Rev-erbα Negatively Regulates Osteoclast and Osteoblast Differentiation through p38 MAPK Signaling Pathway

Fabricating oxygen self-supplying 3D printed bioactive hydrogel scaffold for augmented vascularized bone regeneration

Limited cells and factors, inadequate mechanical properties, and necrosis of defects center have hindered the wide clinical application of bone-tissue engineering scaffolds. Herein, we construct a self-oxygenated 3D printed bioactive hydrogel scaffold by integrating oxygen-generating nanoparticles and hybrid double network hydrogel structure. The hydrogel scaffold possesses the characteristics of extracellular matrix; Meanwhile, the fabricated hybrid double network structure by polyacrylamide and CaCl2-crosslinked sodium carboxymethylcellulose endows the hydrogel favorable compressive strength and 3D printability. Furthermore, the O2 generated by CaO2 nanoparticles encapsulated in ZIF-8 releases steadily and sustainably because of the well-developed microporous structure of ZIF-8, which can significantly promote cell viability and proliferation in vitro, as well as angiogenesis and osteogenic differentiation with the assistance of Zn2+. More significantly, the synergy of O2 and 3D printed pore structure can prevent necrosis of defects center and facilitate cell infiltration by providing cells the nutrients and space they need, which can further induce vascular network ingrowth and accelerate bone regeneration in all areas of the defect in vivo. Overall, this work provides a new avenue for preparing cell/factor-free bone-tissue engineered scaffolds that possess great potential for tissue regeneration and clinical alternative.

The specificities, influencing factors, and medical implications of bone circadian rhythms

Physiological processes within the human body are regulated in approximately 24-h cycles known as circadian rhythms, serving to adapt to environmental changes. Bone rhythms play pivotal roles in bone development, metabolism, mineralization, and remodeling processes. Bone rhythms exhibit cell specificity, and different cells in bone display various expressions of clock genes. Multiple environmental factors, including light, feeding, exercise, and temperature, affect bone diurnal rhythms through the sympathetic nervous system and various hormones. Disruptions in bone diurnal rhythms contribute to the onset of skeletal disorders such as osteoporosis, osteoarthritis and skeletal hypoplasia. Conversely, these bone diseases can be effectively treated when aimed at the circadian clock in bone cells, including the rhythmic expressions of clock genes and drug targets. In this review, we describe the unique circadian rhythms in physiological activities of various bone cells. Then we summarize the factors synchronizing the diurnal rhythms of bone with the underlying mechanisms. Based on the review, we aim to build an overall understanding of the diurnal rhythms in bone and summarize the new preventive and therapeutic strategies for bone disorders.

Cirsilineol inhibits RANKL-induced osteoclast activity and ovariectomy-induced bone loss via NF-κb/ERK/p38 signaling pathways

BACKGROUND

Postmenopausal osteoporosis is a chronic metabolic bone disease caused by excessive osteoclast formation and function. Targeting osteoclast differentiation and activity can modulate bone resorption and alleviate osteoporosis. Cirsilineol, an active constituent of Vestita Wall, has shown numerous biological activities and has been used to treat many metabolic diseases. However, whether cirsilineol inhibits osteoclast activity and prevents postmenopausal osteoporosis still remain unknown.

MATERIALS AND METHODS

Primary bone marrow macrophages (BMMs) and RAW264.7 cells were used. Osteoclast activity was measured by TRAP staining, F-actin staining, and bone resorption assay after BMMs were treated with cirsilineol at concentrations of 0, 1, 2.5 and 5 µM. RT-PCR and western blotting were performed to evaluate the expression of osteoclast-related genes. In addition, female C57BL/6 mice underwent OVX surgery and were treated with cirsilineol (20 mg/kg) to demonstrate the effect of cirsilineol on osteoporosis.

RESULTS

Cirsilineol significantly inhibited receptor activator of nuclear factor-kappa B ligand (RANKL)-induced osteoclast differentiation in a concentration- and time-dependent manner, respectively. Additionally, cirsilineol inhibited F-actin ring formation, thus reducing the activation of bone resorption ability. Cirsilineol suppressed the expression of osteoclast-related genes and proteins via blocking nuclear factor (NF)-κb, ERK, and p38 signaling cascades. More importantly, cirsilineol treatment in mice with osteoporosis alleviated osteoclasts hyperactivation and bone mass loss caused by estrogen depletion.

CONCLUSION

In this study, the protective effect of cirsilineol on osteoporosis has been investigated for the first time. In conclusion, our findings prove the inhibitory effect of cirsilineol on osteoclast activity via NF-κb/ERK/p38 signaling pathways and strongapplication of cirsilineol can be proposed as a potential therapeutic strategy.

Targeting NR1D1 in organ injury: challenges and prospects

Nuclear receptor subfamily 1, group D, member 1 (NR1D1, also known as REV-ERBα) belongs to the nuclear receptor (NR) family, and is a heme-binding component of the circadian clock that consolidates circadian oscillators. In addition to repressing the transcription of multiple clock genes associated with circadian rhythms, NR1D1 has a wide range of downstream target genes that are intimately involved in many physiopathological processes, including autophagy, immunity, inflammation, metabolism and aging in multiple organs. This review focuses on the pivotal role of NR1D1 as a key transcription factor in the gene regulatory network, with particular emphasis on the milestones of the latest discoveries of NR1D1 ligands. NR1D1 is considered as a promising drug target for treating diverse diseases and may contribute to research on innovative biomarkers and therapeutic targets for organ injury-related diseases. Further research on NR1D1 ligands in prospective human trials may pave the way for their clinical application in many organ injury-related disorders.

Genome wide analysis of dexamethasone stimulated mineralization in human dental pulp cells by RNA sequencing

Human dental pulp cells (hDPCs) contain mesenchymal stem cells and are therefore indispensible for reparative dentin formation. Here, we present a pilot study of transcriptomic profiles of mineralized hDPCs isolated from sound human maxillary third molars. We observed altered gene expression of hDPCs between control (dexamethasone free) and experimental (dexamethasone 1 nm) groups. Differential expression analysis revealed up-regulation of several inflammation and mineralization-related genes in the experimental group. After a Gene Ontology analysis for predicting genes involved in biological process, cellular component and molecular function, we found enrichment of genes related to protein binding. Based on the results of Kyoto Encylopedia of Genes and Genomes pathway analysis, it is suggested up-regulated genes in mineralized hDPCs were mostly enriched in the mitogen-activated protein kinase (MAPK) signaling pathway, fluid shear stress and the atherosclerosis signaling pathway, etc. Importantly, Gene Set Enrichment Analysis revealed dexamethasone was positively related to the Janus kinase/signal transducer and activator of transcription, MAPK and Notch signaling pathway. Moreover, it was suggested that dexamethasone regulates signaling pathway in pluripotency of stem cells. Collectively, our work highlights transcriptome level gene regulation and intercellular interactions in mineralized hDPCs. The database produced in the present study paves the way for further investigations looking to explore genes that are involved in dental pulp cells mineralization.

Posttranslational Modifications of Rev-Erbα Protein and Abnormal Inflammatory Response in Gastric Cancer

We reported that Rev-erbα, a transcriptional repressor, is reduced in human gastric cancer and that it inhibits glycolysis in cultured gastric cancer cells. However, it is unclear whether Rev-erbα undergoes posttranslational modifications in gastric cancer. Here, we determined levels of Rev-erbα and its posttranslational modifications including phosphorylation, SUMOylation, and ubiquitination in N-methyl-N-nitrosourea (MNU)/Helicobacter pylori (H. pylori)-induced gastric cancer in mice and in cultured human gastric cancer cells. Administration of MNU plus H. pylori infection successfully induced gastric tumor in C57BL/6J mice. MNU/H. pylori decreased the levels of Rev-erbα in gastric tumor tissues of mice accompanied by an increase in the level of lactic acid. Rev-erbα protein SUMOylation and ubiquitination modifications were significantly increased, whereas phosphorylation was unchanged, in gastric cancer cells line BGC-823 and MNU/H. pylori-induced mouse gastric cancer tissues. Using human gastric cancer tissues, we found that Rev-erbα was specifically reduced in mucosal epithelial cells in gastric tissue. Cytokine levels were increased in MNU/H. pylori-exposed mice compared with control mice. Similarly, the levels of IL-6 IL-10, TNF-α, and VEGF were higher in the BGC-823 cell line compared with GES-1 cells. IL-6 and IL-1 incubation did not affect Rev-erbα levels in BGC-823 cells. Furthermore, Rev-erbα was recruited on the promoters of these cytokine genes, which suppressed their expression. Conclusively, Rev-erbα SUMOylation and subsequent ubiquitination may contribute to its protein reduction, which leads to increased glycolysis and abnormal inflammatory responses during the development of gastric cancer. Targeting Rev-erbα and its SUMOylation represents promising approaches for prevention and management of gastric cancer.

A gene expression profile for the lower osteogenic potent of bone-derived MSCs from osteoporosis with T2DM and the potential mechanism

Background

Osteoporosis (OP) patients complicated with type II diabetes mellitus (T2DM) has a higher fracture risk than the non-diabetic patients, and mesenchymal stem cells (MSCs) from T2DM patients also show a weaker osteogenic potent. The present study aimed to provide a gene expression profile in MSCs from diabetic OP and investigated the potential mechanism.

Methods

The bone-derived MSC (BMSC) was isolated from OP patients complicated with or without T2DM (CON-BMSC, T2DM-BMSC). Osteogenic differentiation was evaluated by qPCR analysis of the expression levels of osteogenic markers, ALP activity and mineralization level. The differentially expressed genes (DEGs) in T2DM-BMSC was identified by RNA-sequence, and the biological roles of DEGs was annotated by bioinformatics analyses. The role of silencing the transcription factor (TF), Forkhead box Q1 (FOXQ1), on the osteogenic differentiation of BMSC was also investigated.

Results

T2DM-BMSC showed a significantly reduced osteogenic potent compare to the CON-BMSC. A total of 448 DEGs was screened in T2DM-BMSC, and bioinformatics analyses showed that many TFs and the target genes were enriched in various OP- and diabetes-related biological processes and pathways. FOXQ1 had the highest verified fold change (abs) among the top 8 TFs, and silence of FOXQ1 inhibited the osteogenic differentiation of CON-BMSC.

Conclusions

Our study provided a comprehensive gene expression profile of BMSC in diabetic OP, and found that downregulated FOXQ1 was responsible for the reduced osteogenic potent of T2DM-BSMC. This is of great importance for the special mechanism researches and the treatment of diabetic OP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03291-2.

Meta-Analysis of Mechanism of Influence of CRY2 on the Differentiation of Mouse Osteoblast through the Regulation of Wnt/Β-Catenin Signaling Pathway

Noncoding RNAs were discovered to control a variety of developmental mechanisms, including osteogenesis. According to emerging evidence, cryptochrome circadian-regulating (CRY) proteins have emerged as essential controllers of osteoblast differentiation. The linked processes, on the other hand, are still unknown. The specific process that underpins osteoblast differentiation and proliferation is yet unknown. This research gives a meta-analysis of CRY2's impact on mouse osteoblast differentiation via the control of the WNT/β-catenin signaling pathways. Western blot and quantitative real-time PCR were used to identify Cry2 expression levels, components in the osteoblast-associated signaling pathway, and osteoblast transcription markers. The osteogenic condition was measured utilizing alkaline phosphatase (ALP) and alizarin red (AR) staining, whereas cell growth rates were measured using CCK8 assays. An ectopic bone formation experiment was used to determine the osteogenic potential of osteoblasts. Cry2 stimulates the osteogenic development of mouse osteoblasts through canonical Wnt/β-catenin signaling, according to the findings.

A Review on the Molecular Mechanisms of Action of Natural Products in Preventing Bone Diseases

The drugs used for treating bone diseases (BDs), at present, elicit hazardous side effects that include certain types of cancers and strokes, hence the ongoing quest for the discovery of alternatives with little or no side effects. Natural products (NPs), mainly of plant origin, have shown compelling promise in the treatments of BDs, with little or no side effects. However, the paucity in knowledge of the mechanisms behind their activities on bone remodeling has remained a hindrance to NPs’ adoption. This review discusses the pathological development of some BDs, the NP-targeted components, and the actions exerted on bone remodeling signaling pathways (e.g., Receptor Activator of Nuclear Factor κ B-ligand (RANKL)/monocyte/macrophage colony-stimulating factor (M-CSF)/osteoprotegerin (OPG), mitogen-activated protein kinase (MAPK)s/c-Jun N-terminal kinase (JNK)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), Kelch-like ECH-associated protein 1 (Keap-1)/nuclear factor erythroid 2–related factor 2 (Nrf2)/Heme Oxygenase-1 (HO-1), Bone Morphogenetic Protein 2 (BMP2)-Wnt/β-catenin, PhosphatidylInositol 3-Kinase (PI3K)/protein kinase B (Akt)/Glycogen Synthase Kinase 3 Beta (GSK3β), and other signaling pathways). Although majority of the studies on the osteoprotective properties of NPs against BDs were conducted ex vivo and mostly on animals, the use of NPs for treating human BDs and the prospects for future development remain promising.

Co-regulation of circadian clock genes and microRNAs in bone metabolism

Mammalian bone is constantly metabolized from the embryonic stage, and the maintenance of bone health depends on the dynamic balance between bone resorption and bone formation, mediated by osteoclasts and osteoblasts. It is widely recognized that circadian clock genes can regulate bone metabolism. In recent years, the regulation of bone metabolism by non-coding RNAs has become a hotspot of research. MicroRNAs can participate in bone catabolism and anabolism by targeting key factors related to bone metabolism, including circadian clock genes. However, research in this field has been conducted only in recent years and the mechanisms involved are not yet well established. Recent studies have focused on how to target circadian clock genes to treat some diseases, such as autoimmune diseases, but few have focused on the co-regulation of circadian clock genes and microRNAs in bone metabolic diseases. Therefore, in this paper we review the progress of research on the co-regulation of bone metabolism by circadian clock genes and microRNAs, aiming to provide new ideas for the prevention and treatment of bone metabolic diseases such as osteoporosis.

Melatonin inhibits osteoclastogenesis via RANKL/OPG suppression mediated by Rev-Erbα in osteoblasts

Diabetic osteoporosis is secondary osteoporosis and a serious complication of diabetes with a high incidence rate and poor prognosis. The specific mechanism of diabetic osteoporosis is unclear, and prevention and treatment options are limited. Recently, melatonin has been found to prevent and treat diabetic osteoporosis. Herein, we investigated the mechanism whereby melatonin inhibits osteoclastogenesis and identified a new target for osteoporosis treatment. We established an in vitro osteoblast–osteoclast co‐culture system as a diabetic osteoporosis model. Osteoclastogenesis was determined using tartrate‐resistant acid phosphatase staining and cathepsin K expression. Real‐time PCR was used to ascertain expression of microRNA mir‐882, targeting Rev‐Erbα. Western blotting was performed to detect the expression of Rev‐Erbα, receptor activator of NF‐kB ligand (RANKL), and osteoprotegerin (OPG), and ELISA was utilized to analyse the secreted form of RANKL. High glucose promoted osteoclastogenesis and elevated the RANKL/OPG ratio in osteoblasts, while melatonin reversed these effects. High glucose inhibited Rev‐Erbα expression, while melatonin promoted its expression. Conversely, high glucose promoted mir‐882 expression, while melatonin inhibited it. We infer that melatonin inhibits RANKL expression in osteoblasts via the mir‐882/Rev‐Erbα axis, thus inhibiting osteoclastogenesis. Our findings provide insights into diabetic osteoporosis and identify a new therapeutic target for osteoporosis.

Bmal1- and Per2-mediated regulation of the osteogenic differentiation and proliferation of mouse bone marrow mesenchymal stem cells by modulating the Wnt/β-catenin pathway

BACKGROUND

Bmal1 and Per2 are the core components of the circadian clock genes (CCGs). Bmal1-/- mice exhibit premature aging, as indicated by hypotrichosis and osteoporosis, with a loss of proliferation ability. The same occurs in Per2-/- mice, albeit to a less severe degree. However, whether the effects of Bmal1 and Per2 on proliferation and osteogenic differentiation are synergistic or antagonistic remains unclear. Thus, our study aimed to explore the effects and specific mechanism.

METHODS AND RESULTS

Lentiviral and adenoviral vectors were constructed to silence or overexpress Bmal1 or Per2 and MTT, flow cytometry, RT-qPCR, WB, immunohistochemistry, alizarin red staining and ChIP-Seq analyses were applied to identify the possible mechanism. The successful knockdown and overexpression of Bmal1/Per2 were detected by fluorescence microcopy. Flow cytometry found out that Bmal1 or Per2 knockdown resulted in G1-phase cell cycle arrest. RT-qPCR showed the different expression levels of Wnt-3a, c-myc1 and axin2 in the Wnt/β-catenin signaling pathway as well as the gene expression change of Rorα and Rev-erbα. Meanwhile, related proteins such as β-catenin, TCF-1, and P-GSK-3β were detected. ALP activity and the amount of mineral nodules were compared. ChIP-Seq results showed the possible mechanism.

CONCLUSIONS

Bmal1 and Per2, as primary canonical clock genes, showed synergistic effects on the proliferation and differentiation of BMSCs. They would inhibit the Wnt/β-catenin signaling pathway by downregulating Rorα expression or upregulating Rev-erbα expression, both of which were also key elements of CCGs. And this may be the mechanism by which they negatively regulate the osteogenic differentiation of BMSCs. Bmal1 and Per2 show synergistic effects in the proliferation of BMSCs. In addition, they play a synergistic role in negatively regulating the osteogenic differentiation ability of BMSCs. Bmal1 and Per2 may regulate the aging of BMSCs by altering cell proliferation and osteogenic differentiation through Rorα and Rev-erbα to affect Wnt/β-catenin pathway.

The circadian clock has roles in mesenchymal stem cell fate decision

The circadian clock refers to the intrinsic biological rhythms of physiological functions and behaviours. It synergises with the solar cycle and has profound effects on normal metabolism and organismal fitness. Recent studies have suggested that the circadian clock exerts great influence on the differentiation of stem cells. Here, we focus on the close relationship between the circadian clock and mesenchymal stem cell fate decisions in the skeletal system. The underlying mechanisms include hormone signals and the activation and repression of different transcription factors under circadian regulation. Additionally, the clock interacts with epigenetic modifiers and non-coding RNAs and is even involved in chromatin remodelling. Although the specificity and safety of circadian therapy need to be further studied, the circadian regulation of stem cells can be regarded as a promising candidate for health improvement and disease prevention.

Transcription Factor Lmx1b Negatively Regulates Osteoblast Differentiation and Bone Formation

The LIM-homeodomain transcription factor Lmx1b plays a key role in body pattern formation during development. Although Lmx1b is essential for the normal development of multiple tissues, its regulatory mechanism in bone cells remains unclear. Here, we demonstrated that Lmx1b negatively regulates bone morphogenic protein 2 (BMP2)-induced osteoblast differentiation. Overexpressed Lmx1b in the osteoblast precursor cells inhibited alkaline phosphatase (ALP) activity and nodule formation, as well as the expression of osteoblast maker genes, including runt-related transcription factor 2 (Runx2), alkaline phosphatase (Alpl), bone sialoprotein (Ibsp), and osteocalcin (Bglap). Conversely, the knockdown of Lmx1b in the osteoblast precursors enhanced the osteoblast differentiation and function. Lmx1b physically interacted with and repressed the transcriptional activity of Runx2 by reducing the recruitment of Runx2 to the promoter region of its target genes. In vivo analysis of BMP2-induced ectopic bone formation revealed that the knockdown of Lmx1b promoted osteogenic differentiation and bone regeneration. Our data demonstrate that Lmx1b negatively regulates osteoblast differentiation and function through regulation of Runx2 and provides a molecular basis for therapeutic targets for bone diseases.

The role of REV-ERB in NASH

REV-ERBs are atypical nuclear receptors as they function as ligand-regulated transcriptional repressors. The natural ligand for the REV-ERBs (REV-ERBα and REV-ERBβ) is heme, and heme-binding results in recruitment of transcriptional corepressor proteins such as N-CoR that mediates repression of REV-ERB target genes. These two receptors regulate a large range of physiological processes including several important in the pathophysiology of non-alcoholic steatohepatitis (NASH). These include carbohydrate and lipid metabolism as well as inflammatory pathways. A number of synthetic REV-ERB agonists have been developed as chemical tools and they show efficacy in animal models of NASH. Here, we will review the functions of REV-ERB with regard to their relevance to NASH as well as the potential to target REV-ERB for treatment of this disease.

Effects of urolithin A on osteoclast differentiation induced by receptor activator of nuclear factor-κB ligand via bone morphogenic protein 2

Urolithin A (UA) is an intestinal microbial metabolite derived from ellagitannins and a promising agent for treating osteoarthritis. However, its effects on osteoporosis are unclear. This study explored the effects of urolithin A (UA) on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclasts and its underlying molecular mechanisms. RANKL treatment significantly increased tartrate-resistant acid phosphatase (TRACP) or osteoclast marker levels (P < 0.05), while adding UA decreased the RANKL-induced levels (P < 0.05) in RAW264.7 cells. Total RNA isolated from RANKL- or RANKL + UA-treated cells was sequenced, and the obtained transcriptome dataset revealed 2,399 differentially expressed genes. They were enriched in multiple pathways involved in rheumatoid arthritis, ERK1 and ERK2 cascade, regulation of inflammatory response, ECM-receptor interactions, and TNF signaling. Scanning electron microscopy showed that RANKL promoted bone resorption pits in bone biopsy specimens, whereas UA inhibited their formation. When bone morphogenic protein 2 (BMP2) was shRNA-silenced, the bone resorption pits were restored. Moreover, while RANKL significantly enhanced the levels of p-ERK2/ERK2, p-p38/p38, p-Akt1/Akt1, p-ERK1/ERK1, and osteoclast-related proteins (P < 0.05), UA reduced them. BMP2 silencing also reversed the UA inhibitory effect. Thus, UA represses the RANKL-induced osteoclast differentiation of RAW264.7 cells by regulating Akt1, p38, and ERK1/2 signaling, and BMP2 likely reverses the UA inhibitory effect via these pathways. We propose BMP2 as a potential drug target for treating bone metabolic diseases, such as osteoporosis.

Downregulation of REV-ERBα is associated with the progression of lung adenocarcinoma

Background

The nuclear receptor REV-ERBα (nuclear receptor subfamily 1, Group D member 1, NR1D1) is one of the essential components of the circadian clock which modulates cell proliferation, glucose metabolism, inflammation, and many other biological processes. Modulation of these processes are also relevant to cancer development. Previous studies have suggested that activation of REV-ERBα correlates with cancer cell senescence and death, but how REV-ERBα play roles in tumor progression require further elucidation.

Methods

We investigated the expression of REV-ERBα in clinical samples by immunohistochemistry (IHC). REV-ERBα is downregulated by shorth hairpin RNA (shRNA). The gene expression level of each group was detected by Western blot analysis. The effects of REV-ERBα downregulation on apoptosis and cell cycles was assessed by flow cytometry assay. A549 cell growth curve under different treatments measured by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Cell invasion ability under different treatments was measured by Transwell assay. Immunostaining analysis was also used for evaluating the effects of downregulation of REV-ERBα on nuclear factor-κB (NF-κB).

Results

Compared to 81.8% (54/66) of samples exhibiting a lower expression level of REV-ERBα in cancer tissue than in paired normal tissue, only 18.2% (12/66) were higher or equally expressed in lung cancer tissue. Furthermore, downregulation of REV-ERBα by RNA interference can significantly enhance the transcription of nuclear factor-κB (NF-κB), while the expression of p53 remained the same. Downregulation of REV-ERBα was also shown to stimulate the invasion and promote the proliferation of lung adenocarcinoma cell line A549.

Conclusions

Our findings suggest that tumorigenesis and progression of lung carcinoma is relevant to downregulation or inhibition of REV-ERBα. This pathophysiological process also correlates with regulation of the NF-κB signaling pathway, indicating that REV-ERBα is a potential target of lung cancer therapy.

Inhibition of Lipopolysaccharide-Induced Inflammatory Bone Loss by Saikosaponin D is Associated with Regulation of the RANKL/RANK Pathway

Background

Osteolytic diseases such as osteoporosis are featured with accelerated osteoclast differentiation and strong bone resorption. Considering the complications and other limitations of current drug treatments, it is necessary to develop a safer and more reliable drug to deal with osteoclast-related diseases. Saikosaponin D (SSD) is the active extract of Bupleurum, which has anti-inflammation, anti-tumor and liver protection functions. However, the role of SSD in regulating the differentiation and function of osteoclasts is not clear.

Purpose

To explore whether SSD could prevent osteoclast differentiation and bone resorption induced by M-CSF and RANKL, and further evaluate the potential therapeutic properties of SSD in LPS-induced inflammatory bone loss mouse models.

Methods

BMMs were cultured in complete medium stimulated by RANKL with different concentrations of SSD. TRAP staining, bone resorption determination, qRT-PCR, immunofluorescence and Western blotting were performed. A mouse model of LPS-induced calvarial bone loss was established and treated with different doses of SSD. The excised calvaria bones were used for TRAP staining, micro-CT scan and histological analysis.

Results

SSD inhibited the formation and bone resorption of osteoclasts induced by RANKL in vitro. SSD suppressed LPS-induced inflammatory bone loss in vivo.

Conclusion

SSD inhibited osteoclastogenesis and LPS-induced osteolysis in mice both which served as a new potential agent for the treatment of osteoclast-related conditions.

Morin attenuates osteoclast formation and function by suppressing the NF-κB, MAPK and calcium signalling pathways

Morin is a natural compound isolated from moraceae family members and has been reported to possess a range of pharmacological activities. However, the effects of morin on bone-associated disorders and the potential mechanism remain unknown. In this study, we investigated the anti-osteoclastogenic effect of morin in vitro and the potential therapeutic effects on ovariectomy (OVX)-induced osteoporosis in vivo. In vitro, by using a bone marrow macrophage-derived osteoclast culture system, we determined that morin attenuated receptor activator of nuclear factor (NF)-κB ligand (RANKL)-induced osteoclast formation via the inhibition of the mitogen-activated protein kinase (MAPK), NF-κB and calcium pathways. In addition, the subsequent expression of nuclear factor of activated T cells c1 (NFATc1) and c-fos was significantly suppressed by morin. In addition, NFATc1 downregulation led to the reduced expression of osteoclastogenesis-related marker genes, such as V-ATPase-d2 and Integrin β3. In vivo, results provided that morin could effectively attenuate OVX-induced bone loss in C57BL/6 mice. In conclusion, our results demonstrated that morin suppressed RANKL-induced osteoclastogenesis via the NF-κB, MAPK and calcium pathways, in addition, its function of preventing OVX-induced bone loss in vivo, which suggested that morin may be a potential therapeutic agent for postmenopausal osteoporosis treatment.

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.

Differential responses of bone to angiotensin II and angiotensin(1-7): beneficial effects of ANG(1-7) on bone with exposure to high glucose

Osteoporosis, diabetes, and hypertension are common concurrent chronic disorders. This study aimed to explore the respective effects of angiotensin II (ANG II) and angiotensin(1-7) [ANG(1-7)], active peptides in the renin-angiotensin system, on osteoblasts and osteoclasts under high-glucose level, as well as to investigate the osteo-preservative effects of ANG II type 1 receptor (AT1R) blocker and ANG(1-7) in diabetic spontaneously hypertensive rats (SHR). ANG II and ANG(1-7), respectively, decreased and increased the formation of calcified nodules and alkaline phosphatase activity in MC3T3-E1 cells under high-glucose level, and respectively stimulated and inhibited the number of matured osteoclasts and pit resorptive area in RANKL-induced bone marrow macrophages. Olmesartan and Mas receptor antagonist A779 could abolish those effects. ANG II and ANG(1-7), respectively, downregulated and upregulated the expressions of osteogenesis factors in MC3T3-E1 cells. ANG II promoted the expressions of cathepsin K and MMP9 in RAW 264.7 cells, whereas ANG(1-7) repressed these osteoclastogenesis factors. ANG II rapidly increased the phosphorylation of Akt and p38 in RAW 264.7 cells, whereas ANG(1-7) markedly reduced the phosphorylation of p38 and ERK under high-glucose condition. After treatments of diabetic SHR with valsartan and ANG(1-7), a significant increase in trabecular bone area, bone mineral density, and mechanical strength was only found in the ANG(1-7)-treated group. Treatment with ANG(1-7) significantly suppressed the increase in renin expression and ANG II content in the bone of SHR. Taken together, ANG II/AT1R and ANG(1-7)/Mas distinctly regulated the differentiation and functions of osteoblasts and osteoclasts upon exposure to high-glucose condition. ANG(1-7) could protect SHR from diabetes-induced osteoporosis.

[Zoledronate regulates osteoclast differentiation and bone resorption in high glucose through p38 MAPK pathway]

OBJECTIVE

To investigate the effect of zoledronate (ZOL) on osteoclast differentiation and bone resorption under high glucose, and the regulation mechanism of p38 mitogen activated kinase (p38 MAPK) signaling pathway in this process.

METHODS

RAW264.7 cells were divided into four groups: low group, high group, low+ZOL group and high+ZOL group after induced into osteoclasts. Cell proliferation activity was determined by MTT assay. The migration of RAW264.7 cells were examined Optical microscopy. Immunofluorescence microscopy was used to observe the cytoskeleton and sealing zones of osteoclasts. After adding group 5: high + ZOL + SB203580 group, trap staining was used to identify the number of positive osteoclasts in each group. The number and area of resorption lacunae were observed by SEM. The mRNA and protein expression of osteoclast related factors were detected by real-time PCR and Western blotting.

RESULTS

The cells in the 5 groups showed similar proliferative activity. High glucose promoted the migration of RAW264.7 cells (P < 0.05), inhibited the clarity of cytoskeleton and the formation of sealing zones in the osteoclasts. Exposure to high glucose significantly lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP, and inhibited osteoclast differentiation and bone absorption (P < 0.05). Treatment with ZOL obviously suppressed the migration ability of RAW264.7 cells, further reduced the clarity of the cytoskeleton, inhibited the formation of sealing zones of the osteoclasts, lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK, and TRAP (P < 0.05), and inhibited osteoclast differentiation and bone absorption. Treatment with SB203580 obviously inhibited osteoclast differentiation and bone resorption and the expressions of P38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP (P < 0.05).

CONCLUSIONS

High glucose inhibits osteoclast differentiation and bone resorption. ZOL inhibits osteoclast differentiation and bone resorption in high-glucose conditions by regulating p38 MAPK pathway, which can be a new pathway for ZOL to regulate diabetic osteoporosis.