Inducible nitric oxide expression in equine articular chondrocytes: effects of antiinflammatory compounds

Chondrotoxicity of Intra-Articular Injection Treatment: A Scoping Review

The purpose of this scoping review was to identify possible chondrotoxic effects caused by drugs usually used for intra-articular injections. PubMed, Scopus, Web of Science and Cochrane were searched. Inclusion criteria required randomized controlled trials written in English that evaluate the toxic effect that damages the cartilage. The literature search resulted in 185 unique articles. 133 full-text articles were screened for inclusion, of which 65 were included. Corticosteroids, with the exception of triamcinolone, along with local anaesthetics, potentially excluding ropivacaine and liposomal bupivacaine, and nonsteroidal anti-inflammatory drugs, exhibited insufficient safety profiles to warrant casual use in clinical settings. Hyaluronic acid, on the other hand, appears to demonstrate safety while also mitigating risks associated with concurrent compounds, thereby facilitating therapeutic combinations. Additionally, there remains a paucity of data regarding platelet-rich plasma, necessitating further evaluation of its potential efficacy and safety. Overall, it seems that results are significantly influenced by the dosage and frequency of injections administered, observed in both human and animal studies.

Longitudinal MRI-defined Cartilage Loss and Radiographic Joint Space Narrowing Following Intra-Articular Corticosteroid Injection for Knee Osteoarthritis: A Systematic Review and Meta-analysis

Background

Intra-articular corticosteroid injections (IACS) are interventions which provide pain relief in knee osteoarthritis (OA). It remains unclear whether IACS have a deleterious effect on knee cartilage structure.

Purpose

To estimate the effect of IACS on cartilage structure in patients with knee OA, using joint space width (JSW) (in radiographic studies), and cartilage thickness (in magnetic resonance imaging).

Materials and methods

A literature search was performed to identify randomized control trials and observational studies published from inception to June 15, 2022. Studies were included if patients received IACS for knee OA, with a control arm. Given the different metrics used in reporting continuous variable outcomes among studies, pooled estimates for cartilage thickness change were assessed using standardized mean differences (defined as the difference between the means of the groups divided by a within-group standard deviation) to odds ratio transformation. Sensitivity analyses were conducted based on outcome metric, imaging modality, and number of injections.

Results

Six studies (1437 participants) were identified. The estimated effect of IACS on cartilage structure revealed greater odds of cartilage structure worsening (Odds Ratio (OR): 2.01, 95% Confidence Interval (CI): 1.18,3.44). Sensitivity analyses revealed similar trends, with significant results for singular injections with preference to JSW (OR: 2.44, 95%CI: 1.23,4.82), radiographic outcomes with preference to KL grade (OR: 2.03, 95%CI: 1.01,4.10), binary outcomes with preference to KL grade (OR: 2.93, 95%CI: 1.18,7.25) and quantitative measures (Standardized Mean Differences (SMD): -0.34, 95%CI: -0.66, -0.02).

Conclusions

IACS use may contribute to imaging features of knee cartilage loss. Further studies are warranted to investigate the underlying pathogenesis.

Agmatine Administration Effects on Equine Gastric Ulceration and Lameness

Osteoarthritis (OA) accounts for up to 60% of equine lameness. Agmatine, a decarboxylated arginine, may be a viable option for OA management, based on reports of its analgesic properties. Six adult thoroughbred horses, with lameness attributable to thoracic limb OA, received either daily oral phenylbutazone (6.6 mg/kg), agmatine sulfate (25 mg/kg) or a control for 30 days, with 21-day washout periods between treatments. Subjective lameness, thoracic limb ground reaction forces (GRF), plasma agmatine and agmatine metabolite levels were evaluated using an established rubric, a force platform, and mass spectrometry, respectively, before, during and after each treatment period. Gastric ulceration and plasma chemistries were evaluated before and after treatments. Braking GRFs were greater after 14 and 29 days of agmatine compared to phenylbutazone administration. After 14 days of phenylbutazone administration, vertical GRFs were greater than for agmatine or the control. Glandular mucosal ulcer scores were lower after agmatine than phenylbutazone administration. Agmatine plasma levels peaked between 30 and 60 min and were largely undetectable by 24 h after oral administration. In contrast, plasma citric acid levels increased throughout agmatine administration, representing a shift in the metabolomic profile. Agmatine may be a viable option to improve thoracic limb GRFs while reducing the risk of glandular gastric ulceration in horses with OA.

Comparative matched-pair cohort analysis of the short-term clinical outcomes of mesenchymal stem cells versus hyaluronic acid treatments through intra-articular injections for knee osteoarthritis

Purpose

Intra-articular injection of hyaluronic acid (HA) has shown promises in reducing pain and improving physical function in knee osteoarthritis (OA). Recently, cell-based therapies using mesenchymal stem cells (MSCs) have emerged as potential treatments. However, few studies have compared the treatment outcomes between MSCs and HA. This study aimed to compare the clinical and radiological outcomes of intra-articular injections of MSCs versus HA in patients with knee OA.

Methods

A cohort of 209 patients with knee OA were retrospectively screened for those who underwent intra-articular injections using MSCs or HA. Thirty MSC-treated patients (MSC group) were pair-matched with thirty HA-treated patients (HA group) based on gender and age. Clinical outcomes were evaluated using the visual analog scale (VAS), International Knee Documentation Committee (IKDC) rating system, and Lysholm scoring system. Radiological evaluation was assessed using the Kellgren-Lawrence (K-L) grading system.

Results

MSC treatment yielded consistent significant improvements in VAS, IKDC and Lysholm scores. In the HA group, VAS scores significantly decreased at 1 month, slightly increased at 3 months, and increased significantly from 3 months to 1 year after injection. The IKDC and Lysholm scores improved significantly until 3 months, but gradually worsened thereafter. Significantly greater improvements in VAS (P = 0.041), IKDC (P = 0.014), and Lysholm (P = 0.020) scores were observed in the MSC group compared to those in the HA group at 1-year post-treatment. The K-L grade worsened in a few patients, especially those in the HA group, albeit no significant difference.

Conclusions

MSC group showed better VAS, IKDC, and Lysholm scores at 1-year post-treatment, compared to the HA group, although earlier clinical improvements were superior in the HA group for the initial 3 months.

Level of Evidence

Therapeutic study, Level III.

Pentosan polysulfate inhibits IL-1β-induced iNOS, c-Jun and HIF-1α upregulation in canine articular chondrocytes

Osteoarthritic (OA) chondrocytes are shown to express inducible nitric oxide synthase (iNOS) which produces high concentrations of nitric oxide (NO), particularly when stimulated with proinflammatory cytokines. NO is involved in OA cartilage degradation. On the other hand, c-Jun N-terminal Kinase (JNK) pathway mediates the activation and transcription of c-Jun, which is required for interleukin-1 (IL-1)-induction of matrix metalloproteinases-13 (MMP-13) in OA pathogenesis. Therefore, the selective inhibition of iNOS and c-Jun is a promising target for treatment and prevention of OA. The purpose of the study was to investigate the inhibitory effects of pentosan polysulfate (PPS) on IL-1β-induced iNOS, c-Jun and HIF-α isoforms upregulation in canine articular chondrocytes (CACs). Primary (P0) chondrocytes were isolated and cultured from femoral head cartilages of three (3) dogs. First passage (P1) chondrocytes were preincubated with 0, 1, 5, 15 and 40 μg/mL of PPS for 4 hr before treatment with 10 ng/mL rhIL-1β for a further 8 hr. In addition, we evaluated the effects of single and multiple cytokine with or without LPS on iNOS protein induction. PPS significantly inhibited (P < 0.05) IL-1β-induced iNOS, c-Jun and HIF-1α mRNA upregulation in a dose-dependent pattern. iNOS mRNA was significantly inhibited at 15 and 40 μg/mL whereas c-Jun and HIF-1α were significantly downregulated at 5, 15 and 40 μg/mL of PPS compared to chondrocytes treated with only rhIL-1β. Intriguingly, CACs were recalcitrant to single IL-1β, TNF-α or LPS-induction of iNOS protein including to a combination of IL-1β+TNF-α, IL-1β+LPS except to TNF-α+LPS and IL-1β+TNF-α+LPS suggestive of a protective mechanism from iNOS detrimental effects on perpetuating OA. IL-1β+TNF-α+LPS-induced iNOS protein expression was significantly abrogated by PPS. We demonstrate for the first time that PPS is a novel inhibitor of IL-1β-induced iNOS, c-Jun, and HIF-1α mRNA upregulation and iNOS protein induction which may be beneficial for prevention and treatment OA.

The Effect of Intra-articular Corticosteroids on Articular Cartilage: A Systematic Review

Background:

Intra-articular (IA) corticosteroid therapy has been used for the treatment of inflammation and pain in the knee since the 1950s.

Purpose:

To review the current literature on the effects of IA corticosteroids on articular cartilage.

Study Design:

Systematic review.

Methods:

A MEDLINE and SCOPUS database search was performed, and studies were selected for basic science and clinical trial research on corticosteroids with direct outcome measures of cartilage health. Preliminary searches yielded 1929 articles, and final analysis includes 40 studies.

Results:

Methylprednisolone, dexamethasone, hydrocortisone, betamethasone, prednisolone, and triamcinolone were reported to display dose-dependent deleterious effects on cartilage morphology, histology, and viability in both in vitro and in vivo models. The beneficial animal in vivo effects of methylprednisolone, hydrocortisone, and triamcinolone occurred at low doses (usually <2-3 mg/dose or 8-12 mg/cumulative total dose in vivo), at which increased cell growth and recovery from damage was observed; the single human clinical trial indicated a beneficial effect of triamcinolone. However, at higher doses (>3 mg/dose or 18-24 mg/cumulative total dose in vivo), corticosteroids were associated with significant gross cartilage damage and chondrocyte toxicity. Dose and time dependency of corticosteroid chondrotoxicity was supported in the in vitro results, however, without clear dose thresholds.

Conclusion:

Corticosteroids have a time- and dose-dependent effect on articular cartilage, with beneficial effects occurring at low doses and durations and detrimental effects at high doses and durations. Clinically, beneficial effects are supported for IA administration, but the lowest efficacious dose should be used.

Oleocanthal, a phenolic derived from virgin olive oil: a review of the beneficial effects on inflammatory disease

Virgin olive oil (VOO) is credited as being one of many healthful components of the Mediterranean diet. Mediterranean populations experience reduced incidence of chronic inflammatory disease states and VOO is readily consumed as part of an everyday dietary pattern. A phenolic compound contained in VOO, named oleocanthal, shares unique perceptual and anti-inflammatory characteristics with Ibuprofen. Over recent years oleocanthal has become a compound of interest in the search for naturally occurring compounds with pharmacological qualities. Subsequent to its discovery and identification, oleocanthal has been reported to exhibit various modes of action in reducing inflammatory related disease, including joint-degenerative disease, neuro-degenerative disease and specific cancers. Therefore, it is postulated that long term consumption of VOO containing oleocanthal may contribute to the health benefits associated with the Mediterranean dietary pattern. The following paper summarizes the current literature on oleocanthal, in terms of its sensory and pharmacological properties, and also discusses the beneficial, health promoting activities of oleocanthal, in the context of the molecular mechanisms within various models of disease.

Comparative Analysis of the Immunomodulatory Properties of Equine Adult-Derived Mesenchymal Stem Cells()

Mesenchymal stem cells (MSCs) derived from bone marrow (BM), adipose tissue (AT), umbilical cord blood (CB), and umbilical cord tissue (CT) are increasingly being used to treat equine inflammatory and degenerative lesions. MSCs modulate the immune system in part through mediator secretion. Animal species and MSC tissue of origin are both important determinants of MSC function. In spite of widespread clinical use, how equine MSCs function to heal tissues is fully unknown. In this study, MSCs derived from BM, AT, CB, and CT were compared for their ability to inhibit lymphocyte proliferation and secrete mediators in response to activation. Five MSC lines from each tissue were isolated. Lymphocyte proliferation was assessed in a mixed leukocyte reaction, and mediator secretion was determined by ELISA. Regardless of tissue of origin, quiescent MSCs did not alter lymphocyte proliferation or secrete mediators, except for transforming growth factor-β (TGF-β1). When stimulated, MSCs of all tissue types decreased lymphocyte proliferation, increased prostaglandin (PGE(2)) and interleukin-6 (IL-6) secretion, and decreased production of tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). BM-MSCs and CB-MSCs also produced nitric oxide (NO), while AT-MSCs and CT-MSCs did not. Equine MSCs did not produce indoleamine 2,3-dioxygenase (IDO). These data suggest that activated equine MSCs derived from BM, AT, CT, and CB secrete high concentration of mediators and are similar to MSCs from rodents and humans in their immunomodulatory profiles. These findings have implication for the treatment of inflammatory lesions dominated by activated lymphocytes and TNF-α and IFN-γ in vivo.

Hyaluronan modulates accumulation of hypoxia-inducible factor-1 alpha, inducible nitric oxide synthase, and matrix metalloproteinase-3 in the synovium of rat adjuvant-induced arthritis model

Introduction

Hypoxia is a feature of the inflamed synovium in rheumatoid arthritis (RA). Intra-articular injection of hyaluronan (HA) may be considered a potential way to treat RA. However, the exact molecular mechanism of HA on decreased cellular responses to hypoxic environment is unclear. The present study has been designed to use the adjuvant-induced arthritis model to examine the effects of HA on the changes of immunohistochemical expressions of hypoxia-inducible factor-1alpha (HIF-1alpha), inducible nitric oxide synthase (iNOS), and matrix metalloproteinase-3 (MMP3) in the synovial tissues at the early phase of arthritic inflammation.

Methods

Monoarthritis was induced in adult male Sprague-Dawley (250-300 g) via intraarticular injection of complete Freund's adjuvant (CFA) into the tibiotarsal joint. The CFA-induction arthritis animals were divided into three groups: treatment (intraarticular injection of HA), placebo (intraarticular injection of saline) and controls (no treatments). Functional evaluations of edema and pain behavior, histology, and HIF-1alpha, iNOS, and MMP3 immunohistochemistry were performed before, after the first injection, three injections, and on the follow-up injection of the treatments.

Results

Intra-articular injection of HA also significantly suppressed the mechanical allodynia (p < 0.001) and overexpressions of HIF-1alpha (p < 0.001), iNOS (p = 0.004) and MMP3 (p < 0.001) immunoreactivity in synovium.

Conclusions

This study demonstrated that early intervention of HA is an effective protection against accumulation of inflammation-induced HIF-1alpha, iNOS, and MMP3 to limit erosive damage in CFA-induced model of arthritis.

Influence of repeated arthrocentesis and exercise on synovial fluid concentrations of nitric oxide, prostaglandin E2 and glycosaminoglycans in healthy equine joints

REASONS FOR PERFORMING STUDY

The importance of osteoarthritis (OA) in the horse and the difficulty in its early diagnosis have led to a search for potential biomarkers of joint disease. If the levels of such markers are to be interpreted accurately, clinicians and researchers need to know whether they are influenced by environmental factors and/or interventions such as exercise and repeated arthrocentesis.

OBJECTIVE

To investigate the influence of repeated arthrocentesis and exercise on nitric oxide (NO), prostaglandin E2 (PGE2) and glycosaminoglycan (GAG) concentrations in synovial fluid (SF) from normal equine joints.

METHODS

SF was collected from the left metacarpophalangeal (MCP), radiocarpal and tarsocrural joints of 16 horses. Half of the horses were exercised and arthrocentesis was repeated 14, 14.5, 17 and 24 days after the start of the exercise programme, in both exercised and control horses. Nitric oxide was determined in SF from the MCP joint only and PGE2 and GAG concentrations were determined in SF from all joints.

RESULTS

Repeated arthrocentesis caused an increase in NO concentration in the MCP joint on Day 145, in PGE2 concentrations in the radiocarpal and tarsocrural joints on Day 145 and the release of GAGs into SF of the MCP and radiocarpal joints on Day 17. Exercise resulted in an increase in PGE2 levels in all joints but did not influence the other parameters measured.

POTENTIAL RELEVANCE

Repeated arthrocentesis is a potential confounding factor for the use of synovial NO, PGE2 and GAG concentrations as markers of joint disease. Based on this study, such a confounding effect can be avoided if one week or more separates arthrocentesis procedures. Moderate exercise causes a transient rise in PGE2 in SF.

Injectable corticosteroid and local anesthetic preparations: a review for radiologists

Corticosteroids and local anesthetics are some of the most commonly administered medications in radiology departments. These medications have marked variability in their formulations, which may increase their adverse event profile for specific procedures. In particular, certain corticosteroid preparations are associated with adverse central nervous system (CNS) sequelae. This is most likely due to distal embolization by particulate formulations. Nonparticulate steroid formulations are not associated with such events. Local anesthetics have severe CNS and cardiac adverse effects if injected intravascularly and have recently been associated with intraarticular chondrolysis if used in large doses. This review discusses these medications with particular emphasis on their established and postulated adverse effects. The administering radiologist should be aware of these potential effects and how best to reduce their occurrence.

Effects of hyaluronan on vascular endothelial growth factor and receptor-2 expression in a rabbit osteoarthritis model

BACKGROUND

Little is known about the expression of vascular endothelial growth factor (VEGF) and its receptor-2 (VEGFR-2) mRNA in the cartilage of a rabbit osteoarthritis model or the influence of intraarticular injection of hyaluronan (HA) on the expression of VEGF and VEGFR-2 in cartilage during the process of osteoarthritis (OA). The therapeutic mechanism of HA is not completely understood, and we hypothesize that the mechanism is through the effects of VEGF and VEGFR2. In this study, we determined the VEGF and VEGFR-2 mRNA expression in a rabbit OA model and assessed the therapeutic mechanism of HA against OA.

METHODS

We carried out this study at the Center Laboratory of Renmin Hospital at Wuhan University and the Key Laboratory of Respiratory Disease of the Ministry of Public Health, Huazhong University of Science and Technology. Between October 2006 and April 2008 a total of 24 mature New Zealand white rabbits were divided into three groups: normal controls, a no-HA group, and an HA group. The no-HA and HA groups underwent unilateral anterior cruciate ligament transection. At 4 weeks after the operation, animals in the HA group received intraarticular injections of 1% sodium hyaluronate (HA) once a week for 5 weeks as per the clinical treatment presently utilized. The no-HA rabbits were not given HA. At death, 11 weeks following surgery, cartilage was harvested and total RNA was extracted. VEGF and VEGFR mRNAs were analyzed using the reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR for each group.

RESULTS

Cartilage damage (both extent and grade) was less severe in the HA group than in the no-HA group. VEGF and VEGFR-2 mRNA expression was enhanced in the cartilage of the OA model. Intraarticular 1% sodium hyaluronate injection inhibited VEGFR-2 expression but had no effect on reducing the VEGF mRNA expression in cartilage.

CONCLUSIONS

These results suggested that VEGF and VEGFR-2 may be involved in the progression of OA and in the therapeutic mechanism of HA at least partly through the influence of VEGFR-2 expression during the development of OA.

Effects of treatment with polysulfated glycosaminoglycan on serum cartilage oligomeric matrix protein and C-reactive protein concentrations, serum matrix metalloproteinase-2 and -9 activities, and lameness in dogs with osteoarthritis

OBJECTIVE

To investigate the effects of polysulfated glycosaminoglycan (PSGAG) treatment on serum cartilage oligomeric matrix protein (COMP) concentration, matrix metal-loproteinase-2 (MMP-2) and -9 (MMP-9) activities, C-reactive protein (CRP) concentration, and lameness scores in dogs with osteoarthritis.

ANIMALS

16 dogs with osteoarthritis and 5 clinically normal dogs.

PROCEDURES

Dogs with osteoarthritis had a history of chronic lameness, and osteophytes were observed on radiographic evaluation of the affected joint. Polysulfated glycosaminoglycan was administered IM twice a week for a total of 8 treatments to all dogs with osteoarthritis and to clinically normal control dogs.

RESULTS

Lameness scores after PSGAG treatment in osteoarthritic dogs improved in 12 of the 16 dogs. Serum COMP concentrations in osteoarthritic dogs were significantly higher than in control dogs before treatment. Lameness scores in osteoarthritic dogs decreased significantly after treatment, compared with before treatment. Lameness scores of 9 dogs with hind limb lameness improved significantly after treatment; these dogs had corresponding decreases in serum COMP concentrations. After treatment, serum COMP concentrations and lameness scores of 7 dogs with forelimb lameness remained high and were significantly higher than those of dogs with hind limb lameness. Serum MMP-9 activities of dogs with forelimb lameness were significantly higher than in dogs with hind limb lameness after treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

IM administration of PSGAG inhibited COMP degradation in dogs with osteoarthritis. Results indicate that decreases in serum COMP concentrations might be related to improvement in lameness after PSGAG treatment.

Effects of hyaluronan on nitric oxide levels and superoxide dismutase activities in synovial fluid in knee osteoarthritis

The aim of the present study was to evaluate the effects of hyaluronan (HA) on nitric oxide (NO) levels and superoxide dismutase (SOD) enzyme activities in synovial fluid (SF) in the treatment of patients with knee osteoarthritis (OA). SF samples were aspirated from OA patients before the commencement of the treatment (n=23) and 6 weeks after they were treated with HA products. NO levels and SOD activities were compared between the pre- and post-treatment of OA patients and of the control group (n=10). SF NO levels were significantly higher in patients with OA before the commencement of the treatment compared with the post-treatment (p<0.001) and the control groups. The SF SOD activity of patients before the commencement of the treatment was lower than the values in the controls and post-treatment (p<0.001). There is no significant correlation between SF NO and SOD levels and the radiographic changes of the OA knee according to Kellgren-Lawrence grading (p>0.05). Also, the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) pain scores and physical function scores were gradually improved. These findings made us think that SF NO was a potent mediator in cartilage damage in OA, whereas SOD was an antioxidant mediator in the same process. Exogenous HA injections might reduce the NO levels and increase SOD activities in synovial fluid. These effects also do not seem to be dependent on the radiographic grading of the OA knee. More comprehensive studies are needed to clarify a possible clinical significance of this topic, and we suggest that this is an important area for further research into new treatment options.

Intra-Articular Injections for Joint Disease in Horses

Lameness remains an important source of reduced performance in many types of horses. Pain referable to joints is among the most common causes, and intra-articular injections remain a common and important means of addressing lameness referable to joints in horses.

Chondroprotective drugs in degenerative joint diseases

Catabolic cytokine and anabolic growth factor pathways control destruction and repair in osteoarthritis (OA). A unidirectional TNF-alpha/IL-1-driven cytokine cascade disturbs the homeostasis of the extracellular matrix of articular cartilage in OA. Although chondrocytes in OA cartilage overexpress anabolic insulin-like growth factor (IGF) and its specific receptor (IGFRI) autocrine TNF-alpha released by apoptotic articular cartilage cells sets off an auto/paracrine IL-1-driven cascade that overrules the growth factor activities that sustain repair in degenerative joint disease. Chondroprotection with reappearance of a joint space that had disappeared has been documented unmistakably in peripheral joints of patients suffering from spondyloarthropathy when treated with TNF-alpha-blocking agents that repressed the unidirectional TNF-alpha/IL-1-driven cytokine cascade. A series of connective tissue structure-modifying agents (CTSMAs) that directly affect IL-1 synthesis and release in vitro and down-modulate downstream IL-1 features, e.g. collagenase, proteoglycanase and matrix metalloproteinase activities, the expression of inducible nitric oxide synthase, the increased release of nitric oxide, and the secretion of prostaglandin E(2), IL-6 and IL-8, have been shown to possess disease-modifying OA drug (DMOAD) activities in experimental models of OA and in human subjects with finger joint and knee OA. Examples are corticosteroids, some sulphated polysaccharides, chemically modified tetracyclines, diacetylrhein/rhein, glucosamine and avocado/soybean unsaponifiables.

Apoptosis and the loss of chondrocyte survival signals contribute to articular cartilage degradation in osteoarthritis

Apoptotic death of articular chondrocytes has been implicated in the pathogenesis of osteoarthritis (OA). Apoptotic pathways in chondrocytes are multi-faceted, although some cascades appear to play a greater in vivo role than others. Various catabolic processes are linked to apoptosis in OA cartilage, contributing to the reduction in cartilage integrity. Recent studies suggest that beta1-integrin mediated cell-matrix interactions provide survival signals for chondrocytes. The loss of such interactions and the inability to respond to IGF-1 stimulation may be partly responsible for the hypocellularity and matrix degradation that characterises OA. Here we have reviewed the literature in this area of cartilage cell biology in an effort to consolidate the existing information into a plausible hypothesis regarding the involvement of apoptosis in the pathogenesis of OA. Understanding of the interactions that promote chondrocyte apoptosis and cartilage hypocellularity is essential for developing appropriately targeted therapies for inhibition of chondrocyte apoptosis and the treatment of OA.

Intra-articular hyaluronan (hyaluronic acid) and hylans for the treatment of osteoarthritis: mechanisms of action

Although the predominant mechanism of intra-articular hyaluronan (hyaluronic acid) (HA) and hylans for the treatment of pain associated with knee osteoarthritis (OA) is unknown, in vivo, in vitro, and clinical studies demonstrate various physiological effects of exogenous HA. HA can reduce nerve impulses and nerve sensitivity associated with the pain of OA. In experimental OA, this glycosaminoglycan has protective effects on cartilage, which may be mediated by its molecular and cellular effects observed in vitro. Exogenous HA enhances chondrocyte HA and proteoglycan synthesis, reduces the production and activity of proinflammatory mediators and matrix metalloproteinases, and alters the behavior of immune cells. Many of the physiological effects of exogenous HA may be a function of its molecular weight. Several physiological effects probably contribute to the mechanisms by which HA and hylans exert their clinical effects in knee OA.

Effects of anti-arthritis preparations on gene expression and enzyme activity of cyclooxygenase-2 in cultured equine chondrocytes

OBJECTIVE

To determine the effects of recombinant equine interleukin -1beta (reIL-1beta) and 4 anti-inflammatory compounds on the expression and activity of cyclooxygenase (COX)-2 in cultured equine chondrocytes.

SAMPLE POPULATION

Articular cartilage from 9 young adult horses.

PROCEDURE

Reverse transcriptase-polymerase chain reaction methods were used to amplify a portion of equine COX-2 to prepare a cDNA probe. Northern blot analysis was used to quantify the expression of COX-2 in first-passage cultures of equine articular chondrocytes propagated in media containing dexamethasone (DEX), phenylbutazone (PBZ), polysulfated glycosaminoglycan, and hyaluronan, each at concentrations of 10 and 100 microg/ml and each with or without reIL-1beta. A commercial immunoassay was used to determine prostaglandin E2 (PGE2) concentrations in conditioned medium of similarly treated cells to quantify COX-2 activity.

RESULTS

Addition of reIL-1beta increased the expression of COX-2 in a dose-dependent manner, which was paralleled by an increased concentration of PGE2 in culture medium. Concentration of PGE2 in spent medium from reIL-beta-treated chondrocytes was significantly reduced by DEX and PBZ; however, only DEX significantly reduced gene expression of COX-2.

CONCLUSIONS AND CLINICAL RELEVANCE

Prostaglandin E2 is considered to be an important mediator in the pathophysiologic processes of arthritis, and cultured chondrocytes respond to interleukin-1 with enhanced expression and activity of COX-2. Palliative relief in affected horses is probably attributable, in part, to inhibition of PGE2 synthesis; however, analysis of these data suggests that of the 4 compounds tested, only DEX affects pretranslational regulation of the COX-2 gene in cultured equine chondrocytes.