Estrogen and bone: osteoclasts take center stage

Exploration of bone metabolism status in the distal femur of mice at different growth stages

The mouse femur, particularly the distal femur, is commonly utilized in orthopedic research. Despite its significance, little is known about the key events involved in the postnatal development of the distal femur. Therefore, investigating the development process of the mouse distal femur is of great importance. In this study, distal femurs of CD-1 mice aged 1, 2, 4, 6, and 8 weeks were examined. We found that the width and height of the distal femur continued to increase till the 4th week, followed with stabilization. Notably, the width to height ratio remained relatively consistent with age. Micro computed tomography analysis demonstrated gradual increases in bone volume/tissue volume, trabecular number, and trabecular thickness from 1 to 6 weeks, alongside a gradual decrease in trabecular separation. Histological analysis further indicated the appearance of the secondary ossification center at approximately 2 weeks, with ossification mostly completed by 4 weeks, leading to the formation of a prototype epiphyseal plate. Subsequently, the epiphyseal plate gradually narrowed at 6 and 8 weeks. Moreover, the thickness and maturity of the bone cortex surrounding the epiphyseal plate increased over time, reaching peak cortical bone density at 8 weeks. In conclusion, to enhance model stability and operational ease, we recommend constructing conventional mouse models of the distal femur between 4 and 8 weeks old.

A Comparative Analysis of the Efficacy of Bacterial Lysate versus Antibiotic Therapy in the Treatment of Experimental Peri-Implantitis in Rats

Peri-implantitis (PI) is a current concern whose understanding and resolution are ongoing. We aimed to evaluate in vivo a new treatment with antibacterial properties, based on bacterial lysates obtained from the strains of Aggregatibacter actinomycetemcomitans, Streptococcus oralis, and Fusobacterium nucleatum. This research was conducted on 30 rats with PI which were divided into three groups and treated with antibiotic and anti-inflammatory (AAi) drugs, bacterial lysates (BLs), and saline (C), respectively. The monitoring period included the clinical and paraclinical examination where hematological, immunological, imaging, and histopathological analysis were performed. No particular clinical signs were observed, but the radiological examination showed the loss of all implants in group C, in contrast to group BL which had the highest survival rate of devices. White cells showed a decrease from the PI period, as did the immunological analysis. Only IL-6 showed an increase in the AAi and BL groups. Histopathologically, the C group presented a high degree of bone destruction, and in the BL group, many attenuated inflammatory phenomena appeared compared to the AAi animals. Bacterial lysates have similar effects to antibiotic-based therapeutic regimens for PI, and their future use may help to improve the current therapeutic management of the disease.

A Standardized Rat Model to Study Peri-implantitis of Transmucosal Osseointegrated Implants

With the high incidence rate, distinctive implant characteristic and unique infection pattern, peri-implantitis (PI) requires a specially designed implant animal model for the researches on the pathogenesis and treatments. Previous small-animal PI models exhibit variability in implant site selection, design, and surgical procedures resulting in unnecessary tissue damage and less effectivity. Herein, a quantitative-analysis-based standardized rat model for transmucosal PI-related research was proposed. After dissecting the anatomic structures of the rat maxilla, we determined that placing the implant anterior to the molars in the rat maxilla streamlined the experimental period and enhanced animal welfare. We standardized the model by controlling the rat strain, gender, and size. The customized implant and a series of matched surgical instruments were appropriately designed. A clear, step-by-step surgical process was established. These designs ensured the success rate, stability, and replicability of the model. Each validation method confirmed the successful construction of the model. This study proposed a quantitative-analysis-based standardized transmucosal PI rat model with improved animal welfare and reliable procedures. This model could provide efficient in vivo insights to study the pathogenesis and treatments of PI and preliminary screening data for further large-animal and clinical trials.

New flavan trimer from Daemonorops draco as osteoclastogenesis inhibitor

Dragon's blood is a red resin obtained from different plants and is considered highly efficacious and used in medicine owing its wound healing function. Two new compounds (7 and 8) were isolated from the dragon's blood of Daemonorops draco fruits, along with eight known compounds (1-6, 9, and 10). Their structures, including their absolute configurations, were elucidated by nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and electronic circular dichroism (ECD) analysis. According to the spectroscopic data, 8 was determined to be a quinone methide derivative of flavan and 7 was deduced to be a flavan trimer. All compounds were evaluated for their anti-osteoclastogenesis activity, compound 1 and 7 exhibited anti-osteoclastogenesis activity with IC50 values of 31.3 and 36.8 μM, respectively.

Integration of osteoclastogenesis through addition of PBMCs in human osteochondral explants cultured ex vivo

The preservation of tissue specific cells in their native 3D extracellular matrix in bone explants provides a unique platform to study remodeling. Thus far, studies involving bone explant cultures showed a clear focus on achieving bone formation and neglected osteoclast activity and resorption. To simulate the homeostatic bone environment ex vivo, both key elements of bone remodeling need to be represented. This study aimed to assess and include osteoclastogenesis in human osteochondral explants through medium supplementation with RANKL and M-CSF and addition of peripheral blood mononuclear cells (PBMCs), providing osteoclast precursors. Osteochondral explants were freshly harvested from human femoral heads obtained from hip surgeries and cultured for 20 days in a two-compartment culture system. Osteochondral explants preserved viability and cellular abundance over the culture period, but histology demonstrated that resident osteoclasts were no longer present after 4 days of culture. Quantitative extracellular tartrate resistant acid phosphatase (TRAP) analysis confirmed depletion of osteoclast activity on day 4 even when stimulated with RANKL and M-CSF. Upon addition of PBMCs, a significant upregulation of TRAP activity was measured from day 10 onwards. Evaluation of bone loss trough μCT registration and measurement of extracellular cathepsin K activity revealed indications of enhanced resorption upon addition of PBMCs. Based on the results we suggest that an external source of osteoclast precursors, such as PBMCs, needs to be added in long-term bone explant cultures to maintain osteoclastic activity, and bone remodeling.

Protection against Osteoporosis by Fermented Mulberry Vinegar Supplementation via Inhibiting Osteoclastic Activity in Ovariectomized Rats and Osteoclastic Cells

Menopause increases the osteoporosis risk, to which phytoestrogen intake can be beneficial. This study hypothesized that mulberry vinegar had a preventive effect on osteoporosis by decreasing osteoclastic activity. The hypothesis was tested in ovariectomized (OVX) rats and RANKL-differentiated osteoclast cells. OVX rats were given 0(OVX-CON), 0.5(OVX-MVL), 1(OVX-MVM), and 2(OVX-MVH) fermented mulberry vinegar (MV) mL/kg body weight (BW) daily for 12 weeks. Sham-operated rats had no MV supplementation (Normal-CON). The osteoporosis-related biomarkers were measured, and Micro-CT determined the bone mass of the femur. RANKL-differentiated Raw 264.7 cells were treated with MV (0–100 μg/mL). The cell viability, osteoporosis-related mRNA expression, and protein contents were measured. MV contained Acetobacter pasteurianus (7.31 log CFU/mL), citric acid (106 mg/mL), lactic acid (19.2 mg/mL), acetic acid (15.0 mg/mL), and rutin (0.36 mg/mL). OVX-MVM elevated the serum 17β-estradiol concentration similar to the Normal-CON group, but it did not prevent the decrease in uterine weight. OVX-MVM prevented the increase in osteoclastic-related parameters, including cathepsin K(CtsK), receptor activator of NF-κB ligand (RANKL), and tartrate-resistant acid phosphatase (TRAP) in the circulation. OVX-MVH also lowered C-telopeptide of type Ⅰ collagen as much as the Normal-CON group (p < 0.05). By contrast, OVX-MVH increased the serum osteoprotegerin concentration, an inhibitor of osteoclasts, better than the Normal-CON group (p < 0.05). These changes were integrated to alter the bone mineral density (BMD) in Micro-CT analysis: OVX-MVM and OVX-MVH prevented BMD decrease after OVX as much as the Normal-CON. In RANKL-differentiated osteoclast cells, the MV treatment for 24 and 48 h decreased RANKL-induced differentiation in osteoclast cells dose-dependently up to 100 µg/mL. Its decrease was related to inhibiting the TRAP activity and reducing TRAP-positive multinucleated cells during the five-day administration of RANKL. MV treatments also decreased mRNA expression of osteoclast-related genes (TRAP, Ctsk, OSCAR, and NFATc1). MV suppressed the protein contents of NFATc1 and c-FOS-related osteoclast. In conclusion, MV intake (1 mg/kg bw) protected against BMD loss mainly by inhibiting the osteoclastic activity (RANKL/RANK/TRAP) in OVX rats. MV may develop as a functional food for anti-osteoporosis in menopausal women.

Monitoring Salivary Levels of Interleukin 1 Beta (IL-1β) and Vascular Endothelial Growth Factor (VEGF) for Two Years of Orthodontic Treatment: A Prospective Pilot Study

Results

A gradual increase in IL-1β and VEGF was observed at alignment, reaching significance at space closure (p = 0.002 and p = 0.025, respectively). At finishing, both IL-1β and VEGF declined, however, without reverting to baseline values (p = 0.172 and p = 0.207, respectively). Bland-Altman analysis showed the agreement between IL-1β and VEGF in terms of a systematic increase, with a higher percentage difference for VEGF.

Conclusions

The salivary levels of both IL-1β and VEGF increased following orthodontic treatment and reached their peaks during the treatment stage of space closure. This novel approach provides a hint on how and when to sample saliva during orthodontic treatment to analyse bone remodelling.

Endocrine role of bone in the regulation of energy metabolism

Bone mainly functions as a supportive framework for the whole body and is the major regulator of calcium homeostasis and hematopoietic function. Recently, an increasing number of studies have characterized the significance of bone as an endocrine organ, suggesting that bone-derived factors regulate local bone metabolism and metabolic functions. In addition, these factors can regulate global energy homeostasis by altering insulin sensitivity, feeding behavior, and adipocyte commitment. These findings may provide a new pathological mechanism for related metabolic diseases or be used in the diagnosis, treatment, and prevention of metabolic diseases such as osteoporosis, obesity, and diabetes mellitus. In this review, we summarize the regulatory effect of bone and bone-derived factors on energy metabolism and discuss directions for future research.

Pantoprazole (PPZ) Inhibits RANKL-Induced Osteoclast Formation and Function In Vitro and Prevents Lipopolysaccharide- (LPS-) Induced Inflammatory Calvarial Bone Loss In Vivo

Bone remodeling is a process delicately balanced between osteoclastic bone resorption and osteoblastic bone formation. Osteoclasts (OCs) are multinucleated giant cells formed through the fusion of monocytic precursors of the hematopoietic stem cells lineage. OCs are the exclusive cells responsible for the resorption and degradation of the mineralized bone matrix. Pantoprazole (PPZ), a proton pump inhibitor (PPI), is commonly prescribed to reduce excess gastric acid production for conditions such as gastroesophageal reflux disease and peptic ulcer disease. Studies have found contradictory effects of PPI therapy on bone metabolism due to the lack of understanding of the exact underlying mechanism. In this study, we found that PPZ inhibits receptor activator of nuclear factor-κB (NF-κB) ligand- (RANKL-) induced osteoclastogenesis from bone marrow monocytic/macrophage (BMMs) precursors and the bone-resorbing activity of mature OCs. Correspondingly, the expression of OC marker genes was also attenuated. At the molecular level, PPZ treatment was associated with reduced activation of the ERK MAPK signaling pathways crucial to OC differentiation. Additionally, the in vivo administration of PPZ protected mice against lipopolysaccharide- (LPS-) induced inflammatory calvarial bone erosion, as a result of the reduced number and activity of OCs on the calvarial bone surface. Although PPI use is associated with increased risk of osteoporosis and bone fractures, our study provides evidence for the direct inhibitory effect of PPZ on OC formation and bone resorption in vitro and in vivo, suggesting a potential therapeutic use of PPZ in the treatment of osteolytic disease with localized bone destruction.

Oestrogen-activated autophagy has a negative effect on the anti-osteoclastogenic function of oestrogen

OBJECTIVES

Oestrogen is known to inhibit osteoclastogenesis, and numerous studies have identified it as an autophagic activator. To date, the role of oestrogen in the autophagy of osteoclast precursors (OCPs) during osteoclastogenesis remains unclear. This study aimed to determine the effect of autophagy regulated by the biologically active form of oestrogen (17β-estradiol) on osteoclastogenesis.

MATERIALS AND METHODS

After treatment with 17β-estradiol in OCPs (from bone marrow-derived macrophages, BMMs) and ovariectomy (OVX) mice, we measured the effect of 17β-estradiol on the autophagy of OCPs in vitro and in vivo. In addition, we studied the role of autophagy in the OCP proliferation, osteoclast differentiation and bone loss regulated by 17β-estradiol using autophagic inhibitor or knock-down of autophagic genes.

RESULTS

The results showed that direct administration of 17β-estradiol enhanced the autophagic response of OCPs. Interestingly, 17β-estradiol inhibited the stimulatory effect of receptor activator of nuclear factor-κB ligand (RANKL) on the autophagy and osteoclastogenesis of OCPs. Moreover, 17β-estradiol inhibited the downstream signalling of RANKL. Autophagic suppression by pharmacological inhibitors or gene silencing enhanced the inhibitory effect of 17β-estradiol on osteoclastogenesis. In vivo assays showed that the autophagic inhibitor 3-MA not only inhibited the autophagic activity of the OCPs in the trabecular bone of OVX mice but also enhanced the ability of 17β-estradiol to ameliorate bone loss.

CONCLUSIONS

In conclusion, our study showed that oestrogen directly enhanced the autophagy of OCPs, which inhibited its anti-osteoclastogenic effect. Drugs based on autophagic inhibition may enhance the efficacy of oestrogen on osteoporosis.

Pregnenolone Inhibits Osteoclast Differentiation and Protects Against Lipopolysaccharide-Induced Inflammatory Bone Destruction and Ovariectomy-Induced Bone Loss

Osteolytic bone disease is characterized by excessive osteoclast bone resorption leading to increased skeletal fragility and fracture risk. Multinucleated osteoclasts formed through the fusion of mononuclear precursors are the principle cell capable of bone resorption. Pregnenolone (Preg) is the grand precursor of most if not all steroid hormones and have been suggested to be a novel anti-osteoporotic agent. However, the effects of Preg on osteoclast biology and function has yet to be shown. Here we examined the effect of Preg on receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclast formation and bone resorption in vitro, and potential therapeutic application in inflammatory bone destruction and bone loss in vivo. Our in vitro cellular assays demonstrated that Preg can inhibit the formation of TRAP^+ve osteoclast formation as well as mature osteoclast bone resorption in a dose-dependent manner. The expression of osteoclast marker genes CTSK, TRAP, DC-STAMP, ATP6V0d2, and NFATc1 were markedly attenuated. Biochemical analyses of RANKL-induced signaling pathways showed that Preg inhibited the early activation of extracellular regulated protein kinases (ERK) mitogen-activated protein kinase (MAPK) and nuclear factor-κB, which consequently impaired the downstream induction of c-Fos and NFATc1. Using reactive oxygen species (ROS) detection assays, we found that Preg exhibits anti-oxidant properties inhibiting the generation of intracellular ROS following RANKL stimulation. Consistent with these in vitro results, we confirmed that Preg protected mice against local Lipopolysaccharide (LPS)-induced inflammatory bone destruction in vivo by suppressing osteoclast formation. Furthermore, we did not find any observable effect of Preg on osteoblastogenesis and mineralization in vitro. Finally Preg was administered to ovariectomy (OVX)-induced bone loss and demonstrated that Preg prevented systemic OVX-induced osteoporosis. Collectively, our observations provide strong evidence for the use of Preg as anti-osteoclastogenic and anti-resorptive agent for the potential treatment of osteolytic bone conditions.

The Role of Bone-Derived Exosomes in Regulating Skeletal Metabolism and Extraosseous Diseases

Bone-derived exosomes are naturally existing nano-sized extracellular vesicles secreted by various cells, such as bone marrow stromal cells, osteoclasts, osteoblasts, and osteocytes, containing multifarious proteins, lipids, and nucleic acids. Accumulating evidence indicates that bone-derived exosomes are involved in the regulation of skeletal metabolism and extraosseous diseases through modulating intercellular communication and the transfer of materials. Following the development of research, we found that exosomes can be considered as a potential candidate as a drug delivery carrier thanks to its ability to transport molecules into targeted cells with high stability, safety, and efficiency. This review aims to discuss the emerging role of bone-derived exosomes in skeletal metabolism and extraosseous diseases as well as their potential role as candidate biomarkers or for developing new therapeutic strategies.

Oleanolic acid exerts inhibitory effects on the late stage of osteoclastogenesis and prevents bone loss in osteoprotegerin knockout mice

Postmenopausal women undergo rapid bone loss, which caused by the accelerated osteoclastic bone resorption. Receptor activator of nuclear factor kappa-B ligand (RANKL) plays critical and essential roles on varied stages of osteoclastogenesis. Oleanolic acid (OA), a naturally derived small compound, has been found suppress osteoclastogenesis in early stage of bone marrow macrophages (BMMs). However, whether OA also regulates the late stage of osteoclastogenesis remains unclear. Here, the regulatory effect of OA on the late stage of osteoclastogenesis was investigated in vitro using RANKL-pretreated BMMs and in vivo using osteoprotegerin (OPG) knockout mice. Our in vitro studies demonstrate that OA inhibits the late stage of osteoclastogenesis from RANKL-pretreated BMMs. For in vivo animal investigation, OA attenuates the bone loss phenotypes in OPG-knockout mice by decreasing the densities of osteoclast, which are in consistent with the finding with in vitro osteoclastogenesis. Mechanistic investigations found that OA largely inhibit the activity of c-Fos and Nuclear factor of activated T-cells c1 (NFATc1) with RANKL-pretreated BMMs and OPG-knockout mice. Furthermore, OA suppresses the activities of osteoclast genes, such as Tartrate resistant acid phosphatase (TRAP), CathepsinK (Ctsk), and Matrix metalloproteinase 9 (MMP9). Taken together these findings, they have not only defined an inhibitory effect of OA in the late stage of osteoclastogenesis but have also gained new molecular mechanisms underlying the process of osteoclast formation.

MiR-210-3p inhibits osteogenic differentiation and promotes adipogenic differentiation correlated with Wnt signaling in ERα-deficient rBMSCs

MicroRNAs (miRNAs) regulate activities in living organisms through various signaling pathways and play important roles in the development and progression of osteoporosis. The balance between osteogenic and adipogenic differentiation of rBMSCs is closely related to the occurrence of osteoporosis. ERα regulates bone metabolism in various tissues. However, the correlation among ERα, miRNAs, and the differentiation of rBMSCs is still unclear. In this study, we used lentivirus transfection into rBMSCs to construct an ERα-deficient model, analyzed the differences in expressed miRNAs between control and ERα-deficient rBMSCs. The results revealed that the expression of 25 miRNAs were upregulated, 164 miRNAs were downregulated, and some of the regulated miRNAs such as miR-210-3p and miR-214-3p were related to osteogenic or adipogenic differentiation, as well as to particular signaling pathways. Next, we overexpressed miR-210-3p to evaluate its effects on the osteogenic and adipogenic differentiation of rBMSCs, and identified the relationship among miR-210-3p, Wnt signaling pathway, and the differentiation of rBMSCs. The results indicated that ERα-deficient inhibited osteogenic differentiation, promoted adipogenic differentiation, and regulated the expression of some miRNAs. Meanwhile, overexpression of miR-210-3p promoted osteogenic differentiation and inhibited adipogenic differentiation of rBMSCs, processes likely to be related to the Wnt signaling pathway. In conclusion, we identified a group of upregulated and downregulated miRNAs in ERα-deficient rBMSCs that might play a vital role in regulating osteogenic or adipogenic differentiation. One of these, miR-210-3p, inhibited osteogenic differentiation and promoted adipogenic differentiation correlated with the Wnt signaling pathway in ERα-deficient rBMSCs, providing new insight into the regulation of bone metabolism.

LYN, a key mediator in estrogen-dependent suppression of osteoclast differentiation, survival, and function

Estrogen insufficiency at menopause cause accelerated bone loss due to unwarranted differentiation and function of osteoclasts. Unraveling the underlying mechanism/s may identify mediators of estrogen action which can be targeted for improved management of osteoporosis. Towards this, we analyzed the effect of 17β-estradiol on the proteomes of differentiating human osteoclasts. The major proteomic changes observed included upregulation of LYN by estrogen. We, therefore, investigated the effect of estrogen on osteoclast differentiation, survival, and function in control and LYN knockdown conditions. In control condition, estrogen treatment increased the apoptosis rate and suppressed the calcium signaling by reducing the intracellular Ca²⁺ levels as well as expression and activation of NFATc1 and c-Src during differentiation, resulting in reduced osteoclastogenesis. These osteoclasts were smaller in size with reduced extent of multinuclearity and produced significantly low levels of bone resorbing enzymes. They also exhibited disrupted sealing zone formation with low podosome density, impaired cell polarization and reduced resorption of dentine slices. Interestingly, in LYN knockdown condition, estrogen failed to induce apoptosis and inhibit activation of NFATc1 and c-Src. Compared to effect of estrogen on osteoclast in control condition, LYN knockdown osteoclasts did not show reduction in production of bone resorbing enzymes and had defined sealing zone formation with high podosome density with no impairment in cell polarization. They resorbed significant area on dentine slices. Thus, the inhibitory action of estrogen on osteoclast was severely restrained in LYN knockdown condition, demonstrating the importance of LYN as a key mediator of the effect of estrogen on osteoclastogenesis.

Gender-independent efficacy of mesenchymal stem cell therapy in sex hormone-deficient bone loss via immunosuppression and resident stem cell recovery

Osteoporosis develops with high prevalence in both postmenopausal women and hypogonadal men. Osteoporosis results in significant morbidity, but no cure has been established. Mesenchymal stem cells (MSCs) critically contribute to bone homeostasis and possess potent immunomodulatory/anti-inflammatory capability. Here, we investigated the therapeutic efficacy of using an infusion of MSCs to treat sex hormone-deficient bone loss and its underlying mechanisms. In particular, we compared the impacts of MSC cytotherapy in the two genders with the aim of examining potential gender differences. Using the gonadectomy (GNX) model, we confirmed that the osteoporotic phenotypes were substantially consistent between female and male mice. Importantly, systemic MSC transplantation (MSCT) not only rescued trabecular bone loss in GNX mice but also restored cortical bone mass and bone quality. Unexpectedly, no differences were detected between the genders. Furthermore, MSCT demonstrated an equal efficiency in rectifying the bone remodeling balance in both genders of GNX animals, as proven by the comparable recovery of bone formation and parallel normalization of bone resorption. Mechanistically, using green fluorescent protein (GFP)-based cell-tracing, we demonstrated rapid engraftment but poor inhabitation of donor MSCs in the GNX recipient bone marrow of each gender. Alternatively, MSCT uniformly reduced the CD3⁺T-cell population and suppressed the serum levels of inflammatory cytokines in reversing female and male GNX osteoporosis, which was attributed to the ability of the MSC to induce T-cell apoptosis. Immunosuppression in the microenvironment eventually led to functional recovery of endogenous MSCs, which resulted in restored osteogenesis and normalized behavior to modulate osteoclastogenesis. Collectively, these data revealed recipient sexually monomorphic responses to MSC therapy in gonadal steroid deficiency-induced osteoporosis via immunosuppression/anti-inflammation and resident stem cell recovery.

Employing different types of phytoestrogens improve bone mineralization in bisphenol A stimulated osteoblast

AIMS

Phytoestrogens and xenoestrogens act as agonists/antagonists in bone formation and differentiation. Strong bones are depending of the ability of osteoblasts to form new tissue and to mineralize the newly formed tissue. Dysfunctional or loss of mineralization leads to weak bone and increased fracture risk. In this study, we reported the effect of different types of phytoestrogens (daidzein, genistein and equol) on mineralization in hFOB 1.19 cells stimulated with bisphenol A (BPA).

MAIN METHODS

Cell mineralization capacity of phytoestrogens was investigated by evaluating calcium, phosphate content and alkaline phosphatase activity. Bone related markers, osteocalcin and osteonectin, responsible in maintaining mineralization were also measured.

KEY FINDINGS

BPA is significantly interfering with bone mineralization in hFOB 1.19 cells. However, the enhanced mineralization efficacy of daidzein and genistein (particularly at a dose of 5 and 40 μg/mL, respectively) was evidenced by increasing calcium and phosphate content, higher ALP activity, compared to the untreated BPA group. The quantitative analyses were confirmed through morphological findings. Osteocalcin and osteonectin levels were increased in phytoestrogens-treated cells. These findings revealed the potential effect of phytoestrogens in reverting the demineralization process due to BPA exposure in hFOB 1.19 cells.

SIGNIFICANCE

We found that osteoblast differentiation and mineralization were maintained following treatment with phytoestrogens under BPA exposure.

The lateral meningocele syndrome mutation causes marked osteopenia in mice

Lateral meningocele syndrome (LMS) is a rare genetic disorder characterized by neurological complications and osteoporosis. LMS is associated with mutations in exon 33 of NOTCH3 leading to a truncated protein lacking sequences for NOTCH3 degradation and presumably causing NOTCH3 gain of function. To create a mouse model reproducing human LMS-associated mutations, we utilized CRISPR/Cas9 to introduce a tandem termination codon at bases 6691-6696 (ACCAAG→TAATGA) and verified this mutation (Notch3^tm1.1Ecan ) by DNA sequencing of F1 mice. One-month-old male and female heterozygous Notch3^tm1.1Ecan mice had cancellous and cortical bone osteopenia but exhibited no obvious neurological alterations, and histopathology of multiple organs revealed no abnormalities. Microcomputed tomography of these mutants revealed a 35-60% decrease in cancellous bone volume associated with a reduction in trabecular number and decreased connectivity. During maturation, cancellous and cortical bones were restored in female but not in male mice, which exhibited cancellous bone osteopenia at 4 months. Cancellous bone histomorphometry revealed increased osteoblast and osteocyte numbers and a modest increase in osteoclast surface and bone formation rate. Notch3^tm1.1Ecan calvarial osteoblasts had increased proliferation and increased bone γ-carboxyglutamate protein (Bglap) and TNF superfamily member 11 (Tnfsf11) mRNA levels and lower Tnfrsf11b levels. Tnfsf11 mRNA was increased in osteocyte-rich femora from Notch3^tm1.1Ecan mice. Cultures of bone marrow-derived macrophages from Notch3^tm1.1Ecan mice revealed increased osteoclast formation, particularly in cocultures with osteoblasts from Notch3^tm1.1Ecan mice. In conclusion, the Notch3^tm1.1Ecan mutation causes osteopenia despite an increase in osteoblast proliferation and function and is associated with enhanced Tnfsf11 expression in osteoblasts and osteocytes.

ST2 regulates bone loss in a site-dependent and estrogen-dependent manner

Interleukin-33 (IL-33) and its receptor, ST2, are implicated in bone remodeling. The lack of estrogen after menopause results in an accelerated bone loss. Here we investigated the role of ST2 in the bone loss induced by estrogen deficiency. ST2-deficient mice (ST2^-/- ) and their littermates (wildtype [WT]) were ovariectomized (OVX), while ovary-intact mice were used as controls. Bone sites were analyzed by microcomputed tomography, histomorphometry, and quantitative real-time polymerase chain reaction (qPCR). Deletion of IL-33 or ST2 resulted in a similar bone loss in the femur and maxilla. Ovariectomy in WT mice caused bone loss in the same areas. The lack of ST2 in OVX mice did not alter bone remodeling in the femur but prevented bone loss in the maxilla. Consistently, ovariectomy increased the IL-33 messenger RNA (mRNA) levels in the maxilla but not in the femur. Under mechanical stimulation, ovariectomy and ST2 deletion independently increased bone remodeling induced by orthodontic tooth movement, which was also associated with a greater number of osteoclasts and a reduced number of osteoblasts in the maxillary bone. ST2^-/- OVX mice, however, displayed twice as many osteoblasts as that of WT OVX mice. Ovariectomy and ST2 deletion differently altered the cytokine mRNA levels in the maxilla. Remarkably, interleukin-10 expression was decreased in both WT OVX and ST2^-/- mice, and this reduction was completely restored in ST2^-/- OVX mice. The results demonstrate that estrogen and IL33/ST2 independently protect against bone loss. However, the ovariectomy-induced bone loss is IL-33/ST2-dependent in the maxilla but not in the femur, indicating a bimodal and site-specific role of ST2 in bone remodeling.

Ovariectomy-induced bone loss in TNFα and IL6 gene knockout mice is regulated by different mechanisms

We examined the effects of tumor necrosis factor-α (TNFα) and interleukin-6 (IL6) gene knockout in preserving the bone loss induced by ovariectomy (OVX) and the mechanisms involved in bone metabolism. Twenty female wild-type (WT), TNFα-knockout (TNFα^-/-) or IL6-knockout (IL6^-/-) mice aged 12 weeks were sham-operated (SHAM) or subjected to OVX and killed after 4 weeks. Bone mass and skeletal microarchitecture were determined using micro-CT. Bone marrow stromal cells (BMSCs) from all three groups (WT, TNFα^-/- and IL6^-/-) were induced to differentiate into osteoblasts or osteoclasts and treated with 17-β-estradiol. Bone metabolism was assessed by histological analysis, serum analyses and qRT-PCR. OVX successfully induced a high turnover in all mice, but a repair effect was observed in TNFα^-/- and IL6^-/- mice. The ratio of femoral trabecular bone volume to tissue volume, trabecular number and trabecular thickness were significantly decreased in WT mice subjected to OVX, but increased in TNFα^-/- mice (1.62, 1.34, 0.27-fold respectively; P < 0.01) and IL6^-/- mice (1.34, 0.80, 0.22-fold respectively; P < 0.01). Furthermore, we observed a 29.6% increase in the trabecular number in TNFα^-/- mice when compared to the IL6^-/- mice. Both, TNFα^-/- and IL6^-/- BMSCs exhibited decreased numbers of TRAP-positive cells and an increase in ALP-positive cells, with or without E2 treatment (P < 0.05). While the knockout of TNFα or IL6 significantly upregulated mRNA expressions of osteoblast-related genes (Runx2 and Col1a1) and downregulated osteoclast-related mRNA for TRAP, MMP9 and CTSK in vivo and in vitro, TNFα knockout appeared to have roles beyond IL6 knockout in upregulating Col1a1 mRNA expression and downregulating mRNA expressions of WNT-related genes (DKK1 and Sost) and TNF-related activation-induced genes (TRAF6). TNFα seemed to be more potentially invasive in inhibiting bone formation and enhancing TRAF6-mediated osteoclastogenesis than IL6, implying that the regulatory mechanisms of TNFα and IL6 in bone metabolism may be different.

Platycodin D Inhibits Osteoclastogenesis by Repressing the NFATc1 and MAPK Signaling Pathway

Platycodon grandiflorum root-derived saponins (Changkil saponins, CKS) are reported to have many pharmacological activities. In our latest research, CKS was proven to have a significant osteogenic effect. However, the detail molecular mechanism of CKS on osteoclastic differentiation has not been fully investigated. Administration of CKS considerably reduced OVX-induced bone loss, and ameliorated the reduction in plasma levels of alkaline phosphatase, calcium, and phosphorus observed in OVX mice. CKS also repressed the deterioration of bone trabecular microarchitecture. Interestingly, platycodin D, the most abundant and major pharmacological constituent of triterpenoid CKS, inhibited receptor activator of NF-κB ligand (RANKL)-induced activation of NF-κB, and ERK and p38 MAPK, ultimately repressing osteoclast differentiation. OVX-induced bone turnover was attenuated by CKS, possibly via repression of osteoclast differentiation by platycodin D, the active component of CKS. Platycodin D can be regarded as an antiosteoporotic candidate for treatment of osteoporosis diseases. J. Cell. Biochem. 118: 860-868, 2017. © 2016 Wiley Periodicals, Inc.

Design, synthesis and SARs of novel salicylanilides as potent inhibitors of RANKL-induced osteoclastogenesis and bone resorption

Inhibiting osteoclastogenesis is a promising therapeutic target for treating osteoclast-related diseases. Herein, we synthesized a series of modified salicylanilides and their corresponding 3-phenyl-2H-benzo[e][1,3]oxazine-2,4(3H)-dione and 10-phenyldibenzo[b,f][1,4]oxazepin-11(10H)-one derivatives, and investigated the effects of such compounds on RANKL-induced osteoclast formation. Among them, a salicylanilide derivative (A04) and its 3-phenyl-2H-benzo[e][1,3]oxazine-2,4(3H)-dione derivative (B04) markedly suppressed RANKL-induced osteoclast differentiation and showed no significant cytotoxic effects at doses higher than that required to inhibit osteoclast formation. Both compounds reduced osteoclast formation and bone resorptive activity of osteoclasts in a dose-dependent manner. Further, the anti-osteoclastogenic effects of A04 and B04 may operate through reducing the RANKL-induced nuclear translocation of NFATc1. Accordingly, we present the potent anti-osteoclastogenic compounds A04 and B04 as promising candidates for further optimization as anti-resorptive agents.

Oestrogen receptor positive breast cancer metastasis to bone: inhibition by targeting the bone microenvironment in vivo

Clinical trials have shown that adjuvant Zoledronic acid (ZOL) reduces the development of bone metastases irrespective of ER status. However, post-menopausal patients show anti-tumour benefit with ZOL whereas pre-menopausal patients do not. Here we have developed in vivo models of spontaneous ER+ve breast cancer metastasis to bone and investigated the effects of ZOL and oestrogen on tumour cell dissemination and growth. ER+ve (MCF7, T47D) or ER-ve (MDA-MB-231) cells were administered by inter-mammary or inter-cardiac injection into female nude mice ± estradiol. Mice were administered saline or 100 μg/kg ZOL weekly. Tumour growth, dissemination of tumour cells in blood, bone and bone turnover were monitored by luciferase imaging, histology, flow cytometry, two-photon microscopy, micro-CT and TRAP/P1NP ELISA. Estradiol induced metastasis of ER+ve cells to bone in 80-100 % of animals whereas bone metastases from ER-ve cells were unaffected. Administration of ZOL had no effect on tumour growth in the fat pad but significantly inhibited dissemination of ER+ve tumour cells to bone and frequency of bone metastasis. Estradiol and ZOL increased bone volume via different mechanisms: Estradiol increased activity of bone forming osteoblasts whereas administration of ZOL to estradiol supplemented mice decreased osteoclast activity and returned osteoblast activity to levels comparable to that of saline treated mice. ER-ve cells require increased osteoclast activity to grow in bone whereas ER+ve cells do not. Zol does not affect ER+ve tumour growth in soft tissue, however, inhibition of bone turnover by ZOL reduced dissemination and growth of ER+ve breast cancer cells in bone.

Bone selective protective effect of a novel bone-seeking estrogen on trabecular bone in ovariectomized rats

The drawbacks of estrogen restrict the clinical use of hormone replacement therapy, and it would be most helpful to explore new estrogenic substances that could prevent bone loss and be free from any adverse effects. We synthesized a new compound named bone-seeking estrogen (SE2) by combining 17β-estradiol (E2) with iminodiacetic acid through the Mannich reaction. E2 and SE2 were labeled with isotope (3)H, and the tissue distribution tests of E2-(3)H and SE2-(3)H were analyzed by the radioactivity. The specific nuclear binding of E2 and SE2 in osteoblasts was measured. SE2 exhibited significantly greater affinity for bone but lower affinity for ovary and uterus than did E2, and SE2 maintained a high affinity for the estrogen receptor alpha similar to that of E2. SE2 administration did not induce uterine hypertrophy. Body weight increase was significantly suppressed by treatment with E2 but not by SE2 after ovariectomy (OVX). SE2 decreased bone turnover as E2 after OVX detected by serum biochemical markers. Bone histology and micro-CT analysis revealed that SE2 administration, similar to E2, could improve bone mass and trabecular architecture after OVX. Biomechanical analyses showed that SE2 treatment effectively increased mechanical properties after OVX. The results suggested that SE2 was effective in preventing OVX-induced bone loss and exhibited few side effects on body weight and uterine hypertrophy, which was beneficial in reducing the adverse effects caused by E2. SE2 may be a better choice than E2 for the prevention of postmenopausal osteoporosis.

Methanol extract of dried exudate of Commiphora mukul prevents bone resorption in ovariectomized rats

CONTEXT

Gum guggul, a resinous exudate of the plant Commiphora mukul Engl. (Burseraceae), has been found efficacious in the treatment of bone fractures, arthritis, and hyperlipidemic disorders.

OBJECTIVE

The present study is an effort to explore the anti-bone-resorptive potential of the dried methanol extract of the gummy exudate of C. mukul (MECM) in ovariectomized rat model.

MATERIALS AND METHODS

The animals were randomly divided into five groups of equal size (n = 6). Animals in all the groups were ovariectomized except group 1, which was sham operated. Groups 3, 4 and 5 were treated with Raloxifene, MECM 250 mg/kg and MECM 500 mg/kg, respectively. The 2nd group was fed with vehicle.

ASSESSMENT

biochemical estimations, viz., alkaline phosphatase (ALP), tartarate resistant acid phosphatase (TRAP), serum calcium (Ca); biomechanical evaluations, and histopathological examinations.

RESULTS

The LD(50) of MECM was found to be > 2500 mg/kg orally. A significant elevation was observed in the ALP, TRAP, Ca and cholesterol levels in the 2nd group with a significant reduction in biomechnical strength. Groups 3, 4 and 5, showed a significant reduction in TRAP and ALP levels (p < 0.001). The Ca levels were normalized in the groups 4 and 5, while cholesterol levels dropped in group 5. The bone strength, however, was normalized in all the groups (p < 0.001) along with the histopathology.

DISCUSSION AND CONCLUSION

Findings suggested a significant gain in bone strength and nearly complete restoration of bone microarchitecture along with lowered levels of TRAP indicating the anti-bone resorptive potential of the extract.

Estradiol influences the mechanical properties of human fetal osteoblasts through cytoskeletal changes

Estrogen is known to have a direct effect on bone forming osteoblasts and bone resorbing osteoclasts. The cellular and molecular effects of estrogen on osteoblasts and osteoblasts-like cells have been extensively studied. However, the effect of estrogen on the mechanical property of osteoblasts has not been studied yet. It is important since mechanical property of the mechanosensory osteoblasts could be pivotal to its functionality in bone remodeling. This is the first study aimed to assess the direct effect of estradiol on the apparent elastic modulus (E∗) and corresponding cytoskeletal changes of human fetal osteoblasts (hFOB 1.19). The cells were cultured in either medium alone or medium supplemented with β-estradiol and then subjected to Atomic Force Microscopy indentation (AFM) to determine E∗. The underlying changes in cytoskeleton were studied by staining the cells with TRITC-Phalloidin. Following estradiol treatment, the cells were also tested for proliferation, alkaline phosphatase activity and mineralization. With estradiol treatment, E∗ of osteoblasts significantly decreased by 43-46%. The confocal images showed that the changes in f-actin network observed in estradiol treated cells can give rise to the changes in the stiffness of the cells. Estradiol also increases the inherent alkaline phosphatase activity of the cells. Estradiol induced stiffness changes of osteoblasts were not associated with changes in the synthesized mineralized matrix of the cells. Thus, a decrease in osteoblast stiffness with estrogen treatment was demonstrated in this study, with positive links to cytoskeletal changes. The estradiol associated changes in osteoblast mechanical properties could bear implications for bone remodeling and its mechanical integrity.

Association between ER-α polymorphisms and bone mineral density in patients with Turner syndrome subjected to estroprogestagen treatment--a pilot study

Reduced bone mineral density (BMD) is present in many women with Turner syndrome (TS), and hypo-estrogenism is known to play a vital role in bone mineralization disturbances. It has been suggested that genetic factors play an important role in the regulation of BMD. The aim of this study was to analyze the association between Pvu II and XbaI ER-α polymorphisms and BMD in TS patients subjected to estroprogestagen (EP) treatment. Thirty-two TS patients aged 17-38 (mean age 22.7 ± 8.2) along with 82 healthy controls were the subjects for this study. Baseline values of hormonal parameters, BMD and bone density markers were measured in the subjects. Subsequently, TS patients underwent 4 years of EP therapy. The results of laboratory parameters and BMD were analyzed in regard to PvuII and XbaI polymorphic variants of the ER-α gene. The increase in BMD of TS subjects was the highest in the 1st (7.5%, p = 0.013) and 2nd (6.6%, p = 0.008) years of treatment. Four years of EP therapy was reflected by a significant increase in BMD z-scores in patients with xx and Xx genotypes of the XbaI gene and in those with with the pp and Pp genotypes of PvuII. In patients with haplotypes other than XXPP, BMD z-scores were significantly higher compared to their baseline after 2 (p = 0.002), 3 (p < 0.001) and 4 (p < 0.001) years of treatment. In conclusion, genotypes xx and pp were shown to be prognostic markers of a good response to EP treatment, whereas the XXPP haplotype carriers were revealed to have the risk factors for insufficient responsiveness against EP treatment in BMD control.

Postpubertal architectural developmental patterns differ between the L3 vertebra and proximal tibia in three inbred strains of mice

An understanding of normal microarchitectural bone development patterns of common murine models is needed. Longitudinal, structural, and mineralization trends were evaluated by in vivo microCT over 12 time points from 6-48 wk of age at the vertebra and tibia of C3H/HeN, C57BL/6, and BALB/C mice. Longitudinal growth occurred rapidly until 8-10 wk, slowed as the growth plate bridged, and fused at 8-10 mo. Structural augmentation occurred through formation of trabeculae at the growth plate and thickening of existing ones. In the vertebrae, BV/TV increased rapidly until 12 wk in all strains. Between 12 and 32 wk, the architecture was stable with BV/TV deviating <1.1%, 1.6%, and 3.4% for the C57BL/6, BALB/C, and C3H/HeN mice. In contrast, the tibial architecture changed continuously but more moderately for BV/TV and TbTh compared with the vertebra and with comparable or larger changes for TbN and TbSp. Age-related trabecular deterioration (decreased BV/TV and TbN; increased TbSp and structure model index) was evident at both sites at 32 wk. In all strains, the cortex continued to develop after trabecular values peaked. The temporal plateau of BMD was variable across mouse strains and site, whereas tissue mineral density was attained at approximately 6 mo for all sites and strains. Geometric changes at the tibial diaphysis occurred rapidly until 8-10 wk, providing the C57BL/6 mice and C3H/HeN mice with the highest torsional and compressive rigidity, respectively. In summary, key skeletal development milestones were identified, and architectural topology at the vertebra was found to be more stable than at the tibia.