Anaplastic Large Cell Lymphoma (ALCL) represents a diverse group of mature T-Cell Lymphomas unified by strong CD30 expression but with different molecular and clinical subtypes. This review summarizes recent molecular advances in ALCL, highlighting key discoveries that have refined its classification, diagnosis, and therapeutic strategies. ALCL comprises four major entities: systemic ALK-positive ALCL, systemic ALK-negative ALCL, Breast Implant-Associated ALCL (BIA-ALCL), and primary cutaneous ALCL. Each subtype exhibits unique phenotypes, along with cytogenetic and molecular alterations that affect clinical outcomes. Nevertheless, different oncogenic mechanisms mediate STAT3 activation. In ALK-positive ALCL, ALK fusion proteins drive oncogenesis via constitutive activation of STAT3 and other signaling pathways. ALK-negative ALCL comprises heterogeneous genetic subtypes, in which JAK/STAT3 pathway alterations and novel gene fusions are gaining recognition as potential therapeutic targets. This review emphasizes the need for integrative molecular diagnostics to improve stratification of ALCL subtypes and targeted treatment approaches. Future research should focus on elucidating the biological mechanisms underlying these alterations and on translating molecular insights into clinical practice.

Abstract Objective This study aimed to describe the performance of a next‐generation sequencing (NGS) panel for the detection of precise genomic alterations in cancer in Spanish clinical practice. The impact of tumor characteristics was evaluated on informative NGS and actionable mutation rates. Materials and Methods A cross‐sectional study was conducted at the Fundación Jiménez Díaz University Hospital (May 2021–March 2022) where molecular diagnostic of 537 Formalin‐Fixed Paraffin‐Embedded (FFPE) tissue samples of diverse solid tumors (lung, colorectal, melanoma, gastrointestinal stromal, among others) was performed using AVENIO Tumor Tissue Targeted Kit. A descriptive analysis of the features of all samples was carried out. Multivariable logistic analysis was conducted to assess the impact of sample characteristics on NGS performance defined by informative results rate (for all tumors and for lung tumors), and on actionable mutations rate (for lung tumors only). Results AVENIO performance rate was 75.2% in all tumor samples and 75.3% in lung cancer samples, and the multivariable analysis showed that surgical specimens are most likely to provide informative results than diagnostic biopsies. Regarding the mutational findings, 727 pathogenic, likely pathogenic, or variant of unknown significance mutations were found in all tumor samples. Single nucleotide variant was the most common genomic alteration, both for all tumor samples (85.3% and 81.9% for all solid tumors and lung samples, respectively). In lung tumors, multivariable analysis showed that it is more likely to find actionable mutations from non‐smokers and patients with adenocarcinoma, large cell, or undifferentiated histologies. Conclusion This is the largest cohort‐level study in Spain to profile the analyses of biopsy samples of different tumors using NGS in routine clinical practice. Our findings showed that the use of NGS routinely provides good rates of informative results and can improve tumor characterization and identify a greater number of actionable mutations.

BackgroundSarcopenia is a frequent comorbidity of rheumatoid arthritis (RA) due to an imbalance in muscle remodelling with dominance of catabolism over anabolism. IL-6/JAK/STAT axis is of particular importance in this regulation because of its dual activity. According to local and acute factors, it promotes muscle healing and hypertrophy, whereas in chronic inflammation, this signalling substantially increases muscle catabolism activating pro-atrophic pathways involving atrogene expression and ubiquitin proteasome system (UPS). JAK/STAT blockade suppresses muscle wasting induced by IL-6, through STAT3 activation. Interestingly, different clinical trials have shown that JAK inhibitors produce an asymptomatic increase in serum creatine kinase (CK) and creatinine levels in RA patients, suggesting an impact on muscle.ObjectivesTo evaluate the effect of JAK inhibition and its effect in muscle remodelling in an experimental model that accurately mimics human rheumatoid sarcopenia.MethodsAn experimental model of antigen-induced arthritis (AIA) was carried out in 14 rabbits by immunization against ovalbumin followed by 4 intra-articular (i.a) injections of this protein. One week after the first i.a injection, 7 of these rabbits received tofacitinib (TOFA, orally 10mg/kg/day) for 2 wk. Animals were euthanized one day after the last i.a injection, when tibialis anterior (TA), extensor digitorum longus (EDL) and gastrocnemius (GN) were isolated from both hind limbs. Histological changes and ATPase staining were analysed in TA, while the number of myonuclei was evaluated in EDL fibres by immunofluorescence studies. C-reactive protein (CRP) and myostatin (MSTN) serum concentration were determined by ELISA. The gene expression of proinflammatory cytokines (IL-1β, IL-6, TNF-α, MCP-1), atrogenes (Atrogin-1, MuRF-1) and MSTN was measured by quantitative PCR, while proliferative muscle marker (PAX-7), differentiation muscle markers (MyoD, Myogenin), pSTAT3, pSTAT1, MSTN and CK protein expression was analysed by western blot in GN. Creatine presence in GN was analysed by a colorimetric assay.ResultsA significant increase in body weight was observed in the AIA+TOFA group vs. AIA at the end of the study. A significant increase in TA cross-sectional area and diameter in the AIA+TOFA, in comparison to AIA, was found, while the decrease in the area of type II fibres observed in the AIA animals was not noticed in AIA+TOFA. Moreover, the number of myonuclei in the EDL that was increased in the AIA group when compared to healthy animals, was significantly decreased in AIA+TOFA. However, systemic inflammation measured by CRP was not modified by TOFA treatment at the end of the study, in comparison to AIA, and so did serum MSTN concentration. TOFA evoked a significant reduction in the gene expression of IL-6, MCP-1, atrogin-1 and MuRF-1 in GN in comparison to untreated AIA rabbits. Notably, AIA+TOFA showed higher protein levels of CK and lower creatine compared to AIA in muscle. Simultaneously, no differences in the proliferative marker PAX-7 were found between groups, while AIA rabbits showed an increase in the differentiation markers MyoD and Myogenin in the muscle that was prevented in AIA+TOFA.ConclusionThese data provide novel insights into the effects of JAK inhibitors in muscle remodelling during rheumatoid cachexia. Despite an elevated systemic inflammatory status, JAK inhibition was able to rapidly increase muscle mass through attenuating IL-6/JAK/STAT activation, decreasing atrogene expression, and restoring to baseline the muscle cell differentiation markers in the tissue. The increase in muscle mass was accompanied by an increase in CK presence, supporting the role of CK as a valuable marker of muscle gain following treatment with JAK inhibitors. However, the low levels of MCP-1 and the disorganization of muscle fibre myonuclei raise the question of whether these treatments could trigger a complete regeneration of muscle fibre cell or just hypertrophy of cells already present.Disclosure of InterestsIsmael Bermejo: None declared, Sandra Pérez-Baos: None declared, Juan Pablo Medina: None declared, Paula Gratal: None declared, Ivan Prieto-Potín: None declared, Raquel Largo: None declared, Gabriel Herrero-Beaumont Grant/research support from: The Bone and Joint Research Unit has received funding from several pharmaceutical laboratories (Pfizer, LILLY...).

Gynecological cancer accounts for an elevated incidence worldwide requiring responsiveness regarding its care. The comprehensive genomic approach agrees with the classification of certain tumor types. We evaluated 49 patients with gynecological tumors undergoing high-throughput sequencing to explore whether identifying alterations in cancer-associated genes could characterize concrete histological subtypes. We performed immune examination and analyzed subsequent clinical impact. We found 220 genomic aberrations mostly distributed as single nucleotide variants (SNV, 77%). Only 3% were classified as variants of strong clinical significance in BRCA1 and BRCA2 of ovarian high-grade serous (HGSC) and uterine endometrioid carcinoma. TP53 and BRCA1 occurred in 72% and 28% of HGSC. Cervical squamous cell carcinoma was entirely HPV-associated and mutations occurred in PIK3CA (60%), as well as in uterine serous carcinoma (80%). Alterations were seen in PTEN (71%) and PIK3CA (60%) of uterine endometrioid carcinoma. Elevated programmed death-ligand 1 (PD-L1) was associated with high TILs. Either PD-L1 augmented in deficient mis-matched repair (MMR) proteins or POLE mutated cases when compared to a proficient MMR state. An 18% received genotype-guided therapy and a 4% immunotherapy. The description of tumor subtypes is plausible through high-throughput sequencing by recognizing clinically relevant alterations. Additional concomitant assessment of immune biomarkers identifies candidates for immunotherapy.

Background Next-generation sequencing (NGS) is a high-throughput technology that has become widely integrated in molecular diagnostics laboratories. Among the large diversity of NGS-based panels, the Trusight Tumor 26 (TsT26) enables the detection of low-frequency variants across 26 genes using the MiSeq platform. Methods We describe the inter-laboratory validation and subsequent clinical application of the panel in 399 patients presenting a range of tumor types, including gastrointestinal (GI, 29%), hematologic (18%), lung (13%), gynecological and breast (8% each), among others. Results The panel is highly accurate with a test sensitivity of 92%, and demonstrated high specificity and positive predictive values (95% and 96%, respectively). Sequencing testing was successful in two-thirds of patients, while the remaining third failed due to unsuccessful quality-control filtering. Most detected variants were observed in the TP53 (28%), KRAS (16%), APC (10%) and PIK3CA (8%) genes. Overall, 372 variants were identified, primarily distributed as missense (81%), stop gain (9%) and frameshift (7%) altered sequences and mostly reported as pathogenic (78%) and variants of uncertain significance (19%). Only 14% of patients received targeted treatment based on the variant determined by the panel. The variants most frequently observed in GI and lung tumors were: KRAS c.35G > A (p.G12D), c.35G > T (p.G12V) and c.34G > T (p.G12C). Conclusions Prior panel validation allowed its use in the laboratory daily practice by providing several relevant and potentially targetable variants across multiple tumors. However, this study is limited by high sample inadequacy rate, raising doubts as to continuity in the clinical setting.

ObjectiveWe aimed to assess whether an increase in chondrocyte size might be a feature of the articular cartilage (AC) hypertrophic-like phenotype both in experimental and in human osteoarthritis (OA). The anatomical location of these enlarged cells in the cartilage layers was also evaluated.MethodsExperimental OA was carried out in female rabbits alone or in combination with osteoporosis (OPOA). The rabbits were subjected to destabilization knee surgery to develop OA. Osteoporosis was induced with ovariectomy and methylprednisolone administration. Human OA samples obtained from knee replacement surgery were also studied. Cartilage lesions and chondrocyte size were assessed in AC sections. Immunostaining of type-X collagen and metalloproteinase-13 were used as markers of the AC hypertrophic transformation. Both the cell size and the gene expression of type-X collagen were further analyzed in primary murine chondrocyte cultures.ResultsCompared to healthy AC, chondrocyte size was increased both in experimental and in human OA, in correlation with the severity of cartilage damage. No differences in chondrocyte size were found between deeper or more superficial regions of AC. In cell cultures, accretion of hypertrophic markers and cell enlargement were found to occur synchronized.ConclusionsWe observed an enhancement in the mean size of chondrocytes at the OA cartilage, which showed correlation with cartilage damage, both in human and in experimental OA. The enlarged chondrocytes were homogeneously distributed throughout the AC. Our results suggest that chondrocyte size could be a reliable measure of disease progression, of potential use in the histopathological assessment of OA cartilage.

Purpose: Osteoarthritis (OA) is a disease characterized by degradation of articular cartilage, osteophyte formation, subchondral sclerosis and synovial proliferation, which results in the loss of joint function and disability. Osteoporosis (OP) is a disorder characterized by reduced bone mass, leading to diminished physical bone strength and increased susceptibility to fracture. In a combined model of OP followed by a destabilization-induced OA in rabbits, we have described microstructural impairment of subchondral bone withincreased remodelling that aggravates cartilage damage. Accordingly, numerous alterations in structural and biomechanical properties have been described in the articular cartilage of different experimental models of low bone mass induced by ovariectomy (OVX). Our aim was to associate the severity of OA and the size of the hyperthropic chondrocytes in articular cartilage in a combined model of OPOA. Methods: New Zealand female rabbits were randomly assigned to four groups: healthy rabbits (control group, n=8), osteoporotic (OP group, n=7), osteoarthritic (OA group, n=8) and OA with previous osteoporosis rabbits (OPOA group, n=8). OP was induced by OVX and administration of metilprednisolone (1mg/kg/day) during six weeks. After this period, OA was induced by anterior cruciate ligand transection and the disease developed over 6 weeks. All animals were euthanized and tibias, femurs, synovium and serum samples were collected. 17-beta estradiol levels were analyzed for OP validation. Macroscopic evaluation and Mankin score were done to analyze joint damage. TRAP staining was performed in the joint to analyze bone resorption. Finally, chondrocyte size was measured in articular cartilage, and we did a correlation between the chondrocyte size and the Mankin score. To carry out statistic studies we used a Kruskal-Wallis test following by a Mann Whitney test. Results: OP induced-rabbits showed lower levels of 17-beta estradiol (pg/ml) than the others (Healthy: 44±8, OP: 26±3, OA: 40±10, OPOA: 28±6, p<0.05 OP and OPOA vs Healthy). Macroscopic evaluation reflected significant differences between control and the rest of the groups, and between OA and OPOA faced to OP (Healthy: 0.25±0.10, OP: 2.0±0.5, OA: 4.6±0.2, OPOA: 4.5±0.2, p<0.05 all groups vs Healthy, and OA-OPOA vs OP). Mankin score showed significant more severity damage in osteoarthritic groups than control rabbits, and OPOA more than OP group (Healthy: 1.6±0.2. OP: 5.0±1.5, OA: 6.0±0.6, OPOA: 7.5±1.3, p<0.05 vs Control). TRAP staining showed that OA and OPOA groups had more number of stained cells than Control and OP rabbits (Healthy: 8.5+2.6, OP: 7.6±3.0, OA: 43±11, OPOA: 80±18). Osteoarthritic groups had larger chondrocyte size than control and OP rabbits, and OPOA chondrocytes were slightly larger than OA chondrocytes. (Healthy: 131±7, OP: 152±12, OA: 187±15, OPOA: 234±16, p<0.005 OA - OPOA vs Healthy, p<0.05 OPOA vs OA). Finally, it was significantly the correlation between Mankin score and chondrocyte size(p<0.05, r= 0.4314). Conclusions: Our results suggest that OPOA model presents more severity than OA in joint damage, and this fact correlated with chondrocyte size in articular cartilage, whose are associated in osteoarthritis with the severity of the disease, being bigger in OPOA rabbits than OA group.

Besides its primary function in locomotion, skeletal muscle (SKM), which represents up to half of human's weight, also plays a fundamental homeostatic role. Through the secretion of soluble peptides, or myokines, SKM interacts with major organs involved in metabolic processes. In turn, metabolic cues from these organs are received by muscle cells, which adapt their response accordingly. This is done through an intricate intracellular signaling network characterized by the cross-talking between anabolic and catabolic pathways. A fine regulation of the network is required to protect the organism from an excessive energy expenditure. Systemic inflammation evokes a catabolic reaction in SKM known as sarcopenia. In turn this response comprises several mechanisms, which vary depending on the nature of the insult and its magnitude. In this regard, aging, chronic inflammatory systemic diseases, osteoarthritis and idiopathic inflammatory myopathies can lead to muscle loss. Interestingly, sarcopenia may persist despite remission of chronic inflammation, an issue which warrants further research. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) system stands as a major participant in muscle loss during systemic inflammation, while it is also a well-recognized orchestrator of muscle cell turnover. Herein we summarize current knowledge about models of sarcopenia, their triggers and major mediators and their effect on both protein and cell growth yields. Also, the dual action of the JAK/STAT pathway in muscle mass changes is discussed. We highlight the need to unravel the precise contribution of this system to sarcopenia in order to design targeted therapeutic strategies.

BACKGROUND:The functional loss of the tumor suppressor protein phosphatase 2A (PP2A) occurs in a wide variety of human cancers including colorectal cancer (CRC), and SET overexpression has been reported as a key contributing mechanism to inhibit PP2A. Although SET binding protein 1 (SETBP1) overexpression and gain of function mutations have been described in several hematological malignancies as common events that increase the expression levels of the PP2A inhibitor SET, thereby leading to PP2A inactivation, the potential existence of SETBP1 alterations in CRC still remains unexplored.METHODS:We studied the expression profile of SETBP1 by Western blot in a set of CRC cell lines and patient samples. Moreover, we performed co-immunoprecipitation assays to analyze the formation of the previously reported SETBP1-SET-PP2A inhibitory complex. Furthermore, we evaluated the mutational status of SETBP1 by pyrosequencing assays in a cohort of 55 CRC patients with metastatic disease after the immunohistochemical characterization of SET and p-PP2A expression in this cohort.RESULTS:We found high SETBP1 expression in several CRC lines but only in two of the patients analyzed. In addition, we demonstrated the formation of the SETBP1-SET-PP2A heterotrimeric complex in CRC cells. However, we failed to detect SETBP1 mutations in any of the CRC patient samples included in the study.CONCLUSIONS:Our results suggest that SETBP1 expression is mainly similar o lower in colorectal cancer tissue compared to normal colonic mucosa. However, its overexpression is a low prevalent alteration which could contribute to inhibit PP2A in CRC through the formation of a SETBP1-SET-PP2A complex in some CRC patients. Moreover, SETBP1 mutations are, if exist, rare events in CRC patients.

Abstract Aim: The aim of this work is to compare the effects of osteoprotegerin (OPG) and testosterone on bone quality in a model of orchidectomised (ORX) rats. Methods: Three-month-old ORX or SHAM operated groups (n = 15 each group) were used. The SHAM and ORX groups received saline. There were two ORX groups, receiving OPG–Fc (10 mg/kg twice weekly) (ORX + OPG–Fc) or testosterone cypionate (1.7 mg/kg/weekly) for 8 weeks. After sacrifice, bone analysis by femoral and lumbar dual-energy X-ray absorptiometry and micro-computed tomography in femora were performed. Histological sections of vertebrae were dyed with hematoxylin–eosin or safranin. Serum osteocalcin (BGP), total alkaline phosphatase (ALP), and C-terminal telopeptide of type I collagen (CTX) were analyzed. Results: ORX resulted in femoral and vertebral bone loss and in microarchitectural deterioration. Treatment with OPG–Fc and testosterone recovered lumbar (L) and femoral (F) bone mineral densitometry bone mineral density (BMD) to SHAM levels. Femoral BMD was significantly higher after treatment with OPG–Fc than after testosterone treatment due to the presence of osteopetrotic changes in the metaphyseal region of long bones. Serum levels of ALP and CTX increased, while OPG levels were unchanged in ORX rats. Treatment with OPG–Fc decreased the levels of BGP, ALP, and CTX. Treatment with testosterone maintained biochemical markers of bone turnover at levels similar to or higher than those of ORX rats.

Treatment of colorectal cancer (CRC) with monoclonal antibodies against epidermal growth factor receptor requires the assessment of the mutational status of exons 2, 3, and 4 of the NRAS and KRAS oncogenes. Moreover, the mutational status of exon 15 of the BRAF oncogene is a marker of poor prognosis in CRC. The Idylla NRAS-BRAF Mutation Test is a reliable, simple (<2 minutes hands-on time), and quick (<2 hours turnaround time) sample-to-result solution, enabling the detection of clinically relevant mutations in NRAS (18 mutations) and BRAF (5 mutations). A multicenter study was conducted in 14 centers using the Idylla NRAS-BRAF Mutation Test to assess the NRAS and BRAF mutational status of 418 formalin-fixed, paraffin-embedded tissue samples from CRC patients. Results were compared with those obtained earlier by routine reference methods, including next-generation sequencing, pyrosequencing, mass spectrometry-based assays, PCR-based assays, and Sanger sequencing. In case of discordance, additional tests were performed by digital droplet PCR. Overall, after testing confirmation and excluding invalids/errors by design, concordances between the Idylla NRAS-BRAF Mutation Test and the reference test results were found in almost perfect agreement. In conclusion, the Idylla NRAS-BRAF Mutation Test enables the routine detection of all NRAS and BRAF mutations deemed clinically relevant according to the latest clinical guidelines, without necessitating molecular expertise or infrastructure.

Metabolic syndrome (MetS) may be associated with knee osteoarthritis (OA), but the association between the individual components and OA are not well-understood. We aimed to study the effect of hypercholesterolemia on synovial inflammation in knee OA.

Inflammatory activity in rheumatoid arthritis may alter the regulation of muscle mass leading to a secondary sarcopenia, commonly termed rheumatoid cachexia (RC). We characterized alterations to muscle structure and various pro-inflammatory, catabolic and regenerative markers in an animal model of RC. Antigen induced arthritis (AiA) was performed in 20 male adult rabbits. AiA animals exhibited significantly less weight gain, a markedly elevated serum C-reactive protein (CRP), lighter muscles with shorter cross-sectional diameter and increased myonuclei when compared to controls. Atrogin-1 and MuRF-1 were up-regulated alongside an increase in IL-1β, active NF-κB and a higher ratio of phosphorylated to inactive p38 MAPK. CCL-2 and TNF levels were reduced and IL-6 was unchanged between groups. We observed decreased pSTAT3, unchanged pSTAT1 and Myf5, but increased Pax7, MyoD and myogenin. AiA rabbits had a reduction in myostatin from gastrocnemii and synovium with a congruent decrease in serum myostatin compared to controls. Chronic arthritis induced an RC-like secondary sarcopenia with increased muscle protein breakdown. Elevated IL-1β may trigger proteolysis via elevated NF-κB and p38 MAPK signaling with a compensatory anabolic response suggested by myonuclear expansion, increased Pax7, MyoD and myogenin, reduced pSTAT3 as well as reduced serum, synovial and muscular myostatin.

Purpose: Metabolic syndrome (MetS) is a well-recognized risk factor for osteoarthritis (OA) initiation and progression. While obesity contribution is well characterized, less known is the effect of each component of this syndrome on its own. Particularly interesting is the role of hypercholesterolemia, given the high incidence of cardiovascular events and atherosclerosis in OA patients. In fact, obesity is characterized by alterations in adipose tissue metabolism and the high production of inflammatory mediators derived from adipose tissue, named adipokines, that seem to be associated to OA progression. In this study, our aim was to study the effect of hypercholesterolemia without any other component of MetS in the synovial inflammation in knee OA. Methods: 16 four month-old male New Zeland rabbits (3 - 3.5 kg body weight) were fed with a high fat diet (HFD) containing 0.5% cholesterol and 4% peanut oil ad libitum. Six weeks later, bilateral osteoarthritis (OA) was induced by anterior cruciate ligament transection (ACLT) and partial medial meniscectomy, in 10 of these animals (OA+HFD group), and in 10 regular chow fed rabbits (OA group). Additionally, 10 healthy rabbits fed with regular chow were simultaneously followed (Control group). Twelve weeks after OA induction, animals were euthanized SM isolated for histological and molecular biology studies. Results: HFD, OA and OA+HFD animals gain significantly less weight than control rabbits at the end of the study. We did not find significant differences in Systolic blood pressure, serum glucose or oral glucose tolerance between the groups studied. Rabbits receiving the HFD showed higher total serum cholesterol, triglycerides and C-Reactive Protein levels than rabbits fed a normal diet. Synovitis score (Krenn scale) was increased in HFD and OA rabbits, and particularly in OA+HFD group, where the more severe score was observed. Synovitis in OA+HFD was characterized by a massive infiltration of foam RAM11+ cells, with higher presence of multinucleated foam cells and stromal fibrosis than in OA. We then characterized the changes in adipocyte size and the percentage of adipose tissue area (%ATA) in the SM of the rabbits. A huge decrease in the %ATA together with a marked decrease in the adipocyte size was observed in OA+HFD in comparison to OA and control animals. Furthermore, perilipin1a synthesis was significantly decreased in OA+HFD in comparison to OA and control rabbits. In comparison to controls, synovial leptin and adiponectin gene expressions were markedly decreased in HFD and OA rabbits, and especially in OA+HFD animals (p<0.01 vs OA), and positively correlated with %ATA in these animals. By contrast, serum leptin was increased in HFD and OA+HFD in comparison to control rabbits. We did not find significant differences in the SM gene expression of the proinflammatory cytokines IL-1β, COX-2 or MCP-1, between OA and OA+HFD animals. However, TNF SM expression was significantly increased in OA+HFD vs. OA, and significantly correlated with the presence of RAM11+ cells in the SM of these rabbits. Conclusions: Our data show that hypercholesterolemia is an aggravating factor for osteoarthritic synovitis, inducing an increased infiltration of macrophages and the disappearance of adipose tissue in the SM. Hypercholesterolemia induced a profound decrease in the adipocyte content in the OA SM, together with a remarkable increase in synovial TNF expression. Furthermore, HFD induced a decrease in the synovial expression of leptin and adiponectin in OA rabbits. However, high levels of serum leptin, probably due to systemic synthesis such as that derived from the liver were found in HFD fed animals. Taken together our data indicate that synovial adipocytes and dyslipemia could play pivotal roles in OA joint deterioration in patients with MetS, and support the concept that the link between obesity and OA transcends mechanical loading.

Background Metabolic syndrome (MetS) is a risk factor for osteoarthritis (OA). While obesity contribution is well characterized, less known is the effect of each component of this syndrome on its own. Particularly interesting is the role of hypercholesterolemia, given the high incidence of cardiovascular events and atherosclerosis in OA patients. Objectives To study the effect of hypercholesterolemia without any other component of MetS in the synovial inflammation in knee OA. Methods 16 New Zeland rabbits were fed with a high fat diet (HFD, 0.5% cholesterol+4% peanut oil). Six weeks later, OA was induced by anterior cruciate ligament transection and partial medial meniscectomy, in 10 of these animals (OA+HFD group), and in 10 regular chow fed rabbits (OA group). 10 healthy rabbits fed with regular chow were simultaneously followed (Control group). Twelve weeks after OA induction, animals were euthanized and SM isolated for histological and molecular biology studies. Results HFD, OA and OA+HFD animals gain significantly less weight than control rabbits at the end of the study. We did not find significant differences in systolic blood pressure, serum glucose or oral glucose tolerance between the groups. HFD fed rabbits showed higher total serum cholesterol, triglycerides and C-Reactive Protein levels than rabbits fed a normal diet. Synovitis score was increased in HFD and OA rabbits, and particularly in OA+HFD group, with the more severe score. Synovitis in OA+HFD was characterized by a massive infiltration of foam RAM11+ cells, with higher presence of multinucleated foam cells and stromal fibrosis than in OA. A huge decrease in the adipose tissue area (%ATA)t ogether with a marked decrease in the adipocyte size was observed in the SM of OA+HFD in comparison to OA and control animals. Furthermore, perilipin1a synthesis was significantly decreased in OA+HFD in comparison to OA and control rabbits. In comparison to controls, synovial leptin and adiponectin gene expressions were markedly decreased in HFD and OA rabbits, and especially in OA+HFD animals (p<0.01 vs OA), and positively correlated with %ATA in these animals. By contrast, serum leptin was increased in HFD and OA+HFD in comparison to control rabbits. We did not find significant differences in the SM gene expression of the proinflammatory cytokines IL-1β, COX-2 or MCP-1, between OA and OA+HFD animals. However, TNF SM expression was significantly increased in OA+HFD vs. OA, and significantly correlated with the presence of RAM11+ cells in the SM of these rabbits. Conclusions Our data show that hypercholesterolemia is an aggravating factor for OA synovitis, inducing an increased infiltration of macrophages and the disappearance of adipose tissue in the SM. Hypercholesterolemia induced a profound decrease in the adipocyte content in the OA SM, together with a remarkable increase in synovial TNF expression. HFD induced a decrease in the synovial expression of leptin and adiponectin in OA rabbits. However, high levels of serum leptin, probably due to systemic synthesis such as that derived from the liver were found in HFD fed animals. Our data indicate that synovial adipocytes and dyslipemia could play pivotal roles in OA joint deterioration in patients with MetS, and support the concept that the link between obesity and OA transcends mechanical loading Disclosure of Interest None declared

Background Rheumatoid arthritis (RA) is an inflammatory arthropathy with a range of additional systemic consequences. Rheumatoid cachexia (RC), the condition of decreased muscle mass with stable or increased fat mass, is one such phenomenon. Muscle atrophy in RC appears to be driven by circulating pro-inflammatory cytokines1. However, alterations to pro-inflammatory gene expression within muscle may also contribute to the wasting process. Objectives Characterise alterations to muscle structure and gene expression in an animal model of chronic inflammatory arthritis. Methods Nineteen male, New Zealand white rabbits were randomly assigned to two groups: control (n=12) and antigen-induced arthritis (AiA; n=7). Chronic arthritis was induced over six weeks via intra-dermal ovalbumin sensitization and four subsequent intra-articular injections. Nineteen gastrocnemius muscles were collected for gene expression studies and 10 tibialis anterior muscles (control n=6; AiA n=4) were collected for both gene expression and histological studies. IL-1β, IL-6, TNF, CCL-2 (MCP-1), myostatin and two atrogenes, MuRF-1 and atrogin-1, were quantified using real-time PCR. Tibialis anterior mid-belly cross-sections were stained with haematoxylin & eosin and for ATPase activity to measure whole muscle cross-sectional diameter (CSD) and type II fibre CSD, respectively. Rabbits were weighed weekly and serum CRP was measured at week 6. Group comparisons were performed using Mann-Whitney tests and associations were tested using Spearman correlation analyses. Results AiA rabbits exhibited significantly less weight gain than controls, with a maximum cumulative difference of -160g vs. +570g (p<0.0001) and a 74-fold increase in serum CRP (p=0.0003). Tibialis anterior of AiA rabbits showed a 16% reduction in type II myofibre CSD (p=0.0159) and a 27% reduction in whole muscle CSD (p=0.0095) alongside a 11-fold increase in IL-1β (p=0.0095), a 21-fold increase in IL-6 (p=0.0381) and a 14-fold increase in CCL-2 mRNA (p=0.0095). Gastrocnemii of AiA rabbits demonstrated similar, yet less pronounced inflammatory activity with a 3-fold increase in IL-1β (p=0.0012), and a 5-fold increase in both IL-6 (p=0.0221) and CCL-2 (p=0.0018) alongside a 3-fold and 2-fold increase in the atrogenes MuRF-1 (p=0.0283) and atrogin-1 (p=0.0130), respectively. Conversely, tibialis anterior and gastrocnemius muscles of AiA rabbits expressed 78% (p=0.0095) and 70% (p=0.0097) less myostatin with no alteration in TNF mRNA. Correlation analyses revealed that tibialis anterior whole muscle CSD and type II myofibre CSD were inversely associated with the expression of pro-inflammatory, muscle-derived cytokines. Conclusions Our model of chronic arthritis induced an RC-like state with reduced animal weight and muscle size, an up-regulation of atrogene expression, indicating muscle protein breakdown, and a parodixcal decrease in myostatin. Arthritis also up-regulated serum CRP and appeared to activate an inflammatory phenotype in skeletal muscle. We propose that inflamed muscle tissue may contribute to the process of RC via a mechanism of autocrine atrophy triggered by increased secretion of muscle-derived, pro-inflammatory mediators. References Summers GD, Metsios GS, Stavropoulos-Kalinoglou A, Kitas GD. Rheumatoid cachexia and cardiovascular disease. Nature Publishing Group. 2010 Aug;6(8):445–51. Disclosure of Interest None declared