Is osteoarthritis a mitochondrial disease?: what is the evidence

Final peer-reviewed manuscript[Abstract] Propose of review: To summarize the evidence that suggests that osteoarthritis (OA) is a mitochondrial disease. Recent findings: Mitochondrial dysfunction together with mtDNA damage could contribute to cartilage degradation via several processes such as: (1) increased apoptosis; (2) decreased autophagy; (3) enhanced inflammatory response; (4) telomere shortening and increased senescence chondrocytes; (5) decreased mitochondrial biogenesis and mitophagy; (6) increased cartilage catabolism; (7) increased mitochondrial fusion leading to further reactive oxygen species production; and (8) impaired metabolic flexibility. Summary: Mitochondria play an important role in some events involved in the pathogenesis of OA, such as energy production, the generation of reactive oxygen and nitrogen species, apoptosis, authophagy, senescence and inflammation. The regulation of these processes in the cartilage is at least partially controlled by retrograde regulation from mitochondria and mitochondrial genetic variation. Retrograde regulation through mitochondrial haplogroups exerts a signaling control over the nuclear epigenome, which leads to the modulation of nuclear genes, cellular functions and development of OA. All these data suggest that OA could be considered a mitochondrial disease as well as other complex chronic disease as cancer, cardiovascular and neurologic diseases.Instituto de Salud Carlos III; PI17/00210Instituto de Salud Carlos III; PI20/00614Instituto de Salud Carlos III; PI19/01206Instituto de Salud Carlos III; RETIC-RIER-RD16/0012/000

Anti-inflammatory activity of APPA (Apocynin and Paeonol) in human articular chondrocytes

[Abstract] Osteoarthritis (OA) is a chronic joint disease leading to cartilage loss and reduction in the joint space which results in pain. The current pharmacological treatment of OA is inadequate and pharmacological interventions focus on symptom management. APPA, a combination of apocynin (AP) and paeonol (PA), is a potential drug for treating OA. The aim of this study was to analyze the effects of APPA on the modulation of the inflammatory response in chondrocytes. Samples were incubated with IL-1β and APPA, and their responses to proinflammatory cytokines, catabolic mediators and redox responses were then measured. The effect of APPA on mitogenesis was also evaluated. Results show that APPA attenuated the expression of IL-8, TNF-α, MMP-3, MMP-13, SOD-2 and iNOS, resulting in the protection of human articular cartilage. APPA decreased PGC-1α gene expression induced by IL-1β. APPA did not modulate the gene expression of Mfn2, Sirt-1 or Sirt-3. The overall findings indicate that APPA may be an effective treatment for OA by targeting several of the pathways involved in OA pathogenesis

Epigenetics as a therapeutic target in osteoarthritis

Review[Abstract] Osteoarthritis (OA) is a heterogenous, complex disease affecting the integrity of diarthrodial joints that, despite its high prevalence worldwide, lacks effective treatment. In recent years it has been discovered that epigenetics may play an important role in OA. Our objective is to review the current knowledge of the three classical epigenetic mechanisms—DNA methylation, histone post-translational modifications (PTMs), and non-coding RNA (ncRNA) modifications, including microRNAs (miRNAs), circular RNAs (circRNAs), and long non-coding RNAs (lncRNAs)—in relation to the pathogenesis of OA and focusing on articular cartilage. The search for updated literature was carried out in the PubMed database. Evidence shows that dysregulation of numerous essential cartilage molecules is caused by aberrant epigenetic regulatory mechanisms, and it contributes to the development and progression of OA. This offers the opportunity to consider new candidates as therapeutic targets with the potential to attenuate OA or to be used as novel biomarkers of the disease.Instituto de Salud Carlos III; PI19/01213Xunta de Galicia; IN607D2022/12Xunta de Galicia; IN607A 2021/

In vitro study of the therapeutic potential of brown crude fucoidans in osteoarthritis treatment

[Abstract] Osteoarthritis, one of the most common joint degenerative pathologies, still has no cure, and current treatments, such as nonsteroidal anti-inflammatory drugs, can cause serious adverse effects when taken for a long time. Brown seaweed crude fucoidans are used for the clinical treatment of several pathologies. In this study, the therapeutical potential of these biocompounds was analyzed in primary chondrocytes and the 260TT human chondrocyte cell line. Crude fucoidan from Undaria pinnatifida (Up) and Sargassum muticum (Sm) was obtained by different extraction techniques (microwave-assisted extraction, pressurized hot-water extraction, ultrasound-assisted extraction) and chemically and structurally characterized by Fourier transform infrared spectroscopy, high-performance size-exclusion chromatography, proton nuclear magnetic resonance, and scanning electron microscopy. Once cell viability was confirmed in chondrocytes treated with crude fucoidans, we evaluated their anti-inflammatory effects, observing a significant reduction in IL-6 production stimulated by IL-1β. Findings were confirmed by analysis of IL-6 and IL-8 gene expression, although only fucoidans from Up achieved a statistically significant reduction. Besides this, the antioxidant capacity of crude fucoidans was observed through the upregulation of Nrf-2 levels and the expression of its transcriptional target genes HO-1 and SOD-2, with compounds from Up again showing a more consistent effect. However, no evidence was found that crude fucoidans modulate senescence, as they failed to reduced β-galactosidase activity, cell proliferation, or IL-6 production in chondrocytes stimulated with etoposide. Thus, the findings of this research seem to indicate that the tested crude fucoidans are capable of partially alleviating OA-associated inflammation and oxidative stress, but fail to attenuate chondrocyte senescence

Prognostic model to predict the incidence of radiographic knee osteoarthritis

[Abstract] Objective: Early diagnosis of knee osteoarthritis (KOA) in asymptomatic stages is essential for the timely management of patients using preventative strategies. We develop and validate a prognostic model useful for predicting the incidence of radiographic KOA (rKOA) in non-radiographic osteoarthritic subjects and stratify individuals at high risk of developing the disease. Methods: Subjects without radiographic signs of KOA according to the Kellgren and Lawrence (KL) classification scale (KL=0 in both knees) were enrolled in the OA initiative (OAI) cohort and the Prospective Cohort of A Coruña (PROCOAC). Prognostic models were developed to predict rKOA incidence during a 96-month follow-up period among OAI participants based on clinical variables and serum levels of the candidate protein biomarkers APOA1, APOA4, ZA2G and A2AP. The predictive capability of the biomarkers was assessed based on area under the curve (AUC), and internal validation was performed to correct for overfitting. A nomogram was plotted based on the regression parameters. Model performance was externally validated in the PROCOAC. Results: 282 participants from the OAI were included in the development dataset. The model built with demographic, anthropometric and clinical data (age, sex, body mass index and WOMAC pain score) showed an AUC=0.702 for predicting rKOA incidence during the follow-up. The inclusion of ZA2G, A2AP and APOA1 data significantly improved the model's sensitivity and predictive performance (AUC=0.831). The simplest model, including only clinical covariates and ZA2G and A2AP serum levels, achieved an AUC=0.826. Both models were internally cross-validated. Predictive performance was externally validated in an independent dataset of 100 individuals from the PROCOAC (AUC=0.713). Conclusion: A novel prognostic model based on common clinical variables and protein biomarkers was developed and externally validated to predict rKOA incidence over a 96-month period in individuals without any radiographic signs of disease. The resulting nomogram is a useful tool for stratifying high-risk populations and could potentially lead to personalised medicine strategies for treating OA.This work has been funded by Instituto de Salud Carlos III (ISCIII) through the projects PI19/01206, PI20/00793, PI20/01409 and PI22/01155, and co-funded by the European Union, and also by the grant RD21/0002/0009 financed by Instituto de Salud Carlos III–European Union-NextGenerationEU-Plan de Recuperación transformación y resiliencia. This study has been also supported by grants IN607A2021/07 and IN607D2020/10 from Xunta de Galicia. The Biomedical Research Networking Center (CIBER) is an initiative from Instituto de Salud Carlos III (ISCIII). LL is supported by Contrato Sara Borrell (CD19/00229), Fondo de Investigación Sanitaria, ISCIII. VC is supported by RICORS-REI RD21/0002/0009.info:eu-repo/grantAgreement/ISCIII/Programa Estatal de Generación de Conocimiento y Fortalecimiento del Sistema Español de I+D+I/PI19%2F01206/ES/VALIDACION CLINICA DE NUEVOS BIOMARCADORES PREDICTIVOS DE DIAGNOSTICO Y PRONOSTICO EN ARTROSIS: EL PROYECTO HPPinfo:eu-repo/grantAgreement/ISCIII/Programa Estatal de Generación de Conocimiento y Fortalecimiento del Sistema Español de I+D+I/PI20%2F00793/ES/DESARROLLO DE SOLUCIONES INTEGRADAS DE ANALITICA PREDICTIVA PARA PERSONALIZAR LA FARMACOTERAPIA EN PACIENTES CON ARTRITIS REUMATOIDEinfo:eu-repo/grantAgreement/ISCIII/Programa Estatal de Generación de Conocimiento y Fortalecimiento del Sistema Español de I+D+I/PI20%2F01409/ES/NUEVAS METODOLOGIAS PARA LA ESTRATIFICACION DE PACIENTES ARTROSICOS (OA) MEDIANTE TECNICAS PROTEOMICA, APRENDIZAJE AUTOMATICO Y BIG DATAinfo:eu-repo/grantAgreement/ISCIII/Programa Estatal para Impulsar la Investigación Científico-Técnica y su Transferencia/PI22%2F01155/ES/MEDICINA PERSONALIZADA EN LA ARTROSIS: INTELIGENCIA ARTIFICIAL APLICADA AL DIAGNÓSTICO DE OA DE RODILLA RAPIDAMENTE PROGRESIVAXunta de Galicia; IN607A2021/07Xunta de Galicia; IN607D2020/1

An atlas of the knee joint proteins and their role in osteoarthritis defined by literature mining

[Abstract] Osteoarthritis (OA) is the most prevalent rheumatic pathology. However, OA is not simply a process of wear and tear affecting articular cartilage but rather a disease of the entire joint. One of the most common locations of OA is the knee. Knee tissues have been studied using molecular strategies, generating a large amount of complex data. As one of the goals of the Rheumatic and Autoimmune Diseases initiative of the Human Proteome Project, we applied a text-mining strategy to publicly available literature to collect relevant information and generate a systematically organized overview of the proteins most closely related to the different knee components. To this end, the PubPular literature-mining software was employed to identify protein-topic relationships and extract the most frequently cited proteins associated with the different knee joint components and OA. The text-mining approach searched over eight million articles in PubMed up to November 2022. Proteins associated with the six most representative knee components (articular cartilage, subchondral bone, synovial membrane, synovial fluid, meniscus, and cruciate ligament) were retrieved and ranked by their relevance to the tissue and OA. Gene ontology analyses showed the biological functions of these proteins. This study provided a systematic and prioritized description of knee-component proteins most frequently cited as associated with OA. The study also explored the relationship of these proteins to OA and identified the processes most relevant to proper knee function and OA pathophysiology.PI19/01206; Instituto de Salud Carlos IIIPI20/00793; Instituto de Salud Carlos IIIPI20/01409; Instituto de Salud Carlos IIIPI22/01155; Instituto de Salud Carlos IIIRICORS-REIRD21/0002/0009; Instituto de Salud Carlos IIIED431E2018/03; Xunta de GaliciaIN607A2021/07; Xunta de GaliciaIN607D2020/10; Xunta de Galici

Increased synovial immunohistochemistry reactivity of TGF-β1 in erosive peripheral psoriatic arthritis

[Abstract] Background: Immune and non-immune cells contribute to the pathology of chronic arthritis, and they can contribute to tissue remodeling and repair as well as disease pathogenesis. The present research aimed to analyze inflammation and bone destruction/regeneration biomarkers in patients with psoriatic arthritis (PsA), rheumatoid arthritis (RA), osteoarthritis (OA), and ankylosing spondylitis (AS). Methods: Samples were obtained from the inflamed knee of patients with knee arthritis who had been referred for undergoing arthroscopies. The synovial membrane was processed for pathological description, IHC analysis, and quantification of mRNA expression ratio by qRT-PCR. Serum levels of TGF-β1, IL-23, IL-6, IL-17 A, IL-22, Dkk1, Sclerostin, BMP2, BMP4, Wnt1, and Wnt5a were measured by ELISA. All these data were analyzed and compared with the demographic, clinical, blood tests, and radiological characteristics of the patients. Results: The synovial membrane samples were obtained from 42 patients for IHC, extraction, and purification of RNA for synovial mRNA expression analysis, and serum for measuring protein levels from 38 patients. IHC reactivity for TGF-β1 in the synovial tissue was higher in patients with psoriatic arthritis (p 0.036) and was positively correlated with IL-17 A (r = 0.389, p = 0.012), and Dkk1 (r = 0.388, p = 0.012). Gene expression of the IL-17 A was higher in PsA patients (p = 0.018) and was positively correlated with Dkk1 (r = 0.424, p = 0.022) and negatively correlated with BMP2 (r = -0.396, p = 0.033) and BMP4 (r = -0.472, p = 0.010). It was observed that IHC reactivity for TGF-β1 was higher in patients with erosive PsA (p = 0.024). Conclusions: The IHC reactivity of TGF-β1 in synovial tissue was higher in patients with erosive psoriatic arthritis, and TGF-β1 was in relation to higher levels of gene expression of IL-17 A and Dkk1.info:eu-repo/grabntAgreement/MICINN/Programa Estatal de Fomento de la Investigación Científica y Técnica de Excelencia/ES/PI11%2F00390/Análisis de biomarcadores sinoviales, implicados en la inflamación y destrucción ósea articular en la artritis psoriásic

Recomendaciones de experto sobre el bloqueo de la interleucina 6 en pacientes con artritis reumatoide

[Abstract] Objective: To draft recommendations on interleukin 6 (IL-6) blockade in rheumatoid arthritis (RA), based on best evidence and experience. Methods: A group of 10 experts on IL-6 blockade in RA was selected. The 2 coordinators formulated 23 questions about IL-6 blockade (indications, efficacy, safety, etc.). A systematic review was conducted to answer the questions. Using this information, inclusion and exclusion criteria were established, as were the search strategies (Medline, EMBASE and the Cochrane Library were searched). Two different reviewers selected the articles. Evidence tables were created. At the same time, European League Against Rheumatism and American College of Rheumatology abstracts were evaluated. Based on this evidence, the coordinators proposed preliminary recommendations that the experts discussed and voted on in a nominal group meeting. The level of evidence and grade of recommendation were established using the Oxford Centre for Evidence Based Medicine and the level of agreement with the Delphi technique (2 rounds). Agreement was established if at least 80% of the experts voted yes (yes/no). Results: The 8 preliminary recommendations were accepted after the Delphi process. They covered aspects such as the use of these therapies in monotherapy, in combination, in patients with refractory disease or intolerant patients, response evaluation, optimization and risk management. Conclusions: The manuscript aims to solve frequently asked questions and aid in decision making strategies when treating RA patients with IL-6 blockade.[Resumen] Objetivo. Generar recomendaciones sobre el bloqueo de la interleucina 6 (IL-6) en pacientes con artritis reumatoide (AR), basadas en la mejor evidencia y experiencia. Métodos. Se seleccionó a 10 expertos reumatólogos en el manejo de los inhibidores de la IL-6. Los 2 coordinadores generaron 23 preguntas sobre el bloqueo de la IL-6 en la AR (perfiles de indicación, eficacia, seguridad, etc.) para ser contestadas mediante una revisión sistemática de la literatura. Con base en las preguntas se definieron los criterios de inclusión y exclusión, y las estrategias de búsqueda (para interrogar Medline, Embase y la Cochrane Library). Dos revisores seleccionaron los artículos resultantes de la búsqueda. Se generaron tablas de evidencia. Paralelamente, se evaluaron abstracts de congresos de EULAR y ACR. Con toda esta evidencia los coordinadores propusieron 8 recomendaciones preliminares que se evaluaron, discutieron y votaron en una reunión de grupo nominal con el resto de los expertos. Para cada recomendación se estableció el nivel de evidencia y grado de recomendación, y el grado de acuerdo mediante un Delphi. Se definió acuerdo si al menos el 80% de los participantes contestaban sí a la recomendación (sí o no). Resultados. Las 8 recomendaciones preliminares se aceptaron tras el Delphi. Abarcan aspectos como su uso en monoterapia, en combinación, en pacientes refractarios o intolerantes, la evaluación de su respuesta, la optimización o la gestión del riesgo. Conclusiones. Este documento pretende resolver algunos interrogantes clínicos habituales y facilitar la toma de decisiones con el bloqueo de la IL-6 en el manejo de la AR

Single nucleotide polymorphism genes and mitochondrial DNA haplogroups as biomarkers for early prediction of knee osteoarthritis structural progressors: use of supervised machine learning classifiers

[Abstract] Background. Knee osteoarthritis is the most prevalent chronic musculoskeletal debilitating disease. Current treatments are only symptomatic, and to improve this, we need a robust prediction model to stratify patients at an early stage according to the risk of joint structure disease progression. Some genetic factors, including single nucleotide polymorphism (SNP) genes and mitochondrial (mt)DNA haplogroups/clusters, have been linked to this disease. For the first time, we aim to determine, by using machine learning, whether some SNP genes and mtDNA haplogroups/clusters alone or combined could predict early knee osteoarthritis structural progressors. Methods. Participants (901) were first classified for the probability of being structural progressors. Genotyping included SNP genes TP63, FTO, GNL3, DUS4L, GDF5, SUPT3H, MCF2L, and TGFA; mtDNA haplogroups H, J, T, Uk, and others; and clusters HV, TJ, KU, and C-others. They were considered for prediction with major risk factors of osteoarthritis, namely, age and body mass index (BMI). Seven supervised machine learning methodologies were evaluated. The support vector machine was used to generate gender-based models. The best input combination was assessed using sensitivity and synergy analyses. Validation was performed using tenfold cross-validation and an external cohort (TASOAC). Results. From 277 models, two were defined. Both used age and BMI in addition for the first one of the SNP genes TP63, DUS4L, GDF5, and FTO with an accuracy of 85.0%; the second profits from the association of mtDNA haplogroups and SNP genes FTO and SUPT3H with 82.5% accuracy. The highest impact was associated with the haplogroup H, the presence of CT alleles for rs8044769 at FTO, and the absence of AA for rs10948172 at SUPT3H. Validation accuracy with the cross-validation (about 95%) and the external cohort (90.5%, 85.7%, respectively) was excellent for both models. Conclusions. This study introduces a novel source of decision support in precision medicine in which, for the first time, two models were developed consisting of (i) age, BMI, TP63, DUS4L, GDF5, and FTO and (ii) the optimum one as it has one less variable: age, BMI, mtDNA haplogroup, FTO, and SUPT3H. Such a framework is translational and would benefit patients at risk of structural progressive knee osteoarthritis

Exploring the differences between radiographic joint space width and MRI cartilage thickness changes using data from the IMI-APPROACH cohort

[Abstract] Objective: Longitudinal weight-bearing radiographic joint space width (JSW) and non-weight-bearing MRI-based cartilage thickness changes often show weak correlations. The current objective was to investigate these correlations, and to explore the influence of different factors that could contribute to longitudinal differences between the two methods. Methods: The current study included 178 participants with medial osteoarthritis (OA) out of the 297 knee OA participants enrolled in the IMI-APPROACH cohort. Changes over 2 years in medial JSW (ΔJSWmed), minimum JSW (ΔJSWmin), and medial femorotibial cartilage thickness (ΔMFTC) were assessed using linear regression, using measurements from radiographs and MRI acquired at baseline, 6 months, and 1 and 2 years. Pearson R correlations were calculated. The influence of cartilage quality (T2 mapping), meniscal extrusion (MOAKS scoring), potential pain-induced unloading (difference in knee-specific pain scores), and increased loading (BMI) on the correlations was analyzed by dividing participants in groups based on each factor separately, and comparing correlations (slope and strength) between groups using linear regression models. Result: Correlations between ΔMFTC and ΔJSWmed and ΔJSWmin were statistically significant (p < 0.004) but weak (R < 0.35). Correlations were significantly different between groups based on cartilage quality and on meniscal extrusion: only patients with the lowest T2 values and with meniscal extrusion showed significant moderate correlations. Pain-induced unloading or BMI-induced loading did not influence correlations. Conclusions: While the amount of loading does not seem to make a difference, weight-bearing radiographic JSW changes are a better reflection of non-weight-bearing MRI cartilage thickness changes in knees with higher quality cartilage and with meniscal extrusion