Long Intergenic Noncoding RNAs Mediate the Human Chondrocyte Inflammatory Response and Are Differentially Expressed in Osteoarthritis Cartilage

Mechanosensitive lncRNA H19 promotes chondrocyte autophagy, but not pyroptosis, by targeting miR-148a in post-traumatic osteoarthritis

Objective

Investigating whether mechanosensitive lncRNA H19 can directly target miR-148a to alleviate cartilage damage in post-traumatic osteoarthritis (PTOA).

Methods

Thirty-two female rats were randomly divided into four groups: Sham-operated group (Sham group, n = 8), treadmill running group (R group, n = 8), anterior cruciate ligament transection (ACLT) group (ACLT group, n = 8), and ACLT + treadmill running group (ACLT + R group, n = 8). Histological evaluation was performed to observe the pathological changes in the cartilage of the rat knee. Micro-CT was performed to detect the bone morphological changes in the subchondral bone. RT-qPCR and Western-Blot were performed to detect changes in mRNA and protein levels of metabolic and inflammatory factors as well as changes in the expression of lncRNA H19 and miR-148a in cartilage. The Flexcell 5000™ Tension System was used to further validate that lncRNA H19 has mechanosensitivity in vitro. Finally, cell transfection techniques were used to knock down the expression of lncRNA H19 in chondrocytes to validate the regulatory role of lncRNA H19/miR-148a in cartilage metabolism.

Results

ACLT combined with treadmill running aggravated the abnormal hyperplasia of subchondral bone in the lateral tibial plateau of the rat knee joint, disturbed the balance of cartilage metabolism, induced cartilage inflammatory response and chondrocyte pyroptosis, which eventually led to cartilage damage and PTOA. Importantly, we found that the expression of lncRNA H19 was significantly downregulated in the cartilage of the ACLT + R group. Bioinformatics analysis revealed that miR-148a may be a direct target of lncRNA H19. Subsequently, we focused on the mechanosensitive of lncRNA H19. Subsequently, moderate-intensity mechanical tension stress reversed the expression of lncRNA H19 and autophagy-related factors in inflammatory chondrocytes, while miR-148a showed an opposite expression trend, demonstrating that mechanosensitive lncRNA H19 may be involved in regulating the chondrocyte inflammatory response by targeting miR-148a and activating autophagy. Cell transfection experiments revealed that lncRNA H19 knockdown upregulated miR-148a expression and significantly inhibited the autophagy level of chondrocytes without significant alteration of chondrocyte pyroptosis, which in turn exacerbated the inflammatory response of chondrocytes.

Conclusions

Mechanosensitive lncRNA H19 can promote chondrocyte autophagy rather than pyroptosis by targeting miR-148a, thus alleviating cartilage damage in PTOA. LncRNA H19 may be a potential therapeutic target for PTOA.

Deciphering the Role of LncRNAs in Osteoarthritis: Inflammatory Pathways Unveiled

Long non-coding RNA (LncRNA), with transcripts over 200 nucleotides in length, play critical roles in numerous biological functions and have emerged as significant players in the pathogenesis of osteoarthritis (OA), an inflammatory condition traditionally viewed as a degenerative joint disease. This review comprehensively examines the influence of LncRNA on the inflammatory processes driving OA progression, focusing on their role in regulating gene expression, cellular activities, and inflammatory pathways. Notably, LncRNAs such as MALAT1, H19, and HOTAIR are upregulated in OA and exacerbate the inflammatory milieu by modulating key signaling pathways like NF-κB, TGF-β/SMAD, and Wnt/β-catenin. Conversely, LncRNA like MEG3 and GAS5, which are downregulated in OA, show potential in dampening inflammatory responses and protecting against cartilage degradation by influencing miRNA interactions and cytokine production. By enhancing our understanding of LncRNA' roles in OA inflammation, we can better leverage them as potential biomarkers for the disease and develop innovative therapeutic strategies for OA management. This paper aims to delineate the mechanisms by which LncRNA influence inflammatory responses in OA and propose them as novel targets for therapeutic intervention.

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.

Identifying autophagy-related mRNAs and potential ceRNA networks in meniscus degeneration based on RNA sequencing and experimental validation

Purpose

The intimate connection between long noncoding RNA (lncRNA) and autophagy has been established in cartilage degeneration. However, their roles in meniscal degeneration remain ambiguous. This study aimed to identify the key autophagy-related lncRNA and its associated regulatory network in meniscal degeneration in the context of osteoarthritis (OA).

Methods

RNA sequencing was performed to identify differentially expressed lncRNAs (DELs) and mRNAs (DEMs), which were then conducted to enrichment analyses using the DAVID database and Metascape. Autophagy-related DEMs were identified by combining DEMs with data from the Human Autophagy Database. Three databases were used to predict miRNA, and the DIANA LncBase Predicted database was utilized to predict miRNA-lncRNA interactions. Based on these predictions, comprehensive competitive endogenous RNA (ceRNA) network were constructed. The expression levels of the classical autophagy markers and autophagy-related ceRNA network were validated. Additionally, Gene Set Enrichment Analysis (GSEA) was performed using autophagy-related DEMs.

Results

310 DELs and 320 DEMs were identified, with five upregulated and one downregulated autophagy-related DEMs. Through reverse prediction of miRNA, paired miRNA-lncRNA interactions, and verification using RT-qPCR, two lncRNAs (PCAT19, CLIP1-AS1), two miRNA (has-miR-3680-3p and has-miR-4795-3p) and two mRNAs (BAG3 and HSP90AB1) were included in the constructed ceRNA regulatory networks. GSEA indicated that the increased expression of autophagy-related mRNAs inhibited glycosaminoglycan biosynthesis in the degenerative meniscus.

Conclusion

This study presented the first construction of regulatory ceRNA network involving autophagy-related lncRNA-miRNA-mRNA interactions in OA meniscus. These findings offered valuable insights into the mechanisms underlying meniscal degeneration and provided potential targets for therapeutic intervention.

FSGT capsule inhibits IL-1β-induced inflammation in chondrocytes and ameliorates osteoarthritis by upregulating LncRNA PACER and downregulating COX2/PGE2

OBJECTIVE

To explore the efficacy and potential mechanism of Fengshi Gutong capsule (FSGTC) in osteoarthritis (OA) inflammation.

METHODS

The impact of FSGTC on laboratory indicators of OA patients was explored using data mining technology and association rule analysis. Then, the OA cell model was constructed by inducing chondrocytes (CHs) with interleukin-1β (IL-1β). In the presence of FSGTC intervention, the regulatory mechanism of PACER/COX2/PGE2 in OA-CH viability and inflammatory responses was evaluated.

RESULTS

Retrospective data mining showed that FSGTC effectively reduced inflammation indexes (ESR, HCRP) of OA patients. Cell experiments showed that LncRNA PACER (PACER) silencing inhibited the proliferation activity of OA-CHs, increased the level of COX2 protein, elevated the levels of PGE2, TNF-α, and IL-1β, and decreased the levels of IL-4 and IL-10 (p < .01). On the contrary, FSGTC-containing serum reversed the effect of PACER silencing on OA-CHs (p < .01). After the addition of COX2 pathway inhibitor, the proliferation activity of OA-CHs was enhanced; the levels of PGE2, TNF-α, and IL-1β were decreased while the levels of IL-4 and IL-10 were increased (p < .01).

CONCLUSION

FSGTC inhibits IL-1β-induced inflammation in CHs and ameliorates OA by upregulating PACER and downregulating COX2/PGE2.

Long non-coding RNAs as emerging regulators of miRNAs and epigenetics in diabetes-related chronic kidney disease

Diabetes is one of the major cause of chronic kidney disease (CKD), including "diabetic nephropathy," and is an increasingly prevalent accelerator of the progression of non-diabetic forms of CKD. The long non-coding RNAs (lncRNAs) have come into the limelight in the past few years as one of the emerging weapons against CKD in diabetes. Available data over the past few years demonstrate the interaction of lncRNAs with miRNAs and epigenetic machinery. Interestingly, the evolving data suggest that lncRNAs play a vital role in diabetes-associated CKD by regulation of epigenetic enzymes such as DNA methyltransferase, histone deacetylases, and histone methyltransferases. LncRNAs are also engaged in the regulation of several miRNAs in diabetic nephropathy. Hence this review will elaborate on the association between lncRNAs and their interaction with epigenetic regulators involved in different aspects and thus the progression of CKD in diabetes.

Downregulation of lncRNA NEAT1 interacts with miR-374b-5p/PGAP1 axis to aggravate the development of osteoarthritis

BACKGROUND

Osteoarthritis (OA), characterized by inflammation and articular cartilage degradation, is a prevalent arthritis among geriatric population. This paper was to scrutinize the novel mechanism of long noncoding RNA (lncRNA) NEAT1 in OA etiology.

METHODS

A total of 10 OA patients and 10 normal individuals was included in this study. Cell model of OA was built in human normal chondrocytes induced by lipopolysaccharide (LPS). An OA Wistar rat model was established through intra-articular injection of L-cysteine and papain mixtures (proportion at 1:2) into the right knee. Quantitative reverse transcription-polymerase chain reaction was employed to ascertain the expression levels of NEAT1, microRNA (miR)-374b-5p and post-GPI attachment to protein 1 (PGAP1), while dual-luciferase reporter experiments were used for the validation of target relationship among them. Cell cycle and apoptosis were calculated by flow cytometry analysis. CCK-8 assay was done to evaluate the proliferative potentials of chondrocytes. The levels of cell cycle-related proteins (Cyclin A1, Cyclin B1 and Cyclin D2) and pro-apoptotic proteins (Caspase3 and Caspase9) were measured by western blotting. Tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and IL-6 levels were determined via ELISA. Hematoxylin & eosin (HE) Staining was used for pathological examination in OA rats.

RESULTS

Pronounced downregulation of NEAT1 and PGAP1 and high amounts of miR-374b-5p were identified in OA patients, LPS-induced chondrocytes and OA rats. NEAT1 targeted miR-374b-5p to control PGAP1 expression. Loss of NEAT1 or upregulation of miR-374b-5p dramatically accelerated apoptosis, led to the G1/S arrest and promoted the secretion of inflammatory cytokines in LPS-induced chondrocytes, while ectopic expression of PGAP1 exhibited the opposite influences on chondrocytes. Additionally, we further indicated that upregulation of miR-374b-5p attenuated the effects of PGAP1 overexpression on LPS-induced chondrocytes.

CONCLUSIONS

Reduced NEAT1 induces the development of OA via miR-374b-5p/PGAP1 pathway. This suggests that the regulatory axis NEAT1/miR-374b-5p/PGAP1 is a novel and prospective target for OA treatment.

METTL3-mediated m6A modification of IGFBP7-OT promotes osteoarthritis progression by regulating the DNMT1/DNMT3a-IGFBP7 axis

Osteoarthritis (OA) is the most common degenerative disorder, affecting approximately half of the elderly population. In this study, we find that the expressions of long noncoding RNA (lncRNA) IGFBP7-OT and its maternal gene, IGFBP7, are upregulated and positively correlated in osteoarthritic cartilage. Overexpression of IGFBP7-OT significantly inhibits chondrocyte viability, promotes chondrocyte apoptosis, and reduces extracellular matrix components, whereas IGFBP7-OT knockdown has the opposite effects. IGFBP7-OT overexpression promotes cartilage degeneration and markedly aggravates the monosodium iodoacetate-induced OA phenotype in vivo. Further mechanistic research reveals that IGFBP7-OT promotes OA progression by upregulating IGFBP7 expression. Specifically, IGFBP7-OT suppresses the occupancy of DNMT1 and DNMT3a on the IGFBP7 promoter, thereby inhibiting methylation of the IGFBP7 promoter. The upregulation of IGFBP7-OT in OA is partially controlled by METTL3-mediated N6-methyladenosine (m6A) modification. Collectively, our findings reveal that m6A modification of IGFBP7-OT promotes OA progression by regulating the DNMT1/DNMT3a-IGFBP7 axis and provide a potential therapeutical target for OA treatment.

Long noncoding RNA NAV2-AS5 relieves chondrocyte inflammation by targeting miR-8082/TNIP2 in osteoarthritis

Osteoarthritis (OA) is a common chronic and frequently occurring orthopedic disease in the middle-aged and elderly individuals. Numerous studies have shown that long noncoding RNAs (lncRNAs) play major roles in various diseases. However, the potential molecular mechanism of action of NAV2-AS5 in OA remains unclear. The present study was designed to explore the influence of NAV2-AS5 on the progression of chondrocyte inflammation and its underlying molecular mechanisms. To simulate the inflammatory environment in OA, the human chondrocyte cell line was treated with LPS. Cell proliferation, cell cycle progression, and apoptosis were assessed using Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine analysis, and flow cytometry. Proliferation- and cycle-related proteins and the release of inflammatory factors were examined by western blot analysis and enzyme-linked immunosorbent assay. The downstream targets of NAV2-AS5 were determined using bioinformatics and confirmed by a luciferase reporter assay. In our study, patients with OA showed downregulation of NAV2-AS5, upregulation of miR-8082, and downregulation of TNFAIP3 interacting protein 2 (TNIP2). Moreover, we found that both overexpression of NAV2-AS5 and miR-8082 inhibitor promoted cell proliferation, inhibited apoptosis, and released inflammatory cytokines in LPS-treated chondrocytes. MiR-8082 was predicted to be a target of both NAV2-AS5 and TNIP2. In addition, rescue experiments showed that silencing of TNIP2 reversed the effects of the miR-8082 inhibitor on proliferation, cell cycle, apoptosis, and inflammatory factors in sh-NAV2-AS5-treated chondrocytes. In conclusion, these findings indicate that NAV2-AS5 relieves chondrocyte inflammation by targeting miR-8082/TNIP2 in OA, which provides a new theoretical basis for OA therapy.

Advances in Research on the Regulatory Roles of lncRNAs in Osteoarthritic Cartilage

Osteoarthritis (OA) is the most common degenerative bone and joint disease that can lead to disability and severely affect the quality of life of patients. However, its etiology and pathogenesis remain unclear. It is currently believed that articular cartilage lesions are an important marker of the onset and development of osteoarthritis. Long noncoding RNAs (lncRNAs) are a class of multifunctional regulatory RNAs that are involved in various physiological functions. There are many differentially expressed lncRNAs between osteoarthritic and normal cartilage tissues that play multiple roles in the pathogenesis of OA. Here, we reviewed lncRNAs that have been reported to play regulatory roles in the pathological changes associated with osteoarthritic cartilage and their potential as biomarkers and a therapeutic target in OA to further elucidate the pathogenesis of OA and provide insights for the diagnosis and treatment of OA.

Dynamic chromatin accessibility tuning by the long noncoding RNA ELDR accelerates chondrocyte senescence and osteoarthritis

Epigenetic reprogramming plays a critical role in chondrocyte senescence during osteoarthritis (OA) pathology, but the underlying molecular mechanisms remain to be elucidated. Here, using large-scale individual datasets and genetically engineered (Col2a1-CreER^T2;Eldr^flox/flox and Col2a1-CreER^T2;ROSA26-LSL-Eldr^+/+ knockin) mouse models, we show that a novel transcript of long noncoding RNA ELDR is essential for the development of chondrocyte senescence. ELDR is highly expressed in chondrocytes and cartilage tissues of OA. Mechanistically, exon 4 of ELDR physically mediates a complex consisting of hnRNPL and KAT6A to regulate histone modifications of the promoter region of IHH, thereby activating hedgehog signaling and promoting chondrocyte senescence. Therapeutically, GapmeR-mediated silencing of ELDR in the OA model substantially attenuates chondrocyte senescence and cartilage degradation. Clinically, ELDR knockdown in cartilage explants from OA-affected individuals decreased the expression of senescence markers and catabolic mediators. Taken together, these findings uncover an lncRNA-dependent epigenetic driver in chondrocyte senescence, highlighting that ELDR could be a promising therapeutic avenue for OA.

Differential expression and effect analysis of lncRNA-mRNA in congenital pseudarthrosis of the tibia

Background: To analyze the lncRNA-mRNA differential expression and co-expression network of periosteal stem cells (PSCs) from congenital pseudarthrosis of the tibia (CPT) and normal patients, and to explore the role of key lncRNAs. Methods: Differentially expressed lncRNAs and mRNAs in PSCs were obtained by sequencing, and biological functions of differentially expressed mRNAs were detected by gene ontology (GO), Kyoto encyclopedia of genes and genomes (KEGG) pathway and protein -protein interaction (PPI) analysis. The co-expression network of lncRNA-mRNA was constructed by correlation analysis of differentially expressed lncRNAs and mRNAs, and the key lncRNAs were screened according to the connectivity degree. After that, the cis-regulated target genes of differential expressed lncRNAs and mRNAs were predicted. Results: A total of 194 differentially expressed lncRNAs were identified, including 73 upregulated and 121 downregulated genes. A total of 822 differentially expressed mRNAs were identified, including 311 upregulated and 511 downregulated genes. GO, KEGG and PPI enrichment analysis showed that the regulatory function of differentially expressed mRNAs were mainly gathered in skeletal system development and tissue morphogenesis. The co-expression network with 226 nodes and 3,390 edges was constructed based on correlation analysis. A total of 10 key lncRNAs, including FAM227B, POM121L9P, AF165147 and AC103702, were screened according to connectivity degree. Prediction of target genes indicated that FAM227B-FGF7 and AC103702-HOXB4/5/6 may play an important role in the pathogenesis of CPT. Conclusion: A total of 10 key lncRNAs, including FAM227B, POM121L9P, AF165147, and AC103702, occupy the core position in the co-expression network, suggesting that these lncRNAs and their target genes may play an important role in the pathogenesis of CPT.

Long non-coding RNA PMS2L2 is down-regulated in osteoarthritis and inhibits chondrocyte proliferation by up-regulating miR-34a

Long non-coding RNA (lncRNA) PMS2L2 has been reported to participate in endotoxin-induced inflammatory responses. As these types of responses can promote osteoarthritis (OA), it was of interest to ascertain if PMS2L2 may be involved in OA. To explore any potential participation of PMS2L2 in OA, synovial fluid was extracted from both OA patients and healthy controls (n = 62 each) and PMS2L2 expression of each sample determined by RT-qPCR. In addition, as miR-34a has a potential binding site on PMS2L2, hypothetical interactions between PMS2L2 and miR-34a in chondrocytes were analyzed by performing over-expression experiments. Furthermore, the role of PMS2L2 and miR-34a in the regulation of chondrocyte proliferation was analyzed using CCK-8 and BrdU assays. The results showed that PMS2L2 expression in OA patient synovial fluid was lower compared to that in control group fluid, and the extent of this reduction was related to disease stage. In in vitro studies, it was seen that endotoxin treatment of chondrocytes led to decreased PMS2L2 expression. It was found that PMS2L2 over-expression caused increased miR-34a expression in OA patient chondrocytes but not in cells from healthy controls. In contrast, miR-34a over-expression in either cell population did not affect PMS2L2 expression. Lastly, over-expression of both PMS2L2 and miR-34a led to inhibited chondrocyte proliferation. Of note, a combined over-expression of PMS2L2 and miR-34a resulted in stronger effects on proliferation compared to that from either single over-expression. Based on the findings that PMS2L2 is down-regulated during ongoing states of OA, and that changes in PMS2L2 expression can lead to increases in chondrocyte expression of miR-34a - resulting in inhibition of chondrocyte proliferation in OA. From these findings, one may conclude that finding means to regulate PMS2L2 could be a promising new target in the development of regimens for the treatment of OA.

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.

p50-associated Cyclooxygenase-2 Extragenic RNA (PACER) and Long Non-coding RNA 13 (LNC13) as potential biomarkers for monitoring tuberculosis treatment

Gaps in early and accurate diagnosis, effective drug control, and treatment monitoring are hindering the global eradication effort of tuberculosis. This infectious disease has become the deadliest worldwide before the outbreak of Covid-19. The search for new molecular biomarkers of tuberculosis will help to reverse this trend. Long non-coding RNAs (lncRNAs) have emerged as important regulators of the host immune response to infection, hence their link with the etiology and diagnosis of tuberculosis has attracted some attention from the research community. However, very little is known about their potential for the monitoring of tuberculosis treatment. This study aimed at assessing the potential of two lncRNAs: p50-associated Cyclooxygenase-2 Extragenic RNA (PACER) and Long Non-coding RNA 13 (LNC13) in the monitoring of tuberculosis treatment. This was a cross-sectional study carried out in Douala, Cameroon from December 2020 to August 2021. A quantitative real-time polymerase chain reaction followed by Cq analysis using the Livak method were performed to measure the relative expression levels of PACER and LNC13 in whole blood of healthy controls, patients with active pulmonary tuberculosis at the initiation of treatment, after two, five, and six months into treatment. Receiver Operating Characteristic curves analysis was used to assess the ability of targeted lncRNAs to discriminate among those groups. The study showed that the lncRNAs PACER and LNC13 were significantly upregulated in patients with active pulmonary tuberculosis at the initiation of treatment than in healthy controls. The expression levels of the two lncRNAs were significantly downregulated in patients during the treatment as compared to the active pulmonary tuberculosis patients. However, the expression levels of the lncRNAs PACER and LNC13 in whole blood of patients after six months of treatment were similar to those in healthy controls. Similarly, lncRNAs PACER and LNC13 showed very good performance in distinguishing between active tuberculosis patients and healthy controls as well as in differentiating between newly diagnosed active tuberculosis patients and those under treatment. Interestingly, those lncRNAs could not discriminate healthy controls from patients after six months of treatment. The lncRNAs PACER and LNC13 are therefore potential biomarkers for the monitoring of tuberculosis treatment.

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

Background

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

Objectives

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

Methods

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

Results

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

Conclusions

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

Long noncoding RNA H19 alleviates inflammation in osteoarthritis through interactions between TP53, IL-38, and IL-36 receptor

Aims

Osteoarthritis (OA) is a common degenerative joint disease characterized by chronic inflammatory articular cartilage degradation. Long noncoding RNAs (lncRNAs) have been previously indicated to play an important role in inflammation-related diseases. Herein, the current study set out to explore the involvement of lncRNA H19 in OA.

Methods

Firstly, OA mouse models and interleukin (IL)-1β-induced mouse chondrocytes were established. Expression patterns of IL-38 were determined in the synovial fluid and cartilage tissues from OA patients. Furthermore, the targeting relationship between lncRNA H19, tumour protein p53 (TP53), and IL-38 was determined by means of dual-luciferase reporter gene, chromatin immunoprecipitation, and RNA immunoprecipitation assays. Subsequent to gain- and loss-of-function assays, the levels of cartilage damage and proinflammatory factors were further detected using safranin O-fast green staining and enzyme-linked immunosorbent assay (ELISA) in vivo, respectively, while chondrocyte apoptosis was measured using Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling (TUNEL) in vitro.

Results

IL-38 was highly expressed in lentivirus vector-mediated OA mice. Meanwhile, injection of exogenous IL-38 to OA mice alleviated the cartilage damage, and reduced the levels of proinflammatory factors and chondrocyte apoptosis. TP53 was responsible for lncRNA H19-mediated upregulation of IL-38. Furthermore, it was found that the anti-inflammatory effects of IL-38 were achieved by its binding with the IL-36 receptor (IL-36R). Overexpression of H19 reduced the expression of inflammatory factors and chondrocyte apoptosis, which was abrogated by knockdown of IL-38 or TP53.

Conclusion

Collectively, our findings evidenced that upregulation of lncRNA H19 attenuates inflammation and ameliorates cartilage damage and chondrocyte apoptosis in OA by upregulating TP53, IL-38, and by activating IL-36R.

Cite this article: Bone Joint Res 2022;11(8):594–607.

LINC00313 alleviates osteoarthritis progression in mice through promoting TRAF1 promoter methylation and inhibiting the ASK1/JNK signaling pathway

OBJECTIVES

This study aimed to explore the underlying role and mechanism of LINC00313 in osteoarthritis (OA) progression.

METHODS

CHON-001 chondrocytes were treated with interleukin (IL)-1β to induce OA in vitro, and then transfected with LINC00313 overexpression plasmids (pcDNA-LINC00313) or small interfering RNA against tumor necrosis factor (TNF) receptor-associated factor 1 (si-TRAF1). Cell viability, apoptosis, levels of inflammatory cytokines tumor necrosis factor-α (TNF-α), IL-6 and IL-8, and expression of extracellular matrix (ECM) degradation related proteins in CHON-001 cells were determined. TRAF1 promoter methylation were was detected with methylation-specific polymerase chain reaction (MSP) assay. Furthermore, a c-Jun N-terminal kinase (JNK) signaling activator was used to confirm whether the apoptosis signal-regulating kinase 1 (ASK1)/JNK signaling pathway was involved in the function of LINC00313/TRAF1 axis in chondrocytes. In addition, an OA mouse model was established and lentivirus LINC00313 overexpression vector (Lv-LINC00313) was injected, and then inflammatory cytokine levels, ECM protein expression, and pathological changes in cartilage tissues were detected.

RESULTS

LINC00313 was downregulated and TRAF1 was upregulated in OA cartilage tissues. LINC00313 overexpression or TRAF1 silencing attenuated IL-1β-induced viability inhibition, apoptosis, inflammation and ECM degradation in CHON-001 cells. Moreover, LINC00313 inhibited TRAF1 expression through promoting DNA methyltransferase 1 (DNMT1) mediated promoter methylation. TRAF1 overexpression reversed the effects of LINC00313 on IL-1β-induced chondrocyte injury. LINC00313 overexpression inhibited the ASK1/JNK signaling pathway, and JNK activator reversed the effect. In addition, Lv-LINC00313 treatment alleviated cartilage tissue damage and cartilage matrix degradation in OA mice.

CONCLUSIONS

LINC00313 alleviated OA progression through inhibiting TRAF1 expression and the ASK1/JNK signaling pathway.

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.

Long intergenic non-protein coding RNA 00707 regulates chondrocyte apoptosis and proliferation in osteoarthritis by serving as a sponge for microRNA-199-3p

It is known that long intergenic non-protein coding RNA 00707 (LINC00707) promotes lipopolysaccharide (LPS)-injury and microRNA-199-3p (miR-199-3p) regulates chondrocyte proliferation and apoptosis. Both processes participate in osteoarthritis (OA). We predicted that LINC00707 and miR-199-3p may interact with each other. Therefore, LINC00707 and miR-199-3p may interact with each other to participate in OA. In this study, the expression of LINC00707 and miR-199-3p in both OA and normal articular cartilage tissues was analyzed using RT-qPCR. The subcellular location of LINC00707 and its direct interaction with miR-199-3p were explored by nuclear fractionation assay, RNA pull-down assay and Luciferase reporter assay, respectively. The role of LINC00707 and miR-199-3p in regulating the expression of each other was analyzed using an overexpression assay, followed by RT-qPCR. The role of LINC00707 and miR-199-3p in regulating OA chondrocyte proliferation and apoptosis was analyzed by BrdU assay and cell apoptosis assay, respectively. OA tissues exhibited increased expression of LINC00707 and decreased expression of miR-199-3p. LINC00707 directly interacted with miR-199-3p in cytoplasm. However, LINC00707 and miR-199-3p overexpression failed to affect each other’s expression. LPS treatment increased LINC00707 expression and decreased miR-199-3p expression in OA chondrocyte. LINC00707 overexpression increased the apoptosis of OA chondrocytes induced by LPS and suppressed the proliferation of OA chondrocytes. Moreover, LINC00707 suppressed the role of miR-199-3p in enhancing cell proliferation and suppressing cell apoptosis. In conclusion, LINC00707 can be detected in cytoplasm and it may sponge miR-199-3p to regulate chondrocyte proliferation and apoptosis in OA.

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.

The regulatory activities of MALAT1 in the development of bone and cartilage diseases

Long non-coding RNAs (lncRNAs) have been comprehensively implicated in various cellular functions by mediating transcriptional or post-transcriptional activities. MALAT1 is involved in the differentiation, proliferation, and apoptosis of multiple cell lines, including BMSCs, osteoblasts, osteoclasts, and chondrocytes. Interestingly, MALAT1 may interact with RNAs or proteins, regulating cellular processes. Recently, MALAT1 has been reported to be associated with the development of bone and cartilage diseases by orchestrating the signaling network. The involvement of MALAT1 in the pathological development of bone and cartilage diseases makes it available to be a potential biomarker for clinical diagnosis or prognosis. Although the potential mechanisms of MALAT1 in mediating the cellular processes of bone and cartilage diseases are still needed for further elucidation, MALAT1 shows great promise for drug development.

Advances on biological functions of exosomal non-coding RNAs in osteoarthritis

Exosomes can be secreted by various cells and function as intercellular communication vehicles by delivering specific cargoes from the donor cells to the recipient cells through their paracrine activity. Recently, an increasing number of studies have shown that non-coding RNAs (ncRNAs) could be entrapped in and transferred between cartilage-related cells as exosomal cargoes to modulate the expression of various target genes by regulation at post-transcriptional and post-translational levels. They are mainly comprised of microRNAs, long non-coding RNAs, and circular RNAs. Articular cartilage degeneration is one of the main pathological features of osteoarthritis. Exosomal ncRNAs are involved in pathological processes of osteoarthritis, such as proliferation, migration, chondrogenesis, chondrocyte differentiation induction, extracellular matrix formation, apoptosis, and inflammation. In this review, we summarize the biological functions of exosomal ncRNAs in cartilage homeostasis and osteoarthritis progression and discuss the perspectives and challenges of exosomal ncRNAs application for osteoarthritis patients in the future. Exosomal ncRNA has an important regulatory role in the pathogenesis of osteoarthritis, but more evidence is needed for clinical application.

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.

The non-coding RNA interactome in joint health and disease

Non-coding RNAs have distinct regulatory roles in the pathogenesis of joint diseases including osteoarthritis (OA) and rheumatoid arthritis (RA). As the amount of high-throughput profiling studies and mechanistic investigations of microRNAs, long non-coding RNAs and circular RNAs in joint tissues and biofluids has increased, data have emerged that suggest complex interactions among non-coding RNAs that are often overlooked as critical regulators of gene expression. Identifying these non-coding RNAs and their interactions is useful for understanding both joint health and disease. Non-coding RNAs regulate signalling pathways and biological processes that are important for normal joint development but, when dysregulated, can contribute to disease. The specific expression profiles of non-coding RNAs in various disease states support their roles as promising candidate biomarkers, mediators of pathogenic mechanisms and potential therapeutic targets. This Review synthesizes literature published in the past 2 years on the role of non-coding RNAs in OA and RA with a focus on inflammation, cell death, cell proliferation and extracellular matrix dysregulation. Research to date makes it apparent that 'non-coding' does not mean 'non-essential' and that non-coding RNAs are important parts of a complex interactome that underlies OA and RA.

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.

Oligonucleotide Therapies in the Treatment of Arthritis: A Narrative Review

Osteoarthritis (OA) and rheumatoid arthritis (RA) are two of the most common chronic inflammatory joint diseases, for which there remains a great clinical need to develop safer and more efficacious pharmacological treatments. The pathology of both OA and RA involves multiple tissues within the joint, including the synovial joint lining and the bone, as well as the articular cartilage in OA. In this review, we discuss the potential for the development of oligonucleotide therapies for these disorders by examining the evidence that oligonucleotides can modulate the key cellular pathways that drive the pathology of the inflammatory diseased joint pathology, as well as evidence in preclinical in vivo models that oligonucleotides can modify disease progression.

PR11-364P22.2/ATF3 protein interaction mediates IL-1β-induced catabolic effects in cartilage tissue and chondrocytes

Osteoarthritis (OA) is a degenerative joint disease which lacks effective medical treatment due to ill-defined molecular mechanisms underlying the pathology. Inflammation is a key factor that induces and aggravates OA. Therefore, the current study aims to explore roles of the dysregulated long non-coding RNAs in the pro-inflammatory cytokine IL-1β-mediated catabolic effects in cartilage tissue and chondrocytes. We identified RP11-364P22.2 as dysregulated in OA patient-derived cartilage tissues and highly responsive to IL-1β stimulus. RNA pull-down coupled with mass spectrometry demonstrated that RP11-364P22.2 physically binds to activating transcription factor 3 (ATF3) and thus increases the protein stability and facilitates its nuclear translocation. Loss- and gain-of-function assays indicated that the interaction between RP11-364P22.2 and ATF3 is indispensable for the detrimental effects of IL-1β including growth inhibition, apoptosis induction as well as degradation of the key chondrocyte structural proteins of type II collage and Aggrecan and synthesis of the extracellular matrix-degrading enzyme MMP13 in chondrocytes. In vivo, depletion of the RP11-364P22.2 effector ATF3 drastically prevented OA development in the rats with surgical destabilization of the medial meniscus (DMM). These results highlight the important roles of lncRNAs in the pathogenesis of OA and indicate the RP11-364P22.2/ATF3 regulatory axis as a potential therapeutic target of inflammation-induced OA.

Role of long non-coding RNAs in adipogenesis: State of the art and implications in obesity and obesity-associated diseases

Obesity is an evolutionary, chronic, and relapsing disease that consists of a pathological accumulation of adipose tissue able to increase morbidity for high blood pressure, type 2 diabetes, metabolic syndrome, and obstructive sleep apnea in adults, children, and adolescents. Despite intense research over the last 20 years, obesity remains today a disease with a complex and multifactorial etiology. Recently, long non-coding RNAs (lncRNAs) are emerging as interesting new regulators as different lncRNAs have been found to play a role in early and late phases of adipogenesis and to be implicated in obesity-associated complications onset. In this review, we discuss the most recent advances on the role of lncRNAs in adipocyte biology and in obesity-associated complications. Indeed, more and more researchers are focusing on investigating the underlying roles that these molecular modulators could play. Even if a significant number of evidence is correlation-based, with lncRNAs being differentially expressed in a specific disease, recent works are now focused on deeply analyzing how lncRNAs can effectively modulate the disease pathogenesis onset and progression. LncRNAs possibly represent new molecular markers useful in the future for both the early diagnosis and a prompt clinical management of patients with obesity.

LncRNA MIR22HG promotes osteoarthritis progression via regulating miR-9-3p/ADAMTS5 pathway

Dysregulation of long non-coding RNAs (lncRNAs) plays a fundamental role in the development and progression of osteoarthritis (OA), but the potential functions of lncRNAs in OA were not fully clarified. In the present work, we want to clarify the underlying functions and mechanisms of MIR22HG in OA. qRT-PCR was employed to detect the mRNA expression of MIR22HG, miR-9-3p, and ADAMTS5, while the protein expressions were measured using Western blot. The cell proliferation was examined through CCK8, while apoptosis was used in flow cytometry. Luciferase reporter assay and RNA immunoprecipitation (RIP) assays were undertaken to investigate the binding relationship among MIR22HG, ADAMTS5, and miR-9-3p. MIR22HG was significantly overexpressed in OA cartilages, OA chondrocytes and IL-1β-induced chondrocytes. Functionally, MIR22HG knockdown promoted cell proliferation, suppressed apoptosis, and contributed to downregulation of MMP13 and ADAMTS5 and upregulation of COL2A1 and ACAN in IL-1β-stimulated chondrocytes. Mechanistically, bioinformatic analysis indicated that MIR22HG may serve as a sponge for miR-9-3p and ADAMTS5 may be a potential targeted gene for miR-9-3p, which were subsequently verified through a dual-luciferase reporter assay. Moreover, rescue experiments showed that MIR22HG participated in the regulation of chondrocytes proliferation, apoptosis, and degradation of extracellular matrix via miR-9-3p/ADAMTS5 pathway. In conclusion, our findings illuminated that inhibition of MIR22HG ameliorated IL-1β-induced apoptosis and ECM degradation of human chondrocytes through miR-9-3p/ADAMTS5 pathway, which may provide a potentially promising target for OA treatment.

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.

Roles of long non‑coding RNA in osteoarthritis (Review)

Osteoarthritis (OA) is a chronic bone and joint disease characterized by articular cartilage degeneration and joint inflammation and is the most common form of arthritis. The clinical manifestations of OA are chronic pain and joint activity disorder, which severely affect the patient quality of life. Long non-coding RNA (lncRNA) is a class of RNA molecules >200 nucleotides long that are expressed in animals, plants, yeast, prokaryotes and viruses. lncRNA molecules lack an open reading frame and are not translated into protein. The present review collated the results of recent studies on the role of lncRNA in the pathogenesis of OA to provide information for the prevention, diagnosis and treatment of OA.

Triptolide Modulates the Expression of Inflammation-Associated lncRNA-PACER and lincRNA-p21 in Mycobacterium tuberculosis-Infected Monocyte-Derived Macrophages

Triptolide is a diterpene triepoxide, which performs its biological activities via mechanisms including induction of apoptosis, targeting of pro-inflammatory cytokines, and reshaping of the epigenetic landscape of target cells. However, the targeting of long non-coding RNAs (lncRNAs) by triptolide has not yet been investigated, despite their emerging roles as key epigenetic regulators of inflammation and immune cell function during Mycobacterium tuberculosis (Mtb) infection. Hence, we investigated whether triptolide targets inflammation-associated lncRNA-PACER and lincRNA-p21 and how this targeting associates with Mtb killing within monocyte-derived macrophages (MDMs).Using RT-qPCR, we found that triptolide induced the expression of lincRNA-p21 but inhibited the expression of lncRNA-PACER in resting MDMs in a dose- and time-dependent manner. Moreover, Mtb infection induced the expression of lincRNA-p21 and lncRNA-PACER, and exposure to triptolide before or after Mtb infection led to further increase of Mtb-induced expression of these lncRNAs in MDMs. We further found that contrary to lncRNA-PACER, triptolide time- and dose-dependently upregulated Ptgs-2, which is a proximal gene regulated by lncRNA-PACER. Also, low-concentration triptolide inhibited the expression of cytokine IL-6, a known target of lincRNA-p21. Mtb infection induced the expression of IL-6 and Ptgs-2, and triptolide treatment further increased IL-6 but decreased Ptgs-2 expression in Mtb-infected MDMs. The inverse relation between the expression of these lncRNAs and their target genes is concordant with the conception that these lncRNAs mediate, at least partially, the cytotoxic and/or anti-inflammatory activities of triptolide in both resting and activated MDMs. Using the CFU count method, we found that triptolide decreased the intracellular growth of Mtb HN878. The alamarBlue assay showed that this decreased Mtb HN878 growth was not as a result of direct targeting of Mtb HN878 by triptolide, but rather evoking MDMs’ intracellular killing mechanisms which we speculate could include triptolide-induced enhancement of MDMs’ effector killing functions mediated by lncRNA-PACER and lincRNA-p21. Altogether, these results provide proof of the modulation of lncRNA-PACER and lincRNA-p21 expression by triptolide, and a possible link between these lncRNAs, the enhancement of MDMs’ effector killing functions and the intracellular Mtb-killing activities of triptolide. These findings prompt for further investigation of the precise contribution of these lncRNAs to triptolide-induced activities in MDMs.

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.

The Expression and Function of Metastases Associated Lung Adenocarcinoma Transcript-1 Long Non-Coding RNA in Subchondral Bone and Osteoblasts from Patients with Osteoarthritis

Metastasis Associated Lung Adenocarcinoma Transcript-1 (MALAT1) is implicated in regulating the inflammatory response and in the pathology of several chronic inflammatory diseases, including osteoarthritis (OA). The purpose of this study was to examine the relationship between OA subchondral bone expression of MALAT1 with parameters of joint health and biomarkers of joint inflammation, and to determine its functional role in human OA osteoblasts. Subchondral bone and blood were collected from hip and knee OA patients (n = 17) and bone only from neck of femur fracture patients (n = 6) undergoing joint replacement surgery. Cytokines were determined by multiplex assays and ELISA, and gene expression by qPCR. MALAT1 loss of function was performed in OA patient osteoblasts using locked nucleic acids. The osteoblast transcriptome was analysed by RNASeq and pathway analysis. Bone expression of MALAT1 positively correlated to serum DKK1 and galectin-1 concentrations, and in OA patient osteoblasts was induced in response to IL-1β stimulation. Osteoblasts depleted of MALAT1 exhibited differential expression (>1.5 fold change) of 155 genes, including PTGS2. Both basal and IL-1β-mediated PGE2 secretion was greater in MALAT1 depleted osteoblasts. The induction of MALAT1 in human OA osteoblasts upon inflammatory challenge and its modulation of PGE2 production suggests that MALAT1 may play a role in regulating inflammation in OA subchondral bone.

Involvements of long noncoding RNAs in obesity-associated inflammatory diseases

Obesity is associated with chronic low-grade inflammation that affects the phenotype of multiple tissues and therefore is implicated in the development and progression of several age-related chronic inflammatory disorders. Importantly, a new family of noncoding RNAs, termed long noncoding RNAs (lncRNAs), have been identified as key regulators of inflammatory signalling pathways that can mediate both pretranscriptional and posttranscriptional gene regulation. Furthermore, several lncRNAs have been identified, which are differentially expressed in multiple tissue types in individuals who are obese or in preclinical models of obesity. In this review, we examine the evidence for the role of several of the most well-studied lncRNAs in the regulation of inflammatory pathways associated with obesity. We highlight the evidence for their differential expression in the obese state and in age-related conditions including insulin resistance, type 2 diabetes (T2D), sarcopenia, osteoarthritis and rheumatoid arthritis, where obesity plays a significant role. Determining the expression and functional role of lncRNAs in mediating obesity-associated chronic inflammation will advance our understanding of the epigenetic regulatory pathways that underlie age-related inflammatory diseases and may also ultimately identify new targets for therapeutic intervention.

Expression profiles of long non-coding RNAs in the cartilage of patients with knee osteoarthritis and normal individuals

Knee osteoarthritis is caused by a multifactorial imbalance in the synthesis and degradation of knee chondrocytes, subchondral bone and extracellular matrix. Abnormal expression of long non-coding RNAs (lncRNAs) affects the metabolism, synovitis, autophagy and apoptosis of chondrocytes, as well as the production of cartilage matrix. The aim of the present study was to identify novel targets for the treatment of osteoarthritis and to examine the pathogenesis of the disease. The lncRNA expression profiles of seven patients with knee osteoarthritis and six healthy controls were examined by RNA-sequencing. Differentially expressed lncRNAs were selected for bioinformatics analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Reverse transcription-quantitative PCR (RT-qPCR) was used to further investigate the differential expression of the lncRNAs. A total of 23,583 lncRNAs were identified in osteoarthritis cartilage, including 5,255 upregulated and 5,690 downregulated lncRNAs, compared with normal cartilage. Although there were more downregulated lncRNAs compared with upregulated lncRNAs, among the changed lncRNAs (fold-change >6), there were more upregulated lncRNAs compared with downregulated lncRNAs. Several lncRNAs exhibiting differences were identified as potential therapeutic targets in knee osteoarthritis. GO and KEGG pathway analyses were performed for the target genes of the differentially expressed lncRNAs. RT-qPCR validation was performed on three randomly selected upregulated and downregulated lncRNAs. The results of RT-qPCR were consistent with the findings obtained by RNA-sequencing analysis. The findings from the present study may contribute to the diagnosis of osteoarthritis and may predict the development of osteoarthritis. Furthermore, the differentially expressed lncRNAs may aid in the identification of novel candidate targets for the treatment of knee osteoarthritis.

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.

Profile Screening of Differentially Expressed lncRNAs of Circulating Leukocytes in Type 2 Diabetes Patients and Differences From Type 1 Diabetes

Long noncoding RNAs (lncRNAs) have been reported to have multiple functions and can be used as markers of various diseases, including diabetes. This study was conducted to determine the lncRNA profile in leukocytes from patients with type 2 diabetes (T2D). Differential expression of lncRNAs in T2D and type 1 diabetes (T1D) was also examined. RNA sequencing was performed in a critically grouped sample of leukocytes from T2D patients and healthy persons. A total of 845 significantly differentially expressed lncRNAs were identified, with 260 downregulated and 585 upregulated lncRNAs in T2D. The analysis of functions of DE-lncRNA and constructed co-expression networks (CNC) showed that 21 lncRNAs and 117 mRNAs harbored more than 10 related genes in CNC. Fourteen of 21 lncRNAs were confirmed to be significantly differentially expressed was detected by qPCR between the T2D and control validation cohorts. We also identified a panel of 4 lncRNAs showing significant differences in expression between T1D and T2D. Collectively, hundreds of novel DE-lncRNAs we identified in leukocytes from T2D patients will aid in epigenetic mechanism studies. Fourteen confirmed DE-lncRNAs can be regarded as diagnostic markers or regulators of T2D, including 4 lncRNAs that chould distinguish T1D and T2D in clinical practice to avoid misdiagnosis.

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.

Elucidating Epigenetic Regulation by Identifying Functional cis-Acting Long Noncoding RNAs and Their Targets in Osteoarthritic Articular Cartilage

Objective

To identify robustly differentially expressed long noncoding RNAs (lncRNAs) with osteoarthritis (OA) pathophysiology in cartilage and to explore potential target messenger RNA (mRNA) by establishing coexpression networks, followed by functional validation.

Methods

RNA sequencing was performed on macroscopically lesioned and preserved OA cartilage from patients who underwent joint replacement surgery due to OA (n = 98). Differential expression analysis was performed on lncRNAs that were annotated in GENCODE and Ensembl databases. To identify potential interactions, correlations were calculated between the identified differentially expressed lncRNAs and the previously reported differentially expressed protein‐coding genes in the same samples. Modulation of chondrocyte lncRNA expression was achieved using locked nucleic acid GapmeRs.

Results

By applying our in‐house pipeline, we identified 5,053 lncRNAs that were robustly expressed, of which 191 were significantly differentially expressed (according to false discovery rate) between lesioned and preserved OA cartilage. Upon integrating mRNA sequencing data, we showed that intergenic and antisense differentially expressed lncRNAs demonstrate high, positive correlations with their respective flanking sense genes. To functionally validate this observation, we selected P3H2‐AS1, which was down‐regulated in primary chondrocytes, resulting in the down‐regulation of P3H2 gene expression levels. As such, we can confirm that P3H2‐AS1 regulates its sense gene P3H2.

Conclusion

By applying an improved detection strategy, robustly differentially expressed lncRNAs in OA cartilage were detected. Integration of these lncRNAs with differential mRNA expression levels in the same samples provided insight into their regulatory networks. Our data indicate that intergenic and antisense lncRNAs play an important role in regulating the pathophysiology of OA.

Involvement of Myeloid Cells and Noncoding RNA in Abdominal Aortic Aneurysm Disease

Significance: Abdominal aortic aneurysm (AAA) is a potentially fatal condition, featuring the possibility of high-mortality rupture. To date, prophylactic surgery by means of open surgical repair or endovascular aortic repair at specific thresholds is considered standard therapy. Both surgical options hold different risk profiles of short- and long-term morbidity and mortality. Targeting early stages of AAA development to decelerate disease progression is desirable. Recent Advances: Understanding the pathomechanisms that initiate formation, maintain growth, and promote rupture of AAA is crucial to developing new medical therapeutic options. Inflammatory cells, in particular macrophages, have been investigated for their contribution to AAA disease for decades, whereas evidence on lymphocytes, mast cells, and neutrophils is sparse. Recently, there has been increasing interest in noncoding RNAs (ncRNAs) and their involvement in disease development, including AAA. Critical Issues: The current evidence on myeloid cells and ncRNAs in AAA largely originates from small animal models, making clinical extrapolation difficult. Although it is feasible to collect surgical human AAA samples, these tissues reflect end-stage disease, preventing examination of critical mechanisms behind early AAA formation. Future Directions: Gaining more insight into how myeloid cells and ncRNAs contribute to AAA disease, particularly in early stages, might suggest nonsurgical AAA treatment options. The utilization of large animal models might be helpful in this context to help bridge translational results to humans.

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.

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.

The long noncoding RNA H19 attenuates force-driven cartilage degeneration via miR-483-5p/Dusp5

Developmental dysplasia of the hip (DDH) is a common hip disease characterized by abnormal development of the acetabulum and femoral head. In most cases, DDH ultimately leads to osteoarthritis. Anomalous biomechanical force plays an important role in cartilage degeneration in DDH. However, in addition to mechanical wear, the underlying molecular mechanisms in cartilage degeneration in DDH remain unclear. This study analyzed the effect of long noncoding RNA (lncRNA)-H19 on DDH cartilage degradation. To elucidate the specific role of lncRNA H19, we established an intermittent cyclic mechanical stress (ICMS) cell force model to simulate abnormal biomechanical environment in vitro. Then, the roles of lncRNA-H19 were also determined in vivo by establishing a model of swaddling DDH. We observed that patients with DDH possessed low levels of lncRNA-H19, COL2A1, and Aggrecan but high levels of MMP3 and Adamts5. The same results were also obtained in a DDH rat model. Furthermore, the data suggested that ICMS promoted cartilage degeneration and caused reorientation of the cytoskeleton, and lncRNA H19 helped inhibit cartilage degeneration. Bioinformatics analysis and lncRNA sequencing were performed, and luciferase assays showed that lncRNA H19 and Dusp5 are both direct targets of miR-483-5p. Moreover, Dups5 plays a negative role in ICMS-induced cartilage degradation by activating the Erk and p38 pathways. In vivo, lncRNA H19 had protective effects on the swaddling DDH model. These findings indicate that lncRNA-H19 played a positive role in cartilage degradation in DDH through the lncRNA H19/miR-483-5p/Dusp5 axis.

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.

Long non-coding RNA MEG3 is involved in osteogenic differentiation and bone diseases (Review)

Osteogenic differentiation originating from mesenchymal stem cells (MSCs) requires tight co-ordination of transcriptional factors, signaling pathways and biomechanical cues. Dysregulation of such reciprocal networks may influence the proliferation and apoptosis of MSCs and osteoblasts, thereby impairing bone metabolism and homeostasis. An increasing number of studies have shown that long non-coding (lnc)RNAs are involved in osteogenic differentiation and thus serve an important role in the initiation, development, and progression of bone diseases such as tumors, osteoarthritis and osteoporosis. It has been reported that the lncRNA, maternally expressed gene 3 (MEG3), regulates osteogenic differentiation of multiple MSCs and also acts as a critical mediator in the development of bone formation and associated diseases. In the present review, the proposed mechanisms underlying the roles of MEG3 in osteogenic differentiation and its potential effects on bone diseases are discussed. These discussions may help elucidate the roles of MEG3 in osteogenic differentiation and highlight potential biomarkers and therapeutic targets for the treatment of bone diseases.

Regulation of the Inflammatory Synovial Fibroblast Phenotype by Metastasis-Associated Lung Adenocarcinoma Transcript 1 Long Noncoding RNA in Obese Patients With Osteoarthritis

OBJECTIVE

To identify long noncoding RNAs (lncRNAs) associated with the inflammatory phenotype of synovial fibroblasts from obese patients with osteoarthritis (OA), and to explore the expression and function of these lncRNAs.

METHODS

Synovium was collected from normal-weight patients with hip fracture (non-OA; n = 6) and from normal-weight (n = 8) and obese (n = 8) patients with hip OA. Expression of RNA was determined by RNA-sequencing and quantitative reverse transcription-polymerase chain reaction. Knockdown of lncRNA was performed using LNA-based GapmeRs. Synovial fibroblast cytokine production was measured by enzyme-linked immunosorbent assay.

RESULTS

Synovial fibroblasts from obese patients with OA secreted greater levels of interleukin-6 (IL-6) (mean ± SEM 162 ± 21 pg/ml; P < 0.001) and CXCL8 (262 ± 67 pg/ml; P < 0.05) compared to fibroblasts from normal-weight patients with OA (IL-6, 51 ± 4 pg/ml; CXCL8, 78 ± 11 pg/ml) or non-OA patients (IL-6, 35 ± 3 pg/ml; CXCL8, 56 ± 6 pg/ml) (n = 6 patients per group). RNA-sequencing revealed that fibroblasts from obese OA patients exhibited an inflammatory transcriptome, with increased expression of proinflammatory messenger RNAs (mRNAs) as compared to that in fibroblasts from normal-weight OA or non-OA patients (>2-fold change, P < 0.05; n = 4 patients per group). A total of 19 lncRNAs were differentially expressed between normal-weight OA and non-OA patient fibroblasts, and a further 19 lncRNAs were differentially expressed in fibroblasts from obese OA patients compared to normal-weight OA patients (>2-fold change, P < 0.05 for each), which included the lncRNA for metastasis-associated lung adenocarcinoma transcript 1 (MALAT1). MALAT1 was rapidly induced upon stimulation of OA synovial fibroblasts with proinflammatory cytokines, and was up-regulated in the synovium from obese OA patients as compared to normal-weight OA patients (1.6-fold change, P < 0.001) or non-OA patients (6-fold change, P < 0.001). MALAT1 knockdown in OA synovial fibroblasts (n = 4 patients) decreased the levels of mRNA expression and protein secretion of CXCL8 (>1.5-fold change, P < 0.01), whereas it increased expression of mRNAs for TRIM6 (>2-fold change, P < 0.01), IL7R (<2-fold change, P < 0.01), HIST1H1C (>1.5-fold change, P < 0.001), and MAML3 (>1.5-fold change, P < 0.001). In addition, MALAT1 knockdown inhibited the proliferation of synovial fibroblasts from obese patients with OA.

CONCLUSION

Synovial fibroblasts from obese patients with hip OA exhibit an inflammatory phenotype. MALAT1 lncRNA may mediate joint inflammation in obese OA patients.