Ovariectomy-induced Bone Loss Research Articles

ERK-estrogen receptor α signaling plays a role in the process of bone marrow mesenchymal stem cell-derived exosomes protecting against ovariectomy-induced bone loss

BackgroundExosomes derived from bone marrow mesenchymal stem cells (BMSC-Exos) are considered as candidates for osteoporosis (OP) therapy. Estrogen is critical in the maintenance of bone homeostasis. However, the role of estrogen and/or its receptor in BMSC-Exos treatment of OP, as well as its methods of regulation during this process remain unclear.MethodsBMSCs were cultured and characterized. Ultracentrifugation was performed to collect BMSC-Exos. Transmission electron microscopy, nanoparticle tracking analysis, and western blotting were used to identify BMSC-Exos. We examined the effects of BMSC-Exos on the proliferation, osteogenic differentiation, mineralization, and cell cycle distribution of MG-63 cells. The protein expression of estrogen receptor α (ERα) and the phosphorylation of ERK were investigated through western blotting. We determined the effects of BMSC-Exos on the prevention of bone loss in female rats. The female Sprague–Dawley rats were divided into three groups: the sham group, ovariectomized (OVX) group, and the OVX + BMSC-Exos group. Bilateral ovariectomy was performed in the OVX and OVX + BMSC-Exos groups, while a similar volume of adipose tissue around the ovary was removed in the sham group. The rats in OVX group and OVX + BMSC-Exos group were given PBS or BMSC-Exos after 2 weeks of surgery. Micro-CT scanning and histological staining were used to evaluate the in vivo effects of BMSC-Exos.ResultsBMSC-Exos significantly enhanced the proliferation, alkaline phosphatase activity, and the Alizarin red S staining in MG-63 cells. The results of cell cycle distribution demonstrated that BMSC-Exos increased the proportion of cells in the G2 + S phase and decreased the proportion of cells in the G1 phase. Moreover, PD98059, an inhibitor of ERK, inhibited both the activation of ERK and the expression of ERα, which were promoted by administration of BMSC-Exos. Micro-CT scan showed that in the OVX + BMSC-Exos group, bone mineral density, bone volume/tissue volume fraction, trabecular number were significantly upregulated. Additionally, the microstructure of the trabecular bone was preserved in the OVX + BMSC-Exos group compared to that in the OVX group.ConclusionBMSC-Exos showed an osteogenic-promoting effect both in vitro and in vivo, in which ERK-ERα signaling might play an important role.

Dysfunction in parkin aggravates inflammatory bone erosion by reinforcing osteoclast activity

BackgroundParkin dysfunction associated with the progression of parkinsonism contributes to a progressive systemic skeletal disease characterized by low bone mineral density. However, the role of parkin in bone remodeling has not yet been elucidated in detail.ResultWe observed that decreased parkin in monocytes is linked to osteoclastic bone-resorbing activity. siRNA-mediated knockdown of parkin significantly enhanced the bone-resorbing activity of osteoclasts (OCs) on dentin without any changes in osteoblast differentiation. Moreover, Parkin-deficient mice exhibited an osteoporotic phenotype with a lower bone volume accompanied by increased OC-mediated bone-resorbing capacity displaying increased acetylation of α-tubulin compared to wild-type (WT) mice. Notably, compared to WT mice, the Parkin-deficient mice displayed increased susceptibility to inflammatory arthritis, reflected by a higher arthritis score and a marked bone loss after arthritis induction using K/BxN serum transfer, but not ovariectomy-induced bone loss. Intriguingly, parkin colocalized with microtubules and parkin-depleted-osteoclast precursor cells (Parkin−/− OCPs) displayed augmented ERK-dependent acetylation of α-tubulin due to failure of interaction with histone deacetylase 6 (HDAC6), which was promoted by IL-1β signaling. The ectopic expression of parkin in Parkin−/− OCPs limited the increase in dentin resorption induced by IL-1β, accompanied by the reduced acetylation of α-tubulin and diminished cathepsin K activity.ConclusionThese results indicate that a deficiency in the function of parkin caused by a decrease in parkin expression in OCPs under the inflammatory condition may enhance inflammatory bone erosion by altering microtubule dynamics to maintain OC activity.

A Mixture of Cervus elaphus sibiricus and Glycine max (L.) Merrill Inhibits Ovariectomy-Induced Bone Loss Via Regulation of Osteogenic Molecules in a Mouse Model.

Osteoporosis is a metabolic skeletal disease characterized by lowered bone mineral density and quality, which lead to an increased risk of fracture. The aim of this study was to evaluate the anti-osteoporosis effects of a mixture (called BPX) of Cervus elaphus sibiricus and Glycine max (L.) Merrill and its underlying mechanisms using an ovariectomized (OVX) mouse model. BALB/c female mice (7 weeks old) were ovariectomized. From 12 weeks of ovariectomy, mice were administered BPX (600 mg/kg) mixed in a chow diet for 20 weeks. Changes in bone mineral density (BMD) and bone volume (BV), histological findings, osteogenic markers in serum, and bone formation-related molecules were analyzed. Ovariectomy notably decreased the BMD and BV scores, while these were significantly attenuated by BPX treatment in the whole body, femur, and tibia. These anti-osteoporosis effects of BPX were supported by the histological findings for bone microstructure from H&E staining, increased activity of alkaline phosphatase (ALP), but a lowered activity of tartrate-resistant acid phosphatase (TRAP) in the femur, along with other parameters in the serum, including TRAP, calcium (Ca), osteocalcin (OC), and ALP. These pharmacological actions of BPX were explained by the regulation of key molecules in the bone morphogenetic protein (BMP) and mitogen-activated protein kinase (MAPK) pathways. The present results provide experimental evidence for the clinical relevance and pharmaceutical potential of BPX as a candidate for anti-osteoporosis treatment, especially under postmenopausal conditions.

Quercetin potentiates the anti-osteoporotic effects of alendronate through modulation of autophagy and apoptosis mechanisms in ovariectomy-induced bone loss rat model.

Osteoporosis is a bone disease leading to bone fracture and affects 200million women worldwide. Autophagy and apoptosis are two fundamental mechanisms that are involved in the development of osteoporosis. In this study we aim to investigate the combined effects of quercetin and alendronate on the markers of osteoporosis, autophagy, and apoptosis in the bone of ovariectomized rats. Fifty adult female Sprague-Dawley rats were ovariectomized and treated with alendronate alone (5µg/kg/day) or alendronate (5µg/kg/day) in combination with quercetin (15mg/kg/day) for 12 weeks. Then, ELISA, stereological tests, Real-time PCR analysis, and immunofluorescence assay were used to measure the markers of osteoporosis, autophagy, and apoptosis in the serum and tibia of rats. The serum osteocalcin was significantly decreased in ovariectomized rats that received quercetin and alendronate compared with alendronate only. Stereological data showed that except for osteoclasts, the total trabecular volume, bone weight, bone volume, osteocyte, and osteoblast numbers were increased in an ovariectomized group that was treated with quercetin and alendronate compared with alendronate alone. Except for Bcl2, the autophagy markers (Beclin-1 and LC3B) and Caspase-3 were significantly downregulated in ovariectomized rats that received quercetin and alendronate compared with those treated with alendronate alone. Our results show that quercetin enhances the anti-osteoporotic effects of alendronate, possibly through the regulation of autophagy and apoptosis mechanisms. These findings suggest that the combination of quercetin and alendronate could be a useful therapeutic strategy in the treatment of osteoporosis in postmenopausal women.

Effect of Menaquinone-4 on Receptor Activator of Nuclear Factor κB Ligand-Induced Osteoclast Differentiation and Ovariectomy-Induced Bone Loss

Osteoporosis is a progressive metabolic disease characterized by decreased bone mineral density and increased fracture risk. Previous studies have shown that higher intake of vitamin K (VK) correlates with a reduced risk of osteoporosis. However, the effect of menaquinone-4 (MK-4), a specific form of VK, still remains obscure. Therefore, in this study, we investigated the effects of MK-4 on osteoclast differentiation by differentiating RAW 264.7 cells into osteoclasts with the help of receptor activator of nuclear factor-kappa B ligand (RANKL), assessed the mRNA expression of osteoclast-specific genes, and studied the effects of MK-4 in vivo in ovariectomized mice, a postmenopausal osteoporosis murine model. MK-4 inhibited osteoclast differentiation, decreased the mRNA expression of nuclear factor of activated T cells c1 (NFATc1), osteoclast-associated receptor (OSCAR), and cathepsin K (CTSK), and inhibited bone loss in ovariectomized mice. The findings strongly suggest that MK-4 is a therapeutic alternative for postmenopausal osteoporosis.

MRL/MpJ Mice Resist to Age-Related and Long-Term Ovariectomy-Induced Bone Loss: Implications for Bone Regeneration and Repair.

Osteoporosis and age-related bone loss increase bone fracture risk and impair bone healing. The need for identifying new factors to prevent or treat bone loss is critical. Previously, we reported that young MRL/MpJ mice have superior bone microarchitecture and biomechanical properties as compared to wild-type (WT) mice. In this study, MRL/MpJ mice were tested for resistance to age-related and long-term ovariectomy-induced bone loss to uncover potential beneficial factors for bone regeneration and repair. Bone tissues collected from 14-month-old MRL/MpJ and C57BL/6J (WT) mice were analyzed using micro-CT, histology, and immunohistochemistry, and serum protein markers were characterized using ELISAs or multiplex assays. Furthermore, 4-month-old MRL/MpJ and WT mice were subjected to ovariectomy (OV) or sham surgery and bone loss was monitored continuously using micro-CT at 1, 2, 4, and 6 months (M) after surgery with histology and immunohistochemistry performed at 6 M post-surgery. Sera were collected for biomarker detection using ELISA and multiplex assays at 6 M after surgery. Our results indicated that MRL/MpJ mice maintained better bone microarchitecture and higher bone mass than WT mice during aging and long-term ovariectomy. This resistance of bone loss observed in MRL/MpJ mice correlated with the maintenance of higher OSX+ osteoprogenitor cell pools, higher activation of the pSMAD5 signaling pathway, more PCNA+ cells, and a lower number of osteoclasts. Systemically, lower serum RANKL and DKK1 with higher serum IGF1 and OPG in MRL/MpJ mice relative to WT mice may also contribute to the maintenance of higher bone microarchitecture during aging and less severe bone loss after long-term ovariectomy. These findings may be used to develop therapeutic approaches to maintain bone mass and improve bone regeneration and repair due to injury, disease, and aging.

Obacunone targets macrophage migration inhibitory factor (MIF) to impede osteoclastogenesis and alleviate ovariectomy-induced bone loss

IntroductionOsteoporosis is the most common bone disorder where the hyperactive osteoclasts represent the leading role during the pathogenesis. Targeting hyperactive osteoclasts is currently the primary therapeutic strategy. However, concerns about the long-term efficacy and side effects of current frontline treatments persist. Alternative therapeutic agents are still needed. ObjectivesObacunone (OB) is a small molecule with a broad spectrum of biological activities, particularly antioxidant and anti-inflammatory effects. This study aims to examine OB’s therapeutic potential on osteoporosis and explore the rudimentary mechanisms. MethodsOsteoclast formation and osteoclastic resorption assays were carried out to examine OB’s inhibitory effects in vitro, followed by the in-vivo studies of OB’s therapeutic effects on ovariectomy-induced osteoporotic preclinical model. To further study the underlying mechanisms, mRNA sequencing and analysis were used to investigate the changes of downstream pathways. The molecular targets of OB were predicted, and in-silico docking analysis was performed. Ligand-target binding was verified by surface plasmon resonance (SPR) assay and Western Blotting assay. ResultsThe results indicated that OB suppressed the formation of osteoclast and its resorptive function in vitro. Mechanistically, OB interacts with macrophage migration inhibitory factor (MIF) which attenuates receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL)-induced signaling pathways, including reactive oxygen species (ROS), NF-κB pathway, and mitogen-activated protein kinases (MAPKs). These effects eventually caused the diminished expression level of the master transcriptional factor of osteoclastogenesis, nuclear factor of activated T cells 1 (NFATc1), and its downstream osteoclast-specific proteins. Furthermore, our data revealed that OB alleviated estrogen deficiency-induced osteoporosis by targeting MIF and thus inhibiting hyperactive osteoclasts in vivo. ConclusionThese results together implicated that OB may represent as a therapeutic candidate for bone disorders caused by osteoclasts, such as osteoporosis.

Gallic acid inhibits osteoclastogenesis and prevents ovariectomy-induced bone loss.

Osteoporosis is a common metabolic bone disease with a rapidly increasing prevalence, characterized by massive bone loss because of excessive osteoclast formation. Gallic acid (GA), a phenolic acid isolated from Cornus officinalis, has anti-inflammatory and anti-oxidant effects, but its effect on osteoclast formation has not been confirmed. In our study, we demonstrated that GA significantly inhibited RANKL-induced osteoclast formation and function of osteoclast in bone marrow monocytes (BMMs) and RAW264.7 cells in a dose-dependent manner without cytotoxicity. For molecular mechanisms, GA repressed osteoclastogenesis by blocking Akt, ERK, and JNK pathways, and suppressed osteoclastogenesis-related marker expression, including nuclear factor of the activated T-cell cytoplasmic 1 (NFATc1), c-Fos, and cathepsin K (CTSK). In addition, we further assessed the effect of GA in an ovariectomized mouse model, which indicated that GA has a notable effect on preventing bone loss. In conclusion, GA exerts notable effects in inhibiting osteoclastogenesis and preventing ovariectomy-induced bone loss, suggesting that GA is a potential agent in osteoporosis treatment.

Prolonged treadmill training is not able to prevent ovariectomy-induced bone loss.

Introduction: Exercise is widely recognized as prophylaxis for osteoporosis. However, exactly which type of exercise is best to prevent loss of bone mass remains undefined. To find an appropriate form of treadmill exercise that would ameliorate postmenopausal loss of cortical and trabecular structures, we compared various training regimen in ovariectomized (OVX) C57BL/6J mice. Methods: Common to all regimen were training durations of 14 weeks including five 30 min-sessions per week. Two groups-one sham operated, one OVX-served as controls that did not perform any training. Three OVX groups ran at constant speed, either without any incline or at 20° in- and 20° decline, respectively. An additional OVX group ran an interval training, an alternation between intensive tempo sections and so-called slower regeneration phases. Femoral and humeral bone structures were assessed via micro-computed tomography (μCT), biomechanical stability of the femora via 3-point bending test, muscle volumes of the posterior extremities via magnetic resonance imaging (MRI), and bone metabolic parameters via ELISA on peripheral blood. Result: OVX resulted in loss of bone mass and stability and a transient rise in the N-terminal collagen type I pro-peptide (PINP). Training resulted in increased muscle volumes of the heart and the lower extremities as well as increased running velocities. However, none of the exercise programs was able to prevent ovariectomyinduced loss of bone mass. Discussion: These data therefore suggest that axial loading and tensile strain do not suffice as prophylaxis for postmenopausal osteoporosis yet may need to be complemented by low dose pharmaceutics or dietary supplements.

Inhibition of FAAH suppresses RANKL-induced osteoclastogenesis and attenuates ovariectomy-induced bone loss partially through repressing the IL17 pathway.

Fatty amide hydrolase (FAAH) is a key degradation enzyme of the endocannabinoid system, mainly responsible for the hydrolysis of arachidonic acid ethanolamine (AEA). Previous investigations have shown that FAAH is involved in a series of biological processes, such as inflammation, immune regulation, and transmembrane signal transduction of neurons. Endogenous cannabinoids and cannabinoid receptors have been reported to participate in the regulation of bone homeostasis by regulating the differentiation of osteoblasts and osteoclasts. We hypothesized that FAAH may play an important role in osteoclastogenesis based on the above evidence. The present study found that the FAAH expression was increased at both mRNA and protein levels during RANKL-induced osteoclastogenesis. Pharmacological and genetic inhibition of FAAH in bone marrow-derived macrophages (BMMs) inhibited osteoclastogenesis, F-actin ring formation, bone resorption, and osteoclast-specific gene expression in vitro. Moreover, intragastric administration of the FAAH inhibitor PF-04457845(PF) ameliorated ovariectomy (OVX)-induced bone loss in mice. Further investigation revealed that nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways were inhibited by PF treatment and FAAH knockdown. RNAseq indicated that the IL17 pathway was blocked by PF, and administration of recombinant murine IL17 protein could partially restore osteoclastogenesis and activate NF-κB and MAPK pathways. To sum up, our findings demonstrate that targeting FAAH could be a promising candidate strategy for treating osteoclast-related diseases, especially osteoporosis.

PiT2 deficiency prevents increase of bone marrow adipose tissue during skeletal maturation but not in OVX-induced osteoporosis.

The common cellular origin between bone marrow adipocytes (BMAds) and osteoblasts contributes to the intimate link between bone marrow adipose tissue (BMAT) and skeletal health. An imbalance between the differentiation ability of BMSCs towards one of the two lineages occurs in conditions like aging or osteoporosis, where bone mass is decreased. Recently, we showed that the sodium-phosphate co-transporter PiT2/SLC20A2 is an important determinant for bone mineralization, strength and quality. Since bone mass is reduced in homozygous mutant mice, we investigated in this study whether the BMAT was also affected in PiT2-/- mice by assessing the effect of the absence of PiT2 on BMAT volume between 3 and 16 weeks, as well as in an ovariectomy-induced bone loss model. Here we show that the absence of PiT2 in juveniles leads to an increase in the BMAT that does not originate from an increased adipogenic differentiation of bone marrow stromal cells. We show that although PiT2-/- mice have higher BMAT volume than control PiT2+/+ mice at 3 weeks of age, BMAT volume do not increase from 3 to 16 weeks of age, leading to a lower BMAT volume in 16-week-old PiT2-/- compared to PiT2+/+ mice. In contrast, the absence of PiT2 does not prevent the increase in BMAT volume in a model of ovariectomy-induced bone loss. Our data identify SLC20a2/PiT2 as a novel gene essential for the maintenance of the BMAd pool in adult mice, involving mechanisms of action that remain to be elucidated, but which appear to be independent of the balance between osteoblastic and adipogenic differentiation of BMSCs.

Berbamine inhibits RANKL- and M-CSF-mediated osteoclastogenesis and alleviates ovariectomy-induced bone loss.

Osteoporosis is a common public health problem characterized by decreased bone mass, increased bone brittleness and damage to the bone microstructure. Excessive bone resorption by osteoclasts is the main target of the currently used drugs or treatment for osteoporosis. Effective antiresorptive drugs without side effects following long-term administration have become a major focus of anti-osteoporotic drugs. In the present study, we investigated the effect of berbamine, a small molecule natural product from Berberis amurensis Rupr, a traditional Chinese medicine, on RANKL-induced osteoclast differentiation in vitro and ovariectomy-induced bone loss in vivo. The results demonstrated that berbamine at a safe and effective dose inhibited osteoclastogenesis and bone resorption function in vitro by suppressing the nuclear factor-κB signaling pathway. In addition, berbamine protected against osteoporosis by inhibiting osteoclastogenesis and bone resorption function without affecting osteogenesis in the ovariectomy mouse model. These findings revealed that berbamine has a protective role against osteoporosis and may represent a novel promising treatment strategy for osteoporosis.

Parkin Inhibits RANKL-Induced Osteoclastogenesis and Ovariectomy-Induced Bone Loss

Osteoporosis and osteoporotic fractures comprise a substantial health and socioeconomic burden. The leading cause of osteoporosis is an imbalance in bone formation and bone resorption caused by hyperactive osteoclasts. Therefore, a new strategy to suppress osteoclastogenesis is needed. Parkin is likely closely associated with bone metabolism, although its role in osteoclastogenesis is unclear. In this study, the Parkin protein inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation, osteoclast-specific gene expression, F-actin ring formation, and bone resorption pit formation in vitro. Moreover, depletion of Parkin enhanced RANKL-induced osteoclast formation, osteoclast-specific gene expression, F-actin ring formation, and bone resorption pit formation. Reactive oxygen species (ROS) activity was suppressed, while autophagy was upregulated with the presence of the Parkin protein. ROS activity was upregulated and autophagy was decreased due to Parkin knockdown. In addition, intravenous administration of Parkin rescued ovariectomy-induced bone loss and reduced osteoclastogenesis in vivo. Collectively, Parkin has therapeutic potential for diseases associated with overactive osteoclasts.

Er-Xian decoction attenuates ovariectomy-induced osteoporosis by modulating fatty acid metabolism and IGF1/PI3K/AKT signaling pathway

Ethnopharmacological relevanceEr-Xian decoction (EXD) is a traditional Chinese medicine (TCM) formula used to treat osteoporosis (OP). However, the anti-OP mechanism of EXD has not yet been fully elucidated. Aim of the studyThe study aimed to verify the anti-OP effect of EXD and to explore its underlying mechanism. MethodsThe anti-OP targets and mechanisms of EXD were predicted by network pharmacological analysis. Then, an ovariectomized (OVX) rat model was established to validate the key anti-OP mechanism of EXD. Firstly, the therapeutic effect of EXD on OP was confirmed using micro-CT bone analysis, pathological observation, and ELISA detection. Secondly, serum metabolites related to key biological processes were detected using an automatic biochemical analyzer and GC-MS. Finally, ELISA, qRT-PCR, and western blot were utilized to further explore the potential key anti-OP pathway of EXD. ResultsA total of 159 anti-OP targets of EXD were identified. Functional annotation revealed that OP treatment using EXD was associated with lipid metabolism, fatty acid (FA) metabolism, and PI3K/AKT signaling pathway. Experimental studies confirmed that EXD ameliorated ovariectomy-induced bone loss and bone microstructure deterioration. EXD treatment also upregulated the level of serum estrogen and downregulated the level of OC, PⅠNP, CTX-1, TC, and LDL-C. Besides, principal component analysis (PCA) and heat map of serum FAs distinguished OVX rats from the SHAM and EXD groups. Serum concentrations of important n-3 FAs, including C20:3N3, C20:5N3, and C22:5N3, were significantly increased in the EXD group. The increased stearoyl-CoA desaturase 1 (SCD1) index 1 and index 2 in the OVX group were reversed by EXD administration. Additionally, EXD reversed the decreased serum IGF1 level and tibia IGF1R, PI3K, and AKT expression in OVX rats. ConclusionEXD ameliorated ovariectomy-induced bone loss by modulating lipid metabolism, FA metabolism, and IGF1/PI3K/AKT pathway.

A Vitronectin-Derived Peptide Restores Ovariectomy-Induced Bone Loss by Dual Regulation of Bone Remodeling.

Bone remodeling is tightly regulated through bone resorption and bone formation; imbalances in bone remodeling can cause various pathological conditions such as osteoporosis. Antiresorptive agents commonly used for treating osteoporosis do not substantially reverse osteoporotic bone loss. We evaluated the effects of the RVYFFKGKQYWE motif (residues 270-281; VnP-16) of human vitronectin on the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and osteoclastogenesis of bone marrow-derived macrophages. The effects of VnP-16 were also assessed in a mouse model of estrogen deficiency-induced osteoporosis (ovariectomized female C57BL/6mice). To assay whether VnP-16 can reverse ovariectomy-induced bone loss, synthetic peptides or vehicle were subcutaneously injected into ovariectomized mice once a week for 4weeks (n = 10/group). To evaluate the bone restorative effects of VnP-16, in-vivo micro-computed tomography analysis and histological staining were performed. VnP-16 induced osteogenic differentiation of hMSCs and inhibited the RANKL-RANK-TRAF6 axis in the osteoclastogenesis signaling pathway. Furthermore, systemic administration of VnP-16 reversed ovariectomy-induced bone loss in the femoral neck, distal femur and lumbar spine by increasing osteoblast differentiation and promoting bone formation, and concomitantly decreasing osteoclastogenesis and inhibiting bone resorption. The bone restorative effect of VnP-16 was observed one week after subcutaneous administration, and although the timing of the effect differed according to bone location, it persisted for at least 3weeks. Our findings suggest that VnP-16 is a potential therapeutic agent for treating osteoporosis that mediates its effects through dual regulation of bone remodeling.

Jin-Tian-Ge ameliorates ovariectomy-induced bone loss in rats and modulates osteoblastogenesis and osteoclastogenesis in vitro

BackgroundTiger bone, which had been one of the most famous traditional Chinese medicine for 2000 years, was originate from the skeleton of Panthera tigris L., and had the actions of anti-inflammatory, analgesic, immune-regulatory and promoting healing of bone fracture, and was used for the treatment of osteoporosis and rheumatoid arthritis. Jin-Tian-Ge (JTG), the artificial tiger bone powder, were prepared from skeletons of several farmed animals to substitute the natural tiger bone, and has been used for the treatment of osteoporosis in clinical practice. However, the characteristic and mechanism of action of JTG for the therapy of osteoporosis need to be further evidenced by using modern pharmacological methods. The aim of this work is to investigate the bone-protective effects of JTG, and explore the possible underlying mechanism.MethodsOvariectomy (OVX) rats were orally administrated JTG or estradiol valerate (EV) for 12 weeks. We investigated the pharmacodynamic effects of JTG on anti-bone loss in OVX rats, and also investigated the role of JTG in promoting osteogenesis and inhibiting osteoclast differentiation.ResultsJTG increased the bone mineral density (BMD), improved the bone microarchitecture and biomechanical properties in ovariectomized rast, whereas reversed the bone high turnover in OVX rats as evidenced by serum biochemical markers in OVX rats. JTG increased osteogenic differentiation of BMSCs in vitro, and up-regulated the expression of the key proteins of BMP and Wnt/β-catenin pathways. JTG also inhibited the osteoclastogenesis of BMM as evidenced by the alteration of the TRAP activity, F-actin construction and the expression of nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), c-Fos, Cathepsin K (Ctsk) and matrix metallopeptidase 9 (MMP9) of OCs induced with RANKL and LPS, reduced the expression and phosphorylation of NF-κB in OCs.ConclusionsJTG prevented bone loss in OVX rats and increased osteogenic differentiation of BMSCs through regulation of the BMP and Wnt/β-catenin pathway, inhibited osteoclastogenesis by suppressing the NF-κB pathway, suggesting that JTG had the potentials for prevention and treatment of osteoporosis by modulating formation and differentiation of osteoblast and osteoclast.

Water Extract of Piper longum Linn Ameliorates Ovariectomy-Induced Bone Loss by Inhibiting Osteoclast Differentiation.

Piper longum linn has traditionally been used for the treatment of respiratory and gastrointestinal disorders in India. Although various pharmacological effects of P. longum have been studied, its effects on bone have not been clearly elucidated. Therefore, this study examined the inhibitory effect of the water extract of P. longum Linn (WEPL) on osteoclast differentiation. WEPL directly affected the osteoclast precursors and suppressed osteoclast differentiation in vitro. In addition, the expression levels of c-Fos and nuclear factor of activated T cells 1, a critical transcription factor for osteoclastogenesis, were significantly downregulated by WEPL via the suppression of the receptor activator of nuclear factor (NF)-κB ligand-induced mitogen-activated protein kinase and NF-κB signaling pathways. Consistent with the in vitro results, oral administration of WEPL (100 and 300 mpk) to ovariectomized mice for six weeks relieved the OVX-induced bone loss. We also identified phytochemicals in WEPL that are reported to exert inhibitory effects on osteoclastogenesis and/or bone loss. Collectively, the findings of our study indicate that WEPL has an anti-osteoporotic effect on OVX-induced bone loss by diminishing osteoclast differentiation, suggesting that it may be useful to treat several bone diseases caused by excessive bone resorption.

Koumine Prevents Ovariectomy-induced Bone Loss by Inhib-iting Osteoclastogenesis in mice

Koumine Prevents Ovariectomy-induced Bone Loss by Inhib-iting Osteoclastogenesis in mice

Isoliensinine Suppresses Osteoclast Formation Through NF-κB Signaling Pathways and Relieves Ovariectomy-Induced Bone Loss.

Osteoporosis is among the major contributors of pathologic fracture in postmenopausal women, which is caused by the bone metabolic disorder owing to the over-activation of osteoclasts. Inhibition of osteoclast differentiation and maturation has become a mainstream research interest in the prevention of osteoporosis. Isoliensinine (Iso) is a dibenzyl isoquinoline alkaloid with antioxidant, anti-inflammatory, and anti-cancer activities. However, whether it can be used as a potential treatment for osteoporosis remains undiscovered. Here, we investigated whether Iso might suppress the differentiation of osteoclasts in vitro and in vivo to play an anti-osteoporosis role. Our results showed that Iso inhibits the formation of mature multinuclear osteoclasts induced by RANKL, the bone resorption, and the osteoclast-specific genes expression by blocking the nuclear translocation of NF-κB p65, and the effect was in a dosage-dependent way. Furthermore, we investigated the therapeutic effect of Iso on osteoporosis in ovariectomized (OVX) mice. We found that Iso attenuated bone loss in the OVX mice and significantly promoted BS, Conn. DN, Tb.Th, TB.N, and BV/TV Index. All in all, Iso showed a prominent effect of osteoclast inhibition, with great promise for treating osteoporosis.

The role of CDK8 in mesenchymal stem cells in controlling osteoclastogenesis and bone homeostasis.

SummaryBone marrow mesenchymal stem cells (MSCs) are critical regulators of postnatal bone homeostasis. Osteoporosis is characterized by bone volume and strength deterioration, partly due to MSC dysfunction. Cyclin-dependent kinase 8 (CDK8) belongs to the transcription-related CDK family. Here, CDK8 in MSCs was identified as important for bone homeostasis. CDK8 level was increased in aged MSCs along with the association with aging-related signals. Mouse genetic studies revealed that CDK8 in MSCs plays a crucial role in bone resorption and homeostasis. Mechanistically, CDK8 in MSCs extrinsically controls osteoclastogenesis through the signal transducer and transcription 1 (STAT1)-receptor activator of the nuclear factor κ Β ligand (RANKL) axis. Moreover, aged MSCs have high osteoclastogenesis-supporting activity, partly through a CDK8-dependent manner. Finally, pharmacological inhibition of CDK8 effectively repressed MSC-dependent osteoclastogenesis and prevented ovariectomy-induced osteoclastic activation and bone loss. These findings highlight that the CDK8-STAT1-RANKL axis in MSCs could play a crucial role in bone resorption and homeostasis.