Human-specific duplicate CHRFAM7A gene is associated with more severe osteoarthritis and amplifies pain behaviours.

OBJECTIVES: CHRFAM7A is a uniquely human fusion gene that functions as a dominant negative regulator of alpha 7 acetylcholine nicotinic receptor (α7nAChR) in vitro. This study determined the impact of CHRFAM7A on α7nAChR agonist responses, osteoarthritis (OA) severity and pain behaviours and investigated mechanisms. METHODS: Transgenic CHRFAM7A (TgCHRFAM7A) mice were used to determine the impact of CHRFAM7A on knee OA histology, pain severity in OA and other pain models, response to nAchR agonist and IL-1ß. Mouse and human cells were used for mechanistic studies. RESULTS: Transgenic (Tg) TgCHRFAM7A mice developed more severe structural damage and increased mechanical allodynia than wild type (WT) mice in the destabilisation of medial meniscus model of OA. This was associated with a decreased suppression of inflammation by α7nAchR agonist. TgCHRFAM7A mice displayed a higher basal sensitivity to pain stimuli and increased pain behaviour in the monoiodoacetate and formalin models. Dorsal root ganglia of TgCHRFAM7A mice showed increased macrophage infiltration and expression of the chemokine fractalkine and also had a compromised antinociceptive response to the α7nAchR agonist nicotine. Both native CHRNA7 and CHRFAM7A subunits were expressed in human joint tissues and the CHRFAM7A/CHRNA7 ratio was increased in OA cartilage. Human chondrocytes with two copies of CHRFAM7A had reduced anti-inflammatory responses to nicotine. CONCLUSION: CHRFAM7A is an aggravating factor for OA-associated inflammation and tissue damage and a novel genetic risk factor and therapeutic target for pain.

Identification of Symptom Phenotypes of Hand Osteoarthritis Using Hierarchical Clustering: Results From the DIGICOD Cohort.

OBJECTIVE: We aimed to delineate phenotypes in hand osteoarthritis (HOA) based on cardinal symptoms (pain, functional limitation, stiffness, and aesthetic discomfort). METHODS: With data from the Digital Cohort Design (DIGICOD), we performed a hierarchical agglomerative clustering analysis based on Australian/Canadian Osteoarthritis Hand Index (AUSCAN) subscores for pain, physical function, stiffness, and visual analog scale for aesthetic discomfort. Kruskal-Wallis and post hoc analyses were used to assess differences between clusters. RESULTS: Among 389 patients, we identified 5 clusters: cluster 1 (n = 88) and cluster 2 (n = 91) featured low and mild symptoms; cluster 3 (n = 80) featured isolated aesthetic discomfort; cluster 4 (n = 42) featured a high level of pain, stiffness, and functional limitation; and cluster 5 (n = 88) had the same features as cluster 4 but with high aesthetic discomfort. For clusters 4 and 5, AUSCAN pain score was >41 of 100, representing only one-third of our patients. Aesthetic discomfort (clusters 3 and 5) was significantly associated with erosive HOA and a higher number of nodes. The highly symptomatic cluster 5 was associated but not significantly with metabolic syndrome, and body mass index and C-reactive protein level did not differ among clusters. Symptom intensity was significantly associated with joint destruction as well as with physical and psychological burden. Patients' main expectations differed among clusters, and function improvement was the most frequent expectation overall. CONCLUSION: The identification of distinct clinical clusters based on HOA cardinal symptoms suggests previously undescribed subtypes of this condition, warranting further study of biological characteristics of such clusters, and opening a path toward phenotype-based personalized medicine in HOA.

Time to Total Knee Arthroplasty after Intra-Articular Hyaluronic Acid or Platelet-Rich Plasma Injections: A Systematic Literature Review and Meta-Analysis.

Intra-articular (IA) hyaluronic acid (HA) and platelet-rich plasma (PRP) injections are increasingly being prescribed for knee osteoarthritis (KOA). However, failure of the medical treatment may result in total knee arthroplasty (TKA). We wondered if IA HA or PRP injections (intervention) may delay the time to TKA (outcome) among KOA patients (population), compared to KOA patients not receiving these injections (comparator). For this systematic literature review (SLR) and meta-analysis, we selected observational studies with at least one group of patients receiving IA HA or PRP and with TKA data available. The main outcome was time from the diagnosis of KOA to TKA. We included 25 articles in the SLR (2,824,401 patients) and four in the meta-analysis. The mean strengthening the reporting of observational studies in epidemiology (STROBE) score was 63%. For patients receiving versus not receiving HA injections, the delay between a declared diagnosis of KOA to TKA was increased by 9.8 months (95% CI (8.2-11.4)). As compared with standard of care, the effect size of HA injections for this outcome was 0.57 (95% CI (0.36-0.76)). Only one study described a median time from PRP injections to TKA of 4.1 years (range 0.3-14.7). IA HA injections were associated with increased time to TKA. Causality cannot be concluded because of missing confounder factors as comorbidities. Data were insufficient to conclude any effect of PRP injections on TKA delay.

Pollutants: a candidate as a new risk factor for osteoarthritis-results from a systematic literature review.

BACKGROUND: Considering non-classical environmental risk factors for osteoarthritis (OA), a systematic literature review (SLR) was performed to summarise existing knowledge on associations between OA and pollutants. METHODS: PubMed was used to identify studies reporting data on OA and pollutants in humans (examples of MeSH terms: "Pesticides" or "Polychlorinated Biphenyls" or 'Lead'). Reports included epidemiological clinical studies, pollutant assessments in ex vivo OA joint, and in vitro effects of pollutants on chondrocytes. RESULTS: Among the 193 potentially relevant articles, 14 were selected and combined with 9 articles obtained by manual search. Among these 23 articles there were: (1) 11 epidemiological studies on the relationship between OA and pollutants exposure, (2) 8 on pollutant concentrations in ex vivo OA joint, (3) 4 on the in vitro effects of pollutants on human chondrocytes. Epidemiological studies investigating mainly chlorinated and fluorinated pollutants suggested a possible link with OA. In cross-sectional studies, radiographic knee OA prevalence increased with higher serum lead levels. There was also a relationship between serum lead levels and serum/urine joint biomarkers. A high concentration of heavy metals in the cartilage tidemark was found in ex vivo joints. In vitro, the viability of chondrocytes was reduced in presence of some pollutants. However, the level of knowledge currently remains low, justifying the need for new methodologically sound studies. CONCLUSIONS: This SLR supports the hypothesis of a possible involvement of pollutants in OA disease risk. Large-scale epidemiological and biological studies and ideally big-data analysis are needed to confirm that pollutants could be risk factors for OA.

Alpha-7 Nicotinic Receptor Dampens Murine Osteoblastic Response to Inflammation and Age-Related Osteoarthritis.

Introduction: Osteoarthritis (OA) is a whole-joint disease characterized by a low-grade inflammation that is involved in both cartilage degradation and subchondral bone remodeling. Since subchondral bone has a cholinergic innervation and that acetylcholine (Ach) might have an anti-inflammatory effect through the α7 nicotinic Ach receptor (α7nAchR), we aimed (i) to determine the expression of non-neuronal cholinergic system and nicotinic receptor subunits by murine and human osteoblasts, (ii) to address the role of α7nAchR in osteoblastic response to inflammation, and (iii) to study the role of α7nAchR in a spontaneous aging OA model. Methods: Primary cultures of WT and α7nAchR knock-out mice (Chrna7-/-) murine osteoblasts and of subchondral bone human OA osteoblasts were performed. The expressions of the non-neuronal cholinergic system and of the nAchR subunits were assessed by PCR. In vitro, IL1ß-stimulated WT, Chrna7-/-, and human osteoblasts were pretreated with nicotine. At 24 h, expressions of interleukin-6 (IL6) and metalloproteinase-3 and -13 (MMP), RANK-ligand (RANKL), and osteoprotegerin (OPG) were quantified by qPCR and ELISA. Spontaneous aging OA was evaluated and compared between male WT and Chrna7-/- mice of 9 and 12 months. Results: Murine WT osteoblasts express the main components of the cholinergic system and α7 subunit composing α7nAchR. Nicotine partially prevented the IL1ß-induced expression and production of IL6, MMP3, and RANKL in WT osteoblasts. The effect for IL6 and MMP was mediated by α7nAchR since nicotine had no effect on Chrna7-/- osteoblasts while the RANKL decrease persisted. Chrna7-/- mice displayed significantly higher cartilage lesions than their WT counterparts at 9 and 12 months, without difference in subchondral bone remodeling. Human OA osteoblasts also expressed the non-neuronal cholinergic system and α7 subunit as well as CHRFAM7A, the dominant negative duplicate of Chrna7. Nicotine pretreatment did not significantly reduce IL6 and MMP3 production in IL-1ß-stimulated human osteoarthritic osteoblasts (n = 4), possibly due to CHRFAM7A. Conclusion: Cholinergic system counteracts murine osteoblastic response to IL-1ß through α7nAchR. Since α7nAchR deletion may limit cartilage degradation during murine age-related OA, enhancing cholinergic system could be a new therapeutic target in OA but may depend on CHRFAM7A expression.

Transcutaneous vagus nerve stimulation in erosive hand osteoarthritis: protocol for the randomised, double-blind, sham-controlled ESTIVAL trial.

INTRODUCTION: Patients with erosive hand osteoarthritis (EHOA) experience pain and inflammation, two features that can be targeted by vagus nerve stimulation using electrical auricular transcutaneous vagus nerve stimulation (tVNS). A pilot study demonstrated the feasibility of the procedure, so we designed a randomised sham-controlled trial to determine the safety and efficacy of tVNS in EHOA. METHODS AND ANALYSIS: ESTIVAL Study (Essai randomisé comparant la STImulation auriculaire transcutanée du nerf Vague versus sham stimulation dans l'Arthrose DigitaLe Érosive symptomatique et inflammatoire) is a superiority, randomised, double-blind sham-controlled trial comparing two parallel arms: active and sham tVNSs in a 1:1 ratio. Patients with symptomatic EHOA (score ≥40/100 mm on a visual analogue scale (VAS) for pain of 0-100 mm) and inflammatory EHOA (≥1 clinical and ultrasonography-determined interphalangeal synovitis) are included in 18 hospital centres (17 rheumatology and 1 rehabilitation departments) in France. Active and sham tVNSs use an auricular electrode connected to the Vagustim device, with no electric current delivered in the sham group. Patients undergo stimulation for 20 min/day for 12 weeks. The follow-up visits take place at weeks 4, 8 and 12. The enrolment duration is 2 years and started in April 2021; 156 patients are scheduled to be included. The primary outcome is the difference in self-reported hand pain in the previous 48 hours measured on a VAS of 0-100 mm between baseline and week 12. Secondary outcomes include other pain outcomes, function, quality of life, serum biomarker levels, compliance and tolerance. For a subset of patients, MRI of the hand is performed at baseline and week 12 to compare the change in Outcome Measures in Rheumatology/Hand Osteoarthritis MRI Scoring System subscores. The primary analysis will be performed at the end of the study according to the intent-to-treat principle. ETHICS AND DISSEMINATION: Ethics approval was obtained from the institutional review board (Comité de Protection des Personnes, 2020-A02213-36). All participants will be required to provide written informed consent. The findings will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04520516; Pre-results. PROTOCOL VERSION AND NUMBER: V.2 of 11 March 2021.

Effect of Transcutaneous Vagus Nerve Stimulation in Erosive Hand Osteoarthritis: Results from a Pilot Trial.

Beyond its effect on vegetative functions, the activation of the vagus nerve inhibits inflammation and reduces pain signaling. The aim of this open-label pilot study was to determine the efficacy and tolerance of transcutaneous auricular VNS (taVNS) on erosive hand osteoarthritis (EHOA) symptoms. Symptomatic EHOA patients with hand pain VAS ≥ 40/100 mm and ≥1 interphalangeal swollen joint(s) were included. The taVNS was performed for 4 weeks using an auricular electrode applied one hour per day and connected to a TENS device with pre-established settings. Clinical efficacy was evaluated by changes between baseline and at 4 weeks with hand pain VAS and the functional index FIHOA score, using a Wilcoxon t-test. The treatment tolerance was also evaluated. Eighteen patients (median age 69 years old, 83% women) were analyzed. At baseline, hand pain VAS was 60 mm [IQR 50; 78.2] and FIHOA 15 [10.7; 20.2]. After 4 weeks, taVNS significantly reduced hand pain VAS, with a median decrease of 23.5 mm [7.7; 37.2] (p = 0.001), as well as FIHOA, with a median decrease of 2 points [0.75; 5.2] (p = 0.01). No serious adverse events were reported. One patient stopped taVNS because of auricular discomfort. This first proof-of-concept trial indicated that taVNS is feasible and may decrease joint inflammation and clinical symptoms in EHOA, arguing for a randomized controlled study versus sham stimulation.

Metacarpophalangeal Joint Impairment in Hand Osteoarthritis and Its Association With Mechanical Factors: Results From the Digital Cohort Osteoarthritis Design Hand Osteoarthritis Cohort.

OBJECTIVE: To determine the prevalence, distribution, and characteristics associated with radiographic metacarpophalangeal (MCP) joint osteoarthritis (OA). METHODS: This was a cross-sectional study of baseline data from the Digital Cohort Osteoarthritis Design, a French monocentric cohort including patients with symptomatic hand OA. We evaluated the prevalence of radiographic MCP joint OA, defined as ≥2 MCP joints with a Kellgren/Lawrence score of ≥2. We compared the prevalence of MCP joint OA in the dominant and nondominant hands. Associations between radiographic MCP joint OA and patient characteristics were studied using univariable and multivariable logistic regression. RESULTS: Radiographic MCP joint OA was present in 138 of the 425 patients (32.5%) but was not severe. Patients with MCP joint OA had a mean age of 69.2 ± 6.9 years, a body mass index of 25 ± 4.2 kg/m2 , and 86.2% were women. MCP joint OA was more frequent in the dominant hand and predominated at the first and second MCP joints. In the multivariable analysis, MCP joint OA was associated with older age (odds ratio [OR] 1.05 [95% confidence interval (95% CI) 1.01, 1.10] for each year), manual occupation (OR 3.74 [95% CI 1.21, 11.54]), scaphotrapezial OA (OR 2.18 [95% CI 1.27, 3.72]), and a high number of proximal interphalangeal joints with radiographic OA. MCP joint OA was not associated with metabolic syndrome or hand OA symptoms. CONCLUSION: In this cross-sectional study using a hospital-based hand OA cohort, radiographic MCP joint OA was frequent and associated with structural hand OA features rather than with symptom severity. Our results suggest that the involvement of MCP joints in hand OA is predominantly related to mechanical rather than systemic factors in this population.

Regulation of the acetylcholine/α7nAChR anti-inflammatory pathway in COVID-19 patients.

The cholinergic system has been proposed as a potential regulator of COVID-19-induced hypercytokinemia. We investigated whole-blood expression of cholinergic system members and correlated it with COVID-19 severity. Patients with confirmed SARS-CoV-2 infection and healthy aged-matched controls were included in this non-interventional study. A whole blood sample was drawn between 9-11 days after symptoms onset, and peripheral leukocyte phenotyping, cytokines measurement, RNA expression and plasma viral load were determined. Additionally, whole-blood expression of native alpha-7 nicotinic subunit and its negative dominant duplicate (CHRFAM7A), choline acetyltransferase and acetylcholine esterase (AchE) were determined. Thirty-seven patients with COVID-19 (10 moderate, 11 severe and 16 with critical disease) and 14 controls were included. Expression of CHRFAM7A was significantly lower in critical COVID-19 patients compared to controls. COVID-19 patients not expressing CHRFAM7A had higher levels of CRP, more extended pulmonary lesions and displayed more pronounced lymphopenia. COVID-19 patients without CHRFAM7A expression also showed increased TNF pathway expression in whole blood. AchE was also expressed in 30 COVID-19 patients and in all controls. COVID-19-induced hypercytokinemia is associated with decreased expression of the pro-inflammatory dominant negative duplicate CHRFAM7A. Expression of this duplicate might be considered before targeting the cholinergic system in COVID-19 with nicotine.

The DIGICOD cohort: A hospital-based observational prospective cohort of patients with hand osteoarthritis - methodology and baseline characteristics of the population.

OBJECTIVE: Despite its prevalence, there are few worldwide hand osteoarthritis (HOA) cohorts. The main objective of DIGItal COhort Design (DIGICOD) cohort is to investigate prognostic clinical, biological, genetic and imaging factors of clinical worsening after 6years follow-up. METHODS: DIGICOD is a hospital-based prospective cohort including patients>35years-old with symptomatic HOA fulfilling: (i) ACR criteria for HOA with≥2 symptomatic joints among proximal/distal interphalangeal joints or 1st interphalangeal joint with Kellgren-Lawrence (KL)≥2; or (ii) symptomatic thumb base OA with KL≥2. Main exclusion criteria were inflammatory arthritis and crystal arthropathies. Annual clinical evaluations were scheduled with imaging (X-rays of the hands and of other OA symptomatic joints) and biological sampling every 3years. Hand radiographs are scored using KL and anatomical Verbruggen-Veys scores. Follow-up visits are ongoing. Cohort methodology and baseline characteristics are presented. RESULTS: Between April 2013 and June 2017, from the 436 HOA included patients, 426 have been analysed of whom 357 (84%) are women. Mean age±standard deviation was 66.7±7.3years and mean disease duration was 12.6±9.6years. Metabolic syndrome affected 151 (36.5%) patients. Mean Visual Analog Scale (VAS) hand pain (0-100mm) was 44.4±26.7mm at activity. Mean FIHOA (0-100) was 19.9±18.6. Elevated serum CRP level (≥5mg/L) involved 10% patients. Mean KL score (0-128) was 46.7±18 and the mean number of joint with KL≥2 was 15.1±6.3. Erosive HOA (defined as≥1 Erosive or Remodeling phase joint according to Verbruggen-Veys score) involved 195/426 (45.8%) patients and the median number (interquartile range) of erosive joints in erosive patients was 3.0 (1.0-5.0). CONCLUSION: DIGICOD is a unique prospective HOA cohort with a long-term 6years standardized assessment and has included severe radiologically HOA patients with a high prevalence of erosive disease.

Vagus nerve stimulation in musculoskeletal diseases.

The vagus nerve is the main nerve of the parasympathetic autonomic nervous system. Beyond its vegetative functions, the vagus nerve possesses anti-inflammatory and analgesic properties. Initially developed in the treatment of refractory epilepsy, vagus nerve stimulation (VNS) is currently being evaluated in several musculoskeletal diseases. VNS can be invasive by placing an electrode around the cervical vagus nerve and connected to a generator implanted subcutaneously or non-invasive stimulating the cervical vagus nerve branch percutaneously (auricular or cervical). In rheumatoid arthritis (RA) patients, VNS has been shown to dampen the inflammatory response of circulatory peripheral cells. Several open-labeled small pilot studies have demonstrated that VNS, either invasive or transcutaneous, is associated with a significant decrease of RA disease activity. As well, other studies have shown that VNS could limit fatigue in Sjogren's syndrome and systemic lupus, or decrease pain in fibromyalgia as well as in erosive hand osteoarthritis. However, some questions remain, such as the settings of stimulation, the duration of treatment, or the optimal stimulation route. Finally, randomized controlled trials versus sham stimulation with large samples of patients are mandatory to definitively conclude about the efficacy of VNS.

Recommendations of the French Society of Rheumatology on pharmacological treatment of knee osteoarthritis.

OBJECTIVES: To establish recommendations for pharmacological treatment of knee osteoarthritis specific to France. METHODS: On behalf of the French Society of Rheumatology (SFR), a bibliography group analyzed the literature on the efficacy and safety of each pharmacological treatment for knee osteoarthritis. This group joined a multidisciplinary working group to draw up recommendations. Strength of recommendation and quality of evidence level were assigned to each recommendation. A review committee gave its level of agreement. RESULTS: Five general principles were established: 1) need to combine pharmacological and non-pharmacological treatments, 2) personalization of treatment, 3) symptomatic and/or functional aim of pharmacological treatments, 4) need to regularly re-assess the treatments and 5) discussion about arthroplasty if medical treatment fails. Six recommendations involved oral treatments: 1) paracetamol should not necessarily be prescribed systematically and/or continuously, 2) NSAIDs, possibly as first-line, 3) weak opioids, 4) strong opioids, 5) symptomatic slow-acting drugs of osteoarthritis, and 6) duloxetine (off-label use). Two recommendations involved topical agents (NSAIDs and capsaicin<1%). Three recommendations involved intra-articular treatments: corticosteroid or hyaluronic acid injections that can be proposed to patients. The experts did not draw a conclusion about the benefits of platelet-rich plasma injections. CONCLUSION: These are the first recommendations of the SFR on the pharmacological treatment of knee osteoarthritis.

The Role of the Non-neuronal Cholinergic System in Inflammation and Degradation Processes in Osteoarthritis.

OBJECTIVE: The non-neuronal cholinergic system represents non-neuronal cells that have the biochemical machinery to synthetize de novo and/or respond to acetylcholine (ACh). We undertook this study to investigate this biochemical machinery in chondrocytes and its involvement in osteoarthritis (OA). METHODS: Expression of the biochemical machinery for ACh metabolism and nicotinic ACh receptors (nAChR), particularly α7-nAChR, in human OA and murine chondrocytes was determined by polymerase chain reaction and ligand-binding. We investigated the messenger RNA expression of the human duplicate α7-nACh subunit, called CHRFAM7A, which is responsible for truncated α7-nAChR. We assessed the effect of nAChR on chondrocytes activated by interleukin-1ß (IL-1ß) and the involvement of α7-nAChR using chondrocytes from wild-type (WT) and α7-deficient Chrna7-/- mice. The role of α7-nAChR in OA was explored after medial meniscectomy in WT and Chrna7-/- mice. RESULTS: Human and murine chondrocytes express the biochemical partners of the non-neuronal cholinergic system and a functional α7-nAChR at their cell surface (n = 5 experiments with 5 samples each). The expression of CHRFAM7A in human OA chondrocytes (n = 23 samples) correlated positively with matrix metalloproteinase 3 (MMP-3) (r = 0.38, P < 0.05) and MMP-13 (r = 0.48, P < 0.05) expression. Nicotine decreased the IL-1ß-induced IL-6 and MMP expression, in a dose-dependent manner, in WT chondrocytes but not in Chrna7-/- chondrocytes. Chrna7-/- mice that underwent meniscectomy (n = 7) displayed more severe OA cartilage damage (mean ± SD Osteoarthritis Research Society International [OARSI] score 4.46 ± 1.09) compared to WT mice that underwent meniscectomy (n = 9) (mean ± SD OARSI score 3.05 ± 0.9; P < 0.05). CONCLUSION: The non-neuronal cholinergic system is functionally expressed in chondrocytes. Stimulation of nAChR induces antiinflammatory and anticatabolic activity through α7-nAChR, but the anticatabolic activity may be mitigated by truncated α7-nAChR in human chondrocytes. In vivo experiments strongly suggest that α7-nAChR has a protective role in OA.

Clearing method for 3-dimensional immunofluorescence of osteoarthritic subchondral human bone reveals peripheral cholinergic nerves.

The cholinergic system plays a major anti-inflammatory role in many diseases through acetylcholine (Ach) release after vagus nerve stimulation. Osteoarthritis (OA) is associated with local low-grade inflammation, but the regulatory mechanisms are unclear. Local Ach release could have anti-inflammatory activity since articular cells express Ach receptors involved in inflammatory responses. Using the 3DISCO clearing protocol that allows whole-sample 3-dimensional (3D) analysis, we cleared human OA cartilage-subchondral bone samples to search for cholinergic nerve fibres able to produce Ach locally. We analysed 3 plugs of knee cartilage and subchondral bone from 3 OA patients undergoing arthroplasty. We found no nerves in the superficial and intermediate articular cartilage layers, as evidenced by the lack of Peripherin staining (a peripheral nerves marker). Conversely, peripheral nerves were found in the deepest layer of cartilage and in subchondral bone. Some nerves in the subchondral bone samples were cholinergic because they coexpressed peripherin and choline acetyltransferase (ChAT), a specific marker of cholinergic nerves. However, no cholinergic nerves were found in the cartilage layers. It is therefore feasible to clear human bone to perform 3D immunofluorescence. Human OA subchondral bone is innervated by cholinergic fibres, which may regulate local inflammation through local Ach release.

[Is there one or more osteoarthritis ?] / Une arthrose ou des arthroses ?

Osteoarthritis (OA), the most common osteoarticular disease, is a all joint disease. It affects several joint (spine, knee, hip, hands) that are subject to different degrees of mechanical stress. As well, the clinical forms of OA could differ significantly from one subject to another: some could have mono or polyarticular, erosive hand OA or recurrent effusion while we do not know what governs these different clinical presentations. We now consider the pathophysiology of OA according to the patient's risk factors because we know that they involve different pathogenic mechanisms. Thus, four major clinical phenotypes are defined based on risk factors which are age, trauma, obesity/ metabolic syndrome, and family history. Osteoarthritis is therefore a much more complex disease than it has been thought for a long time. The lack of efficient therapeutic may be due in part to the lack of knowledge of these different phenotypes that are always all grouped together in studies. It is therefore necessary to better characterize the different OA to meet the growing needs of care.

L'arthrose, pathologie ostéoarticulaire la plus fréquente, est une maladie de l'ensemble des tissus articulaires. Elle affecte différentes localisations (rachis, genou, hanche, mains) qui sont soumises à différents degrés de stress mécanique. Sa présentation clinique diffère parfois de manière importante d'un sujet à l'autre : il existe ainsi des formes mono- ou polyarticulaires, des atteintes digitales érosives, des atteintes plus inflammatoires avec un épanchement sans que l'on comprenne bien les déterminants de ces formes cliniques. On envisage maintenant la physiopathologie de l'arthrose en fonction des facteurs de risque du patient car on sait qu'ils impliquent des mécanismes physiopathologiques distincts. Ainsi, on définit quatre grands phénotypes cliniques fondés sur les facteurs de risque que sont l'âge, les traumatismes, l'obésité/syndrome métabolique et les antécédents familiaux. L'arthrose est donc une maladie plus complexe que ce qu'on l'on a pensé pendant longtemps. Le manque de moyens thérapeutiques provient sans doute en partie du manque de connaissance de ces différents phénotypes qui sont regroupés dans toutes les études. Il est donc nécessaire de mieux caractériser les différentes arthroses afin de répondre aux besoins de prise en charge grandissants.

Impairment of glyoxalase-1, an advanced glycation end-product detoxifying enzyme, induced by inflammation in age-related osteoarthritis.

BACKGROUND: Accumulation of advanced glycation end-products (AGEs) is involved in age-related osteoarthritis (OA). Glyoxalase (Glo)-1 is the main enzyme involved in the removal of AGE precursors, especially carboxymethyl-lysine (CML). We aimed to investigate the expression of several AGEs and Glo-1 in human OA cartilage and to study chondrocytic Glo-1 regulation by inflammation, mediated by interleukin (IL)-1ß. METHODS: Ex vivo, we quantified AGEs (pentosidine, CML, methylglyoxal-hydroimidazolone-1) in knee cartilage from 30 OA patients. Explants were also incubated with and without IL-1ß, and we assessed Glo-1 protein expression and enzymatic activity. In vitro, primary cultured murine chondrocytes were stimulated with increasing concentrations of IL-1ß to assess Glo-1 enzymatic activity and expression. To investigate the role of oxidative stress in the IL-1ß effect, cells were also treated with inhibitors of mitochondrial oxidative stress or nitric oxide synthase. RESULTS: Ex vivo, only the human cartilage CML content was correlated with patient age (r = 0.78, p = 0.0031). No statistically significant correlation was found between Glo-1 protein expression and enzymatic activity in human cartilage and patient age. We observed that cartilage explant stimulation with IL-1ß decreased Glo-1 protein expression and enzymatic activity. In vitro, we observed a dose-dependent decrease in Glo-1 mRNA, protein quantity, and enzymatic activity in response to IL-1ß in murine chondrocytes. Inhibitors of oxidative stress blunted this downregulation. CONCLUSION: Glo-1 is impaired by inflammation mediated by IL-1ß in chondrocytes through oxidative stress pathways and may explain age-dependent accumulation of the AGE CML in OA cartilage.