Oral treatment with PD-0200347, an ?2? ligand, reduces the development of experimental osteoarthritis by inhibiting metalloproteinases and inducible nitric oxide synthase gene expression and synthesis in cartilage chondrocytes

Transcriptomic changes in porcine articular cartilage one year following disruption of the anterior cruciate ligament

To determine the transcriptomic changes seen in early- to mid-stage posttraumatic osteoarthritis (PTOA) development, 72 Yucatan minipigs underwent transection of the anterior cruciate ligament. Subjects were randomized to no further intervention, ligament reconstruction, or ligament repair, followed by articular cartilage harvesting and RNA-sequencing at three different postoperative timepoints (1, 4, and 52 weeks). Six additional subjects received no ligament transection and provided cartilage tissue to serve as controls. Differential gene expression analysis between post-transection cartilage and healthy cartilage revealed an initial increase in transcriptomic differences at 1 and 4 weeks followed by a stark reduction in transcriptomic differences at 52 weeks. This analysis also showed how different treatments genetically modulate the course of PTOA following ligament disruption. Specific genes (e.g., MMP1, POSTN, IGF1, PTGFR, HK1) were identified as being upregulated in the cartilage of injured subjects across all timepoints regardless of treatment. At the 52-week timepoint, 4 genes (e.g., A4GALT, EFS, NPTXR, ABCA3) that-as far as we know-have yet to be associated with PTOA were identified as being concordantly differentially expressed across all treatment groups when compared to controls. Functional pathway analysis of injured subject cartilage compared to control cartilage revealed overarching patterns of cellular proliferation at 1 week, angiogenesis, ECM interaction, focal adhesion, and cellular migration at 4 weeks, and calcium signaling, immune system activation, GABA signaling, and HIF-1 signaling at 52 weeks.

Effects of Gabapentin and Pregabalin on Calcium Homeostasis: Implications for Physical Rehabilitation of Musculoskeletal Tissues

PURPOSE OF REVIEW

In this review, we discuss the mechanism of action of gabapentinoids and the potential consequences of long-term treatment with these drugs on the musculoskeletal system.

RECENT FINDINGS

Gabapentinoids, such as gabapentin (GBP) and pregabalin (PGB) were designed as antiepileptic reagents and are now commonly used as first-line treatment for neuropathic pain and increasingly prescribed off-label for other pain disorders such as migraines and back pain. GBP and PGB exert their analgesic actions by selectively binding the α₂δ₁ auxiliary subunit of voltage-sensitive calcium channels, thereby inhibiting channel function. Numerous tissues express the α₂δ₁ subunit where GBP and PGB can alter calcium-mediated signaling events. In tissues such as bone, muscle, and cartilage, α₂δ₁ has important roles in skeletal formation, mechanosensation, and normal tissue function/repair that may be affected by chronic use of gabapentinoids. Long-term use of gabapentinoids is associated with detrimental musculoskeletal outcomes, including increased fracture risk. Therefore, understanding potential complications is essential for clinicians to guide appropriate treatments.

Systematic Review of Voltage-Gated Calcium Channel α2δ Subunit Ligands for the Treatment of Chronic Neuropathic Pain and Insight into Structure-Activity Relationship (SAR) by Pharmacophore Modeling

BACKGROUND

Neuropathic pain (NP) is a complex symptom related to the nerve damage. The discovery of new drugs for treating chronic NP has been continuing for several decades, while more progress is still needed to be made because of the unsatisfactory efficacy and the side effects of the currently available drugs. Among all the approved drugs for chronic NP, voltage-gated calcium channel (VGCC) α2δ subunit ligands, also known as gabapentinoids, are among the first-line treatment and represent a class of efficacious and relatively safe therapeutic agents. However, new strategies are still needed to be explored due to the unsatisfied response rate.

OBJECTIVES

To review the latest status of the discovery and development of gabapentinoids for the treatment of chronic NP by covering both the marketed and the preclinical/clinical ones. To analyze the structure-activity relationship (SAR) of gabapentinoids to facilitate the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

METHODS

We searched PubMed Central, Embase, Cochrane Library, Web of Science, Scopus and Espacenet for the literature and patents of diabetic peripheral neuropathic pain, postherpetic neuralgia, fibromyalgia, voltage-gated calcium channel α2δ subunit and related therapeutic agents from incipient to June 10, 2021. The SAR of gabapentinoids were analyzed by pharmacophore modeling using Phase module in Schrödinger suite.

RESULTS

A variety of gabapentinoids were identified as VGCC α2δ ligands that have ever been under development for the treatment of chronic NP. Among them, four gabapentinoids are marketed, one is at the active late clinical trials, and eight have been discontinued. Pharmacophore models were generated by using Phase module in Schrödinger suite, and common pharmacophores were predicted based on pharmacophoric features and analyzed.

CONCLUSION

The latest progress of the discovery and development of gabapentinoids for the treatment of chronic NP was reviewed. Moreover, the structure-activity relationship (SAR) of gabapentinoids is analyzed by pharmacophore modeling, which will be valuable for the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

ERK1/2-mediated activation of DRP1 regulates mitochondrial dynamics and apoptosis in chondrocytes

OBJECTIVE

To determine the Dynamin-related protein 1 (DRP1) regulation of mitochondrial fission in chondrocytes under pathological conditions, an area which is underexplored in osteoarthritis pathogenesis.

DESIGN

DRP1 protein expression was determined by immunohistochemistry (IHC) or immunofluorescence (IF) staining of cartilage sections. IL-1β-induced DRP1 mRNA expression in chondrocytes was quantified by qPCR and protein expression by immunoblotting. Mitochondrial fragmentation in chondrocytes was visualized by MitoTracker staining or IF staining of mitochondrial marker proteins or by transient expression of mitoDsRed. Mitochondrial reactive oxygen species (ROS) levels were determined by MitoSOX staining. Apoptosis was determined by lactate dehydrogenase (LDH) release assay, Caspase 3/7 activity assay, propidium iodide (PI), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and IF staining of cleaved caspase 3. Cytochrome c release was determined by confocal microscopy. Surgical destabilization of the medial meniscus (DMM) was used to induce osteoarthritis (OA) in mice.

RESULTS

Expression of DRP1 and mitochondrial damage was high in human OA cartilage and in the joints of mice subjected to DMM surgery which also showed increased chondrocytes apoptosis. IL-1β-induced mitochondrial network fragmentation and chondrocyte apoptosis via modulation of DRP1 expression and activity and induce apoptosis via Bax-mediated release of Cytochrome c. Pharmacological inhibition of DRP1 activity by Mdivi-1 blocked IL-1β-induced mitochondrial damage and apoptosis in chondrocytes. Additionally, IL-1β-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) is crucial for DRP1 activation and induction of mitochondrial network fragmentation in chondrocytes as these were blocked by inhibiting ERK1/2 activation.

CONCLUSIONS

These findings demonstrate that ERK1/2 is a critical player in DRP1-mediated induction of mitochondrial fission and apoptosis in IL-1β-stimulated chondrocytes.

DUSP5 suppresses interleukin-1β-induced chondrocyte inflammation and ameliorates osteoarthritis in rats

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by deterioration of articular cartilage. Dual specificity phosphatase 5 (DUSP5), a member of the DUSP subfamily, is known to regulate cellular inflammation. Here, we studied the relationship between DUSP5 and OA by knockdown and overexpression DUSP5, respectively. Results from in vitro experiments demonstrated that the knockdown of DUSP5 increased interleukin-1β (IL-1β)-induced expression of inflammatory genes, such as inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX2), and matrix metalloproteinases (MMPs) in chondrocytes, whereas it decreased the expression of anti-inflammatory genes, such as tissue inhibitor of metalloproteinase 3 (TIMP3) and IL-10. Conversely, the overexpression of DUSP5 suppressed the IL-1β-induced expression of iNOS, COX-2, and MMPs, and upregulated the expression of TIMP3 and IL-10. Moreover, knockdown of DUSP5 enhanced the IL-1β-induced activation of NF-κB and ERK pathways, whereas its overexpression inhibited these pathways. DUSP5 overexpression prevented cartilage degeneration in a rat OA model, while its knockdown reversed that effect. Our findings reveal that DUSP5 suppresses IL-1β-induced chondrocyte inflammation by inhibiting the NF-κB and ERK signaling pathways and ameliorates OA.

A dietary polysaccharide from Eucheuma cottonii downregulates proinflammatory cytokines and ameliorates osteoarthritis-associated cartilage degradation in obese rats

Osteoarthritis (OA) is a common form of arthritis, which is characterized by the degeneration of articular cartilage, leading to joint dysfunction. Oral drug therapy seems to ameliorate some signs and symptoms of OA, but may be accompanied by side effects and does not appear to be effective long-term. Seaweed has received much attention for pharmacological application due to its various biomedical properties, including the anti-inflammation, antitumor, and antioxidant effects. This study investigated the ameliorative effects of a dietary polysaccharide from Eucheuma cottonii extract (ECE) on an anterior cruciate ligament transection with partial medial meniscectomy surgery (ACLT+MMx) to induce OA in high-fat diet (HFD)-induced obese rats. Male Sprague-Dawley rats were fed an HFD for 12 weeks before ACLT+MMx surgery, after which they were administered a daily oral gavage of saline (Sham, OB Sham, and OBOA) and either low-dose ECE (100 mg per kg body weight), high-dose ECE (400 mg per kg body weight), or glucosamine sulfate as a positive control (OBOAGS; 200 mg per kg body weight) for 5 weeks. Treatment with ECE decreased the body weight, triglyceride and total cholesterol (TC) levels, and the TC/high-density lipoprotein (HDL)-C ratio in the obese rats. Additionally, ECE downregulated the expression of proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, and leptin, and suppressed nuclear factor-kappa B and extracellular-signal-regulated kinase-1/2 expression, resulting in a decrease in the levels of matrix metalloproteinase (MMP)-1 and MMP-13 and prostaglandin-E₂ and attenuated cartilage degradation. These results demonstrate that the dietary polysaccharide from ECE can suppress OA development in obese rats, suggesting its potential efficacy as a promising candidate for OA treatment.

Evaluation of the effects of pregabalin on chondrocyte proliferation and CHAD, HIF-1α, and COL2A1 gene expression

INTRODUCTION

The aim of the present study is to investigate the effects of pregabalin (PGB) on chondrocyte proliferation and collagen type II (COL2A1), hypoxia-inducible factor 1-α (HIF-1α), and chondroadherin (CHAD) gene expression in osteoarthritic chondrocytes.

MATERIAL AND METHODS

Standard primary chondrocyte cultures were prepared using osteochondral tissues that were surgically obtained from 6 patients with gonarthrosis. Cell morphology was evaluated using an inverted microscope, and cell death and proliferation were determined through MTT analysis, which was confirmed by AO/PI staining and statistically evaluated. The expression levels of CHAD, COL2A1, and HIF-1α genes were assessed using gene-specific TaqMan Gene Expression Assays.

RESULTS

MTT analyses showed that PGB administration did not have a negative or toxic effect on cell viability and proliferation in cultured chondrocytes (p < 0.001), but in our morphological evaluation extracellular matrix development was observed to be weaker in cultures treated with PGB. After 24 h of treatment, COL2A1, HIF-1α, and CHAD gene expression decreased in the groups to which PGB was applied compared to gene expression before the experiment (at 0 h); at 48 h, CHAD and HIF-1α expression increased to the same level as the control group, but the expression of COL2A1 continued to decrease.

CONCLUSIONS

Further studies need to be conducted with more participants to prove that there is a negative correlation between extracellular matrix formation and PGB administration. Our preliminary data show that even at low doses and over short-term administration, PGB may affect chondrocyte cells at the gene-expression level.

Pro-inflammatory cytokines and structural biomarkers are effective to categorize osteoarthritis phenotype and progression in Standardbred racehorses over five years of racing career

Background

Joint impact injuries initiate a progressive articular damage finally leading to post-traumatic osteoarthritis (PTOA). Racehorses represent an ideal, naturally available, animal model of the disease. Standardbred racehorses developing traumatic osteoarthritis of the fetlock joint during the first year of their career were enrolled in our study. Age-matched controls were contemporarily included. Biomarker levels of equine osteoarthritis were measured in serum and synovial fluid (SF) at baseline, and repeated yearly over the next 4 years of training (from T1 to T4). The effect of time and disease on the biomarker concentrations were analysed, and their relationship with clinical and radiographic parameters were assessed. We hypothesized that the kinetics of pro-inflammatory cytokines and structural biomarkers of joint disease would demonstrate progression of degenerative joint status during post-traumatic osteoarthritis and clarify the effect of early joint trauma.

Results

The concentrations of IL1-ß, IL-6, TNF-α in the SF of PTOA group peaked at T0, decreased at T1, and then progressively increased with time, reaching levels higher than those observed at baseline starting from T3. CTXII and COMP levels were similar in PTOA and control horses at baseline, and increased in serum and synovial fluid of PTOA horses starting from T2 (serum and synovial CTXII, and serum COMP) or T3 (synovial COMP). The percentual change of TNF-α in the SF of the affected joints independently contributed to explaining the radiological changes at T3 vs T2 and T4 vs T3.

Conclusions

Temporal changes of selected biomarkers in STBRs with an acute episode of traumatic fetlock OA demonstrated that long-term increased concentrations of inflammatory cytokines, type II collagen fragments and COMP, in the SF and serum, are related to PTOA. Based on the observed decrease in inflammatory merkers at T1, we hypothesize that the progression of PTOA could be effectively modulated by proper treatment strategies. Annual variations of synovial concentration of TNF-α can reliably predict radiographic progression of PTOA.

Voltage-dependent calcium channels in chondrocytes: roles in health and disease

Chondrocytes, the single cell type in adult articular cartilage, have conventionally been considered to be non-excitable cells. However, recent evidence suggests that their resting membrane potential (RMP) is less negative than that of excitable cells, and they are fully equipped with channels that control ion, water and osmolyte movement across the chondrocyte membrane. Amongst calcium-specific ion channels, members of the voltage-dependent calcium channel (VDCC) family are expressed in chondrocytes where they are functionally active. L-type VDCC inhibitors such as nifedipine and verapamil have contributed to our understanding of the roles of these ion channels in chondrogenesis, chondrocyte signalling and mechanotransduction. In this narrative review, we discuss published data indicating that VDCC function is vital for chondrocyte health, especially in regulating proliferation and maturation. We also highlight the fact that activation of VDCC function appears to accompany various inflammatory aspects of osteoarthritis (OA) and, based on in vitro data, the application of nifedipine and/or verapamil may be a promising approach for ameliorating OA severity. However, very few studies on clinical outcomes are available regarding the influence of calcium antagonists, which are used primarily for treating cardiovascular conditions in OA patients. This review is intended to stimulate further research on the chondrocyte 'channelome', contribute to the development of novel therapeutic strategies and facilitate the retargeting and repositioning of existing pharmacological agents currently used for other comorbidities for the treatment of OA.

Use of thiazolidinediones and the risk of elective hip or knee replacement: a population based case-control study

AIMS

Osteoarthritis (OA) is the most common musculoskeletal condition in the elderly population. However, no disease modifying drug exists for this disease. In vivo animal studies have suggested that thiazolidinediones (TZD) may be used as disease modifying osteoarthritis drugs (DMOADs). To our knowledge, this has not yet been examined in humans before. The aim was to determine the risk of total joint replacement (TJR) in patients using TZDs compared with diabetic patients using other antidiabetic drugs.

METHODS

A population based case-control study was performed using the Clinical Practice Research Datalink (CPRD). Cases (n = 94 609) were defined as patients >18 years of age who had undergone total knee (TKR) or hip replacement (THR) between 2000 and 2012. Controls were matched by age, gender and practice/surgery. Conditional logistic regression analyses were used to estimate the risk of TKR and THR with the use of TZDs in patients currently using one or more antidiabetic drugs. In order to determine effect with prolonged use, we also stratified TZD users by total number of prescriptions prior to surgery. We statistically adjusted our analyses for lifestyle factory, comorbidities and concomitant drug use.

RESULTS

There was no difference in risk of TKR (OR 1.09, 95% CI 0.93, 1.27) and THR (OR 0.92, 95% CI 0.76, 1.10) when TZD users were compared with other AD users. Furthermore, we did not find an association with prolonged use of TZDs and TJR.

CONCLUSION

Despite promising results from animal in vivo studies, this study did not find any evidence for a disease modifying osteoarthritic effect of TZDs.

2015 AAHA/AAFP Pain Management Guidelines for Dogs and Cats

Rationale:

The robust advances in pain management for companion animals underlie the decision of the American Animal Hospital Association (AAHA) and American Association of Feline Practitioners (AAFP) to expand on the information provided in the 2007 AAHA/AAFP Pain Management Guidelines. The 2015 Guidelines summarize and offer a discriminating review of much of this new knowledge.

Relevance:

Pain management is central to veterinary practice, alleviating pain, improving patient outcomes, and enhancing both quality of life and the veterinarian–client–patient relationship. These Guidelines support veterinarians in incorporating pain management into practice, improving patient care.

Approaches:

The management of pain requires a continuum of care that includes anticipation, early intervention, and evaluation of response on an individual patient basis. A team-oriented approach, including the owner, is essential for maximizing the recognition, prevention and treatment of pain in animals.

Evidence base:

The Guidelines include both pharmacologic and non-pharmacologic modalities to manage pain; they are evidence-based insofar as possible and otherwise represent a consensus of expert opinion. Behavioral changes are currently the principal indicator of pain and its course of improvement or progression, and the basis for recently validated pain scores. Post-surgical pain is eminently predictable but a strong body of evidence exists supporting strategies to mitigate adaptive as well as maladaptive forms. Chronic pain is dominated by degenerative joint disease (DJD), which is one of the most significant and under-diagnosed diseases of cats and dogs. DJD is ubiquitous, found in pets of all ages, and inevitably progresses over time; evidence-based strategies for management are established in dogs, and emerging in cats.

Adjunctive, pain-modifying, analgesic drugs

Outside the realm of nonsteroidal antiinflammatory drug(NSAID) and opioid exist a broad range of medications that exert an analgesic effect, or otherwise modify and protect against pain, by manipulating various targets along the nociceptive pathway. Strength of evidence for dogs and cats can vary widely, and this article will review the available literature that may guide clinical usage in these species.

Intracellular calcium oscillations in articular chondrocytes induced by basic calcium phosphate crystals lead to cartilage degradation

OBJECTIVE

Basic calcium phosphate (BCP) crystals, including octacalcium phosphate (OCP), carbonated-apatite (CA) and hydroxyapatite (HA) crystals are associated with destructive forms of osteoarthritis. Mechanisms of BCP-induced cartilage breakdown remain incompletely understood. We assessed the ability of BCP to induce changes in intracellular calcium (iCa(2+)) content and oscillations and the role of iCa(2+) in BCP-induced cartilage degradation.

METHODS

Bovine articular chondrocytes (BACs) and bovine cartilage explants (BCEs) were stimulated with BCP or monosodium urate (MSU) crystals. iCa(2+) levels were determined by spectrofluorimetry and oscillations by confocal microscopy. mRNA expression of matrix metalloproteinase 3 (MMP-3), a disintegrin and metalloprotease with thrombospondin-like motifs 4 (ADAMTS-4) and ADAMTS-5 was assessed by quantitative real-time PCR. Glycosaminoglycan (GAG) release was measured in the supernatants of BCE cultures.

RESULTS

All three BCP crystals significantly increased iCa(2+) content. OCP also induced iCa(2+) oscillations. Rate of BACs displaying iCa(2+) oscillations increased over time, with a peak after 20 min of stimulation. OCP-induced iCa(2+) oscillations involved both extracellular Ca(2+) (eCa(2+)) influx and iCa(2+) stores. Indeed, OCP-induced iCa(2+) oscillations decreased rapidly in Ca(2+)-free medium. Both voltage- and non-voltage-dependent Ca(2+) channels were involved in eCa(2+) influx. BCP crystal-induced variation in iCa(2+) content was associated with BCP crystal-induced cartilage matrix degradation. However, iCa²(+) was not associated with OCP crystal-induced mRNA expression of MMP-3, ADAMTS-4 or ADAMTS-5.

CONCLUSION

BCP crystals can induce variation in iCa(2+) content and oscillations in articular chondrocytes. Furthermore, BCP crystal-induced changes in iCa(2+) content play a pivotal role in BCP catabolic effects on articular cartilage.

cAMP response element-binding (CREB) recruitment following a specific CpG demethylation leads to the elevated expression of the matrix metalloproteinase 13 in human articular chondrocytes and osteoarthritis

Osteoarthritis is a degenerative joint disease characterized by a progressive and irreversible loss of the articular cartilage, due in main part to the cleavage of type II collagen within the matrix by the enzyme matrix metalloproteinase (MMP)13. Here, we examined the methylation status of MMP13 promoter and report the demethylation of specific CpG dinucleotides within its promoter in osteoarthritic compared to normal cartilage, which correlates with increased MMP13 expression. Of the promoter CpG sites examined, the -104 CpG was consistently demethylated following treatment of human articular chondrocytes with 10 μM DNA-methyltransferase inhibitor 5-aza-2'-deoxycytidine, again correlating with increased MMP13 expression. Methylation of the -104 CpG site resulted in reduced promoter activity in the chondrosarcoma cell line SW1353 as shown by CpG-free luciferase reporter. Using electrophoretic mobility shift assays, we identified CREB as the regulating factor able to only bind to the MMP13 promoter when the -104 CpG is demethylated, and confirmed this binding by chromatin immunoprecipitation. Finally, we demonstrated that CREB induces MMP13 expression only following treatment of SW1353 with 0.5 μM Ca(2+) ionophore A23187. In summary, the -104 CpG is demethylated in osteoarthritic cartilage, correlating with the elevated MMP13 expression and cartilage destruction, providing a highly novel link between epigenetic status and arthritic disease.

Tiludronate treatment improves structural changes and symptoms of osteoarthritis in the canine anterior cruciate ligament model

Introduction

The aim of this prospective, randomized, controlled, double-blind study was to evaluate the effects of tiludronate (TLN), a bisphosphonate, on structural, biochemical and molecular changes and function in an experimental dog model of osteoarthritis (OA).

Methods

Baseline values were established the week preceding surgical transection of the right cranial/anterior cruciate ligament, with eight dogs serving as OA placebo controls and eight others receiving four TLN injections (2 mg/kg subcutaneously) at two-week intervals starting the day of surgery for eight weeks. At baseline, Week 4 and Week 8, the functional outcome was evaluated using kinetic gait analysis, telemetered locomotor actimetry and video-automated behaviour capture. Pain impairment was assessed using a composite numerical rating scale (NRS), a visual analog scale, and electrodermal activity (EDA). At necropsy (Week 8), macroscopic and histomorphological analyses of synovium, cartilage and subchondral bone of the femoral condyles and tibial plateaus were assessed. Immunohistochemistry of cartilage (matrix metalloproteinase (MMP)-1, MMP-13, and a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS5)) and subchondral bone (cathepsin K) was performed. Synovial fluid was analyzed for inflammatory (PGE₂ and nitrite/nitrate levels) biomarkers. Statistical analyses (mixed and generalized linear models) were performed with an α-threshold of 0.05.

Results

A better functional outcome was observed in TLN dogs than OA placebo controls. Hence, TLN dogs had lower gait disability (P = 0.04 at Week 8) and NRS score (P = 0.03, group effect), and demonstrated behaviours of painless condition with the video-capture (P < 0.04). Dogs treated with TLN demonstrated a trend toward improved actimetry and less pain according to EDA. Macroscopically, both groups had similar level of morphometric lesions, TLN-treated dogs having less joint effusion (P = 0.01), reduced synovial fluid levels of PGE₂ (P = 0.02), nitrites/nitrates (P = 0.01), lower synovitis score (P < 0.01) and a greater subchondral bone surface (P < 0.01). Immunohistochemical staining revealed lower levels in TLN-treated dogs of MMP-13 (P = 0.02), ADAMTS5 (P = 0.02) in cartilage and cathepsin K (P = 0.02) in subchondral bone.

Conclusion

Tiludronate treatment demonstrated a positive effect on gait disability and joint symptoms. This is likely related to the positive influence of the treatment at improving some OA structural changes and reducing the synthesis of catabolic and inflammatory mediators.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the dog

The dog is a common model for study of osteoarthritis (OA). Subjective histologic scoring systems have often served as the reference standard for presence and severity of OA. However, these scoring systems have perceived shortcomings. The system developed for this report attempts to address these shortcomings by providing a standardized methodology for global assessment of the joint, versatility and the potential for relative weighting of pathology, allowing for comparison among time points, studies, and centers, and critical analysis of the system's reliability. The proposed system for assessment of canine tissues appears to provide an effective method for global assessment of articular pathology in OA. The system is versatile, comprehensive, and reliable and appears to have advantages over conventional scoring systems.

Targeted therapies in osteoarthritis: a systematic review of the trials on www.clinicaltrials.gov

A systematic review of the clinical trials in osteoarthritis registered on the public website of the Clinical Trials Data Bank at the National Institutes of Health (NIH) has been performed. Such a review should cover the majority of the ongoing or forthcoming trials in the disease. This review focusses on trials designed to test safety and/or efficacy of targeted therapies in osteoarthritis.

The chondroprotective agent ITZ-1 inhibits interleukin-1beta-induced matrix metalloproteinase-13 production and suppresses nitric oxide-induced chondrocyte death

In a screening program aimed at discovering anti-osteoarthritis (OA) drugs, we identified an imidazo[5,1-c][1,4]thiazine derivative, ITZ-1, that suppressed both interleukin-1beta (IL-1beta)-induced proteoglycan and collagen release from bovine nasal cartilage in vitro and suppressed intra-articular infusion of IL-1beta-induced cartilage proteoglycan degradation in rat knee joints. ITZ-1 did not inhibit enzyme activities of various matrix metalloproteinases (MMPs), which have pivotal roles in cartilage degradation, while it selectively inhibited IL-1beta-induced production of MMP-13 in human articular chondrocytes (HAC). IL-1beta-induced MMP production has been shown to be mediated by extracellular signal-regulated protein kinase (ERK), p38 kinase, and c-Jun N-terminal kinase (JNK) of the mitogen-activated protein kinase (MAPK) family signal transduction molecules. An ERK-MAPK pathway inhibitor (U0126), but not a p38 kinase inhibitor (SB203580) or a JNK inhibitor (SP600125), also selectively inhibited IL-1beta-induced MMP-13 production in HAC. Furthermore, ITZ-1 selectively inhibited IL-1beta-induced ERK activation without affecting p38 kinase and JNK activation, which may account for its selective inhibition of MMP-13 production. Inhibition of nitric oxide (NO)-induced chondrocyte apoptosis has been another area of interest as a therapeutic strategy for OA, and ITZ-1 also suppressed NO-induced death in HAC. These results suggest that ITZ-1 is a promising lead compound for a disease modifying anti-OA drug program.

Phase 2 enzyme inducer sulphoraphane blocks matrix metalloproteinase production in articular chondrocytes

OBJECTIVES

In addition to its chemopreventive activity, phase 2 enzyme inducers have been recently found to have anti-inflammatory activity. In this study, we examined the influence of sulphoraphane (SPN), one of the most potent inducers of the phase II enzymes on the production of MMPs by pro-inflammatory cytokines in human articular chondrocytes.

METHODS

Articular cartilages were obtained from knee OA patients and were cultured in monolayers and explants. Induction of a phase II enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), in chondrocytes was assayed after incubation with various concentrations of SPN. Chondrocytes were stimulated with IL-1 or TNF-alpha with or without pre-incubation with SPN. The expression and activation of MMP-1, -3 and -13 was evaluated by an ELISA, gel zymography and RT-PCR. MAP kinases [p38, extracellular signal-regulated protein kinase (ERK) and C-Jun N terminal kinase (JNK)] and NF-kappaB activation were evaluated by western blotting and by an electrophoretic mobility shift assay, respectively.

RESULTS

SPN significantly induced NQO1 activity in chondrocytes and the induction was maximal at 24 h. SPN inhibited the production of MMP-1, -3 and -13 protein and mRNA induced by either IL-1 or TNF-alpha in a dose-dependent manner. This inhibition of MMP by SPN was accompanied by the inhibition of NF-kappaB and JNK activation.

CONCLUSIONS

SPN was found to inhibit MMP production in pro-inflammatory cytokine-stimulated chondrocytes. Delineation of the biochemical mechanism regulating cartilage catabolism by SPN may identify safe and effective therapeutic targets for the inhibition of cartilage degradation.

Protective effects of total fraction of avocado/soybean unsaponifiables on the structural changes in experimental dog osteoarthritis: inhibition of nitric oxide synthase and matrix metalloproteinase-13

INTRODUCTION

The aims of this study were, first, to investigate the in vivo effects of treatment with avocado/soybean unsaponifiables on the development of osteoarthritic structural changes in the anterior cruciate ligament dog model and, second, to explore their mode of action.

METHODS

Osteoarthritis was induced by anterior cruciate ligament transection of the right knee in crossbred dogs. There were two treatment groups (n = 8 dogs/group), in which the animals received either placebo or avocado/soybean unsaponifiables (10 mg/kg per day), which were given orally for the entire duration of the study (8 weeks). We conducted macroscopic and histomorphological analyses of cartilage and subchondral bone of the femoral condyles and/or tibial plateaus. We also conducted immunohistochemical analyses in cartilage for the following antigens: inducible nitric oxide synthase, matrix metalloproteinase (MMP)-1, MMP-13, a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS)4 and ADAMTS5.

RESULTS

The size of macroscopic lesions on the tibial plateaus was decreased (P = 0.04) in dogs treated with the avocado/soybean unsaponifiables. Histologically, in these animals the severity of cartilage lesions on both tibial plateaus and femoral condyles, and the cellular infiltration in synovium were significantly decreased (P = 0.0002 and P = 0.04, respectively). Treatment with avocado/soybean unsaponifiables also reduced loss of subchondral bone volume (P < 0.05) and calcified cartilage thickness (P = 0.01) compared with placebo. Immunohistochemical analysis of cartilage revealed that avocado/soybean unsaponifiables significantly reduced the level of inducible nitric oxide synthase (P < 0.05) and MMP-13 (P = 0.01) in cartilage.

CONCLUSIONS

This study demonstrates that treatment with avocado/soybean unsaponifiables can reduce the development of early osteoarthritic cartilage and subchondral bone lesions in the anterior cruciate ligament dog model of osteoarthritis. This effect appears to be mediated through the inhibition of inducible nitric oxide synthase and MMP-13, which are key mediators of the structural changes that take place in osteoarthritis.

Signal transduction in electrically stimulated articular chondrocytes involves translocation of extracellular calcium through voltage-gated channels

OBJECTIVE

To ascertain, using specific inhibitors, the potential role of calcium-related signal transduction pathways in the mechanism of cartilage matrix protein gene induction and metalloproteinase gene suppression by capacitively coupled electric fields.

METHODS

Articular chondrocytes were isolated from adult bovine patellae and cultured in high density for 7 days. To study matrix protein expression, cells cultured in the absence or presence of specific calcium pathway inhibitors were exposed to a capacitively coupled electrical field (60 kHz, 20 mV/cm): for aggrecan 1h at 50% duty cycle and for type II collagen 6h at 8.3% duty cycle. To study metalloproteinase expression in the presence of interleukin 1 beta (IL-1beta), cells were cultured as above but exposed for only 30 min to a 100% duty cycle signal. At harvest, total mRNA was isolated and aggrecan, type II collagen, matrix metalloproteinase (MMP-1, -3 and -13) and aggrecanase [a disintegrin and metalloproteinase with thrombospondin repeats (ADAMTS-4 and -5)] mRNA expression were measured by quantitative real-time polymerase chain reaction (qPCR).

RESULTS

(1) In the absence of inhibitors, appropriate electrical stimulation induces a 3-4-fold up-regulation of both aggrecan and type II collagen mRNA and a 3.7-9.6-fold down-regulation of IL-1beta-induced metalloproteinases; (2) the presence of inhibitors alone does not affect any target mRNA levels; (3) inhibitors of intracellular calcium regulation and inositol 1,4,5-triphosphate (IP(3)) formation [8-(diethylamino)octyl-3,4,5,-trimethoxybenzoate hydrochloride (TMB-8) and neomycin, respectively] have no effect on regulation of target mRNA levels by electrical stimulation; and (4) inhibitors of voltage-gated calcium channels (verapamil), calmodulin activation (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride, W-7), calcineurin activity (cyclosporin A), phospholipase C activity (bromophenacyl bromide, BPB) and prostaglandin E(2) (PGE(2)) synthesis (indomethacin) completely inhibit the effects of electrical stimulation.

CONCLUSIONS

The results are consistent with the effects of electrical stimulation involving a pathway of extracellular Ca(2+) influx via voltage-gated calcium channels rather than from intracellular Ca(2+) repositories; and with downstream roles for calmodulin, calcineurin and nuclear factor of activated T-cells (NF-AT) rather than for phospholipase C and IP(3).

Adjunctive analgesic therapy in veterinary medicine

Adjunctive analgesic therapies are interventions for pain that involve agents or techniques other than the traditional analgesics (opioids, nonsteroidal anti-inflammatory drugs, and local anesthetics). Adjunctive therapies may be pharmacologic or nonpharmacologic in nature. The focus of this article is on pharmacologic interventions with potential utility as adjunctive analgesics in veterinary medicine. Pharmacology of selected agents, including medetomidine, ketamine, amantadine, gabapentin, systemic lidocaine, and pamidronate, is discussed in addition to evidence for their safety and efficacy and guidelines for their use in veterinary patients.

Mitogen-activated protein kinases as therapeutic targets in osteoarthritis

PURPOSE OF REVIEW

The mitogen-activated protein (MAP) kinases are intracellular signaling proteins which play a central role in controlling the activity of pathways that regulate production and activity of multiple mediators of joint tissue destruction. The therapeutic potential of MAP kinase inhibition in osteoarthritis was reviewed.

RECENT FINDINGS

Results from basic research studies support the role of MAP kinases as central mediators that regulate expression of proinflammatory cytokines and metalloproteinases but also as potential pain mediators as well. Cell culture and animal model studies suggest that inhibition of MAP kinases might slow progression of osteoarthritis but trials of MAP kinase inhibitors in humans with osteoarthritis have not yet been reported. Safety concerns of the currently available inhibitors have limited their initial use to trials in conditions considered more severe than osteoarthritis.

SUMMARY

MAP kinase inhibition has the potential to slow disease progression in osteoarthritis and also might reduce pain; however, safety concerns have limited the use of general MAP kinase inhibitors in humans. Further understanding of the function of specific isoforms of the MAP kinases as well as upstream and downstream effectors may lead to the development of more specific inhibitors with less toxicity that could eventually be used as structure-modifying drugs for osteoarthritis.

Study of subchondral bone adaptations in a rodent surgical model of OA using in vivo micro-computed tomography

OBJECTIVE

To non-invasively investigate the changes to epiphyseal bone occurring in a longitudinal pre-clinical model of osteoarthritis (OA) using in vivo micro-computed tomography (micro-CT).

DESIGN

In vivo micro-CT images were acquired using a bench-top micro-CT scanner, which produces three-dimensional data with isotropic voxel spacing of 0.046 mm. Male rodents were scanned prior to surgical destabilization, consisting of anterior cruciate ligament transection and partial medial menisectomy (ACLX). Subsequent scans were performed every 4 weeks post-ACLX, for up to 5 months. Volumetric bone mineral density (vBMD) was measured in specific, anatomically segmented regions within each image. The ACLX rodent data were compared with the contralateral non-operated hind limb of the same animal, as well as a sham-operated group (SHAM) of animals, for each time point. End-point histology compared changes to cartilage and bone between the ACLX and control animals.

RESULTS

The micro-CT protocol produced sufficient spatial resolution and signal-to-noise ratio (SNR=19) to quantify subchondral bone pathology, with an acceptable entrance exposure to radiation (0.36 Gy). Significantly lower vBMD was measured in the ACLX group, vs SHAM rodents, at 1, 4, and 5 months post-surgery (P<0.05). Qualitative observations of ACLX joints revealed significant loss of cartilage, subchondral bone cysts, and calcification of tendon similar to changes found in humans.

CONCLUSIONS

This study demonstrates in vivo micro-CT as an effective method for investigating the development of rodent knee OA longitudinally. This method can be applied, in future pre-clinical trials, to non-destructively monitor the efficacy of pharmacological interventions.

Activation of proteinase-activated receptor 2 in human osteoarthritic cartilage upregulates catabolic and proinflammatory pathways capable of inducing cartilage degradation: a basic science study

Proteinase-activated receptors (PARs) belong to a family of G protein-coupled receptors. PARs are activated by a serine-dependent cleavage generating a tethered activating ligand. PAR-2 was shown to be involved in inflammatory pathways. We investigated the in situ levels and modulation of PAR-2 in human normal and osteoarthritis (OA) cartilage/chondrocytes. Furthermore, we evaluated the role of PAR-2 on the synthesis of the major catabolic factors in OA cartilage, including metalloproteinase (MMP)-1 and MMP-13 and the inflammatory mediator cyclooxygenase 2 (COX-2), as well as the PAR-2-activated signalling pathways in OA chondrocytes. PAR-2 expression was determined using real-time reverse transcription-polymerase chain reaction and protein levels by immunohistochemistry in normal and OA cartilage. Protein modulation was investigated in OA cartilage explants treated with a specific PAR-2-activating peptide (PAR-2-AP), SLIGKV-NH₂ (1 to 400 μM), interleukin 1 beta (IL-1β) (100 pg/mL), tumor necrosis factor-alpha (TNF-α) (5 ng/mL), transforming growth factor-beta-1 (TGF-β1) (10 ng/mL), or the signalling pathway inhibitors of p38 (SB202190), MEK1/2 (mitogen-activated protein kinase kinase) (PD98059), and nuclear factor-kappa B (NF-κB) (SN50), and PAR-2 levels were determined by immunohistochemistry. Signalling pathways were analyzed on OA chondrocytes by Western blot using specific phospho-antibodies against extracellular signal-regulated kinase 1/2 (Erk1/2), p38, JNK (c-jun N-terminal kinase), and NF-κB in the presence or absence of the PAR-2-AP and/or IL-1β. PAR-2-induced MMP and COX-2 levels in cartilage were determined by immunohistochemistry. PAR-2 is produced by human chondrocytes and is significantly upregulated in OA compared with normal chondrocytes (p < 0.04 and p < 0.03, respectively). The receptor levels were significantly upregulated by IL-1β (p < 0.006) and TNF-α (p < 0.002) as well as by the PAR-2-AP at 10, 100, and 400 μM (p < 0.02) and were downregulated by the inhibition of p38. After 48 hours of incubation, PAR-2 activation significantly induced MMP-1 and COX-2 starting at 10 μM (both p < 0.005) and MMP-13 at 100 μM (p < 0.02) as well as the phosphorylation of Erk1/2 and p38 within 5 minutes of incubation (p < 0.03). Though not statistically significant, IL-1β produced an additional effect on the activation of Erk1/2 and p38. This study documents, for the first time, functional consequences of PAR-2 activation in human OA cartilage, identifies p38 as the major signalling pathway regulating its synthesis, and demonstrates that specific PAR-2 activation induces Erk1/2 and p38 in OA chondrocytes. These results suggest PAR-2 as a potential new therapeutic target for the treatment of OA.

Managing osteoarthritis pain when your patient fails simple analgesics and NSAIDs and is not a candidate for surgery

With no disease-modifying osteoarthritis drugs on the immediate horizon, the goal of osteoarthritis therapy remains management of pain and maintenance of function. Evidence supports use of nonpharmacologic measures including patient education, judicious exercise and weight loss, and assistive devices when appropriate to reduce pain and further loss of function. First line pharmacotherapy is acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs). However, toxicities are associated with long-term use of these drugs. Evidence also supports the use of opioids in osteoarthritis pain management when other interventions are insufficient. NSAIDs and opioids are mutually dose sparing and combining relatively low doses of a drug from each class provides synergistic analgesia while limiting toxicity. Alternative therapies include tramadol and intra-articular injections of steroids and hyaluronic acid. There is evidence to support glucosamine as an adjunct in treating osteoarthritis. Evidence is lacking to support the use of chondroitin, S-adenosyl-methionine, or dimethyl sulfoxide in osteoarthritis pain management.

The peroxisome proliferator-activated receptor gamma agonist pioglitazone reduces the development of cartilage lesions in an experimental dog model of osteoarthritis: in vivo protective effects mediated through the inhibition of key signaling and catabolic pathways

OBJECTIVE

Emerging evidence indicates that peroxisome proliferator-activated receptor gamma (PPARgamma) may have protective effects in osteoarthritis (OA). The aim of this study was to evaluate the in vivo effect of a PPARgamma agonist, pioglitazone, on the development of lesions in a canine model of OA, and to explore the influence of pioglitazone on the major signaling and metabolic pathways involved in OA pathophysiologic changes.

METHODS

OA was surgically induced in dogs by sectioning of the anterior cruciate ligament. The dogs were then randomly divided into 3 treatment groups in which they were administered either placebo, 15 mg/day pioglitazone, or 30 mg/day pioglitazone orally for 8 weeks. Following treatment, the severity of cartilage lesions was scored. Cartilage specimens were processed for histologic and immunohistochemical evaluations; specific antibodies were used to study the levels of matrix metalloproteinase 1 (MMP-1), ADAMTS-5, and inducible nitric oxide synthase (iNOS), as well as phosphorylated MAPKs ERK-1/2, p38, JNK, and NF-kappaB p65.

RESULTS

Pioglitazone reduced the development of cartilage lesions in a dose-dependent manner, with the highest dosage producing a statistically significant change (P < 0.05). This decrease in lesions correlated with lower cartilage histologic scores. In addition, pioglitazone significantly reduced the synthesis of the key OA mediators MMP-1, ADAMTS-5, and iNOS and, at the same time, inhibited the activation of the signaling pathways for MAPKs ERK-1/2, p38, and NF-kappaB.

CONCLUSION

These results indicate the efficacy of pioglitazone in reducing cartilage lesions in vivo. The results also provide new and interesting insights into a therapeutic intervention for OA in which PPARgamma activation can inhibit major signaling pathways of inflammation and reduce the synthesis of cartilage catabolic factors responsible for articular cartilage degradation.

Forced mobilization accelerates pathogenesis: characterization of a preclinical surgical model of osteoarthritis

Preclinical osteoarthritis (OA) models are often employed in studies investigating disease-modifying OA drugs (DMOADs). In this study we present a comprehensive, longitudinal evaluation of OA pathogenesis in a rat model of OA, including histologic and biochemical analyses of articular cartilage degradation and assessment of subchondral bone sclerosis. Male Sprague-Dawley rats underwent joint destabilization surgery by anterior cruciate ligament transection and partial medial meniscectomy. The contralateral joint was evaluated as a secondary treatment, and sham surgery was performed in a separate group of animals (controls). Furthermore, the effects of walking on a rotating cylinder (to force mobilization of the joint) on OA pathogenesis were assessed. Destabilization-induced OA was investigated at several time points up to 20 weeks after surgery using Osteoarthritis Research Society International histopathology scores, in vivo micro-computed tomography (CT) volumetric bone mineral density analysis, and biochemical analysis of type II collagen breakdown using the CTX II biomarker. Expression of hypertrophic chondrocyte markers was also assessed in articular cartilage. Cartilage degradation, subchondral changes, and subchondral bone loss were observed as early as 2 weeks after surgery, with considerable correlation to that seen in human OA. We found excellent correlation between histologic changes and micro-CT analysis of underlying bone, which reflected properties of human OA, and identified additional molecular changes that enhance our understanding of OA pathogenesis. Interestingly, forced mobilization exercise accelerated OA progression. Minor OA activity was also observed in the contralateral joint, including proteoglycan loss. Finally, we observed increased chondrocyte hypertrophy during pathogenesis. We conclude that forced mobilization accelerates OA damage in the destabilized joint. This surgical model of OA with forced mobilization is suitable for longitudinal preclinical studies, and it is well adapted for investigation of both early and late stages of OA. The time course of OA progression can be modulated through the use of forced mobilization.

Animal models of osteoarthritis: lessons learned while seeking the "Holy Grail"

PURPOSE OF REVIEW

Difficulties in studying osteoarthritis in humans that stem from both the low sensitivity of diagnostic tools and the low availability of diseased tissues explain why research on animal models remains highly dynamic. This review will summarize the recent advances in this field.

RECENT FINDINGS

With regard to the etiology of osteoarthritis, synovial macrophages mediate osteophyte formation, whereas increased ligament laxity could be responsible for spontaneous osteoarthritis in guinea pigs. The concomitant changes in subchondral bone and cartilage reported in several models, and the structure-modifying effects of some bone inhibitors have confirmed the importance of bone in osteoarthritis. With regard to cartilage pathobiology, ADAMTS-5 is the major aggrecanase responsible for cartilage destruction, whereas inadequate control of oxidative stress and decreased expression of transforming growth factor-beta receptors could predispose to osteoarthritis. New models include a postmenopausal rat model, the groove model and a joint-specific bone morphogenetic receptor-deficient mouse. The iodoacetate model was also validated as the first pain model of osteoarthritis.

SUMMARY

In view of the multiple animal models available, there is a need to reach a consensus on one or several gold standard animal model(s). New studies indicate that important differences in therapeutic response exist between young and old animals, and between spontaneous and surgical models, suggesting that not all models are adequate models of osteoarthritis.

Oral treatment options for degenerative joint disease--presence and future

Alleviation of pain and inhibition of inflammation are the primary goals of pharmacotherapy of osteoarthritis (OA). These therapeutic goals can almost always be accomplished by the use of analgesics and nonsteroidal anti-inflammatory drugs (NSAID). One of the main problems of NSAIDs is their gastrointestinal toxicity, for which a prophylactic medication should be considered particularly amongst risk groups. Recent studies have shown that COX-2-selective and maybe also non-selective NSAIDs increase the cardiovascular risk so that their application is getting now drastically restricted. Pharmacological results published until now suggest that a clinically relevant minor analgesic and/or anti-inflammatory effect can be attained with the use of some of the SYmptomatic Slow Acting Drugs in OA (SYSADOAs). However, no clinical studies exist, which can positively confirm prevention, slowing down or reversal of any advanced joint cartilage destruction by any individual medication. Disease modifying therapy is still in its infancy; discovery and development of novel therapeutic targets and agents are an extremely difficult task, currently challenging many pharmaceutical companies and academic institutions.

PD-0200347, an alpha2delta ligand of the voltage gated calcium channel, inhibits in vivo activation of the Erk1/2 pathway in osteoarthritic chondrocytes: a PKCalpha dependent effect

OBJECTIVE

To explore the in vivo effects of PD-0200347, an alpha(2)delta ligand of voltage gated Ca(2+) channels, on cell signalling in osteoarthritic (OA) chondrocytes from an experimental dog model, and examine the effect of PD-0200347 on the major signalling pathways involved in OA cartilage degradation.

METHODS

OA was surgically induced in dogs by sectioning the anterior cruciate ligament. OA dogs were divided into three groups and treated orally with (a) placebo; (b) 15 mg/kg/day PD-0200347, or (c) 90 mg/kg/day PD-0200347. The animals were killed 12 weeks after surgery. Cartilage specimens from femoral condyles and tibial plateaus were processed for immunohistochemistry. Specific antibodies against the phosphorylated form of PKCalpha, Ras, c-Raf, the MAP kinases Erk1/2, p38, JNK, and the transcription factors, CREB and Elk-1, were used.

RESULTS

Levels of all the tested signalling mediators were increased in the placebo treated (OA) group compared with the normal group. PD-0200347 treatment significantly reduced the levels of the active forms of PKCalpha, c-Raf, Erk1/2, and Elk-1; however, the levels of the active forms of Ras, p38, JNK, and CREB were not affected by the PD-0200347 treatment.

CONCLUSION

The action of PD-0200347 on OA chondrocytes is probably mediated through the inhibition of Erk1/2 activation via a Ras independent mechanism. This effect is associated with reduction of the activation of transcription factors such as Elk-1, which leads to the inhibition of the induction of the major catabolic factors involved in the degradation process of OA cartilage.

The protective effect of licofelone on experimental osteoarthritis is correlated with the downregulation of gene expression and protein synthesis of several major cartilage catabolic factors: MMP-13, cathepsin K and aggrecanases

This study sought to evaluate the levels of mRNA expression and protein synthesis of MMP-13, cathepsin K, aggrecanase-1 (ADAMTS-4), aggrecanase-2 (ADAMTS-5) and 5-lipoxygenase (5-LOX) in cartilage in the experimental anterior cruciate ligament (ACL) dog model of osteoarthritis (OA), and to examine the effects of treatment with licofelone, a 5-lipoxygenase (LOX)/cyclooxygenase (COX) inhibitor, on the levels of these catabolic factors. Sectioning of the ACL of the right knee was performed in three experimental groups: group 1 received no active treatment (placebo group); and groups 2 and 3 received therapeutic concentrations of licofelone (2.5 or 5.0 mg/kg/day orally, respectively) for 8 weeks, beginning the day following surgery. A fourth group consisted of untreated dogs that were used as normal controls. Specimens of cartilage were selected from lesional areas of OA femoral condyles and tibial plateaus, and were processed for real-time quantitative PCR and immunohistochemical analyses. The levels of MMP-13, cathepsin K, ADAMTS-4, ADAMTS-5 and 5-LOX were found to be significantly increased in OA cartilage. Licofelone treatment decreased the levels of both mRNA expression and protein synthesis of the factors studied. Of note was the marked reduction in the level of 5-LOX gene expression. The effects of the drug were about the same at both tested dosages. In vivo treatment with therapeutic dosages of licofelone has been found to reduce the degradation of OA cartilage in experimental OA. This, coupled with the results of the present study, indicates that the effects of licofelone are mediated by the inhibition of the major cartilage catabolic pathways involved in the destruction of cartilage matrix macromolecules. Moreover, our findings also indicate the possible auto-regulation of 5-LOX gene expression by licofelone in OA cartilage.