Epigenetics and Osteoarthritis

Nutritional Epigenomics: Bioactive Dietary Compounds in the Epigenetic Regulation of Osteoarthritis

Nutritional epigenomics is exceptionally important because it describes the complex interactions among food compounds and epigenome modifications. Phytonutrients or bioactive compounds, which are secondary metabolites of plants, can protect against osteoarthritis by suppressing the expression of inflammatory and catabolic mediators, modulating epigenetic changes in DNA methylation, and the histone or chromatin remodelling of key inflammatory genes and noncoding RNAs. The combination of natural epigenetic modulators is crucial because of their additive and synergistic effects, safety and therapeutic efficacy, and lower adverse effects than conventional pharmacology in the treatment of osteoarthritis. In this review, we have summarized the chondroprotective properties of bioactive compounds used for the management, treatment, or prevention of osteoarthritis in both human and animal studies. However, further research is needed into bioactive compounds used as epigenetic modulators in osteoarthritis, in order to determine their potential value for future clinical applications in osteoarthritic patients as well as their relation with the genomic and nutritional environment, in order to personalize food and nutrition together with disease prevention.

A potential link between inflammatory profiles, clinical pain, pain catastrophizing and long-term outcomes after total knee arthroplasty surgery

BACKGROUND

Chronic postoperative pain after total knee replacement (TKR) is a major clinical problem. It is still unclear if specific inflammatory mediators are associated with long-term postoperative pain complications. The current exploratory study aimed to (1) evaluate a multiplex of inflammatory mediators 5 years after TKR surgery in patients with different degrees of postoperative pain intensities and (2) study any association of the markers with clinical pain intensity, cognitive and functional outcomes.

METHODS

Plasma samples were collected 5 years after TKR surgery from 76 knee patients (43 females; 33 males) and analysed for 44 inflammatory markers. Pain (using visual analogue scale, VAS), the pain catastrophizing scale (PCS) and the Oxford knee score (OKS) were evaluated. Patients were categorized as high or low groups based on VAS, PCS and OKS scores. Associations between inflammatory markers, VAS, PCS and OKS were analysed and the marker expressions were compared between groups.

RESULTS

Pearson's correlations found 12 biomarkers associated with VAS (p < 0.05), 4 biomarkers with PCS and 3 biomarkers with OKS (p < 0.05). Four markers were altered in patients suffering from high compared to low chronic postoperative pain, three markers were altered in high compared to low catastrophizers and three markers were altered in patients with poor functional scores (p < 0.05).

CONCLUSIONS

The present exploratory study suggests that low-grade inflammation might be present in a subset of patients with high pain, high catastrophizing and low function 5 years after TKR. These exploratory results provide insights into some of the long-term postoperative complications after TKR surgery.

SIGNIFICANCE STATEMENT

This exploratory study evaluated a subset of inflammatory markers and the association to clinical pain intensity, knee function and pain catastrophizing in patients 5 years after total knee replacement surgery. Our results provide insights into the understanding of the underlying mechanisms that may drive the long experience of pain after TKR surgery.

Unraveling the molecular landscape of osteoarthritis: A comprehensive review focused on the role of non-coding RNAs

Osteoarthritis (OA) poses a significant global health challenge, with its prevalence anticipated to increase in the coming years. This review delves into the emerging molecular biomarkers in OA pathology, focusing on the roles of various molecules such as metabolites, noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Advances in omics technologies have transformed biomarker identification, enabling comprehensive analyses of the complex pathways involved in OA pathogenesis. Notably, ncRNAs, especially miRNAs and lncRNAs, exhibit dysregulated expression patterns in OA, presenting promising opportunities for diagnosis and therapy. Additionally, the intricate interplay between epigenetic modifications and OA progression highlights the regulatory role of epigenetics in gene expression dynamics. Genome-wide association studies have pinpointed key genes undergoing epigenetic changes, providing insights into the inflammatory processes and chondrocyte hypertrophy typical of OA. Understanding the molecular landscape of OA, including biomarkers and epigenetic mechanisms, holds significant potential for developing innovative diagnostic tools and therapeutic strategies for OA management.

Inflammatory biomarkers in patients with painful knee osteoarthritis: exploring the potential link to chronic postoperative pain after total knee arthroplasty-a secondary analysis

ABSTRACT

Total knee arthroplasty (TKA) is the end-stage treatment of knee osteoarthritis (OA), and approximately 20% of patients experience chronic postoperative pain. Studies indicate that inflammatory biomarkers might be associated with pain in OA and potentially linked to the development of chronic postoperative pain after TKA. This study aimed to (1) evaluate preoperative serum levels of inflammatory biomarkers in patients with OA and healthy control subjects, (2) investigate preoperative differences of inflammatory biomarker profiles in subgroups of patients, and (3) compare subgroups of patients with and without postoperative pain 12 months after surgery. Serum samples from patients with OA scheduled for TKA (n = 127) and healthy participants (n = 39) were analyzed. Patients completed the Knee-injury-and-Osteoarthritis-Outcome-Score (KOOS) questionnaire and rated their clinical pain intensity using a visual analog scale (VAS) before and 12 months after TKA. Hierarchical cluster analysis and Orthogonal Partial Least Squares Discriminant Analysis were used to compare groups (patients vs control subjects) and to identify subgroups of patients in relation to postoperative outcomes. Difference in preoperative and postoperative VAS and KOOS scores were compared across subgroups. Twelve inflammatory markers were differentially expressed in patients when compared with control subjects. Cluster analysis identified 2 subgroups of patients with 23 proteins being significantly different ( P < 0.01). The 12-months postoperative VAS and KOOS scores were significantly different between subgroups of patients ( P < 0.05). This study identified differences in specific inflammatory biomarker profiles when comparing patients with OA and control subjects. Cluster analysis identified 2 subgroups of patients with OA, with one subgroup demonstrating comparatively worse 12-month postoperative pain intensity and function scores.

DNA demethylation of promoter region orchestrates SPI-1-induced ADAMTS-5 expression in articular cartilage of osteoarthritis mice

Osteoarthritis (OA) is one of the most prevalent joint diseases in aged people and characterized by articular cartilage degeneration, synovial inflammation, and abnormal bone remodeling. Recent advances in OA research have clearly shown that OA development is associated with aberrant DNA methylation status of many OA-related genes. As one of most important cartilage degrading proteases in OA, a disintegrin and metalloproteinase with thrombospondin motifs subtype 5 (ADAMTS-5) is activated to mediate cartilage degradation in human OA and experimental murine OA models. The pathological factors and signaling pathways mediating ADAMTS-5 activation during OA development are not well defined and have been a focus of intense research. ADAMTS-5 promoter is featured by CpG islands. So far there have been no reports concerning the DNA methylation status in ADAMTS-5 promoter during OA development. In this study, we sought to investigate DNA methylation status in ADAMTS-5 promoter, the role of DNA methylation in ADAMTS-5 activation in OA, and the underlying mechanisms. The potential for anti-OA intervention therapy which is based on modulating DNA methylation is also explored. Our results showed that DNA methyltransferases 1 (Dnmt1) downregulation-associated ADAMTS-5 promoter demethylation played an important role in ADAMTS-5 activation in OA, which facilitated SPI-1 binding on ADAMTS-5 promoter to activate ADAMTS-5 expression. More importantly, OA pathological phenotype of mice was alleviated in response to Dnmt1-induced DNA methylation of ADAMTS-5 promoter. Our study will benefit not only for deeper insights into the functional role and regulation mechanisms of ADAMTS-5 in OA, but also for the discovery of disease-modifying OA drugs on the basis of ADAMTS-5 via modulating DNA methylation status.

Epigenetic PPARγ preservation attenuates temporomandibular joint osteoarthritis

OBJECTIVE

Previous studies have demonstrated that PPARγ deficiency is associated with osteoarthritis in the knee joint. However, whether epigenetic PPARγ dysregulation has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. This study aims to determine the role and mechanism of epigenetic PPARγ dysregulation in TMJOA.

METHODS

Partial TMJ discectomy was performed to induce TMJOA in rat. Primary condylar chondrocytes were isolated, and TNF-α-induced inflammatory condition was created in vitro. The expressions of PPARγ and DNA methyltransferase were investigated in vivo and in vitro. The association of PPARγ and DNA methylation was further studied by treating chondrocytes with DNA demethylation agent 5-Aza-2'-deoxycytidine (5Aza) and transfecting with siRNA of DNA methyltransferase (DNMT)1 and DNMT3a, and the methylation level of PPARγ promoter was evaluated by Bisulfite-sequencing PCR. The chondroprotective effects of 5Aza were explored in vitro and in vivo.

RESULTS

PPARγ suppression and upregulated DNMT1/DNMT3a expression exist in TMJOA cartilage in vivo and primary condylar chondrocytes under TNF-α-induced inflammatory conditions in vitro. DNMT1 and DNMT3a elevation contributes to PPARγ-promoter hypermethylation in TMJ chondrocytes under TNF-α-induced inflammation conditions. DNA demethylation intervention by 5Aza protects chondrocytes from inflammation response in vitro. Mechanistically, 5Aza reversed the hypermethylation of the PPARγ promoter and subsequently resulted in PPARγ restoration and decreased expression of cartilage-catabolic factors in chondrocytes. Rat TMJOA model revealed that 5Aza, by reversing PPARγ suppression, effectively attenuated cartilage degeneration and stabilized cartilage homeostasis by balancing anabolic factor and catabolic factor expression.

CONCLUSION

Epigenetic PPARγ suppression may play a causal role in TMJOA pathogenesis, which can be alleviated by DNA demethylation with 5Aza treatment. This study provides new insights into the pathogenic mechanism and therapeutic strategy of TMJOA.

MicroRNA-15a/β1,4-GalT-I axis contributes to cartilage degeneration via NF-κB signaling in osteoarthritis

OBJECTIVE

Osteoarthritis is a condition characterized by articular cartilage degradation. The increased expression of β1,4-Galactosyltransferase-I (β1,4-GalT-I) in the articular cartilage of osteoarthritis patients was related to an inflammatory response. The aim of this study was to elucidate the role of β1,4-GalT-I in osteoarthritis. This study aimed to determine the function of 1,4-GalT-I in osteoarthritis.

METHODS

The osteoarthritis mouse model with the destabilization of the medial meniscus was established by microsurgical technique. Pathological changes in articular cartilage were observed by hematoxylin and eosin staining and safranin O-fast green staining. Quantitative real-time polymerase chain reaction, western blot, and enzyme-linked immunosorbent assays were used to observe mRNA and protein expression, respectively. RNA interactions were verified by a luciferase reporter assay. SA-β-Gal staining was used to assess chondrocyte senescence. Immunofluorescence staining was conducted to observe the localization of Nuclear Factor-kappaB (NF-κB).

RESULTS

β1,4-GalT-I and microRNA-15a (miR-15a) show high and low expression in the articular cartilage of osteoarthritis, respectively. MiR-15a inhibits the mRNA translation of β1,4-GalT-I. β1,4-GalT-I promotes extracellular matrix degradation, senescence, and NF-κB activation in IL-1β-stimulated chondrocytes, which can be reversed by overexpression of miR-15a. Intra-articular injection of microRNA-15a ameliorates cartilage degeneration by inhibiting β1,4-GalT-I and phosphorylation of NF-κB in vivo.

CONCLUSION

The authors clarified that the miR-15a/β1,4-GalT-I axis inhibits the phosphorylation of NF-κB thereby inhibiting extracellular matrix degradation and senescence in chondrocytes to alleviate cartilage degeneration in osteoarthritis. MiR-15a and β1,4-GalT-I may serve as potentially effective targets for the future treatment of osteoarthritis.

How are Aging and Osteoarthritis Related?

Osteoarthritis is the most prevalent degenerative joint disease and one of the leading causes of physical impairment in the world's aging population. The human lifespan has significantly increased as a result of scientific and technological advancements. According to estimates, the world's elderly population will increase by 20% by 2050. Aging and age-related changes are discussed in this review in relation to the development of OA. We specifically discussed the cellular and molecular changes that occur in the chondrocytes during aging and how these changes may make synovial joints more susceptible to OA development. These changes include chondrocyte senescence, mitochondrial dysfunction, epigenetic modifications, and decreased growth factor response. The age-associated changes occur not only in the chondrocytes but also in the matrix, subchondral bone, and synovium. This review aims to provide an overview of the interplay between chondrocytes and matrix and how age-related changes affect the normal function of cartilage and contribute to OA development. Understanding the alterations that affect the function of chondrocytes will emerge new possibilities for prospective therapeutic options for the treatment of OA.

Current understanding of osteoarthritis pathogenesis and relevant new approaches

Osteoarthritis (OA) is the most common degenerative joint disease that causes painful swelling and permanent damage to the joints in the body. The molecular mechanisms of OA are currently unknown. OA is a heterogeneous disease that affects the entire joint, and multiple tissues are altered during OA development. To better understand the pathological mechanisms of OA, new approaches, methods, and techniques need to be used to understand OA pathogenesis. In this review, we first focus on the epigenetic regulation of OA, with a particular focus on DNA methylation, histone modification, and microRNA regulation, followed by a summary of several key mediators in OA-associated pain. We then introduce several innovative techniques that have been and will continue to be used in the fields of OA and OA-associated pain, such as CRISPR, scRNA sequencing, and lineage tracing. Next, we discuss the timely updates concerning cell death regulation in OA pathology, including pyroptosis, ferroptosis, and autophagy, as well as their individual roles in OA and potential molecular targets in treating OA. Finally, our review highlights new directions on the role of the synovial lymphatic system in OA. An improved understanding of OA pathogenesis will aid in the development of more specific and effective therapeutic interventions for OA.

Potential Methods of Targeting Cellular Aging Hallmarks to Reverse Osteoarthritic Phenotype of Chondrocytes

Osteoarthritis (OA) is a chronic degenerative joint disease that causes pain, physical disability, and life quality impairment. The pathophysiology of OA remains largely unclear, and currently no FDA-approved disease-modifying OA drugs (DMOADs) are available. As has been acknowledged, aging is the primary independent risk factor for OA, but the mechanisms underlying such a connection are not fully understood. In this review, we first revisit the changes in OA chondrocytes from the perspective of cellular hallmarks of aging. It is concluded that OA chondrocytes share many alterations similar to cellular aging. Next, based on the findings from studies on other cell types and diseases, we propose methods that can potentially reverse osteoarthritic phenotype of chondrocytes back to a healthier state. Lastly, current challenges and future perspectives are summarized.

Chondrocyte Aging: The Molecular Determinants and Therapeutic Opportunities

Osteoarthritis (OA) is a joint degenerative disease that is an exceedingly common problem associated with aging. Aging is the principal risk factor for OA, but damage-related physiopathology of articular chondrocytes probably drives the mechanisms of joint degeneration by a progressive decline in the homeostatic and regenerative capacity of cells. Cellular aging is the manifestation of a complex interplay of cellular and molecular pathways underpinned by transcriptional, translational, and epigenetic mechanisms and niche factors, and unraveling this complexity will improve our understanding of underlying molecular changes that affect the ability of the articular cartilage to maintain or regenerate itself. This insight is imperative for developing new cell and drug therapies for OA disease that will target the specific causes of age-related functional decline. This review explores the key age-related changes within articular chondrocytes and discusses the molecular mechanisms that are commonly perturbed as cartilage ages and degenerates. Current efforts and emerging potential therapies in treating OA that are being employed to halt or decelerate the aging processes are also discussed.

MicroRNA-197 regulates chondrocyte proliferation, migration, and inflammation in pathogenesis of osteoarthritis by targeting EIF4G2

Recent studies have demonstrated that microRNAs (miRNAs) are involved in many pathological conditions including osteoarthritis (OA). In the present study, we aimed to investigate the role of miR-197 in OA and the potential molecular mechanism. The expression levels of miR-197 were detected by quantitative real-time PCR analysis. Cell proliferation and migration abilities were performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide and transwell assays. The concentrations of inflammatory cytokines, including IL-1β, IL-6, and TNF-α, were detect using ELISA assay. Furthermore, luciferase reporter and rescue assays were applied to identify the functional target gene of miR-197 in OA. The results showed that miR-197 expression was significantly down-regulated in the OA cartilage tissues compared with normal cartilage tissues, accompanied by up-regulation of EIF4G2 expression. An inverse correlation was found between EIF4G2 and miR-197 expressions in OA cartilage tissues. Treatment with miR-197 mimics promoted the growth and migration abilities of chondrocytes, while miR-197 inhibitors induced the opposite effects. Furthermore, restoration of miR-197 significantly decreased IL-1β, IL-6, and TNF-α expression, whereas knockdown of miR-197 led to a induction in these inflammatory mediators. Moreover, EIF4G2 was predicted and confirmed as a directly target of miR-197. Overexpressed miR-197 could down-regulate EIF4G2 expression in chondrocytes, while miR-197 knockdown could elevate EIF4G2 expression. Additionally, EIF4G2 overexpression reversed the effects of miR-197 mimics on chondrocytes proliferation, migration, and inflammation. Taken together, our study demonstrated that miR-197 promotes chondrocyte proliferation, increases migration, and inhibits inflammation in the pathogenesis of OA by targeting EIF4G2, indicating the potential therapeutic targets of the miR-197/EIF4G2 axis for OA treatment.

Understanding osteoarthritis pathogenesis: a multiomics system-based approach

PURPOSE OF REVIEW

Osteoarthritis is a heterogeneous, multifactorial condition regulated by complex biological interactions at multiple levels. Comprehensive understanding of these regulatory interactions is required to develop feasible advances to improve patient outcomes. Improvements in technology have made extensive genomic, transcriptomic, epigenomic, proteomic, and metabolomic profiling possible. This review summarizes findings over the past 20 months related to omics technologies in osteoarthritis and examines how using a multiomics approach is necessary for advancing our understanding of osteoarthritis as a disease to improve precision osteoarthritis treatments.

RECENT FINDINGS

Using the search terms 'genomics' or 'transcriptomics' or 'epigenomics' or 'proteomics' or 'metabolomics' and 'osteoarthritis' from January 1, 2018 to August 31, 2019, we identified advances in omics approaches applied to osteoarthritis. Trends include untargeted whole genome, transcriptome, proteome, and metabolome analyses leading to identification of novel molecular signatures, cell subpopulations and multiomics validation approaches.

SUMMARY

To address the complexity of osteoarthritis, integration of multitissue analyses by multiomics approaches with the inclusion of longitudinal clinical data is necessary for a comprehensive understanding of the disease process, and for appropriate development of efficacious diagnostics, prognostics, and biotherapeutics.

LncRNA, Important Player in Bone Development and Disease

BACKGROUND

Bone is an important tissue and its normal function requires tight coordination of transcriptional networks and signaling pathways, and many of these networks/ pathways are dysregulated in pathological conditions affecting cartilage and bones. Long non-coding RNA (lncRNA) refers to a class of RNAs with a length of more than 200 nucleotides, lack of protein-coding potential, and exhibiting a wide range of biological functions. Although studies on lcnRNAs are still in their infancy, they have emerged as critical players in bone biology and bone diseases. The functions and exact mechanism of bone-related lncRNAs have not been fully classified yet.

OBJECTIVE

The objective of this article is to summarize the current literature on lncRNAs on the basis of their role in bone biology and diseases, focusing on their emerging molecular mechanism, pathological implications and therapeutic potential.

DISCUSSION

A number of lncRNAs have been identified and shown to play important roles in multiple bone cells and bone disease. The function and mechanism of bone-related lncRNA remain to be elucidated.

CONCLUSION

At present, majority of knowledge is limited to cellular levels and less is known on how lncRNAs could potentially control the development and homeostasis of bone. In the present review, we highlight some lncRNAs in the field of bone biology and bone disease. We also delineate some lncRNAs that might have deep impacts on understanding bone diseases and providing new therapeutic strategies to treat these diseases.

Epigenetics of osteoarthritis: Histones and TGF-β1

Osteoarthritis (OA) is the most common musculoskeletal and joint disorder. However, no disease-modifying therapy for OA is currently available, and the etiology of OA is poorly understood. Epigenetics has emerged as a new and important area of research on OA. Differing from genetics, Epigenetic factors are known to be tissue-specific and highly dynamic, being dependent on environmental stimuli and developmental stages. Therefore, human studies into OA epigenetics are sensitive to confounding and reverse causation. Here, we will review the epigenetic mechanism in OA onset and progression by focusing on the opposing action of two families of enzymes: histone methyltransferases and histone demethylases, such as DOT1L, KDM4B, KDM6A, KDM6B, EZH2, and LSD1. Moreover, the TGF-β1 signaling pathway has proven to be one of the key factors in cartilage and bone formation, and in recent research, was found to initiate and develop OA disease by TGF-β1 overexpression. Besides the introduction of enzymes and TGF-β1 signaling, some special epigenetic regulation mechanisms associated with key transcription factors (e.g. RUNX2, NFAT1, and SOX9) in OA disease are also reviewed here in detail to clarify the OA epigenetic mechanism. The overall understanding of these epigenetic mechanisms underlying the issues will accelerate the development of novel therapeutic strategies for OA.

Genetics in Cartilage Lesions: Basic Science and Therapy Approaches

Cartilage lesions have a multifactorial nature, and genetic factors are their strongest determinants. As biochemical and genetic studies have dramatically progressed over the past decade, the molecular basis of cartilage pathologies has become clearer. Several homeostasis abnormalities within cartilaginous tissue have been found, including various structural changes, differential gene expression patterns, as well as altered epigenetic regulation. However, the efficient treatment of cartilage pathologies represents a substantial challenge. Understanding the complex genetic background pertaining to cartilage pathologies is useful primarily in the context of seeking new pathways leading to disease progression as well as in developing new targeted therapies. A technology utilizing gene transfer to deliver therapeutic genes to the site of injury is quickly becoming an emerging approach in cartilage renewal. The goal of this work is to provide an overview of the genetic basis of chondral lesions and the different approaches of the most recent systems exploiting therapeutic gene transfer in cartilage repair. The integration of tissue engineering with viral gene vectors is a novel and active area of research. However, despite promising preclinical data, this therapeutic concept needs to be supported by the growing body of clinical trials.

Mesenchymal Stem Cell Therapy in Chondral Defects of Knee: Current Concept Review

PURPOSE

Full-thickness cartilage defects if left alone would increase the risk of osteoarthritis (OA) with severe associated pain and functional disability. Articular cartilage defect may result from direct trauma or chronic degeneration. The capability of the mesenchymal stem cells (MSCs) to repair and regenerate cartilage has been widely investigated. This review describes current trends in MSC biology, the sourcing, expansion, application and role of MSCs in chondral defects of human knees.

METHODS

The studies referencing MSCs and knee osteoarthritis were searched (from1998 to 2020) using PubMed, EMBASE, Cochrane Library, Web of Science and the ClinicalTrials.gov with keywords (MSCs, chondral defects or cartilage degeneration of knee, cartilage regeneration, chondrogenesis, tissue engineering, efficacy and safety). The inclusion criteria were based on use of MSCs for treatment of chondral defects and osteoarthritis of the knee, English language and human studies.

RESULTS

The history of MSC research from the initial discovery of their multipotency to the more recent recognition of their role in cartilage defects of knee is elucidated. Several studies have demonstrated promising results in the clinical application for repair of chondral defects as an adjuvant or independent procedure. Intra-articular MSCs provide improvements in pain and function in knee osteoarthritis at short-term follow-up in many studies. The tendency of MSCs to differentiate into fibrocartilage affecting the outcome is a common issue faced by researchers.

CONCLUSION

Some efficacy has been shown of MSCs for cartilage repair in osteoarthritis; however, the evidence of efficacy of intra-articular MSCs on both clinical outcomes and cartilage repair remains limited. Despite the high quality of evidence to support, MSC therapy has emerged but further refinement of methodology will be necessary to support its routine clinical use.

CircRNA-UBE2G1 regulates LPS-induced osteoarthritis through miR-373/HIF-1a axis

Osteoarthritis (OA) is a very common chronic and degenerative joint disease characterized by persistent destruction of articular cartilage. Recently, increasing evidence showed that circular RNAs (circRNAs) play critical roles in OA progression. However, the functions of circRNAs in OA and their underlying mechanisms of action remain unclear. In the present study, the expression levels of circRNA-UBE2G1 and HIF-1a were significantly increased in OA tissues, whereas miR‑373 expression was downregulated. Function assays showed that circRNA-UBE2G1 inhibition reduced the effects of LPS on C28/I2 cells viability and apoptosis. In terms of mechanism, we revealed that circRNA-UBE2G1 binds to miR‑373 as competing endogenous RNAs (ceRNAs). HIF-1a might act as a target of miR‑373. Moreover, miR‑373 suppression or HIF-1a overexpression restored the effects of circRNA-UBE2G1 downregulation on LPS-induced chondrocytes injury. Collectively, our data suggest that circRNA-UBE2G1 facilitates the progression in the LPS-induced OA cell model via regulating the miR‑373/HIF-1a axis.

ABBREVIATIONS

OA: Osteoarthritis; Circular RNAs; miRNAs: MicroRNAs; Mut: Mutant; WT: Wild type; UTR: Untranslated region.

Identification of Candidate Genetic Markers and a Novel 4-genes Diagnostic Model in Osteoarthritis through Integrating Multiple Microarray Data

BACKGROUND

Osteoarthritis (OA) is a joint disease that leads to a high disability rate and a low quality of life. With the development of modern molecular biology techniques, some key genes and diagnostic markers have been reported. However, the etiology and pathogenesis of OA are still unknown.

OBJECTIVE

To develop a gene signature in OA.

METHOD

In this study, five microarray data sets were integrated to conduct a comprehensive network and pathway analysis of the biological functions of OA related genes, which can provide valuable information and further explore the etiology and pathogenesis of OA.

RESULTS AND DISCUSSION

Differential expression analysis identified 180 genes with significantly expressed expression in OA. Functional enrichment analysis showed that the up-regulated genes were associated with rheumatoid arthritis (p < 0.01). Down-regulated genes regulate the biological processes of negative regulation of kinase activity and some signaling pathways such as MAPK signaling pathway (p < 0.001) and IL-17 signaling pathway (p < 0.001). In addition, the OA specific protein-protein interaction (PPI) network was constructed based on the differentially expressed genes. The analysis of network topological attributes showed that differentially upregulated VEGFA, MYC, ATF3 and JUN genes were hub genes of the network, which may influence the occurrence and development of OA through regulating cell cycle or apoptosis, and were potential biomarkers of OA. Finally, the support vector machine (SVM) method was used to establish the diagnosis model of OA, which not only had excellent predictive power in internal and external data sets (AUC > 0.9), but also had high predictive performance in different chip platforms (AUC > 0.9) and also had effective ability in blood samples (AUC > 0.8).

CONCLUSION

The 4-genes diagnostic model may be of great help to the early diagnosis and prediction of OA.

MicroRNA-375 exacerbates knee osteoarthritis through repressing chondrocyte autophagy by targeting ATG2B

Objective: This study aimed to explore the underlying mechanism of miR-375 in exacerbating osteoarthritis (OA).

Results: MiR-375 expression were upregulated in OA cartilage tissues, whereas ATG2B expression was decreased. MiR-375 targeted ATG2B 3’ UTR and inhibited its expression in the chondrocytes, and then suppressed autophagy and promoted endoplasmic reticulum stress (ERs). The apoptosis rate of chondrocytes was increased after being transfected with miR-375 mimics. In vivo results further verified that inhibition of miR-375 could relieve OA-related symptoms.

Conclusion: miR-375 can inhibit the expression of ATG2B in chondrocytes, suppress autophagy and promote the ERs. It suggests that miR-375 could be considered to be a key therapy target for OA.

Methods: Differential expression analyses for mRNA and miRNA microarray datasets from ArrayExpress were performed. MiR-375 and ATG2B expressions in cartilage tissues were detected by qRT-PCR. Dual luciferase assay was applied to verify the targeting relationship between ATG2B and miR-375. In vitro, the role of miR-375 on chondrocyte autophagy and ERs was investigated by western blot and immunofluorescence. The apoptotic rate was quantified by flow cytometry. In vivo, OA mice model was established, HE and Safranin O and Fast Green staining, as well as the OARSI and modified Mankin scores, were applied to measure the OA cartilage damage severity.

MicroRNA-1202 plays a vital role in osteoarthritis via KCNQ1OT1 has-miR-1202-ETS1 regulatory pathway

BACKGROUND

This study aimed to explore the molecular mechanism of osteoarthritis (OA) and provide information about new genes as potential targets for OA treatment.

METHODS

Gene expression profile of GSE105027, including 12 OA serum samples (OA group) and 12 healthy serum samples (ctrl group), was downloaded. The differentially expressed miRNAs (DEMs) as well as miRNA-mRNAs interactions were investigated, followed by function and pathway investigation. Then the protein-protein interaction (PPI) network was performed. Furthermore, the long non-coding RNA (lncRNA)-miRNA-mRNA interactions (competing endogenous RNAs, ceRNAs) were investigated.

RESULTS

A total of 17 downregulated miRNAs were revealed between OA and ctrl groups. These DEMs such as has-miR-1202 were mainly enriched in GO functions like histone acetyltransferase binding and KEGG pathways like cellular senescence. The integrated PPI network analysis showed that has-miR-1202, has-miR-33b-3p, has-miR-940, has-miR-4284, and has-miR-4281 were 5 downregulated miRNAs in this network. Furthermore, the lncRNA-miRNA-mRNA interactions such as KCNQ1OT1-has-miR-1202-ETS1 were revealed in the present ceRNA network.

CONCLUSION

Key DEMs such as miR-33b-3p, miR-940, and miR-1202 may be involved in OA. miR-1202 may regulate OA development via histone acetyltransferase pathway binding function and cellular senescence pathway. Furthermore, KCNQ1OT1-has-miR-1202-ETS1 might be vital for the process of OA.

Identification and functional analysis of long non-coding RNAs in the synovial membrane of osteoarthritis patients

Osteoarthritis (OA), the most common chronic joint disease in the elderly, has become a significant economic burden for families and societies worldwide. Although treatments are continually improving, current drugs only target joint pain, with no effective therapies modifying OA progression. Long noncoding RNAs (lncRNAs), which have received increasing attention in recent years, are abnormally expressed in OA cartilage. In the present study, weighted coexpression network analysis (WGCNA) was applied to identify modules related to certain OA clinical traits. In total, 4404 coding genes and 161 lncRNAs were differentially expressed based on two OA expression profile data sets and normal control samples. Subsequently, 11 independent modules were acquired, and the green module, with a total of 49 hub genes, was identified as the most relevant to OA. These hub genes were validated using the GSE12021 data set. There was only one lncRNA among the hub genes, namely, NONHSAG034351. Thus, we further explored the function of NONHSAG034351‐related genes in the network. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that NONHSAG034351‐associated genes are involved in the response to lipopolysaccharide, angiogenesis, tumour necrosis factor (TNF) signalling, and mitogen‐activated protein kinase (MAPK) signalling pathways. In conclusion, we identified modules through WGCNA related to OA clinical traits. NONHSAG034351, the only hub‐lncRNA, was downregulated in OA synovial tissue and might play a significant role in the pathological progression of this disease. Our findings have important clinical implications and could provide novel biomarkers that indicate the molecular mechanisms of OA and act as potential therapeutic targets.

Significance of this study

Long noncoding RNAs (lncRNAs) have been reported to be abnormally expressed in osteoarthritis (OA), which is the most common chronic joint disease among the elderly. In the present study, we report the expression profiles of lncRNAs in OA and the identification of modules through WGCNA related to OA clinical traits. NONHSAG034351, the only hub‐lncRNA identified to be downregulated in the synovial tissue of OA patients, might play a significant role in the pathological progression of OA. Furthermore, our findings provide novel biomarkers associated with the molecular mechanisms underlying OA pathogenesis, thus implying potential therapeutic targets with important clinical implications.

Targeting downstream subcellular YAP activity as a function of matrix stiffness with Verteporfin-encapsulated chitosan microsphere attenuates osteoarthritis

Changes in the stiffness of chondrocyte extracellular matrix (ECM) are involved in the pathological progression of osteoarthritis (OA). However, the downstream responses of cartilage ECM stiffness are still unclear. YAP (Yes-associated protein) has been extensively studied as a mechanotransducer, we thus hypothesized that by targeting the downstream molecule activity of ECM stiffness could maintain chondrocyte phenotype and prevent cartilage degeneration in OA. Here, we showed that human cartilage matrix stiffened during pathological progression of OA, and the chondrocyte YAP activity was associated with ECM stiffness. We then mimicked the physiological and pathological stiffness of human cartilage by using PDMS-based substrates, and found that YAP was activated in chondrocytes seeded on stiff substrate, gradually losing their phenotype. In addition, it was observed that YAP was also significantly activated in mice OA development, and conditional knockout (cKO) of YAP in mice preserved collagen II expression and protected cartilage from degeneration in the OA model. Furthermore, intra-articular injection of YAP-selective inhibitor, Verteporfin, significantly maintained cartilage homeostasis in mice OA model. This study indicates that the application of mechanotransducer-targeted drugs could be a potential therapeutic approach for cartilage repair in OA.

Synovial chondromatosis of the foot: Two case reports and literature review

BACKGROUND

Primary synovial chondromatosis (PSC) is a rare arthropathy of the synovial joints characterized by the formation of cartilaginous nodules, which may detach and become loose bodies within the joint and may undergo secondary proliferation. PSC of the foot and ankle is exceedingly rare, with only a few cases reported in the literature. The diagnosis may be difficult and delayed until operative treatment, when it is confirmed by histological assessment. PSC may degenerate into chondrosarcoma. Operative treatment is the gold standard aiming to minimize pain, improve function, prevent or limit progression of arthritis. Surgical treatment consists in debridement by arthrotomic or arthroscopic management, but there is no consensus in the literature about timing of surgery and surgical technique. Thus, the aim of this study is to report the outcomes of the surgical treatment of two cases, together with a literature review.

CASE SUMMARY

We report two cases of patients affected by PSC of the foot in stage III, according to the Milgram classification: the former PSC localized in the ankle that underwent open surgery consisted of loose bodies removal; the latter in the subtalar joint, and the choice of treatment was the arthrotomy and debridement from loose bodies, in addition to the subtalar arthrodesis. Both patients returned to complete daily and working life after surgery.

CONCLUSION

Synovial chondromatosis is a rare benign pathology, even rarer in the ankle joint and especially in the foot. Surgery should be minimal in patients with ankle PSC, choosing the correct timing, waiting if possible until stage III. More aggressive and early surgery should be performed in patients with PSC of the foot, particularly the subtalar joint, due to the high risk of arthritic evolution.

PPARγ preservation via promoter demethylation alleviates osteoarthritis in mice

OBJECTIVES

Osteoarthritis (OA) is the most common degenerative joint disease in aged population and its development is significantly influenced by aberrant epigenetic modifications of numerous OA susceptible genes; however, the precise mechanisms that DNA methylation alterations affect OA pathogenesis remain undefined. This study investigates the critical role of epigenetic PPARγ (peroxisome proliferator-activated receptor-gamma) suppression in OA development.

METHODS

Articular cartilage expressions of PPARγ and bioactive DNA methyltransferases (DNMTs) from OA patients and mice incurred by DMM (destabilisation of medial meniscus) were examined. DNA methylation status of both human and mouse PPARγ promoters were assessed by methylated specific PCR and/or bisulfite-sequencing PCR. OA protections by a pharmacological DNA demethylating agent 5Aza (5-Aza-2'-deoxycytidine) were compared between wild type and PPARγ knockout mice.

RESULTS

Articular cartilages from both OA patients and DMM mice display substantial PPARγ suppressions likely due to aberrant elevations of DNMT1 and DNMT3a and consequential PPARγ promoter hypermethylation. 5Aza known to inhibit both DNMT1 and DNMT3a reversed the PPARγ promoter hypermethylation, recovered the PPARγ loss and effectively attenuated the cartilage damage in OA mice. 5Aza also inhibited the OA-associated excessive inflammatory cytokines and deficit anti-oxidant enzymes, which were blocked by a specific PPARγ inhibitor in cultured chondrocytes. Further, 5Aza-confered protections against the cartilage damage and the associated abnormalities of OA-susceptible factors were significantly abrogated in PPARγ knockout mice.

CONCLUSION

Epigenetic PPARγ suppression plays a key role in OA development and PPARγ preservation via promoter demethylation possesses promising therapeutic potentials in clinical treatment of OA and the related joint diseases.

Blood leukocyte LINE-1 hypomethylation and oxidative stress in knee osteoarthritis

Aim

Joints inflammation is one of the most pathologic processes leading to the development of osteoarthritis (OA), possibly leading to genomic instability. LINE-1 is transposable elements, and alterations in LINE-1 methylation induced by 8-hydroxy-2′-deoxyguanosine (8-OHdG) can cause genomic instability contributing to OA development. Herein, the present study examined associations between LINE-1 methylation, 8-OHdG, and knee OA severity.

Methods

LINE-1 methylation levels were measured in 104 knee OA patients and 96 healthy controls by quantitative combined bisulfite restriction analysis. 8–OHdG was investigated by ELISA. The knee OA severity was appraised by questionnaires (VAS, WOMAC, KOOS, and lequesne index) and radiological severity based on the grading of Kellgren and Lawrence (KL) standard criteria.

Key findings

Blood leukocyte LINE-1 methylation levels were significantly lower in knee OA patients than in healthy controls. Interestingly, individuals with LINE-1 hypomethylation were significantly associated with an elevated risk of knee OA. Linear regression analysis revealed that LINE-1 methylation was independently associated with KL grading of knee OA. Furthermore, plasma 8–OHdG levels in OA cases were not significantly different from those in healthy volunteers, whereas synovial fluid 8–OHdG values were considerably higher than in paired plasma specimens of the OA subjects.

Significance

This study demonstrated that LINE-1 hypomethylation in blood leukocytes was associated with increased risk and radiographic severity of knee OA, and increased synovial fluid 8–OHdG levels were observed in knee OA patients. Collectively, LINE-1 hypomethylation and elevated 8–OHdG could emerge as biomarkers indicating the severity of knee OA and may take a possible part in the pathological process of knee OA.

Exosomal miR-95-5p regulates chondrogenesis and cartilage degradation via histone deacetylase 2/8

MicroRNAs play critical roles in the pathogenesis of osteoarthritis, the most common chronic degenerative joint disease. Exosomes derived from miR-95-5p-overexpressing primary chondrocytes (AC-miR-95-5p) may be effective in treating osteoarthritis. Increased expression of HDAC2/8 occurs in the tissues and chondrocyte-secreted exosomes of patients with osteoarthritis and mediates cartilage-specific gene expression in chondrocytes. We have been suggested that exosomes derived from AC-miR-95-5p (AC-miR-95-5p-Exos) would enhance chondrogenesis and prevent the development of osteoarthritis by directly targeting HDAC2/8. Our in vitro experiments showed that miR-95-5p expression was significantly lower in osteoarthritic chondrocyte-secreted exosomes than in normal cartilage. Treatment with AC-miR-95-5p-Exos promoted cartilage development and cartilage matrix expression in mesenchymal stem cells induced to undergo chondrogenesis and chondrocytes, respectively. In contrast, co-culture with exosomes derived from chondrocytes transfected with an antisense inhibitor of miR-95-5p (AC-anti-miR-95-5p-Exos) prevented chondrogenic differentiation and reduced cartilage matrix synthesis by enhancing the expression of HDAC2/8. MiR-95-5p suppressed the activity of reporter constructs containing the 3'-untranslated region of HDAC2/8, inhibited HDAC2/8 expression and promoted cartilage matrix expression. Our results suggest that AC-miR-95-5p-Exos regulate cartilage development and homoeostasis by directly targeting HDAC2/8. Thus, AC-miR-95-5p-Exos may act as an HDAC2/8 inhibitor and exhibit potential as a disease-modifying osteoarthritis drug.

Down-regulated in OA cartilage, SFMBT2 contributes to NF-κB-mediated ECM degradation

The interplay between anabolic and catabolic factors regulates cartilage matrix homoeostasis. In OA, this balance is disrupted which results in cartilage degradation involving a plethora of inflammatory factors. Here, we identify a novel gene "Scm-like with four MBT domains protein 2" (SFMBT2) negatively regulated in OA cartilage. Articular cartilage from human OA patients undergoing knee arthroplasty surgery exhibited significantly decreased levels of SFMBT2 compared to the normal controls. Down-regulation of SFMBT2 by specific siRNA disturbed the metabolic homoeostasis and led to decreased expression of anabolic genes (SOX9, COL2A1) while increasing the expression of catabolic genes (MMP13 and ADAMTS4), in human chondrocytes. Finally, we revealed that SFMBT2 intervention by siRNA contributed to the catabolic phenotype of human chondrocytes mediated by NF-kB pathway.

MicroRNAs and Osteoarthritis

An imbalance in gene expressional events skewing chondrocyte anabolic and catabolic pathways toward the latter causes an aberrant turnover and loss of extracellular matrix proteins in osteoarthritic (OA) articular cartilage. Thus, catabolism results in the elevated loss of extracellular matrix proteins. There is also evidence of an increase in the frequency of chondrocyte apoptosis that compromises the capacity of articular cartilage to undergo repair. Although much of the fundamental OA studies over the past 20 years identified and characterized many genes relevant to pro-inflammatory cytokines, apoptosis, and matrix metalloproteinases (MMPs)/a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS), more recent studies focused on epigenetic mechanisms and the associated role of microRNAs (miRs) in regulating gene expression in OA cartilage. Thus, several miRs were identified as regulators of chondrocyte signaling pathways, apoptosis, and proteinase gene expression. For example, the reduced expression of miR-146a was found to be coupled to reduced type II collagen (COL2) in OA cartilage, whereas MMP-13 levels were increased, suggesting an association between MMP-13 gene expression and COL2A1 gene expression. Results of these studies imply that microRNAs could become useful in the search for diagnostic biomarkers, as well as providing novel therapeutic targets for intervention in OA.

Epigenetics and bone diseases

Owing to the development of new technologies, the epigenome, a second dimensional method for genome analysis has emerged. Epigenetic mechanisms, including DNA methylation, histone modifications and noncoding RNAs, regulate gene expression without changing the genetic sequence. These epigenetic mechanisms normally modulate gene expression, trans-generational effects and inherited expression states in various biological processes. Abnormal epigenetic patterns typically cause pathological conditions, including cancers, age-related diseases, and specific cartilage and bone diseases. Facing the rapidly developing epigenetic field, we reviewed epigenetic mechanisms and their involvement with the skeletal system and their role in skeletal development, homeostasis and degeneration. Finally, we discuss the prospects for the future of epigenetics.

Interplay of Inflammatory Mediators with Epigenetics and Cartilage Modifications in Osteoarthritis

Osteoarthritis (OA), a degenerative disease of diarthrodial joints, is influenced by mechanical and inflammatory factors with aging, obesity, chronic injuries, and secondary diseases thought to be major factors driving the process of articular cartilage degeneration. Chondrocytes, the cellular component of cartilage, reside in an avascular environment and normally have limited potential to replicate. However, extrinsic factors such as injury to the joint or intrinsic alterations to the chondrocytes themselves can lead to an altered phenotype and development of OA. Synovial inflammation is also a pivotal element of the osteoarthritic, degenerative process: influx of pro-inflammatory cytokines and production of matrix metalloproteinases accelerate advanced cellular processes such as synovitis and cartilage damage. As well as a genetic input, recent data have highlighted epigenetic factors as contributing to disease. Studies conducted over the last decade have focused on three key aspects in OA; inflammation and the immune response, genome-wide association studies that have identified important genes undergoing epigenetic modifications, and finally how chondrocytes transform in their function during development and disease. Data highlighted here have identified critical inflammatory genes involved in OA and how these factors impact chondrocyte hypertrophy in the disease. This review also addresses key inflammatory factors in synovial inflammation, epigenetics, and chondrocyte fate, and how agents that inhibit epigenetic mechanisms like DNA methylation and histone modifications could aid in development of long-term treatment strategies for the disease.

Effects of different concentrations of type-I collagen hydrogel on the growth and differentiation of chondrocytes

The objective of this study was to analyze the effects of type-I collagen hydrogel of different concentrations on the growth and differentiation of rabbit chondrocytes. Articular cartilage from New Zealand white rabbits was harvested and cultured. Second-generation chondrocytes were collected for in vitro culture with 10, 7, and 5 mg/ml type-I collagen hydrogel, respectively (denoted as groups A, B, and C). After in vitro culture for 1 day, chondrocytes were stained with fluorescein diacetate (FDA)/propidium iodide (PI), and cell viability was observed by laser confocal microscopy. After in vitro culture for 14 days, the histological patterns were observed by H&E and toluidine blue staining. The expression of chondrocyte-related genes were measured by real-time quantitative RT-PCR. After in vitro culture for 1 day, FDA/PI staining showed that the cell density of group A was significantly higher than that of group B and C. After in vitro culture for 14 days, H&E staining showed that chondrocytes showed obvious aggregation in group A, partial proliferation and aggregation in group B, and uniform distribution in group C. Toluidine blue staining showed that chondrocytes in group A had aggregation areas and some were stained purple-red, fewer chondrocytes were aggregated with different staining around them in group B, and the aggregation of chondrocytes was not obvious. However, the distribution of chondrocytes was uniform with different staining in group C. After in vitro culture for 2 weeks, the levels of polymerized proteoglycan and type-II collagen mRNA were not significantly different between the three groups (P>0.05). The levels of type-I collagen, type-X collagen, and Sox9 mRNA in group A were significantly higher than those in group B and C (P<0.05). In conclusion, high concentration type-I collagen hydrogel can promote chondrocyte fibrosis and upregulation of type-I collagen, type-X collagen, and Sox9 mRNA.

Oral herbal medicines marketed in Brazil for the treatment of osteoarthritis: A systematic review and meta-analysis

Herbal medications are commonly used to manage symptoms associated with osteoarthritis (OA). This systematic review evaluated the effectiveness and safety of oral medications used in Brazil for the treatment of OA. Randomized clinical trials involving adults with OA treated by a herbal medicine or a control group were eligible. The primary outcomes measured were pain, physical function, swelling, stiffness and quality of life; and the secondary outcomes were adverse events, activity limitations and treatment satisfaction. Sixteen studies were included (n = 1,741 patients) in the systematic review and nine studies in the meta-analysis, representing 6 of the 13 herbal medicines studied: Boswellia serrata (n = 2), Curcuma longa (n = 3), Harpagophytum procumbens (n = 1), Salix daphnoides (n = 3), Uncaria guianensis (n = 2) and Zingiber officinale (n = 5). B. serrata was more effective than both placebo and valdecoxib for improvement of pain and physical function. No difference was observed for H. procumbens, C. longa and U. guianensis compared with control. Z. officinale showed improvement of pain over placebo. The evidence was insufficient to support the effective and safe use of these herbal medicines, because the quality of evidence of studies was low. This study guides managers of the Brazilian public health system and prescribers in decision-making regarding the use of these herbal medicines for OA. Copyright © 2017 John Wiley & Sons, Ltd.

TGF β1 gene polymorphisms correlate with the susceptibility of osteoarthritis

PURPOSE

We investigated the potential role of transforming growth factor beta 1 (TGF β1) gene polymorphisms (rs1800470 and rs1800469) in the occurrence of osteoarthritis (OA).

METHODS

Genotypes of TGF β1 gene polymorphisms (rs1800470 and 1800469) were genotyped by TaqMan method in 111 OA patients and 129 healthy controls. The representativeness of case and control was inspected by Hardy-Weinberg equilibrium (HWE). Genotype and allele distribution differences between case and control groups were calculated by Chi-square test. Odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs) were utilized to emerge the relative risk of OA.

RESULTS

Genotype distributions of the two TGF β1 gene polymorphisms were according to HWE examination. TT genotype of rs1800470 was significantly associated with the occurrence of OA (P=0.046, OR=2.093, 95% CI=1.009-4.340). For rs1800469, both TT genotype and T allele had significant association with the susceptibility of OA (P=0.000, OR=3.650, 95% CI=1.759-7.575; P=0.000, OR=1.957, 95% CI=1.360-2.817).

CONCLUSION

TT genotype of rs1800470, TT genotype and T allele of rs1800469 were increased the risk of OA. We conjectured that the polymorphisms of TGF β1 gene might increase the individual susceptible of OA.

Cartilage repair by mesenchymal stem cells: Clinical trial update and perspectives

Osteoarthritis is a degenerative disease of joints with destruction of articular cartilage associated with subchondral bone hypertrophy and inflammation. OA is the leading cause of joint pain resulting in significant worsening of the quality-of-life in the elderly. Numerous efforts have been spent to overcome the inherently poor healing ability of articular cartilage. Mesenchymal stem cells (MSCs) have been in the limelight of cell-based therapies to promote cartilage repair. Despite progressive advancements in MSC manipulation and the introduction of various bioactive scaffolds and growth factors in preclinical studies, current clinical trials are still at early stages with preliminary aims to evaluate safety, feasibility and efficacy. This review summarises recently reported MSC-based clinical trials and discusses new research directions with particular focus on the potential application of MSC-derived extracellular vehicles, miRNAs and advanced gene editing techniques which may shed light on the development of novel treatment strategies. The translational potential of this article: This review summarises recent MSC-related clinical research that focuses on cartilage repair. We also propose a novel possible translational direction for hyaline cartilage formation and a new paradigm making use of extra-cellular signalling and epigenetic regulation in the application of MSCs for cartilage repair.

The importance of genetic factors for the development of arthropathy: a longitudinal study of children and adolescents with haemophilia A

Haemophilia A is a congenital bleeding disorder characterised by recurrent haemorrhages into the major joints. Haemophilic arthropathy is a well-established outcome of recurrent joint bleeding; however, it is clear that multiple factors determine the extent and severity of its occurrence. We sought to identify genetic factors related to abnormalities in range of motion (ROM) in the knees, ankles and elbows in a cohort of children and adolescents with haemophilia A not treated primarily with regular prophylaxis. Using data from the Haemophilia Growth and Development Study, we examined associations between 13,342 genetic markers and ROM scores measured at six-month intervals for up to seven years. As a first step, ordered logistic regression models were fit for each joint separately. A subset of SNP markers showing significant effects (p<0.01) on the right and left sides for at least two joints were included in a full model fit using a multivariate generalised linear mixed model assuming an ordinal response. The models contained all ROM scores obtained at all visits. Twenty-five markers analysed in the full model showed either increased or decreased risk of ROM abnormalities at the p<0.001 level. Several genes identified at either the first or second stage of the analysis have been associated with arthritis in a variety of large studies. Our results support the likelihood that risk for haemophilic arthropathy is associated with genetic factors, the identification of which holds promise for further advancing the individualisation of treatment.

Building and maintaining joints by exquisite local control of cell fate

We owe the flexibility of our bodies to sophisticated articulations between bones. Establishment of these joints requires the integration of multiple tissue types: permanent cartilage that cushions the articulating bones, synovial membranes that enclose a lubricating fluid-filled cavity, and a fibrous capsule and ligaments that provide structural support. Positioning the prospective joint region involves establishment of an "interzone" region of joint progenitor cells within a nascent cartilage condensation, which is achieved through the interplay of activators and inhibitors of multiple developmental signaling pathways. Within the interzone, tight regulation of BMP and TGFβ signaling prevents the hypertrophic maturation of joint chondrocytes, in part through downstream transcriptional repressors and epigenetic modulators. Synovial cells then acquire further specializations through expression of genes that promote lubrication, as well as the formation of complex structures such as cavities and entheses. Whereas genetic investigations in mice and humans have uncovered a number of regulators of joint development and homeostasis, recent work in zebrafish offers a complementary reductionist approach toward understanding joint positioning and the regulation of chondrocyte fate at joints. The complexity of building and maintaining joints may help explain why there are still few treatments for osteoarthritis, one of the most common diseases in the human population. A major challenge will be to understand how developmental abnormalities in joint structure, as well as postnatal roles for developmental genes in joint homeostasis, contribute to birth defects and degenerative diseases of joints. WIREs Dev Biol 2017, 6:e245. doi: 10.1002/wdev.245 For further resources related to this article, please visit the WIREs website.

Investigation of candidate genes for osteoarthritis based on gene expression profiles

OBJECTIVE

To explore the mechanism of osteoarthritis (OA) and provide valid biological information for further investigation.

METHODS

Gene expression profile of GSE46750 was downloaded from Gene Expression Omnibus database. The Linear Models for Microarray Data (limma) package (Bioconductor project, http://www.bioconductor.org/packages/release/bioc/html/limma.html) was used to identify differentially expressed genes (DEGs) in inflamed OA samples. Gene Ontology function enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enrichment analysis of DEGs were performed based on Database for Annotation, Visualization and Integrated Discovery data, and protein-protein interaction (PPI) network was constructed based on the Search Tool for the Retrieval of Interacting Genes/Proteins database. Regulatory network was screened based on Encyclopedia of DNA Elements. Molecular Complex Detection was used for sub-network screening. Two sub-networks with highest node degree were integrated with transcriptional regulatory network and KEGG functional enrichment analysis was processed for 2 modules.

RESULTS

In total, 401 up- and 196 down-regulated DEGs were obtained. Up-regulated DEGs were involved in inflammatory response, while down-regulated DEGs were involved in cell cycle. PPI network with 2392 protein interactions was constructed. Moreover, 10 genes including Interleukin 6 (IL6) and Aurora B kinase (AURKB) were found to be outstanding in PPI network. There are 214 up- and 8 down-regulated transcription factor (TF)-target pairs in the TF regulatory network. Module 1 had TFs including SPI1, PRDM1, and FOS, while module 2 contained FOSL1. The nodes in module 1 were enriched in chemokine signaling pathway, while the nodes in module 2 were mainly enriched in cell cycle.

CONCLUSION

The screened DEGs including IL6, AGT, and AURKB might be potential biomarkers for gene therapy for OA by being regulated by TFs such as FOS and SPI1, and participating in the cell cycle and cytokine-cytokine receptor interaction pathway.

Candidate methylated genes in osteoarthritis explored by bioinformatics analysis

BACKGROUND

This study aimed to explore potential novel genes correlated with osteoarthritis (OA).

METHODS

The gene expression profile of GSE48422 was downloaded from the Gene Expression Omnibus (GEO) database. This dataset included five arthritic cartilage samples and five non-arthritic cartilage samples from five female OA patients. Differentially methylated genes (DMGs) between the two kinds of samples were identified, followed by their functional analysis and protein-protein interaction (PPI) analysis. Furthermore, the Comparative Toxicogenomics Database (CTD) was used to further identify OA-related genes among these DMGs.

RESULTS

In total, 965 hypermethylated genes and 112 hypomethylated genes were identified in the arthritic cartilage samples. The hypermethylated genes (e.g., ADCY4 and ADCY6) were significantly related to the calcium signaling pathway and gonadotropin-releasing hormone signaling pathway, while the hypomethylated genes were implicated in the mammalian target of rapamycin signaling pathway. In the PPI network, several genes had a higher degree, such as ADCY4, ADCY6 and GPR17, and they interacted with each other. Additionally, 565 DMGs were predicted to be associated with OA, and five of them (e.g., COMP and EDIL3) were previously identified as OA markers.

CONCLUSIONS

The methylation of genes ADCY4, ADCY6 and GPR17, as well as the gonadotropin-releasing hormone signaling pathway, was newly found to be potentially associated with OA. They may be novel OA markers.

Brazilian oral herbal medication for osteoarthritis: a systematic review protocol

BACKGROUND

Osteoarthritis affects 1 % of the world's population and is the most common cause of musculoskeletal impairment in the elderly. Herbal medications are commonly used in Brazil to manage symptoms associated with osteoarthritis, and some of them are financed by the Brazilian government; however, the effectiveness of most of these agents is uncertain. The aim was to systematically review the efficacy and safety of 13 oral herbal medications used in Brazil for the treatment of osteoarthritis.

METHODS

Randomized clinical trials eligible for our systematic review will enroll adults with osteoarthritis treated by a Brazilian herbal medication or a control group (placebo or active control). Using terms to include all forms of osteoarthritis combined with herbal medications, we will search the following electronic databases: Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; CINAHL; Web of Science; Health Star; AMED, the database of the Cochrane Complementary Medicine Field, LILACS; CAB abstracts, Clinical trial.gov, WHO trials registry, and Bank of Brazil Thesis (CAPES), to 31 January 2016, without restrictions concerning language or status of publication. Outcomes of interest include the following: symptom relief (e.g., pain), adverse events (gastrointestinal bleeding, epigastric pain, nausea, and allergic reactions), discontinuation due to adverse events, quality of life, and the satisfaction with the treatment. Dichotomous data will be summarized as risk ratios; continuous data will be given as standard average differences with 95 % confidence intervals. A team of reviewers will assess each citation independently for eligibility and in duplicate it. For eligible studies, the same reviewers will perform data extraction, bias risk assessment, and determination of the overall quality of evidence for each of the outcomes using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) classification system.

DISCUSSION

This is the first study that will evaluate the use of herbal medications used in Brazil for the treatment of pain caused by osteoarthritis. The results could guide prescribers in decision-making in clinical practice, to inform the patients with pain caused by osteoarthritis in relation to effective and safe treatment options and to inform the managers of the public health system which of the plants could actually be financed by the Brazilian government.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO 42015019793.

Smoking and alcohol behaviours in people following hip and knee arthroplasty: Data from the Osteoarthritis Initiative

BACKGROUND

Smoking and alcohol consumption has a negative effect on overall health. Limited evidence has been presented as to how these health behaviours may change between pre- and postoperative intervals in the initial 12 months post-arthroplasty. The purpose of this study was to address this uncertainty.

HYPOTHESIS

Smoking and alcohol consumption differs between pre- and post-THA/TKA and it differs between non-arthroplasty cohorts.

MATERIALS AND METHODS

Data from the Osteoarthritis Initiative (OAI), a population-based observational study in the USA, were gathered. In total, data from 287 people who had undergone THA or TKA from baseline to month 48 OAI follow-up assessments were analysed. Data on this cohort were compared to 287 age- and gender-matched people with osteoarthritis. Mean change from pre- to post-arthroplasty, and differences between arthroplasty and non-arthroplasty participants for smoking and alcohol consumption were assessed descriptively and through Wilcoxin-matched pairs test and Student t-tests (as appropriate).

RESULTS

The lifetime prevalence of smoking was high for people who received THA (99%) and TKA (96%). Prevalence of current smoking significantly decreased from 5 to 3% across the THA and TKA cohort in the initial 12 months post-arthroplasty (P<0.05). Similarly, there was a statistically significant decrease in weekly alcohol consumption post-arthroplasty for people who underwent THA and TKA (P<0.01), although the mean difference was only by 0.9 alcoholic drinks. The only statistically significant difference in smoking and alcohol consumption for arthroplasty to non-arthroplasty participants was in weekly alcohol consumption, which was higher by 0.3 drinks in the non-arthroplasty cohort (P=0.04).

CONCLUSIONS

Smoking and alcohol consumption decreased in the initial 12 months post-THA and TKA. This was not significantly different to an age- and gender-matched non-arthroplasty cohort. Whilst this is positive, a small group of patients still present with unhealthy lifestyle choices in relation to these behaviours post-arthroplasty.

LEVEL OF EVIDENCE

Level III - prospective case control study.

Attenuation of the progression of articular cartilage degeneration by inhibition of TGF-β1 signaling in a mouse model of osteoarthritis

Transforming growth factor beta 1 (TGF-β1) is implicated in osteoarthritis. We therefore studied the role of TGF-β1 signaling in the development of osteoarthritis in a developmental stage-dependent manner. Three different mouse models were investigated. First, the Tgf-β receptor II (Tgfbr2) was specifically removed from the mature cartilage of joints. Tgfbr2-deficient mice were grown to 12 months of age and were then euthanized for collection of knee and temporomandibular joints. Second, Tgfbr2-deficient mice were subjected to destabilization of the medial meniscus (DMM) surgery. Knee joints were then collected from the mice at 8 and 16 weeks after the surgery. Third, wild-type mice were subjected to DMM at the age of 8 weeks. Immediately after the surgery, these mice were treated with the Tgfbr2 inhibitor losartan for 8 weeks and then euthanized for collection of knee joints. All joints were characterized for evidences of articular cartilage degeneration. Initiation or acceleration of articular cartilage degeneration was not observed by the genetic inactivation of Tgfbr2 in the joints at the age of 12 months. In fact, the removal of Tgfbr2 and treatment with losartan both delayed the progression of articular cartilage degeneration induced by DMM compared with control littermates. Therefore, we conclude that inhibition of Tgf-β1 signaling protects adult knee joints in mice against the development of osteoarthritis.

Predicting Knee Osteoarthritis

Treatment options for osteoarthritis (OA) beyond pain relief or total knee replacement are very limited. Because of this, attention has shifted to identifying which factors increase the risk of OA in vulnerable populations in order to be able to give recommendations to delay disease onset or to slow disease progression. The gold standard is then to use principles of risk management, first to provide subject-specific estimates of risk and then to find ways of reducing that risk. Population studies of OA risk based on statistical associations do not provide such individually tailored information. Here we argue that mechanistic models of cartilage tissue maintenance and damage coupled to statistical models incorporating model uncertainty, united within the framework of structural reliability analysis, provide an avenue for bridging the disciplines of epidemiology, cell biology, genetics and biomechanics. Such models promise subject-specific OA risk assessment and personalized strategies for mitigating or even avoiding OA. We illustrate the proposed approach with a simple model of cartilage extracellular matrix synthesis and loss regulated by daily physical activity.