RANKL as a key figure in bridging between the bone and immune system: Its physiological functions and potential as a pharmacological target

Strategies to enhance the therapeutic efficacy of anti-PD-1 antibody, anti-PD-L1 antibody and anti-CTLA-4 antibody in cancer therapy

Although immune checkpoint inhibitors (anti-PD-1 antibody, anti-PD-L1 antibody, and anti-CTLA-4 antibody) have displayed considerable success in the treatment of malignant tumors, the therapeutic effect is still unsatisfactory for a portion of patients. Therefore, it is imperative to develop strategies to enhance the effect of these ICIs. Increasing evidence strongly suggests that the key to this issue is to transform the tumor immune microenvironment from a state of no or low immune infiltration to a state of high immune infiltration and enhance the tumor cell-killing effect of T cells. Therefore, some combination strategies have been proposed and this review appraise a summary of 39 strategies aiming at enhancing the effectiveness of ICIs, which comprise combining 10 clinical approaches and 29 foundational research strategies. Moreover, this review improves the comprehensive understanding of combination therapy with ICIs and inspires novel ideas for tumor immunotherapy.

Effects of repeated alcohol abstinence on within-subject prefrontal cortical gene expression in rhesus macaques

Male rhesus monkeys (n = 24) had a biopsy of prefrontal cortical area 46 prior to chronic ethanol self-administration (n = 17) or caloric control (n = 7). Fourteen months of daily self-administration (water vs. 4% alcohol, 22 h access/day termed "open-access") was followed by two cycles of prolonged abstinence (5 weeks) each followed by 3 months of open-access alcohol and a final abstinence followed by necropsy. At necropsy, a biopsy of Area 46, contralateral to the original biopsy, was obtained. Gene expression data (RNA-Seq) were collected comparing biopsy/necropsy samples. Monkeys were categorized by drinking status during the final post-abstinent drinking phase as light (LD), binge (BD), heavy (HD) and very heavy (VHD drinkers). Comparing pre-ethanol to post-abstinent biopsies, four animals that converted from HD to VHD status had significant ontology enrichments in downregulated genes (necropsy minus biopsy n = 286) that included immune response (FDR < 9 × 10-7) and plasma membrane changes (FDR < 1 × 10-7). Genes in the immune response category included IL16 and 18, CCR1, B2M, TLR3, 6 and 7, SP2 and CX3CR1. Upregulated genes (N = 388) were particularly enriched in genes associated with the negative regulation of MAP kinase activity (FDR < 3 × 10-5), including DUSP 1, 4, 5, 6 and 18, SPRY 2, 3, and 4, SPRED2, BMP4 and RGS2. Overall, these data illustrate the power of the NHP model and the within-subject design of genomic changes due to alcohol and suggest new targets for treating severe escalated drinking following repeated alcohol abstinence attempts.

Thyroid hormone receptor Thra and Thrb knockout differentially affects osteoblast biology and thyroid hormone responsiveness in vitro

Thyroid hormones (TH) are important modulators of bone remodeling and thus, thyroid diseases, in particular hyperthyroidism, are able to compromise bone quality and fracture resistance. TH actions on bone are mediated by the thyroid hormone receptors (TR) TRα1 and TRβ1, encoded by Thra and Thrb, respectively. Skeletal phenotypes of mice lacking Thra (Thra0/0 ) and Thrb (Thrb-/- ) are well-described and suggest that TRα1 is the predominant mediator of TH actions in bone. Considering that bone cells might be affected by systemic TH changes seen in these mutant mice, here we investigated the effects of TR knockout on osteoblasts exclusively at the cellular level. Primary osteoblasts obtained from Thra0/0 , Thrb-/- , and respective wildtype (WT) mice were analyzed regarding their differentiation potential, activity and TH responsiveness in vitro. Thra, but not Thrb knockout promoted differentiation and activity of early, mature and late osteoblasts as compared to respective WT cells. Interestingly, while mineralization capacity and expression of osteoblast marker genes and TH target gene Klf9 was increased by TH in WT and Thra-deficient osteoblasts, Thrb knockout mitigated the responsiveness of osteoblasts to short (48 h) and long term (10 d) TH treatment. Further, we found a low ratio of Rankl, a potent osteoclast stimulator, over osteoprotegerin, an osteoclast inhibitor, in Thrb-deficient osteoblasts and in line, supernatants obtained from Thrb-/- osteoblasts reduced numbers of primary osteoclasts in vitro. In accordance to the increased Rankl/Opg ratio in TH-treated WT osteoblasts only, supernatants from these cells, but not from TH-treated Thrb-/- osteoblasts increased the expression of Trap and Ctsk in osteoclasts, suggesting that osteoclasts are indirectly stimulated by TH via TRβ1 in osteoblasts. In conclusion, our study shows that both Thra and Thrb differentially affect activity, differentiation and TH response of osteoblasts in vitro and emphasizes the importance of TRβ1 to mediate TH actions in bone.

Osteoclasts in Osteosarcoma: Mechanisms, Interactions, and Therapeutic Prospects

Osteosarcoma is an extremely malignant tumor, and its pathogenesis is complex and remains incompletely understood. Most cases of osteosarcoma are accompanied by symptoms of bone loss or result in pathological fractures due to weakened bones. Enhancing the survival rate of osteosarcoma patients has proven to be a long-standing challenge. Numerous studies mentioned in this paper, including in-vitro, in-vivo, and in-situ studies have consistently indicated a close association between the symptoms of bone loss associated with osteosarcoma and the presence of osteoclasts. As the sole cells capable of bone resorption, osteoclasts participate in a malignant cycle within the osteosarcoma microenvironment. These cells interact with osteoblasts and osteosarcoma cells, secreting various factors that further influence these cells, disrupting bone homeostasis, and shifting the balance toward bone resorption, thereby promoting the onset and progression of osteosarcoma. Moreover, the interaction between osteoclasts and various other cells types, such as tumor-associated macrophages, myeloid-derived suppressor cells, DCs cells, T cells, and tumor-associated fibroblasts in the osteosarcoma microenvironment plays a crucial role in disease progression. Consequently, understanding the role of osteoclasts in osteosarcoma has sparked significant interest. This review primarily examines the physiological characteristics and functional mechanisms of osteoclasts in osteosarcoma, and briefly discusses potential therapies targeting osteoclasts for osteosarcoma treatment. These studies provide fresh ideas and directions for future research on the treatment of osteosarcoma.

Metformin Reduces Bone Resorption in Apical Periodontitis Through Regulation of Osteoblast and Osteoclast Differentiation

INTRODUCTION

We have previously demonstrated that auxiliary metformin therapy promotes healing of apical periodontitis. Here we aimed to investigate the effects of metformin on osteoblast differentiation and osteoclast formation in cultured cells and rat apical periodontitis.

METHODS

Murine pre-osteoblasts MC3T3-E1 and macrophages RAW264.7 were cultured under hypoxia (2% oxygen) or normoxia (21% oxygen) and stimulated with receptor activator of nuclear factor-κB ligand (RANKL) when indicated. Metformin was added to the cultures to evaluate its anti-hypoxic effects. Expressions of osteoblast differentiation regulator runt-related transcription factor 2 (RUNX2), RANKL, and osteoclast marker tartrate-resistant acid phosphatase (TRAP) were assessed by Western blot. Apical periodontitis was induced in mandibular first molars of 10 Sprague-Dawley rats. Root canal therapy with or without metformin supplement was performed. Periapical bone resorption was measured by micro-computed tomography. Immunohistochemistry was used to examine RUNX2, RANKL, and TRAP expressions.

RESULTS

Hypoxia suppressed RUNX2 expression and enhanced RANKL synthesis in pre-osteoblasts. TRAP production increased in macrophages after hypoxia and/or RANKL stimulation. Metformin reversed hypoxia-induced RUNX2 suppression and RANKL synthesis in pre-osteoblasts. Metformin also inhibited hypoxia and RANKL-enhanced TRAP synthesis in macrophages. Intracanal metformin diminished bone loss in rat apical periodontitis. Comparing with vehicle control, cells lining bone surfaces in metformin-treated lesions had significantly stronger expression of RUNX2 and decreased synthesis of RANKL and TRAP.

CONCLUSIONS

Alleviation of bone resorption by intracanal metformin was associated with enhanced osteoblast differentiation and diminished osteoclast formation in rat apical periodontitis. Our results endorsed the role of metformin as an effective medicament for inflammatory bone diseases.

GelMA Hydrogel as a Promising Delivery System for Osthole in the Treatment of Rheumatoid Arthritis: Targeting the miR-1224-3p/AGO1 Axis

Rheumatoid arthritis (RA) is a multifaceted, chronic, progressive autoimmune disease. This study aims to explore the potential benefits of an enhanced drug delivery system utilizing optimized Gelatin Methacryloyl (GelMA) vectors in RA management. We evaluated the levels of miR-1124-3p and AGO1 in RA tissues and cell lines using qPCR, WB, and immunofluorescence. The effects of osthole on inflammatory response and joint morphology were determined by qPCR, H&E staining, and micro-CT. The data showed that miR-1224-3p was downregulated in RA tissues and HUM-iCell-s010RA cells, while the overexpression of miR-1224-3p in HUM-iCell-s010RA cells reduced the expression of IL-6 and IL-1β. Luciferase assay demonstrated that AGO1 was a direct target gene of miR-1224-3p. Additionally, osthole treatment increased miR-1224-3p levels and decreased AGO1 expression. The release data showed that osthole loaded on GelMA was released at a slower rate than free osthole. Further studies in a mouse model of CIA confirmed that osthole-loaded GelMA was more effective in attenuating osteopenia in RA as well as alleviating autoimmune arthritis. These findings suggest that osthole can regulate the miR-1224-3p/AGO1 axis in RASFs cells and has the potential to be developed as a clinical anti-RA drug. GelMA could provide a new approach to long-term RA treatment.

RhoA promotes osteoclastogenesis and regulates bone remodeling through mTOR-NFATc1 signaling

BACKGROUND

The cytoskeletal architecture of osteoclasts (OCs) and bone resorption activity must be appropriately controlled for proper bone remodeling, which is associated with osteoporosis. The RhoA protein of GTPase plays a regulatory role in cytoskeletal components and contributes to osteoclast adhesion, podosome positioning, and differentiation. Although osteoclast investigations have traditionally been performed by in vitro analysis, however, the results have been inconsistent, and the significance of RhoA in bone physiology and pathology is still unknown.

METHODS

We generated RhoA knockout mice by specifically deleting RhoA in the osteoclast lineage to understand more about RhoA's involvement in bone remodeling. The function of RhoA in osteoclast differentiation and bone resorption and the mechanisms were assessed using bone marrow macrophages (BMMs) in vitro. The ovariectomized (OVX) mouse model was adopted to examine the pathological effect of RhoA in bone loss.

RESULTS

Conditional deletion of RhoA in the osteoclast lineage causes a severe osteopetrosis phenotype, which is attributable to a bone resorption suppression. Further mechanistic studies suggest that RhoA deficiency suppresses Akt-mTOR-NFATc1 signaling during osteoclast differentiation. Additionally, RhoA activation is consistently related to the significant enhancement the osteoclast activity, which culminates in the development of an osteoporotic bone phenotype. Furthermore, in mice, the absence of RhoA in osteoclast precursors prevented occurring OVX-induced bone loss.

CONCLUSION

RhoA promoted osteoclast development via the Akt-mTOR-NFATc1 signaling pathway, resulting a osteoporosis phenotype, and that manipulating RhoA activity might be a therapeutic strategy for osteoporotic bone loss.

OP3-4 peptide sustained-release hydrogel inhibits osteoclast formation and promotes vascularization to promote bone regeneration in a rat femoral defect model

Bone injury caused changes to surrounding tissues, leading to a large number of osteoclasts appeared to clear the damaged bone tissue before bone regeneration. However, overactive osteoclasts will inhibit bone formation. In this study, we prepared methacrylylated gelatin (GelMA)-based hydrogel to co-crosslink with OP3-4 peptide, a receptor activator of NF-κB ligand (RANKL) binding agent, to achieve the slow release of OP3-4 peptide to inhibit the activation of osteoclasts, thus preventing the long-term existence of osteoclasts from affecting bone regeneration, and promoting osteogenic differentiation. Moreover, CXCL9 secreted by osteoblasts will bind to endogenous VEGF and inhibit vascularization, finally hinder bone formation. Thus, anti-CXCL9 antibodies (A-CXCL9) were also loaded in the hydrogel to neutralize excess CXCL9. The hydrogel slow released of OP3-4 cyclic peptide and A-CXCL9 to simultaneously inhibiting osteoclast activation and promoting vascularization, thereby accelerating the healing of femur defect. Further analysis of osteogenic protein expression and signal pathways showed that the hydrogel may be through activating the AKT-RUNX2-ALP pathway and ultimately promote osteogenic differentiation. This dual-acting hydrogel can effectively prevent nonunion caused by low vascularization and provide long-term support for the treatment of bone injury.

The role of Th17 cells in endocrine organs: Involvement of the gut, adipose tissue, liver and bone

T Helper 17 (Th17) cells are adaptive immune cells that play myriad roles in the body. Immune-endocrine interactions are vital in endocrine organs during pathological states. Th17 cells are known to take part in multiple autoimmune diseases over the years. Current evidence has moved from minimal to substantial that Th17 cells are closely related to endocrine organs. Diverse tissue Th17 cells have been discovered within endocrine organs, including gut, adipose tissue, liver and bone, and these cells are modulated by various secretions from endocrine organs. Th17 cells in these endocrine organs are key players in the process of an array of metabolic disorders and inflammatory conditions, including obesity, insulin resistance, nonalcoholic fatty liver disease (NAFLD), primary sclerosing cholangitis (PSC), osteoporosis and inflammatory bowel disease (IBD). We reviewed the pathogenetic or protective functions played by Th17 cells in various endocrine tissues and identified potential regulators for plasticity of it. Furthermore, we discussed the roles of Th17 cells in crosstalk of gut-organs axis.

Sharks Provide Evidence for a Highly Complex TNFSF Repertoire in the Jawed Vertebrate Ancestor

Cytokines of the TNF superfamily (TNFSF) control many immunological processes and are implicated in the etiology of many immune disorders and diseases. Despite their obvious biological importance, the TNFSF repertoires of many species remain poorly characterized. In this study, we perform detailed bioinformatic, phylogenetic, and syntenic analyses of five cartilaginous fish genomes to identify their TNFSF repertoires. Strikingly, we find that shark genomes harbor ∼30 TNFSF genes, more than any other vertebrate examined to date and substantially more than humans. This is due to better retention of the ancestral jawed vertebrate TNFSF repertoire than any other jawed vertebrate lineage, combined with lineage-specific gene family expansions. All human TNFSFs appear in shark genomes, except for lymphotoxin-α (LTA; TNFSF1) and TNF (TNFSF2), and CD70 (TNFSF7) and 4-1BBL (TNFSF9), which diverged by tandem duplications early in tetrapod and mammalian evolution, respectively. Although lacking one-to-one LTA and TNF orthologs, sharks have evolved lineage-specific clusters of LTA/TNF co-orthologs. Other key findings include the presence of two BAFF (TNFSF13B) genes along with orthologs of APRIL (TNFSF13) and BALM (TNFSF13C) in sharks, and that all cartilaginous fish genomes harbor an ∼400-million-year-old cluster of multiple FASLG (TNFSF6) orthologs. Finally, sharks have retained seven ancestral jawed vertebrate TNFSF genes lost in humans. Taken together, our data indicate that the jawed vertebrate ancestor possessed a much larger and diverse TNFSF repertoire than previously hypothesized and oppose the idea that the cartilaginous fish immune system is “primitive” compared with that of mammals.

Inhibition of RGS10 Aggravates Periapical Periodontitis via Upregulation of the NF-κB Pathway

INTRODUCTION

Periapical periodontitis develops due to the interplay between root canal microorganisms and host defenses. The mechanism underlying the pathogenesis of periapical periodontitis remains unclear. Regulator of G protein signaling protein 10 (RGS10) has been suggested to play a role in regulating inflammation. This study explored the potential regulatory effects of RGS10 on periapical periodontitis and the pro-inflammatory pathway of NF-κB.

METHODS

Disease models of periapical inflammation in mice were established, and adenovirus-associated virus (AAV) was used to inhibit RGS10 expression. Periapical lesions were detected using microcomputed tomography. Quantitative real-time PCR (qRT-PCR), western blotting (WB), enzyme-linked immunosorbent assay (ELISA), enzyme activity staining of tartrate-resistant acid phosphatase, and immunohistochemistry were conducted to assess the role of RGS10 expression on NF-κB pro-inflammatory signaling, OPG, RANKL, and osteoclasts in the periapical regions of each group. TNFα was used to stimulate L929 cells alone or with small interfering RNA (siRNA). To assess the expression of associated molecules, WB, immunofluorescence, qRT-PCR, and ELISA were performed.

RESULTS

RGS10 inhibition increased alveolar bone destruction in periapical periodontitis lesions and substantially enhanced the NF-κB pro-inflammatory signaling pathway activation level. Furthermore, RGS10 inhibition upregulated the ratio of OPG/RANKL and the maturation of osteoclasts during alveolar bone resorption. L929 cell TNFα stimulation and siRNA transfection confirmed these in vivo results.

CONCLUSION

RGS10 negatively regulates NF-κB pro-inflammatory signaling in periapical periodontitis and participates in bone remodeling. Therefore, RGS10 is a promising treatment option for long-term chronic periapical inflammation and may be a new target for the artificial regulation of inflammation.

Biosimilar monoclonal antibodies in China: A patent review

Biosimilars play an important role in reducing the burden on patients and increasing the market competition. Biosimilar monoclonal antibodies are currently one of the hotspots of research and development in China with policies support. With the continuous improvement of policies, the enthusiasm for the research and development of biosimilars has increased year by year. The policy requirements in different periods have different degrees of impact on the patent applications of pharmaceutical companies. This review introduces the biosimilar monoclonal antibodies market status and approval process in China, analyzes the patents in this field, and helps pharmaceutical companies protect their intellectual property rights.

α-Mangostin inhibits LPS-induced bone resorption by restricting osteoclastogenesis via NF-κB and MAPK signaling

Background

Excessive osteoclast activation is an important cause of imbalanced bone remodeling that leads to pathological bone destruction. This is a clear feature of many osteolytic diseases such as rheumatoid arthritis, osteoporosis, and osteolysis around prostheses. Because many natural compounds have therapeutic potential for treating these diseases by suppressing osteoclast formation and function, we hypothesized that α-mangostin, a natural compound isolated from mangosteen, might be a promising treatment as it exhibits anti‐inflammatory, anticancer, and cardioprotective effects.

Methods

We evaluated the therapeutic effect of α-mangostin on the processes of osteoclast formation and bone resorption. The receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL) induces osteoclast formation in vitro, and potential pathways of α-mangostin to inhibit osteoclast differentiation and function were explored. A mouse model of lipopolysaccharide‐induced calvarial osteolysis was established. Subsequently, micro-computed tomography and histological assays were used to evaluate the effect of α-mangostin in preventing inflammatory osteolysis.

Results

We found that α-mangostin could inhibit RANKL-induced osteoclastogenesis and reduced osteoclast‐related gene expression in vitro. F-actin ring immunofluorescence and resorption pit assays indicated that α-mangostin also inhibited osteoclast functions. It achieved these effects by disrupting the activation of NF-κB/mitogen-activated protein kinase signaling pathways. Our in vivo data revealed that α-mangostin could protect mouse calvarial bone from osteolysis.

Conclusions

Our findings demonstrate that α-mangostin can inhibit osteoclastogenesis both in vitro and in vivo and may be a potential option for treating osteoclast-related diseases.

Lipid metabolism within the bone micro-environment is closely associated with bone metabolism in physiological and pathophysiological stages

Recent advances in society have resulted in the emergence of both hyperlipidemia and obesity as life-threatening conditions in people with implications for various types of diseases, such as cardiovascular diseases and cancer. This is further complicated by a global rise in the aging population, especially menopausal women, who mostly suffer from overweight and bone loss simultaneously. Interestingly, clinical observations in these women suggest that osteoarthritis may be linked to a higher body mass index (BMI), which has led many to believe that there may be some degree of bone dysfunction associated with conditions such as obesity. It is also common practice in many outpatient settings to encourage patients to control their BMI and lose weight in an attempt to mitigate mechanical stress and thus reduce bone pain and joint dysfunction. Together, studies show that bone is not only a mechanical organ but also a critical component of metabolism, and various endocrine functions, such as calcium metabolism. Numerous studies have demonstrated a relationship between metabolic dysfunction in bone and abnormal lipid metabolism. Previous studies have also regarded obesity as a metabolic disorder. However, the relationship between lipid metabolism and bone metabolism has not been fully elucidated. In this narrative review, the data describing the close relationship between bone and lipid metabolism was summarized and the impact on both the normal physiology and pathophysiology of these tissues was discussed at both the molecular and cellular levels.

Azilsartan Suppresses Osteoclastogenesis and Ameliorates Ovariectomy-Induced Osteoporosis by Inhibiting Reactive Oxygen Species Production and Activating Nrf2 Signaling

Osteoporosis is characterized by a decrease in bone mass and destruction of the bone microarchitecture, and it commonly occurs in postmenopausal women and the elderly. Overactivation of osteoclasts caused by the inflammatory response or oxidative stress leads to osteoporosis. An increasing number of studies have suggested that intracellular reactive oxygen species (ROS) are strongly associated with osteoclastogenesis. As a novel angiotensin (Ang) II receptor blocker (ARB), azilsartan was reported to be associated with the inhibition of intracellular oxidative stress processes. However, the relationship between azilsartan and osteoclastogenesis is still unknown. In this study, we explored the effect of azilsartan on ovariectomy-induced osteoporosis in mice. Azilsartan significantly inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclastogenesis and downregulated the expression of osteoclast-associated markers (Nfatc1, c-Fos, and Ctsk) in vitro. Furthermore, azilsartan reduced RANKL-induced ROS production by increasing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2). Mechanistically, azilsartan inhibited the activation of MAPK/NF-κB signaling pathways, while Nrf2 silencing reversed the inhibitory effect of azilsartan on MAPK/NF-κB signaling pathways. Consistent with the in vitro data, azilsartan administration ameliorated ovariectomy (OVX)-induced osteoporosis, and decreased ROS levels in vivo. In conclusion, azilsartan inhibited oxidative stress and may be a novel treatment strategy for osteoporosis caused by osteoclast overactivation.

Plasma Membrane Receptors Involved in the Binding and Response of Osteoclasts to Noncellular Components of the Bone

Osteoclasts differentiate from hematopoietic cells and resorb the bone in response to various signals, some of which are received directly from noncellular elements of the bone. In vitro, adherence to the bone triggers the reduction of cell–cell fusion events between osteoclasts and the activation of osteoclasts to form unusual dynamic cytoskeletal and membrane structures that are required for degrading the bone. Integrins on the surface of osteoclasts are known to receive regulatory signals from the bone matrix. Regulation of the availability of these signals is accomplished by enzymatic alterations of the bone matrix by protease activity and phosphorylation/dephosphorylation events. Other membrane receptors are present in osteoclasts and may interact with as yet unidentified signals in the bone. Bone mineral has been shown to have regulatory effects on osteoclasts, and osteoclast activity is also directly modulated by mechanical stress. As understanding of how osteoclasts and other bone cells interact with the bone has emerged, increasingly sophisticated efforts have been made to create bone biomimetics that reproduce both the structural properties of the bone and the bone’s ability to regulate osteoclasts and other bone cells. A more complete understanding of the interactions between osteoclasts and the bone may lead to new strategies for the treatment of bone diseases and the production of bone biomimetics to repair defects.

Irisin recouples osteogenesis and osteoclastogenesis to protect wear-particle-induced osteolysis by suppressing oxidative stress and RANKL production

The disruption of bone homeostasis with the decrease in osteoblastic bone formation and facilitated osteoclastic bone resorption is the leading cause of periprosthetic osteolysis. Accumulative studies have indicated that irisin has the function of maintaining and rebalancing bone homeostasis. In this study, we explored the protective effect of irisin on wear-particle-induced osteolysis in mice. The results showed that irisin effectively inhibited titanium (Ti) particle-induced calvarial osteolysis, supported by a lower bone loss and existence of more collagen, compared with the ones stressed by Ti particles. Further analysis demonstrated that irisin not only rescued Ti-particle-impaired osteogenesis derived from bone mesenchymal stem cells (BMSCs) but also alleviated the increase in wear-particle-induced nuclear factor-κB ligand (RANKL) secreted by BMSCs-derived osteoblasts, which consequently restrained the activation of osteoclasts. Meanwhile, irisin inhibited osteoclastogenesis by the direct inactivation of reactive oxygen species (ROS) signaling. These results revealed that irisin functions to fight against osteolysis caused by wear particles through rebalancing the periprosthetic bone homeostasis microenvironment, which may provide a potential therapeutic strategy for the management of osteolysis and induced prosthetic loosening.

Sesamolin Protects Mice From Ovariectomized Bone Loss by Inhibiting Osteoclastogenesis and RANKL-Mediated NF-κB and MAPK Signaling Pathways

This article was submitted to Experimental Pharmacology and Drug Discovery, a section of the journal Frontiers in Pharmacology. Postmenopausal osteoporosis (PMOP), which increases the risk of fracture, is the most common bone disease in women. PMOP not only increases the risk of death but also imposes a financial burden on countless families. At present, most of the drugs used to treat osteoporosis have significant side effects, so it is important to find effective anti-osteoporosis medications without major side effects. Sesamolin (Ses) is a kind of natural lignan extracted from sesame oil. Many researches have shown that Ses has anti-inflammatory, antioxidative, and anticancer effects, however it is still unknown whether it has any effect on osteoporosis. In this research, we explored the therapeutic effect of Ses in the process of osteoclast formation and bone resorption and found that Ses effectively inhibited osteoclast formation in vitro through TRAcP staining and hydroxyapatite resorption assays. Through Western blot analysis of the NF-κB pathway, MAPK pathway, c-Fos and NFATc1, it was found that Ses not only effectively inhibited the activation of NF-κB and MAPK signaling pathways induced by RANKL but also significantly reduced the protein expression of c-Fos and NFATc1. Several genes specifically expressed in osteoclasts were determined by qPCR, and Ses was also found to play a significant inhibitory role on the expression of these genes. Besides, an osteoporosis model induced in ovariectomized (OVX) mice was employed to verify that Ses could effectively reduce bone loss caused by estrogen deficiency in vivo. In conclusion, Ses showed promise as a new treatment for postmenopausal osteoporosis.

Dual effect of IL-7/IL-7R signalling on the osteoimmunological system: a potential therapeutic target for rheumatoid arthritis

The IL-7/IL-7R pathway plays a vital role in the immune system, especially in the inflammatory response. Monocytes/macrophages (osteoclast precursors) have been recently recognized as important participants in the osteoclastogenesis of rheumatoid arthritis (RA) patients. Here, we aimed to investigate the therapeutic potential of IL-7/IL-7R pathway in RA and to determine whether it could restrain osteoclastogenic functions and therefore ameliorate RA. Firstly, collagen-induced arthritis (CIA) mice were administered with IL-7Rα-target antibodies to assess their therapeutic effect on arthritis. We found that blockade of the IL-7/IL-7R pathway protected CIA mice from bone destruction in addition to inducing inflammatory remission, by altering the RANKL/RANK/OPG ratio and consequently decreasing osteoclast formation. To explore the effect and mechanism of this pathway, bone marrow cells were induced to osteoclasts and treated with IL-7, a STAT5 inhibitor or supernatants from T cells. The results showed that the IL-7/IL-7R pathway played a direct inhibitory role in osteoclast differentiation via STAT5 signalling pathway in a RANKL-induced manner. We applied flow cytometry to analyse the effect of IL-7 on T-cell RANKL expression and found that IL-7/IL-7R pathway had an indirect role in the osteoclast differentiation process by enhancing the RANKL expression on T cells. In conclusion, the IL-7/IL-7R pathway exhibited a dual effect on osteoclastogenesis of CIA mice by interacting with osteoimmunology processes and could be a novel therapeutic target for autoimmune diseases such as RA.