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Mineralized Nodule Formation (mineralized + nodule_formation)
Selected AbstractsRelevance of a new rat model of osteoblastic metastases from prostate carcinoma for preclinical studies using zoledronic acidINTERNATIONAL JOURNAL OF CANCER, Issue 4 2008François Lamoureux Abstract Animal models that mimic osteoblastic metastases associated with prostate carcinoma are required to improve the therapeutic options in humans. A new model was then developed and characterized in immunocompetent rats. The bisphosphonate zoledronic acid (ZOL) was tested to validate this model as a therapeutic application. Rat AT6-1 prostate tumor cells were characterized in vitro at the transcriptional (bone and epithelial markers) and functional (induction of mineralized nodules) levels. The bone lesions induced after their direct injection into the femur bone marrow were characterized by radiography, microscanner and histology analyses. ZOL effects were studied in vivo on bone lesion development and in vitro on AT6-1 cell proliferation, apoptosis and cell cycle analysis. Apart from epithelial markers, AT6-1 cells express an osteoblast phenotype as they express osteoblastic markers and are able to induce mineralized nodule formation in vitro. A disorganization of the trabecular bone at the growth zone level was observed in vivo after intraosseous AT6-1 cell injection as well as cortical erosion. The tumor itself is associated with bone formation as revealed by SEM analysis and polarized light microscopy. ZOL prevents the development of such osteoblastic lesions, related to a direct inhibitory effect on tumor cell proliferation independent of caspase 3 activation, but associated with cell cycle arrest. A new rat model of osteoblastic bone metastases was validated in immunocompetent rats and used to show the relevance of using ZOL in such lesions, as this compound shows bifunctional effects on both bone remodelling and tumor cell proliferation. İ 2007 Wiley-Liss, Inc. [source] Climbing Exercise Increases Bone Mass and Trabecular Bone Turnover Through Transient Regulation of Marrow Osteogenic and Osteoclastogenic Potentials in Mice,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2003Toshiharu Mori Abstract To investigate the relationship between the effects of bone turnover and bone marrow cell development in bone cells, we developed a mouse voluntary climbing exercise model. Climbing exercise increased bone volume and transient osteogenic potential of bone marrow. This model would be suitable for investigating the mechanistic roles of mechanical loading. Introduction: The relationship between bone mass gain and local bone formation and resorption in mechanically loaded bone is not well understood. Materials and Methods: Sixty-five C57BL/6J mice, 8 weeks of age, were assigned to five groups: a baseline control and two groups each of ground control and climbing exercise mice for 2 and 4 weeks. Mice were housed in a 100-cm tower and had to climb toward a bottle placed at the top to drink water. Results: Compared with the ground control, bone mineral density of the left femur increased in the climbing mice at 4 weeks. At 2 and 4 weeks, bone formation rate (BFR/BS) of periosteal surface, the cross-sectional area, and moment of inertia were increased in the climbing mice, whereas BFR/BS and eroded surface (ES/BS) of endosteal surface did not differ. The trabecular bone volume (BV/TV) of the proximal tibia increased in climbing mice, and osteoclast surface (Oc.S/BS) and osteoclast number decreased at 2 weeks. At 4 weeks, there were increases in BV/TV and parameters of bone formation, including mineralized surface, mineral apposition rate, and bone formation rate. In marrow cell cultures from the tibia, the number of alkaline phosphatase+ colony forming units-fibroblastic and the area of mineralized nodule formation in climbing mice were increased, and the number of osteoclast-like TRACP+ multinucleated cells was lower at 2 weeks. At 4 weeks, these parameters recovered to the levels of the ground controls. Conclusion: Our results indicate that climbing increased trabecular bone volume and reduced bone resorption, with a subsequent increase in bone formation. Intermittent climbing downregulates marrow osteoclastogenic cells and upregulates osteogenic cells initially, but further exercise seemed to desensitize them. Cortical envelopes were enlarged earlier, but the response seems to differ from trabecular bone. [source] Prostaglandin E2 -Mediated Anabolic Effect of a Novel Inhibitor of Phosphodiesterase 4, XT-611, in the In Vitro Bone Marrow Culture,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2003Ken-Ichi Miyamoto Abstract The mechanism of osteoblast formation by a novel PDE4 inhibitor, XT-611, was studied in the in vitro bone marrow culture system. The compound potentiated the osteoblast differentiation through accumulation of cyclic AMP after autocrine stimulation of EP4 receptor by PGE2 in pro-osteoblastic cells. Introduction: We previously reported that inhibitors of phosphodiesterase (PDE)4 isoenzyme increase osteoblast formation in an in vitro bone marrow culture system and inhibit bone loss in animal osteoporosis models. Here we investigated the mechanism of the effect of a novel PDE4 inhibitor, 3,4-dipropyl-4,5,7,8-tetrahydro-3H -imidazo[1,2- i]-purin-5-one (XT-611), on osteoblast formation in the in vitro bone marrow culture system. Materials and Methods: Rodent bone marrow cells were cultured in the presence of 0.2 mM ascorbic acid phosphate ester, 1 mM ,-glycerophosphate, and 10 nM dexamethasone for 10 days. Drug treatments were done for 24 h on day 3 of culture. Results: PDE4 inhibitors, including XT-611, but not PDE3 and PDE5 inhibitors, increased mineralized nodule formation in rat and mouse bone marrow cell cultures. During culture of the bone marrow cells, prostaglandin E2 (PGE2) production increased with a peak on day 4, but the increase was completely inhibited by indomethacin, an unselective cyclo-oxygenase (COX) inhibitor. Spontaneous and XT-611-induced mineralized-nodule formation was also inhibited by indomethacin and COX-2 inhibitors, in a similar potential. Alkaline phosphatase-positive nodule formation in the absence or presence of XT-611 was inhibited by an antagonist of EP4 receptor, AH23848B, and synergistically potentiated by 11-deoxy-PGE1, but it was not influenced by other EP antagonists and agonists examined. The expression of PDE4 and EP4 mRNAs was observed in bone marrow cells. The effect of XT-611 was also confirmed to involve an increase of cyclic AMP and the cyclic AMP-dependent protein kinase pathway. Conclusion: These results suggest that PGE2 stimulates differentiation of osteoblast progenitor cells through the EP4 receptor in an autocrine manner, and the PDE4 inhibitor potentiates the differentiation by inhibiting hydrolysis of cyclic AMP in the cells. [source] Differential Expression of Estrogen Receptor-Related Receptor , and Estrogen Receptors , and , in Osteoblasts In Vivo and In Vitro,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2002Edith Bonnelye Abstract The orphan nuclear estrogen receptor-related receptor (ERR) , is expressed by osteoblastic cells, is known to transactivate at least one osteoblast-associated gene osteopontin (OPN) and plays a functional role in osteoprogenitor cell proliferation and differentiation. To dissect further the role of ERR-, in bone formation, we compared its expression to that of the estrogen receptor (ER) , and ER-, in rat calvaria (RC) and fetal tibia in vivo and in RC and rat bone marrow (RBM) cells in vitro. We found that ERR-, is highly and widely expressed in most, if not all, cells in RC cell cultures from early proliferation stages through mineralized nodule formation; ER-, was localized similarly but at lower levels and ER-,, although present, was barely detectable. These patterns of expression in vitro correlated with what we observed in vivo in sections of 21-day fetal RC, in which ERR-, appeared to be more highly expressed than either of the ERs. Interestingly, ERR-, also is highly expressed in RBM cells, while ER-, and ER-, mRNA is expressed, but at lower levels. Moreover, we found that ERR-,, ER-,, and ER-, were all expressed in osteoblasts in fetal and adult tibia whereas they were expressed differentially in calvaria in vivo in subsets of osteoblasts, supporting the hypothesis that ERR-, may interact with one or both of the ERs in those osteoblasts in which they are coexpressed and that all three receptors may be required for bone formation but at different times and for different functions. [source] Retinoic acid is a potential negative regulator for differentiation of human periodontal ligament cellsJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2005Natsuko Shibuya Background and objectives:, Retinoic acid (RA) exerts a wide variety of effects on development, cellular differentiation and homeostasis in various tissues. However, little is known about the effects of RA on the differentiation of periodontal ligament cells. In this study, we investigated whether RA can affect the dexamethasone-induced differentiation of periodontal ligament cells. Methods and results:, Human periodontal ligament cells were differentiated via culturing in the presence of dexamethasone, ascorbic acid, and ,-glycerophosphate for mineralized nodule formation, as characterized by von Kossa staining. Continuous treatment with all- trans -RA inhibited the mineralization in a dose-dependent manner, with complete inhibition over 1 µm RA. Other RA analogs, 9- cis -RA and 13- cis -RA, were also effective. Furthermore, addition of RA for just the first 4 days completely inhibited the mineralization; however, as RA was added at later stages of culture, the inhibitory effect was diminished, suggesting that RA had a phase-dependent inhibition of mineralization. RA receptor (RAR)-, agonist (AM-580), but not retinoid X receptor agonist (methoprene acid), inhibited the mineralization, and reverse transcription,polymerase chain reaction analysis revealed that RAR-, was expressed on the cells, suggesting that RAR-, was involved in the inhibitory mechanism. This inhibition was accompanied by inhibition of alkaline phosphatase activity; however, neither expression of platelet-derived growth factor (PDGF) receptor-,, PDGF receptor-,, or epidermal growth factor (EGF) receptor, nor phosphorylation of extracellular signal-regulated kinases triggered by PDGF-ascorbic acid or PDGF-BB was changed, as assessed by flow cytometry or western blot analyses. Conclusions:, These findings suggest that RA is a potential negative regulator for differentiation of human periodontal ligament cells. [source] | ||||||||||