Aberrant NF-κB activation in odontoblasts orchestrates inflammatory matrix degradation and mineral resorption / 国际口腔科学杂志·英文版

Inflammation-associated proteinase functions are key determinants of inflammatory stromal tissues deconstruction. As a specialized inflammatory pathological process, dental internal resorption (IR) includes both soft and hard tissues deconstruction within the dentin-pulp complex, which has been one of the main reasons for inflammatory tooth loss. Mechanisms of inflammatory matrix degradation and tissue resorption in IR are largely unclear. In this study, we used a combination of Cre-loxP reporter, flow cytometry, cell transplantation, and enzyme activities assay to mechanistically investigate the role of regenerative cells, odontoblasts (ODs), in inflammatory mineral resorption and matrices degradation. We report that inflamed ODs have strong capabilities of matrix degradation and tissue resorption. Traditionally, ODs are regarded as hard-tissue regenerative cells; however, our data unexpectedly present ODs as a crucial population that participates in IR-associated tissue deconstruction. Specifically, we uncovered that nuclear factor-kappa b (NF-κB) signaling orchestrated Tumor necrosis factor α (TNF-α)-induced matrix metalloproteinases (Mmps) and Cathepsin K (Ctsk) functions in ODs to enhance matrix degradation and tissue resorption. Furthermore, TNF-α increases Rankl/Opg ratio in ODs via NF-κB signaling by impairing Opg expression but increasing Rankl level, which utterly makes ODs cell line 17IIA11 (A11) become Trap+ and Ctsk+ multinucleated cells to perform resorptive actions. Blocking of NF-κB signaling significantly rescues matrix degradation and resorptive functions of inflamed ODs via repressing vital inflammatory proteinases Mmps and Ctsk. Utterly, via utilizing NF-κB specific small molecule inhibitors we satisfactorily attenuated inflammatory ODs-associated human dental IR in vivo. Our data reveal the underlying mechanisms of inflammatory matrix degradation and resorption via proteinase activities in IR-related pathological conditions.

Interacción del microbioma intestinal y el hueso / Interaction between the intestinal microbiome and bone

El "microbioma" no solo está constituido por los microbios, sino por todos los componen-tes que viven en el mismo hábitat conforman-do un nicho ecológico. Es decir, está conformado por los microorganismos (bacterias, hongos, protozoos, etc.), todo el espectro de moléculas producidas por ellos tales como sus componentes estructurales (ácidos nucleicos, proteínas, lípidos y glúcidos), meta-bolitos, toxinas, etc., y las moléculas producidas por el huésped. El microbioma intestinal (MI) ha emergido como un factor que tiene un gran efecto sobre la cantidad, calidad y fuerza del hueso. Las investigaciones revelan que la homeostasis ósea está ligada al micro-bioma saludable, mientras que la disbiosis (alteración en la biodiversidad microbiana) puede exacerbar la actividad osteoclástica y promover la osteoporosis. Los mecanismos potenciales involucrados en la interacción del microbioma intestinal y el hueso son la influencia del metabolismo del huésped, el mantenimiento de la integridad intestinal y regulación de la absorción de nutrientes, la regulación del eje intestino-sistema inmune y la modulación del sistema endocrino. Es decir que hay múltiples vías por las cuales el MI influye sobre el hueso, pero estos y otros mecanismos deben profundizarse más aún. También es necesario que se identifiquen y caractericen mejor los microorganismos que están asociados a las enfermedades óseas. El conocimiento de estos aspectos podría ser útil para el desarrollo de herramientas terapéuticas basadas en el MI que puedan mejorar la eficacia de los distintos tratamientos existentes. (AU)

The microbiome is not only constituted by microbes, but by all the components that live in the same habitat forming an ecological niche. It is conformed by the microorganisms ( bacteria, fungi, protozoa, etc), the entire spectrum of molecules produced by them (nucleic acids, proteins, lipid and carbohydrates, metabolites, toxins, etc) and the molecules produced by the host. The intestinal microbiome (IM) has emerged as a factor with great effects on the quantity, quality and strength of bone. The investigations reveal that bone homeostasis is linked to the healthy microbiome, while the dysbiosis (alteration in the microbial biodiversity) can exacerbate the osteoclastic activity and promote osteoporosis. The potential mechanisms involved in the interaction between IM and bone are the influence of the host metabolism, the maintenance of the intestinal integrity and regulation of the nutrient absorption, the regulation of the intestine/ immune system axis and the modulation of the endocrine system. That is, there are multiple ways through which IM influences on bone, but these and other mechanisms need to be further studied. It is also necessary to identify and characterize the microorganisms associated with the bone diseases. Knowledge of these aspects could be useful to develop therapeutical tools based on the IM that could improve the efficacy of the current treatments. (AU)

TRAF6/ERK/p38 pathway is involved in interleukin-17-mediated autophagy to promote osteoclast precursor cell differentiation / 浙江大学学报·医学版

To investigate the effects of interleukin (IL)-17-mediated autophagy on the TNF receptor associated factor (TRAF6)/extracellular signal-regulated kinase (ERK)/p38 pathway and osteoclast differentiation. Mouse bone marrow-derived macrophages (BMM) were cultured with a medium containing 30 ng/mL macrophage colony stimulating factor and 50 ng/mL receptor activator of nuclear factor-kappa B ligard (RANKL), and IL-17 (0.01, 0.1, 1.0, 10 ng/mL) was added for intervention (IL-17 group). Tartrate-resistant acid phosphatase (TRAP) staining was used to observe TRAP positive multinucleated cells; phalloidin fluorescent staining was used to detect actin ring circumference; toluidine blue staining was used to analyze bone resorption lacuna formation. To further examine the mechanism of the effect of IL-17-mediated autophagy on the differentiation of osteoclasts, the control group used RANKL medium to culture mouse macrophage RAW264.7 cells, while the IL-17 group was treated with IL-17 (0.01, 0.1, 1.0, /mL). Western blot was used to detect the expression of autophagy-related proteins Beclin-1, microtubule-associated protein 1 light chain 3 (LC3) and osteoclast-related proteins c-fos and nuclear factor of activated T cell 1 (NFATc1) after treatment with different concentrations of IL-17. The expression of LC3, NFATc1, TRAF6/ERK/p38 signaling pathway related proteins were detected in IL-17 and autophagy inhibitor 3-MA group. The number of TRAP positive multinucleated cells, the circumference of the actin ring and the area of bone resorption lacuna in IL-17 group treated with IL-17 (0.01, 0.1, were significantly higher than those in the control group. In IL-17 treated RAW264.7 cells, the expression of c-fos, NFATc1, Beclin-1, LC3, TRAF6, p-ERK, and p-p38 was all significantly up-regulated (all 0.05). After treatment with the autophagy inhibitor 3-MA, the expression levels of LC3, NFATc1, TRAF6, p-ERK, and p-p38 all decreased significantly (all 0.05). IL-17 can promote the expression of autophagy proteins and enhance the differentiation ability of osteoclast precursor cells, and the TRAF6/ERK/p38 signaling pathway may be involved in this process.

Up-regulated expression of CD147 gene in malignant bone tumor and the possible induction mechanism during osteoclast formation

It is increasingly evident that the microenvironment of bone can influence cancer phenotype in many ways that favor growth in bone. CD147, a transmembrane protein of the immunoglobulin (Ig) superfamily, was identified independently in different species and has many designations across different species. However, expression levels of CD147 mRNA in bone cancer have not been described. In this study, we have used real-time fluorescence quantification (RT-PCR) to demonstrate CD147 expression in malignant bone cancer and benign bone tumor tissues. The results suggested that the expression of CD147 gene was significantly up-regulated in malignant bone cancer. Moreover, we found that over-expressed RANKL progressively enhanced osteoclast formation up to 48 h, which suggested that RANKL could promote the formation of osteoclast, indicating that both CD147 and RANKL play important roles in the formation of osteoclasts. Furthermore, the expressions of four osteoclast specific expression genes, including TRACP, MMP-2, MMP-9 and c-Src, were analyzed using RT-PCR. The results indicated that four osteoclast-specific expression genes were detectable in all osteoclast with different treatments. However, the highest expression level of these four osteoclast-specific expression genes appears in the CD147+ RANKL group and the lowest expression level of these four osteoclast-specific expression genes appears with si-RANKL treatment. Characterization of the role of CD147 in the development of tumors should lead to a better understanding of the changes occurring at the molecular level during the development and progression of primary human bone cancer.

MLO-Y4 osteocytic cell clones express distinct gene expression patterns characteristic of different stages of osteocyte differentiation / Clones de las células osteocíticas MLO-Y4 tienen diferentes patrones de expresión génica característicos de diferentes estadíos de diferenciación osteocítica

Osteocytes are the most abundant bone cell and are formed when osteoblasts become embedded in the bone matrix. Through changes in gene expression and paracrine effects, osteocytes regulate the number of osteoblasts, bone forming cells, and osteoclasts, bone resorbing cells, which are needed to maintain bone mass. MLO-Y4 is the better characterized osteocytic cell line; however, lacks expression of sclerostin, the product of the SOST gene, which is fundamental for osteocyte function and blocks bone formation. With the objective to isolate MLO-Y4 clones with different gene expression profiles, we performed cultures at very low density of MLO-Y4 cells stably transfected with nuclear green fluorescent protein (MLOnGFP). Cell morphology was visualized under a fluorescence microscope. Once the cells reached 80% confluency, RNA was extracted and quantitative real time PCR was performed. Clones exhibit different sizes and morphology, with some cells showing a spindle-like shape and others with abundant projections and a star-like shape. Gene expression also differed among clones. However, none of the clones examined expressed SOST. We conclude that the MLO-nGFP clones constitute a useful tool to study osteocyte differentiation and the role of osteocytes in the control of bone formation and resorption in vitro. (AU)

Los osteocitos son las células más abundantes del hueso y se forman cuando los osteoblastos se encuentran rodeados de matriz ósea. A través de cambios en la expresión génica y efectos paracrinos, los osteocitos controlan el número de osteoblastos que forman el hueso, y osteoclastos que resorben el hueso, células necesarias para mantener la masa ósea. Las células MLO-Y4 son la línea celular osteocítica más investigada; sin embargo, no expresan esclerostina, el pro esclerostina, el producto del gen SOST que bloquea la formación ósea y es indispensable para la función de los osteocitos. Con el objetivo de aislar clones de las células MLO-Y4 con diferentes perfiles de expresión génica, realizamos cultivos a muy baja densidad de las células transfectadas en forma estable con proteína verde fluorescente nuclear (MLO-nGFP). La morfología celular fue evaluada utilizando un microscopio de fluorescencia. Una vez que las células alcanzaron el 80% de confluencia, el ARN fue extraído y analizado por PCR cuantitativa en tiempo real. Las células de los diferentes clones tienen diferentes tamaños y morfología, algunas células son fusiformes y otras con proyecciones citoplasmáticas abundantes y en forma de estrella. La expresión de los genes también varió en los distintos clones. Sin embargo, ninguno de ellos expresó SOST. En conclusión, los clones de las células MLO-nGFP constituyen una herramienta útil para estudiar la diferenciación de los osteocitos y el rol de estas células en el control de la formación y resorción ósea in vitro. (AU)

Modulation of in vitro osteoclast activity mediated by different doses of parathyroid hormone / Modulación in vitro de la actividad osteoclástica mediada por diferentes dosis de hormona paratiroidea

Bone remodeling is a process regulated by the interaction between cells and various molecules such as parathyroid hormone (PTH). The aim of the study was to evaluate the effect of different doses of PTH on osteoclast activity in a culture model of bone organs. Six-day-old male C57BL/6 mice (n=14) were euthanized and the calvariae were dissected and sectioned in the middle, keeping the periosteal and endosteal. The bone fragments were divided into three groups: Group I (control - without adding PTH), Group II (addition of 3 nM PTH) and Group III (30 nM PTH), all cultured in aMEM for up to 72 h osteoclast activity was evaluated by biochemical quantification of calcium released in the culture medium at intervals of 24, 48, and 72 h and by histomorphometric analysis of bone resorption lacunae at 72 h our results show that group II exhibited significantly higher values of calcium levels in the medium compared to group I (p<0.05) in all intervals, also being higher for group III at 24 hours (p<0.05). Group II promoted a greater demineralization area (22068 ± 2193 mm2) than those found in group I (2084 ± 38 mm2) and group III (8952 ± 246 mm2), with statistically significant difference (p<0.001) among all groups. We concluded that in culture model of bone organs PTH promotes higher bone resorption when administered in lower doses.

La remodelación ósea es un proceso regulado por la interacción entre las células y varias moléculas como la hormona paratiroidea (PTH). El objetivo de este estudio fue evaluar el efecto de diferentes dosis de PTH sobre la actividad de los osteoclastos en un modelo de cultivo de órganos óseos. Se sacrificaron ratones C57BL/6 machos, de 6 días de edad (n = 14), y se disecaron y seccionaron las calvarias, manteniendo el periostio y endostio. Los fragmentos óseos se dividieron en tres grupos: Grupo I (control - sin adición de PTH), Grupo II (adición de 3 mM de PTH) y Grupo III (30 nM de PTH), todos cultivados en aMEM hasta 72 horas. La actividad de los osteoclastos se evaluó mediante la cuantificación bioquímica de calcio liberado en medio de cultivo, a intervalos de 24, 48 y 72 horas, y por análisis histomorfométrico de las lagunas de resorción ósea a las 72 horas. Nuestros resultados muestran que el grupo II exhibió valores significativamente más altos de calcio en el medio, comparado con el grupo I (p <0.05) en todos los intervalos, siendo también más alto para el grupo III a las 24 horas (p <0.05). El grupo II promovió una mayor área de desmineralización (22068 ± 2193 mm2) que los encontrados en el grupo I (2084 ± 38 mm2) y en el grupo III (8952 ± 246 mm2), con diferencia estadísticamente significativa (p <0,001) entre todos los grupos. Concluimos que en el modelo de cultivo de órganos óseos la PTH promueve una mayor resorción ósea cuando se administra en dosis más bajas.

A Proton Pump Inhibitor's Effect on Bone Metabolism Mediated by Osteoclast Action in Old Age: A Prospective Randomized Study

BACKGROUND/AIMS: Proton pump inhibitors (PPIs) act by irreversibly binding to the H+-K+-ATPase of the proton pump in parietal cells and may possibly affect the vacuolar H+-ATPase in osteoclasts. METHODS: We investigated the effect of 8 weeks of PPI treatment on the parameters of bone turnover and compared PPI with revaprazan, which acts by reversibly binding to H+-K+-ATPase in proton pumps. This study was a parallel randomized controlled trial. For 8 weeks, either a PPI or revaprazan was randomly assigned to patients with gastric ulcers. The parameters of bone turnover were measured at the beginning of and after the 8-week treatment period. RESULTS: Twenty-six patients (PPI, n=13; revaprazan, n=13) completed the intention-to-treat analysis. After the 8-week treatment period, serum calcium and urine deoxypyridinoline (DPD) were increased in the PPI group (serum calcium, p=0.046; urine DPD, p=0.046) but not in the revaprazan group. According to multivariate linear regression analysis, age > or =60 years was an independent predictor for the changes in serum calcium and urine DPD. CONCLUSIONS: In elderly patients, administering a PPI for 8 weeks altered bone parameters. Our study suggested that PPIs might directly alter bone metabolism via the vacuolar H+-ATPase in osteoclasts.

The multiple effects of thyroid disorders on bone and mineral metabolism / Os múltiplos efeitos das disfunções tireoidianas sobre o metabolismo osteomineral

Differently from most hormones, which commonly are specialized molecules able to influence other cells, tissues and systems, thyroid hormones (TH) are pleiotropic peptides, whose primordial function is difficult to identify. The complex action of TH on human economy can be easily witnessed by examining the diverse consequences of TH excess and deficiency during development and after maturity. In particular, different manifestations in bone modeling and remodeling reflect the circumstantial consequences of thyroid disturbances, which are age dependent. While hyperthyroidism during childhood enhances bone mineralization and accelerates epiphyseal maturation, in adults it induces bone loss by predominant activation of osteoclast activity. Furthermore, the syndrome of TH resistance is a multifaceted condition in which different sites exhibit signs of hormone excess or deficiency depending on the configuration of the TH receptor isoform. The investigation of the impact of TH resistance on the skeleton still remains to be elucidated. We present here a thorough review of the action of TH on bone and of the impact of thyroid disorders, including hyper- and hypothyroidism and the syndrome of TH resistance, on the skeleton.

Diferentemente da maioria dos hormônios, que usualmente são moléculas especializadas capazes de influenciar outras células, tecidos e sistemas, os hormônios da tireoide (HT) são peptídeos pleiotrópicos, cuja função primordial é difícil de identificar. A ação complexa dos HT na fisiologia humana pode ser facilmente reconhecida ao observar as diversas consequências do excesso e da deficiência de HT durante e após o pleno desenvolvimento. Em particular as diferentes manifestações na modelação e remodelação óssea refletem que as consequências esqueléticas das disfunções tireoidianas dependem das circunstâncias e variam com a idade. Enquanto o hipertireoidismo durante a infância aumenta a mineralização óssea e acelera a maturação epifisária, em adultos induz a perda óssea pela ativação predominante da ação osteoclástica. Além disso, a síndrome de resistência ao HT é uma condição multifacetada na qual diferentes tecidos apresentam sinais de excesso ou deficiência hormonal, dependendo da predominância da expressão das diversas isoformas do receptor de HT. O impacto da resistência ao HT sobre o esqueleto ainda é motivo de investigação. Apresentamos aqui uma revisão abrangente sobre as ações ósseas dos HT e o impacto no esqueleto dos distúrbios da tireoide, incluindo hipo e hipertireoidismo e síndrome de resistência ao HT.

BMP-2 and titanium particles synergistically activate osteoclast formation

A previous study showed that BMP-2 (bone morphogenetic protein-2) and wear debris can separately support osteoclast formation induced by the receptor activator of NF-κB ligand (RANKL). However, the effect of BMP-2 on wear debris-induced osteoclast formation is unclear. In this study, we show that neither titanium particles nor BMP-2 can induce osteoclast formation in RAW 264.7 mouse leukemic monocyte macrophage cells but that BMP-2 synergizes with titanium particles to enhance osteoclast formation in the presence of RANKL, and that at a low concentration, BMP-2 has an optimal effect to stimulate the size and number of multinuclear osteoclasts, expression of osteoclast genes, and resorption area. Our data also clarify that the effects caused by the increase in BMP-2 on phosphorylated SMAD levels such as c-Fos expression increased throughout the early stages of osteoclastogenesis. BMP-2 and titanium particles stimulate the expression of p-JNK, p-P38, p-IkB, and P50 compared with the titanium group. These data suggested that BMP-2 may be a crucial factor in titanium particle-mediated osteoclast formation.

IL-17-deficient allogeneic bone marrow transplantation prevents the induction of collagen-induced arthritis in DBA/1J mice

IL-17-producing CD4+ T cells (Th17) play important functions in autoimmune diseases and allograft rejection of solid organs. We examined the effects of IL 17 and its mechanism of action on arthritis in a murine collagen-induced arthritis (CIA) model using bone marrow transplantation (BMT) system. DBA/1J mice were administered a lethal radiation dose and then rescued with bone marrow derived from either wild-type (WT) or IL-17-/- mice on C57BL/6 background mice. CIA was induced after the bone marrow transplant, and disease progression was characterized. DBA/1J mice with CIA that received IL-17-/- donor bone marrow showed potently inhibited development and severity of clinical arthritis as compared with CIA mice that received WT bone marrow. Reduced secretion of the pro-inflammatory cytokines tumor necrosis factor-alpha, IL-1beta, and IL-6, and collagen-specific T cell responses were observed in mice that received IL-17-/- bone marrow. IL-17 blockade also inhibited effector T cell proliferation by reciprocally regulating the Treg/Th17 ratio. IL-17 blockade prevented joint destruction in mice with CIA. These findings suggest that CIA with BMT is a viable method of immunological manipulation and that IL-17 deficiency suppresses severe joint destruction and inflammation in CIA mice. There may be clinical benefits in blocking IL-17 and BMT in the treatment of rheumatoid arthritis.

Triiodothyronine (T3) does not induce Rankl expression in rat Ros 17/2.8 cells

Osteoclastogenesis may be regulated via activation of the RANK/RANKL (receptor activator of nuclear factor-kappa B/ receptor activator of nuclear factor-kappa B ligand) system, which is mediated by osteoblasts. However, the bone loss mechanism induced by T3 (triiodothyronine) is still controversial. In this study, osteoblastic lineage rat cells (ROS 17/2.8) were treated with T3 (10-8 M, 10-9 M, and 10-10 M), and RANKL mRNA (messenger RNA) expression was measured by semiquantitative RT-PCR. Our results show that T3 concentrations used did not significantly enhance RANKL expression compared to controls without hormone treatment. This data suggests that other mechanisms, unrelated to the RANK/RANKL system, might be to activate osteoclast differentiation in these cells.

A osteoclastogênese pode ser regulada via ativação do sistema RANK/RANKL (receptor ativador do fator nuclear kapa B/ ligante do receptor do fator nuclear kapa B), que é mediado pelos osteoblastos. Entretanto, o mecanismo de perda óssea induzido pelo T3 (triiodotironina) ainda é controverso. Neste estudo, a linhagem osteoblástica de células de rato ROS 17/2.8 foi tratada com T3 (10-8 M, 10-9 M e 10-10 M), e a expressão do mRNA do RANKL foi medida por RT-PCR semiquantitativo. Nossos resultados mostraram que as concentrações de T3 utilizadas não induziram significativamente a expressão do RANKL, comparado ao controle (sem tratamento hormonal). Estes dados sugerem que outros mecanismos, não relacionados ao sistema RANK/RANKL, são usados para ativar a diferenciação osteoclástica nestas células.

Expression of Osteoprotegerin and RANK Ligand in Breast Cancer Bone Metastasis

Bone destruction is primarily mediated by osteoclastic bone resorption, and cancer cells stimulate the formation and activation of osteoclasts next to metastatic foci. Accumulating evidences indicate that receptor activator of NF-kB ligand (RANKL) is the ultimate extracellular mediator that stimulates osteoclast differentiation into mature osteoclasts. In contrast, osteoprotegerin (OPG) inhibits osteoclast development. In order to elucidate a mechanism for cancer-induced osteoclastogenesis, cells from a human breast cancer line, MDA-MB-231, were directly co-cultured with ST2, MC3T3-E1, or with primary mouse calvarial cells. Osteoclast-like cells and tartarate resistant acid phosphatase (TRAP) activities were then quantitated. We examined these cell lines and samples from breast cancer by RT-PCR for the expressions of OPG and RANKL mRNA. Compared to controls, co-culture of MDA-MB-231 cells with stromal or osteoblastic cells induced an increase in number of osteoclasts and TRAP activities. MDA-MB-231 cells alone or breast cancer samples did not express RANKL mRNA. However, co-culture of these cancer cells with stromal or osteoblastic cells induced RANKL mRNA expression and decreased OPG mRNA expression. These experiments demonstrate that direct interactions between breast cancer and stromal or osteoblastic cells induce osteoclastogenesis in vitro through modulating RANKL expression.