Divergent Mononuclear Cell Participation and Cytokine Release Profiles Define Hip and Knee Osteoarthritis

Identification and analysis of microplastics in human lower limb joints

Microplastics (MPs) have been detected in various human tissues, including the liver, placenta, and blood. However, studies about MPs in the human locomotor system are limited. This study evaluated the presence of MPs in the synovium of 45 patients undergoing hip or knee arthroplasty using micro-Fourier transform infrared spectroscopy, scanning electron microscopy, and Raman microscopy and investigated their association with clinical indicators and local cellular responses. A total of 343 MPs of nine common types were identified, with a mean abundance of 5.24 ± 2.07 particles/g and ranging from 1.16 to 10.77 particles/g. Although there was no clear correlation between MP abundance and demographics, MP abundance was higher in hip samples than in knee samples. In addition, a potential association was observed between MP abundance and specific clinical diagnoses. Transcriptomic analysis revealed that a three-fold increase in MP abundance corresponded to enhanced local cellular stress responses, particularly heat shock protein reactions. Our findings demonstrate the presence of MPs in human joints and suggest that further studies are needed to explore the intricate associations between MPs and anatomical location, clinical diagnosis, and local cellular responses.

Identification of Diagnostic Markers in Synovial Tissue of Osteoarthritis by Weighted Gene Coexpression Network

Osteoarthritis (OA) is a serious threat to human health. However, the etiology and pathogenesis of the disease are not fully understood. Most researchers believe that the degeneration and imbalance of articular cartilage, extracellular matrix, and subchondral bone are the fundamental causes of osteoarthritis. However, recent studies have shown that synovial lesions may precede cartilage, which may be an important precipitating factor in the early stage of OA and the whole course of the disease. This study aimed to conduct an analysis based on sequence data from the Gene Expression Omnibus (GEO) database to investigate the presence of effective biomarkers in the synovial tissue of osteoarthritis for the diagnosis and control of OA progression. In this study, the differentially expressed OA-related genes (DE-OARGs) in osteoarthritis synovial tissues were extracted in the GSE55235 and GSE55457 datasets using the Weighted Gene Co-expression Network Analysis (WGCNA) and limma. Least-Absolute Shrinkage and Selection Operator (LASSO) algorithm was used to select the diagnostic genes based on the DE-OARGs by glmnet package. 7 genes were selected as diagnostic genes including SAT1, RLF, MAFF, SIK1, RORA, ZNF529, and EBF2. Subsequently, the diagnostic model was constructed and the results of the Area Under the Curve (AUC) demonstrated that the diagnostic model had high diagnostic performance for OA. Additionally, among the 22 immune cells of the Cell type Identification By Estimating Relative Subsets Of RNA Transcripts (CIBERSORT) and the 24 immune cells of the single sample Gene Set Enrichment Analysis (ssGSEA), 3 immune cells and 5 immune cells were different between the OA and normal samples, respectively. The expression trends of the 7 diagnostic genes were consistent in the GEO datasets and the results of the real-time reverse transcription PCR (qRT-PCR). The results of this study demonstrate that these diagnostic markers have important significance in the diagnosis and treatment of OA, and will provide further evidence for the clinical and functional studies of OA.

Cathepsin S Upregulation Measured in the Peripheral Blood Mononuclear Cells Prior to Surgery Points to Postoperative Pain Development in Patients with Hip Osteoarthritis

Disability caused by hip osteoarthritis has increased due to population aging, obesity, and lifestyle behaviors. Joint failure after conservative therapies results in total hip replacement, which is considered to be one of the most successful interventions. However, some patients experience long-term postoperative pain. Presently, there are no reliable clinical biomarkers for the prognosis of postoperative pain prior to surgery. Molecular biomarkers can be considered as intrinsic indicators of pathological processes and as links between clinical status and disease pathology, while recent innovative and sensitive approaches such as RT-PCR have extended the prognostic value of clinical traits. In light of this, we examined the importance of cathepsin S and proinflammatory cytokine gene expression in peripheral blood in addition to the clinical traits of patients with end-stage hip osteoarthritis (HOA) to predict postoperative pain development prior to surgery. This study included 31 patients with radiographic Kellgren and Lawrence grade III-IV HOA who underwent total hip arthroplasty (THA) and 26 healthy volunteers. Before surgery, a visual analog scale (VAS), DN4, PainDETECT, and the Western Ontario and McMaster Universities osteoarthritis index scores were used for pain and function assessment. Three and six months post-surgery, VAS pain scores of 30 mm and higher were reported. The intracellular protein levels of cathepsin S were measured using ELISA. The expression of the cathepsin S, tumor necrosis factor α, interleukin-1β, and cyclooxygenase-2 genes in peripheral blood mononuclear cells (PBMCs) was assessed using quantitative real-time RT-PCR. Pain persisted in 12 (38.7%) patients after THA. Patients who developed postoperative pain demonstrated significantly higher cathepsin S gene expression in the PBMCs and higher rates of neuropathic pain based on the DN4 testing compared to the other HOA subjects that were examined. No significant differences in proinflammatory cytokine gene expression were noted in either patient cohort prior to THA. The development of postoperative pain in patients with hip osteoarthritis might be associated with disturbances in pain perception, while increased expression of cathepsin S in the peripheral blood prior to surgery may serve as its prognostic biomarker and could be used in clinical settings to improve medical service for patients with end-stage hip OA.

Long noncoding and micro-RNA expression in a model of articular chondrocyte degeneration induced by stromal cell-derived factor-1

Background

Gene regulatory network analysis has found that long noncoding ribonucleic acids (lncRNAs) are strongly associated with the pathogenesis of osteoarthritis.

Objectives

To determine the differential expression of lncRNAs and microRNAs (miRNAs) in normal chondrocytes and those from a model of articular chondrocyte degeneration.

Methods

Chondrocytes were cultured from cartilage obtained from patients diagnosed with osteoarthritis of the knee. Stromal cell-derived factor-1 (SDF-1) was used to induce their degeneration. Total RNA was extracted, analyzed, amplified, labeled, and hybridized on a chip to determine expression. The set of enriched differentially expressed miRNAs was analyzed by gene ontology and the Kyoto Encyclopedia of Genes and Genomes to describe the functional properties of the key biological processes and pathways. We conducted a bioinformatics analysis using Cytoscape to elucidate the interactions between miRNAs and proteins.

Results

We found that the expression of 186 lncRNAs was significantly different in the model of chondrocyte degeneration, in which 88 lncRNAs were upregulated, and 98 were downregulated. Expression of 684 miRNAs was significantly different. Analysis of the protein-protein interaction (PPI) network indicated that the genes for CXCL10, ISG15, MYC, MX1, OASL, IFIT1, RSAD2, MX2, IFI44L, and BST2 are the top 10 core genes, identifying the most important functional modules to elucidate the differential expression of miRNAs.

Conclusions

These data may provide new insights into the molecular mechanisms of chondrocyte degeneration in osteoarthritis, and the identification of lncRNAs and miRNAs may provide potential targets for the differential diagnosis and therapy of osteoarthritis.

Effect of cell receptors in the pathogenesis of osteoarthritis: Current insights

Osteoarthritis (OA) is a chronic arthritic disease characterized by cartilage degradation, synovial inflammation, and subchondral bone lesions. The studies on the pathogenesis of OA are complex and diverse. The roles of receptors signaling in chondrocyte anabolism, inflammatory factors expression of synovial fibroblast, and angiogenesis in subchondral bone are particularly important for exploring the pathological mechanism of OA and clinical diagnosis and treatment. By reviewing the relevant literature, this article elaborates on the abnormal expression of receptors and the signaling transduction pathways from different pathological changes of OA anatomical components, aiming to provide new research ideas and clinical therapeutic value for OA pathogenesis.

The potential role of mesenchymal stem cells in modulating antiageing process

Ageing and age-related diseases share some basic origin that largely converges on inflammation. Precisely, it boils down to a common pathway characterised by the appearance of a fair amount of proinflammatory cytokines known as inflammageing. Among the proposed treatment for antiageing, MSCs gained attention in recent years. Since mesenchymal stem cells (MSCs) can differentiate itself into a myriad of terminal cells, previously it was believed that these cells migrate to the site of injury and perform their therapeutic effect. However, with the more recent discovery of huge amounts of paracrine factors secreted by MSCs, it is now widely accepted that these cells do not engraft upon transplantation but rather unveil their benefits through excretion of bioactive molecules namely those involved in inflammatory and immunomodulatory activities. Conversely, the true function of these paracrine changes has not been thoroughly investigated all these years. Hence, this review will describe in detail on ways MSCs may capitalize its paracrine properties in modulating antiageing process. Through a comprehensive literature search various elements in the antiageing process, we aim to provide a novel treatment perspective of MSCs in antiageing related clinical conditions.

Angelicin Alleviates Post-Trauma Osteoarthritis Progression by Regulating Macrophage Polarization via STAT3 Signaling Pathway

Post-trauma osteoarthritis (PTOA) is the most common articular disease characterized by degeneration and destruction of articular cartilage (Bultink and Lems, Curr. Rheumatol Rep., 2013, 15, 328). Inflammatory response of local joint tissue induced by trauma is the most critical factor accelerating osteoarthritis (OA) progression (Sharma et al., 2019; Osteoarthritis. Cartilage, 28, 658–668). M1/M2 macrophages polarization and repolarization participates in local inflammation, which plays a major role in the progression of OA (Zhang et al., 2018; Ann. Rheum. Dis., 77, 1524–1534). The regulating effect of macrophage polarization has been reported as a potential therapy to alleviate OA progression. Synovitis induced by polarized macrophages could profoundly affect the chondrocyte and cartilage matrix (Zhang et al., 2018; Ann. Rheum. Dis., 77, 1524–1534). Generally, anti-inflammatory medications widely used in clinical practice have serious side effects. Therefore, we focus on exploring a new therapeutic strategy with fewer side effects to alleviate the synovitis. Angelicin (ANG) is traditional medicine used in various folk medicine. Previous studies have revealed that angelicin has an inhibitory effect on inflammation (Wei et al., 2016; Inflammation, 39, 1876–1882), tumor growth (Li et al., 2016; Oncology reports, 36, 3,504–3,512; Wang et al., 2017; Molecular Medicine Reports, 16, 5441–5449), DNA damage (Li et al., 2019; Exp. Ther. Med., 18, 1899–1906), and virus proliferation (Li et al., 2018; Front. Cell. Infect. Microbiol., 8, 178). But its specific effects on influencing the process of OA were rarely reported. In this study, the molecular mechanism of angelicin in vivo and in vitro was clearly investigated. Results showed that angelicin could regulate the M1/M2 ratio and function and alleviate the development of PTOA in the meanwhile. Bone marrow monocytes were isolated and induced by macrophage colony-stimulating factor (M-CSF), lipopolysaccharide (LPS) and interferon (IFN)-γ for M1 polarization and interleukin (IL)-4/IL-13 for M2 polarization. Subsequently, repolarization intervention was performed. The results indicate that angelicin can repolarize M1 toward M2 macrophages by upregulating the expression of CD9. Besides, angelicin can also protect and maintain M2 polarization in the presence of LPS/IFN-γ, and subsequently downregulate the expression of inflammatory mediators such as IL-1β and TNF-α. Mechanistically, angelicin can activate the p-STAT3/STAT3 pathway by conducting CD9/gp130 to repolarize toward M2 macrophages. These results suggest angelicin can alleviate the progression of OA by regulating M1/M2 polarization via the STAT3/p-STAT3 pathway. Therefore, angelicin may have a promising application and potential therapeutic value in OA clinical treatment.

T Helper Cell Infiltration in Osteoarthritis-Related Knee Pain and Disability

Despite the growing body of literature demonstrating a crucial role of T helper cell (Th) responses in the pathogenesis of osteoarthritis (OA), only few clinical studies have assessed interactions between Th cells and OA—related symptoms. Yet, the inclusion of clinical data in the interpretation of cellular analyses of Th cell infiltration is essential to reveal the mechanisms underlying the complex pathophysiology of OA pain and disability. Thus, the aim of the study was to analyze the infiltration pattern of Th cells in systemic (peripheral blood) and joint-derived (synovial membrane and fluid) samples from patients with knee OA in relation to OA-induced pain and disability. Therefore, radiographic OA severity, knee pain and function of 47 OA patients undergoing knee arthroplasty were evaluated prior to surgery. In parallel, samples of peripheral blood (PB), synovial membrane (SM) and synovial fluid (SF) were harvested and analyzed for different Th subsets using flow cytometry. According to surface marker expression Th cells (CD3⁺ CD4⁺ CD8⁻) were assigned to the Th subsets Th1 (CXCR3⁺, CCR5⁺), Th2 (CCR3⁺, CCR4⁺) and Th17 (CD161⁺, CCR6⁺). Interestingly, infiltration of the SM with all Th subtypes (Th1, Th2, Th17) significantly correlated with OA-induced disability. Most importantly, synovial CCR5⁺ and CCR3⁺ Th cell infiltration was associated with OA-related knee pain and disability. Furthermore, higher percentage rates of CXCR3⁺ Th cells in all tissue samples (PB, SM, SF) showed significant associations with OA severity. In contrast, increasing percentage rates of CD161⁺ Th cells in SM samples corresponded to a better functional outcome. In conclusion, the current study provides an extensive profile of the Th cell infiltration pattern in PB, SF and SM from patients with clinically relevant knee OA. Th cell infiltration of the SM might play a crucial role not only in the pathogenesis of OA but also in the development of OA-related knee pain and disability.

Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations

Being the most common musculoskeletal progressive condition, osteoarthritis is an interesting target for research. It is estimated that the prevalence of knee osteoarthritis (OA) among adults 60 years of age or older is approximately 10% in men and 13% in women, making knee OA one of the leading causes of disability in elderly population. Today, we know that osteoarthritis is not a disease characterized by loss of cartilage due to mechanical loading only, but a condition that affects all of the tissues in the joint, causing detectable changes in tissue architecture, its metabolism and function. All of these changes are mediated by a complex and not yet fully researched interplay of proinflammatory and anti-inflammatory cytokines, chemokines, growth factors and adipokines, all of which can be measured in the serum, synovium and histological samples, potentially serving as biomarkers of disease stage and progression. Another key aspect of disease progression is the epigenome that regulates all the genetic expression through DNA methylation, histone modifications, and mRNA interference. A lot of work has been put into developing non-surgical treatment options to slow down the natural course of osteoarthritis to postpone, or maybe even replace extensive surgeries such as total knee arthroplasty. At the moment, biological treatments such as platelet-rich plasma, bone marrow mesenchymal stem cells and autologous microfragmented adipose tissue containing stromal vascular fraction are ordinarily used. Furthermore, the latter two mentioned cell-based treatment options seem to be the only methods so far that increase the quality of cartilage in osteoarthritis patients. Yet, in the future, gene therapy could potentially become an option for orthopedic patients. In the following review, we summarized all of the latest and most important research in basic sciences, pathogenesis, and non-operative treatment.

Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations

Being the most common musculoskeletal progressive condition, osteoarthritis is an interesting target for research. It is estimated that the prevalence of knee osteoarthritis (OA) among adults 60 years of age or older is approximately 10% in men and 13% in women, making knee OA one of the leading causes of disability in elderly population. Today, we know that osteoarthritis is not a disease characterized by loss of cartilage due to mechanical loading only, but a condition that affects all of the tissues in the joint, causing detectable changes in tissue architecture, its metabolism and function. All of these changes are mediated by a complex and not yet fully researched interplay of proinflammatory and anti-inflammatory cytokines, chemokines, growth factors and adipokines, all of which can be measured in the serum, synovium and histological samples, potentially serving as biomarkers of disease stage and progression. Another key aspect of disease progression is the epigenome that regulates all the genetic expression through DNA methylation, histone modifications, and mRNA interference. A lot of work has been put into developing non-surgical treatment options to slow down the natural course of osteoarthritis to postpone, or maybe even replace extensive surgeries such as total knee arthroplasty. At the moment, biological treatments such as platelet-rich plasma, bone marrow mesenchymal stem cells and autologous microfragmented adipose tissue containing stromal vascular fraction are ordinarily used. Furthermore, the latter two mentioned cell-based treatment options seem to be the only methods so far that increase the quality of cartilage in osteoarthritis patients. Yet, in the future, gene therapy could potentially become an option for orthopedic patients. In the following review, we summarized all of the latest and most important research in basic sciences, pathogenesis, and non-operative treatment.

Recent advances in the treatment of osteoarthritis

Osteoarthritis (OA) is one of the most debilitating diseases and is associated with a high personal and socioeconomic burden. So far, there is no therapy available that effectively arrests structural deterioration of cartilage and bone or is able to successfully reverse any of the existing structural defects. Efforts to identify more tailored treatment options led to the development of strategies that enabled the classification of patient subgroups from the pool of heterogeneous phenotypes that display distinct common characteristics. To this end, the classification differentiates the structural endotypes into cartilage and bone subtypes, which are predominantly driven by structure-related degenerative events. In addition, further classifications have highlighted individuals with an increased inflammatory contribution (inflammatory phenotype) and pain-driven phenotypes as well as senescence and metabolic syndrome phenotypes. Most probably, it will not be possible to classify individuals by a single definite subtype, but it might help to identify groups of patients with a predominant pathology that would more likely benefit from a specific drug or cell-based therapy. Current clinical trials addressed mainly regeneration/repair of cartilage and bone defects or targeted pro-inflammatory mediators by intra-articular injections of drugs and antibodies. Pain was treated mostly by antagonizing nerve growth factor (NGF) activity and its receptor tropomyosin-related kinase A (TrkA). Therapies targeting metabolic disorders such as diabetes mellitus and senescence/aging-related pathologies are not specifically addressing OA. However, none of these therapies has been proven to modify disease progression significantly or successfully prevent final joint replacement in the advanced disease stage. Within this review, we discuss the recent advances in phenotype-specific treatment options and evaluate their applicability for use in personalized OA therapy.