Upregulation of lncRNA HOTAIR contributes to IL-1β-induced MMP overexpression and chondrocytes apoptosis in temporomandibular joint osteoarthritis

Mechanisms Underlying Sex Differences in Temporomandibular Disorders and Their Comorbidity with Migraine

Sexual dimorphism in temporomandibular disorders (TMDs) and their comorbidity with migraine are important phenomena observed in clinics. TMDs are the most prevalent orofacial pain conditions with jaw joint and masseter muscle dysfunction. Migraine is the predominant headache commonly associated with TMDs. Women much more often suffer from this orofacial pain than men. However, currently, there is no gender-specific therapy for such pain conditions. Understanding the pathophysiological mechanisms behind sex differences in TMDs as well as their comorbidity with migraines is essential for developing novel approaches for gender-specific treatment of TMDs and related orofacial pain comorbidity. In this review, we summarize recent research progress regarding sex differences in TMDs, focusing on the underlying mechanisms including craniofacial anatomy, hormonal regulation, and roles of opioids, transient receptor potential channels, and endocannabinoid systems. We also discuss the mechanisms of comorbid TMDs and migraine. The information covered in this review will provide mechanistic insights into sex differences in TMDs and their comorbidity with migraine, which could aid in developing effective treatment strategies for the overlapping orofacial pain condition.

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.

Transcriptomics analyses of IL-1β-stimulated rat chondrocytes in temporomandibular joint condyles and effect of platelet-rich plasma

The biological mechanism of action of platelet-rich plasma (PRP) in the treatment of temporomandibular joint (TMJ) osteoarthritis remains unclear. This study explored the mechanisms underlying interleukin (IL)-1β-induced inflammation and investigated the effect of PRP on TMJ condylar chondrocytes. Primary chondrocytes were isolated from the TMJ condyle of 4-week-old rats, and differentially expressed genes among three treatment groups (phosphate-buffered saline [control], IL-1β, and IL-1β + PRP) were identified using RNA-seq and characterized using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes path-enrichment analyses. IL-1β caused inflammatory injury to chondrocytes by upregulating the TNF, NF-κB, and IL-17 signaling pathways and downregulating the MAPK and PI3K/Akt signaling pathways. PRP activated the MAPK and PI3K/Akt signaling pathways, exerting a protective effect on IL-1β-induced chondrocytes. PRP also activated the TNF and IL-17 signaling pathways, producing an inflammatory effect. Additionally, PRP increased the mRNA expression of the matrix catabolism-related genes Mmp3, Mmp9, and Mmp13; the proliferative markers Mki67 and PCNA; and the anti-apoptotic genes of the Bcl-2 family (Bcl2a1 and Bok), while reducing the expression of the pro-apoptotic genes Casp4 and Casp12. The findings suggest that the protective effect of PRP on IL-1β-induced chondrocyte injury is mainly achieved via MAPK-PI3K/Akt signaling, increasing cell proliferation and inhibiting cell apoptosis.

Level of Disability after Total Hip Replacement in Patients with Some COMT Gene Polymorphism

BACKGROUND

The COMT gene encodes the enzyme catechol-O-methyltransferase, which is a key modulator of dopaminergic and adrenergic neurotransmission. Hip osteoarthritis is accompanied by reduced mobility and some level of disability. In our study, we analyzed the association between some COMT gene polymorphisms and reduced mobility in patients after total hip replacement (THR).

METHODS

The operative procedures were performed on 195 patients with symptomatic and radiologically advanced hip osteoarthritis. In the postoperative follow-up, we assessed hip function with the Harris Hip Score (HHS) and the degree of disability with the Oswestry Disability Index (ODI). These procedures were repeated three times at defined intervals (one week, six weeks, and six months) after the total hip replacement. Genomic DNA was extracted from peripheral blood. SNPs in the COMT genes rs4680:A>G, rs6269:A>G, rs4633:C>T, and rs4818:C>G were genotyped.

RESULTS

Our findings suggest an association between COMT gene variability and the level of disability measured by the Oswestry Disability Index (ODI) in patients after total hip replacement (THR).

CONCLUSIONS

A higher number of COMT G alleles (rs4818) is an independent factor in a significant reduction in disability degree at both one week and six months after total hip replacement (THR), regardless of age or gender.

The emerging role of lncRNAs in osteoarthritis development and potential therapy

Osteoarthritis impairs the functions of various joints, such as knees, hips, hands and spine, which causes pain, swelling, stiffness and reduced mobility in joints. Multiple factors, including age, joint injuries, obesity, and mechanical stress, could contribute to osteoarthritis development and progression. Evidence has demonstrated that genetics and epigenetics play a critical role in osteoarthritis initiation and progression. Noncoding RNAs (ncRNAs) have been revealed to participate in osteoarthritis development. In this review, we describe the pivotal functions and molecular mechanisms of numerous lncRNAs in osteoarthritis progression. We mention that long noncoding RNAs (lncRNAs) could be biomarkers for osteoarthritis diagnosis, prognosis and therapeutic targets. Moreover, we highlight the several compounds that alleviate osteoarthritis progression in part via targeting lncRNAs. Furthermore, we provide the future perspectives regarding the potential application of lncRNAs in diagnosis, treatment and prognosis of osteoarthritis.

Biological principles of adult degenerative scoliosis

The global aging population has led to an increase in geriatric diseases, including adult degenerative scoliosis (ADS). ADS is a spinal deformity affecting adults, particularly females. It is characterized by asymmetric intervertebral disc and facet joint degeneration, leading to spinal imbalance that can result in severe pain and neurological deficits, thus significantly reducing the quality of life. Despite improved management, molecular mechanisms driving ADS remain unclear. Current literature primarily comprises epidemiological and clinical studies. Here, we investigate the molecular mechanisms underlying ADS, with a focus on angiogenesis, inflammation, extracellular matrix remodeling, osteoporosis, sarcopenia, and biomechanical stress. We discuss current limitations and challenges in the field and highlight potential translational applications that may arise with a better understanding of these mechanisms.

The p65-LOC727924-miR-26a/KPNA3-p65 regulatory loop mediates vasoactive intestinal peptide effects on osteoarthritis chondrocytes

Loss and dysfunction of articular chondrocytes, which disrupt the homeostasis of extracellular matrix formation and breakdown, promote the onset of osteoarthritis (OA). Targeting inflammatory pathways is an important therapeutic strategy for OA. Vasoactive intestinal peptide (VIP) is an immunosuppressive neuropeptide with potent anti-inflammatory effects; however, its role and mechanism in OA remain unclear. In this study, microarray expression profiling from the Gene Expression Omnibus database and integrative bioinformatics analyses were performed to identify differentially expressed lncRNAs in OA samples. qRT-PCR validation of the top ten different expressed lncRNAs indicated that the expression level of intergenic non-protein coding RNA 2203 (LINC02203, also named LOC727924) was the highest in OA cartilage compared to normal cartilage. Hence, the LOC727924 function was further investigated. LOC727924 was upregulated in OA chondrocytes, with a dominant sub-localization in the cytoplasm. In OA chondrocytes, LOC727924 knockdown boosted cell viability, suppressed cell apoptosis, reactive oxygen species (ROS) accumulation, increased aggrecan and collagen II, decreased matrix metallopeptidase (MMP)-3/13 and ADAM metallopeptidase with thrombospondin type 1 motif (ADAMTS)-4/5 levels, and reduced the levels of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6). LOC727924 could interact with the microRNA 26a (miR-26a)/ karyopherin subunit alpha 3 (KPNA3) axis by competitively targeting miR-26a for KPNA3 binding, therefore down-regulating miR-26a and upregulating KPNA3; in OA chondrocytes, miR-26a inhibition partially abolished LOC727924 knockdown effects on chondrocytes. miR-26a inhibited the nuclear translocation of p65 through targeting KPNA3 and p65 transcriptionally activated LOC727924, forming a p65-LOC727924-miR-26a/KPNA3-p65 regulatory loop to modulate OA chondrocyte phenotypes. In vitro, VIP improved OA chondrocyte proliferation and functions, down-regulated LOC727924, KPNA3, and p65 expression, and upregulated miR-26a expression; in vivo, VIP ameliorated destabilization of the medial meniscus (DMM)-induced damages on the mouse knee joint, down-regulated KPNA3, inhibited the nuclear translocation of p65. In conclusion, the p65-LOC727924-miR-26a/KPNA3-p65 regulatory loop modulates OA chondrocyte apoptosis, ROS accumulation, extracellular matrix (ECM) deposition, and inflammatory response in vitro and OA development in vivo, being one of the mechanisms mediating VIP ameliorating OA.

LincRNA-EPS Alleviates Inflammation in TMJ Osteoarthritis by Binding to SRSF3

Temporomandibular joint osteoarthritis (TMJOA) is a common inflammatory disease that can cause pain, cartilage degradation, and subchondral bone loss. However, the key regulatory factors and new targets for the treatment of TMJOA have yet to be determined. Long noncoding RNAs (lncRNAs) have shown remarkable potential in regulating tissue homeostasis and disease development. The long intergenic RNA-erythroid prosurvival (lincRNA-EPS) is reported to be an effective inhibitor of inflammation, but its role in TMJOA is unexplored. Here, we found that lincRNA-EPS is downregulated and negatively correlated with inflammatory factors in the condyles of TMJOA mice. LincRNA-EPS knockout aggravated inflammation and tissue destruction after TMJOA modeling. The in vitro studies confirmed that loss of lincRNA-EPS facilitated inflammatory factor expression in condylar chondrocytes, while recovered expression of lincRNA-EPS showed anti-inflammatory effects. Mechanistically, RNA sequencing revealed that the inflammatory response pathway nuclear factor-kappa B (NF-κB) was mostly affected by lincRNA-EPS deficiency. Moreover, lincRNA-EPS was proved to effectively bind to serine/arginine-rich splicing factor 3 (SRSF3) and inhibit its function in pyruvate kinase isoform M2 (PKM2) formation, thus restraining the PKM2/NF-κB pathway and the expression of inflammatory factors. In addition, local injection of the lincRNA-EPS overexpression lentivirus significantly alleviated inflammation, cartilage degradation, and subchondral bone loss in TMJOA mice. Overall, lincRNA-EPS regulated the inflammatory process of condylar chondrocytes by binding to SRSF3 and showed translational application potential in the treatment of TMJOA.

Potential pathological and molecular mechanisms of temporomandibular joint osteoarthritis

Temporomandibular joint osteoarthritis (TMJ OA) is a progressive degenerative disease of the temporomandibular joint (TMJ). The unclear etiology and mechanisms of TMJ OA bring great difficulties to early diagnosis and effective treatment, causing enormous burdens to patients' life and social economics. In this narrative review, we summarized the main pathological changes of TMJ OA, including inflammatory responses, degeneration of extracellular matrix (ECM), abnormal cell biological behaviors (apoptosis, autophagy, and differentiation) in TMJ tissue, and aberrant angiogenesis. All pathological features are closely linked to each other, forming a vicious cycle in the process of TMJ OA, which results in prolonged disease duration and makes it difficult to cure. Various molecules and signaling pathways are involved in TMJ OA pathogenesis, including nuclear factor kappa-B (NF-κB), mitogen-activated protein kinases (MAPKs), extracellular regulated protein kinases (ERKs) and transforming growth factor (TGF)-β signaling pathways et al. One molecule or pathway can contribute to several pathological changes, and the crosstalk between different molecules and pathways can further lead to a complicated condition TMJ OA. TMJ OA has miscellaneous etiology, complex clinical status, depressed treatment results, and poor prognosis. Therefore, novel in-vivo and in-vitro models, novel medicine, materials, and approaches for therapeutic procedures might be helpful for further investigation of TMJ OA. Furthermore, the role of genetic factors in TMJ OA needs to be elucidated to establish more reasonable and effective clinical strategies for diagnosing and treating TMJ OA.

LncRNA ZFAS1 protects chondrocytes from IL-1β-induced apoptosis and extracellular matrix degradation via regulating miR-7-5p/FLRT2 axis

BACKGROUND

Increasing evidence suggested that long non-coding RNAs (lncRNAs) played vital roles in osteoarthritis (OA) progression. In this study, we aimed to reveal the protective roles of lncRNA ZFAS1 in osteoarthritis (OA) and further investigated its underlying mechanism.

METHODS

The chondrocytes were stimulated by IL-1β to establish an in vitro OA model. Then, the expression of ZFAS1, miR-7-5p, and FLRT2 in chondrocytes was determined by qRT-PCR. Gain- and loss-of-function assays of ZFAS1, miR-7-5p and FLRT2 were conducted. CCK-8 assay and flow cytometry analysis were performed to detect cell viability and apoptosis rate. The expression levels of cartilage-related proteins, including MMP13, ADAMTS5, Collagen II, and Aggrecan, were measured by western blot analysis. The interaction between ZFAS1 and miR-7-5p, as well as miR-7-5p and FLRT2, was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay.

RESULTS

The expression of ZFAS1 and FLRT2 was down-regulated, while the expression of miR-7-5p was up-regulated in chondrocytes exposed to IL-1β. ZFAS1 overexpression promoted cell viability and suppressed apoptosis in IL-1β-treated chondrocytes. Besides, ZFAS1 overexpression suppressed the expression of MMP13 and ADAMTS5, but promoted the expression of Collagen II and Aggrecan to suppress ECM degradation. The mechanistic study showed that ZFAS1 sponged miR-7-5p to regulate FLRT2 expression. Furthermore, the overexpression of miR-7-5p could neutralize the effect of ZFAS1 in IL-1β-treated chondrocytes, and suppression of FLRT2 counteracted the miR-7-5p down-regulation role in IL-1β-treated chondrocytes.

CONCLUSIONS

ZFAS1 could promote cell viability of IL-1β-treated chondrocytes via regulating miR-7-5p/FLRT2 axis. Trial registration Not applicable.

Role of Long Noncoding RNAs in the Regulation of Cellular Immune Response and Inflammatory Diseases

Long noncoding RNAs (lncRNAs) are recently discovered genetic regulatory molecules that regulate immune responses and are closely associated with the occurrence and development of various diseases, including inflammation, in humans and animals. Under specific physiological conditions, lncRNA expression varies at the cell or tissue level, and lncRNAs can bind to specific miRNAs, target mRNAs, and target proteins to participate in certain processes, such as cell differentiation and inflammatory responses, via the corresponding signaling pathways. This review article summarizes the regulatory role of lncRNAs in macrophage polarization, dendritic cell differentiation, T cell differentiation, and endothelial and epithelial inflammation. In addition, it describes the molecular mechanism of lncRNAs in acute kidney injury, hepatitis, inflammatory injury of the lung, osteoarthritis, mastitis, and neuroinflammation to provide a reference for the molecular regulatory network as well as the genetic diagnosis and treatment of inflammatory diseases in humans and animals.

lncRNA-mediated synovitis in rheumatoid arthritis: A perspective for biomarker development

Long noncoding RNAs (lncRNAs) are a regulatory class of noncoding RNAs with a wide range of activities such as transcriptional and post-transcriptional regulations. Emerging evidence has demonstrated that various lncRNAs contribute to the initiation and progression of Rheumatoid Arthritis (RA) through distinctive mechanisms. The present study reviews the recent findings on lncRNA role in RA development. It focuses on the involvement of different lncRNAs in the main steps of RA pathogenesis including T cell activation, cytokine dysregulation, fibroblast-like synoviocyte (FLS) activation and joint destruction. Besides, it discusses the current findings on RA diagnosis and the potential of lncRNAs as diagnostic, prognostic and predictive biomarkers in Rheumatology clinic.

Exosomes as Potential Functional Nanomaterials for Tissue Engineering

Exosomes are cell-derived extracellular vesicles of 40-160 nm diameter, which carry numerous biomolecules and transmit information between cells. They are used as functional nanomaterials with great potential in biomedical areas, such as active agents and delivery systems for advanced drug delivery and disease therapy. In recent years, potential applications of exosomes in tissue engineering have attracted significant attention, and some critical progress has been made. This review gives a complete picture of exosomes and their applications in the regeneration of various tissues, such as the central nervous systems, kidney, bone, cartilage, heart, and endodontium. Approaches employed for modifying exosomes to equip them with excellent targeting capacity are summarized. Furthermore, current concerns and future outlook of exosomes in tissue engineering are discussed.

Emerging role of lncRNAs in osteoarthritis: An updated review

Osteoarthritis (OA) is a prevalent joint disease, which is associated with progressive articular cartilage loss, synovial inflammation, subchondral sclerosis and meniscus injury. The molecular mechanism underlying OA pathogenesis is multifactorial. Long non-coding RNAs (lncRNAs) are non-protein coding RNAs with length more than 200 nucleotides. They have various functions such as modulating transcription and protein activity, as well as forming endogenous small interfering RNAs (siRNAs) and microRNA (miRNA) sponges. Emerging evidence suggests that lncRNAs might be involved in the pathogenesis of OA which opens up a new avenue for the development of new biomarkers and therapeutic strategies. The purpose of this review is to summarize the current clinical and basic experiments related to lncRNAs and OA with a focus on the extensively studied H19, GAS5, MALAT1, XIST and HOTAIR. The potential translational value of these lncRNAs as therapeutic targets for OA is also discussed.

Long non-coding RNA Gm37494 alleviates osteoarthritis chondrocyte injury via the microRNA-181a-5p/GABRA1 axis

Objective

This study was conducted to investigate the effect of long non-coding RNA (lncRNA) Gm37494 on osteoarthritis (OA) and its related molecular mechanism.

Methods

The cartilage tissues were obtained from OA patients, and an OA mouse model was induced by the destabilization of the medial meniscus, followed by measurement of Gm37494, microRNA (miR)-181a-5p, GABRA1 mRNA, and the encoded GABA_AR_α1 protein expression. Thereafter, a cellular model was induced by interleukin-1β (IL-1β) treatment in chondrocytes, followed by ectopic and silencing experiments. Chondrocyte proliferation was detected by CCK-8 and EdU assays, chondrocyte apoptosis by flow cytometry and western blot, and the levels of inflammatory factors by ELISA. The binding of Gm37494 to miR-181a-5p was evaluated by dual-luciferase reporter gene and RIP assays, and that of GABRA1 to miR-181a-5p by dual-luciferase reporter gene and RNA pull-down assays.

Results

OA patients and mice had decreased GABRA1 mRNA and GABA_AR_α1 protein levels and elevated miR-181a-5p expression in cartilage tissues. Additionally, Gm37494 was poorly expressed in OA mice. Mechanistically, Gm37494 directly bound to and inversely modulated miR-181a-5p that negatively targeted GABRA1. In IL-1β-induced chondrocytes, Gm37494 overexpression enhanced cell proliferation and suppressed cell apoptosis and inflammation, whereas further miR-181a-5p up-regulation or GABRA1 silencing abolished these trends.

Conclusions

Conclusively, Gm37494 elevated GABRA1 expression by binding to miR-181a-5p, thus ameliorating OA-induced chondrocyte damage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03202-5.

Effects of interleukin 1β on long noncoding RNA and mRNA expression profiles of human synovial fluid derived mesenchymal stem cells

Synovial fluid-derived mesenchymal stem cells (SFMSCs) play important regulatory roles in the physiological balance of the temporomandibular joint. Interleukin (IL)-1β regulates the biological behavior of SFMSCs; however, the effects of IL-1β on long noncoding RNA (lncRNA) and mRNA expression in SFMSCs in the temporomandibular joint are unclear. Here, we evaluated the lncRNA and mRNA expression profiles of IL-1β-stimulated SFMSCs. Using microarrays, we identified 264 lncRNAs (203 upregulated, 61 downregulated) and 258 mRNAs (201 upregulated, 57 downregulated) that were differentially expressed after treatment with IL-1β (fold changes ≥ 2, P < 0.05). Kyoto Encyclopedia of Genes and Genomes pathway analysis found that one of the most significantly enriched pathways was the NF-κB pathway. Five paired antisense lncRNAs and mRNAs, eight paired enhancer lncRNAs and mRNAs, and nine paired long intergenic noncoding RNAs and mRNAs were predicted to be co-expressed. A network constructed by the top 30 K-score genes was visualized and evaluated. We found a co-expression relationship between RP3-467K16.4 and IL8 and between LOC541472 and IL6, which are related to NF-κB pathway activation. Overall, our results provide important insights into changes in lncRNA and mRNA expression in IL-1β-stimulated SFMSCs, which can facilitate the identification of potential therapeutic targets.

Transcriptomic Analysis of Trigeminal Ganglion and Spinal Trigeminal Nucleus Caudalis in Mice with Inflammatory Temporomandibular Joint Pain

Background

Persistent facial pain heavily impacts the quality of life in patients with temporomandibular joint (TMJ) disorders. Previous studies have demonstrated that long non-coding ribonucleic acid (lncRNA) is an important regulator of pain. In this study, we aimed to analyze lncRNA expression in the whole transcriptome of trigeminal ganglia (TG) and spinal trigeminal nucleus caudalis (Sp5C) in a chronic inflammatory TMJ pain mouse model.

Methods

Chronic inflammatory TMJ pain was induced by intra-TMJ injection of complete Freund’s adjuvant (CFA). Mouse TG and Sp5C tissues were harvested on day 4 after CFA injection. The lncRNA expression patterns in the whole transcriptome of TG and Sp5C were profiled with RNA sequencing.

Results

We observed that 38 lncRNAs and 849 mRNAs were differentially expressed after CFA treatment. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis further revealed relationships among those differentially expressed lncRNAs and mRNAs and their potential functions. Specific categories of biological process, cellular processes, and molecular function of the differentially expressed transcripts were ascertained.

Conclusion

Our results suggest that lncRNA expression in the whole transcriptome of trigeminal nociceptive system could contribute to the molecular mechanisms that underlie chronic inflammatory TMJ pain.

Epigenetic Regulation of Chondrocytes and Subchondral Bone in Osteoarthritis

The aim of this review is to provide an updated review of the epigenetic factors involved in the onset and development of osteoarthritis (OA). OA is a prevalent degenerative joint disease characterized by chronic inflammation, ectopic bone formation within the joint, and physical and proteolytic cartilage degradation which result in chronic pain and loss of mobility. At present, no disease-modifying therapeutics exist for the prevention or treatment of the disease. Research has identified several OA risk factors including mechanical stressors, physical activity, obesity, traumatic joint injury, genetic predisposition, and age. Recently, there has been increased interest in identifying epigenetic factors involved in the pathogenesis of OA. In this review, we detail several of these epigenetic modifications with known functions in the onset and progression of the disease. We also review current therapeutics targeting aberrant epigenetic regulation as potential options for preventive or therapeutic treatment.

Krill Oil Attenuates Inflammation in Monosodium Iodoacetate-Induced Osteoarthritic Rats, SW982 Synovial Cell Line, and Primary Chondrocytes

The aim of this study was to investigate the effects of krill oil (FJH-KO) in monoiodoacetate (MIA)-induced osteoarthritis in rat models, and H₂O₂- or lipopolysaccharide (LPS)-treated primary chondrocytes and the SW982 synovial cell line. We found that 150 mg/kg b.w. FJH-KO supplementation increased running speed, stride, and foot pressure in MIA-induced osteoarthritic rats. In the H₂O₂-treated SW982 synovial cell line and primary chondrocytes, FJH-KO treatment prevented cell death and suppressed matrix degradation by increasing the levels of anabolic factors of cartilage tissue, including aggrecan, collagen type Ⅰ, collagen type Ⅱ, tissue inhibitors of metalloproteinase (TIMP)-1, and TIMP-3, and decreasing those of catabolic factors of cartilage tissue, including phosphorylation of Smad, MMP-3, and MMP-13. In addition, FJH-KO treatment suppressed the activation of inflammation and apoptosis pathways in the LPS-treated SW982 synovial cell line and primary chondrocytes. We suggest that FJH-KO supplementation may help prevent osteoarthritis progression because of its direct effects on inflammation and apoptosis of chondrocytes.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

Long Non-coding RNAs in Rheumatology

The last decade has seen an enormous increase in long non-coding RNA (lncRNA) research within rheumatology. LncRNAs are arbitrarily classed as non-protein encoding RNA transcripts that exceed 200 nucleotides in length. These transcripts have tissue and cell specific patterns of expression and are implicated in a variety of biological processes. Unsurprisingly, numerous lncRNAs are dysregulated in rheumatoid conditions, correlating with disease activity and cited as potential biomarkers and targets for therapeutic intervention. In this chapter, following an introduction into each condition, we discuss the lncRNAs involved in rheumatoid arthritis, osteoarthritis and systemic lupus erythematosus. These inflammatory joint conditions share several inflammatory signalling pathways and therefore not surprisingly many commonly dysregulated lncRNAs are shared across these conditions. In the interest of translational research only those lncRNAs which are strongly conserved have been addressed. The lncRNAs discussed here have diverse roles in regulating inflammation, proliferation, migration, invasion and apoptosis. Understanding the molecular basis of lncRNA function in rheumatology will be crucial in fully determining the inflammatory mechanisms that drive these conditions.

Downregulation of LncRNA OIP5-AS1 Induced by IL-1β Aggravates Osteoarthritis via Regulating miR-29b-3p/PGRN

BACKGROUND

Long noncoding RNA (lncRNA) OIP5 antisense RNA 1 (OIP5-AS1) is an oncogenic lncRNA; however, its role in osteoarthritis (OA) pathology still remains unknown.

MATERIALS AND METHODS

qRT-PCR was performed to measure the expressions of OIP5-AS1, miR-29b-3p and progranulin (PGRN) mRNA in OA cartilage tissues and normal cartilage tissues. Chondrocyte cell lines, CHON-001 and ATDC5, were treated with different doses of interleukin-1β (IL-1β) to induce the inflammatory response. Overexpression plasmids, microRNA mimics, microRNA inhibitors and small interfering RNAs were constructed and transfected into CHON-001 and ATDC5 cells. CCK-8 assay was used for determining the cell viability and Transwell assay was used for monitoring cell migration. Western blot was applied to measure the expressions of apoptosis-related proteins. Enzyme-linked immunosorbent assay (ELISA) was adopted to measure the contents of inflammatory factors. StarBase and TargetScan were used to predict the binding sites between OIP5-AS1 and miR-29b-3p, miR-29b-3p and 3'-UTR of PGRN respectively, which were verified by dual luciferase reporter assay.

RESULTS

OIP5-AS1 and PGRN mRNA were downregulated while miR-29b-3p was upregulated in OA tissues and models. The up-regulated OIP5-AS1 facilitated the proliferation and migration of CHON-001 and ATDC5 cells, while ameliorated the apoptosis and inflammatory response. However, miR-29b-3p had opposite effects. PGRN was identified as a target gene of miR-29b-3p, which could be indirectly suppressed by OIP5-AS1 knockdown.

CONCLUSION

Downregulation of OIP5-AS1 induced by IL-1β could inhibit the proliferation and migration abilities of CHON-001 and ATDC5 cells and facilitate the apoptosis and inflammation response via regulating miR-29b-3p/PGRN axis.

LncRNA MEG3 Inhibits the Degradation of the Extracellular Matrix of Chondrocytes in Osteoarthritis via Targeting miR-93/TGFBR2 Axis

BACKGROUND

As a degenerative joint disease, osteoarthritis (OA) is characterized by articular cartilage degradation. Long noncoding RNAs (lncRNAs) act critical roles in the regulation of OA development, including affecting the proliferation, apoptosis, extracellular matrix (ECM) degradation, and inflammatory response of chondrocytes. The current study's aim was to investigate the regulatory function and the underlying molecular mechanism of lncRNA MEG3 in ECM degradation of chondrocytes in OA.

METHODS

In the current study, chondrocytes were induced by interleukin-1β (IL-1β) to simulate OA condition, and further assessed cell viability, lncRNA MEG3 and miR-93 expression levels. Overexpression or knockdown of lncRNA MEG3 in chondrocytes treated with IL-1β were performed to investigate the function of MEG3 in regulating cell proliferation, apoptosis and ECM degradation using EdU assay, flow cytometry, quantitative reverse transcription polymerase chain reaction (qRT-PCR), and Western blot. The interaction between MEG3 and miR-93 was assessed using qRT-PCR. Furthermore, overexpression of miR-93 was performed as recovery experiment to explore the functional mechanism of MEG3.

RESULTS

MEG3 was significantly downregulated in chondrocytes treated with IL-1β, whereas miR-93 was upregulated concomitantly. Overexpression of MEG3 induced the proliferation, suppressed the apoptosis, and relieved the degradation of ECM in IL-1β-induced chondrocytes. By contrast, knockdown of MEG3 suppressed the proliferation, promoted the apoptosis, and aggravated ECM degradation in IL-1β induced chondrocytes. In addition, MEG3 was found to relieve the inhibitive expression of TGFBR2 as a competitive endogenous RNA (ceRNA) of miR-93, and then activated transforming growth factor-β (TGF-β) signaling pathway, regulated chondrocytes ECM degradation in IL-1β induced chondrocytes subsequently.

CONCLUSION

LncRNA MEG3 targeted miR-93/TGFBR2 axis, regulated the proliferation, apoptosis and ECM degradation of chondrocytes in OA.

Potential of Exosomes as Cell-Free Therapy in Articular Cartilage Regeneration: A Review

Treatment of cartilage defects such as osteoarthritis (OA) and osteochondral defect (OCD) remains a huge clinical challenge in orthopedics. OA is one of the most common chronic health conditions and is mainly characterized by the degeneration of articular cartilage, shown in the limited capacity for intrinsic repair. OCD refers to the focal defects affecting cartilage and the underlying bone. The current OA and OCD management modalities focus on symptom control and on improving joint functionality and the patient’s quality of life. Cell-based therapy has been evaluated for managing OA and OCD, and its chondroprotective efficacy is recognized mainly through paracrine action. Hence, there is growing interest in exploiting extracellular vesicles to induce cartilage regeneration. In this review, we explore the in vivo evidence of exosomes on cartilage regeneration. A total of 29 in vivo studies from the PubMed and Scopus databases were identified and analyzed. The studies reported promising results in terms of in vivo exosome delivery and uptake; improved cartilage morphological, histological, and biochemical outcomes; enhanced subchondral bone regeneration; and improved pain behavior following exosome treatment. In addition, exosome therapy is safe, as the included studies documented no significant complications. Modifying exosomal cargos further increased the cartilage and subchondral bone regeneration capacity of exosomes. We conclude that exosome administration is a potent cell-free therapy for alleviating OA and OCD. However, additional studies are needed to confirm the therapeutic potential of exosomes and to identify the standard protocol for exosome-based therapy in OA and OCD management.

The role of the multifaceted long non-coding RNAs: A nuclear-cytosolic interplay to regulate hyaluronan metabolism

In the extracellular matrix (ECM), the glycosaminoglycan (GAG) hyaluronan (HA) has different physiological roles favouring hydration, elasticity and cell survival. Three different isoforms of HA synthases (HAS1, 2, and 3) are responsible for the production of HA. In several pathologies the upregulation of HAS enzymes leads to an abnormal HA accumulation causing cell dedifferentiation, proliferation and migration thus favouring cancer progression, fibrosis and vascular wall thickening. An intriguing new player in HAS2 gene expression regulation and HA production is the long non-coding RNA (lncRNA) hyaluronan synthase 2 antisense 1 (HAS2-AS1). A significant part of mammalian genomes corresponds to genes that transcribe lncRNAs; they can regulate gene expression through several mechanisms, being involved not only in maintaining the normal homeostasis of cells and tissues, but also in the onset and progression of different diseases, as demonstrated by the increasing number of studies published through the last decades. HAS2-AS1 is no exception: it can be localized both in the nucleus and in the cytosol, regulating cancer cells as well as vascular smooth muscle cells behaviour.

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Hyaluronan is a component of the extracellular matrix and is synthetised by three isoenzymes named HAS1, 2, and 3.

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In several pathologies an upregulation of HAS2 leads to an abnormal accumulation of HA.

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The long non-coding RNA is a new specific epigenetic regulator of HAS2.

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In the nucleus HAS2-AS1 modulates chromatin structure around HAS2 promoter increasing transcription.

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In the cytosol, HAS2-AS1 can interact with several miRNAs altering the expression of several genes as well as can stabilise HAS2 mRNA forming RNA: RNA duplex.

Knockdown of long noncoding RNA HOTAIR inhibits osteoarthritis chondrocyte injury by miR-107/CXCL12 axis

BACKGROUND

Osteoarthritis (OA) is a joint disease characterized via destruction of cartilage. Chondrocyte damage is associated with cartilage destruction during OA. Long noncoding RNAs (lncRNAs) are implicated in the regulation of chondrocyte damage in OA progression. This study aims to investigate the role and underlying mechanism of lncRNA homeobox antisense intergenic RNA (HOTAIR) in OA chondrocyte injury.

METHODS

Twenty-three OA patients and healthy controls without OA were recruited. Chondrocytes were isolated from OA cartilage tissues. HOTAIR, microRNA-107 (miR-107) and C-X-C motif chemokine ligand 12 (CXCL12) levels were measured by quantitative real-time polymerase chain reaction and western blot. Cell proliferation, apoptosis and extracellular matrix (ECM) degradation were measured using cell counting kit-8, flow cytometry and western blot. The target interaction was explored by bioinformatics, luciferase reporter and RNA immunoprecipitation assays.

RESULTS

HOTAIR expression was enhanced, and miR-107 level was reduced in OA cartilage samples. HOTAIR overexpression inhibited cell proliferation, but induced cell apoptosis and ECM degradation in chondrocytes. HOTAIR knockdown caused an opposite effect. MiR-107 was sponged and inhibited via HOTAIR, and knockdown of miR-107 mitigated the effect of HOTAIR silence on chondrocyte injury. CXCL12 was targeted by miR-107. CXCL12 overexpression attenuated the roles of miR-107 overexpression or HOTAIR knockdown in the proliferation, apoptosis and ECM degradation. CXCL12 expression was decreased by HOTAIR silence, and restored by knockdown of miR-107.

CONCLUSION

HOTAIR knockdown promoted chondrocyte proliferation, but inhibited cell apoptosis and ECM degradation in OA chondrocytes by regulating the miR-107/CXCL12 axis.

Blocking HOTAIR protects human chondrocytes against IL-1β-induced cell apoptosis, ECM degradation, inflammatory response and oxidative stress via regulating miR-222-3p/ADAM10 axis

BACKGROUND

Long non-coding RNA (lncRNA) HOX transcript antisense RNA (HOTAIR) contributes to cartilage damages including osteoarthritis (OA). While, its role and mechanism in chondrocytes is incompletely clear.

METHODS

HOTAIR, microRNA (miR)-222-3p and ADAM metalloproteinase-like domain 10 (ADAM10) expressions were detected by real-time quantitative PCR and western blotting. The interaction between miR-222-3p and HOTAIR or ADAM10 was confirmed by dual-luciferase reporter assay. Cell injury was measured by MTS method, flow cytometry, western blotting, enzyme-linked immunosorbent assay for collagen Type II, type X, sex determining region Y-box 9 (SOX9), matrix metalloproteinase (MMP)-13, interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α, and special assay kits for malondialdehyde (MDA), reactive oxygen species (ROS) and superoxide dismutase (SOD).

RESULTS

HOTAIR was highly expressed in human OA cartilages and IL-1β-induced OA model in immortalized chondrocytes (C-28/I2). Under IL-1β stress, blocking HOTAIR was responsible to high mitochondrial activity and low early apoptosis rate, accompanied with increased B cell lymphoma (Bcl)-2 and LC3B-II/I proteins, boosted IL-10 and SOD productions, suppressed cleaved caspase-3 and p62 proteins, and decreased MDA and ROS levels, as well as elevated secretions of Type II collagen, Type X collagen, SOX9, MMP-13, IL-6, and TNF-α. Moreover, miR-222-3p was a target of HOTAIR, and its overexpression and knockdown could suppress and aggravate IL-1β-induced chondrocytes injury. Furthermore, restoring ADAM10, a target gene of miR-222-3p, counteracted the protective role of miR-222-3p upregulation.

CONCLUSION

HOTAIR might contribute to IL-1β-induced chondrocytes death, inflammation, extracellular matrix degradation, and oxidative stress in OA via miR-222-3p/ADAM10 axis.

Overexpression of long non-coding RNA AP001505.9 inhibits human hyaline chondrocyte dedifferentiation

Autologous chondrocyte implantation (ACI) is an effective method for treating chronic articular cartilage injury and degeneration; however, it requires large numbers of hyaline chondrocytes, and human hyaline chondrocytes often undergo dedifferentiation in vitro. Moreover, although long non-coding RNAs (lncRNAs) regulate gene expression in many pathological and physiological processes, their role in human hyaline chondrocyte dedifferentiation remains unclear. Here, we examined lncRNA and mRNA expression profiles in human hyaline chondrocyte dedifferentiation using microarray analysis. Among the many lncRNAs and mRNAs that showed differential expression, lncRNA AP001505.9 (ENST00000569966) was significantly downregulated in chondrocytes after dedifferentiation. We next performed gene ontology, pathway, and CNC (coding-non-coding gene co-expression) analyses to investigate potential regulatory mechanisms for AP001505.9. Pellet cultures were then used to redifferentiate dedifferentiated chondrocytes, and AP001505.9 expression was upregulated after redifferentiation. Finally, both in vitro and in vivo experiments demonstrated that AP001505.9 overexpression inhibited dedifferentiation of chondrocytes. This study characterizes lncRNA expression profiles in human hyaline chondrocyte dedifferentiation, thereby identifying new potential mechanisms of chondrocyte dedifferentiation worthy of further investigation.

LncRNA KCNQ1OT1 attenuates osteoarthritic chondrocyte dysfunction via the miR-218-5p/PIK3C2A axis

The occurrence of osteoarthritis is closely related to chondrocyte dysfunction caused by cellular inflammatory response and matrix degradation, which seriously affect the quality of life of patients. Therefore, this study aimed to investigate the role of potassium voltage-gated channel subfamily Q member 1 overlapping transcript 1 (KCNQ1OT1), a member of the lncRNA voltage-gated channel subfamily Q, in the development of osteoarthritis. In this study, RT-qPCR results showed that KCNQ1OT1 expression was downregulated in osteoarthritic chondrocytes compared with normal chondrocytes. In addition, upregulation of KCNQ1OT1 significantly enhanced the viability of osteoarthritic chondrocytes, inhibited cell apoptosis, and reduced the release of inflammatory cytokines and metal matrix enzymes. Next, bioinformatics analysis and luciferase reporter gene analysis predicted and validated the targeting relationship between KCNQ1OT1 and miR-218-5p. We found that the expression of miR-218-5p was significantly upregulated in osteoarthritic chondrocytes, and knockdown of miR-218-5p significantly enhanced the viability of osteoarthritic chondrocytes, inhibited apoptosis, and decreased the abundance of inflammatory cytokines and metal matrix enzymes. Furthermore, the targeting relationship between miR-218-5p and recombinant phosphoinositide-3-kinase class-2-alpha polypeptide (PIK3C2A) was identified, and overexpression of PIK3C2A enhanced cell viability, and reduced apoptosis and secretion of inflammatory factors. Finally, we found that miR-218-5p overexpression reversed the protective effect of overexpression of KCNQ1OT1 or PIK3C2A on osteoarthritic chondrocytes. In conclusion, our results demonstrated that KCNQ1OT1 upregulated PIK3C2A and activated the PI3K/AKT/mTOR pathway to reduce chondrocyte dysfunction by targeting miR-218-5p, providing new insights into the pathogenesis of osteoarthritis.

Long non-coding RNA PCAT-1 regulates apoptosis of chondrocytes in osteoarthritis by sponging miR-27b-3p

BACKGROUND

Osteoarthritis (OA) is a non-inflammatory degenerative disease, with progressive damages on the articular cartilages. In recent years, researchers have paid many efforts in the diagnostics and treatments of OA. However, no effective therapeutic method has been revealed to help inhibit the development of OA. Herein, we studied the roles and associations of PCAT-1 and miR-27-3p in the pathogenesis OA.

METHODS

OA articular cartilages and healthy articular cartilages were isolated for investigation. The chondrocytes were isolated from articular cartilage samples. QRT-PCR and western blotting were used for the detection of expression of genes and proteins. cell Titer 96® AQueous one proliferation kit was applied for detect cell viability of Chondrocytes transfected with negative control vector, pcDNA3.1 PCAT-1 plasmid or siRNA against PCAT-1. RNA pull-down assays and Luciferase reporter assay were used to confirm the connection. SPSS 17.0 was employed for statistical analysis.

RESULTS

We found that the expressions of PCAT-1 were up-regulated in OA chondrocytes compared with normal chondrocytes. si-PCAT-1 suppressed apoptotic OA chondrocytes. Over-expression of PCAT-1 enhanced the apoptosis of normal chondrocytes. In addition, the online database and luciferase assay confirmed that PCAT-1 could directly target miR-27b-3p. PCAT-1 could promote the apoptosis of OA and normal chondrocytes through binding with miR-27b-3p.

CONCLUSIONS

Based on the comparisons and analysis, we could conclude that lncRNA PCAT-1 regulated the apoptosis of chondrocytes through sponging miR-27b-3p in OA. PCAT-1 has potential values to act as a new therapeutic target for OA patients.

Long non-coding RNA HOTAIR knockdown alleviates gouty arthritis through miR-20b upregulation and NLRP3 downregulation

This study aimed to determine the mechanism underlying the regulation of gout by the HOX transcript antisense RNA (HOTAIR) long non-coding RNA (lncRNA). The expression levels of HOTAIR, miR-20b, and Nlrp3 were estimated by qRT-PCR and western blotting. The methylation level of HOTAIR was detected by methylation-specific PCR. The recruitment of DNA methyltransferase 1 (DNMT1) to the lncRNA HOTAIR promoter was confirmed by a ChIP assay. RNA immunoprecipitation and RNA pull-down assays were used to confirm the interaction between HOTAIR and miR-20b. LncRNA HOTAIR and Nlrp3 expression was upregulated, and that of miR-20b was downregulated in synovial fluid mononuclear cells (SFMCs) collected from patients with gouty arthritis and monosodium urate (MSU)-stimulated THP-1 cells. Interleukin (IL)-1β level increased substantially upon stimulation by MSU crystals. The methylation percentage of HOTAIR was reduced in SFMCs from patients with gouty arthritis and MSU-stimulated THP-1 cells. DNMT1 expression was downregulated in MSU-stimulated THP-1 cells, and DNMT1 knockdown increased lncRNA HOTAIR expression. In addition, the interaction of HOTAIR with miR-20b was confirmed. HOTAIR knockdown suppressed Nlrp3 expression and the secretion of inflammatory cytokines via miR-20b regulation. Finally, in vivo experiments showed that HOTAIR knockdown alleviated ankle swelling in a mouse model of gouty arthritis. These findings suggest that lncRNA HOTAIR knockdown suppresses inflammatory cytokine secretion by upregulating miR-20b and downregulating NLRP3, thereby alleviating ankle swelling in gouty arthritis.

Osteopontin-induced lncRNA HOTAIR expression is involved in osteoarthritis by regulating cell proliferation

Background

Osteopontin plays critical roles in osteoarthritis (OA) by regulating the functions of osteoclasts. It is known that osteopontin can induce the expression of lncRNA HOX transcript antisense RNA (HOTAIR), indicating the involvement of HOTAIR in OA. This study was carried out to investigate the role of HOTAIR in OA.

Methods

Synovial fluid was extracted from both OA patients (n = 58) and healthy controls (n = 58). Expression of osteopontin and HOTAIR in synovial fluid was determined by RT-qPCR. Osteopontin was used to treat chondrocytes at dosages of 0, 1, 5 and 10 µg/ml, followed by measurement of HOTAIR expression by RT-qPCR. The role of osteopontin and HOTAIR overexpression, as well as HOTAIR knockdown in regulating the proliferation of chondrocytes was analyzed by cck-8 assay.

Results

HOTAIR was upregulated in OA. A positive correlation between HOTAIR and osteopontin was observed. In the primary chondrocytes, osteopontin treatment increased HOTAIR expression, while HOTAIR overexpression and knockdown failed to significantly affect osteopontin expression. In addition, osteopontin and HOTAIR overexpression increased chondrocyte proliferation, while HOTAIRE knockdown decreased chondrocyte proliferation. In addition, HOTAIR knockdown reduced the effects of osteopontin treatment on cell proliferation.

Conclusions

Osteopontin-induced HOTAIR expression is involved in osteoarthritis by regulating cell proliferation.

LncRNA HOTTIP leads to osteoarthritis progression via regulating miR-663a/ Fyn-related kinase axis

BACKGROUND

Long non-coding RNA (lncRNA) has been implicated in the progression of osteoarthritis (OA). This study was aimed to explore the role and molecular mechanism of lncRNA HOXA terminal transcriptional RNA (HOTTIP) in the development of OA.

METHODS

The expression of HOTTIP, miR-663a and Fyn-related kinase (FRK) in the OA articular cartilage and OA chondrocyte model induced by IL-1β was determined by qRT-PCR. CCK-8, colony formation and flow cytometry were used to determine the cell proliferation and apoptosis of OA chondrocytes. The specific molecular mechanism of HOTTIP in OA chondrocytes was determined by dual luciferase reporter assay, qRT-PCR, western blotting and RNA pull-down.

RESULTS

The expression of HOTTIP and FRK were up-regulated, while miR-663a was down-regulated in OA cartilage tissues. Knockdown of HOTTIP decreased the proliferation and induced the apoptosis of OA cartilage model cells, while overexpression of HOTTIP increased the proliferation and reduced the apoptosis of OA cartilage model cells. Moreover, HOTTIP could bind to miR-663a as competitive endogenous RNA. Inhibition of miR-663a expression could alleviate the effect of HOTTIP knockdown on the proliferation and apoptosis of OA cartilage model cells. Furthermore, FRK was found to be a direct target of miR-663a, which could markedly down-regulate the expression of FRK in OA chondrocytes, while HOTTIP could remarkably up-regulate the expression of FRK. In addition, miR-663a inhibition increased the proliferation and reduced the apoptosis of OA cells, while FRK knockdown reversed the effect of miR-663a inhibition on the proliferation and apoptosis of OA cells. Meanwhile, overexpression of miR-663a decreased the proliferation and induced the apoptosis of OA cells, while overexpression of FRK reversed the effect of miR-663a overexpression on the proliferation and apoptosis of OA cells.

CONCLUSION

HOTTIP was involved in the proliferation and apoptosis of OA chondrocytes via miR-663a/ FRK axis, and HOTTIP/miR-663a/FRK might be a potential target for the treatment of OA.

Apoptosis in the Extraosseous Calcification Process

Extraosseous calcification is a pathologic mineralization process occurring in soft connective tissues (e.g., skin, vessels, tendons, and cartilage). It can take place on a genetic basis or as a consequence of acquired chronic diseases. In this last case, the etiology is multifactorial, including both extra- and intracellular mechanisms, such as the formation of membrane vesicles (e.g., matrix vesicles and apoptotic bodies), mitochondrial alterations, and oxidative stress. This review is an overview of extraosseous calcification mechanisms focusing on the relationships between apoptosis and mineralization in cartilage and vascular tissues, as these are the two tissues mostly affected by a number of age-related diseases having a progressively increased impact in Western Countries.

Regulation of bone marrow mesenchymal stem cell fate by long non-coding RNA

Bone mesenchymal stem cells (BMSCs) are progenitor cells isolated from bone marrow, which keep potential to differentiate into several kinds of cells including osteoblasts and adipocytes. A dynamic mutual regulation exists between osteogenesis and adipogenesis processes. Long non-coding RNA (lncRNA) performs diverse functions in biological activities including regulation of BMSCs commitment. Evidence has shown that lncRNA regulates key signaling pathways including TGFβ/BMP, Wnt and Notch pathways, and several transcription factors in BMSCs differention. Dysregulation of lncRNA in BMSCs leads to disruption of osteo-adipogenesis difffrentiation and results in impairment of bone homeostasis. In this review, we focus on the role of lncRNA in several critical signaling pathways that involved in regulation of osteo-adipogenesis of BMSC and prospects the potential clinical application of lncRNA.

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.

Long non-coding RNA XIST regulates chondrogenic differentiation of synovium-derived mesenchymal stem cells from temporomandibular joint via miR-27b-3p/ADAMTS-5 axis

OBJECTIVE

Temporomandibular joint osteoarthritis (TMJOA) is a common degenerative disease in jaw joint, accompanied by articular cartilage destruction. Differentiation of stem cells to cartilage has important therapeutic implications in TMJ cartilage repair. Previous studies revealed that lncRNA XIST participated in various biological processes. However, the effect of XIST on chondrogenic differentiation of synovium-derived mesenchymal stem cells (SMSCs) remains unclear. Our study aimed to investigate the function of XIST in chondrogenic differentiation of human SMSCs from TMJ.

METHODS

Alcian blue staining was performed to determine proteoglycan in SMSCs. qPCR, western blotting and immunofluorescence assays were allowed to assess sex determining region Y-box 9 (SOX9), Collagen type II alpha 1 chain (COL2A1) and Aggrecan (ACAN) expression. The direct interaction between miR-27b-3p and XIST or ADAMTS-5 was confirmed by dual luciferase reporter assay or RNA immunoprecipitation (RIP) assay.

RESULTS

XIST was remarkably down-regulated in chondrogenic differentiation of SMSCs. Functional analysis demonstrated that XIST silencing promoted chondrogenic differentiation of SMSCs. Dual luciferase reporter and RIP assays identified that XIST acted as a sponge for miR-27b-3p. Moreover, XIST regulated ADAMTS-5 expression by directly binding miR-27b-3p. More importantly, miR-27b-3p/ADAMTS-5 rescued the effects of XIST on chondrogenic differentiation of SMSCs.

CONCLUSION

The results suggest that XIST modulates SMSCs chondrogenic differentiation via the miR-27b-3p/ADAMTS-5 axis, which provides new targets for TMJOA treatment.

Galuteolin suppresses proliferation and inflammation in TNF-α-induced RA-FLS cells by activating HMOX1 to regulate IKKβ/NF-κB pathway

OBJECTIVE

Galuteolin (Galu) is a substance extracted and purified from honeysuckle. The purpose of this study was to explore the effects of Galu on the TNF-α-induced RA-FLS cells (synoviocytes) and reveal its potential molecular mechanism from the perspectives of anti-apoptosis and anti-inflammation.

METHODS

After TNF-α stimulation, cell proliferation of RA-FLS was assessed by CCK-8 assay. TUNEL staining was used to detect the apoptosis. Western blot was used to detect the expressions of Iκκβ, p-p65, p65, p-IκB, IκB, Cleaved-caspase3, Caspase-3, Bcl-2, and Bax. HO-1 were determined by RT-PCR. The contents of pro-inflammatory cytokines IL-1β, IL-6, IL-8, and MMP-1 were determined by ELISA.

RESULTS

Galu significantly suppressed cell proliferation in a dose-dependent manner. Additionally, Galu obviously promotes cell apoptosis rate of RA-FLS cells and elevated the expression levels of HO-1, caspase-3, and Bax, while reducing the expression level of Bcl-2. Furthermore, Galu apparently inhibited the levels of Iκκβ, p-p65, and p-IκB. Moreover, Galu also significantly reduced the levels of pro-inflammatory factors IL-1β, IL-6, IL-8, and MMP-1 in RA-FLS cells.

CONCLUSION

Galuteolin exerts protective effects against TNF-α-induced RA-FLS cells by inhibiting apoptosis and inflammation, which can guide the clinical use of rheumatoid arthritis.

Overexpression of MMPs, cytokines, and RANKL/OPG in temporomandibular joint osteoarthritis and their association with joint pain, mouth opening, and bone degeneration: A preliminary report

OBJECTIVE

This study aimed to determine the expression of distinct matrix metalloproteinases, cytokines, and bone resorptive factors in temporomandibular joint osteoarthritis (TMJ-OA) patients and their association with joint pain, mouth opening, and subchondral bone degeneration.

MATERIALS AND METHODS

Twelve patients affected with TMJ-OA (n = 5), disk displacement without reduction (DDWoR) (n = 3), or disk displacement with reduction (DDWR) (n = 4) were selected. Joint pain was quantified by using visual analog scale, mouth opening was quantified at the maximum pain-free aperture, and bone degeneration was quantified using joint imaging. Synovial fluid samples were collected and immediately processed for cell and synovial fluid recovering. From cells, the MMP-1, MMP-2, MMP-8, MMP-13, IL-6, IL-23, and TNF-α expression was quantified by qPCR. From synovial fluid, the RANKL and OPG levels were quantified by ELISA.

RESULTS

Higher levels of MMP-1, MMP-8, MMP-13, IL-6, IL-23, TNF-α, and RANKL/OPG ratio were detected in TMJ-OA compared with DDWoR and DDWR patients (p < .05). Joint pain significantly correlated with TNF-α levels (r = .975, p = .029). Besides, imaging signs of bone degeneration significantly correlated with RANKL/OPG ratio (r = .949, p = .042). Conversely, mouth opening did not correlate with any of the analyzed mediators.

CONCLUSION

During TMJ-OA, a pathological response characterized by the overexpression of TNF-α and RANKL/OPG could be involved in joint pain and subchondral bone degeneration.

LncRNA ARFRP1 knockdown inhibits LPS-induced the injury of chondrocytes by regulation of NF-κB pathway through modulating miR-15a-5p/TLR4 axis

AIMS

Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been reported as the important regulators in osteoarthritis (OA). However, the detailed mechanism is implicated. The aim of this study is to reveal the functional mechanism of lncRNA ARFRP1 and miR-15a-5p in osteoarthritis.

MATERIALS AND METHODS

The expression level of genes was detected by quantitative real time polymerase chain reaction (qRT-PCR) or western blot assay. Cell Counting Kit-8 (CCK-8) was used to assess cell viability. Cell apoptosis rate was analyzed by flow cytometry analysis. Furthermore, Enzyme-linked immunosorbent assay (ELISA) was performed to measure tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β contents. The interaction between miR-15a-5p and ARFRP1 or Toll-like receptor 4 (TLR4) was predicted by miRcode or PITA, and then confirmed by the dual luciferase reporter assay or pull down assay. Besides, NF-κB-driven luciferase activity was determined using NF-κB luciferase reporter assay.

KEY FINDINGS

ARFRP1 and TLR4 levels were increased and miR-15a-5p level was decreased in OA cartilage tissues and lipopolysaccharides (LPS)-induced chondrocytes. ARFRP1 knockdown inhibited LPS-induced the injury of chondrocytes. Interestingly, miR-15a-5p downregulated by ARFRP1 negatively modulated TLR4 expression through interaction. ARFRP1 mediated LPS-induced the injury of chondrocytes via regulating miR-15a-5p/TLR4 axis. Furthermore, ARFRP1 exerted function by modulation of NF-κB pathway.

SIGNIFICANCE

Our findings confirmed that ARFRP1 mediated LPS-induced the injury of chondrocytes through regulating NF-κB pathway by modulation of miR-15a-5p/TLR4 axis, providing theoretical basis for the treatment of OA patients.

The emerging role of lncRNAs in chondrocytes from osteoarthritis patients

Long non-coding RNAs (lncRNAs) play important roles in many physiological and pathological processes, including osteoarthritis (OA). Recent studies have demonstrated that lncRNAs are involved in the pathogenesis of OA by affecting various essential cellular features of chondrocytes, such as proliferation, apoptosis, inflammation, and degradation of the extracellular matrix (ECM). However, there are only a limited number of studies in this area, indicating that the role of lncRNAs in OA may have been overlooked. The aim of this literature review is to summarize the versatile roles and molecular mechanisms of lncRNAs in chondrocytes involved in OA. At the end of this article, the function of the lncRNA HOX transcript antisense RNA (HOTAIR) in chondrocytes in OA is highlighted. Because lncRNAs affect proliferation, apoptosis, inflammatory responses, and ECM degradation by chondrocytes in OA, they may serve as potential biomarkers or therapeutic targets for the diagnosis or treatment of OA. The specific role and related mechanisms of lncRNAs in OA warrants further investigation.

TLR-4, TLR-5 and IRF4 are diagnostic markers of knee osteoarthritis in the middle-aged and elderly patients and related to disease activity and inflammatory factors

Expression and diagnostic value of serum toll-like receptor-4 (TLR-4), Toll-like receptor-5 (TLR-5) and interferon regulatory factor 4 (IRF4) in middle-aged and elderly patients with knee osteoarthritis (KOA) and their correlation with Interleukin 1β (IL-1β), interleukin-6 (IL-6), matrix metalloproteinase-1 and tumor necrosis factor-α (TNF-α) were investigated. Sixty-eight middle-aged and elderly patients with KOA in Puyang Hospital of Traditional Chinese Medicine were selected as the study group and 49 healthy people receiving physical examination were the control group. Levels of serum TLR-4, TLR-5, IRF4, IL-1β, IL-6, MMP-1 and TNF-α were measured by enzyme linked immunosorbent assay (ELISA). Correlation between the expression levels of serum TLR-4, TLR-5, IRF4 and K-L grades was determined by Spearman correlation analysis. The diagnostic efficacy of serum TLR-4, TLR-5 and IRF4 for KOA was analyzed by the receiver operator characteristics analysis (ROC). Expression of serum TLR-4, TLR-5 and IRF4 in the study group was significantly higher than those in the control group. The sensitivity and specificity of TLR-4 in the diagnosis of KOA were, respectively, 76.47 and 93.88%, those of TLR-5 were 73.29 and 87.76%, those of IRF4 were 72.06 and 95.92%, and those of TLR-4, TLR-5 and IRF4 were 94.12 and 97.96%. Expression of serum TLR-4, TLR-5 and IRF4 was significantly higher in the severe group than in the moderate group, and significantly higher in the moderate group than those the in mild group, and significantly higher in the mild group than those in the suspected mild group. Expression of TLR-4, TLR-5 and IRF4 in serum was positively correlated with the concentration of IL-1β, IL-6, MMP-1 and TNF-α, respectively (P<0.001). The combined detection of TLR-4, TLR-5 and IRF4 can be used for early diagnosis of KOA, and they are positively correlated with IL-1β and IL-6, MMP-1 and TNF-α.

Epigenetic regulation of matrix metalloproteinases in inflammatory diseases: a narrative review

With the acceleration of urbanization and aging and the change of lifestyle, inflammatory diseases have become one of the important threats to the health of the global population. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are involved in the metabolism of extracellular matrix (ECM). They play a key role in inflammation-related diseases. Factors such as inflammation, oxidative stress and growth factors stimulate the production of MMPs with subsequent ECM remodeling. Recently, the studies of epigenetic regulation, including the ability to predict disease progression, important pathophysiological deficiencies as well as treatment methods have been extensively discussed. This article reviews the current studies on epigenetic alterations in MMPs during inflammatory response. It is likely to provide new insights into development of efficient medications of epigenetic therapy for inflammatory diseases.

Long-chain non-coding RNA HOTAIR promotes the progression of osteoarthritis via sponging miR-20b/PTEN axis

AIMS

Cumulative evidence suggests that long-chain non-coding RNA (lncRNA) is involved in the pathogenesis of osteoarthritis (OA). The present study aimed to explore the regulatory role and related mechanisms of HOX transcript antisense intergenic RNA (HOTAIR) in OA.

MATERIAL AND METHODS

The OA mouse model was constructed by the medial meniscus (DMM) method, and Interleukin (IL)-1β-induced chondrocytes were used to simulate OA in vitro.

KEY FINDINGS

Results found that HOTAIR was significantly up-regulated in articular cartilage tissues of OA mice and IL-1β-induced chondrocytes, accompanied by down-regulation of miR-20b and increased expression of the phosphatase and tensin homolog (PTEN). HOTAIR silencing improved cartilage tissue damage in OA mice, and promoted the expression of collagen II and aggrecan in cartilage tissue, while inhibited the expression of matrix metalloproteinases (MMP)-13 and ADAMTS-5. Overexpression of HOTAIR inhibited the proliferation of IL-1β-induced chondrocytes and promoted apoptosis and extracellular matrix (ECM) degradation, whereas the effect of HOTAIR knockdown was reversed. Bioinformatics software and luciferase reporter experiments confirmed that HOTAIR could negatively regulate miR-20b, and PTEN was a target gene of miR-20b. An increase in PTEN expression induced by HOTAIR overexpression could be reversed by the introduction of miR-20b mimic. HOTAIR overexpression significantly reversed miR-20 mimic-mediated inhibition of apoptosis and ECM degradation in IL-1β-induced chondrocytes, whereas the introduction of si-HOTAIR eliminated anti-miR-20b-mediated apoptosis and ECM degradation.

SIGNIFICANCE

HOTAIR can participate in OA by promoting chondrocyte apoptosis and ECM degradation, which may be related to its targeted regulation of miR-20b/PTEN axis.

A long non-coding RNA, HOTAIR, promotes cartilage degradation in osteoarthritis by inhibiting WIF-1 expression and activating Wnt pathway

BACKGROUND

Long noncoding RNAs (lncRNAs) are recently found to be critical regulators of the epigenome. However, our knowledge of their role in osteoarthritis (OA) development is limited. This study investigates the mechanism by which HOTAIR, a key lncRNA with elevated expression in OA, affects OA disease progression.

RESULTS

HOTAIR expression was greatly elevated in osteoarthritic compared to normal chondrocytes. Silencing and over-expression of HOTAIR in SW1353 cells respectively reduced and increased the expression of genes associated with cartilage degradation in OA. Investigation of molecular pathways revealed that HOTAIR acted directly on Wnt inhibitory factor 1 (WIF-1) by increasing histone H3K27 trimethylation in the WIF-1 promoter, leading to WIF-1 repression that favours activation of the Wnt/β-catenin pathway.

CONCLUSIONS

Activation of Wnt/β-catenin signalling by HOTAIR through WIF-1 repression in osteoarthritic chondrocytes increases catabolic gene expression and promotes cartilage degradation. This is the first study to demonstrate a direct link between HOTAIR, WIF-1 and OA progression, which may be useful for future investigations into disease biomarkers or therapeutic targets.

Cell cycle-related lncRNAs and mRNAs in osteoarthritis chondrocytes in a Northwest Chinese Han Population

BACKGROUND

A group of differentially expressed long non-coding RNAs (lncRNAs) have been shown to play key roles in osteoarthritis (OA), although they represented only a small proportion of lncRNAs that may be biologically and physiologically relevant. Since our knowledge of regulatory functions of non-coding RNAs is still limited, it is important to gain better understanding of their relation to the pathogenesis of OA.

METHODS

We performed mRNA and lncRNA microarray analysis to detect differentially expressed RNAs in chondrocytes from three OA patients compared with four healthy controls. Then, enrichment analysis of the differentially expressed mRNAs was carried out to define disease molecular networks, pathways and gene ontology (GO) function. Furthermore, target gene prediction based on the co-expression network was performed to reveal the potential relationships between lncRNAs and mRNAs, contributing an exploration of a role of lncRNAs in OA mechanism. Quantitative RT-PCR analyses were used to demonstrate the reliability of the experimental results.

FINDINGS

Altogether 990 lncRNAs (666 up-regulated and 324 down-regulated) and 546 mRNAs (419 up-regulated and 127 down-regulated) were differentially expressed in OA samples compared with the normal ones. The enrichment analysis revealed a set of genes involved in cell cycle. In total, 854 pairs of mRNA and lncRNA were highly linked, and further target prediction appointed 12 genes specifically for their corresponding lncRNAs. The lncRNAs lncRNA-CTD-2184D3.4, ENST00000564198.1, and ENST00000520562.1 were predicted to regulate SPC24, GALM, and ZNF345 mRNA expressions in OA.

INTERPRETATION

This study uncovered several novel genes potentially important in pathogenesis of OA, and forecast the potential function of lnc-CTD-2184D3.4, especially for the cell cycle in the chondrocytes. These findings may promote additional aspects in studies of OA.

Knockdown of long non‑coding RNA AK094629 attenuates the interleukin‑1β induced expression of interleukin‑6 in synovium‑derived mesenchymal stem cells from the temporomandibular joint

Interleukin (IL)‑1β is a key promotor in the pathogenesis of temporomandibular joint osteoarthritis. Differentiation of stem cells to cartilage is a crucial repair mechanism of articular cartilage damage, and IL‑1β has been reported to impede the differentiation by upregulating the secretion of IL‑6, an important inflammatory factor. Long non‑coding RNAs (lncRNAs) regulate a number of physiological and pathological processes, but whether lncRNA AK094629 contributes to the IL‑1β mediated induction of inflammation remains unclear. Therefore, the aim of the present study was to investigate the effect of AK094629 on IL‑1β‑induced IL‑6 expression in synovial‑derived mesenchymal stem cells (SMSCs) of the temporomandibular joints. The results of the present study demonstrated that the expression of AK094629 in the synovial tissue of patients with osteoarthritis was positively correlated with IL‑1β. In addition, IL‑1β upregulated the expression of AK094629 in the SMSCs in vitro, and AK094629 knockdown inhibited the IL‑1β mediated upregulation of IL‑6. The present study also demonstrated that AK094629 knockdown downregulated the expression of the mitogen‑activated protein kinase kinase kinase 4 (MAP3K4), which is upregulated by IL‑1β, whereas knockdown of MAP3K4 did not affect the expression of AK094629, but reversed the upregulation of IL‑6 in SMSCs. In conclusion, AK094629 knockdown attenuated the expression of IL‑1β‑regulated IL‑6 in the SMSCs of the temporomandibular joint by inhibiting MAP3K4. Therefore, AK094629 may be a potential novel therapeutic target for the treatment of temporomandibular joint osteoarthritis.

LncRNA CTBP1-AS2 is upregulated in osteoarthritis and increases the methylation of miR-130a gene to inhibit chondrocyte proliferation

OBJECTIVES

LncRNA CTBP1-AS2 has been reported to be involved in type 2 diabetes and cardiomyocyte hypertrophy, while its roles in other human diseases are unknown. Our preliminary deep sequencing analysis showed altered expression of CTBP1-AS2 in osteoarthritis (OA). In addition, CTBP1-AS2 was inversely correlated with miR-130a. This study was therefore carried out to investigate the interactions between CTBP1-AS2 and miR-130a in OA.

METHODS

Synovial fluid was collected from 62 OA patients and 62 healthy controls. RT-qPCR was performed to determine the expression levels of CTBP1-AS2 and miR-130a in synovial fluid. Cell transfections were performed to investigate the interactions between CTBP1-AS2 and miR-130a. Methylation-specific PCR (MSP) was performed to assess the effects of CTBP1-AS2 on the methylation of miR-130a. Cell counting Kit-8 (CCK-8) assay was performed to evaluate the roles of CTBP1-AS2 and miR-130a in regulating proliferation of chondrocytes.

RESULTS

The results showed that CTBP1-AS2 was upregulated in OA and inversely correlated with miR-130a. In chondrocytes of OA patients, overexpression of CTBP1-AS2 led to increased methylation of miR-130a gene and downregulated expression of miR-130a, while overexpression of miR-130a did not affect the expression of CTBP1-AS2. In contrast, no interaction between CTBP1-AS2 and miR-130a was observed in chondrocytes from healthy adults. Analysis of chondrocyte proliferation showed that overexpression of miR-130a led to increased proliferation rate of chondrocytes extracted from OA patients. Overexpression of CTBP1-AS2 led to decreased proliferation rate of chondrocytes and reversed the effects of overexpressing miR-130a.

CONCLUSION

Therefore, CTBP1-AS2 is upregulated in OA and may increase the methylation of miR-130a gene to inhibit chondrocyte proliferation. Key Points • CTBP1-AS2 is overexpressed in OA and may downregulate miR-130a through methylation to suppress the proliferation of chondrocytes. • The interaction between CTBP1-AS2 and miR-130a is indirect and mediated by certain pathological mediators.