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

Role of MAPKs in TGF-β1-induced maturation and mineralization in human osteoblast-like cells

OBJECTIVES

Our study aimed to clarify the role of mitogen-activated protein kinases (MAPKs) in transforming growth factor (TGF)-β1-stimulated mineralization in the human osteoblast-like MG63 cells.

METHODS

The viability of MG63 cells under TGF-β1 stimulation was assessed by MTS assay. Western blotting determined TGF-β1-mediated activation of extracellular signal-related protein kinase (ERK), p38, and c-Jun amino-terminal kinase (JNK). Mineralization-related gene expression was examined by quantitative real-time PCR, and mineral deposition levels were evaluated by alizarin red S staining.

RESULTS

TGF-β1 had no effect on MG63 cell proliferation. Activation of p38 was observed at 3 h post TGF-β1 stimulation. Moreover, JNK phosphorylation was upregulated by TGF-β1 from 1 to 6 h post stimulation, but had no activation on ERK phosphorylation throughout the experimental period. Treatment with JNK inhibitor diminished the alizarin red S-stained area in a dose-dependent manner. Mineral deposition was unaffected by MEK inhibitor, whereas p38 inhibitor increased the red-stained area. Gene expression levels of ALP and BSP were significantly decreased under treatment with JNK inhibitor and p38 inhibitor. The MEK inhibitor had no effect on the TGF-β1-mediated upregulation of ALP and BSP. Although all three inhibitors suppressed expression of COL I, none were found to stimulate expression of OCN.

CONCLUSIONS

Human osteoblast-like MG63 cells maturation and mineralization are induced through JNK activation of MAPK signaling in response to TGF-β1.

Isolation of Pro-Osteogenic Compounds from Euptelea polyandra That Reciprocally Regulate Osteoblast and Osteoclast Differentiation

Plants contain a large number of small-molecule compounds that are useful for targeting human health and in drug discovery. Healthy bone metabolism depends on the balance between bone-forming osteoblast activity and bone-resorbing osteoclast activity. In an ongoing study searching for 22 plant extracts effective against osteoporosis, we found that the crude extract of Euptelea polyandra Sieb. et Zucc (E. polyandra) had osteogenic bioactivity. In this study, we isolated two compounds, isoquercitrin (1) and astragalin (2), responsible for osteogenic bioactivity in osteoblastic MC3T3-E1 cells from the leaf of E. polyandra using column chromatography and the spectroscopic technique. This is the first report to isolate astragalin from E. polyandra. Compounds (1) and (2) promoted osteoblast differentiation by increasing alkaline phosphatase (ALP) activity and alizarin red S stain-positive calcium deposition, while simultaneously suppressing tartrate-resistant acid phosphatase (TRAP)-positive osteoclast differentiation in RAW264.7 cells at non-cytotoxic concentrations. Isoquercitrin (1) and astragalin (2) increased the expression of osteoblastic differentiation genes, Osterix, ALP, and Osteoprotegerin in the MC3T3-E1 cells, while suppressing osteoclast differentiation genes, TRAP, Cathepsin K, and MMP 9 in the RAW264.7 cells. These compounds may be ideal targets for the treatment of osteoporosis due to their dual function of promoting bone formation and inhibiting bone resorption.

Myricitrin: A promising herbal therapy for periodontitis in immunosuppressed status

Background

Periodontitis is a complex chronic inflammatory disease aggravated in immunosuppressed patients. However, adjuvant therapies can alleviate severe inflammation and slow down disease progression.

Objective

To evaluate the efficacy of myricitrin, a herbal flavonoid glycoside, in reducing immunosuppression-associated periodontitis and compare its effects with that of alendronate on alveolar bone regeneration.

Methods

Fifty albino Wistar rats were randomly allocated to the control, periodontitis, immunosuppressant, myricitrin, and alendronate groups. Ligature-associated periodontitis was induced in all groups, except the control group. Cyclosporin A (CsA) was administered subcutaneously in the immunosuppressant group for immunosuppression. The myricitrin group received CsA and myricitrin, whereas the alendronate group received CsA and alendronate. The therapeutic efficacies of myricitrin and alendronate were compared histologically, morphometrically, and biochemically.

Results

Myricitrin reversed bone destruction in the periodontitis and immunosuppressant groups. Morphometrically, myricitrin showed comparable improvements to alendronate in terms of gaining more bone area to 49.4 ± 4.6 and 59.5 ± 2%, respectively (P < 0.001 in relation to the untreated periodontitis group). Concomitantly, myricitrin increased osteoblast count significantly to 28.4 ± 4.7 closer to the 34.5 ± 2.4 count in the alendronate group (P < 0.001 compared with 22.5 ± 2.6 count of the immunosuppressant group). Moreover, myricitrin restored the serum calcium to 9.4 ± 0.6 mg/dL and alkaline phosphatase up to 112.9 ± 2.9 IU/L, which were almost normal levels similar to the control cohort (P > 0.05).

Conclusion

Myricitrin showed beneficial effects in counteracting bone resorption in subjects with immunosuppression-associated periodontitis. Its efficacy in slowing down disease progression was comparable to that of alendronate.

Biocompatibility of Veratric Acid-Encapsulated Chitosan/Methylcellulose Hydrogel: Biological Characterization, Osteogenic Efficiency with In Silico Molecular Modeling

The limitations of graft material, and surgical sites for autografts in bone defects treatment have become a significant challenge in bone tissue engineering. Phytocompounds markedly affect bone metabolism by activating the osteogenic signaling pathways. The present study investigated the biocompatibility of the bio-composite thermo-responsive hydrogels consisting of chitosan (CS), and methylcellulose (MC) encapsulated with veratric acid (VA) as a restorative agent for bone defect treatment. The spectroscopy analyses confirmed the formation of CS/MC hydrogels and VA encapsulated CS/MC hydrogels (CS/MC-VA). Molecular analysis of the CS-specific MC decamer unit with VA complex exhibited a stable integration in the system. Further, Runx2 (runt-related transcription factor 2) was found in the docking mechanism with VA, indicating a high binding affinity towards the functional site of the Runx2 protein. The formulated CS/MC-VA hydrogels exhibited biocompatibility with the mouse mesenchymal stem cells, while VA promoted osteogenic differentiation in the stem cells, which was verified by calcium phosphate deposition through the von Kossa staining. The study results suggest that CS/MC-VA could be a potential therapeutic alternative source for bone regeneration.

Apigenin Modulates AnxA6- and TNAP-Mediated Osteoblast Mineralization

Mineralization-competent cells like osteoblasts and chondrocytes release matrix vesicles (MVs) which accumulate Ca2+ and Pi, creating an optimal environment for apatite formation. The mineralization process requires the involvement of proteins, such as annexins (Anx) and tissue-nonspecific alkaline phosphatase (TNAP), as well as low molecular-weight compounds. Apigenin, a flavonoid compound, has been reported to affect bone metabolism, but there are doubts about its mechanism of action under physiological and pathological conditions. In this report, apigenin potency to modulate annexin A6 (AnxA6)- and TNAP-mediated osteoblast mineralization was explored using three cell lines: human fetal osteoblastic hFOB 1.19, human osteosarcoma Saos-2, and human coronary artery smooth muscle cells HCASMC. We compared the mineralization competence, the morphology and composition of minerals, and the protein distribution in control and apigenin-treated cells and vesicles. The mineralization ability was monitored by AR-S/CPC analysis, and TNAP activity was determined by ELISA assay. Apigenin affected the mineral structure and modulated TNAP activity depending on the concentration. We also observed increased mineralization in Saos-2 cells. Based on TEM-EDX, we found that apigenin influenced the mineral composition. This flavonoid also disturbed the intracellular distribution of AnxA6 and TNAP, especially blocking AnxA6 aggregation and TNAP attachment to the membrane, as examined by FM analysis of cells and TEM-gold analysis of vesicles. In summary, apigenin modulates the mineralization process by regulating AnxA6 and TNAP, as well as through various effects on normal and cancer bone tissues or atherosclerotic soft tissue.

Myricetin: targeting signaling networks in cancer and its implication in chemotherapy

The gaps between the complex nature of cancer and therapeutics have been narrowed down due to extensive research in molecular oncology. Despite gathering massive insight into the mysteries of tumor heterogeneity and the molecular framework of tumor cells, therapy resistance and adverse side effects of current therapeutic remain the major challenge. This has shifted the attention towards therapeutics with less toxicity and high efficacy. Myricetin a natural flavonoid has been under the spotlight for its anti-cancer, anti-oxidant, and anti-inflammatory properties. The cutting-edge molecular techniques have shed light on the interplay between myricetin and dysregulated signaling cascades in cancer progression, invasion, and metastasis. However, there are limited data available regarding the nano-delivery platforms composed of myricetin in cancer. In this review, we have provided a comprehensive detail of myricetin-mediated regulation of different cellular pathways, its implications in cancer prevention, preclinical and clinical trials, and its current available nano-formulations for the treatment of various cancers.

Antiosteoporosis effects of a marine antimicrobial peptide pardaxin via regulation of the osteogenesis pathway

Antimicrobial peptides (AMPs) are known to play an important role in natural immunity. Moreover, the diverse biological activities of AMPs showed great potency in treating many diseases. Thus, in this study, we used an AMP, that is, pardaxin, from a marine fish (Pardachirus marmoratus), which has been reported to possess antibacterial and antitumor activities. We first investigated the mechanisms of pardaxin in promoting osteogenic differentiation in vitro and in vivo. As per our data, it was determined that pardaxin could stimulate bone morphogenetic protein-2 (BMP-2) and downstream cascade. The activation of BMP-2 could further induce the phosphorylation of Akt and extracellular signal-regulated kinase (ERK). Additionally, the activation of p-Akt and p-ERK could prompt the elevation and translocation of runt-related transcription factor 2 (runx-2), which is associated with osteoblast differentiation. The translocation of runx-2 initiated transcription and translation of osteogenesis-related markers, including alkaline phosphatase (ALP), osterix, and osteocalcin. Pardaxin significantly facilitated preosteoblast cells in mineralization and reversed dexamethasone- (DM-) induced zebrafish bone formation deficiency by activating the osteogenesis pathway. Therefore, we suggest that pardaxin could be a possible candidate for osteoporosis treatment and a promising therapeutic agent.

Flavonoids: Classification, Function, and Molecular Mechanisms Involved in Bone Remodelling

Flavonoids are polyphenolic compounds spotted in various fruits, vegetables, barks, tea plants, and stems and many more natural commodities. They have a multitude of applications through their anti-inflammatory, anti-oxidative, anti-carcinogenic properties, along with the ability to assist in the stimulation of bone formation. Bone, a rigid connective body tissue made up of cells embedded in a mineralised matrix is maintained by an assemblage of pathways assisting osteoblastogenesis and osteoclastogenesis. These have a significant impact on a plethora of bone diseases. The homeostasis between osteoblast and osteoclast formation decides the integrity and structure of the bone. The flavonoids discussed here are quercetin, kaempferol, icariin, myricetin, naringin, daidzein, luteolin, genistein, hesperidin, apigenin and several other flavonoids. The effects these flavonoids have on the mitogen activated protein kinase (MAPK), nuclear factor kappa β (NF-kβ), Wnt/β-catenin and bone morphogenetic protein 2/SMAD (BMP2/SMAD) signalling pathways, and apoptotic pathways lead to impacts on bone remodelling. In addition, these polyphenols regulate angiogenesis, decrease the levels of inflammatory cytokines and play a crucial role in scavenging reactive oxygen species (ROS). Considering these important effects of flavonoids, they may be regarded as a promising agent in treating bone-related ailments in the future.

Myricetin 3-O-β-D-Galactopyranoside Exhibits Potential Anti-Osteoporotic Properties in Human Bone Marrow-Derived Mesenchymal Stromal Cells via Stimulation of Osteoblastogenesis and Suppression of Adipogenesis

Natural bioactive substances are promising lead compounds with beneficial effects on various health problems including osteoporosis. In this context, the goal of this study was to investigate the effect of myricetin 3-O-β-D-galactopyranoside (M3G), a glycoside of a known bioactive phytochemical myricetin, on bone formation via osteogenic differentiation of human bone marrow-derived mesenchymal stromal cells (hBM-MSCs). The hBM-MSCs were induced to differentiate into osteoblasts and adipocytes in the presence or absence of M3G and the differentiation markers were analyzed. Osteoblastogenesis-induced cells treated with M3G exhibited stimulated differentiation markers: cell proliferation, alkaline phosphatase (ALP) activity, and extracellular mineralization. In terms of intracellular signaling behind the stimulatory effect of M3G, the expression of RUNX2 and osteopontin transcription factors were upregulated. It has been shown that M3G treatment increased the activation of Wnt and BMP as a suggested mechanism of action for its effect. On the other hand, M3G treatment during adipogenesis-inducement of hBM-MSCs hindered the adipogenic differentiation shown as decreased lipid accumulation and expression of PPARγ, SREBP1c, and C/EBPα, adipogenic transcription factors. In conclusion, M3G treatment stimulated osteoblast differentiation and inhibited adipocyte differentiation in induced hBM-MSCs. Osteoblast formation was stimulated via Wnt/BMP and adipogenesis was inhibited via the PPARγ pathway. This study provided necessary data for further studies to utilize the therapeutic potential of M3G against osteoporosis via regulation of bone marrow stromal cell differentiation.

Marantodes pumilum Var Alata (Kacip Fatimah) ameliorates derangement in RANK/RANKL/OPG pathway and reduces inflammation and oxidative stress in the bone of estrogen-deficient female rats with type-2 diabetes

BACKGROUND

M. pumilum has been claimed to protect the bone against the adverse effect of estrogen deficiency. Additionally, it also exhibits anti-diabetic activity. In view of these, this study aims to identify the mechanisms underlying the bone protective effect of M. pumilum in the presence of both estrogen deficiency and diabetes mellitus (DM).

METHODS

Ovariectomized, diabetic female rats were given M. pumilum leave aqueous extract (MPLA) (50 and 100 mg/kg/day), estrogen, glibenclamide and estrogen plus glibenclamide for 28 consecutive days. At the end of the treatment, fasting blood glucose (FBG), serum insulin, Ca²⁺, PO₄^3- and bone alkaline phosphatase (BALP) levels were measured. Rats were sacrificed and femur bones were harvested for determination of expression level and distribution of RANK, RANKL, OPG and oxidative stress and inflammatory proteins by molecular biological techniques.

RESULTS

100 mg/kg/day MPLA treatment decreased the FBG and BALP levels but increased the serum insulin, Ca²⁺ and PO₄^3- levels in estrogen deficient, diabetic rats. Expression and distribution of RANKL, NF-κB p65, IKKβ, IL-6, IL-1β and Keap-1 decreased however expression and distribution of RANK, OPG, BMP-2, Type-1 collagen, Runx2, TRAF6, Nrf2, NQO-1, HO-1, SOD and CAT increased in the bone of estrogen deficient, diabetic rats which received 100 mg/kg/day MPLA with greater effects than estrogen-only, glibenclamide-only and estrogen plus glibenclamide treatments.

CONCLUSION

MPLA helps to overcome the adverse effect of estrogen deficiency and DM on the bone and thus this herb could potentially be used for the treatment and prevention of osteoporosis in postmenopausal women with diabetes.

Application of Ligature-Induced Periodontitis in Mice to Explore the Molecular Mechanism of Periodontal Disease

Periodontitis is an inflammatory disease characterized by the destruction of the periodontium. In the last decade, a new murine model of periodontitis has been widely used to simulate alveolar bone resorption and periodontal soft tissue destruction by ligation. Typically, 3-0 to 9-0 silks are selected for ligation around the molars in mice, and significant bone loss and inflammatory infiltration are observed within a week. The ligature-maintained period can vary according to specific aims. We reviewed the findings on the interaction of systemic diseases with periodontitis, periodontal tissue destruction, the immunological and bacteriological responses, and new treatments. In these studies, the activation of osteoclasts, upregulation of pro-inflammatory factors, and excessive immune response have been considered as major factors in periodontal disruption. Multiple genes identified in periodontal tissues partly reflect the complexity of the pathogenesis of periodontitis. The effects of novel treatment methods on periodontitis have also been evaluated in a ligature-induced periodontitis model in mice. This model cannot completely represent all aspects of periodontitis in humans but is considered an effective method for the exploration of its mechanisms. Through this review, we aimed to provide evidence and enlightenment for future studies planning to use this model.

Bioactivity and Delivery Strategies of Phytochemical Compounds in Bone Tissue Regeneration

Plant-derived secondary metabolites represent a reservoir of phytochemicals for regenerative medicine application because of their varied assortment of biological properties including anti-oxidant, anti-inflammatory, antibacterial, and tissue remodeling properties. In addition, bioactive phytochemicals can be easily available, are often more cost-effective in large-scale industrialization, and can be better tolerated compared to conventional treatments mitigating the long-lasting side effects of synthetic compounds. Unfortunately, their poor bioavailability and lack of long-term stability limit their clinical impact. Nanotechnology-based delivery systems can overcome these limitations increasing bioactive molecules’ local effectiveness with reduction of the possible side effects on healthy bone. This review explores new and promising strategies in the area of delivery systems with particular emphasis on solutions that enhance bioavailability and/or health effects of plant-derived phytochemicals such as resveratrol, quercetin, epigallocatechin-3-gallate, and curcumin in bone tissue regeneration.

Diosmetin reduces bone loss and osteoclastogenesis by regulating the expression of TRPV1 in osteoporosis rats

Background

Osteoporosis is a systemic skeletal disorder and occurs frequently in postmenopausal women and older men. This study aimed to examine whether diosmetin (DIO) can relieve estrogen deficiency—induced osteoporosis and to explore the underlying mechanisms of this potential effect.

Methods

Forty-nine Sprague-Dawley (SD) rats were divided into seven groups. Six groups underwent bilateral ovariectomy (OVX), while the sham group underwent ovarian exposure surgery. DIO and evodiamine were administered 3 days before surgery, and then subcutaneously every 3 days for 3 months in the following fashion: group I, DIO (100 mg/kg); group II, OVX; group III, OVX + DIO (50 mg/kg); group IV, OVX + DIO (100 mg/kg); group V, OVX + evodiamine (10 mg/kg) group; group VI, OVX + DIO (100 mg/kg) + evodiamine (10 mg/kg) group. Bone histopathological damage, bone loss, osteoclast production, and the expression level of transient receptor potential vanilloid 1 (TRPV1) were detected.

Results

Compared with the sham group, the expression of bone resorption–related genes, osteoclast-associated receptor (OSCAR) (1.00%±0.16% versus 4.5%±0.28%, **, P<0.01) and tartrate-resistant acid phosphatase (TRAP) (2.0%±0.6% versus 18.00±1.2%, ***, P<0.001), was increased significantly. The protein level of osteogenic marker proteins, osterix (Osx) (1.0%±0.1% versus 0.03%±0.01%, **, P<0.01) and type 1 collagen (COL1A1) (1.0%±0.13% versus 0.13%±0.05%, **, P<0.01) was decreased significantly with the increase of TRPV1 (1.0%±0.15% versus 2.89%±0.28%, **, P<0.01) protein level. Notably, DIO can alleviate some abnormal symptoms related to osteoporosis.

Conclusions

DIO can relieve typical osteoporosis symptoms in an OVX osteoporosis rat model. The underlying mechanism may be associated with the downregulation of TRPV1.

DMY protects the knee joints of rats with collagen-induced arthritis by inhibition of NF-κB signaling and osteoclastic bone resorption

Collagen-induced arthritis (CIA) is a widely used animal model for studying rheumatoid arthritis (RA), which manifests serious joint dysfunction, progressive bone erosion and articular cartilage destruction. Considering that joint damage in RA is caused by systemic inflammation and dihydromyricetin (DMY), the main flavonoid of Ampelopsis Michx, possesses anti-inflammatory properties, in the present study we have investigated the potential capability of DMY to inhibit inflammation-mediated joint damage and explore the underlying mechanisms. A rat model of RA induced by CIA was administered with DMY for 5 weeks. Prior to histological analysis, the knee joints were scanned by microcomputed tomography (μCT) to detect bone damage. Articular cartilage destruction was assessed by Alcian blue and Toluidine blue staining and the pathological alteration of osteoblasts and osteoclasts in joints was evaluated by hematoxylin-eosin (H&E) and tartrate-resistant acid phosphatase (TRAP) staining, respectively. The effects of DMY on osteoblast differentiation and osteoclast formation in vitro were investigated. Consistent with the in vivo results, DMY had no significant effect on osteoblast differentiation but an inhibitory effect on osteoclast formation. Furthermore, we determined that the mechanism of the DMY-suppressed osteoclast formation was blocking the phosphorylation of I-κB kinase (IKK) so as to hinder the activation of nuclear factor-κB (NF-κB). Collectively, DMY could ameliorate knee joint damage, especially in articular cartilage, which is the weight-bearing region, by inhibiting osteoclast formation through NF-κB signaling.

Bacillus subtilis Fermentation of Malva verticillata Leaves Enhances Antioxidant Activity and Osteoblast Differentiation

Malva verticillata, also known as Chinese mallow, is an herbaceous plant with colorful flowers and has been used as a medicine for thousands of years. This study investigated this herb for potential antioxidant activity or an association with osteoblast differentiation. M. verticillate leaves were fermented with B. subtilis MV1 at 30 °C for 7 days to enhance their biological activities. The resultant aqueous extract (MVW) and the fermented leaves (MVB) were measured for antioxidant and osteoblast differentiation. The results showed that the total phenolic, flavonoid, and antioxidant activity, as well as the osteoblast differentiation of the MVB increased (2 to 6 times) compared with those of the MVW. MVB induced phosphorylation of p38, extracellular signal-regulated kinase in C3H10T1/2 cells, and the phosphorylation was attenuated via transforming growth factor-β (TGF-β) inhibitors. Moreover, runt-related transcription factor 2 and osterix in the nucleus increased in a time-dependent manner. The messenger RNA expression of alkaline phosphatase and bone sialoprotein increased about 9.4- and 65-fold, respectively, compared to the non-treated cells. MVB stimulated C3H10T1/2 cells in the osteoblasts via TGF-β signaling. Thus, fermented M. verticillata extract exhibited enhanced antioxidant activity and osteoblast differentiation.

NMR Characterization of the Influence of Zinc(II) Ions on the Structural and Dynamic Behavior of the New Delhi Metallo-β-Lactamase-1 and on the Binding with Flavonols as Inhibitors

New Delhi metallo-β-lactamase-1 (NDM-1) has recently emerged as a global threat because of its ability to confer resistance to all common β-lactam antibiotics. Understanding the molecular basis of β-lactam hydrolysis by NDM is crucial for designing NDM inhibitors or β-lactams resistant to their hydrolysis. In this study, for the first time, NMR was used to study the influence of Zn(II) ions on the dynamic behavior of NDM-1. Our results highlighted that the binding of Zn(II) in the NDM-1 active site induced several structural and dynamic changes on active site loop 2 (ASL2) and L9 loops and on helix α2. We subsequently studied the interaction of several flavonols: morin, quercetin, and myricetin were identified as natural and specific inhibitors of NDM-1. Quercetin conjugates were also synthesized in an attempt to increase the solubility and bioavailability. Our NMR investigations on NDM-1/flavonol interactions highlighted that both Zn(II) ions and the residues of the NDM-1 ASL1, ASL2, and ASL4 loops are involved in the binding of flavonols. This is the first NMR interaction study of NDM-1/inhibitors, and the models generated using HADDOCK will be useful for the rational design of more active inhibitors, directed against NDM-1.

Possible osteoprotective effects of myricetin in STZ induced diabetic osteoporosis in rats

Myricetin is a flavonoid which has many pharmacological effects. However, to date there is no evidence study on the effect of myricetin in diabetic condition. This study was aimed to investigate whether myricetin could protect against diabetic osteoporosis in streptozotocin induced rats. Female Wistar rats were randomly allocated to four equal groups: diabetic group (DG), diabetic group with myricetin (50 mg per kilogram per day), (D) diabetic group with myricetin (100 mg/kg/day) and normal control group (CG). Body weight was recorded once a week. After treatment with myricetin for 12 weeks, serum biochemical analyses, the microarchitecture of femora, and histological changes were evaluated. We found that the bone mineral density (BMD) of myricetin (100 mg per kilogram per day)treatment group significantly increased than in the diabetic group (P < 0.05). The alkaline phosphatase and osteocalcin were markedly blocked in diabetic rats relative to normal control group (P < 0.05); however, the inhibition was prevented by the myricetin treatment group. Results also showed that myricetin treatment could dramatically improve trabecular bone microarchitecture through increasing bone mass such as trabecular number (Tb.N), bone volume per tissue volume (BV/TV), and decreasing that of structure model index (SMI) and trabecular separation (Tb.Sp), comparing with the control group. We also found that myricetin could significantly lower the oxidative damage and up-regulate the activity of superoxide dismutase (SOD) and catalase activity. In summary, we showed that myricetin can effectively improve abnormal bone metabolism in streptozotocin induced rats, which may provide a beneficial medicine on diabetic bone disease.

Osteostimulatory effect of biocomposite scaffold containing phytomolecule diosmin by Integrin/FAK/ERK signaling pathway in mouse mesenchymal stem cells

Non-availability of an ideal alternative for autografts in treating critical-size bone defects is a major challenge in orthopedics. Phytocompounds have been proven to enhance osteogenesis via various osteogenic signaling pathways, but its decreased bioavailability and increased renal clearance limit its application. In this study, we designed a biocomposite scaffold comprising gelatin (Gel) and nanohydroxyapatite (nHAp) incorporated with diosmin (DM) and we investigated its bone forming potential in vitro and in vivo. Physiochemical characterization of the scaffold showed that DM had no effect on altering the material characteristics of the scaffold. The addition of DM enhanced the osteoblast differentiation potential of the scaffold in mouse mesenchymal stem cells at both cellular and molecular levels, possibly via the integrin-mediated activation of FAK and ERK signaling components. Using the rat tibial bone defective model, we identified the effect of DM in Gel/nHAp scaffold on enhancing bone formation in vivo. Based on our results, we suggest that Gel/nHAp/DM can be a potential therapeutic agent in scaffold-mediated bone regeneration.

Isolated Compounds from Turpinia formosana Nakai Induce Ossification

Bone metabolism is a homeostatic process, imbalance in which leads to the onset of diseases such as osteoporosis and osteopenia. Although several drugs are currently available to treat such conditions, they are associated with severe side effects and do not enhance bone formation. Thus, identifying alternative treatment strategies that focus on enhancing bone formation is essential. Herein, we explored the osteogenic potential of Turpinia formosana Nakai using human osteoblast (HOb) cells. The plant extract was subjected to various chromatographic techniques to obtain six compounds, including one new compound: 3,3′-di-O-methylellagic acid-4-O-α-l-arabinofuranoside (1). Compounds 3,3′-di-O-methylellagic acid-4-O-α-l-arabinofuranoside (1), gentisic acid 5-O-β-d-(6′-O-galloyl) glucopyranoside (2), strictinin (3), and (-)-epicatechin-3-O-β-d-allopyranoside (6) displayed no significant cytotoxicity toward HOb cells, and thus their effects on various osteogenic markers were analyzed. Results showed that 1–3 and 6 significantly increased alkaline phosphatase (ALP) activity up to 120.0, 121.3, 116.4, and 125.1%, respectively. Furthermore, 1, 2, and 6 also markedly enhanced the mineralization process with respective values of up to 136.4, 118.9, and 134.6%. In addition, the new compound, 1, significantly increased expression levels of estrogen receptor-α (133.4%) and osteogenesis-related genes of Runt-related transcription factor 2 (Runx2), osteopontin (OPN), bone morphogenetic protein (BMP)-2, bone sialoprotein (BSP), type I collagen (Col-1), and brain-derived neurotropic factor (BDNF) by at least 1.5-fold. Our results demonstrated that compounds isolated from T. formosana possess robust osteogenic potential, with the new compound, 1, also exhibiting the potential to enhance the bone formation process. We suggest that T. formosana and its isolated active compounds deserve further evaluation for development as anti-osteoporotic agents.

EDACO, a derivative of myricetin, inhibits the differentiation of Gaoyou duck embryonic osteoclasts in vitro

1. This study determined the effects of (E)-3-(2-(4-(3-(2,4-dimethoxyphenyl)acryloyl)phenoxy)ethoxy)-5,7-dimethoxy-2-(3,4,5-trimethoxyphenyl)-4H-chromen-4-one (EDACO) on the differentiation of Gaoyou duck embryonic osteoclasts cultured in vitro. 2. Bone marrow mononuclear cells (BM-MNC) were collected from 23-d-old Gaoyou duck embryos and induced by macrophage colony-stimulating factor and receptor activator of nuclear factor κB ligand in the presence of EDACO at different concentrations (i.e. 10, 20, 40, 80 and 160 µM). Tartrate-resistant acid phosphatase (TRAP) staining and resorption ability determination were conducted. 3. Results suggested that EDACO suppressed the shaping of positive multinucleated cells and the number of TRAP-positive cells in the 20, 40, 80 and 160 μM EDACO groups was significantly decreased (P < 0.05 or P < 0.01). Besides, the absorption activity of differentiated duck embryonic osteoclasts was significantly inhibited (P < 0.05) in both 80 and 160 μM EDACO groups. 4. Overall, EDACO can inhibit the differentiation of BM-MNC into mature osteoclasts in duck embryos.1.

Polyphenol uses in biomaterials engineering

Polyphenols are micronutrients obtained from diet that have been suggested to play an important role in health. The health benefits of polyphenols and their protective effects in food systems as antioxidant compounds are well known and have been extensively investigated. However, their functional roles as a "processing cofactor" in tissue engineering applications are less widely known. This review focuses on the functionality of polyphenols and their application in biomaterials. Polyphenols have been used to stabilize collagen and to improve its resistance to degradation in biological systems. Therefore, they have been proposed to improve the performance of biomedical devices used in cardiovascular systems by improving the mechanical properties of grafted heart valves, enhancing microcirculation through the relaxation of the arterial walls and improving the capillary blood flow and pressure resistance. Polyphenols have been found to stimulate bone formation, mineralization, as well as the proliferation, differentiation, and the survival of osteoblasts. These effects are brought about by the stimulatory effect of polyphenols on osteoblast cells and their protective effect against oxidative stress and inflammatory cytokines. In addition, polyphenols inhibit the differentiation of the osteoclast cells. Collectively, these actions lead to promote bone formation and to reduce bone resorption, respectively. Moreover, polyphenols can increase the cross-linking of dentine and hence its mechanical stability. Overall, polyphenols provide interesting properties that will stimulate further research in the bioengineering field.

Tridax procumbens flavonoids: a prospective bioactive compound increased osteoblast differentiation and trabecular bone formation

Background

The Tridax procumbens extracts (TPE) are known for their ethno-medicinal properties to increase osteogenic functioning in mesenchymal stem cells. Recently, we found that the T. procumbens flavonoids (TPF) significantly suppressed the RANKL-induced osteoclasts differentiation and bone resorption. The TPF also promoted osteoblasts differentiation and bone formation demonstrated by increasing bone formation markers in cultured mouse primary osteoblasts. However, the effects of the TPF on in vivo bone formation remain unclear. In this study, we investigated the effects of the TPF on in vivo bone formation, injected the TPF (20 mg/kg) twice a day in the low calcium diet mice and killed them after 21 day. Radiographic and histomorphometric analyses were performed on the dissected bones to determine the anabolic effects of the TPF.

Results

Bone mineral density and bone mineral content of the TPF-treated mice were significantly increased compared to the control mice. Bone formation-related indices like osteoblast number, osteoblast surface, bone volume, mineralizing surface, mineral apposition rate and bone formation rate were significantly increased in the TPF-treated mice compared to the control mice.

Conclusion

Our findings point towards the stimulation of bone formation by TPF, suggested that the TPF could be a potential natural anabolic agent to treat patients with bone loss-associated diseases such as osteoporosis.

Molecular signaling mechanisms behind polyphenol-induced bone anabolism

For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.

Optimization of ultrasound-assisted hydroalcoholic extraction of phenolic compounds from walnut leaves using response surface methodology

Context Walnut leaves are highly appreciated for their pharmacological effects and therapeutic properties which are mainly attributed to their high content of phenolic compounds. Objective This study optimizes ultrasound assisted hydroalcoholic extraction (UAE) of phenolic compounds from dried walnut leaves by the maximization of total phenolics content (TPC) and total flavanoids content (TFC) of the extracts. Materials and methods Optimal conditions with regard to ethanol concentration (X1: 12.17-95.83% v/v), extraction time (X2: 8.17-91.83 min) and liquid-to-solid ratio (X3: 4.96-25.04 v/w) were identified using central composite design combined with response surface methodology. A high-performance liquid chromatography method with diode-array detection was used to quantify phenolic acids (gallic, vanillic, chlorogenic, caffeic, syringic, p-coumaric, ferulic, sinapic, salicylic, ellagic and trans-cinnamic), flavonoids (catechin, epicatechin, rutin, myricetin and quercetin) and juglone in the extracts. Results Liquid-to-solid ratio and ethanol concentration proved to be the primary factors affecting the extraction efficiency. The maximum predicted TPC, under the optimized conditions (61% ethanol concentration, 51.28 min extraction time and 4.96 v/w liquid-to-solid ratio) was 10125.4 mg gallic acid equivalents per liter while maximum TFC (2925 mg quercetin equivalents per liter) occurred at 67.83% ethanol concentration, 4.96 v/w liquid-to-solid ratio and 49.37 min extraction time. High significant correlations were found between antioxidant activity and both TPC (R(2 )=( )0.81) and TFC (R(2 )=( )0.78). Discussion and conclusion Extracts very rich in polyphenols could be obtained from walnut leaves by using UAE, aimed at preparing dietary supplements, nutraceuticals or functional food ingredients.

Myricetin Prevents Alveolar Bone Loss in an Experimental Ovariectomized Mouse Model of Periodontitis

Periodontitis is a common chronic inflammatory disease, which leads to alveolar bone resorption. Healthy and functional alveolar bone, which can support the teeth and enable their movement, is very important for orthodontic treatment. Myricetin inhibited osteoclastogenesis by suppressing the expression of some genes, signaling pathways, and cytokines. This study aimed to investigate the effects of myricetin on alveolar bone loss in an ovariectomized (OVX) mouse model of periodontitis as well as in vitro osteoclast formation and bone resorption. Twenty-four healthy eight-week-old C57BL/J6 female mice were assigned randomly to four groups: phosphate-buffered saline (PBS) control (sham) OVX + ligature + PBS (vehicle), and OVX + ligature + low or high (2 or 5 mg∙kg⁻¹∙day⁻¹, respectively) doses of myricetin. Myricetin or PBS was injected intraperitoneally (i.p.) every other day for 30 days. The maxillae were collected and subjected to further examination, including micro-computed tomography (micro-CT), hematoxylin and eosin (H&E) staining, and tartrate-resistant acid phosphatase (TRAP) staining; a resorption pit assay was also performed in vitro to evaluate the effects of myricetin on receptor activator of nuclear factor κ-B ligand (RANKL)-induced osteoclastogenesis. Myricetin, at both high and low doses, prevented alveolar bone resorption and increased alveolar crest height in the mouse model and inhibited osteoclast formation and bone resorption in vitro. However, myricetin was more effective at high dose than at low dose. Our study demonstrated that myricetin had a positive effect on alveolar bone resorption in an OVX mouse model of periodontitis and, therefore, may be a potential agent for the treatment of periodontitis and osteoporosis.

Myricetin: A Dietary Molecule with Diverse Biological Activities

Myricetin is a common plant-derived flavonoid and is well recognised for its nutraceuticals value. It is one of the key ingredients of various foods and beverages. The compound exhibits a wide range of activities that include strong anti-oxidant, anticancer, antidiabetic and anti-inflammatory activities. It displays several activities that are related to the central nervous system and numerous studies have suggested that the compound may be beneficial to protect against diseases such as Parkinson's and Alzheimer's. The use of myricetin as a preserving agent to extend the shelf life of foods containing oils and fats is attributed to the compound's ability to protect lipids against oxidation. A detailed search of existing literature revealed that there is currently no comprehensive review available on this important molecule. Hence, the present work includes the history, synthesis, pharmaceutical applications and toxicity studies of myricetin. This report also highlights structure-activity relationships and mechanisms of action for various biological activities.

Wine and bone health: a review

A light-to-moderate wine consumption has been shown to provide several beneficial effects on the skeletal system, including reduced risk of bone mass loss and fractures. Wine is rich in phenolic compounds, strong phytoestrogens and natural antioxidants, to which bone protection is mainly attributed. The objective of this review was to give an overview of the exact mechanisms by which wine consumption is involved in bone protection. We found a great variety of in vitro research on the beneficial effects of isolated wine phenolics on the skeletal system, with a significant lack of evidence of their in vivo effects. In addition, we found almost no studies investigating how wine, a mixture of these phenolics dissolved in ethanol, affects the skeletal system. Our results warrant further research on this interesting topic.

Association between dietary intake of flavonoid and bone mineral density in middle aged and elderly Chinese women and men

SUMMARY

This large cross-sectional study examined the associations of dietary intakes of total flavonoids and their subtypes with bone density in women and men. We found that greater flavonoid intake was associated with higher bone density in women but not in men.

INTRODUCTION

Studies in vitro and in animal models suggest a potential effect of flavonoids on bone health. Few studies have examined the association between the habitual intake of flavonoids and bone mineral density (BMD) in humans.

METHODS

The cross-sectional study recruited 2,239 women and 1,078 men. A semiquantitative food frequency questionnaire was administered in face-to-face interviews to assess habitual dietary flavonoid intake using food composition databases. BMD was measured over the whole body (WB) and in the femoral neck (FN) and lumbar spine (LS) by dual-energy X-ray absorptiometry (DXA).

RESULTS

After adjusting for covariates, women who consumed higher total flavonoids, and the subtypes of flavonols, flavan-3-ols, flavones, and proanthocyanidins tended to have greater BMD at the WB, LS, and FN (all P-trend < 0.05). Women in the highest (vs. the lowest) quartile of total flavonoids intake had 0.020 (1.91 %), 0.021 (2.51 %), and 0.013 (1.99 %) g/cm(2) greater BMD at the whole body, LS, and FN, respectively. For the subtypes of flavonoids, the corresponding differences in BMD (in g/cm(2)) were 0.012-0.021 (flavan-3-ols), 0.013-0.020 (flavonols), 0.016-0.019 (flavones), and 0.014-0.016 (proanthocyanidins), respectively. A higher intake of flavonones was associated with a greater BMD at the whole body (P-trend 0.041) and the FN (P-trend 0.022). In men, there were no significant positive associations between the consumption of total flavonoids and the subclasses and BMD at any sites.

CONCLUSION

Dietary flavonoids intake was positively associated with BMD in women. Further large studies are needed to clarify this issue in men.

Stimulation of osteogenic activity in human osteoblast cells by edible Uraria crinita

Uraria crinita is an edible herb used as a natural food for childhood skeletal dysplasia. Ethyl acetate, n-butanol, and aqueous fractions of a 95% ethanol crude extract of U. crinita were obtained and the active ingredients isolated and purified using a bioguided method. In this manner, we isolated and identified a new active flavone glycoside, apigenin 6-C-β-d-apiofuranosyl(1→2)-α-d-xylopyranoside (3) and 10 known components with stimulatory activity on human osteoblast cells. The new compound 3 at 100 μM significantly increased alkaline phosphatase activity (114.10 ± 4.41%), mineralization (150.10 ± 0.80%), as well as osteopontin (1.39 ± 0.01-fold), bone morphogenetic protein-2 (BMP-2, 1.30 ± 0.04-fold), and runt-related transcription factor 2 (Runx2, 1.43 ± 0.10-fold) mRNA expression through the activation of the BMP-2/Runx2 pathway. Two other components, dalbergioidin (1) and byzantionoside B (9), displayed similar effects. These results show that U. crinita and its active compounds may have the potential to stimulate bone formation and regeneration.

Stimulative effect of ginsenosides Rg5:Rk1 on murine osteoblastic MC3T3-E1 cells

Panax ginseng C.A. Meyer (P. ginseng), hereafter referred to as P. ginseng, is known to exert a wide range of pharmacological effects both in vitro and in vivo; however, few studies have investigated the effects of ginseng on bone metabolism. We therefore investigated the potential antiosteoporotic properties of ginseng on the growth and differentiation of murine MC3T3-E1 cells. Rg5:Rk1 is a mixture of protopanaxadiol-type ginsenosides, isolated from fresh P. ginseng root, via a repetitive steaming and drying process. In this study, we examined the stimulatory effects of Rg5:Rk1 on the differentiation and mineralization of MC3T3-E1 cells. Undifferentiated cells were treated with a range of concentrations of Rg5:Rk1 (1-50 µg/mL), and cell viability was measured with the 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Treatment with Rg5:Rk1 significantly increased cell viability in a dose-dependent manner. To investigate the possible mechanisms by which Rg5:Rk1 affects the early differentiation phase of MC3T3-E1 cells, the cells were treated with Rg5:Rk1 for 14-24 days before assessing the levels of multiple osteoblastic markers. The markers examined included alkaline phosphatase (ALP) activity type I collagen content (Coll-I), calcium deposition (by Alizarin Red S staining), extracellular mRNA expression of bone morphogenetic protein-2 (BMP-2), and the level of Runt-related transcription factor 2 (Runx2). Rg5:Rk1 treatment also increased the activities of proteins associated with osteoblast growth and differentiation in a dose-dependent manner. Overall, we found that the Rg5:Rk1 mixture of ginsenosides improved the osteoblastic function of MC3T3-E1 cells by increasing their proliferative capacity. This improvement is due to the action of Rg5:Rk1 on BMP-2, which is mediated by Runx2-dependent pathways.

Gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens

This study investigated gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens. Thirty male chickens were caponized at 8 weeks (capons); 15 capons were injected with estrogen (5 mg/bird estradiol 3-benzoate) every 2 weeks from 8 to 28 weeks, and 15 sham-operated male (shams) chickens and 15 females were selected for this trial. The results showed that the shams had lower relative abdominal and chest subcutaneous fat than females (P < 0.05). The estrogen-treated capons had greater relative abdominal and chest subcutaneous fat than shams and capons (P < 0.05), which might result from higher blood very low-density lipoproteins and triacylglycerol concentrations (P < 0.05). Caponization could dramatically increase relative abdominal fat (506%; P < 0.05). The shams had higher tibia weight and biomechanical properties, such as maximum bone strength and bending moment values than the capons (P < 0.05). Tibia biomechanical properties were reduced by estrogen treatment (P < 0.05). The females obtained the lowest biomechanical value in all treatments (P < 0.05). Histological examination revealed cavity formation in the cortical bone of estrogen-treated capons and female chickens, which suggested that estrogen reduced bone biomechanical properties by destroying its structural integrity.

Salidroside stimulates osteoblast differentiation through BMP signaling pathway

Salidroside (SAL) is one of main active components of Rhodiola rosea L. and possesses diverse pharmacological effects. However, the direct role of SAL in bone metabolism remains elusive. In this study, effects of SAL on osteoblast differentiation of murine pluripotent mesenchymal cell line C3H10T1/2 and osteoblastic cell line MC3T3-E1 were examined. We first identified SAL as a potential BMP2 activator in a cell-based screening assay. SAL (0.5-10 μM) could slightly promote the proliferation and greatly increase the alkaline phosphatase (ALP) activity in both cells. Furthermore, SAL increased the mRNA expressions of osteoblast marker genes in either C3H10T1/2 or MC3T3-E1 cells after treatment for different time. Moreover, the mineralization of C3H10T1/2 cells assayed by Alizarin red S staining was dose-dependently increased by SAL. Mechanistically, SAL increased the mRNA level of genes involved in the regulation of BMP signaling pathway, including BMP2, BMP6 and BMP7 and enhanced the phosphorylation of Smad1/5/8 and ERK1/2. The osteogenic effect of SAL was abolished by BMP antagonist noggin or by BMP receptor kinase inhibitor dorsomorphin. Further in vivo study demonstrated that SAL reversed bone loss in ovariectomized rats. Collectively, our findings indicate that SAL regulates bone metabolism through BMP signaling pathway.

Downregulated LncRNA-ANCR promotes osteoblast differentiation by targeting EZH2 and regulating Runx2 expression

Long noncoding RNAs (lncRNAs) are key regulators of diverse biological processes such as transcriptional regulation, cell growth and differentiation. Previous studies have demonstrated that the lncRNA-ANCR (anti-differentiation ncRNA) is required to maintain the undifferentiated cell state within the epidermis. However, little is known about whether ANCR regulates osteoblast differentiation. In this study, we found that the ANCR expression level is significantly decreased during hFOB1.19 cell differentiation. ANCR-siRNA blocks the expression of endogenous ANCR, resulting in osteoblast differentiation, whereas ANCR overexpression is sufficient to inhibit osteoblast differentiation. We further demonstrated that ANCR is associated with enhancer of zeste homolog 2 (EZH2) and that this association results in the inhibition of both Runx2 expression and subsequent osteoblast differentiation. These data suggest that ANCR is an essential mediator of osteoblast differentiation, thus offering a new target for the development of therapeutic agents to treat bone diseases.

Ugonin K promotes osteoblastic differentiation and mineralization by activation of p38 MAPK- and ERK-mediated expression of Runx2 and osterix

Ugonin K is a flavonoid isolated from the roots of Helminthostachys zeylanica, a folk medicine used to strengthen bone mass and cure bone fracture. It is of interest to determine whether ugonin K has beneficial effect on osteoblast maturation. In this study, MC3T3-E1 osteoblasts were treated with ugonin K. Cell differentiation and mineralization were identified by alkaline phosphatase (ALP) activity and Alizarin red S staining, respectively. RT-PCR and Western blot were used to analyze osteoblast-associated gene expression and signaling pathways. Our results showed that ugonin K significantly induced the increase of ALP activity, expressions of bone sialoprotein (BSP) and osteocalcin (OCN), and mineralization. The mRNA expressions of the transcription factors Runx2 and osterix were also up-regulated by ugonin K. Ugonin K increased the phosphorylated level of p38 and ERK, respectively. In the presence of SB203580, ugonin K induced expressions of Runx2 and osterix, ALP activity, BSP level and bone nodule formation were all completely inhibited, but ugonin K induced OCN expression was not affected. On the other hand, ugonin K-induced ALP activity and mineralization were mildly attenuated by PD98059, but the over-expressed Runx2, osterix, BSP and OCN also were significantly repressed by PD98059. These suggested that both p38 and ERK participate in regulating ugonin K evoked osteogenesis but p38 seemed to play a more important role. Take together, the potential anabolic effect of ugonin K on bone might act through activations of p38- and ERK-mediated Runx2 and osterix expressions to induce the synthesis of osteoids and formation of bone nodule.

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.

Identification of kaempferol-regulated proteins in rat calvarial osteoblasts during mineralization by proteomics

Kaempferol, a flavonoid, promotes osteoblast mineralization in vitro and bone formation in vivo; however, its mechanism of action is yet unknown. We adopted proteomic approach to identify the differential effect of kaempferol on rat primary calvarial osteoblasts during mineralization. The primary rat calvarial osteoblasts were treated with kaempferol (5.0 microM) for 9 days under mineralizing condition that resulted in significant increase in alkaline phosphatase activity and mineralization of the cells. Further, 2-D analysis of the kaempferol-treated osteoblast lysates revealed 18 differentially expressed proteins (nine upregulated and nine downregulated) on the basis of >/<2.0-fold as cut-off (p<0.01) that were then identified by MALDI-TOF MS. These included cytoskeletal proteins, intracellular signaling protein, chaperone, extracellular matrix protein, and proteins involved in glycolysis and cell-matrix interactions. Proteomics data were confirmed by Western blotting and quantitative real-time PCR by randomly selecting two upregulated and two downregulated proteins. Western blot analysis confirmed upregulation of HSP-70 and cytokeratin-14 levels, and downregulation of aldose reductase and caldesmon expression. We further demonstrated that kaempferol treatment inhibits aldose reductase activity in osteoblasts indicating an altered cellular metabolism by decelerating polyol pathway that was associated with the kaempferol-induced osteoblast mineralization. In conclusion, this is a first comprehensive study on the differential regulation of proteins by kaempferol in primary osteoblast, which would further help to elucidate the role of the identified proteins in the process of osteoblast mineralization.