Background and Objectives: Heterotopic ossification (HO) involves abnormal bone growth in soft tissues. Current treatments are ineffective and prone to adverse effects, suggesting the need for new HO therapies. Intramembranous bone growth is led by osteoblasts. Since osteoblastogenesis and adipogenesis are opposed and mutually controlled processes, this study aims to identify a new repurposed therapeutic tool to inhibit osteoblastogenesis through adipogenesis promotion. Methods: We performed docking experiments between peroxisome proliferator-activated receptor-γ and bone metabolism-affecting drugs, namely, thiazolidinediones (rosiglitazone, pioglitazone), indomethacin, and dexamethasone, to test tritherapy antiosteoblastogenic effect. Mouse mesenchymal stem cells (C3H10T1/2), human osteoblast-like cells (SaOS2 and primary preosteoblasts), and mouse chondrocytes (ATDC5) were differentiated in the presence of these compounds. The effects on osteoblastogenesis, adipogenesis, and endochondral ossification were analysed through marker gene expression via RT–qPCR. Additionally, primary human HO cells and a congenital HO patient were treated with the selected drug combination (P-tritherapy). Results: Tritherapy significantly and synergistically promoted the expression of an adipogenic marker (fatty acid-binding protein 4) and decreased the expression of an osteoblastogenic marker (osteopontin). In an endochondral ossification model, it reduced ossification markers (collagen-2α1) expression, and in HO cells, it increased adipogenesis markers’ expression. Clinically, P-tritherapy administration prompted bone resorption in a patient with progressive osseous heteroplasia. Conclusions: Tritherapy induced adipogenesis while inhibiting osteoblastogenesis and endochondral ossification, demonstrating its potential as a new therapeutic tool to prevent abnormal bone growth. These results were consistent with bone turnover modification observed in a congenital HO patient. This concordance underscores tritherapy potential for rapid and safe translation to prevent HO.

The gut microbiota has been implicated in the onset and progression of Rheumatoid Arthritis (RA). It has been proposed that gut dysbiosis impairs gut barrier function, leading to alterations in mucosal integrity and immunity. This disruption allows bacterial translocation, contributing to the perpetuation of the inflammatory process. Since diet is recognised as a key environmental factor influencing the gut microbiota, nutritional interventions targeting RA activity are currently being explored. This study aims to investigate whether a dietary intervention based on a typical Mediterranean Diet enriched with fermented foods (MedDiet +) can impact the gut microbiota, intestinal permeability, and RA-related outcomes. One hundred RA patients are being recruited at Unidade Local de Saúde (ULS) Santa Maria in Lisbon, Portugal, and randomly assigned to either the intervention (MedDiet +) or the control group. The 12-week nutritional intervention includes a personalised dietary plan following the MedDiet + pattern, along with educational resources, food basket deliveries, and clinical culinary workshops, all developed and monitored weekly by registered dietitians. The control group receives standardised general healthy diet recommendations at baseline. The intervention's effects will be assessed by evaluating disease activity, functional status, quality of life, intestinal permeability, endotoxemia, inflammatory biomarkers, intestinal and oral microbiota, serum proteomics, and serum glycome profile characterisation. We anticipate obtaining integrative insights into the interplay between diet, the gut, and RA, while also exploring the underlying mechanisms driving these changes. This study, conducted by a multidisciplinary research team of registered dietitians, rheumatologists, biologists, and immunologists, aims to bridge the current gap between nutrition-related knowledge and RA. Registered in ClinicalTrials.gov (NCT06758817; date of registry: January 6th 2025).

OBJECTIVE:To investigate the presence and bioactivity of lipopolysaccharides (LPS) in synovial fluid (SF) of osteoarthritis (OA) patients and elucidate mechanisms modulating their inflammatory potential. METHODS:SF samples from 56 OA, 7 rheumatoid arthritis and 39 trauma patients were analysed for LPS concentration and bioactivity. Lipid A composition was assessed using liquid chromatography-mass spectrometry (LC-MS). In a rat model, LPS was administered systemically for 32 days to evaluate its impact on joint degeneration. The interaction between LPS and synovial proteins, particularly fibronectin (Fn), was examined through in vitro assays and a 3D synovial membrane model. RESULTS:LPS was detected in all SF samples with comparable concentrations and lipid A profiles across all groups. LC-MS measurements indicated higher LPS levels than those obtained from standard endotoxin assays, suggesting limitations in conventional detection methods. Despite elevated LPS presence, bioactivity assays revealed minimal proinflammatory responses, implying the existence of intrinsic SF factors neutralising LPS. In vivo, prolonged systemic LPS exposure did not induce OA-like changes in rat joints. Notably, LPS colocalised with Fn in the synovial membrane, and Fn binding attenuated LPS bioactivity and hindered its migration in vitro. CONCLUSIONS:LPS is prevalent in SF across various joint conditions but exhibits low bioactivity, indicating it is not a primary driver of joint inflammation. Fn plays a crucial role in sequestering and neutralising LPS within the synovial environment, offering a protective mechanism against LPS-induced inflammation. These findings underscore the need for accurate LPS measurement techniques and suggest potential therapeutic targets for modulating joint inflammation.

Objectives: This study investigates the role of retinol binding protein 4 (RBP4) in an articular context. RBP4, a vitamin A transporter, is linked to various metabolic diseases. Methods: Synovial fluid RBP4 levels were assessed in crystalline arthritis (CA) patients using ELISA. RBP4’s impact on articular cell types was analysed in vitro through RT-PCR and flow cytometry. Proteomic analysis was conducted on primary human osteoarthritis chondrocytes (hOACs). Results: Synovial fluid RBP4 concentrations in CA patients correlated positively with glucose levels and negatively with synovial leukocyte count and were elevated in hypertensive patients. In vitro, these RBP4 concentrations activated neutrophils, induced the expression of inflammatory factors in hOACs as well as synoviocytes, and triggered proteomic changes consistent with inflammation. Moreover, they increased catabolism and decreased anabolism, mitochondrial dysfunction, and glycolysis promotion. Both in silico and in vitro experiments suggested that RBP4 acts through TLR4. Conclusions: This study identifies relevant RBP4 concentrations in CA patients’ synovial fluids, linking them to hypertensive patients with a metabolic disruption. Evidence is provided that RBP4 acts as a DAMP at these concentrations, inducing robust inflammatory, catabolic, chemotactic, and metabolic responses in chondrocytes, synoviocytes, and neutrophils. These effects may explain RBP4-related metabolic diseases’ contribution to joint destruction in various rheumatic conditions like CA.

Osteoarthritis (OA) is hallmarked as a silent progressive rheumatic disease of the whole joint. The accumulation of inflammatory and catabolic factors such as IL6, TNFα, and COX2 drives the OA pathophysiology into cartilage degradation, synovia inflammation, and bone destruction. There is no clinical available OA treatment. Although traditional ayurvedic medicine has been using Boswellia serrata extracts (BSE) as an antirheumatic treatment for a millennium, none of the BSE components have been clinically approved. Recently, β boswellic acid (BBA) has been shown to reduce in vivo OA-cartilage loss through an unknown mechanism. We used computational pharmacology, proteomics, transcriptomics, and metabolomics to present solid evidence of BBA therapeutic properties in mouse and primary human OA joint cells. Specifically, BBA binds to the innate immune receptor Toll-like Receptor 4 (TLR4) complex and inhibits both TLR4 and Interleukin 1 Receptor (IL1R) signaling in OA chondrocytes, osteoblasts, and synoviocytes. Moreover, BBA inhibition of TLR4/IL1R downregulated reactive oxygen species (ROS) synthesis and MAPK p38/NFκB, NLRP3, IFNαβ, TNF, and ECM-related pathways. Altogether, we present a solid bulk of evidence that BBA blocks OA innate immune responses and could be transferred into the clinic as an alimentary supplement or as a therapeutic tool after clinical trial evaluations.

Background Knowledge about regulating transcription factors (TFs) for osteoblastogenesis from mesenchymal stem cells (MSCs) is limited. Therefore, we investigated the relationship between genomic regions subject to DNA-methylation changes during osteoblastogenesis and the TFs known to directly interact with these regulatory regions. Results The genome-wide DNA-methylation signature of MSCs differentiated to osteoblasts and adipocytes was determined using the Illumina HumanMethylation450 BeadChip array. During adipogenesis no CpGs passed our test for significant methylation changes. Oppositely, during osteoblastogenesis we identified 2462 differently significantly methylated CpGs (adj. p < 0.05). These resided outside of CpGs islands and were significantly enriched in enhancer regions. We confirmed the correlation between DNA-methylation and gene expression. Accordingly, we developed a bioinformatic tool to analyse differentially methylated regions and the TFs interacting with them. By overlaying our osteoblastogenesis differentially methylated regions with ENCODE TF ChIP-seq data we obtained a set of candidate TFs associated to DNA-methylation changes. Among them, ZEB1 TF was highly related with DNA-methylation. Using RNA interference, we confirmed that ZEB1, and ZEB2, played a key role in adipogenesis and osteoblastogenesis processes. For clinical relevance, ZEB1 mRNA expression in human bone samples was evaluated. This expression positively correlated with weight, body mass index, and PPARγ expression. Conclusions In this work we describe an osteoblastogenesis-associated DNA-methylation profile and, using these data, validate a novel computational tool to identify key TFs associated to age-related disease processes. By means of this tool we identified and confirmed ZEB TFs as mediators involved in the MSCs differentiation to osteoblasts and adipocytes, and obesity-related bone adiposity.

Beer consumption has been identified as a risk factor for osteoarthritis (OA), a rheumatic disease characterised by cartilage degradation, joint inflammation, and eventual joint failure. One of the main isoflavonoids in beer is formononetin (FNT), an estrogenic compound also found in multiple plants and herbs. In this study, we aimed to investigate the effect of FNT on chondrocyte viability, inflammation, and metabolism. Cells were treated with FNT with or without IL-1β for 48 h and during 7 days of differentiation. Cell viability was determined via MTT assay. Nitrite accumulation was determined by Griess reaction. The expression of genes involved in inflammation and metabolism was determined by RT-PCR. The results revealed that a low concentration of FNT had no deleterious effect on cell viability and decreased the expression of inflammation-related genes. However, our results suggest that FNT overexposure negatively impacts on chondrocytes by promoting catabolic responses. Finally, these effects were not mediated by estrogen receptors (ERs) or aryl hydrocarbon receptor (AhR). In conclusion, factors that favour FNT accumulation, such as long exposure times or metabolic disorders, can promote chondrocyte catabolism. These data may partially explain why beer consumption increases the risk of OA.

It is well known that patients with attention deficit hyperactivity disorder treated with stimulants, such as methylphenidate hydrochloride (MPH), have reduced height and weight. Even though MPH has an anorexigenic effect, an additional impact of this drug on the growth plate cannot be discarded. In this study, we aimed to determine the cellular effect of MPH on an in vitro growth plate model. We tested the effects of MPH on the viability and proliferation of a prechondrogenic cell line via an MTT assay. In vitro differentiation of this cell line was performed, and cell differentiation was evaluated through the expression of cartilage- and bone-related genes as measured via RT-PCR. MPH did not alter the viability or proliferation of prechondrogenic cells. However, it reduced the expression of cartilage extracellular matrix-related genes (type II collagen and aggrecan) and increased the expression of genes involved in growth plate calcification (Runx2, type I collagen, and osteocalcin) at different phases of their differentiation process. Our results evidence that MPH upregulates genes associated with growth plate hypertrophic differentiation. This may induce premature closure of the growth plate, which would contribute to the growth retardation that has been described to be induced by this drug.

Adipogenesis-osteoblastogenesis balance-rupture is relevant in multiple diseases. Current human mesenchymal stem cells (hMSCs) in vitro differentiation models are expensive, and are hardly reproducible. Their scarcity and variability make an affordable and reliable method to study adipocyte-osteoblast-equilibrium difficult. Moreover, media composition has been inconstant throughout the literature. Our aims were to compare improved differentiation lab-made media with consensus/commercial media, and to identify a cell-line to simultaneously evaluate both MSCs differentiations. Lab-made media were compared with consensus and commercial media in C3H10T1/2 and hMSC, respectively. Lab-made media were tested on aged women primary pre-osteoblast-like cells. To determine the optimum cell line, C3H10T1/2 and hMSC-TERT cells were differentiated to both cell fates. Differentiation processes were evaluated by adipocytic and osteoblastic gene-markers expression and staining. Lab-made media significantly increased consensus medium induction and overcame commercial media in hMSCs differentiation to adipocytes and osteoblasts. Pre-osteoblast-like cells only properly differentiate to adipocyte. Lab-made media promoted adipocyte gene-markers expression in C3H10T1/2 and hMSC-TERT, and osteoblast gene-markers in C3H10T1/2. Oil Red O and Alizarin Red staining supported these findings. Optimized lab-made media were better at differentiating MSCs compared to consensus/commercial media, and evidenced the adipogenic commitment of pre-osteoblast-like cells from aged-women. C3H10T1/2 is an optimum MSC line by which to study adipocyte-osteoblast differentiation balance.

Current lifestyle and environmental factors contribute to obesity development, leading to low-grade chronic inflammation (LGCI). Apart from obesity, LGCI is also related to rheumatic diseases such as osteoporosis (OP) and osteoarthritis (OA). In these, an excessive accumulation of adipose tissue has been linked to an excessive production of proinflammatory factors, such as adipokines. This work’s aim is to stablish the effect of obesity-associated LGCI in major rheumatic diseases and to determine optimal strategies to reduce it. Obesity is a risk factor for developing OA, where a systemic LGCI state has been found. Concretely, obesity-associated LGCI has been described as an OA instauration and progression promoter. To avoid this, several therapeutical approaches (diet control, physical exercise, or nutraceuticals) have been tested. OP is another major rheumatic disease where a basal LGCI has been described, being worsened by obesity. As in OA, diet management and supplementation with vitamin D or probiotics have been proposed as approaches to treat obesity-associated LGCI in this pathology. Currently, the increase in the prevalence of rheumatic diseases is unstoppable. Nonetheless, obesity is a risk factor that can be controlled. Thus, the study of new interventions to control the impact of obesity-associated LGCI is a challenge for the management of patients with rheumatic diseases.

Osteoarthritis (OA) affects more than 300 million people worldwide and it is about to become the first disabling disease. OA is characterized by the progressive degradation of the articular cartilage but is a disease of the whole joint. Articular innate immune responses (IIR) associated with tissue degradation contribute to its progression. However, no treatment is available to block these IIRs. Through data text mining and computational pharmacology, we identified two clinical available drugs, naloxone, and thalidomide, with potential inhibitory properties on toll-like receptor 4 (TLR4), a major activator of these IIR. Proteome analysis confirmed that activation of this receptor or the IL1 receptor generated OA-like and gout-like proteomic changes in human primary chondrocytes. Both compounds were found to block TLR4 complex and inhibit TLR4 and IL1R-mediated IIR in OA chondrocytes, osteoblasts, and synoviocytes. Furthermore, naloxone and thalidomide inhibitory effects involved the downregulation of the NLRP3 inflammasome pathway, which is downstream of TLR4/IL1R signaling. We demonstrated that these compounds, within a therapeutic range of concentrations, exhibited anti-inflammatory and anti-catabolic properties in joint primary OA cells without any toxic effect. This data underpins naloxone & thalidomide repurpose to treat OA-associated inflammatory responses.

Background Heterotopic ossification (HO) consists in abnormal bone growth in soft tissues, in a non-porrostoeblastogenic environment. This pathology origin can be congenital (progressive osseus heteroplasia, progressive osseous fibrodysplasia, …) or acquired (burnt, big traumas, electrocutions, articular replacement surgeries, …). Currently, the available therapies (radiotherapy and removal surgery) are aggressive, associated to multiple adverse effects, and not suitable for every populations. Therefore, new therapeutic tools are needed to HO. Osteoblast is the cell type in charge of bone growth. These cells share a mesenchymal origin with adipocytes. Interestingly, osteoblastogenesis and adipogenesis are opposed and mutually controlled processes. Objectives The aim of this work is to study osteoblastogenesis inhibition through adipogenesis promotion using a new therapy (Tri-therapy) composed by a PPARG agonist, a NSAID, and a corticoid. Methods Mice mesenchymal stem cells (C3H10T1/2) were differentiated towards adipogenesis and osteoblastogenesis for 7 days, in the presence of the Tri-therapy compounds alone and combined. Simultaneously, human preosteoblast cells (SaOS2) were differentiated to osteoblast for 14 days, being treated with the Tri-therapy. Human HO cells (acquired HO and congenital HO independently), obtained from HO explants, were exposed to an adipogenic environment in the presence of the Tri-therapy for 7 days. Osteoblastogenic (ALPL, SPP1, GPNMB, RUNX2) and adipogenic (FABP4, PLIN2, ADIPOQ, PPARG) marker genes mRNA expression measured by RT-PCR was used to evaluate differentiation processes. All the results were expressed as the media± SEM of, at least, 3 independent replicates. Results In C3H10T1/2 differentiations Tri-therapy synergically induced FABP4, PLIN2, ADIPOQ expression in both cell fates, demonstrating therefore its ability to promote adipogenesis. In SaOS2, the proposed therapy diminished osteoblastogenic marker genes expression (SPP1, GPNMB, RUNX2), being this effect greater than PPARG agonists’ themselves. In HO cells, Tri-therapy augmented adipogenesis markers expression, showing a partial effect in osteoblastogenic marker genes expression. Conclusion Pro-adipogenic switch in differentiation marker genes expression induced by the Tri-therapy suggested the clinical use of this drugs combination to treat and prevent HO and abnormal bone growth. Disclosure of Interests None declared

Background and PurposeOsteoarthritis, a major cause of disability in developed countries does not have effective treatment. Activation of TLR4 and innate immune response factors contribute to osteoarthritis progressive cartilage degradation. There are no clinically available TLR4 inhibitors. Interestingly, the antidepressant amitriptyline could block this receptor. Thus, we evaluated amitriptyline anti‐TLR4 effects on human osteoarthritis chondrocytes in order to repurpose it as an inhibitor of innate immune response in joint inflammatory pathologies.Experimental ApproachUsing in silico docking analysis, RT‐PCR, siRNA, elisa, proteomics and clinical data mining of drug consumption, we explored the clinical relevance of amitriptyline blockade of TLR4‐mediated innate immune responses in human osteoarthritis chondrocytes.Key ResultsAmitriptyline bound TLR4 but not IL‐1 receptor. Interestingly, amitriptyline binding to TLR4 inhibited TLR4‐ and IL‐1 receptor‐mediated innate immune responses in human osteoarthritis chondrocytes, synoviocytes and osteoblasts cells. Amitriptyline reduced basal innate immune responses and promoted anabolic effects in human osteoarthritis chondrocytes. Supporting its anti‐innate immune response effects, amitriptyline down‐regulated basal and induced expression of NLRP3, an inflammasome member from IL‐1 receptor signalling linked to osteoarthritis and gout pathologies. Accordingly, mining of dissociated and aggregated drug consumption data from 107,172 elderly patients (>65 years) revealed that amitriptyline consumption was significantly associated with lower colchicine consumption associated with inflammatory gout flare treatment.Conclusion and ImplicationsAmitriptyline blocks TLR4‐, IL‐1 receptor and NLRP3‐dependent innate immune responses. This together with clinical data amitriptyline could be repurposed for systemic or local innate immune response management in diverse joint inflammatory pathologies.

Ethnopharmacological relevance: Virola oleifera (Schott) A.C. Smith, Myristicaceae, has been widely used in traditional medicine in Brazil to treat rheumatic pain, joint tumours, skin diseases, halitosis, bronchial asthma, haemorrhoids, and intestinal worms. Recently, research data showed the antioxidant properties in several oxidative stress-related models. However, there is no experimental evidence supporting its potential use in managing rheumatic diseases and bone malignancies. Aims of the study: To evaluate the therapeutic potential of the resin from Virola oleifera in joint and bone diseases, namely arthritis, osteosarcoma, chondrosarcoma, and multiple myeloma. Materials and methods: To determine Virola oleifera resin (VO) effects on arthritis-associated inflammation and cartilage degradation, the LPS-induced NO production, and mRNA and protein expression of ADAMTS5, MMP13, COL2, and ACAN, were evaluated in chondrocytes (ATDC5 and TC28 cell lines). The cytotoxic effects of VO (0.05-50 mu g/ml) on multiple myeloma (ARH-77), osteosarcoma (SAOS-2), and chondrosarcoma (SW-1353) cell lines were analysed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The VO effects, combined with dexamethasone or bortezomib, were evaluated in a multiple myeloma cell line. The mechanisms of VO, alone or in combination with bortezomib, were determined by cell cycle analysis through flow cytometry, while expression levels of p-Akt/Akt, p-ERK/ERK, p-p38/p38 MAPK, Bax, Bcl-2, and cleavedcaspase-3/caspase-3 proteins by Western blot. Results: VO had no significant effect on LPS-induced NO production in chondrocytes at non-cytotoxic concentrations. VO treatment diminished the mRNA levels of metalloproteinases and ECM components; however, any significant effect was observed on the protein expression levels. The cell viability of a multiple myeloma cell line was strongly reduced by VO treatment in a dose- and time-dependent manner, while osteosarcoma and chondrosarcoma cell lines viability was significantly affected only by the highest dose assessed. In multiple myeloma cells, VO leads to G2/M cell cycle arrest. Furthermore, it synergizes with dexamethasone by increasing cell toxicity. Finally, VO reverts bortezomib activity by counteracting ERK1/2, Bax, and caspase-3 activation. Conclusions: The current work supports the ethnopharmacological use of Virola oleifera (Schott) A.C. Smith in bone and joint diseases, but there is no evidence for the amelioration of arthritis-associated inflammatory or catabolic processes. Our data also supports the potential use of Virola oleifera as adjuvant therapy to optimize the pharmacologic effects of current chemotherapeutic drugs. However, possible herb-drug interactions should be considered before clinical application.

Background: Osteoarthritis (OA) incidence has skyrocketed in the last decade and yet a definitive treatment has still to be found. This worldwide disease is depriving our society from their life quality and has become a grave economic burden. Research on anti-inflammatory tools has been done on traditional Asian medicine. Boswellic acid is a plant-derived molecule from the Boswellia species that has shown to prevent cartilage loss in an OA mouse model[1]. However, the specific mechanism of action is still unclear. The activation of innate immune receptors, such Toll-like receptor 4 (TLR4) has been involved in chondrocyte-mediated inflammatory responses and OA development. Although, boswellic acid has shown an inhibitory effect on TLR4-mediated inflammatory responses little is known about its role on TLR4-mediated chondrocyte inflammatory and catabolic responses. Objectives: Determine the ability of beta boswellic acid (BBA) to block TLR4-mediated innate immune responses in chondrocytes and synoviocytes. Methods: In silico The binding affinity of beta boswellic acid (BBA) to TLR4 complex signalling was determined by optimized docking algorithm in the BIO-HPC Research Group facilities. In vitro Cellular proteome and secretome profiling (LC-MALDI/TOFF) was used to study inflammatory pathways induced by the agonist of TLR4 (LPS [100ng/ml]) and IL1R (IL1β [0.1ng/ml]). The effect of BBA on TLR4-mediated innate immune responses was determined by RT-PCR, Western Blot and ELISA in primary human OA chondrocytes (hOC), murine ATDC5 chondrocytes, human synoviocytes (SW982) and primary human osteoblasts (hOB). Cell viability was tested using the methyl-thiazolyl-tetrazolium (MTT) reagent. Nitric oxide production in cell culture media was assessed by Griess reaction. Green Malachite Assay was used to semi-quantify the whole phosphoproteome. Ethics This study was approved by the CEIC (CAEIG 2014/310). Results: Cellular proteome and secretome profiling validated the activation of TLR4 and IL1R signalling by LPS and IL1β ligands and revealed an enrichment in innate immune responses (NF-Kβ, NLRP3, MMPs, Interleukins, etc). Non-toxic doses of BBA [0.5-1000nM] prevented the activation of TLR4 in multiple articular joint cells and inhibited TLR4 & IL1R-dependant innate immune responses at the mRNA and protein level such as inflammatory factors IL6, NOS2, COX2, LCN2, MMP1, -3, -9, -13 and ADAMTS4, among others. Furthermore, NF-Kβ/IKBα and NLRP3/PYCARD/IL1β axis were also severely inhibited after BBA treatment. Moreover, these results were validated by in silico docking analysis that showed BBA interacted with TLR4/NF-Kβ. Conclusion: We prove that BBA inhibit TLR4 & IL1R -dependent innate immune responses in multiple human joint cells (Figure 1). We show that NF-Kβ & NLRP3 signalling, both associated to OA, are blocked (mRNA and protein) after BBA treatment (Figure 1). Our data support previous studies showing the prevention of cartilage loss in an OA animal models by BBA might come from its ability to inhibit TLR4 signalling. In the clinical practice of rheumatologists, Boswellia Serrata could be a useful nutraceutical to manage OA inflammation due to its content in BBA. Figure 1. References: [1]Wang, Q.; Pan, X.; Wong, H.H.; Wagner, C.A.; Lahey, L.J.; Robinson, W.H.; Sokolove, J. Oral and topical boswellic acid attenuates mouse osteoarthritis. Osteoarthr. Cartil. 2014 , 22 , 128–132, doi:10.1016/j.joca.2013.10.012. Acknowledgements: Eloi Franco-Trepat and Ana Lois-Iglesias contributed equally to this work. This research has been funded by the non-profit FER (Fundación Española de Reumatologia /Spanish Foundation of Rheumatology) through the project “Búsqueda de nuevos fármacos bloqueantes de la inflamación asociada a TLR4 en condrocitos humanos artrósicos”. Disclosure of Interests: None declared

C-reactive protein (CRP) is an acute-phase protein that is used as an established biomarker to follow disease severity and progression in a plethora of inflammatory diseases. However, its pathophysiologic mechanisms of action are still poorly defined and remain elusive. CRP, in its pentameric form, exhibits weak anti-inflammatory activity. On the contrary, the monomeric isoform (mCRP) exhibits potent pro-inflammatory properties in endothelial cells, leukocytes, and platelets. So far, no data exists regarding mCRP effects in human or mouse chondrocytes. This work aimed to verify the pathophysiological relevance of mCRP in the etiology and/or progression of osteoarthritis (OA). We investigated the effects of mCRP in cultured human primary chondrocytes and in the chondrogenic ATDC5 mouse cell line. We determined mRNA and protein levels of relevant factors involved in inflammatory responses and the modulation of nitric oxide synthase type II (NOS2), an early inflammatory molecular target. We demonstrate, for the first time, that monomeric C reactive protein increases NOS2, COX2, MMP13, VCAM1, IL-6, IL-8, and LCN2 expression in human and murine chondrocytes. We also demonstrated that NF-kB is a key factor in the intracellular signaling of mCRP-driven induction of pro-inflammatory and catabolic mediators in chondrocytes. We concluded that mCRP exerts a sustained catabolic effect on human and murine chondrocytes, increasing the expression of inflammatory mediators and proteolytic enzymes, which can promote extracellular matrix (ECM) breakdown in healthy and OA cartilage. In addition, our results implicate the NF-kB signaling pathway in catabolic effects mediated by mCRP.

Background:Abatacept (ABA) is a selective T-cell co-stimulatory modulator. After its approval, changes in therapeutic recommendations, the arrival of new drugs (e.g., biosimilars or Janus kinase inhibitors) and growing focus on comprehensive patient care may have changed prescription patterns, channeling ABA use towards specific patient subtypes. To date, studies analyzing these aspects in clinical practice settings are scarce.Objectives:We aimed to evaluate the epidemiological profile of ABA users and compare it to other DMARD groups included in the register.Methods:We performed an observational study based on the nationwide Spanish register BIOBADASER, which includes patients with rheumatic diseases receiving biologic disease-modifying antirheumatic drugs (bDMARDs) or targeted synthetic DMARDs (tsDMARDs) from 28 tertiary centers. For this analysis, all RA patients included from December 2015 to December 2020 were examined. Baseline features were analyzed descriptively grouping all b/tsDMARDs by mode of action. Clinical effectiveness was assessed through drug survival obtained by the Kaplan-Meier method. Patients were right-censored if data were not available if they were still on treatment at the time of data analysis. The safety profile was assessed by the adverse events (AE) and serious AE incidence rates (IR) expressed as events per 1000 patient-years.Results:There were 628 ABA-treated patients, 471 (75%) using the subcutaneous presentation. Only 142 (23%) were on first-line while 381 (61%) were on third or later-line therapy. ABA users were older and more likely to present certain comorbidities compared to the other b/tsDMARD groups. The biggest relative differences were seen for interstitial lung disease (ILD), chronic obstructive pulmonary disease (COPD), diabetes and ischemic heart disease. (Table 1)Table 1.This 12-month interim analysis includes 496 patients (336 with axSpA, 98 with RA and 62 with PsA)NABAIL-6CD20JAKiTNFi6287861816691787Mean age, years (SD)64.1 (12.0)50.7 (12.7)63.2 (12.3)59.6 (12.3)60.7 (13.1)Female sex, n (%)482 (77)652 (83)135 (75)537 (80)1418 (79)Median disease duration (p25-p75)10.1 (5.1-16.5)9.4 (4.6-15.9)13.3 (8.3-20.6)10.4 (5.0-17.2)7.4 (3.2-13.7)ACPA, n (%)352 (72)425 (71)113 (79)407 (70)875 (70)RF, n (%)380 (77)454 (75)124 (86)411 (70)915 (72)Current smokers, n (%)98 (16)137 (17)338 (19)90 (20)259 (18)ILD, n (%)64 (13)21 (3)25 (2)8 (2)19 (2)COPD, n (%)38 (6)23(3)52 (3)14 (3)43 (3)Chronic Kidney Disease, n (%)18 (3)13 (2)19 (1)13 (3)18 (1)Diabetes73 (12)66 (8)13 (7)46 (10)100 (7)Ischemic Heart Disease, n (%)36 (6)23 (3)012 (3)30 (2)Hypertension, n (%)197 (31)198 (25)416 (23)131 (30)338 (23)Heart Failure, n (%)19 (4)12 (2)10 (1)6 (2)5 (1)Osteoporosis, n (%)133 (21)141 (18)26 (14)72 (16)215 (15)IL-6: Tocilizumab and Sarilumab; CD20: Rituximab and biosimilars; JAKi: Janus kinase inhibitors (Tofacitinib and Baricitinib); TNFi: TNF inhibitors and biosimilars; ACPA: anti-citrullinated peptide antibodies; RF: rheumatoid factor; ILD: interstitial lung disease; COPD: chronic obstructive pulmonary disease.Overall, 63% of patients remained on ABA at 1 year, 48% at 2 and 31% at 5 years after drug initiation. The corresponding proportions were 79%, 65% and 52% for bionaïve and 59%, 43% and 30% for those in third or later-line therapy. From 394 total discontinuations, loss of efficacy in 225 (57%) and AE in 98 (25%) were the main reasons. This trend was consistent among all therapy lines.The total IR of AE was 886.5 (837.3-938.5) and 156.4 (136.5-179.2) for SAE. Infections were the most frequent AE overall, IR 44.4 (34.4-57.3), and the highest IR was seen among bionaïve patients (69.6 (44.9-107.9)).Conclusion:ABA-treated RA patients in Spain are older and have more comorbidities (vs other b/tsDMARDs), especially ILD, COPD, ischemic heart disease and diabetes and receive ABA as third or later-line therapy. Although these features are associated with worse response to treatment and a higher risk of infection, ABA presents a good drug survival and infectious AE are not the main cause of discontinuation.Acknowledgements:On behalf of the BIOBADASER Working groupDisclosure of Interests:Sebastián C Rodriguez-García Speakers bureau: Sanofi, MSD, UCB-Pharma, Bristol-Myers-Squibb, Novartis, Janssen, Consultant of: Bristol-Myers-Squibb, Galápagos, Carlos Sánchez-Piedra: None declared, Raul Castellanos-Moreira Speakers bureau: Roche, Sanofi, MSD, UCB-Pharma, Bristol-Myers-Squibb, Novartis, Lilly, and Pfizer., Dolores Ruiz-Montesinos: None declared, Manuel Pombo: None declared, Fernando Sánchez-Alonso: None declared, Juan J. Gómez-Reino Consultant of: Pfizer, Grant/research support from: Abbvie, Lilly, MSD, Pfizer, Roche, and UCB.

Since its discovery in 1994, leptin has been considered as an adipokine with pleiotropic effects. In this review, we summarize the actual information about the impact of this hormone on cartilage metabolism and pathology. Leptin signalling depends on the interaction with leptin receptor LEPR, being the long isoform of the receptor (LEPRb) the one with more efficient intracellular signalling. Chondrocytes express the long isoform of the leptin receptor and in these cells, leptin signalling, alone or in combination with other molecules, induces the expression of pro-inflammatory molecules and cartilage degenerative enzymes. Leptin has been shown to increase the proliferation and activation of immune cells, increasing the severity of immune degenerative cartilage diseases. Leptin expression in serum and synovial fluid are related to degenerative diseases such as osteoarthritis (OA), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Inhibition of leptin signalling showed to have protective effects in these diseases showing the key role of leptin in cartilage degeneration.

Regulation of transcription occurs in a cell type specific manner orchestrated by epigenetic mechanisms including DNA methylation. Methylation changes may also play a key role in lineage specification during stem cell differentiation. To further our understanding of epigenetic regulation in chondrocytes we characterised the DNA methylation changes during chondrogenesis of mesenchymal stem cells (MSCs) by Infinium 450 K methylation array. Significant DNA hypomethylation was identified during chondrogenic differentiation including changes at many key cartilage gene loci. Integration with chondrogenesis gene expression data revealed an enrichment of significant CpGs in upregulated genes, while characterisation of significant CpG loci indicated their predominant localisation to enhancer regions. Comparison with methylation profiles of other tissues, including healthy and diseased adult cartilage, identified chondrocyte-specific regions of hypomethylation and the overlap with differentially methylated CpGs in osteoarthritis. Taken together we have associated DNA methylation levels with the chondrocyte phenotype. The consequences of which has potential to improve cartilage generation for tissue engineering purposes and also to provide context for observed methylation changes in cartilage diseases such as osteoarthritis.