Identification of miR-1 as a micro RNA that supports late-stage differentiation of growth cartilage cells

Comprehensive analysis of differently expression mRNA and non-coding RNAs, and their regulatory mechanisms on relationship in thiram-induced tibial dyschondroplasia in chicken

Thiram pollution is one of the main causes of tibial dyschondroplasia (TD) induced by feed sources. Several studies have speculated that miRNA, circRNA and lncRNA may have significant impact on the development of TD, however, the specific mRNAs and noncoding RNAs and their respective regulatory mechanisms and functions in the development of TD have not been explored. Therefore, in this present study, we screened the differentially expressed mRNA, miRNA, circRNA and lncRNA by whole-transcriptome sequencing (RNA-seq) and differentially expressed genes (DEGs) enrichment, as well as constructed the interaction network among the mRNA-miRNA, mRNA-lncRNA and mRNA-miRNA-circRNA. The sequencing results were verified by fluorescence real-time quantitative PCR (RT-qPCR). The results obtained in this study, revealed that the cells were atrophied and disordered in the TD group, and the expression of BMP6, TGF-β and VEGF were significantly reduced. A total of 141 mRNAs, 10 miRNAs, 23 lncRNAs and 35 circRNAs of DEGs were obtained (p<0.05) Theses DEGs were enriched in the adhere junction and insulin signaling pathways. In addition, the mRNA-miRNA-circRNA network suggested that several pivotal ceRNA showed a regulatory relationship between the transcripts with miRNA, circRNA or lncRNA. Taken together, the results in the present study, represent an insight for further functional research on the ceRNA regulatory mechanism of TD in broilers.

miRNAs Related to Different Processes of Fracture Healing: An Integrative Overview

Fracture healing is a complex, dynamic process that is directed by cellular communication and requires multiple cell types, such as osteoblasts, osteoclasts, and immune cells. Physiological fracture healing can be divided into several phases that consist of different processes, such as angiogenesis, osteogenesis, and bone resorption/remodelling. This is needed to guarantee proper bone regeneration after fracture. Communication and molecular regulation between different cell types and within cells is therefore key in successfully orchestrating these processes to ensure adequate bone healing. Among others, microRNAs (miRNAs) play an important role in cellular communication. microRNAs are small, non-coding RNA molecules of ~22 nucleotides long that can greatly influence gene expression by post-transcriptional regulation. Over the course of the past decade, more insights have been gained in the field of miRNAs and their role in cellular signalling in both inter- and intracellular pathways. The interplay between miRNAs and their mRNA targets, and the effect thereof on different processes and aspects within fracture healing, have shown to be interesting research topics with possible future diagnostic and therapeutic potential. Considering bone regeneration, research moreover focusses on specific microRNAs and their involvement in individual pathways. However, it is required to combine these data to gain more understanding on the effects of miRNAs in the dynamic process of fracture healing, and to enhance their translational application in research, as well as in the clinic. Therefore, this review aims to provide an integrative overview on miRNAs in fracture healing, related to several key aspects in the fracture healing cascade. A special focus will be put on hypoxia, angiogenesis, bone resorption, osteoclastogenesis, mineralization, osteogenesis, osteoblastogenesis, osteocytogenesis, and chondrogenesis.

MicroRNA-1 Modulates Chondrocyte Phenotype by Regulating FZD7 of Wnt/ β-Catenin Signaling Pathway

OBJECTIVE

Osteoarthritis (OA) is an incurable joint disease characterized by pronounced pain. MicroRNAs constitute epigenetic mechanisms that may affect OA progression by contributing to changes in chondrocyte phenotype. This study investigates for the first time whether there is a link between miRNA-1 (miR-1) and OA pathogenesis, and the molecular mechanisms involved.

DESIGN

OA-associated gene expression, including MMP-13, ADAMTS5, and COL2A1 was compared in chondrocytes from non-OA and OA cartilage, and in SW1353 cells over- and underexpressing miR-1. Bioinformatics and luciferase reporter assay were conducted to confirm whether FZD7 was a target of miR-1. The effects of miR-1 on FZD7 expression and downstream Wnt/β-catenin signalling were investigated.

RESULTS

Non-OA and OA chondrocytes differed significantly in the expression of miR-1 and OA-associated genes. MiR-1 over- and underexpression in SW1353 cells, respectively, reduced and enhanced gene expression associated with cartilage catabolism. FZD7, which has an important role in the Wnt/β-catenin signaling pathway, was shown to be a potential target of miR-1. MiR-1 binding to FZD7 increased the levels of phosphorylated (inactivated) β-catenin, thereby preventing downstream β-catenin signaling.

CONCLUSIONS

Inhibition of Wnt/β-catenin signaling by miR-1 in chondrocytes may attenuate the expression of genes that regulate the activity of catabolic enzymes. This finding may be useful for future investigations of molecular targets for OA treatment.

Excessive expression of miR-1a by statin causes skeletal injury through targeting mitogen-activated protein kinase kinase kinase 1

Backgrounds: A major side effect of statin, a widely used drug to treat hyperlipidemia, is skeletal myopathy through cell apoptosis. The aim of this study is to investigate the roles of microRNA in statin-induced injury.

Methods: Apolipoprotein E knockout (ApoE-/-) mice were administered with simvastatin (20 mg/kg/day) for 8 weeks. Exercise capacity was evaluated by hanging grid test, forelimb grip strength, and running tolerance test.

Results: In cultured skeletal muscle cells, statin increased the levels of miR-1a but decreased the levels of mitogen-activated protein kinase kinase kinase 1 (MAP3K1) in a time or dose dependent manner. Both computational target-scan analysis and luciferase gene reporter assay indicated that MAP3K1 is the target gene of miR-1a. Statin induced cell apoptosis of skeletal muscle cells, but abolished by downregulating of miR-1a or upregulation of MAP3K1. Further, the effects of miR-1a inhibition on statin-induced cell apoptosis were ablated by MAP3K1 siRNA. In ApoE-/- mice, statin induced cell apoptosis of skeletal muscle cells and decreased exercise capacity in mice infected with vector, but not in mice with lentivirus-mediated miR-1a gene silence.

Conclusion: Statin causes skeletal injury through induction of miR-1a excessive expression to decrease MAP3K1 gene expression.

A microRNA Signature for Impaired Wound-Healing and Ectopic Bone Formation in Humans

BACKGROUND

Heterotopic ossification (HO) is characterized by the abnormal growth of ectopic bone in soft tissues, frequently occurring within the military population because of extensive orthopaedic combat trauma. MicroRNAs (miRNAs) are small noncoding RNAs that act as post-transcriptional regulators of gene expression. We hypothesized that a clinically relevant miRNA signature could be detected in patients following injury that progressed to form HO (HO+) or did not form HO (HO-).

METHODS

Tissue samples were obtained from injured servicemembers during their initial surgical debridements, and miRNA profiling was performed using a real-time miRNA polymerase chain reaction (PCR) array. Primary mesenchymal progenitor cells (MPCs) were harvested from debrided traumatized human muscle tissue, and cells were isolated and cultured in vitro. Mimic miRNAs were transfected into MPCs, followed by downstream in vitro analyses.

RESULTS

The investigation of the miRNA expression profile in the tissue of HO+ compared with HO- patients demonstrated a molecular signature that included the upregulation of miR-1, miR-133a, miR-133b, miR-206, miR-26a, and miR-125b. Transfection of each of these mature miRNAs into MPCs followed by osteogenic induction demonstrated that miR-1, miR-133a, miR-133b, and miR-206 enhanced osteogenic differentiation compared with control treatments. In silico and in vitro analyses identified the transcription factor SOX9 as a candidate downstream target of miR-1 and miR-206 miRNAs.

CONCLUSIONS

Our data demonstrated a molecular signature of miRNAs in the soft tissue of wounded servicemembers that was associated with the development of HO, providing novel insights into the underlying molecular mechanisms associated with posttraumatic HO.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

MicroRNA-1 promotes cartilage matrix synthesis and regulates chondrocyte differentiation via post-transcriptional suppression of Ihh expression

Indian hedgehog signaling molecule (Ihh) is known to play critical roles in chondrogenesis and cartilage development. However, it remains largely unknown how Ihh is regulated during the process. Previous studies suggest that Ihh plays an important regulatory role in the growth and development of articular cartilage, but whether it is regulated by miRNAs is unclear. The present study aimed to investigate the effects of miR‑1 on chondrocyte differentiation and matrix synthesis, and to determine whether miR‑1 can regulate the Ihh signaling pathway. In the present study, the expression level of miR‑1 was altered via transfection of the miR‑1 mimic or inhibitor in mouse thorax chondrocytes, and the impact on chondrocyte phenotypes and Ihh expression was examined. Overexpression of miR‑1 promoted the expression of the matrix synthesis‑associated molecules collagen (Col)‑II and aggrecan, two key components in cartilage matrix. Conversely, overexpression of miR‑1 significantly downregulated the expression of chondrocyte differentiation markers Col‑X and matrix metallopeptidase 13. Moreover, overexpression of miR‑1 dose‑dependently inhibited endogenous Ihh expression, and an association was observed between miR‑1 and Ihh expression. The 3' untranslated region (UTR) of Ihh from various species contains two miR‑1 binding sites. Luciferase reporter assays indicated that miR‑1 post‑transcriptionally suppressed Ihh expression, which was dependent on the binding of miR‑1 to one of the two putative binding sites of the Ihh 3'UTR. Furthermore, via inhibition of Ihh expression, miR‑1 decreased the expression of molecules downstream of Ihh in the Hedgehog signaling pathway in mouse thorax chondrocytes. This study provided new insight into the molecular mechanisms of miR‑1 in regulating chondrocyte phenotypes via targeting the Ihh pathway.

Identification of differentially expressed MiRNAs profile in a thiram-induced tibial dyschondroplasia

Tetramethyl thiuram disulfide (thiram) is a dithiocarbamate, which is widely used on seeds and storing food grains. The incorporation of thiram into the food chain could be a risk for both human beings and animals. Thiram-contaminated feed has been considered a common cause of tibial dyschondrolplasia (TD) in many avian species. The molecular mechanism of action of thiram on TD involving microRNA (miRNA) is not fully understood. For this purpose, the morbidity and pathologic changes were evaluated to understand the TD, and high-throughput RNA sequencing (RNA-Seq) was performed to explore the differentially expressed miRNAs (DEGs). RT-qPCR was used to confirm the validity as compared with sequencing data. The results showed that the marked alterations in the growth plate of the TD chickens were noticeable, with shrinking cells and irregular chondrocyte columns as compared with control group. In this study, we identified total 375 (p < 0.1), 340 (p < 0.05) and 266 (p < 0.01) significant DEGs between the TD and control groups. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs showed that the target miRNAs were significantly enriched in different treatment groups, such as apoptosis, mRNA surveillance pathway, mitophagy-animal, etc. This study provides theoretical basis for in-depth understanding the pathogenesis of thiram-induced TD and explore the new insights towards the proposed molecular mechanism of specific miRNA as biomarkers for effective gene diagnosis and treatment of TD in broilers.

MicroRNA‑31 promotes chondrocyte proliferation by targeting C‑X‑C motif chemokine ligand 12

The present study aimed to investigate the biological function and underlying molecular mechanisms of miR-31 in osteoarthritis (OA). Reverse transcription-quantitative polymerase chain reaction was used to detect miR-31 expression, and it was found that miR-31 was downregulated in the cartilage tissues of OA patients. microRNA.org was used to predict the gene targets of miR-31, and dual luciferase reporter assays were used to verify that C-X-C motif chemokine ligand 12 (CXCL12) was a direct target of miR-31. The human chondrocyte cell line CHON-001 was used to perform MTT and cell migration assays. Western blotting was used to measure the protein expression of CXCL12, type I collagen and aggrecan. The results suggested that CXCL12 was a target of miR-31, and the expression of CXCL12 was negatively regulated by miR-31 in CHON-001 cells. miR-31 increased CHON-001 cell viability and migration, as well as the expression of type I collagen and aggrecan. Furthermore, the overexpression of CXCL12 eliminated the effects of miR-31 mimics on CHON-001 cells. In conclusion, the data indicated that miR-31 promoted chondrocyte viability and migration by directly targeting CXCL12, which provided evidence for CXCL12 as a potential target in OA therapy.

miR‑486‑5p is upregulated in osteoarthritis and inhibits chondrocyte proliferation and migration by suppressing SMAD2

Osteoarthritis (OA) is the most common form of arthritis and is caused by the breakdown of joint cartilage. The present study aimed to investigate an effective method for the treatment of OA. It was demonstrated that, compared with other patients, patients with OA exhibited lower mRNA expression levels of SMAD family member 2 (SMAD2). MicroRNA (miR)‑486‑5p was predicted to bind with SMAD2, which was verified by dual‑luciferase reporter assay. Compared withcontrol patients who had no known history of OA or rheumatoid arthritis, patients with OA exhibited higher miR‑486‑5p expression level. Treatment with miR‑486‑5p mimics inhibited proliferation and migration of CHON‑001 human chondrocytes, and also inhibited the expression levels of type II collagen and aggrecan. However, treatment with a miR‑486‑5p inhibitor promoted proliferation and migration, and the expression of type II collagen and aggrecan. Short interfering RNA‑directed silencing of SMAD2 reversed the upregulated proliferation and migration and the expression level of type II collagen and aggrecan induced by the miR‑486‑5p inhibitor. In conclusion, the results of the present study indicated that miR‑486‑5p was upregulated in OA and may inhibit chondrocyte proliferation and migration by suppressing SMAD2.

Expression of miR-625 and Fas in cervical vertebral cartilage endplate

The aim of the present study was to assess miR-625 and Fas expression in normal and degenerative cervical cartilage endplate (CEP) tissues. Following biof-informatics analysis, the Fas gene was predicted to be one of the targets of miR-625. Quantitative PCR (qPCR) and western blotting were used to detect miR-625 and Fas expression in normal and degenerative CEP. A luciferase reporter assay was used to identify whether miR-625 could directly target the 3' untranslated region (3'-UTR) of Fas. Lentiviral overexpression and/or inhibition vectors of miR-625 (pre-miR-625)/antigomiR-625 were constructed to determine whether overexpression or inhibition of miR-625 could affect Fas and B-cell lymphoma 2 (Bcl-2) expression in cartilaginous endplate cells (CECs) and tissues. qPCR analysis demonstrated that miR-625 expression in degenerative CEP was significantly lower than in normal CEP tissue, while the production of Fas in degenerated CEP was significantly higher. Results from western blotting also showed a significant increase in Fas expression in degenerative CEP. miR-625 can bind directly to the 3'-UTR of the Fas gene. However, this inhibition was attenuated by a target mutation in the miR-625-binding site of the 3'-UTR of Fas mRNA. In addition, following transfection of CECs with pre-miR-625 and antigomiR-625, expression of Fas significantly decreased and increased, respectively, and Bcl-2 expression was upregulated and downregulated, respectively. Upregulation of miR-625 can inhibit Fas expression and further affect Bcl-2 expression in CEP degeneration, suggesting that miR-625-mediated inhibition of the Fas gene is important in cervical degeneration.

Epigenetics in osteoarthritis: Potential of HDAC inhibitors as therapeutics

Osteoarthritis (OA) is the most common joint disease and the leading cause of chronic disability in middle-aged and older populations worldwide. The development of disease modifying therapy for OA is in its infancy largely because the regulatory mechanisms for the molecular effectors of OA pathogenesis are poorly understood. Recent studies identified epigenetic events as a critical regulator of molecular players involved in the induction and development of OA. Epigenetic mechanisms include DNA methylation, non-coding RNA and histone modifications. The aim of this review is to briefly highlight the recent advances in the epigenetics of cartilage and potential of HDACs (Histone deacetylases) inhibitors in the therapeutic management of OA. We summarize the recent studies utilizing HDAC inhibitors as potential therapeutics for inhibiting disease progression and preventing the cartilage destruction in OA. HDACs control normal cartilage development and homeostasis and understanding the impact of HDACs inhibitors on the disease pathogenesis is of interest because of its importance in affecting overall cartilage health and homeostasis. These findings also shed new light on cartilage disease pathophysiology and provide substantial evidence that HDACs may be potential novel therapeutic targets in OA.

miR-195 inhibits the proliferation and migration of chondrocytes by targeting GIT1

Previous studies have demonstrated that G-protein coupled receptor kinase interacting protein-1 (GIT1) and microRNAs (miRNAs) serve an important role in chondrocyte proliferation and migration. However, a limited number of studies conducted thus far have investigated the association between GIT1 and miRNAs. In the present study, putative miR‑195 binding sites in the GIT1 3'‑untranslated region were identified using common bioinformatic algorithms (miRanda, TargetScan, miRBase and miRWalk), and it was demonstrated that they may be involved in regulating GIT1 expression. Following transfection of miR‑195 mimics in chondrocytes, the expression of GIT1 was significantly reduced, whereas the expression was significantly increased following transfection with miR‑195 inhibitors. In addition, the results of the current study demonstrated that increased miR‑195 expression may downregulate chondrocyte proliferation and reduce cell migration. However, chondrocyte proliferation and migration was enhanced following suppression of miR‑195 expression. Furthermore, upon co‑transfection of miR‑195 and GIT1 expression vectors, the inhibitory effect of miR‑195 on chondrocyte proliferation and migration was attenuated. Therefore, miR‑195 may affect chondrocyte proliferation and migration via targeted regulation of GIT1 expression. The results of the current study provide novel evidence for the regulatory mechanisms of miRNAs in bone and cartilage tissues, which may facilitate further research and provide a greater understanding of different osteoarticular diseases.

The Role of miRNAs in Cartilage Homeostasis

Osteoarthritis (OA) is an age-related disease with poorly understood pathogenesis. Recent studies have demonstrated that miRNA might play a key role in OA initiation and development. We reviewed recent publications and elucidated the connection between miRNA and OA cartilage anabolic and catabolic signals, including four signaling pathways: TGF-β/Smads and BMPs signaling, associated with cartilage anabolism; and MAPK and NF-KB signaling, associated with cartilage catabolism. We also explored the relationships with MMP, ADAMTS and NOS (NitricOxide Synthases) families, as well as with the catabolic cytokines IL-1 and TNF-α. The potential role of miRNAs in biological processes such as cartilage degeneration, chondrocyte proliferation, and differentiation is discussed. Collective evidence indicates that miRNAs play a critical role in cartilage degeneration. These findings will aid in understanding the molecular network that governs articular cartilage homeostasis and in to elucidate the role of miRNA in the pathogenesis of OA.

Roles of the canonical myomiRs miR-1, -133 and -206 in cell development and disease

MicroRNAs are small non-coding RNAs that participate in different biological processes, providing subtle combinational regulation of cellular pathways, often by regulating components of signalling pathways. Aberrant expression of miRNAs is an important factor in the development and progression of disease. The canonical myomiRs (miR-1, -133 and -206) are central to the development and health of mammalian skeletal and cardiac muscles, but new findings show they have regulatory roles in the development of other mammalian non-muscle tissues, including nerve, brain structures, adipose and some specialised immunological cells. Moreover, the deregulation of myomiR expression is associated with a variety of different cancers, where typically they have tumor suppressor functions, although examples of an oncogenic role illustrate their diverse function in different cell environments. This review examines the involvement of the related myomiRs at the crossroads between cell development/tissue regeneration/tissue inflammation responses, and cancer development.

Cartilage tissue engineering: recent advances and perspectives from gene regulation/therapy

Diseases in articular cartilages affect millions of people. Despite the relatively simple biochemical and cellular composition of articular cartilages, the self-repair ability of cartilage is limited. Successful cartilage tissue engineering requires intricately coordinated interactions between matrerials, cells, biological factors, and phycial/mechanical factors, and still faces a multitude of challenges. This article presents an overview of the cartilage biology, current treatments, recent advances in the materials, biological factors, and cells used in cartilage tissue engineering/regeneration, with strong emphasis on the perspectives of gene regulation (e.g., microRNA) and gene therapy.

The role of microRNAs in cellular senescence and age-related conditions of cartilage and bone

BACKGROUND AND PURPOSE

We reviewed the current state of research on microRNAs in age-related diseases in cartilage and bone.

METHODS

PubMed searches were conducted using separate terms to retrieve articles on (1) the role of microRNAs on aging and tissue degeneration, (2) specific microRNAs that influence cellular and organism senescence, (3) microRNAs in age-related musculoskeletal conditions, and (4) the diagnostic and therapeutic potential of microRNAs in age-related musculoskeletal conditions.

RESULTS

An increasing number of studies have identified microRNAs associated with cellular aging and tissue degeneration. Specifically in regard to frailty, microRNAs have been found to influence the onset and course of age-related musculoskeletal conditions such as osteoporosis, osteoarthritis, and posttraumatic arthritis. Both intracellular and extracellular microRNAs may be suitable to function as diagnostic biomarkers.

INTERPRETATION

The research data currently available suggest that microRNAs play an important role in orchestrating age-related processes and conditions of the musculoskeletal system. Further research may help to improve our understanding of the complexity of these processes at the cellular and extracellular level. The option to develop microRNA biomarkers and novel therapeutic agents for the degenerating diseases of bone and cartilage appears to be promising.

MicroRNAs in cartilage development, homeostasis, and disease

microRNAs (miRNAs) regulate gene expression mainly at the posttranscriptional level. Many different miRNAs are expressed in chondrocytes, and each individual miRNA can regulate hundreds of target genes, creating a complex gene regulatory network. Experimental evidence suggests that miRNAs play significant roles in various aspects of cartilage development, homeostasis, and pathology. The possibility that miRNAs can be novel therapeutic targets for cartilage diseases led to vigorous investigations to understand the role of individual miRNAs in skeletal tissues. Here, we summarize our current understanding of miRNAs in chondrocytes and cartilage. In the first part, we discuss roles of miRNAs in growth plate development and chondrocyte differentiation. In the second part, we put a particular focus on articular cartilage and discuss the significance of variety of findings in the context of osteoarthritis, the most common degenerative joint disease.

MicroRNAs involved in bone formation

During skeletal development, mesenchymal progenitor cells undergo a multistage differentiation process in which they proliferate and become bone- and cartilage-forming cells. This process is tightly regulated by multiple levels of regulatory systems. The small non-coding RNAs, microRNAs (miRNAs), post-transcriptionally regulate gene expression. Recent studies have demonstrated that miRNAs play significant roles in all stages of bone formation, suggesting the possibility that miRNAs can be novel therapeutic targets for skeletal diseases. Here, we review the role and mechanism of action of miRNAs in bone formation. We discuss roles of specific miRNAs in major types of bone cells, osteoblasts, chondrocytes, osteoclasts, and their progenitors. Except a few, the current knowledge about miRNAs in bone formation has been obtained mainly by in vitro studies; further validation of these findings in vivo is awaited. We also discuss about several miRNAs of particular interest in the light of future therapies of bone diseases.

MicroRNAs play a role in chondrogenesis and osteoarthritis (review)

Osteoarthritis (OA) is one of the most widespread degenerative joint diseases affecting the elderly. Research into the regulatory mechanisms underlying the pathogenesis of OA is therefore warranted, and over the past decade, there has been an increased focus on the functional role of microRNAs (miRNAs or miRs). In this systematic review, we aimed to review the evidence implicating miRNAs in the pathogenesis of chondrogenesis and OA. Systematic reviews of PubMed and Embase were performed to search for studies using strings of miRNAs, non-coding RNAs, cartilage, chondrocytes, chondrogenesis, chondrocytogenesis and OA. The identified studies were retrieved, and the references provided were searched. The selected studies were required to focus on the role of miRNAs in chondrogenesis and OA. The results of this review indicated that more than 25 miRNAs have been implicated in chondrogenesis and OA. In particular, chondrocytogenesis, chondrogenic differentiation, chondrocyte proliferation, chondrocyte hypertrophy, endochondral ossification, and proteolytic enzyme regulation are targeted or facilitated by more than 1 miRNA. To date, limited efforts have been performed to evaluate translational applications for this knowledge. Novel therapeutic strategies have been developed and are under investigation to selectively modulate miRNAs, which could potentially enable personalized OA therapy. miRNAs appear to be important modulators of chondrogenesis and OA. Their expression is frequently altered in OA, and many are functionally implicated in the pathogenesis of the disease. The translational roles and therapeutic potential of miRNAs remains to be evaluated.

MicroRNA-dependent targeting of the extracellular matrix as a mechanism of regulating cell behavior

BACKGROUND

MicroRNAs are small noncoding RNAs which regulate gene expression at the posttranscriptional level by inducing mRNA degradation or translational repression. MicroRNA-dependent modulation of the extracellular matrix and its cellular receptors has emerged as a novel mechanism of regulating numerous matrix-dependent processes, including cell proliferation and apoptosis, cell adhesion and migration, cell differentiation and stem cell properties.

SCOPE OF REVIEW

In this review, we will present different mechanisms by which microRNAs and extracellular matrix constituents mutually regulate their expression, and we will demonstrate how these expression changes affect cell behavior. We will also highlight the importance of dysregulated matrix-related microRNA expression for the pathogenesis of inflammatory and malignant disease, and discuss the potential for diagnostic and therapeutic applications.

MAJOR CONCLUSIONS

MicroRNAs and matrix-dependent signal transduction processes form novel regulatory circuits, which profoundly affect cell behavior. As misexpression of microRNAs targeting extracellular matrix constituents is observed in a variety of diseases, a pharmacological intervention with these processes has therapeutic potential, as successfully demonstrated in vitro and in advanced animal models. However, a deeper mechanistic understanding is required to address potential side effects prior to clinical applications in humans.

GENERAL SIGNIFICANCE

A full understanding of the role and function of microRNA-dependent regulation of the extracellular matrix may lead to new targeted therapies and new diagnostics for malignant and inflammatory diseases in humans. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Two non-coding RNAs, MicroRNA-101 and HOTTIP contribute cartilage integrity by epigenetic and homeotic regulation of integrin-α1

Non-coding RNAs have been less studied in cartilage development and destruction regulated by sophisticated molecular events despite their considerable theranostic potential. In this study, we identified significant down-regulation of mR-101 and up-regulation of lncRNA, HOTTIP in the processes of endochondral ossification and osteoarthritic progression. In wing mesenchymal cells, up-expression of miR-101 by TGF-β3 treatment is targeting DNMT-3B and thereby altered the methylation of integrin-α1 addressed as a positive regulator of endochondral ossification in this study. In like manner, down-regulation of miR-101 also coordinately up-regulated DNMT-3B, down-regulated integrin-α1, and resulted in cartilage destruction. In an OA animal model, introduction of lentiviruses that encoded miR-101 or integrin-α1 successfully reduced cartilage destruction. In like manner, long non-coding RNA (lncRNA), HOTTIP, a known regulator for HoxA genes, was highly up-regulated and concurrent down-regulation of HoxA13 displayed the suppression of integrin-α1 in OA chondrocytes. In conclusion, two non-coding RNAs, miR-101 and HOTTIP regulate cartilage development and destruction by modulating integrin-α1 either epigenetically by DNMT-3B or transcriptionally by HoxA13 and data further suggest that these non-coding RNAs could be a potent predictive biomarker for OA as well as a therapeutic target for preventing cartilage-related diseases.

microRNAs and cartilage

microRNAs are small non-coding RNAs that in the last decade have emerged as overarching regulators of gene expression. Their abundance, ability to repress a large number of target genes and overlapping target specificity indicate a complex network of interactions that is still being defined. A number of studies focused on the role of microRNAs in cartilage have identified a small number, including miR-140 and -675 as playing important roles in regulation of cartilage homeostasis and together with the broader description of the activity of microRNAs in other tissues are beginning to define the function of microRNAs in cartilage development and homeostasis.

Epigenetics in osteoarthritis and its implication for future therapeutics

INTRODUCTION

Changes occurring in the chondrocyte gene that control articular cartilage are important for the onset and progression of osteoarthritis (OA). However, actual development of the disease may be also controlled by changes in epigenome.

AREAS COVERED

Topics include the association of the three components of epigenetic modification, i.e., DNA methylation, histone modification, and microRNA expression, with the pathogenesis and progression of OA. The cross talk between genetics and epigenetics as well as the implication of epigenetics as a therapeutic measure for OA is also introduced.

EXPERT OPINION

Epigenetic markers that detect various chondrocyte phenotypes, including those involving chondrogenic differentiation, articular cartilage homeostasis, and progression of OA, may provide a novel means to detect early OA. Recent report of dietary supplement such as glucosamine that prevents demethylation of promoters of inflammatory cytokine is encouraging. Although already available, the toxicity and off-target side effects of histone deacetylase inhibitors are concerns for benign nonlethal disease like OA. miRNA-based treatment may present another therapeutic modality without potentially detrimental off-target side effects. Future studies are needed to search for additional miRNA that can modulate the course of OA and to identify key targets of currently known miRNA that impact OA pathogenesis and disease progression.

Unraveling 50-Year-Old Clues Linking Neurodegeneration and Cancer to Cycad Toxins: Are microRNAs Common Mediators?

Recognition of overlapping molecular signaling activated by a chemical trigger of cancer and neurodegeneration is new, but the path to this discovery has been long and potholed. Six conferences (1962–1972) examined the puzzling neurotoxic and carcinogenic properties of a then-novel toxin [cycasin: methylazoxymethanol (MAM)-β-d-glucoside] in cycad plants used traditionally for food and medicine on Guam where a complex neurodegenerative disease plagued the indigenous population. Affected families showed combinations of amyotrophic lateral sclerosis (ALS), parkinsonism (P), and/or a dementia (D) akin to Alzheimer’s disease (AD). Modernization saw declining disease rates on Guam and remarkable changes in clinical phenotype (ALS was replaced by P-D and then by D) and in two genetically distinct ALS-PDC-affected populations (Kii-Japan, West Papua-Indonesia) that used cycad seed medicinally. MAM forms DNA lesions – repaired by O⁶-methylguanine methyltransferase (MGMT) – that perturb mouse brain development and induce malignant tumors in peripheral organs. The brains of young adult MGMT-deficient mice given a single dose of MAM show DNA lesion-linked changes in cell-signaling pathways associated with miRNA-1, which is implicated in colon, liver, and prostate cancers, and in neurological disease, notably AD. MAM is metabolized to formaldehyde, a human carcinogen. Formaldehyde-responsive miRNAs predicted to modulate MAM-associated genes in the brains of MGMT-deficient mice include miR-17-5p and miR-18d, which regulate genes involved in tumor suppression, DNA repair, amyloid deposition, and neurotransmission. These findings marry cycad-associated ALS-PDC with colon, liver, and prostate cancer; they also add to evidence linking changes in microRNA status both to ALS, AD, and parkinsonism, and to cancer initiation and progression.

MicroRNAs in chondrogenesis, articular cartilage, and osteoarthritis: implications for tissue engineering

Coordinated actions of various regulators, including morphogens are required for chondrogenesis and maintenance of articular cartilage function. Bone morphogenetic proteins, and related signaling molecules and transcription factors form a complex regulatory network. MicroRNAs (miRNAs) are noncoding small RNAs that negatively regulate the expression of downstream targets by repressing the translation or inducing the cleavage of messenger RNAs (mRNAs). Increasing evidence indicates that miRNAs are an integral part of the regulatory network in chondrocyte differentiation and cartilage function. The aim of this article is to review the progress in miRNA expression and target genes in cartilage differentiation, homeostasis, and in the pathobiology of osteoarthritis. The recent progress in miRNAs in cartilage has implications for tissue engineering.

Hyaline cartilage tissue is formed through the co-culture of passaged human chondrocytes and primary bovine chondrocytes

To circumvent the problem of a sufficient number of cells for cartilage engineering, the authors previously developed a two-stage culture system to redifferentiate monolayer culture-expanded dedifferentiated human articular chondrocytes by co-culture with primary bovine chondrocytes (bP0). The aim of this study was to analyze the composition of the cartilage tissue formed in stage 1 and compare it with bP0 grown alone to determine the optimal length of the co-culture stage of the system. Biochemical data show that extracellular matrix accumulation was evident after 2 weeks of co-culture, which was 1 week behind the bP0 control culture. By 3 to 4 weeks, the amounts of accumulated proteoglycans and collagens were comparable. Expression of chondrogenic genes, Sox 9, aggrecan, and collagen type II, was also at similar levels by week 3 of culture. Immunohistochemical staining of both co-culture and control tissues showed accumulation of type II collagen, aggrecan, biglycan, decorin, and chondroitin sulfate in appropriate zonal distributions. These data indicate that co-cultured cells form cartilaginous tissue that starts to resemble that formed by bP0 after 3 weeks, suggesting that the optimal time to terminate the co-culture stage, isolate the now redifferentiated cells, and start stage 2 is just after 3 weeks.

Epigenomic and microRNA-mediated regulation in cartilage development, homeostasis, and osteoarthritis

Osteoarthritis (OA) is a multifactorial disease subject to the effects of many genes and environmental factors. Alterations in the normal pattern of chondrocyte gene control in cartilage facilitate the onset and progression of OA. Stable changes in patterns of gene expression, not associated with alterations in DNA sequences, occur through epigenetic changes, including DNA methylation, histone modifications, and alterations in chromatin structure, as well as by microRNA (miRNA)-mediated mechanisms. Moreover, the ability of the host to repair damaged cartilage is reflected in alterations in gene control circuits, suggestive of an epigenetic and miRNA-dependent tug-of-war between tissue homeostasis and OA disease pathogenesis. Herein, we summarize epigenetic and miRNA-mediated mechanisms impacting on OA progression and in this context offer potential therapeutic strategies for OA treatment.

The expression and function of microRNAs in chondrogenesis and osteoarthritis

OBJECTIVE

To use an in vitro model of chondrogenesis to identify microRNAs (miRNAs) with a functional role in cartilage homeostasis.

METHODS

The expression of miRNAs was measured in the ATDC5 cell model of chondrogenesis using microarray and was verified using quantitative reverse transcription-polymerase chain reaction. MicroRNA expression was localized by in situ hybridization. Predicted miRNA target genes were validated using 3'-untranslated region-Luc reporter plasmids containing either wild-type sequences or mutants of the miRNA target sequence. Signaling through the Smad pathway was measured using a (CAGA)(12) -Luc reporter.

RESULTS

The expression of several miRNAs was regulated during chondrogenesis. These included 39 miRNAs that are coexpressed with miRNA-140 (miR-140), which is known to be involved in cartilage homeostasis and osteoarthritis (OA). Of these miRNAs, miR-455 resides within an intron of COL27A1 that encodes a cartilage collagen. When human OA cartilage was compared with cartilage obtained from patients with femoral neck fractures, the expression of both miR-140-5p and miR-455-3p was increased in OA cartilage. In situ hybridization showed miR-455-3p expression in the developing limbs of chicks and mice and in human OA cartilage. The expression of miR-455-3p was regulated by transforming growth factor β (TGFβ) ligands, and miRNA regulated TGFβ signaling. ACVR2B, SMAD2, and CHRDL1 were direct targets of miR-455-3p and may mediate its functional impact on TGFβ signaling.

CONCLUSION

MicroRNA-455 is expressed during chondrogenesis and in adult articular cartilage, where it can regulate TGFβ signaling, suppressing the Smad2/3 pathway. Diminished signaling through this pathway during the aging process and in OA chondrocytes is known to contribute to cartilage destruction. We propose that the increased expression of miR-455 in OA exacerbates this process and contributes to disease pathology.

Nutrition and bone growth in pediatrics

Children's growth is a hallmark of their normal development and the association between nutrition and linear growth in children is well accepted. Growth requires an adequate supply of many different nutritional factors, some form the "building materials," whereas others play regulatory roles. In this article we describe the growth of the growth plate and discuss the role of nutritional affected hormones on this process. In addition we describe the effect of local regulators and nutritional factors on the growth process and suggest the involvement of new regulatory factors in the translation of nutrition to growth.

MicroRNA-146a is linked to pain-related pathophysiology of osteoarthritis

Because miR-146a is linked to osteoarthritis (OA) and cartilage degeneration is associated with pain, we have characterized the functional role of miR-146a in the regulation of human articular cartilage homeostasis and pain-related factors. Expression of miRNA 146a was analyzed in human articular cartilage and synovium, as well as in dorsal root ganglia (DRG) and spinal cord from a rat model for OA-related pain assessment. The functional effects of miR-146a on human chondrocytic, synovial, and microglia cells were studied in cells transfected with miR-146a. Using real-time PCR, we assessed the expression of chondrocyte metabolism-related genes in chondrocytes, genes for inflammatory factors in synovial cells, as well as pain-related proteins and ion channels in microglial cells. Previous studies showed that miR-146a is significantly upregulated in human peripheral knee OA joint tissues. Transfection of synthetic miR-146a significantly suppresses extracellular matrix-associated proteins (e.g., Aggrecan, MMP-13, ADAMTS-5, collagen II) in human knee joint chondrocytes and regulates inflammatory cytokines in synovial cells from human knee joints. In contrast, miR-146a is expressed at reduced levels in DRGs and dorsal horn of the spinal cords isolated from rats experiencing OA-induced pain. Exogenous supplementation of synthetic miR-146a significantly modulates inflammatory cytokines and pain-related molecules (e.g., TNFα, COX-2, iNOS, IL-6, IL8, RANTS and ion channel, TRPV1) in human glial cells. Our findings suggest that miR-146a controls knee joint homeostasis and OA-associated algesia by balancing inflammatory responses in cartilage and synovium with pain-related factors in glial cells. Hence, miR-146a may be useful for the treatment of both cartilage regeneration and pain symptoms caused by OA.