Bone morphogenetic protein-2 and -4 (BMP-2 and -4) mediates fraxetin-induced maturation and differentiation in human osteoblast-like cell lines

Synthesis and Structure-Activity Relationships of Novel Benzofuran Derivatives with Osteoblast Differentiation-Promoting Activity

Osteoporosis is caused by an imbalance between bone resorption and formation, which decreases bone mass and strength and increases the risk of fracture. Therefore, osteoporosis is treated with oral resorption inhibitors, such as bisphosphonates, and parenteral osteogenic drugs, including parathyroid hormone and antisclerostin antibodies. However, orally active osteogenic drugs have not yet been developed. In the present study, to find novel candidates for oral osteogenic drugs, various benzofuran derivatives were synthesized and their effects on osteoblast differentiation were examined in mouse mesenchymal stem cells (ST2 cells). Among the compounds tested, 3-{4-[2-(2-isopropoxyethoxy)ethoxy]phenyl}benzofuran-5-carboxamide (23d) exhibited potent osteoblast differentiation-promoting activity, estimated as EC200 for increasing alkaline phosphatase activity, and good oral absorption in female rats, resulting in high Cmax/EC200. Dual-energy X-ray absorptiometry scanning revealed that 23d at 10 mg/kg/d for 8 weeks increased femoral bone mineral density in ovariectomized rats with an elevation in plasma bone-type alkaline phosphatase activity, and micro-computed tomography showed that it increased bone volume, mineral contents, and strength in femoral diaphysis cortical, but not trabecular bone during the experiment period. 23d potently inhibited cyclin-dependent kinase 8 (CDK8) activity, suggesting that its osteoblastogenic activity is mediated by the suppression of CDK8, as previously reported for diphenylether derivatives. In conclusion, the structure-activity relationships of novel benzofuran derivatives were clarified and 3,5-disubstituted benzofuran was identified as a useful scaffold for orally active osteogenic compounds. Compound 23d exhibited potent osteoblastogenic activity through CDK8 inhibition and osteogenic effects in ovariectomized rats, indicating its potential as an orally active anti-osteoporotic drug.

Health benefits of fraxetin: From chemistry to medicine

Fraxetin is a bioactive molecule present in various natural plants, especially Cortex Fraxini. Evidenced outcomes in phytochemical and biological analyses for this agent are now available in the literature, but an insightful review is yet unknown. The goal of the current research is to offer a panoramic illustration of natural observation, biosynthesis, synthesis, pharmacology, and pharmacokinetics for fraxetin. Esculetin and ferulic acid acted as precursors in the enzymatic biosynthetic route, whereas fraxetin could be easily synthesized from simple phenols. A great deal of interest was obtained in using this molecule for pharmacological targets. Herein, its pharmacological value included anticancer, antioxidative, anti-inflammatory, antidiabetic, antiobesity, and antimicrobial activities, as well as the protection of the liver, neurons, heart, bone, lung, kidney, and others. Anticancer activity may involve the inhibition of proliferation, invasion, and migration, together with apoptotic induction. Health benefits from this molecule were deduced from its ability to suppress cytokines and protect the immune syndrome. Various signaling pathways, such as Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3), phosphoinositide 3 kinase (PI3K)/protein kinase B (Akt), nuclear factor kappa B (NF-κB)/NLRP3, Akt/AMPK, have been proposed for in vitro and in vivo mechanisms of action. Fraxetin is highly distributed to rat plasma and several organs. However, more pharmacokinetic studies to improve its bioavailability are needed since its solubility in water is still limited.

Chemically heparinized PEEK via a green method to immobilize bone morphogenetic protein-2 (BMP-2) for enhanced osteogenic activity

Osseointegration remains one of the major challenges in the success of bone-related implants. Recently, polyetheretherketone (PEEK) has emerged as an alternative material in orthopedic and dental applications due to its bone-mimicking mechanical properties. However, its bioinertness resulting in poor osseointegration has limited its potential application. So, the surface modification of PEEK with bone morphogenetic protein-2 (BMP-2) can be a potential approach for improving osseointegration. In this study, we proposed the chemical modification of heparin onto PEEK through an environmentally benign method to exploit the BMP-2 binding affinity of heparin. The heparin was successfully functionalized on the PEEK surface via a combination of ozone and UV treatment without using organic solvents or chemicals. Furthermore, BMP-2 was efficiently immobilized on PEEK and exhibited a sustained release of BMP-2 compared to the pristine PEEK with enhancement of bioactivity in terms of proliferation as well as osteogenic differentiation of MG-63. The significant synergistic effect of BMP-2 and heparin grafting on osteogenic differentiation of MG-63 was observed. Overall, we demonstrated a relatively safe method where no harsh chemical reagent or organic solvent was involved in the process of heparin grafting onto PEEK. The BMP-2 loaded, heparin-grafted PEEK could serve as a potential platform for osseointegration improvement of PEEK-based bone implants.

Bone morphogenetic protein 4 is involved in cadmium-associated bone damage

Cadmium (Cd) is a well-characterized bone toxic agent and can induce bone damage via inhibiting osteogenic differentiation. Bone morphogenetic protein (BMP)/SMAD signaling pathway can mediate osteogenic differentiation, but the association between Cd and BMP/SMAD signaling pathway is yet to be illuminated. To understand what elements of BMPs and SMADs are affected by Cd to influence osteogenic differentiation and if BMPs can be the biomarkers of which Cd-induced osteoporosis, human bone marrow mesenchymal stem cells (hBMSCs) were treated with cadmium chloride (CdCl2) in vitro to detect the expression of BMPs and SMADs, and 134 subjects were enrolled to explore if the BMPs can be potential biomarkers of Cd-associated bone damage. Our results showed that Cd exposure significantly promoted the adipogenic differentiation of hBMSCs and inhibited its osteogenic differentiation by inhibiting the expression of BMP-2/4, SMAD4, and p-SMAD1/5/9 complex. And mediation analyses yielded that BMP-4 mediated 39.32% (95% confidence interval 7.47, 85.00) of the total association between the Cd and the risk of Cd-associated bone damage. Moreover, during differentiation, BMP-4 had the potential to enhance mineralization compared with CdCl2 only group. These results reveal that BMP-4 can be a diagnostic biomarker and therapeutic target for Cd-associated bone damage.

The Effects of Astaxanthin on Proliferation and Differentiation of MG-63 Osteosarcoma Cells via Aryl Hydrocarbon Receptor (AhR) Pathway: A Comparison with AhR Endogenous Ligand

Background: Osteosarcoma (OS) is the most prevalent bone-related malignancy with a high mortality rate among children and adolescents. In the present study, first we explored the effects of astaxanthin (AST) on proliferation and differentiation of the MG-63 osteosarcoma cell line, and then compared its effects with AhR endogenous ligand (FICZ).Methods: Cell proliferation and cytotoxicity assay were performed using MTT. To identify possible mechanisms underlying AST-induced changes in osteogenic metabolism via the AHR pathway, we defined changes in CYP1A1, osteocalcin, osteopontin, type I collagen, and Runx2 gene expression using RT-PCR.Results: AST upregulated CYP1A1, osteocalcin, osteopontin, type I collagen, and Runx2 expression in trends of increasing its concentration. FICZ showed a biphasic effect on MG-63 cell proliferation. At high concentrations, it significantly decreased the cell viability, while at lower concentrations it was increased as compared to the control. Increasing FICZ concentrations from 1 nm to 1 μM, down-regulated the expression of Runx2, osteopontin, osteocalcin and collagen type 1 at the transcriptional levels. It seems that AST can augment the proliferation and differentiation of MG-63 via the AhR-dependent pathway, while FICZ suppresses the proliferation and differentiation of MG-63.Conclusion: We concluded that various AhR ligands show different behaviors in the modulation of MG-63 cells.

Hedgehog signaling regulates osteoblast differentiation in zebrafish larvae through modulation of autophagy

Impaired osteoblast differentiation may result in bone metabolic diseases such as osteoporosis. It was reported recently that hedgehog (Hh) signaling and autophagy are two important regulators of bone differentiation. In order to further dissect their relationship in bone development, we used a zebrafish larvae model to investigate how disruption of one of these signals affects the function of the other and impacts osteoblast differentiation. Our results showed that activation of Hh signaling negatively regulated autophagy. However, suppression of autophagy by knocking down atg5 expression did not alter Hh signaling, but dramatically upregulated the expression of osteoblast-related genes and increased bone mineralization, especially in the den region. On the contrary, inhibition of the Hh signaling pathway by cyclopamine treatment suppressed the expression of osteoblast-related genes and decreased bone mineralization. In agreement with these findings, blocking Hh signaling through knockdown SHH and Gli2 genes led to defective osteoblast differentiation, while promoting Hh signaling by knockdown Ptch1 was beneficial to osteoblast differentiation. Our results thus support that activation of the Hh signaling pathway negatively regulates autophagy and consequentially promotes osteoblast differentiation. On the contrary, induction of autophagy inhibits osteoblast differentiation. Our work reveals the mechanism underlying Hh signaling pathway regulation of bone development.

Summary: Our report of an essential regulation role of hedgehog signaling and autophagy on osteoblast differentiation may contribute to research on bone development biology, hedgehog signaling and the autophagy pathway.

Effect of apatite formation of biphasic calcium phosphate ceramic (BCP) on osteoblastogenesis using simulated body fluid (SBF) with or without bovine serum albumin (BSA)

Although biphasic calcium phosphate ceramic (BCP) holds promise in therapy of bone defect, surface mineralization prior to implantation may improve the bioactivity to better integrate with the host. Immersion in simulated body fluid (SBF) and bovine serum albumin-simulated body fluid (BSA-SBF) are common methods to form apatite interface layer. This study was intended to investigate the effect of SBF and BSA-SBF treatment on the bioactivity of BCP in vitro. In this study, osteoblasts were grown on BCP with or without treatment of SBF or BSA-SBF, and detected with general observation, scanning electron microscope (SEM), cell proliferation assay, morphology observation, viability assay, alkaline phosphatase (ALP) activity assay, and osteogenic specific gene expression of alkaline phosphatase (ALPL), bone gamma-carboxyglutamate (gla) protein (BGLAP), bone morphogenetic protein 2 (BMP2), bone sialoprotein (BSP), type I collagen (COLI) and runt-related transcription factor 2 (RUNX2) after culture of 2, 5 and 8days. As the results shown, BCP pre-incubated in SBF and BSA-SBF up-regulated ALP activity and osteogenic related genes and proteins, which testified the positive effect of SBF and BSA-SBF. Especially, BSA-SBF enhanced the cell growth significantly. This study indicated that treatment by BSA-SBF is of importance for BCP before clinical application.

Calophyllolide content in Calophyllum inophyllum at different stages of maturity and its osteogenic activity

Calophyllum inophyllum is a coastal plant rich in natural substances. Its ingredients have been used for the development of an anti-human immunodeficiency virus (HIV) drug. In this study, we collected C. inophyllum fruit, and the ethanol extract of the fruit was chromatographically separated using silica gel and Sephadex LH-20 columns to obtain the major compound, calophyllolide. The fruits were harvested from September to December in 2011; a quantitative analysis of the calophyllolide content was conducted using HPLC to explore the differences between the different parts of the fruit during the growing season. The results showed that in fruits of C. inophyllum, calophyllolide exists only in the nuts, and dried nuts contain approximately 2 mg·g⁻¹ of calophyllolide. The calophyllolide levels in the nuts decreased during maturity. In addition, calophyllolide dose-dependently enhanced alkaline phosphatase (ALP) activity in murine osteoblastic MC3T3-E1 cells, without significant cytotoxicity. The expression of osteoblastic genes, ALP and osteocalcin (OCN), were increased by calophyllolide. Calophyllolide induced osteoblasts differentiation also evidenced by increasing mineralization and ALP staining.

Effect of Fermented Red Ginseng Extract Enriched in Ginsenoside Rg3 on the Differentiation and Mineralization of Preosteoblastic MC3T3-E1 Cells

In this study, red ginseng extract (RGE) was converted into high-content minor ginsenosides by fermenting with Bgp1 enzymes at 37°C for 5 days. Compared to the RGE, the minor ginsenoside contents were increased in fermented red ginseng extract (FRGE). Moreover, the amount of minor ginsenosides such as Rh1 (11%) and Rg2 (16%) was slightly augmented, while the level of Rg3 (33%) was significantly increased after bioconversion. Furthermore, we also examined and compared the effect of RGE and FRGE on the differentiation and mineralization of preosteoblastic MC3T3-E1 cells. Similarly, the level of mRNA expression of intracellular alkaline phosphatase (ALP) activity, type-1 collagen (Col-I) was also increased. Based on the comparison, it is clear that the FRGE has improved effects on bone formation and differentiation of preosteoblastic MC3T3-E1 cells.

Calcitonin gene-related peptide stimulates BMP-2 expression and the differentiation of human osteoblast-like cells in vitro

AIM

To investigate whether bone morphogenic protein-2 (BMP-2) expression was involved in calcitonin gene-related peptide (CGRP)-induced osteogenesis in human osteoblast-like cells in vitro.

METHODS

MG-63 osteogenic human osteosarcoma cells were treated with CGRP (10-8 mol/L) for 48 h. Cell cycle phases were determined using flow cytometry assay. The protein levels of BMP-2, ALP, Osteocalcin, ColIa1, CREB, and pCREB were measured with Western blotting, while the mRNA level of BMP-2 was measured with qR-T PCR. The expression of ALP in MG-63 cells was also studied using immunofluorescence staining. The level of cAMP was measured with ELISA assay.

RESULTS

CGRP treatment significantly stimulated proliferation of MG-63 cells, and increased the expression of BMP-2 and the osteogenic proteins ALP, Osteocalcin and ColIa1. Pretreatment with the BMP signaling inhibitor Noggin (100 ng/mL) did not affect CGRP-stimulated proliferation and BMP-2 expression, but abolished the CGRP-induced increases of the osteogenic proteins ALP, Osteocalcin and ColIa1. Furthermore, CGRP treatment markedly increased cAMP level in MG-63 cells, whereas pretreatment with the cAMP pathway inhibitor H89 (5 μmol/L) abolished the CGRP-induced increases of cAMP level and BMP-2 expression.

CONCLUSION

In MG-63 cells, the BMP pathway is involved in CGRP-induced osteogenic differentiation but not in proliferation, whereas the cAMP/pCREB pathway is involved in the expression of BMP-2.

8-Prenylkaempferol accelerates osteoblast maturation through bone morphogenetic protein-2/p38 pathway to activate Runx2 transcription

AIMS

In this study, we investigated the effect of 8-prenylkaempferol (8-PK), a prenyl-flavonoid isolated from Sophora flavescens, on osteoblast differentiation and maturation.

MAIN METHODS

MC3T3-E1 cells were exposed to 8-PK and the cytotoxicity was assayed. Osteoblast differentiation and maturation were evaluated by analyzing alkaline phosphatase (ALP) activity and cell mineralization, respectively. RT-PCR and Western blot were executed to determine the effects of 8-PK on osteoblast differentiation-related gene expression and signaling pathway.

KEY FINDINGS

8-PK significantly promoted ALP activity, up-regulated mRNA expressions of osteocalcin, osteopontin, and type I collagen, and induced bone nodules formation. Induction of differentiation by 8-PK was associated with increased bone morphogenetic protein (BMP)-2 expression, and sequentially up-regulated the phosphorylations of Smad1/5/8 and p38, and increased the nuclear translocation of runt-related transcription factor 2 (Runx2). Addition of BMP-2 antagonist noggin blocked 8-PK and recombinant mouse BMP-2-induced ALP activity, reconfirming that BMP-2 production is required in 8-PK-mediated osteoblast differentiation. Noggin also abrogated 8-PK evoked phosphorylations of Smad1/5/8 and p38, suggesting that BMP-2 signaling is required for p38 activation in 8-PK-treated cells. Application of p38 inhibitor SB203580 repressed not only 8-PK-mediated activation of ALP, but also the nuclear translocation of Runx2 and bone nodules formation.

SIGNIFICANCE

The present results suggested that BMP-2/p38/Runx2 pathways were involved in 8-PK-induced differentiation/maturation of MC3T3-E1 osteoblasts and firstly demonstrated that 8-PK might be a promising agent for inducing osteogenesis.

Virtual screening and selection of drug-like compounds to block noggin interaction with bone morphogenetic proteins

Noggin is a major natural extracellular antagonist to bone morphogenetic proteins (BMPs) which binds to BMPs and blocks binding of them to BMP-specific receptors and thus negatively regulates BMP-induced osteoblastic differentiation. Bone morphogenetic proteins (BMPs) signal through heteromeric protein complexes composed of type I and type II serine/threonine kinase receptors. Preventing the BMP-2/noggin interaction will preserve free BMP-2 and enhance the efficacy of BMP-2 to induce bone formation. This work is an attempt to use the current understanding of BMP-2, and its interaction with its receptors and antagonist to design an inhibitor of BMP-2/noggin interaction with the goal of lowering the dose of BMP-2 required in clinical applications. The crystal structure of the BMP-7/noggin complex, the BMP-2/BMP receptor IA ectodomain complex and the extracellular domain of BMP receptor II monomer are known. We modeled the BMP-2 based on the structure of its homologue BMP-7 and its binding complex with noggin. We also modeled a complex of BMP-2/BMPRIA/BMPRII by modeling BMPRII and replacing ActRIIB in the BMP-2/BMPRIA/ActRIIB complex. We then identified the binding region of noggin with BMP-2 and the receptors with BMP-2. From the analysis of structures of these complexes and modeling we identified the key amino acids present in the entire interacting surfaces among these proteins that play important physiological role in the regulation of cell differentiation and bone metabolism. By in silico screening we selected and ranked several compounds that have high theoretical scores to bind to noggin to block BMP-noggin interaction.

Treatment of rabbit femoral defect by firearm with BMP-4 gene combined with TGF-beta1

BACKGROUND

Firearm bone fractures are difficult to treat compared with general ones as both soft tissue and bone are injured more extensively and severely with contamination in the wound track. The bone morphogenetic protein (BMP) and transforming growth factor (TGF)-beta play an important role in bone fracture healing. Therefore, BMP-4 combined with TGF-beta1 was used to improve and accelerate the repair of rabbit femoral defect resulting from firearm.

METHODS

Femoral defect was made with 0.375 g steel ball fired at 350 m/s. At 6 hours after wounding, the debridement and irrigation were performed, followed by trimming the ends of defected bone at day 7. Plasmid-encoded BMP-4 gene identified in vitro and TGF-beta1 were injected into the tissue of upper and lower parts and the epicenter of the defected area at 2 weeks after wounding, again TGF-beta1 was given at 5 weeks. At 3, 7, 11, and 15 weeks after wounding, the expression of mRNA and protein of BMP-4 were detected by reverse transcription-polymerase chain reaction and Western blot. The activity of alkaline phosphatase and calcium content were measured for describing osteogenetic ability. The course and quality of osteogenesis were determined quantitatively by pathohistological and X-ray examinations.

RESULTS

In vivo BMP-4 mRNA and protein could be continually expressed for 8 weeks. The determination of alkaline phosphatase activity and calcium content showed osteogenetic ability was significantly enhanced by BMP-4 gene combined with TGF-beta1. The pathohistological and X-ray examinations revealed that osteogenetic speed was prominently accelerated, and the quality was improved after the treatment.

CONCLUSION

The repair of rabbit femoral defect resulting from firearm can be significantly improved and accelerated by BMP-4 gene combined with TGF-beta1.

Myricetin induces human osteoblast differentiation through bone morphogenetic protein-2/p38 mitogen-activated protein kinase pathway

Myricetin (3,3',4',5,5',7-hexahydroxyflavone), a flavonoid compound, is present in vegetables and fruits. By means of alkaline phosphatase (ALP) activity, osteocalcin, and type I collagen enzyme-linked immunosorbent assay (ELISA), we have shown that myricetin exhibits a significant induction of differentiation in MG-63 and hFOB human osteoblasts. Alkaline phosphatase and osteocalcin are phenotypic markers for early-stage differentiated osteoblasts and terminally differentiated osteoblasts, respectively. Our results indicate that myricetin stimulates osteoblast differentiation at various stages, from maturation to terminally differentiated osteoblasts. Induction of differentiation by myricetin is associated with increased bone morphogenetic protein-2 (BMP-2) production. The BMP-2 antagonist noggin blocked myricetin-mediated ALP activity and osteocalcin secretion enhancement, indicating that BMP-2 production is required in myricetin-mediated osteoblast maturation and differentiation. Induction of differentiation by myricetin is associated with increased activation of SMAD1/5/8 and p38 mitogen-activated protein kinases. Cotreatment of p38 inhibitor SB203580 inhibited myricetin-mediated ALP upregulation and osteocalcin production. In conclusion, myricetin increased BMP-2 synthesis, and subsequently activated SMAD1/5/8 and p38 MAPK, and this effect may contribute to its action on the induction of osteoblast maturation and differentiation, followed by an increase of bone mass.