Bone Loss In Conditions Research Articles

Exosome-guided bone targeted delivery of Antagomir-188 as an anabolic therapy for bone loss

The differentiation shift from osteogenesis to adipogenesis of bone marrow mesenchymal stem cells (BMSCs) characterizes many pathological bone loss conditions. Stromal cell-derived factor-1 (SDF1) is highly enriched in the bone marrow for C-X-C motif chemokine receptor 4 (CXCR4)-positive hematopoietic stem cell (HSC) homing and tumor bone metastasis. In this study, we displayed CXCR4 on the surface of exosomes derived from genetically engineered NIH-3T3 cells. CXCR4+ exosomes selectively accumulated in the bone marrow. Then, we fused CXCR4+ exosomes with liposomes carrying antagomir-188 to produce hybrid nanoparticles (NPs). The hybrid NPs specifically gathered in the bone marrow and released antagomir-188, which promoted osteogenesis and inhibited adipogenesis of BMSCs and thereby reversed age-related trabecular bone loss and decreased cortical bone porosity in mice. Taken together, this study presents a novel way to obtain bone-targeted exosomes via surface display of CXCR4 and a promising anabolic therapeutic approach for age-related bone loss.

Regulation of Osteoclast Differentiation and Activity by Lipid Metabolism.

Bone is a dynamic tissue and is constantly being remodeled by bone cells. Metabolic reprogramming plays a critical role in the activation of these bone cells and skeletal metabolism, which fulfills the energy demand for bone remodeling. Among various metabolic pathways, the importance of lipid metabolism in bone cells has long been appreciated. More recent studies also establish the link between bone loss and lipid-altering conditions—such as atherosclerotic vascular disease, hyperlipidemia, and obesity—and uncover the detrimental effect of fat accumulation on skeletal homeostasis and increased risk of fracture. Targeting lipid metabolism with statin, a lipid-lowering drug, has been shown to improve bone density and quality in metabolic bone diseases. However, the molecular mechanisms of lipid-mediated regulation in osteoclasts are not completely understood. Thus, a better understanding of lipid metabolism in osteoclasts can be used to harness bone cell activity to treat pathological bone disorders. This review summarizes the recent developments of the contribution of lipid metabolism to the function and phenotype of osteoclasts.

Low bone mineral density in HIV-positive young Italians and migrants.

Human immunodeficiency virus (HIV) infected individuals may have osteoporosis. We aimed to evaluate the bone mineral density (BMD) in naïve antiretroviral (ARV) treated HIV positive patients comparing native Italian group (ItG) to a Migrants group (MiG) upon arrival in Italy. We conducted a cross-sectional study on 83 HIV patients less than 50 years old. We used the dual-energy X-ray absorptiometry (DXA) within six months from the HIV diagnosis. Participants were categorized as having low BMD if the femoral neck or total lumbar spine Z-score was- 2 or less. MiG showed low BMD more often than ItG (37.5% vs.13.6%), especially for the female gender (16.7% vs. 0.0%). A low CD4 rate (<200 cells/μl) was most often detected in MiG than ItG. In particular, we found most often male Italians with abnormal CD4 than male migrants (67.8% vs. 33.3%) and vice versa for females (30.5% vs. 66.7%). We found an abnormal bone mineral density at the lumbar site. Low BMD at the lumbar site was more frequently observed in female migrants than female Italians. Both male and female migrants had a Z-score value significantly lower than male and female Italians, respectively. By logistic regression low vitamin-D level was positively correlated to low BMD in ItG only. All data were verified and validated using a triple code identifier. Both DXA and vitamin-D evaluation should be offered after the diagnosis of HIV infection. Lumbar site low BMD is an initial condition of bone loss in HIV young patients, especially in female migrants. Vitamin D levels and supplementation may be considered after HIV diagnosis independently of age to improve bone health. This study evaluates the frequency of bone mineral density in HIV positive patients naive to antiretroviral therapy. It compares the density of the native Italian population with that of HIV Migrants upon arrival in Italy. The results show that HIV positive migrants, even if younger than 50 years of age, are at risk for osteoporosis, especially if they are female.

Risk Factors for Tooth Loss in Patients Undergoing Mid-Long-Term Maintenance: A Retrospective Study.

In this retrospective study, we identified risk factors for tooth loss in patients undergoing mid–long-term maintenance therapy. We surveyed 674 maintenance patients for ≥5 years after active treatment who visited a dental clinic between January 2015 and December 2016. Of these, 265 were men (mean age 54.6 ± 8.0 years old) and 409 were women (mean age 54.0 ± 7.9 years old). Study variables included patient compliance, sex, number of teeth lost, cause of tooth loss (dental caries, periodontal disease, root fracture, others, vital or non-vital teeth), age at start of maintenance, number of remaining teeth at start of maintenance, smoking, use of salivary secretion inhibitors, presence of diabetes mellitus, condition of periodontal bone loss, and use of a removable denture. Most lost teeth were non-vital teeth (91.7% of all cases) and the most common cause of tooth loss was tooth fracture (62.1% of all cases). A statistically significant risk factors for tooth loss was number of remaining teeth at the start of maintenance (p = 0.003).

Guidance for the assessment and management of prostate cancer treatment-induced bone loss. A consensus position statement from an expert group

Context and objectiveIncidence of prostate cancer (PC) is increasing, but androgen deprivation therapy (ADT) and other therapies are substantially improving survival. In this context, careful consideration of skeletal health is required to reduce the risk of treatment-related fragility fractures and their associated morbidity and mortality. This risk is currently not well-managed. ADT causes significant loss of bone mineral density (BMD). In the metastatic setting, systemic treatments (e.g. chemotherapy, abiraterone, enzalutamide) are used alongside ADT and may require concomitant glucocorticoids. Both ADT and glucocorticoids pose significant challenges to skeletal health in a population of patients already likely to have ongoing age-related bone loss and/or comorbid conditions. Current PC guidelines lack specific recommendations for optimising bone health. This guidance presents evidence for assessment and management of bone health in this population, with specific recommendations for clinical practitioners in day-to-day PC management. MethodsStructured meetings of key opinion leaders were integrated with a systematic literature review. Input and endorsement was sought from patients, nursing representatives and specialist societies. Summary of guidanceAll men starting or continuing long-term ADT should receive lifestyle advice regarding bone health. Calcium/vitamin D supplementation should be offered if required. Fracture risk should be calculated (using the FRAX® tool), with BMD assessment included where feasible. BMD should always be assessed where fracture risk calculated using FRAX® alone is close to the intervention threshold. Intervention should be provided if indicated by local or national guidelines e.g. UK National Osteoporosis Guideline Group (NOGG) thresholds. Men requiring bone protection therapy should be further assessed (e.g. renal function), with referral to specialist centres if available and offered appropriate treatment to reduce fracture risk. Those near to, but below an intervention threshold, and patients going on to additional systemic therapies (particularly those requiring glucocorticoids), should have FRAX® (including BMD) repeated after 12–18 months. Patient summaryModern treatments for prostate cancer have led to significant improvements in survival and quality of life. However, some of these treatments may lead to weakening of patient’s bones with risk of fracture and it is therefore important to monitor patients’ bone health and provide bone protection where needed. This paper provides specific guidance to clinical teams, based on the most recent research evidence, to ensure optimal bone health in their patients.

CD39 Produced from Human GMSCs Regulates the Balance of Osteoclasts and Osteoblasts through the Wnt/β-Catenin Pathway in Osteoporosis.

Osteoporosis is a disease in which the density and quality of bone are reduced, causing bones to become weak and so brittle that a fall or even mild stresses can cause a fracture. Current drug treatment consists mainly of antiresorptive agents that are unable to stimulate new bone formation. Our recent studies have defined a critical role of gingiva-derived mesenchymal stem cells (GMSCs) in attenuating autoimmune arthritis through inhibition of osteoclast formation and activities, but it remains to be ruled out whether the administration of GMSCs to patients with osteoporosis could also regulate osteoblasts and eventually affect bone formation and protection. With the use of an ovariectomized mouse model, we here demonstrated that adoptive transfer of GMSCs regulated the balance of osteoclasts and osteoblasts, eventually contributing to dynamic bone formation. Validation by RNA sequencing (RNA-seq), single-cell sequencing, revealed a unique population of CD39+ GMSC that plays an important role in promoting bone formation. We further demonstrated that CD39 produced from GMSC exerted its osteogenic capacity through the Wnt/β-catenin pathway. Our results not only establish a previously unidentified role and mechanism of GMSC for bone promotion but also a potential therapeutic target for management of patients with osteoporosis and other bone loss conditions.

The Study of Cellular Mechanism of Triptolide in the Treatment of Cancer, Bone Loss and Cardiovascular Disease and Triptolide’s Toxicity

Triptolide (TPL), the active component of Tripterygium wilfordii Hook F (Twhf) has been used to treat cancer and bone loss conditions for over two hundred years in traditional Chinese medicine (TCM). In this paper, we reviewed the specific molecular mechanisms in the treatment of cancer, bone loss and cardiovascular disease. In addition, we analyze the toxicity of TPL and collect some optimized derivatives extracted from TPL. Although positive results were obtained in most cell culture and animal studies, further studies are needed to substantiate the beneficial effects of TPL.

Hyperbaric Oxygen Therapy Improves the Osteogenic and Vasculogenic Properties of Mesenchymal Stem Cells in the Presence of Inflammation In Vitro.

Hyperbaric oxygen (HBO) therapy has been reported to be beneficial for treating many conditions of inflammation-associated bone loss. The aim of this work was to in vitro investigate the effect of HBO in the course of osteogenesis of human Mesenchymal Stem Cells (MSCs) grown in a simulated pro-inflammatory environment. Cells were cultured with osteogenic differentiation factors in the presence or not of the pro-inflammatory cytokine Tumor Necrosis Factor-α (TNF-α), and simultaneously exposed daily for 60 min, and up to 21 days, at 2,4 atmosphere absolute (ATA) and 100% O2. To elucidate osteogenic differentiation-dependent effects, cells were additionally pre-committed prior to treatments. Cell metabolic activity was evaluated by means of the MTT assay and DNA content quantification, whereas osteogenic and vasculogenic differentiation was assessed by quantification of extracellular calcium deposition and gene expression analysis. Metabolic activity and osteogenic properties of cells did not differ between HBO, high pressure (HB) alone, or high oxygen (HO) alone and control if cells were pre-differentiated to the osteogenic lineage. In contrast, when treatments started contextually to the osteogenic differentiation of the cells, a significant reduction in cell metabolic activity first, and in mineral deposition at later time points, were observed in the HBO-treated group. Interestingly, TNF-α supplementation determined a significant improvement in the osteogenic capacity of cells subjected to HBO, which was not observed in TNF-α-treated cells exposed to HB or HO alone. This study suggests that exposure of osteogenic-differentiating MSCs to HBO under in vitro simulated inflammatory conditions enhances differentiation towards the osteogenic phenotype, providing evidence of the potential application of HBO in all those processes requiring bone regeneration.

The effect of implant neck microthread design on stress distribution of peri-implant bone with different level: A finite element analysis

Background/purposeSignificant research has proposed that the implant with microthread in the neck can significantly reduce marginal bone loss, but whether it is consistent in the condition of marginal bone loss is still unknown. The objective of this study is to investigate the effect of microthread on stress distribution in peri-implant bone with different bone level using finite element analysis. Materials and methodsA series of computational models of mandible segments with different bone resorption and implant models with or without microthread in the neck was installed by computer-aided design software. The simulated occlusal force of 150N was applied buccolingually on the top center point of implant. The FEA was performed, and the von Mises stress, principal stress and shear stress in peri-implant bone were recorded and analyzed. ResultsIn all models, the T-neck group exhibits higher von Mises stress and principal stress, as well as lower shear stress than S-neck group. Three types of stresses increase with the depth of bone resorption developed, but the differences of shear stress between two groups of implants were gradually decreased. ConclusionThe micro-thread design in implant neck can reduce marginal bone loss by decreasing shear stress in peri-implant bone, but this effect is gradually weakened with the decline of the marginal bone level.

A retrospective study on ultra-wide diameter dental implants for immediate molar replacement.

Although immediate implant placement for single rooted teeth is well documented, the prognosis of ultra-wide implants in molar sockets lacks data. To evaluate the outcome of ultra-wide implants, immediately placed in molar sockets. Patients treated with immediate ultra-wide diameter implants that have been in function for at least 40 months, were invited for a clinical evaluation. A radiograph was taken to measure marginal bone loss. Probing depths as well as plaque and bleeding scores were recorded at the implant and contralateral tooth. Crown and soft tissue dimensions were measured, and patients filled out an OHIP-14 questionnaire. Eighty-five out of 230 patients (37%) were evaluated. Twenty-eight implants received a bone graft to fill the residual space. Average bone loss was 0.19 mm after a mean follow-up of 67 months, with no significant changes over time (P = 0.170). There was no significant difference in bone loss between the maxilla and mandible (P = 0.797), male or female (P = 0.128), smoking and nonsmoking (P = 0.219), grafted and nongrafted sites (P = 0.098), or the different bio-types (P = 0.404). The distal papillae were significantly higher if a contact point was present (P = 0.002). Plaque was more frequent at the contralateral tooth (P < 0.001), but more bleeding on probing was observed around the implants (P = 0.021). Overall, 63.5% of the patients experienced no problems at all. Ultra-wide diameter implants for immediate molar replacement demonstrate little bone loss and stable soft tissue conditions over a 4 to 7-year period.

Evaluation of Alveolar Bone on Dental Implant Treatment using Cone Beam Computed Tomography

Objective: To observe the outcomes of dental implant treatment based on the evaluation of bone conditions using Cone Beam Computed Tomography (CBCT). Material and Methods: A total of 31 dental implants were collected for the present study. Subsequently, mesial and distal bone losses were examined, while buccal and lingual bone thickness were measured at 7 levels. Evaluation and interpretation of CBCT results was performed by 3 independent examiners. Results: The average of mesial bone loss was 1.08 mm and 1.36 mm on distal bone. Every dental implant had lingual/palatal bone on level 1 to 3, only 1 (6.5%) didn’t have bone on level 4, 3 implants (9.7%) had no bone at level 5 and 6, and 22 implants (74.2%) had no bone at level 7/implant platform. There were 8 implants (25.8%) didn’t have buccal bone at level 7, only 1 implant (3.2%) didn’t have buccal bone at level 2,4,5 and 6, and there were 2 implants (6.5%) had no buccal bone on level 3. Dehiscence / fenestration can be seen on 90% of the implant subjects. Conclusion: These bone loss condition could be consequence of several factors such as infection, diagnosis, treatment plan, and operator’s surgery skills. The implants that placed without CBCT could lead to operator miscalculation on bone condition, therefore in moderate to advanced cases, the use of CBCT should be mandatory for treatment plan.

Glucose dependent miR-451a expression contributes to parathyroid hormone mediated osteoblast differentiation

Parathyroid hormone (PTH; amino acid 1-34, known as teriparatide) has reported promoting differentiation and glucose uptake in osteoblasts. However, how PTH regulates glucose metabolism to facilitate osteoblast differentiation is not understood. Here, we report that PTH promotes glucose dependent miR-451a expression which stimulates osteoblast differentiation. In addition to glucose uptake, PTH suppresses AMPK phosphorylation via PI3K-mTOR-AKT axis thereby preventing phosphorylation and inactivation of octamer-binding transcription factor 1 (OCT-1) which has been reported to act on the promoter region of miR-451a. Modulation of AMPK activity controls miR-451a levels in differentiating osteoblasts. Moreover, pharmacological inhibition of PI3K-mTOR-AKT axis suppressed miR-451a via increased AMPK activity. We report that this glucose regulated miRNA is an anabolic target and transfection of miR-451a mimic induces osteoblast differentiation and mineralization in vitro. These actions were mediated through the suppression of Odd-skipped related 1 (Osr1) and activation of Runx2 transcription. When injected in vivo, the miR-451a mimic significantly increased osteoblastogenesis, mineralization, reversed ovariectomy induced bone loss and improved bone strength. Together, these findings suggest that enhanced osteoblast differentiation associated with bone formation in case of PTH therapy is also a consequence of elevated miR-451a levels via glucose regulation. Consequently, this miRNA has the potential to be a therapeutic target for conditions of bone loss.

Zinc Promotes Osteoblast Differentiation in Human Mesenchymal Stem Cells Via Activation of the cAMP-PKA-CREB Signaling Pathway.

The crucial trace element zinc stimulates osteogenesis in vitro and in vivo. However, the pathways mediating these effects remain poorly understood. This study aimed to investigate the effects of zinc on osteoblast differentiation in human bone marrow-derived mesenchymal stem cells (hBMSCs) and to identify the molecular mechanisms of these effects. In hBMSCs, zinc exposure resulted in a dose-dependent increase in osteogenesis and increased mRNA and protein levels of the master transcriptional factor RUNX2. Analyzing the upstream signaling pathways of RUNX2, we found that protein kinase A (PKA) signaling inhibition blocked zinc-induced osteogenic effects. Zinc exposure increased transcriptional activity and protein levels of phospho-CREB and enhanced translocation of phospho-CREB into the nucleus. These effects were reversed by H-89, a potent inhibitor of PKA. Moreover, zinc exposure led to dose-dependent increases in levels of intracellular cyclic adenosine monophosphate (cAMP). These findings indicate that zinc activates the PKA signaling pathway by triggering an increase in intracellular cAMP, leading to enhanced osteogenic differentiation in hBMSCs. Our results suggest that zinc exerts osteogenic effects in hBMSCs by activation of RUNX2 via the cAMP-PKA-CREB signaling pathway. Zinc supplementation may offer a promise as a potential pharmaceutical therapy for osteoporosis and other bone loss conditions.

Immunoporosis: Immunology of Osteoporosis-Role of T Cells.

The role of immune system in various bone pathologies, such as osteoporosis, osteoarthritis, and rheumatoid arthritis is now well established. This had led to the emergence of a modern field of systems biology called as osteoimmunology, an integrated research between fields of immunology and bone biology under one umbrella. Osteoporosis is one of the most common inflammatory bone loss condition with more than 200 million individuals affected worldwide. T helper (Th) cells along with various other immune cells are major players involved in bone homeostasis. In the present review, we specifically discuss the role of various defined T lymphocyte subsets (Th cells comprising Th1, Th2, Th9, Th17, Th22, regulatory T cells, follicular helper T cells, natural killer T cells, γδ T cells, and CD8+ T cells) in the pathophysiology of osteoporosis. The study of the specific role of immune system in osteoporosis has now been proposed by our group as “immunoporosis: the immunology of osteoporosis” with special emphasis on the role of various subsets of T lymphocytes. The establishment of this new field had been need of the hour due to the emergence of novel roles of various T cell lymphocytes in accelerated bone loss observed during osteoporosis. Activated T cells either directly or indirectly through the secretion of various cytokines and factors modulate bone health and thereby regulate bone remodeling. Several studies have summarized the role of inflammation in pathogenesis of osteoporosis but very few reports had delineated the precise role of various T cell subsets in the pathobiology of osteoporosis. The present review thus for the first time clearly highlights and summarizes the role of various T lymphocytes in the development and pathophysiology of osteoporosis, giving birth to a new field of biology termed as “immunoporosis”. This novel field will thus provide an overview of the nexus between the cellular components of both bone and immune systems, responsible for the observed bone loss in osteoporosis. A molecular insight into the upcoming and novel field of immunoporosis would thus leads to development of innovative approaches for the prevention and treatment of osteoporosis.

Outer-Boundary Assisted Segmentation and Quantification of Trabecular Bones by an Imagej Plugin

Micro-computed tomography (micro-CT) is routinely used to assess bone quantity and trabecular microstructural properties in small animals under different bone loss conditions. However, the standard approach for trabecular analysis of micro-CT images is slice-by-slice semi-automatic hand-contouring, which is labor intensive and error prone. Described here is an efficient method for automatic segmentation of trabecular bones according to the bone's outer boundaries, where trabecular bones can be identified and segmented automatically with accuracy with less operator bias when appropriate segmentation parameters are set. To profile satisfactory segmentation parameters, an image stack of segmentation results is displayed, where all possible combinations of the segmentation parameters are changed one by one in sequence, and segmentation results with associated parameters can easily be visually checked. As a quality-control feature of the plugin, simulated standard objects are quantified where the measured quantities can be compared with theoretical values. Layer-by-layer quantification of trabecular properties and trabecular thicknesses are reported by such a plugin, and the distributions of such properties within the selected regions can be profiled easily. Although layer-by-layer quantification retains more information about trabecular bones and facilitates further statistical analysis of structural changes, such measures are unavailable from the output of current commercial software, where only a single quantified value for each parameter is reported for each sample. Therefore, the described workflows are better approaches for analyzing trabecular bones with accuracy and efficiency.

Outer-Boundary Assisted Segmentation and Quantification of Trabecular Bones by an Imagej Plugin.

Micro-computed tomography (micro-CT) is routinely used to assess bone quantity and trabecular microstructural properties in small animals under different bone loss conditions. However, the standard approach for trabecular analysis of micro-CT images is slice-by-slice semi-automatic hand-contouring, which is labor intensive and error prone. Described here is an efficient method for automatic segmentation of trabecular bones according to the bone's outer boundaries, where trabecular bones can be identified and segmented automatically with accuracy with less operator bias when appropriate segmentation parameters are set. To profile satisfactory segmentation parameters, an image stack of segmentation results is displayed, where all possible combinations of the segmentation parameters are changed one by one in sequence, and segmentation results with associated parameters can easily be visually checked. As a quality-control feature of the plugin, simulated standard objects are quantified where the measured quantities can be compared with theoretical values. Layer-by-layer quantification of trabecular properties and trabecular thicknesses are reported by such a plugin, and the distributions of such properties within the selected regions can be profiled easily. Although layer-by-layer quantification retains more information about trabecular bones and facilitates further statistical analysis of structural changes, such measures are unavailable from the output of current commercial software, where only a single quantified value for each parameter is reported for each sample. Therefore, the described workflows are better approaches for analyzing trabecular bones with accuracy and efficiency.

Identification of novel microRNA inhibiting actin cytoskeletal rearrangement thereby suppressing osteoblast differentiation.

We report the role of miR-1187 in regulation of osteoblast functions. Over-expression of miR-1187 inhibited osteoblast differentiation. Target prediction analysis tools and experimental validation by luciferase 3' UTR reporter assay identified BMPR-II and ArhGEF-9 as direct targets of miR-1187. ArhGEF-9 activates Cdc42 which has a major role in actin reorganization. BMP-2 also induces actin polymerization. Role of miR-1187 in actin reorganization was determined by western blotting, immunofluorescence, and in vivo gene silencing studies. Reduced protein levels of BMPR-II, activated Cdc42, and downstream signaling molecules were observed in miR-1187-transfected osteoblasts. miR-1187 over-expression resulted in decreased actin polymerization. Additionally, P-cofilin, which does not bind F-actin, was decreased in miR-1187-transfected cells. These results were corroborated by administration of BMPR-II exogenously in miR-1187-transfected osteoblasts. Silencing of miR-1187 in neonatal mice mitigated all the inhibitory effects of miR-1187 on actin cytoskeletal rearrangement. Importantly, in vivo treatment of miR-1187 inhibitor to ovariectomized BALB/c mice led to significant improvement in trabecular bone microarchitecture. Overall, miR-1187 functions as a negative regulator of osteogenesis by repressing BMPR-II and ArhGEF-9 expression thus suppressing non-Smad BMP2/Cdc42 signaling pathway and inhibiting actin reorganization. miR-1187 functions as a negative regulator of osteogenesis by repressing BMPR-II expression, which in turn, suppresses non-Smad BMP2/Cdc42 signaling pathway, thus inhibiting actin cytoskeletal rearrangement. Silencing of miR-1187 significantly improves trabecular bone microarchitecture. As miR-1187 exerts a negative regulatory role in osteoblasts function, hence, we propose that therapeutic approaches targeting miR-1187 could be useful in enhancing the bone formation and treatment of pathological conditions of bone loss.

New Strategies for the Prevention and Treatment of Bone Loss - From Mechanical Loading Point of View.

In contemporary society, a large number of adults experience more or less decrease in bone mass or bone density. It is known that bone, in response to mechanical loading, undergoes continuous remodeling throughout life, which helps in the growth and maintenance of the skeleton. Since mechanical loading acts as an important stimulus for bone growth and maintenance, it can be used as a strategy to prevent and treat the conditions of bone loss. This review summarizes the current knowledge about the effects of mechanical loading on bone, in the level of cells and tissue.

Efficacy of anti-IL-23 monotherapy versus combination therapy with anti-IL-17 in estrogen deficiency induced bone loss conditions.

Recent studies have identified that Interleukin (IL)-23/IL-17 axis plays crucial role in pathogenesis of inflammation and bone destruction. IL-23 is thought to promote joint destruction in arthritis by stimulating Th17 cells. IL-23 directly mediates bone loss by inducing osteoclastogenesis and receptor activator of kappa B ligand (RANKL) expression in T cells. IL-23 also promotes tartrate-resistant acid phosphatase (TRAP) activity of osteoclast in osteoblast-osteoclast co-culture. The role of IL-23 has not been studied in estrogen deficiency induced bone loss. Here, we study the effect of IL-23 neutralization in ovariectomized (Ovx) estrogen deficient mice on various immune and skeletal parameters. We also determine whether the combination of anti-IL-23 and anti-IL17 has enhanced osteoprotective effects compared to monotherapies. Treatment of anti-IL-23 and its combination with anti-IL-17 suppressed Th17 cell differentiation and promoted development of T regulatory cells. Anti-IL-23 and its combination with anti-IL-17 prevented bone loss. However, the individual monotherapies of anti-IL-23 and anti-IL-17 were more effective than combination therapy. Treatment of IL-17 and IL-23 cytokines to bone marrow stromal cells led to increased differentiation towards osteoblast lineage. Double neutralization of IL-23 and IL-17 might be inhibiting this phenomenon thus producing less potent effects. Our studies thus support bone protective effects of anti-IL-23 and that the monotherapies of neutralizing antibodies against IL-17 and IL-23 may be a more accepted mode of treatment in management of post-menopausal bone loss rather than combination therapy.

Absence of vitamin D receptor in mature osteoclasts results in altered osteoclastic activity and bone loss

Mature osteoclasts express the vitamin D receptor (VDR) and are able to synthesise and respond to 1,25(OH)2D3 via CYP27B1 enzyme activity. Whether vitamin D signalling within osteoclasts is necessary for the regulation of osteoclastic bone resorption in an in vivo setting is unclear. To determine the requirement for the VDR- and CYP27B1-mediated activity in mature osteoclasts, conditional deletion mouse models were created whereby either Vdr or Cyp27b1 gene was inactivated by breeding either Vdrfl/fl or Cyp27b1fl/fl mice with Cathepsin K-Cre transgenic mice (CstkCre) to generate CtskCre/Vdr−/− and CtskCre/Cyp27b1−/− mice respectively. To account for potential CtskCre-meaited off-target deletion of Vdr, Dmp1Cre were also used determine the effect of Vdr deletion in osteocytes. Furthermore, CtskCre/Vdr−/− mice were ovariectomised (OVX) to assess the role of VDR in osteoclasts under bone-loss conditions and bone marrow precursor cells were cultured under osteoclastogenic conditions to assess osteoclast formation. Six-week-old CtskCre/Vdr−/− female mice demonstrated a 15% decrease in femoral BV/TV (p<0.05). In contrast, BV/TV remained unchanged in CtskCre/Cyp27b1−/− mice as well as in Dmp1Cre/VDR−/− mice. When CtskCre/Vdr−/− mice were subjected to OVX, the bone loss that occurred in CtskCre/Vdr−/− was predominantly due to a diminished volume of thinner trabeculae when compared to control levels. These changes in bone volume in CtskCre/Vdr−/− mice occurred without an observable histological change in osteoclast numbers or size. However, while cultured bone marrow-derived osteoclasts from CtskCre/Vdr−/− mice were marginally increased when compared to VDRfl/fl mice, elevated expression of genes such as Cathepsin K, Nfatc1 and VATPase was observed. Collectively, these data indicate that the absence of VDR in mature osteoclasts causes exacerbated bone loss in young mice and during OVX which is associated with enhanced osteoclastic activity and without increased osteoclastogenesis.