Osteoarthritis year in review 2018: genetics and epigenetics

Exploring m6A-linked aging genes in osteoarthritis and broad cancer spectrum: Prospects for diagnostic and therapeutic advancements

Osteoarthritis (OA) is a prevalent degenerative joint disease that significantly impacts individuals and healthcare systems worldwide. However, the exploration of N6-methyladenosine (m6A)-related aging genes in OA pathogenesis remains largely underexplored. This study aimed to elucidate the role of m6A-related aging genes in OA and to develop a robust diagnostic model based on their expression profiles. Leveraging publicly available gene expression datasets, we conducted consensus clustering to categorize OA into distinct subtypes, guided by the expression patterns of m6A-related aging genes. Utilizing XGBoost, a cutting-edge machine learning approach, we identified key diagnostic genes and constructed a predictive model. Our investigation extended to the immune functions of these genes, shedding light on potential therapeutic targets and underlying regulatory mechanisms. Our analysis unveiled specific OA subtypes, each marked by unique expression profiles of m6A-related aging genes. We pinpointed a set of pivotal diagnostic genes, offering potential therapeutic avenues. The developed diagnostic model exhibited exceptional capability in distinguishing OA patients from healthy controls. To corroborate our computational findings, we performed quantitative real-time polymerase chain reaction analyses on two cell lines: HC-OA (representing adult osteoarthritis cells) and C-28/I2 (representative of normal human chondrocytes). The gene expression patterns observed were consistent with our bioinformatics predictions, further validating our initial results. In conclusion, this study underscores the significance of m6A-related aging genes as promising biomarkers for diagnosis and prognosis, as well as potential therapeutic targets in OA. Although these findings are encouraging, further validation and functional analyses are crucial for their clinical application.

Paeoniflorin shows chondroprotective effects under IL-1β stress by regulating circ-PREX1/miR-140-3p/WNT5B axis

BACKGROUND

Osteoarthritis (OA) is a chronic and degenerative bone and joint disease, and paeoniflorin shows anti-arthritis role in OA. This study planned to investigate the mechanism related to chondroprotective role of paeoniflorin in OA.

METHODS

Real-time quantitative PCR and western blotting were performed to measure expression levels of circ-PREX1, microRNA (miR)-140-3p, Wingless-type MMTV integration site family, member 5B (WNT5B), B cell lymphoma (Bcl)-2, and Bcl-2 Associated X Protein (Bax). MTT assay, EdU assay, flow cytometry and enzyme-linked immunosorbent assay evaluated cell viability, proliferation, apoptosis and inflammatory response, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation assay identified the relationship among circ-PREX1, miR-140-3p, and WNT5B.

RESULTS

IL-1β highly induced apoptosis rate, Bax expression and TNF-α product, accompanied with decreased cell viability, cell proliferation and IL-10 secretion, whereas these effects were partially reversed after paeoniflorin pretreatment. Expression of circ-PREX1 was upregulated and miR-140-3p was downregulated in cartilage tissues of patients with knee OA (KOA) and IL-1β-induced human chondrocytes (C28/I2). Circ-PREX1 overexpression and miR-140-3p silencing attenuated the suppressive effect of paeoniflorin in IL-1β-induced C28/I2 cells. Furthermore, miR-140-3p was negatively regulated by circ-PREX1. WNT5B was a downstream target of miR-140-3p and could be modulated by the circ-PREX1/miR-140-3p pathway in IL-1β-induced C28/I2 cells.

CONCLUSION

Paeoniflorin might protect human chondrocytes from IL-1β-induced inflammatory injury via circ-PREX1-miR-140-3p-WNT5B pathway, suggesting a potential preventative agent and a novel target for the treatment of KOA.

The identification of hub-methylated differentially expressed genes in osteoarthritis patients is based on epigenomic and transcriptomic data

Introduction

Osteoarthritis (OA) refers to a commonly seen degenerative joint disorder and a major global public health burden. According to the existing literature, osteoarthritis is related to epigenetic changes, which are important for diagnosing and treating the disease early. Through early targeted treatment, costly treatments and poor prognosis caused by advanced osteoarthritis can be avoided.

Methods

This study combined gene differential expression analysis and weighted gene co-expression network analysis (WGCNA) of the transcriptome with epigenome microarray data to discover the hub gene of OA. We obtained 2 microarray datasets (GSE114007, GSE73626) in Gene Expression Omnibus (GEO). The R software was utilized for identifying differentially expressed genes (DEGs) and differentially methylated genes (DMGs). By using WGCNA to analyze the relationships between modules and phenotypes, it was discovered that the blue module (MEBlue) has the strongest phenotypic connection with OA (cor = 0.92, p = 4e-16). The hub genes for OA, also known as the hub methylated differentially expressed genes, were identified by matching the MEblue module to differentially methylated differentially expressed genes. Furthermore, this study used Gene set variation analysis (GSVA) to identify specific signal pathways associated with hub genes. qRT-PCR and western blotting assays were used to confirm the expression levels of the hub genes in OA patients and healthy controls.

Results

Three hub genes were discovered: HTRA1, P2RY6, and RCAN1. GSVA analysis showed that high HTRA1 expression was mainly enriched in epithelial-mesenchymal transition and apical junction; high expression of P2RY6 was mainly enriched in the peroxisome, coagulation, and epithelial-mesenchymal transition; and high expression of RCAN1 was mainly enriched in epithelial-mesenchymal-transition, TGF-β-signaling, and glycolysis. The results of the RT-qPCR and WB assay were consistent with the findings.

Discussion

The three genes tested may cause articular cartilage degeneration by inducing chondrocyte hypertrophy, regulating extracellular matrix accumulation, and improving macrophage pro-inflammatory response, resulting in the onset and progression of osteoarthritis. They can provide new ideas for targeted treatment of osteoarthritis.

MicroRNA Signatures in Cartilage Ageing and Osteoarthritis

Osteoarthritis is the most common degenerative joint disorder. MicroRNAs are gene expression regulators that act post-transcriptionally to control tissue homeostasis. Microarray analysis was undertaken in osteoarthritic intact, lesioned and young intact cartilage. Principal component analysis showed that young intact cartilage samples were clustered together; osteoarthritic samples had a wider distribution; and osteoarthritic intact samples were separated into two subgroups, osteoarthritic-Intact-1 and osteoarthritic-Intact-2. We identified 318 differentially expressed microRNAs between young intact and osteoarthritic lesioned cartilage, 477 between young intact and osteoarthritic-Intact-1 cartilage and 332 between young intact and osteoarthritic-Intact-2 cartilage samples. For a selected list of differentially expressed microRNAs, results were verified in additional cartilage samples using qPCR. Of the validated DE microRNAs, four-miR-107, miR-143-3p, miR-361-5p and miR-379-5p-were selected for further experiments in human primary chondrocytes treated with IL-1β. Expression of these microRNAs decreased in human primary chondrocytes treated with IL-1β. For miR-107 and miR-143-3p, gain- and loss-of-function approaches were undertaken and associated target genes and molecular pathways were investigated using qPCR and mass spectrometry proteomics. Analyses showed that WNT4 and IHH, predicted targets of miR-107, had increased expression in osteoarthritic cartilage compared to young intact cartilage and in primary chondrocytes treated with miR-107 inhibitor, and decreased expression in primary chondrocytes treated with miR-107 mimic, suggesting a role of miR-107 in chondrocyte survival and proliferation. In addition, we identified an association between miR-143-3p and EIF2 signalling and cell survival. Our work supports the role of miR-107 and miR-143-3p in important chondrocyte mechanisms regulating proliferation, hypertrophy and protein translation.

Inhibition of KDM7A/B histone demethylases restores H3K79 methylation and protects against osteoarthritis

OBJECTIVES

In osteoarthritis, methylation of lysine 79 on histone H3 (H3K79me), a protective epigenetic mechanism, is reduced. Histone methylation levels are dynamically regulated by histone methyltransferases and demethylases. Here, we aimed to identify which histone demethylases regulate H3K79me in cartilage and investigate whether their targeting protects against osteoarthritis.

METHODS

We determined histone demethylase expression in human non-osteoarthritis and osteoarthritis cartilage using qPCR. The role of histone demethylase families and subfamilies on H3K79me was interrogated by treatment of human C28/I2 chondrocytes with pharmacological inhibitors, followed by western blot and immunofluorescence. We performed C28/I2 micromasses to evaluate effects on glycosaminoglycans by Alcian blue staining. Changes in H3K79me after destabilisation of the medial meniscus (DMM) in mice were determined by immunohistochemistry. Daminozide, a KDM2/7 subfamily inhibitor, was intra-articularly injected in mice upon DMM. Histone demethylases targeted by daminozide were individually silenced in chondrocytes to dissect their role on H3K79me and osteoarthritis.

RESULTS

We documented the expression signature of histone demethylases in human non-osteoarthritis and osteoarthritis articular cartilage. Inhibition of Jumonji-C demethylase family increased H3K79me in human chondrocytes. Blockade of KDM2/7 histone demethylases with daminozide increased H3K79me and glycosaminoglycans. In mouse articular cartilage, H3K79me decayed rapidly upon induction of joint injury. Early and sustained intra-articular treatment with daminozide enhanced H3K79me and exerted protective effects in mice upon DMM. Individual silencing of KDM7A/B demethylases in human chondrocytes demonstrated that KDM7A/B mediate protective effects of daminozide on H3K79me and osteoarthritis.

CONCLUSION

Targeting KDM7A/B histone demethylases could be an attractive strategy to protect joints against osteoarthritis.

The long non-coding RNA SNHG1 attenuates chondrocyte apoptosis and inflammation via the miR-195/IKK-α axis

Multiple studies have suggested that long non-coding RNAs (lncRNAs) are involved in the development and progression of osteoarthritis (OA). However, how lncRNA SNHG1 regulates OA remains unknown. This study aimed to explore how SNHG1 regulates chondrocyte apoptosis and inflammation. Our data showed that H₂O₂-treated chondrocytes exhibited lower expression of SNHG1 and secreted higher levels of IL-6, IL-8, and TNF-α than untreated cells. Further, overexpressing SNHG1 reduced chondrocyte apoptosis and production of inflammatory factors. Additionally, SNHG1 targets miR-195 directly, and IKK-α has direct biding sites for miR-195. Of note, IKK-α acts as an inhibitor of the NF-κB signaling pathway. These findings suggest that SNHG1 can upregulate IKK-α by inhibiting miR-195 and thus, inhibit NF-κB activity. Our in vivo experiments validate our in vitro findings. Thus, under oxidative stress, SNHG1 inhibits the activation of NF-κB to attenuate chondrocyte apoptosis and inflammation via the miR-195/IKK-α axis. Targeting SNHG1 may serve as a potential novel therapeutic approach for OA.

Bardoxolone methyl ameliorates osteoarthritis by inhibiting osteoclastogenesis and protecting the extracellular matrix against degradation

Inflammation and oxidative damage are closely related to the development of osteoarthritis. Bardoxolone methyl (CDDO-Me), a semisynthetic oleanane triterpenoid, plays a strong anti-inflammatory and antioxidant role. The purpose of our research was to explore fundamental mechanisms of CDDO-Me in orthopaedics development. The results showed that CDDO-Me inhibited nuclear factor-κB ligand (RANKL)-induced osteoclast formation and extracellular matrix (ECM) degradation by activating the Nrf2/HO-1 signaling pathways and inhibiting NF-κB pathway activation and excess ROS production. In vivo, CDDO-Me significantly attenuated articular cartilage proteoglycan loss and the number of TRAP-positive osteoclasts in a destabilized medial meniscus (DMM) mouse model of OA. Taken together, these data demonstrate that CDDO-Me inhibits osteoclastogenesis and ECM degradation, underscoring its potential therapeutic value in treating OA.

Role of macrophage polarization in osteoarthritis (Review)

Osteoarthritis (OA) is a disease involving the whole joint that seriously reduces the living standards of individuals. Traditional treatments include physical therapy, administration of anti-inflammatory and analgesic drugs and injection of glucocorticoids or hyaluronic acid into the joints. However, these methods have limited efficacy and it is difficult to reverse the progression of OA, therefore it is urgent to find new effective treatment methods. Immune microenvironment is significant in the occurrence and development of OA. Recent studies have shown that macrophages are important targets for the treatment of OA. Macrophages are polarized into M1 pro-inflammatory phenotype and M2 anti-inflammatory phenotype under stimulation of different factors, which release and regulate inflammatory response and cartilage growth. Accumulating studies have tried to alleviate OA by regulating macrophage homeostasis. The present study summarized the related studies, discuss the mechanism of various therapeutic reagents on OA, expound the molecular mechanism of drug effect on OA and attempted to provide clues for the treatment of OA.

Osteoarthritis & stroke: a bidirectional mendelian randomization study

OBJECTIVE

The epidemiological evidence on the link between osteoarthritis (OA) and stroke remains inconclusive. Herein, we adopted a two-sample bidirectional Mendelian randomization (MR) study to determine the causality relationship between OA and stroke.

DESIGN

Summary-level data derived from the published genome-wide association studies (GWAS) were employed for analyses. The data for OA at any site (n = 455,211), knee OA (n = 403,124), and hip OA (n = 393,873) were obtained from a meta-analysis of GWAS available in the UK Biobank and Arthritis Research UK Osteoarthritis Genetics resources. The MEGASTROKE consortium provided data for stroke (n = 446,696), ischemic stroke (IS) (n = 440,328) and its subtypes, and intracerebral hemorrhage (ICH) (n = 3,026). The main MR analysis was conducted by the inverse variance weighted (IVW) method. MR-Egger regression, MR pleiotropy residual sum and outlier, weighted median, Cochran Q statistic, and leave-one-out analysis approach were leveraged as supplements.

RESULTS

We detected that higher risk of hip OA was significantly associated with overall stroke [IVW odds ratio (OR): 1.12, 95% confidence interval (CI): 1.06-1.20, P = 0.0002], IS (OR: 1.13, 95%CI: 1.06-1.21, P = 0.0003), and small vessel IS (OR: 1.25, 95%CI: 1.10-1.42, P = 0.0006). However, we found no evidence that stroke and subtypes had casual effects on OA in the reverse MR analyses.

CONCLUSIONS

The present study provides genetic support that hip OA is a potential risk factor for overall stroke, IS, and small vessel IS. Further studies are warranted to elucidate the underlying mechanisms of causal associations between site-specific OA and stroke subtypes.

The lncRNA PILA promotes NF-κB signaling in osteoarthritis by stimulating the activity of the protein arginine methyltransferase PRMT1

Inflammatory cytokine-induced activation of nuclear factor κB (NF-κB) signaling plays a critical role in the pathogenesis of osteoarthritis (OA). We identified PILA as a long noncoding RNA (lncRNA) that enhances NF-κB signaling and OA. The abundance of PILA was increased in damaged cartilage from patients with OA and in human articular chondrocytes stimulated with the proinflammatory cytokine tumor necrosis factor (TNF). Knockdown of PILA inhibited TNF-induced NF-κB signaling, extracellular matrix catabolism, and apoptosis in chondrocytes, whereas ectopic expression of PILA promoted NF-κB signaling and matrix degradation. PILA promoted PRMT1-mediated arginine methylation of DExH-box helicase 9 (DHX9), leading to an increase in the transcription of the gene encoding transforming growth factor β-activated kinase 1 (TAK1), an upstream activator of NF-κB signaling. Furthermore, intra-articular injection of an adenovirus vector encoding PILA triggered spontaneous cartilage loss and exacerbated posttraumatic OA in mice. This study provides insight into the regulation of NF-κB signaling in OA and identifies a potential therapeutic target for this disease.

Patients with Osteoarthritis and Kashin-Beck Disease Display Distinct CpG Methylation Profiles in the DIO2, GPX3, and TXRND1 Promoter Regions

OBJECTIVE

We aimed to analyze deoxycytidine-deoxyguanosine dinucleotide (CpGs) methylation profiles in DIO2, GPX3, and TXNRD1 promoter regions in osteoarthritis (OA) and Kashin-Beck disease (KBD) patients.

METHODS

Blood samples were collected from 16 primary OA patients and corresponding 16 healthy individuals and analyzed for methylations in the CpGs of DIO2, GPX3, and TXNRD1 promoter regions using MALDI-TOF-MS. The methylation profiles of these regions were then compared between OA and KBD patients.

RESULTS

DIO2-1_CpG_2 and DIO2-1_CpG_3 methylations were significantly lower in OA than KBD patients (P < 0.05). A similar trend was observed for GPX3-1_CpG_4, GPX3-1_CpG_7, GPX3-1_CpG_8.9.10, GPX3-1_CpG_13.14.15 and GPX3-1_CpG_16 (P < 0.05) as well as TXNRD1-1_CpG_1 and TXNRD1-1_CpG_2 methylation between OA and KBD patients (P < 0.05). However, there was no difference in methylation levels of other CpGs between the 2 groups (P > 0.05).

CONCLUSION

OA and KBD patients display distinct methylation profiles in the CpG sites of DIO2, GPX3, and TXNRD1 promoter regions. These findings provide a strong background and new perspective for future studies on mechanisms underlying epigenetic regulation of selenoprotein genes associated with OA and KBD diseases.

Involvement of an FTO gene polymorphism in the temporomandibular joint osteoarthritis

Objectives

The FTO gene has been reported as an obesity-associated gene and is also considered a risk gene for osteoarthritis (OA). However, its exact function is unclear, and there is conflicting evidence on the involvement of FTO polymorphisms in OA via obesity. The purpose of this study was to determine the effects of FTO polymorphism rs8044769 alleles on OA in the temporomandibular joint (TMJ), which is minimally affected by body weight.

Materials and methods

A total of 324 TMJs (113 with OA and 211 without OA, serving as controls) from 162 Japanese patients with temporomandibular disorders and undergoing MRI examination were analyzed. Genotyping was conducted, and multivariate analysis was performed after adjusting for the effects of age, sex, body mass index, and TMJ disc abnormalities.

Results

Mean age, BMI, and sex did not differ between the TMJs with OA and the TMJs without OA, but a significant difference was found for positional and dynamic disc abnormalities (P < 0.05). The allele frequency of FTO polymorphisms also differed significantly between the TMJs with OA and the TMJs without OA (P = 0.011). Moreover, logistic regression analysis showed no significant association between BMI (P = 0.581) and the occurrence of TMJOA but also indicated that the CC allele of rs8044769 is a risk factor for TMJOA (P = 0.040).

Conclusions

Our results show that rs8044769 in the FTO gene might be involved in TMJOA.

Clinical relevance

The present study provides a basis for a deeper understanding of the mechanism underlying degenerative skeletal diseases and the more effective selection and development of treatment strategies based on the patients’ genetic characteristics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-04278-9.

DUSP4 alleviates LPS-induced chondrocyte injury in knee osteoarthritis via the MAPK signaling pathway

Knee osteoarthritis (KOA) is characterized by cartilage damage, and the associated pathogenesis is complex. The expression of dual specificity protein phosphatase 4 (DUSP4) is significantly decreased in osteoarthritis (OA); however, the specific role and mechanism underlying DUSP4 in OA are yet to be elucidated. ATDC5 cells were treated with lipopolysaccharide (LPS) to establish the cell injury model. The expression levels of DUSP4 were decreased in OA chondrocytes, demonstrated by reverse transcription-quantitative PCR and western blot analysis. Following overexpression of DUSP4 by cell transfection, Cell Counting Kit-8, ELISA, TUNEL and western blotting assays were used to detect the cell viability, oxidative stress, inflammation and apoptosis levels of LPS-induced ATDC5 cells. Overexpression of DUSP4 inhibited the activation of the MAPK signaling pathway, thereby reducing oxidative stress levels, inflammatory response and apoptosis in the OA cell model. The mechanisms underlying DUSP4 in OA were further explored following the addition of MAPK signaling pathway agonist, phorbol 12-myristate 13-acetate (PMA). The addition of PMA reversed the inhibitory effects of DUSP4 overexpression on oxidative stress, inflammatory response and apoptosis in cells. In summary, DUSP4 alleviated LPS-induced chondrocyte injury in KOA via the MAPK signaling pathway.

An evolutionary perspective of DNA methylation patterns in skeletal tissues using a baboon model of osteoarthritis

Epigenetic factors, such as DNA methylation, play an influential role in the development of the degenerative joint disease osteoarthritis (OA). These molecular mechanisms have been heavily studied in humans, and although OA affects several other animals in addition to humans, few efforts have taken an evolutionary perspective. This study explores the evolution of OA epigenetics by assessing the relationship between DNA methylation variation and knee OA development in baboons (Papio spp.) and by comparing these findings to human OA epigenetic associations. Genome-wide DNA methylation patterns were identified in bone and cartilage of the right distal femora from 56 pedigreed, adult baboons (28 with and 28 without knee OA) using the Illumina Infinium MethylationEPIC BeadChip. Several significantly differentially methylated positions (DMPs) and regions were found between tissue types. Substantial OA-related differential methylation was also identified in cartilage, but not in bone, suggesting that cartilage epigenetics may be more influential in OA than bone epigenetics. Additionally, some genes containing OA-related DMPs overlap with and display methylation patterns similar to those previously identified in human OA, revealing a mixture of evolutionarily conserved and divergent OA-related methylation patterns in primates. Overall, these findings reinforce the current etiological perspectives of OA and enhance our evolutionary understanding of epigenetic mechanisms associated with OA. This study further establishes baboons as a valuable nonhuman primate model of OA, and continued investigations in baboons will help to disentangle the molecular mechanisms contributing to OA and their evolutionary histories.

LncRNA THUMPD3-AS1 enhances the proliferation and inflammatory response of chondrocytes in osteoarthritis

OBJECTIVE

Long noncoding RNAs (lncRNAs) regulate the occurrence and development of osteoarthritis (OA), whereas the biological roles and mechanisms of the lncRNA THUMPD3-AS1 (THUMPD3 antisense RNA 1) in OA remain still unclear. This study described the role and molecular mechanism of lncRNA THUMPD3-AS1 in regulating OA biology.

METHOD

The knee normal and OA cartilage tissues from ten participants were sequenced to reveal the differentially expressed lncRNAs. The interleukin (IL)-1β-stimulated C28/I2 cell served as OA cells. Flow cytometry assays, Western blot, enzyme-linked immunosorbent assays were used for our experiments.

RESULTS

The results revealed that lncRNA THUMPD3-AS1 was downregulated in OA cartilage tissues and IL-1β-stimulated chondrocyte cell line. Overexpression of lncRNA THUMPD3-AS1 alleviated cell apoptosis and facilitated inflammatory responses, whereas knockdown had opposite effects. LncRNA THUMPD3-AS1 markedly increased the cyclin E2, cyclin-dependent kinase 4, B-cell lymphoma 2, tumor necrosis factor-α, nitric oxide, and IL-6 levels, and decreased the caspase-3 level. Furthermore, the target proteins of phosphorylation were identified as nuclear factor-κB p65 and mitogen-activated protein kinase p38, which could be indirectly suppressed by lncRNA THUMPD3-AS1 knockdown.

CONCLUSION

Our findings highlight the different effects of lncRNA THUMPD3-AS1 on cell apoptosis and inflammatory response, which extend the multiple functions of lncRNA epigenetics in OA biology.

Long noncoding RNA ZFAS1 suppresses chondrocytes apoptosis via miR-302d-3p/SMAD2 in osteoarthritis

Osteoarthritis (OA) seriously affects people's quality of life due to joint pain, stiffness, disability, and dyskinesia worldwide. Long noncoding RNA zinc finger antisense 1 (ZFAS1) is downregulated and tightly associated with proliferation, migration, apoptosis, and matrix synthesis of chondrocyte in OA. However, the molecular mechanisms of ZFAS1 in OA remain unknown. The expression correlation between ZFAS1, miR-302d-3p, and SMAD2 in OA tissues was analyzed by Pearson correlation analysis. ZFAS1 was a lower expression, and expedited proliferation and repressed apoptosis of chondrocytes. MiR-302d-3p was a direct target of ZFAS1. MiR-302d-3p hindered proliferation and facilitated apoptosis of chondrocytes. MiR-302d-3p partially reversed the effect of ZFAS1 on proliferation and apoptosis of chondrocytes. SMAD2 was positively regulated by the ZFAS1/miR-302d-3p. MiR-302d-3p-mediated proliferation and apoptosis were partly abrogated by targeting SMAD2. ZFAS1 promoted chondrocytes proliferation and repressed apoptosis possibly by regulating miR-302d-3p/SMAD2 axis, providing a potential target for OA treatment.

Role of lincRNA-Cox2 targeting miR-150 in regulating the viability of chondrocytes in osteoarthritis

Osteoarthritis (OA) is a joint disease characterised by progressive cartilage degradation and inflammation, but the detailed pathogenesis of OA remains unclear. The present study aimed to investigate the role of long intergenic non-coding RNA (lincRNA)-Cox2 in OA progression and the potential mechanism. An OA mouse model was used for in vivo experiments, and IL-1β-induced injury of mouse chondrocytes was conducted for in vitro experiments. Small interfering (si)-Cox2 was transfected into chondrocytes to elucidate the effect of lincRNA-Cox2 on OA. Quantitative reverse transcription PCR assays were conducted to detect the expression of lincRNA-Cox2 and microRNA (miR)-150. Cell proliferation and apoptosis were analysed based on an MTT assay and annexin V/propidium iodide staining, respectively. Western blotting was performed to evaluate the protein expression levels of Ki-67, PCNA, Bax, cleaved (c)-Caspase-3, c-Caspase-9 and Wnt/β-catenin pathway-associated proteins in chondrocytes. High levels of lincRNA-Cox2 were observed in cartilage tissues of the OA mouse model in vivo. In the in vitro experiments, the expression of lincRNA-Cox2 was increased in IL-1β-treated chondrocytes. Knockdown of lincRNA-Cox2 promoted the proliferation and inhibited the apoptosis of chondrocytes. Mechanistically, lincRNA-Cox2 was found to directly target miR-150, acting as a competing endogenous RNA, and the effect of si-Cox2 on the proliferation and apoptosis of chondrocytes was reversed by miR-150 inhibitors. Moreover, lincRNA-Cox2 activated the Wnt/β-catenin pathway to regulate chondrocyte proliferation and apoptosis. The present study demonstrated that silencing lincRNA-Cox2 expression plays a protective role in OA by enhancing the proliferation and suppressing the apoptosis of chondrocytes, which is related to increased miR-150 expression and activation of the Wnt/β-catenin pathway.

Exhausting circ_0136474 and Restoring miR-766-3p Attenuate Chondrocyte Oxidative Injury in IL-1β-Induced Osteoarthritis Progression Through Regulating DNMT3A

Circular RNA circ_0136474 is a new contributor of human osteoarthritis (OA) by suppressing chondrocyte proliferation. However, its role and mechanism in OA chondrocyte injury remain ill defined. Herein, we performed real-time quantitative PCR to detect RNA expression of circ_0136474, microRNA (miR)-766-3p, and DNA methyltransferase 3A (DNMT3A) and utilized Western blotting to measure protein expression of DNMT3A, matrix metalloproteinase-1 (MMP1), MMP13, collagen II, proliferating cell nuclear antigen (PCNA) and B cell lymphoma (Bcl)-2, and Bcl-2-associated X protein (Bax). Direct interaction between miR-766-3p and circ_0136474 or DNMT3A was confirmed by bioinformatics algorithms, dual-luciferase reporter assay, and RNA immunoprecipitation. Functional experiments including cell counting kit-8 assay, flow cytometry, and special assay kits were employed to measure oxidative injury in interleukin (IL)-1β-induced OA-like chondrocytes. First, IL-1β administration induced cell viability inhibition, collagen II suppression, and promotion of MMP1 and MMP13 in human chondrocyte CHON-001 cells. Expression of circ_0136474 and DNMT3A was upregulated, and miR-766-3p was downregulated in human OA cartilages and IL-1β-induced CHON-001 cells. Functionally, both blocking circ_0136474 and upregulating miR-766-3p could rescue cell viability and levels of PCNA, Bcl-2, reduced glutathione (GSH), and total superoxide dismutase (SOD), and attenuate apoptosis rate and levels of Bax, reactive oxygen species (ROS), and lipid peroxidation malondialdehyde (MDA). Mechanically, circ_0136474 served as miR-766-3p sponge to govern miR-766-3p-targeted DNMT3A expression. Accidently, restoring DNMT3A counteracted the miR-766-3p upregulation role, and silencing miR-766-3p weakened circ_0136474 knockdown effect in IL-1β-induced CHON-001 cells. In conclusion, exhausting circ_0136474 could mitigate OA chondrocyte oxidative injury through regulating miR-766-3p/DNMT3A axis.

Effect of DNA methylation on gene transcription is associated with the distribution of methylation sites across the genome in osteoarthritis

Genetics and epigenetics are important subjects in the field of osteoarthritis (OA) research. DNA methylation may affect gene transcription, but the specific mechanisms have remained to be fully elucidated. In the present study, the ChAMP methylation analysis package was used to identify differentially methylated genes (DMGs) from the dataset GSE63695 from the Gene Expression Omnibus (GEO) database. The distribution of differentially methylated sites (DMS) and the total array sites across the genome were analyzed by enrichment analysis. Subsequently, two mRNA expression profiling datasets, GSE114007 and GSE113825, were obtained from the GEO database and common differentially expressed genes (DEGs) were identified using the Limma package. Key genes were screened by analyzing the distribution of DMS across the genome consisting of DEGs and DMGs. A total of 1,662 and 1,986 DEGs were identified between OA and normal human cartilage from the GSE113825 and GSE114007 dataset, respectively. A further screening revealed 292 genes with common differences between the two datasets. A total of 574 DMS containing 394 DMGs were observed between OA and normal cartilage. Integrative analysis revealed a corresponding subset of 15 genes. Of these, 6 genes were verified by reverse transcription-quantitative PCR, confirming that the mRNA expression of 5 genes (MAP1B, FNDC1, ANLN, SCNN1A and STC2) in OA cartilage was consistent with the mRNA expression from the analysis of the datasets. Upon treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine, the mRNA levels of FNDC1 and SCNN1A were decreased, and no significant alteration in the mRNA levels of MAP1B, ANLN, KCNN4 and STC2 was observed. The incidence of differential methylation varied in subregions of the genome and the effects on transcription were associated with the distribution of DEGs across the genome. The regulation of this appears more complex than initially postulated. Combining the data on epigenetic differences of OA with the genome or transcriptome data for analysis may improve the understanding of the pathophysiological processes of OA. FNDC1 and SCNN1A may potentially be valuable biomarkers for OA.

Graphene Oxide-Doped Gellan Gum-PEGDA Bilayered Hydrogel Mimicking the Mechanical and Lubrication Properties of Articular Cartilage

Articular cartilage (AC) is a specialized connective tissue able to provide a low-friction gliding surface supporting shock-absorption, reducing stresses, and guaranteeing wear-resistance thanks to its structure and mechanical and lubrication properties. Being an avascular tissue, AC has a limited ability to heal defects. Nowadays, conventional strategies show several limitations, which results in ineffective restoration of chondral defects. Several tissue engineering approaches have been proposed to restore the AC's native properties without reproducing its mechanical and lubrication properties yet. This work reports the fabrication of a bilayered structure made of gellan gum (GG) and poly (ethylene glycol) diacrylate (PEGDA), able to mimic the mechanical and lubrication features of both AC superficial and deep zones. Through appropriate combinations of GG and PEGDA, cartilage Young's modulus is effectively mimicked for both zones. Graphene oxide is used as a dopant agent for the superficial hydrogel layer, demonstrating a lower friction than the nondoped counterpart. The bilayered hydrogel's antiwear properties are confirmed by using a knee simulator, following ISO 14243. Finally, in vitro tests with human chondrocytes confirm the absence of cytotoxicity effects. The results shown in this paper open the way to a multilayered synthetic injectable or surgically implantable filler for restoring AC defects.

Comprehensive analysis of lncRNA and mRNA based on expression microarray profiling reveals different characteristics of osteoarthritis between Tibetan and Han patients

Background

Osteoarthritis (OA) is thought to be the most prevalent chronic joint disease, especially in Tibet of China. Here, we aimed to explore the integrative lncRNA and mRNA landscape between the OA patients of Tibet and Han.

Methods

The lncRNA and mRNA expression microarray profiling was performed by SurePrint G3 Human Gene Expression 8x60K v2 Microarray in articular cartilage samples from OA patients of Han nationality and Tibetans, followed by GO, KEGG, and trans-regulation and cis-regulation analysis of lncRNA and mRNA.

Results

We found a total of 117 lncRNAs and 297 mRNAs differently expressed in the cartilage tissues of Tibetans (n = 5) comparing with those of Chinese Han (n = 3), in which 49 lncRNAs and 158 mRNAs were upregulated, and 68 lncRNAs and 139 mRNAs were downregulated. GO and KEGG analysis showed that several unreported biological processes and signaling pathways were particularly identified. LncRNA-mRNA co-expression analysis revealed a remarkable lncRNA-mRNA relationship, in which OTOA may play a critical role in the different mechanisms of the OA progression between Tibetans and Chinese Han.

Conclusion

This study identified different lncRNA/mRNA expression profiling between OA patients of Tibetans and Han, which were involved in many characteristic biological processes and signaling pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02213-y.

Therapeutic effects of turmeric or curcumin extract on pain and function for individuals with knee osteoarthritis: a systematic review

Purpose

To determine whether supplementation with turmeric or curcumin extract effects pain and physical function in individuals with knee osteoarthritis (OA). Second, we investigated the therapeutic response (pain and function) of turmeric compared with non-steroidal anti-inflammatory drugs (NSAIDs).

Methods

A search was conducted in MEDLINE, Embase, CINAHL and Cochrane Review. Inclusion criteria included randomised controlled trials reporting pain and physical function in humans with knee OA comparing turmeric therapy with NSAIDs or no therapy. Two reviewers screened 5273 abstracts. Risk of bias and quality were assessed via Cochrane Collaboration tool and CONSORT (Consolidated Standards of Reporting Trials) 2010, respectively.

Results

Ten studies were included in the final analysis. Eight had high methodological quality and two were categorised as good with a mean CONSORT quality score of 21.1. Nine studies had adequate sequence generation and six had adequate allocation concealment. Participants and outcome assessors were blinded in eight studies. Three of the studies compared turmeric therapy to NSAIDs. All 10 studies showed improvement in pain and function from baseline with turmeric therapy (p≤0.05). In three studies comparing turmeric to NSAIDs, there were no differences in outcome scores (p>0.05). In all studies there were no significant adverse events in the turmeric therapy group.

Conclusion

Compared with placebo, there appears to be a benefit of turmeric on knee OA pain and function. Based on a small number of studies the effects are similar to that of NSAIDs. Variables such as optimal dosing, frequency and formulation remain unclear at this time.

The physiological function of long-noncoding RNAs

The physiological processes of cells and organisms are regulated by various biological macromolecules, including long-noncoding RNAs (lncRNAs), which cannot be translated into protein and are different from small-noncoding RNAs on their length. In animals, lncRNAs are involved in development, metabolism, reproduction, aging and other life events by cis or trans effects. For many functional lncRNAs, there is growing evidence that they play different roles on cellular level and organismal level. On the other hand, many annotated lncRNAs are not essential and could be transcription noises. In this minireview, we investigate the physiological function of lncRNAs in cells and focus on their functions and functional mechanisms on the organismal level. The studies on lncRNAs using different classic animal models such as worms and flies are summarized and discussed in this article.

Circular RNA CircCDH13 contributes to the pathogenesis of osteoarthritis via CircCDH13/miR-296-3p/PTEN axis

Circular RNAs (circRNAs) are involved in a variety of human diseases; however, the function of circRNAs in osteoarthritis (OA) remains largely unknown. In this study, we investigated the role of CircCDH13 in OA and its underlying mechanisms. CircRNA expression profiles in OA and normal cartilage tissues were detected by microarray. The expression pattern, functional role, and mechanisms of CircCDH13 in OA were studied in vitro and in vivo. Gain-of-function and loss-of-function approaches were used to demonstrate the participation of CircCDH13 in OA. The regulatory relationship between CircCDH13 and miR-296-3p and miR-296-3p and phosphatase and tensin homolog (PTEN) was predicted by bioinformatics and verified by RNA pulldown and luciferase assay. Adeno-associated virus was also used to reveal the role and mechanisms of CircCDH13 in destabilization of medial meniscus (DMM)-induced OA mice. The upregulation of CircCDH13 in OA cartilage tissues significantly induces chondrocyte apoptosis, promotes extracellular matrix (ECM) catabolism, and inhibits ECM anabolism. Mechanistically, CircCDH13 contributes to OA pathogenesis by functioning as a sponge of miR-296-3p and regulating the miR-296-3p-PTEN pathway. Silencing of CircCDH13 in vivo markedly alleviated DMM-induced OA in mice. Our study revealed an important role of CircCDH13 in OA pathogenesis. Silencing of CircCDH13 could reduce chondrocyte apoptosis, inhibit ECM catabolism, and promote ECM anabolism through the miR-296-3p-PTEN pathway. It provides a potential target for developing effective interventions in treating OA.

Resveratrol alleviates the interleukin-1β-induced chondrocytes injury through the NF-κB signaling pathway

BACKGROUND

Osteoarthritis (OA) is a regular age-related disease that affects millions of people. Resveratrol (RSV) is a flavonoid with a stilbene structure with different pharmacological effects. The purpose of the experiment was to evaluate the protective role of RSV against the human OA chondrocyte injury induced by interleukin-1β (IL-1β).

METHODS

Chondrocytes were isolated from OA patients and identified by type II collagen, safranin O staining, and toluidine blue staining. Differentially expressed genes in chondrocytes treated RSV were identified by RNA sequencing. Kyoto encyclopedia of genes and genomes (KEGG) pathway as well as gene ontology (GO) were further conducted through Metascape online tool. A cell counting kit-8 (CCK-8) assay was applied to discover the viability of chondrocytes (6, 12, 24, and 48 μM). Many genes associated with inflammation and matrix degradation are evaluated by real-time PCR (RT-PCR) as well as western blot (WB). The mechanism of RSV for protecting IL-1β induced chondrocytes injury was further measured through immunofluorescence and WB assays.

RESULTS

A total of 845 differentially expressed genes (upregulated = 499, downregulated = 346) were found. These differentially expressed genes mainly enriched into negative regulation of catabolic process, autophagy, and cellular catabolic process, intrinsic apoptotic, apoptotic, and regulation of apoptotic signaling pathway, cellular response to abiotic stimulus, external stimuli, stress, and radiation. These differentially expressed genes were obviously enriched in NF-kB signaling pathway. RSV at the concentration of 48 μM markedly weakened the viability of the cells after 24 h of treatment (87% vs 100%, P < 0.05). No obvious difference was observed between the 6, 12, and 24 μM groups (106% vs 100%, 104% vs 100%, 103% vs 100%, P > 0.05). RSV (24 μM) also markedly depressed the levels of PGE2 and NO induced by IL-1β by 25% and 29% respectively (P < 0.05). Our experiment pointed out that RSV could dramatically inhibit the inflammatory response induced by IL-1β, including the MMP-13, MMP-3, and MMP-1 in human OA chondrocytes by 50%, 35%, and 33% respectively. On the other hand, RSV inhibited cyclooxygenase-2 (COX-2), matrix metalloproteinase-1 (MMP-1), MMP-3, MMP-13, and inducible nitric oxide synthase (iNOs) expression (P < 0.05), while increased collagen-II and aggrecan levels (P < 0.05). From a mechanistic perspective, RSV inhibited the degradation of IκB-α as well as the activation of nuclear factor-kappa B (NF-κB) induced by IL-1β.

CONCLUSION

In summary, RSV regulates the signaling pathway of NF-κB, thus inhibiting inflammation and matrix degradation in chondrocytes. More studies should be focused on the treatment efficacy of RSV for OA in vivo.

Nomilin targets the Keap1-Nrf2 signalling and ameliorates the development of osteoarthritis

Osteoarthritis (OA) is a long-term and inflammatory disorder featured by cartilage erosion. Here, we describe nomilin (NOM), a triterpenoid with inflammation modulatory properties in variety of disorders. In this study, we demonstrated the latent mechanism of NOM in alleviating the progress of OA both in vitro and in vivo studies. The results showed that NOM pre-treatment suppressed the IL-1β-induced over-regulation of pro-inflammation factors, such as NO, IL-6, PGE2 , iNOS, TNF-α and COX-2. Moreover, NOM also down-regulates the degradation of ECM induced by IL-1β. Mechanistically, the NOM suppressed NF-κB signalling via disassociation of Keap1-Nrf2 in chondrocytes. Furthermore, NOM delays the disease progression in the mouse OA model. To sum up, this research indicated NOM possessed a new potential therapeutic option in osteoarthritis.

Association study of the functional variants of the GLIS3 gene with risk of knee osteoarthritis

INTRODUCTION/OBJECTIVES

Osteoarthritis (OA) ranks the most common joint disorder and the leading cause of disability. Growing evidence has revealed that OA has a strong genetic background, except for aging and obesity. The aim of this study is to determine the associations between potential functional variants of the GLIS3 and GLIS3-AS1 gene and risk of knee OA among a Chinese population.

METHODS

In this case-control study with 810 knee OA cases and 900 healthy controls, seven selected functional SNPs of the GLIS3 and GLIS3-AS1 gene were evaluated.

RESULTS

We found minor alleles of rs10116772 (OR: 0.80, 95% CI: 0.69-0.92, P = 0.002), rs7045410 (OR: 0.74, 95% CI: 0.61-0.92, P = 0.005), and rs7032713 (OR: 0.76, 95% CI: 0.63-0.93, P = 0.006) were significantly associated with decreased risk of knee OA. Results of the dominant and recessive model, stratified analyses using Kellgren-Lawrence (KL) grading presented that the significant associations were not materially changed. Haplotype analysis indicated that haplotype CGT (OR: 0.66, 95% CI: 0.46-0.96, P = 0.031) and ATT (OR: 0.76, 95% CI: 0.6-0.95, P = 0.017) were significantly associated with decreased risk of knee OA. Further, they were also significantly associated with lower expression level of GLIS3, as well as higher expression level of GLIS3-AS1 in the articular cartilage specimens. Genotype-tissue expression (GTEX) data also validated that minor alleles of rs7045410 and rs7032713 were significantly associated with higher expression level of GLIS3-AS1 in thyroid and pituitary tissues (P < 0.001).

CONCLUSIONS

These findings revealed the essential role of genetic variants of the GLIS3 and GLIS3-AS1 gene in the occurrence of knee OA together. Key Point • Functional variants of the GLIS3 and GLIS3-AS1 gene were significantly associated with decreased risk of knee OA.

LncRNA LOXL1-AS1 is transcriptionally activated by JUND and contributes to osteoarthritis progression via targeting the miR-423-5p/KDM5C axis

AIMS

This study focused on investigating the potential role of long non-coding RNA (lncRNA) lysyl oxidase like 1 antisense RNA 1 (LOXL1-AS1) in the progression of osteoarthritis (OA).

MATERIALS AND METHODS

qRT-PCR assay was applied to detect gene expression, while western blot was performed to measure levels of apoptosis-related proteins. CCK-8, colony formation and TUNEL assays were conducted to explore the functional role of LOXL1-AS1 in OA. ChIP assay was utilized to assess the affinity between JunD proto-oncogene, AP-1 transcription factor subunit (JUND) and LOXL1-AS1 promoter. Mechanism experiments were implemented to investigate the underlying molecular mechanism of LOXL1-AS1.

KEY FINDINGS

LOXL1-AS1 was up-regulated in OA cartilage tissues. Silencing LOXL1-AS1 hampered proliferation and inflammation, yet promoting apoptosis in chondrocytes. LOXL1-AS1 was transcriptionally activated by JUND1. LOXL1-AS1 sequestered miR-423-5p and abolished miR-423-5p-mediated repression on lysine demethylase 5C (KDM5C), thus promoted the development of OA.

SIGNIFICANCE

LncRNA LOXL1-AS1 is transcriptionally activated by JUND and facilitates the proliferation and inflammation of chondrocytes via elevating miR-423-5p-mediated KDM5C in OA, which may provide potential therapeutic target for OA.

Stabilization of HIF-1α alleviates osteoarthritis via enhancing mitophagy

Mitochondrial dysfunction leads to osteoarthritis (OA) and disc degeneration. Hypoxia inducible factor-1α (HIF-1α) mediated mitophagy has a protective role in several diseases. However, the underlying mechanism of HIF-1α mediated mitophagy in OA remains largely unknown. This current study was performed to determine the effect of HIF-1α mediated mitophagy on OA. Therefore, X-ray and tissue staining including HE staining, safranin O-fast green (S-O) and Alcian Blue were used to assess imageology and histomorphology differences of mouse knee joint. Transcriptional analysis was used to find the possible targets in osteoarthritis. Western blot analysis, RT-qPCR and immunofluorescence staining were used to detect the changes in gene and protein levels in the vitro experiment. The expression of HIF-1α was increased in human and mouse OA cartilage. HIF-1α knockdown by siRNA further impair the hypoxia-induced mitochondrial dysfunction; In contrast, HIF-1α mediated protective role was reinforced by prolylhydroxylase (PHD) inhibitor dimethyloxalylglycine (DMOG). In addition, HIF-1α stabilization could alleviate apoptosis and senescence via mitophagy in chondrocytes under hypoxia condition, which could also ameliorate surgery-induced cartilage degradation in mice OA model. In conclusion, HIF-1α mediated mitophagy could alleviate OA, which may serve as a promising strategy for OA treatment.

CircGCN1L1 promotes synoviocyte proliferation and chondrocyte apoptosis by targeting miR-330-3p and TNF-α in TMJ osteoarthritis

Altered expression of circular RNAs (circRNAs) has been identified in various human diseases. In this study, we investigated whether circRNAs function as competing endogenous RNAs to regulate the pathological process of temporomandibular joint osteoarthritis (TMJOA). High-throughput sequencing of mRNA (RNA seq) was performed to detect the expression of circRNAs in TMJOA and control synovial tissues isolated from humans. The differentially upregulated circGCN1L1 (hsa_circ_0000448) in synoviocyte was validated in vitro and in vivo. Here we demonstrate the interactions between circGCN1L1 and both miR-330-3p and tumor necrosis factor-α (TNF-α) through bioinformatics predictions, luciferase report assays, and fluorescence in situ hybridization. mRNA expression profiles of TNF-α-stimulated synoviocyte showed that circGCN1L1 and p65 expressions were upregulated by TNF-α. Moreover, miR-330-3p was negatively correlated with TNF-α secretion. Further, we found that miR-330-3p directly targeted TNF and restrained the production of matrix-degrading enzymes (MMP3, MMP13, and ADAMTS4). Mechanistic studies unveiled that circGCN1L1 in TMJOA synovial tissues and cells may be associated with condylar chondrocyte apoptosis and synoviocyte hyperplasia. Moreover, intra-articular injection of shcircGCN1L1 alleviated TMJOA progression in rat models. Altogether, we elucidated the important roles of a novel circRNA, namely, circGCN1L1, which induced inflammation in TMJ synoviocytes and decreased anabolism of the extracellular matrix (ECM) through miR-330-3p and TNF-α gene. This circRNA may represent a potentially effective therapeutic strategy against TMJOA progression at an early stage.

Impact of miR-SNP rs2910164 on miR-146a expression in osteoarthritic chondrocytes

PURPOSE

MiR-146a acts as a negative inflammatory mediator in different diseases and has been implicated in osteoarthritis (OA) pathogenesis. In our study, we investigated the association between miR-SNP rs2910164 and OA susceptibility and its role on the expression of miR-146a, inflammatory and catabolic mediators in osteoarthritic chondrocytes.

MATERIALS AND METHODS

Genetic association analysis was performed in 1688 knee OA patients and healthy individuals of Greek origin. Genomic DNA was extracted from blood and genotyped for rs2910164 (G > C) using Restriction-Fragment Length Polymorphism (RFLP). Total RNA was extracted from chondrocytes of 18 OA patients and miR-146a, IL-1 Receptor-Associated Kinase 1 (IRAK-1), TNF Receptor-Associated Factor 6 (TRAF-6), A Disintegrin and Metalloproteinase with Thrombospondin Motifs 5 (ADAMTS-5), Matrix Metalloproteinase-13 (MMP-13), Interleukin-6 (IL-6), Interleukin-1 Beta (IL-1β) and Tumor Necrosis Factor-Alpha (TNF-α) expression was evaluated using quantitative Real-Time PCR (qRT-PCR).

RESULTS

OA patients carrying rs2910164-GC and CC genotypes did not have an increased risk for OA development compared to GG genotype carriers. MiR-146a expression in OA chondrocytes was significantly lower in patients with rs2910164-GC genotype than in the GG carriers. OA patients carrying the rs2910164-GC genotype in their chondrocytes exhibited increased IRAK-1, TRAF-6, MMP-13, IL-1β and IL-6 expression levels compared with rs2910164-GG carriers.

CONCLUSION

We demonstrate, for the first time, that miR-SNP rs2910164 in miR-146a gene is associated with reduced miR-146a and increased inflammatory and catabolic mediators' expression in OA chondrocytes. Our data imply that genetic variations in miRNAs linked to OA pathogenesis may regulate their expression levels, suggesting new therapeutic strategies for patients with cartilage diseases.

Silence of lncRNA MIAT protects ATDC5 cells against lipopolysaccharides challenge via up-regulating miR-132

The over-expanding role of lncRNA myocardial infarction associated transcript (MIAT) in various human diseases has been recently revealed. This study attempted to see the role of MIAT in a cell model of osteoarthritis (OA). ATDC5 cells were subjected to lipopolysaccharides (LPS) to mimic a cell model of OA. The effects of MIAT on the model were tested by performing CCK-8 assay, flow cytometry, qRT-PCR, western blot and ELISA. The downstream miRNA and signalling pathways were studied by utilizing qRT-PCR and western blot. Transfection of ATDC5 cells with the shRNA specific against MIAT significantly attenuated LPS-evoked apoptosis and cytokines release. At the meantime, the viability loss and the cleavage of caspases were ameliorated as well. MIAT overexpressed lead to the opposite result. Further, miR-132 was found to be negatively regulated by MIAT. The protective effects of MIAT silence were flattened when miR-132 expression was suppressed. Besides that the inhibitory effects of MIAT silence on LPS-evoked NF-κB and JNK activation were eliminated by miR-132 silence. This study illustrated that silence of MIAT protected ATDC5 cells against LPS challenge. The chondroprotective effects of MIAT silence may be via up-regulation of miR-132 and inhibition of NF-κB and JNK pathways.

DNA methyltransferase genes polymorphisms are associated with primary knee osteoarthritis: a matched case-control study

DNA methylation is an epigenetic mechanism involved in the development of primary osteoarthritis (OA). The association between DNA methyltransferases (DNMTs) genes polymorphisms and diseases in which DNA methylation plays a role in their pathogenesis has been described (e.g., cancer); however, its relationship with OA has not been investigated. The aim of this study was to analyze the association between DNMT1, DNMT3A, and DNMT3B polymorphisms with radiologic primary knee OA in Mexican mestizo population. A matched case-control study was conducted (ratio, 1:1). Cases included 244 subjects with definite radiographic knee OA (grade ≥ 2). Controls were matched by age and gender and were subjects with no definite radiographic knee OA/normal (grade < 2). The DNMTs polymorphisms were genotyped by TaqMan allelic discrimination assays. Conditional logistic regression was carried out, and the genetic association was tested under co-dominant, dominant, and recessive inheritance models. Haplotypes for DNMT1 polymorphisms were constructed and their associations were also tested. The CC genotypes of rs2228611 and rs2228612 of DNMT1 were associated with a lower risk for primary knee OA under a co-dominant and a recessive model [OR (95% CI) 0.4 (0.2-0.8)/0.5 (0.3-0.8) and 0.3 (0.1-0.8)/0.3 (0.1-0.7), respectively]. The CT haplotype of DNMT1 polymorphisms was associated with a lower risk [OR (95% CI) 0.71 (0.51-0.97)]. The CC genotype of rs2424913 of DNMT3B was associated with an increased risk under a co-dominant and a dominant model [OR (95% CI) 3.0 (1.1-8.0), and 1.6 (1.1-2.4), respectively]. Our results show that DNMTs polymorphisms are associated with primary knee OA.

Association of Nicotine with Osteochondrogenesis and Osteoarthritis Development: The State of the Art of Preclinical Research

The deleterious effects of nicotine on various health conditions have been well documented. Although many orthopedic diseases are adversely affected by nicotine, little is known about its preclinical effects on chondrogenesis or osteogenesis, cartilage formation, osteoarthritis (OA), and osteochondral repair. A systematic review was conducted examining the current scientific evidence on the effects of nicotine on chondrogenesis or osteogenesis in vitro, possible consequences of prenatal nicotine exposure (PNE) on cartilage and OA susceptibility in the offspring, and whether nicotine affects OA development and osteochondral repair in vivo, always focusing on their underlying mechanisms. The data reveal dose-dependent effects on articular chondrocytes and on the chondrogenesis and osteogenesis of medicinal signaling cells in vitro, with lower doses often resulting in positive effects and higher doses causing negative effects. PNE negatively affects articular cartilage development and induces OA in the offspring without or with nicotine exposure. In contrast, protective effects on OA development were only reported in monosodium iodoacetate-induced small animal models. Finally, nicotine repressed MSC-based osteochondral repair in vivo. Future studies need to investigate dose-dependent clinical effects of smoking on cartilage quality in offspring, OA susceptibility and progression, and osteochondral repair more in detail, thus identifying possible thresholds for its pathological effects.

LncRNA PART-1 targets TGFBR2/Smad3 to regulate cell viability and apoptosis of chondrocytes via acting as miR-590-3p sponge in osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease that commonly occurs in the elderly. This study focused on apoptosis and explored the modulating effects of long non‐coding (lncRNAs) prostate androgen‐regulated transcript‐1 (PART‐1) on chondrocytes apoptosis. In the present study, the PART‐1 expression level was down‐regulated in the OA cartilages. Silence of PART‐1 decreased the cell viability and promoted chondrocytes apoptosis. Overexpression of PART‐1 could reverse the effects induced by interleukin 1β (IL‐1β) stimulation, thus slowing down the apoptosis rate. MiR‐590‐3p was found to be the potential target, and RNA immunoprecipitation and luciferase activity assay confirmed the binding between PART‐1 and miR‐590‐3p. Moreover, miR‐590‐3p was down‐regulated by PART‐1 and was negatively associated with PART‐1. Transforming growth factor‐beta receptor type 2 (TGFBR2) was positively associated with PART‐1. Down‐regulation of PART‐1 decreased cell viability and induced cell apoptosis, which was partially reversed by miR‐590‐3p silence or TGFBR2 overexpression; while overexpression of PART‐1 increased the cell viability and decreased the caspase 3 activity and apoptotic rates, and the effects were partially attenuated by miR‐590‐3p overexpression or silence of TGFBR2 in IL‐1β‐stimulated chondrocytes. Knock‐down of PART‐1 down‐regulated both Smad3 and p‐Smad3 protein levels, which was reversed by miR‐590‐3p inhibition or TGFBR2 overexpression. Smad3 expression level was lower in the OA group than that in the normal group and was positively associated with the PART‐1 expression level. Collectively, the study revealed that lncRNA PART‐1 regulates the apoptosis of chondrocytes in OA by acting as a sponge for miR‐590‐3p, which subsequently regulates TGFBR2/Smad3 signalling.

Renin-angiotensin system in osteoarthritis: A new potential therapy

Osteoarthritis (OA) is one of the most common chronic joint diseases. However, the mechanism remains unclear. The traditional renin-angiotensin system (RAS) is an important system for regulating homeostasis and controlling balance. In recent years, RAS-related components have played an important role in the occurrence of OA. The purpose of this review is to summarize the research results of RAS-related components that are associated with OA. This study systematically searched e-medical databases such as PubMed, Embase, Medline, and Web of Science. The search targets included English publications describing the effects of RAS-related components in OA, including the role of renin, angiotensin-converting enzyme (ACE), Angiotensin II (Ang II), and angiotensin receptor (ATR). Additionally, this study summarizes the potential pathways for RAS-related components to intervene in OA. This study found that RAS-related components including renin, ACE, Ang II, AT1R and AT2R are involved in inflammation and chondrocyte hypertrophy in OA. RAS is involved in signaling pathways including the NF-κB, JNK, VEGFR/Tie-2, and the Axna2/Axna2R axis ones, which may be potential targets for the treatment of OA. Although there are few studies on RAS in the field of OA, the pathogenic effect of RAS-related components is still an important topic in OA treatment, and great progress may be made in this aspect in future studies.

Chondroitin Sulfate Safety and Quality

The industrial production of chondroitin sulfate (CS) uses animal tissue sources as raw material derived from different terrestrial or marine species of animals. CS possesses a heterogeneous structure and physical-chemical profile in different species and tissues, responsible for the various and more specialized functions of these macromolecules. Moreover, mixes of different animal tissues and sources are possible, producing a CS final product having varied characteristics and not well identified profile, influencing oral absorption and activity. Finally, different extraction and purification processes may introduce further modifications of the CS structural characteristics and properties and may lead to extracts having a variable grade of purity, limited biological effects, presence of contaminants causing problems of safety and reproducibility along with not surely identified origin. These aspects pose a serious problem for the final consumers of the pharmaceutical or nutraceutical products mainly related to the traceability of CS and to the declaration of the real origin of the active ingredient and its content. In this review, specific, sensitive and validated analytical quality controls such as electrophoresis, eHPLC (enzymatic HPLC) and HPSEC (high-performance size-exclusion chromatography) able to assure CS quality and origin are illustrated and discussed.