MicroRNAs' Involvement in Osteoarthritis and the Prospects for Treatments. Evid Based Complement Alternat Med. 2015;2015:236179. [PMID: 26587043 PMCID: PMC4637488 DOI: 10.1155/2015/236179]

Tetrahedral framework nucleic acids-based delivery of microRNA-155 alleviates intervertebral disc degeneration through targeting Bcl-2/Bax apoptosis pathway

Intervertebral disc degeneration (IDD) is one of the most common causes of chronic low back pain, which does great harm to patients' life quality. At present, the existing treatment options are mostly aimed at relieving symptoms, but the long-term efficacy is not ideal. Tetrahedral framework nucleic acids (tFNAs) are regarded as a type of nanomaterial with excellent biosafety and prominent performance in anti-apoptosis and anti-inflammation. MicroRNA155 is a non-coding RNA involved in various biological processes such as cell proliferation and apoptosis. In this study, a complex named TR155 was designed and synthesised with microRNA155 attached to the vertex of tFNAs, and its effects on the nucleus pulposus cells of intervertebral discs were evaluated both in vitro and in vivo. The experimental results showed that TR155 was able to alleviate the degeneration of intervertebral disc tissue and inhibit nucleus pulposus cell apoptosis via Bcl-2/Bax pathway, indicating its potential to be a promising option for the treatment of IDD.

Exploring the Impact of TLR-2 Signaling on miRNA Dysregulation in Intervertebral Disc Degeneration

Toll-like receptors (TLRs) are key mediators of inflammation in intervertebral disc (IVD) degeneration. TLR-2 activation contributes to the degenerative process by increasing the expression of extracellular matrix-degrading enzymes, pro-inflammatory cytokines, and neurotrophins. As potent post-transcriptional regulators, microRNAs can modulate intracellular mechanisms, and their dysregulation is known to contribute to numerous pathologies. This study aims to investigate the impact of TLR-2 signaling on miRNA dysregulation in the context of IVD degeneration. Small-RNA sequencing of degenerated IVD cells shows the dysregulation of ten miRNAs following TLR-2 activation by PAM2CSK4. The miR-155-5p is most significantly upregulated in degenerated and non-degenerated annulus fibrosus and nucleus pulposus cells. Sequence-based target and pathway prediction shows the involvement of miR-155-5p in inflammation- and cell fate-related pathways and TLR-2-induced miR-155-5p expression leads to the downregulation of its target c-FOS. Furthermore, changes specific to the activation of TLR-2 through fragmented fibronectin are seen in miR-484 and miR-487. Lastly, miR-100-3p, miR-320b, and miR-181a-3p expression exhibit degeneration-dependent changes. These results show that TLR-2 signaling leads to the dysregulation of miRNAs in IVD cells as well as their possible downstream effects on inflammation and degeneration. The identified miRNAs provide important opportunities as potential therapeutic targets for IVD degeneration and low back pain.

Plasma microRNA-320c as a Potential Biomarker for the Severity of Knee Osteoarthritis and Regulates cAMP Responsive Element Binding Protein 5 (CREB5) in Chondrocytes

Objective

Osteoarthritis (OA) is a commonly known prevalent joint disease, with limited therapeutic methods. This study aimed to investigate the expression of plasma microRNA-320c (miR-320c) in patients with knee OA and to explore the clinical value and potential mechanism of miR-320c in knee OA.

Methods

Forty knee OA patients and 20 healthy controls were enrolled. The levels of plasma miR-320c and plasma inflammatory cytokines were measured by real-time PCR or ELISA. Correlations of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores and cytokine levels with the miR-320c expression level were evaluated by Pearson correlation analysis. Then, a receiver operating characteristic (ROC) curve was drawn to analyse the diagnostic value of miR-320c in OA. Finally, the interaction of miR-320c and cAMP responsive element binding protein 5 (CREB5) was determined using a luciferase reporter assay, and the effect of CREB5 on the cAMP pathway was assessed.

Results

The expression level of plasma miR-320c was significantly higher in OA patients than in healthy controls (p  < 0.05). The increased plasma miR-320c level was positively correlated with the WOMAC score (r = 0.796, p  < 0.001) and the plasma interleukin (IL)-1β (r = 0.814, p  < 0.001) and IL-6 (r = 0.695, p  < 0.001) levels in patients with OA. ROC curve analysis demonstrated the relatively high diagnostic accuracy of plasma miR-320c for OA. Furthermore, the luciferase reporter assay results showed that miR-320c regulates CREB5 expression by binding to the CREB5 3'-untranslated region. Moreover, suppression of CREB5 significantly reduced the expression levels of c-fos and c-jun.

Conclusion

Our results indicate that plasma miR-320c may serve as a potential novel predictor of the severity of knee OA and that miR-320c may play an important role in the pathogenesis of OA through inhibiting the cAMP pathway by targeting CREB5.

Exploring the Feasibility of Circulating miRNAs as Diagnostic and Prognostic Biomarkers in Osteoarthritis: Challenges and Opportunities

Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by progressive cartilage degradation and joint inflammation. As the most common aging-related joint disease, OA is marked by inadequate extracellular matrix synthesis and the breakdown of articular cartilage. However, traditional diagnostic methods for OA, relying on clinical assessments and radiographic imaging, often need to catch up in detecting early-stage disease or i accurately predicting its progression. Consequently, there is a growing interest in identifying reliable biomarkers that can facilitate early diagnosis and prognosis of OA. MicroRNAs (miRNAs) have emerged as potential candidates due to their involvement in various cellular processes, including cartilage homeostasis and inflammation. This review explores the feasibility of circulating miRNAs as diagnostic and prognostic biomarkers in OA, focusing on knee OA while shedding light on the challenges and opportunities associated with their implementation in clinical practice.

Chondrocyte Homeostasis and Differentiation: Transcriptional Control and Signaling in Healthy and Osteoarthritic Conditions

Chondrocytes are the main cell type in articular cartilage. They are embedded in an avascular, abundant, and specialized extracellular matrix (ECM). Chondrocytes are responsible for the synthesis and turnover of the ECM, in which the major macromolecular components are collagen, proteoglycans, and non-collagen proteins. The crosstalk between chondrocytes and the ECM plays several relevant roles in the regulation of cell phenotype. Chondrocytes live in an avascular environment in healthy cartilage with a low oxygen supply. Although chondrocytes are adapted to anaerobic conditions, many of their metabolic functions are oxygen-dependent, and most cartilage oxygen is supplied by the synovial fluid. This review focuses on the transcription control and signaling responsible for chondrocyte differentiation, homeostasis, senescence, and cell death and the changes that occur in osteoarthritis. The effects of chondroitin sulfate and other molecules as anti-inflammatory agents are also approached and analyzed.

Osteoarthritis and microRNAs: Do They Provide Novel Insights into the Pathophysiology of This Degenerative Disorder?

Osteoarthritis (OA) is one of the most prevalent degenerative joint diseases in older adults and a leading cause of disability. Recent research studies have evidenced the importance of mi-croRNAs (miRs) in the pathogenesis of OA. In the present review, we focused on current literature findings on dysregulated miRs involved in the pathophysiology of OA. From the 35 case-control studies including OA patients compared to healthy controls, a total of 54 human miRs were identified to be dysregulated in OA. In total, 41 miRs were involved in the pathophysiological processes of OA, including apoptosis, inflammation, and proliferation, having either a protective or a progressive role in OA. The discovery of altered miR levels in OA patients compared to healthy controls determines a better understanding of the molecular mechanisms involved in the pathophysiology of OA and could open novel horizons in the field of orthopedics.

The lncRNA MIAT/miR-181a-5p axis regulates osteopontin (OPN)-mediated proliferation and apoptosis of human chondrocytes in osteoarthritis

Osteoarthritis (OA) is a slow-progressing degenerative joint disease mainly characterized by progressive cartilage loss and subchondral bone remodeling. Osteopontin (OPN) is a matrix extracellular glyco-phosphoprotein capable of regulating the expression levels of multiple factors linked with OA pathogenesis. This study explores the upstream regulatory molecular mechanism of OPN on proliferation and apoptosis of human chondrocytes in OA. Chondrocytes were isolated from OA cartilage and identified by toluidine blue staining and immunofluorescent staining of type II collagen. An MTT assay was used for cell viability, and a BrdU assay was applied for DNA synthesis. Cell apoptosis was detected by a flow cytometry assay. A lncRNA MIAT/miR-181a-5p/OPN axis regulating OA chondrocyte proliferation and apoptosis were identified. miR-181a-5p directly targeted OPN and inhibited OPN expression in OA chondrocytes. miR-181a-5p overexpression inhibited OA chondrocyte viability, suppressed DNA synthesis, and promoted apoptosis. OPN overexpression exerted opposite effects on OA chondrocytes and significantly attenuated the roles of miR-181a-5p overexpression in OA chondrocytes. A total of six long non-coding RNAs (lncRNAs) were predicted to target miR-181a-5p, and MIAT was the most up-regulated in OA cartilage tissues among the six lncRNAs. Through direct targeting, MIAT inhibited miR-181a-5p expression. MIAT silencing inhibited cell viability, suppressed DNA synthesis, and promoted cell apoptosis. Moreover, miR-181a-5p inhibition partially reversed the effects of MIAT silencing on OA chondrocytes. The lncRNA MIAT/miR-181a-5p/OPN axis could modulate OA chondrocyte proliferation and apoptosis. The comprehensive function of this axis on OA requires further in vivo and clinical investigations.

Extracellular Vesicles Allow Epigenetic Mechanotransduction between Chondrocytes and Osteoblasts

MicroRNAs (miRNAs) can be transported in extracellular vesicles (EVs) and are qualified as possible messengers for cell–cell communication. In the context of osteoarthritis (OA), miR-221-3p has been shown to have a mechanosensitive and a paracrine function inside cartilage. However, the question remains if EVs with miR-221-3p can act as molecular mechanotransducers between cells of different tissues. Here, we studied the effect of EV-mediated transport in the communication between chondrocytes and osteoblasts in vitro in a rat model. In silico analysis (Targetscan, miRWalk, miRDB) revealed putative targets of miRNA-221-3p (CDKN1B/p27, TIMP-3, Tcf7l2/TCF4, ARNT). Indeed, transfection of miRNA-221-3p in chondrocytes and osteoblasts resulted in regulation of these targets. Coculture experiments of transfected chondrocytes with untransfected osteoblasts not only showed regulation of these target genes in osteoblasts but also inhibition of their bone formation capacity. Direct treatment with chondrocyte-derived EVs validated that chondrocyte-produced extracellular miR-221-3p was responsible for this effect. Altogether, our study provides a novel perspective on a possible communication pathway of a mechanically induced epigenetic signal through EVs. This may be important for processes at the interface of bone and cartilage, such as OA development, physiologic joint homeostasis, growth or fracture healing, as well as for other tissue interfaces with differing biomechanical properties.

Role of microRNA Shuttled in Small Extracellular Vesicles Derived From Mesenchymal Stem/Stromal Cells for Osteoarticular Disease Treatment

Osteoarticular diseases (OD), such as rheumatoid arthritis (RA) and osteoarthritis (OA) are chronic autoimmune/inflammatory and age-related diseases that affect the joints and other organs for which the current therapies are not effective. Cell therapy using mesenchymal stem/stromal cells (MSCs) is an alternative treatment due to their immunomodulatory and tissue differentiation capacity. Several experimental studies in numerous diseases have demonstrated the MSCs’ therapeutic effects. However, MSCs have shown heterogeneity, instability of stemness and differentiation capacities, limited homing ability, and various adverse responses such as abnormal differentiation and tumor formation. Recently, acellular therapy based on MSC secreted factors has raised the attention of several studies. It has been shown that molecules embedded in extracellular vesicles (EVs) derived from MSCs, particularly those from the small fraction enriched in exosomes (sEVs), effectively mimic their impact in target cells. The biological effects of sEVs critically depend on their cargo, where sEVs-embedded microRNAs (miRNAs) are particularly relevant due to their crucial role in gene expression regulation. Therefore, in this review, we will focus on the effect of sEVs derived from MSCs and their miRNA cargo on target cells associated with the pathology of RA and OA and their potential therapeutic impact.

Preoperative serum circulating microRNAs as potential biomarkers for chronic postoperative pain after total knee replacement

Background

Chronic postoperative pain affects approximately 20% of patients with knee osteoarthritis after total knee replacement. Circulating microRNAs can be found in serum and might act as biomarkers in a variety of diseases. The current study aimed to investigate the preoperative expression of circulating microRNAs as potential predictive biomarkers for the development of chronic postoperative pain in the year following total knee replacement.

Methods

Serum samples, collected preoperatively from 136 knee osteoarthritis patients, were analyzed for 21 circulatory microRNAs. Pain intensity was assessed using a visual analog scale before and one year after total knee replacement. Patients were divided into a low-pain relief group (pain relief percentage <30%) and a high-pain relief group (pain relief percentage >30%) based on their pain relief one year after total knee replacement, and differences in microRNAs expression were analyzed between the two groups.

Results

We found that three microRNAs were preoperatively dysregulated in serum in the low-pain relief group compared with the high-pain relief group. MicroRNAs hsa-miR-146a-5p, -145-5p, and -130 b-3p exhibited fold changes of 1.50, 1.55, and 1.61, respectively, between the groups (all P values < 0.05). Hsa-miR-146a-5p and preoperative pain intensity correlated positively with postoperative pain relief (respectively, R = 0.300, P = 0.006; R = 0.500, P < 0.001).

Discussion

This study showed that patients with a low postoperative pain relief present a dysregulation of circulating microRNAs. Altered circulatory microRNAs expression correlated with postoperative pain relief, indicating that microRNAs can serve as predictive biomarkers of pain outcome after surgery and hence may foster new strategies for preventing chronic postoperative pain after total knee replacement (TKR).

Control of the Autophagy Pathway in Osteoarthritis: Key Regulators, Therapeutic Targets and Therapeutic Strategies

Autophagy is involved in different degenerative diseases and it may control epigenetic modifications, metabolic processes, stem cells differentiation as well as apoptosis. Autophagy plays a key role in maintaining the homeostasis of cartilage, the tissue produced by chondrocytes; its impairment has been associated to cartilage dysfunctions such as osteoarthritis (OA). Due to their location in a reduced oxygen context, both differentiating and mature chondrocytes are at risk of premature apoptosis, which can be prevented by autophagy. AutophagomiRNAs, which regulate the autophagic process, have been found differentially expressed in OA. AutophagomiRNAs, as well as other regulatory molecules, may also be useful as therapeutic targets. In this review, we describe and discuss the role of autophagy in OA, focusing mainly on the control of autophagomiRNAs in OA pathogenesis and their potential therapeutic applications.

Equine synovial fluid small non-coding RNA signatures in early osteoarthritis

BACKGROUND

Osteoarthritis remains one of the greatest causes of morbidity and mortality in the equine population. The inability to detect pre-clinical changes in osteoarthritis has been a significant impediment to the development of effective therapies against this disease. Synovial fluid represents a potential source of disease-specific small non-coding RNAs (sncRNAs) that could aid in the understanding of the pathogenesis of osteoarthritis. We hypothesised that early stages of osteoarthritis would alter the expression of sncRNAs, facilitating the understanding of the underlying pathogenesis and potentially provide early biomarkers.

METHODS

Small RNA sequencing was performed using synovial fluid from the metacarpophalangeal joints of both control and early osteoarthritic horses. A group of differentially expressed sncRNAs was selected for further validation through qRT-PCR using an independent cohort of synovial fluid samples from control and early osteoarthritic horses. Bioinformatic analysis was performed in order to identify putative targets of the differentially expressed microRNAs and to explore potential associations with specific biological processes.

RESULTS

Results revealed 22 differentially expressed sncRNAs including 13 microRNAs; miR-10a, miR-223, let7a, miR-99a, miR-23b, miR-378, miR-143 (and six novel microRNAs), four small nuclear RNAs; U2, U5, U11, U12, three small nucleolar RNAs; U13, snoR38, snord96, and one small cajal body-specific RNA; scarna3. Five sncRNAs were validated; miR-223 was significantly reduced in early osteoarthritis and miR-23b, let-7a-2, snord96A and snord13 were significantly upregulated. Significant cellular actions deduced by the differentially expressed microRNAs included apoptosis (P < 0.0003), necrosis (P < 0.0009), autophagy (P < 0.0007) and inflammation (P < 0.00001). A conservatively filtered list of 57 messenger RNA targets was obtained; the top biological processes associated were regulation of cell population proliferation (P < 0.000001), cellular response to chemical stimulus (P < 0.000001) and cell surface receptor signalling pathway (P < 0.000001).

CONCLUSIONS

Synovial fluid sncRNAs may be used as molecular biomarkers for early disease in equine osteoarthritic joints. The biological processes they regulate may play an important role in understanding early osteoarthritis pathogenesis. Characterising these dynamic molecular changes could provide novel insights on the process and mechanism of early osteoarthritis development and is critical for the development of new therapeutic approaches.

miR-155-5p regulates macrophage M1 polarization and apoptosis in the synovial fluid of patients with knee osteoarthritis

Osteoarthritis (OA) is one of the most prevalent degenerative joint diseases that affects millions of individuals worldwide. During OA, proinflammatory factors (including IL-1, IL-6, IL-17 and TNF-α) are released from chondrocytes and proliferating synoviocytes potentiate the proinflammatory microenvironment of the synovial fluid (SF). The altered SF microenvironment affects the infiltration, polarization and apoptosis of macrophages, though the underlying mechanisms are not completely understood. In the present study, the hypothesis that the knee synovial fluid of patients with knee osteoarthritis (KOA SF) promotes the polarization of peripheral blood mononuclear cell (PBMC)-derived M1 macrophages and inhibits PBMC-derived macrophage apoptosis was investigated. KOA SF increased PBMC-derived macrophage M1 polarization via the microRNA (miR)-155-5p/suppressor of cytokine signaling 1 signaling pathway. Caspase-3 (CASP3) was identified as a novel target of miR-155-5p, where KOA SF inhibited macrophage apoptosis via the miR-155-5p/CASP3 signaling pathway. The results suggested that the proinflammatory environment of KOA SF promoted macrophage M1 polarization and reduced macrophage apoptosis via miR-155-5p. The results provided a potential explanation for the increased number of M1 macrophages observed in KOA SF during OA. In addition, the present study suggested that miR-155-5p may serve as a potential therapeutic target for KOA.

LncRNA-GAS5 Inhibits Expression of miR 103 and Ameliorates the Articular Cartilage in Adjuvant-Induced Arthritis in Obese Mice

We explored whether long noncoding RNA growth arrest-specific transcript 5 (LncRNA-GAS5) small interfering RNA (siRNA) reduced cartilage destruction in obese mice with adjuvant-induced arthritis. We studied the effects of LncRNA-GAS5 siRNA on the polyarthritis index; hind paw swelling; and the serum levels of certain biochemicals, cytokines, and oxidative stress parameters. We measured the expression levels of matrix metalloproteinases (MMP)-13, NF-κB, fibroblast growth factor (FGF) 21, p38, Akt, and PI3K in cartilage via Western blotting and quantitative reverse transcription PCR. Long noncoding RNA-GAS5 siRNA reduced joint swelling; the serum levels of arthritis-associated biochemicals, cytokines, and oxidative stress markers; and cartilage MMP-13, NF-κB, FGF21, p38, Akt, and PI3K levels. Cartilage miR-103 expression was reduced. Histopathologically, LncRNA-GAS5 siRNA ameliorated the pathological changes of cartilage. Long noncoding RNA-GAS5 siRNA prevented cartilage destruction by inhibiting miR-103 expression.

miRNA-103 promotes chondrocyte apoptosis by down-regulation of Sphingosine kinase-1 and ameliorates PI3K/AKT pathway in osteoarthritis

OBJECTIVES

The aim of the present study was to determine the effects of miRNA-103 on chondrocyte apoptosis and molecular mechanisms in osteoarthritis (OA) progression.

METHODS

The cell proliferation, apoptosis, and recovery ability were measured by cell counting kit-8 (CCK-8), flow cytometry, and wound healing assays. The interaction of miRNA-103 and Sphingosine kinase-1 (SPHK1) were determined by using luciferase reporter assay. The expression of mRNA and proteins were measured by qRT-PCR and Western blot. OA rat model was established by surgery stimulation.

RESULTS

miRNA-103 expression was significantly increased in the cartilage of OA patients and surgery-induced OA rat models. miRNA-103 transfection into primary rat chondrocytes reduced SPHK1 expression, induced apoptosis, inhibited cell proliferation, and impeded scratch assay wound closure. Moreover, expression of total AKT, and p-AKT were significantly reduced in miRNA-103-overexpressing chondrocytes while SPHK1 up-regulation increased the expression of phosphatidylinsitol-3-kinase (PI3K) and p-AKT, and reversed the proliferation suppression induced by the miRNA-103 mimic.

CONCLUSIONS

Our studies suggest that miRNA-103 contributes to chondrocyte apoptosis, promoting OA progression by down-regulation of PI3K/AKT pathway through the reduction in SPHK1 activity.

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

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

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

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

MicroRNAs in Intervertebral Disc Degeneration, Apoptosis, Inflammation, and Mechanobiology

Intervertebral disc (IVD) degeneration is a multifactorial pathological process associated with low back pain, the leading cause of years lived in disability worldwide. Key characteristics of the pathological changes connected with degenerative disc disease (DDD) are the degradation of the extracellular matrix (ECM), apoptosis and senescence, as well as inflammation. The impact of nonphysiological mechanical stresses on IVD degeneration and inflammation, the mechanisms of mechanotransduction, and the role of mechanosensitive miRNAs are of increasing interest. As post-transcriptional regulators, miRNAs are known to affect the expression of 30% of proteincoding genes and numerous intracellular processes. The dysregulation of miRNAs is therefore associated with various pathologies, including degenerative diseases such as DDD. This review aims to give an overview of the current status of miRNA research in degenerative disc pathology, with a special focus on the involvement of miRNAs in ECM degradation, apoptosis, and inflammation, as well as mechanobiology.

microRNA-9 might be a novel protective factor for osteoarthritis patients

BACKGROUND

The study aimed to identify the targeting genes and miRNAs using the microarray expression profile dataset for Osteoarthritis (OA) patients. Differentially expressed genes (DEGs) between OA and control samples were identified using Bayes method of limma package. Subsequently, a protein-protein interaction (PPI) network was constructed. miRNAs and transcription factor (TFs) based on DEGs in PPI network were identified using Webgestalt and ENCODE, respectively. Finally, MCODE, Gene Ontology (GO) function, and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed. The expressions of several DEGs and predicted miRNAs in OA rats were detected by RT-PCR.

RESULTS

A total of 594 DEGs were identified. In PPI network, there were 313 upregulated DEGs and 22 downregulated DEGs. Besides, the regulatory relationships included 467 upregulated interactions and 85 downregulated interactions (miR-124A → QKI and MAP 1B) between miRNA and DEGs in PPI network. The module from downregulated DEGs-TFs-miRNA networks was mainly enriched to low-density lipoprotein particle clearance, response to linoleic acid, and small molecule metabolic process BP terms. Moreover, QKI, MAP 1B mRNA and miR-9 expressions were significantly reduced in OA rats.

CONCLUSION

miR-9 might be a protective factor for OA patients via inhibiting proliferation and differentiation of cartilage progenitor cells. miR-124A might play an important role in progression of OA through targeting QKI and MAP 1B.

γ-Mangostin isolated from Garcinia mangostana L. suppresses inflammation and alleviates symptoms of osteoarthritis via modulating miR-124-3p/IL-6/NF-κB signaling

Osteoarthritis (OA) a disease associated with joints and become severe with age, due to softening, inflammation and degradation of cartilage in joints. The agents that can target OA is needed, specifically without any side effects. Garcinia mangostana L. (Mangosteen) a tropical fruit used to treat many skin and stomach associated ailments. γ- Mangostin (γ-MS) a key bioactive substance present in mangosteen. Here, we aimed to explore γ-MS potential in targeting the pro-inflammatory cytokine, factors and miRs in OA progression. Significantly, γ-MS suppresses the inflammatory cytokines (IL-6, TNF-α, and INF- γ) and factors (NF-κB, STAT3, and COX-2) which regulates/participate in the catabolic process of cartilage destruction. Result of Hematoxylin-eosin (H&E) staining of tissue sections of OA joints of γ-MS treated and non-treated mice confirm γ-MS improves the signs of injuries, and maintains the structural integrity of the articular cartilage (epiphyseal disk joints and bone marrow) and reduces inflammation. Mechanistically, γ-MS targets miR-98-5p and miR-124-3p which are found to suppress the expression IL-6 and NF-κB, respectively. But in OA these miRs are inhibited, especially miR-124-3p which regulates not only NF-κB but also TNF-α, IL-6 and MMP7. With a further investigation underway, γ-MS represents an important source for treating and managing OA.

Combination of low intensity electromagnetic field with chondrogenic agent induces chondrogenesis in mesenchymal stem cells with minimal hypertrophic side effects

Background: There are different methods to develop in vitro neo-chondral tissues from adipose-derived stem cells (ADSCs). Application of electromagnetic field (EMF) on ADSCs is one of popular approaches, which results in chondrogenesis. If chondrogenic impact of EMF on ADSCs is supposed to be generalized as a protocol in translational medicine field, possible emergence of early or late hypertrophic maturation, mineralization and inflammatory side effects in chondrogenically differentiating ADSCs should be considered.Methods: The advent of chondrogenic and hypertrophic markers by differentiated cells under standard, platelet-rich plasma (PRP)-based or EMF treatments were monitored. Along with monitoring the expressions of chondrogenic markers, inflammatory and hypertrophic markers, VEGF/TNFα secretion, calcium deposition and ALP activity were evaluated.Results: Accordingly, treatment with %5 PRP results in higher GAG production, enhanced SOX9 transcription, lowered TNFα and VEGF secretions compared to other treatments. Although PRP up-regulates miR-146a and miR-199a in early and late stages of chondrogenesis, respectively, application of EMF + PRP down regulates miR-101 and -145 while up-regulates miR-140 and SOX9 expression.Conclusion: Comparing our results with previous reports suggests that presented EMF-ELF in this study with f = 50 Hz, EMF intensity of less than 30 mT, and 5% PRP (v/v), would facilitate chondrogenesis via mesenchymal stem cells with minor inflammation and hypertrophic maturation.Abbreviations: MSCs: mesenchymal stem cells; TGFβ: transforming growth factor-beta; PRP: platelet-rich plasma; ELF-EMF: extremely low-frequency electromagnetic fields; GAGs: glycosaminoglycans; ADSCs: adipose-derived stem cells; VEGF: vascular endothelial growth factor; TNFα: tumor necrosis factor alpha; ALP: alkaline phosphatase.

Comparative impact of platelet rich plasma and transforming growth factor-β on chondrogenic differentiation of human adipose derived stem cells

Introduction: Transforming growth factor-beta (TGF-β) is known as standard chondrogenic differentiation agent, even though it comes with undesirable side effects such as early hypertrophic maturation, mineralization, and secretion of inflammatory/angiogenic factors. On the other hand, platelet-rich plasma (PRP) is found to have a chondrogenic impact on mesenchymal stem cell proliferation and differentiation, with no considerable side effects. Therefore, we compared chondrogenic impact of TGF-β and PRP on adipose-derived stem cells (ADSCs), to see if PRP could be introduced as an alternative to TGF-β.

Methods: Differentiation of ADSCs was monitored using a couple of methods including glycosaminoglycan production, miRNAs expression, vascular endothelial growth factor (VEGF)/tumor necrosis factor alpha (TNFα) secretion, alkaline phosphatase (ALP) and calcium content assays.

Results: Accordingly, the treatment of differentiating cells with 5% (v/v) PRP resulted in higher glycosaminoglycan production, enhanced SOX9 transcription, and lowered TNFα and VEGF secretion compared to the control and TGF-β groups. Besides, the application of PRP to the media up-regulated miR-146a and miR-199a in early and late stages of chondrogenesis, respectively.

Conclusion: PRP induces in vitro chondrogenesis, as well as TGF-β with lesser inflammatory and hypertrophic side effects.

Application of mesenchymal stem cell therapy for the treatment of osteoarthritis of the knee: A concise review

Osteoarthritis (OA) refers to a chronic joint disease characterized by degenerative changes of articular cartilage and secondary bone hyperplasia. Since articular cartilage has a special structure, namely the absence of blood vessels as well as the low conversion rate of chondrocytes in the cartilage matrix, the treatment faces numerous clinical challenges. Traditional OA treatment (e.g., arthroscopic debridement, microfracture, autologous or allogeneic cartilage transplantation, chondrocyte transplantation) is primarily symptomatic treatment and pain management, which cannot contribute to regenerating degenerated cartilage or reducing joint inflammation. Also, the generated mixed fibrous cartilage tissue is not the same as natural hyaline cartilage. Mesenchymal stem cells (MSCs) have turned into the most extensively explored new therapeutic drugs in cell-based OA treatment as a result of their ability to differentiate into chondrocytes and their immunomodulatory properties. In this study, the preliminary results of preclinical (OA animal model)/clinical trials regarding the effects of MSCs on cartilage repair of knee joints are briefly summarized, which lay a solid application basis for more and deeper clinical studies on cell-based OA treatment.

Interaction with hyaluronan matrix and miRNA cargo as contributors for in vitro potential of mesenchymal stem cell-derived extracellular vesicles in a model of human osteoarthritic synoviocytes

BACKGROUND

Osteoarthritis (OA) is the most prevalent joint disease, and to date, no options for effective tissue repair and restoration are available. With the aim of developing new therapies, the impact of mesenchymal stem cells (MSCs) has been explored, and the efficacy of MSCs started to be deciphered. A strong paracrine capacity relying on both secreted and vesicle-embedded (EVs) protein or nucleic acid-based factors has been proposed as the principal mechanism that contributes to tissue repair. This work investigated the mechanism of internalization of extracellular vesicles (EVs) released by adipose-derived MSCs (ASCs) and the role of shuttled miRNAs in the restoration of homeostasis in an in vitro model of human fibroblast-like synoviocytes (FLSs) from OA patients.

METHODS

ASC-EVs were isolated by differential centrifugation and validated by flow cytometry and nanoparticle tracking analysis. ASC-EVs with increased hyaluronan (HA) receptor CD44 levels were obtained culturing ASCs on HA-coated plastic surfaces. OA FLSs with intact or digested HA matrix were co-cultured with fluorescent ASC-EVs, and incorporation scored by flow cytometry and ELISA. ASC-EV complete miRNome was deciphered by high-throughput screening. In inflamed OA FLSs, genes and pathways potentially regulated by ASC-EV miRNA were predicted by bioinformatics. OA FLSs stimulated with IL-1β at physiological levels (25 pg/mL) were treated with ASC-EVs, and expression of inflammation and OA-related genes was measured by qRT-PCR over a 10-day time frame with modulated candidates verified by ELISA.

RESULTS

The data showed that HA is involved in ASC-EV internalization in FLSs. Indeed, both removal of HA matrix presence on FLSs and modulation of CD44 levels on EVs affected their recruitment. Bioinformatics analysis of EV-embedded miRNAs showed their ability to potentially regulate the main pathways strictly associated with synovial inflammation in OA. In this frame, ASC-EVs reduced the expression of pro-inflammatory cytokines and chemokines in a chronic model of FLS inflammation.

CONCLUSIONS

Given their ability to affect FLS behavior in a model of chronic inflammation through direct interaction with HA matrix and miRNA release, ASC-EVs confirm their role as a novel therapeutic option for osteoarthritic joints.

miR‑146a‑5p expression is upregulated by the CXCR4 antagonist TN14003 and attenuates SDF‑1‑induced cartilage degradation

Osteoarthritis (OA) is an aseptic inflammatory disease which is associated with the stromal cell-derived factor 1/C-X-C chemokine receptor type 4 (SDF-1/CXCR4) axis. Accumulating studies have identified numbers of microRNAs (miRNAs) that serve important roles in the pathogenesis of OA. However, whether and how the inhibition of the SDF-1/CXCR4 axis induces alterations in miRNA expression remains largely unclear. miRNA profiling was performed in OA chondrocytes stimulated with SDF-1 alone, or SDF-1 with the CXCR4 antagonist TN14003 by miRNA microarray. Candidate miRNAs were verified by reverse transcription quantitative polymerase chain reaction. Bioinformatic analyses including target prediction, gene ontology (GO) and pathway analysis were performed to explore the potential functions of candidate miRNAs. Notably, 7 miRNAs (miR-146a-5p, miR-221-3p, miR-126-3p, miR-185-5p, miR-155-5p, miR-124-3p and miR-130a-3p) were significantly differentially expressed. GO analysis indicated that miR-146a-5p and its associated genes were enriched in receptor regulatory activity, nuclear factor-kappa-light-chain-enhancer of activated B cells (NF-κB)-inducing kinase activity, cellular response to interleukin-1, cytokine-cytokine receptor interaction, NF-κB signaling pathway and osteoclast differentiation pathways. CXCR4 was predicted to be a target of miR-146a-5p with high importance. The mRNA and protein levels of key factors involved in cartilage degeneration were measured following manipulation of the expression levels of miR-146a-5p in OA chondrocytes. CXCR4 and MMP-3 levels were negatively associated with miR-146a-5p expression, while the levels of type II collagen and aggrecan were positively associated. These data reveal that TN14003 upregulates miR-146a-5p expression, and also pinpoints a novel role of miR-146a-5p in inhibiting cartilage degeneration by directly targeting the SDF-1/CXCR4 axis.

Identification of miRNA Reference Genes in Extracellular Vesicles from Adipose Derived Mesenchymal Stem Cells for Studying Osteoarthritis

Osteoarthritis (OA) leads to chronic pain and disability, and traditional conservative treatments are not effective in the long term. The intra-articular injection of mesenchymal stem cells (MSCs) is considered a novel therapy for OA whose efficacy mainly relies on the adaptive release of paracrine molecules which are either soluble or extracellular vesicles (EVs) embedded. The correct quantification of EV-miRNAs using reliable reference genes (RGs) is a crucial step in optimizing this future therapeutic cell-free approach. The purpose of this study is to rate the stabilities of literature-selected proposed RGs for EV-miRNAs in adipose derived-MSCs (ASCs). EVs were isolated by ultracentrifugation from ASCs cultured with or without inflammatory priming mimicking OA synovial fluid condition. Expression of putative RGs (let-7a-5p, miR-16-5p, miR-23a-3p, miR-26a-5p, miR-101-3p, miR-103a-3p, miR-221-3p, miR-423-5p, miR-425-5p, U6 snRNA) was scored by using the algorithms geNorm, NormFinder, BestKeeper and ΔCt method. miR-16a-5p/miR-23a-3p yielded the most stable RGs, whereas let-7a-5p/miR-425-5p performed poorly. Outcomes were validated by qRT-PCR on miR-146a-5p, reported to be ASC-EVs enriched and involved in OA. Incorrect RG selection affected the evaluation of miR-146a-5p abundance and modulation by inflammation, with both values resulting strongly donor-dependent. Our findings demonstrated that an integrated approach of multiple algorithms is necessary to identify reliable, stable RGs for ASC-EVs miRNAs evaluation. A correct approach would increase the accuracy of embedded molecule assessments aimed to develop therapeutic strategies for the treatment of OA based on EVs.

Core regulatory RNA molecules identified in articular cartilage stem/progenitor cells during osteoarthritis progression

Aim: To assess cartilage-derived stem/progenitor cells (CSPCs) in osteoarthritis (OA) by employing mRNA-miRNA-circRNA-lncRNA network biology approach. Methods: Differentially expressed (DE) RNAs in CSPCs from 2-/4-/8-month-old STR/Ort and CBA mice were identified to construct networks via RNA sequencing. Results: Compared with age-matched CBA mice, 4-/8-month-old STR/Ort mice had cartilage lesions and their CSPCs exhibited lower proliferative and differentiation capacity (decreased CD44 and CD90), and identified 7082 DE RNAs in STR/Ort mice were associated with strain differences or OA progression. OA-related core RNAs were identified via the networks constructed with the predominant DE RNAs, which were involved in the signaling pathways (NF-κB/MAPK/Hippo/Wnt/TGF-β/cytoskeleton organization). The core RNAs (miR-322-5p/miR-493-5p/miR-378c/CPNE1/Cdh2/PRDM16/CTGF/NCAM1) were validated in CSPCs from OA patients. Conclusion: RNA-based networks identifying core RNAs and signaling pathways contribute to CSPC-dependent OA mechanisms.

A LINC00341-mediated regulatory pathway supports chondrocyte survival and may prevent osteoarthritis progression

Osteoarthritis (OA) is the most common degenerative joint disease and results from progressive loss and destruction of articular cartilage and the underlying bone. The disease affects millions of people worldwide with an associated risk of mobility disability. However, the molecular basis underlying OA initiation and progression is not well understood and, currently, there is no effective intervention available to decelerate disease progression or restore degraded cartilage. We have found that lncRNA long intergenic nonprotein coding RNA 341 (LINC00341) is aberrantly downregulated in OA patient tissues and cultured OA chondrocytes. This is likely responsible for the increased apoptosis of chondrocytes and pathological destruction of cartilage. Further investigation has revealed that LINC00341 interacts with miR-141 to suppress its functional binding to the 3'-untranslated region of YY1-associated factor 2 (YAF2) messenger RNA. Aberrant downregulation of LINC00341 thus may ultimately lead to inhibition of the YAF2 protein, which has been implicated to be an antiapoptotic factor. Our study has revealed a new noncoding RNA-mediated regulatory network that highly likely protects chondrocytes by preventing apoptosis under normal conditions. The results will help further explore the molecular details pertaining to the progression of OA and stimulate efforts to develop effective therapies.

Models of Disease

Osteochondral (OC) lesions are a major cause of chronic musculoskeletal pain and functional disability, which reduces the quality of life of the patients and entails high costs to the society. Currently, there are no effective treatments, so in vitro and in vivo disease models are critically important to obtain knowledge about the causes and to develop effective treatments for OC injuries. In vitro models are essential to clarify the causes of the disease and the subsequent design of the first barrier to test potential therapeutics. On the other hand, in vivo models are anatomically more similar to humans allowing to reproduce the pattern and progression of the lesion in a controlled scene and offering the opportunity to study the symptoms and responses to new treatments. Moreover, in vivo models are the most suitable preclinical model, being a fundamental and a mandatory step to ensure the successful transfer to clinical trials. Both in vitro and in vitro models have a number of advantages and limitation, and the choice of the most appropriate model for each study depends on many factors, such as the purpose of the study, handling or the ease to obtain, and cost, among others. In this chapter, we present the main in vitro and in vivo OC disease models that have been used over the years in the study of origin, progress, and treatment approaches of OC defects.

Combating Osteoarthritis through Stem Cell Therapies by Rejuvenating Cartilage: A Review

Knee osteoarthritis (OA) is a chronic degenerative disorder which could be distinguished by erosion of articular cartilage, pain, stiffness, and crepitus. Not only aging-associated alterations but also the metabolic factors such as hyperglycemia, dyslipidemia, and obesity affect articular tissues and may initiate or exacerbate the OA. The poor self-healing ability of articular cartilage due to limited regeneration in chondrocytes further adversely affects the osteoarthritic microenvironment. Traditional and current surgical treatment procedures for OA are limited and incapable to reverse the damage of articular cartilage. To overcome these limitations, cell-based therapies are currently being employed to repair and regenerate the structure and function of articular tissues. These therapies not only depend upon source and type of stem cells but also on environmental conditions, growth factors, and chemical and mechanical stimuli. Recently, the pluripotent and various multipotent mesenchymal stem cells have been employed for OA therapy, due to their differentiation potential towards chondrogenic lineage. Additionally, the stem cells have also been supplemented with growth factors to achieve higher healing response in osteoarthritic cartilage. In this review, we summarized the current status of stem cell therapies in OA pathophysiology and also highlighted the potential areas of further research needed in regenerative medicine.

miR-29b regulates expression of collagens I and III in chondrogenically differentiating BMSC in an osteoarthritic environment

Osteoarthritis (OA) is characterized by a slowly progressing, irreversible loss of articular cartilage. Tissue engineering approaches for cartilage regeneration include stem cell-based strategies but not much is known about their repair capacity in an OA microenvironment. The aim of the present study was to identify factors regulating collagen expression during chondrogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSC) in an OA microenvironment. Coculture with OA cartilage induced miR-29b expression in BMSC which inhibited collagen I and III expression. Elevated miR-29b expression resulted in higher caspase 3/7 activity and promoted apoptosis of BMSC in part by directly inhibiting the anti-apoptotic proteins Bcl-2 and Mcl-1. Stimulation with IFN-γ induced miR-29b expression in BMSC. Our results suggest that miR-29b affects BMSC-based OA cartilage regeneration because expression of collagen III, mainly produced by undifferentiated BMSC, and collagen I, a marker for dedifferentiated chondrocytes, are inhibited by miR-29b thus influencing composition of the newly formed ECM. This might be critical to avoid formation of inferior fibrocartilage instead of hyaline cartilage. Furthermore, higher miR-29b expression promotes apoptosis either preventing excessive cell growth or reducing the number of BMSC undergoing chondrogenesis. Thus, miR-29b has both supportive but possibly also unfavourable effects on BMSC-based OA cartilage regeneration.

Identification of key mRNAs and microRNAs in the pathogenesis and progression of osteoarthritis using microarray analysis

Osteoarthritis (OA) is a common type of disease affecting the joints that results from the breakdown of joint cartilage and the underlying bone; currently, its pathogenesis is still unclear. The aim of the present study was to identify key mRNAs and miRNAs involved in the pathogenesis and progression of OA using microarray analysis. The gene expression profile of GSE27492 was downloaded from the Gene Expressed Omnibus database, and included 49 arthritic mouse ankle samples collected at 6 time points (0, 1, 3, 7, 12 and 18 days) following the induction of arthritis via serum transfer. Differentially expressed genes (DEGs) were identified in ankle samples taken on days 1, 3, 7, 12 and 18 following serum transfer compared with day 0 samples, and overlapping DEGs in day 3, 7, 12 and 18 samples were identified. The Database for Annotation, Visualization and Integrated Discovery online tool was used to perform functional and pathway enrichment analyses of the overlapping DEGs. The miRWalk database was used to identify potential micro (mi) RNAs regulating the selected overlapping DEGs, and regulatory miRNA‑target mRNA pairs were obtained. The Cytoscape platform was used to establish and visualize the miRNA‑mRNA regulatory network. The present results revealed that 35, 103, 62 and 75 DEGs were identified in day 3, 7, 12 and 18 samples, respectively. A total of 17 overlapping DEGs were identified among the 4 sample sets, and revealed to be enriched in 14 gene ontology terms and 3 Kyoto Encyclopedia of Genes and Genomes pathways. miRWalk analysis identified 242 potential miRNA‑mRNA regulatory pairs and 211 nodes were revealed to be involved in the miRNA‑mRNA regulatory network. The present study identified potential genes, including C‑type lectin domain family 4 member D, chemokine (C‑X‑C motif) ligand 1 and C‑C motif chemokine ligand, and pathways, including chemokine signaling pathways, cytokine‑cytokine receptor interactions and nucleotide‑binding oligomerization domain‑like receptor signaling pathways, which may be involved in the pathogenesis and progression of OA. These findings may help elucidate the molecular mechanisms underlying OA pathophysiology, and may be useful for the development of novel therapeutic targets for the treatment of patients with OA.

MicroRNA Profiling in Cartilage Ageing

Osteoarthritis (OA) is the most common age-related joint disorder in man. MicroRNAs (miRNA), a class of small noncoding RNAs, are potential therapeutic targets for regulating molecular mechanisms in both disease and ageing. Whilst there is an increasing amount of research on the roles of miRNAs in ageing, there has been scant research on age-related changes in miRNA in a cartilage. We undertook a microarray study on young and old human cartilages. Findings were validated in an independent cohort. Contrasts between these samples identified twenty differentially expressed miRNAs in a cartilage from old donors, derived from an OA environment which clustered based on OA severity. We identified a number of recognised and novel miRNAs changing in cartilage ageing and OA including miR-126: a potential new candidate with a role in OA pathogenesis. These analyses represent important candidates that have the potential as cartilage ageing and OA biomarkers and therapeutic targets.

Suppression of miR-301a alleviates LPS-induced inflammatory injury in ATDC5 chondrogenic cells by targeting Sirt1

Osteoarthritis is one of the most common joint diseases and is characterized by joint inflammation. MicroRNAs (miRNA) play an important role in osteoarthritis. In this study, we examined the role of miR-301a in lipopolysaccharide (LPS)-treated murine chondrogenic ATDC5 cells. LPS at 10 µg/mL concentration was used to induce inflammatory injury in chondrogenic cells. Cell Counting Kit-8 assay was used to measure cell viability and flow cytometry was used to measure cell apoptosis. Effect of miR-301a on concentrations of inflammatory cytokines was measured using ELISA, and on mRNA expressions was measured using qRT-PCR. The miR-301 target was identified by luciferase reporter assay. Western blot analysis was used to measure the expressions of apoptotic proteins, Sirt1, and PI3K/AKT and NF-κB pathways proteins. Treatment with LPS decreased cell viability, and increased apoptosis, inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α) level, and miR-301a expression. Overexpression of miR-301a aggravated the effects of LPS on the chondrogenic cells and the inflammatory cytokines by negatively regulating Sirt1 expression. Sirt1 was identified as a target of miR-301. Suppression of miR-301a showed the opposite effects. Western blot showed that suppression of miR-301a increased the expression of PI3K/AKT and NF-κB pathways proteins. Suppression of miR-301a expression alleviated LPS-induced chondrogenic cell injury by upregulating Sirt1 and activating the PI3K/AKT and NF-κB signal pathways.

NEAT1/miR-181c Regulates Osteopontin (OPN)-Mediated Synoviocyte Proliferation in Osteoarthritis

Osteoarthritis (OA) is characterized by progressive destruction of articular cartilage, resulting in significant disability. Inflammatory cytokines commonly initiate the extreme changes in the synovium and cartilage microenvironment of the OA patients, subsequently resulting in cell dysfunctions, especially synoviocyte dysfunction. We revealed that the expression of osteopontin (OPN), which has been reported to regulate expression of various inflammatory factors associating with the pathogenesis of OA including matrix metalloprotease 13 (MMP13), interlukine-6 and 8 (IL-6 and IL-8), is significantly upregulated in OA tissues. In the present study, online tools were used to screen out the candidate miRNAs of OPN. Among the candidate miRNAs, miR-181c inhibited OPN mRNA expression the most strongly. Ectopic expression of miR-181c significantly repressed synoviocyte proliferation, as well as the levels of OPN, MMP13, IL-6, and IL-8. Further, the candidate lncRNAs of miR-181c were screened out by using DianaTools; among which NEAT1 showed to inversely regulate miR-181c. By performing Luciferase assays, we revealed that NEAT1 competed with OPN for miR-181c binding. After NEAT1 knockdown, MMP13, IL-6, and IL-8 expression was reduced; the synoviocyte proliferation was repressed, as well as OPN protein levels; the suppressive effect of NETA1 knockdown on synoviocyte proliferation and the indicated factors were partially reversed by miR-181c inhibition. In OA tissues, OPN mRNA, and NEAT1 expression was upregulated, whereas miR-181c expression was downregulated, indicating that targeting NEAT1 to rescue miR-181c expression so as to inhibit OPN expression and synoviocyte proliferation might be an efficient strategy for OA treatment. J. Cell. Biochem. 118: 3775-3784, 2017. © 2017 Wiley Periodicals, Inc.

Osteoarthritis year in review 2016: genetics, genomics and epigenetics

The purpose of this narrative review is to provide an overview of last year's publications in the field of genetics, genomics and epigenetics in the osteoarthritis (OA) field. Major themes arising from a Pubmed search on (epi)genetics in OA were identified. In addition, general developments in the fast evolving field of (epi)genetics are reviewed and relevance for the OA field is summarized. In the last 5 years, a number of genome-wide association studies have identified a modest number of genetic loci associated to OA. Continued functional research into these DNA variants is showing putative biological mechanisms underlying these associations. Over the last year, no additional large genome-wide association studies were published, but there clearly remains much to be discovered in the OA genetic field. A lot of research has been done into the epigenetics of OA over the last year. Several genome-wide screens examining the methylome of osteoarthritic cartilage were done. Pathway analysis confirmed deregulation of developmental and extracellular pathways in OA cartilage. Over the last year many microRNAs (miRNAs) have been identified that potentially play important roles in cartilage homeostasis and/or OA process. Continued research will learn whether these identified miRNAs are truly causal and can be used in clinical applications. Many of the epigenetic findings need further confirmation, but they highlight potential novel pathways involved in cartilage biology and OA.

The Role of miRNAs in Common Inflammatory Arthropathies: Osteoarthritis and Gouty Arthritis

MicroRNAs (miRNAs) are small, non-coding RNA species that are highly evolutionarily conserved, from higher invertebrates to man. Up to 1000 miRNAs have been identified in human cells thus far, where they are key regulators of the expression of numerous targets at the post-transcriptional level. They are implicated in various processes, including cell differentiation, metabolism, and inflammation. An expanding list of miRNAs is known to be involved in the pathogenesis of common, non-autoimmune inflammatory diseases. Interestingly, osteoarthritis (OA) is now being conceptualized as a metabolic disease, as there is a correlation among hyperuricemia and metabolic syndrome (MetS). Experimental evidence suggests that metabolic deregulation is a commonality between these different pathological entities, and that miRNAs are key players in the modulation of metabolic routes. In light of these findings, this review discusses the role of miRNAs in OA and gouty arthritis, as well as the possible therapeutic targetability of miRNAs in these diseases.

The Role of MicroRNAs and Their Targets in Osteoarthritis

Micro ribonucleic acid (microRNA) regulation and expression has become an emerging field in determining the mechanisms regulating a variety of inflammation-mediated diseases. Several studies have focused on specific microRNAs that are differentially expressed in cases of osteoarthritis. Furthermore, several targets of these miRNAs important in disease progression have also been identified. In this review, we focus on microRNA biogenesis, regulation, detection, and quantification with an emphasis on cellular localization and how these concepts may be linked to disease processes such as osteoarthritis. Next, we review the relationships of specific microRNAs to certain features and risk factors associated with osteoarthritis such as inflammation, obesity, autophagy, and cartilage homeostasis. We also identify certain microRNAs that are differentially expressed in osteoarthritis but have unidentified targets and functions in the disease state. Lastly, we identify the potential use of microRNAs for therapeutic purposes and also mention certain remedies that regulate microRNA expression.

Integrated Study of Globally Expressed microRNAs in IL-1β-stimulated Human Osteoarthritis Chondrocytes and Osteoarthritis Relevant Genes: A Microarray and Bioinformatics Analysis

This study was undertaken to identify and characterize the globally expressed microRNAs (miRNAs) involved in interleukin-1β (IL-1β)-induced joint damage and to predict whether miRNAs can regulate the catabolic effects in osteoarthritis (OA) chondrocytes. Out of 1347 miRNAs analyzed by microarrays in IL-1β-stimulated OA chondrocytes, 35 miRNAs were down-regulated, 1 miRNA was up-regulated, and the expression of 1311 miRNAs remained unchanged. Bioinformatics analysis showed the key inflammatory mediators and key molecular pathways are targeted by differentially expressed miRNAs. Novel miRNAs identified could have important diagnostic and therapeutic potentials in the development of novel therapeutic strategies for pain managements in OA.

MicroRNA-127-5p regulates osteopontin expression and osteopontin-mediated proliferation of human chondrocytes

The aim of this study was to determine the specific microRNA (miRNA) that regulates expression of osteopontin (OPN) in osteoarthritis (OA). The potential regulatory miRNAs for OPN messenger RNA (mRNA) were predicted by miRNA prediction programs. Among eight potential regulatory miRNAs, miR-220b, miR-513a-3p and miR-548n increased, while miR-181a, miR-181b, miR-181c, miR-181d and miR-127-5p decreased in OA patients. miRNA-127-5p mimics suppressed OPN production as well as the activity of a reporter construct containing the 3'-UTR of human OPN mRNA. In addition, mutation of miR-127-5p binding site in the 3'-UTR of OPN mRNA abolished miR-127-5p-mediated repression of reporter activity. Conversely, treatment with miR-127-5p inhibitor increased reporter activity and OPN production. Interestingly, miR-127-5p inhibited proliferation of chondrocytes through OPN. In conclusion, miRNA-127-5p is an important regulator of OPN in human chondrocytes and may contribute to the development of OA.