Endogenous production of TGF-beta is essential for osteoclastogenesis induced by a combination of receptor activator of NF-kappa B ligand and macrophage-colony-stimulating factor.
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Differentiation of osteoclasts, the cells primarily responsible for bone resorption, is controlled by a variety of osteotropic hormones and cytokines. Of these factors, receptor activator of NF-kappaB (RANK) ligand (RANKL) has been recently cloned as an essential inducer of osteoclastogenesis in the presence of M-CSF. Here, we isolated a stroma-free population of monocyte/macrophage (M/Mphi)-like hemopoietic cells from mouse unfractionated bone cells that were capable of differentiating into mature osteoclasts by treatment with soluble RANKL (sRANKL) and M-CSF. However, the efficiency of osteoclast formation was low, suggesting the requirement for additional factors. The isolated M/Mphi-like hemopoietic cells expressed TGF-beta and type I and II receptors of TGF-beta. Therefore, we examined the effect of TGF-beta on osteoclastogenesis. TGF-beta with a combination of sRANKL and M-CSF promoted the differentiation of nearly all M/Mphi-like hemopoietic cells into cells of the osteoclast lineage. Neutralizing anti-TGF-beta Ab abrogated the osteoclast generation. These TGF-beta effects were also observed in cultures of unfractionated bone cells, and anti-TGF-beta blocked the stimulatory effect of 1, 25-dihydroxyvitamin D(3). Translocation of NF-kappaB into nuclei induced by sRANKL in TGF-beta-pretreated M/Mphi-like hemopoietic cells was greater than that in untreated cells, whereas TGF-beta did not up-regulate the expression of RANK, the receptor of RANKL. Our findings suggest that TGF-beta is an essential autocrine factor for osteoclastogenesis. (+info)
TGF-beta 1 and IFN-gamma direct macrophage activation by TNF-alpha to osteoclastic or cytocidal phenotype.
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TNF-related activation-induced cytokine (TRANCE; also called receptor activator of NF-kappaB ligand (RANKL), osteoclast differentiation factor (ODF), osteoprotegerin ligand (OPGL), and TNFSF11) induces the differentiation of progenitors of the mononuclear phagocyte lineage into osteoclasts in the presence of M-CSF. Surprisingly, in view of its potent ability to induce inflammation and activate macrophage cytocidal function, TNF-alpha has also been found to induce osteoclast-like cells in vitro under similar conditions. This raises questions concerning both the nature of osteoclasts and the mechanism of lineage choice in mononuclear phagocytes. We found that, as with TRANCE, the macrophage deactivator TGF-beta(1) strongly promoted TNF-alpha-induced osteoclast-like cell formation from immature bone marrow macrophages. This was abolished by IFN-gamma. However, TRANCE did not share the ability of TNF-alpha to activate NO production or heighten respiratory burst potential by macrophages, or induce inflammation on s.c. injection into mice. This suggests that TGF-beta(1) promotes osteoclast formation not only by inhibiting cytocidal behavior, but also by actively directing TNF-alpha activation of precursors toward osteoclasts. The osteoclast appears to be an equivalent, alternative destiny for precursors to that of cytocidal macrophage, and may represent an activated variant of scavenger macrophage. (+info)
The osteoclast differentiation factor osteoprotegerin-ligand is essential for mammary gland development.
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Osteoprotegerin-ligand (OPGL) is a key osteoclast differentiation/activation factor essential for bone remodeling. We report that mice lacking OPGL or its receptor RANK fail to form lobulo-alveolar mammary structures during pregnancy, resulting in death of newborns. Transplantation and OPGL-rescue experiments in opgl-/- and rank-/- pregnant females showed that OPGL acts directly on RANK-expressing mammary epithelial cells. The effects of OPGL are autonomous to epithelial cells. The mammary gland defect in female opgl-/- mice is characterized by enhanced apoptosis and failures in proliferation and PKB activation in lobulo-alveolar buds that can be reversed by recombinant OPGL treatment. These data provide a novel paradigm in mammary gland development and an evolutionary rationale for hormonal regulation and gender bias of osteoporosis in females. (+info)
Expression of osteoclast differentiation factor in rheumatoid arthritis.
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OBJECTIVE: To analyze the expression pattern of osteoclast differentiation factor (ODF) and its contribution to osteoclastogenesis in rheumatoid arthritis (RA). METHODS: The expression of ODF was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) in RA synovial fibroblasts (RASF) isolated from 7 RA patients and in normal skin fibroblasts. Using RNA probes specific for ODF, in situ hybridization was performed. Immunohistochemical double labeling for CD68 was applied to characterize the ODF-expressing cells. ODF protein and messenger RNA (mRNA) expression by RASF with or without 1,25(OH)2D3 was studied by Western blot analysis and quantitative real-time PCR. In addition, we performed coculture experiments with RASF and normal peripheral blood mononuclear cells with or without 1,25(OH)2D3. RESULTS: By RT-PCR, ODF mRNA expression was found in all RASF investigated, but not in normal skin fibroblasts. In situ hybridization revealed that in RA synovial tissues, ODF mRNA was expressed mainly in the lining layer and at sites where synovium was attached to bone. Immunohistochemical double labeling demonstrated ODF mRNA expression mainly in CD68-fibroblast-like synoviocytes and CD68+ multinucleated osteoclast-like cells. By Western blotting, all RASF expressed ODF protein. However, different levels of ODF expression were found in the RASF from different patients. Interestingly, RASF expressing higher levels of ODF induced a larger number of osteoclast-like cells than did RASF expressing only low levels of ODF. Although 1,25(OH)2D3 did not alter the levels of ODF expression in RASF on either Western blot or quantitative real-time PCR, osteoclastogenesis required the presence of 1,25(OH)2D3. CONCLUSION: The present results suggest that activated RASF, by expressing ODF, play an important role in rheumatoid bone destruction. Moreover, the data provide evidence that RASF not only activate osteoclasts, but also contribute directly to osteoclastogenesis. (+info)
Impaired bone resorption by lipopolysaccharide in vivo in mice deficient in the prostaglandin E receptor EP4 subtype.
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In a previous study we showed that the involvement of EP4 subtype of the prostaglandin E (PGE) receptor is crucial for lipopolysaccharide (LPS)-induced osteoclast formation in vitro. The present study was undertaken to test whether EP4 is actually associated with LPS-induced bone resorption in vivo. In wild-type (WT) mice, osteoclast formation in vertebrae and tibiae increased 5 days after systemic LPS injection, and urinary excretion of deoxypyridinoline, a sensitive marker for bone resorption, statistically increased 10 days after injection. In EP4 knockout (KO) mice, however, LPS injection caused no significant changes in these parameters throughout the experiment. LPS exposure for 4 h strongly induced osteoclast differentiation factor (ODF) mRNA expression in primary osteoblastic cells (POB) both from WT and EP4 KO mice, and this expression was not inhibited by indomethacin, suggesting prostaglandin (PG) independence. LPS exposure for 24 h further induced ODF expression in WT POB, but not in EP4 KO POB. Indomethacin partially inhibited ODF expression in WT POB, but not in EP4 KO POB. These data suggest that ODF is induced both PG dependently and PG independently. LPS exposure for 24 h induced slightly greater osteoclastgenesis inhibitory factor (OCIF) mRNA expression in EP4 KO than in WT POB. These findings suggest that the reduced ODF expression and apparently increased OCIF expression also are responsible for the markedly reduced LPS-induced osteoclast formation in EP4 KO mice. Our results show that the EP4 subtype of the PGE receptor is involved in LPS-induced bone resorption in vivo also. Since LPS is considered to be largely involved in bacterially induced bone loss, such as in periodontitis and osteomyelitis, our study is expected to help broaden our understanding of the pathophysiology of these conditions. (+info)
Regulation of peripheral lymph node genesis by the tumor necrosis factor family member TRANCE.
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Proper lymph node (LN) development requires tumor necrosis factor-related activation-induced cytokine (TRANCE) expression. Here we demonstrate that the defective LN development in TRANCE(-/)- mice correlates with a significant reduction in lymphotoxin (LT)alphabeta(+)alpha(4)beta(7)(+)CD45(+)CD4(+)CD3(-) cells and their failure to form clusters in rudimentary mesenteric LNs. Transgenic TRANCE overexpression in TRANCE(-/)- mice results in selective restoration of this cell population into clusters, and results in full LN development. Transgenic TRANCE-mediated restoration of LN development requires LTalphabeta expression on CD45(+) CD4(+)CD3(-) cells, as LNs could not be induced in LTalpha(-/)- mice. LTalpha(-/)- mice also showed defects in the fate of CD45(+)CD4(+)CD3(-) cells similar to TRANCE(-/)- mice. Thus, we propose that both TRANCE and LTalphabeta regulate the colonization and cluster formation by CD45(+) CD4(+)CD3(-) cells in developing LNs, the degree of which appears to correlate with the state of LN organogenesis. (+info)
Estrogen deficiency induces bone loss by enhancing T-cell production of TNF-alpha.
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Estrogen deficiency induces bone loss by upregulating osteoclastogenesis by mechanisms not completely defined. We found that ovariectomy-enhanced T-cell production of TNF-alpha, which, acting through the TNF-alpha receptor p55, augments macrophage colony-stimulating factor-induced (M-CSF-induced) and RANKL-induced osteoclastogenesis. Ovariectomy failed to induce bone loss, stimulate bone resorption, or increase M-CSF- and RANKL-dependent osteoclastogenesis in T-cell deficient mice, establishing T cells as essential mediators of the bone-wasting effects of estrogen deficiency in vivo. These findings demonstrate that the ability of estrogen to target T cells, suppressing their production of TNF-alpha, is a key mechanism by which estrogen prevents osteoclastic bone resorption and bone loss. (+info)
Activation of p38 mitogen-activated protein kinase is crucial in osteoclastogenesis induced by tumor necrosis factor.
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Tumor necrosis factor (TNF) induces osteoclast differentiation from bone marrow cells in the presence of macrophage colony-stimulating factor. Treatment of bone marrow cells with SB203580 but not PD98059 inhibited TNF-induced osteoclast differentiation. In RAW264 cells which differentiate into osteoclast-like multinucleated cells by TNF treatment alone, activation of p38 mitogen-activated protein (MAP) kinase induced by murine TNF was comparable to and independent of the receptor activator of necrosis factor-kappaB ligand. Moreover, the number of multinucleated osteoclasts induced by TNF in bone marrow cell cultures derived from p38 MAP kinase gene deficient mice was significantly less than that from control mice. These results indicate that the p38 MAP kinase pathway plays a crucial role in TNF-mediated osteoclast differentiation. (+info)