Functional annotation of rheumatoid arthritis and osteoarthritis associated genes by integrative genome-wide gene expression profiling analysis

Cell-specific gene networks and drivers in rheumatoid arthritis synovial tissues

Rheumatoid arthritis (RA) is a common autoimmune and inflammatory disease characterized by inflammation and hyperplasia of the synovial tissues. RA pathogenesis involves multiple cell types, genes, transcription factors (TFs) and networks. Yet, little is known about the TFs, and key drivers and networks regulating cell function and disease at the synovial tissue level, which is the site of disease. In the present study, we used available RNA-seq databases generated from synovial tissues and developed a novel approach to elucidate cell type-specific regulatory networks on synovial tissue genes in RA. We leverage established computational methodologies to infer sample-specific gene regulatory networks and applied statistical methods to compare network properties across phenotypic groups (RA versus osteoarthritis). We developed computational approaches to rank TFs based on their contribution to the observed phenotypic differences between RA and controls across different cell types. We identified 18 (fibroblast-like synoviocyte), 16 (T cells), 19 (B cells) and 11 (monocyte) key regulators in RA synovial tissues. Interestingly, fibroblast-like synoviocyte (FLS) and B cells were driven by multiple independent co-regulatory TF clusters that included MITF, HLX, BACH1 (FLS) and KLF13, FOSB, FOSL1 (B cells). However, monocytes were collectively governed by a single cluster of TF drivers, responsible for the main phenotypic differences between RA and controls, which included RFX5, IRF9, CREB5. Among several cell subset and pathway changes, we also detected reduced presence of Natural killer T (NKT) cells and eosinophils in RA synovial tissues. Overall, our novel approach identified new and previously unsuspected Key driver genes (KDG), TF and networks and should help better understanding individual cell regulation and co-regulatory networks in RA pathogenesis, as well as potentially generate new targets for treatment.

Association of integrin-β2 polymorphism and expression with the risk of rheumatoid arthritis and osteoarthritis in Egyptian patients

BACKGROUND

The genetic architecture of rheumatoid arthritis (RA) and osteoarthritis (OA) are still unclear. Although RA and OA have quite different causes, they share synovial inflammation, risk factors, and some disease-associated genes, including the integrin subunit β2 (ITGB2)/CD18 gene involved in extracellular matrix interactions and immune cell signaling. However, the functional role of ITGB2 genetic variants, its circulating expression pattern, and their clinical usefulness in RA and OA remain unexplored. Our study appraised the association of ITGB2 rs2070946 single nucleotide polymorphism with the vulnerability to RA and OA and its influence on ITGB2 mRNA expression, along with the potential of serum ITGB2 expression in RA and OA diagnosis.

METHODS

This study included 70 RA patients, 70 primary OA patients, and 60 healthy volunteers. Genotyping and gene expression analysis were performed using qPCR. Bioinformatics analysis was employed to construct the protein-protein interaction (PPI) network of ITGB2.

RESULTS

Serum ITGB2 mRNA expression was upregulated in both RA and OA compared to healthy controls. ITGB2 rs2070946 was associated with escalating risk of both diseases. RA patients harboring the rs2070946 CC or TC + CC genotypes had higher serum ITGB2 expression than the TT genotype carriers. Likewise, OA patients having the minor homozygote CC genotype had higher serum ITGB2 expression than those carrying the TT, TC or TT + TC genotypes. Serum ITGB2 expression showed profound diagnostic potential for RA and OA in receiver-operating characteristic analysis. In RA, serum ITGB2 expression positively correlated with rheumatoid factor and disease activity score 28 (DAS28). The ITGB2-PPI network enriched in cell-cell adhesion, ICAM-3 receptor activity, T-cell activation, leukocyte adhesion, complement binding, and NF-κB, tumor necrosis factor, and interleukin signaling pathways.

CONCLUSION

These findings embrace the impact of ITGB2 rs2070946 as a novel genetic biomarker of both RA and OA, which could alter the ITGB2 expression. Serum ITGB2 expression could aid in timely diagnosis of RA and OA.

SelectBCM tool: a batch evaluation framework to select the most appropriate batch-correction methods for bulk transcriptome analysis

Bulk transcriptomes are an essential data resource for understanding basic and disease biology. However, integrating information from different experiments remains challenging because of the batch effect generated by various technological and biological variations in the transcriptome. Numerous batch-correction methods to deal with this batch effect have been developed in the past. However, a user-friendly workflow to select the most appropriate batch-correction method for the given set of experiments is still missing. We present the SelectBCM tool that prioritizes the most appropriate batch-correction method for a given set of bulk transcriptomic experiments, improving biological clustering and gene differential expression analysis. We demonstrate the applicability of the SelectBCM tool on analyses of real data for two common diseases, rheumatoid arthritis and osteoarthritis, and one example to characterize a biological state, where we performed a meta-analysis of the macrophage activation state. The R package is available at https://github.com/ebi-gene-expression-group/selectBCM.

Melatonin promotes sirtuin 1 expression and inhibits IRE1α–XBP1S–CHOP to reduce endoplasmic reticulum stress–mediated apoptosis in chondrocytes

Osteoarthritis (OA) is the most common chronic disease characterized by a loss of chondrocytes and the degeneration of cartilage. Inflammation plays an important role in the pathogenesis and progression of OA via the activation of the endoplasmic reticulum (ER) stress signaling pathway. In this study, we stimulated human primary chondrocytes with lipopolysaccharide (LPS) to reduce cell viability and induce chondrocyte apoptosis. LPS–stimulated human primary chondrocytes induced ER stress and significantly upregulated the ER chaperone glucose–regulated protein 78 (GRP78) and increased the expression level of C/EBP–homologous protein (CHOP), a key mediator of ER stress––induced apoptosis. Interestingly, melatonin treatment attenuated ER stress–mediated chondrocyte apoptosis. Melatonin inhibited the expression of cleaved caspase-3, cleaved caspase-10, Bax, CHOP, GRP78, cleaved caspase-4, phospho–inositol–requiring enzyme 1α (P-IRE1α), and spliced X-box-binding protein 1 (XBP1S). In an anterior cruciate ligament transection mouse model of OA, melatonin (50 and 150 mg/kg) dose–dependently relieved joint cartilage degeneration and inhibitied of chondrocyte apoptosis. Immunohistochemical analysis indicated that melatonin could promote SIRT1 the expression and inhibit CHOP and cleaved caspase-3 expression in OA mice. In conclusion, our findings demonstrate for the first time that melatonin inhibits the IRE1α-XBP1S-CHOP signaling pathway by promoting the expression of SIRT1 in LPS-treated human chondrocytes and delaying OA progression in vivo.

Classifying Integrated Signature Molecules in Macrophages of Rheumatoid Arthritis, Osteoarthritis, and Periodontal Disease: An Omics-Based Study

Rheumatoid arthritis (RA), osteoarthritis (OA), and periodontal disease (PD) are chronic inflammatory diseases that are globally prevalent, and pose a public health concern. The search for a potential mechanism linking PD to RA and OA continues, as it could play a significant role in disease prevention and treatment. Recent studies have linked RA, OA, and PD to Porphyromonas gingivalis (PG), a periodontal bacterium, through a similar dysregulation in an inflammatory mechanism. This study aimed to identify potential gene signatures that could assist in early diagnosis as well as gain insight into the molecular mechanisms of these diseases. The expression data sets with the series IDs GSE97779, GSE123492, and GSE24897 for macrophages of RA, OA synovium, and PG stimulated macrophages (PG-SM), respectively, were retrieved and screened for differentially expressed genes (DEGs). The 72 common DEGs among RA, OA, and PG-SM were further subjected to gene–gene correlation analysis. A GeneMANIA interaction network of the 47 highly correlated DEGs comprises 53 nodes and 271 edges. Network centrality analysis identified 15 hub genes, 6 of which are DEGs (API5, ATE1, CCNG1, EHD1, RIN2, and STK39). Additionally, two significantly up-regulated non-hub genes (IER3 and RGS16) showed interactions with hub genes. Functional enrichment analysis of the genes showed that “apoptotic regulation” and “inflammasomes” were among the major pathways. These eight genes can serve as important signatures/targets, and provide new insights into the molecular mechanism of PG-induced RA, OA, and PD.

Histone demethylase JMJD3 downregulation protects against aberrant force-induced osteoarthritis through epigenetic control of NR4A1

Osteoarthritis (OA) is a prevalent joint disease with no effective treatment strategies. Aberrant mechanical stimuli was demonstrated to be an essential factor for OA pathogenesis. Although multiple studies have detected potential regulatory mechanisms underlying OA and have concentrated on developing novel treatment strategies, the epigenetic control of OA remains unclear. Histone demethylase JMJD3 has been reported to mediate multiple physiological and pathological processes, including cell differentiation, proliferation, autophagy, and apoptosis. However, the regulation of JMJD3 in aberrant force-related OA and its mediatory effect on disease progression are still unknown. In this work, we confirmed the upregulation of JMJD3 in aberrant force-induced cartilage injury in vitro and in vivo. Functionally, inhibition of JMJD3 by its inhibitor, GSK-J4, or downregulation of JMJD3 by adenovirus infection of sh-JMJD3 could alleviate the aberrant force-induced chondrocyte injury. Mechanistic investigation illustrated that aberrant force induces JMJD3 expression and then demethylates H3K27me3 at the NR4A1 promoter to promote its expression. Further experiments indicated that NR4A1 can regulate chondrocyte apoptosis, cartilage degeneration, extracellular matrix degradation, and inflammatory responses. In vivo, anterior cruciate ligament transection (ACLT) was performed to construct an OA model, and the therapeutic effect of GSK-J4 was validated. More importantly, we adopted a peptide-siRNA nanoplatform to deliver si-JMJD3 into articular cartilage, and the severity of joint degeneration was remarkably mitigated. Taken together, our findings demonstrated that JMJD3 is flow-responsive and epigenetically regulates OA progression. Our work provides evidences for JMJD3 inhibition as an innovative epigenetic therapy approach for joint diseases by utilizing p5RHH-siRNA nanocomplexes.

Metabolic discrimination of synovial fluid between rheumatoid arthritis and osteoarthritis using gas chromatography/time-of-flight mass spectrometry

INTRODUCTION

Rheumatoid arthritis (RA) and osteoarthritis (OA) are clinicopathologically different.

OBJECTIVES

We aimed to assess the feasibility of metabolomics in differentiating the metabolite profiles of synovial fluid between RA and OA using gas chromatography/time-of-flight mass spectrometry.

METHODS

We first compared the global metabolomic changes in the synovial fluid of 19 patients with RA and OA. Partial least squares-discriminant, hierarchical clustering, and univariate analyses were performed to distinguish metabolites of RA and OA. These findings were then validated using synovial fluid samples from another set of 15 patients with RA and OA.

RESULTS

We identified 121 metabolites in the synovial fluid of the first 19 samples. The score plot of PLS-DA showed a clear separation between RA and OA. Twenty-eight crucial metabolites, including hypoxanthine, xanthine, adenosine, citrulline, histidine, and tryptophan, were identified to be capable of distinguishing RA metabolism from that of OA; these were found to be associated with purine and amino acid metabolism.

CONCLUSION

Our results demonstrated that metabolite profiling of synovial fluid could clearly discriminate between RA and OA, suggesting that metabolomics may be a feasible tool to assist in the diagnosis and advance the comprehension of pathological processes for diseases.

Exercise for Osteoarthritis: A Literature Review of Pathology and Mechanism

Osteoarthritis (OA) has a very high incidence worldwide and has become a very common joint disease in the elderly. Currently, the treatment methods for OA include surgery, drug therapy, and exercise therapy. In recent years, the treatment of certain diseases by exercise has received increasing research and attention. Proper exercise can improve the physiological function of various organs of the body. At present, the treatment of OA is usually symptomatic. Limited methods are available for the treatment of OA according to its pathogenesis, and effective intervention has not been developed to slow down the progress of OA from the molecular level. Only by clarifying the mechanism of exercise treatment of OA and the influence of different exercise intensities on OA patients can we choose the appropriate exercise prescription to prevent and treat OA. This review mainly expounds the mechanism that exercise alleviates the pathological changes of OA by affecting the degradation of the ECM, apoptosis, inflammatory response, autophagy, and changes of ncRNA, and summarizes the effects of different exercise types on OA patients. Finally, it is found that different exercise types, exercise intensity, exercise time and exercise frequency have different effects on OA patients. At the same time, suitable exercise prescriptions are recommended for OA patients.

Identifying hub genes and immune infiltration of osteoarthritis using comprehensive bioinformatics analysis

Background

Osteoarthritis (OA) is the most common chronic degenerative joint disorder globally that is characterized by synovitis, cartilage degeneration, joint space stenosis, and sub-cartilage bone hyperplasia. However, the pathophysiologic mechanisms of OA have not been thoroughly investigated.

Methods

In this study, we conducted various bioinformatics analyses to identify hub biomarkers and immune infiltration in OA. The gene expression profiles of synovial tissues from 29 healthy controls and 36 OA samples were obtained from the gene expression omnibus database to identify differentially expressed genes (DEGs). The CIBERSORT algorithm was used to explore the association between immune infiltration and arthritis.

Results

Eighteen hub DEGs were identified as critical biomarkers for OA. Through gene ontology and pathway enrichment analyses, it was found that these DEGs were primarily involved in PI3K-Akt signaling pathway and Rap1 signaling pathway. Furthermore, immune infiltration analysis revealed differences in immune infiltration between patients with OA and healthy controls. The hub gene ZNF160 was closely related to immune cells, especially mast cell activation in OA.

Conclusion

Overall, this study presented a novel method to identify hub DEGs and their correlation with immune infiltration, which may provide novel insights into the diagnosis and treatment of patients with OA.

Human Bone Mesenchymal Stem Cell-Derived Exosomes Inhibit IL-1β-Induced Inflammation in Osteoarthritis Chondrocytes

Objective

Human bone marrow mesenchymal stem cell (hBMSC)-derived exosomes exhibit protective effects against inflammatory diseases. This study aimed to explore the effects of hBMSC-derived exosomes on osteoarthritis (OA) in vitro and its related mechanisms.

Materials and Methods

In this experimental study, we characterised exosomes derived from hBMSCs by transmission electron microscopy, nanoparticle tracking and Western blot analysis. Cellular uptake of exosomes was observed by fluorescent microscopy. Cell viability of chondrocytes exposed to interleukin-1 beta (IL-1β) was determined by the Cell Counting Kit-8 (CCK-8). Real-time quantitative polymerase chain reaction (RT-qPCR) was used to determine expression levels of genes related to apoptosis, inflammation, cartilage collagen metabolism and mitogen-activated protein kinases.

Results

Fluorescence microscopy revealed that hBMSC-derived exosomes could be taken up by chondrocytes. hBMSC-derived exosomes could significantly enhance cell viability of chondrocytes in response to IL-1β treatment. RT-qPCR showed significant up-regulation of Survivin, Versican, IL-1β, IL-6, NF-κB, MMP-13, MAPK p38, JNK, ERK, Aggrecan and SOX9 expression levels by IL-1β treatment, while their mRNA expression levels decreased after co- culture with exosomes. The anti-inflammatory gene TGF-β was markedly suppressed by IL-1β treatment; however, we observed its expression after co-culture with exosomes. Additionally, the pro-inflammatory genes IL-1β, IL-6, NF-κB, TNF-α and TNF-β displayed significantly elevated expression levels in the IL-1β group and reduced expression levels after co-culture with exosomes.

Conclusion

hBMSC-derived exosomes may play a protective role in chondrocytes through inhibiting cell apoptosis and the inflammatory response. These results will provide a novel therapeutic strategy for OA.

Cross-Tissue Transcriptomic Analysis Leveraging Machine Learning Approaches Identifies New Biomarkers for Rheumatoid Arthritis

There is an urgent need to identify biomarkers for diagnosis and disease activity monitoring in rheumatoid arthritis (RA). We leveraged publicly available microarray gene expression data in the NCBI GEO database for whole blood (N=1,885) and synovial (N=284) tissues from RA patients and healthy controls. We developed a robust machine learning feature selection pipeline with validation on five independent datasets culminating in 13 genes: TNFAIP6, S100A8, TNFSF10, DRAM1, LY96, QPCT, KYNU, ENTPD1, CLIC1, ATP6V0E1, HSP90AB1, NCL and CIRBP which define the RA score and demonstrate its clinical utility: the score tracks the disease activity DAS28 (p = 7e-9), distinguishes osteoarthritis (OA) from RA (OR 0.57, p = 8e-10) and polyJIA from healthy controls (OR 1.15, p = 2e-4) and monitors treatment effect in RA (p = 2e-4). Finally, the immunoblotting analysis of six proteins on an independent cohort confirmed two proteins, TNFAIP6/TSG6 and HSP90AB1/HSP90.

Identification of novel biomarkers and candidate small molecule drugs in rheumatoid arthritis and osteoarthritis based on bioinformatics analysis of high-throughput data

Background: Rheumatoid arthritis (RA) and osteoarthritis (OA) are two major types of joint diseases. The present study aimed to identify hub genes involved in the pathogenesis and further explore the potential treatment targets of RA and OA.

Methods: The gene expression profile of GSE12021 was downloaded from Gene Expression Omnibus (GEO). Total 31 samples (12 RA, 10 OA and 9 NC samples) were used. The differentially expressed genes (DEGs) in RA versus NC, OA versus NC and RA versus OA groups were screened using limma package. We also verified the DEGs in GSE55235 and GSE100786. Functional annotation and protein–protein interaction (PPI) network construction of OA‐ and RA‐specific DEGs were performed. Finally, the candidate small molecules as potential drugs to treat RA and OA were predicted in CMap database.

Results: 165 up-regulated and 163 down-regulated DEGs between RA and NC samples, 73 up-regulated and 293 down-regulated DEGs between OA and NC samples, 92 up-regulated and 98 down-regulated DEGs between RA and OA samples were identified. Immune response and TNF signaling pathway were significantly enriched pathways for RA‐ and OA‐specific DEGs, respectively. The hub genes were mainly associated with ‘Primary immunodeficiency’ (RA vs. NC group), ‘Ribosome’ (OA vs. NC group), and ‘Chemokine signaling pathway’ (RA vs. OA group). Arecoline and Cefamandole were the most promising small molecule to reverse the RA and OA gene expression.

Conclusion: Our findings suggest new insights into the underlying pathogenesis of RA and OA, which may improve the diagnosis and treatment of these intractable chronic diseases.

Novel role of circRSU1 in the progression of osteoarthritis by adjusting oxidative stress

Osteoarthritis (OA), characterized as an end-stage syndrome caused by risk factors accumulated with age, significantly impacts quality of life in the elderly. Circular RNAs (circRNAs) are receiving increasing attention regarding their role in OA progression and development; however, their role in the regulation of age-induced and oxidative stress-related OA remains unclear.

Methods: Herein, we explored oxidative stress in articular cartilage obtained from patients of different ages. The presence of circRSU1 was detected using RNA sequencing of H₂O₂-stimulated primary human articular chondrocytes (HCs), and validated in articular cartilage and HCs using fluorescence in situ hybridization (FISH) staining. miR-93-5p and mitogen-activated protein kinase kinase kinase 8 (MAP3K8) were identified as interactive circRSU1 partners based on annotation and target prediction databases, and their associations were identified through dual-luciferase reporter analysis. The effect of the circRSU1-miR-93-5p-MAP3K8 axis on HCs was confirmed using western blot, quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and reactive oxygen species (ROS) analyses. CircRSU1 and its mutant were ectopically expressed in mice to assess their effects in destabilization of the medial meniscus (DMM) in mice.

Results: We found a marked upregulation of circRSU1 in H₂O₂-treated HCs and OA articular cartilage from elderly individuals. circRSU1 was induced by IL-1β and H₂O₂ stimulation, and it subsequently regulated oxidative stress-triggered inflammation and extracellular matrix (ECM) maintenance in HCs, by modulating the MEK/ERK1/2 and NF-κB cascades. Ectopic expression of circRSU1 in mouse joints promoted the production of ROS and loss of ECM, which was rescued by mutation of the mir-93-5p target sequence in circRSU1.

Conclusion: We identified a circRSU1-miR-93-5p-MAP3K8 axis that modulates the progression of OA via oxidative stress regulation, which could serve as a potential target for OA therapy.

Analysis of differentially expressed genes in rheumatoid arthritis and osteoarthritis by integrated microarray analysis

BACKGROUND

Rheumatoid arthritis (RA) and osteoarthritis (OA) were two major types of joint diseases. This study aimed to explore the mechanism underlying OA and RA and analyze their difference by integrated analysis of multiple gene expression data sets.

METHODS

Gene expression data sets of RA and OA were downloaded from The Gene Expression Omnibus. Shared and specific differentially expressed genes (DEGs) in RA and OA were identified by integrated analysis of multiple gene expression data sets. Functional annotation and protein-protein interaction (PPI) network construction of OA- and RA-specific DEGs were performed to further explore the molecular mechanisms underlying RA and OA and analyze the mechanism differences between them.

RESULTS

Compared with normal controls, 3757 and 2598 DEGs were identified in RA and OA, respectively. Among them, 2176 DEGs were RA-specific DEGs and 1017 DEGs were OA-specific DEGs. Moreover, the expression of 17 DEGs played opposite pattern in RA and OA compared with normal controls. Chemokine signaling pathway and oxidative phosphorylation were significantly enriched pathways for RA- and OA-specific DEGs, respectively. BIRC2 and CSNK1E were respective hub genes of RA- and OA-specific PPI network.

CONCLUSION

Our findings provided clues for the specific mechanism and developing specific biomarkers for RA and OA.

Efficacy of Integrating a Novel 16-Gene Biomarker Panel and Intelligence Classifiers for Differential Diagnosis of Rheumatoid Arthritis and Osteoarthritis

Introducing novel biomarkers for accurately detecting and differentiating rheumatoid arthritis (RA) and osteoarthritis (OA) using clinical samples is essential. In the current study, we searched for a novel data-driven gene signature of synovial tissues to differentiate RA from OA patients. Fifty-three RA, 41 OA, and 25 normal microarray-based transcriptome samples were utilized. The area under the curve random forests (RF) variable importance measurement was applied to seek the most influential differential genes between RA and OA. Five algorithms including RF, k-nearest neighbors (kNN), support vector machines (SVM), naïve-Bayes, and a tree-based method were employed for the classification. We found a 16-gene signature that could effectively differentiate RA from OA, including TMOD1, POP7, SGCA, KLRD1, ALOX5, RAB22A, ANK3, PTPN3, GZMK, CLU, GZMB, FBXL7, TNFRSF4, IL32, MXRA7, and CD8A. The externally validated accuracy of the RF model was 0.96 (sensitivity = 1.00, specificity = 0.90). Likewise, the accuracy of kNN, SVM, naïve-Bayes, and decision tree was 0.96, 0.96, 0.96, and 0.91, respectively. Functional meta-analysis exhibited the differential pathological processes of RA and OA; suggested promising targets for further mechanistic and therapeutic studies. In conclusion, the proposed genetic signature combined with sophisticated classification methods may improve the diagnosis and management of RA patients.

Endoplasmic Reticulum Stress Is Involved in Baicalin Protection on Chondrocytes From Patients With Osteoarthritis

Osteoarthritis (OA) affects elderly population worldwide and endoplasmic reticulum (ER) stress is known to be positively correlated with OA development. Previous reports prove the cytoprotective effects of baicalin on chondrocytes, whereas the mechanisms are hardly reported. Hence, we aimed to investigate the links between OA, ER stress, and baicalin. Chondrocytes from patients with OA were subjected to H₂O₂ treatment with or without baicalin pretreatment, and cell viability was assessed via Cell Counting Kit-8. Messenger RNA (mRNA) amounts of apoptosis-related genes (Bax, Bcl-2, and Caspase-3), extracellular matrix (ECM)-related genes (Collange I, Collange II, Aggrecan, and Sox9) and ER stress hallmarks (binding immunoglobulin protein [BiP] C/EBP homologous protein [CHOP]) were evaluated via quantitative real-time PCR. Bax, Bcl-2, BiP, and CHOP protein levels were analyzed via Western blot. Baicalin suppressed the changes in cell viability and apoptosis-related gene expressions caused by H₂O₂. Reactive oxygen species and glutathione/oxidized glutathione assay showed that H₂O₂ enhanced oxidative stress. Baicalin suppressed H₂O₂-induced downregulation of mRNA expression of ECM-related genes. Moreover, baicalin reduced H₂O₂-stimulated increase in oxidative stress and the expression of ER stress hallmarks. Endoplasmic reticulum stress inducer abolished the protective activities, whereas ER stress inhibitor did not exhibit extra protective effects. Baicalin pretreatment protected patient-derived chondrocytes from H₂O₂ through ER stress inhibition.

Taurine alleviates endoplasmic reticulum stress in the chondrocytes from patients with osteoarthritis

Osteoarthritis (OA), characterized by pain and stiffness, swelling, deformity and dysfunction of joints, affects large numbers of population. The purpose of this study was to discover the effects of taurine in human OA chondrocytes and explore the underlying mechanisms. 46 patients with different grades of OA were recruited. Of these patients, 24 underwent total knee replacement and cartilages were harvested. The mRNA expressions of type II collagen (Collagen II) and endoplasmic reticulum (ER) stress markers (GRP78, GADD153 and Caspase-12) in cartilages were quantified by qRT-PCR. Cell viability and apoptosis of patient-derived chondrocytes were assessed by the CCK-8 assay and flow cytometry assay, respectively. Meanwhile, protein levels of Collagen II and ER stress markers both in cartilages and chondrocytes were evaluated by Western blot. The mRNA and protein levels of Collagen II decreased as OA progressed, while the expressions of ER stress markers increased dramatically. H₂O₂ induced ER stress in chondrocytes, as shown by the significant increase in the expression of ER stress markers, inhibited chondrocyte viability and Collagen II synthesis, promoted apoptosis. However, taurine treatment inhibited these above phenomena. These results indicated that taurine exhibited anti-OA effect by alleviating H₂O₂ induced ER stress and subsequently inhibiting chondrocyte apoptosis.

Identification of key genes in rheumatoid arthritis and osteoarthritis based on bioinformatics analysis

Rheumatoid arthritis (RA) and osteoarthritis (OA) comprise the most common forms of arthritis. The aim of this study was to identify differentially expressed genes (DEGs) and associated biological processes between RA and OA using a bioinformatics approach to elucidate their potential pathogenesis.The gene expression profiles of the GSE55457 datasets, originally produced through use of the high-throughput Affymetrix Human Genome U133A Array, were downloaded from the Gene Expression Omnibus (GEO) database. The GSE55457 dataset contains information from 33 samples, including 10 normal control (NC) samples, 13 RA samples, and 10 OA samples. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were performed to identify functional categories and associated molecular and biochemical pathways, respectively, for the identified DEGs, and a protein-protein interaction (PPI) network of the DEGs was constructed using Cytoscape software.GO and KEGG results suggested that several biological pathways (ie, "immune response," "inflammation," and "osteoclast differentiation") are commonly involved in the development of both RA and OA, whereas several other pathways (eg, "MAPK signaling pathway," and "ECM-receptor interaction") presented significant differences between these disorders.This study provides further insights into the underlying pathogenesis of RA and OA, which may facilitate the diagnosis and treatment of these diseases.

Cell-type-specific gene expression patterns in the knee cartilage in an osteoarthritis rat model

Osteoarthritis (OA) is a chronic degenerative disease that leads to joint failure, pain, and disability. Gene regulation is implicated as a driver of the imbalance between the expression of catabolic and anabolic factors that eventually leads to the degeneration of osteoarthritic cartilage. In our model, knee-joint OA was induced in male Wistar rats by intra-articular sodium monoiodoacetate (MIA) injections. Whole-genome microarrays were used to analyse the alterations in gene expression during the time-course of OA development (at 2, 14, and 28 days post-injection) in rat knee joints. The identified co-expressed groups of genes were analysed for enriched regulatory mechanisms, functional classes, and cell-type-specific expression. This analysis revealed 272 regulated transcripts (ANOVA FDR < 0.1% and fold > 2). Functionally, the five major gene expression patterns (A–E) were connected to PPAR signalling and adipogenesis (in cluster A), WNT signalling (in cluster B), endochondral ossification (in cluster C), matrix metalloproteinases and the ACE/RAGE pathway (in cluster D), and the Toll-like receptor, and IL-1 signalling pathways (in cluster E). Moreover, the dynamic profiles of these transcriptional changes were assigned to cellular compartments of the knee joint. Classifying the molecular processes associated with the development of cartilage degeneration provides novel insight into the OA disease process. Our study identified groups of co-regulated genes that share functional relationships and that may play an important role in the early and intermediate stages of OA.

Osteoarthritis: toward a comprehensive understanding of pathological mechanism

Osteoarthritis (OA) is the most common degenerative joint disease and a major cause of pain and disability in adult individuals. The etiology of OA includes joint injury, obesity, aging, and heredity. However, the detailed molecular mechanisms of OA initiation and progression remain poorly understood and, currently, there are no interventions available to restore degraded cartilage or decelerate disease progression. The diathrodial joint is a complicated organ and its function is to bear weight, perform physical activity and exhibit a joint-specific range of motion during movement. During OA development, the entire joint organ is affected, including articular cartilage, subchondral bone, synovial tissue and meniscus. A full understanding of the pathological mechanism of OA development relies on the discovery of the interplaying mechanisms among different OA symptoms, including articular cartilage degradation, osteophyte formation, subchondral sclerosis and synovial hyperplasia, and the signaling pathway(s) controlling these pathological processes.

Inflammation and epigenetic regulation in osteoarthritis

Osteoarthritis (OA) was once defined as a non-inflammatory arthropathy, but it is now well-recognized that there is a major inflammatory component to this disease. In addition to synovial cells, articular chondrocytes and other cells of diarthrodial joints are also known to express inflammatory mediators. It has been proposed that targeting inflammation pathways could be a promising strategy to treat OA. There have been many reports of cross-talk between inflammation and epigenetic factors in cartilage. Specifically, inflammatory mediators have been shown to regulate levels of enzymes that catalyze changes in DNA methylation and histone structure, as well as alter levels of non-coding RNAs. In addition, expression levels of a number of these epigenetic factors have been shown to be altered in OA, thereby suggesting potential interplay between inflammation and epigenetics in this disease. This review provides information on inflammatory pathways in arthritis and summarizes published research on how epigenetic regulators are affected by inflammation in chondrocytes. Furthermore, we discuss data showing how altered expression of some of these epigenetic factors can induce either catabolic or anti-catabolic effects in response to inflammatory signals. A better understanding of how inflammation affects epigenetic factors in OA may provide us with novel therapeutic strategies to treat this condition.

Autophagy in the pathogenesis of ankylosing spondylitis

The pathogenesis of ankylosing spondylitis (AS) is not well understood, and treatment options have met with limited success. Autophagy is a highly conserved mechanism of controlled digestion of damaged organelles within a cell. It helps in the maintenance of cellular homeostasis. The process of autophagy requires the formation of an isolation membrane. They form double-membraned vesicles called "autophagosomes" that engulf a portion of the cytoplasm. Beyond the role in maintenance of cellular homeostasis, autophagy has been demonstrated as one of the most remarkable tools employed by the host cellular defense against bacteria invasion. Autophagy also affects the immune system and thus is implicated in several rheumatic disease processes. In this article, we explore the potential role of autophagy in the pathogenesis of AS.