Osteogenic differentiation of fibroblast-like synovial cells in rheumatoid arthritis is induced by microRNA-218 through a ROBO/Slit pathway

The role of non-coding RNAs in fibroblast-like synoviocytes in rheumatoid arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by synovial hyperplasia, and fibroblast-like synoviocytes (FLSs) constitute the majority of cells in the synovial tissue, playing a crucial role in the onset of RA. Dysregulation of FLSs function is a critical strategy in treating joint damage associated with RA. Non-coding RNAs, a class of RNA molecules that do not encode proteins, participate in the development of various diseases. This article aims to review the progress in the study of long non-coding RNAs, microRNAs, and circular RNAs in FLSs. Non-coding RNAs are involved in the pathogenesis of RA, directly or indirectly regulating FLSs' proliferation, migration, invasion, apoptosis, and inflammatory responses. Furthermore, non-coding RNAs also influence DNA methylation and osteogenic differentiation in FLSs. Therefore, non-coding RNAs hold promise as biomarkers for diagnosing RA. Targeting non-coding RNAs in FLSs locally represents a potential strategy for future therapies in RA.

Metabolic changes in fibroblast-like synoviocytes in rheumatoid arthritis: state of the art review

Fibroblast-like synoviocytes (FLS) are important components of the synovial membrane. They can contribute to joint damage through crosstalk with inflammatory cells and direct actions on tissue damage pathways in rheumatoid arthritis (RA). Recent evidence suggests that, compared with FLS in normal synovial tissue, FLS in RA synovial tissue exhibits significant differences in metabolism. Recent metabolomic studies have demonstrated that metabolic changes, including those in glucose, lipid, and amino acid metabolism, exist before synovitis onset. These changes may be a result of increased biosynthesis and energy requirements during the early phases of the disease. Activated T cells and some cytokines contribute to the conversion of FLS into cells with metabolic abnormalities and pro-inflammatory phenotypes. This conversion may be one of the potential mechanisms behind altered FLS metabolism. Targeting metabolism can inhibit FLS proliferation, providing relief to patients with RA. In this review, we aimed to summarize the evidence of metabolic changes in FLS in RA, analyze the mechanisms of these metabolic alterations, and assess their effect on RA phenotype. Finally, we aimed to summarize the advances and challenges faced in targeting FLS metabolism as a promising therapeutic strategy for RA in the future.

Role of MicroRNAs in Inflammatory Joint Diseases: A Review

Inflammatory arthritis commonly initiates in the soft tissues lining the joint. This lining swells, as do the cells in it and inside the joint fluid, producing chemicals that induce inflammation signs such as heat, redness, and swelling. MicroRNA (miRNA), a subset of non-coding small RNA molecules, post-transcriptionally controls gene expression by targeting their messenger RNA. MiRNAs modulate approximately 1/3 of the human genome with their multiple targets. Recently, they have been extensively studied as key modulators of the innate and adaptive immune systems in diseases such as allergic disorders, types of cancer, and cardiovascular diseases. However, research on the different inflammatory joint diseases, such as rheumatoid arthritis, gout, Lyme disease, ankylosing spondylitis, and psoriatic arthritis, remains in its infancy. This review presents a deeper understanding of miRNA biogenesis and the functions of miRNAs in modulating the immune and inflammatory responses in the above-mentioned inflammatory joint diseases. According to the literature, it has been demonstrated that the development of inflammatory joint disorders is closely related to different miRNAs and their specific regulatory mechanisms. Furthermore, they may present as possible prognostic and diagnostic biomarkers for all diseases and may help in developing a therapeutic response. However, further studies are needed to determine whether manipulating miRNAs can influence the development and progression of inflammatory joint disorders.

DKK1-targeting cholesterol-modified siRNA implication in hair growth regulation

Despite advancements in medical research, androgenetic alopecia (AGA) remains a humankind problem that still needs to be overcome. To date, clinical practice lacks an ideal treatment for AGA. The Wnt/β-catenin signaling pathway is evidenced to play a key role in hair regrowth, hence, modulating this signaling pathway for AGA therapy appears to be rational. One of the major inhibitors of the canonical Wnt/β-catenin signaling pathway is dickkopf-related protein 1 (DKK1). In this report, we have selected a small interfering RNA (siRNA) targeting DKK1 in vitro via qPCR and then tested its efficacy in vivo on the depilated dorsal skin of the mice. The changes in hair growth in different groups were observed over time. Moreover, the visual observation of the hair growth and hematoxylin and eosin (HE) staining showed that DKK1-targeting siRNA reveals non-inferior results compared with the mice treated with the Food and Drug Administration (FDA)-approved, commercially available minoxidil (5%) topical solution that was used as a positive control. Both- positive control and DKK1-targeting siRNA groups demonstrated significantly superior results compared with the control group that received negative control siRNA. Consequently, siRNAs targeting DKK1 may promote hair growth regulation in the AGA population via potentially activating the Wnt/β-catenin signaling pathway.

Role of miRNAs in Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease characterized by autoimmunity, synovial inflammation and joint destruction. Pannus formation in the synovial cavity can cause irreversible damage to the joint and cartilage and eventually permanent disability. Current conventional treatments for RA have limitations regarding efficacy, safety and cost. microRNA (miRNA) is a type of non-coding RNA (ncRNA) that regulates gene expression at the post-transcriptional level. The dysregulation of miRNA has been observed in RA patients and implicated in the pathogenesis of RA. miRNAs have emerged as potential biomarkers or therapeutic agents. In this review, we explore the role of miRNAs in various aspects of RA pathophysiology, including immune cell imbalance, the proliferation and invasion of fibroblast-like synovial (FLS) cell, the dysregulation of inflammatory signaling and disturbance in angiogenesis. We delve into the regulatory effects of miRNAs on Treg/Th17 and M1/M2 polarization, the activation of the NF-κB/NLRP3 signaling pathway, neovascular formation, energy metabolism induced by FLS-cell-induced energy metabolism, apoptosis, osteogenesis and mobility. These findings shed light on the potential applications of miRNAs as diagnostic or therapeutic biomarkers for RA management. Furthermore, there are some strategies to regulate miRNA expression levels by utilizing miRNA mimics or exosomes and to hinder miRNA activity via competitive endogenous RNA (ceRNA) network-based antagonists. We conclude that miRNAs offer a promising avenue for RA therapy with unlimited potential.

Mir-4699 promotes the osteogenic differentiation of mesenchymal stem cells

INTRODUCTION

Mesenchymal stem cells (MSCs) are drawing considerable attention in the field of regenerative medicine due to their differentiation capabilities. The miRNAs are among the most important epigenetic regulators of MSC differentiation. Our previous study identified miR-4699 as a direct suppressor of the DKK1 and TNSF11 gene expression. However, the precise osteogenic-related phenotype or mechanism caused by miR-4699 change has yet to be dealt with in depth.

MATERIAL AND METHODS

In the present study, miR-4699 mimics were transfected into human Adipose tissue-derived mesenchymal stem cells (hAd-MSCs) and osteoblast marker gene expression (RUNX2, ALP, and OCN), was analyzed to investigate whether miR-4699 promotes osteoblast differentiation of hAd-MSCs through targeting the DKK-1 and TNFSF11. We further examined and compared the effects of recombinant human BMP2 with miR-4699 on cell differentiation. In addition to quantitative PCR, analysis of alkaline phosphatase activity, calcium content assay, and Alizarin red staining were used to explore osteogenic differentiation. To evaluate the effect of miR-4699 on its target gene (on protein level) we utilized the western blotting technique.

RESULTS

The overexpression of miR-4699 in hAd-MSCs resulted in the stimulation of alkaline phosphatase activity, osteoblast mineralization, and the expression of RUNX2, ALP, and OCN osteoblast marker genes.

CONCLUSION

Our findings indicated that miR-4699 supported and synergized the BMP2-induced osteoblast differentiation of mesenchymal stem cells. We suggest, thereof, the utilization of hsa-miR-4699 for further in vivo experimental investigation to reveal the potential therapeutic impact of regenerative medicine for different types of bone defects.

Identification of chondrocyte subpopulations in osteoarthritis using single-cell sequencing analysis

Osteoarthritis (OA) is the most common joint disease. Previous studies were focused on general functions of chondrocyte population in OA without elucidating the existence of chondrocyte subpopulations. To investigate the heterogeneity of chondrocyte, here we conducted detailed analysis on the single-cell sequencing data of cartilage cells from OA patients. After quality control, unsupervised K-mean clustering identified seven different subpopulations of chondrocytes in OA. Those subpopulations of chondrocytes were nominated based on Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis: stress-metabolizing chondrocytes (cluster 1), rhythmic chondrocytes (cluster 2), apoptotic chondrocytes (cluster 3), matrix-synthesis-related chondrocytes (cluster 4), developmental chondrocytes (cluster 5), protein-synthesis-related chondrocytes (cluster 6 and 8), and osteogenesis chondrocytes (cluster 7). We further noticed that the stress-metabolizing chondrocytes (cluster 1) were dominant in early stages of cartilage damage with increased metabolic levels inhibiting cartilage tissue degeneration, while the matrix-synthesis-related chondrocytes (cluster 4) were mainly existed in the late stages of cartilage damage which reorganized collagen fibers with type III collagen disrupting the extracellular matrix and further cartilage damages. Besides, we identified genes NFKBIA and TUBB2B as potential markers for the stress-metabolizing chondrocytes and the matrix synthesis related chondrocytes, respectively. Our study identifies different chondrocyte subpopulations in OA, and highlights the potential different functions of chondrocyte subpopulations in the early versus late stages of cartilage damage.

Comprehensive overview of microRNA function in rheumatoid arthritis

MicroRNAs (miRNAs), a class of endogenous single-stranded short noncoding RNAs, have emerged as vital epigenetic regulators of both pathological and physiological processes in animals. They direct fundamental cellular pathways and processes by fine-tuning the expression of multiple genes at the posttranscriptional level. Growing evidence suggests that miRNAs are implicated in the onset and development of rheumatoid arthritis (RA). RA is a chronic inflammatory disease that mainly affects synovial joints. This common autoimmune disorder is characterized by a complex and multifaceted pathogenesis, and its morbidity, disability and mortality rates remain consistently high. More in-depth insights into the underlying mechanisms of RA are required to address unmet clinical needs and optimize treatment. Herein, we comprehensively review the deregulated miRNAs and impaired cellular functions in RA to shed light on several aspects of RA pathogenesis, with a focus on excessive inflammation, synovial hyperplasia and progressive joint damage. This review also provides promising targets for innovative therapies of RA. In addition, we discuss the regulatory roles and clinical potential of extracellular miRNAs in RA, highlighting their prospective applications as diagnostic and predictive biomarkers.

Pulsed Electromagnetic Field Therapy and Direct Current Electric Field Modulation Promote the Migration of Fibroblast-like Synoviocytes to Accelerate Cartilage Repair In Vitro

Articular cartilage injuries are a common source of joint pain and dysfunction. As articular cartilage is avascular, it exhibits a poor intrinsic healing capacity for self-repair. Clinically, osteochondral grafts are used to surgically restore the articular surface following injury. A significant challenge remains with the repair properties at the graft-host tissue interface as proper integration is critical toward restoring normal load distribution across the joint. A key to addressing poor tissue integration may involve optimizing mobilization of fibroblast-like synoviocytes (FLS) that exhibit chondrogenic potential and are derived from the adjacent synovium, the specialized connective tissue membrane that envelops the diarthrodial joint. Synovium-derived cells have been directly implicated in the native repair response of articular cartilage. Electrotherapeutics hold potential as low-cost, low-risk, non-invasive adjunctive therapies for promoting cartilage healing via cell-mediated repair. Pulsed electromagnetic fields (PEMFs) and applied direct current (DC) electric fields (EFs) via galvanotaxis are two potential therapeutic strategies to promote cartilage repair by stimulating the migration of FLS within a wound or defect site. PEMF chambers were calibrated to recapitulate clinical standards (1.5 ± 0.2 mT, 75 Hz, 1.3 ms duration). PEMF stimulation promoted bovine FLS migration using a 2D in vitro scratch assay to assess the rate of wound closure following cruciform injury. Galvanotaxis DC EF stimulation assisted FLS migration within a collagen hydrogel matrix in order to promote cartilage repair. A novel tissue-scale bioreactor capable of applying DC EFs in sterile culture conditions to 3D constructs was designed in order to track the increased recruitment of synovial repair cells via galvanotaxis from intact bovine synovium explants to the site of a cartilage wound injury. PEMF stimulation further modulated FLS migration into the bovine cartilage defect region. Biochemical composition, histological analysis, and gene expression revealed elevated GAG and collagen levels following PEMF treatment, indicative of its pro-anabolic effect. Together, PEMF and galvanotaxis DC EF modulation are electrotherapeutic strategies with complementary repair properties. Both procedures may enable direct migration or selective homing of target cells to defect sites, thus augmenting natural repair processes for improving cartilage repair and healing.

The monocyte-to-osteoclast transition in rheumatoid arthritis: Recent findings

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation leading to joint destruction and deformity. The crucial role of osteoclasts in the bone erosion in RA has been demonstrated. Deregulated osteoclastogenesis which is affected by environmental factors including the inflammatory state, as well as genetic and epigenetic factors, is one of hallmarks of RA pathogenesis. An enhanced-monocyte-to-osteoclast transition plays an important role in osteoclast upregulation in RA because under specific stimuli, circulating monocytes might migrate to a specific location in the bones and fuse with each other to become mature multinucleated osteoclasts. To understand the mechanism of bone damage in RA and to develop novel treatments targeting osteoclast upregulation, it is important to clarify our understanding of the monocyte-to-osteoclast transition in RA. Several potential targets which inhibit both inflammation and osteoclastogenesis, as well as regulators that affect the monocyte-to-osteoclast transition have been revealed by recent studies. Here, we review the factors affecting osteoclastogenesis in RA, summarize the anti-osteoclastogenic effects of current RA treatments, and identify promising therapeutic targets relating to both inflammation and osteoclastogenesis.

MicroRNA-Mediated Epigenetic Regulation of Rheumatoid Arthritis Susceptibility and Pathogenesis

MicroRNAs (miRNAs) play crucial roles in regulating the transcriptome and development of rheumatoid arthritis (RA). Currently, a comprehensive map illustrating how miRNAs regulate transcripts, pathways, immune system differentiation, and their interactions with terminal cells such as fibroblast-like synoviocytes (FLS), immune-cells, osteoblasts, and osteoclasts are still laking. In this review, we summarize the roles of miRNAs in the susceptibility, pathogenesis, diagnosis, therapeutic intervention, and prognosis of RA. Numerous miRNAs are abnormally expressed in cells involved in RA and regulate target genes and pathways, including NF-κB, Fas-FasL, JAK-STAT, and mTOR pathways. We outline how functional genetic variants of miR-499 and miR-146a partly explain susceptibility to RA. By regulating gene expression, miRNAs affect T cell differentiation into diverse cell types, including Th17 and Treg cells, thus constituting promising gene therapy targets to modulate the immune system in RA. We summarize the diagnostic and prognostic potential of blood-circulating and cell-free miRNAs, highlighting the opportunity to combine these miRNAs with antibodies to cyclic citrullinated peptide (ACCP) to allow accurate diagnosis and prognosis, particularly for seronegative patients. Furthermore, we review the evidence implicating miRNAs as promising biomarkers of efficiency and response of, and resistance to, disease-modifying anti-rheumatic drugs and immunotherapy. Finally, we discuss the autotherapeutic effect of miRNA intervention as a step toward the development of miRNA-based anti-RA drugs. Collectively, the current evidence supports miRNAs as interesting targets to better understand the pathogenetic mechanisms of RA and design more efficient therapeutic interventions.

Identification of Tissue-Specific Expressed Hub Genes and Potential Drugs in Rheumatoid Arthritis Using Bioinformatics Analysis

Background: Rheumatoid arthritis (RA) is a common autoimmune disease characterized by progressive, destructive polyarthritis. However, the cause and underlying molecular events of RA are not clear. Here, we applied integrated bioinformatics to identify tissue-specific expressed hub genes involved in RA and reveal potential targeted drugs.

Methods: Three expression profiles of human microarray datasets involving fibroblast-like synoviocytes (FLS) were downloaded from the Gene Expression Omnibus (GEO) database, the differentially expressed mRNAs (DEGs), miRNAs (DEMs), and lncRNAs (DELs) between normal and RA synovial samples were screened using GEO2R tool. BioGPS was used to identified tissue-specific expressed genes. Functional and pathway enrichment analyses were performed for common DEGs using the DAVID database, and the protein-protein interaction (PPI) network of common DEGs was constructed to recognize hub genes by the STRING database. Based on receiver operating characteristic (ROC) curve, we further investigated the prognostic values of tissue-specific expressed hub genes in RA patients. Connectivity Map (CMap) was run to identify novel anti-RA potential drugs. The DEM–DEG pairs and ceRNA network containing key DEMs were established by Cytoscape.

Results: We obtain a total of 418 DEGs, 23 DEMs and 49 DELs. 64 DEGs were verified as tissue-specific expressed genes, most derive from the hematologic/immune system (20/64, 31.25%). GO term and KEGG pathway enrichment analysis showed that DEGs focused primarily on immune-related biological process and NF-κB pathway. 10 hub genes were generated via using MCODE plugin. Among them, SPAG5, CUX2, and THEMIS2 were identified as tissue-specific expressed hub genes, these 3 tissue-specific expressed hub genes have superior diagnostic value in the RA samples compared with osteoarthritis (OA) samples. 5 compounds (troleandomycin, levodopa, trichostatin A, LY-294002, and levamisole) rank among the top five in connectivity score. In addition, 5 miRNAs were identified to be key DEMs, the lncRNA–miRNA–mRNA network with five key DEMs was formed. The networks containing tissue-specific expressed hub genes are as follows: ARAP1-AS2/miR-20b-3p/TRIM3, ARAP1-AS2/miR-30c-3p/FRZB.

Conclusion: This study indicates that screening for identify tissue-specific expressed hub genes and ceRNA network in RA using integrated bioinformatics analyses could help us understand the mechanism of development of RA. Besides, SPAG5 and THEMIS2 might be candidate biomarkers for diagnosis of RA. LY-294002, trichostatin A, and troleandomycin may be potential drugs for RA.

miRNAs as Biomarkers and Possible Therapeutic Strategies in Rheumatoid Arthritis

Within the past years, more and more attention has been devoted to the epigenetic dysregulation that provides an additional window for understanding the possible mechanisms involved in the pathogenesis of autoimmune rheumatic diseases. Rheumatoid arthritis (RA) is a heterogeneous disease where a specific immunologic and genetic/epigenetic background is responsible for disease manifestations and course. In this field, microRNAs (miRNA; miR) are being identified as key regulators of immune cell development and function. The identification of disease-associated miRNAs will introduce us to the post-genomic era, providing the real probability of manipulating the genetic impact of autoimmune diseases. Thereby, different miRNAs may be good candidates for biomarkers in disease diagnosis, prognosis, treatment and other clinical applications. Here, we outline not only the role of miRNAs in immune and inflammatory responses in RA, but also present miRNAs as diagnostic/prognostic biomarkers. Research into miRNAs is still in its infancy; however, investigation into these novel biomarkers could progress the use of personalized medicine in RA treatment. Finally, we discussed the possibility of miRNA-based therapy in RA patients, which holds promise, given major advances in the therapy of patients with inflammatory arthritis.

Perspectives on miRNAs Targeting DKK1 for Developing Hair Regeneration Therapy

Androgenetic alopecia (AGA) remains an unsolved problem for the well-being of humankind, although multiple important involvements in hair growth have been discovered. Up until now, there is no ideal therapy in clinical practice in terms of efficacy and safety. Ultimately, there is a strong need for developing a feasible remedy for preventing and treating AGA. The Wnt/β-catenin signaling pathway is critical in hair restoration. Thus, AGA treatment via modulating this pathway is rational, although challenging. Dickkopf-related protein 1 (DKK1) is distinctly identified as an inhibitor of canonical Wnt/β-catenin signaling. Thus, in order to stimulate the Wnt/β-catenin signaling pathway, inhibition of DKK1 is greatly demanding. Studying DKK1-targeting microRNAs (miRNAs) involved in the Wnt/β-catenin signaling pathway may lay the groundwork for the promotion of hair growth. Bearing in mind that DKK1 inhibition in the balding scalp of AGA certainly makes sense, this review sheds light on the perspectives of miRNA-mediated hair growth for treating AGA via regulating DKK1 and, eventually, modulating Wnt/β-catenin signaling. Consequently, certain miRNAs regulating the Wnt/β-catenin signaling pathway via DKK1 inhibition might represent attractive candidates for further studies focusing on promoting hair growth and AGA therapy.

The Expression of Non-Coding RNAs and Their Target Molecules in Rheumatoid Arthritis: A Molecular Basis for Rheumatoid Pathogenesis and Its Potential Clinical Applications

Rheumatoid arthritis (RA) is a typical autoimmune-mediated rheumatic disease presenting as a chronic synovitis in the joint. The chronic synovial inflammation is characterized by hyper-vascularity and extravasation of various immune-related cells to form lymphoid aggregates where an intimate cross-talk among innate and adaptive immune cells takes place. These interactions facilitate production of abundant proinflammatory cytokines, chemokines and growth factors for the proliferation/maturation/differentiation of B lymphocytes to become plasma cells. Finally, the autoantibodies against denatured immunoglobulin G (rheumatoid factors), EB virus nuclear antigens (EBNAs) and citrullinated protein (ACPAs) are produced to trigger the development of RA. Furthermore, it is documented that gene mutations, abnormal epigenetic regulation of peptidylarginine deiminase genes 2 and 4 (PADI2 and PADI4), and thereby the induced autoantibodies against PAD2 and PAD4 are implicated in ACPA production in RA patients. The aberrant expressions of non-coding RNAs (ncRNAs) including microRNAs (miRs) and long non-coding RNAs (lncRNAs) in the immune system undoubtedly derange the mRNA expressions of cytokines/chemokines/growth factors. In the present review, we will discuss in detail the expression of these ncRNAs and their target molecules participating in developing RA, and the potential biomarkers for the disease, its diagnosis, cardiovascular complications and therapeutic response. Finally, we propose some prospective investigations for unraveling the conundrums of rheumatoid pathogenesis.

miRNA-218-5p increases cell sensitivity by inhibiting PRKDC activity in radiation-resistant lung carcinoma cells

BACKGROUND

Non-small cell lung carcinoma (NSCLC) is a malignancy with the highest mortality rate. Currently, surgery combined with radiotherapy is the first choice in the clinical treatment of lung carcinoma (LC); however, long-term radiotherapy leads to radiation resistance in patients, resulting in treatment failure.

METHODS

In this study, a new microRNA-218-5p (miRNA-218-5p) was identified, and its function in LC was investigated.

RESULTS

Reverse transcription quantitative polymerase chain reaction (RT-qPCR) results revealed that miRNA-218-5p was downregulated in LC. Overexpression or inhibition of miRNA-218-5p in LC and targeted binding of protein kinase, DNA-activated, catalytic polypeptide (PRKDC) to miRNA-218-5p were confirmed by comprehensive bioinformatic analysis. Exosomes from A549 and H1299 cells were cocultured with miRNA-218-5p and then cotransfected into radiation-resistant A549R and H1299R cells; the proliferation of radiation-resistant LC cells was found to be effectively inhibited and apoptosis was induced. Overexpression of miRNA-218-5p and X-irradiation could enhance the radiosensitivity of LC cells. Exogenous miRNA-218-5p derived from A549 and H1299 cells could be transfected into radiation-resistant LC cells and could inhibit PRKDC expression, thus accelerating DNA damage, apoptosis, and radiation sensitization of LC cells.

CONCLUSIONS

miRNA-218-5p could induce apoptosis and enhance the radiosensitivity of LC cells through regulatory activities, thus suggesting its application as a potential target for LC treatment.

Crosstalk between Bone and Nerves within Bone

For the past two decades, the function of intrabony nerves on bone has been a subject of intense research, while the function of bone on intrabony nerves is still hidden in the corner. In the present review, the possible crosstalk between bone and intrabony peripheral nerves will be comprehensively analyzed. Peripheral nerves participate in bone development and repair via a host of signals generated through the secretion of neurotransmitters, neuropeptides, axon guidance factors and neurotrophins, with additional contribution from nerve-resident cells. In return, bone contributes to this microenvironmental rendezvous by housing the nerves within its internal milieu to provide mechanical support and a protective shelf. A large ensemble of chemical, mechanical, and electrical cues works in harmony with bone marrow stromal cells in the regulation of intrabony nerves. The crosstalk between bone and nerves is not limited to the physiological state, but also involved in various bone diseases including osteoporosis, osteoarthritis, heterotopic ossification, psychological stress-related bone abnormalities, and bone related tumors. This crosstalk may be harnessed in the design of tissue engineering scaffolds for repair of bone defects or be targeted for treatment of diseases related to bone and peripheral nerves.

A Systems Biology Approach for miRNA-mRNA Expression Patterns Analysis in Rheumatoid Arthritis

Objective:

Considering the molecular complexity and heterogeneity of rheumatoid arthritis (RA), the identification of novel molecular contributors involved in RA initiation and progression using systems biology approaches will open up potential therapeutic strategies. The bioinformatics method allows the detection of associated miRNA-mRNA as both therapeutic and prognostic targets for RA.

Methods:

This research used a system biology approach based on a systematic re-analysis of the RA-related microarray datasets in the NCBI Gene Expression Omnibus (GEO) database to find out deregulated miRNAs. We then studied the deregulated miRNA-mRNA using Enrichr and Molecular Signatures Database (MSigDB) to identify novel RA-related markers followed by an overview of miRNA-mRNA interaction networks and RA-related pathways.

Results:

This research mainly focused on mRNA and miRNA interactions in all tissues and blood/serum associated with RA to obtain a comprehensive knowledge of RA. Recent systems biology approach analyzed seven independent studies and presented important RA-related deregulated miRNAs (miR-145-5p, miR-146a-5p, miR-155-5p, miR-15a-5p, miR-29c-3p, miR- 103a-3p, miR-125a-5p, miR-125b-5p, miR-218); upregulation of miR-125b is shown in the study (GSE71600). While the findings of the Enrichr showed cytokine and vitamin D receptor pathways and inflammatory pathways. Further analysis revealed a negative correlation between the vitamin D receptor (VDR) and miR-125b in RA-associated gene expression.

Conclusion:

Since vitamin D is capable of regulating the immune homeostasis and decreasing the autoimmune process through its receptor (VDR), it is regarded as a potential target for RA. According to the results obtained, a comparative correlation between negative expression of the vitamin D receptor (VDR) and miR-125b was suggested in RA. The increasing miR-125b expression would reduce the VitD uptake through its receptor.

Mechanism of miR-218-5p in autophagy, apoptosis and oxidative stress in rheumatoid arthritis synovial fibroblasts is mediated by KLF9 and JAK/STAT3 pathways

This study was aimed to investigate the effects of miR-218-5p on the proliferation, apoptosis, autophagy, and oxidative stress of rheumatoid arthritis synovial fibroblasts (RASFs), and the related mechanisms. Quantitative reverse transcription-PCR showed that the expression of miR-218-5p in rheumatoid arthritis synovial tissue was significantly higher than that in healthy synovial tissue. Compared with healthy synovial fibroblasts, miR-218-5p expression was obviously upregulated in RASFs, while KLF9 protein expression was markedly downregulated. Mechanistically, miR-218-5p could directly bind to the 3' untranslated region of KLF9 to inhibit the expression of KLF9. Additionally, transfection of miR-218-5p small interfering RNA (siRNA) inhibited the proliferation but promoted apoptosis and autophagy of RASFs. Simultaneously, miR-218-5p silencing reduced reactive oxygen species and malondialdehyde levels and increased superoxide dismutase and glutathione peroxidase activity to improve oxidative stress in RASFs. More importantly, the introduction of KLF9 siRNA reversed the effects of miR-218-5p siRNA transfection on RASF proliferation, apoptosis, autophagy, and oxidative stress. What is more, silencing miR-218-5p inhibited the activation of JAK2/STAT3 signaling pathway by targeting KLF9. Collectively, knockdown of miR-218-5p could regulate the proliferation, apoptosis, autophagy and oxidative stress of RASFs by increasing the expression of KLF9 and inhibiting the activation of the JAK2/STAT3 signaling pathway, which may provide a potential target for the mechanism research of RA.

Rheumatoid Arthritis in the View of Osteoimmunology

Rheumatoid arthritis is characterized by synovial inflammation and irreversible bone erosions, both highlighting the immense reciprocal relationship between the immune and bone systems, designed osteoimmunology two decades ago. Osteoclast-mediated resorption at the interface between synovium and bone is responsible for the articular bone erosions. The main triggers of this local bone resorption are autoantibodies directed against citrullinated proteins, as well as pro-inflammatory cytokines and the receptor activator of nuclear factor-κB ligand, that regulate both the formation and activity of the osteoclast, as well as immune cell functions. In addition, local bone loss is due to the suppression of osteoblast-mediated bone formation and repair by inflammatory cytokines. Similarly, inflammation affects systemic bone remodeling in rheumatoid arthritis with the net increase in bone resorption, leading to systemic osteoporosis. This review summarizes the substantial progress that has been made in understanding the pathophysiology of systemic and local bone loss in rheumatoid arthritis.

MiR-218 affects hypertrophic differentiation of human mesenchymal stromal cells during chondrogenesis via targeting RUNX2, MEF2C, and COL10A1

Background

Human mesenchymal stromal cells (MSC) hold hopes for cartilage regenerative therapy due to their chondrogenic differentiation potential. However, undesirable occurrence of calcification after ectopic transplantation, known as hypertrophic degeneration, remains the major obstacle limiting application of MSC in cartilage tissue regeneration approaches. There is growing evidence that microRNAs (miRs) play essential roles in post-transcriptional regulation of hypertrophic differentiation during chondrogenesis. Aim of the study was to identify new miR candidates involved in repression of hypertrophy-related targets.

Methods

The miR expression profile in human articular chondrocytes (AC) was compared to that in hypertrophic chondrocytes derived from human MSC by microarray analysis, and miR expression was validated by qPCR. Putative targets were searched by in silico analysis and validated by miR reporter assay in HEK293T, by functional assays (western blotting and ALP-activity) in transiently transfected SaOS-2 cells, and by a miR pulldown assay in human MSC. The expression profile of miR-218 was assessed by qPCR during in vitro chondrogenesis of MSC and re-differentiation of AC. MSC were transfected with miR-218 mimic, and differentiation outcome was assessed over 28 days. MiR-218 expression was quantified in healthy and osteoarthritic cartilage of patients.

Results

Within the top 15 miRs differentially expressed between chondral AC versus endochondral MSC differentiation, miR-218 was selected as a candidate miR predicted to target hypertrophy-related genes. MiR-218 was downregulated during chondrogenesis of MSC and showed a negative correlation to hypertrophic markers, such as COL10A1 and MEF2C. It was confirmed in SaOS-2 cells that miR-218 directly targets hypertrophy-related COL10A1, MEF2C, and RUNX2, as a gain of ectopic miR-218 mimic caused drop in MEF2C and RUNX2 protein accumulation, with attenuation of COL10A1 expression and significant concomitant reduction of ALP activity. A miR pulldown assay confirmed that miR-218 directly targets RUNX2, MEF2C in human MSC. Additionally, the gain of miR-218 in human MSC attenuated hypertrophic markers (MEF2C, RUNX2, COL10A1, ALPL), although with no boost of chondrogenic markers (GAG deposition, COL2A1) due to activation of WNT/β-catenin signaling. Moreover, no correlation between miR-218 expression and a pathologic phenotype in the cartilage of osteoarthritis (OA) patients was found.

Conclusions

Although miR-218 was shown to target pro-hypertrophic markers MEF2C, COL10A1, and RUNX2 in human MSC during chondrogenic differentiation, overall, it could not significantly reduce the hypertrophic phenotype or boost chondrogenesis. This could be explained by a concomitant activation of WNT/β-catenin signaling counteracting the anti-hypertrophic effects of miR-218. Therefore, to achieve a full inhibition of the endochondral pathway, a whole class of anti-hypertrophic miRs, including miR-218, needs to be taken into consideration.

Slit2 is a potential biomarker for renal impairment in systemic lupus erythematosus

Slit2 glycoprotein has been described to regulate the inflammatory response and be involved in autoimmune diseases. Here, we investigated the expression of Slit2 and its potential significance in systemic lupus erythematosus (SLE). A total of 103 patients with SLE participated in our study. The levels of serum Slit2 were measured by enzyme-linked immunosorbent assay, and the expression of Slit2 in renal tissue was detected by immunohistochemistry. Patients with active disease had higher levels of serum Slit2 than patients with inactive disease and controls. Patients with sole skin impairment or sole renal impairment or both skin and renal impairment had higher levels of serum Slit2 than patients with neither skin nor renal impairment. Patients with chronic kidney disease (CKD) had higher levels of serum Slit2 than patients with no CKD. Levels of serum Slit2 in patients with active disease were positively correlated with the SLE Disease Activity Index, complement C4, and anti-dsDNA antibody. Levels of serum Slit2 in patients with CKD were positively correlated with serum creatinine, urine protein, and glomerular filtration rate. The expression of Slit2 and its receptor Roundabout1 (Robo1) in the renal tissue of patients with lupus nephritis were higher than controls. Moreover, renal Slit2 was positively correlated with renal chronic index. Our data indicated that Slit2 may contribute to renal impairment and this may be a potential biomarker for SLE.

Unique, Gender-Dependent Serum microRNA Profile in PLS3 Gene-Related Osteoporosis

Plastin 3 (PLS3), encoded by PLS3, is a newly recognized regulator of bone metabolism, and mutations in the encoding gene result in severe childhood-onset osteoporosis. Because it is an X chromosomal gene, PLS3 mutation-positive males are typically more severely affected whereas females portray normal to increased skeletal fragility. Despite the severe skeletal pathology, conventional metabolic bone markers tend to be normal and are thus insufficient for diagnosing or monitoring patients. Our study aimed to explore serum microRNA (miRNA) concentrations in subjects with defective PLS3 function to identify novel markers that could differentiate subjects according to mutation status and give insight into the molecular mechanisms by which PLS3 regulates skeletal health. We analyzed fasting serum samples for a custom-designed panel comprising 192 miRNAs in 15 mutation-positive (five males, age range 8-76 years, median 41 years) and 14 mutation-negative (six males, age range 8-69 years, median 40 years) subjects from four Finnish families with different PLS3 mutations. We identified a unique miRNA expression profile in the mutation-positive subjects with seven significantly upregulated or downregulated miRNAs (miR-93-3p, miR-532-3p, miR-133a-3p, miR-301b-3p, miR-181c-5p, miR-203a-3p, and miR-590-3p; p values, range .004-.044). Surprisingly, gender subgroup analysis revealed the difference to be even more distinct in female mutation-positive subjects (congruent p values, range .007-.086) than in males (p values, range .127-.843) in comparison to corresponding mutation-negative subjects. Although the seven identified miRNAs have all been linked to bone metabolism and two of them (miR-181c-5p and miR-203a-3p) have bioinformatically predicted targets in the PLS3 3' untranslated region (3'-UTR), none have previously been reported to associate with PLS3. Our results indicate that PLS3 mutations are reflected in altered serum miRNA levels and suggest there is crosstalk between PLS3 and these miRNAs in bone metabolism. These provide new understanding of the pathomechanisms by which mutations in PLS3 lead to skeletal disease and may provide novel avenues for exploring miRNAs as biomarkers in PLS3 osteoporosis or as target molecules in future therapeutic applications. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

MiR-20a inhibits the progression of human arthritis fibroblast-like synoviocytes and inflammatory factor expression by targeting ADAM10

MiR-20a has been reported as a key regulator to pro-inflammatory factor release in fibroblast-like synoviocytes (FLS), which caused rheumatoid arthritis (RA). However, the molecular mechanism of miR-20a in RA remains to be further elucidated. This study aimed to investigate the roles of miR-20a in RA pathology. RA (n = 24) and osteoarthritis (OA, n = 20) and normal healthy tissues (n = 16) were collected from operation. TargetScan and dual-luciferase reporter were performed to predict and confirm the potential binding sites of miR-20a on ADAM metallopeptidase domain 10 (ADAM10). Pearson's analysis was adopted to evaluate the correlation between miR-20a and ADAM10 expression. It was found that MiR-20a was downregulated in RA tissues, and overexpressed miR-20a inhibited cell viability, migration and invasion, and the expression of inflammatory factors in RA-FLS MH7A cells. ADAM10 was identified as the target gene of miR-20a, and upregulation of ADAM10 reversed the inhibitory effects of miR-20a. In conclusion, miR-20a inhibits the progression of RA-FLS as well as the inflammatory factor expression by targeting ADAM10.

Conversion of Neural Stem Cells into Functional Neuron-Like Cells by MicroRNA-218: Differential Expression of Functionality Genes

Conversion of mesenchymal stem cells (MSC) into neuron-like cells (NLC) is a feasible cell therapy strategy for replacing lost neurons in neuronal disorders. In this study, adipose-derived MSC (ADMSC) were converted into neural stem cells (NSC) via neurosphere. The resulting NSC were then differentiated into NLC by transduction with microRNA-218, using a lentiviral vector. ADMSC, NSC, and NLC were first characterized by flow cytometry, RT-PCR, and immunocytochemistry. The functionality of the NLC was evaluated by qRT-PCR and patch clamp recording. Immunophenotyping of ADMSC showed their immunoreactivity to MSC markers CD90, CD73, CD105, and CD49d, but not to CD31 and CD45. RT-PCR results demonstrated the expression of nestin, neurogenin, neurod1, neurofilament light, and GAP43 genes in NSC while NLC expressed synaptophysin, neurofilament heavy, and GAP43. In addition, NSC morphology changed into multipolar with long processes after transduction with miR-218. Moreover, using qRT-PCR, the expression levels of miR-218 and functionality genes CACNA1C, SNAP25, KCNH1, KCNMA1, and SCN9A were significantly increased in NLC, compared with NSC, and ADMSC at 3 weeks and 5 months post-transduction. Furthermore, the generated NLC expressed significantly higher protein levels of neurofilament heavy polypeptide (NFh) and enolase 2 (Eno2) neuronal markers, compared with ADMSC and NSC. Finally, action potentials were successfully recorded by the generated NLC, using patch clamp. In summary, ADMSC-derived NSC differentiated into functional NLC by transduction with miR-218. The generated NLC expressed functional SNAP25, CACNA1C, KCNH1, KCNMA1, and SCN9A and produced an action potential, which provides useful insights into the generation of functional neuronal cells.

Recent findings regarding the effects of microRNAs on fibroblast-like synovial cells in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease with severe joint inflammation and destruction characterized by marked hyperplasia of the lining layer of the synovium. Fibroblast-like synovial cells (FLS) is a key cellular component within the synovia; it plays pivotal roles in RA pathogenesis by unfavorable behaviors such as producing inflammatory cytokines and chemokines, and hyperproliferation. MicroRNAs are evolutionarily conserved small non-coding RNAs (length is 18-25 nucleotides) that regulate gene expression at the post-transcriptional level. There is increasing interest in the involvement of microRNAs in autoimmune diseases including RA. Recent studies revealed the regulation of the function of FLS by microRNAs. Here, we review the known functional microRNAs in RA and summarize the potential uses of these small molecules in the treatment of RA.

MicroRNAs in rheumatoid arthritis: From pathogenesis to clinical impact

Over the last decade, many epigenetic mechanisms that contribute in the pathogenesis of autoimmune disorders have been revealed. MicroRNAs (miRNAs) are small, non-coding, RNA molecules that bind to messenger RNAs and disrupt the transcription of target genes. Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease in which a plethora of epigenetic changes take place. Current research on RA epigenetics has focused mainly on miRNAs. Genetic variance of some miRNA genes, especially miR-499, might predispose an individual to RA development. Additionally, altered expression of many miRNAs has been discovered in several cells, tissues and body fluids in patients with RA. MiRNAs expression also differs depending on disease's stage and activity. Serum miR-22 and miR-103a might predict RA development in susceptible individuals (pre-RA), while serum miR-16, miR-24, miR-125a and miR-223 levels are altered in early RA (disease duration <12 months) patients compared to established RA or healthy individuals. Moreover, serum miR-223 levels have been associated with RA activity and disease relapse. What is more, serum levels of several miRNAs, including miR-125b and miR-223, could be used to predict response to RA treatment. Finally, miRNA analogs or antagonists have been used as therapeutic regimens in experimental arthritis models and have demonstrated promising results. In conclusion, the research on the miRNA alterations in RA sheds light to several aspects of RA pathogenesis, introduces new biomarkers for RA diagnosis and treatment response prediction and offers the opportunity to discover new, targeted drugs for patients with RA.

Downregulation of microRNA-16-5p accelerates fracture healing by promoting proliferation and inhibiting apoptosis of osteoblasts in patients with traumatic brain injury

Patients who suffered a traumatic brain injury (TBI) show a faster fracture healing than patients with isolated fractures. Prior studies have suggested that this process may be accelerated through the inhibition of key microRNAs. In this study, we aimed to explore the mechanisms underlying this phenomenon, with a special focus on miR-16-5p, which is markedly decreased in patients with TBI. In vitro, miR-16-5p over-expression significantly inhibited cell proliferation in MC3T3-E1 cells transfected with agomiR-16-5p. Flow cytometry analysis further demonstrated that the overexpression of miR-16-5p induced cell cycle G1/S phase arrest and apoptosis. Moreover, target prediction and luciferase reporter assay demonstrated that miR-16-5p could negatively regulate Bcl-2 and Cyclin-D1 expression. Meanwhile, Bcl-2 and Cyclin-D1 were up-regulated after osteogenic differentiation while the down-regulation of endogenous Bcl-2 and Cyclin-D suppressed the osteogenic differentiation of MC3T3-E1 cells. In vivo, PBS, agomiR-16-5p and antagomiR-16-5p were injected into fracture sites to assess any improvements in fracture healing, which further confirmed the negative effect of miR-16-5p on fracture healing. Together, these results demonstrate miR-16-5p downregulation may accelerate fracture healing by enhancing the proliferation and inhibiting the apoptosis of osteoblasts in patients with both fractures and TBI. These phenomena may be exploited in the treatment of fractures.

miR-124a inhibits the proliferation and inflammation in rheumatoid arthritis fibroblast-like synoviocytes via targeting PIK3/NF-κB pathway

Abnormal hyperplasia of fibroblast-like synoviocytes (FLS) leads to the progression of rheumatoid arthritis (RA). This study aimed to investigate the role of miR-124a in the pathogenesis of RA. The viability and cell cycle of FLS in rheumatoid arthritis (RAFLS) were evaluated by Cell Counting Kit 8 and flow cytometry assay. The expression of PIK3CA, Akt, and NF-κB in RAFLS was examined by real-time PCR and Western blot analysis. The production of tumour necrosis factor (TNF)-α and interleukin (IL)-6 was detected by ELISA. The joint swelling and inflammation in collagen-induced arthritis (CIA) mice were examined by histological and immunohistochemical analysis. We found that miR-124a suppressed the viability and proliferation of RAFLS and increased the percentage of cells in the G1 phase. miR-124a suppressed PIK3CA 3'UTR luciferase reporter activity and decreased the expression of PIK3CA at mRNA and protein levels. Furthermore, miR-124a inhibited the expression of the key components of the PIK3/Akt/NF-κB signal pathway and inhibited the expression of pro-inflammatory factors TNF-α and IL-6. Local overexpression of miR-124a in the joints of CIA mice inhibited inflammation and promoted apoptosis in FLS by decreasing PIK3CA expression. In conclusion, miR-124a inhibits the proliferation and inflammation in RAFLS via targeting PIK3/NF-κB pathway. miR-124a is a promising therapeutic target for RA.