Reduced miR-144-3p expression in serum and bone mediates osteoporosis pathogenesis by targeting RANK

Isolation and characterization of bone mesenchymal cell small extracellular vesicles using a novel mouse model

Extracellular vesicles (EVs) are key mediators of cell-cell communication and are involved in transferring specific biomolecular cargo to recipient cells to regulate their physiological functions. A major challenge in the understanding of EV function in vivo is the difficulty ascertaining the origin of the EV particles. The recent development of the "Snorkel-tag," which includes EV-membrane-targeted CD81 fused to a series of extra-vesicular protein tags, can be used to mark EVs originating from a specific source for subsequent isolation and characterization. We developed an in vivo mouse model, termed "CAGS-Snorkel," which expresses the Snorkel-tag under the control of the Cre-lox system, and crossed this mouse with either Prx1-Cre (mesenchymal progenitors) or Ocn-Cre (osteoblasts/osteocytes) and isolated Snorkel-tagged EVs from the mouse bone marrow plasma using a magnetic bead affinity column. miRNA-sequencing was performed on the isolated EVs, and although similar profiles were observed, a few key miRNAs involved in bone metabolism (miR-106b-5p, miRs-19b-3p, and miRs-219a-5p) were enriched in the Ocn-derived relative to the Prx1-derived EV subpopulations. To characterize the effects of these small EVs on a bone cell target, cultured mouse bone marrow stromal cells were treated with Prx1 or Ocn EVs, and mRNA-sequencing was performed. Pathways involved in ossification, bone development, and extracellular matrix interactions were regulated by both EV subpopulations, whereas a few pathways including advanced glycation end-products signaling were uniquely regulated in the Ocn EV subpopulation, underlying important biological effects of specific EV subpopulations within the bone marrow microenvironment. These data demonstrate that EV isolation in vivo using the CAGS-Snorkel mouse model is a useful tool in characterizing the cargo and understanding the biology of tissue-specific EVs. Moreover, while bone mesenchymal cell populations share a common EV secretory profile, we uncover key differences based on the stage of osteoblastic differentiation that may have important biological consequences.

The Involvement of microRNAs in Bone Remodeling Signaling Pathways and Their Role in the Development of Osteoporosis

Bone remodeling, crucial for maintaining the balance between bone resorption and formation, relies on the coordinated activity of osteoclasts and osteoblasts. During osteoclastogenesis, hematopoietic stem cells (HSCs) differentiate into the osteoclast lineage through the signaling pathways OPG/RANK/RANKL. On the other hand, during osteoblastogenesis, mesenchymal stem cells (MSCs) differentiate into the osteoblast lineage through activation of the signaling pathways TGF-β/BMP/Wnt. Recent studies have shown that bone remodeling is regulated by post-transcriptional mechanisms including microRNAs (miRNAs). miRNAs are small, single-stranded, noncoding RNAs approximately 22 nucleotides in length. miRNAs can regulate virtually all cellular processes through binding to miRNA-response elements (MRE) at the 3' untranslated region (3'UTR) of the target mRNA. miRNAs are involved in controlling gene expression during osteogenic differentiation through the regulation of key signaling cascades during bone formation and resorption. Alterations of miRNA expression could favor the development of bone disorders, including osteoporosis. This review provides a general description of the miRNAs involved in bone remodeling and their significance in osteoporosis development.

Common miRNAs of Osteoporosis and Fibromyalgia: A Review

A significant clinical association between osteoporosis (OP) and fibromyalgia (FM) has been shown in the literature. Given the need for specific biomarkers to improve OP and FM management, common miRNAs might provide promising tracks for future prevention and treatment. The aim of this review is to identify miRNAs described in OP and FM, and dysregulated in the same direction in both pathologies. The PubMed database was searched until June 2023, with a clear mention of OP, FM, and miRNA expression. Clinical trials, case-control, and cross-sectional studies were included. Gray literature was not searched. Out of the 184 miRNAs found in our research, 23 are shared by OP and FM: 7 common miRNAs are dysregulated in the same direction for both pathologies (3 up-, 4 downregulated). The majority of these common miRNAs are involved in the Wnt pathway and the cholinergic system and a possible link has been highlighted. Further studies are needed to explore this relationship. Moreover, the harmonization of technical methods is necessary to confirm miRNAs shared between OP and FM.

Sharing Circulating Micro-RNAs between Osteoporosis and Sarcopenia: A Systematic Review

Background: Osteosarcopenia, a combination of osteopenia/osteoporosis and sarcopenia, is a common condition among older adults. While numerous studies and meta-analyses have been conducted on osteoporosis biomarkers, biomarker utility in osteosarcopenia still lacks evidence. Here, we carried out a systematic review to explore and analyze the potential clinical of circulating microRNAs (miRs) shared between osteoporosis/osteopenia and sarcopenia. Methods: We performed a systematic review on PubMed, Scopus, and Embase for differentially expressed miRs (p-value < 0.05) in (i) osteoporosis and (ii) sarcopenia. Following screening for title and abstract and deduplication, 83 studies on osteoporosis and 11 on sarcopenia were identified for full-text screening. Full-text screening identified 54 studies on osteoporosis, 4 on sarcopenia, and 1 on both osteoporosis and sarcopenia. Results: A total of 69 miRs were identified for osteoporosis and 14 for sarcopenia. There were 9 shared miRs, with evidence of dysregulation (up- or down-regulation), in both osteoporosis and sarcopenia: miR-23a-3p, miR-29a, miR-93, miR-133a and b, miR-155, miR-206, miR-208, miR-222, and miR-328, with functions and targets implicated in the pathogenesis of osteosarcopenia. However, there was little agreement in the results across studies and insufficient data for miRs in sarcopenia, and only three miRs, miR-155, miR-206, and miR-328, showed the same direction of dysregulation (down-regulation) in both osteoporosis and sarcopenia. Additionally, for most identified miRs there has been no replication by more than one study, and this is particularly true for all miRs analyzed in sarcopenia. The study quality was typically rated intermediate/high risk of bias. The large heterogeneity of the studies made it impossible to perform a meta-analysis. Conclusions: The findings of this review are particularly novel, as miRs have not yet been explored in the context of osteosarcopenia. The dysregulation of miRs identified in this review may provide important clues to better understand the pathogenesis of osteosarcopenia, while also laying the foundations for further studies to lead to effective screening, monitoring, or treatment strategies.

Micro-RNA: A Future Approach to Personalized Diagnosis of Bone Diseases

Osteoporosis is a highly prevalent bone disease worldwide and the most studied bone-associated pathological condition. Although its diagnosis makes use of advanced and clinically relevant imaging and biochemical tools, the information suffers from several limitations and has little or no prognostic value. In this context, circulating micro-RNAs represent a potentially attractive alternative or a useful addition to the diagnostic arsenal and offer a greater prognostic potential than the conventional approaches. These short non-coding RNA molecules act as inhibitors of gene expression by targeting messenger RNAs with different degrees of complementarity, establishing a complex multilevel network, the basis for the fine modulation of gene expression that finally regulates every single activity of a cell. Micro-RNAs may passively and/or actively be released in the circulation by source cells, and being measurable in biological fluids, their concentrations may be associated to specific pathophysiological conditions. Mounting, despite debatable, evidence supports the use of micro-RNAs as markers of bone cell metabolic activity and bone diseases. Indeed, several micro-RNAs have been associated with bone mineral density, fractures and osteoporosis. However, concerns such as absence of comparability between studies and, the lack of standardization and harmonization of the methods, limit their application. In this review, we describe the pathophysiological bases of the association between micro-RNAs and the deregulation of bone cells activity and the processes that led to the identification of potential micro-RNA-based markers associated with metabolic bone diseases.

Mining Potential Drug Targets for Osteoporosis Based on CeRNA Network

OBJECTIVE

To identify key pathological hub genes, micro RNAs (miRNAs), and circular RNAs (circRNAs) of osteoporosis (OP) and construct their ceRNA network in an effort to explore the potential biomarkers and drug targets for OP therapy.

METHODS

GSE7158, GSE201543, and GSE161361 microarray datasets were downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified by comparing OP patients with healthy controls and hub genes were screened by machine learning algorithms. Target miRNAs and circRNAs were predicted by FunRich and circbank, then ceRNA network were constructed by Cytoscape. Pathways affecting OP were identified by functional enrichment analysis. The hub genes were verified by receiver operating characteristic (ROC) curve and real time quantitative PCR (RT-qPCR). Potential drug molecules related to OP were predicted by DSigDB database and molecular docking was analyzed by autodock vina software.

RESULTS

A total of 179 DEGs were identified. By combining three machine learning algorithms, BAG2, MME, SLC14A1, and TRIM44 were identified as hub genes. Three OP-associated target miRNAs and 362 target circRNAs were predicted to establish ceRNA network. The ROC curves showed that these four hub genes had good diagnostic performance and their differential expression was statistically significant in OP animal model. Benzo[a]pyrene was predicted which could successfully bind to protein receptors related to the hub genes and it was served as the potential drug molecules.

CONCLUSION

An mRNA-miRNA-circRNA network is reported, which provides new ideas for exploring the pathogenesis of OP. Benzo[a]pyrene, as potential drug molecules for OP, may provide guidance for the clinical treatment.

Bone-Metabolism-Related Serum microRNAs to Diagnose Osteoporosis in Middle-Aged and Elderly Women

Objective: Postmenopausal osteoporosis (PMOP), a chronic systemic metabolic disease prevalent in middle-aged and elderly women, heavily relies on bone mineral density (BMD) measurement as the diagnostic indicator. In this study, we investigated serum microRNAs (miRNAs) as a possible screening tool for PMOP. Methods: This investigation recruited 83 eligible participants from 795 community-dwelling postmenopausal women between June 2020 and August 2021. The miRNA expression profiles in the serum of PMOP patients were evaluated via miRNA microarray (six PMOP patients and four postmenopausal women without osteoporosis (n-PMOP) as controls). Subsequently, results were verified in independent sample sets (47 PMOP patients and 26 n-PMOP controls) using quantitative real-time PCR. In addition, the target genes and main functions of the differentially expressed miRNAs were explored by bioinformatics analysis. Results: Four highly expressed miRNAs in the serum of patients (hsa-miR-144-5p, hsa-miR-506-3p, hsa-miR-8068, and hsa-miR-6851-3p) showed acceptable disease-independent discrimination performance (area under the curve range: 0.747-0.902) in the training set and verification set, outperforming traditional bone turnover markers. Among four key miRNAs, hsa-miR-144-5p is the only one that can simultaneously predict changes in BMD in lumbar spine 1-4, total hip, and femoral neck (β = -0.265, p = 0.022; β = -0.301, p = 0.005; and β = -0.324, p = 0.003, respectively). Bioinformatics analysis suggested that the differentially expressed miRNAs were targeted mainly to YY1, VIM, and YWHAE genes, which are extensively involved in bone metabolism processes. Conclusions: Bone-metabolism-related serum miRNAs, such as hsa-miR-144-5p, hsa-miR-506-3p, hsa-miR-8068, and hsa-miR-6851-3p, can be used as novel biomarkers for PMOP diagnosis independent of radiological findings and traditional bone turnover markers. Further study of these miRNAs and their target genes may provide new insights into the epigenetic regulatory mechanisms of the onset and progression of the disease.

The miRNA-144-5p/IRS1/AKT axis regulates the migration, proliferation, and mineralization of osteoblasts: A mechanism of bone repair in diabetic osteoporosis

Diabetic osteoporosis (DOP) is a disorder of bone metabolism induced by multiple mechanisms. Previous studies have revealed that microRNAs (miRNAs) play crucial roles in bone metabolism. MiRNA-144-5p has been proven to participate in the regulation of osteoblast activities; however, its specific mechanism in DOP has not been elucidated. This study investigated whether high glucose (HG) inhibited osteoblasts by regulating miRNA-144-5p. Our results showed that HG inhibited bone formation not only in vivo but also in vitro. We observed that HG severely hindered the migration, proliferation and mineralization of osteoblasts, while miRNA-144-5p was upregulated by way of the cell counting kit-8 assay, wound healing assay, alkaline phosphatase (ALP) activity assay and alizarin red staining. Double luciferase reporter experiments showed that miRNA-144-5p directly targeted insulin receptor substrate 1 (IRS1). The IRS1/AKT signaling pathway is closely related to osteoblasts' migration, proliferation, and mineralization. Silencing miRNA-144-5p promoted the mRNA, and protein expression of IRS1, thereby letting the expression of total AKT down, and then preventing phosphorylation of AKT into the nucleus to regulate migration, proliferation, and mineralization genes of osteoblasts. In conclusion, this study indicated that HG regulated the migration, proliferation, and mineralization of osteoblasts via the miRNA-144-5p/IRS1/AKT axis, which suggested a possible mechanism for DOP pathology.

Regulation of osteoclast-mediated bone resorption by microRNA

Osteoclast-mediated bone resorption is responsible for bone metabolic diseases, negatively impacting people's health and life. It has been demonstrated that microRNA influences the differentiation of osteoclasts by regulating the signaling pathways during osteoclast-mediated bone resorption. So far, the involved mechanisms have not been fully elucidated. This review introduced the pathways involved in osteoclastogenesis and summarized the related microRNAs binding to their specific targets to mediate the downstream pathways in osteoclast-mediated bone resorption. We also discuss the clinical potential of targeting microRNAs to treat osteoclast-mediated bone resorption as well as the challenges of avoiding potential side effects and producing efficient delivery methods.

METTL3-mediated LINC00657 promotes osteogenic differentiation of mesenchymal stem cells via miR-144-3p/BMPR1B axis

N6-methyladenosine (m6A) modification plays a crucial role in the progression of osteoporosis (OP). The study aimed to explore the effects of methyltransferase-like 3 (METTL3) in OP. The levels of METTL3, LINC00657, miR-144-3p and BMPR1B were detected using qPCR. Osteogenesis was assessed using alizarin red and alkaline phosphatase (ALP) staining assays. The protein expression of Bglap, Runx2 and Col1a1 was measured by western blot. The targets of LINC00657 and miR-144-3p were screened by bioinformatic analysis. The interaction between miR-144-3p and LINC00657 or BMPR1B was analyzed by dual-luciferase reporter assay and RNA pull-down assay. The results showed that METTL3 was downregulated in OP. METTL3 mediated m6A methylation of LINC00657 to promote the development of osteogenesis. Further study indicated that LINC00657 functioned as a ceRNA to upregulate BMPR1B via sponging miR-144-3p. Additionally, BMPR1B knockdown alleviated the effects of METTL3 on osteogenesis of bone marrow mesenchymal stem cells (BMSCs). Taken together, METTL3 facilitated osteogenic differentiation of BMSCs via the LINC00657/miR-144-3p/BMPR1B axis. Our findings may provide a novel insight of m6A methylation in the development of OP.

Effect of Nerve Training Technology on Apoptosis of Cartilage and Osteoblasts and Expression of Aggrecan Protein in Osteoporotic Arthritis

Arthritis and osteoporosis are two common disorders in the world, especially for the elder, but the current treatments have limited efficacy. Herein, we aimed to determine whether the novel technique, neurological training can alleviate osteoporosis complicated with arthritis in rat model. Thirty rats were assigned into normal group, model group, and treatment group (treated with forsythin and neurological training) (n = 10) followed by assessment of chondrocytes and osteoblasts using Mankin score, apoptosis by TUNEL and flow cytometry, and IL-1β, TNF-α, and Aggrecan levels. Apoptotic chondrocytes of treatment group (27.43±1.34) was lower than model group (p < 0.05), whereas amount of osteoblast was increased upon forsythin and neurological training, with lower Mankin’s score (6.38±0.76). Besides, the content of IL-1β and TNF-α of treatment group was significantly lower but Aggrecan mRNA and protein expression was significantly higher. In conclusion, neurological training could protect and alleviate osteoporosis complicated with arthritis.

The Emerging Role of MicroRNAs in Bone Diseases and Their Therapeutic Potential

MicroRNAs (miRNAs) are a class of small (20-24 nucleotides), highly conserved, non-coding RNA molecules whose main function is the post-transcriptional regulation of gene expression through sequence-specific manners, such as mRNA degradation or translational repression. Since these key regulatory molecules are implicated in several biological processes, their altered expression affects the preservation of cellular homeostasis and leads to the development of a wide range of pathologies. Over the last few years, relevant investigations have elucidated that miRNAs participate in different stages of bone growth and development. Moreover, the abnormal expression of these RNA molecules in bone cells and tissues has been significantly associated with the progression of numerous bone diseases, including osteoporosis, osteosarcoma, osteonecrosis and bone metastasis, among others. In fact, miRNAs regulate multiple pathological mechanisms, including altering either osteogenic or osteoblast differentiation, metastasis, osteosarcoma cell proliferation, and bone loss. Therefore, in this present review, aiming to impulse the research arena of the biological implications of miRNA transcriptome in bone diseases and to explore their potentiality as a theragnostic target, we summarize the recent findings associated with the clinical significance of miRNAs in these ailments.

GATA4 regulates osteogenic differentiation by targeting miR-144-3p

Numerous studies have demonstrated that microRNAs (miRNAs or miRs) play an important role in regulating osteogenic differentiation, but their specific regulatory mechanism requires further investigation. In the present study, it was revealed that during osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs), the expression level of miR-144-3p was decreased with increased osteogenic induction duration and was negatively associated with osteogenic marker gene expression. Overexpression of miR-144-3p inhibited osteogenic differentiation, while inhibition of miR-144-3p expression promoted osteogenic differentiation. In addition, dual-luciferase activity analysis and adenovirus infection experiments revealed that GATA binding protein 4 targeted miR-144-3p for regulation and that overexpression of GATA4 promoted the expression of miR-144-3p. These data indicated that miR-144-3p plays a role in inhibiting BMSC osteogenic differentiation and that GATA4 inhibits osteogenic differentiation by targeting miR-144-3p expression.

A systematic review of miRNAs as biomarkers in osteoporosis disease

Background

Osteoporosis is often considered to be a disease of the elderly, which is characterized by two characteristics: low bone mineral density (BMD) and increased risk of fracture. MicroRNAs (miRNAs) have been reported to play a potential role in bone formation and resorption, bone remodeling, bone homeostasis regulation, and bone cell differentiation. Therefore, altered expression of different miRNAs may impact the pathology of bone diseases such as osteoporosis. A systematic review was conducted to extract all miRNA found to be significantly dys-regulated in the peripheral blood.

Methods

This review was carried out using a systematically search on PubMed, Scopus, Embase, Web of Science (WoS), and Cochrane databases from 1990 to 2018 to explore the diagnostic value of miRNAs as a biomarker in osteoporosis.

Results

A total of 31 studies were identified in the systematic review that indicated more than 30 kinds of up-regulated and down-regulated miRNAs in three categories; postmenopausal osteoporosis, postmenopausal osteoporosis with fracture risk, and other types of osteoporosis and fracture risk.

Conclusion

The collective data presented in this review indicate that miRNAs could serve as biomarkers for the diagnosis (onset) and prognosis (progression of osteoporosis), while the clinical application of these findings has yet to be verified.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-021-00873-5.

Perspective of the GEMSTONE Consortium on Current and Future Approaches to Functional Validation for Skeletal Genetic Disease Using Cellular, Molecular and Animal-Modeling Techniques

The availability of large human datasets for genome-wide association studies (GWAS) and the advancement of sequencing technologies have boosted the identification of genetic variants in complex and rare diseases in the skeletal field. Yet, interpreting results from human association studies remains a challenge. To bridge the gap between genetic association and causality, a systematic functional investigation is necessary. Multiple unknowns exist for putative causal genes, including cellular localization of the molecular function. Intermediate traits ("endophenotypes"), e.g. molecular quantitative trait loci (molQTLs), are needed to identify mechanisms of underlying associations. Furthermore, index variants often reside in non-coding regions of the genome, therefore challenging for interpretation. Knowledge of non-coding variance (e.g. ncRNAs), repetitive sequences, and regulatory interactions between enhancers and their target genes is central for understanding causal genes in skeletal conditions. Animal models with deep skeletal phenotyping and cell culture models have already facilitated fine mapping of some association signals, elucidated gene mechanisms, and revealed disease-relevant biology. However, to accelerate research towards bridging the current gap between association and causality in skeletal diseases, alternative in vivo platforms need to be used and developed in parallel with the current -omics and traditional in vivo resources. Therefore, we argue that as a field we need to establish resource-sharing standards to collectively address complex research questions. These standards will promote data integration from various -omics technologies and functional dissection of human complex traits. In this mission statement, we review the current available resources and as a group propose a consensus to facilitate resource sharing using existing and future resources. Such coordination efforts will maximize the acquisition of knowledge from different approaches and thus reduce redundancy and duplication of resources. These measures will help to understand the pathogenesis of osteoporosis and other skeletal diseases towards defining new and more efficient therapeutic targets.

Osteoporosis, fracture, osteoarthritis & sarcopenia: A systematic review of circulating microRNA association

Circulating microRNAs (c-miRs) show promise as biomarkers. This systematic review explores their potential association with age-related fracture/osteoporosis (OP), osteoarthritis (OA) and sarcopenia (SP), as well as cross-disease association. Most overlap occurred between OA and OP, suggesting potentially shared microRNA activity. There was little agreement in results across studies. Few reported receiver operating characteristic analysis (ROC) and many identified significant dysregulation in disease, but direction of effect was commonly conflicting. c-miRs with most evidence for consistency in dysregulation included miR-146a, miR-155 and miR-98 for OA (upregulated). Area under the curve (AUC) for miR-146a biomarker performance was AUC 0.92, p = 0.028. miR-125b (AUC 0.76-0.89), miR-100, miR-148a and miR-24 were consistently upregulated in OP. Insufficient evidence exists for c-miRs in SP. Study quality was typically rated intermediate/high risk of bias. Wide study heterogeneity meant meta-analysis was not possible. We provide detailed critique and recommendations for future approaches in c-miR analyses based on this review.

Circulating miR-122-5p and miR-375 as Potential Biomarkers for Bone Mass Recovery after Parathyroidectomy in Patients with Primary Hyperparathyroidism: A Proof-of-Concept Study

Primary hyperparathyroidism (PHPT) is the leading cause of secondary osteoporosis. Although bone mineral density (BMD) tends to recover after parathyroidectomy in PHPT patients, the degree of recovery varies. Circulating microRNAs (miRNAs) profiles are known to be correlated with osteoporosis and fracture. We aimed to investigate whether osteoporotic fracture-related miRNAs are associated with postoperative BMD recovery in PHPT. Here, 16 previously identified osteoporotic fracture-related miRNAs were selected. We analyzed the association between the preoperative level of each miRNA and total hip (TH) BMD change. All 12 patients (among the 18 patients enrolled) were cured of PHPT after parathyroidectomy as parathyroid hormone (PTH) and calcium levels were restored to the normal range. Preoperative miR-19b-3p, miR-122-5p, and miR-375 showed a negative association with the percent changes in TH BMD from baseline. The association remained robust for miR-122-5p and miR-375 even after adjusting for sex, age, PTH, and procollagen type 1 N-terminal propeptide levels in a multivariable model. In conclusion, preoperative circulating miR-122-5p and miR-375 levels were negatively associated with TH BMD changes after parathyroidectomy in PHPT patients. miRNAs have the potential to serve as predictive biomarkers of treatment response in PHPT patients, which merits further investigation.

Upregulation of miR-144-3p expression attenuates glioma cell viability and invasion by targeting BCL6

Glioma remains to be an aggressive type of cancer with poor prognosis irrespective of the type of standard treatment applied. Therefore, identification of accurate early diagnostic methods and therapeutic strategies for glioma is imperative for the treatment of this disease. The expression of a number of miRNAs in glioma have been reported to be associated with the regulation of tumorigenic progression, cancer cell proliferation, metastasis, invasion, angiogenesis and drug resistance. The aim of the present study was to assess the function of the microRNA (miR/miRNA)-144-3p/BCL6 axis in glioma. Reverse transcription-quantitative PCR was used to measure miR-144-3p and BCL6 expression. Western blotting was used for measuring BCL6 expression. Luciferase reporter assay was used to assess the association between miR-144-3p and BCL6 and a tumor xenograft model was established for assess tumor growth. The data demonstrated that miR-144-3p was decreased whereas BCL6 expression was increased in glioma tissues compared with those in healthy human brain tissues, where miR-144-3p suppressed BCL6 expression by targeting the 3'-UTR sequence of BCL6. miR-144-3p overexpression alleviated proliferation and invasion in U251 cells whereas transfection with the BCL6-overexpressing plasmid rescued the suppressive effects of miR-144-3p upregulation on the proliferation and invasion of U251 cells. In addition, miR-144-3p overexpression and BCL6 downregulation inhibited tumor progression in a mouse tumor xenograft model. The present findings suggest that miR-144-3p and BCL6 may serve to be indicator of proliferation and invasion for patients with glioma. Furthermore, BCL6 may serve an important role in the miR-144-3p-mediated regulation of proliferation and invasion of glioma cells, where the miR-144-3p/BCL6 axis can be used to target patients with glioma therapeutically.

lncRNA GAS5 regulates angiogenesis by targeting miR‑10a‑3p/VEGFA in osteoporosis

Osteoporosis is a severe bone disease commonly occurring in older males and postmenopausal females. Previous studies have shown that long non‑coding (lnc)RNA growth arrest‑specific 5 (GAS5) serves an important role in osteoporosis. However, its role is unclear and requires further exploration. The relative expression levels of GAS5 and miR‑10a‑3p in the serum samples of patients with osteoporosis, as well as the relative expression levels of GAS5, microRNA (miR)‑10a‑3p and vascular endothelial growth factor A (VEGFA) mRNA in osteoblasts, were detected by reverse transcription‑quantitative PCR. ELISA and western blotting were used to detect the expression levels of VEGFA. A Matrigel angiogenesis test was used to assess the effects on angiogenesis. RNA binding interactions between GAS5/miR‑10a‑3p and miR‑10a‑3p/VEGFA were evaluated using dual‑luciferase reporter assays. Furthermore, the effects of the GAS5/miR‑10a‑3p/VEGFA axis were investigated via ELISA, western blotting and Matrigel angiogenesis. GAS5 was significantly downregulated and miR‑10a‑3p was upregulated in patients with osteoporosis. Overexpression of GAS5 promoted angiogenesis. GAS5 acted as a sponge of miR‑10a‑3p; VEGFA was a target gene of miR‑10a‑3p. GAS5 induced angiogenesis by inhibiting miR‑10a‑3p and enhancing VEGFA expression. These results indicated that GAS5 overexpression increased angiogenesis by inhibiting miR‑10a‑3p, promoting the expression of VEGFA. The present study revealed a novel mechanism and provided novel targets for the clinical treatment of osteoporosis.

MicroRNA-151a-3p Functions in the Regulation of Osteoclast Differentiation: Significance to Postmenopausal Osteoporosis

BACKGROUND

Studies have found the pivotal role of miRNAs in the progression of postmenopausal osteoporosis (OP). However, the function of miRNAs in OP is unclear. This study aimed to explore the biological functions of microRNA-151a-3p in OP.

METHODS

RT-qPCR was employed to assess the expression of microRNA-151a-3p in serum isolated from OP patients and healthy controls. Dual-energy X-ray absorptiometry (DXA) was used to measure the bone mineral density (BMD) of the lumbar spine. The expression levels of c-Fos, NFATc1, and TRAP were tested by Western blot. Ovariectomized (OVX) rats were treated with antago microRNA-151a-3p or antago NC, and then serum and lumbar vertebrae were collected for ELISA and bone histomorphology analysis.

RESULTS

The expression of microRNA-151a-3p in postmenopausal women with osteoporosis was significantly up-regulated, and microRNA-151a-3p level was negatively correlated with BMD. During osteoclastogenesis, microRNA-151a-3p level was obviously increased. Overexpression of microRNA-151a-3p promoted the differentiation of RANKL-induced THP-1 and RAW264.7 cells into osteoclasts, whereas silencing of microRNA-151a-3p resulted in the opposite results. Silencing of microRNA-151a-3p in OVX rats altered osteoclastogenesis-related factors and raised BMD.

CONCLUSION

MicroRNA-151a-3p could partly regulate osteoporosis by promoting osteoclast differentiation, and miRNA-151a-3p could be a potential therapeutic target for postmenopausal osteoporosis.

Application of microRNA in Human Osteoporosis and Fragility Fracture: A Systemic Review of Literatures

MicroRNAs (miRNAs) could serve as ideal entry points to the deregulated pathways in osteoporosis due to their relatively simple upstream and downstream relationships with other molecules in the signaling cascades. Our study aimed to give a comprehensive review of the already identified miRNAs in osteoporosis from human blood samples and provide useful information for their clinical application. A systematic literature search for relevant studies was conducted in the Pubmed database from inception to December 2020. We set two essential inclusion criteria: human blood sampling and design of controlled studies. We sorted the results of analysis on human blood samples according to the study settings and compiled the most promising miRNAs with analyzed diagnostic values. Furthermore, in vitro and in vivo evidence for the mechanisms of the identified miRNAs was also illustrated. Based on both diagnostic value and evidence of mechanism from in vitro and in vivo experiments, miR-23b-3p, miR-140-3p, miR-300, miR-155-5p, miR-208a-3p, and miR-637 were preferred candidates in diagnostic panels and as therapeutic agents. Further studies are needed to build sound foundations for the clinical usage of miRNAs in osteoporosis.

Plumbagin, a Biomolecule with (Anti)Osteoclastic Properties

Plumbagin is a plant-derived naphthoquinone that is widely used in traditional Asian medicine due to its anti-inflammatory and anti-microbial properties. Additionally, plumbagin is cytotoxic for cancer cells due to its ability to trigger reactive oxygen species (ROS) formation and subsequent apoptosis. Since it was reported that plumbagin may inhibit the differentiation of bone resorbing osteoclasts in cancer-related models, we wanted to elucidate whether plumbagin interferes with cytokine-induced osteoclastogenesis. Using C57BL/6 mice, we unexpectedly found that plumbagin treatment enhanced osteoclast formation and that this effect was most pronounced when cells were pre-treated for 24 h with plumbagin before subsequent M-CSF/RANKL stimulation. Plumbagin caused a fast induction of NFATc1 signalling and mTOR-dependent activation of p70S6 kinase which resulted in the initiation of protein translation. In line with this finding, we observed an increase in RANK surface expression after Plumbagin stimulation that enhanced the responsiveness for subsequent RANKL treatment. However, in Balb/c mice and Balb/c-derived RAW264.7 macrophages, these findings could not be corroborated and osteoclastogenesis was inhibited. Our results suggest that the effects of plumbagin depend on the model system used and can therefore either trigger or inhibit osteoclast formation.

Intake of Natural Compounds and Circulating microRNA Expression Levels: Their Relationship Investigated in Healthy Subjects With Different Dietary Habits

Diet has a strong influence on many physiological processes, which in turn have important implications on a variety of pathological conditions. In this respect, microRNAs (miRNAs), a class of small non-coding RNAs playing a relevant epigenetic role in controlling gene expression, may represent mediators between the dietary intake and the healthy status. Despite great advances in the field of nutri-epigenomics, it remains unclear how miRNA expression is modulated by the diet and, specifically, the intake of specific nutrients. We investigated the whole circulating miRNome by small RNA-sequencing performed on plasma samples of 120 healthy volunteers with different dietary habits (vegans, vegetarians, and omnivores). Dietary intakes of specific nutrients were estimated for each subject from the information reported in the food-frequency questionnaire previously validated in the EPIC study. We focused hereby on the intake of 23 natural compounds (NCs) of the classes of lipids, micro-elements, and vitamins. We identified 78 significant correlations (rho > 0.300, p-value < 0.05) among the estimated daily intake of 13 NCs and the expression levels of 58 plasma miRNAs. Overall, vitamin D, sodium, and vitamin E correlated with the largest number of miRNAs. All the identified correlations were consistent among the three dietary groups and 22 of them were confirmed as significant (p-value < 0.05) by age-, gender-, and body-mass index-adjusted Generalized Linear regression Model analysis. miR-23a-3p expression levels were related with different NCs including a significant positive correlation with sodium (rho = 0.377) and significant negative correlations with lipid-related NCs and vitamin E. Conversely, the estimated intake of vitamin D was negatively correlated with the expression of the highest number of circulating miRNAs, particularly miR-1277-5p (rho = −0.393) and miR-144-3p (rho = −0.393). Functional analysis of the targets of sodium intake-correlated miRNAs highlighted terms related to cardiac development. A similar approach on targets of those miRNAs correlated with vitamin D intake showed an enrichment in genes involved in hormone metabolisms, while the response to chronic inflammation was among the top enriched processes involving targets of miRNAs negatively related with vitamin E intake. Our findings show that nutrients through the habitual diet influence circulating miRNA profiles and highlight that this aspect must be considered in the nutri-epigenomic research.

Role of MicroRNAs in Bone Pathology during Chikungunya Virus Infection

Chikungunya virus (CHIKV) is an alphavirus, transmitted by mosquitoes, which causes Chikungunya fever with symptoms of fever, rash, headache, and joint pain. In about 30%-40% of cases, the infection leads to polyarthritis and polyarthralgia. Presently, there are no treatment strategies or vaccine for Chikungunya fever. Moreover, the mechanism of CHIKV induced bone pathology is not fully understood. The modulation of host machinery is known to be essential in establishing viral pathogenesis. MicroRNAs (miRNAs) are small non-coding RNAs that regulate major cellular functions by modulating gene expression. Fascinatingly, recent reports have indicated the role of miRNAs in regulating bone homeostasis and altered expression of miRNAs in bone-related pathological diseases. In this review, we summarize the altered expression of miRNAs during CHIKV pathogenesis and the possible role of miRNAs during bone homeostasis in the context of CHIKV infection. A holistic understanding of the different signaling pathways targeted by miRNAs during bone remodeling and during CHIKV-induced bone pathology may lead to identification of useful biomarkers or therapeutics.

Circulating MicroRNAs as Novel Biomarkers for Osteoporosis and Fragility Fracture Risk: Is There a Use in Assessment Risk?

Osteoporosis is a multifactorial skeletal disease that is associated with both bone mass decline and microstructure damage. The fragility fractures-especially those affecting the femur-that embody the clinical manifestation of this pathology continue to be a great medical and socioeconomic challenge worldwide. The currently available diagnostic tools, such as dual energy X-ray absorptiometry, Fracture Risk Assessment Tool (FRAX) score, and bone turnover markers, show limited specificity and sensitivity; therefore, the identification of alternative approaches is necessary. As a result of their advantageous features, such as non-invasiveness, biofluid stability, and easy detection, circulating cell-free miRs are promising new potential biomarkers for the diagnosis of osteoporosis and low-traumatic fracture risk assessment. However, due to the absence of both standardized pre-analytical, analytical, and post-analytical protocols for their measurement and universally accepted guidelines for diagnostic use, their clinical utility is limited. The aim of this review was to record all the data currently available in the literature concerning the use of circulating microRNAs as both potential biomarkers for osteoporosis diagnosis and fragility fracture risk evaluation, and group them according to the experimental designs, in order to support a more conscious choice of miRs for future research in this field.

Involvement of Noncoding RNAs in the Differentiation of Osteoclasts

As the most important bone-resorbing cells, osteoclasts play fundamental roles in bone remodeling and skeletal health. Much effort has been focused on identifying the regulators of osteoclast metabolism. Noncoding RNAs (ncRNAs) reportedly regulate osteoclast formation, differentiation, survival, and bone-resorbing activity to participate in bone physiology and pathology. The present review intends to provide a general framework for how ncRNAs and their targets regulate osteoclast differentiation and the important events of osteoclastogenesis they are involved in, including osteoclast precursor generation, early differentiation, mononuclear osteoclast fusion, and multinucleated osteoclast function and survival. This framework is beneficial for understanding bone biology and for identifying the potential biomarkers or therapeutic targets of bone diseases. The review also summarizes the results of in vivo experiments and classic experiment methods for osteoclast-related researches.

Circulating miRNAs: A New Opportunity in Bone Fragility

Osteoporosis, one of the leading causes of bone fractures, is characterized by low bone mass and structural deterioration of bone tissue, which are associated with a consequent increase in bone fragility and predisposition to fracture. Current screening tools are limited in estimating the proper assessment of fracture risk, highlighting the need to discover novel more suitable biomarkers. Genetic and environmental factors are both implicated in this disease. Increasing evidence suggests that epigenetics and, in particular, miRNAs, may represent a link between these factors and an increase of fracture risk. miRNAs are a class of small noncoding RNAs that negatively regulate gene expression. In the last decade, several miRNAs have been associated with the development of osteoporosis and bone fracture risk, opening up new possibilities in precision medicine. Recently, these molecules have been identified in several biological fluids, and the possible existence of a circulating miRNA (c-miRNA) signature years before the fracture occurrence is suggested. The aim of this review is to provide an overview of the c-miRNAs suggested as promising biomarkers for osteoporosis up until now, which could be helpful for early diagnosis and monitoring of treatment response, as well as fracture risk assessment, in osteoporotic patients.

MiR-144-3p Inhibits BMSC Proliferation and Osteogenic Differentiation Via Targeting FZD4 in Steroid-Associated Osteonecrosis

BACKGROUND

MicroRNAs have recently been recognized to be engaged in the development of bone diseases.

OBJECTIVE

This study was performed to elucidate the effects of miR-144-3p on proliferation and osteogenesis of mesenchymal stem cells (MSCs) from the patients with steroid-associated osteonecrosis (ONFH) and its related mechanism.

METHOD

The expression level of miR-144-3p in the MSCs from the proximal femur of the patients was examined by Real-time PCR. The cell proliferation ability was assayed by MTT. The differentiation ability of MSCs was assayed by Alizarin Red S (ARS) staining. The interaction between miR-144-3p and frizzled4 (FZD4) was investigated by Real-time PCR, western blot and luciferase reporter assay.

RESULTS

ONFH samples had the obviously high expression of miR-144-3p compared to the control. MiR-144-3p had a negative effect on the proliferation and osteogenesis of MSCs. Via targeting FZD4, miR-144-3p decreased β-catenin nuclear translocation, the transcription of RUNX2 and COL1A1. Over-expression of FZD4 partially reversed miR-144-3p-induced decrease in the proliferation and osteogenesis of MSCs.

CONCLUSION

MiR-144-3p might play an important role in the development of ONFH and might be used as a novel class of therapeutic targets for this disease.

LINC00963 Functions as an Oncogene in Bladder Cancer by Regulating the miR-766-3p/MTA1 Axis

Purpose

Long non-coding RNAs have been found to be involved in bladder cancer development. This article studied LINC00963 effects on bladder cancer progression to provide a novel treatment target.

Patients and Methods

Totally 56 bladder cancer patients participated in this research. Bladder cancer cells were transfected. Cell counting kit 8 assay and clone formation experiment were used for cell viability and colony formation detection. Cell migration and invasion were determined by Transwell experiment. LINC00963 distribution was explored by cytoplasmic and nuclear extract isolation and quantitative real-time polymerase chain reaction. Luciferase reporter experiment and RNA pulldown experiment were performed to detect the relationship between these two genes. The cancer genome atlas analysis was used for the detection of metastasis-associated protein 1 (MTA1) expression in bladder cancer.

Results

LINC00963 was seriously up-regulated in bladder cancer patients. High LINC00963 expression indicated high histological grade and low survival. LINC00963 was obviously up-regulated in bladder cancer cells. Knockdown of LINC00963 significantly reduced bladder cancer cells viability, colony formation, migration and invasion. Luciferase reporter experiment and RNA pulldown experiment revealed that LINC00963 promoted MTA1 expression via directly inhibiting miR-766-3p. MTA1 was up-regulated in bladder cancer patients. MTA1 up-regulation reversed the inhibitory effect of LINC00963 knockdown on bladder cancer cell viability, migration and invasion.

Conclusion

LINC00963 functions as an oncogene in bladder cancer by regulating the miR-766-3p/MTA1 axis.

The Clinical Potential of Circulating miRNAs as Biomarkers: Present and Future Applications for Diagnosis and Prognosis of Age-Associated Bone Diseases

Osteoporosis, related fracture/fragility, and osteoarthritis are age-related pathologies that, over recent years, have seen increasing incidence and prevalence due to population ageing. The diagnostic approaches to these pathologies suffer from limited sensitivity and specificity, also in monitoring the disease progression or treatment. For this reason, new biomarkers are desirable for improving the management of osteoporosis and osteoarthritis patients. The non-coding RNAs, called miRNAs, are key post-transcriptional factors in bone homeostasis, and promising circulating biomarkers for pathological conditions in which to perform a biopsy can be problematic. In fact, miRNAs can easily be detected in biological fluids (i.e., blood, serum, plasma) using methods with elevated sensitivity and specificity (RT-qPCR, microarray, and NGS). However, the analytical phases required for miRNAs' evaluation still present some practical issues that limit their use in clinical practice. This review reveals miRNAs' potential as circulating biomarkers for evaluating predisposition, diagnosis, and prognosis of osteoporosis (postmenopausal or idiopathic), bone fracture/fragility, and osteoarthritis, with a focus on pre-analytical, analytical, and post-analytical protocols used for their validation and thus on their clinical applicability. These evidences may support the definition of early diagnostic tools based on circulating miRNAs for bone diseases and osteoarthritis as well as for monitoring the effects of specific treatments.

Urinary miRNAs as biomarkers for idiopathic osteonecrosis of femoral head: A multicentre study

Objectives

Urinary microRNAs (miRNAs) have shown great diagnostic and prognostic values for multiple diseases. The profile of urinary miRNAs in patients with idiopathic osteonecrosis of femoral head (ONFH) is currently unclear.

Methods

We first randomly chose ten patients with each Association Research Circulation Osseous (ARCO) stage (I, II, III and IV) and ten healthy participants from the entire cohorts for initial screening. The miRNA polymerase chain reaction (PCR) array was then performed to identify the differentially abundant miRNAs in urine of these participants. We then verified the findings in the entire cohort. Clinical features including age, gender, bone mass index (BMI), lesion size and stages were recorded. We then analysed the association between the level of urinary miRNAs and clinical features.

Results

Our data indicated that there were 13 differentially abundant miRNAs among all groups. Urinary miR-150 demonstrated the highest diagnostic value among all candidates. Urinary miR-185 and miR-133a increased by ARCO staging. The levels of urinary miR-4824 abruptly decreased after femoral head collapse (ARCO stage III and IV). Urinary miR-144 was the only marker that correlated with lesion size.

Conclusions

The levels of urinary miRNAs are valuable biomarkers for idiopathic ONFH. Given the noninvasive nature of this test, it is potentially useful for diagnosis and monitoring of idiopathic ONFH progression.

The translational potential of this article

This article gives novel methods for ONFH diagnosis and progression monitoring in a convenient and non-invasive way.

Scaffold-Based Gene Therapeutics for Osteochondral Tissue Engineering

Significant progress in osteochondral tissue engineering has been made for biomaterials designed to deliver growth factors that promote tissue regeneration. However, due to diffusion characteristics of hydrogels, the accurate delivery of signaling molecules remains a challenge. In comparison to the direct delivery of growth factors, gene therapy can overcome these challenges by allowing the simultaneous delivery of growth factors and transcription factors, thereby enhancing the multifactorial processes of tissue formation. Scaffold-based gene therapy provides a promising approach for tissue engineering through transfecting cells to enhance the sustained expression of the protein of interest or through silencing target genes associated with bone and joint disease. Reports of the efficacy of gene therapy to regenerate bone/cartilage tissue regeneration are widespread, but reviews on osteochondral tissue engineering using scaffold-based gene therapy are sparse. Herein, we review the recent advances in gene therapy with a focus on tissue engineering scaffolds for osteochondral regeneration.

miR-144-3p Suppresses Osteogenic Differentiation of BMSCs from Patients with Aplastic Anemia through Repression of TET2

Reduced osteogenic capacity of bone marrow mesenchymal stem cells (BMSCs) has been causally linked to the development of aplastic anemia. In this work, we aimed to identify novel microRNAs (miRNAs) that participate in the regulation of differentiation of BMSCs from patients with aplastic anemia. We show that miR-144-3p is significantly upregulated in BMSCs from patients with aplastic anemia relative to control equivalents. Depletion of miR-144-3p significantly enhances osteogenic differentiation of BMSCs from patients with aplastic anemia after culturing in osteogenesis-inducing medium. Conversely, overexpression of miR-144-3p blocks osteogenic differentiation of BMSCs. Mechanistically, miR-144-3p negatively regulates the expression of ten-eleven translocation 2 (TET2) in BMSCs. Reduced TET2 expression is associated with a significant decrease in global 5-hydroxymethyl-cytosine (5hmC) levels and osteogenic gene expression. Knockdown of miR-144-3p elevates the expression of TET2 and total 5hmC levels in BMSCs. Silencing of TET2 inhibits the osteogenic differentiation of BMSCs. Overexpression of TET2 reverses miR-144-3p-mediated inhibition of osteogenesis. In addition, there is a significant negative correlation between the expression of miR-144-3p and TET2 in BMSCs from patients with aplastic anemia. Overall, miR-144-3p impairs the osteogenic capacity of BMSCs from patients with aplastic anemia through repression of TET2. Therefore, the targeting of miR-144-3p may be a therapeutic strategy against aplastic anemia.

Perspectives on miRNAs as Epigenetic Markers in Osteoporosis and Bone Fracture Risk: A Step Forward in Personalized Diagnosis

Aging is associated with an increased incidence of age-related bone diseases. Current diagnostics (e.g., conventional radiology, biochemical markers), because limited in specificity and sensitivity, can distinguish between healthy or osteoporotic subjects but they are unable to discriminate among different underlying causes that lead to the same bone pathological condition (e.g., bone fracture risk). Among recent, more sensitive biomarkers, miRNAs — the non-coding RNAs involved in the epigenetic regulation of gene expression, have emerged as fundamental post-transcriptional modulators of bone development and homeostasis. Each identified miRNA carries out a specific role in osteoblast and osteoclast differentiation and functional pathways (osteomiRs). miRNAs bound to proteins or encapsulated in exosomes and/or microvesicles are released into the bloodstream and biological fluids where they can be detected and measured by highly sensitive and specific methods (e.g., quantitative PCR, next-generation sequencing). As such, miRNAs provide a prompt and easily accessible tool to determine the subject-specific epigenetic environment of a specific condition. Their use as biomarkers opens new frontiers in personalized medicine. While miRNAs circulating levels are lower than those found in the tissue/cell source, their quantification in biological fluids may be strategic in the diagnosis of diseases that affect tissues, such as bone, in which biopsy may be especially challenging. For a biomarker to be valuable in clinical practice and support medical decisions, it must be (easily) measurable, validated by independent studies, and strongly and significantly associated with a disease outcome. Currently, miRNAs analysis does not completely satisfy these criteria, however. Starting from in vitro and in vivo observations describing their biological role in bone cell development and metabolism, this review describes the potential use of bone-associated circulating miRNAs as biomarkers for determining predisposition, onset, and development of osteoporosis and bone fracture risk. Moreover, the review focuses on their clinical relevance and discusses the pre-analytical, analytical, and post-analytical issues in their measurement, which still limits their routine application. Taken together, research and clinical findings may be helpful for creating miRNA-based diagnostic tools in the diagnosis and treatment of bone diseases.

Deregulated miRNAs in osteoporosis: effects in bone metastasis

Starting from their role exerted on osteoblast and osteoclast differentiation and activity pathways, microRNAs (miRNAs) have been recently identified as regulators of different processes in bone homeostasis. For this purpose, in a recent review, we highlighted, as deregulated miRNAs could be involved in different bone diseases such as osteoporosis. In addition, recent studies supported the concept that osteoporosis-induced bone alterations might offer a receptive site for cancer cells to form bone metastases, However, to date, no data on specific-shared miRNAs between osteoporosis and bone metastases have been considered and described to clarify the evidence of this link. The main goal of this review is to underline as deregulated miRNAs in osteoporosis may have specific roles in the development of bone metastases. The review showed that several circulating osteoporotic miRNAs could facilitate tumor progression and bone-metastasis formation in several tumor types, i.e., breast cancer, prostate cancer, non-small-cell lung cancer, esophageal squamous cell carcinoma, and multiple myeloma. In detail, serum up-regulation of pro-osteoporotic miRNAs, as well as serum down-regulation of anti-osteoporotic miRNAs are common features of all these tumors and are able to promote bone metastasis. These results are of key importance and could help researcher and clinicians to establish new therapeutic strategies connected with deregulation of circulating miRNAs and able to interfere with pathogenic processes of osteoporosis, tumor progressions, and bone-metastasis formation.

Up-regulated CST5 inhibits bone resorption and activation of osteoclasts in rat models of osteoporosis via suppression of the NF-κB pathway

Here, we aim at exploring the effect of CST5 on bone resorption and activation of osteoclasts in osteoporosis (OP) rats through the NF‐κB pathway. Microarray analysis was used to screen the OP‐related differentially expressed genes. Osteoporosis was induced in rats by intragastric retinoic acid administration. The serum levels of tartrate‐resistant acid phosphatase (TRAP), bone alkaline phosphatase (BALP) and osteocalcin (OC) and the expression of CD61 on the surface of osteoclasts were examined. The number of osteoclasts and the number and area of resorption pits were detected. Besides, the pathological changes and bone mineral density in bone tissues of rats were assessed. Also, the relationship between CST5 and the NF‐κB pathway was identified through determining the expression of CST5, RANKL, RANK, OPG, p65 and IKB. Poorly expressed CST5 was indicated to affect the OP. CST5 elevation and inhibition of the NF‐κB pathway decreased serum levels of TRAP, BALP and OC and expression of CD61 in vivo and in vitro. In OP rats, CST5 overexpression increased trabecular bones and bone mineral density of bone tissues, but decreased trabecular separation, fat within the bone marrow cavities and the number of osteoclasts through inhibiting the NF‐κB pathway. In vivo experiments showed that CST5 elevation inhibited growth in number and area of osteoclastic resorption pits and restrained osteoclastic bone absorption by inhibiting the NF‐κB pathway. In summary, overexpression of CST5 suppresses the activation and bone resorption of osteoclasts by inhibiting the activation of the NF‐κB pathway.

MiR-320a was highly expressed in postmenopausal osteoporosis and acts as a negative regulator in MC3T3E1 cells by reducing MAP9 and inhibiting PI3K/AKT signaling pathway

BACKGROUND

Postmenopausal osteoporosis (PMO), as a frequent disease in postmenopausal women, is mainly caused by the lack of estrogen. MiR-320a has been found to abate osteoblast function and induce oxidative stress before osteoporosis. However, studies on the downstream target gene and related signaling pathway of miR-320a in PMO are still obscure. This study aims to deal with these problems.

METHODS

The expression levels of miR-320a and microtubule-associated protein 9 (MAP9) in patients with osteoporosis were analyzed on the basis of the GEO database. The cells viability was determined by methylthiazolyl tetrazolium bromide (MTT). Flow cytometry and western blot were used to detect the cells apoptosis and the expression of apoptosis-related proteins, respectively. The cells differentiation-related proteins were detected by qRT-PCR and western blot. The interaction between miR-320a and MAP9 was predicted by biological software and verified by dual luciferase reporter assay and rescue assay. The expression levels of PI3K, p-PI3K, AKT and p-AKT in MC3T3-E1 cells were assessed by western blot.

RESULTS

We observed that miR-320a was over-expressed in PMO patients and exhibited inhibitory effects on MC3T3-E1 cells activity and differentiation, as well as promoting effects on MC3T3-E1 cells apoptosis. MAP9 was verified as a target gene of miR-320a and was negatively regulated by miR-320a. Based on the GEO database, MAP9 was found to be lower expressed in PMO patients. Rescue assay demonstrated that down-regulation of MAP9 could alleviate the promoting effects of miR-320a inhibitor on MC3T3-E1 cells activity and differentiation and the inhibitory effects of miR-320a inhibitor on MC3T3-E1 cells apoptosis. Mechanically, miR-320a/MAP9 possibly took part in MC3T3-E1 cells viability, differentiation and apoptosis via mediating PI3K/AKT signaling pathway.

CONCLUSIONS

Our outcomes demonstrated that miR-320a promoted MC3T3-E1 cells apoptosis, suppressed MC3T3-E1 cells viability and differentiation through targeting MAP9 and modulating PI3K/AKT signaling pathway, which provided theoretical support for miR-320a/MAP9 as promising targets for the treatment and prevention of PMO.

Lack of Association Between Select Circulating miRNAs and Bone Mass, Turnover, and Fractures: Data From the OFELY Cohort

Postmenopausal osteoporosis is characterized by the occurrence of fragility fracture with an increase in morbidity and mortality. Recently, microRNAs (miRNAs) have raised interest as regulators of translational repression, mediating a number of key processes, including bone tissue in both physiological and diseased states. The aim of this study was to examine the serum levels of 32 preselected miRNAs with reported function in bone and their association with osteoporotic fracture. We performed cross-sectional and longitudinal analyses from the OFELY Cohort. Serum levels of the miRNAs were quantified by qRT-PCR in 682 women: 99 premenopausal and 583 postmenopausal women, with 1 and 122 women with prevalent fragility fractures in each group, respectively. We have collected clinical variables (such as age, prevalent, and incident fractures), bone turnover markers (BTMs), BMD by dual X-ray absorptiometry, and bone microarchitecture with HRpQCT. We observed a number of miRNAs to be associated with fragility fractures (prevalent or incident), BTMs, BMD, and microarchitecture. This effect, however, was negated after age adjustment. This may be because age was also strongly associated with the serum levels of the 32 miRNAs (correlation coefficient up to 0.49), confirming previous findings. In conclusion, in a well-characterized prospective cohort with a sizeable sample size, we found no evidence that these 32 preselected miRNAs were not associated with BTMs, BMD, microarchitecture, and or fragility fractures. © 2019 American Society for Bone and Mineral Research.

MicroRNAs: Key Regulators to Understand Osteoclast Differentiation?

MicroRNAs (miRNAs) are small non-coding single-stranded RNAs that represent important posttranscriptional regulators of protein-encoding genes. In particular, miRNAs play key roles in regulating cellular processes such as proliferation, migration, and cell differentiation. Recently, miRNAs emerged as critical regulators of osteoclasts (OCs) biology and have been involved in OCs pathogenic role in several disorders. OCs are multinucleated cells generated from myeloid precursors in the bone marrow, specialized in bone resorption. While there is a growing number of information on the cytokines and signaling pathways that are critical to control the differentiation of osteoclast precursors (OCPs) into mature OCs, the connection between OC differentiation steps and miRNAs is less well-understood. The present review will first summarize our current understanding of the miRNA-regulated pathways in the sequential steps required for OC formation, from the motility and migration of OCPs to the cell-cell fusion and the final formation of the actin ring and ruffled border in the functionally resorbing multinucleated OCs. Then, considering the difficulty of working on primary OCs and on the generation of robust data we will give an update on the most recent advances in the detection technologies for miRNAs quantification and how these are of particular interest for the understanding of OC biology and their use as potential biomarkers.