Phillygenin prevents osteoclast differentiation and bone loss by targeting RhoA.

Forsythia suspensa tea is a popular traditional Chinese medicine decoction for its healthy and therapeutic benefits. However, its effects in bone metabolism were not clear. In recent study, we uncovered anti-osteoclastogenesis property of Phillygenin (Phi), a compound abundant in Forsythia suspensa leaves, and aimed to investigate the effect and mechanism of Phi on bone metabolism in vivo and in vitro. Lipopolysaccharides-induced murine calvaria osteolysis and ovariectomy-induced bone loss animal models were used to identify the bone-protective effect of Phi in vivo and micro-CT, pQCT, and TRAP staining were applied. We used CCK8, TUNEL, BrdU, and TRAP staining to evaluate the efficacy of Phi on the proliferation and formation of OCs in primary mBMMs. RNA sequence, activity-based protein profiling, molecular docking, G-LISA, and WB were used to inspect the target and underlying mechanism of Phi's actions in mBMMs. We found Phi significantly inhibited bone resorption in vivo and inhibited mBMMs osteoclastogenesis in vitro. Ras homolog gene family member A (RhoA) was identified as the direct target of Phi. It counteracted the effects of RhoA activator and acted as a RhoA inhibitor. By targeting RhoA, Phi modulated Rho-associated coiled-coil containing protein kinase 1 (ROCK1) activity and regulated its downstream NF-κB/NFATc1/c-fos pathway. Furthermore, Phi depressed the disassembling of F-actin ring through cofilin and myosin1a. Our findings provided Phi as a potential option for treating bone loss diseases by targeting RhoA and highlighted the importance of F. suspensa as a preventive approach in bone disorders.

Protective effect of zinc supplementation on tricalcium phosphate particles-induced inflammatory osteolysis in mice.

Zinc (Zn), an essential trace element, can stimulate bone formation and inhibit osteoclastic bone resorption, which controls the growth and maintenance of bone. However, the effect of Zn supplementation on tricalcium phosphate (TCP) wear particles-induced osteolysis remains unknown. Here, we doped Zn into TCP particles (ZnTCP), and explore the protective effects of Zn on TCP particles-induced osteolysis in vivo. TCP particles and ZnTCP particles were embedded under the periosteum around the middle suture of the mouse calvaria. After 2 weeks, blood, the periosteal tissue, and the calvaria were collected to determine serum levels of Zn and osteocalcin, pro-inflammatory cytokines, bone biochemical markers, osteoclastogenesis and bone resorption area, and to explain its mechanism. Data revealed that Zn significantly prevented TCP particles-induced osteoclastogenesis and bone loss, and increased bone turnover. The Zn supplement remarkably suppressed the release of pro-inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, and IL-6. Immunoblotting demonstrated that Zn alleviated expression levels of ER stress-related proteins such as glucose-regulated protein 78 (GRP78), PKR-like ER kinase (PERK), phospho-PERK (p-PERK), eukaryotic initiation factor 2α (eIF2α), phospho-eIF2α (p-eIF2α), activating transcription factor 4 (ATF4), inositol-requiring enzyme 1α (IRE1-α) and transcription factor X-box binding protein spliced (XBP1s), leading to decreasing the ratios of p-PERK/PERK and p-eIF2α/eIF2α. Taken together, Zn supplementation strongly prevents TCP particles-induced periprosthetic osteolysis via inhibition of the ER stress pathway, and it may be a novel therapeutic approach for the treatment of aseptic prosthesis loosening.

The Molecular Mechanism of Traditional Chinese Medicine Prescription: Gu-tong Formula in Relieving Osteolytic Bone Destruction.

Bone metastasis is a common complication in patients with advanced tumors, causing pain and bone destruction and affecting their quality of life. Typically, complementary and alternative medicine (CAM), with unique theoretical guidance, has played key roles in the treatment of tumor-related diseases. Gu-tong formula (GTF), as a representative prescription of traditional Chinese medicine, has been demonstrated to be an effective clinical medication for the relief of cancer pain. However, the molecular mechanism of GTF in the treatment of osteolytic metastasis is still unclear. Herein, we employ network pharmacology and molecular dynamics methods to uncover the potential treatment mechanism, indicating that GTF can reduce the levels of serum IL6 and TGFB1 and thus limit the scope of bone cortical damage. Among the active compounds, sesamin and deltoin can bind stably with IL6 and TGFB1, respectively, and have the potential to become anti-inflammatory and anticancer drugs. Although the reasons for the therapeutic effect of GTF are complex and comprehensive, this work provides biological plausibility in the treatment of osteolytic metastases, which has a guiding significance for the treatment of cancer pain with CAM.

The potential role of herbal extract Wedelolactone for treating particle-induced osteolysis: an in vivo study.

BACKGROUND: Osteolysis is one of the most prevalent clinical complications affecting people who undergo total joint replacement (TJR). Wedelolactone (WDL) is a coumestan compound derived from the Wedelia chinensis plant and has been demonstrated to exhibit anti-inflammatory properties. This study aimed to investigate the oral administration of WDL as a potential treatment for particle-induced osteolysis using a well-established mice calvarial disease model. METHODS: Thirty-two C57BL/6 J mice were randomized into four groups: Sham, vehicle, osteolysis group with oral WDL treatment for 4 weeks (WDL 4w), and osteolysis group treated for 8 weeks (WDL 8w). Micro-CT was used to quantitatively analyze the bone mineral density (BMD), bone volume/tissue volume (BV/TV) and trabecular bone thickness (Tb.Th). Osteoclast numbers were also measured from histological slides by two investigators who were blind to the treatment used. RESULTS: The results from micro-CT observation showed that BMD in the WDL 8w group improved significantly over the vehicle group (p < 0.05), but there was no significant difference between WDL 4w and 8w for BV/TV and Tb.Th. Osteoclast numbers in the WDL 4w group were also lower than the vehicle group (p < 0.05), but the difference between WDL 8w and 4w groups was not significant. CONCLUSIONS: Particle-induced osteolysis is an inevitable long-term complication after TJR. The results of this animal study indicate that an oral administration of WDL can help reduce the severity of osteolysis without adverse effects.

Corilagin attenuates osteoclastic osteolysis by enhancing HO-1 and inhibiting ROS.

Chinese herbal medicine has well-established therapeutic effects in various diseases. Corilagin (Cor), a gallic acid tannin in Phyllanthus niruri L., has anti-inflammatory and antioxidant effects in many diseases. However, its role in osteoclast-related bone diseases has not been determined. In vitro, bone marrow macrophages (BMMs) were extracted and isolated to differentiate into osteoclasts. The effects of Cor on osteoclast formation, bone resorption, and reactive oxygen species (ROS) production were performed. In addition, quantitative real-time polymerase chain reaction and western blot analysis were used to evaluate the effect of Cor on oxidative stress-related pathways, which are nuclear factors-κB ligand-receptor activator (RANKL) stimulates important downstream pathways. Furthermore, microcomputed tomography and bone histomorphometry were performed to analyze the therapeutic effect of Cor in mouse models of lipopolysaccharide (LPS)-mediated bone defects in vivo. Cor influenced the nuclear factor of activated T cells 1 (NFATc1) signaling pathway and reduced ROS in RANKL-treated osteoclasts, thereby inhibiting osteoclast formation and bone resorption. Moreover, Cor protected against LPS-mediated skull defects in vivo. In sum, our results confirm that Cor can inhibit osteoclastogenesis and intracellular oxidative stress. In addition, the inflammatory bone defect induced by LPS was also attenuated by Cor. Accordingly, Cor is a new candidate therapeutic agent for osteoclast-mediated osteolytic diseases.

Protocatechualdehyde inhibits receptor activator of nuclear factor kappa-B ligand-induced osteoclastogenesis and attenuates lipopolysaccharide-induced inflammatory osteolysis.

Inflammatory osteolysis as a consequence of chronic bacterial infection underlies several lytic bone conditions, such as otitis media, osteomyelitis, septic arthritis, periodontitis, periprosthetic infection, and aseptic loosening of orthopedic implants. In consideration of the lack of effective preventive or treatments options against infectious osteolysis, the exploitation of novel pharmacological compounds/agents is critically required. The present study assessed the effect of protocatechualdehyde (PCA), a natural occurring polyphenolic compound with diverse biological activities including but not limited to antibacterial and antiinflammatory properties, on nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in vitro and lipopolysaccharide (LPS)-induced bone loss in vivo. In the present study, it was found that PCA potently inhibited RANKL-induced osteoclast formation, fusion, and activation toward bone resorption in a dose-dependent manner via the suppression of the ERK/c-Fos/nuclear factor of activated T-cells, cytoplasmic 1 signaling axis. It was further demonstrated that the in vivo administration of PCA could effectively protect mice against the deleterious effects of LPS-induced calvarial bone destruction by attenuating osteoclast formation and activity in a dose-dependent manner. Collectively, these findings provided evidence for the potential therapeutic application of PCA in the prevention and treatment of infectious osteolytic conditions, and potentially other osteoclast-mediated bone diseases.

Carnosol suppresses RANKL-induced osteoclastogenesis and attenuates titanium particles-induced osteolysis.

Osteolysis is a common medical condition characterized by excessive activity of osteoclasts and bone resorption, leading to severe poor quality of life. It is essential to identify the medications that can effectively suppress the excessive differentiation and function of osteoclasts to prevent and reduce the osteolytic conditions. It has been reported that Carnosol (Car), isolated from rosemary and salvia, has anti-inflammatory, antioxidative, and anticancer effects, but its activity on osteolysis has not been determined. In this study, we found that Car has a strong inhibitory effect on the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation dose-dependently without any observable cytotoxicity. Moreover, Car can inhibit the RANKL-induced osteoclastogenesis and resorptive function via suppressing NFATc1, which is a result of affecting MAPK, NF-κB and Ca2+ signaling pathways. Moreover, the particle-induced osteolysis mouse model confirmed that Car could be effective for the treatment of bone loss in vivo. Taken together, by suppressing the formation and function of RANKL-induced osteoclast, Car, may be a therapeutic supplementary in the prevention or the treatment of osteolysis.

Skeletal impact of 17ß-estradiol in T cell-deficient mice: age-dependent bone effects and osteosarcoma formation.

Estrogen (E2)-dependent ER+ breast cancer, the most common breast cancer subtype, is also the most likely to metastasize to bone and form osteolytic lesions. However, ER+ breast cancer bone metastasis human xenograft models in nude mice are rarely studied due to complexities associated with distinguishing possible tumoral vs. bone microenvironmental effects of E2. To address this knowledge gap, we systematically examined bone effects of E2 in developing young (4-week-old) vs. skeletally mature (15-week-old) female Foxn1nu nude mice supplemented with commercial 60-day slow-release E2 pellets and doses commonly used for ER+ xenograft models. E2 pellets (0.05-0.72 mg) were implanted subcutaneously and longitudinal changes in hind limb bones (vs. age-matched controls) were determined over 6 weeks by dual-energy X-ray absorptiometry (DXA), microCT, radiographic imaging, and histology, concurrent with assessment of serum levels of E2 and bone turnover markers. All E2 doses tested induced significant and identical increases in bone density (BMD) and volume (BV/TV) in 4-week-old mice with high bone turnover, increasing bone mineral content (BMC) while suppressing increases in bone area (BA). E2 supplementation, which caused dose-dependent changes in circulating E2 that were not sustained, also led to more modest increases in BMD and BV/TV in skeletally mature 15-week-old mice. Notably, E2-supplementation induced osteolytic osteosarcomas in a subset of mice independent of age. These results demonstrate that bone effects of E2 supplementation should be accounted for when assessing ER+ human xenograft bone metastases models.

Nirogacestat suppresses RANKL-Induced osteoclast formation in vitro and attenuates LPS-Induced bone resorption in vivo.

Bone resorption, initiated by osteoclasts (OCs), plays an essential role in bone homeostasis. The abnormalities of bone resorption may induce a series of diseases, including osteoarthritis, osteoporosis and aseptic peri-implant loosening. Nirogacestat (PF-03084014, PF), a novel gamma-secretase inhibitor, has been used in phase II clinical trial for treatment of desmoid tumor. However, whether it has the therapeutic effect on abnormal bone resorption remains to be evaluated. In this study, we investigated the role of PF in the regulation of receptor activator of nuclear factor-kB ligand (RANKL)-induced osteoclastogenesis in vitro, and the lipopolysaccharide (LPS)-induced bone resorption in vivo. It was found that PF could suppress the formation of osteoclasts from bone marrow macrophages (BMMs) without causing cytotoxicity, inhibit bone resorption and downregulate the mRNA level of osteoclast-specific markers, including calcitonin receptor (CTR), tartrate resistant acid phosphatase (TRAP), cathepsin K (CTSK), dendritic cell-specific transmembrane protein (Dc-stamp), Atp6v0d2 (V-ATPase d2) and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1). Furthermore, Notch2 signaling, as well as RANKL-induced AKT signaling was significantly inhibited in BMMs. Consistent with in vitro observation, we found that PF greatly ameliorated LPS-induced bone resorption. Taken together, our study demonstrated that PF has a great potential to be used in management of osteolytic diseases.

Daphnetin attenuates LPS-induced osteolysis and RANKL mediated osteoclastogenesis through suppression of ERK and NFATc1 pathways.

Aseptic prosthetic loosening and periprosthetic infection resulting in inflammatory osteolysis is a leading complication of total joint arthroplasty (TJA). Excessive bone destruction around the bone and prosthesis interface plays a key role in the loosening prostheses leading to revision surgery. The bacterial endotoxins or implant-derived wear particles-induced inflammatory response is the major cause of the elevated osteoclast formation and activity. Thus, agents or compounds that can attenuate the inflammatory response and/or inhibit the elevated osteoclastogenesis and excessive bone resorption would provide a promising therapeutic avenue to prevent aseptic prosthetic loosening in TJA. Daphnetin (DAP), a natural coumarin derivative, is clinically used in Traditional Chinese Medicine for the treatment of rheumatoid arthritis due to its anti-inflammatory properties. In this study, we report for the first time that DAP could protect against lipopolysaccharide-induced inflammatory bone destruction in a murine calvarial osteolysis model in vivo. This protective effect of DAP can in part be attributed to its direct inhibitory effect on RANKL-induced osteoclast differentiation, fusion, and bone resorption in vitro. Biochemical analysis found that DAP inhibited the activation of the ERK and NFATc1 signaling cascades. Collectively, our findings suggest that DAP as a natural compound has potential for the treatment of inflammatory osteolysis.

Vitexin suppresses RANKL-induced osteoclastogenesis and prevents lipopolysaccharide (LPS)-induced osteolysis.

Osteolytic diseases are characterized by an increase in the number and/or activity of bone-resorbing osteoclasts. Identification of natural compounds that can suppress osteoclast formation and function is crucial for the prevention and treatment of osteolytic diseases. Vitexin, a naturally-derived flavonoid extracted from various medicinal plant species, demonstrates a broad range of pharmacological properties including anticancer and anti-inflammatory effects. Here in this study, we showed that vitexin exerts antiosteoclastogenic effects by directly inhibiting receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation and bone resorption in vitro and protected against lipopolysaccharide (LPS)-induced inflammatory osteolysis in vivo. Vitexin suppressed the early activation of ERK and p38 MAPK pathways in response to RANKL thereby attenuating the downstream induction of c-Fos and NFATc1, and abrogating the expression of osteoclast marker genes. Collectively, these results provide evidence for the therapeutic application of vitexin in the treatment of osteoclast-mediated bone lytic diseases.

Curcumin Attenuation of Wear Particle-Induced Osteolysis via RANKL Signaling Pathway Suppression in Mouse Calvarial Model.

Wear particle-induced chronic inflammation and osteoclastogenesis are two critical factors in the osteolytic process. Curcumin (CUR) is an active compound of the medicinal herb Curcuma longa and has anti-inflammatory and antiosteoclastogenic properties. Our study tested the hypothesis that CUR might attenuate polymethylmethacrylate- (PMMA-) induced inflammatory osteolysis using mouse calvaria osteolysis model in vivo and in vitro. The mice were divided into four groups: phosphate-buffered saline group, CUR, PMMA, and PMMA + CUR groups. Three days before PMMA particle implantation, the mice were intraperitoneally injected with CUR (25 mg/kg/day). Ten days after the operation, the mouse calvaria was harvested for microcomputed tomography, histomorphometry, and molecular biology analysis. As expected, CUR markedly reduced the secretion of tumor necrosis factor-α, interleukin- (IL-) 1ß, and IL-6 in the calvarial organ culture. Moreover, CUR suppressed osteoclastogenesis and decreased bone resorption in vivo compared with PMMA-stimulated calvaria. Furthermore, CUR downregulated the osteoclast-specific gene expression and reversed the receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin messenger RNA and protein ratio in PMMA particle-stimulated mice. These results suggest that CUR attenuated PMMA particle-induced inflammatory osteolysis by suppressing the RANKL signaling pathway in the murine calvarium, which could be a candidate compound to prevent and treat AL.

Picroside II Inhibits RANKL-Mediated Osteoclastogenesis by Attenuating the NF-κB and MAPKs Signaling Pathway In Vitro and Prevents Bone Loss in Lipopolysaccharide Treatment Mice.

Picroside II, one of the major components isolated from the seed of natural plant picrorhiza, is widely used in traditional Chinese medicine. The present study was performed to define effects of picroside II on nuclear factor-kappaB ligand (RANKL)-stimulated osteoclast differentiation in vitro and on lipopolysaccharide (LPS)-induced bone loss in vivo. The bone marrow cells (BMMs) were harvested and induced with RANKL followed by treatment with picroside II at several doses, and the differentiation of osteoclasts from these cells was evaluated by tartrate-resistant acid phosphatase (TRAP) staining and resorption pit formation assay. The effects of picroside II on osteoclastogenesis were studied by examining RANKL-induced osteoclast F-actin ring formation and osteoclast bone resorption. Moreover, we explored the mechanisms of these downregulation effects by performed Western blotting and quantitative RT-PCR examination. Results demonstrated picroside II strongly inhibited RANKL-induced osteoclast formation when added during the early stage of BMMs cultures, suggesting that it acts on osteoclast precursors to inhibit RANKL/RANK signaling. Moreover, picroside II markedly decreased the phosphorylation of p38, ERK, JNK, p65, and I-κB degradation, and significantly suppressed c-Fos and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), both the key transcription factors during osteoclastogenesis. Furthermore, in vivo studies verified the bone protection effects of picroside II. These results collectively suggested that picroside II acted as an anti-resorption agent by blocking osteoclast activation. J. Cell. Biochem. 118: 4479-4486, 2017. © 2017 Wiley Periodicals, Inc.

Anthocyanin suppresses CoCrMo particle-induced osteolysis by inhibiting IKKα/ß mediated NF-κB signaling in a mouse calvarial model.

Wear particle-induced osteolysis and bone resorption have been identified as critical factors of implant failure and total joint revision, in which nuclear factor kappa B (NF-κB) signaling and chronic inflammation have been shown to play key roles. Although anthocyanin is known to have anti-inflammatory function via blocking NF-κB pathway, it is still unclear whether anthocyanin has a protective effect on particle-induced osteolysis. In the present study, we aimed to investigate the detailed effects and the underlying mechanism of anthocyanin on CoCrMo particle-induced osteolysis in a mouse calvavial model. One hundred and twelve male BALB/c mice were divided randomly into four groups: sham group (sham operation and injection with PBS), vehicle group (CoCrMo particle treatment and injection with PBS), low-dose anthocyanin group (CoCrMo particle treatment and injecting anthocyanin with 0.1mg/g/day), and high-dose anthocyanin group (CoCrMo particle treatment and injecting anthocyanin with 0.4mg/g/day). Mice were sacrificed after two weeks, harvesting the calvariae tissue for in depth analysis by micro-CT, histomorphometry, immunohistochemical and molecular biology analysis. As expected, anthocyanin markedly inhibited CoCrMo particle-induced inflammatory infiltration and decreased bone loss in vivo. Anthocyanin also reversed the increase in the ratio of receptor activator of nuclear factor kappa B ligand (RANKL)/osteoproteger (OPG) and suppressed osteoclast formation in CoCrMo particle-stimulated calvaria. Additionally, anthocyanin significantly reduced the expression and secretion of tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and interleukin-6 (IL-6) in the calvaria of CoCrMo-stimulated mice. Furthermore, we confirmed that anthocyanin attenuated osteolysis by blocking NF-κB pathway via inhibiting inhibitor of nuclear factor kappa-B kinase α/ß (IKKα/ß) phosphorylation. In conclusion, our study demonstrated that anthocyanin can protect against CoCrMo particle-induced inflammatory osteolysis via inhibiting the IKKα/ß-NF-κB pathway, and have a potential therapeutic effect on the treatment of wear particle-induced osteolysis.

Scutellarin inhibits RANKL-mediated osteoclastogenesis and titanium particle-induced osteolysis via suppression of NF-κB and MAPK signaling pathway.

Aseptic prosthetic loosening is a major complication after hip joint replacement. Wear particle-induced periprosthetic osteolysis plays a key role in aseptic prosthetic loosening. Attempting to modulate receptor activator of nuclear factor-κB (RANKL) mediated signaling pathways is a promising strategy to prevent aseptic prosthetic loosening. In the present study, we determined the effect of scutellarin (SCU) on titanium (Ti) particle-induced osteolysis in a mouse calvarial model and RANKL-mediated osteoclastogenesis. We determined that SCU, the major effective constituent of breviscapine isolated from a Chinese herb, has potential effects on preventing Ti particle-caused osteolysis in calvarial model of mouse. In vitro, SCU could suppress RANKL-mediated osteoclastogenesis, the function of osteoclast bone resorption, and the expression levels of osteoclast-specific genes (tartrate-resistant acid phosphatase (TRAP), cathepsin K, c-Fos, NFATc1). Further investigation indicated that SCU could inhibit RANKL-mediated MAPK and NF-κB signaling pathway, including JNK1/2, p38, ERK1/2, and IκBα phosphorylation. Taken together, these results indicate that SCU could inhibit osteoclastogenesis and prevent Ti particle-induced osteolysis by suppressing RANKL-mediated MAPK and NF-κB signaling pathway. These results suggest that SCU is a promising therapeutic agent for preventing wear particle-induced periprosthetic osteolysis.

Icariin attenuates titanium-particle inhibition of bone formation by activating the Wnt/ß-catenin signaling pathway in vivo and in vitro.

Wear-debris-induced periprosthetic osteolysis (PIO) is a common clinical condition following total joint arthroplasty, which can cause implant instability and failure. The host response to wear debris promotes bone resorption and impairs bone formation. We previously demonstrated that icariin suppressed wear-debris-induced osteoclastogenesis and attenuated particle-induced osteolysis in vivo. Whether icariin promotes bone formation in a wear-debris-induced osteolytic site remains unclear. Here, we demonstrated that icariin significantly attenuated titanium-particle inhibition of osteogenic differentiation of mesenchymal stem cells (MSCs). Additionally, icariin increased bone mass and decreased bone loss in titanium-particle-induced osteolytic sites. Mechanistically, icariin inhibited decreased ß-catenin stability induced by titanium particles in vivo and in vitro. To confirm icariin mediated its bone-protective effects via the Wnt/ß-catenin signaling pathway, we demonstrated that ICG-001, a selective Wnt/ß-catenin inhibitor, attenuated the effects of icariin on MSC mineralization in vitro and bone formation in vivo. Therefore, icariin could induce osteogenic differentiation of MSCs and promote new bone formation at a titanium-particle-induced osteolytic site via activation of the Wnt/ß-catenin signaling pathway. These results further support the protective effects of icariin on particle-induced bone loss and provide novel mechanistic insights into the recognized bone-anabolic effects of icariin and an evidence-based rationale for its use in PIO treatment.

Inhibitory Effects of Lanthanum Chloride on Wear Particle-Induced Osteolysis in a Mouse Calvarial Model.

Osteolysis is a bone disorder associated with progressive destruction of bone tissues. However, the effects of lanthanum chloride (LaCl3) on osteolysis remain unknown. Therefore, the aim of this study was to determine the effects of LaCl3 on osteolysis in vivo. In a mouse calvarial model, C57BL/6J mice were injected with wear particles with or without LaCl3. Microcomputed tomography, hematoxylin and eosin staining, and tartrate-resistant acid phosphatase staining were performed for the pathological characterization of calvariae, and eight calvariae per group were prepared for the assay of TNF-α, IL-1ß, and RANKL secretion using quantitative enzyme-linked immunosorbent assay (ELISA). In mice treated with high-dose LaCl3, particle-induced osteolysis and inflammatory reaction were reduced compared with that in the vehicle-treated control. Moreover, treatment with high-dose LaCl3 suppressed the wear particle-induced decrease in bone mineral content, bone mineral density, and bone volume fraction. Bone destruction and resorption were higher in the LaCl3-treated group than in the saline-treated group but lower than those in the wear particle group. Finally, our results showed that treatment with a high dose of LaCl3 suppressed osteoclastogenesis. Thus, LaCl3 may represent a novel therapeutic agent for the treatment or prevention of wear particle-induced osteolysis and aseptic loosening.

Icariin protects against titanium particle-induced osteolysis and inflammatory response in a mouse calvarial model.

Periprosthetic osteolysis and subsequent aseptic loosening are common in implant failure, a complication with revision surgery being the only established treatment. Wear particle-induced inflammation and extensive osteoclastogenesis play critical roles in periprosthetic osteolysis. A recent approach in limiting osteolysis is therefore focused on inhibiting osteoclastic bone resorption. This study aimed to investigate the potential impact of icariin, the major ingredient of Epimedium, on titanium particle-induced osteolysis in a mouse calvarial model. Eighty-four male C57BL/J6 mice were divided randomly into four groups. Mice in the sham group underwent sham surgery only, whereas animals in the vehicle, low- and high-concentration icariin groups received titanium particles. Mice in the low- and high-concentration icariin groups were gavage-fed with icariin at 0.1 or 0.3 mg/g/day, respectively, until sacrifice. Mice in the sham and vehicle groups received phosphate-buffered saline daily. After 2 weeks, mouse calvariae were collected for micro-computed tomography, histomorphometry and molecular analysis. Icariin significantly reduced particle-induced bone resorption compared with the vehicle group. Icariin also prevented an increase in receptor activator of nuclear factor kappa B ligand/osteoprotegerin ratio and subsequently suppressed osteoclast formation in titanium particle-charged calvariae. In addition, immunohistochemical analysis and enzyme-linked immunosorbent assay showed icariin significantly reduced expression and secretion of tumor necrosis factor-α, interleukin-1ß and interleukin-6 in the calvariae of titanium-stimulated mice. Collectively, these results suggest that icariin represents a potential treatment for titanium particle-induced osteolysis and could be developed as a new therapeutic candidate for the prevention and treatment of aseptic loosening.

Triptolide inhibits osteoclast formation, bone resorption, RANKL-mediated NF-қB activation and titanium particle-induced osteolysis in a mouse model.

The RANKL-induced NF-κB signaling pathway is required for osteoclast formation and function. By screening for compounds that inhibit RANKL-induced NF-κB activation using a luciferase reporter gene assay in RAW264.7 cells, we identified triptolide (PG490), as a candidate compound targeting osteoclast differentiation and osteoclast-mediated osteolysis. Triptolide (PG490) is an active compound of the medicinal herb Tripterygium wilfordii Hook F (TWHF) or Lei Gong Teng with known anti-inflammatory properties. We found that triptolide inhibited osteoclastogenesis and bone resorption, as well as RANKL-induced NF-қB activities as monitored by luciferase reporter gene assays and the nuclear translocation of p65. In vivo studies showed that triptolide attenuates titanium-induced osteolysis and osteoclast formation in a mouse calvarial model. Considering that drugs which protect against localized bone loss are critically needed for the effective treatment of particle-induced osteolysis, our data suggest that triptolide might have therapeutic potential for the treatment of bone lytic diseases caused by prosthetic wear particles.

Moderate zinc supplementation during prolonged steroid therapy exacerbates bone loss in rats.

The present study was conducted to understand the influence of zinc on bone mineral metabolism in prednisolone-treated rats. Disturbance in bone mineral metabolism was induced in rats by subjecting them to prednisolone treatment for a period of 8 weeks. Female rats aged 6-8 weeks weighing 150 to 200 g were divided into four treatment groups, viz., normal control, prednisolone-treated (40 mg/kg body weight orally, thrice a week), zinc-treated (227 mg/L in drinking water, daily), and combined prednisolone + zinc-treated groups. Parameters such as changes in mineral levels in the bone and serum, bone mineral density (BMD), bone mineral content (BMC), and bone 99m-technetium-labeled methylene diphosphonate ((99m)Tc-MDP) uptake were studied in various treatment groups. Prednisolone treatment caused an appreciable decrease in calcium levels both in the bone and serum and also in bone dry weight, BMC, and BMD in rats. Prednisolone-treated rats when supplemented with zinc showed further reduction in calcium levels, bone dry weight, BMD, and BMC. The study therefore revealed that moderate intake of zinc as a nutritional supplement during steroid therapy could enhance calcium deficiency in the body and accelerate bone loss.