MicroRNA-455-3p modulates cartilage development and degeneration through modification of histone H3 acetylation

Role of microRNAs deregulation in initiation of rheumatoid arthritis: A retrospective observational study

Rheumatoid arthritis (RA) is a joint disorder and is considered an important public health concern nowadays. So, identifying novel biomarkers and treatment modalities is urgently needed to improve the health standard of RA patients. Factors involved in RA pathogenesis are genetic/epigenetic modification, environment, and lifestyle. In the case of epigenetic modification, the expression deregulation of microRNAs and the role of histone deacetylase (HDAC) in RA is an important aspect that needs to be addressed. The present study is designed to evaluate the expression pattern of microRNAs related to the HDAC family. Five microRNAs, miR-92a-3p, miR-455-3p, miR-222, miR-140, and miR-146a related to the HDAC family were selected for the present study. Real-time polymerase chain reaction was used to estimate the level of expression of the above-mentioned microRNAs in 150 patients of RA versus 150 controls. Oxidative stress level and histone deacetylation status were measured using the enzyme-linked immunosorbent assay. Statistical analysis showed significant downregulation (P < .0001) of selected microRNAs in RA patients versus controls. Significantly raised level of HDAC (P < .0001) and 8-hydroxy-2'-deoxyguanosine (P < .0001) was observed in patients versus controls. A good diagnostic potential of selected microRNAs in RA was shown by the receiver operating curve analysis. The current study showed a significant role of deregulated expression of the above-mentioned microRNAs in RA initiation and can act as an excellent diagnostic marker for this disease.

Mesenchymal stem cells under epigenetic control - the role of epigenetic machinery in fate decision and functional properties

Mesenchymal stem cells (mesenchymal stromal cells, MSC) are multipotent stem cells that can differentiate into cells of at least three mesodermal lineages, namely adipocytes, osteoblasts, and chondrocytes, and have potent immunomodulatory properties. Epigenetic modifications are critical regulators of gene expression and cellular differentiation of mesenchymal stem cells (MSCs). Epigenetic machinery controls MSC differentiation through direct modifications to DNA and histones. Understanding the role of epigenetic machinery in MSC is crucial for the development of effective cell-based therapies for degenerative and inflammatory diseases. In this review, we summarize the current understanding of the role of epigenetic control of MSC differentiation and immunomodulatory properties.

A Review of Recent Innovations in Cartilage Regeneration Strategies for the Treatment of Primary Osteoarthritis of the Knee: Intra-articular Injections

Background

The pathology of primary osteoarthritis (OA) begins with structural cartilage damage, which initiates a self-propagating inflammatory pathway that further exacerbates cartilage deterioration. Current standard of care for knee primary OA involves treating the inflammatory symptoms to manage pain, which includes intra-articular (IA) injections of cortisone, an anti-inflammatory steroid, followed by a series of joint-cushioning hyaluronic acid gel injections. However, these injections do not delay the progression of primary OA. More focus on the underlying cellular pathology of OA has prompted researchers to develop treatments targeting the biochemical mechanisms of cartilage degradation.

Purpose

Researchers have yet to develop a United States Food and Drug Administration (FDA)-approved injection that has been demonstrated to significantly regenerate damaged articular cartilage. This paper reviews the current research on experimental injections aimed at achieving cellular restoration of the hyaline cartilage tissue of the knee joint.

Study Design

Narrative review.

Methods

The authors conducted a narrative literature review examining studies on primary OA pathogenesis and a systematic review of non-FDA-approved IA injections for the treatment of primary OA of the knee, described as "disease-modifying osteoarthritis drugs" in phase 1, 2, and 3 clinical trials.

Conclusion

New treatment approaches for primary OA investigate the potential of genetic therapies to restore native cartilage. It is clear that the most promising IA injections that could improve treatment of primary OA are bioengineered advanced-delivery steroid-hydrogel preparations, ex vivo expanded allogeneic stem cell injections, genetically engineered chondrocyte injections, recombinant fibroblast growth factor therapy, injections of selective proteinase inhibitors, senolytic therapy via injections, injectable antioxidant therapies, injections of Wnt pathway inhibitors, injections of nuclear factor-kappa β inhibitors, injections of modified human angiopoietin-like-3, various potential viral vector-based genetic therapy approaches, and RNA genetic technology administered via injections.

Regulation of osteogenesis in bone marrow-derived mesenchymal stem cells via histone deacetylase 1 and 2 co-cultured with human gingival fibroblasts and periodontal ligament cells

OBJECTIVE

This study aimed to determine the regulatory mechanism of bone marrow-derived mesenchymal stem cell (BM-MSC) differentiation mediated by humoral factors derived from human periodontal ligament (HPL) cells and human gingival fibroblasts (HGFs). We analyzed histone deacetylase (HDAC) expression and activity involved in BM-MSC differentiation and determined their regulatory effects in co-cultures of BM-MSCs with HPL cells or HGFs.

BACKGROUND

BM-MSCs can differentiate into various cell types and can, thus, be used in periodontal regenerative therapy. However, the mechanism underlying their differentiation remains unclear. Transplanted BM-MSCs are affected by periodontal cells via direct contact or secretion of humoral factors. Therefore, their activity is regulated by humoral factors derived from HPL cells or HGFs.

METHODS

BM-MSCs were indirectly co-cultured with HPL cells or HGFs under osteogenic or growth conditions and then analyzed for osteogenesis, HDAC1 and HDAC2 expression and activity, and histone H3 acetylation. BM-MSCs were treated with trichostatin A, or their HDAC1 or HDAC2 expression was silenced or overexpressed during osteogenesis. Subsequently, they were evaluated for osteogenesis or the effects of HDAC activity.

RESULTS

BM-MSCs co-cultured with HPL cells or HGFs showed suppressed osteogenesis, HDAC1 and HDAC2 expression, and HDAC phosphorylation; however, histone H3 acetylation was enhanced. Trichostatin A treatment remarkably suppressed osteogenesis, decreasing HDAC expression and enhancing histone H3 acetylation. HDAC1 and HDAC2 silencing negatively regulated osteogenesis in BM-MSCs to the same extent as that achieved by indirect co-culture with HPL cells or HGFs. Conversely, their overexpression positively regulated osteogenesis in BM-MSCs.

CONCLUSION

The suppressive effects of HPL cells and HGFs on BM-MSC osteogenesis were regulated by HDAC expression and histone H3 acetylation to a greater extent than that mediated by HDAC activity. Therefore, regulation of HDAC expression has prospects in clinical applications for effective periodontal regeneration, mainly, bone regeneration.

Lithium-Containing Biomaterials Stimulate Cartilage Repair through Bone Marrow Stromal Cells-Derived Exosomal miR-455-3p and Histone H3 Acetylation

The repair of damaged cartilage still remains a great challenge in clinic. It is demonstrated that bone marrow stromal cells (BMSCs)-chondrocytes communication is of great significance for cartilage repair. Moreover, BMSCs have been confirmed to enhance biological function of chondrocytes via exosome-mediated paracrine pathway. Lithium-containing scaffolds have been reported to effectively promote cartilage regeneration; however, whether lithium-containing biomaterial could facilitate cartilage regeneration through regulating BMSCs-derived exosomes has not been illustrated. In the study, the model lithium-substituted bioglass ceramic (Li-BGC) is selected and regulatory effects of BMSCs-derived exosomes after Li-BGC treatment (Li-BGC-Exo) are systemically evaluated. The data reveal that Li-BGC-Exo notably promotes chondrogenesis, which attributes to the upregulated exosomal miR-455-3p transfer, consequently leads to suppression of histone deacetylase 2 (HDAC2) and enhanced histone H3 acetylation in chondrocytes. Notably, BMSCs-derived exosomes after LiCl treatment (LiCl-Exo) exhibits the similar regulatory effect with Li-BGC-Exo, indicating that the pro-chondrogenesis capability of them is mainly owing to the lithium ions. Furthermore, the in vivo study proves that LiCl-Exo remarkably facilitates cartilage regeneration. The research may provide novel possibility for the intrinsic mechanism of chondrogenesis trigged by lithium-containing biomaterials, and suggests that application of lithium-containing scaffolds may be a promising strategy for cartilage regeneration.

MicroRNAs and long non-coding RNAs in cartilage homeostasis and osteoarthritis

During the last decade, osteoarthritis (OA) has become one of the most prevalent musculoskeletal diseases worldwide. OA is characterized by progressive loss of articular cartilage, abnormal remodeling of subchondral bone, hyperplasia of synovial cells, and growth of osteophytes, which lead to chronic pain and disability. The pathological mechanisms underlying OA initiation and progression are still poorly understood. Non-coding RNAs (ncRNAs) constitute a large portion of the transcriptome that do not encode proteins but function in numerous biological processes. Cumulating evidence has revealed a strong association between the changes in expression levels of ncRNA and the disease progression of OA. Moreover, loss- and gain-of-function studies utilizing transgenic animal models have demonstrated that ncRNAs exert vital functions in regulating cartilage homeostasis, degeneration, and regeneration, and changes in ncRNA expression can promote or decelerate the progression of OA through distinct molecular mechanisms. Recent studies highlighted the potential of ncRNAs to serve as diagnostic biomarkers, prognostic indicators, and therapeutic targets for OA. MiRNAs and lncRNAs are two major classes of ncRNAs that have been the most widely studied in cartilage tissues. In this review, we focused on miRNAs and lncRNAs and provided a comprehensive understanding of their functional roles as well as molecular mechanisms in cartilage homeostasis and OA pathogenesis.

Epigenetic Regulation in Knee Osteoarthritis

Osteoarthritis (OA) is a complicated disease with both hereditary and environmental causes. Despite an increase in reports of possible OA risk loci, it has become clear that genetics is not the sole cause of osteoarthritis. Epigenetics, which can be triggered by environmental influences and result in transcriptional alterations, may have a role in OA pathogenesis. The majority of recent research on the epigenetics of OA has been focused on DNA methylation, histone modification, and non-coding RNAs. However, this study will explore epigenetic regulation in OA at the present stage. How genetics, environmental variables, and epigenetics interact will be researched, shedding light for future studies. Their possible interaction and control processes open up new avenues for the development of innovative osteoarthritis treatment and diagnostic techniques.

Cartilage Homeostasis and Osteoarthritis

Healthy limb joints are important for maintaining health and attaining longevity. Endochondral ossification (the replacement of cartilage with bone, occurring during skeletal development) is essential for bone formation, especially in long-axis bones. In contrast to endochondral ossification, chondrocyte populations in articular cartilage persist and maintain joint tissue into adulthood. Articular cartilage, a connective tissue consisting of chondrocytes and their surrounding extracellular matrices, plays an essential role in the mechanical cushioning of joints in postnatal locomotion. Osteoarthritis (OA) pathology relates to disruptions in the balance between anabolic and catabolic signals, that is, the loss of chondrocyte homeostasis due to aging or overuse of cartilages. The onset of OA increases with age, shortening a person’s healthy life expectancy. Although many people with OA experience pain, the mainstay of treatment is symptomatic therapy, and no fundamental treatment has yet been established. To establish regenerative or preventative therapies for cartilage diseases, further understanding of the mechanisms of cartilage development, morphosis, and homeostasis is required. In this review, we describe the general development of cartilage and OA pathology, followed by a discussion on anabolic and catabolic signals in cartilage homeostasis, mainly microRNAs.

Histone Modifications and Non-Coding RNAs: Mutual Epigenetic Regulation and Role in Pathogenesis

In the last few years, more and more scientists have suggested and confirmed that epigenetic regulators are tightly connected and form a comprehensive network of regulatory pathways and feedback loops. This is particularly interesting for a better understanding of processes that occur in the development and progression of various diseases. Appearing on the preclinical stages of diseases, epigenetic aberrations may be prominent biomarkers. Being dynamic and reversible, epigenetic modifications could become targets for a novel option for therapy. Therefore, in this review, we are focusing on histone modifications and ncRNAs, their mutual regulation, role in cellular processes and potential clinical application.

Regulation of FGF-2, FGF-18 and Transcription Factor Activity by Perlecan in the Maturational Development of Transitional Rudiment and Growth Plate Cartilages and in the Maintenance of Permanent Cartilage Homeostasis

The aim of this study was to highlight the roles of perlecan in the regulation of the development of the rudiment developmental cartilages and growth plate cartilages, and also to show how perlecan maintains permanent articular cartilage homeostasis. Cartilage rudiments are transient developmental templates containing chondroprogenitor cells that undergo proliferation, matrix deposition, and hypertrophic differentiation. Growth plate cartilage also undergoes similar changes leading to endochondral bone formation, whereas permanent cartilage is maintained as an articular structure and does not undergo maturational changes. Pericellular and extracellular perlecan-HS chains interact with growth factors, morphogens, structural matrix glycoproteins, proteases, and inhibitors to promote matrix stabilization and cellular proliferation, ECM remodelling, and tissue expansion. Perlecan has mechanotransductive roles in cartilage that modulate chondrocyte responses in weight-bearing environments. Nuclear perlecan may modulate chromatin structure and transcription factor access to DNA and gene regulation. Snail-1, a mesenchymal marker and transcription factor, signals through FGFR-3 to promote chondrogenesis and maintain Acan and type II collagen levels in articular cartilage, but prevents further tissue expansion. Pre-hypertrophic growth plate chondrocytes also express high Snail-1 levels, leading to cessation of Acan and CoI2A1 synthesis and appearance of type X collagen. Perlecan differentially regulates FGF-2 and FGF-18 to maintain articular cartilage homeostasis, rudiment and growth plate cartilage growth, and maturational changes including mineralization, contributing to skeletal growth.

Comprehensive expression profiles of mRNAs, lncRNAs and miRNAs in Kashin-Beck disease identified by RNA-sequencing

Kashin-Beck disease (KBD) is a chronic, endemic and deforming osteochondropathy, whose basic pathological alterations include apoptosis and necrosis of chondrocytes in articular cartilage and growth plates and imbalanced extracellular matrix metabolism. Numerous studies have reported that long noncoding RNAs (lncRNAs) and microRNA (miRNAs) are aberrantly expressed in KBD. Our study was comprised of 5 KBD patients and 5 healthy individuals and we compared the expression profiles of mRNAs, lncRNAs and miRNAs through RNA-sequencing (RNA-seq). Bioinformatic analysis of GO and KEGG was employed to conduct functional annotation and pathway enriched analysis. In total, 3194 mRNAs, 4103 lncRNAs and 1550 miRNAs were detected to be differentially expressed by RNA-seq (P < 0.05; |log₂FC| ≥1). The lysosome pathway, Wnt signaling pathway, TNF signaling pathway, endocytosis and mTOR signaling pathway were identified to be involved in the KBD development according to the result of the KEGG analysis. In addition, a ceRNA network based on lncRNA-miRNA-mRNA was constructed to probe the intricate regulatory mechanism and interaction between transcripts, which was visualized using the Cytoscape software. The ce-lncRNAs of four aberrantly expressed genes, FOSB, EGR3, BCAM and SOX6, were determined through the network. Among the identified DElncRNAs, we selected 8 differentially expressed lncRNAs to confirm the reliability of RNA-seq data by qRT-PCR in 11 KBD patients and 11 healthy individuals. We aimed to provide a comprehensive understanding ofmRNA, lncRNA and miRNA alterations between KBD patients and healthy individuals, and meanwhile reveal several potential causative molecular and signaling pathways involved in KBD.

Clinical significance of the serum miR-455-5p expression in patients with neonatal sepsis

Sepsis is a systemic inflammatory response caused by infection and is a major cause of neonatal death. This study explored the miR-455-5p in neonatal sepsis, and further investigated the diagnostic and prognostic value of miR-455-5p in neonatal sepsis (NS). The levels of serum miR-455-5p in 88 healthy controls and 90 NS patients were examined by quantitative real-time polymerase chain reaction (qRT-PCR). Pearson correlation coefficient was used to evaluate the correlation between miR-455-5p and clinical features. Receiver operating characteristic (ROC) curve analysis was performed for the diagnostic evaluation on miR-455-5p. The prognostic value of miR-455-5p in NS was analyzed by Kaplan-Meier survival curve and multivariate Cox regression. The expression of serum miR-455-5p in NS patients was highly expressed in comparison to healthy controls (P < 0.001), and the level of miR-455-5p was positively correlated with white blood cell count (WBC) and other clinical characteristics (P < 0.01). The AUC value of ROC curve was 0.895, suggesting that miR-455-5p had diagnostic value for NS. Survival analysis illustrated that patient with high miR-455-5p expression had poor prognosis (log rank P = 0.015), and miR-455-5p may be a potential prognostic marker for NS (HR = 3.454, 95% CI = 1.165-10.234, P = 0.025). The expression of miR-455-5p had the ability to distinguish NS from healthy people, and highly expressed miR-455-5p was associated with poor prognosis in NS patients.

The miR-455-3p/HDAC2 axis plays a pivotal role in the progression and reversal of liver fibrosis and is regulated by epigenetics

Histone deacetylases (HDACs), especially HDAC2, play a role in alleviating liver fibrosis; however, the specific upstream regulation mechanism is unknown. Herein, TargetScan was used to predict the potential upstream targets of HDAC2, and the role of miR-455-3p was explored. The dual luciferase reporter assay showed that miR-455-3p binds to the 3' UTR of HDAC2 mRNA. Additionally, miR-455-3p was downregulated in the liver tissues of patients with cirrhosis and mice with liver fibrosis, as well as in primary HSCs isolated from fibrotic mouse livers and TGF-β-treated LX-2 cells. In contrast, it is highly expressed in the reversal stage of hepatic fibrosis and MDI-cultured LX-2 cells. Our functional analyses showed that miR-455-3p overexpression facilitated apoptosis and reduced the expression of pro-fibrotic markers and the proliferation of activated LX-2 cells. On the contrary, miR-455-3p inhibition converted inactivated LX-2 cells into activated, proliferative, fibrogenic cells. Interestingly, restoration of HDAC2 expression partially blocked the function of miR-455-3p. Downregulated miR-455-3p expression can be restored by DNA methyltransferases in activated LX-2 cells. Methylation-specific PCR, bisulfite sequencing PCR, and chromatin immunoprecipitation assays indicated that the methylation level of miR-455-3p promoter CpG islands was elevated in TGF-β-treated LX-2 cells and that miR-455-3p was downregulated in activated LX-2 cells by DNA hypermethylation, which is mediated by DNMT3b and DNMT1. In conclusion, miR-455-3p acts as a liver fibrosis suppressor by targeting HDAC2, and its deficiency further aggravates the reversal phase of fibrosis. Thus, the epigenetics mediated miR-455-3p/HDAC2 axis may serve as a novel potential therapeutic target for clinical treatment of hepatic fibrosis.

What Are the Potential Roles of Nuclear Perlecan and Other Heparan Sulphate Proteoglycans in the Normal and Malignant Phenotype

The recent discovery of nuclear and perinuclear perlecan in annulus fibrosus and nucleus pulposus cells and its known matrix stabilizing properties in tissues introduces the possibility that perlecan may also have intracellular stabilizing or regulatory roles through interactions with nuclear envelope or cytoskeletal proteins or roles in nucleosomal-chromatin organization that may regulate transcriptional factors and modulate gene expression. The nucleus is a mechano-sensor organelle, and sophisticated dynamic mechanoresponsive cytoskeletal and nuclear envelope components support and protect the nucleus, allowing it to perceive and respond to mechano-stimulation. This review speculates on the potential roles of perlecan in the nucleus based on what is already known about nuclear heparan sulphate proteoglycans. Perlecan is frequently found in the nuclei of tumour cells; however, its specific role in these diseased tissues is largely unknown. The aim of this review is to highlight probable roles for this intriguing interactive regulatory proteoglycan in the nucleus of normal and malignant cell types.

Histone Modifications and Chondrocyte Fate: Regulation and Therapeutic Implications

The involvement of histone modifications in cartilage development, pathology and regeneration is becoming increasingly evident. Understanding the molecular mechanisms and consequences of histone modification enzymes in cartilage development, homeostasis and pathology provides fundamental and precise perspectives to interpret the biological behavior of chondrocytes during skeletal development and the pathogenesis of various cartilage related diseases. Candidate molecules or drugs that target histone modifying proteins have shown promising therapeutic potential in the treatment of cartilage lesions associated with joint degeneration and other chondropathies. In this review, we summarized the advances in the understanding of histone modifications in the regulation of chondrocyte fate, cartilage development and pathology, particularly the molecular writers, erasers and readers involved. In addition, we have highlighted recent studies on the use of small molecules and drugs to manipulate histone signals to regulate chondrocyte functions or treat cartilage lesions, in particular osteoarthritis (OA), and discussed their potential therapeutic benefits and limitations in preventing articular cartilage degeneration or promoting its repair or regeneration.

Histone acetyl transferases and their epigenetic impact on bone remodeling

Bone remodeling is a complex event that maintains bone homeostasis. The epigenetic mechanism of the regulation of bone remodeling has been a major research focus over the past decades. Histone acetylation is an influential post-translational modification in chromatin architecture. Acetylation affects chromatin structure by offering binding signals for reader proteins that harbor acetyl-lysine recognition domains. This review summarizes recent data of histone acetylation in bone remodeling. The crux of this review is the functional role of histone acetyltransferases, the key promoters of histone acetylation. The functional regulation of acetylation via noncoding RNAs in bone remodeling is also discussed. Understanding the principles governing histone acetylation in bone remodeling would lead to the development of better epigenetic therapies for bone diseases.

A New Discovery of MicroRNA-455-3p in Alzheimer's Disease

MicroRNA-455-3p (miR-455-3p) is identify as a member of broadly conserved miRNA family expressed in most of the phylum and species. In humans, miR-455 is present on the human chromosome 9 at locus 9q32 and encoded by the human COL27A1 gene (collagen type XXVII alpha 1 chain). The role of miR-455 has been implicated in various human diseases such as cartilage development, adipogenesis, preeclampsia, and cancers, e.g., colon cancer, prostate cancer, hepatocellular carcinoma, renal cancer, oral squamous cancer, skin cancer, and non-small cell lung cancer. Recently, our laboratory discovered the biomarker and therapeutic relevance of miR-455-3p in Alzheimer's disease (AD). Our global microarray analysis of serum samples from AD patients, mild cognitive individuals (MCI), and healthy subjects unveiled the high level of miR-455-3p in AD patients relative to MCI and healthy controls. Further, validation analysis using different kinds of AD samples such as serum, postmortem brains, AD fibroblasts, AD B-lymphocytes, AD cell lines, AD mouse models, and AD cerebrospinal fluid confirmed the biomarker potential of miR-455-3p. The mechanistic link of miR-455-3p in AD was determined via modulation of amyloid-β protein precursor (AβPP) and amyloid-β (Aβ) levels. Luciferase reporter assay confirmed AβPP as validated target of miR-455-3p. Our study on mouse neuroblastoma cells revealed the protective role of miR-455-3p against Aβ-induced toxicities. We also noticed that miR-455-3p enhances cell survival and lifespan extension. High level of miR-455-3p reduces Aβ toxicity, enhances mitochondrial biogenesis and synaptic activity, and maintains healthy mitochondrial dynamics. Based on these evidences, we cautiously conclude that miR-455-3p is a promising peripheral biomarker and therapeutic candidate for AD.

The Role of HDACs and HDACi in Cartilage and Osteoarthritis

Epigenetics plays an important role in the pathogenesis and treatment of osteoarthritis (OA). In recent decades, HDAC family members have been associated with OA. This paper aims to describe the different role of HDACs in the pathogenesis of OA through interaction with microRNAs and the regulation of relevant signaling pathways. We found that HDACs are involved in cartilage and chondrocyte development but also play a crucial role in OA. However, the distinct HDAC mechanism in the pathogenesis and treatment of OA require further investigation. Furthermore, HDAC inhibitors (HDACi) can protect cartilage from disease, which may represent a potential therapeutic approach against OA.

MicroRNA-455-3p promotes TGF-β signaling and inhibits osteoarthritis development by directly targeting PAK2

MicroRNAs (miRNAs, miR) play a key role in the pathogenesis of osteoarthritis (OA). Few studies have examined the regulatory role of P21-activated kinases (PAKs), a family of serine/threonine kinases, in OA. The aim of this study was to determine whether miR-455-3p can regulate cartilage degeneration in OA by targeting PAK2. MiR-455-3p knockout mice showed significant degeneration of the knee cartilage. MiR-455-3p expression increased and PAK2 expression decreased in the late stage of human adipose-derived stem cell (hADSC) chondrogenesis and in chondrocytes affected by OA. Furthermore, in both miR-455-3p-overexpressing chondrocytes and PAK2-suppressing chondrocytes, cartilage-specific genes were upregulated, and hypertrophy-related genes were downregulated. A luciferase reporter assay confirmed that miR-455-3p regulates PAK2 expression by directly targeting the 3′-untranslated regions (3′UTRs) of PAK2 mRNA. IPA-3, a PAK inhibitor, inhibited cartilage degeneration due to OA. Moreover, suppressing PAK2 promoted R-Smad activation in the TGF/Smad signaling pathway in chondrocytes. Altogether, our results suggest that miR-455-3p promotes TGF-β/Smad signaling in chondrocytes and inhibits cartilage degeneration by directly suppressing PAK2. These results thus indicate that miR-455-3p and PAK2 are novel potential therapeutic agents and targets, respectively, for the treatment of OA.

Functional insights into a short RNA strand that prevents cartilage degeneration could lead to new therapeutic strategies for treating osteoarthritis. The microRNA miR-455-3p regulates genes in tissues throughout the body, but Weiming Liao and Zhiqi Zhang of the First Affiliated Hospital of Sun Yat-sen University in Guangzhou, China have observed that it appears to play a particularly prominent role in cartilage-producing chondrocyte cells. Liao, Zhang and colleagues have now explored this mechanism in detail, and determined that miR-455-3p selectively blocks the effects of a protein called PAK2 in chondrocytes. PAK2 normally inhibits an important signaling pathway underlying cartilage generation, and such inhibition has previously been observed in MDCK epithelial cells. The authors conclude that this microRNA or other drugs that replicate its PAK2-inhibiting effects could prevent or slow the joint damage associated with this degenerative disorder.

Regulation of Histone Deacetylases by MicroRNAs in Bone

Formation of new bone by osteoblasts is mediated via the activation of signaling pathways, such as TGF-β, BMP, and Wnt. A number of transcription factors participate in the signaling cascades that are tightly regulated by other regulatory factors. Histone deacetylases (HDACs) are one such class of regulatory factors that play an essential role in influencing chromatin architecture and regulate the expression of the genes that play a role in osteoblast differentiation by the mechanism of deacetylation. Four classes of HDACs have been identified namely, class I, class II A, class II B, class III and class IV. MicroRNAs (miRNAs) are small fragments of non-coding RNAs typically 19-25 nucleotides long that target mRNAs to upregulate or downregulate gene expression at a post-transcriptional level. A number of miRNAs that target HDACs in bone have been recently reported. Hence, in this review, we elaborate on the various miRNAs that target the different classes of HDACs and impact of the same on osteogenesis.

Long Non-coding RNA HOTTIP Promotes CCL3 Expression and Induces Cartilage Degradation by Sponging miR-455-3p

Long non-coding RNAs (lncRNAs) play pivotal roles in diseases such as osteoarthritis (OA). However, knowledge of the biological roles of lncRNAs is limited in OA. We aimed to explore the biological function and molecular mechanism of HOTTIP in chondrogenesis and cartilage degradation. We used the human mesenchymal stem cell (hMSC) model of chondrogenesis, in parallel with, tissue biopsies from normal and OA cartilage to detect HOTTIP, CCL3, and miR-455-3p expression in vitro. Biological interactions between HOTTIP and miR-455-3p were determined by RNA silencing and overexpression in vitro. We evaluated the effect of HOTTIP on chondrogenesis and degeneration, and its regulation of miR-455-3p via competing endogenous RNA (ceRNA). Our in vitro ceRNA findings were further confirmed within animal models in vivo. Mechanisms of ceRNAs were determined by bioinformatic analysis, a luciferase reporter system, RNA pull-down, and RNA immunoprecipitation (RIP) assays. We found reduced miR-455-3p expression and significantly upregulated lncRNA HOTTIP and CCL3 expression in OA cartilage tissues and chondrocytes. The expression of HOTTIP and CCL3 was increased in chondrocytes treated with interleukin-1β (IL-1β) in vitro. Knockdown of HOTTIP promoted cartilage-specific gene expression and suppressed CCL3. Conversely, HOTTIP overexpression reduced cartilage-specific genes and increased CCL3. Notably, HOTTIP negatively regulated miR-455-3p and increased CCL3 levels in human primary chondrocytes. Mechanistic investigations indicated that HOTTIP functioned as ceRNA for miR-455-3p enhanced CCL3 expression. Taken together, the ceRNA regulatory network of HOTTIP/miR-455-3p/CCL3 plays a critical role in OA pathogenesis and suggests HOTTIP is a potential target in OA therapy.

MicroRNA-320c inhibits development of osteoarthritis through downregulation of canonical Wnt signaling pathway

AIMS

Osteoarthritis (OA) is a leading cause of deformity in aging people. Emerging evidence suggests that microRNAs and Wnt signaling pathway are associated with its pathogenesis. We aimed to determine whether microRNA-320c inhibits the development of osteoarthritis by suppressing Wnt signaling pathway.

MATERIALS AND METHODS

MiR-320c and β-catenin expression was assessed in human adipose derived stem cells (hADSCs) model of chondrogenesis and in normal and OA primary human chondrocytes. OA chondrocytes were transfected with miR-320c or its antisense inhibitor and β-catenin siRNA respectively. Direct interaction between miR-320c and β-catenin mRNA as well as activity of β-catenin/TCF complex were confirmed by luciferase reporter assay. Mmu-miR-320-3p agomir was intra-articularly injected in collagenase-induced OA mouse model. OA progression was evaluated histologically and immunohistochemically.

KEY FINDINGS

MiR-320c was decreased and β-catenin was increased in OA chondrocytes and late stage of hADSCs chondrogenesis. Overexpression of miR-320c and knockdown of β-catenin had similar effects that the cartilage-specific genes were elevated and hypertrophy-related genes were down-regulated in OA chondrocytes. Luciferase reporter assay confirm that miR-320c regulated the expression of β-catenin by directly targeting 3'UTR of β-catenin mRNA and decreased the relative transcriptional activity of the β-catenin/TCF complex. Injection of mmu-miR-320-3p attenuated OA progression in the OA mouse model.

SIGNIFICANCE

Our results supports that miR-320c can inhibits the degeneration of osteoarthritis chondrocytes via suppressing the canonical Wnt signaling pathway and indicates the potential of miR-320c as a novel therapeutic agent for osteoarthritis treatment.

Expression of exosomal microRNAs during chondrogenic differentiation of human bone mesenchymal stem cells

The aim of the current study was to compare the expression of microRNAs (miRNAs) in exosomes derived from human bone mesenchymal stem cells (hBMSCs) with and without chondrogenic induction. Exosomes derived from hBMSCs were isolated and identified. Microarray analysis was performed to compare miRNA expression between exosomes derived from hBMSCs with and without chondrogenic induction, and quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the differentially expressed miRNAs. hBMSCs were transfected with miRNA mimic to extract miRNA-overexpressed exosomes. The results showed that most exosomes exhibited a cup-shaped or round-shaped morphology with a diameter of approximately 50-200 nm and expressed CD9 and CD63. We detected 141 miRNAs that were differentially expressed with and without chondrogenic induction by over a twofold change, including 35 upregulated miRNAs, such as miR-1246, miR-1290, miR-193a-5p, miR-320c, and miR-92a, and 106 downregulated miRNAs, such as miR-377-3p and miR-6891-5p. qRT-PCR analysis validated these results. Exosomes derived from hBMSCs overexpressing miR-320c were more efficient than normal exosomes derived from control hBMSCs at promoting osteoarthritis chondrocyte proliferation, down-regulated matrix metallopeptidase 13 and up-regulated (sex determining region Y)-box 9 expression during hBMSC chondrogenic differentiation. In conclusion, we identified a group of upregulated miRNAs in exosomes derived from hBMSCs with chondrogenic induction that may play an important role in mesenchymal stem cell-derived exosomes in cartilage regeneration and, ultimately, the treatment of arthritis. We demonstrated the potential of these modified exosomes in the development of novel therapeutic strategies.

Inhibitory effect of microRNA-455-5p on biological functions of esophageal squamous cell carcinoma Eca109 cells via Rab31

The aim of the present study was to examine microRNA (miRNA or miR)-455-5p expression in esophageal squamous cell carcinoma (ESCC) at the tissue and cellular levels in order to elucidate its biological roles. A total of 60 patients with ESCC were enrolled in the present study and reverse transcription-quantitative polymerase chain reaction was used to measure the expression of miR-455-5p. ESCC Eca109 cells were transfected with miR-NC, miR-455-5p mimics or inhibitor and a Cell Counting Kit-8 assay was used to assess proliferation. To investigate the migration and invasion abilities of Eca109 cells, Transwell and Matrigel assays were performed. Western blotting was employed to measure Rab31 protein expression, while a rescue assay was utilized to study the biological roles of miR-455-5p and Rab31 in Eca109 cells. To determine whether Rab31 is a direct target of miR-455-5p, a dual luciferase reporter assay was performed. The results revealed that miR-455-5p expression was decreased in ESCC tissues and was negatively correlated with metastasis and pathogenesis. In vitro overexpression of miR-455-5p inhibited the proliferation, migration and invasion of ESCC Eca109 cells. Furthermore, miR-455-5p regulated the expression of Rab31 protein in Eca109 cells. Rab31 overexpression promoted the proliferation, migration and invasion of Eca109 cells. Luciferase reporter assay results revealed that miR-455-5p is able to bind with the 3'-untranslated region of Rab31 mRNA to regulate its expression. In summary, the results of the present study suggest that miR-455-5p expression is decreased in ESCC tissues and is miR-455-5p is negatively correlated with lymphatic metastasis and differentiation. As a tumor-suppressor gene, miR-455-5p inhibits the proliferation, migration and invasion of ESCC Eca109 cells by suppressing the expression of Rab31.

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

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

MiR-455-3p inhibits the degenerate process of chondrogenic differentiation through modification of DNA methylation

The aim of this work was to determine whether miR-455-3p regulates DNA methylation during chondrogenic differentiation of hMSCs. The expression of miR-455-3p and de novo methyltransferase DNMT3A was assessed in micromass culture of hBMSCs, which induced chondrogenic differentiation in vitro, and in E16.5 mice in vivo. A luciferase reporter assay was used to confirm whether miR-455-3p directly targets DNMT3A by interaction with the 3′-UTR. Using an Illumina Infinium Methylation EPIC microarray, genome-wide DNA methylation of hBMSCs with or without overexpressed miR-455-3p was examined for 28 days during induced chondrogenic differentiation. Here, we showed that miR-455-3p was more expressed during the middle stage of hBMSC chondrogenic differentiation, and less expressed in the late stage. DNMT3A was less expressed in the middle stage and more expressed in the late stage, and was also more expressed in the palms of miR-455-3p deletion mice compared to those of wild-type mice. The luciferase reporter assay demonstrated that miR-455-3p directly targets DNMT3A 3′-UTR. miR-455-3p overexpression inhibits the degenerate process during chondrogenic differentiation, while deletion of miR-455-3p in mice accelerated cartilage degeneration. Genome-wide DNA methylation analysis showed miR-455-3p overexpression regulates DNA methylation of cartilage-specific genes. GO analysis revealed PI3K-Akt signaling pathway was most hypomethylated. Our data show that miR-455-3p can regulate hMSC chondrogenic differentiation by affecting DNA methylation. Overexpression of miR-455-3p and DNA methylation inhibitors can thus potentially be utilized to optimize chondrogenic differentiation.

MicroRNA-193b-3p regulates chondrogenesis and chondrocyte metabolism by targeting HDAC3

Histone deacetylase 3 (HDAC3) plays a pivotal role in the repression of cartilage-specific gene expression in human chondrocytes. The aim of this study was to determine whether microRNA-193b-3p (miR-193b-3p) regulates the expression of HDAC3 during chondrogenesis and chondrocyte metabolism. Methods: miR-193b-3p expression was assessed in a human mesenchymal stem cell (hMSC) model of chondrogenesis, in interleukin-1β (IL-1β)-treated primary human chondrocytes (PHCs), and in non-degraded and degraded cartilage. hMSCs and PHCs were transfected with miR-193b-3p or its antisense inhibitor. A direct interaction between miR-193b-3p and its putative binding site in the 3'-untranslated region (3'-UTR) of HDAC3 mRNA was confirmed by performing luciferase reporter assays. Chondrocytes were transfected with miR-193b-3p before performing a chromatin immunoprecipitation assay with an anti-acetylated histone H3 antibody. To investigate miR-193b-3p-transfected PHCs in vivo, they were seeded in tricalcium phosphate-collagen-hyaluronate (TCP-COL-HA) scaffolds, which were then implanted in nude mice. In addition, plasma exosomal miR-193b-3p in samples from normal controls and patients with osteoarthritis (OA) were measured. Results: miR-193b-3p expression was elevated in chondrogenic and hypertrophic hMSCs, while expression was significantly reduced in degraded cartilage compared to non-degraded cartilage. In addition, miR-193b-3p suppressed the activity of reporter constructs containing the 3'-UTR of HDAC3, inhibited HDAC3 expression, and promoted histone H3 acetylation in the COL2A1, AGGRECAN, COMP, and SOX9 promoters. Treatment with the HDAC inhibitor trichostatin A (TSA) increased cartilage-specific gene expression and enhanced hMSCs chondrogenesis. TSA also increased AGGRECAN expression and decreased MMP13 expression in IL-1β-treated PHCs. Further, 8 weeks after implanting PHC-seeded TCP-COL-HA scaffolds subcutaneously in nude mice, we found that miR-193b overexpression strongly enhanced in vivo cartilage formation compared to that found under control conditions. We also found that patients with OA had lower plasma exosomal miR-193b levels than control subjects. Conclusions: These findings indicate that miR-193b-3p directly targets HDAC3, promotes H3 acetylation, and regulates hMSC chondrogenesis and metabolism in PHCs.

MicroRNA-455-3p as a Potential Biomarker for Alzheimer's Disease: An Update

A non-invasive and early-detectable peripheral biomarker is urgently needed for Alzheimer's disease (AD). The present study is a step forward to verify the biomarker properties of human microRNA-455-3p (Hsa-miR-455-3p) in AD patients. Our previous findings on mild cognitive impaired subjects, AD patients and AD cells and mouse models unveiled the miR-455-3p as a potential peripheral biomarker for AD. In the current study, we verified the differential expression of miR-455-3p in postmortem AD brains obtained from NIH NeuroBioBank, and fibroblasts and B-lymphocytes from both familial and sporadic AD patients from Coriell Cell Repository of National Institutes on Aging. Total RNA was extracted from the fibroblasts, B-lymphocytes and AD postmortem brains, and expression of miR-455-3p was measured by real-time reverse-transcriptase RT-PCR. Our real-time RT-PCR analysis showed a significant (P = 0.0002) upregulation of miR-455-3p expression in AD postmortem brains compared to healthy control samples. Expression of miR-455-3p was also upregulated in the fibroblasts from AD patients, however a significant difference in miR-455-3p level was observed in the cells from sporadic AD patients (P = 0.014) compared to healthy controls. Similarly, in B-lymphocytes, miR-455-3p level was also higher (P = 0.044) especially in sporadic AD cases compared to controls. Receiver operating characteristic (ROC) curve analysis indicated the significant area under ROC curve (AUROC) value of miR-455-3p in AD postmortem brain (AUROC = 0.792; P = 0.001) and AD fibroblasts cells (AUROC = 0.861; P = 0.03), whereas in B-lymphocytes AUROC value of miR-455-3p was not significant. Further, in-silico analysis for miRNA targets predictions showed the binding capacity of miR-455-3p with several AD associated key genes such as APP, NGF, USP25, PDRG1, SMAD4, UBQLN1, SMAD2, TP73, VAMP2, HSPBAP1, and NRXN1. Hence, these observations further revealed that miR-455-3p is a potential biomarker for AD and its possible therapeutic target for AD.

miR-27b promotes type II collagen expression by targetting peroxisome proliferator-activated receptor-γ2 during rat articular chondrocyte differentiation

MicroRNAs (miRNAs) play an essential role in articular cartilage development and growth. However, the exact mechanisms involved in this process remain unknown. In the present study, we investigated the biological functions of miR-27b during hypertrophic differentiation of rat articular chondrocytes. Based on in situ hybridization and immunohistochemistry, we report that miR-27b expression is reduced in the hypertrophic zone of articular cartilage, but expression of peroxisome proliferator-activated receptor γ (Pparγ) is increased. Dual-luciferase reporter gene assay and Western blot analysis demonstrated that Pparγ2 is a target of miR-27b Overexpression of miR-27b inhibited expression of Pparγ2, as well as type X collagen (Col10a1) and matrix metalloproteinase 13 (Mmp13), while significantly promoting the expression of Sex-determining Region-box 9 (Sox9) and type II collagen (Col2a1) at both the mRNA and protein levels. Rosiglitazone, a Pparγ agonist, suppressed Col2a1 expression, while promoting expression of runt-related transcription factor 2 (Runx2) and Col10a1 in a concentration-dependent manner. siRNA-mediated knockdown of Pparγ2 caused an increase in protein levels of Col2a1. The present study demonstrates that miR-27b regulates chondrocyte hypertrophy in part by targetting Pparγ2, and that miR-27b may have important therapeutic implications in cartilage diseases.

[Effect of chondrogenesis related miR-4287 on expression of aggrecanase-1 in human chondrocytes]

Objective

To investigate the effect and mechanism of miR-4287, a chondrogenesis associated microRNA, regulated the expression of aggrecanase-1 (a disintegrin and metalloproteinase with thrombospondin motif 4, ADAMTS4) in human chondrocytes.

Methods

First, the voluntarily donated normal and osteoarthritic knee articular cartilages were used to detect the expressions of miR-4287 and ADAMTS4 mRNA by real-time fluorescence quantitative PCR. Then, chondrocytes were isolated from knee articular cartilages. The effect of IL-1β on the expression of miR-4287 and ADAMTS4 mRNA was validated by the first generation of osteoarthritic chondrocytes. To confirm the influence of IL-1β signal pathways on the expression of miR-4287 and ADAMTS4 mRNA, osteoarthritic chondrocytes were pretreated with MAPK signal pathway inhibitor SP600125, NF-κB pathway inhibitor SN50, and finally stimulated with IL-1β. Chondro cytes were transfected with miR-4287 mimics and mimics negative control, inhibitors and inhibitors negative control respectively to value the effect of miR-4287 on ADAMTS4 expression. Luciferase reporter assay was used to verify the direct interaction between miR-4287 and putative site in the 3-untranslated region (3'UTR) of ADAMTS4 mRNA.

Results

Compared with normal knee articular cartilages, the miR-4287 expression was markedly diminished and conversely ADAMTS4 mRNA expression was raised in osteoarthritis cartilages ( P<0.05). Stimulation with IL-1β led to a reduction in miR-4287 expression and upregulation in ADAMTS4 mRNA expression, showing significant difference when compared with the untreated groups ( P<0.05). Pretreatment with IL-1β signal pathway inhibitors induced miR-4287 expression and attenuated ADAMTS4 mRNA expression in human chondrocytes, which were significantly different from that of unstimulated cells ( P<0.05). ADAMTS4 mRNA and protein were suppressed by transfection with miR-4287 mimics ( P<0.05) and elevated by transfection with miR-4287 inhibitors ( P<0.05). As luciferase reporter assay showed, overexpression miR-4287 failed to alter the luciferase activity of a reporter construct containing either wild or mutant 3'UTR of ADAMTS4 mRNA ( P>0.05).

Conclusion

miR-4287, a chondrogenesis associated microRNA, may play an important role in cartilage degeneration. miRNA-4287 is able to regulate ADAMTS4 expression in human chondrocytes, but not by means of directly targeted the ADAMTS4 mRNA 3'UTR. The exact mechanisms need to be further addressed.

MiR-455-3p activates Nrf2/ARE signaling via HDAC2 and protects osteoblasts from oxidative stress

BACKGROUND

The important role of miR-455-3p in the pathogenesis of bone metabolism associated diseases is gradually emerging. This study aims to ascertain the involvement of miR-455-3p and its underlying mechanisms in osteoporosis.

METHODS

The osteoblast cell lines MC3T3-E1 was treated with ferric ammonium citrate (FAC) to mimic a pathological environment for osteoporosis. The cytotoxic effect of iron overload was assessed by proliferation, apoptosis and oxidative stress of osteoblasts using commercial kits. Molecular biological methods, including qRT-PCR analysis, cell transfection and luciferase reporter assays were used to explain the role of miR-455-3p and its potential mechanisms in osteoblast apoptosis.

RESULTS

FAC dramatically inhibited the proliferation of osteoblast cells MC3T3-E1 but increased the apoptosis. We also observed that FAC significantly down-regulated miR-455-3p in MC3T3-E1 cells but enhanced HDAC2 protein level. Moreover, miR-455-3p overexpression eliminated the effects of iron overload on osteoblast cell proliferation, apoptosis and oxidative stress. In addition, miR-455-3p regulated osteoblast cell proliferation, apoptosis and oxidative stress through regulating HDAC2-Nrf2/ARE signaling pathway. MiR-455-3p overexpression alleviated the oxidative stress injury in osteoporosis mice.

CONCLUSION

Our results demonstrated that miR-455-3p activated Nrf2/ARE signal pathway through suppressing Keap1 via negative regulating HDAC2 protein level, thereby suppressing oxidative stress and promoting osteoblasts growth.

MicroRNA-455-3p as a potential peripheral biomarker for Alzheimer's disease

The purpose of our study was to identify microRNAs (miRNAs) as early detectable peripheral biomarkers in Alzheimer's disease (AD). To achieve our objective, we assessed miRNAs in serum samples from AD patients and Mild cognitive impairment (MCI) subjects relative to healthy controls. We used Affymetrix microarray analysis and validated differentially expressed miRNAs using qRT-PCR. We further validated miRNA data using AD postmortem brains, amyloid precursor protein transgenic mice and AD cell lines. We identified a gradual upregulation of four miRNAs: miR-455-3p, miR-4668-5p, miR-3613-3p and miR-4674. A fifth miRNA, mir-6722, was down-regulated in persons with AD and mild cognitive impairment compared with controls. Validation analysis by qRT-PCR showed significant upregulation of only miR-455-3p (P = 0.007) and miR-4668-5p (P = 0.016) in AD patients compared with healthy controls. Furthermore, qRT-PCR analysis of the AD postmortem brains with different Braak stages also showed upregulation of miR-455-3p (P = 0.016). However, receiver operating characteristic curves (ROC) curve analysis revealed a significant area under curve (AUC) value only for miR-455-3p in the serum (AUROC = 0.79; P = 0.015) and brains (AUROC = 0.86; P = 0.016) of AD patients. Expression analysis of amyloid precursor protein transgenic mice also revealed high level of mmu-miR-455-3p (P = 0.004) in the cerebral cortex (AD-affected) region of brain and low in the non-affected area, i.e. cerebellum. Furthermore, human and mouse neuroblastoma cells treated with the amyloid-β(1-42) peptide also showed a similarly higher expression of miR-455-3p. Functional analysis of differentially expressed miRNAs via the miR-path indicated that miR-455-3p was associated in the regulation of several biological pathways. Genes associated with these pathways were found to have a crucial role in AD pathogenesis. An increase in miR-455-3p expression found in AD patients and Aβ pathologies unveiled its biomarker characteristics and a precise role in AD pathogenesis.

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.

microRNA-455 targets cullin 3 to activate Nrf2 signaling and protect human osteoblasts from hydrogen peroxide

Over-production of hydrogen peroxide (H₂O₂) will lead to human osteoblast dysfunction and apoptosis, causing progression of osteoporosis and osteonecrosis. NF-E2-related factor 2 (Nrf2) is a well-characterized anti-oxidant signaling. Cullin 3 (Cul3) ubiquitin E3 ligase dictates Nrf2 degradation. We demonstrate that microRNA-455 ("miR-455") is a putative Cul3-targeting microRNA. Forced-expression of miR-455 in both hFOB1. 19 osteoblast cell line and primary human osteoblasts induced Cul3 degradation and Nrf2 protein stabilization, which led to subsequent transcription of ARE (anti-oxidant response element)-dependent genes (NQO1, HO1 and GCLC). Cul3 silencing, by expressing miR-455 or targeted-shRNA, protected human osteoblasts from H₂O₂. Reversely, miR-455 anti-sense caused Cul3 accumulation and Nrf2 degradation, which exacerbated H₂O₂ damages in hFOB1. 19 cells. Moreover, forced over-expression of Cul3 in hFOB1. 19 cells silenced Nrf2 and sensitized H₂O₂. Together, we propose that miR-455 activated Nrf2 signaling and protected human osteoblasts from oxidative stress possibly via targeting Cul3.