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Mouse ligature-induced periodontitis (LIP) has been used to study bone loss in periodontitis. However, the role of osteocytes in LIP remains unclear. Furthermore, there is no consensus on the choice of alveolar bone parameters and time points to evaluate LIP. Here, we investigated the dynamics of changes in osteoclastogenesis and bone volume (BV) loss in LIP over 14 days. Time-course analysis revealed that osteoclast induction peaked on days 3 and 5, followed by the peak of BV loss on day 7. Notably, BV was restored by day 14. The bone formation phase after the bone resorption phase was suggested to be responsible for the recovery of bone loss. Electron microscopy identified bacteria in the osteocyte lacunar space beyond the periodontal ligament (PDL) tissue. We investigated how osteocytes affect bone resorption of LIP and found that mice lacking receptor activator of NF-κB ligand (RANKL), predominantly in osteocytes, protected against bone loss in LIP, whereas recombination activating 1 (RAG1)-deficient mice failed to resist it. These results indicate that T/B cells are dispensable for osteoclast induction in LIP and that RANKL from osteocytes and mature osteoblasts regulates bone resorption by LIP. Remarkably, mice lacking the myeloid differentiation primary response gene 88 (MYD88) did not show protection against LIP-induced bone loss. Instead, osteocytic cells expressed nucleotide-binding oligomerization domain containing 1 (NOD1), and primary osteocytes induced significantly higher Rankl than primary osteoblasts when stimulated with a NOD1 agonist. Taken together, LIP induced both bone resorption and bone formation in a stage-dependent manner, suggesting that the selection of time points is critical for quantifying bone loss in mouse LIP. Pathogenetically, the current study suggests that bacterial activation of osteocytes via NOD1 is involved in the mechanism of osteoclastogenesis in LIP. The NOD1-RANKL axis in osteocytes may be a therapeutic target for bone resorption in periodontitis. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Hexavalent chromium Cr (VI) is a primary human carcinogen with damaging toxic effects on multiple organs. Cr (VI) exposure can induce hepatotoxicity through oxidative stress, but its exact mechanism of action was still unclear. In our study, a model of acute Cr (VI) induced liver injury was established by exposing mice to different concentrations (0, 40, 80, and 160 mg/kg) of Cr (VI); RNA-seq was used to characterize changes in liver tissue transcriptome of C57BL/6 mice after exposing to 160 mg/kg Bw of Cr (VI). Changes in liver tissue structures, proteins, and genes were observed by hematoxylin and eosin (H&E), western blot, immunohistochemistry and RT-PCR. After Cr (VI) exposure, abnormal liver tissue structure, hepatocyte injury, and hepatic inflammatory response were observed in mice in a dose-dependent manner. RNA-seq transcriptome results indicated that oxidative stress, apoptosis, and inflammatory response pathways were increased after Cr (VI) exposure; KEGG pathway analysis found that activation of NF-κB signaling pathway was significantly upregulated. Consistent with the RNA-seq results, immunohistochemistry showed that Cr (VI) exposure resulted in infiltrating of Kupffer cells and neutrophils, increasing expression of inflammatory factors (TNF-α, IL-6, IL-1ß), and activating of NF-κB signaling pathways (p-IKKα/ß and p-p65). However, ROS inhibitor, N-acetyl-L-cysteine (NAC), could reduce infiltration of Kupffer cells and neutrophils and expression of inflammatory factors. Besides, NAC could inhibit NF-κB signaling pathway activation, and alleviate Cr (VI)-induced liver tissue damage. Our findings strongly suggested that inhibition of ROS by NAC might help in the development of new strategies for Cr (VI)-associated liver fibrosis. Our findings revealed for the first time that Cr (VI) induced liver tissue damage through the inflammatory response mediated by the NF-κB signaling pathway, and inhibition of ROS by NAC might help in the development of new strategies for Cr (VI)-associated hepatotoxicity.
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Enfermedad Hepática Inducida por Sustancias y Drogas , FN-kappa B , Ratones , Humanos , Animales , FN-kappa B/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Ratones Endogámicos C57BL , Transducción de Señal , Cromo/toxicidad , Acetilcisteína/farmacologíaRESUMEN
As kinds of porous crystalline compounds, zeolitic imidazolate frameworks (ZIFs) have been developed quickly and attracted considerable attention for use in nano drug delivery systems, which raised concerns about cardiovascular disorders. At the present, the cytotoxic mechanism of ZIFs in cardiovascular disorders was still unclear. Our experiment explored the toxicity of ZIF-8, a typical kind of ZIFs, on human EA.hy926 vascular endothelial cells. The cell viability, ROS formation, apoptosis level, inflammatory response level, wound healing ability and atherosclerosis-related indicators of EA.hy926 endothelial cells were analyzed after ZIF-8 treatment. Meanwhile, we evaluated the ability of antioxidant N-Acetyl-L-cysteine (NAC) to attenuate the toxicity of ZIF-8 on EA.hy926 endothelial cells. As results, NAC attenuated ROS formation, cell apoptosis, LDH formation and endothelial dysfunction caused by ZIF-8. As the Wnt/ß-catenin pathway was involved in endothelial cell dysfunction, we also studied the expression level of ß-catenin and LEF1 in ZIF-8 and/or NAC treated EA.hy926 cells. As expected, ZIF-8 increased the protein expressions of ß-catenin and LEF1in the IC50 group, which was significantly inhibited by co-treatment with NAC. Taken together, this study could help improve our understanding about the mechanism of ZIF-8-induced endothelial cells injury and NAC had therapeutic potential in preventing ZIF-8-associated endothelial dysfunction by wnt/ß-catenin pathway.
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Acetilcisteína , Células Endoteliales , beta Catenina , Humanos , Acetilcisteína/farmacología , beta Catenina/metabolismo , Células Endoteliales/efectos de los fármacos , Células Endoteliales/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Vía de Señalización WntRESUMEN
Frailty is the hallmark of aging that can be delayed with exercise. The present studies were initiated based on the hypothesis that long-term voluntary wheel running (VWR) in female mice from 12 to 18 or 22 months of age would have beneficial effects on the musculoskeletal system. Mice were separated into high (HBW) and low (LBW) body weight based on final body weights upon termination of experiments. Bone marrow fat was significantly higher in HBW than LBW under sedentary conditions, but not with VWR. HBW was more protective for soleus size and function than LBW under sedentary conditions, however VWR increased soleus size and function regardless of body weight. VWR plus HBW was more protective against muscle loss with aging. Similar effects of VWR plus HBW were observed with the extensor digitorum longus, EDL, however, LBW with VWR was beneficial in improving EDL fatigue resistance in 18 mo mice and was more beneficial with regards to muscle production of bone protective factors. VWR plus HBW maintained bone in aged animals. In summary, HBW had a more beneficial effect on muscle and bone with aging especially in combination with exercise. These effects were independent of bone marrow fat, suggesting that intrinsic musculoskeletal adaptions were responsible for these beneficial effects.
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Actividad Motora , Condicionamiento Físico Animal , Ratones , Femenino , Animales , Actividad Motora/fisiología , Peso Corporal , Músculo Esquelético , Envejecimiento/fisiologíaRESUMEN
With the spread of hexavalent chromium (Cr(VI)) contamination, Cr(VI)-induced hepatotoxicity has attracted increasing attention in recent years. To date, however, the exact mechanism of Cr(VI) toxicity remains unclear. In this study, we investigated the role of apoptosis signal-regulating kinase 1 (ASK1)/c-Jun amino-terminal kinase (JNK) in Cr(VI)-induced hepatic toxicity and the possible related mechanisms. AML-12 hepatocyte cell-lines were treated with 0, 1, 4, and 16 µmol/Lof Cr(VI) with or without GS-444271 (an ASK1 inhibitor). Adult male mice were administered with 0, 2, 8, and 32 mg/kg body mass (BM)/day of Cr(VI) for 5 days. The level of hepatocyte apoptosis/proliferation, generation of reactive oxygen species (ROS), and expression levels of mRNAs and proteins related to ASK1/JNK and nuclear factor-E2-related factor 2 (Nrf2) signaling were assessed. Results showed that high Cr(VI) exposure induced hepatocyte apoptosis and liver injury by generation of ROS and down-regulation of Nrf2 signaling. In addition, ASK1/JNK signaling activity was upregulated in the Cr(VI)-treated group. Furthermore, GS-444217 treatment significantly rescued Cr(VI)-induced hepatocyte apoptosis and liver dysfunction in vitro and in vivo by down-regulation of ASK1/JNK signaling. Thus, ASK1/JNK signaling appears to play an important role in Cr(VI)-induced hepatocyte apoptosis and liver injury. This study should help improve our understanding of the mechanism of Cr(VI)-induced liver injury and provide support for future investigations on liver disease therapy.
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MAP Quinasa Quinasa Quinasa 5 , Factor 2 Relacionado con NF-E2 , Animales , Apoptosis , Cromo/metabolismo , Cromo/toxicidad , Hepatocitos/metabolismo , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , MAP Quinasa Quinasa Quinasa 5/metabolismo , Masculino , Ratones , Factor 2 Relacionado con NF-E2/metabolismo , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Glycogen storage disease type Ia (GSD-Ia) is caused by a deficiency in the glucose-6-phosphatase (G6Pase, G6pc) enzyme, which catalyses the final step of gluconeogenesis and glycogenolysis. Accumulation of G6pc can lead to an increase in glycogen and development of fatty liver. Ductular reactions refer to the proliferation of cholangiocytes and hepatic progenitors, which worsen fatty liver progress. To date, however, ductular reactions in GSD-Ia remain poorly understood. Here, we studied the development and potential underlying mechanism of ductular reactions in GSD-Ia in mice. We first generated GSD-Ia mice using CRISPR/Cas9 to target the exon 3 region of the G6pc gene. The typical GSD-Ia phenotype in G6pc -/- mice was then analysed using biochemical and histological assays. Ductular reactions in G6pc -/- mice were tested based on the expression of cholangiocytic markers cytokeratin 19 (CK19) and epithelial cell adhesion molecule (EpCAM). Yes-associated protein 1 (Yap) signalling activity was measured using western blot (WB) analysis and quantitative real-time polymerase chain reaction (qRT-PCR). Verteporfin was administered to the G6pc -/- mice to inhibit Yap signalling. The CRISPR/Cas9 system efficiently generated G6pc -/- mice, which exhibited typical GSD-Ia characteristics, including retarded growth, hypoglycaemia, and fatty liver disease. In addition, CK19- and EpCAM-positive cells as well as Yap signalling activity were increased in the livers of G6pc -/- mice. However, verteporfin treatment ameliorated ductular reactions and decreased Yap signalling activity. This study not only improves our understanding of GSD-Ia pathophysiology, but also highlights the potential of novel therapeutic approaches for GSD-Ia such as drug targeting of ductular reactions.
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Bone formation, remodeling and repair are dynamic processes, involving cell migration, ECM assembly, osteocyte embedding, and bone resorption. Using live-cell imaging, we previously showed that osteoblast assembly of the ECM proteins fibronectin and collagen is highly dynamic and is integrated with cell motility. Additionally, osteoblast-to-osteocyte transition involved arrest of cell motility, followed by dendrite extension and retraction that may regulate positioning of embedding osteocytes. To further understand how osteocytes differentiate and embed in collagen, mice were generated that co-expressed GFPtopaz-tagged collagen with a Dmp1-Cre-inducible tdTomato reporter targeted to preosteocytes/osteocytes. Dual live-cell imaging of collagen and osteocyte dynamics in mineralizing primary calvarial cell cultures showed that Dmp1-Cre/tdTomato turned on in early bone nodule forming regions, demarcated by foci of concentrated GFP-collagen bundles that appeared structurally distinct from the surrounding collagen. Dmp1-Cre/tdTomato-positive cells were post-mitotic and were continuously induced throughout the 2 week timecourse, whereas the majority of collagen was assembled by day 7. GFP-collagen fibrils showed global (tissue-level) motions, suggesting coordinated cell layer movement, and local fibril motions mediated by cell-generated forces. Condensation of collagen fibril networks occurred within bone nodules prior to mineralization. Intravital imaging confirmed a similar structural appearance of GFP-collagen in calvarial bone, with analogous global motions of mineralizing areas adjacent to sutures. In early (unmineralized) calvarial cell cultures, Dmp1-Cre/tdTomato-positive cells were motile (mean velocity 4.8 µm/h), moving freely in and around the forming bone nodule, with a small number of these cells embedded in collagen, constraining their motion. In mineralizing cultures, the average velocity of Dmp1-Cre/tdTomato-positive cells was significantly reduced (0.7 µm/h), with many immobilized in the mineralizing nodule. Three apparent mechanisms for embedding of Dmp1-Cre/tdTomato-positive cells were observed. In some cases, a previously motile Dmp1-Cre/tdTomato-positive cell became immobilized in collagen fibril networks that were newly assembled around the cell, thereby entrapping it. In other cases, a motile Dmp1-Cre/tdTomato-positive cell moved into an already formed "collagen lacuna," arrested its motility and became embedded. Alternatively, some cells switched on tdTomato expression in situ within a lacuna. These data provide new insight into the dynamic process of bone collagen assembly and suggest multiple mechanisms for osteocyte entrapment in collagen matrix.
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Osteocytes, the most abundant cells in bone, were once thought to be inactive, but are now known to have multifunctional roles in bone, including in mechanotransduction, regulation of osteoblast and osteoclast function and phosphate homeostasis. Because osteocytes are embedded in a mineralized matrix and are challenging to study, there is a need for new tools and cell models to understand their biology. We have generated two clonal osteogenic cell lines, OmGFP66 and OmGFP10, by immortalization of primary bone cells from mice expressing a membrane-targeted GFP driven by the Dmp1-promoter. One of these clones, OmGFP66, has unique properties compared with previous osteogenic and osteocyte cell models and forms 3-dimensional mineralized bone-like structures, containing highly dendritic GFP-positive osteocytes, embedded in clearly defined lacunae. Confocal and electron microscopy showed that structurally and morphologically, these bone-like structures resemble bone in vivo, even mimicking the lacunocanalicular ultrastructure and 3D spacing of in vivo osteocytes. In osteogenic conditions, OmGFP66 cells express alkaline phosphatase (ALP), produce a mineralized type I collagen matrix, and constitutively express the early osteocyte marker, E11/gp38. With differentiation they express osteocyte markers, Dmp1, Phex, Mepe, Fgf23, and the mature osteocyte marker, Sost. They also express RankL, Opg, and Hif1α, and show expected osteocyte responses to PTH, including downregulation of Sost, Dmp1, and Opg and upregulation of RankL and E11/gp38. Live cell imaging revealed the dynamic process by which OmGFP66 bone-like structures form, the motile properties of embedding osteocytes and the integration of osteocyte differentiation with mineralization. The OmGFP10 clone showed an osteocyte gene expression profile similar to OmGFP66, but formed less organized bone nodule-like mineral, similar to other osteogenic cell models. Not only do these cell lines provide useful new tools for mechanistic and dynamic studies of osteocyte differentiation, function, and biomineralization, but OmGFP66 cells have the unique property of modeling osteocytes in their natural bone microenvironment. © 2019 American Society for Bone and Mineral Research.
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Huesos/anatomía & histología , Diferenciación Celular , Línea Celular/citología , Proteínas Fluorescentes Verdes/metabolismo , Minerales/metabolismo , Osteocitos/citología , Osteogénesis , Animales , Biomarcadores/metabolismo , Huesos/ultraestructura , Diferenciación Celular/efectos de los fármacos , Proteínas de la Matriz Extracelular/metabolismo , Factor-23 de Crecimiento de Fibroblastos , Regulación de la Expresión Génica/efectos de los fármacos , Ratones Transgénicos , Modelos Biológicos , Osteocitos/efectos de los fármacos , Osteocitos/ultraestructura , Osteogénesis/efectos de los fármacos , Hormona Paratiroidea/farmacología , Factores de TiempoRESUMEN
PURPOSE: Transgenic Cre lines are a valuable tool for conditionally inactivating or activating genes to understand their function. Here, we provide an overview of Cre transgenic models used for studying gene function in bone cells and discuss their advantages and limitations, with particular emphasis on Cre lines used for studying osteocyte and osteoclast function. RECENT FINDINGS: Recent studies have shown that many bone cell-targeted Cre models are not as specific as originally thought. To ensure accurate data interpretation, it is important for investigators to test for unexpected recombination events due to transient expression of Cre recombinase during development or in precursor cells and to be aware of the potential for germ line recombination of targeted genes as well as the potential for unexpected phenotypes due to the Cre transgene. Although many of the bone-targeted Cre-deleter strains are imperfect and each model has its own limitations, their careful use will continue to provide key advances in our understanding of bone cell function in health and disease.
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Enfermedades Óseas/genética , Modelos Animales de Enfermedad , Integrasas/genética , Ratones , Osteoclastos/metabolismo , Osteocitos/metabolismo , Animales , Enfermedades Óseas/metabolismo , Técnicas de Inactivación de Genes , Ratones TransgénicosRESUMEN
Osteogenesis imperfecta (OI) is a heritable connective tissue disorder primarily due to mutations in the type I collagen genes (COL1A1 and COL1A2), leading to compromised biomechanical integrity in type I collagen-containing tissues such as bone. Bone is inherently mechanosensitive and thus responds and adapts to external stimuli, such as muscle mass and contractile strength, to alter its mass and shape. Myostatin, a member of the TGF-ß superfamily, signals through activin receptor type IIB to negatively regulate muscle fiber growth. Because of the positive impact of myostatin deficiency on bone mass, we utilized a soluble activin receptor type IIB-mFc (sActRIIB-mFc) fusion protein in two molecularly distinct OI mouse models (G610C and oim) and evaluated their bone properties. Wild-type (WT), +/G610C, and oim/oim mice were treated from 2 to 4 months of age with either vehicle (Tris-buffered saline) or sActRIIB-mFc (10 mg/kg). Femurs of sActRIIB-mFc-treated mice exhibited increased trabecular bone volume regardless of genotype, whereas the cortical bone microarchitecture and biomechanical strength were only improved in WT and +/G610C mice. Dynamic histomorphometric analyses suggest the improved cortical bone geometry and biomechanical integrity reflect an anabolic effect due to increased mineral apposition and bone formation rates, whereas static histomorphometric analyses supported sActRIIB-mFc treatment also having an anti-catabolic impact with decreased osteoclast number per bone surface on trabecular bone regardless of sex and genotype. Together, our data suggest that sActRIIB-mFc may provide a new therapeutic direction to improve both bone and muscle properties in OI. © 2018 American Society for Bone and Mineral Research.
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Receptores de Activinas Tipo II/uso terapéutico , Huesos/patología , Osteogénesis Imperfecta/tratamiento farmacológico , Osteogénesis Imperfecta/patología , Receptores de Activinas Tipo II/farmacología , Animales , Biomarcadores/sangre , Fenómenos Biomecánicos , Huesos/fisiopatología , Modelos Animales de Enfermedad , Femenino , Fémur/patología , Masculino , Ratones Endogámicos C57BL , Osteoblastos/metabolismo , Osteoblastos/patología , Osteoclastos/metabolismo , Osteocitos/metabolismo , Osteogénesis Imperfecta/sangre , Osteogénesis Imperfecta/fisiopatología , Fragmentos de Péptidos/sangre , Procolágeno/sangre , Proteínas Recombinantes de Fusión/farmacología , Proteínas Recombinantes de Fusión/uso terapéutico , Solubilidad , Torsión MecánicaRESUMEN
Age-related bone loss and associated fracture risk are major problems in musculoskeletal health. Osteocytes have emerged as key regulators of bone mass and as a therapeutic target for preventing bone loss. As aging is associated with changes in the osteocyte lacunocanalicular system, we focused on the responsible cellular mechanisms in osteocytes. Bone phenotypic analysis was performed in young-(5mo) and aged-(22mo) C57BL/6 mice and changes in bone structure/geometry correlated with alterations in osteocyte parameters determined using novel multiplexed-3D-confocal imaging techniques. Age-related bone changes analogous to those in humans were observed, including increased cortical diameter, decreased cortical thickness, reduced trabecular BV/TV and cortical porosities. This was associated with a dramatic reduction in osteocyte dendrite number and cell density, particularly in females, where osteocyte dendricity decreased linearly from 5, 12, 18 to 22mo and correlated significantly with cortical bone parameters. Reduced dendricity preceded decreased osteocyte number, suggesting dendrite loss may trigger loss of viability. Age-related degeneration of osteocyte networks may impair bone anabolic responses to loading and gender differences in osteocyte cell body and lacunar fluid volumes we observed in aged mice may lead to gender-related differences in mechanosensitivity. Therapies to preserve osteocyte dendricity and viability may be beneficial for bone health in aging.
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Envejecimiento/patología , Huesos/patología , Osteocitos/patología , Osteoporosis/patología , Animales , Modelos Animales de Enfermedad , Femenino , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
Osteocytes appear to mobilize calcium within minutes in response to PTH injections; we have previously shown that osteocytes remove their perilacunar matrix during lactation through activation of the PTH type 1 receptor. Mechanisms utilized by osteocytes to mobilize calcium are unknown but we hypothesized that the molecular components may be similar to those used by osteoclasts. Here we show, using IDG-SW3 cells that ATP6V0D2, an essential component of vacuolar ATPase in osteoclasts, and other genes associated with osteoclastic bone resorption, increase with osteoblast to osteocyte differentiation. Furthermore, PTHrP increases ATP6V0D2 expression and induces proton generation by primary osteocytes, which is blocked by bafilomycin, a vacuolar ATPase inhibitor. These in vitro proton measurements raised the question of osteocyte viability in an acidic environment. Interestingly, osteocytes, showed enhanced viability at pH as low as 5 compared to osteoblasts and fibroblasts in vitro. To study in vivo acidification by osteocytes, virgin and lactating CD1 mice on a low calcium diet were injected with the pH indicator dye, acridine orange, and their osteocyte lacuno-canalicular system imaged by confocal microscopy. Lower pH was observed in lactating compared to virgin animals. In addition, a novel transgenic mouse line with a topaz variant of green fluorescent protein (GFPtpz)-tagged collagen α2(I) chain was used. Instead of the expected reduction in GFP-fluorescence only in the perilacunar matrix, reduced fluorescence was observed in the entire bone matrix of lactating mice. Based on our experiments showing quenching of GFP in vitro, we propose that the observed reduction in GFP fluorescence in lactating mice is due to quenching of GFP by the acidic pH generated by osteocytes. Together these findings provide novel mechanistic insight into how osteocytes remove calcium from their perilacunar/pericanalicular matrices through active acidification of their microenvironment and show that osteocytes, like osteoclasts, are resistant to the negative effects of acid on viability. © 2017 American Society for Bone and Mineral Research.
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Microambiente Celular/efectos de los fármacos , Lactancia/metabolismo , Osteocitos/metabolismo , Proteína Relacionada con la Hormona Paratiroidea/farmacología , ATPasas de Translocación de Protón Vacuolares/metabolismo , Animales , Línea Celular Transformada , Supervivencia Celular/efectos de los fármacos , Femenino , Concentración de Iones de Hidrógeno , Macrólidos/farmacología , Ratones , Osteocitos/citología , ATPasas de Translocación de Protón Vacuolares/antagonistas & inhibidoresRESUMEN
Treatment with bisphosphonates within the first 10 days of severe burn injury completely prevents bone loss. We therefore postulated that bone resorption occurs early post burn and is the primary explanation for acute bone loss in these patients. Our objective was to assess bone for histological and biomechanical evidence of early resorption post burn. We designed a randomized controlled study utilizing a sheep model of burn injury. Three sheep received a 40 % total body surface area burn under isoflurane anesthesia, and three other sheep received cotton-smoke inhalation and served as control. Burned sheep were killed 5 days post procedure and controls were killed 2 days post procedure. Backscatter scanning electron microscopy was performed on iliac crests obtained immediately postmortem along with quantitative histomorphometry and compression testing to determine bone strength (Young's modulus). Blood ionized Ca was also determined in the first 24 h post procedure as was urinary CTx. Three of three sheep killed at 5 days had evidence of scalloping of the bone surface, an effect of bone resorption, whereas none of the three sheep killed at 2 days post procedure had scalloping. One of the three burned sheep killed at 5 days showed quantitative doubling of the eroded surface and halving of the bone volume compared to sham controls. Mean values of Young's modulus were approximately one third lower in the burned sheep killed at 5 days compared to controls, p = 0.08 by unpaired t test, suggesting weaker bone. These data suggest early post-burn bone resorption. Urine CTx normalized to creatinine did not differ between groups at 24 h post procedure because the large amounts of fluids received by the burned sheep may have diluted urine creatinine and CTx and because the urine volume produced by the burned sheep was threefold that of the controls. We calculated 24 h urinary CTx excretion, and with this calculation CTx excretion/24 h in the burned sheep was nearly twice that of the controls. Moreover, whole blood ionized Ca measured at 3- to 6-h intervals over the first 24 h in both burn and control sheep showed a 6 % reduction versus baseline in the burned sheep with <1 % reduction in the control animals. This sheep model was previously used to demonstrate upregulation of the parathyroid calcium-sensing receptor within the timeframe of the present study. Because both early bone resorption, supported by this study, and calcium-sensing receptor upregulation, consistent with the observed reduction in blood ionized Ca, are mediated by proinflammatory cytokines that are present as part of the post-burn systemic inflammatory response, we may postulate that post-burn upregulation of the parathyroid calcium-sensing receptor may be an adaptive response to clear the blood of excess calcium liberated by cytokine-mediated bone resorption.
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Resorción Ósea/fisiopatología , Quemaduras/fisiopatología , Animales , Huesos/lesiones , Huesos/patología , Modelos Animales de Enfermedad , Femenino , Humanos , Microscopía Electrónica de Rastreo , Ovinos , Factores de TiempoRESUMEN
The mechanisms by which inorganic phosphate (P(i)) homeostasis controls bone biology are poorly understood. Here we used Dmp1 null mice, a hypophosphatemic rickets/osteomalacia model, combined with a metatarsal organ culture and an application of neutralizing fibroblast growth factor 23 (FGF-23) antibodies to gain insight into the roles of P(i) in bone biology. We showed (1) that abnormal bone remodeling in Dmp1 null mice is due to reduced osteoclast number, which is secondary to a reduced ratio of RANKL/OPG expressed by osteoclast supporting cells and (2) that osteoblast extracellular matrix mineralization, growth plate maturation, secondary ossification center formation, and osteoblast differentiation are phosphate-dependent. Finally, a working hypothesis is proposed to explain how phosphate and DMP1 control osteocyte maturation.
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Diferenciación Celular , Osteocitos/patología , Osteogénesis/fisiología , Fósforo/metabolismo , Animales , Anticuerpos/administración & dosificación , Anticuerpos/farmacología , Biomarcadores/metabolismo , Remodelación Ósea/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , Proteínas de la Matriz Extracelular/deficiencia , Factor-23 de Crecimiento de Fibroblastos , Factores de Crecimiento de Fibroblastos/inmunología , Homeostasis/efectos de los fármacos , Ratones , Ratones Noqueados , Osteoblastos/efectos de los fármacos , Osteoblastos/metabolismo , Osteoblastos/patología , Osteoclastos/efectos de los fármacos , Osteoclastos/metabolismo , Osteoclastos/patología , Osteocitos/efectos de los fármacos , Osteocitos/metabolismo , Osteogénesis/efectos de los fármacos , Fosfatos/metabolismoRESUMEN
Dentin matrix protein 1 (DMP-1) is a key molecule in controlling osteocyte formation and phosphate homeostasis. Based on observations that full-length DMP-1 is not found in bone, but only cleaved fragments of 37 and 57 kDa are present, and in view of the finding that mutations in the 57-kDa fragment result in disease, we hypothesized that the 57-kDa C-terminal fragment is the functional domain of DMP-1. To test this hypothesis, a 3.6-kb type I collagen promoter was used to express this 57-kDa C-terminal fragment for comparison with full-length DMP-1 in Dmp1 null osteoblasts/osteocytes. Not only did expression of the full-length DMP-1 in bone cells fully rescue the skeletal abnormalities of Dmp1 null mice, but the 57-kDa fragment also had similar results. This included rescue of growth plate defects, osteomalacia, abnormal osteocyte maturation, and the abnormal osteocyte lacunocanalicular system. In addition, the abnormal fibroblast growth factor 23 (FGF-23) expression in osteocytes, elevated circulating FGF-23 levels, and hypophosphatemia were rescued. These results show that the 57-kDa C-terminal fragment is the functional domain of DMP-1 that controls osteocyte maturation and phosphate metabolism.
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Proteínas de la Matriz Extracelular/metabolismo , Osteocitos/citología , Animales , Huesos/metabolismo , Condrocitos/citología , Factor-23 de Crecimiento de Fibroblastos , Factores de Crecimiento de Fibroblastos/química , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microscopía Electrónica de Rastreo/métodos , Microscopía Electrónica de Transmisión/métodos , Osteoblastos/citología , Estructura Terciaria de Proteína , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Microtomografía por Rayos X/métodosRESUMEN
Granulin epithelin precursor (GEP) is a new growth factor that functions in brain development, chondrogenesis, tissue regeneration, tumorigenesis, and inflammation. The goal of this study was to study whether GEP was critical for odontogenesis and amelogenesis both in vivo and in vitro. The in situ hybridization and immunohistochemistry data showed that GEP was expressed in both odontoblast and ameloblast cells postnatally. Knockdown of GEP by crossing U6-ploxPneo-GEP and Sox2-Cre transgenic mice led to a reduction of dentin thickness, an increase in predentin thickness, and a reduction in mineral content in enamel. The in vitro application of recombinant GEP up-regulated molecular markers important for odontogenesis (DMP1, DSPP, and ALP) and amelogenesis (ameloblastin, amelogenin and enamelin). In conclusion, both the in vivo and the in vivo data support an important role of GEP in tooth formation during postnatal development.
Asunto(s)
Amelogénesis/fisiología , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Odontogénesis/fisiología , Ameloblastos/citología , Ameloblastos/metabolismo , Amelogénesis/genética , Animales , Animales Recién Nacidos , Diferenciación Celular/genética , Diferenciación Celular/fisiología , Línea Celular , Proliferación Celular , Esmalte Dental/metabolismo , Dentina/metabolismo , Femenino , Hibridación in Situ , Péptidos y Proteínas de Señalización Intercelular/genética , Masculino , Ratones , Ratones Noqueados , Odontoblastos/citología , Odontoblastos/metabolismo , Odontogénesis/genética , Reacción en Cadena de la Polimerasa , ProgranulinasRESUMEN
Mutations in FAM20C were recently identified as the cause of lethal osteosclerotic bone dysplasia, which highlighted the important role of this molecule in biomineralization. No systematic studies have been performed to evaluate the expression pattern of this relatively new molecule in the developmental processes of bone and tooth. In the present study, we analyzed in detail the expression profile of FAM20C during osteogenesis and odontogenesis using ISH and IHC approaches. The specimens analyzed were mouse tissues spanning embryonic day 13.5 (E13.5) to postnatal 8 weeks. The earliest presence of FAM20C was observed at E14.5. During osteogenesis, FAM20C mRNA was detected in the chondrocytes and osteoblasts of the long bone, whereas its protein was observed in the extracellular matrix (ECM) of bone and in the cytoplasm of the chondrocytes, osteoblasts, and osteocytes. During odontogenesis, FAM20C mRNA was detected in the ameloblasts, odontoblasts, cementoblasts, and periodontal ligament fibroblasts, whereas its protein was observed in the matrices of dentin, enamel, and alveolar bone and in the cytoplasm of the aforementioned cells. The temporospatial expression profile revealed in this study indicates that FAM20C is an ECM protein that may play an important role in controlling the mineralization of bone and tooth.
Asunto(s)
Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Proteínas de la Matriz Extracelular/genética , Proteínas de la Matriz Extracelular/metabolismo , Regulación del Desarrollo de la Expresión Génica , Odontogénesis/genética , Osteogénesis/genética , Animales , Especificidad de Anticuerpos , Huesos/metabolismo , Proteínas de Unión al Calcio/análisis , Proteínas de Unión al Calcio/inmunología , Línea Celular , Proteínas de la Matriz Extracelular/análisis , Proteínas de la Matriz Extracelular/inmunología , Humanos , Ratones , Proteínas Recombinantes/análisis , Proteínas Recombinantes/genética , Proteínas Recombinantes/inmunología , Proteínas Recombinantes/metabolismo , Diente/crecimiento & desarrollo , Diente/metabolismoRESUMEN
DMP1 mutations in autosomal recessive hypophosphatemic rickets (ARHR) patients and mice lacking Dmp1 display an overlapping pathophysiology, such as hypophosphatemia. However, subtle differences exist between the mouse model and human ARHR patients. These differences could be due to a species specificity of human versus mouse, or it may be that the mutant DMP1 in humans maintains partial function of DMP1. In this study we report a deformed tooth phenotype in a human DMP1 deletion mutation case. Unexpectedly, the deletion of nucleotides 1484 to 1490 (c.1484_1490delCTATCAC, delMut, resulting in replacement of the last 18 residues with 33 random amino acids) showed a severe dentin and enamel defect similar to a dentinogenesis imperfecta (DI) III-like phenotype. To address the molecular mechanism behind this phenotype, we generated delMut transgenic mice with the endogenous Dmp1 gene removed. These mutant mice did not recapture the abnormal phenotype observed in the human patient but displayed a mild rachitic tooth phenotype in comparison with that in the Dmp1-null mice, suggesting that the DI III-like phenotype may be due to an as-yet-undetermined acquired gene modifier. The mechanism studies showed that the mutant fragment maintains partial function of DMP1 such as stimulating MAP kinase signaling in vitro. Last, the in vitro and in vivo data support a role of odontoblasts in the control of fibroblast growth factor 23 (FGF-23) regulation during early postnatal development, although this regulation on Pi homeostasis is likely limited.
Asunto(s)
Proteínas de la Matriz Extracelular/fisiología , Raquitismo Hipofosfatémico Familiar/genética , Diente/patología , Animales , Secuencia de Bases , Cartilla de ADN , Modelos Animales de Enfermedad , Proteínas de la Matriz Extracelular/genética , Raquitismo Hipofosfatémico Familiar/patología , Factor-23 de Crecimiento de Fibroblastos , Humanos , Hibridación in Situ , Ratones , Ratones Mutantes , Fenotipo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Tomografía Computarizada por Rayos X , Diente/diagnóstico por imagen , TransgenesRESUMEN
Granulin epithelin precursor (GEP) has been implicated in development, tissue regeneration, tumorigenesis, and inflammation. Herein we report that GEP stimulates chondrocyte differentiation from mesenchymal stem cells in vitro and endochondral ossification ex vivo, and GEP-knockdown mice display skeleton defects. Similar to bone morphogenic protein (BMP) 2, application of the recombinant GEP accelerates rabbit cartilage repair in vivo. GEP is a key downstream molecule of BMP2, and it is required for BMP2-mediated chondrocyte differentiation. We also show that GEP activates chondrocyte differentiation through Erk1/2 signaling and that JunB transcription factor is one of key downstream molecules of GEP in chondrocyte differentiation. Collectively, these findings reveal a novel critical role of GEP growth factor in chondrocyte differentiation and the molecular events both in vivo and in vitro.
Asunto(s)
Proteína Morfogenética Ósea 2/metabolismo , Condrogénesis/fisiología , Péptidos y Proteínas de Señalización Intercelular/fisiología , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Proteínas Proto-Oncogénicas c-jun/metabolismo , Animales , Biomarcadores/metabolismo , Western Blotting , Cartílago/citología , Cartílago/metabolismo , Diferenciación Celular , Células Cultivadas , Condrocitos/citología , Condrocitos/metabolismo , Inmunoprecipitación de Cromatina , Feto/citología , Feto/metabolismo , Perfilación de la Expresión Génica , Humanos , Técnicas para Inmunoenzimas , Hibridación in Situ , Células Madre Mesenquimatosas/metabolismo , Ratones , Ratones Endogámicos C3H , Ratones Noqueados , Análisis de Secuencia por Matrices de Oligonucleótidos , Progranulinas , Sondas ARN , ARN Mensajero/genética , ARN Mensajero/metabolismo , Conejos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de SeñalRESUMEN
Dmp1-null mice and patients with mutations in dentin matrix protein 1 (DMP1) resulting in autosomal recessive hypophosphatemic rickets display similar skeletal defects. As mutations were observed in the last 18 amino acids of DMP1 in 1 subset of patients and as fragments of intact DMP1, a 37-kDa N-terminal and a 57-kDa C-terminal fragment, have been purified from bone and dentin, we hypothesized that the cleaved 57-kDa C-terminal fragment is the essential functional domain of DMP1. To test this hypothesis, different forms of recombinant DMP1 were expressed in 293EBNA, CHO and 2T3 cells. The results showed that DMP1 was processed into a 37-kDa N-terminal and a 57-kDa C-terminal fragment in vitro in all cell lines examined. DMP1 processing in CHO cells was blocked by a furin protease inhibitor, decanoyl-Arg-Val-Lys-Arg-chloromethyl ketone, in a dose-dependent manner. Coexpression of PHEX, a potential upstream protease, had no apparent effect on DMP1 cleavage in 293EBNA cells, suggesting that PHEX may not be required for DMP1 processing. To test the in vivo role of the C-terminal fragment, transgenic mice overexpressing full-length DMP1 or the 57-kDa fragment controlled by the 3.6-kb Col1 promoter were generated. Overexpression of these transgenes had no effect on the wild-type skeleton, but on the Dmp1-null background showed expression in the osteoblast layer and throughout the bone matrix leading to the rescue of the null bone phenotype. This suggests that the 57-kDa C-terminal fragment may be able to recapitulate the function of intact DMP1 in vivo.