Effects of high mobility group box protein-1, interleukin-1β, and interleukin-6 on cartilage matrix metabolism in three-dimensional equine chondrocyte cultures

Equine Autologous Conditioned Serum and Autologous Protein Solution

Orthobiologics are used with increasing frequency in equine musculoskeletal disease to improve the quality of the repair tissue and prevent reinjury. Autologous blood-based products, or hemoderivatives, are made by processing the patient's blood using different systems to produce a final therapeutic product. Autologous conditioned serum (ACS) and autologous protein solution (APS) are commonly used to treat joint disorders and can also be used treat tendon and ligament injuries. Hemoderivatives contain increased concentrations of anti-inflammatory and immunomodulatory cytokines, and growth factors that help direct tissue healing and repair. The specifics of ACS and APS for treatment of musculoskeletal injuries are discussed.

Conditioned serum in vitro treatment of chondrocyte pellets and osteoarthritic explants

BACKGROUND

Autologous conditioned serum (ACS) is used to treat osteoarthritis in horses, although its effects are not fully investigated.

OBJECTIVES

To investigate the effects of equine serum and conditioned serum on chondrocytes stimulated with interleukin (IL)-1β and cartilage explants with mild osteoarthritis.

STUDY DESIGN

In vitro experimental study.

METHODS

The effect of three different serum preparations (unincubated control [PS], serum incubated 24 h [PS24h] and serum incubated 24 h in ACS containers [PCS]) pooled from lame horses were tested in two in vitro models. IL-1β and IL-1 receptor antagonist (IL-1Ra) concentrations were measured in all sera. In model 1, chondrocyte pellet cultures were stimulated with IL-1β prior to treatment with the serum preparations for 2 and 48 h. Microarray, polymerase chain reaction, and matrix metallopeptidase-13 analyses were performed. In model 2, cartilage explants from horses with structural osteoarthritis were treated with PS or PCS on days 0, 6 and 12, or left untreated, and evaluated at day 24 using the OARSI grading scale for histological evaluation of articular cartilage.

RESULTS

The IL-1Ra concentration in PS24h and PCS was significantly higher than in PS. In model 1, inflammation- and cartilage matrix degradation-related genes were upregulated after 48 h in all treatment groups versus untreated controls. Cartilage matrix molecules, aggrecan and collagens, were downregulated in PS24h- and PCS-treated pellets versus untreated controls. Growth factor signalling genes were upregulated-FGF7 in all treatment groups, BMP2 in PS24h-, and INHBA in PCS-treated-compared with untreated controls. In model 2, the OARSI score at day 24 was not significantly different between treatment groups.

MAIN LIMITATIONS

Results from in vitro models cannot be directly translated to in vivo situations.

CONCLUSIONS

In vitro treatment with conditioned serum did not alleviate IL-1β-induced responses in chondrocyte pellets or lead to morphological improvement in osteoarthritic cartilage explants.

Distinct differences in immunological properties of equine orthobiologics revealed by functional and transcriptomic analysis using an activated macrophage readout system

Introduction

Multiple biological therapies for orthopedic injuries are marketed to veterinarians, despite a lack of rigorous comparative biological activity data to guide informed decisions in selecting a most effective compound. Therefore, the goal of this study was to use relevant bioassay systems to directly compare the anti-inflammatory and immunomodulatory activity of three commonly used orthobiological therapies (OTs): mesenchymal stromal cells (MSC), autologous conditioned serum (ACS), and platelet rich plasma (PRP).

Methods

Equine monocyte-derived macrophages were used as the readout system to compare therapies, including cytokine production and transcriptomic responses. Macrophages were stimulated with IL-1ß and treated 24 h with OTs, washed and cultured an additional 24 h to generate supernatants. Secreted cytokines were measured by multiplex immunoassay and ELISA. To assess global transcriptomic responses to treatments, RNA was extracted from macrophages and subjected to full RNA sequencing, using an Illumina-based platform. Data analysis included comparison of differentially expressed genes and pathway analysis in treated vs. untreated macrophages.

Results

All treatments reduced production of IL-1ß by macrophages. Secretion of IL-10 was highest in MSC-CM treated macrophages, while PRP lysate and ACS resulted in greater downregulation of IL-6 and IP-10. Transcriptomic analysis revealed that ACS triggered multiple inflammatory response pathways in macrophages based on GSEA, while MSC generated significant downregulation of inflammatory pathways, and PRP lysate induced a mixed immune response profile. Key downregulated genes in MSC-treated cultures included type 1 and type 2 interferon response, TNF-α and IL-6. PRP lysate cultures demonstrated downregulation of inflammation-related genes IL-1RA, SLAMF9, ENSECAG00000022247 but concurrent upregulation of TNF-α, IL-2 signaling, and Myc targets. ACS induced upregulation of inflammatory IL-2 signaling, TNFα and KRAS signaling and hypoxia, but downregulation of MTOR signaling and type 1 interferon signaling.

Discussion

These findings, representing the first comprehensive look at immune response pathways for popular equine OTs, reveal distinct differences between therapies. These studies address a critical gap in our understanding of the relative immunomodulatory properties of regenerative therapies commonly used in equine practice to treat musculoskeletal disease and will serve as a platform from which further in vivo comparisons may build.

The expression of nerve growth factor in healthy and inflamed equine chondrocytes analysed by capillary western immunoassay

Nerve Growth Factor (NGF) is a signalling molecule for pain and inflammation. NGF is increased in synovial fluid from osteoarthritic humans and animals, compared to healthy controls. Monoclonal antibody therapy directed against NGF has been approved to treat pain in osteoarthritic dogs but despite many years of trialling, therapy has not been approved for human use. One reason for this is that adverse reactions with rapidly progressing osteoarthritis has occurred in some individuals. More detailed knowledge of NGF expression in joints is needed. In this study, capillary-based Simple Western was used to analyse NGF in cultured equine chondrocytes. Chondrocytes were collected post mortem from three macroscopically healthy intercarpal joints and three intercarpal joints with mild osteoarthritic changes. The chondrocytes were expanded to passage one and seeded in chondrogenic medium to maintain the phenotype. On day four, cells were either stimulated with LPS or kept untreated in medium. All cells were harvested on day five. Wes analysis of lysates did not show mature NGF but two proforms, 40 and 45 kDa, were identified. Results were confirmed with western blot. The same proforms were expressed in chondrocytes from healthy and osteoarthritic joints. Acute inflammation induced by LPS stimulation did not change the forms of expressed NGF. Capillary Simple Western offers a sensitive and sample-sparing alternative to traditional western blot. However, confirmation of peaks is imperative in order to avoid misinterpretation of findings. In addition, in this case the method did not offer the possibility of quantification advertised by the manufacturers.

Bupivacaine in combination with sildenafil (Viagra) and vitamin D3 have anti-inflammatory effects in osteoarthritic chondrocytes

Aims

To treat osteoarthritic chondrocytes and thereby reduce the inflammation with a drug combination that primarily affects 5-HT- and ATP-evoked Ca²⁺ signaling. In osteoarthritic chondrocytes, Ca²⁺ signaling is elevated, resulting in increased production of ATP and inflammatory mediators. The expression of TLR4 and Na⁺/K⁺-ATPase was used to evaluate the inflammatory status of the cells.

Main methods

Equine chondrocytes were collected from joints with mild structural osteoarthritic changes and cultured in monolayers. The cells were treated with a combination of bupivacaine (1 pM) and sildenafil (1 ​μM) in combination with vitamin D3 (100 ​nM). A high-throughput screening system, the Flexstation 3 microplate reader, was used to measure intra- and extracellular Ca²⁺ signaling after exposure to 5-HT, glutamate, or ATP. Expression of inflammatory receptors was assessed by Western blotting.

Key findings

Drug treatment substantially reduced 5-HT- and ATP-evoked intracellular Ca²⁺ release and TLR4 expression compared to those in untreated chondrocytes. The combination of sildenafil, vitamin D3 together with metformin, as the ability to take up glucose is limited, increased Na⁺/K⁺-ATPase expression.

Significance

The combination of these three therapeutic substances at concentrations much lower than usually used, reduced expression of the inflammatory receptor TLR4 and increased the cell membrane enzyme Na⁺/K⁺-ATPase, which regulates cell volume and reduces increased intracellular Ca²⁺ concentrations. These remarkable results indicate that this drug combination has disease-modifying osteoarthritis drug (DMOAD) properties and may be a new clinical therapy for osteoarthritis (OA).

The GSK‑3β/β‑catenin signaling pathway is involved in HMGB1‑induced chondrocyte apoptosis and cartilage matrix degradation

Knee osteoarthritis (KOA) is a common joint disease with a high incidence rate among middle‑aged and elderly individuals. However, the precise underlying pathological mechanisms and effective treatment of this disease remain to be determined. To explore the effect of high mobility group box 1 (HMGB1) on chondrocyte apoptosis and catabolism, the ATDC5 cell line was cultured as an in vitro model for cartilage research. Cultured cells were treated with recombinant HMGB1 at different concentrations. Hoechst staining and flow cytometry demonstrated that HMGB1 administration significantly induced apoptosis of ATDC5 cells, which was the same as the effect of interleukin‑1β treatment. HMGB1 also induced cartilage matrix degradation, as shown by Alcian blue staining. Moreover, HMGB1 markedly upregulated the expression levels of matrix metallopeptidases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), while genetic silencing of HMGB1 significantly suppressed their expressions. The glycogen synthase kinase (GSK)‑3β/β‑catenin pathway was activated upon HMGB1 treatment. Pharmacological inhibitors or HMGB1 knockdown inactivated the GSK‑3β/β‑catenin pathway, inhibited the expression levels of downstream genes, including MMPs and ADAMTS, and attenuated the apoptosis of ATDC5 cells. Furthermore, the data demonstrated that HMGB1 promoted chondrocyte dysfunction via the regulation of estrogen sulfotransferase and Runt‑related transcription factor 2. Thus, the findings of the present study demonstrated that HMGB1 induces chondrocyte cell apoptosis via activation of GSK‑3β/β‑catenin and the subsequent expression of multiple targeted genes.

Serotonin-evoked cytosolic Ca2+ release and opioid receptor expression are upregulated in articular cartilage chondrocytes from osteoarthritic joints in horses

Osteoarthritis is a pain-associated progressive disease and pain mediators, such as opioid receptors, expressed in articular cartilage could represent novel therapeutic targets. Acute and chronic stages of OA indicate different metabolic abilities of the chondrocytes depending on inflammatory state. This study aimed to investigate the response of healthy and osteoarthritic chondrocytes and their expression and release of pain mediators in response to acute inflammation. Interleukin-1 beta (IL-1β) and lipopolysaccharide (LPS) were used to induce an acute inflammatory response in cultured equine chondrocytes harvested from healthy joints (HC) and osteoarthritic joints (OAC), the latter representing acute exacerbation of a chronic inflammatory state. Intracellular Ca2+ release was determined after exposure to serotonin (5-hydroxytryptamine (5-HT), glutamate or ATP. Protein expression levels of F- and G-actin, representing actin rearrangement, and opioid receptors were investigated. Glutamate concentrations in culture media were measured. Cartilage was immunohistochemically stained for µ (MOR), κ (KOR), and δ (DOR) opioid receptors. Upon exposure to acute inflammatory stimuli, OAC showed increased intracellular Ca2+ release after 5-HT stimulation and increased expression of MOR and KOR. When cells were stimulated by inflammatory mediators, glutamate release was increased in both HC and OAC. Immunostaining for MOR was strong in OA cartilage, whereas KOR was less strongly expressed. DOR was not expressed by cultured HC and OAC and immunostaining of OA cartilage equivocal. We show that chondrocytes in different inflammatory stages react differently to the neurotransmitter 5-HT with respect to intracellular Ca2+ release and expression of peripheral pain mediators. Our findings suggest that opioids and neurotransmitters are important in the progression of equine OA. The inflammatory stage of OA (acute versus chronic) should be taken into consideration when therapeutic strategies are being developed.

Elevated Glucose Levels Preserve Glucose Uptake, Hyaluronan Production, and Low Glutamate Release Following Interleukin-1β Stimulation of Differentiated Chondrocytes

OBJECTIVE

Chondrocytes are responsible for remodeling and maintaining the structural and functional integrity of the cartilage extracellular matrix. Because of the absence of a vascular supply, chondrocytes survive in a relatively hypoxic environment and thus have limited regenerative capacity during conditions of cellular stress associated with inflammation and matrix degradation, such as osteoarthritis (OA). Glucose is essential to sustain chondrocyte metabolism and is a precursor for key matrix components. In this study, we investigated the importance of glucose as a fuel source for matrix repair during inflammation as well as the effect of glucose on inflammatory mediators associated with osteoarthritis.

DESIGN

To create an OA model, we used equine chondrocytes from 4 individual horses that were differentiated into cartilage pellets in vitro followed by interleukin-1β (IL-1β) stimulation for 72 hours. The cells were kept at either normoglycemic conditions (5 mM glucose) or supraphysiological glucose concentrations (25 mM glucose) during the stimulation with IL-1β.

RESULTS

We found that elevated glucose levels preserve glucose uptake, hyaluronan synthesis, and matrix integrity, as well as induce anti-inflammatory actions by maintaining low expression of Toll-like receptor-4 and low secretion of glutamate.

CONCLUSIONS

Adequate supply of glucose to chondrocytes during conditions of inflammation and matrix degradation interrupts the detrimental inflammatory cycle and induces synthesis of hyaluronan, thereby promoting cartilage repair.

The Effect of Autologous Protein Solution on the Inflammatory Cascade in Stimulated Equine Chondrocytes

Cartilage injury occurs commonly in equine athletes, often precipitating posttraumatic osteoarthritis (PTOA). Orthobiologics such as autologous conditioned serum (ACS) and autologous protein solution (APS) may be useful in decreasing posttraumatic inflammation, thereby preventing PTOA. The objective of this study was to quantify cytokine concentrations in ACS and APS and evaluate the protective effects of ACS and APS on inflamed chondrocytes cultured in vitro. We hypothesized that the combination of platelet-derived growth factors (PDGF) and anti-inflammatory cytokines present in APS would be superior in decreasing the inflammatory and catabolic cascade in inflamed chondrocytes when compared to ACS in which platelets are excluded from the preparation. Chondrocytes were isolated from the cartilage of femoral trochlear ridges of 6 horses and cultured in 12-well transwell plates. Treatment groups included: (1) control, (2) APS (Pro-Stride; Owl Manor), and (3) ACS (IRAP II; Arthrex). Each group was unstimulated or stimulated with IL-1β and TNF-α for 48 h. The concentration of IL-1β, IL-6, TNF-α, MMP-3, MMP-13, and IL-10 was quantified using a fluorescent bead-based multiplex assay. IL-1Ra concentration was quantified using ELISA. APS and ACS both had significantly increased concentrations of IL-1Ra without a concurrent increase in IL-1β concentration. After 48 h of culture, media from chondrocytes treated with APS contained significantly increased concentrations of IL-1Ra and IL-10. APS-treated cultures had increased concentrations of IL-6. Overall, APS effectively concentrated IL-1Ra without an incubation period and media from APS-treated chondrocytes had increased concentrations of chondroprotective (IL-1Ra and IL-10) and modulatory (IL-6) cytokines, which may be beneficial in the treatment of inflammatory conditions such as PTOA.

Effects of medical ozone upon healthy equine joints: Clinical and laboratorial aspects

OBJECTIVE

The aim of this study was to verify whether transient inflammatory reactions induced by intra-articular medicinal ozone administration affect joint components, by in vivo evaluation of inflammatory (prostaglandin E2, Substance P, Interleukin-6, Interleukine-1, Tumor Necrosis Factor), anti-inflammatory (Interleukin-10) and oxidative (superoxide dismutase activity and oxidative burst) biomarkers and extracellular matrix degradation products (chondroitin sulphate and hyaluronic acid) in synovial fluid.

METHODS

The effects of medicinal ozone were analyzed at two ozone concentrations (groups A and B, 20 and 40 μg/ml, respectively), using oxygen-injected joints as controls (group C); each group received ten treatments (15 ml gas per treatment). Physical evaluation, evaluation of lameness, ultrasonography, and synovial fluid analysis were performed.

RESULTS

All joints presented mild and transient effusion throughout the study. Group B exhibited the highest lameness score on day 14 (P<0.05), detected by the lameness measurement system, probably because of the higher ozone concentration. All groups exhibited increased ultrasonography scores on day 14 (P < 0.05). Groups A and B exhibited increased proteins concentrations on day 21 (P<0.05). There was no change in hyaluronic acid concentration or the percentage of high-molecular weight hyaluronic acid throughout the experiment. Chondroitin sulfate concentrations decreased in group B, and did not change in group A and C, indicating that neither treatment provoked extracellular matrix catabolism. Cytokine and eicosanoid concentrations were not significantly changed.

CONCLUSIONS

The ozonetherapy did not cause significant inflammation process or cartilage degradation, therefore, ozonetherapy is safe at both evaluated doses.

Molecular influence of anterior cruciate ligament tear remnants on chondrocytes: a biologic connection between injury and osteoarthritis

OBJECTIVE

Anterior cruciate ligament (ACL) injury initiates a cascade of events often leading to osteoarthritis (OA). ACL reconstruction does not alter the course of OA, suggesting that heightened OA risk is likely due to factors in addition to the joint instability. We showed that torn ACL remnants express periostin (POSTN) in the acute phase of injury. Considering that ACL injury predisposes to OA and that POSTN is associated with cartilage metabolism, we hypothesize that ACL injury affects chondrocytes via POSTN.

DESIGN

Cartilage was obtained from osteoarthritic patients and ACL remnants were collected from patients undergoing ACL reconstruction. Crosstalk between ACL remnants and chondrocytes was studied in a transwell co-culture system. Expression of POSTN and other anabolic and catabolic genes was assessed via real-time polymerase chain reaction (PCR). Immunostaining for periostin was performed in human and mouse cartilage. The impact of exogenous periostin and siRNA-mediated ablation of periostin on matrix metabolism and cell migration was examined. Furthermore, the effect of anabolic (transforming growth factor beta 1 [TGF-β1]) and catabolic (interleukin 1 beta [IL-1β]) factors on POSTN expression was investigated.

RESULTS

ACL remnants induced expression of POSTN, MMP13 and ADAMTS4. Periostin levels were significantly higher in osteoarthritic compared to normal cartilage. Exogenous periostin induced MMP13 expression and cell migration, and repressed COL1A1 expression while POSTN knockdown inhibited expression of both anabolic and catabolic genes and impeded cell migration. TGF-β1 and IL-1β treatment did not alter POSTN expression but influenced chondrocyte metabolism as determined by quantification of anabolic and catabolic genes via real-time PCR.

CONCLUSIONS

ACL remnants can exert paracrine effects on cartilage, altering cellular homeostasis. Over time, this metabolic imbalance could contribute to OA development.

Biochemical alterations in inflammatory reactive chondrocytes: evidence for intercellular network communication

Chondrocytes are effectively involved in the pathophysiological processes of inflammation in joints. They form cellular processes in the superficial layer of the articular cartilage and form gap junction coupled syncytium to facilitate cell-to-cell communication. However, very little is known about their physiological cellular identity and communication. The aim with the present work is to evaluate the physiological behavior after stimulation with the inflammatory inducers interleukin-1β and lipopolysaccharide. The cytoskeleton integrity and intracellular Ca²⁺ release were assessed as indicators of inflammatory state. Cytoskeleton integrity was analyzed through cartilage oligomeric matrix protein and actin labeling with an Alexa 488-conjugated phalloidin probe. Ca²⁺ responses were assessed through the Ca²⁺ sensitive fluorophore Fura-2/AM. Western blot analyses of several inflammatory markers were performed. The results show reorganization of the actin filaments. Glutamate, 5-hydoxytryptamine, and ATP evoked intracellular Ca²⁺ release changed from single peaks to oscillations after inflammatory induction in the chondrocytes. The expression of toll-like receptor 4, the glutamate transporters GLAST and GLT-1, and the matrix metalloproteinase-13 increased. This work demonstrates that chondrocytes are a key part in conditions that lead to inflammation in the cartilage. The inflammatory inducers modulate the cytoskeleton, the Ca²⁺ signaling, and several inflammatory parameters. In conclusion, our data show that the cellular responses to inflammatory insults from healthy and inflammatory chondrocytes resemble those previously observed in astrocyte and cardiac fibroblasts networks.

DAMPs Synergize with Cytokines or Fibronectin Fragment on Inducing Chondrolysis but Lose Effect When Acting Alone

OBJECTIVE AND DESIGN

To investigate whether endogenous damage-associated molecular patterns (DAMPs) or alarmins originated from mitochondria or nucleus stimulates inflammatory response in articular chondrocytes to cause chondrolysis which leads to cartilage degradation featured in posttraumatic osteoarthritis (PTOA).

MATERIALS

Primary cultures of bovine or human chondrocytes isolated from cartilage of weight-bearing joints.

TREATMENT

Chondrocytes were subjected to mitochondrial DAMPs (MTDs) or HMGB1, a nuclear DAMP (NuD), with or without the presence of an N-terminal 29 kDa fibronectin fragment (Fn-f) or proinflammatory cytokines (IL-1β and TNF-α). Injured cartilage-conditioned culturing medium containing a mixture of DAMPs was employed as a control. After 24 hrs, the protein expression of cartilage degrading metalloproteinases and iNOS in culture medium or cell lysates was examined with Western blotting, respectively.

RESULTS

HMGB1 was synergized with IL-1β in upregulating expression of MMP-3, MMP-13, ADAMTS-5, ADAM-8, and iNOS. Moreover, a moderate synergistic effect was detected between HMGB1 and Fn-f or between MTDs and TNF-α on MMP-3 expression. However, when acting alone, MTDs or HMGB1 did not upregulate cartilage degrading enzymes or iNOS.

CONCLUSION

MTDs or HMGB1 could only stimulate inflammatory response in chondrocytes with the presence of cytokines or Fn-f.

IL-1β mediating high mobility group box protein-1 expression in condylar chondrocyte during temporomandibular joint inflammation

BACKGROUND

Temporomandibular joint (TMJ) osteoarthritis(OA)characterized with cartilage degen-eration is associated with inflammation. High mobility group box chromosomal protein-1(HMGB-1)is a potent mediator of inflammation and the trigger of OA. The expression of HMGB-1 in TMJ OA was uncovered, but the role of HMGB-1 in TMJ cartilage degeneration is not fully understood. In this study, the regulation of HMGB-1 in TMJ condylar cartilage was revealed.

METHODS

A complete Freund's adjuvant (CFA)-induced TMJ inflammation animal model was employed and the expression of HMGB-1 was detected at 1st, 2nd, and 6th weeks by immunohistochemistry. TMJ condylar chondrocytes were incubated with IL-1β (10 and 40 ng/ml) at 24, 48, and 72 h, and the translocation and protein level of HMGB-1 were evaluated by immunofluorescence and Western blot.

RESULT

Nuclear HMGB-1 staining was predominantly located in chondrocytes of both the fibrosis and proliferative zones in healthy TMJ. 1st week and 2nd week after CFA injection, immunoreaction could be detected in the cytoplasms of HMGB-1-positive cells and cartilage matrix especially in hypertrophic zone. At 6th week after CFA injection, cartilage matrix expression was disappeared and the cytoplasm expression of HMGB-1 was very weak in hypertrophic zone. HMGB-1 was translocated from the nucleus to the cytoplasm at 48 h after incubated with IL-1β (10 ng/ml and 40 ng/ml). The protein level of HMGB-1 was increased after stimulation and had a peak at 48 h.

CONCLUSION

HMGB-1 might be associated with TMJ inflammation and OA. Insight into the role of HMGB-1 in TMJ inflammation is helpful to add the new knowledge into the pathogenesis of TMJ OA.

Interleukin-6 enhances acid-induced apoptosis via upregulating acid-sensing ion channel 1a expression and function in rat articular chondrocytes

The inflammatory cytokine interleukin-6 (IL-6) is a causative agent of rheumatoid arthritis (RA), a chronic inflammatory disease complicated with degenerative arthritic cartilage. However, the precise mechanism of IL-6 on chondrocyte apoptosis is largely unclear. Acid-sensing ion channels (ASICs), a family of extracellular H(+)-activated cation channels, can be transiently activated by extracellular acid and play a pivotal role in acid-induced cell injury. In the present study, to investigate the role of IL-6 in regulating acid-induced articular chondrocyte apoptosis, primary rat articular chondrocytes were subjected to different treatments with or without IL-6 in the presence of acid. The results showed that the mRNA and protein expressions of ASIC1a were significantly increased in articular cartilage and chondrocytes of adjuvant arthritis (AA) rats. IL-6 could dramatically upregulate the level of ASIC1a in a time- and dose-dependent manner, and induce the activation of JAK2, STAT3, ERK, JNK and NF-κB in articular chondrocytes. Moreover, both the respective inhibitors of these signaling pathways and the specific antibody against IL-6 receptor (tocilizumab) could partially abrogate the ASIC1a upregulation induced by IL-6. Furthermore, IL-6 inhibited the cell viability and enhanced LDH release, [Ca(2+)]i elevation, and apoptosis in acid-induced articular chondrocytes, and these changes could be reversed by using psalmotoxin 1(PcTX1), which is the specific antagonist of ASIC1a. In addition, pretreatment with PcTX1 could inhibit the downregulated expression of Bcl-2 and the upregulated expression of Bax induced by IL-6 in acid-induced articular chondrocytes. Taken together, these results indicated that IL-6 could enhance acid-induced articular chondrocyte apoptosis, the mechanism of which might partially be involved with its ability of regulating the activation of ASIC1a-dependent JAK2/STAT3 and MAPK/NF-κB signaling pathways.

Silencing of miR-101 Prevents Cartilage Degradation by Regulating Extracellular Matrix-related Genes in a Rat Model of Osteoarthritis

Osteoarthritis (OA) is a common, degenerative joint disease characterized by articular cartilage degradation. Currently, clinical trials based on microRNA therapy have been performed to treat various diseases. However, no treatment has been found for arthritis. This study investigated the functions of miR-101 in cartilage degradation in vivo and evaluated the feasibility of using miR-101 as a therapeutic agent for OA. Mono-iodoacetate-induced arthritis (MIA) rats were used as an animal model of OA. miR-101 mimic or miR-101 inhibitor was injected into the rats' knees to evaluate its effects on cartilage degradation. Cartilage degradation aggravated at 14 days after the injection of miR-101 mimic. By contrast, miR-101 silencing reduced cartilage degradation. Moreover, the administration of miR-101 mimic is sufficient to cause cartilage degradation in the normal cartilage of rats. By contrast, miR-101 inhibitor could prevent this change. Microarray and qPCR were used to investigate the different expressed genes after injecting miR-101 mimic and miR-101 inhibitor in the rats' articular cartilage. Several cartilage degradation-related genes were selected and validated to function in cartilage degradation with miR-101. Our results demonstrated the therapeutic effect of miR-101 inhibition on cartilage degradation in MIA rats by regulating several cartilage degradation-related genes.

Proteomic analysis of tendon extracellular matrix reveals disease stage-specific fragmentation and differential cleavage of COMP (cartilage oligomeric matrix protein)

During inflammatory processes the extracellular matrix (ECM) is extensively remodeled, and many of the constituent components are released as proteolytically cleaved fragments. These degradative processes are better documented for inflammatory joint diseases than tendinopathy even though the pathogenesis has many similarities. The aims of this study were to investigate the proteomic composition of injured tendons during early and late disease stages to identify disease-specific cleavage patterns of the ECM protein cartilage oligomeric matrix protein (COMP). In addition to characterizing fragments released in naturally occurring disease, we hypothesized that stimulation of tendon explants with proinflammatory mediators in vitro would induce fragments of COMP analogous to natural disease. Therefore, normal tendon explants were stimulated with IL-1β and prostaglandin E₂, and their effects on the release of COMP and its cleavage patterns were characterized. Analyses of injured tendons identified an altered proteomic composition of the ECM at all stages post injury, showing protein fragments that were specific to disease stage. IL-1β enhanced the proteolytic cleavage and release of COMP from tendon explants, whereas PGE₂ had no catabolic effect. Of the cleavage fragments identified in early stage tendon disease, two fragments were generated by an IL-1-mediated mechanism. These fragments provide a platform for the development of neo-epitope assays specific to injury stage for tendon disease.

Interleukin-6 is elevated in synovial fluid of patients with focal cartilage defects and stimulates cartilage matrix production in an in vitro regeneration model

Introduction

This study aimed to determine whether, as in osteoarthritis, increased levels of interleukin-6 (IL-6) are present in the synovial fluid of patients with symptomatic cartilage defects and whether this IL-6 affects cartilage regeneration as well as the cartilage in the degenerated knee.

Methods

IL-6 concentrations were determined by ELISA in synovial fluid and in conditioned media of chondrocytes regenerating cartilage. Chondrocytes were obtained from donors with symptomatic cartilage defects, healthy and osteoarthritic donors. The effect of IL-6 on cartilage regeneration and on metabolism of the resident cartilage in the knee was studied by both inhibition of endogenous IL-6 and addition of IL-6, in a regeneration model and in osteoarthritic explants in the presence of synovial fluid, respectively. Readout parameters were DNA and glycosaminoglycan (GAG) content and release. Differences between controls and IL-6 blocked or supplemented samples were determined by univariate analysis of variance using a randomized block design.

Results

Synovial fluid of patients with symptomatic cartilage defects contained more IL-6 than synovial fluid of healthy donors (P = 0.001) and did not differ from osteoarthritic donors. IL-6 production of osteoarthritic chondrocytes during cartilage regeneration was higher than that of healthy and defect chondrocytes (P < 0.001). Adding IL-6 increased GAG production by healthy chondrocytes and decreased GAG release by osteoarthritic chondrocytes (P < 0.05). Inhibition of IL-6 present in osteoarthritic synovial fluid showed a trend towards decreased GAG content of the explants (P = 0.06).

Conclusions

Our results support a modest anabolic role for IL-6 in cartilage matrix production. Targeting multiple cytokines, including IL-6, may be effective in improving cartilage repair in symptomatic cartilage defects and osteoarthritis.

Effects of cleavage by a disintegrin and metalloproteinase with thrombospondin motifs-4 on gene expression and protein content of versican and aggrecan in the digital laminae of horses with starch gruel-induced laminitis

OBJECTIVE

To determine whether increased gene expression of a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4) in laminae of horses with starch gruel-induced laminitis was accompanied by increased enzyme activity and substrate degradation.

SAMPLE

Laminae from the forelimb hooves of 8 healthy horses and 17 horses with starch gruel-induced laminitis (6 at onset of fever, 6 at onset of Obel grade 1 lameness, and 5 at onset of Obel grade 3 lameness).

PROCEDURES

Gene expression was determined by use of cDNA and real-time quantitative PCR assay. Protein expression and processing were determined via SDS-PAGE and quantitative western blotting. Protein distribution and abundance were determined via quantitative immunofluorescent staining.

RESULTS

ADAMTS-4 gene expression was increased and that of versican decreased in laminitic laminae, compared with expression in healthy laminae. Catalytically active ADAMTS-4 also was increased in the tissue, as were ADAMTS-4-cleavage fragments of versican. Immunofluorescent analyses indicated that versican was depleted from the basal epithelia of laminae of horses at onset of Obel grade 3 lameness, compared with results for healthy laminae, and this was accompanied by regional separation of basal epithelial cells from the basement membrane. Aggrecan gene and protein expression were not significantly affected.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in gene and protein expression of ADAMTS-4 and versican in the basal epithelium of laminitic laminae indicated a fundamental change in the physiology of basal epithelial cells. This was accompanied by and may have caused detachment of these cells from the basement membrane.

Interleukin-1β promotes proliferation and inhibits differentiation of chondrocytes through a mechanism involving down-regulation of FGFR-3 and p21

The proinflammatory cytokine IL-1β is elevated in many childhood chronic inflammatory diseases as well as obesity and can be associated with growth retardation. Here we show that IL-1β affects bone growth by directly disturbing the normal sequence of events in the growth plate, resulting in increased proliferation and widening of the proliferative zone, whereas the hypertrophic zone becomes disorganized, with impaired matrix structure and increased apoptosis and osteoclast activity. This was also evident in vitro: IL-1β increased proliferation and caused a G1-to-S phase shift in the cell cycle in ATDC5 chondrocytes, accompanied by a reduction in fibroblast growth factor receptor-3 (FGFR-3) and its downstream gene, the cell-cycle inhibitor p21 and its family member p57, whereas the cell-cycle promoter E2F-2 was increased. The reduction in FGFR-3, p21, and p57 was followed by delayed cell differentiation, manifested by decreases in proteoglycan synthesis, mineralization, alkaline phosphatase activity, and the expression of Sox9, RunX2, collagen type II, collagen type X, and other matrix proteins. Taken together, we suggest that IL-1β alters normal chondrogenesis and bone growth through a mechanism involving down-regulation of FGFR-3 and p21.