNF-α. Moreover, HPG reversed TNF-α induced degradation of the extracellular matrix of chondrocytes. TNF-α treatment induced down-regulation of the mRNA/protein levels of proliferative markers Bcl2, CDK1 and Cyclin D1 were also recovered. HPG can inhibit TNF-α-induced inflammatory response through glycolytic metabolic pathways. HPG can restore TNF-α-induced upregulation of GRP78/IRE1α, and downregulation of AMPK proteins. In vivo experiments demonstrated that after HPG treatment, the appearance and physiological structure of articular cartilage were more integrated with highly organized chondrocytes and rich cartilage matrix compared with OA group. Finally, the molecular docking of HPG and selected key factors in glycolysis results showed that HPG had good binding potential with PFKM, PFKP, PFKFB3, PKM, HK2, and PFKL. In conclusion, the results shown HPG protects and activates chondrocytes, inhibits TNF-α-induced inflammatory response by glycolysis pathway in rat articular chondrocytes, and plays a role in the treatment of OA.

Role of Interleukin-17 family cytokines in disease severity of patients with knee osteoarthritis

BACKGROUND

Interleukin-17 (IL-17) family plays a role in the pathogenesis of knee osteoarthritis (KOA) by contributing to the inflammatory and destructive processes in the affected joint. This study aimed to measure levels of IL-17 A and IL-25 (IL-17E) in serum of KOA patients and determine their roles in the disease severity of patients.

METHODS

In this, 34 patients with KOA and 30 age and sex-matched healthy subjects (HS) were enrolled. Patients were categorized based on their Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Visual Analog Scale (VAS), and Body Mass Index (BMI) scores. The enzyme-linked immunosorbent assay (ELISA) technique was employed to measure serum levels of IL-17 A and IL-25.

RESULTS

Level of IL-25 was significantly higher (P < 0.0001) in the KOA subjects than HS. IL-17 A level was significantly higher in KOA cases with WOMAC < 40 (P < 0.0001) in comparison to HS. IL-25 level was significantly higher in the KOA cases with WOMAC < 40 (P < 0.0001) and with WOMAC ≥ 40 (P < 0.0001) compared to HS. IL-17 A concentration was significantly higher in the KOA cases with VAS < 5 (P < 0.0001) compared to HS. IL-25 level was significantly higher in the KOA cases with VAS < 5 (P < 0.0001) and with VAS ≥ 5 (P < 0.0001) in comparison to HS. KOA patients with BMI ≥ 30 had significantly higher IL-17 A and IL-25 concentration in comparison to HS.

CONCLUSIONS

The serum level of IL-25 in KOA patients is increased probably due to negative controlling feedback on inflammatory responses, which can be associated with obesity and disease activity.

The Single Intra-Articular Injection of Platelet-Rich Plasma vs. Non-Steroidal Anti-Inflammatory Drugs as Treatment Options for Canine Cruciate Ligament Rupture and Patellar Luxation

Cranial cruciate ligament rupture (CCLR) and patellar luxation (PL) are common pathologies affecting canines. Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used as a non-surgical treatment plan in these cases. Clinical usage of platelet-rich plasma (PRP) is an emerging area of interest in veterinary medicine. There is a lack of studies comparing those two different treatment methods in veterinary medicine. The main purpose of this study was to evaluate and compare the use of oral NSAIDs and single intra-articular injection of PRP on treatment outcomes in cases of canine CCLR and PL. Dogs diagnosed with CCRL (n = 12) and PL (n = 10) were subgrouped by the severity of pathologies and administered treatment: half of the CCRL and PL groups were orally administered NSAIDs and supplements for 14 days, and the other half received a single intra-articular PRP injection into affected stifle joint. We measured serum TNF-α levels and clinical outcomes (lameness scores, painfulness to manipulations, goniometry of stifle joint in flexion and extension, and muscle strength) before treatment, at day 14 and day 28 of treatment. The results of TNF-α concentration indicates a significant difference between groups of differently treated partial CCLR groups on d14 (p = 0.006). Results of group CCLR-P1 on d14 were decreased, while results of group CCLR-P2 on d14 were increased. When comparing TNF-α concentration between all CCLR cases treated with NSAIDs and treated with PRP, there was a significant difference between those groups on d14 (p = 0.001). The results of TNF-α concentration indicates a significant difference between groups of differently treated PL-III on d28 (p = 0.036). Results of group PL-III1 indicate growth of TNF-α concentration, while at the same d28, results of group PL-III2 indicate decreased levels of cytokine, comparing results between the subgroups at the same time point and within subgroups from baseline. Results indicate a significant difference in muscle strength between group CCLR-P1 and group CCLR-P2 on d28 (p = 0.007), indicating an increment in muscle strength in group CCLR-P1 up to d14 and its reduction up to d28, and muscle strength of group CCLR-P2 increasing up to d28. When comparing the muscle strength between all CCLR cases treated with NSAIDs and treated with PRP, there was a significant difference between those groups on d28 (p = 0.007). In conclusion, a single intra-articular injection of PRP has a superior effect on management of inflammatory processes, has better clinical outcomes, and longer duration of action than oral NSAIDs, in the treatment of canine CCRL or PL.

Air pollution exposure and auto-inflammatory and autoimmune diseases of the musculoskeletal system: a review of epidemiologic and mechanistic evidence

Auto-inflammatory and autoimmune diseases of the musculoskeletal system can be perceived as a spectrum of rheumatic diseases, with the joints and connective tissues are eroded severely that progressively develop chronic inflammation and lesion. A wide range of risk factors represented by genetic and environmental factors have been uncovered by population-based surveys and experimental studies. Lately, the exposure to air pollution has been found to be potentially involved in the mechanisms of occurrence or development of such diseases, principally manifest in oxidative stress, local and systemic inflammation, and epigenetic modifications, as well as the mitochondrial dysfunction, which has been reported to participate in the intermediate links. The lungs might serve as a starting area of air pollutants, which would cause oxidative stress-induced bronchial-associated lymphoid tissue (iBALT) to further to influence T, B cells, and the secretion of pro-inflammatory cytokines. The binding of aromatic hydrocarbon receptor (AhR) to the corresponding contaminant ligands tends to regulate the reaction of Th17 and Tregs. Furthermore, air pollution components might spur on immune and inflammatory responses by damaging mitochondria that could interact with and exacerbate oxidative stress and pro-inflammatory cytokines. In this review, we focused on the association between air pollution and typical auto-inflammatory and autoimmune diseases of the musculoskeletal system, mainly including osteoarthritis (OA), rheumatoid arthritis (RA), spondyloarthritis (SpA) and juvenile idiopathic arthritis (JIA), and aim to collate the mechanisms involved and the potential channels. A complete summary and in-depth understanding of the autoimmune and inflammatory effects of air pollution exposure should hopefully contribute new perspectives on how to formulate better public health policies to alleviate the adverse health effects of air pollutants.

Polymeric Nanoparticles for Drug Delivery in Osteoarthritis

Osteoarthritis (OA) is a degenerative musculoskeletal disorder affecting the whole synovial joint and globally impacts more than one in five individuals aged 40 and over, representing a huge socioeconomic burden. Drug penetration into and retention within the joints are major challenges in the development of regenerative therapies for OA. During the recent years, polymeric nanoparticles (PNPs) have emerged as promising drug carrier candidates due to their biodegradable properties, nanoscale structure, functional versatility, and reproducible manufacturing, which makes them particularly attractive for cartilage penetration and joint retention. In this review, we discuss the current development state of natural and synthetic PNPs for drug delivery and OA treatment. Evidence from in vitro and pre-clinical in vivo studies is used to show how disease pathology and key cellular pathways of joint inflammation are modulated by these nanoparticle-based therapies. Furthermore, we compare the biodegradability and surface modification of these nanocarriers in relation to the drug release profile and tissue targeting. Finally, the main challenges for nanoparticle delivery to the cartilage are discussed, as a function of disease state and physicochemical properties of PNPs such as size and surface charge.

Magnolin exhibits anti-inflammatory effects on chondrocytes via the NF-κB pathway for attenuating anterior cruciate ligament transection-induced osteoarthritis

Purpose: This study aimed to investigate whether magnolin (MGL) possesses the capability of suppressing inflammatory responses that can in turn alleviate osteoarthritis (OA).Methods: We investigated the effects of MGL on the viability of rat chondrocytes at concentrations of 5 to 100 µM, and selected 10 µM for further study. We elucidated the molecular mechanisms and signaling pathways mediating these effects via RNA sequencing, qRT-PCR, immunofluorescent staining, and Western blotting techniques. Following this, we established an anterior cruciate ligament (ACL) transection-induced OA rat model, and injected MGL into the knee articular cavities to verify the in vivo anti-inflammatory effects of MGL.Results: We found that MGL could recover the TNF-α-induced upregulation of IL-1β, COX2, ADAMTS-5, and MMP-1/3/13 at the gene/protein level, as well as the downregulation of cartilaginous ECM synthesis. Gene expression profiles of different groups identified 49 common differentially expressed genes (DEGs), which were mainly enriched in the structural constituents of the ribosome, the extracellular space, and inflammatory response. The NF-κB pathway was highly enriched, and the expression levels of DEGs associated with it (Nfkbia, Ptgs2, Rela, Tnfrsf1a, Tradd, Traf2) under TNF-α stimulation were reversed by MGL. Further studies proved that MGL simultaneously suppressed the cell nucleus translocation of p65 and the phosphorylation of IκBα. Moreover, in vivo, MGL suppressed cartilage matrix degradation, inhibited MMP-13 expression, and promoted cartilage matrix construction by upregulating SOX9 synthesis.Conclusion: MGL demonstrated significant anti-inflammatory bioactivity on chondrocytes by suppressing the activation of NF-κB pathway, which in turn exhibited a significant alleviation of OA.

Blocking TNFα attenuates progressive cartilage matrix degradation in inflammatory arthritis

Because damage to hyaline cartilage is irreversible, relieving progressive cartilage destruction is an important therapeutic approach for inflammatory arthritis. In the present study, human hyaline chondrocytes were isolated from total knee replacements of 15 patients with osteoarthritis (OA) and three with rheumatoid arthritis (RA). Synovial fluid of OA (n=25) and RA (n=34) were collected to measure tumor necrosis factor α (TNFα) using ELISA. Consistent with previous studies, the synovial fluid exhibited high TNFα levels and hyaline cartilage was severely destroyed in patients with RA. TNFα-treated chondrocytes were used as model for inflammatory arthritis. TNFα did not influence proliferation or extracellular matrix expression in chondrocytes, but induced matrix metalloproteinase (MMP)1, 3 and 13 expression levels in chondrocytes, which was accompanied by activation of nuclear factor-κB signaling. During chondrogenic differentiation, TNFα attenuated mRNA expression levels of anabolic factors (collagen type 2 and aggrecan) and enhanced mRNA expression of catabolic factors (MMP1, MMP3 and MMP13) in chondrocytes. Moreover, anti-TNFα agents (Golimumab) inhibited the TNFα-induced metabolic shift in chondrocytes and chondrogenic differentiation. The present study revealed a mechanism by which TNFα may induce metabolic shift in chondrocytes, leading to progressive chondrocyte destruction.

Interleukin-1-Interleukin-17 Signaling Axis Induces Cartilage Destruction and Promotes Experimental Osteoarthritis

Osteoarthritis (OA), which is the most common degenerative joint disorder, has been considered a non-inflammatory disease with abnormal mechanics. Interleukin (IL)-17 is a pleiotropic cytokine involved in inflammatory diseases and their production is driven by the cytokine including IL-1 and IL-23. However, little is known about the mechanism of IL-17 in the development of OA. Here, we investigated the role of IL-17 in the pathogenesis of OA using monosodium iodoacetate (MIA)-injected IL-17 and IL-1 receptor antagonist (IL-1Ra) double-deficient mice. In MIA-injected IL-1Ra KO mice, nociceptive properties, degree of cartilage damage, and the level of inflammatory factors in articular cartilage were increased compared to MIA-injected wild-type mice. Interestingly, the intestinal architecture was impaired in IL-1Ra KO mice compared to wild-type mice and the damage was further exacerbated by MIA injection. Deficiency of IL-17 reduced nociceptive properties and cartilage destruction, as well as inflammation-related factors in MIA-injected IL-1Ra KO mice compared to MIA-injected wild-type mice. Furthermore, IL-17-treated chondrocytes from OA patients showed enhanced expression of catabolic factors that are involved in the destruction of cartilage in OA. IL-17 accelerates the destruction of cartilage and small intestine via regulation of several inflammatory mediators in an OA murine model. These results suggest that IL-17 plays a critical role in the development of OA.

Psoralen Protects Chondrocytes, Exhibits Anti-Inflammatory Effects on Synoviocytes, and Attenuates Monosodium Iodoacetate-Induced Osteoarthritis

Current study examined whether psoralen (PSO) exhibits anti-inflammatory responses, protection and activation of chondrocytes, and relieve osteoarthritis (OA). Rats chondrocytes and human synoviocytes were cultured in tumor necrosis factor-α (TNF-α) conditioned culture medium with/without PSO to test the cell morphologies and cytotoxicities in vitro. Cartilaginous extracellular matrix (ECM) and proliferative gene/protein expression levels were evaluated in chondrocytes. Meanwhile, matrix metalloproteinases (MMPs) and interleukins (ILs) gene/protein expression were analyzed in synoviocytes. SD rats of monosodium iodoacetate (MIA) induced OA model were used in order to assess the effects of PSO on attenuating degeneration of the articular cartilage in vivo. Results showed TNF-α conditioned culturing with/without PSO (1-100 µM) had no any toxicity on both the cell lines. PSO (10 µM) activated cartilaginous specific ECM expression along with up-regulation of proliferative genes at transcriptional levels. Interestingly, PSO significantly reversed TNF-α induced up-regulation of MMP13 and ILs synoviocytes in a dose-dependent manner (1 to 20 µM), while down-regulated cartilaginous ECM production. Following six weeks of PSO treatments to articular cartilage osteoarthritis, compared to MIA-induced group, the appearance and physiological structure of articular cartilage was more integrated with greatly organized chondrocytes and abundant cartilage matrix. In conclusion, PSO protects and activates chondrocytes, antagonizing the expression of MMPs and ILs secreted by synovial cells, and effectively attenuates MIA-induced OA.

The Therapeutic Effect of STAT3 Signaling-Suppressed MSC on Pain and Articular Cartilage Damage in a Rat Model of Monosodium Iodoacetate-Induced Osteoarthritis

Osteoarthritis (OA) is a degenerative disease that induces pain, cartilage deformation, and joint inflammation. Mesenchymal stem cells (MSCs) are potential therapeutic agents for treatment of OA. However, MSC therapy can cause excessive inflammation. Signal transducer and activator of transcription 3 (STAT3) modulates secretion of many proinflammatory cytokines. Experimental OA was induced by intra-articular (IA) injection of monosodium iodoacetate (MIA) to the right knee of rats. MSCs from OA patients (OA-MSCs) were treated with STA21, a small molecule that blocks STAT3 signaling, by IA or intravenous (IV) injection after MIA injection. Pain severity was quantified by assessment of secondary tactile allodynia using the von Frey assessment test. Cartilage degradation was measured by microcomputed tomography image analysis, histological analysis, and the Mankin score. Protein and gene expression was evaluated by enzyme-linked immunosorbent assay, immunohistochemistry, and real-time polymerase chain reaction. MSCs increased production of proinflammatory cytokines under inflammatory conditions. STA21 significantly decreased expression of these proinflammatory molecules via inhibition of STAT3 activity but increased gene expression of molecules related to migration potential and immunomodulation in OA-MSCs. STAT3-inhibited OA-MSCs administrated by IV or IA injection decreased pain severity and cartilage damage in rats with MIA-induced OA rats by decreasing proinflammatory cytokines in the joints. Combined IA and IV-injected STAT3-inhibited OA-MSCs had an additive effect of pain relief in MIA-induced OA rats. STAT3 inhibition may optimize the therapeutic activities of MSCs for treating OA by attenuating pain and progression of MIA by inhibiting inflammation and cartilage damage.

Kartogenin inhibits pain behavior, chondrocyte inflammation, and attenuates osteoarthritis progression in mice through induction of IL-10

Osteoarthritis (OA) is a major degenerative joint condition that causes articular cartilage destruction. It was recently found that enhancement of chondroclasts and suppression in Treg cell differentiation are involved in the pathogenesis of OA. Kartogenin (KGN) is a small drug-like molecule that induces chondrogenesis in mesenchymal stem cells (MSCs). This study aimed to identify whether KGN can enhance severe pain behavior and improve cartilage repair in OA rat model. Induction of OA model was loaded by IA-injection of MIA. In the OA rat model, treatment an intra-articular injection of KGN. Pain levels were evaluated by analyzing PWL and PWT response in animals. Histological analysis and micro-CT images of femurs were used to analyze cartilage destruction. Gene expression was measured by real-time PCR. Immunohistochemistry was analyzed to detect protein expression. KGN injection significantly decreased pain severity and joint destruction in the MIA-induced OA model. KGN also increased mRNA levels of the anti-inflammatory cytokine IL-10 in OA patients’ chondrocytes stimulated by IL-1β. Decreased chondroclast expression, and increased Treg cell expression. KGN revealed therapeutic activity with the potential to reduce pain and improve cartilage destruction. Thus, KGN could be a therapeutic molecule for OA that inhibits cartilage damage.

Lactobacillus acidophilus ameliorates pain and cartilage degradation in experimental osteoarthritis

Osteoarthritis (OA) is a chronic and degenerative disease that causes pain, cartilage deformation, and joint inflammation. Lactobacillus species have been used as dietary supplements to induce the production of antimicrobial and anti-inflammatory factors. The goal of this study was to determine whether Lactobacillus acidophilus ameliorates monosodium iodoacetate-induced OA. L. acidophilus showed anti-nociceptive properties and protected against cartilage destruction. It also downregulated the levels of proinflammatory cytokines and increased the levels of anti-inflammatory cytokines in the joints of OA rats. L. acidophilus additionally restored the balance between anabolic and catabolic factors in chondrocytes from OA patients. These results suggest that L. acidophilus can alleviate OA-associated pain and delay the progression of the disease by inhibiting proinflammatory cytokine production and reducing cartilage damage.

Protective Effects of Garlic-Derived S-Allylmercaptocysteine on IL-1β-Stimulated Chondrocytes by Regulation of MMPs/TIMP-1 Ratio and Type II Collagen Expression via Suppression of NF-κB Pathway

Background

Garlic-derived S-allylmercaptocysteine (SAMC) has widely been used in many disease therapies. However, the potential effects and mechanism of SAMC on IL-1β-stimulated chondrocytes are unclear.

Methods

Chondrocytes were isolated, and 5 ng/mL of IL-1β was added to mimic the in vitro osteoarthritis (OA) model. SAMC (20 and 60 μM) was used for the treatment in OA model. Cell viability was assessed by MTT method. Western blotting, Quantitative RT-PCR, and ELISA were performed to evaluate the mechanisms in SAMC treated OA model.

Results

Following 48 h of IL-1β exposure, SAMC exhibited protection effect on IL-1β-injured chondrocyte viability. Type II collagen was elevated with reduced degradation products, as a consequence of altered MMPs/TIMP-1 ratio after SAMC treatment in IL-1β-treated chondrocytes. The protein and mRNA level of TNF-α in cellular supernatant and cells were downregulated in a dose-dependent manner. Besides, IκBα in cytoplasmic fraction was increased, while p65 level in nuclear fraction was decreased after SAMC treatment in OA.

Conclusions

This study showed that SAMC may play a protective role in IL-1β induced osteoarthritis (OA) model. This effect may be through inhibiting the NF-κB signaling pathway, therefore altering the MMPs/TIMP-1 ratio change which induced type II collagen destruction and decreasing inflammatory cytokine secretion such as TNF-α.

Genome-Wide DNA Methylation Study Identifies Significant Epigenomic Changes in Osteoarthritic Subchondral Bone and Similarity to Overlying Cartilage

OBJECTIVE

To perform a genome-wide DNA methylation study to identify differential DNA methylation patterns in subchondral bone underlying eroded and intact cartilage from patients with hip osteoarthritis (OA) and to compare these with DNA methylation patterns in overlying cartilage.

METHODS

Genome-wide DNA methylation profiling using Illumina HumanMethylation 450 arrays was performed on eroded and intact cartilage and subchondral bone from within the same joint of 12 patients undergoing hip arthroplasty. Genes with differentially methylated CpG sites were analyzed to identify shared pathways, upstream regulators, and overrepresented gene ontologies, and these patterns were compared with those of the overlying cartilage. Histopathology was graded by modified Mankin score and assessed for correlation with DNA methylation.

RESULTS

We identified 7,316 differentially methylated CpG sites in subchondral bone underlying eroded cartilage, most of which (∼75%) were hypomethylated, and 1,397 sites in overlying eroded cartilage, 126 of which were shared. Samples clustered into 3 groups with distinct histopathologic scores. We observed differential DNA methylation of genes including the RNA interference-processing gene AGO2, the growth factor TGFB3, the OA suppressor NFATC1, and the epigenetic effector HDAC4. Among known susceptibility genes in OA, 32 were differentially methylated in subchondral bone, 8 were differentially methylated in cartilage, and 5 were shared. Upstream regulator analysis using differentially methylated genes in OA subchondral bone showed a strong transforming growth factor β1 signature (P = 1 × 10(-40) ) and a tumor necrosis factor family signature (P = 3.2 × 10(-28) ), among others.

CONCLUSION

Our data suggest the presence of an epigenetic phenotype associated with eroded OA subchondral bone that is similar to that of overlying eroded OA cartilage.

Oxygen tension modulates the effects of TNFα in compressed chondrocytes

OBJECTIVE AND DESIGN

Oxygen tension and biomechanical signals are factors that regulate inflammatory mechanisms in chondrocytes. We examined whether low oxygen tension influenced the cells response to TNFα and dynamic compression.

MATERIALS AND METHODS

Chondrocyte/agarose constructs were treated with varying concentrations of TNFα (0.1-100 ng/ml) and cultured at 5 and 21 % oxygen tension for 48 h. In separate experiments, constructs were subjected to dynamic compression (15 %) and treated with TNFα (10 ng/ml) and/or L-NIO (1 mM) at 5 and 21 % oxygen tension using an ex vivo bioreactor for 48 h. Markers for catabolic activity (NO, PGE₂) and tissue remodelling (GAG, MMPs) were quantified by biochemical assay. ADAMTS-5 and MMP-13 expression were examined by real-time qPCR. 2-way ANOVA and a post hoc Bonferroni-corrected t test were used to analyse data.

RESULTS

TNFα dose-dependently increased NO, PGE₂ and MMP activity (all p < 0.001) and induced MMP-13 (p < 0.05) and ADAMTS-5 gene expression (pp < 0.01) with values greater at 5 % oxygen tension than 21 %. The induction of catabolic mediators by TNFα was reduced by dynamic compression and/or L-NIO (all p < 0.001), with a greater inhibition observed at 5% than 21 %. The stimulation of GAG synthesis by dynamic compression was greater at 21 % than 5 % oxygen tension and this response was reduced with TNFα or reversed with L-NIO.

CONCLUSIONS

The present findings revealed that TNFα increased production of NO, PGE₂ and MMP activity at 5 % oxygen tension. The effects induced by TNFα were reduced by dynamic compression and/or the NOS inhibitor, linking both types of stimuli to reparative activities. Future therapeutics should develop oxygen-sensitive antagonists which are directed to interfering with the TNFα-induced pathways.

Spontaneously developed osteoarthritis in the temporomandibular joint in STR/ort mice

Temporomandibular joint (TMJ) osteoarthritis is typically a slowly progressive asymmetric disease. Little is known regarding the natural destruction of TMJ articular tissues. The aim of the present study was to investigate morphological changes in the TMJ of STR/ort mice, known to be the model for spontaneous osteoarthritis in the knee joint, and to evaluate STR/ort mice as a suitable animal model for TMJ osteoarthritis. TMJs from 32 STR/ort mice euthanized at 30, 40, 50 or 60 weeks of age, and from 6 CBA mice euthanized at 30, 40 or 60 weeks of age were examined. Toluidine blue and tartrate-resistant acid phosphatase staining were used to assess histological changes in the articular cartilage. Morphological changes in the articular cartilage of the TMJ were evaluated using microcomputed tomography. At the age of 40-50 weeks, 17 (68%) of the 25 STR/ort mice had loss of articular cartilage on histology, with cavitation and erosion of the exposed bone and gradual changes in condylar shape. Furthermore, osteoarthritic morphological changes, and structural alterations were observed by microcomputed tomography. The STR/ort mouse strain appears to develop spontaneous osteoarthritis-like lesions in the TMJ with age, and would be a useful model to study the pathogenesis of TMJ osteoarthritis.

Tissue engineering strategies to study cartilage development, degeneration and regeneration

Cartilage tissue engineering has primarily focused on the generation of grafts to repair cartilage defects due to traumatic injury and disease. However engineered cartilage tissues have also a strong scientific value as advanced 3D culture models. Here we first describe key aspects of embryonic chondrogenesis and possible cell sources/culture systems for in vitro cartilage generation. We then review how a tissue engineering approach has been and could be further exploited to investigate different aspects of cartilage development and degeneration. The generated knowledge is expected to inform new cartilage regeneration strategies, beyond a classical tissue engineering paradigm.

Effects of cyclic tensile strain on chondrocyte metabolism: a systematic review

Chondrocytes reorganize the extracellular matrix of articular cartilage in response to externally applied loads. Thereby, different loading characteristics lead to different biological responses. Despite of active research in this area, it is still unclear which parts of the extracellular matrix adapt in what ways, and how specific loading characteristics affect matrix changes. This review focuses on the influence of cyclic tensile strain on chondrocyte metabolism in vitro. It also aimed to identify anabolic or catabolic chondrocyte responses to different loading protocols. The key findings show that loading cells up to 3% strain, 0.17 Hz, and 2 h, resulted in weak or no biological responses. Loading between 3–10% strain, 0.17–0.5 Hz, and 2–12 h led to anabolic responses; and above 10% strain, 0.5 Hz, and 12 h catabolic events predominated. However, this review also discusses that various other factors are involved in the remodeling of the extracellular matrix in response to loading, and that parameters like an inflammatory environment might influence the biological response.

Expression of gelatinases (MMP-2, MMP-9) in human articular cartilage

Osteoarthritis (OA) is a chronic degenerative joint disorder characterized by destruction of the articular cartilage, subchondral bone alterations and synovitis. Matrix metalloproteinases (MMPs) are expressed in joint tissues of patients with osteoarthritis (OA). The objective of this study was to define the steady state levels of two different MMPs to provide more insight into the role of MMPs in cartilage destruction in OA. We investigated the expression of gelatinases through immunohistochemistry Our results show that high levels of MMP-2 and MMP-9 are present in OA and suggest that once these MMPs are fully activated they may contribute to the cartilage destruction in OA.

Influence of the molecular weight of poly(lactide-co-glycolide) on the in vivo cartilage repair by a construct of poly(lactide-co-glycolide)/fibrin gel/mesenchymal stem cells/transforming growth factor-β1

The poly(lactide-co-glycolide) (PLGA, LA/GA 75/25) sponges with different weight average molecular weights (Mw 52, 122, and 177 kDa) were fabricated and were used to build the constructs of PLGA/fibrin gel/mesenchymal stem cells (MSCs)/transforming growth factor-β1 (TGF-β1). The PLGA 177 with the highest Mw (177 kDa) had the fastest degradation rate at the initial stage, whereas the PLGA 122 had the moderate degradation rate and smallest mass loss. After implantation in rabbit knees for 12 weeks, the full-thickness defects (both cartilage and subchondral bone were destroyed with a diameter and depth of 4 mm) repaired by the PLGA 122 group had formed a hyaline cartilage-like tissue with abundant glycosaminoglycans on the top layer and subchondral bone on the bottom layer. The group also achieved the best macroscopic (11.3 ± 0.8) and histological scoring (Wakitani, 0.5 ± 0.6). To unveil the mechanism of the cartilage repair outcome and the PLGA degradation behaviors, the chondrogenesis-related genes, inflammatory cytokines, and matrix metalloproteinase (MMP) activity were analyzed by quantitative reverse transcription-polymerase chain reaction at week 1, 3, and 6 postsurgery. At each time point, the regenerated tissues by the PLGA 122 group had the highest mRNA expression of SOX9 and collagen type II, but the smallest mRNA expression of interleukin-1β and tumor necrosis factor α, and MMP-13 and MMP-3. In summary, as a scaffolding matrix, the PLGA with different Mw shows a huge difference in cartilage regeneration in vivo. The one with a moderate Mw (122 kDa) causes the weakest inflammatory response and results in the best cartilage regeneration.

The role of changes in extracellular matrix of cartilage in the presence of inflammation on the pathology of osteoarthritis

Osteoarthritis (OA) is a degenerative disease that affects various tissues surrounding joints such as articular cartilage, subchondral bone, synovial membrane, and ligaments. No therapy is currently available to completely prevent the initiation or progression of the disease partly due to poor understanding of the mechanisms of the disease pathology. Cartilage is the main tissue afflicted by OA, and chondrocytes, the sole cellular component in the tissue, actively participate in the degeneration process. Multiple factors affect the development and progression of OA including inflammation that is sustained during the progression of the disease and alteration in biomechanical conditions due to wear and tear or trauma in cartilage. During the progression of OA, extracellular matrix (ECM) of cartilage is actively remodeled by chondrocytes under inflammatory conditions. This alteration of ECM, in turn, changes the biomechanical environment of chondrocytes, which further drives the progression of the disease in the presence of inflammation. The changes in ECM composition and structure also prevent participation of mesenchymal stem cells in the repair process by inhibiting their chondrogenic differentiation. This review focuses on how inflammation-induced ECM remodeling disturbs cellular activities to prevent self-regeneration of cartilage in the pathology of OA.

Expression of peroxisome proliferator-activated receptors α, β, γ, and H- and L-prostaglandin D synthase during osteoarthritis in the spontaneous hartley guinea pig and experimental dog models

OBJECTIVE

To investigate the expression of peroxisome proliferator-activated receptors (PPAR) α, β, and γ, and hematopoietic and lipocalin-type prostaglandin D synthase (H- and L-PGDS) over the course of osteoarthritis (OA) in the spontaneous Hartley guinea pig and the anterior cruciate ligament transection dog models.

METHODS

Guinea pigs were sacrificed at 2 (control group), 4, 8, and 12 months of age (n = 5 per group). Non-operated (control) and operated dogs were sacrificed at 4, 8, and 12 weeks postsurgery. Cartilage was evaluated histologically using the Osteoarthritis Research Society International (OARSI) guidelines. The expression of PPAR-α, β, γ, and H- and L-PGDS was evaluated by real-time PCR and immunohistochemistry. The nonparametric Spearman test was used for correlation analysis.

RESULTS

PPAR-α, β, and γ were detected in medial tibial plateau from control animals in both the spontaneous and surgical models. Levels of PPAR-α and β did not change over the course of OA, whereas PPAR-γ levels decreased during progression of disease. We also observed that the expression of H-PGDS remained unchanged, whereas L-PGDS increased over the course of OA. PPAR-γ levels correlated negatively, whereas L-PGDS levels correlated positively, with the histological score of OA.

CONCLUSION

The level of PPAR-γ decreased, whereas level of L-PGDS increased during the progression of OA. These data suggest that reduced expression of PPAR-γ may contribute to the pathogenesis of OA, whereas enhanced expression of L-PGDS may be part of a reparative process.

The effect of therapeutic ultrasound to apoptosis of chondrocyte and caspase-3 and caspase-8 expression in rabbit surgery-induced model of knee osteoarthritis

Recent studies have shown a positive correlation between the degree of severity of OA and the number of apoptotic chondrocytes. The purpose of our study was to determine the effect of therapeutic ultrasound on apoptosis in articular cartilage of rabbits with knee osteoarthritis (KOA). Thirty 3-month New Zealand White rabbits were randomizingly divided into three groups, 10 in each group. Two groups underwent anterior cruciate ligament transaction in the right knee and another group left intact. Six weeks later, one group of the operated rabbits (OA-US) underwent ultrasound therapy (300 mW/cm(2), 1 MHz, 20% duty cycle, 10 min each day) for 2 weeks, while the other two groups (OA-Control and Normal Control) left untreated. Eight weeks after transection, all animals were killed. Microscopic morphologic grading was made for histological assessment. The caspases expressions and chondrocytes apoptosis were tested using the immunohistochemistry and TUNEL assessment, respectively. The mean grading of OA-US group was significantly higher than Normal Control group (P = 0.002), but significantly lower than OA-Control group (P = 0.002). Percentage of apoptosis and the optic density of cells expressing caspase-3 and caspase-8 in the three groups showed no statistical significances. Therapeutic ultrasound (300 mW/cm(2), 1 MHz, and 20% duty cycle) could relieve the degree of severity of induced KOA, while it had no effect on apoptosis and the expression of caspase-3 and caspase-8. These findings may provide a certain support for therapeutic ultrasound as an effective access to managing KOA.

Serum resistin level is associated with radiographic changes in hand osteoarthritis: cross-sectional study

OBJECTIVE

The aim of this study was to determine whether adipokines such as adiponectin and resistin were related to radiographic outcomes in patients with hand osteoarthritis (OA).

METHODS

A total of 156 female subjects (46 controls, 60 non-radiographic hand OA, and 50 radiographic hand OA) were enrolled. We measured serum adiponectin and resistin concentrations using an enzyme-linked immunosorbent assay (ELISA). Radiographic hand OA was defined by the presence of a ≥2 Kellgren-Lawrence radiological grade after assessment for 20 joints of both hands. The association between radiographic hand OA and each adipokine was assessed using multivariate logistic regression models controlling for confounding clinical parameters.

RESULTS

Serum resistin levels in radiographic hand OA patients were higher than in non-radiographic hand OA and controls (p(adj)=0.020 and p(adj)=0.019, respectively), whereas there were no significant differences in serum adiponectin levels. The presence of radiographic changes in hand OA was shown to be dependent on serum resistin levels (p(adj)=0.028). Specifically, subchondral erosion in radiographic hand OA was associated with serum resisitin (p(adj)=0.028). However, there were no associations of serum adipokines with joint space narrowing, bony ankylosis, and cortical destruction.

CONCLUSIONS

This study suggests that resistin is involved in radiographic changes in hand OA, and that adipokines contribute to pathogenesis in radiographic outcomes in hand OA.

Treatment with TNF-α inhibitor infliximab might reduce hand osteoarthritis in patients with rheumatoid arthritis

OBJECTIVES

To investigate the association between systemic and local inflammation and incident and progressive radiographic secondary osteoarthritis (OA) in interphalangeal joints (IPJs) over 3 years in rheumatoid arthritis (RA) patients and the effect of tumor necrosis factor alpha (TNF-α) inhibitor infliximab on secondary OA in IPJs.

METHODS

In the present observational longitudinal study baseline and 3-year hand X-rays of 416 recent-onset RA patients were scored for osteophytes and erosions in IPJs, blinded for time, using Osteoarthritis Research Society International atlas and Sharp-van der Heijde score. The associations between inflammatory factors and incident and progressive secondary OA in distal IPJs (DIPJs) and proximal IPJs (PIPJs) and the effect of infliximab compared to disease-modifying anti-rheumatic drug treatment on secondary OA were analyzed by multivariable regression and generalised estimating equations analyses.

RESULTS

Sixty-seven percent of the patients were female with, at baseline, a mean age of 54 years and OA present in DIPJs and PIPJs in 37% and 13%. Three years later, new secondary OA in DIPJs and PIPJs was seen in 11% and 10%, and progressive secondary OA in 36% and 35%. High erythrocyte sedimentation rate over 3 years and progressive erosive damage were risk factors for incident secondary OA in DIPJs, but not in PIPJs. At joint level, progression of erosions was associated with both incident and progressive secondary OA, only in DIPJs. Infliximab treatment was associated with lower incident secondary OA in PIPJs [relative risk 0.5 (95% confidence interval 0.2, 1.0)], independent of decrease in inflammation.

CONCLUSION

Incident and progressive secondary OA in DIPJs over 3 years was associated with high inflammatory activity in RA. Infliximab treatment reduced incident secondary OA in PIPJs independent of decrease in inflammation, suggesting that anti-TNF-α therapy might be effective against secondary hand OA via other pathways than suppression of inflammation. Further studies in populations of primary hand OA are necessary to determine the role of anti-TNF-α in treatment of primary hand OA.

Erosive osteoarthritis: a current review of a clinical challenge

Erosive osteoarthritis, a less common subtype of osteoarthritis, is often described as a more severe form. This combination of cartilage degeneration with pathologic features suggestive of inflammatory synovial changes generally manifests in women around the time of menopause and hormonal levels as well as genetics are thought to play a role in its onset. The hands are most often involved with the sudden onset of palpable pain and swelling of the distal interphalangeal joints and proximal interphalangeal joints most frequently, but other joints have been reported. Phalangeal deformities appearing as wavy or subluxed as well as Heberden and Bouchard nodes can be seen clinically. Laboratory tests for systemic inflammation are usually normal but small studies looking at markers of bone resorption have shown increased levels in these patients. Radiographs reveal central joint erosions implying an inflammatory process which has been described in synovial specimens. Treatment options that have been tried include those utilized for general osteoarthritis as well as those for rheumatoid arthritis. Since prolonged disability in hand function can occur, further studies looking at its pathogenesis and targeted treatment options are needed.

Evolutional patterns of articular cartilage following growth plate injury in rats

BACKGROUND

No study to date has analyzed the damage of the articular cartilage and its relation to growth plate injury. The purpose of this study was to test whether primary injury to the growth plate contributes to secondary damage to the articular cartilage in rats.

METHODS

A total of 109 two-week-old male Wistar rats were allocated to four lesional groups. In group I (controls) no surgery took place. In the remaining animals, an injury was caused in the proximal physis of the left tibia: group II, perichondrial ring injury; group III, direct injury to the growth plate; group IV, traumatic separation of the epiphysis where a Salter-Harris II-type injury was created. The results were assessed at 1 week, 6 weeks, and 6 months. A growth plate score was used. The stereological and histological changes in the articular cartilage were analyzed, and the results were subjected to statistical analysis.

RESULTS

Histological studies showed discrete degenerative changes in the articular cartilage in the injured growth plate. Changes in the cell density, mean cell volume, and articular cartilage occurred in the injured growth plate. The changes appeared to be transient in groups II and III.

CONCLUSIONS

Primary injury to the growth plate contributes to secondary damage to the articular cartilage in young rats. Our data -- extrapolated to the clinical view -- suggests that a Salter-Harris type II injury does not seem to have impunity to subsequent joint degeneration.

Cyclic AMP regulates extracellular matrix gene expression and metabolism in cultured primary rat chondrocytes

In osteo- and rheumatoid arthritis, the synovial fluid surrounding chondrocytes contains increased levels of prostaglandin E(2) (PGE(2)), an agent known to elevate intracellular cyclic AMP (cAMP). However, the effect of PGE(2)/cAMP on mRNA expression in chondrocytes is largely unknown. In this report, we assess the effect of the cell-permeable cAMP analog adenosine 8-(4-chloro-phenylthio)-3',5'-cyclic monophosphate (CPT-cAMP) and PGE(2) on mRNA expression in primary neonatal rat chondrocytes. CPT-cAMP decreased type II collagen, link protein, parathyroid hormone/parathyroid hormone-related peptide receptor and alkaline phosphatase, increased glyceraldehyde-3-phosphate dehydrogenase mRNA and lactate efflux, but did not alter type X collagen or aggrecan mRNA. The effect of CPT-cAMP on type II collagen and link protein mRNAs and chondrocyte metabolism were attenuated by the transcriptional inhibitor actinomycin D, indicating that the ability of CPT-cAMP to suppress mRNA expression was not due to alterations in mRNA stability, but were instead likely due to transcriptional mechanisms. CPT-cAMP-treatment induced GSK3 beta phosphorylation and beta-catenin-mediated transcriptional activity. Pharmacological inhibition of GSK3 beta paralleled the effects of CPT-cAMP on type II collagen, link protein and chondrocyte metabolism, suggesting that the effect of CPT-cAMP on chondrocytes may be GSK3 beta/beta-catenin-dependent. The effects of CPT-cAMP on beta-catenin-mediated transcription, cell metabolism and mRNA expression were mimicked by the cAMP-elevating agent PGE(2), providing a physiologically relevant context for our studies. Collectively, these results suggest that agents that elevate cAMP signaling may impair chondrocyte function in conditions such as arthritis.

Treatment of erosive osteoarthritis of the hands by intra-articular infliximab injections: a pilot study

Our pilot study aimed to investigate the efficacy and tolerability of intra-articular (i.a.) injections of infliximab as a therapy for erosive osteoarthritis of the hands. Ten women with bilateral involvement of the hands and typical erosive osteoarthritis radiographic findings were enrolled and followed for 12 months. All the patients were refractory to conventional drugs. Treatment consisted in monthly i.a. injections of 0.2 ml of infliximab (0.1 mg/ml) in each affected proximal and distal interphalangeal joint of the most involved hand, identified on the basis of clinical and radiological examinations. The other hand was treated with physiological saline (control). The patients did not know which hand was receiving infliximab. Clinical response was evaluated at enrollment, after 6 and 12 months. Posteroanterior radiographs of both hands were obtained at baseline and 12 months later. At 6 months all the patients experienced relief from spontaneous pain and pain on lateral pressure in the hand treated with infliximab and these findings became statistically significant after 1 year. No important modifications were recognized in the hand treated with physiological saline. The anatomical lesion progression system radiological score indicated a reduction, even if not statistically significant, in the hand treated with infliximab and a tendency to slow worsening in the hand treated with physiological saline at 12-month follow-up. No local or systemic adverse reactions were recorded. Our study shows the symptomatic effect and a possible disease modifying action of i.a. infliximab in erosive osteoarthritis of the hands.

Egr-1 inhibits the expression of extracellular matrix genes in chondrocytes by TNFalpha-induced MEK/ERK signalling

Introduction

TNFα is increased in the synovial fluid of patients with rheumatoid arthritis and osteoarthritis. TNFα activates mitogen-activated kinase kinase (MEK)/extracellular regulated kinase (ERK) in chondrocytes; however, the overall functional relevance of MEK/ERK to TNFα-regulated gene expression in chondrocytes is unknown.

Methods

Chondrocytes were treated with TNFα with or without the MEK1/2 inhibitor U0126 for 24 hours. Microarray analysis and real-time PCR analyses were used to identify genes regulated by TNFα in a MEK1/2-dependent fashion. Promoter/reporter, immunoblot, and electrophoretic mobility shift assays were used to identify transcription factors whose activity in response to TNFα was MEK1/2 dependent. Decoy oligodeoxynucleotides bearing consensus transcription factor binding sites were introduced into chondrocytes to determine the functionality of our results.

Results

Approximately 20% of the genes regulated by TNFα in chondrocytes were sensitive to U0126. Transcript regulation of the cartilage-selective matrix genes Col2a1, Agc1 and Hapln1, and of the matrix metalloproteinase genes Mmp-12 and Mmp-9, were U0126 sensitive – whereas regulation of the inflammatory gene macrophage Csf-1 was U0126 insensitive. TNFα-induced regulation of Sox9 and NFκB activity was also U0126 insensitive. Conversely, TNFα-increased early growth response 1 (Egr-1) DNA binding was U0126 sensitive. Transfection of chondrocytes with cognate Egr-1 oligodeoxynucleotides attenuated the ability of TNFα to suppress Col2a1, Agc1 or Hapln1 mRNA expression.

Conclusions

Our results suggest that MEK/ERK and Egr1 are required for TNFα-regulated catabolic and anabolic genes of the cartilage extracellular matrix, and hence may represent potential targets for drug intervention in osteoarthritis or rheumatoid arthritis.

Regulation of Sox9 activity by crosstalk with nuclear factor-kappaB and retinoic acid receptors

Introduction

Sox9 and p300 cooperate to induce expression of cartilage-specific matrix proteins, including type II collagen, aggrecan and link protein. Tumour necrosis factor (TNF)-α, found in arthritic joints, activates nuclear factor-κB (NF-κB), whereas retinoic acid receptors (RARs) are activated by retinoid agonists, including all-trans retinoic acid (atRA). Like Sox9, the activity of NF-κB and RARs depends upon their association with p300. Separately, both TNF-α and atRA suppress cartilage matrix gene expression. We investigated how TNF-α and atRA alter the expression of cartilage matrix genes.

Methods

Primary cultures of rat chondrocytes were treated with TNF-α and/or atRA for 24 hours. Levels of transcripts encoding cartilage matrix proteins were determined by Northern blot analyses and quantitative real-time PCR. Nuclear protein levels, DNA binding and functional activity of transcription factors were assessed by immunoblotting, electrophoretic mobility shift assays and reporter assays, respectively.

Results

Together, TNF-α and atRA diminished transcript levels of cartilage matrix proteins and Sox9 activity more than each factor alone. However, neither agent altered nuclear levels of Sox9, and TNF-α did not affect protein binding to the Col2a1 48-base-pair minimal enhancer sequence. The effect of TNF-α, but not that of atRA, on Sox9 activity was dependent on NF-κB activation. Furthermore, atRA reduced NF-κB activity and DNA binding. To address the role of p300, we over-expressed constitutively active mitogen-activated protein kinase kinase kinase (caMEKK)1 to increase p300 acetylase activity. caMEKK1 enhanced basal NF-κB activity and atRA-induced RAR activity. Over-expression of caMEKK1 also enhanced basal Sox9 activity and suppressed the inhibitory effects of TNF-α and atRA on Sox9 function. In addition, over-expression of p300 restored Sox9 activity suppressed by TNF-α and atRA to normal levels.

Conclusion

NF-κB and RARs converge to reduce Sox9 activity and cartilage matrix gene expression, probably by limiting the availability of p300. This process may be critical for the loss of cartilage matrix synthesis in inflammatory joint diseases. Therefore, agents that increase p300 levels or activity in chondrocytes may be useful therapeutically.

Effects of intra-articular administration of glucosamine and a peptidyl-glucosamine derivative in a rabbit model of experimental osteoarthritis: a pilot study

The aim of this pilot study was to analyze the effects of glucosamine (GlcN) and its N-acetyl-phenylalanine derivative (NAPA) in Vitamin A model of osteoarthritis (OA) in rabbits. GlcN or NAPA or saline solution was intra-articularly administered in rabbit OA knees. Histological analysis revealed that treatment with GlcN or NAPA was associated with more homogeneous chondrocyte cellularity, absence of fissures and fragmentation and more intense staining of the matrix with Alcian Blue compared to the articular surfaces of the knees treated with saline solution. Comparative in vitro study performed on rabbit primary chondrocytes revealed that GlcN and NAPA were also able to counteract the IL-1beta-upregulation of genes coding for metalloproteases and inflammatory cytokines. Our preliminary in vivo and in vitro studies suggest that GlcN and NAPA could play a disease-modifying protective role in OA by an anti-catabolic effect and an anti-inflammatory activity on chondrocytes.

Cytokines as therapeutic targets for osteoarthritis

Osteoarthritis (OA) is a debilitating, progressive disease of diarthrodial joints associated with the aging process. With the exception of anti-inflammatory corticosteroids and nonsteroidal anti-inflammatory drugs which inhibit cyclo-oxygenase-2, the enzyme responsible for prostaglandin biosynthesis in inflammation, no specific therapy based on fundamental intracellular pathways of chondrocytes and synoviocytes exists for the medical management of OA. At the molecular level, OA is characterized by an imbalance between chondrocyte anabolism and catabolism. Disruption of chondrocyte homeostasis primarily affects the cartilage extracellular matrix (ECM), which is responsible for the biomechanical properties of the tissue. Recent evidence has implicated cytokines, among which interleukin (IL)-1, tumor necrosis factor-alpha, IL-6, and IL-17 seem most involved in the OA process of cartilage destruction. The primary role of these cytokines is to modulate the expression of matrix metalloproteinases and cartilage ECM proteins. Cartilage repair that could restore the functional integrity of the joint is also impaired because chondrocytes in OA cartilage appear unable to respond to insulin-like growth factor-1 or respond abnormally to transforming growth factor-beta. As these growth factors also modulate cytokine expression, they may prove useful in designing strategies for suppressing 'chondrocyte activation'. Although cytokines and growth factors provide a potential therapeutic target for OA, it will be necessary to elucidate the fundamental mechanisms that cytokines employ to cause chondrocyte and synoviocyte dysfunction before 'anti-cytokine' therapy can be employed in the medical management of the disease.

The fate of chondrocyte in osteoarthritic cartilage of transgenic mice expressing bovine GH

OBJECTIVE

The aim of the present study was to demonstrate whether bGH transgenic mice develop OA. We therefore studied in this animal model the structural features of cartilage and the subchondral bone changes of the knee joints that may be associated with osteoarthritic lesion.

METHOD

Degenerative changes in the knee joints of bGH transgenic female mice (N = 11) and control mice (N = 11) were histologically analyzed at the age of 7 months. Histochemical and stereological studies were conducted. Immunohistochemistry on cell cyclin activity (assessed by anti-PCNA labeling) and cell viability (assessed by bcl-2 expression), as well as ribosomal activity (AgNOR), TNF-alpha expression and apoptosis (TUNEL technique) were performed. In ten 7-month-old female mice (Tg+ N = 5; control N = 5) the knee articular cartilages were studied with electron microscopy techniques.

RESULTS

Disruption of the articular surface (18.2%), cleft (63.7%), cloning (81.8%), hypocellularity of chondrocytes (18.2%), moderate (54.6%) to severe (45.4%) loss of safranin-O staining, and duplication and rupture of the tidemark (54.5%) were some of the main features observed in articular cartilage chondrocytes of bGH transgenic mice. Furthermore, cell cyclin activity and cell viability decreased, while TNF-alpha expression and TUNEL+ cells increased. These chondrocytes also showed an increase in the number of black dots per cell, as revealed by the AgNOR technique.

CONCLUSION

Our results show that bGH transgenic mice develop a lesion of the articular cartilage consistent with that described in osteoarthritis.

TNFα suppresses link protein and type II collagen expression in chondrocytes: Role of MEK1/2 and NF-κB signaling pathways

Tumor necrosis factor alpha (TNFalpha) inhibits matrix synthesis by chondrocytes in rheumatoid arthritis and osteoarthritis; however, the underlying signaling pathways are poorly characterized. This study investigated the TNFalpha-activated pathways regulating expression of two key components of the cartilage matrix-link protein and type II collagen. In rat articular chondrocytes, TNFalpha decreased link protein and type II collagen mRNA to undetectable levels within 48 h. Levels of link protein mRNA recovered more readily than type II collagen mRNA following removal of the cytokine. TNFalpha-mediated reduction in mRNA of both matrix molecules occurred at the level of transcription and, for link protein, mRNA stability. Turnover of type II collagen and link protein mRNA was dependent on new protein synthesis. In both prechondrocytes and articular chondrocytes, TNFalpha induced concentration-dependent activation of MEK1/2 and NF-kappaB, but not p38 or JNK. Sustained activation of NF-kappaB was observed for up to 72 h following continuous or transient exposure to TNFalpha. Using pharmacological and molecular approaches, the MEK1/2 and NF-kappaB pathways were found to mediate inhibition of type II collagen and link protein gene expression by TNFalpha. Both prechondrocytes and articular chondrocytes are targets of TNFalpha. This study identifies pathways through which TNFalpha perturbs the synthesis and organization of articular cartilage matrix during inflammation.

Association of metalloproteinases, tissue inhibitors of matrix metalloproteinases, and proteoglycans with development, aging, and osteoarthritis processes in mouse temporomandibular joint

The temporomandibular joint (TMJ) is an important growth and articulation center in the craniofacial complex. In aging it develops spontaneous degenerative osteoarthritic (OA) lesions. Metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPS) play key roles in extracellular matrix remodeling and degradation. Gelatinase activities and immunohistochemical localization of MMP-2, -3, -8, -9, and -13 and TIMP-1 and -2 were examined in mandibular condyle cartilage of neonatal mice up to 18 months old. The most intense immunostaining for all enzymes and TIMPs and the peak of gelatinase activities were found in animals in the stages of early growth (1 week to 3 months) followed by a decrease during maturation and aging. However, clusters of positively immunoreactive chondrocytes were detected in cartilages of old animals displaying OA lesions. Positive safranin-O staining, indicative of sulfated proteoglycans (PGs), was prominent in the TMJ of newborn mice up to 3 months old followed by reduction during maturation and aging, except in regions displaying OA lesions. Temporal codistribution of PGs, MMPs, and TIMPs during skeletal maturation reflected an active growth phase, whereas their reduction coincided with the more quiescent articulating and maintenance phase in the joint cartilage. Osteoarthritic lesions were associated with both increased PG synthesis and MMP immunoreactivity, indicating limited repair activity during initial stages of osteoarthritis.

Presence of pannus-like tissue on osteoarthritic cartilage and its histological character

OBJECTIVE

To investigate and characterize pannus-like tissue which is often present on osteoarthritic articular cartilage.

DESIGN

Cartilage specimens from 15 knee and five hip joints of patients with osteoarthritis (OA) undergoing arthroplasty were stained for HE and Safranin-O. They were also immunostained by antitype I collagen, type II collagen, CD68, IL-1beta and MMP3 antibodies.

RESULTS

Ninety percent of joints have pannus-like tissue on the articular surface, preferentially in a marginal area. The articular cartilage was divided into three regions according to the location: the marginal zone, the intermediate zone and the paraeburnated zone. Pannuslike tissue in OA knee joint occurred 45.9%, 27.5% and 11.1% of the surface of each region respectively. Histologically, pannus-like tissue could be classified into the vascular type and the fibrous type. Extracellular matrix of both types of tissues were negative for Safranin-O and type II collagen, but positive for type I collagen. IL-1beta and MMP3 expressing cells are predominant in pannus-like tissue, whereas CD68 positive cells were infiltrated in only a few samples. Vascular type tissue kept continuity with bone marrow suggesting mesenchymal origin.

CONCLUSION

Pannus-like tissue exists in advanced OA cartilage, preferentially in the marginal zone. It expressed IL-1beta and MMP3, which strongly suggests that it contributes to cartilage degradation.

Effects of carprofen (R and S enantiomers and racemate) on the production of IL-1, IL-6 and TNF-alpha by equine chondrocytes and synoviocytes

Chondrocytes and synoviocytes harvested from the joints of healthy horses were maintained in tissue culture. Production of the cytokines interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) in response to lipopolysaccharide (LPS), and the effects of addition of carprofen (racemate and R and S enantiomers) were determined. Lipopolysaccharide failed to stimulate TNF-alpha activity in both cell types but concentrations of IL-1 and IL-6 were both increased in a concentration and time-related manner. Both carprofen enantiomers and the racemic mixture attenuated the increase in IL-6 induced by LPS in synoviocytes, and S carprofen exerted a similar effect on chondrocytes. Neither enantiomer nor the racemate of carprofen suppressed the increase in IL-1 release produced by LPS in chondrocytes and synoviocytes. An action of carprofen to suppress IL-6 release might contribute to the actions which occur in vivo.

Synovial fluid markers of osteoarthritis in dogs

Although none of these markers currently have any clinical applications, researchers have made strong advances in understanding molecular markers of OA and remain optimistic that the goal of identifying clinically useful markers of OA is attainable.(3-6,8,9) Much of this positive sentiment arises from the large array of molecules that have been identified.(8) Molecular markers of the greatest potential clinical use will be those that allow early detection of OA, permit disease progression to be monitored, or allow efficacy of various treatment regimens to be assessed. Earlier and more sensitive detection of OA changes may increase effective opportunities for treatment intervention during reversible phases of the OA disease process and allow more objective assessment of treatment efficacy and prognosis.(6)

Synovial fluid gelatinase concentrations and matrix metalloproteinase and cytokine expression in naturally occurring joint disease in horses

OBJECTIVES

To determine concentrations of matrix metalloproteinase (MMP)-2 and -9 in synovial fluid; and mRNA expression of MMP-1, -13, and -3; interleukin[IL]-1alpha and beta; and tumor necrosis factor (TNF)-alpha in synovial membrane and articular cartilage from horses with naturally occurring joint disease.

SAMPLE POPULATION

Synovial fluid (n = 76), synovial membrane (59), and articular cartilage (45) from 5 clinically normal horses and 55 horses with joint disease categorized as traumatic (acute [AT] or chronic [CT]), osteochondritis dissecans (OCD), or septic (S).

PROCEDURE

Synovial fluid gelatinase concentrations were analyzed, using zymography. Synovial membrane and articular cartilage mRNA expression for MMP-1, -3, and -13, IL-1alpha and beta, TNF-alpha, type-II collagen, and aggrecan were analyzed, using quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Synovial fluid pro-MMP-2 concentration was significantly higher in diseased joints than normal joints. Septic joints had significantly higher concentrations of pro and active MMP-9. Stromelysin-1 was expressed in > or = 80% of synovial membrane and articular cartilage samples and was strongly influenced by age. Collagenases were rarely expressed, with MMP-13 expressed only in diseased joints. Interleukin-1beta expression was significantly higher in all OCD samples and was influenced by age. Tumor necrosis factor-alpha expression was significantly higher in cartilage from joints with AT and OCD. There was no correlation between MMP or cytokines and type-II collagen or aggrecan expression.

CONCLUSIONS AND CLINICAL RELEVANCE

Matrix metalloproteinase-2 and -3 are abundant in naturally occurring joint disease and normal joints. Interleukin-1beta and TNF-alpha may be important in the pathogenesis of OCD. Age affects MMP and IL-1beta concentrations.

Expression of vitamin D receptors and matrix metalloproteinases in osteoarthritic cartilage and human articular chondrocytes in vitro

OBJECTIVES

To examine the in situ distributions of vitamin D receptors (VDR) and matrix metalloproteinases (MMPs) in osteoarthritic cartilage for comparison with non-arthritic, normal cartilage; and to assess the in vitro effects of 1alpha,25 dihydroxyvitaminD(3)(1alpha,25(OH)(2)D(3)) on MMPs-1, -3 and -9 and prostaglandin E(2)(PGE(2)) production by cultures of human articular chondrocytes (HAC) shown to be VDR-positive.

METHODS

Using immunohistochemistry VDR expression in different specimens of osteoarthritic cartilage (N=11) was compared to that in normal cartilage (N=6), along with the immunodetection of MMPs-1, -3 and -9. The effects of 1alpha25(OH)(2)D(3)on MMP and PGE(2)production by HAC in vitro, with and without stimulation by TNFalpha or phorbol myristate acetate (PMA), was evaluated using ELISA methodology.

RESULTS

VDR was demonstrated in HAC of all specimens of osteoarthritic cartilage, especially the superficial zone, whereas only two of five normal cartilage specimens were VDR(+)for a minor proportion of HAC. Immunolocalization of MMPs-1, -3 and -9 was often seen in areas where chondrocytes were VDR(+), and dual immunolocalization has demonstrated individual chondrocytes positive for both VDR and MMP-3 in situ. In vitro, 1alpha25(OH)(2)D(3)alone had no effect on MMP-1, -9 and PGE(2)production by HAC, but MMP-3 production was up-regulated by 1alpha25(OH)(2)D(3)either with or without stimulation with TNFalpha or PMA. By contrast the increased production of MMP-9 and PGE(2)induced by PMA was significantly suppressed by concomitant treatment with 1alpha25(OH)(2)D(3).

CONCLUSIONS

The demonstration of VDR expression by HAC in osteoarthritic cartilage was often associated with sites where MMP expression was prevalent, observations in contrast to their virtual absence in normal age-matched cartilage. Together with HAC in vitro studies, the data suggests that 1alpha25(OH)(2)D(3)contributes to the regulation of MMP and PGE(2)production by HAC in osteoarthritic cartilage.

Matrix metalloproteinase and proinflammatory cytokine production by chondrocytes of human osteoarthritic cartilage: associations with degenerative changes

OBJECTIVE

To examine by immunohistochemistry the relative distributions of 6 matrix metalloproteinases (MMPs 1, 2, 3, 8, 9, and 13) and the 2 proinflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) in osteoarthritic (OA) cartilage compared with normal, age-matched articular cartilage.

METHODS

Articular cartilage samples were obtained from the tibial plateau of OA knees removed at arthroplasty and from normal, nonarthritic, knees obtained at autopsy. Specimens were promptly fixed in Carnoy's fixative, processed, embedded in paraffin, sectioned, and examined by immunohistochemistry for MMP and cytokine production. In addition, human articular chondrocytes (HAC) were treated in vitro with either IL-1beta, TNFalpha, or phorbol myristate acetate (PMA) to assess their potential to produce each of the MMPs, as determined by Western blotting and gelatin zymography.

RESULTS

Immunodetection of the collagenases (MMPs 1, 8, and 13) and stromelysin 1 (MMP-3) was demonstrated in a proportion of chondrocytes in the superficial zone of almost all of the OA specimens that had degenerative matrix changes. The gelatinases (MMPs 2 and 9) were also demonstrated by immunohistochemistry but were not so prominent. IL-1beta- and TNFalpha-positive chondrocytes were also observed in a proportion of cells in the superficial zones of OA specimens. Much less immunostaining for MMPs and cytokines was observed in the deep zone of all OA specimens, where the cartilage matrix and chondrocyte morphology appeared normal. In contrast, full-thickness normal cartilage specimens showed virtually no immunostaining for these MMPs or cytokines. Confirmation that chondrocytes can produce these 6 MMPs was obtained from HAC cultures treated with either IL-1beta, TNFalpha, or PMA; conditioned medium from activated HAC contained all the MMPs demonstrated by immunohistochemistry. Dual immunolocalization studies of OA cartilage specimens demonstrated the coexpression of IL-1 with MMP-8 by individual chondrocytes in situ.

CONCLUSION

These results indicate that the superficial zone of OA cartilage specimens, which is characterized by fibrillations, chondrocyte clusters, and degenerative matrix changes, contains a variable proportion of cells that immunostain for IL-1beta, TNFalpha, and 6 different MMPs. These observations support the concept that cytokine-MMP associations reflect a modified chondrocyte phenotype and an intrinsic process of cartilage degradation in OA.

The role of cytokines as inflammatory mediators in osteoarthritis: lessons from animal models

Studies in animal models of osteoarthritis (OA) have been used extensively to gain insight into the pathogenesis of OA, but early studies largely ignored inflammation except as a secondary phenomenon. Synovitis has often been noted as a feature in experimental OA, and more recent work has established a central role for inflammatory cytokines as biochemical signals which stimulate chondrocytes to release cartilage-degrading proteinases. Thus, proteinase inhibitors, cytokine antagonists and receptor blocking antibodies, and growth/differentiation factors have been considered as potential therapeutic agents and targets for gene therapy. Although there is some disagreement, it is generally accepted that IL-1 is the pivotal cytokine at early and late stages, while TNF-alpha is involved primarily in the onset of arthritis. Other cytokines released during the inflammatory process in the OA joint may be regulatory (IL-6, IL-8) or inhibitory (IL-4, IL-10, IL-13, IFN-gamma). Furthermore, studies in animal models have illustrated the potentially beneficial effects of anticytokine therapy with monoclonal antibodies or receptor antagonists, although local rather than systemic delivery would be necessary for the largely localized OA in humans. Transgenic or knockout mice have also provided insights into general mechanisms of cytokine-induced cartilage degradation but have not directly addressed OA pathogenesis. Similarly, animals with spontaneous or transgenic modifications in cartilage matrix components, growth/differentiation factors, or developmentally regulated transcription factors have provided information about potential gene defects that predispose to OA without addressing the role of inflammatory mediators in cartilage destruction. Although the multiple etiologies of human OA indicate that it is more complex than any animal model, the use of appropriate, well-defined animal models will establish the feasibility of novel forms of therapy.

Tumor necrosis factor alpha can contribute to focal loss of cartilage in osteoarthritis

OBJECTIVE; To evaluate the potential for tumor necrosis factor alpha (TNFalpha)-induced focal loss of cartilage in osteoarthritic (OA) knee joints.

DESIGN

Fresh cartilage from specified regions of OA joints was immunostained for TNF-receptor (R) bearing chondrocytes. Cartilage explants from the same regions were cultured with or without small amounts of TNFalpha and cumulative GAG release into supernatants measured. Concentrations of TNFalpha, p55 and p75 soluble (s) TNF-R in supernatants from cultured OA and non-arthritic (NA) synovium were measured by ELISA.

RESULTS

TNF-R bearing chondrocytes were identified in OA cartilage; more specimens contained p55 TNF-R- than p75 TNF-R-bearing chondrocytes and differences in TNF-R distribution were apparent in cartilage from different regions of the same knees. TNFalpha at 5, 1, 0.5 and 0.25 ng/ml (but not 0.1 ng/ml) significantly increased glycosaminoglycans (GAG) release from cartilage explants in a dose-dependent manner. Variation in susceptibility to TNFalpha was observed in explants from different sites. TNFalpha and p75 sTNF-R, but not p55 sTNF-R, concentrations were significantly higher in OA, as compared with NA, supernatants. A significant correlation between TNFalpha and p75 sTNF-R measurements was apparent only in NA supernatants.

CONCLUSIONS

Variations in chondrocyte TNF-R expression occur in OA cartilage in vivo. TNFalpha at concentrations produced by OA synovium in vitro, can degrade cartilage matrix. In most OA supernatants sTNF-R concentrations were insufficient to abrogate the effects of TNFalpha. Thus conditions exist in some OA knees for TNFalpha to contribute to focal loss of cartilage.