Receptor Activator Of Nuclear factor-κB Ligand Research Articles

Immunohistochemical analysis of osteoclastic and osteoblastic activity in ossifying fibroma and juvenile ossifying fibroma: A comparative study.

Cemento-ossifying fibroma (COF) and juvenile ossifying fibroma (JOF) have been considered distinct entities within the category of fibro-osseous lesions. This study aimed to assess osteoblast and osteoclast activity in COF and JOF by investigating bone resorption markers, specifically receptor activator of nuclear factor-kB (RANK), RANK ligand (RANKL), and its inhibitor osteoprotegerin (OPG). A comparative analysis of these markers was performed on all lesions. Immunohistochemistry was employed to evaluate and quantify the expression of these biomarkers in a sample of 20 cases of cemento-ossifying fibroma (COF), 15 cases of psammomatoid juvenile ossifying fibroma (PsJOF), and 10 cases of trabecular juvenile ossifying fibroma (TrJOF). The expression of osteoprotegerin was significantly higher in cemento-ossifying fibroma (33.9±13.0) compared to trabecular juvenile ossifying fibroma (27.3±9.2) and psammatoid ossifying fibroma (25.2±14.9), with the COF showing the highest expression followed by the latter two (p=0.037). There was a higher percentage (80%) of stromal fibroblast cells that showed positive expression of RANKL in cemento-ossifying fibroma (COF) compared to psammomatoid juvenile ossifying fibroma (PsJOF) (33.3%) and trabecular juvenile ossifying fibroma (TrJOF) (30.0%) when considering a positive expression score of 3 (p=0.024). Cemento-ossifying fibroma demonstrated the highest expression of osteoprotegerin and RANKL-positive stromal fibroblast cells, followed by psammomatoid juvenile ossifying fibroma and trabecular juvenile ossifying fibroma. These findings provide valuable insights into the pathogenesis of these lesions.

Osteoporosis management in primary care.

Osteoporosis is the most prevalent bone disease in the US. Once diagnosed, osteoporosis requires ongoing management; therefore, primary care providers are vital in managing both primary and secondary fracture prevention. Safe, efficacious, and economical medications are available, but osteoporosis remains underdiagnosed and undertreated. Bisphosphonates, selective estrogen receptor modulators (raloxifene), conjugated estrogens/bazedoxifene, estrogen therapy/hormone therapy, parathyroid hormone analogues, RANK ligand inhibitors (denosumab), sclerostin inhibitors (romosozumab), and calcitonin are all drugs or drug classes commonly used to treat osteoporosis that are discussed in this article.

Concomitant induction of SLIT3 and microRNA-218–2 in macrophages by toll-like receptor 4 activation limits osteoclast commitment

BackgroundToll-like receptor 4 (TLR4) conducts a highly regulated inflammatory process by limiting the extent of inflammation to avoid toxicity and tissue damage, even in bone tissues. Thus, it is plausible that strategies for the maintenance of normal bone-immunity to prevent undesirable bone damage by TLR4 activation can exist, but direct evidence is still lacking.MethodsOsteoclast precursors (OCPs) obtained from WT or Slit3-deficient mice were differentiated into osteoclast (OC) with macrophage colony-stimulating factor (M-CSF), RANK ligand (RANKL) and lipopolysaccharide (LPS) by determining the number of TRAP-positive multinuclear cells (TRAP+ MNCs). To determine the alteration of OCPs population, fluorescence-activated cell sorting (FACS) was conducted in bone marrow cells in mice after LPS injection. The severity of bone loss in LPS injected WT or Slit3-deficient mice was evaluated by micro-CT analysis.ResultWe demonstrate that TLR4 activation by LPS inhibits OC commitment by inducing the concomitant expression of miR-218–2-3p and its host gene, Slit3, in mouse OCPs. TLR4 activation by LPS induced SLIT3 and its receptor ROBO1 in BMMs, and this SLIT3-ROBO1 axis hinders RANKL-induced OC differentiation by switching the protein levels of C/EBP-β isoforms. A deficiency of SLIT3 resulted in increased RANKL-induced OC differentiation, and the elevated expression of OC marker genes including Pu.1, Nfatc1, and Ctsk. Notably, Slit3-deficient mice showed expanded OCP populations in the bone marrow. We also found that miR-218–2 was concomitantly induced with SLIT3 expression after LPS treatment, and that this miRNA directly suppressed Tnfrsf11a (RANK) expression at both gene and protein levels, linking it to a decrease in OC differentiation. An endogenous miR-218–2 block rescued the expression of RANK and subsequent OC formation in LPS-stimulated OCPs. Aligned with these results, SLIT3-deficient mice displayed increased OC formation and reduced bone density after LPS challenge.ConclusionOur findings suggest that the TLR4-dependent concomitant induction of Slit3 and miR-218–2 targets RANK in OCPs to restrain OC commitment, thereby avoiding an uncoordinated loss of bone through inflammatory processes. These observations provide a mechanistic explanation for the role of TLR4 in controlling the commitment phase of OC differentiation.CNR6qWg43XLt4z6Q5VLfxQVideo

Co-targeting RANK pathway treats and prevents acquired resistance to CDK4/6 inhibitors in luminal breast cancer

The combination of endocrine therapy (ET) and cyclin-dependent kinase 4/6 (CDK4/6) inhibitors (CDK4/6i) was a hallmark in metastatic luminal breast cancer (BC). However, intrinsic and acquired resistance affects long-term efficacy. Here, we study the role of the receptor activator of nuclear factor-κB (RANK) pathway in CDK4/6i resistance. We find that RANK overexpression in luminal BC is associated with intrinsic resistance to CDK4/6i, both invitro and in mouse xenografts, and decreased proliferation rate and chronic interferon (IFN) γ response are highlighted as resistance drivers. Gene expression data from the NeoPalAna CDK4/6i clinical trial, and studies with palbociclib-resistant cell lines, show that RANK is upregulated after treatment with CDK4/6i, supporting a role in acquired resistance. Our study shows that RANK ligand (RANKL) inhibitors can restore sensitivity to CDK4/6i and prevent acquired resistance. On the basis of these findings, we conclude that pharmacological inhibition of the RANK pathway through RANKL blocking could represent an add-on to ET+ CDK4/6i, warranting further clinical studies.

Endocrinology for the hepatologist.

Endocrinology for the hepatologist.

TRPS1 regulates the opposite effect of progesterone via RANKL in endometrial carcinoma and breast carcinoma

Medroxyprogesterone (MPA) has therapeutic effect on endometrial carcinoma (EC), while it could promote the carcinogenesis of breast cancer (BC) by activating receptor activator of NF-kB ligand (RANKL). However, the selective mechanism of MPA in endometrium and breast tissue remains obscure. Multiomics analysis of chromatin immunoprecipitation sequencing (ChIP-seq) and RNA sequencing (RNA-seq) were performed in cell lines derived from endometrial cancer and mammary tumor to screen the differential co-regulatory factors of progesterone receptor (PR). Dual-luciferase assays and ChIP-PCR assays were used to validate the transcriptional regulation. Co-immunoprecipitation (Co-IP) and immunofluorescence assays were carried out to explore molecular interactions between PR, the cofactor transcriptional repressor GATA binding 1 (TRPS1), and histone deacetylase 2 (HDAC2). Subsequently, human endometrial cancer/breast cancer xenograft models were established to investigate the regulation effect of cofactor TRPS1 in vivo. In the current study, we found that MPA downregulated RANKL expression in a time- and dose-dependent manner in EC, while had the opposite effect on BC. Then PR could recruit cofactor TRPS1 to the promoter of RANKL, leading to histone deacetylation of RANKL to repress its transcription in EC, whereas MPA disassociated the PR/TRPS1/HDAC2 complex to enhance RANKL histone acetylation in BC. Therefore, TRPS1, the coregulator recruited by PR played a critical role in the selective mechanism of progesterone in EC and BC and could become a potential candidate for targeted therapy to improve the anticancer effect of MPA on EC and avoid its carcinogenic effect on BC.

Treatment options for postmenopausal osteoporosis

Osteoporosis is a systemic skeletal disease, characterized by a decrease of bone mass and bone quality, with a subsequent reduction of bone strenght and an increased risk of fracture. Hormone Therapy for menopausal women can significantly prevent osteopenia and osteoporosis, thus reducing the fracture risk. The use of HT, according to guidelines, is for postmenopausal women within 10 years since last menstruation or under the age of 60 years. Only HT at standard dose is able to reduce the fracture risk, while low-dose HT can prevent bone loss. Estrogens (with and without the addition of a progestin) and tibolone showed a fracture risk reduction effect. Also Tissue Selective Estrogen Complex (TSEC) can reduce the bone loss in postmenopause. For women without climacteric symptoms (as hot flushes and/or night sweats) the use of Selective Estrogen Receptor Modulators (SERMs) can be indicated, with a reduction of risk of vertebral fracture (for raloxifene and bazedoxifene), and non-vertebral fracture in high-risk women (for bazedoxifene). In more advence ages, antiresoptive agents as Bisphosphonates (Alendronate, Risedronate, Ibandronate and Zoledronate) can reduce the risk of vertebral, non-vertebral and hip fracture risk. Denosumab (DMAB), monoclonal antibobody against Rank-ligand (RANKL), providing an increased bone mass, significantly decreases risk of vertebral, non-vertebral and hip fracture. A drug holiday or treatment interruption is not recommended with DMAB, and DMAB dosing should not stopped without subsequent antiresorptive or other therapy to prevent a "rebound effect" with a possible increased risk of multiple vertebral fracture. Teriparatide (fraction 1-34 of recombinant PTH, administered daily 20 mcg sc) can stimulate osteoblast activity, with an important increase of bone mass and a significant reduction of risk of vertebral fracture, and of multiple vertebral fractures, but also of non-vertebral fragility fracture. Romosozumab (RMZ, adimnistered monlty 210 mg sc), is a bone-forming monoclonal antibody that binds to and inhibits sclerostin, with a dual effect of increasing bone formation and decreasing bone resorption. RMZ has showed to give marked increases in spine and hip bone density after 1 year of administration, also reducing fracture risk. The differences among the various treatments is the basis for the individualization of osteoporosis treatment, according to combination and/or sequential regimens of administration.

CHARLI: A phase Ib/II trial of ipilimumab-nivolumab-denosumab or nivolumab-denosumab in patients with unresectable stage III and IV melanoma.

9525 Background: Denosumab (deno) is an antibody directed against Receptor Activator of NF Kappa-b ligand (RANKL) with established indications as a bone anti-resorptive agent in several cancers. Pre-clinical studies and several case series suggest anti-RANKL can enhance the anti-tumor effect of immune checkpoint inhibitors possibly via modulation of Treg and M2 macrophages. We did a multicentre phase Ib/II trial (NCT03161756) to investigate the safety and efficacy of deno in combination with nivolumab (nivo) or ipilimumab-nivolumab (ipi-nivo). Methods: Patients (pts) with unresectable stage III or IV melanoma were recruited to either Arm A (nivo-deno) or Arm B (ipi-nivo-deno) as first-line therapy. In Arm A pts received nivo 3 mg/kg IV q2 weekly for 4 doses and deno 120 mg SC on D1, D8, D15, D29 and then maintenance nivo 480 mg IV with deno 120 mg SC q 4 weekly. In Arm B pts received combined ipi 3mg/kg with nivo 1 mg/kg IV 3 weekly for 4 doses with deno 120 mg SC on D1, D8, D15, D29 followed by 4 weekly maintenance nivo 480 mg with deno 120 mg. Co-primary endpoints were median PFS and grade 3-4 treatment related adverse events (TRAE) of interest. Secondary endpoints were objective response rate (ORR) and overall survival (OS). Results: 27 pts (15 males, median age 67 years, 48% (13/27) stage IVM1c, 26% elevated LDH, 31% BRAFV600 mutant) were enrolled in Arm A and 24 of 25 evaluable pts (16 males, median age 62, 46% (11/24) stage IVM1c, 13% (3/24) stage IVM1d, 30% elevated LDH and 33% BRAFV600 mutant) were enrolled in Arm B. Median follow up was 30.8 months (m) for Arm A and 24.8 m for Arm B. The RECIST 1.1 ORR was 56% (n=15/27, 15% [4/27] complete responses [CR] and 41% [11/27] partial response [PR]) for Arm A and 71% (17/24, 25% [6/24) CR and 46% [11/24] PR) for Arm B. The median PFS in both arms has not been reached with 12 month PFS rates of 59% (95%CI: 43-81) and 63% (95%CI: 46-88) for Arms A & B, respectively. Grade 3-4 TRAE were 11% (3/27) in Arm A and 71% (17/24) in Arm B. Common TRAE (≥10%) in Arm A was rash (52%), pruritus (30%), fatigue (26%), nausea (19%), diarrhoea/colitis (15%), arthralgia (11%), vitiligo (11%), hyperthyroidism (11%). Common TRAE (≥10%) in Arm B included rash (63%), fatigue (54%), diarrhoea/colitis (54%), hepatitis (46%), hyperthyroidism (29%), pneumonitis (29%), pruritus (25%), increased GGT (17%), hypothyroidism (17%), hypocalcaemia (13%). Arm B G3-4 TRAE included diarrhoea/colitis (25%), pneumonitis (17%) and hepatitis (13%). Conclusions: Nivo-deno and ipi-nivo-deno had numerically similar G3-4 TRAE compared to nivo and ipi-nivo. The median PFS, 12 month PFS and ORR for nivo-deno and ipi-nivo-deno are encouraging compared with CHECKMATE 067. Clinical trial information: NCT03161756 . [Table: see text]

Eribulin mesylate induces bone mass loss by promoting osteoclastic bone resorption in mice

Over the past few decades, the clinical outcomes of patients with cancer have significantly improved mostly owing to the development of effective chemotherapeutic treatments. However, chronic health conditions such as bone mass loss and risk of fragility fractures caused by chemotherapy have also emerged as crucial issues in patients treated for cancer. In this study, we aimed to understand the effect of eribulin mesylate (ERI), a microtubule-targeting agent currently used to treat metastatic breast cancer and certain subtypes of advanced sarcomas, on bone metabolism in mice. The administration of ERI reduced bone mass in mice, mainly by promoting osteoclast activity. Gene expression analysis of skeletal tissues revealed no change in the expression levels of the transcripts for RANK ligand, one of the master regulators of osteoclastogenesis; however, the transcript levels of osteoprotegerin, which neutralizes RANK ligand, were significantly reduced in ERI-treated mice compared with those in vehicle-treated controls, indicating a relative increase in RANK ligand availability after ERI treatment. In line with the increased bone resorption in ERI-treated mice, we found that zoledronate administration effectively suppressed bone loss in these mice. These results reveal a previously unrecognized effect of ERI on bone metabolism and suggest the application of bisphosphonates for patients with cancer undergoing treatment with ERI.

Association of RANKL and EGFR gene expression with bone metastases in patients with metastatic non-small cell lung cancer.

Bone metastases are frequent in patients with non-small cell lung cancer (NSCLC). The receptor activator of Nuclear Factor κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) pathway is important in bone metastases development. Furthermore, epidermal growth factor receptor (EGFR) signaling promotes osteoclast formation and stimulation. The understanding of the biological mechanism of bone metastases development might have implications for treatment strategies. Therefore, we studied whether there is an association between EGFR, RANKL, RANK and OPG gene expression in the tumor and presence of bone metastases in patients with NSCLC. From an updated multicenter study, including patients with EGFR mutated (EGFR+), Kirsten rat sarcoma (KRAS+) and EGFR/KRAS wildtype metastatic NSCLC, all patients with available formalin-fixed paraffin-embedded (FFPE) tumor samples were selected. Ribonucleic Acid (RNA) was isolated from these samples and gene expressions of EGFR, RANKL, OPG and RANKL were determined via quantitative Polymerase Chain Reaction (qPCR). Data on demographics, histology and molecular subtyping, sample origin, presence of bone metastasis, SREs and bone progression were collected. Primary endpoint was relation between EGFR, RANK, RANKL, OPG gene expression, RANKL: OPG ratio and bone metastases. In 73/335 (32% EGFR+, 49% KRAS+, 19% EGFR/KRAS wildtype) samples from unique patients, gene expression analysis could be performed. Of these 73 patients, 46 (63%) had bone metastases at diagnosis or developed bone metastases during the disease course. No association was found between EGFR expression and presence of bone metastases. Patients with bone metastases had a significantly higher RANKL expression and RANKL: OPG ratio compared to those without. An increased RANKL: OPG ratio resulted in a 1.65x increased risk to develop bone metastases, especially in the first 450 days after diagnosis of metastatic NSCLC. Increased RANKL gene expression and RANKL: OPG ratio, but not EGFR expression, was associated with presence of bone metastases. Additionally, an increased RANKL: OPG gene ratio was associated with a higher incidence of bone metastases development.

10 Extra-label bisphosphonate effects on bone turnover biomarkers in juvenile, exercising horses

Bisphosphonates, such as clodronate disodium (CD), modulate bone metabolism and, though their extra-label use in young horses is common, impacts on skeletal development and longevity are unknown. The objective of the current study was to determine the effects of CD use on systemic biomarkers of bone turnover in juvenile, exercising horses. We hypothesized that bone resorption would decrease, and bone formation would increase as a result of CD administration and repeat treatments would have a greater effect. To test this, 32 juvenile Quarter Horses were used in a 168-d trial. Horses were stratified by age (500 ± 13 d), BW (336 ± 26 kg), sex (n = 16 geldings; n = 16 fillies), and initial bone optical density and randomly allocated to one of 4 treatment groups receiving either 1.8 mg/kg BW CD (OSPHOS®) or isovolumetric saline (placebo). Investigators were blinded to treatments which included a control (CON; n = 8), single-dose CD on d 84 (1X; n = 8), 2-doses CD on d 0 and 84 (2X; n = 8), and 4-doses CD on d 0, 42, 84, and 126 (4X; n = 8). Horses were housed individually in stalls (3.6 × 7.3 m), fed 1% BW/d concentrate, and allowed ad libitum access to Coastal bermudagrass hay and water. Horses exercised 5 d/wk using a free stall exerciser with a phase-based progressive workload; phase I (d 0–84) simulated sales preparation and phase II (d 85–168) mimicked an early training program. Blood was collectedon d 0, 42, 84, 126, and 168, before treatment injections on days of administration. Serum was analyzed for receptor activator of nuclear factor kB ligand (RANKL), tartrate resistant acid phosphatase 5b (TRAP5b), c-terminal crosslinks of type I collagen (CTX-1) and bone-specific alkaline phosphatase (BAP) via commercial ELISA or EIA kits. All data were analyzed using PROC MIXED of SAS with a baseline covariate for BAP and BAP:TRAP5b. No differences were seen in osteoclastic differentiation signal RANKL (P ≥ 0.24). In contrast, a treatment × time interaction was noted for osteoclastic TRAP5b (P = 0.03); specifically, TRAP5b decreased in 4X from d 0 to 126 before returning to baseline at d 168 and decreased in 2X at d 84 compared with baseline, while CON and 1X increased or remained the same over time. Concentrations of CTX-1, a type I collagen degradation marker, increased over time (P < 0.01) in all treatments. Likewise, osteoblastic BAP (P < 0.01) and BAP:TRAP5b (P = 0.04) increased from d 42 to 84 and remained elevated until d 168. These results indicate that multiple doses of CD (2X and 4X) over 168 d reduced activity of osteoclasts despite having no measurable effect on bone formation or type I collagen degradation.

Histochemical assessment of osteoclast-like giant cells in Rankl−/− mice

ObjectivesWe examined mice with gene deletion of Receptor activator of nuclear factor-κB (Rank) ligand (Rankl) to histologically clarify whether they contained progenitor cells committed to osteoclastic differentiation up to the stage requiring RANK/RANKL signaling. MethodsThe tibiae and femora of ten-week-old male wild-type, c-fos−/−, and Rankl−/− mice were used for immunohistochemistry and transmission electron microscopy (TEM). ResultsIn Rankl−/− mice, we observed osteoclast-like giant cells, albeit in low numbers, with single or two nuclei, engulfing the mineralized extracellular matrix. TEM revealed that these giant cells contained large numbers of mitochondria, vesicles/vacuoles, and clear zone-like structures but no ruffled borders. They often engulfed fragmented bony/cartilaginous components of the extracellular matrix that had been degraded. Additionally, osteoclast-like giant cells exhibited immunoreactivity for vacuolar H+-ATPase, galectin-3, and siglec-15 but not for tartrate-resistant acid phosphatase, cathepsin K, or MMP-9, all of which are classical hallmarks of osteoclasts. Furthermore, osteoclast-like giant cells were ephrinB2-positive as they were near EphB4-positive osteoblasts that are also positive for alkaline phosphatase and Runx2 in Rankl−/− mice. Unlike Rankl−/− mice, c-fos−/− mice lacking osteoclast progenitors and mature osteoclasts had no ephrinB2-positive osteoclast-like cells or alkaline phosphatase-positive/Runx2-reactive osteoblasts. This suggests that similar to authentic osteoclasts, osteoclast-like giant cells might have the potential to activate osteoblasts in Rankl−/− mice. ConclusionsIt seems plausible that osteoclast-like giant cells may have acquired some osteoclastic traits and the ability to resorb mineralized matrices even when the absence of RANK/RANKL signaling halted the osteoclastic differentiation cascade.

Oncostatin M stimulates prostaglandin D2-induced osteoprotegerin and interleukin-6 synthesis in osteoblasts

Oncostatin M produced by osteal macrophages plays a significant role in fracture healing. Osteoprotegerin (OPG) secreted by osteoblasts, binds to the receptor activator of nuclear factor-κB (RANK) ligand (RANKL) as a decoy receptor and prevents RANKL from binding to RANK, resulting in bone resorption suppression. Interleukin-6 (IL-6) is a pro-inflammatory cytokine and generally regulates bone resorption. However, accumulating evidence suggests that IL-6 plays pivotal roles in bone formation. We previously showed that prostaglandin D2 (PGD2) induces OPG synthesis by activating p38 mitogen-activated protein (MAP) kinase, stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), and p44/p42 MAP kinase in osteoblast-like MC3T3-E1 cells. Furthermore, we demonstrated that PGD2 stimulates IL-6 synthesis by activating p38 MAP kinase and p44/p42 MAP kinase in MC3T3-E1 cells. In the present study, we investigated whether oncostatin M affects PGD2-stimulated OPG and IL-6 synthesis in MC3T3-E1 cells through MAP kinase activation. The osteoblast-like MC3T3-E1 cells and normal human osteoblasts were treated with oncostatin M and subsequently stimulated with PGD2. Consequently, oncostatin M significantly increased the PGD2-stimulated OPG and IL-6 release in both cells. Oncostatin M significantly enhanced mRNA expression levels of OPG and IL-6 induced by PGD2 similarly in both cells. Regarding the signaling mechanism, oncostatin M did not affect the phosphorylation of p38 MAP kinase, SAPK/JNK, and p44/p42 MAP kinase. Our results suggest that oncostatin M upregulates the PGD2-stimulated OPG and IL-6 synthesis in osteoblasts and therefore affects bone remodeling. However, OPG and IL-6 synthesis are not mediated through p38 MAP kinase, p44/p42 MAP kinase, or SAPK/JNK pathways.

Therapeutics of Charcot neuroarthropathy and pharmacological mechanisms: A bone metabolism perspective.

Charcot neuroarthropathy (CN) is a chronic, destructive, and painless damage of the skeletal system that affects the life quality of patients. CN, with an unclear mechanism, is characterized with invasive destruction of bones and a serious abnormality of bone metabolism. Unfortunately, development of an effective prevention and treatment strategy for CN is still a great challenge. Of note, recent studies providing an insight into the molecular mechanisms of bone metabolism and homeostasis have propelled development of novel CN therapeutic strategies. Therefore, this review aims to shed light on the pathogenesis, diagnosis, and treatment of CN. In particular, we highlight the eminent role of the osteoprotegerin (OPG)-receptor activator of nuclear factor-κB (RANK)-RANK ligand (RANKL) system in the development of CN. Furthermore, we summarize and discuss the diagnostic biomarkers of CN as well as the potential pharmacological mechanisms of current treatment regimens from the perspective of bone metabolism. We believe that this review will enhance the current state of knowledge on the diagnosis, prevention, and therapeutic efficacy of CN.

Adverse Effects of Denosumab in Kidney Transplant Recipients: A 20-Year Retrospective Single-Center Observation Study in Central Taiwan

Bone loss can be noted in kidney transplantation recipients (KTRs) and can be related to fracture events. Denosumab, a potent monoclonal antibody to RANK ligand, increases lumbar bone mineral density. However, safety data for denosumab remain limited regarding transplant recipients. Hypocalcemia and increased genital tract infections have been mentioned as adverse effects in KTRs after being prescribed denosumab. We retrospectively analyzed the electronic medical records of KTRs during the recent 20 years who had been prescribed antiresorptive therapy and were >18 years old. Medical records and their clinical data were reviewed and analyzed. We compared the frequency of adverse effects between denosumab with other antiresorptive therapies. A total of 70 KTRs were enrolled, with 46 patients being given denosumab and the first injection being noted on October 31, 2014. No significant differences were seen in mortality rate, opportunistic infection, pneumonia, or genitourinary tract infection. One diagnosis of osteonecrosis of the jaw was noted in the denosumab group (2.2%). A higher incidence of hypocalcemia (<8.4 mg/dL) was noted in the denosumab group (34.8%), and a higher but nonsignificant difference in the incidence of severe hypocalcemia was also noted in the group. Denosumab may be considered as safe as other antiresorptive therapies for KTRs. However, more hypocalcemia events have been noted, so medical personnel may need to be cautious when prescribing its use.

STING-dependent interferon signatures restrict osteoclast differentiation and bone loss in mice

Stimulator of interferon genes (STING) is a key mediator of type-I interferon (IFN-I) signaling in response to a variety of stimuli, but the contribution of STING to homeostatic processes is not fully characterized. Previous studies showed that ligand activation of STING limits osteoclast differentiation invitro through the induction of IFNβ and IFN-I interferon-stimulated genes (ISGs). In a disease model (SAVI) driven by the V154M gain-of-function mutation in STING, fewer osteoclasts form from SAVI precursors in response to receptor activator of NF-kappaB ligand (RANKL) in an IFN-I-dependent manner. Due to the described role of STING-mediated regulation of osteoclastogenesis in activation settings, we sought to determine whether basal STING signaling contributes to bone homeostasis, an unexplored area. Using whole-body and myeloid-specific deficiency, we show that STING signaling prevents trabecular bone loss in mice over time and that myeloid-restricted STING activity is sufficient for this effect. STING-deficient osteoclast precursors differentiate with greater efficiency than wild types. RNA sequencing of wild-type and STING-deficient osteoclast precursor cells and differentiating osteoclasts reveals unique clusters of ISGs including a previously undescribed ISG set expressed in RANKL naïve precursors (tonic expression) and down-regulated during differentiation. We identify a 50 gene tonic ISG signature that is STING dependent and shapes osteoclast differentiation. From this list, we identify interferon-stimulated gene 15 (ISG15) as a tonic STING-regulated ISG that limits osteoclast formation. Thus, STING is an important upstream regulator of tonic IFN-I signatures shaping the commitment to osteoclast fates, providing evidence for a nuanced and unique role for this pathway in bone homeostasis.

The mechanism underlying the remodeling effect of lactoferrin on midpalatal sutures during maxillary expansion and relapse in rats

The remodeling effects of intragastric administration and intramaxillary injection of lactoferrin (LF) on midpalatal sutures (MPS) during maxillary expansion and relapse in rats were studied to explore the underlying bone remodeling mechanism. Using a rat model of maxillary expansion and relapse, rats were treated with LF by intragastric administration (1 g·kg-1·d-1) or intramaxillary injection (5 mg·25 μl-1·d-1). The effects of LF on the osteogenic and osteoclast activities of MPS were observed by microcomputed tomography, histologic staining, and immunohistochemical staining, and the expressions of key factors in the extracellular regulated protein kinase 1/2 (ERK1/2) pathway and osteoprotegerin (OPG)-receptor activator of nuclear factor-KB ligand (RANKL)-receptor activator of nuclear factor-KB (RANK) axis were detected. Compared with the group with maxillary expansion alone, osteogenic activity was relatively enhanced, whereas osteoclast activity was relatively weakened in the groups administered LF, and the phosphorylated-ERK1/2: ERK1/2 and OPG: RANKL expression ratios increased significantly. The difference was more significant in the group administered LF intramaxillary. Administration of LF promoted osteogenic activity at MPS and inhibited osteoclast activity during maxillary expansion and relapse in rats, which may have occurred through regulation of the ERK1/2 pathway and the OPG-RANKL-RANK axis. The efficiency of intramaxillary LF injection was greater than that of intragastric LF administration.

Histopathological response to denosumab in giant cell tumours of bone - A review of 11 cases.

Giant cell tumor (GCT) of the bone is a locally aggressive primary bone tumor, that can rarely metastasize. Arising mostly in epiphysis of the long bones in young adults, the tumor is composed of mononuclear cells that are admixed with osteoclastic giant cells(OLGCs), which express RANK ligand and RANK respectively. Denosumab a monoclonal antibody against RANK ligand has been shown to reduce the tumor by causing bone lysis by inhibiting RANKL. Histological changes in 11 patients of GCT who were treated with denosumab are presented here. Clinical records and slides of 11 patients of GCT who had been administered neoadjuvant denosumab were included in the study. Evaluation of pre and post therapy GCT specimens was performed by two pathologists (RK and VM). There were 4 males and 7 females. Their mean age was 30 years. All the patients received 120 mg denosumab subcutaneously every week with additional 120 mg on days 8 and 15 of therapy. The histological slides were reviewed and following points noted: 1) degree of ossification,2) fibrosis,3) loss of osteoclastic giant cells,4) proliferation of mononuclear cells,5) atypia,6) Permeation of osteoid by malignant cells. Out of 11 cases, 2 cases did not show any significant histological improvement. 7 cases showed reduction in giant cells, increased fibrosis, enhanced mononuclear cell proliferation and ossification consistent with a pathological response. Atypia and osteoid permeation were noted in 2 cases which showed transformation to osteosarcoma. Denosumab treated giant cell tumor show dramatic histological changes. The post therapy lesions may bear no resemblance to pretherapy lesion. There may be complete resolution or may be confused with benign or malignant lesions Rarely they may show sarcomatous transformation. It is imperative that the pathologist is aware of these changes to prevent diagnostic pitfalls as it poses therapeutic and prognostic implications.

Obacunone inhibits RANKL/M-CSF-mediated osteoclastogenesis by suppressing integrin- FAK-Src signaling.

Disrupted osteoblastogenesis or aberrant activation of osteoclastogenesis usually results in the break of bone homeostasis thus causing bone-associated diseases like osteoporosis. Obacunone, as a natural compound present in citrus fruits, has been demonstrated for various biological activities including anti-cancer and anti-inflammatory properties. However, the role of obacunone in regulating osteoclastogenesis has not been elucidated so far. Here, using in vitro cell models of RANKL (Receptor activator of nuclear factor-kB ligand) and M-CSF (Macrophage-colony-stimulating factor)-induced osteoclastogenesis, we showed that obacunone inhibited osteoclast differentiation in RAW264.7 cells and bone marrow macrophages (BMMs), as evidenced by obacunone dose-dependent reduction in numbers of osteoclasts and downregulated expressions of osteoclastogenesis-associated key genes. The anti-osteoclastic properties of obacunone were associated with downregulated expressions of Integrin α1 and attenuated activation of Focal adhesion kinase (FAK) and Steroid receptor coactivator (Src) signaling. Functional Integrin α1 blockade or FAK-Src inhibition suppressed RANKL/M-CSF-induced osteoclastogenesis, while Integrin α1 overexpression or FAK/Src activation partially attenuated obacunone's effects on suppressing RANKL/M-CSF-induced osteoclast differentiation. Furthermore, in vivo administration of obacunone displayed super therapeutic effects in attenuating ovariectomy-induced bone loss in mice, as indicated by decreases in serum biomarkers of bone turnover, restoring of femur fracture maximum force, and reversing of the worsened bone-related parameters in ovariectomized animals. Taken together, these findings demonstrate that obacunone has pharmacological activities to suppress osteoclast differentiation through modulating the Integrin-FAK-Src pathway, and suggest that obacunone is a therapeutic candidate for the treatment and prevention of bone diseases such as osteoporosis.

Muramyl dipeptide alleviates estrogen deficiency-induced osteoporosis through canonical Wnt signaling.

Wnt signaling is a positive regulator of bone formation through the induction of osteoblast differentiation and down-regulation of osteoclast differentiation. We previously reported that muramyl dipeptide (MDP) increases bone volume by increasing osteoblast activity and attenuating osteoclast activity in receptor activator of nuclear factor-κBligand(RANKL)-induced osteoporotic model mice. In this study, we investigated whether MDP could alleviate post-menopausal osteoporosis through Wnt signaling regulation inan ovariectomy (OVX)-induced mouse osteoporosis model. MDP-administered OVX mice exhibited higher bone volume and bone mineral density than mice of the control group. MDP significantly increased P1NP in the serum of OVX mice, implying increased bone formation. The expression of pGSK3β and β-catenin in the distal femur of OVX mice was lower than that in the distal femur of sham-operated mice. Yet, the expression of pGSK3β and β-catenin was increased in MDP-administered OVX mice compared with OVX mice. In addition, MDP increased the expression and transcriptional activity of β-catenin in osteoblasts. MDP inhibited the proteasomal degradation of β-catenin via the down-regulation of its ubiquitination by GSK3β inactivation. When osteoblasts were pretreated with Wnt signaling inhibitors, DKK1 or IWP-2, the induction of pAKT, pGSK3β, and β-catenin was not observed. In addition, nucleotide oligomerization domain-containing protein 2-deficient osteoblasts were not sensitive to MDP. MDP-administered OVX mice exhibited fewer tartrate-resistant acid phosphatase (TRAP)-positive cells than did OVX mice, attributed to a decrease in the RANKL/OPG ratio. In conclusion, MDP alleviates estrogen deficiency-induced osteoporosis through canonical Wnt signaling and could be an effective therapeutic for the treatment of post-menopausal bone loss. © 2023 The Pathological Society of Great Britain and Ireland.