Effects of intermedin on proliferation, apoptosis and the expression of OPG/RANKL/M-CSF in the MC3T3-E1 osteoblast cell line

Zoledronate promotes osteoblast differentiation in high-glucose conditions via the p38MAPK pathway

Zoledronate (ZOL) were found to inhibit bone resorption in an animal model of diabetes, high glucose concentrations have been shown to decreased the osteogenesis-related gene expression. But the molecular mechanism by which high glucose levels affect osteoblasts and the effects of ZOL on osteoblast differentiation in a high-glucose environment remain unclear. Therefore, we aimed to investigate the effect of ZOL on osteoblast differentiation in a high-glucose environment and determine the responsible mechanism. Cell proliferation was detected by MTT assay, and cell differentiation was evaluated by immunofluorescence staining for alkaline phosphatase expression, alizarin red staining, cytoskeletal arrangement, and actin fiber formation. Real-time PCR and western blot analyses were performed to detect the mRNA and protein expression of p38MAPK, phosphorylated (p)-p38MAPK, CREB, p-CREB, collagen (COL) I, osteoprotegerin (OPG), and RANKL. The results showed that cell proliferation activity did not differ among the groups. But high glucose inhibited osteoblast differentiation; actin fiber formation; and p38MAPK, p-p38MAPK, CREB, p-CREB, COL I, and OPG expression, while promoting RANKL expression. However, we found that treatment with ZOL reversed these effects of high glucose. And further addition of a p38MAPK inhibitor led to inhibition of osteoblast differentiation and actin fiber formation, and lower p38MAPK, p-p38MAPK, CREB, p-CREB, COL I, and OPG expression than in the high glucose +ZOL group with higher RANKL expression than in the high glucose +ZOL group. Collectively, this study demonstrates that high glucose inhibits the differentiation of osteoblasts, and ZOL could partly overcome these effects by regulating p38MAPK pathway activity.

Upregulation of osteoprotegerin inhibits tert‑butyl hydroperoxide‑induced apoptosis of human chondrocytes

Necrosis of the femoral head (NFH) is an orthopedic disease characterized by a severe lack of blood supply to the femoral head and a marked increase in intraosseous pressure. NFH is associated with numerous factors, such as alcohol consumption and hormone levels. The present study focused on the expression levels of osteoprotegerin (OPG) in NFH and the effect of OPG overexpression on chondrocyte apoptosis. The results demonstrated that OPG expression was markedly decreased in the femoral head of patients with NFH compared with normal femoral heads. Lentivirus-mediated overexpression of OPG in human chondrocytes reversed the decrease in cell viability and the increase in reactive oxygen species production induced by an oxidative stress-inducing factor, tert-butyl hydroperoxide. Flow cytometry and TUNEL assays revealed that OPG overexpression inhibited the apoptosis of chondrocytes. In addition, it was revealed that OPG exerted its anti-apoptotic effect mainly by promoting Bcl-2 expression and Akt phosphorylation and inhibiting caspase-3 cleavage and Bax expression. The present study revealed that OPG may be an important regulator of NFH.

MicroRNA-346-5p Regulates Differentiation of Bone Marrow-Derived Mesenchymal Stem Cells by Inhibiting Transmembrane Protein 9

The molecular mechanisms how bone marrow-derived mesenchymal stem cells (BMSCs) differentiate into osteoblast need to be investigated. MicroRNAs (miRNAs) contribute to the osteogenic differentiation of BMSCs. However, the effect of miR-346-5p on osteogenic differentiation of BMSCs is not clear. This study is aimed at elucidating the underlying mechanism by which miR-346-5p regulates osteogenic differentiation of human BMSCs. Results of alkaline phosphatase (ALP) and Alizarin Red S (ARS) staining indicated that upregulation of miR-346-5p suppressed osteogenic differentiation of BMSCs, whereas downregulation of miR-346-5p enhanced this process. The protein levels of the osteoblastic markers Osterix and Runt-related transcription factor 2 (Runx2) were decreased in cells treated with miR-346-5p mimic at day 7 and day 14 after being differentiated. By contrast, downregulation of miR-346-5p elevated the protein levels of Osterix and Runx2. Moreover, a dual-luciferase reporter assay revealed that Transmembrane Protein 9 (TMEM9) was a target of miR-346-5p. In addition, the Western Blot results demonstrated that the TMEM9 protein level was significantly reduced by the miR-346-5p mimic whereas downregulation of miR-346-5p improved the protein level of TMEM9. These results together demonstrated that miR-346-5p served a key role in BMSC osteogenic differentiation of through targeting TMEM9, which may provide a novel target for clinical treatments of bone injury.

miR‑483‑3p promotes the osteogenesis of human osteoblasts by targeting Dikkopf 2 (DKK2) and the Wnt signaling pathway

Osteoporosis is a systemic metabolic bone disease during which bone mass decreases and bone quality is reduced. Maintaining the bone formation capacity of osteoblasts is crucial for the treatment of osteoporosis. In the present study, bioinformatics analysis was performed on online microarray expression profiles to identify miRNA(s) related to osteoblast proliferation and bone marrow‑derived mesenchymal stem cell (BMSC) osteogenic differentiation. The specific effects of candidate miRNAs on cell proliferation, osteogenic differentiation and Wnt signaling‑related factors were examined. As regards the downstream mechanisms, online tools were employed to predict the downstream targets of candidate miRNAs and the predicted miRNA‑mRNA binding was verified. Finally, the dynamic effects of miRNAs and mRNAs were examined. The results revealed that miR‑483‑3p expression was decreased in bone tissue samples from patients with osteoporosis. In miR‑483‑3p‑overexpressing human osteoblasts, cell viability, DNA synthesis capacity and osteogenesis were promoted, and the protein levels of Wnt1, β‑catenin and cyclin D1 were increased. However, the protein receptor activator of nuclear factor kappa‑Β ligand (RANKL)/osteoprotegerin (OPG) ratio and cell apoptotic rate were decreased. The Wnt signaling, antagonist Dikkopf 2 (DKK2), was targeted and negatively regulated by miR‑483‑3p. DKK2 knockdown exerted similar effects as miR‑483‑3p overexpression, while DKK2 overexpression inhibited cell viability, DNA synthesis capacity and osteogenesis. DKK2 overexpression also decreased the Wnt1, β‑catenin, and cyclin D1 protein levels, whereas it promoted the the RANKL/OPG ratio and the apoptosis of human osteoblasts. DKK2 overexpression reversed the functions of miR‑483‑3p overexpression. On the whole, the findings of the present study demonstrate that the miR‑483‑3p/DKK2 axis modulates the bone formation process by affecting osteoblast proliferation, pre‑osteoblast differentiation into mature osteoblasts and new bone matrix formation.

Calcitonin and Bone Physiology: In Vitro, In Vivo, and Clinical Investigations

Calcitonin was discovered as a peptide hormone that was known to reduce the calcium levels in the systemic circulation. This hypocalcemic effect is produced due to multiple reasons such as inhibition of bone resorption or suppression of calcium release from the bone. Thus, calcitonin was said as a primary regulator of the bone resorption process. This is the reason why calcitonin has been used widely in clinics for the treatment of bone disorders such as osteoporosis, hypercalcemia, and Paget's disease. However, presently calcitonin usage is declined due to the development of efficacious formulations of new drugs. Calcitonin gene-related peptides and several other peptides such as intermedin, amylin, and adrenomedullin (ADM) are categorized in calcitonin family. These peptides are known for the structural similarity with calcitonin. Aside from having a similar structure, these peptides have few overlapping biological activities and signal transduction action through related receptors. However, several other activities are also present that are peptide specific. In vitro and in vivo studies documented the posttreatment effects of calcitonin peptides, i.e., positive effect on bone osteoblasts and their formation and negative effect on osteoclasts and their resorption. The recent research studies carried out on genetically modified mice showed the inhibition of osteoclast activity by amylin, while astonishingly calcitonin plays its role by suppressing osteoblast and bone turnover. This article describes the review of the bone, the activity of the calcitonin family of peptides, and the link between them.

The Activity of Peptides of the Calcitonin Family in Bone

Calcitonin was discovered over 50 yr ago as a new hormone that rapidly lowers circulating calcium levels. This effect is caused by the inhibition of calcium efflux from bone, as calcitonin is a potent inhibitor of bone resorption. Calcitonin has been in clinical use for conditions of accelerated bone turnover, including Paget's disease and osteoporosis; although in recent years, with the development of drugs that are more potent inhibitors of bone resorption, its use has declined. A number of peptides that are structurally similar to calcitonin form the calcitonin family, which currently includes calcitonin gene-related peptides (αCGRP and βCGRP), amylin, adrenomedullin, and intermedin. Apart from being structurally similar, the peptides signal through related receptors and have some overlapping biological activities, although other activities are peptide specific. In bone, in vitro studies and administration of the peptides to animals generally found inhibitory effects on osteoclasts and bone resorption and positive effects on osteoblasts and bone formation. Surprisingly, studies in genetically modified mice have demonstrated that the physiological role of calcitonin appears to be the inhibition of osteoblast activity and bone turnover, whereas amylin inhibits osteoclast activity. The review article focuses on the activities of peptides of the calcitonin family in bone and the challenges in understanding the relationship between the pharmacological effects and the physiological roles of these peptides.

miR-145-5p Increases Osteoclast Numbers In Vitro and Aggravates Bone Erosion in Collagen-Induced Arthritis by Targeting Osteoprotegerin

BACKGROUND Osteoprotegerin (OPG) inhibits bone resorption and binds with strong affinity to receptor activator of NF κB ligand (RANKL), thereby preventing RANKL from binding to its receptor RANK. Osteoclasts have documented effects on bone erosion of rheumatoid arthritis (RA). The aim of this study was to examine the role of miR-145-5p in the regulation of RA osteoclast differentiation and bone erosion. MATERIAL AND METHODS Expression of microRNA-145-5p in human peripheral blood mononuclear cells (PBMC) and synovial tissue was assayed by real-time polymerase chain reaction (RT-PCR). OPG, RANK, and RANKL expression in RAW-264.7 cells was examined by RT-PCR and Western blot analysis. Osteoclast formation was detected by tartrate-resistant acid phosphatase (TRAP) staining. The effect of miR-145-5p on predicted target mRNAs was examined by luciferase reporter assays. Collagen-induced arthritis (CIA) was induced by injecting DBA/1 mice with bovine type II collagen (CII), and miR-145-5p agomir was administered by intravenous injection. Morphological changes in the CIA joint were assessed by micro-computed tomography (CT) and histopathology. RESULTS miR-145-5p levels significantly increased in RA PBMC and synovial tissue compared with normal PBMC and osteoarthritis (OA) tissue. After transfection of RAW-264.7 cells with miR-145-5p, RANK and RANKL expression increased significantly, while OPG expression decreased significantly. TRAP staining results showed osteoclast numbers increased. Micro-CT analysis of the arthritic joints showed that the miR-145-5p agomir caused bone erosion in mice, and histopathological analysis revealed that miR-145-5p agomir aggravates cartilage erosion. CONCLUSIONS Our findings indicate that administration of miR-145-5p aggravates joint erosion in CIA mice. This suggests that miR-145-5p is a potential target for the treatment of RA.

Cancer Metastases to Bone: Concepts, Mechanisms, and Interactions with Bone Osteoblasts

The skeleton is a unique structure capable of providing support for the body. Bone resorption and deposition are controlled in a tightly regulated balance between osteoblasts and osteoclasts with no net bone gain or loss. However, under conditions of disease, the balance between bone resorption and deposition is upset. Osteoblasts play an important role in bone homeostasis by depositing new bone osteoid into resorption pits. It is becoming increasingly evident that osteoblasts additionally play key roles in cancer cell dissemination to bone and subsequent metastasis. Our laboratory has evidence that when osteoblasts come into contact with disseminated breast cancer cells, the osteoblasts produce factors that initially reduce breast cancer cell proliferation, yet promote cancer cell survival in bone. Other laboratories have demonstrated that osteoblasts both directly and indirectly contribute to dormant cancer cell reactivation in bone. Moreover, we have demonstrated that osteoblasts undergo an inflammatory stress response in late stages of breast cancer, and produce inflammatory cytokines that are maintenance and survival factors for breast cancer cells and osteoclasts. Advances in understanding interactions between osteoblasts, osteoclasts, and bone metastatic cancer cells will aid in controlling and ultimately preventing cancer cell metastasis to bone.

Intermedin promotes hepatocellular carcinoma cell proliferation through the classical Wnt signaling pathway

The proliferative activity of hepatic carcinoma cells is directly associated with tumorigenesis, tumor development, metastasis and invasion. A variety of cytokines and peptides serve important roles in the development of hepatic carcinoma. The aim of the present study was to examine the effect of intermedin (IMD) on hepatic carcinoma cell proliferation and its mechanism of action. HepG2 hepatic carcinoma cell lines were treated with human recombinant IMD1-53 and its receptor antagonist IMD17-47. Cell proliferation was detected using a Cell Counting kit-8. The activation of the classical Wnt signaling pathway was demonstrated by the ratio of TOPflash:FOPflash luciferase activity. The expression of c-Myc and cyclin D1 downstream of the Wnt signaling pathway were detected using reverse transcription-quantitative polymerase chain reaction analysis. It was demonstrated that IMD may promote the proliferation of HepG2 cells in a time-dependent manner, and that the IMD receptor antagonist IMD17-47 could eliminate this promotion. IMD may activate classical Wnt signaling pathway transcriptional activity and the mRNA levels of certain downstream target genes. Furthermore, blocking of the Wnt signaling pathway may inhibit IMD-induced HepG2 cell proliferation to a certain extent. IMD may promote hepatic carcinoma cell proliferation by binding with receptor antagonist IMD17-47 and activating the Wnt signaling cascade, thus providing a novel avenue for the treatment of hepatic carcinoma.

Effects of Osteogenic-Conditioned Medium from Human Periosteum-Derived Cells on Osteoclast Differentiation

Stem/progenitor cell-based regenerative medicine using the osteoblast differentiation of mesenchymal stem cells (MSCs) is regarded as a promising approach for the therapeutic treatment of various bone defects. The effects of the osteogenic differentiation of stem/progenitor cells on osteoclast differentiation may have important implications for use in therapy. However, there is little data regarding the expression of osteoclastogenic proteins during osteoblastic differentiation of human periosteum-derived cells (hPDCs) and whether factors expressed during this process can modulate osteoclastogenesis. In the present study, we measured expression of RANKL in hPDCs undergoing osteoblastic differentiation and found that expression of RANKL mRNA was markedly increased in these cells in a time-dependent manner. RANKL protein expression was also significantly enhanced in osteogenic-conditioned media from hPDCs undergoing osteoblastic differentiation. We then isolated and cultured CD34+ hematopoietic stem cells (HSCs) from umbilical cord blood (UCB) mononuclear cells (MNCs) and found that these cells were well differentiated into several hematopoietic lineages. Finally, we co-cultured human trabecular bone osteoblasts (hOBs) with CD34+ HSCs and used the conditioned medium, collected from hPDCs during osteoblastic differentiation, to investigate whether factors produced during osteoblast maturation can affect osteoclast differentiation. Specifically, we measured the effect of this osteogenic-conditioned media on expression of osteoclastogenic markers and osteoclast cell number. We found that osteoclastic marker gene expression was highest in co-cultures incubated with the conditioned medium collected from hPDCs with the greatest level of osteogenic maturation. Although further study will be needed to clarify the precise mechanisms that underlie osteogenic-conditioned medium-regulated osteoclastogenesis, our results suggest that the osteogenic maturation of hPDCs could promote osteoclastic potential.

Dexmedetomidine attenuates H2O2-induced cell death in human osteoblasts

Background

Reactive oxygen species play critical roles in homeostasis and cell signaling. Dexmedetomidine, a specific agonist of the α₂-adrenoceptor, has been commonly used for sedation, and it has been reported to have a protective effect against oxidative stress. In this study, we investigated whether dexmedetomidine has a protective effect against H₂O₂-induced oxidative stress and the mechanism of H₂O₂-induced cell death in normal human fetal osteoblast (hFOB) cells.

Methods

Cells were divided into three groups: control group—cells were incubated in normoxia without dexmedetomidine, hydrogen peroxide (H₂O₂) group—cells were exposed to H₂O₂ (200 µM) for 2 h, and Dex/H₂O₂ group—cells were pretreated with dexmedetomidine (5 µM) for 2 h then exposed to H₂O₂ (200 µM) for 2 h. Cell viability and apoptosis were evaluated. Osteoblast maturation was determined by assaying bone nodular mineralization. Expression levels of bone-related proteins were determined by western blot.

Results

Cell viability was significantly decreased in the H₂O₂ group compared with the control group, and this effect was improved by dexmedetomidine. The Hoechst 33342 and Annexin-V FITC/PI staining revealed that dexmedetomidine effectively decreased H₂O₂-induced hFOB cell apoptosis. Dexmedetomidine enhanced the mineralization of hFOB cells when compared to the H₂O₂ group. In western blot analysis, bone-related protein was increased in the Dex/H₂O₂ group.

Conclusions

We demonstrated the potential therapeutic value of dexmedetomidine in H₂O₂-induced oxidative stress by inhibiting apoptosis and enhancing osteoblast activity. Additionally, the current investigation could be evidence to support the antioxidant potential of dexmedetomidine in vitro.