Increased Osteoclast Activity Research Articles

Aging and menopause reprogram osteoclast precursors for aggressive bone resorption

Women gradually lose bone from the age of ~35 years, but around menopause, the rate of bone loss escalates due to increasing bone resorption and decreasing bone formation levels, rendering these individuals more prone to developing osteoporosis. The increased osteoclast activity has been linked to a reduced estrogen level and other hormonal changes. However, it is unclear whether intrinsic changes in osteoclast precursors around menopause can also explain the increased osteoclast activity. Therefore, we set up a protocol in which CD14+ blood monocytes were isolated from 49 female donors (40–66 years old). Cells were differentiated into osteoclasts, and data on differentiation and resorption activity were collected. Using multiple linear regression analyses combining in vitro and in vivo data, we found the following: (1) age and menopausal status correlate with aggressive osteoclastic bone resorption in vitro; (2) the type I procollagen N-terminal propeptide level in vivo inversely correlates with osteoclast resorption activity in vitro; (3) the protein level of mature cathepsin K in osteoclasts in vitro increases with age and menopause; and (4) the promoter of the gene encoding the dendritic cell-specific transmembrane protein is less methylated with age. We conclude that monocytes are “reprogrammed” in vivo, allowing them to “remember” age, the menopausal status, and the bone formation status in vitro, resulting in more aggressive osteoclasts. Our discovery suggests that this may be mediated through DNA methylation. We suggest that this may have clinical implications and could contribute to understanding individual differences in age- and menopause-induced bone loss.

Current perspectives of osteoclastogenesis through estrogen modulated immune cell cytokines

Estrogen is a hormone responsible for modulating several physiological processes such as immune response and bone homeostasis. Physiological fluctuations of estrogen concentration are one of the defining principles behind its mechanism. In cases of estrogen deficiency, such as in menopausal women, a more intense bone resorption may occur due to an increase in osteoclast activity. One of the main factors that influence osteoclast formation and response is the immune system, mainly through cytokines secreted by B and T cells. The purpose of this review is to highlight how estrogen can modulate the secretion of cytokines that can alter bone physiology, thereby establishing an axis between estrogen, immune cells, and osteoclastogenesis.

Alteration of tooth movement by reveromycin A in osteoprotegerin-deficient mice

Osteoprotegerin-deficient mice develop severe high-turnover osteoporosis with porous low-density trabecular bone from an age-related increase in osteoclast activity and are useful alveolar bone models of osteoporosis or frail periodontal tissue. Bisphosphonate (BP), a first-line drug for osteoporosis, is bone-avid, causing side effects such as brittle and fragile bones and jaw osteonecrosis after tooth extraction. In orthodontics, active movement is precisely controlled by temporarily suppressing and resuming movement. BP impedes such control because of its long half-life of several years in bone. Therefore, we investigated the novel osteoclast-specific inhibitor reveromycin A (RMA), which has a short half-life in bone. We hypothesized that tooth movement could be precisely controlled through temporary discontinuation and re-administration of RMA. Osteoprotegerin-deficient mice and wild-type mice were developed as tooth movement models under constant orthodontic force. A constant orthodontic force of 10g was induced using a nickel-titanium closed coil spring to move the maxillary first molar for 14days. We administered BP (1.25mg/kg) or RMA (1.0mg/kg) continuously and then discontinued it to reveal how the subsequent movement of teeth and surrounding alveolar bone was affected. Continuous BP or RMA administration suppressed osteoclast activity and preserved alveolar bone around the roots, apparently normalizing bone metabolism. Tooth movement remained suppressed after BP discontinuation but resumed at a higher rate after discontinuation of RMA. RMA appears useful for controlling orthodontic tooth movement because it can be suppressed and resumed through administration and discontinuation, respectively.

Synovial Fluid Interleukin-16 Contributes to Osteoclast Activation and Bone Loss through the JNK/NFATc1 Signaling Cascade in Patients with Periprosthetic Joint Infection.

Because of lipopolysaccharide (LPS)-mediated effects on osteoclast differentiation and bone loss, periprosthetic joint infection (PJI) caused by Gram-negative bacteria increases the risk of aseptic loosening after reimplantation. Synovial fluid interleukin-16 (IL-16) expression was higher in patients with PJI than in patients without joint infection. Thus, we explored the effects of IL-16 on bone. We investigated whether IL-16 modulates osteoclast or osteoblast differentiation in vitro. An LPS-induced bone loss mice model was used to explore the possible advantages of IL-16 inhibition for the prevention of bone loss. IL-16 directly activated p38 and c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) signaling and increased osteoclast activation markers, including tartrate-resistant acid phosphatase (TRAP), cathepsin K, and nuclear factor of activated T cells 1 (NFATc1). IL-16 directly caused monocytes to differentiate into TRAP-positive osteoclast-like cells through NFATc1 activation dependent on JNK/MAPK signaling. Moreover, IL-16 did not alter alkaline phosphatase activity or calcium deposition during osteoblastic differentiation. Finally, IL-16 inhibition prevented LPS-induced trabecular bone loss and osteoclast activation in vivo. IL-16 directly increased osteoclast activation through the JNK/NFATc1 pathway. IL-16 inhibition could represent a new strategy for treating infection-associated bone loss.

Abstract P3-01-25: Hedgehog signaling-mediated adaptation to hypoxic microenvironment promotes osteoclastogenesis in advanced breast cancer

Abstract Primary tumors often experience hypoxic microenvironment due to increased demand for oxygen in the proliferating cells. Moreover, the proportions of hypoxic tumor cells in the primary tumor strongly correlate to the incidence of metastasis, with bone presenting as the preferred site for breast cancer metastasis. Hence, studying how breast cancer adapts to its hypoxic microenvironment is crucial to understanding the process of breast cancer metastasis to bones. Previous studies in our lab have shown that the developmental signaling pathway, Hh pathway promotes osteopontin (OPN) and parathyroid hormone-related (PTHrP) expression in breast cancer. Additionally, activation of the Hh signaling in breast cancer enables an increase in osteoclastic activity facilitating osteolysis invivo. Hence, we hypothesized that inhibition of Hh signaling diminishes the ability of breast cancer cells to adapt to hypoxia and consequently their metastatic potential. Hh signaling can be canonically activated through smoothened (SMO) dependent activation of the transcriptional regulator GLI. Hence, we inhibited Hh signaling using small molecule inhibitor GANT61 (GLI inhibitor) and pharmacological inhibitor BMS833923 (SMO inhibitor). Since hypoxic microenvironment is prevalent in the bone, we investigated the effect of conditioned medium from breast cancer cells in hypoxic condition on bone marrow-derived macrophages (BMDMs). We found that hypoxia increases osteoclastogenesis and osteoclastic activity, whereas abrogating GLI1 and GLI2 dampens this effect as evidenced by TRAP and toluidine blue staining. Hypoxia-dependent increase in glucose consumption and lactate production were also dampened in Hh inhibited breast cancer cells. Additionally, we found increased nuclear localization of GLI1 and activation of Hh signaling in breast cancer cells in hypoxic condition compared to the control indicating hypoxia-dependent Hh signaling upregulation. To understand the importance of the Hh activation in hypoxic condition, we inhibited Hh signaling pathway with BMS and GANT61. Interestingly, our results indicate that cellular adaptation to hypoxia is dependent on Hh signaling-mediated stabilization of hypoxia-inducible factors (HIF-1α) and its transcriptional activity. This crosstalk suggests a feed-forward mechanism between Hh signaling and HIF-1α. In the future, we will further investigate the mechanistic role of Hh signaling-mediated modulation of HIF-1α. This study will possibly yield new therapeutic targets in controlling hypoxia-mediated cancer metabolism and tumorigenesis of breast cancer. This work is supported by NIH grant R01CA169202 Citation Format: Tshering Dolma Lama-Sherpa, Shamik Das, Ann Hanna, Sarah Kammerud, Lalita A Shevde. Hedgehog signaling-mediated adaptation to hypoxic microenvironment promotes osteoclastogenesis in advanced breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-25.

Bench to Bedside: Animal Models of Radiation Induced Musculoskeletal Toxicity.

Ionizing radiation is a critical aspect of current cancer therapy. While classically mature bone was thought to be relatively radio-resistant, more recent data have shown this to not be the case. Radiation therapy (RT)-induced bone loss leading to fracture is a source of substantial morbidity. The mechanisms of RT likely involve multiple pathways, including changes in angiogenesis and bone vasculature, osteoblast damage/suppression, and increased osteoclast activity. The majority of bone loss appears to occur rapidly after exposure to ionizing RT, with significant changes in cortical thickness being detectable on computed tomography (CT) within three to four months. Additionally, there is a dose–response relationship. Cortical thinning is especially notable in areas of bone that receive >40 gray (Gy). Methods to mitigate toxicity due to RT-induced bone loss is an area of active investigation. There is an accruing clinical trial investigating the use of risderonate, a bisphosphonate, to prevent rib bone loss in patients undergoing lung stereotactic body radiation therapy (SBRT). Additionally, several other promising therapeutic/preventative approaches are being explored in preclinical studies, including parathyroid hormone (PTH), amifostine, and mechanical loading of irradiated bones.

Numerical analysis of the flow field in the lacunar-canalicular system under different magnitudes of gravity.

Irreversible osteoporosis may occur in astronauts during long-term space flight. The flow field of tissue fluid in the lacunar-canalicular system (LCS) of osteon and the mechanical response of osteocytes to the flow field under different gravity fields were studied by numerical simulation. This study is expected to explain how the decrease in liquid transmission within microgravity can be a cause of osteoporosis in astronauts from the perspective of biomechanics using a fundamental research approach. A 3D axisymmetric fluid-solid coupling finite element model of an osteon with a two-stage pore structure (Haversian canals and lacunar-canalicular network) and osteocytes was established. The model compared the influence of differences in pulsating pressure of arterioles in Haversian canal, from 33mmHg to 45mmHg within a microgravity field (0g), Earth's gravity field (1g), and a high G gravitational fields (2-8g). The liquid flow velocity in the LCS within a microgravity field was less than that within a normal gravitational field, and the flow velocity increased with gravitational acceleration. There was a significant liquid pressure gradient in the osteocytes within a normal and higher gravitational field compared with in microgravity. A reduction in the fluid flow velocity and fluid shear stress on osteocytes in different zones in microgravity compared with Earth's gravitational field. For these reasons, possibly causing a decrease in mechanical conduction and biochemical function, even cell death, leads to increased osteoclast activity, eventually causing the loss of a large quantity of bone. Graphical abstract A 3D axisymmetric fluid-solid coupling finite element model of an osteon with a two-stage pore structure was established. The model compared the influence of magnitudes of gravity on liquid transmission in LCS and mechanical response of osteocytes. The mean flow velocity of liquid in various layers (shallow, middle, and deep) increased linearly as acceleration due to gravity increased, and there was a significant liquid pressure gradient in osteocytes within a normal gravitational field compared with in microgravity. In microgravity environment, the osteocytes were unable to experience the pressure difference compared to that of Earth, possibly causing a decrease in mechanical conduction and biochemical function, even cell death, leading to increased osteoclast activity, eventually causing the loss of a large quantity of bone.

F2r negatively regulates osteoclastogenesis through inhibiting the Akt and NFκB signaling pathways.

G-protein-coupled receptors (GPCRs) are pivotal drug targets for many diseases. Coagulation Factor II Thrombin Receptor (F2R) is an important member of GPCR family that is highly expressed in osteoclasts. However, the role of F2r in osteoclasts is still unclear. Here, to examine the functions of F2r on osteoclast formation, differentiation, activation, survival, and acidification, we employed loss-of-function and gain-of-function approaches to study F2r using F2r-targeted short hairpin RNA (sh-F2r) lentivirus and overexpression plasmid pLX304-F2r lentivirus respectively, in mouse bone marrow cells (MBMs) induced osteoclasts. We used three shRNAs targeting F2r which had the ability to efficiently and consistently knock down the expression of F2r at different levels. Notably, F2r knockdown trigged a significant increase in osteoclast activity, number, and size, as well as promoted bone resorption and F-actin ring formation with increased osteoclast marker gene expression. Moreover, F2r overexpression blocked osteoclast formation, maturation, and acidification, indicating that F2r negatively regulates osteoclast formation and function. Furthermore, we investigated the mechanism(s) underlying the role of F2r in osteoclasts. We detected RANKL-induced signaling pathways related protein changes F2r knockdown cells and found significantly increased pAkt levels in sh-F2r infected cells, as well as significantly enhanced phosphorylation of p65 and IKBα in early stages of RANKL stimulation. These data demonstrated that F2r responds to RANKL stimulation to attenuate osteoclastogenesis through inhibiting the both F2r-Akt and F2r-NFκB signaling pathways, which lead a reduction in the expression of osteoclast genes. Our study suggests that targeting F2r may be a novel therapeutic approach for bone diseases, such as osteoporosis.

Regulation of Bone Resorption by the Actin-Bundling Protein L-Plastin in Osteoclasts

Osteoporosis is related to estrogen deficiency and aging. Bone loss can also occur as a result of inflammation-associated diseases such as rheumatoid arthritis and periodontitis, which share several pathologic features with osteoporosis. Estrogen deficiency is associated with increased osteoclast activation, decreased osteoblast function, and increased inflammatory bone-resorbing cytokines (e.g., interleukin-1, -6, and tumor necrosis factor –α). The differentiation of osteoclasts is regulated by the cytokines macrophage colony-stimulating factor, RANK ligand, and osteoprotegerin secreted by osteoblasts. Bone resorption is the unique function of osteoclasts. Podosomes are essential features of osteoclast migration. Podosomes are F-actin rich structures joined radially by actin fibers called F-actin cloud. Upon attachment to the bone surface, osteoclasts reorganize their cytoskeleton to form sealing zones. Sealing zone formation is required for efficient bone resorption to occur by osteoclasts. Integrin αvβ3 and TNF-alpha mediated signaling mechanisms regulate the assembly/disassembly of podosomes during migration and the organization of sealing zones during bone resorption. A brief description is provided on these aspects in this review.

Osteoporosis in a murine model of postmenopausal lupus.

Postmenopausal women with systemic lupus erythematosus have an increased risk of osteoporosis and associated fractures. Their increased osteoporosis risk is probably caused by a high level of inflammation, use of glucocorticoids, impaired kidney function, and early menopause as these are known risk factors for osteoporosis. Due to these risk factors and the lack of safe and effective treatments, new therapies for the treatment of osteoporosis in this group of patients are needed. Ovariectomized MRL/lpr mice constitute a well-established model for studies of postmenopausal systemic lupus erythematosus; however, it is not clear to what extent this experimental model is associated with the development of osteoporosis. Thus, the aim of this study was to characterize the skeleton of ovariectomized MRL/lpr mice to determine the suitability of this model in studies of prospective new therapies for osteoporosis in postmenopausal systemic lupus erythematosus patients. Skeletal parameters were measured in MRL/lpr mice and MRL/++ control mice, using peripheral quantitative computed tomography, high-resolution micro-computed tomography and biomechanical analyses. mRNA expression of bone-remodeling markers was measured by quantitative polymerase chain reaction and serological markers of lupus disease were evaluated using ELISA. Total bone mineral density was reduced in MRL/lpr mice compared with MRL/++ mice and MRL/lpr mice had reduced cortical and trabecular bone thickness compared with MRL/++ mice. In line with the low bone mass of MRL/lpr mice, gene expression analysis of cortical bone from these mice indicated an increased osteoclast activity as well as a decreased osteoblastogenesis and osteoblast activity, compared with MRL/++ mice. Ovariectomized MRL/lpr mice constitute a valuable experimental model for studies of osteoporosis development in postmenopausal systemic lupus erythematosus and this model is thus suitable for future studies of osteoporosis treatment in systemic lupus erythematosus.

Relationship between gonadal maturation and kyphosis in cultured yellowtail (Seriola quinqueradiata)

The risk of onset of vertebral deformity, including kyphosis, in cultured yellowtail increases during spawning season. Farmers suffer an economic loss due to decreased product value as a result of kyphosis. The purpose of this study is to provide a basis for developing measures to reduce the risk of kyphosis occurring by clarifying what causes it.We focused on the relationship between sexual maturation and kyphosis, and the mechanism of kyphosis onset using two-year-old yellowtail collected in February, April, May, and June. We analyzed the gonadosomatic index (GSI), the gonadal stage, serum levels of sex steroid hormones, X-ray images of the caudal vertebrae, the strength of the vertebrae, bone density, and the osteoblast and osteoclast activity of the vertebrae. We found that sexual maturation occurs from April to May. Moreover, the decrease in vertebrae strength and bone density, thinning of compact bone, increase in bone porosity relative to the total spongy bone area of vertebrae, and increase in osteoclast activity were also observed from April to May.To clarify the mechanisms responsible for the weakening of vertebrae, yellowtail juveniles bred in the tank were used. Juveniles were implanted with 17α, 20β-dihydroxy-4-pregnen-3-one (DHP), a hormone that has the ability to induce sexual maturation. In the group of DHP-implanted fish, thinning of the bone and compact substance, and decrease in osteoblastic activity were observed. These results indicate that DHP induced weakening of vertebrae.Our study revealed that changes in physiological conditions such as hormone levels during the breeding period compromised the vertebral structure and increased the incidence of kyphosis.

AAV-Anti-miR-214 Prevents Collapse of the Femoral Head in Osteonecrosis by Regulating Osteoblast and Osteoclast Activities

Osteonecrosis of the femoral head, an intractable but common disease that eventually triggers collapse of the femoral head, is characterized by increased osteoclast activity and markedly decreased osteoblast activity in the necrotic region of the femoral head. MicroRNA (miRNA)-214 (miR-214) may play important roles in vertebrate skeletal development by inhibiting osteoblast function by targeting activating transcription factor 4 (ATF4) and promoting osteoclast function via phosphatase and tensin homolog (PTEN). This study revealed significantly increased levels of miR-214 in necrotic regions, with commensurate changes in the numbers of its target cells (both osteoblasts and osteoclasts). To investigate whether targeting miR-214 could prevent femoral head collapse, we constructed an adeno-associated virus (AAV)-associated anti-miR-214 (AAV-anti-miR-214) and evaluated its function in vivo. AAV-anti-miR-214 promoted osteoblast activity and diminished osteoclast activity, effectively preventing collapse of the femoral head in a rat model of osteonecrosis.

Charcot Foot and the Osteoclast: More Than Just Cytokines

Category:Basic Sciences/BiologicsIntroduction/Purpose:Charcot foot is a serious complication of diabetes present in up to 13% carrying with high morbidity (dislocations, fractures, deformities) and up to 14% mortality. In Charcot, osteoclasts are found in increased numbers and with increased activity3,4 while C-telopeptide of type I collagen (CTX) is upregulated as opposed to ALP suggesting this is indeed an osteoclast and not an osteoblast disease.Methods:The scientific literature was reviewed to identify relevant osteoclastic activators and their role in the hyper activated state. We will also show videos of our current micromanipulation research techniques used to study osteoclast inhibitors in the lab.Results:The blood of Charcot patients is different at the nano level. Micro-nano-particles are extracellular vesicles derived from cells into plasma. Microparticles are found in increased quantity in Charcot;which contain more cytokines; known osteoclast activators. MicroRNAs – Epigenetic changes also are in Charcot; 16 different circulating microRNA known osteoclast activators are associated with Charcot. Advanced glycation end products (AGE). The hyperglycemic state in Charcot is a driving force in pathogenesis. AGEs are normal proteins turned dud after hyperglycemic induced glycation, a post translational modification which is irreversible affects both intracellular and extracellular proteins. AGEs may bind receptor RAGE, increasing osteoclast activity . RANKL is the main osteoclast differentiator and activator. RANKL has been the target of osteoclast control almost since it was found in 1998 .Conclusion:Charcot mediated bony destruction and remodeling; both of which are mediated by the osteoclast has traditionally had a tremendous cytokine focus. Our review suggests the mechanism for modifying a Charcot response on a local and systemic level. It is interesting to note that osteoclast inhibitors Denosumab, Bisphosphonates, Calcitonin and osteoblcast activators rPTH are not completely effective in switching off the Charcot response, implying there is a far more complex interaction between the inflammatory response, osteoclastic stimulators and osteoblastic inhibitors.

Therapeutic Irradiation: Consequences for Bone and Bone Marrow Adipose Tissue.

Radiotherapy continues to be one of the most accepted medical treatments for cancer. Localized irradiation is the most common treatment for prostate, pancreatic, rectal, cervical and endometrial malignancies. Conventional localized fractions are total doses of 30-62Gy at 1.8-2Gy per fraction, with administration of ~60Gy often used for tumor ablation. However, even the lowest dose of localized irradiation exposure can result in adverse complications to adjacent organs, tissues, and vessels, which absorb a portion of the treatment. Skeletal complications are common amongst cancer patients undergoing these localized treatments. Irradiation exposure causes deterioration to the overall quantity and quality of bone by interfering with the trabecular architecture through increased osteoclast activity and decreased osteoblast activity. Irradiation-induced bone damage parallels adipocyte infiltration of the bone marrow (BM) resulting in compositional alterations of the microenvironment that may further affect bone quality and disease state. There may also be direct effects of irradiation on the BM adipocyte/pre-adipocyte, although in vitro findings do not always agree and cellular response is dependent on irradiation dosage. Hematopoietic cells also become apoptotic upon irradiation, which causes a range of skeletal effects. Bone loss leaves patients at a greater risk for osteopenia, osteoporosis, osteonecrosis, and skeletal fractures that drastically reduce quality of life. Osteoanabolic agents stimulate bone formation and reduce fracture risk in patients with low bone density; thus, osteoanabolic or anti-resorptive agents may be useful co-treatments with irradiation. This review discusses these topics and proposes further research directions using novel or combination therapies to enhance bone health during irradiation.

Absence of Dipeptidyl Peptidase 3 Increases Oxidative Stress and Causes Bone Loss.

Controlling oxidative stress through the activation of antioxidant pathways is crucial in bone homeostasis, and impairments of the cellular defense systems involved contribute to the pathogenesis of common skeletal diseases. In this work we focused on the dipeptidyl peptidase 3 (DPP3), a poorly investigated ubiquitous zinc-dependent exopeptidase activating the Keap1-Nrf2 antioxidant pathway. We showed Dpp3 expression in bone and, to understand its role in this compartment, we generated a Dpp3 knockout (KO) mouse model and specifically investigated the skeletal phenotype. Adult Dpp3 KO mice showed a mild growth defect, a significant increase in bone marrow cellularity, and bone loss mainly caused by increased osteoclast activity. Overall, in the mouse model, lack of DPP3 resulted in sustained oxidative stress and in alterations of bone microenvironment favoring the osteoclast compared to the osteoblast lineage. Accordingly, in vitro studies revealed that Dpp3 KO osteoclasts had an inherent increased resorptive activity and ROS production, which on the other hand made them prone to apoptosis. Moreover, absence of DPP3 augmented bone loss after estrogen withdrawal in female mice, further supporting its relevance in the framework of bone pathophysiology. Overall, we show a nonredundant role for DPP3 in the maintenance of bone homeostasis and propose that DPP3 might represent a possible new osteoimmunological player and a marker of human bone loss pathology. © 2019 American Society for Bone and Mineral Research.

Brown Tumors Secondary to Parathyroid Carcinoma Masquerading as Skeletal Metastases on 18F-FDG PET/CT: A Case Report

Brown tumors develop as skeletal manifestations of hyperparathyroidism. Increased osteoclast activity leads to accumulation of highly active giant cells and to excess cortical bone resorption, producing fibrous cysts. Though most often reported in patients with parathyroid adenomas, brown tumors secondary to parathyroid carcinoma create a clinical dilemma. Increased signal uptake on 2-deoxy-2-(fluorine-18)fluoro-D-glucose positron emission tomography (18F-FDG PET)/computed tomography (CT) seen within brown tumors may be indistinguishable from bone metastases. We report a case of parathyroid carcinoma in a 38-year-old man presenting with osteolytic bone lesions on 18F-FDG PET/CT that were diagnosed as brown tumors by biopsy. We describe the patient history, presentation, diagnostic studies, and treatment. We report a case of a 38-year-old man diagnosed with parathyroid carcinoma with associated hypercalcemia and elevated parathyroid hormone levels who had undergone 3 surgical resections for local recurrences and had persistent hypercalcemia. He was found to have multiple osteolytic lesions throughout his skeleton on 18F-FDG PET/CT imaging 2 months after diagnosis. Biopsy of a right scapula lesion confirmed a brown tumor. The role of 18F-FDG PET/CT in management of parathyroid carcinoma has not been systematically evaluated. Skeletal manifestations of parathyroid carcinoma may be present in this imaging modality. Clinicians should consider the possibility of brown tumors in patients with parathyroid carcinoma who undergo 18F-FDG PET/CT imaging.

High Concentrations of Polyelectrolyte Complex Nanoparticles Decrease Activity of Osteoclasts.

Fracture treatment in osteoporotic patients is still challenging. Osteoporosis emerges when there is an imbalance between bone formation and resorption in favor of resorption by osteoclasts. Thus, new implant materials for osteoporotic fracture treatment should promote bone formation and reduce bone resorption. Nanoparticles can serve as drug delivery systems for growth factors like Brain-Derived Neurotrophic Factor (BDNF), which stimulated osteoblast differentiation. Therefore, polyelectrolyte complex nanoparticles (PEC-NPs) consisting of poly(l-lysine) (PLL) and cellulose sulfate (CS), with or without addition of BDNF, were used to analyze their effect on osteoclasts in vitro. Live cell images showed that osteoclast numbers decreased after application of high PLL/CS PEC-NPs concentrations independent of whether BDNF was added or not. Real-time RT-PCR revealed that relative mRNA expression of cathepsin K and calcitonin receptor significantly declined after incubation of osteoclasts with high concentrations of PLL/CS PEC-NPs. Furthermore, Enzyme-Linked Immunosorbent Assay indicated that tartrate-resistant acidic phosphatase 5b activity was significantly reduced in the presence of high PLL/CS PEC-NPs concentrations. Consistent with these results, the pit formation analysis showed that less hydroxyapatite was resorbed by osteoclasts after incubation with high concentrations of PLL/CS PEC-NPs. BDNF had no influence on osteoclasts. We conclude that highly concentrated PLL/CS PEC-NPs dosages decreased osteoclastogenesis and osteoclasts activity. Moreover, BDNF might be a promising growth factor for osteoporotic fracture treatment since it did not increase osteoclast activity.

Evaluation of Short Term Effects of Hyperbaric Oxygen and Enoxaparin Treatments in Avascular Necrosis of Femoral Head

ABSTRACT Aim: Avascular necrosis of the femoral head (AVN) is the necrosis of the bone and the bone marrow resulting from the injury or the occlusion of the blood supplying vessels of the femoral head. Specially it is seen in mostly young and middle aged individuals and requiring mostly surgical procedures. Despite all advances in the surgical procedures, still a high rate of the hip prosthesis is a requirement in the treatment. Hyperbaric Oxygen Therapy (HBOT) alone or in combination with surgery is reported to be effective in some clinical AVN cases. HBOT is also a treatment method which is used in ischemic diseases resulting from vascular injuries or occlusions. Enoxaparin is an antagonist of factor Xa which is found in the coagulation system. Beside its anticoagulant effect it has been shown that it has an osteopenic effect, inhibits osteoblast maturation and increases osteoclast activity in the bone. Material and Methods: In this study effects of enoxaparin and HBOT were investigated in the treatment of experimentally formed AVN of the femoral heads of the rats. For this purpose, avascular necrosis model was applied to the left femoral heads of 64 rats and the results of the treatments alone and together were investigated. Results: In this study results have shown that an increase in the new bone formation, and remodelisation with less changes in the cartilage tissue than in the controls. An increase in the necrotic tissue clearing rate observed in the HBOT applied groups. The best results were achieved with the HBOT and enoxaparin combined applications. Conclusion: In this study HBOT alone, enoxaparin alone or combination of these two treatments have a positive effect in the experimental femoral head AVN and supporting the clinical studies in the femoral head AVN. Keywords: Hyperbaric oxygen therapy, avascular necrosis, enoxaparin

Alveolar Bone Osteoclast Profile in the Periodontitis Wistar Rats Model with the Snail Slime (Achatina Fulica) Application.

BACKGROUND:Bone damage is a result of periodontal disease that occurs due to changes in osteoclast and osteoblast activity in response to local inflammation. The bacteria Aggregatibacter actinomycetemcomitans produces Lipopolysaccharide (LPS), which can increase osteoclast activity.AIM:This study aimed to analyse the decrease in alveolar bone osteoclasts in periodontitis rats’ model with the application of snail slime.METHODS:Wistar rats (27) with periodontitis divided into three groups, namely the control group (debridement), P1 group (debridement and application of oral snail slime) 300 Mg/Kg Body weight, P2 group (debridement, application of topical snail slime) 0.1 Mg. Osteoclast profile analysis was carried out by HE staining procedure to determine the histological feature of osteoclasts. The statistical significance was determined using the Shapiro-Wilk Test, One Way ANOVA, and Post Hoc test (p < 0.05).RESULTS:Osteoclast profile in rats with periodontitis applied with snail slime significantly decreased the number of osteoclasts with both oral and topical administration, there were significant differences in the number of osteoclasts between groups (one way ANOVA, p < 0.05) and there were no significant differences between groups P1 and P2 (Post Hoc, p > 0.05).CONCLUSION:In this study, there was a decrease in the number of osteoclasts which were slipped by snail slime in Wistar rats with periodontitis; this indicates a periodontitis healing process.

MiR-377 inhibits wear particle-induced osteolysis via targeting RANKL.

Periprosthetic osteolysis caused by wear particles is the main factor that affectsthe long-term efficacy of artificial joint replacement, and macrophages playa vital role in the pathogenesis of periprosthetic osteolysis, while the potential mechanism underlying thisisstill unclear. To investigate the underlying role of miR-377 in wear particle-induced osteolysis (PIO), blood samples from patients undergoing arthroplasty were collected for analyzing the correlation between miR-377 expression and the clinicopathological parameters of PIO. Peripheral blood macrophages were obtained to compare the miR-377 and receptor activator of NF-κB ligand (RANKL) expressions. Bone marrow macrophages (BMMs) following titanium (Ti) particle treatment and/or miR-377 mimic transfection wereused. The expressions of RANKL, pro-inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α) and the osteoclast-related molecules tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CTSK) were determined using real-time polymerase chain reaction or western blotting or enzyme-linked immunosorbent assay or TRAP staining, when appropriate. The interaction between miR-377 and RANKL was assessed by luciferase reporter assay. The in vivo role of miR-377 in PIO was evaluated using a mouse calvarial osteolysis model. There were significant differences in downregulated miR-377 expression between the different numbers of particles in the joint prostheses. The Ti particle treatment increased pro-inflammatory cytokine levels, downregulated RANKL and increased osteoclast activity in BMMs, while miR-377 overexpression led to the opposite effect. Taken together, miR-377 downregulated the target gene RANKL, resulting in PIO inhibition. MiR-377 relieved PIO by negatively regulating RANKL.