Genistein stimulates the osteoblastic differentiation via NO/cGMP in bone marrow culture

Pharmacological and mechanistic aspects of quercetin in osteoporosis

Osteoporosis (OP) is a bone disease associated with increasing age. Currently, the most common medications used to treat OP are anabolic agents, anti-resorptive agents, and medications with other mechanisms of action. However, many of these medications have unfavorable adverse effects or are not intended for long-term use, potentially exerting a severe negative impact on a patient's life and career and placing a heavy burden on families and society. There is an urgent need to find new drugs that can replace these and have fewer adverse effects. Quercetin (Que) is a common flavonol in nature. Numerous studies have examined the therapeutic applications of Que. However, a comprehensive review of the anti-osteoporotic effects of Que has not yet been conducted. This review aimed to describe the recent studies on the anti-osteoporotic effects of Que, including its biological, pharmacological, pharmacokinetic, and toxicological properties. The outcomes demonstrated that Que could enhance OP by increasing osteoblast differentiation and activity and reducing osteoclast differentiation and activity via the pathways of Wnt/β-catenin, BMP/SMAD/RUNX2, OPG/RANKL/RANK, ERK/JNK, oxidative stress, apoptosis, and transcription factors. Thus, Que is a promising novel drug for the treatment of OP.

Systems genetics and bioinformatics analyses using ESR1-correlated genes identify potential candidates underlying female bone development

Estrogen receptor α (ESR1) is involved in E2 signaling and plays a major role in postmenopausal bone loss. However, the molecular network underlying ESR1 has not been explored. We used systems genetics and bioinformatics to identify important genes associated with Esr1 in postmenopausal bone loss. We identified ~2300 Esr1-coexpressed genes in female BXD bone femur, functional analysis of which revealed 'osteoblast signaling' as the most enriched pathway. PPI network led to the identification of 25 'female bone candidates'. The gene-regulatory analysis revealed RUNX2 as a key TF. ANKRD1 and RUNX2 were significantly different between osteoporosis patients and healthy controls. Sp7, Col1a1 and Pth1r correlated with multiple femur bone phenotypes in BXD mice. miR-3121-3p targeted Csf1, Ankrd1, Sp7 and Runx2. β-estradiol treatment markedly increased the expression of these candidates in mouse osteoblast. Our study revealed that Esr1-correlated genes Ankrd1, Runx2, Csf1 and Sp7 may play important roles in female bone development.

Activating Wnt/β-catenin signaling by autophagic degradation of APC contributes to the osteoblast differentiation effect of soy isoflavone on osteoporotic mesenchymal stem cells

The functional role of autophagy in regulating differentiation of bone marrow mesenchymal stem cells (MSCs) has been studied extensively, but the underlying mechanism remains largely unknown. The Wnt/β-catenin signaling pathway plays a pivotal role in the initiation of osteoblast differentiation of mesenchymal progenitor cells, and the stability of core protein β-catenin is tightly controlled by the APC/Axin/GSK-3β/Ck1α complex. Here we showed that genistein, a predominant soy isoflavone, stimulated osteoblast differentiation of MSCs in vivo and in vitro. Female rats were subjected to bilateral ovariectomy (OVX); four weeks after surgery the rats were orally administered genistein (50 mg·kg-1·d-1) for 8 weeks. The results showed that genistein administration significantly suppressed the bone loss and bone-fat imbalance, and stimulated bone formation in OVX rats. In vitro, genistein (10 nM) markedly activated autophagy and Wnt/β-catenin signaling pathway, and stimulated osteoblast differentiation in OVX-MSCs. Furthermore, we found that genistein promoted autophagic degradation of adenomatous polyposis coli (APC), thus initiated β-catenin-driven osteoblast differentiation. Notably, genistein activated autophagy through transcription factor EB (TFEB) rather than mammalian target of rapamycin (mTOR). These findings unveil the mechanism of how autophagy regulates osteogenesis in OVX-MSCs, which expands our understanding that such interplay could be employed as a useful therapeutic strategy for treating postmenopausal osteoporosis.

Genistein and coumestrol reduce MCF-7 breast cancer cell viability and inhibit markers of preferential metastasis, bone matrix attachment and tumor-induced osteoclastogenesis

The propensity of breast cancer to preferentially metastasize to the skeleton is well known. Once established in bone metastatic breast cancers have a poor prognosis due to their ability to promote extensive bone loss which augments tumor burden. Unfortunately, current anti-resorptive therapies for skeletal metastasis are typically prescribed after secondary tumors have formed and are palliative in nature. One group of compounds with the potential to reduce both tumor burden and osteolysis are phytoestrogens (PE), but the mechanisms mediating a beneficial effect are unclear. Therefore, the current study examined the effect of genistein and coumestrol alone or in combination on breast cancer cell number, expression of mediators of preferential skeletal metastasis, bone matrix attachment and tumor-induced osteoclast formation. Results showed that genistein and coumestrol significantly reduced viable cell number in an estrogen receptor dependent manner (p < 0.05), whereas combinations of PE had no effect. In addition, genistein and coumestrol significantly reduced expression of genes driving epithelial to mesenchymal transition (snail), bone attachment (CXCR4 and integrin αV) and osteolysis (PTHrP and TNF-α). In keeping with this genistein and coumestrol significantly suppressed attachment of breast cancer cells to bone matrix and inhibited tumor and RANKL-induced osteoclast formation. Our data suggests that phytoestrogens not only decrease breast cancer cell viability but also antagonize essential tumor bone interactions that establish and drive the progression of skeletal metastasis.

Electrosprayed Regeneration-Enhancer-Element Microspheres Power Osteogenesis and Angiogenesis Coupling

Electrosprayed microspheres for bone regeneration are conventionally restricted by the lack of osteogenic modulation for both encapsulated stem cells and surrounding cells at the defect site. Here, sodium alginate microspheres encapsulating L-arginine doped hydroxyapatite nanoparticles (Arg/HA NPs) and bone mesenchymal stem cells (BMSCs) as regeneration-enhancer-element reservoirs (Arg/HA-SA@BMSC) for bone healing are electrosprayed. The Arg/HA NPs serve as a container of L-arginine and Ca²⁺ and the BMSCs inside the microspheres metabolize the released L-arginine into bioactive gas nitric oxide (NO) in the presence of Ca²⁺ to activate the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling pathway. Meanwhile, the generated NO diffuses out of the microspheres together with the Ca²⁺ and L-arginine as exterior enhancers to promote the osteogenesis-angiogenesis coupling of surrounding BMSCs and endothelial cells (ECs) at the bone defect site, generating an internal/external modulation loop between the encapsulated cells and surrounding native cells. It is demonstrated that such regeneration-enhancer-element reservoirs could effectively increase the bone tissue formation and neovasculature using rat calvarial defect models. It is envisioned that the microsphere system could streamline vascularized bone regeneration therapy as a high throughput, minimally invasive yet highly effective strategy to accelerate bone healing.

The differentiation of mesenchymal bone marrow stem cells into nerve cells induced by Chromolaena odorata extracts

Background: Mesenchymal stem cells (MSCs) can differentiate into nerve cells with an induction from chemical compounds in medium culture. Chromolaena odorata contains active compounds, such as alkaloids and flavonoids, that can initiate the transformation of MSCs into nerve cells. The aim of this study was to determine the potential of methanol extracted C. odorata leaf to induce the differentiation of bone marrow MSCs into nerve cells.

Methods: A serial concentration of C. odorata leaf extract (0.7–1.0 mg/mL) with two replications was used. The parameters measured were the number of differentiated MSCs into nerve cells (statistically analyzed using ANOVA) and cell confirmation using reverse transcription polymerase chain reaction (RT-PCR).

Results: The results showed that the C. odorata extract had a significant effect on the number MSCs differentiating into nerve cells ( p < 0.05) on the doses of 0.8 mg/ml with 22.6%. Molecular assay with RT-PCR confirmed the presence of the nerve cell gene in all of the samples.

Conclusions: In conclusion, this study showed the potential application of C. odorata leaf extract in stem cell therapy for patients experiencing neurodegeneration by inducing the differentiation of MSCs into nerve cells.

Puerarin action on stem cell proliferation, differentiation and apoptosis: Therapeutic implications for geriatric diseases

BACKGROUND

Aging is associated with a decline in cognitive and physical functions and various geriatric diseases, such as cardiovascular and neurodegenerative diseases. Puerarin (Pue), one of the main active flavonoids of Radix Puerariae (R. pueraria), is reportedly effective in treating geriatric diseases, including cardiovascular disease and hypertension.

PURPOSE

This review aims to summarize and discuss the profound physiological impact of Pue on various stem cell populations and provide new insights into the use of Pue for the prevention and treatment of geriatric diseases.

METHODS

The literature was retrieved from the core collection of electronic databases, such as Web of Science, Google Scholar, PubMed, and Science Direct, using the following keywords and terms: Puerarin, Stem Cell, Proliferation, Differentiation, Apoptosis, and Geriatric diseases. These keywords were used in multiple overlapping combinations.

RESULTS

Pue is effective in the treatment and management of age-related diseases, such as cardiovascular disease, diabetes, hypertension, and cerebrovascular disease. Pue exerts significant physiological effects on various stem cell populations, including their self-renewal/proliferation, differentiation and apoptosis. Most importantly, it could improve the efficiency and accuracy of stem cell therapy for treating various geriatric diseases. Further studies are essential to improve our understanding of the underlying mechanisms and elucidate their significance for future clinical applications.

CONCLUSION

The effects of Pue on various stem cell populations and their regulatory mechanisms are discussed in detail to provide new insights into the use of Pue in the prevention and treatment of geriatric diseases.

Icariin regulates miR-23a-3p-mediated osteogenic differentiation of BMSCs via BMP-2/Smad5/Runx2 and WNT/β-catenin pathways in osteonecrosis of the femoral head

Icariin is commonly used for the clinical treatment of osteonecrosis of the femoral head (ONFH). miR-23a-3p plays a vital role in regulating the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). The present study aimed to investigate the roles of icariin and miR-23a-3p in the osteogenic differentiation of BMSCs and an ONFH model. BMSCs were isolated and cultured in vitro using icariin-containing serum at various concentrations, and BMSCs were also transfected with a miR-23a inhibitor. The alkaline phosphatase (ALP) activity and cell viability as well as BMP-2/Smad5/Runx2 and WNT/β-catenin pathway-related mRNA and protein expression were measured in BMSCs. Additionally, a dual-luciferase reporter assay and pathway inhibitors were used to verify the relationship of icariin treatment/miR-23a and the above pathways. An ONFH rat model was established in vivo, and a 28-day gavage treatment and lentivirus transfection of miR-23a-3p inhibitor were performed. Then, bone biochemical markers (ELISA kits) in serum, femoral head (HE staining and Digital Radiography, DR) and the above pathway-related proteins were detected. Our results revealed that icariin treatment/miR-23a knockdown promoted BMSC viability and osteogenic differentiation as well as increased the mRNA and protein expression of BMP-2, BMP-4, Runx2, p-Smad5, Wnt1 and β-catenin in BMSCs and ONFH model rats. In addition, icariin treatment/miR-23a knockdown increased bone biochemical markers (ACP-5, BAP, NTXI, CTXI and OC) and improved ONFH in ONFH model rats. In addition, a dual-luciferase reporter assay verified that Runx2 was a direct target of miR-23a-3p. These data indicated that icariin promotes BMSC viability and osteogenic differentiation as well as improves ONFH by decreasing miR-23a-3p levels and regulating the BMP-2/Smad5/Runx2 and WNT/β-catenin pathways.

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.

Soy isoflavone metabolite equol inhibits cancer cell proliferation in a PAP associated domain containing 5-dependent and an estrogen receptor-independent manner

Isoflavone is a species of polyphenol found mainly in soy and soy products. Many studies have demonstrated its estrogen receptor (ER)-dependent action. Equol is an intestinal metabolite of a major soy isoflavone daidzein. We aimed to elucidate the mechanism for ER-independent actions of equol. Equol has been shown to inhibit proliferation of HeLa human cervical cancer cells and mouse melanoma B16 cells in an ER-independent manner. Using functional genetic screening, PAP associated domain containing 5 (PAPD5), which is a non-canonical poly(A) polymerase, was identified as an essential molecule in the ER-independent action. While peroral administration of equol inhibited tumor growth of control B16 cells subcutaneously inoculated in mice, it had little effect on the growth of PAPD5-ablated B16 cells. Intriguingly, equol progressed tumor growth of the PAPD5-ablated human breast cancer MCF-7 cells, which have high ERα expression. Equol has been found to induce polyadenylation of snoRNAs in a PAPD5-depdendent manner. Furthermore, peroral equol administration increased microRNA miR-320a expression in tumors. Together, these results suggest that equol may have a dual effect on ER-positive cancer cells, acting with, antiproliferative activity through PAPD5 and exhibiting proliferative activity via ERα and the former could be associated with miR-320a.

Effect of pinocembrin isolated from Alpinia zerumbet on osteoblast differentiation

Bone mass is regulated by osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Osteoporosis is a bone metabolism disorder in which bone mass decreases due to increased bone resorption rather than bone formation. We focused on the traditional plant Alpinia zerumbet in Okinawa, Japan, and searched for promising compounds for the prevention and treatment of osteoporosis. Pinocembrin isolated from the leaves of A. zerumbet showed enhanced alkaline phosphatase (ALP) activity and mineralization and increased mRNA expression of osteoblast-related genes Alp and Osteocalcin (Ocn) in MC3T3-E1 cells. Pinocembrin increased the mRNA expression of Runx2 and Osterix, which are important transcription factors in osteoblast differentiation, and the mRNA expression of Dlx5 and Msx2, which are enhancers of these transcription factors. The bone morphogenetic protein (BMP) antagonist noggin, its receptor kinase inhibitor LDN-193189 and p38 MAPK inhibitor SB203580 attenuated pinocembrin-promoted ALP activity. Pinocembrin increased the mRNA of Bmp-2 and its target gene Id1. In addition, the estrogen receptor (ER) inhibitor ICI182780 suppressed pinocembrin-stimulated ALP activity. Pinocembrin may increase BMP-2 expression via ER. Then, the BMP-2 promotes osteoblast specific genes expression and mineralization through both Smad-dependent and independent pathway following Runx2 and Osterix induction. Our findings suggest that pinocembrin has bone anabolic effects and may be useful for the prevention and treatment of bone metabolic diseases such as osteoporosis.

Genistein contributes to cell cycle progression and regulates oxidative stress in primary culture of osteoblasts along with osteoclasts attenuation

Background

The present study was designed to examine the role of isoflavone genistein (GS) on bone formation, regulating oxidative stress and cell cycle in primary osteoblasts, as well as attenuation of osteoclast formation.

Methods

Primary calvaria osteoblasts were isolated from 2 to 3 days old neonatal rat pups (n = 6–8) of Sprague Dawley rats. Osteoblasts were incubated with varying concentrations of GS and different assays viz. cell proliferation, differentiation, calcium deposition, cell cycle progression, antioxidant ability, and osteogenic gene expression were performed. Tartrate-resistant acid phosphatase (TRAP) staining and immunolocalization of cathepsin K protein were assessed in bone marrow-derived osteoclasts.

Results

Results revealed that GS markedly induced cell growth and osteoblast differentiation depending upon dose. The fluorescent dye DCFH-DA staining data proved the antioxidant ability of GS, which reduced the H₂O₂- induced intracellular oxidative stress in osteoblasts. Quantitative real-time PCR analysis revealed that GS treatment upregulated the expression of osteoblastic genes of Runt-related transcription factor 2 (Runx2), bone morphogenetic proteins 2 (BMP2), and osteocalcin. Immunolocalization of BMP2 also indicated the osteogenic efficacy of GS. Furthermore, TRAP staining and cathepsin K expression depicted that GS inhibited multinucleated osteoclasts formation.

Conclusions

In conclusion, GS isoflavone might impart protective effects against oxidative stress-induced bone loss and thus, could maintain skeletal growth.

Lysed Erythrocyte Membranes Promote Vascular Calcification

BACKGROUND

Intraplaque hemorrhage promotes atherosclerosis progression, and erythrocytes may contribute to this process. In this study we examined the effects of red blood cells on smooth muscle cell mineralization and vascular calcification and the possible mechanisms involved.

METHODS

Erythrocytes were isolated from human and murine whole blood. Intact and lysed erythrocytes and their membrane fraction or specific erythrocyte components were examined in vitro using diverse calcification assays, ex vivo by using the murine aortic ring calcification model, and in vivo after murine erythrocyte membrane injection into neointimal lesions of hypercholesterolemic apolipoprotein E-deficient mice. Vascular tissues (aortic valves, atherosclerotic carotid artery specimens, abdominal aortic aneurysms) were obtained from patients undergoing surgery.

RESULTS

The membrane fraction of lysed, but not intact human erythrocytes promoted mineralization of human arterial smooth muscle cells in culture, as shown by Alizarin red and van Kossa stain and increased alkaline phosphatase activity, and by increased expression of osteoblast-specific transcription factors (eg, runt-related transcription factor 2, osterix) and differentiation markers (eg, osteopontin, osteocalcin, and osterix). Erythrocyte membranes dose-dependently enhanced calcification in murine aortic rings, and extravasated CD235a-positive erythrocytes or Perl iron-positive signals colocalized with calcified areas or osteoblast-like cells in human vascular lesions. Mechanistically, the osteoinductive activity of lysed erythrocytes was localized to their membrane fraction, did not involve membrane lipids, heme, or iron, and was enhanced after removal of the nitric oxide (NO) scavenger hemoglobin. Lysed erythrocyte membranes enhanced calcification to a similar extent as the NO donor diethylenetriamine-NO, and their osteoinductive effects could be further augmented by arginase-1 inhibition (indirectly increasing NO bioavailability). However, the osteoinductive effects of erythrocyte membranes were reduced in human arterial smooth muscle cells treated with the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide or following inhibition of NO synthase or the NO receptor soluble guanylate cyclase. Erythrocytes isolated from endothelial NO synthase-deficient mice exhibited a reduced potency to promote calcification in the aortic ring assay and after injection into murine vascular lesions.

CONCLUSIONS

Our findings in cells, genetically modified mice, and human vascular specimens suggest that intraplaque hemorrhage with erythrocyte extravasation and lysis promotes osteoblastic differentiation of smooth muscle cells and vascular lesion calcification, and also support a role for erythrocyte-derived NO.

Biochemistry and use of soybean isoflavones in functional food development

Soybeans and their food products exist in the market in various forms, ranging from crude oils and bean meals to nutritious products (e.g. soy milk powers). With the availability of technologies for mass production of soy products and for enrichment of soy components (e.g. phospholipids, saponins, isoflavones, oligosaccharides and edible fiber), the nutritional values of soy products have been enhanced remarkably, offering the potential for functional food development. Among different bioactive components in soybeans, one important component is isoflavones, which have been widely exploited for health implications. While there are studies supporting the health benefits of isoflavones, concerns on adverse effects have been raised in the literature. The objective of this article is to review the recent understanding of the biological activities, adverse effects, and use of isoflavones in functional food development.

Synergistic Phytochemicals Fail to Protect Against Ovariectomy Induced Bone Loss in Rats

Menopause induces a loss of bone as a result of estrogen deficiency. Despite pharmaceutical options for the treatment of osteopenia and osteoporosis, many aging women use dietary supplements with estrogenic activity to prevent bone loss and other menopausal-related symptoms. Such supplements are yet to be tested for efficacy against a Food and Drug Administration (FDA) approved medication for menopausal bone loss such as zoledronic acid (ZA). The postmenopausal rat model was used to investigate the efficacy of various synergistic phytochemical blends mixed into the diet for 16 weeks. Retired-breeder, Fischer 344 rats were randomly assigned to sham or ovariectomy surgery and 4 treatment groups: ZA; genistein supplementation; and a low dose and high dose blend of genistein, resveratrol, and quercetin. Ovariectomy resulted in a loss of both trabecular and cortical bone which was prevented with ZA. The phytochemical blends tested were unable to reverse these losses. Despite the lack of effectiveness in preventing bone loss, a significant dose-response trend was observed in the phytochemical-rich diets in bone adipocyte number compared to ovariectomized control rats. Data from this study indicate that estrogenic phytochemicals are not as efficacious as ZA in preventing menopausal-related bone loss but may have beneficial effects on bone marrow adiposity in rats.

The phytoestrogen genistein prevents trabecular bone loss and affects thyroid follicular cells in a male rat model of osteoporosis

As a major phytoestrogen of soy, genistein effectively prevents bone loss in both humans and rat models of osteoporosis. However, although the bone-sparing effects of genistein are achieved directly through estrogen receptors, its mode of action on bone by modulation of other endocrine functions is not entirely clear. Thus, thyroid hormones and calcitonin (CT) have an essential influence on bone metabolism. Besides its action on bones, in this study we examined the effect of genistein on the activity of two different endocrine cell populations, thyroid follicular and C-cells. Fifteen-month-old Wistar rats were either bilaterally orchidectomized (Orx) or sham-operated (SO). Two weeks after surgery, half of the Orx rats were treated chronically with 30 mg kg^-1 b.w. genistein (Orx + G) subcutaneously (s.c.) every day for 3 weeks, while the remaining Orx rats and the SO rats were given the same volume of sterile olive oil to serve as controls. For histomorphometrical analysis of the trabecular bone microarchitecture an ImageJ public domain image processing programme was used. Thyroid sections were analysed histologically and stereologically after visualization of follicular and C-cells by immunohistochemical staining for thyroglobulin and CT. Thyroid follicular epithelium, interstitium, colloid and CT-immunopositive C-cells were examined morphometrically. Serum concentrations of osteocalcin (OC), triiodothyronine (T₃ ), thyroxine (T₄ ) and CT were determined as well as urinary calcium (Ca²⁺ ) concentrations. Genistein treatment significantly increased cancellous bone area (B.Ar), trabecular thickness (TbTh) and trabecular number (TbN) (P < 0.05), but trabecular separation (Tb.Sp) was decreased (P < 0.05) compared with control Orx rats. In the thyroid, genistein treatment significantly elevated the relative volume density (Vv) of the follicular cells (P < 0.05) compared with Orx, whereas Vv of the colloid was lower (P < 0.05) than in the Orx. Evaluation of the biochemical parameters showed significant reductions in serum OC, T₃ , T₄ and urinary Ca²⁺ concentrations (P < 0.05), compared with Orx rats. These data indicate that genistein treatment improves the trabecular microarchitecture of proximal tibia, induces histomorphometrical changes in thyroid glands, and decreases circulating thyroid hormone levels in orchidectomized rat model of male osteoporosis.

In vitro evaluation of the potential therapeutic role of Dendropanax morbifera extract in ameliorating osteoporosis and resultant bone impairment using MC3T3-E1 cells

Osteoporosis is a widespread musculoskeletal deformity that affects thousands of older people every year, leading to bone abnormalities and ultimately increasing the risk of bone fractures in both genders. It is considered a lethal disease causing death in thousands of people at the late stage of life. Dendropanax morbifera Leveille is a subtropical broad-leaved prevalent species in Korea. Extracts of the leaves, stems, roots, and seeds of D. morbifera have been used in traditional medicine for the treatment of numerous diseases such as diabetes, atherogenesis, skin disorders, and headaches. However, the anti-osteoporosis effects of D. morbifera have not been examined. The primary objectives of this study were to elucidate the anti-osteoporosis effect of D. morbifera extract through an in vitro study using pre-osteoblastic MC3T3-E1 cells. We found that D. morbifera strongly increased the expression of bone metabolic markers such as alkaline phosphatase (ALP) activity, type I collagen (Col-I) level, and mineralization. Additionally, D. morbifera extract also upregulated the mRNA expression levels of osteogenic genes including ALP, osteocalcin (OCN), osterix (Osx), and runt-related transcription factor 2 (Runx2) in MC3T3-E1 cells via upregulation of bone morphogenetic protein 2 (BMP-2)/p38 MAPK/JNK and Smad1/5/8 signaling pathways. Moreover, addition of D. morbifera significantly suppressed the inhibitory effect of SB203580 (p38 inhibitor). In conclusion, the current study demonstrated that D. morbifera extract significantly increased osteoblast differentiation and mineralization in MC3T3-E1 cells by regulating BMP-2/p38/JNK and Smad1/5/8. Our study might be helpful in the discovery and development of new anti-osteoporosis therapeutic agents.

Understanding the functional role of genistein in the bone differentiation in mouse osteoblastic cell line MC3T3-E1 by RNA-seq analysis

Genistein, a phyto-estrogen, can potentially replace endogenous estrogens in postmenopausal women, but the underlying molecular mechanisms remain incompletely understood. To obtain insight into the effect of genistein on bone differentiation, RNA sequencing (RNA-seq) analysis was used to detect differentially expressed genes (DEGs) in genistein-treated vs. untreated MC3T3-E1 mouse osteoblastic cells. Osteoblastic cell differentiation was monitored by measuring osteoblast differentiation factors (ALP production, bone mineralization, and expression of osteoblast differentiation markers). From RNA-seq analysis, a total of 132 DEGs (including 52 up-regulated and 80 down-regulated genes) were identified in genistein-treated cells (FDR q-value < 0.05 and fold change > 1.5). KEGG pathway and Gene Ontology (GO) enrichment analyses were performed to estimate the biological functions of DEGs and demonstrated that these DEGs were highly enriched in functions related to chemotactic cytokines. The functional relevance of DEGs to genistein-induced osteoblastic cell differentiation was further evaluated by siRNA-mediated knockdown in MC3T3-E1 cells. These siRNA knockdown experiments (of the DEGs validated by real-time qPCR) demonstrated that two up-regulated genes (Ereg and Efcab2) enhance osteoblastic cell differentiation, while three down-regulated genes (Hrc, Gli, and Ifitm5) suppress the differentiation. These results imply their major functional roles in bone differentiation regulated by genistein.

Diet and Exercise: a Match Made in Bone

PURPOSE OF REVIEW

Multiple dietary components have the potential to positively affect bone mineral density in early life and reduce loss of bone mass with aging. In addition, regular weight-bearing physical activity has a strong positive effect on bone through activation of osteocyte signaling. We will explore possible synergistic effects of dietary components and mechanical stimuli for bone health by identifying dietary components that have the potential to alter the response of osteocytes to mechanical loading.

RECENT FINDINGS

Several (sub)cellular aspects of osteocytes determine their signaling towards osteoblasts and osteoclasts in response to mechanical stimuli, such as the osteocyte cytoskeleton, estrogen receptor α, the vitamin D receptor, and the architecture of the lacunocanalicular system. Potential modulators of these features include 1,25-dihydroxy vitamin D3, several forms of vitamin K, and the phytoestrogen genistein. Multiple dietary components potentially affect osteocyte function and therefore may have a synergistic effect on bone health when combined with a regime of physical activity.

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.

Melanin extract from Gallus gallus domesticus promotes proliferation and differentiation of osteoblastic MG-63 cells via bone morphogenetic protein-2 signaling

BACKGROUND/OBJECTIVES

Gallus gallus domesticus (GD) is a natural mutant breed of chicken in Korea with an atypical characterization of melanin in its tissue. This study investigated the effects of melanin extracts of GD on osteoblast differentiation and inhibition of osteoclast formation.

MATERIALS/METHODS

The effects of the melanin extract of GD on human osteoblast MG-63 cell differentiation were examined by evaluating cell viability, osteoblast differentiation, and expression of osteoblast-specific transcription factors such as bone morphogenetic protein 2 (BMP-2), small mothers against decapentaplegic homologs 5 (SMAD5), runt-related transcription factor 2 (RUNX2), osteocalcin and type 1 collagen (COL-1) by reverse transcription-polymerase chain reaction and western blotting analysis. We investigated the inhibitory effect of melanin on the osteoclasts formation through tartrate-resistant acid phosphatase (TRAP) activity and TRAP stains in Raw 264.7 cell.

RESULTS

The melanin extract of GD was not cytotoxic to MG-63 cells at concentrations of 50-250 µg/mL. Alkaline phosphatase (ALP) activity and bone mineralization of melanin extract-treated cells increased in a dose-dependent manner from 50 to 250 µg/mL and were 149% and 129% at 250 µg/mL concentration, respectively (P < 0.05). The levels of BMP-2, osteocalcin, and COL-1 gene expression were significantly upregulated by 1.72-, 4.44-, and 2.12-fold in melanin-treated cells than in the control cells (P < 0.05). The levels of RUNX2 and SMAD5 proteins were higher in melanin-treated cells than in control vehicle-treated cells. The melanin extract attenuated the formation of receptor activator of nuclear factor kappa-B ligand-induced TRAP-positive multinucleated RAW 264.7 cells by 22%, and was 77% cytotoxic to RAW 264.7 macrophages at a concentration of 500 µg/mL.

CONCLUSIONS

This study provides evidence that the melanin extract promoted osteoblast differentiation by activating BMP/SMADs/RUNX2 signaling and regulating transcription of osteogenic genes such as ALP, type I collagen, and osteocalcin. These results suggest that the effective osteoblastic differentiation induced by melanin extract from GD makes it potentially useful in maintaining bone health.

Role of the ER/NO/cGMP Signaling Pathway in the Promotion of Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stem Cells by Actaea racemosa Extract

Purpose/Objective. To investigate the effect of Actaea racemosa (AR) extract on in vitro osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs) via the ER/NO/cGMP signaling pathway. Methods/Materials. Rat BMSCs were treated with osteogenic differentiation-inducing medium containing AR; estrogen receptor antagonist, ICI 182,780 (10^-6 mol/L); and nitric oxide synthase inhibitor, L-nitro arginine methyl ester (L-NAME, 6 × 10^-3 mol/L). Markers of osteogenic differentiation (alkaline phosphatase [ALP] activity, osteocalcin secretion, and calcium ion deposit levels) and the levels of key signaling molecules (nitric oxide synthase [NOS], nitric oxide [NO], and cyclic guanosine monophosphate [cGMP]) were assessed. Results. AR (10^-1-10^-6 g/L) increased ALP activity in a dose-dependent manner, and the highest ALP, osteocalcin, and osteoprotegerin activities were achieved at an AR concentration of 10^-4 g/L. Therefore, the concentration of 10^-4 g/L was used for promoting osteogenic differentiation of BMSCs in subsequent analyses. At this concentration, AR increased the levels of NO and cGMP, and such effects could be blocked by the estrogen receptor antagonist (ICI 182,780) and nitric oxide synthase inhibitor (L-NAME). Conclusion. AR induced osteogenic differentiation of rat BMSCs through the ER/NO/cGMP signaling pathway. This finding provides the theoretical foundation for the mechanism of AR in the treatment of postmenopausal osteoporosis.

Combined Effects of Soy Isoflavones and β-Carotene on Osteoblast Differentiation

Soy isoflavones, genistein, daidzein and its metabolite equol, as well as β-carotene have been reported to be effective for maintaining bone health. However, it remains to be elucidated whether combining soy isoflavones with β-carotene is beneficial to bone formation. This study investigated the combined effect of soy isoflavones and β-carotene on the differentiation of MC3T3-E1 preosteoblastic cells. Daidzein and genistein alone did not affect cell growth but increased alkaline phosphatase (ALP) activity. Beta-carotene alone inhibited cell growth and markedly enhanced ALP activity. Soy isoflavones combined with β-carotene resulted in higher ALP activity than treatment with isoflavones or β-carotene alone. We observed significant main effects of β-carotene on the enhanced expression of Runx2, ALP, and ostepontin mRNA, whereas there was a significant main effect of soy isoflavones on the expression of osterix mRNA. To investigate how β-carotene affected osteoblast differentiation, MC3T3-E1 cells were treated with retinoic acid receptor (RAR) pan-antagonist combined with β-carotene. Osteopontin and ALP mRNA expression levels, which were increased following treatment with β-carotene, were significantly suppressed by the RAR pan-antagonist. This suggests treatment with β-carotene enhanced early osteoblastic differentiation, at least in part via RAR signaling. These results indicate that a combination of isoflavones and β-carotene may be useful for maintaining a positive balance of bone turnover by inducing osteoblast differentiation.

Puerarin enhances proliferation and osteoblastic differentiation of human bone marrow stromal cells via a nitric oxide/cyclic guanosine monophosphate signaling pathway

Puerarin, a major active isoflavone extracted from the Traditional Chinese Medicine Radix Puerariae, has been studied for its comprehensive biological effects. However, to date, its effect on bone formation and the underlying mechanism of action have not been well investigated. The present study investigated the effect of puerarin on cell proliferation and osteoblastic maturation in cultured human bone marrow stromal cells (hBMSC) in vitro. Puerarin (2.5-100 µM) increased hBMSC growth in a dose-dependent manner, as indicated by an MTT assay, and stimulated osteoblastic maturation as indicated by assessment of alkaline phosphatase (ALP) activity, as well as calcium deposition into the extracellular matrix detected by alizarin red S staining. Furthermore, polymerase chain reaction analysis showed that the expression of osteoblastic markers, including Runt-related transcription factor 2/core-binding factor alpha 1, osterix and osteocalcin, were increased in hBMSCs following incubation with puerarin. Further experiments indicated that puerarin increased the nitric oxide (NO) production and cyclic guanosine monophosphate (cGMP) content in hBMSCs. The effects of puerarin were mimicked by 17β-estrodiol (10(-8) M) and were abolished in the presence of estrogen receptor antagonist ICI182780 (10(-7) M). A NO synthase inhibitor, Nx-nitro-L-arginine methylester (6 x 10(-3) M), significantly attenuated puerarin-induced increases in NO production and cGMP content, in parallel with a reduction of cell proliferation and osteoblastic differentiation as well as the expression of osteoblastic markers. These results suggested that puerarin may prevent osteoporosis by exerting stimulatory effects on bone formation and the NO/cGMP pathway, which has an important role in puerarin-induced hBMSC proliferation and osteoblastic differentiation.

Role of nitric oxide in the maintenance of pluripotency and regulation of the hypoxia response in stem cells

Stem cell pluripotency and differentiation are global processes regulated by several pathways that have been studied intensively over recent years. Nitric oxide (NO) is an important molecule that affects gene expression at the level of transcription and translation and regulates cell survival and proliferation in diverse cell types. In embryonic stem cells NO has a dual role, controlling differentiation and survival, but the molecular mechanisms by which it modulates these functions are not completely defined. NO is a physiological regulator of cell respiration through the inhibition of cytochrome c oxidase. Many researchers have been examining the role that NO plays in other aspects of metabolism such as the cellular bioenergetics state, the hypoxia response and the relationship of these areas to stem cell stemness.

Icariin stimulates the osteogenic differentiation of rat bone marrow stromal cells via activating the PI3K-AKT-eNOS-NO-cGMP-PKG

Icariin, a prenylated flavonol glycoside isolated from Epimedii herba, has been found to be a potent stimulator of osteogenic differentiation and has potential application in preventing bone loss. However, the signaling pathway underlying its osteogenic effect remains unclear. We hypothesized that the osteogenic activity of icariin is related to the nitric oxide (NO) signal pathway and PI3K/AKT pathway in its upstream. Rat bone marrow stromal cells (rBMSCs) were cultured in osteogenic medium and treated with icariin or together with L-NAME, ODQ, PDE5, and/or LY294002 (the inhibitor of NOS, sGC, cGMP, and PI3K respectively), and effects were examined on the expression of signal messengers (NOS, NO, sGC, cGMP, PKG and PI3K) and the levels of osteogenic markers (alkaline phosphatase or ALP, osteocalcin and calcified nodules). It was found that icariin dose-dependently increased ALP activity, and treatment at the optimal concentration (10(-5)M) increased NOS activity, iNOS and eNOS expression, NO production, sGC and cGMP contents and PKG expression besides the phosphorylation of AKT. The addition of L-NAME, ODQ and PDE5 significantly inhibited the icariin effects on above markers respectively. The addition of LY294002 decreased the p-AKT level, NOS activity, eNOS expression and NO production significantly, but had no significant effect on iNOS expression. The addition of any of the four inhibitors also abolished the osteogenic effect of icariin on rBMSCs as indicated by ALP activity, osteocalcin synthesis, calcium deposition and the number and areas of calcified nodules. These results suggest that the osteogenic effect of icariin involves the PI3K-AKT-eNOS-NO-cGMP-PKG signal pathway. Furthermore, dosage response studies showed that icariin at 10(-6)M (a physiologically achievable concentration in vivo) also activated this signal pathway.

Oral administration of soluble guanylate cyclase agonists to rats results in osteoclastic bone resorption and remodeling with new bone formation in the appendicular and axial skeleton

Orally administered small molecule agonists of soluble guanylate cyclase (sGC) induced increased numbers of osteoclasts, multifocal bone resorption, increased porosity, and new bone formation in the appendicular and axial skeleton of Sprague-Dawley rats. Similar histopathological bone changes were observed in both young (7- to 9-week-old) and aged (42- to 46-week-old) rats when dosed by oral gavage with 3 different heme-dependent sGC agonist (sGCa) compounds or 1 structurally distinct heme-independent sGCa compound. In a 7-day time course study in 7- to 9-week-old rats, bone changes were observed as early as 2 to 3 days following once daily compound administration. Bone changes were mostly reversed following a 14-day recovery period, with complete reversal after 35 days. The mechanism responsible for the bone changes was investigated in the thyroparathyroidectomized rat model that creates a low state of bone modeling and remodeling due to deprivation of thyroid hormone, calcitonin (CT), and parathyroid hormone (PTH). The sGCa compounds tested increased both bone resorption and formation, thereby increasing bone remodeling independent of calciotropic hormones PTH and CT. Based on these studies, we conclude that the bone changes in rats were likely caused by increased sGC activity.

The flavonoid fisetin promotes osteoblasts differentiation through Runx2 transcriptional activity

SCOPE

Flavonoids represent a group of polyphenolic compounds commonly found in daily nutrition with proven health benefits. Among this group, the flavonol fisetin has been previously shown to protect bone by repressing osteoclast differentiation. In the present study, we investigated the role of fisetin in regulating osteoblasts physiology.

METHODS AND RESULTS

In vivo mice treated with LPSs exhibited osteoporosis features associated with a dramatic repression of osteoblast marker expression. In this model, inhibition of osteocalcin and type I collagen alpha 1 transcription was partially countered by a daily consumption of fisetin. Interestingly, in vitro, fisetin promoted both osteoblast alkaline phosphatase activity and mineralization process. To decipher how fisetin may exert its positive effect on osteoblastogenesis, we analyzed its ability to control the runt-related transcription factor 2 (Runx2), a key organizer in developing and maturing osteoblasts. While fisetin did not impact Runx2 mRNA and protein levels, it upregulated its transcriptional activity. Actually, fisetin stimulated the luciferase activity of a reporter plasmid driven by the osteocalcin gene promoter that contains Runx2 binding sites and promoted the mRNA expression of osteocalcin and type I collagen alpha 1 targets.

CONCLUSION

Bone sparing properties of fisetin also rely on its positive influence on osteoblast differentiation and activity.

Effects of phytoestrogens and other plant-derived compounds on mesenchymal stem cells, bone maintenance and regeneration

Phytoestrogens and other plant-derived compounds and extracts have been developed for the treatment of menopause-related complaints and disorders, e.g. hot flushes and osteoporosis. Since estrogens have been discussed to enhance the risk for hormone-sensitive cancers, research activities try to find alternatives. Phytoestrogens like genistein and resveratrol as well as other plant-derived compounds are capable of substituting for estrogens to some extent. Their effects on mesenchymal stem cells and the tissues derived therefrom have been investigated in vitro and in preclinical settings. Besides their well-known estrogenic, i.e. mainly antiresorptive effects on bone via estrogen receptor (ER) signalling, they also directly or indirectly affect osteogenic and adipogenic pathways. As a novel mechanism, phytoestrogens and plant-derived saponins and flavonoids like kaempferol and xanthohumol have been described to reciprocally affect the osteogenic versus the adipogenic differentiation pathway. Both, ER-mediated and other pathways mediate a shift towards osteogenesis by inhibiting PPARγ and C/EBPα, the key adipogenic transcription factors (TFs), while stimulating the key osteogenic TFs Runx2 and Sp7. Besides ER signalling, the broad spectrum of molecular mechanisms supporting osteogenesis comprises the modulation of PPARγ, Wnt/β-catenin, and Sirt1 signalling, which inversely influence the transcription or transactivation of osteogenic versus adipogenic TFs. Preventing the age- and hormone deficiency-related shift towards adipogenesis without provoking adverse estrogenic effects represents a very promising strategy for treating bone loss and other metabolic diseases beyond bone. Research on plant-derived compounds will have to be pursued in vitro as well as in preclinical studies and controlled clinical trials in humans are urgently needed. This article is part of a Special Issue entitled 'Phytoestrogens'.

Genistein promotion of osteogenic differentiation through BMP2/SMAD5/RUNX2 signaling

To investigate the effects of Genistein on the osteogenic related gene expression profiles during osteoblastic differentiation of human bone marrow mesenchymal stem cell (hBMSC) cultures, the hBMSCs were cultured under osteogenic differentiation medium with the addition of Genistein (10(-8)∼10(-5) M) for 12 days. The cell proliferation was measured by BrdU incorporation, while the osteoblastic differentiation in hBMSC cultures was assessed by cellular alkaline phosphatase (ALP) activity. The cell apoptosis was determined by caspase 3/7 activation. GEArray Q series human osteogenesis gene array was used to analyze large-scale gene expression in Genistein-treated hBMSC cultures compared to the control group. Quantitative real-time RT-PCR, small interfering RNA (siRNA), and western blot analysis were used to confirm the microarray data in five representative transcripts. Genistein (10(-8)∼10(-6) M) dose- and time-dependently increased cell proliferation and cellular ALP activity, but had no significant effect on cell apoptosis in hBMSC cultures. The 96-gene array analysis indicated that 22 genes were upregulated more than 2-fold and 7 genes were downregulated at least 1.5-fold. The expressions of bone morphogenetic proteins (BMPs), small mothers against decapentaplegic homologs (SMADs), and Runt-related transcription factor 2 (RUNX2) were concomitantly increased under Genistein treatment while insulin-like growth factor 2 and inhibitory SMADs 6 and 7 expressions were significantly decreased. The results of the real-time RT-PCR had a correlation with the results of microarray analysis and were estrogen-receptor dependent. Specific gene siRNAs knock-down further confirmed the osteogenic effects of Genistein on BMP2, SMAD5 and RUNX2 protein expression. Genistein enhanced osteogenic differentiation in cultured hBMSCs mainly through the BMP-dependent SMADs and RUNX2 signaling.

The possibility of genistein as a new direct pulp capping agent

Genistein, kind of soy isoflavones, is well-known as natural ingredients and consumed as health foods and supplements. They are expected to improve renal function. They have high-affinity to estrogen receptor β expressed predominantly in bone tissue, they prevent osteoporosis specifically and safely. We examined whether genistein can be a new direct capping agent. In this study, we examined the effect of genistein for the proliferation and differentiation of rat dental pulp cells in vitro and the ability of tertiary dentin formation in vivo. As a result, rat dental pulp cells with genistein were increased activity of ALPase and showed alizarin red positive-staining. Calcification-related genes expression has been confirmed by the addition of genistein. From in vivo study, high quality of tertiary dentin formation and minor pulp reaction were observed. From these findings, it was suggested that genistein may be useful agent for direct pulp capping.

Genistein induces oestrogen receptor-α gene expression in osteoblasts through the activation of mitogen-activated protein kinases/NF-κB/activator protein-1 and promotes cell mineralisation

Oestrogen and oestrogen receptors (ER) play critical roles in the maintenance of bone remodelling. Genistein, structurally similar to 17β-oestradiol, is a phyto-oestrogen that may be beneficial for treating osteoporosis. In the present study, we evaluated the effects of genistein on the regulation of ERα gene expression and osteoblast mineralisation using MC3T3-E1 cells and primary rat calvarial osteoblasts as our experimental models. Exposure of MC3T3-E1 cells and primary rat osteoblasts to genistein at ≤ 10 μm for 24 h did not affect the cell morphology or viability. However, treatment of MC3T3-E1 cells with 10 μm-genistein enhanced the phosphorylation of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase 1/2 in a time-dependent manner. Sequentially, genistein increased the translocation of NF-κB and c-Jun from the cytoplasm to the nucleus. Consequently, exposure of MC3T3-E1 cells to genistein induced ERα mRNA expression in concentration- and time-dependent manners. In parallel, the amounts of cytosolic and nuclear ERα in MC3T3-E1 cells were increased following genistein administration. Additionally, genistein also increased the levels of ERα mRNA and nuclear ERα protein in rat calvarial osteoblasts. A bioinformatic search revealed that there are several ERα-specific DNA-binding elements in the 5'-promoter regions of the bone morphogenetic protein-6, collagen type I and osteocalcin genes. As a result, genistein could induce the expressions of these osteoblast differentiation-related genes in primary rat osteoblasts. Co-treatment with genistein and traditional differentiation reagents synergistically increased osteoblast mineralisation. Therefore, the present study showed that genistein can induce ERα gene expression via the activation of MAPK/NF-κB/activator protein-1 and accordingly stimulates differentiation-related gene expressions and osteoblast mineralisation.

The beneficial effect of icaritin on osteoporotic bone is dependent on the treatment initiation timing in adult ovariectomized rats

BACKGROUND

Epimedium-derived flavonoids (EFs) have a potential to treat established osteoporosis in postmenopausal women. However, one of the main disadvantages of the compound is the high volume and dosage during long-term administration period. Meanwhile, the beneficial effect of EFs on osteoporotic bone depends greatly on the intervention timing. Whether icaritin (ICT), an active molecular compound from EFs, can exert beneficial effect on osteoporotic bone and whether the beneficial effect is also dependent on the intervention timing remain unknown.

OBJECTIVE

The objective of this study was to evaluate the effect of the early and late ICT treatment on bone turnover markers, trabecular architecture, bone remodeling, biomechanics, colony formation of bone marrow stromal cells and osteoblast, adipocyte and osteoclast-related gene expression in adult ovariectomized rats.

METHODS

Eighty 9-month-old female rats (n=8/group) were sham-operated (Sham) or ovariectomized (OVX). The OVX rats were subjected to ICT treatment initiation at 1 month (early treatment) and 3 months (late treatment) post-operation, respectively. The vehicle-treated Sham and OVX rats starting at month 1 and month 3 post-operation served as the corresponding controls (Sham and OVX controls) for early and late ICT treatment, respectively. Those Sham and OVX rats sacrificed immediately before early and late ICT treatment served as the pretreatment baseline controls. Both ICT and vehicle treatments lasted for 2 months. The bone turnover markers, trabecular architecture, bone remodeling and bone biomechanical properties were analyzed with biochemistry, microCT, histomorphometry and mechanical testing, respectively. The population of bone marrow stromal cells (BMSCs) and osteoblasts were evaluated with colony formation assays, respectively. The expression levels of osteoblast, adipocyte and osteoclast-related genes in bone marrow were assessed by real-time polymerase chain reaction (PCR), respectively.

RESULTS

At the tissue level, early ICT treatment remarkably restored the trabecular bone mass, trabecular architecture and bone biomechanical properties towards pretreatment Sham levels, and significantly increased bone formation from pretreatment OVX level and markedly inhibited bone resorption towards pretreatment Sham level, whereas late ICT treatment failed to have any effect. At the cellular and molecular level, early ICT treatment significantly increased the number of osteoblastic colonies and the level of osteoblast-related gene expression compared to pretreatment OVX levels and remarkably decreased adipocyte and osteoclast-related gene expression towards pretreatment Sham levels. Late ICT treatment failed to have beneficial effect on any of these parameters.

CONCLUSION

ICT can exert anabolic and anti-resorptive effect on osteoporotic bone. The beneficial effect of ICT treatment is dependent on the intervention timing in established osteoporosis induced by estrogen depletion.

Functions and action mechanisms of flavonoids genistein and icariin in regulating bone remodeling

Increasingly natural products particularly flavonoids are being explored for their therapeutic potentials in reducing bone loss and maintaining bone health. This study has reviewed previous studies on the two better known flavonoids, genistein and icariin, their structures, functions, action mechanisms, relative potency, and potential application in regulating bone remodeling and preventing bone loss. Genistein, an isoflavone abundant in soy, has dual functions on bone cells, able to inhibit bone resorption activity of osteoclasts and stimulate osteogenic differentiation and maturation of bone marrow stromal progenitor cells (BMSCs) and osteoblasts. Genistein is an estrogen receptor (ER)-selective binding phytoestrogen, with a greater affinity to ERβ. Genistein inhibits tyrosine kinases and inhibits DNA topoisomerases I and II, and may act as an antioxidant. Genistein enhances osteoblastic differentiation and maturation by activation of ER, p38MAPK-Runx2, and NO/cGMP pathways, and it inhibits osteoclast formation and bone resorption through inducing osteoclastogenic inhibitor osteoprotegerin (OPG) and blocking NF-κB signaling. Icariin, a prenylated flavonol glycoside isolated from Epimedium herb, stimulates osteogenic differentiation of BMSCs and inhibits bone resorption activity of osteoclasts. Icariin, whose metabolites include icariside I, icariside II, icaritin, and desmethylicaritin, has no estrogenic activity. However, icariin is more potent than genistein in promoting osteogenic differentiation and maturation of osteoblasts. The existence of a prenyl group on C-8 of icariin molecular structure has been suggested to be the reason why icariin is more potent than genistein in osteogenic activity. Thus, the prenylflavonoids may represent a class of flavonoids with a higher osteogenic activity.

Isoflavones suppress the expression of the FcεRI high-affinity immunoglobulin E receptor independent of the estrogen receptor

Isoflavones found in soybeans and soy products possess clinically relevant properties. However, the anti-allergic effect of isoflavones has been poorly studied. We examined the effects of isoflavones, genistein, daidzein, and equol, on the expression of the high-affinity immunoglobulin E (IgE) receptor, FcεRI, which plays a central role in IgE-mediated allergic response. Flow cytometric analysis showed that all of these isoflavones reduced the cell surface expression of FcεRI on mouse bone-marrow-derived mast cells and human basophilic KU812 cells. All isoflavones decreased the levels of the FcεRIα mRNA in the cells. Genistein reduced the mRNA expression of the β chain, and daidzein and equol downregulated that of the γ chain. The suppressive effects of isoflavones on FcεRI expression were unaffected by ICI 182,780, an estrogen receptor antagonist, suggesting that these effects were independent of estrogen receptors.

Curcumin induces differentiation of embryonic stem cells through possible modulation of nitric oxide-cyclic GMP pathway

Curcumin, an active ingredient of dietary spice used in curry, has been shown to exhibit anti-oxidant, anti-inflammatory and anti-proliferative properties. Using EB directed differentiation protocol of H-9 human embryonic stem (ES) cells; we evaluated the effect of curcumin (0-20 μmol/L) in enhancing such differentiation. Our results using real time PCR, western blotting and immunostaining demonstrated that curcumin significantly increased the gene expression and protein levels of cardiac specific transcription factor NKx2.5, cardiac troponin I, myosin heavy chain, and endothelial nitric oxide synthase during ES cell differentiation. Furthermore, an NO donor enhanced the curcumin-mediated induction of NKx2.5 and other cardiac specific proteins. Incubation of cells with curcumin led to a dose dependent increase in intracellular nitrite to the same extent as giving an authentic NO donor. Functional assay for second messenger(s) cyclic AMP (cAMP) and cyclic GMP (cGMP) revealed that continuous presence of curcumin in differentiated cells induced a decrease in the baseline levels of cAMP but it significantly elevated baseline contents of cGMP. Curcumin addition to a cell free assay significantly suppressed cAMP and cGMP degradation in the extracts while long term treatment of intact cells with curcumin increased the rates of cAMP and cGMP degradation suggesting that this might be due to direct suppression of some cyclic nucleotide-degrading enzyme (phosphodiesterase) by curcumin. These studies demonstrate that polyphenol curcumin may be involved in differentiation of ES cells partly due to manipulation of nitric oxide signaling.

Alternative therapies for the prevention and treatment of osteoporosis

Osteoporosis is a medical condition that affects millions of men and women. People with this condition have low bone mass, which places them at increased risk for bone fracture after minor trauma. The surgeries and treatments required to repair and heal bone fractures involve long recovery periods and can be expensive. Because osteoporosis occurs frequently in the elderly, the financial burden it places on society is likely to be large. In the United States, the Food and Drug Administration has approved several drugs for use in the prevention and treatment of osteoporosis. However, all of the currently available agents have severe side effects that limit their efficacy and underscore the urgent need for new treatment options. One promising approach is the development of alternative (nonpharmaceutical) strategies for bone maintenance, as well as for the prevention and treatment of osteoporosis. This review examines the currently available nonpharmaceutical alternatives that have been evaluated in in vitro and in vivo studies. Certain plants from the following families have shown the greatest benefits on bone: Alliceae, Asteraceae, Thecaceae, Fabaceae, Oleaceae, Rosaceae, Ranunculaceae, Vitaceae, Zingiberaceae. The present review discusses the most promising findings from studies of these plant families.

Nitric oxide-cyclic GMP signaling in stem cell differentiation

The nitric oxide-cyclic GMP (NO-cGMP) pathway mediates important physiological functions associated with various integrative body systems including the cardiovascular and nervous systems. Furthermore, NO regulates cell growth, survival, apoptosis, proliferation, and differentiation at the cellular level. To understand the significance of the NO-cGMP pathway in development and differentiation, studies have been conducted both in developing embryos and in stem cells. Manipulation of the NO-cGMP pathway, by employing activators and inhibitors as pharmacological probes, and genetic manipulation of NO signaling components have implicated the involvement of this pathway in the regulation of stem cell differentiation. This review focuses on some of the work pertaining to the role of NO-cGMP in the differentiation of stem cells into cells of various lineages, particularly into myocardial cells, and in stem cell-based therapy.

Effects of pomegranate extracts on cartilage, bone and mesenchymal cells of mouse fetuses

Pomegranate is a rich source of polyphenols, which are believed to be responsible for the oestrogenic activities of extracts of this fruit in mice. One of these potential activities is the prevention of bone loss. The objectives of the present study were to determine the effects of pomegranate extract on chondrogenesis and osteogenesis in mouse embryos in vivo and limb bud cultures in vitro. A total of fifty pregnant Balb/c mice were given vehicle, pomegranate juice extract (PJE), pomegranate husk extract (PHE) or a mixture of husk and juice extract (PME). Their embryos were stained with alizarin red S and alcian blue, and the length of the femur, tibia and their ossification zones were measured on day 19 of gestation. Bone Ca content in pregnant mice was also measured. Mice treated with PJE showed an increase in bone Ca content. Dietary supplementation with all extracts significantly increased embryo femur length and osteogenesis index. Mesenchymal cells from fetal limb buds were cultured and exposed to 10, 100, 1000 and 10 000 μg/ml of PJE, PHE or PME. The number of viable cells was greater in cultures exposed to the extracts than in control cultures. The number of cartilage nodules and their diameters were greater in extract-treated cell cultures, a finding which reflected increased cell proliferation and differentiation rates. In conclusion, the findings of the present study suggest that pomegranate is able to enhance bone formation.

Sinusoidal electromagnetic field stimulates rat osteoblast differentiation and maturation via activation of NO-cGMP-PKG pathway

Nitric oxide (NO) is an important intracellular and intercellular messenger, critically affecting bone metabolism. The purpose of this research is to investigate whether the effect of sinusoidal electromagnetic field (SEMF) on the differentiation and maturation of osteoblasts is mediated by the NO-cGMP-PKG signal pathway. We examined the impact of SEMF on nitric oxide synthase (NOS) activity, and found that L-NAME, nitric oxide synthase's inhibitor, prevents SEMF-mediated increase in NOS activity and NO levels. We showed that an inhibitor of soluble guanylyl cyclase (ODQ) blocks the increase in cGMP levels triggered by exposure to SEMF. The inhibitor PDE5, which hydrolyzes 3',5'-cyclic-GMP to 5'-GMP, prevents the SEMF's stimulation of PKG activity. We also blocked the NO-cGMP-PKG pathway to determine whether the maturation and mineralization of osteoblasts, stimulated by SEMF, would be inhibited. This was evaluated by measuring alkaline phosphatase (ALP) activity, osterix gene expression and mineralized bone modulus. After treatment with SEMF, the NOS activity increases in comparison with the control group (P<0.01), reaching the highest level after 0.5h. Osterix gene expression, ALP activity and mineralized bone nodules in the SEMF experimental group also increase significantly. However, these effects are partially blocked in the L-NAME treated cultures. Surprisingly, all the osteogenic markers in the SEMF+L-NAME group were slightly higher than in the control culture, but lower than in the cells exposed to SEMF only. We conclude that the NO-cGMP-PKG signal pathway is activated by SEMF treatment, the stimulatory effect of SEMF on the differentiation and mineralization of osteoblasts is attenuated when the pathway is blocked.

Medicarpin, a legume phytoalexin, stimulates osteoblast differentiation and promotes peak bone mass achievement in rats: evidence for estrogen receptor β-mediated osteogenic action of medicarpin

Dietary isoflavones including genistein and daidzein have been shown to have favorable bone conserving effects during estrogen deficiency in experimental animals and humans. We have evaluated osteogenic effect of medicarpin (Med); a phytoalexin that is structurally related to isoflavones and is found in dietary legumes. Med stimulated osteoblast differentiation and mineralization at as low as 10⁻¹⁰ M. Studies with signal transduction inhibitors demonstrated involvement of a p38 mitogen activated protein kinase-ER-bone morphogenic protein-2 pathway in mediating Med action in osteoblasts. Co-activator interaction studies demonstrated that Med acted as an estrogen receptor (ER) agonist; however, in contrast to 17β-estradiol, Med had no uterine estrogenicity and blocked proliferation of MCF-7 cells. Med increased protein levels of ERβ in osteoblasts. Selective knockdown of ERα and ERβ in osteoblasts established that osteogenic action of Med is ERβ-dependent. Female Sprague-Dawley (weaning) rats were administered Med at 1.0- and 10.0 mg.kg⁻¹ doses by gavage for 30 days along with vehicle control. Med treatment resulted in increased formation of osteoporgenitor cells in the bone marrow and osteoid formation (mineralization surface, mineral apposition/bone formation rates) compared with vehicle group. In addition, Med increased cortical thickness and bone biomechanical strength. In pharmacokinetic studies, Med exhibited oral bioavailability of 22.34% and did not produce equol. Together, our results demonstrate Med stimulates osteoblast differentiation likely via ERβ, promotes achievement of peak bone mass, and is devoid of uterine estrogenicity. In addition, given its excellent oral bioavailability, Med can be potential osteogenic agent.

Genistein inhibits osteolytic bone metastasis and enhances bone mineral in nude mice

In this study, the effective activity of genistein on osteolytic bone metastasis and bone mineral was investigated. Female BALB/c-nu/nu mice were injected with estrogen receptor-negative human breast cancer cells, MDA-MB-231, into left cardiac ventricle to form osteolytic bone metastases, and administered genistein subcutaneously after radiologically small but defined osteolytic metastases had been observed (protocol 1), simultaneously with cancer cells inoculation (protocol 2) and prophylactically 7 days before inoculation of cancer cells (protocol 3). In all protocols, genistein (10mg/kg/day) markedly reduced the number and volume of osteolytic bone metastases assessed by radiography and the number of osteoclasts. Furthermore, histomorphometrical analysis revealed that genistein markedly increased trabecular area (Tb.Ar%), trabecular thickness (Tb.Th) and trabecular number (Tb.N), and decreased trabecular separation (Tb.Sp). These results thus demonstrate that genistein could inhibit osteolytic bone metastases, suppress bone resorption, increase bone mass and improve bone microstructure in bone metastases of breast cancer.

Icariin isolated from Epimedium pubescens regulates osteoblasts anabolism through BMP-2, SMAD4, and Cbfa1 expression

Epimedii herba is one of the most frequently used herbs in formulas prescribed for the treatment of osteoporosis in China. The main active flavonoid glucoside extracted from Epimedium pubescens is Icariin, which has been reported to enhance bone healing and reduce osteoporosis occurrence. However, the detailed molecular mechanisms remain unclear. In this present study, we examine the molecular mechanisms of icariin by using primary osteoblast cell cultures obtained from adult mice. The osteoblast cells were harvested from 8-month old female Imprinting Control Region (ICR) mice. The effects of icariin stimulation on the proliferation, differentiation and maturation of osteoblasts were examined. The production of nitric oxide (NO) and caspase-3 were analyzed, along with the gene expressions of bone morphogenetic protein-2 (BMP-2), SMAD4, Cbfa1/Runx2, OPG, and RANKL. The viability of the osteoblasts reached its maximum at 10(-8)M icariin. At this concentration, icariin increased the proliferation and matrix mineralization of osteoblasts and promoted NO synthesis. With icariin treatment, the BMP-2, SMAD4, Cbfa1/Runx2, and OPG gene expressions were up-regulated; the RANKL gene expression was however down-regulated. Concurrent treatment involving the BMP antagonist (Noggin) or the NOS inhibitor (L-NAME) diminished the icariin-induced cell proliferation, ALP activity, NO production, as well as the BMP-2, SMAD4, Cbfa1/Runx2, OPG, RANKL gene expressions. In this study, we demonstrate that in vitro icariin is a bone anabolic agent that may exert its osteogenic effects through the induction of BMP-2 and NO synthesis, subsequently regulating Cbfa1/Runx2, OPG, and RANKL gene expressions. This effect may contribute to its action on the induction of osteoblasts proliferation and differentiation, resulting in bone formation.

YC-1 enhances natural killer cell differentiation from hematopoietic stem cells

NK cells play crucial roles in innate immunity and adaptive immunity. The detailed mechanisms, however, governing NK cell development remains unclear. In this study, we report that YC-1 significantly enhances NK cell populations differentiated from human umbilical cord blood hematopoietic stem cells (HSCs). NK cells increased by YC-1 display both phenotypic and functional features of fully mature NK (mNK) cells, but YC-1 does not affect the activation of mNK cells. YC-1 did not affect cGMP production and phosphorylation of STAT-5 which is essential for IL-15R signaling. On the other hand, YC-1 increased p38 MAPK phosphorylation during NK cell differentiation. Furthermore, p38 inhibitor SB203580 inhibited the differentiation of NK cells enhanced by YC-1. Taken together, these data suggest that YC-1 enhances NK cell differentiation through the activation of p38 MAPK which is involved in NK cell differentiation.

Dose-dependent effects of Runx2 on bone development

Runx2 controls the commitment of mesenchymal cells to the osteoblastic lineage. Distinct promoters, designated P1 and P2, give rise to functionally similar Runx2-II and Runx2-I isoforms. We postulate that this dual promoter gene structure permits temporal and spatial adjustments in the amount of Runx2 isoforms necessary for optimal bone development. To evaluate the gene dose-dependent effect of Runx2 isoforms on bone development, we intercrossed selective Runx2-II(+/-) with nonselective Runx2-II(+/-)/Runx2-I(+/-) mice to create compound mutant mice: Runx2-II(+/-), Runx2-II(+/-)/Runx2-I(+/-), Runx2-II(-/-), Runx2-II(-/-)/Runx2-I(+/-), Runx2-II(-/-)/Runx2-I(-/-). Analysis of the different Runx2-deficient genotypes showed gene dose-dependent differences in the level of expression of the Runx2 isoforms. In addition, we found that Runx2-I is predominately expressed in the perichondrium and proliferating chondrocytes, whereas Runx2-II is expressed in hypertrophic chondrocytes and metaphyseal osteoblasts. Newborn mice showed impaired development of a mineralized skeleton, bone length, and widening of the hypertrophic zone that were proportionate to the reduction in total Runx2 protein expression. Osteoblast differentiation ex vivo was also proportionate to total amount of Runx2 expression that correlated with reduced Runx2 binding to the osteocalcin promoter by quantitative chromatin immunoprecipitation analysis. Functional analysis of P1 and P2 promoters showed differential regulation of the two promoters in osteoblastic cell lines. These findings support the possibility that the total amount of Runx2 derived from two isoforms and the P1 and P2 promoters, by regulating the time, place, and amount of Runx2 in response to changing environmental cues, impacts on bone development.

Phytochemicals from Flemingia vestita (Fabaceae) and Stephania glabra (Menispermeaceae) alter cGMP concentration in the cestode Raillietina echinobothrida

Cyclic GMP (cGMP) mediates various physiological functions of nitric oxide (NO) synthesized by nitric oxide synthase (NOS). A crude peel extract and purified fraction of Flemingia vestita, as well as a crude rhizome extract of Stephania glabra and fractions were tested with respect to the activity of NOS, NO efflux and cGMP concentration in the cestode Raillietina echinobothrida in order to find out the possible mode of anthelmintic action of these plant-derived components. For comparison purposes, the parasites were also treated with pure genistein, sodium nitroprusside (SNP-a known NO donor), and the reference drug, praziquantel (PZQ). At the time of onset of paralysis in the parasites, a significant increase (32%-87%) in the NOS activity and a two to three fold increase of NO efflux into the incubation medium were observed in the treated parasites in comparison to their respective controls. The cGMP concentration in the treated parasites' tissue was also increased by 44%-103%. However, in the presence of NG-nitro-L-arginine methyl ester, a potent inhibitor of NOS, there was no increase in the cGMP concentration in the parasite tissue. This study indicates that the phytochemicals, in particular genistein and tetrahydropalmatine, from F. vestita and S. glabra, respectively, disturb the downstream signalling pathway of NO, as indicated by the change in cGMP concentration in the parasite tissue.