Decreased microRNA-182-5p helps alendronate promote osteoblast proliferation and differentiation in osteoporosis via the Rap1/MAPK pathway

Mechanically strained osteocyte-derived exosomes contained miR-3110-5p and miR-3058-3p and promoted osteoblastic differentiation

BACKGROUND

Osteocytes are critical mechanosensory cells in bone, and mechanically stimulated osteocytes produce exosomes that can induce osteogenesis. MicroRNAs (miRNAs) are important constituents of exosomes, and some miRNAs in osteocytes regulate osteogenic differentiation; previous studies have indicated that some differentially expressed miRNAs in mechanically strained osteocytes likely influence osteoblastic differentiation. Therefore, screening and selection of miRNAs that regulate osteogenic differentiation in exosomes of mechanically stimulated osteocytes are important.

RESULTS

A mechanical tensile strain of 2500 με at 0.5 Hz 1 h per day for 3 days, elevated prostaglandin E2 (PGE2) and insulin-like growth factor-1 (IGF-1) levels and nitric oxide synthase (NOS) activity of MLO-Y4 osteocytes, and promoted osteogenic differentiation of MC3T3-E1 osteoblasts. Fourteen miRNAs differentially expressed only in MLO-Y4 osteocytes which were stimulated with mechanical tensile strain, were screened, and the miRNAs related to osteogenesis were identified. Four differentially expressed miRNAs (miR-1930-3p, miR-3110-5p, miR-3090-3p, and miR-3058-3p) were found only in mechanically strained osteocytes, and the four miRNAs, eight targeted mRNAs which were differentially expressed only in mechanically strained osteoblasts, were also identified. In addition, the mechanically strained osteocyte-derived exosomes promoted the osteoblastic differentiation of MC3T3-E1 cells in vitro, the exosomes were internalized by osteoblasts, and the up-regulated miR-3110-5p and miR-3058-3p in mechanically strained osteocytes, were both increased in the exosomes, which was verified via reverse transcription quantitative polymerase chain reaction (RT-qPCR).

CONCLUSIONS

In osteocytes, a mechanical tensile strain of 2500 με at 0.5 Hz induced the fourteen differentially expressed miRNAs which probably were in exosomes of osteocytes and involved in osteogenesis. The mechanically strained osteocyte-derived exosomes which contained increased miR-3110-5p and miR-3058-3p (two of the 14 miRNAs), promoted osteoblastic differentiation.

DEHP induces apoptosis and autophagy of the thyroid via Rap1 signaling pathway: In vivo and in vitro study

OBJECTIVE

DEHP has thyroid toxicity and affects thyroid function. However, the mechanism is unclear.

METHODS

The offspring of SD rats were gavaged with different doses of DEHP from in utero to 8 or 12 weeks old. We observed the thyroid morphology with HE and autophagosomes with TEM. The THs levels were tested with ELISA. The apoptosis level was tested by flow cytometry. The levels of apoptosis-related genes, autophagy-related genes and Rap1 pathway genes, were measured with qRT-PCR and Western blot. We established an MEHP-treated Nthy-ori 3-1 cell model and inhibited the Rap1 to verify the mechanism.

RESULTS

DEHP could cause pathological damage and ultrastructure damage of thyroids in offspring rats. After DEHP exposure, the THs levels were altered, the apoptosis levels increased, and autophagosomes appeared. DEHP significantly affected the levels of apoptosis-related genes and autophagy-related genes. DEHP also affected the levels of Rap1 pathway, which was correlated with the levels of apoptosis and autophagy. After inhibiting Rap1 in Nthy-ori 3-1 cells, the THs levels were altered. Rap1 pathway was inhibited and the levels of apoptosis and autophagy were down-regulated.

CONCLUSION

DEHP could induce the apoptosis and autophagy of the thyroid, and Rap1 signaling pathway may play a significant role.

Long non-coding RNA Homeobox D gene cluster antisense growth-associated long noncoding RNA/microRNA-182-5p/Homeobox protein A10 alleviates postmenopausal osteoporosis via accelerating osteoblast differentiation of bone marrow mesenchymal stem cells

BACKGROUND

Studies have illuminated that long non-coding RNA (lncRNA) influences bone cell differentiation and formation. Nevertheless, whether lncRNA Homeobox D gene cluster antisense growth-associated long noncoding RNA (HAGLR) was implicated in postmenopausal osteoporosis (PMOP) was yet uncertain.

PURPOSE

The research was to explore HAGLR's role in the osteogenic differentiation (OD) process of bone marrow mesenchymal stem cells (BMSCs).

METHODS

BMSCs were isolated from mouse bone marrow tissues and identified by electron microscope and flow cytometry. HAGLR, microRNA (miR)-182-5p, and homeobox protein A10 (Hoxa10) levels in BMSCs were detected. Mouse BMSC OD process was induced, and calcium deposition and alkaline phosphatase content were analyzed, as well as expressions of runt-related transcription factor 2, osteopontin, and osteocalcin, and cell apoptosis. Bilateral ovaries were resected from mice to construct the ovariectomized model and bone mineral density, maximum bending stress, maximum load, and elastic modulus of the femur were tested, and the femur was histopathologically evaluated. Chondrocyte apoptosis in the articular cartilage of mice was analyzed. Analysis of the interaction of HAGLR, miR-182-5p with Hoxa10 was conducted.

RESULTS

HAGLR and Hoxa10 were down-regulated and miR-182-5p was elevated in PMOP patients. During the BMSC OD process, HAGLR and Hoxa10 levels were suppressed, while miR-182-5p was elevated. Promotion of HAGLR or suppression of miR-182-5p accelerated OD of BMSCs. Inhibition of miR-182-5p reversed the inhibitory effect of HAGLR on BMSC OD. In in vivo experiments, up-regulating HAGLR alleviated PMOP, while silencing Hoxa10 reversed the effects of upregulating HAGLR. HAGLR performed as a sponge for miR-182-5p, while miR-182-5p targeted Hoxa10.

CONCLUSION

In general, HAGLR boosted the OD process of BMSCs and relieved PMOP via the miR-182-5p/Hoxa10 axis. These data preliminarily reveal the key role of HAGLR in PMOP, and the research results have a certain reference for the treatment of PMOP.

Characterisation of miRNA Expression in Dental Pulp Cells during Epigenetically-Driven Reparative Processes

Within regenerative endodontics, exciting opportunities exist for the development of next-generation targeted biomaterials that harness epigenetic machinery, including microRNAs (miRNAs), histone acetylation, and DNA methylation, which are used to control pulpitis and to stimulate repair. Although histone deacetylase inhibitors (HDACi) and DNA methyltransferase inhibitors (DNMTi) induce mineralisation in dental pulp cell (DPC) populations, their interaction with miRNAs during DPC mineralisation is not known. Here, small RNA sequencing and bioinformatic analysis were used to establish a miRNA expression profile for mineralising DPCs in culture. Additionally, the effects of a HDACi, suberoylanilide hydroxamic acid (SAHA), and a DNMTi, 5-aza-2'-deoxycytidine (5-AZA-CdR), on miRNA expression, as well as DPC mineralisation and proliferation, were analysed. Both inhibitors increased mineralisation. However, they reduced cell growth. Epigenetically-enhanced mineralisation was accompanied by widespread changes in miRNA expression. Bioinformatic analysis identified many differentially expressed mature miRNAs that were suggested to have roles in mineralisation and stem cell differentiation, including regulation of the Wnt and MAPK pathways. Selected candidate miRNAs were demonstrated by qRT-PCR to be differentially regulated at various time points in mineralising DPC cultures treated with SAHA or 5-AZA-CdR. These data validated the RNA sequencing analysis and highlighted an increased and dynamic interaction between miRNA and epigenetic modifiers during the DPC reparative processes.

miRNAs as potential game-changers in bone diseases: Future medicinal and clinical uses

MicroRNAs (miRNAs), short, highly conserved non-coding RNA, influence gene expression by sequential mechanisms such as mRNA breakdown or translational repression. Many biological processes depend on these regulating substances, thus changes in their expression have an impact on the maintenance of cellular homeostasis and result in the emergence of a variety of diseases. Relevant studies have shown in recent years that miRNAs are involved in many stages of bone development and growth. Additionally, abnormal production of miRNA in bone tissues has been closely associated with the development of numerous bone disorders, such as osteonecrosis, bone cancer, and bone metastases. Many pathological processes, including bone loss, metastasis, the proliferation of osteosarcoma cells, and differentiation of osteoblasts and osteoclasts, are under the control of miRNAs. By bringing together the most up-to-date information on the clinical relevance of miRNAs in such diseases, this study hopes to further the study of the biological features of miRNAs in bone disorders and explore their potential as a therapeutic target.

Bone Cells Metabolic Changes Induced by Ageing

Bone is a living organ that exhibits active metabolic processes, presenting constant bone formation and resorption. The bone cells that maintain local homeostasis are osteoblasts, osteoclasts, osteocytes and bone marrow stem cells, their progenitor cells. Osteoblasts are the main cells that govern bone formation, osteoclasts are involved in bone resorption, and osteocytes, the most abundant bone cells, also participate in bone remodeling. All these cells have active metabolic activities, are interconnected and influence each other, having both autocrine and paracrine effects. Ageing is associated with multiple and complex bone metabolic changes, some of which are currently incompletely elucidated. Ageing causes important functional changes in bone metabolism, influencing all resident cells, including the mineralization process of the extracellular matrix. With advancing age, a decrease in bone mass, the appearance of specific changes in the local microarchitecture, a reduction in mineralized components and in load-bearing capacity, as well as the appearance of an abnormal response to different humoral molecules have been observed. The present review points out the most important data regarding the formation, activation, functioning, and interconnection of these bone cells, as well as data on the metabolic changes that occur due to ageing.

Shared mechanisms and crosstalk of COVID-19 and osteoporosis via vitamin D

Recently accumulated evidence implicates a close association of vitamin D (VitD) insufficiency to the incidence and clinical manifestations of the COVID-19 caused by severe acute respiratory syndrome coronavirus-2 (SARS-COV-2). Populations with insufficient VitD including patients with osteoporosis are more susceptible to SARS-COV-2 infection and patients with COVID-19 worsened or developed osteoporosis. It is currently unknown, however, whether osteoporosis and COVID-19 are linked by VitD insufficiency. In this study, 42 common targets for VitD on both COVID-19 and osteoporosis were identified among a total of 243 VitD targets. Further bioinformatic analysis revealed 8 core targets (EGFR, AR, ESR1, MAPK8, MDM2, EZH2, ERBB2 and MAPT) in the VitD-COVID-19-osteoporosis network. These targets are involved in the ErbB and MAPK signaling pathways critical for lung fibrosis, bone structural integrity, and cytokines through a crosstalk between COVID-19 and osteoporosis via the VitD-mediated conventional immune and osteoimmune mechanisms. Molecular docking confirmed that VitD binds tightly to the predicted targets. These findings support that VitD may target common signaling pathways in the integrated network of lung fibrosis and bone structural integrity as well as the immune systems. Therefore, VitD may serve as a preventive and therapeutic agent for both COVID-19 and osteoporosis.

The role of circadian rhythm in osteoporosis; a review

Osteoporosis is characterized by a high incidence rate, with significant effects on people’s lives. The underlying mechanisms are complex, with no treatments for the condition. Recent studies have indicated that melatonin can be used to treat osteoporosis by promoting osteoblast proliferation and differentiation, and inhibiting osteoclast differentiation. Specifically, in vivo mechanisms are initiated by stabilizing biological rhythms in bone tissue. In healthy organisms, these biological rhythms are present in bone tissue, and are characterized by bone formation during the day, and bone resorption at night. When this rhythm is disrupted, osteoporosis occurs. Thus, taking appropriate medication at different times of the day could produce different effects on osteoporosis rhythms. In this review, we characterized these processes, and provided treatments and management strategies for individuals with osteoporosis.

Inhibition of miR‑98‑5p promotes high glucose‑induced suppression of preosteoblast proliferation and differentiation via the activation of the PI3K/AKT/GSK3β signaling pathway by targeting BMP2

Osteoporosis (OP) is a bone metabolic disease, in which low bone mass and the microarchitectural deterioration of bone tissue contribute to the fragility of bones and increase the risk of fracture. The aim of the present study was to determine the role of microRNA (miR)-98-5p in high glucose (HG)-induced preosteoblasts. HG was used to induce preosteoblasts treated in a differentiation medium to establish an in vitro OP model. Next, miR-98-5p expression was determined using reverse transcription-quantitative PCR. Following the transfection of an miR-98-5p inhibitor into HG-treated osteoblasts, cell viability was assessed using a Cell Counting Kit-8 assay, while alkaline phosphatase (ALP) activity, differentiation ability and the expression of differentiation-regulated genes osteocalcin and osteopontin were measured using the corresponding ALP, Alizarin red staining, reverse transcription-quantitative PCR and western blotting assays. The association between miR-98-5p and the PI3K/AKT/GSK3β signaling pathway was determined using western blotting. Next, the binding relationship between miR-98-5p and bone morphogenetic protein 2 (BMP2) was predicted and verified, and the role of BMP2 in the regulation of the PI3K/AKT/GSK3β signaling pathway was explored using western blotting. The results revealed that miR-98-5p expression was upregulated in HG-induced osteoblasts, and the inhibition of miR-98-5p resulted in enhanced cell viability, alkaline phosphatase activity and differentiation in osteoblasts following HG induction. It was also discovered that miR-98-5p inhibition activated PI3K/AKT/GSK3β signaling, while knockdown of BMP2, which binds to miR-98-5p, enhanced the activation of this signaling pathway and the differentiation ability of osteoblasts. In conclusion, the findings of the present study suggested that the inhibition of miR-98-5p expression may activate PI3K/AKT/GSK3β signaling to promote HG-induced suppression of preosteoblast viability and differentiation by targeting BMP2, which provides a novel insight into future potential molecular markers for OP treatment.

MiR-27a-3p binds to TET1 mediated DNA demethylation of ADCY6 regulates breast cancer progression via epithelial-mesenchymal transition

Introduction

Adenylyl cyclase isoform 6 (ADCY6) is a member of membrane-bound adenylate cyclase family that converts adenosine triphosphate (ATP) into cAMP and pyrophosphate. An increasing number of researchers have studied the role of ADCY6 in cancer. However, its specific role in breast cancer remains unknown.

Methods

Bioinformatics and clinical data were used to analyse the expression of ADCY6 in breast cancer. ADCY6 DNA methylation was analysed using DNA methylation-specific PCR and Bisulfite Sanger sequencing. Using lentiviral stable miRNA transfection together with cell biology functional assays and gene expression/target analysis, we investigated the interaction between miR-27a-3p, TET1 and ADCY6 in breast cancer.

Results

We found that ADCY6 is expressed at low levels in breast cancer and leads to increases in the proliferation, invasion and migration of breast cancer cells. The low expression of ADCY6 is due to the lower demethylation of ten-eleven translocation methylcytosine dioxygenase 1 (TET1), and the methylation of ADCY6 can be altered by TET1. More importantly, bioinformatics analysis showed that TET1 is regulated by miR-27a-3p and regulates the methylation of ADCY6 to affect the EMT process of breast cancer cells, thereby affecting the malignant biological behaviour of breast cancer.

Conclusions

Our study demonstrates that the methylation modification of ADCY6 is regulated by TET1 and leads to ADCY6 activation. miR-27a-3p negatively regulates the expression of TET1 and affects the EMT process of breast cancer through ADCY6, thereby promoting the malignant biological behaviour of breast cancer. Our results may provide new research ideas and directions for DNA methylation and EMT changes in breast cancer.

N,N-Dimethylformamide inhibits high glucose-induced osteoporosis via attenuating MAPK and NF-κB signalling

Aims

The role of N,N-dimethylformamide (DMF) in diabetes-induced osteoporosis (DM-OS) progression remains unclear. Here, we aimed to explore the effect of DMF on DM-OS development.

Methods

Diabetic models of mice, RAW 264.7 cells, and bone marrow macrophages (BMMs) were established by streptozotocin stimulation, high glucose treatment, and receptor activator of nuclear factor-κB ligand (RANKL) treatment, respectively. The effects of DMF on DM-OS development in these models were examined by micro-CT analysis, haematoxylin and eosin (H&E) staining, osteoclast differentiation of RAW 264.7 cells and BMMs, H&E and tartrate-resistant acid phosphatase (TRAP) staining, enzyme-linked immunosorbent assay (ELISA) of TRAP5b and c-terminal telopeptides of type 1 (CTX1) analyses, reactive oxygen species (ROS) analysis, quantitative reverse transcription polymerase chain reaction (qRT-PCR), Cell Counting Kit-8 (CCK-8) assay, and Western blot.

Results

The established diabetic mice were more sensitive to ovariectomy (OVX)-induced osteoporosis, and DMF treatment inhibited the sensitivity. OVX-treated diabetic mice exhibited higher TRAP5b and c-terminal telopeptides of type 1 (CTX1) levels, and DMF treatment inhibited the enhancement. DMF reduced RAW 264.7 cell viability. Glucose treatment enhanced the levels of TRAP5b, cathepsin K, Atp6v0d2, and H⁺-ATPase, ROS, while DMF reversed this phenotype. The glucose-increased protein levels were inhibited by DMF in cells treated with RANKL. The expression levels of antioxidant enzymes Gclc, Gclm, Ho-1, and Nqo1 were upregulated by DMF. DMF attenuated high glucose-caused osteoclast differentiation by targeting mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signalling in BMMs.

Conclusion

DMF inhibits high glucose-induced osteoporosis by targeting MAPK and NF-κB signalling.

Cite this article: Bone Joint Res 2022;11(4):200–209.

Alendronate Enhances Functional Recovery after Spinal Cord Injury

Spinal cord injury is a destructive disease characterized by motor/sensory dysfunction and severe inflammation. Alendronate is an anti-inflammatory molecule and may therefore be of benefit in the treatment of the inflammation associated with spinal cord injury. This study aimed to evaluate whether alendronate attenuates motor/sensory dysfunction and the inflammatory response in a thoracic spinal cord clip injury model. Alendronate was intraperitoneally administered at 1 mg/kg/day or 5 mg/kg/day from day (D) 0 to 28 post-injury (PI). The histopathological evaluation showed an alleviation of the inflammatory response, including the infiltration of inflammatory cells, and a decrease in gliosis. Alendronate also led to reductions in the levels of inflammation-related molecules, including mitogen-activated protein kinase, p53, pro-inflammatory cytokines, and pro-inflammatory mediators. Neuro-behavioral assessments, including the Basso, Beattie, and Bresnahan scale for locomotor function, the von Frey filament test, the hot plate test, and the cold stimulation test for sensory function, and the horizontal ladder test for sensorimotor function improved significantly in the alendronate-treated group at D28PI. Taken together, these results suggest that alendronate treatment can inhibit the inflammatory response in spinal cord injury thus improving functional responses.

Fucoidan (Undaria pinnatifida)/Polydopamine Composite-Modified Surface Promotes Osteogenic Potential of Periodontal Ligament Stem Cells

Fucoidan, a marine-sulfated polysaccharide derived from brown algae, has been recently spotlighted as a natural biomaterial for use in bone formation and regeneration. Current research explores the osteoinductive and osteoconductive properties of fucoidan-based composites for bone tissue engineering applications. The utility of fucoidan in a bone tissue regeneration environment necessitates a better understanding of how fucoidan regulates osteogenic processes at the molecular level. Therefore, this study designed a fucoidan and polydopamine (PDA) composite-based film for use in a culture platform for periodontal ligament stem cells (PDLSCs) and explored the prominent molecular pathways induced during osteogenic differentiation of PDLSCs through transcriptome profiling. Characterization of the fucoidan/PDA-coated culture polystyrene surface was assessed by scanning electron microscopy and X-ray photoelectron spectroscopy. The osteogenic differentiation of the PDLSCs cultured on the fucoidan/PDA composite was examined through alkaline phosphatase activity, intracellular calcium levels, matrix mineralization assay, and analysis of the mRNA and protein expression of osteogenic markers. RNA sequencing was performed to identify significantly enriched and associated molecular networks. The culture of PDLSCs on the fucoidan/PDA composite demonstrated higher osteogenic potency than that on the control surface. Differentially expressed genes (DEGs) (n = 348) were identified during fucoidan/PDA-induced osteogenic differentiation by RNA sequencing. The signaling pathways enriched in the DEGs include regulation of the actin cytoskeleton and Ras-related protein 1 and phosphatidylinositol signaling. These pathways represent cell adhesion and cytoskeleton organization functions that are significantly involved in the osteogenic process. These results suggest that a fucoidan/PDA composite promotes the osteogenic potential of PDLSCs by activation of critical molecular pathways.

Approaches Toward Targeting Matrix Metalloproteases for Prognosis and Therapies in Gynecological Cancer: MicroRNAs as a Molecular Driver

Gene expression can be regulated by small non-coding RNA molecules like microRNAs (miRNAs) which act as cellular mediators necessary for growth, differentiation, proliferation, apoptosis, and metabolism. miRNA deregulation is often observed in many human malignancies, acting both as tumor-promoting and suppressing, and their abnormal expression is linked to unrestrained cellular proliferation, metastasis, and perturbation in DNA damage as well as cell cycle. Matrix Metalloproteases (MMPs) have crucial roles in both growth, and tissue remodeling in normal conditions, as well as in promoting cancer development and metastasis. Herein, we outline an integrated interactive study involving various MMPs and miRNAs and also feature a way in which these communications impact malignant growth, movement, and metastasis. The present review emphasizes on important miRNAs that might impact gynecological cancer progression directly or indirectly via regulating MMPs. Additionally, we address the likely use of miRNA-mediated MMP regulation and their downstream signaling pathways towards the development of a potential treatment of gynecological cancers.

Human Umbilical Cord Wharton Jelly Cells Treatment Prevents Osteoporosis Induced by D-Galactose

METHODS

Sixteen male mice were randomly divided into 4 groups: control (ordinary feeding), D-gal (D-galactose) group, D-gal + MSC (human umbilical cord Wharton jelly cells), and D-gal + MSC-TNFα groups. Except for the control group (fed with same amount of saline solution), other mice received gastric feeding of 250 mg/kg D-galactose every day for 8 weeks. TNFα (10 ng/mL for 24 h) cocultured or noncocultured HUCWJCs (5 × 10⁵) were suspended in 0.1 ml of sterile PBS and injected into tail veins every other week in D-gal + MSC-TNFα and D-gal + MSC groups, respectively, and only 0.1 ml of sterile PBS for control and D-gal groups. The bone mass was detected by qPCR, ELISA, microcomputed tomography (μCT), and hematoxylin-eosin staining. Proliferation, apoptosis, and differentiation of periosteal-derived osteoblasts (POB) were assessed. Transwell assay and scratch healing were performed to detect POB migration and invasion ability. The effect of HUCWJCs on POB signaling pathway expression was evaluated by immunoblotting.

RESULTS

The malondialdehyde (MDA) in serum was higher and superoxide dismutase (SOD) was lower in the D-gal group compared to the other groups (p < 0.05). Mice in D-gal group showed significantly decreased bone mass when compared to the control group, while HUCWJCs treatment partially rescued the phenotype, as demonstrated by μCT and histology (p < 0.05). Mechanically, HUCWJCs treatment partially promoted proliferation and migration and decreased apoptosis of POB induced by oxidative stress via activating the mitogen-activated protein kinase (MAPK) signaling pathway.

CONCLUSION

HUCWJCs can prevent the progression of osteoporosis by inhibiting oxidative stress, which may act by regulating osteoblasts fate through the MAPK signaling pathway.

Mechanosensitive miR-100 coordinates TGFβ and Wnt signaling in osteocytes during fluid shear stress

Organism scale mechanical forces elicit cellular scale changes through coordinated regulation of multiple signaling pathways. The mechanisms by which cells integrate signaling to generate a unified biological response remains a major question in mechanobiology. For example, the mechanosensitive response of bone and other tissues requires coordinated signaling by the transforming growth factor beta (TGFβ) and Wnt pathways through mechanisms that are not well‐defined. Here we report a new microRNA‐dependent mechanism that mediates mechanosensitive crosstalk between TGFβ and Wnt signaling in osteocytes exposed to fluid shear stress (FSS). From 60 mechanosensitive microRNA (miRs) identified by small‐RNAseq, miR100 expression is suppressed by in vivo hindlimb loading in the murine tibia and by cellular scale FSS in OCY454 cells. Though FSS activates both TGFβ and Wnt signaling in osteocytes, only TGFβ represses miR‐100 expression. miR‐100, in turn, antagonizes Wnt signaling by targeting and inhibiting expression of Frizzled receptors (FZD5/FZD8). Accordingly, miR‐100 inhibition blunts FSS‐ and TGFβ‐inducible Wnt signaling. Therefore, our results identify FSS‐responsive miRNAs in osteocytes, including one that integrates the mechanosensitive function of two essential signaling pathways in the osteoanabolic response of bone to mechanical load.

Contribution of miRNAs and lncRNAs in osteogenesis and related disorders

Non-coding RNAs have been found to regulate several developmental processes among them is osteogenesis. Although these transcripts have several distinct classes, two classes i.e. microRNAs and long non-coding RNAs have attained more attention. These transcripts regulate intramembranous as well as endochondral ossification processes. The effects of microRNAs on osteogenesis are mostly mediated through modulation of Wnt/β-catenin and TGFβ/BMP pathways. Long non-coding RNAs can directly affect expression of these pathways or osteogenic transcription factors. Moreover, they can serve as a molecular sponge for miRNAs. MALAT1/miR-30, MALAt1/miR-214, LEF1-AS1/miR-24-3p, MCF2L-AS1/miR-33a, MSC-AS1/miR-140-5p and KCNQ1OT1/miR-214 are examples of such kind of interaction between lncRNAs and miRNAs in the context of osteogenesis. In the current paper, we explain these two classes of non-coding RNAs in the osteogenesis and related disorders.

Recent Progresses in the Treatment of Osteoporosis

Osteoporosis (OP) is a chronic bone disease characterized by aberrant microstructure and macrostructure of bone, leading to reduced bone mass and increased risk of fragile fractures. Anti-resorptive drugs, especially, bisphosphonates, are currently the treatment of choice in most developing countries. However, they do have limitations and adverse effects, which, to some extent, helped the development of anabolic drugs such as teriparatide and romosozumab. In patients with high or very high risk for fracture, sequential or combined therapies may be considered with the initial drugs being anabolic agents. Great endeavors have been made to find next generation drugs with maximal efficacy and minimal toxicity, and improved understanding of the role of different signaling pathways and their crosstalk in the pathogenesis of OP may help achieve this goal. Our review focused on recent progress with regards to the drug development by modification of Wnt pathway, while other pathways/molecules were also discussed briefly. In addition, new observations made in recent years in bone biology were summarized and discussed for the treatment of OP.

Role of Exosomal MicroRNAs and Their Crosstalk with Oxidative Stress in the Pathogenesis of Osteoporosis

Osteoporosis (OP) is an aging-related disease involving permanent bone tissue atrophy. Most patients with OP show high levels of oxidative stress (OS), which destroys the microstructure of bone tissue and promotes disease progression. Exosomes (exos) help in the delivery of microRNAs (miRNAs) and allow intercellular communication. In OP, exosomal miRNAs modulate several physiological processes, including the OS response. In the present review, we aim to describe how exosomal miRNAs and OS contribute to OP. We first summarize the relationship of OS with OP and then detail the features of exos along with the functions of exo-related miRNAs. Further, we explore the interplay between exosomal miRNAs and OS in OP and summarize the functional role of exos in OP. Finally, we identify the advantages of exo-based miRNA delivery in treatment strategies for OP. Our review seeks to improve the current understanding of the mechanism underlying OP pathogenesis and lay the foundation for the development of novel theranostic approaches for OP.

Longitudinal Changes of Circulating miRNAs During Bisphosphonate and Teriparatide Treatment in an Animal Model of Postmenopausal Osteoporosis

MicroRNAs regulate bone homeostasis, and circulating microRNAs have been proposed as novel bone biomarkers. The effect of anti-osteoporotic treatment on circulating microRNAs has not been described in detail. Therefore, we performed a comprehensive analysis of microRNA serum levels in ovariectomized (OVX) and sham-operated (SHAM) rats over 12 weeks of antiresorptive or osteoanabolic treatment. Forty-two Sprague Dawley rats underwent SHAM surgery (n = 10) or ovariectomy (n = 32). After 8 weeks, OVX rats were randomized to antiresorptive treatment with zoledronate (n = 11), osteoanabolic treatment with teriparatide (n = 11), or vehicle treatment (n = 10). Serum samples were collected at weeks 8, 12, 16, and 20 after surgery. A total of 91 microRNAs were analyzed by RT-qPCR in serum samples collected at week 20. Based on the results, 29 microRNAs were selected for longitudinal analysis at all four study time points. Changes in bone mineral density and microstructure were followed up by in vivo micro-CT and ex vivo nano-CT. Ovariectomy resulted in the loss of trabecular bone, which was reversed by osteoanabolic and antiresorptive treatment. Differential expression analysis identified 11 circulating miRNAs that were significantly regulated after treatment. For example, miR-107 and miR-31-5p increased in vehicle-treated OVX animals, whereas they decreased during teriparatide treatment. Additional miRNAs were identified that showed significant correlations to bone microstructure or bone miRNA expression, including miR-203a-3p, which exhibited a significant negative correlation to vertebral and tibial trabecular bone volume fraction (%). Longitudinal analysis confirmed eight microRNAs with significant changes in serum over time that were prevented by teriparatide and zoledronate treatment (miR-34a-5p, miR-31-5p, miR-30d-3p, miR-378a-5p) or teriparatide treatment only (miR-375-3p, miR-183-5p, miR-203a-3p, miR-203b-3p). Gene target network analysis identified WNT and Notch signaling as the main signaling pathways controlled by these miRNAs. Thus, ovariectomy results in time-dependent deregulation of circulating miRNAs compared with SHAM animals. Anti-osteoporotic treatments can rescue this effect, showing that bone-related miRNAs might act as novel biomarkers for treatment monitoring. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

SPTBN1 Prevents Primary Osteoporosis by Modulating Osteoblasts Proliferation and Differentiation and Blood Vessels Formation in Bone

Osteoporosis is a common systemic skeletal disorder that leads to increased bone fragility and increased risk of fracture. Although βII-Spectrin (SPTBN1) has been reported to be involved in the development of various human cancers, the function and underlying molecular mechanisms of SPTBN1 in primary osteoporosis remain unclear. In this study, we first established a primary osteoporosis mouse model of senile osteoporosis and postmenopausal osteoporosis. The results showed that the expression of SPTBN1 was significantly downregulated in primary osteoporosis mice model compared with the control group. Furthermore, silencing of SPTBN1 led to a decrease in bone density, a small number of trabecular bones, wider gap, decreased blood volume fraction and number of blood vessels, as well as downregulation of runt-related transcription factor 2 (Runx2), Osterix (Osx), Osteocalcin (Ocn), and vascular endothelial growth factor (VEGF) in primary osteoporosis mice model compared with the control group. Besides, the silencing of SPTBN1 inhibited the growth and induced apoptosis of mouse pre-osteoblast MC3T3-E1 cells compared with the negative control group. Moreover, the silencing of SPTBN1 significantly increased the expression of TGF-β, Cxcl9, and the phosphorylation level STAT1 and Smad3 in MC3T3-E1 cells compared with the control group. As expected, overexpression of SPTBN1 reversed the effect of SPTBN1 silencing in the progression of primary osteoporosis both in vitro and in vivo. Taken together, these results suggested that SPTBN1 suppressed primary osteoporosis by facilitating the proliferation, differentiation, and inhibition of apoptosis in osteoblasts via the TGF-β/Smad3 and STAT1/Cxcl9 pathways. Besides, overexpression of SPTBN1 promoted the formation of blood vessels in bone by regulating the expression of VEGF. This study, therefore, provided SPTBN1 as a novel therapeutic target for osteoporosis.

Uncovering the Key miRNAs and Targets of the Liuwei Dihuang Pill in Diabetic Nephropathy-Related Osteoporosis based on Weighted Gene Co-Expression Network and Network Pharmacology Analysis

BACKGROUND

Diabetic nephropathy-related osteoporosis (DNOP) is the most common comorbid bone metabolic disorder associated with diabetes mellitus (DM). The Liuwei Dihuang Pill (LWD) is a traditional Chinese herbal medicine widely used to treat diabetic complications, including diabetic nephropathy (DN). This study aimed to identify the biomarkers of the mechanisms of DNOP in LWD with systems biology approaches.

METHODS

Herein, we performed an integrated analysis of the GSE51674 and GSE63446 datasets from the GEO database via weighted gene co-expression network and network pharmacology (WGCNA) analysis. In addition, a network pharmacology approach, including bioactive compounds, was used with oral bioavailability (OB) and drug-likeness (DL) evaluation. Next, target prediction, functional enrichment analysis, network analysis, and virtual docking were used to investigate the mechanisms of LWD in DNOP.

RESULTS

WGCNA successfully identified 63 DNOP-related miRNAs. Among them, miR-574 was significantly upregulated in DN and OP samples. A total of 117 targets of 22 components associated with LWD in DNOP were obtained. The cellular response to nitrogen compounds, the AGE-RAGE signaling pathway in diabetic complications, and the MAPK signaling pathway were related to the main targets. Network analysis showed that kaempferol and quercetin were the most significant components. MAPK1 was identified as a potential target of miR-574 and the hub genes in the protein-protein interaction (PPI) network. The docking models demonstrated that kaempferol and quercetin had a strong binding affinity for Asp 167 of MAPK1.

CONCLUSION

This study demonstrated that miR-574 may play important roles in DNOP, and the therapeutic effects of kaempferol and quercetin on LWD in DNOP might be mediated by miR-574 by targeting MAPK1. Our results provide new perspectives for further studies on the anti-DNOP mechanism of LWD.

Alendronate promotes the gene expression of extracellular matrix mediated by SP-1/SOX-9

BACKGROUND AND PURPOSE

Osteoarthritis (OA) is a disease with significant degenerative changes of articular cartilage, which is reported to be closely related to the integrity of chondrocytes extracellular matrix (ECM). Alendronate belongs to the family of bisphosphonates with promising cartilage repair function. In the present study, the effects of Alendronate on the gene expression of chondrocytes ECM and the potential mechanism will be investigated to explore the potential therapeutic property of Alendronate on OA.

METHODS

Human SW1353 chondrocytes were stimulated with 1 and 2 μM Alendronate for 12 h. The gene expression of Col2α1, COL9α2, and Acan in the treated chondrocytes was determined by qRT-PCR. QRT-PCR and western blot analysis were used to evaluate the expression level of SOX-9 in the treated chondrocytes. The expression level of SP-1 was checked by qRT-PCR and immunostaining. SiRNA against SP-1 was transfected into chondrocytes to knockdown the expression of SP-1. The levels of p-ERK1/2 and total ERK1/2 were examined using western blot analysis. TNF-α was used to induce an OA-like in vitro model in the chondrocytes for therapeutic evaluations.

RESULTS

Treatment with Alendronate increased the levels of ECM related genes (Col2α1, COL9α2, and Acan) in a dose-dependent manner through increasing the expression of SOX-9, a central regulator of ECM genes. Additionally, our findings demonstrate that the effects of Alendronate in the expression of SOX-9 are mediated by SP-1 as silencing of SP-1 abolished these effects. Notably, Alendronate increased the phosphorylation of ERK1/2 and inhibition of ERK1/2 using its specific inhibitor U0126 blocked the expression of SP-1. Finally, we found that treatment with Alendronate could rescue TNF-α-induced reduction of Col2α1, COL9α2, Acan and SOX-9.

CONCLUSION

Our data indicated that Alendronate might promote the gene expression of extracellular matrix through SOX-9 mediated by the ERK1/2/SP1 signaling pathway.

The role of microRNAs in bone development

Epigenetic regulation is critical for proper bone development. Evidence from a large body of published literature informs us that microRNAs (miRNAs) are important epigenetic factors that control many aspects of bone development, homeostasis, and repair processes. These small non-coding RNAs function at the post-transcriptional level to suppress expression of specific target genes. Many target genes may be affected by one miRNA resulting in alteration in cellular pathways and networks. Therefore, changes in levels or activity of a specific miRNA (e.g. via genetic mutations, disease scenarios, or by over-expression or inhibition strategies in vitro or in vivo) can lead to substantial changes in cell processes including proliferation, metabolism, apoptosis and differentiation. In this review, Section 1 briefly covers general background information on processes that control bone development as well as the biogenesis and function of miRNAs. In Section 2, we discuss the importance of miRNAs in skeletal development based on findings from in vivo mouse models and human clinical reports. Section 3 focuses on describing more recent data from the last three years related to miRNA regulation of osteoblast differentiation in vitro. Some of these studies also involve utilization of an in vivo rodent model to study the effects of miRNA modulation in scenarios of osteoporosis, bone repair or ectopic bone formation. In Section 4, we provide some recent information from studies analyzing the potential of miRNA-mediated crosstalk in bone and how exosomes containing miRNAs from one bone cell may affect the differentiation or function of another bone cell type. We then conclude by summarizing where the field currently stands with respect to miRNA-mediated regulation of osteogenesis and how information gained from developmental processes can be instructive in identifying potential therapeutic miRNA targets for the treatment of certain bone conditions.

circRNA expression pattern and ceRNA network in the pathogenesis of aseptic loosening after total hip arthroplasty

Increasing evidence has demonstrated that circular RNA (circRNA) exerts important function in the pathogenesis of some diseases. While, the contributions of circRNAs to aseptic loosening after total hip arthroplasty (THA) remain largely unknown. Our research is to explore the differentially expressed circRNAs (DEcircRNAs) and elucidate complex regulated mechanism of circRNAs in aseptic loosening. The DEcircRNAs were identified by RNA sequencing (RNA-seq) analysis. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was adopted to corroborate these DEcircRNAs. The potential function of circRNAs in aseptic loosening tissue was identified by competing endogenous RNA (ceRNA) analysis. Enrichment analysis was performed for target mRNAs and host genes of the DEcircRNAs by Gene Oncology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). 257 DEcircRNAs were obtained from RNA-seq results. Following the RT-qPCR corroboration, 6 circRNAs (hsa_circ_0007482, hsa_circ_0005232, hsa_circ_0000994, hsa_circ_0000690, hsa_circ_0058092 and hsa_circ_0004496) were selected for further analysis. By circRNA-miRNA and miRNA-mRNA prediction, 6 circRNAs, 138 miRNAs and 1667 mRNAs were identified. Then, circRNA-miRNA-mRNA network was established. The result of GO and KEGG enrichment analysis suggested that the circRNAs were related with some biological functions and pathways of aseptic loosening. A novel pathogenesis and treatment strategy about aseptic loosening after THA was revealed from our study of circRNA-miRNA-mRNA network.

Melatonin inhibits RANKL‑induced osteoclastogenesis through the miR‑882/Rev‑erbα axis in Raw264.7 cells

Melatonin, secreted in a typical diurnal rhythm pattern, has been reported to prevent osteoporosis; however, its role in osteoclastogenesis remains unclear. In the present study, the ability of melatonin to inhibit receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and the associated mechanism were investigated. Raw264.7 cells were cultured with RANKL (100 ng/ml) and macrophage colony-stimulating factor (M-CSF; 30 ng/ml) for 7 days, and tartrate-resistant acid phosphatase (TRAP) staining was used to detect osteoclastogenesis following treatment with melatonin. In addition, the effect of melatonin on cathepsin K and microRNA (miR)-882 expression was investigated via western blotting and reverse transcription-quantitative PCR. Melatonin significantly inhibited RANKL-induced osteoclastogenesis in Raw264.7 cells. From bioinformatics analysis, it was inferred that nuclear receptor subfamily 1 group D member 1 (NR1D1/Rev-erbα) may be a target of miR-882. In vitro, melatonin upregulated Rev-erbα expression and downregulated miR-882 expression in the osteoclastogenesis model. Rev-erbα overexpression boosted the anti-osteoclastogenesis effects of melatonin, whereas miR-882 partially diminished these effects. The present results indicated that the miR-882/Rev-erbα axis may serve a vital role in inhibiting osteoclastogenesis following RANKL and M-CSF treatment, indicating that Rev-erbα agonism or miR-882 inhibition may represent mechanisms through which melatonin prevents osteoporosis.

A Review of the Pharmacological Properties of Psoralen

Psoralen is the principal bioactive component in the dried fruits of Cullen corylifolium (L.) Medik (syn. Psoralea corylifolia L), termed "Buguzhi" in traditional Chinese medicine (TCM). Recent studies have demonstrated that psoralen displays multiple bioactive properties, beneficial for the treatment of osteoporosis, tumors, viruses, bacteria, and inflammation. The present review focuses on the research evidence relating to the properties of psoralen gathered over recent years. Firstly, multiple studies have demonstrated that psoralen exerts strong anti-osteoporotic effects via regulation of osteoblast/osteoclast/chondrocyte differentiation or activation due to the participation in multiple molecular mechanisms of the wnt/β-catenin, bone morphogenetic protein (BMP), inositol-requiring enzyme 1 (IRE1)/apoptosis signaling kinase 1 (ASK1)/c-jun N-terminal kinase (JNK) and the Protein Kinase B(AKT)/activator protein-1 (AP-1) axis, and the expression of miR-488, peroxisome proliferators-activated receptor-gamma (PPARγ), and matrix metalloproteinases (MMPs). In addition, the antitumor properties of psoralen are associated with the induction of ER stress-related cell death via enhancement of PERK: Pancreatic Endoplasmic Reticulum Kinase (PERK)/activating transcription factor (ATF), 78kD glucose-regulated protein (GRP78)/C/EBP homologous protein (CHOP), and 94kD glucose-regulated protein (GRP94)/CHOP signaling, and inhibition of P-glycoprotein (P-gp) or ATPase that overcomes multidrug resistance. Furthermore, multiple articles have shown that the antibacterial, anti-inflammatory and neuroprotective effects of psoralen are a result of its interaction with viral polymerase (Pol), destroying the formation of biofilm, and regulating the activation of tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-β), interleukin 4/5/6/8/12/13 (IL-4/5/6/8/12/13), GATA-3, acetylcholinesterase (AChE), and the hypothalamic-pituitary-adrenal (HPA) axis. Finally, the toxic effects and mechanisms of action of psoralen have also been reviewed.

The Role of Micro RNA and Long-Non-Coding RNA in Osteoporosis

Osteoporosis is a major concern worldwide and can be attributed to an imbalance between osteoblastic bone formation and osteoclastic bone resorption due to the natural aging process. Heritable factors account for 60-80% of optimal bone mineralization; however, the finer details of pathogenesis remain to be elucidated. Micro RNA (miRNA) and long-non-coding RNA (lncRNA) are two targets that have recently come into the spotlight due to their ability to control gene expression at the post-transcriptional level and provide epigenetic modification. miRNAs are a class of non-coding RNAs that are approximately 18-25 nucleotides long. It is thought that up to 60% of human protein-coding genes may be regulated by miRNAs. They have been found to regulate gene expression that controls osteoblast-dependent bone formation and osteoclast-related bone remodeling. lncRNAs are highly structured RNA transcripts longer than 200 nucleotides that do not translate into proteins. They have very complex secondary and tertiary structures and the same degradation processes as messenger RNAs. The fact that they have a rapid turnover is due to their sponge function in binding the miRNAs that lead to a degradation of the lncRNA itself. They can act as signaling, decoy, and framework molecules, or as primers. Current evidence suggests that lncRNAs can act as chromatin and transcriptional as well as post-transcriptional regulators. With regards to osteoporosis, lncRNA is thought to be involved in the proliferation, apoptosis, and inflammatory response of the bone. This review, which is based on a systematic appraisal of the current literature, provides current molecular and genetic opinions on the roles of miRNAs and lncRNAs in osteoporosis. Further research into the epigenetic modification and the regulatory roles of these molecules will bring us closer to potential disease-modifying treatment for osteoporosis. However, more issues regarding the detailed actions of miRNAs and lncRNAs in osteoporosis remain unknown and controversial and warrant future investigation.

Comparative profiles of DNA methylation and differential gene expression in osteocytic areas from aged and young mice

Altered DNA methylation upon ageing may result in many age-related diseases such as osteoporosis. However, the changes in DNA methylation that occur in cortical bones, the major osteocytic areas, remain unknown. In our study, we extracted total DNA and RNA from the cortical bones of 6-month-old and 24-month-old mice and systematically analysed the differentially methylated regions (DMRs), differentially methylated promoters (DMPs) and differentially expressed genes (DEGs) between the mouse groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of the DMR-related genes revealed that they were mainly associated with metabolic signalling pathways, including glycolysis, fatty acid and amino acid metabolism. Other genes with DMRs were related to signalling pathways that regulate the growth and development of cells, including the PI3K-AKT, Ras and Rap1 signalling pathways. The gene expression profiles indicated that the DEGs were mainly involved in metabolic pathways and the PI3K-AKT signalling pathway, and the profiles were verified through real-time quantitative PCR (RT-qPCR). Due to the pivotal roles of the affected genes in maintaining bone homeostasis, we suspect that these changes may be key factors in age-related bone loss, either together or individually. Our study may provide a novel perspective for understanding the osteocyte and its relationship with osteoporosis during ageing. SIGNIFICANCE OF THE STUDY: Our study identified age-related changes in gene expressions in osteocytic areas through whole-genome bisulfite sequencing (WGBS) and RNA-seq, providing new theoretical foundations for the targeted treatment of senile osteoporosis.

miR-205 regulates bone turnover in elderly female patients with type 2 diabetes mellitus through targeted inhibition of Runx2

The present study aimed to explore the expression of microribonucleic acid (microRNA) (miR)-205 in bone tissues and serum of elderly female patients with type 2 diabetes mellitus (T2DM) complicated with osteoporosis (OP), and to investigate the effect of miR-205 on osteogenesis/adipogenesis of bone marrow mesenchymal stem cells (BMSCs) and its mechanism in elderly female mice with T2DM + OP. The bone tissues and serum of 24 female patients with T2DM + OP at the Third Affiliated Hospital of Qiqihar Medical University were collected as the research group, while those of 24 healthy people were collected as the control group. The expression level of miR-205 was detected in both groups via reverse transcription-polymerase chain reaction (RT-PCR). Then the elderly female mouse model of T2DM + OP was established as a model group, while normal mice of the same age were used as the control group. The mice in the model and control groups were transfected with miR-205 mimic, negative control (NC)-mimic, miR-205-inhibitor and NC-inhibitor. Alizarin red S (ARS) staining and RT-PCR were conducted after osteogenic induction for 21 days, and oil red O (ORO) staining and RT-PCR were performed after adipogenic induction for 24 days. The overexpression of miR-205 inhibited osteogenic differentiation and promoted adipogenic differentiation of BMSCs in elderly female mice with T2DM + OP, while knockdown of miR-205 promoted osteogenic differentiation and inhibited adipogenic differentiation of BMSCs in elderly female mice with T2DM + OP. In addition, miR-205 was able to directly suppress the expression of its target gene RUNX family transcription factor 2 (Runx2). The expression level of miR-205 was obviously increased in female patients with T2DM + OP and the elderly female mouse model of T2DM + OP. In addition, miR-205 was able to regulate the osteogenic/adipogenic differentiation of BMSCs, and miR-205/Runx2 may be a new method and target for the treatment of female patients with T2DM + OP.

Common and Unique microRNAs in Multiple Carcinomas Regulate Similar Network of Pathways to Mediate Cancer Progression

Cancer is a complex disease with a fatal outcome. Early detection of cancer, by monitoring appropriate molecular markers is very important for its therapeutic management. In this regard, the short non-coding RNA molecules, microRNAs (miRNAs) have shown great promise due to their availability in circulating fluids facilitating non-invasive detection of cancer. In this study, an in silico comparative analysis was performed to identify specific signature miRNAs dysregulated across multiple carcinomas and simultaneously identify unique miRNAs for each cancer type as well. The miRNA-seq data of cancer patient was obtained from GDC portal and their differential expressions along with the pathways regulated by both common and unique miRNAs were analyzed. Our studies show twelve miRNAs commonly dysregulated across seven different cancer types. Interestingly, four of those miRNAs (hsa-mir-210, hsa-mir-19a, hsa-mir-7 and hsa-mir-3662) are already reported as circulatory miRNAs (circRNAs); while, the miR-183 cluster along with hsa-mir-93 have been found to be incorporated in exosomes signifying the importance of the identified miRNAs for their use as prospective, non-invasive biomarkers. Further, the target mRNAs and pathways regulated by both common and unique miRNAs were analyzed, which interestingly had significant commonality. This suggests that miRNAs that are commonly de-regulated and specifically altered in multiple cancers might regulate similar pathways to promote cancer. Our data is of significance because we not only identify a set of common and unique miRNAs for multiple cancers but also highlight the pathways regulated by them, which might facilitate the development of future non-invasive biomarkers conducive for early detection of cancers.

Pathogenesis of Osteoporosis

Osteoporosis is a condition where bone resorption exceeds bone formation leading to degeneration. With an aging population, the prevalence of osteoporosis is on the rise. Although advances in the field have made progress in targeting the mechanisms of the disease, the efficacy of current treatments remains limited and is complicated by unexpected side effects. Therefore, to overcome this treatment gap, new approaches are needed to identify and elucidate the cellular mechanisms mediating the pathogenesis of osteoporosis, which requires a strong understanding of bone biology. This chapter will focus on bone cells (osteoclasts, osteoblasts, and osteocytes) and their role in the bone turnover process in normal physiology and in pathology. With regard to osteoclast function, the regulators and underpinning signaling pathways leading to bone resorption will be discussed. Decreased osteoblastogenesis also contributes to bone deterioration with aging and osteoporosis; hence the factors and signaling pathways mediating osteoblast formation and function will be examined. Osteocytes are mature osteoblasts embedded in bone matrix and act as endocrine cells; their role in bone health and pathology will also be reviewed. In addition, this chapter will explore the emerging role of adipocytes in bone biology and the implications of increased bone marrow fat infiltration with aging on bone degeneration. In conclusion, a greater understanding of the pathogenesis of osteoporosis is of utmost importance in order to develop more effective treatments for osteoporosis and other bone diseases.

Non-coding RNAs in bone remodelling and bone metastasis: Mechanisms of action and translational relevance

Bone metastases are frequent complications in patients with advanced cancer, which can be fatal or may rapidly impede the quality of life of patients. Current treatments for patients with bone metastases are palliative. Therefore, a better understanding of the molecular mechanisms that precede the overt development of skeletal lesions could lead to better therapeutic interventions. In this review, we present evidence that non-coding RNAs (ncRNAs) such as long ncRNAs, microRNAs, and circular RNAs are emerging as master regulators of bone metastasis formation. We highlight potential opportunities for the therapeutic targeting of ncRNAs. Furthermore, we discuss the possibility that ncRNAs may be used as biomarkers in the context of bone metastases, which might provide insight for improving the response to current bone-targeting therapies. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

MicroRNA-182-3p negatively regulates cytokines expression by targeting TLR5M in orange-spotted grouper, Epinephelus coioides

Toll-like receptors (TLRs) as essential pattern recognition receptors in innate immunity, can recognize pathogens and trigger immune response to eliminate invading pathogens. MicroRNAs regulates multiple biological processes by suppressing mRNA translation or resulting in mRNA degradation. MiR-182 has previously been implicated in DNA repair, disease and cancer aspects. The potential role of miR-182-3p in TLR signaling pathway against pathogens is unclear. In this study, we found that the expression of miR-182-3p was up-regulated after Vibrio parahaemolyticus flagellin stimulation in grouper spleen (GS) cells, and negatively correlated with the expression of orange-spotted grouper (Epinephelus coioides) TLR5M (EcTLR5M). Then we found that miR-182-3p could directly target EcTLR5M by using bioinformatic analysis and dual-luciferase reporter assay. Dual-luciferase reporter assay also showed that miR-182-3p down-regulated the wild-type EcTLR5M 3'UTR in luciferase activity rather than the mutant group in HEK 293T cells. We further verified the effect of miR-182-3p on the activation of Nuclear factor-κB (NF-κB) signaling pathway, and found that miR-182-3p inhibitors significantly augmented flagellin-induced NF-κB phosphorylation. Additionally, we also demonstrated that the increased expression of miR-182-3p significantly suppressed the flagellin-induced EcTLR5M, pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) mRNA expression. And the endogenous miR-182-3p knockdown experiments reversely verified the regulatory effect of miR-182-3p. These results suggested that miR-182-3p post-transcriptionally controls EcTLR5M expression and thereby suppresses the expression of pro-inflammatory cytokines. This study is the first to demonstrate that miR-182-3p suppresses pro-inflammatory cytokines expression by regulating the TLR signaling pathway.

MiR-135-5p promotes osteoblast differentiation by targeting HIF1AN in MC3T3-E1 cells

Background

MicroRNAs (miRNAs or miRs) serve crucial roles in the progression of osteoporosis. This study investigated the role and specific molecular mechanism of miR-135-5p in regulating osteoblast differentiation and calcification.

Methods

Bone morphogenetic protein 2 (BMP2) was employed to interfere with the differentiation of MC3T3-E1. Then, miR-135-5p mimic or miR-135-5p inhibitor was transfected into MC3T3-E1, and quantitative RT-PCR was used to measure the expression of miR-135-5p. The expressions of runt-related transcription factor 2 (Runx2), osterix (OSX), osteopontin (OPN), and osteocalcin (OCN) were determined using western blot. Alkaline phosphatase (ALP) activity was measured using an appropriate kit assay. Calcium nodule staining was evaluated with alizarin red staining. A luciferase reporter assay was used to verify the target of miR-135-5p. Hypoxia-inducible factor 1 α inhibitor (HIF1AN) overexpression was applied to investigate its own role in the mechanism and a miR-135-5p rescue experiment was also performed.

Results

Overexpression of miR-135-5p promoted osteogenic differentiation and calcification, as shown by the increase in ALP activity, calcification and osteogenic marker levels, including Runx2, OSX, OPN and OCN. Knockdown of miR-135-5p yielded the opposite results. HIF1AN was confirmed as a direct target of miR-135-5p. HIF1AN overexpression inhibited osteogenic differentiation and calcification while miR-135-5p reversed these effects.

Conclusions

These results indicate that miR-135-5p might have a therapeutic application related to its promotion of bone formation through the targeting of HIF1AN.