Paracrine and endocrine actions of bone——the functions of secretory proteins from osteoblasts, osteocytes, and osteoclasts

The skeleton is a dynamic organ that is constantly remodeled. Proteins secreted from bone cells, namely osteoblasts, osteocytes,and osteoclasts exert regulation on osteoblastogenesis, osteclastogenesis, and angiogenesis in a paracrine manner. Osteoblasts secrete a range of different molecules including RANKL/OPG, M-CSF, SEMA3A, WNT5A, and WNT16 that regulate osteoclastogenesis. Osteoblasts also produce VEGFA that stimulates osteoblastogenesis and angiogenesis. Osteocytes produce sclerostin（SOST） that inhibits osteoblast differentiation and promotes osteoclast differentiation. Osteoclasts secrete factors including BMP6, CTHRC1, EFNB2, S1P, WNT10B, SEMA4D, and CT-1 that act on osteoblasts and osteocytes, and thereby influencea A osteogenesis. Osteoclast precursors produce the angiogenic factor PDGF-BB to promote the formation of Type H vessels, which then stimulate osteoblastogenesis. Besides, the evidences over the past decades show that at least three hormones or ＂osteokines＂from bone cells have endocrine functions. FGF23 is produced by osteoblasts and osteocytes and can regulate phosphate metabolism. Osteocalcin（OCN） secreted by osteoblasts regulates systemic glucose and energy metabolism, reproduction, and cognition. Lipocalin-2（LCN2） is secreted by osteoblasts and can influence energy metabolism by suppressing appetite in the brain.We review the recent progresses in the paracrine and endocrine functions of the secretory proteins of osteoblasts, osteocytes, and osteoclasts, revealing connections of the skeleton with other tissues and providing added insights into the pathogenesis of degenerative diseases affecting multiple organs and the drug discovery process.

Interaction between Schwann Cells and Osteoblasts In Vitro

Aim Given the well-known properties of Schwann cells in promoting nerve regeneration, transplanting Schwann cells into implant sockets might be an effective method to promote sensory responses of osseointegrated implants. The aim of this study was to evaluate the interaction between Schwann cells and osteoblasts. Methodology Schwann cells derived from the sciatic nerves of neonatal rat were co-culured with osteoblasts using Transwell inserts. The proliferation of Schwann cells in the co-culture system was evaluated using methylthiazol tetrazolium （MTT） colorimetric method. Moreover, the secretions and mRNA levels of brain-derived neurotrophic factor （BDNF） and nerve growth factor （NGF） were measured by enzyme-linked immunosorbent assay （ELISA） and quantitative real-time PCR, respectively. In order to test the effect of Schwann cells on osteoblasts, alkaline phosphatase （ALP） staining and Alizerin red staining were performed as well. Results Schwann cells, which were co-cultured with the osteoblasts, showed an intact proliferation during the observation period. Moreover, the gene expression and synthesis of BDNF and NGF were not impaired by the osteoblasts. Meanwhile, co-cultured osteoblasts exhibited a significant increase in the proliferation on day 3 and 6 （P〈 0.05）. Co-culture of these two types of cells also led to a more intense staining of ALP and an elevated number of calcified nodules. Conclusion These findings demonstrate that, in the in vitro indirect co-culture environment, Schwann cells can maintain their normal ability to synthesize neurotrophins, which then enhance the proliferation and differentiation of osteoblasts.

Cloning and Expression of Rat Transforming Growth Factor β1 cDNA in Osteoblasts

Summary: Rat transforming growth factor β1 (rTGFβ1) cDNA from rat lymphocytes was cloned by RT-PCR and inserted into pcDNA3 to construct an eukaryotic expression vector, which was named pcDNA3-TGFβ1. The cloned gene was confirmed to code rat TGFβ1 by restriction enzyme analysis. pcDNA3-TGFβ1 plasmid was transfected into rat osteoblasts by using liposome-mediated gene transfer technique and the expression of TGFβ1 was detected by using irnmunohistochemical staining assay. It was found that the rat TGFβ1 expression product was obviously detectable in the transfected osteoblasts in 48 h. High expression of TGFβ1 was obtained in the rat osteoblasts in which the constructed TGFβ1 expression vector was transfected.

NUMB maintains bone mass by promoting degradation of PTEN and GLI1 via ubiquitination in osteoblasts

The adaptor protein NUMB is involved in asymmetric division and cell fate determination and recognized as an antagonist of Notch.Previous studies have proved that Notch activation in osteoblasts contributes to a high bone mass. In this study, however, an osteopenic phenotype was found in 9-week-old mice using osteoblastic specific Col1a1–2.3-Cre to ablate both Numb and its homologue Numbl. The trabecular bone mass decreased dramatically while the cortical bone mass was unaffected. Here, the Notch signal was not activated,while the tensin homologue deleted on human chromosome 10(PTEN), which dephosphorylates phosphatidylinositide 3-kinases, was elevated, attenuating protein kinase B(Akt). The ubiquitination assay revealed that NUMB may physiologically promote PTEN ubiquitination in the presence of neural precursor cell-expressed developmentally downregulated protein 4–1. In addition, the deficiency of Numb/Numbl also activated the Hedgehog pathway through GLI1. This process was found to improve the ratio of the receptor activator of nuclear factor-k B ligand to osteoprotegerin, which enhanced the differentiation of osteoclasts and bone resorption. In conclusion, this study provides an insight into new functons of NUMB and NUMBL on bone homeostasis.

The heterodimeric structure of heterogeneous nuclear ribonucleoprotein C1/C2 dictates 1,25-dihydroxyvitamin D-directed transcriptional events in osteoblasts

Heterogeneous nuclear ribonucleoprotein （hnRNP） C plays a key role in RNA processing but also exerts a dominant negative effect on responses to 1,25-dihydroxyvitamin D （1,25（OH）2D） by functioning as a vitamin D response element-binding protein （VDRE-BP）. hnRNPC acts a tetramer of hnRNPC1 （huC1） and hnRNPC2 （huC2）, and organization of these subunits is critical to in vivo nucleic acid-binding. Overexpression of either huC1 or huC2 in human osteoblasts is sufficient to confer VDRE-BP suppression of 1,25（OH）2D-mediated transcription. However, huC1 or huC2 alone did not suppress 1,25（OH）2D-induced transcription in mouse osteoblastic cells. By contrast, overexpression of huC1 and huC2 in combination or transfection with a bone-specific polycistronic vector using a ＂self-cleaving＂ 2A peptide to co-express huC1/C2 suppressed 1,25D-mediated induction of osteoblast target gene expression. Structural diversity of hnRNPC between human/NWPs and mouse/rat/rabbit/dog was investigated by analysis of sequence variations within the hnRNP CLZ domain. The predicted loss of distal helical function in hnRNPC from lower species provides an explanation for the altered interaction between huC1/C2 and their mouse counterparts. These data provide new evidence of a role for hnRNPC1/C2 in 1,25（OH）2D-driven gene expression, and further suggest that species-specific tetramerization is a crucial determinant of its actions as a regulator of VDR-directed transactivation.

Gene expression profiles associated with osteoblasts differentiated from bone marrow stromal cells

Objective:To study the changes of gene expression profiles associated with osteoblasts differentiated from rat bone marrow stromal cells in vitro by gene chip technique.Methods:rat Rone marrow stromal cells were isolated and cultured,and differentiation was induced by dexamethasone,β-glycerol phosphate and vitamin C.Cellular mRNA was extracted and reverse transcribed into cDNA,thus related genes expression differences were detected by gene expression profile chip.Results:Calcifying nodules were visible in the induced cells.There were27.7%genes expressed differentially,three times more than the normal and induced cells,and some genes were related to transcription,translation,glycosylation modification.Extracellular matrix,signal molecules and metabolism were up—regulated.Conclusions:The gene chip technique can be used to detect the multi-gene different expression in the differentiationinduceed rat BMSCs,and these differentially expressed genes are necessary genes related to rat BMSCs proliferation and induction of osteoblastic differentiation.

Effect of cerium ion on the proliferation,differentiation and mineralization function of primary mouse osteoblasts in vitro

The effects of cerium ion(Ce3+) on the proliferation,differentiation,adipocytic transdifferentiation and mineralization function of primary mouse osteoblasts(OBs) were investigated.The results indicated that Ce3+ at all concentrations(1×10-9,1×10-8,1×10-7,1×10-6,1×10-5,and 1×10-4 mol/L) promoted the proliferation of osteoblasts(OBs).On day 1 and 3,Ce3+ promoted the differentiation of OBs at concentrations of 1×10-9,1×10-7,and 1×10-6 mol/L,but inhibited the differentiation of OBs at higher concentrations.On ...

Culture conditions for equine bone marrow mesenchymal stem cells and expression of key transcription factors during their differentiation into osteoblasts

Background： The use of equine bone marrow mesenchymal stem cells （BMSC） is a novel method to improve fracture healing in horses. However, additional research is needed to identify optimal culture conditions and to determine the mechanisms involved in regulating BMSC differentiation into osteoblasts. The objectives of the experiments were to determine： 1） if autologous or commercial serum is better for proliferation and differentiation of equine BMSC into osteoblasts, and 2） the expression of key transcription factors during the differentiation of equine BMSC into osteoblasts. Equine BMSC were isolated from the sterna of 3 horses, treated with purchased fetal bovine serum （FBS） or autologous horse serum （HS）, and cell proliferation determined. To induce osteoblast differentiation, cells were incubated with L-ascorbic acid-2-phosphate and glycerol-2-phosphate in the presence or absence of human bone morphogenetic protein2 （BMP2）, dexamethasone （DEX）, or combination of the two. Alkaline phosphatase （ALP） activity, a marker of osteoblast differentiation, was determined by ELISA. Total RNA was isolated from differentiating BMSC between d 0 to 18 to determine expression of runt-reloted tronscrJption foctor2 （Runx2）, osterix （Osx）, and T-box3 （Tbx3）. Data were analyzed by ANOVA. Results： Relative to control, FBS and HS increased cell number （133 ± 5 and 116 ± 5%, respectively; P 〈 0.001） and 5-bromo- 2＇-deoxyuridine （BrdU） incorporation （167 ± 6 and 120 ± 6%, respectively; P 〈 0.001）. Treatment with DEX increased ALP activity compared with control （1,638 ± 38%; P 〈 0.001）. In the absence and presence of Dex, BMP-2 did not alter ALP activity （P 〉 0.8）. Runt-reloted transcription foctor2 expression increased 3-fold （P 〈 0.001） by d 6 of culture. Osterix expression increased 94old （P 〈 0.05） by d 18 of culture. Expression of Tbx3 increased 1.8-fold at d 3 （P 〈 0.01）; however expression was reduced 4-fold at d 18 （P 〈 0.01）. Conclusions： Dexamethasone, but not BMP-2, is required for differentiation of equine BMSC into osteoblasts. In addition, expression of Runx2 and osterix increased and expression of Tbx3 is reduced during differentiation.

Activation of PPAR-γ Inhibits Differentiation of Rat Osteoblasts by Reducing Expression of Connective Tissue Growth Factor

Long-term treatment with an agonist of peroxisome proliferator-activated receptor （PPAR）-γ is associated with bone fractures in the clinical practice. However, the mechanisms underlying the frac- tures are not fully understood. This study was aimed to examine the effect of rosiglitazone （an agonist of PPAR-T） of different doses on the proliferation, differentiation, and transforming growth factor beta 1 （TGF-131）-induced expression of connective tissue growth factor （CTGF） in primary rat osteoblasts in vitro. Osteoblasts were isolated from newly born SD rats and treated with different doses of rosiglita- zone （0-20 gmol/L）. The proliferation and differentiation of osteoblasts were measured by MTT assay and NPP assay, respectively. The expression of CTGF was determined by RT-PCR and Western blotting. The results showed that most isolated osteoblasts displayed strong alkaline phosphatase （ALP） activity and treatment with different doses of rosiglitazone did not affect their proliferation, but significantly in- hibited the differentiation of osteoblasts in a dose-dependent manner. Moreover, treatment with different doses of rosiglitazone significantly reduced the TGF-131-induced CTGF mRNA transcription and protein expression in a dose-dependent manner in rat osteoblasts. It was concluded that the activation of PPAR-y may inhibit the differentiation of osteoblasts by reducing the TGF-131-induced CTGF expres- sion in vitro.

N-acetylcyteine and flavonoid rich diet:The protective effect of 15 different antioxidants on cigarette smoke-damaged primary human osteoblasts

Cigarette consumption increases oxidative stress in many organs. Increased oxidative stress harms bone cells, which negatively affects bone-matter and -stability. This leads to an increased fracture risk and delayed fracture healing in smokers. A supporting therapy with antioxidants could be of great benefit for surgeons dealing with delayed fracture healing due to increased oxidative stress. In this article we complement and compare our published data with hitherto unpublished data and show the protective effect of 15 different antioxidants on cigarette smoke induced damage in primary human osteoblasts. Exposure to cigarette smoke medium (CSM) rapidly induces formation of ROS in osteoblasts in a concentration- and time-dependent manner. Massive cell damage is seen already after 4 h (EC50 ≈ 0.75 OD320). Pre-, co- and post-incubation with the different antioxidants reduces the formation of ROS and consequently improves the viability of the CSM exposed osteoblasts. Small compounds, e.g. N-acetylcysteine, proved highly effective if pre- or co-incubated before exposure to the CSM. Thus, they are good candidates for acute therapy support as they can be administered in high doses. However, our data suggest that a balanced daily diet could lead to an accumulation of various natural antioxidants (flavonoids) that effectively protect osteoblasts from oxidative stress-induced damage in all three settings investigated. Together with their partly phytoestrogenic properties this may even abate alterations in bone and thus reduce fracture risk on the long run.

The Influence of Type and Thickness of Sol-gel Derived Coatings on the in vitro Osteoblasts Behavior

To evaluate the cellular response to the most commonly studied coatings fabricated by the sol-gel route, the influence of the coating thickness on the cellular response was studied. 1, 3, 5 layers of hydroxyapatite （ HA ）, fluorohydroxyapatite （ FHA ） and titania （ TiO2 ） were coated on the surface of commercially pure titanium （ cpTi ） discs respectively by the sol- gel route. CpTi discs were taken as control. XRD and SEM were employed to characterize the type and thickness of these coatings. In vitro osteoblasts behavior on the coatings was studied by the culture of MG63 cell line. The experimental results show all groups have good biocompatibilhy to osteoblasts . However, the type and thickness of the coatings influence the osteoblast response. The optimal type and thickness of sol-gel derived biocoatings were concluded.

Study on biocompatibility of PDLLA/HA/DBM with co-cultured human osteoblasts in vitro

Objective: To evaluate the osteocompatibility of D, L-polylactic/hydroxyapatite/decalcifying bone matrix (PDLLA/HA/DBM), and compare with PDLLA and DBM. Methods: Human primary osteoblasts isolated from the femoral head of patients were inoculated onto PDLLA/HA/DBM, PLA and DBM respectively. The proliferation rate and collagen Ⅰ expression were detected. The interface between biomaterial and osteoblasts was investigated with phase contrast microscopy and electron scanning microscopy. Results: Best proliferation rate was observed with the PDLLA/HA/DBM and followed by DBM and PLA, suggesting that PDLLA/HA/DBM satisfying most requirements for the cultivation of human osteoblasts. Scanning electron microscopy showed the morphology of osteoblasts was correlated with the proliferation data. The cells, well spread and flattened, were attached closely on the surface of biomaterial with an arched structure and had normal morphology. The extracellular collagenous matrixs covered the surface of biomaterial and packed the granules of biomaterial. Conclusion: PDLLA/HA/DBM can form osteointerface early and have a good biocompability.

Study of Rat Osteoblasts Transfected by Transforming Growth Factorβ_(1)Gene

Summary:In order to investigate the effect of TGFβ_(1) gene transfer on the biological characteristics,the effects of gene transfer and supernatant of transfected osteoblasts on the proliferation and ALP activity of osteoblasts were detected by ^(3)H-TdR and MTT.Our results showed that TGFβ_(1) gene transfer had no effect on the biological characteristics and the activated supernatant of transfected osteoblasts stimulated proliferation and inhibited ALP activity of osteoblasts.TGFβ_(1) gene transfer could promote the expression of TGFβ_(1) and the biological characteristics of transfected osteoblasts were stable,which might be helpful for gene therapy of bone defects in vivo.

A cost-effective method to enhance adenoviral transduction of primary murine osteoblasts and bone marrow stromal cells

We report here a method for the use of poly-L-lysine （PLL） to markedly improve the adenoviral transduction efficiency of primary murine osteoblasts and bone marrow stromal cells （BMSCs） in culture and in situ, which are typically difficult to transduce. We show by fluorescence microscopy and flow cytometry that the addition of PLL to the viral-containing medium significantly increases the number of green fluorescence protein （GFP）-positive osteoblasts and BMSCs transduced with an enhanced GFP-expressing adenovirus. We also demonstrate that PLL can greatly enhance the adenoviral transduction of osteoblasts and osteocytes in situ in ex vivo tibia and calvaria, as well as in long bone fragments. In addition, we validate that PLL can improve routine adenoviral transduction studies by permitting the use of low multiplicities of infection to obtain the desired biologic effect. Ultimately, the use of PLL to facilitate adenoviral gene transfer in osteogenic cells can provide a cost-effective means of performing efficient gene transfer studies in the context of bone research.

Study on the protective effect of icariin in different concentrations on the inflammatory response of osteoblasts in fetal rats

Objective:To verify whether icariin has drug toxicity to osteoblasts and its pre protective effect on inflammatory osteoblasts induced by lipopolysaccharide.Methods:(1)The osteoblasts of newborn SD rats were extracted,cultured and passaged.By observing the morphology of osteoblasts and ALP staining,the activity and proliferation of osteoblasts were determined.(2)CCK-8 method was used to observe the effect of Icariin on osteoblast activity.(3)Different concentrations of lipopolysaccharide(LPS)were used to induce inflammatory osteoblasts in fetal rats.CCK-8 method was used to select the best concentration for induction.(4)This experiment was divided into control group,low concentration group,middle concentration group and high concentration group.CCK-8 method was used to observe whether icariin could protect osteoblasts from inflammatory reaction.Results:(1)The number of osteoblasts in the third generation increased,the shape of osteoblasts overlapped like tiles,most of osteoblasts grew in the center,the center was dense and the specific shape was difficult to see.After ALP staining,the positive cells showed gray black granules in cytoplasm and irregular cell body shape under inverted microscope;(2)DWhen the concentration of icariin was lower than 1μg/ml,it had no significant effect on osteoblasts(P<0.05);when it was higher than 10μg/ml,icariin had no significant effect on osteoblasts(P<0.05);(3)When the concentration of lipopolysaccharide was higher than 80μg/ml,there was a significant trend of inflammatory damage to osteoblasts,which was statistically significant(P<0.01).Therefore,80μg/ml was selected as the best injury concentration in this experiment;(4)When the concentration of icariin was lower than 1μg/ml,there was no significant pre protective effect on the inflammatory response of osteoblasts(P<0.05);when it was higher than 10μg/ml,there was significant pre protective effect on the inflammatory response of osteoblasts(P<0.05).Conclusion:When the concentration of icariin reaches a certain level,it can promote the proliferation of osteoblasts and has a certain pre protective effect on inflammatory osteoblasts.

Tissue Engineered Osteogenesis in Bone Defects by Homologous Osteoblasts Loaded on Sterile Bioresorbable Coral Scaffold in Rabbits

Objectives: This study explores feasibility of tissue-engineered osteogenesis using sterile coral implants loaded with homologous osteoblasts to repair bone defects. Study Design: A unilateral 4 mm transverse dis- continuity defect was produced approximately mid-way along left radius of young female rabbits using ro- tary diamond disc under continuous saline irrigation and stabilised with autoclaved steel miniplate and screws. The defect was then fitted with sterile bioresorbable coral implant loaded with homologous neonatal calvarial osteoblasts or control implants without osteoblasts. All animals underwent radiography immedi- ately post-operative, at weekly intervals for four weeks and at fortnightly intervals thereafter. Operated bones were histologically evaluated for osteogenesis at 12 weeks. Results: Findings demonstrate osteogenesis and complete repair of bioresorbable coral implant by homologous osteoblasts loaded on coral scaffold. Conclu- sions: Single stage surgery using this technique to induce osteogenesis and closure of discontinuity bone de- fects including palatal clefts and peripheral reduction of large craniofacial defects might prove better thera- peutic modality than autologous bone grafting or tissue distraction osteogenesis.

Effects of Hydrocortisone, Glycerophosphate and Retinol on the Differentiation of Mesenchymal Stem Cells and Vascular Endothelial Cells to Osteoblasts

Vascular calcification, which causes occlusion and rupture of the vascular, is often observed in patients in the advanced stages of arteriosclerosis. One of the best procedures for inhibiting the accumulation of vascular calcification is to obstruct the differentiation of mesenchymal stem cells (MSCs) and/or vascular endothelial cells (VECs) in the vascular to osteoblasts. In this study, we evaluated the biochemical and genetic characteristics of the process of differentiation of MSCs and VECs to osteoblasts. C3H10T1/2 MSCs, TKD2 VECs and MC3T3-E1 preosteoblasts (POBs) were cultured in medium containing both hydrocortisone and glycerophosphate. These compounds showed strong effects promoting the differentiation of VECs as well as POBs, although the effect was weak in the MSCs. Moreover, C3H10T1/2 MSCs and TKD2 VECs were cultured in medium containing 10 mM retinol, after which the alkali phosphatase (ALP) activity of the MSCs and production of calcified nodules of TKD2 were significantly increased, whereas the marker genes for the osteoblasts were not. These results suggest that retinol does not have an effect in inducing the differentiation of VECs to osteoblasts, but rather exhibits a strong promoting effect on differentiation.

Survivin activity in normal human osteoblasts and osteosarcoma cells

PURPOSE: This study was designed to investigate and compare in vitro survivin activity in normal human osteoblast and MG-63 osteosarcoma cell cultures with and without vitamin D3. METHODS: Normal human alveolar bone explants were recovered from extraction sites of non-carious teeth of 9 healthy donors and cultured to the 2nd passage. MG-63 osteosarcoma cells were obtained from ATCC. To compare the survivin activities in these two types of cells and to determine the effect of vitamin D3 on survivin expression and associated activities of cell proliferation and differentiation, levels of survivin, osteocalcin and alkaline phosphatase were measured at 7-20 day cultures with and without vitamin D3 in both cultures of normal osteoblasts and osteosarcoma cells. Matched pair t-test and two sample independent t-test were applied for statistical analysis of the data. P values of 0.05 or less were considered statistically significant. RESULTS: A significantly higher level of survivin was detected in normal osteoblasts compared to osteosarcoma cells at 7 days without vitamin D3 treatment (P<0.01). Survivin expression in normal osteoblasts significantly decreased after vitamin D3 treatment at 7 days (P<0.05), but not at 20 days of culture (P=NS), compared to that in normal osteoblast culture without vitamin D3 treatment. Vitamin D3 had no effect on survivin expression in osteosarcoma cells at 7 or 20 days (P=NS). CONCLUSIONS: Expression of survivin in cultured normal human osteoblasts and osteosarcoma cells was positively identified. There is a positive correlation between higher expression of survivin and less differentiated osteoblasts that still retain their proliferative ability. Vitamin D3 has significant negative effect on expression of survivin in normal human osteoblasts but not on that in osteosarcoma cells.

Modulation of Isoflavones on Bone-nodule Formation in Rat Calvaria Osteoblasts in vitro

Objective To observe the effects of two main isoflavones, daidzein and genistein on the bone-nodule formation in rat calvaria osteoblasts in vitro. Methods Osteoblasts obtained from newborn Sprague-dawley rat calvarias were cultured for several generations. The second generation cells were cultured in Minimum Essential Medium supplemented with ascorbic acid and Na-beta-glycerophosphate for several days, in the presence of daidzein and genistein, with or without the estrogen receptor antagonist ICI 182780. Number of nodules was counted at the end of the incubation period (day 20) by staining with Alizarin Red S calcium stain. The release of osteocalcin, as a marker of osteoblast activity, was also determined on day 7 and day 12 during the incubation period. Results Compared with the control, the numbers of nodules were both increased by incubation with daidzein and genistein. 17β-estradiol was used as a positive control and proved to be a more effective inducer of the increase in bone-nodules formation than daidzein and genistein. The release of osteocalcin into culture media was also increased in the presence of daidzein and genistein, as well as 17β-estradiol on day 7 and day 12 (day 12 were higher). The estrogen receptor antagonist ICI 182780 completely blocked the genistein- and 17β-estradiol-induced increase of nodule numbers and osteocalcin release in osteoblasts. However, the effects induced by daidzein could not be inhibited by ICI 182780. Conclusion These findings suggest that geinistein can stimulate bone-nodule formation and increase the release of osteocalcin in rat osteoblasts. The effects, like those induced by 17β-estradiol, are mediated by the estrogen receptor dependent pathway. Daidzein also can stimulate bone-nodule formation and increase the release of osteocalcin in rat osteoblasts, but it is not, at least not merely, mediated by the estrogen receptor dependent pathway.