Resorption Activity Research Articles

Biomarkers in External Apical Root Resorption: An Evidence-based Scoping Review in Biofluids.

External apical root resorption (EARR), an unwanted sequela of orthodontic treatment, is difficult to diagnose radiographically. Hence, the current scoping review was planned to generate critical evidence related to biomarkers in oral fluids, i.e. gingival crevicular fluid (GCF), saliva, and blood, of patients showing root resorption, compared to no-resorption or physiologic resorption. A literature search was conducted in major databases along with a manual search of relevant articles in the library, and further search from references of the related articles in March 2021. The initial search was subjected to strict inclusion and exclusion criteria according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Following PRISMA guidelines, 20 studies were included in the final review. The studies included human clinical trials and cross-sectional and prospective studies with/without control groups with no date/language restriction. Various biomarkers identified in EARR included dentinal proteins, enzymes, cytokines, and salivary proteins. Severe resorption had higher dentin sialoprotein (DSP) and resorption protein concentrations as well as lower granulocyte-macrophage colony-stimulating factor (GM-CSF) as compared with mild resorption. Increased DSP and dentin phosphophoryn (DPP) expression was found in physiologic resorption. Compared to controls, resorbed teeth showed a higher receptor activator of nuclear factor kappa B ligand/osteoprotegerin (RANKL/OPG) ratio. In contrast, levels of anti-resorptive mediators (IL-1RA, IL-4) was significantly decreased. Differences in force levels (150 g and 100 g) showed no difference in resorption, but a significant rise in biomarkers (aspartate transaminase [AST] and alkaline phosphatase [ALP]) for 150 g force. Moderate to severe resorption in young patients showed a rise in specific salivary proteins, requiring further validation. Limitations of the studies were heterogeneity in study design, biomarker collection, sample selection, and confounding inflammatory conditions. Various biomarkers in biofluids indicate active resorption, while resorption severity was associated with DSP and GM-CSF in GCF, and a few salivary proteins. However, a robust study design in the future is mandated.

The bone-protective mechanisms of active components from TCM drugs in rheumatoid arthritis treatment.

Rheumatoid arthritis (RA) is an autoimmune disease whose hallmarks are synovial inflammation and irreversible bone destruction. Bone resorption resulting from osteoclasts involves the whole immune and bone systems. Breakdown of bone remodeling is attributed to overactive immune cells that produce large quantities of cytokines, upregulated differentiation of osteoclasts with enhanced resorptive activities, suppressed differentiation of osteoblasts, invading fibroblasts and microbiota dysbiosis. Despite the mitigation of inflammation, the existing treatment in Western medicine fails to prevent bone loss during disease progression. Traditional Chinese medicine (TCM) has been used for thousands of years in RA treatment, showing great efficacy in bone preservation. The complex components from the decoctions and prescriptions exhibit various pharmacological activities. This review summarizes the research progress that has been made in terms of the bone-protective effect of some representative compounds from TCM drugs and proposes the substantial mechanisms involved in bone metabolism to provide some clues for future studies. These active components systemically suppress bone destruction via inhibiting joint inflammation, osteoclast differentiation, and fibroblast proliferation. Neutrophil, gut microenvironment and microRNA has been proposed as future focus.

Deer Antler Reserve Mesenchyme Cell-Conditioned Medium Reduces the Destruction of Periodontitis in Mice.

Reserve mesenchyme cells (RMCs) are a type of antler stem cells (ASCs) that contribute to the rapid growth of deer antlers, the only known mammalian organ that can fully regenerate annually. Based on the prior evidence, ASC-conditioned medium could improve regenerative cutaneous healing in rats. The purpose of the study was to evaluate the therapeutic effects of RMC-conditioned medium (RMC-CM) on reducing the destruction in the mice periodontitis (PD) model and the underlying mechanisms. The lipopolysaccharide (LPS)-stimulated RAW264.7 cells were used in vitro to verify the effects of RMC-CM. The results revealed that RMC-CM could significantly reduce bone resorption and osteoclast activation, upregulate anti-inflammatory macrophages (M2) related interleukin (IL)-10 and CD206, and downregulate pro-inflammatory macrophages (M1) related tumor necrosis factor alpha (TNF-α) and inducible nitric oxide synthase in vivo. In vitro, RMC-CM could significantly promote LPS-stimulated RAW264.7 cells migration, reduce osteoclast differentiation, downregulate the expression of TNF-α, IL-6, and IL-1β, and upregulate the expression of IL-10 and arginase 1. According to the results, we concluded that RMC-CM could significantly reduce alveolar bone resorption and inhibit inflammation in gingival tissue by decreasing the activation of osteoclasts and inducing macrophage polarization toward the M2 phenotype. This study may serve as the experimental foundation for RMC-CM in the treatment of PD.

Periplaneta Americana extract inhibits osteoclastic differentiation in vitro.

Periplaneta americana extract (PAE) is proven to be promising in treating fever, wound healing, liver fibrosis, and cardiovascular disease. However, the role of PAE in skeletal disorders remains unclear. This study investigated whether PAE regulates osteoclastic differentiation in vitro via the culture using RAW264.7 cells and bone marrow derived macrophages (BMDMs). RAW264.7 cells and BMDMs were cultured and induced for osteoclastic differentiation supplementing with different concentrations of PAE (0, 0.1, 1, and 10mg/mL). Cell counting kit-8 (CCK-8) assay was used to detect the cytotoxicity and cell proliferation. TRAP staining, actin ring staining, real-time quantitative PCR (RT-qPCR), and bone resorption activity test were performed to detect osteoclastic differentiation. RT-qPCR and enzyme-linked immunosorbent assay (ELISA) were conducted to assay the expression and secretion of inflammatory factors. RNA sequencing (RNA-seq) and western blot analysis were carried out to uncover the underlying mechanism. CCK-8 results showed that 10mg/mL and a lower concentration of PAE did not affect cell proliferation. RT-qPCR analysis verified that PAE down-regulated the osteoclastic genes Nfatc1, Ctsk, and Acp5 in macrophages. Moreover, PAE restrained the differentiation, formation, and function of osteoclasts. Besides, RT-qPCR and ELISA assays showed that PAE decreased inflammatory genes expression and reduced the secretion of inflammatory factors, including IL1β, IL6, and TNFα. Subsequent RNA-seq analysis identified possible genes and signaling pathways of PAE-mediated osteoclastogenesis suppression. Our study indicates that PAE has inhibitive effects on osteoclastogenesis and may be a potential therapeutic alternative for bone diseases.

Astragalin mitigates inflammatory osteolysis by negatively modulating osteoclastogenesis via ROS and MAPK signaling pathway

Inflammatory bone destruction has gradually attracted attention worldwide and has been observed in several kinds of pathological bone diseases, such as osteoarthritis, osteomyelitis, rheumatic arthritis, and other infectious clinical trials in the skeletal system. In this regard, excessive osteoclasts and bone resorption activity participate in osteolytic processes. Thus, negatively modulating osteoclast differentiation and bone erosion has been considered an effective therapeutic strategy to limit the poor progression of inflammatory osteolysis. Astragalin (AST) is a bioactive component of traditional Chinese drugs, such as Rosa agrestis, which presents anti-inflammatory and antioxidant effects. However, it is unclear how AST may play an essential role in regulating the dynamic balance of the bone matrix by affecting osteoclastogenesis. This study found that AST could inhibit osteoclastic formation and bone resorption activity in a dose‐dependent manner without cytotoxicity. Administration of AST also inhibited the expression of cathepsin K, c-Fos, NFATc1, and TRAP at different stages of mRNA and protein levels during osteoclastogenesis. Reactive oxygen species (ROS) signalling could also be modulated by treatment with AST during RANKL-induced osteoclast differentiation through the Nrf2-HO1 signalling pathway. Additionally, AST could negatively regulate mitogen-activated protein kinase (MAPK) signalling in this process. In vivo, AST significantly reduced lipopolysaccharide (LPS)-induced bone loss in an osteolytic mouse model. AST might be a promising therapeutic candidate for treating osteolytic bone diseases in the future.

Transcriptomic analysis of the liver in aged laying hens with different eggshell strength

Eggshell is composed of a very ordered and mineralized structure and is important for egg quality. Eggshell strength is particularly important because of its direct association with economic outcomes and egg safety. Various factors related to laying hens and their environment affects eggshell strength. However, the molecular mechanisms of liver functions related to decreased eggshell strength of aged laying hens are largely unknown. Therefore, this study aimed to identify potential factors affecting eggshell strength in aged laying hens at the hepatic transcriptomic level. A total of five hundred 92-wk-old Hy-line Brown laying hens were screened to select those exhibiting the greatest variation in eggshell strength. Based on the final eggshell strength, 12 hens producing eggs with strong eggshell strength (SES) and weak eggshell strength (WES) were finally selected (n=6) for liver tissue sampling. The RNA-sequencing was performed to identify differentially expressed genes (DEGs) between the 2 groups. We identified a total of 2,084 DEGs, of which 1,358 genes were upregulated and 726 genes were downregulated in the WES group compared with SES group. According to the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, the DEGs indicated the mammalian target of rapamycin signaling pathway, the Janus kinase-signal transducer and activator of transcription pathway, the mitogen‑activated protein kinase signaling pathway, and the insulin resistance pathways. Genes related to fatty liver disease were upregulated in WES group compared with SES group. In addition, expression of several genes associated with oxidative stress and bone resorption activity was altered in aged laying hens with different eggshell strength. Overall, these findings contribute to the identification of genes involved in different intensity of eggshell strength, enabling more understanding of the hepatic molecular mechanism underlying in decreased eggshell strength of aged laying hens.

Increased concentrations of conjugated bile acids are associated with osteoporosis in PSC patients

Primary sclerosing cholangitis (PSC) is an idiopathic cholestatic liver disease characterized by chronic inflammation and progressive fibrosis of intra- and extrahepatic bile ducts. Osteoporosis is a frequent comorbidity in PSC, and we could previously demonstrate that IL17-dependent activation of bone resorption is the predominant driver of bone loss in PSC. Since we additionally observed an unexpected heterogeneity of bone mineral density in our cohort of 238 PSC patients, the present study focused on a comparative analysis of affected individuals with diagnosed osteoporosis (PSCOPO, n = 10) or high bone mass (PSCHBM, n = 7). The two groups were not distinguishable by various baseline characteristics, including liver fibrosis or serum parameters for hepatic function. In contrast, quantification of serum bile acid concentrations identified significant increases in the PSCOPO group, including glycoursodeoxycholic acid (GUDCA), an exogenous bile acid administered to both patient groups. Although cell culture experiments did not support the hypothesis that an increase in circulating bile levels is a primary cause of PSC-associated osteoporosis, the remarkable differences of endogenous bile acids and GUDCA in the serum of PSCOPO patients strongly suggest a yet unknown impairment of biliary metabolism and/or hepatic bile acid clearance in this patient subgroup, which is independent of liver fibrosis.

Rare case of paget’s disease with co-existing features of ankylosing spondylitis

Introduction: Paget’s disease is an uncommon metabolic skeletal disorder characterized by increased osteoclast-mediated bone resorption & compensatory excessive osteoblastic activation. It is often an incidental finding & can also rarely co-exist with other disorders like ankylosing spondylitis.Materials & Methods: Observational type of case study using computed tomography (CT) and X-Ray. 80 years old male came with complaints of giddiness & fall & decreased speech output. CT scans showed intraventricular hemorrhage & patient was treated for the same. However, CT scans revealed features suggesting Paget’s disease with co-existing ankylosing spondylitis & a bone survey for whole body was done. Increased S. Alkaline Phosphatase (187 U/L) & low Calcium (7.5 mg/dl) was noted.Results: CT Brain showed mixed lytic sclerotic changes with widened diploic space & coarse trabeculae involving calvarium fully giving a cotton wool appearance. Spine imaging revealed, picture framing of some vertebrae, anterior & lateral syndesmophytic fusion giving a bamboo spine appearance & diffuse osteopenia with multiple sclerotic areas. X-Ray pelvis showed of Kohler tear drop & sclerosis with near complete fusion of bilateral sacroiliac joints. Conclusion: Paget disease of bone shows an abundance of patterns on imaging that are related to pathologic stage of disease. Recognition of imaging spectrum usually allows early diagnosis & differentiation of its complications, which helps guide therapy & improve patient management.

The Risk of the Development and Relationship of Kidney Stone Disease and Osteoporosis (Literature review)

Urinary stone disease (USD) is a common pathology with the formation of calculi in the kidneys, ureter, and bladder. Besides the family history, hyperparathyroidism, hypo- and hypervitaminosis of vitamin D, hypercalciuria, and hyperoxaluria are the high risk factors for USD development. This is due primarily to the activation of bone resorption with increased hypercalciuria. It is known that in the urine of every person there is a small amount of urea, inorganic salts, uric acid, creatinine and other substances. The main reason for the formation of calculi is a certain metabolic disorder, which leads to the formation of insoluble salts from which stones are formed – urates, phosphates, oxalates, etc. One of the unsolved problems in the metaphylaxis of USD is the treatment and prevention of osteoporosis which is comorbid with it, since calcium and vitamin D preparations are widely used for the prevention and treatment of osteoporosis. Osteoporosis and arterial calcification often coincide in the nature of the manifestation, which indicates an imbalance in the redistribution of calcium with a predominant direction in the vascular the wall. Vitamin K2 deficiency is closely related to the process of vascular calcification. In the cardiovascular system, with the use of vitamin K antagonists or vitamin K deficiency, calcification of the endothelium of blood vessels occurs. The effect of osteocalcin protein on stone formation processes is controversial. For example, some researchers have found that high serum level of Glaprotein is associated with a lower risk of kidney stones. Based on the results of a daily urinalysis study, the EAU Guidelines (2022) updated the recommendations on metaphylactic USD regarding the benefit/harm of additional calcium and vitamin D use in patients with nephrolithiasis depending on the type of crystalluria. The absence of recommendations for the management of patients with combined pathologies (USD, osteoporosis, cardiovascular diseases) prompts a comprehensive assessment of common risk factors, as well as the formation of programs and algorithms for early diagnosis and the development of recommendations for the prevention and avoidance of complications. Based on the literature analysis, it was established that today the issue of choosing the optimal management for diagnosis and treatment of USD and osteoporosis is still very controversial and ambiguous. There is a necessity for detailed study of this problem, the development of a complex differentiated approach to diagnosis and treatment of patients.

Dehydromiltirone inhibits osteoclast differentiation in RAW264.7 and bone marrow macrophages by modulating MAPK and NF-κB activity.

Background: Osteoporosis is a type of systematic metabolic bone disease caused by the decrease in osteogenic activity or excessive resorption of bone with the relative enhancement of osteoclast function. As osteoporosis seriously affects the quality of patients’ life, effective drugs are needed to treat this disease. Based on the combination of network pharmacology and cellular studies, this study aimed to investigate the probable mechanism of Dehydromiltirone (DHT) in the treatment of osteoporosis. Method: The targets of DHT in osteoporosis were searched using the PharmGKB, OMIM, and Genecard platforms. The PPI core targets, and the GO and KEGG enrichment analysis results were obtained using Cytoscape software, and the David and Metascape databases, respectively. The network pharmacology results were also verified via in vitro cellular experiments. Results: Through network pharmacology and docking analysis, we found DHT was involved in peptide tyrosine phosphorylation, cell surface receptor tyrosine kinase signaling pathways, and MAPK signaling pathways. According to the molecular docking results, the binding of DHT to MAPK14 was more stable than other proteins, which suggests that DHT may affect osteoclast formation through the MAPK signaling pathway. Moreover, DHT was found to inhibit the expression of osteoclast-associated genes, including NFATc1, CTSK, c-Fos, Acp5, and MMP9; as well as the phosphorylation of P38, ERK, and JNK of the MAPK signaling pathway; and the degradation of IκB-α of NF-κB signaling pathway. Conclusion: DHT exhibited an anti-osteoclastogenesis effect by reducing the expression of related genes, ultimately inhibiting bone resorption in vitro.

GSK 650394 Inhibits Osteoclasts Differentiation and Prevents Bone Loss via Promoting the Activities of Antioxidant Enzymes In Vitro and In Vivo.

Osteoporosis (OP) is one of the most common bone disorders among the elderly, characterized by abnormally elevated bone resorption caused by formation and activation of osteoblast (OC). Excessive reactive oxygen species (ROS) accumulation might contribute to the formation process of OC as an essential role. Although accumulated advanced treatment target on OP have been proposed in recent years, clinical outcomes remain unexcellence attributed to severe side effects. The purpose of present study was to explore the underlying mechanisms of GSK 650394 (GSK) on inhibiting formation and activation of OC and bone resorption in vitro and in vivo. GSK could inhibit receptor activator of nuclear-κB ligand (RANKL-)-mediated Oc formation via suppressing the activation of NF-κB and MAPK signaling pathways, regulating intracellular redox status, and downregulate the expression of nuclear factor of activated T cells c1 (NFATc1). In addition, quantitative RT-PCR results show that GSK could suppress the expression of OC marker gene and antioxidant enzyme genes. Consistent with in vitro cellular results, GSK treatment improved bone density in the mouse with ovariectomized-induced bone loss according to the results of CT parameters, HE staining, and Trap staining. Furthermore, GSK treatment could enhance the capacity of antioxidant enzymes in vivo. In conclusion, this study suggested that GSK could suppress the activation of osteoclasts and therefore maybe a potential therapeutic reagent for osteoclast activation-related osteoporosis.

Investigation of bone invasion and underlying mechanisms of oral cancer using a cell line-derived xenograft model.

The cancer stroma regulates bone invasion in oral squamous cell carcinoma (OSCC). However, data on normal stroma are limited. In the present study, the effects of gingival and periodontal ligament tissue-derived stromal cells (G-SCs and P-SCs, respectively) and human dermal fibroblasts (HDFs) on bone resorption and osteoclast activation were assessed using hematoxylin and eosin and tartrate-resistant acid phosphatase staining in a cell line-derived xenograft model. The results demonstrated that G-SCs promoted bone invasion and osteoclast activation and inhibited osteoclast proliferation following crosstalk with the human OSCC HSC-3 cell line, whereas P-SCs inhibited bone resorption and promoted osteoclast proliferation in vitro but had a minimal effect on osteoclast activation both in vitro and in vivo following crosstalk with HSC-3 cells. Furthermore, the effects of G-SCs, P-SCs and HDFs on protein expression levels of matrix metalloproteinase (MMP)-9, membrane type 1 MMP (MT1-MMP), Snail, parathyroid hormone-related peptide (PTHrP) and receptor activator of NF-κB ligand (RANKL) in HSC-3 cells in OSCC bone invasion regions were assessed using immunohistochemistry. The results demonstrated that G-SCs had a more prominent effect on the expression of MMP-9, MT1-MMP, Snail, PTHrP, and RANKL, whereas P-SCs only promoted RANKL and PTHrP expression and exerted a minimal effect on MMP-9, MT1-MMP and Snail expression. The potential genes underlying the differential effects of G-SCs and P-SCs on bone invasion in OSCC were evaluated using a microarray, which indicated that cyclin-dependent kinase 1, insulin, aurora kinase A, cyclin B1 and DNA topoisomerase II alpha underlaid these differential effects. Therefore, these results demonstrated that G-SCs promoted bone invasion in OSCC by activating osteoclasts on the bone surface, whereas P-SCs exerted an inhibitory effect. These findings could indicate a potential regulatory mechanism for bone invasion in OSCC.

Contribution of diabetes mellitus to periodontal inflammation during orthodontic tooth movement.

This study aims to clarify the effects of diabetes mellitus (DM) on inflammatory profile during orthodontic tooth movement (OTM) and explore potential mechanisms. OTM models were established in healthy (Ctrl) and DM rats for 0, 3, 7 or 14 days. The tooth movement distance and bone structural parameters were analyzed through micro-CT. The bone resorption activity and periodontal inflammation status were evaluated through histological staining. RNA sequencing was performed to detect differentially expressed genes in force loading-treated periodontal ligament fibroblasts (PDLFs) with or without high glucose. The differential expression of inflammatory genes associated with NOD-like receptor family pyrin domain containing 3 (NLRP3) between groups was tested in vitro and in vivo. DM caused remarkable reduction of alveolar bone height and density around the moved tooth, corresponding with the higher bone resorption activity and inflammatory scores of DM group. For force loading-treated PDLFs, high glucose induced the activation of inflammatory pathways, including NLRP3. Elevated expression of NLRP3 and cascade molecules (Caspase-1, GSDMD, and IL-1β) were validated by RT-qPCR, Western blot, and immunohistochemistry staining. DM alters the inflammatory status of periodontium and affects tissue reconstruction during OTM. NLRP3 inflammasome may involve in diabetes-induced periodontal changes.

Analysis of Osteoclasts and Root Resorption in Corticotomy-Facilitated Orthodontics with Ibuprofen Administration-An Animal Study.

Following corticotomy surgery, patients experience moderate to severe post-operative pain that necessitates prescriptions of analgesics. The prostaglandin inhibitory effect of ibuprofen influences the mobility of teeth during orthodontic treatment. This study aimed to determine how ibuprofen affects histological reactions and dental root resorption during orthodontic tooth movement aided by corticotomy. Forty-two male Wistar rats were divided into three groups by random selection: (1) control group, (2) corticotomy group (CO), and (3) corticotomy with 0.6 mL of 15 mg/kg ibuprofen group (CI). On each buccal and palatal alveolar bone, two decortication points were made. Orthodontic tooth movement was induced on the maxillary first molar for 21 days utilizing a NiTi-closed coil spring with 10 g of force. Hematoxylin and eosin were used to prepare and stain the histological sections. The numbers of osteoclasts on days 0, 7, 14, and 21 were determined, and the root resorption area on days 0 and 21 was measured. Compared to the control group, the osteoclast counts in the CO and CI groups were considerably greater (p < 0.002). No significant differences were observed between the CO and CI groups in the numbers of osteoclasts or the percentages of root resorption (p > 0.05). The amounts of osteoclast activity and root resorption were unaffected by the administration of ibuprofen in corticotomy-facilitated tooth movement.

Anti‑osteoclastogenic effects of Coriandrum sativumL. via the NF‑κB and ERK‑mediated NFATc1 signaling pathways.

Coriandrum sativumL. (CSL) is an aromatic plant that belongs to the Apiaceae family. The present study aimed to determine the effects of the ethanol extract of the aerial part of CSL on osteoclast formation invitro and invivo, and the underlying molecular mechanism of its anti‑osteoclastogenic effect. The levels of osteoclast formation and bone resorption were evaluated by tartrate‑resistant acid phosphatase staining and bone resorption pit assays. The expression levels of osteoclast‑related molecules were analyzed by reverse transcription‑quantitative PCR and western blotting. The ethanol extract of CSL suppressed osteoclast formation in a mouse co‑culture system. In osteoblasts, CSL exerted a minor effect on the mRNA ratio of receptor activator of nuclear factor‑κB (NF‑κB) ligand (RANKL) to osteoprotegerin, suggesting a direct effect of CSL on osteoclast precursors. Notably, CSL inhibited RANKL‑induced osteoclast differentiation and bone resorption activity in bone marrow‑derived macrophage cultures. Mechanistically, CSL abolished RANKL‑induced NF‑κB and extracellular signal‑regulated kinase (ERK) MAPK activation, which effectively impaired the induction of c‑Fos and nuclear factor of activated Tcells (NFATc1). Finally, the ethanol extract of CSL prevented osteoclast formation in a lipopolysaccharide‑induced calvarial bone loss model invivo. The findings of the present study suggested that CSL may suppress osteoclast differentiation and function by downregulating the NF‑κB and ERK/c‑Fos/NFATc1 signaling pathways. Thus, CSL could be explored as a potential candidate for the prevention and treatment of osteolytic diseases.

Thiaplakortone B attenuates RANKL‐induced NF‐κB and MAPK signaling and dampens OVX‐induced bone loss in mice

Osteoclasts play an important role in maintaining the relative stability of bone mass. Abnormal number and function of osteoclasts are closely related to osteoporosis and osteolytic diseases. Thiaplakortone B (TPB), a natural compound derived from the Great Barrier Reef sponge Plakortis lita, has been reported to inhibit the growth of the malaria parasite, Plasmodium falciparum, but its effect on osteoclastogenesis has not been previously investigated. In our study, we found that TPB suppresses the receptor activator of nuclear factor‐κB (NF-κB) ligand (RANKL)-induced osteoclast formation and resorption activity by tartrate‐resistant acid phosphatase (TRAcP) staining, immunofluorescence staining of F-actin belts and hydroxyapatite resorption assay. Furthermore, using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting analysis, we discovered that TPB inhibits osteoclast-specific genes and proteins expression. Mechanistically, TPB blocks multiple upstream pathways including calcium oscillation, NF‐κB, mitogen-activated protein kinase (MAPK) and nuclear factor of activated T cells 1(NFATc1) signaling pathways. In vivo, TPB could dampen bone loss in an ovariectomy (OVX) mouse model by micro-CT assessment and histological staining. Therefore, TPB may serve as a potential therapeutic candidate for the treatment of osteoporosis and osteolysis.

Zebrafish mutants reveal unexpected role of Lrp5 in osteoclast regulation.

Low-density Lipoprotein Receptor-related Protein 5 (LRP5) functions as a co-receptor for Wnt ligands, controlling expression of genes involved in osteogenesis. In humans, loss-of-function mutations in LRP5 cause Osteoporosis-Pseudoglioma syndrome, a low bone mass disorder, while gain-of-function missense mutations have been observed in individuals with high bone mass. Zebrafish (Danio rerio) is a popular model for human disease research, as genetic determinants that control bone formation are generally conserved between zebrafish and mammals. We generated lrp5- knock-out zebrafish to study its role in skeletogenesis and homeostasis. Loss of lrp5 in zebrafish leads to craniofacial deformities and low bone mineral density (total body and head) at adult ages. To understand the mechanism and consequences of the observed phenotypes, we performed transcriptome analysis of the cranium of adult lrp5 mutants and siblings. Enrichment analysis revealed upregulation of genes significantly associated with hydrolase activity: mmp9, mmp13a, acp5a. acp5a encodes Tartrate-resistant acid phosphatase (TRAP) which is commonly used as an osteoclast marker, while Matrix metalloprotease 9, Mmp9, is known to be secreted by osteoclasts and stimulate bone resorption. These genes point to changes in osteoclast differentiation regulated by lrp5. To analyze these changes functionally, we assessed osteoclast dynamics in mutants and observed increased TRAP staining, significantly larger resorption areas, and developmental skeletal dysmorphologies in the mutant, suggesting higher resorptive activity in the absence of Lrp5 signaling. Our findings support a conserved role of Lrp5 in maintaining bone mineral density and revealed unexpected insights into the function of Lrp5 in bone homeostasis through moderation of osteoclast function.

Wnt5a-Ror2 signaling mediates root resorption

This study aimed to investigate the role of wingless-type MMTV integration site family member 5a (Wnt5a)-receptor tyrosine kinase-like orphan receptor 2 (Ror2) signaling in root resorption. The messenger RNA (mRNA) expression of Wnt5a, Ror2, and RANKL in periodontal ligament cells (PDLCs) under compression force (CF) with or without Ror2 small interfering RNA (siRNA) were measured by quantitative reverse transcription-polymerase chain reaction, and these proteins released into culture supernatants were measured using enzyme-linked immunosorbent assay. Then these PDLC-conditioned media under CF with or without Ror2 siRNA were used to culture osteoclast precursors to detect osteoclastogenesis effects via tartrate-resistant acid phosphatase staining. In invivo studies, the odontoclast number and the root resorption volume under excessive CF with or without Ror2 siRNA were investigated by tartrate-resistant acid phosphatase immunohistochemical staining and microcomputed tomography. The protein levels for Wnt5a, Ror2, and receptor activator of nuclear factor-kappa B ligand (RANKL) in the periodontal ligament tissues were also detected using immunohistochemical staining. Finally, the odontoclast number, root resorption volume, and the mRNA and protein expressions were compared between immature and mature teeth. The mRNA production and protein release level of Wnt5a, Ror2, and RANKL increased after CF, whereas they were significantly downregulated with Ror2 siRNA. The osteoclast number increased treating with culture medium from PDLC applying CF, but the increase was inhibited after adding Ror2 siRNA. In the animal model, the odontoclast number and root resorption volume significantly increased in the CF group but decreased in the CF with the Ror2 siRNA group. The protein levels of Wnt5a, Ror2, and RANKL in periodontal ligament were upregulated under excessive CF, and the pathway was inhibited with Ror2 siRNA. In the immature tooth group, the odontoclast number, root resorption volume, and the mRNA and protein expressions of Wnt5a-Ror2 signaling were reduced. Wnt5a-Ror2 signaling in PDLCs enhanced by excessive CF could promote RANKL release and induce precursor differentiation, partly leading to increased odontoclast activity and ultimate root resorption. The less resorption of the immature tooth may be due to odontoclastogenesis inhibition by decreased expression of Wnt5a-Ror2 signaling.

LIM Homeobox Transcription Factor 1-β Expression is Upregulated in Patients with Osteolysis after Total Ankle Arthroplasty and Inhibits Receptor Activator of Nuclear Factor-κB Ligand-Induced Osteoclast Differentiation in Vitro.

BackgroundOsteolysis is one of the most common problems that occurs after total hip and knee arthroplasty and has recently become a significant problem after total ankle arthroplasty (TAA). In this study, we investigated the role of LIM homeobox transcription factor 1-β (Lmx1b) in osteoclast differentiation. By evaluating the expression profiles associated with osteolysis following TAA treatment, Lmx1b was found to be differentially expressed in patients with osteolysis after TAA.MethodsTo identify the important genes associated with osteolysis after TAA, RNA sequencing was performed by analyzing 8 patient samples: 5 primary TAA samples (control group) and 3 TAA samples revised for flexion instability (osteolysis group). By analyzing the differentially expressed genes and gene ontologies, Lmx1b expression was found to be upregulated in the osteolysis group compared to that in the control group. Focusing on the role of Lmx1b in bone cells, Lmx1b was overexpressed by a retrovirus in osteoclast precursor cells. The cultured cells were stained with tartrate-resistant acid phosphatase, and the expression of osteoclast-related genes was analyzed using real-time polymerase chain reaction.ResultsLmx1b overexpression in osteoclast precursors suppresses osteoclast formation and resorptive activity. The expression of osteoclast marker genes was significantly reduced during osteoclast differentiation by Lmx1b overexpression. Furthermore, Lmx1b is associated with nuclear factor of activated T cells 1 (NFATc1) and inhibited NFATc1 translocation into the nucleus.ConclusionsThese results provide novel insights into the anti-bone resorptive effect of Lmx1b on osteolysis after TAA and may lead to the development of effective preventative and therapeutic strategies for peri-implant osteolysis.

Anti-Osteoclast Effect of Exportin-1 Inhibitor Eltanexor on Osteoporosis Depends on Nuclear Accumulation of IκBα-NF-κB p65 Complex.

Osteoporosis affects around 200 million people globally, with menopausal women accounting for the bulk of cases. In the occurrence and development of osteoporosis, a key role is played by osteoclasts. Excessive osteoclast-mediated bone resorption activity reduces bone mass and increases bone fragility, resulting in osteoporosis. Thus, considerable demand exists for designing effective osteoporosis treatments based on targeting osteoclasts. Eltanexor (Elt; KPT-8602) is a selective nuclear-export inhibitor that covalently binds to and blocks the function of the nuclear-export protein exportin-1 (XPO1), which controls the nucleus-to-cytoplasm transfer of certain critical proteins related to growth regulation and tumor suppression, such as p53, IκBα [nuclear factor-κB (NF-κB) inhibitor α] and FOXO1; among these proteins, IκBα, a critical component of the NF-κB signaling pathway that primarily governs NF-κB activation and transcription. How Elt treatment affects osteoclasts remains poorly elucidated. Elt inhibited the growth and activity of RANKL-induced osteoclasts in vitro in a dose-dependent manner, and Elt exerted no cell-killing effect within the effective inhibitory concentration. Mechanistically, Elt was found to trap IκBα in the nucleus and thus protect IκBα from proteasome degradation, which resulted in the blocking of the translocation of IκBα and NF-κB p65 and the consequent inhibition of NF-κB activity. The suppression of NF-κB activity, in turn, inhibited the activity of two transcription factors (NFATc1 and c-Fos) essential for osteoclast formation and led to the downregulation of genes and proteins related to bone resorption. Our study thus provides a newly identified mechanism for targeting in the treatment of osteoporosis.