RANKL诱导破骨细胞前体细胞分化成熟

目的 用核因子-κB受体活化因子配体(RANKL)诱导破骨细胞前体细胞分化成熟,建立获取成熟破骨细胞的方法.方法 用破骨细胞前体细胞RAW264.7细胞为模型,RANKL诱导培养4～9 d,抗酒石酸酸性磷酸酶(TRAP)染色观察TRAP阳性多核细胞形成,罗丹明-鬼笔环肽荧光染色观察纤维性肌动蛋白(F-actin)环,DAPI染色观察细胞核,甲苯胺蓝染色观察牛骨片表面的吸收陷窝情况.结果 RANKL可诱导RAW264.7细胞形成TRAP染色阳性的多核细胞,形成F-actin环,骨片吸收陷窝明显.结论 RANKL可诱导RAW264.7细胞向成熟破骨细胞分化,该诱导模型可用于破骨细胞分化研究.     

Ascorbic acid inhibits osteoclastogenesis of RAW264.7 cells induced by receptor activated nuclear factor kappaB ligand (RANKL) in vitro

Ascorbic acid (AA) plays a key role in the regulation of differentiation and activation of osteoclast (OCL). It was reported that AA might induce the formation of OCL in cocultures of mouse bone marrow cells and ST2 cells, but it is not clear whether AA has a direct impact on the OCL precursors. The purpose of this study was to examine the effect of AA on the differentiation of OCL precursor RAW264.7 cells, cultured with receptor-activated nuclear factor kappaB ligand (RANKL). The results showed that AA remarkably inhibited the cell proliferation at a higher concentration and RANKL alone is sufficient for osteoclastogenesis. The expression of carbonic anhydrase (CAII) mRNA and protein, the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs), and the percentage area of resorption lacunae induced by RANKL were decreased when AA was added to the cultures. The results demonstrate that AA inhibits RANKL-induced differentiation of OCL precursor cells into mature OCL and reduces the formation of bone resorption pits in vitro.     

Increased osteoclast formation and activity by peripheral blood mononuclear cells in chronic liver disease patients with osteopenia

Osteoporosis is a common complication of chronic liver disease, and the underlying mechanisms are not understood. We aimed to determine if osteoclasts develop from osteoclast precursors in peripheral blood mononuclear cells (PBMCs) of chronic liver disease patients with osteopenia compared with controls. PBMCs were isolated and fluorescence-activated cell sorting was performed to quantify the activated T lymphocyte population and receptor activator of nuclear factor kappabeta ligand (RANKL) expression. The activated T lymphocyte populations were comparable for all 3 groups, and RANKL was not detectable. The percentage of CD14+CD11b+ cells containing osteoclast precursors was comparable between the 3 groups. To assess the formation and functional activity of osteoclasts formed from circulating mononuclear cells, PBMCs were cultured (1) without addition of cytokines, (2) with macrophage colony-stimulating factor (M-CSF), (3) with M-CSF and osteoprotegerin, and (4) with M-CSF and RANKL. The number of tartrate-resistant acid phosphatase-positive multinucleated cells and bone resorption was assessed. PBMCs from chronic liver disease patients with osteopenia formed more osteoclast-like cells, which, when cultured in the presence of M-CSF and RANKL resorbed more bone than controls. The number of osteoclast-like cells and the amount of bone resorption correlated with lumbar bone densities. Addition of M-CSF increased numbers of osteoclast-like cells formed in healthy controls; however, this was not observed in either of the chronic liver disease groups. Plasma levels of M-CSF were elevated in both patient groups compared with healthy controls. CONCLUSION: Circulating mononuclear cells from chronic liver disease patients with osteopenia have a higher capacity to become osteoclasts than healthy controls or chronic liver disease patients without osteopenia. This could partially be due to priming with higher levels of M-CSF in the circulation.     

The synthetic triterpenoid TP-222 inhibits RANKL stimulation of osteoclastogenesis and matrix metalloproteinase-9 expression

OBJECTIVE: Receptor activator of nuclear factor-kappaB ligand (RANKL) promotes osteoclast differentiation from monocyte precursors by inducing a cohort of genes, including tartrate-resistant acid phosphatase (TRAP) and matrix metalloproteinase-9 (MMP-9). A family of synthetic triterpenoids with antiinflammatory and pro-apoptotic properties was described to modulate differentiation in monocytic cell lineages. We therefore investigated the ability of the potent and bioavailable synthetic triterpenoid TP-222 to inhibit RANKL-induced osteoclast formation and MMP-9 expression from monocytic precursor cells. METHODS: Osteoclast formation was assayed by staining for TRAP-positive multinucleated cells. MMP-9 expression was measured by quantitative RT-PCR, Western blot, immunohistochemistry, and gel zymography. In vivo effects of TP-222 were assessed by daily intraperitoneal injection of 4-week-old mice for 7 days followed by measurement of osteoclast number and MMP-9 expression at the cartilage/bone junction of the epiphyseal growth plate. RESULTS: RANKL promoted and TP-222 (300 nM) inhibited osteoclast formation in cultures of RAW264.7 cells or bone marrow-derived monocytes. RANKL also induced MMP-9 expression in RAW264.7 cells and this was reduced by concurrent or subsequent addition of TP-222. TP-222 treatment significantly reduced the mean number of osteoclasts present at the cartilage/bone interface compared to vehicle-injected control mice. Morphometric analyses of tissue sections showed that TP-222 treatment reduced the amount of immunoreactive MMP-9 present in both mononucleated pre-osteoclasts and osteoclasts. CONCLUSION: Our data demonstrate that TP-222 inhibits osteoclast formation and MMP-9 expression in vitro and in vivo, and suggest that triterpenoids may be useful compounds for modulating bone resorption diseases.     

Expression of osteoclast differentiation factor at sites of bone erosion in collagen-induced arthritis

OBJECTIVE: To investigate the cellular mechanism of bone destruction in collagen-induced arthritis (CIA). METHODS: After induction of CIA in DA rats, a histologic study of the advanced arthritic lesion was carried out on whole, decalcified joints from the hindpaws of affected animals. To conclusively identify osteoclasts, joint tissue sections were stained for tartrate-resistant acid phosphatase (TRAP) enzyme activity, and calcitonin receptors (CTR) were identified using a specific rabbit polyclonal antibody. The expression of messenger RNA (mRNA) for the osteoclast differentiation factor (also known as receptor activator of nuclear factor kappaB ligand [RANKL]) was investigated using in situ hybridization with a specific riboprobe. RESULTS: TRAP-positive and CTR-positive multinucleated cells were invariably detected in arthritic lesions that were characterized by bone destruction. Osteoclasts were identified at the pannus-bone and pannus-subchondral bone junctions of arthritic joints, where they formed erosive pits in the bone. TRAP-positive multinucleated cells were detected within synovium and at the bone erosive front; however, CTR-positive multinucleated cells were present only at sites adjacent to bone. RANKL mRNA was highly expressed in the synovial cell infiltrate in arthritic joints, as well as by osteoclasts at sites of bone erosion. CONCLUSION: Focal bone erosion in CIA is attributed to cells expressing definitive features of osteoclasts, including CTR. The expression of RANKL by cells within inflamed synovium suggests a mechanism for osteoclast differentiation and activation at sites of bone erosion. Inhibitors of RANKL may represent a novel approach to treatment of bone loss in rheumatoid arthritis.     

Imaging of gout: New tools and biomarkers?

While joint aspiration and crystal identification by polarizing microscopy remain the gold standard for diagnosing tophaceous gout, agreement among medical and ancillary health personnel examining synovial fluid using polarizing microscopy for the detection of monosodium urate (MSU) crystals appears to be poor. Imaging modalities, including conventional radiography (CR), ultrasonography (US), magnetic resonance imaging (MRI), and dual-energy computed tomography (DECT), have been found to provide information on the deposition of MSU crystals in tissues, and the consequences of such deposition. CR can demonstrate typical “punched out lesions” with marginal overhangs, but the sensitivity for erosion detection is better for DECT and US. US is inexpensive and can identify tophus deposition in and around joints, erosions, and tissue inflammation if power Doppler US is used. MRI can show tophi, bone marrow edema, and inflammation, but MRI findings of tophi may be nonspecific. DECT can identify and color-code tophaceous material, and provide an overview of the tophus burden of a joint area. Because of the lower number of available studies, the strength of evidence for the newer imaging can be improved through further research.     

Synovial macrophage-osteoclast differentiation in inflammatory arthritis

BACKGROUND: Pathological bone resorption (marginal erosions and juxta-articular osteoporosis) by osteoclasts commonly occurs in rheumatoid arthritis (RA). OBJECTIVES: To define the nature of the mononuclear precursor cells from which osteoclasts are formed in inflamed synovial tissues and to determine the cellular and humoral factors which influence osteoclast differentiation. METHOD: Macrophage (CD14+), non-macrophage (CD14-), and unsorted (CD14+/CD14-) synovial cell populations from RA and inflammatory/non-inflammatory osteoarthritis (OA) synovium were cultured in the presence of receptor activator for nuclear factor kappaB ligand (RANKL) and monocyte-colony stimulating factor (M-CSF; in the presence/absence of prostaglandin E(2) (PGE(2)), interleukin 1beta (IL1beta), tumour necrosis factor alpha (TNFalpha), and IL6). Osteoclast differentiation was assessed by expression of tartrate resistant acid phosphatase (TRAP), vitronectin receptor (VNR), and lacunar resorption. RESULTS: TRAP+ and VNR+ multinucleated cells capable of lacunar resorption were only formed in cultures of CD14+-containing synovial cell populations (that is, CD14+ and CD14+/CD14- cells). No difference in the extent of osteoclast formation was noted in cultures of CD14+ cells isolated from RA, inflammatory OA, and non-inflammatory OA synovium. However, more TRAP+/VNR+ cells and more lacunar resorption was noted in CD14+/CD14- cells from RA and inflammatory OA synovial tissues. The addition of PGE(2), IL1beta, TNFalpha, and IL6 did not increase RANKL/M-CSF-induced osteoclast formation and lacunar resorption of both CD14+/CD14- and CD14+ synovial cell populations. CONCLUSIONS: Osteoclast precursors in synovial tissues are CD14+ monocyte/macrophages. The increase in osteoclast formation in cultures of CD14+/CD14- compared with CD14+ synovial cells in RA and inflammatory OA points to a role for CD14- cells in promoting osteoclast differentiation and bone resorption in inflamed synovial tissues by a mechanism which does not involve a direct effect of proinflammatory cytokines/prostaglandins on RANKL-induced macrophage-osteoclast differentiation.     

铁超载对小鼠单核细胞RAW264．7向破骨细胞分化的影响

]目的探讨铁超载对小鼠单核细胞RAW264．7向成熟破骨细胞分化的影响。方法实验分为正常对照组、低铁对照组、高铁干预组3组,用含有核因子KB受体活化因子配体（RANKL）和巨噬细胞集落刺激因子（M—CSF）的培养基诱导RAW264．7向破骨细胞分化,在此过程中加入去铁胺（DFO）和不同浓度的枸橼酸铁铵（FAC）。对培养第4天和第7天的细胞进行抗酒石酸酸性磷酸酶（TRAP）染色,对TRAP阳性细胞进行计数,用酶联免疫吸附法（ELISA）检测培养基中TRAP-Sb的含量。结果（1）高铁干预组的TRAP阳性细胞数高于正常对照组和低铁对照组（P〈0．05）,具有时间和浓度依赖性;（2）高铁干预组的TRAP-Sb的含量高于正常对照组（P〈0．05）,具有浓度依赖性。结论铁超载能促进RAW264．7向破骨细胞分化。     

Increase in expression of receptor activator of nuclear factor κB at sites of bone erosion correlates with progression of inflammation in evolving collagen‐induced arthritis

Objective

The receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL) pathway is critical in osteoclastogenesis and bone resorption and has been implicated in the process of focal bone erosion in arthritis. This study was undertaken to identify in vivo the hitherto‐unknown origin and localization of RANK‐expressing osteoclast precursor cells at sites of bone erosion in arthritis.

Methods

DBA‐1 mice were immunized with bovine type II collagen/Freund's complete adjuvant and were given an intraperitoneal booster injection of type II collagen on day 21. Arthritis was monitored visually, and joint pathology was examined histologically. RANK and RANKL expression were analyzed using specific immunohistochemistry, and tartrate‐resistant acid phosphatase (TRAP) staining was performed. In addition, TRAP and cathepsin K messenger RNA expression were analyzed by in situ hybridization.

Results

A marked increase in the number of cells expressing RANK correlated with the progression of synovial inflammation and clinical disease severity in evolving collagen‐induced arthritis (CIA). Interestingly, RANK expression demonstrated a gradient pattern with increased numbers of RANK‐positive cells within the synovial infiltrate in areas closer to periosteum and cortical bone. Cells expressing RANK included cells in synovial tissue, bone lining cells on the surface of trabecular bone at sites of erosion, and cells in periosteal areas adjacent to synovial inflammation. In areas where RANK‐positive cells were abundant, TRAP‐positive, multinucleated osteoclast‐like cells were also present at sites of focal bone erosion, suggesting differentiation of synovially derived RANK‐positive osteoclast precursor cells into osteoclasts. In addition, TRAP– and cathepsin K–double‐positive osteoclast‐like cells were detected on the synovial side of cortical bone at sites of early and advanced cortical bone erosion. Sites of RANK expression also correlated well with sites of RANKL expression, and there was a close correlation of the temporal expression of the receptor–ligand pair.

Conclusion

Cells expressing RANK increased in abundance with the progression of arthritis in evolving CIA, and sites of RANK‐expressing cells correlated with sites of TRAP‐positive, multinucleated osteoclast‐like cells as well as with sites of RANKL expression. These data support the hypothesis that the RANK/RANKL pathway plays an important role in the process of bone erosion in CIA.

     

TNF-related apoptosis-inducing ligand (TRAIL) blocks osteoclastic differentiation induced by RANKL plus M-CSF

The role of the tumor necrosis factor (TNF) superfamily member receptor activator of nuclear factor kappa B ligand (RANKL) in promoting the differentiation of osteoclasts has been extensively characterized. In this study, we have investigated the effect of TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily of cytokines, in osteoclastogenesis, by using human peripheral blood mononuclear cells and the RAW264.7 murine monocytic cell line. Both cell models differentiate into osteoclast-like cells in presence of RANKL plus macrophage-colony-stimulating factor (M-CSF), as evaluated in terms of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and bone resorption activity. Unexpectedly, when added in culture in combination with RANKL plus M-CSF, TRAIL inhibited osteoclastic differentiation in both cell models. To investigate the molecular mechanism underlining such inhibitory activity, we analyzed the effect of TRAIL on the mitogen-activated protein kinases (MAPKs) pathways, which play a key role in osteoclastogenesis. Treatment with RANKL plus M-CSF activated both the ERK1/2 and p38/MAPK pathways, which are essential for proliferation and differentiation of preosteoclasts, respectively. Of note, the addition of TRAIL to RANKL plus M-CSF did not affect ERK1/2 but it profoundly inhibited p38/MAPK phosphorylation. Thus, our data demonstrate that TRAIL blocks osteoclastic differentiation and suggest that inhibition of the p38/MAPK pathway by TRAIL likely plays an important role in this process.     

Increase in expression of receptor activator of nuclear factor kappaB at sites of bone erosion correlates with progression of inflammation in evolving collagen-induced arthritis

OBJECTIVE: The receptor activator of nuclear factor kappaB (RANK)/RANK ligand (RANKL) pathway is critical in osteoclastogenesis and bone resorption and has been implicated in the process of focal bone erosion in arthritis. This study was undertaken to identify in vivo the hitherto-unknown origin and localization of RANK-expressing osteoclast precursor cells at sites of bone erosion in arthritis. METHODS: DBA-1 mice were immunized with bovine type II collagen/Freund's complete adjuvant and were given an intraperitoneal booster injection of type II collagen on day 21. Arthritis was monitored visually, and joint pathology was examined histologically. RANK and RANKL expression were analyzed using specific immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining was performed. In addition, TRAP and cathepsin K messenger RNA expression were analyzed by in situ hybridization. RESULTS: A marked increase in the number of cells expressing RANK correlated with the progression of synovial inflammation and clinical disease severity in evolving collagen-induced arthritis (CIA). Interestingly, RANK expression demonstrated a gradient pattern with increased numbers of RANK-positive cells within the synovial infiltrate in areas closer to periosteum and cortical bone. Cells expressing RANK included cells in synovial tissue, bone lining cells on the surface of trabecular bone at sites of erosion, and cells in periosteal areas adjacent to synovial inflammation. In areas where RANK-positive cells were abundant, TRAP-positive, multinucleated osteoclast-like cells were also present at sites of focal bone erosion, suggesting differentiation of synovially derived RANK-positive osteoclast precursor cells into osteoclasts. In addition, TRAP- and cathepsin K-double-positive osteoclast-like cells were detected on the synovial side of cortical bone at sites of early and advanced cortical bone erosion. Sites of RANK expression also correlated well with sites of RANKL expression, and there was a close correlation of the temporal expression of the receptor-ligand pair. CONCLUSION: Cells expressing RANK increased in abundance with the progression of arthritis in evolving CIA, and sites of RANK-expressing cells correlated with sites of TRAP-positive, multinucleated osteoclast-like cells as well as with sites of RANKL expression. These data support the hypothesis that the RANK/RANKL pathway plays an important role in the process of bone erosion in CIA.     

Multiple microcrystal deposition disease in a patient with systemic lupus erythematosus.

A 17-year-old female patient with systemic lupus erythematosus (SLE) developed chronic tophaceous gout, chondrocalcinosis and articular capsule calcification in several joints. Analysis of synovial fluid and tophi revealed the coexistence of monosodium urate, calcium pyrophosphate, hydroxyapatite, and cholesterol crystals.     

Osteoclast differentiation factor induces synovial macrophage–osteoclast differentiation in rheumatoid arthritis

The aim of this study was to clarify the role of osteoclast differentiation factor (ODF) and osteoprotegerin (OPG) in synovial macrophage–osteoclast differentiation. Synovial macrophages were cultured in the presence of macrophage-colony-stimulating factor (M-CSF) and/or ODF. OPG was added to cocultures of synovial macrophages and UMR106. The cultures on glass coverslips were stained with osteoclast-associated markers, tartrate-resistant acid phosphatase (TRAP), and vitronectin receptor (VNR), as well as macrophage-associated markers CD11b and CD14. Functional evidence of osteoclast formation was determined by a resorption pit assay. To investigate whether rheumatoid arthritis (RA) synovial cells expressed messenger RNA (mRNA) for ODF, OPG, and the receptor activator of NF-κB (RANK), we performed a polymerase chain reaction (PCR) analysis. The addition of M-CSF or ODF alone induced TRAP-positive multinucleated cell formation. Resorption pits were rarely detected with M-CSF alone. ODF was capable of inducing bone resorption and enhancing osteoclastogenesis, as well as bone resorption in the presence of M-CSF. In the coculture system, both osteoclast formation and bone resorption were inhibited by OPG in a dose-dependent manner. In all experiments, synovial cells, including macrophages and fibroblasts, expressed the mRNA for RANK, ODF, and OPG. Our findings suggest that ODF plays a role in regulating RA synovial macrophage–osteoclast differentiation, and that synovial cells might have the ability to produce ODF. OPG might be further developed as a new strategy for treating bone destruction in RA joints. Received: January 30, 2001 / Accepted: May 18, 2001     

Osteoclast differentiation factor induces synovial macrophage–osteoclast differentiation in rheumatoid arthritis

Abstract

The aim of this study was to clarify the role of osteoclast differentiation factor (ODF) and osteoprotegerin (OPG) in synovial macrophage–osteoclast differentiation. Synovial macrophages were cultured in the presence of macrophage-colony-stimulating factor (M-CSF) and/or ODF. OPG was added to cocultures of synovial macrophages and UMR106. The cultures on glass coverslips were stained with osteoclast-associated markers, tartrate-resistant acid phosphatase (TRAP), and vitronectin receptor (VNR), as well as macrophage-associated markers CD11b and CD14. Functional evidence of osteoclast formation was determined by a resorption pit assay. To investigate whether rheumatoid arthritis (RA) synovial cells expressed messenger RNA (mRNA) for ODF, OPG, and the receptor activator of NF-κB (RANK), we performed a polymerase chain reaction (PCR) analysis. The addition of M-CSF or ODF alone induced TRAP-positive multinucleated cell formation. Resorption pits were rarely detected with M-CSF alone. ODF was capable of inducing bone resorption and enhancing osteoclastogenesis, as well as bone resorption in the presence of M-CSF. In the coculture system, both osteoclast formation and bone resorption were inhibited by OPG in a dose-dependent manner. In all experiments, synovial cells, including macrophages and fibroblasts, expressed the mRNA for RANK, ODF, and OPG. Our findings suggest that ODF plays a role in regulating RA synovial macrophage–osteoclast differentiation, and that synovial cells might have the ability to produce ODF. OPG might be further developed as a new strategy for treating bone destruction in RA joints.     

Expression and role of mannose receptor/terminal high-mannose type oligosaccharide on osteoclast precursors during osteoclast formation

Osteoclasts are formed from hematopoietic precursors via cell-cell fusion. We have previously reported that mannose residues are expressed on the outer membranes of monocytes during osteoclast differentiation. In the present study, we have attempted to demonstrate the pattern of expression levels of terminal high-mannose type oligosaccharide and to show that the mannose receptor is expressed on osteoclast precursor cells. Osteoclasts were formed using three different systems, namely mouse bone marrow cell culture, co-culture of mouse spleen cells with stromal cells, and RAW264.7 cell cultures. During osteoclast differentiation, the expression of terminal high-mannose type oligosaccharide gradually increased and then peaked at the stage of fusion in all three systems. Expression of the mannose receptor gradually increased during osteoclast differentiation in bone marrow cells and the co-culture system. In contrast, that in RAW264.7 cells had already been detected in the absence of the soluble receptor activator of NF-kappaB ligand and did not change during osteoclast differentiation. To ascertain whether expression of high-mannose type oligosaccharide is involved in tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cell (MNC) formation, glycosidase inhibitors were used on RAW264.7 cell culture. Castanospermine, an inhibitor of glucosidase I, inhibited the TRAP-positive MNCs, and deoxymannojirimycin, an inhibitor of alpha-mannosidase I, increased the TRAP-positive MNC formation. These results indicate that the binding of terminal high-mannose and mannose receptor is important for the process of cellular fusion in osteoclast formation.     

The effect of long-term treatment with steroid hormones or tamoxifen on oestrogen receptors (alpha and beta) in the endometrium of ovariectomized cynomolgus macaques

A number of bone diseases characterised by excessive osteolysis (e.g. osteoporosis and Paget's disease) exhibit a marked gender difference in prevalence and are more common in the elderly population. Bone resorption is carried out by osteoclasts, which are formed by fusion of circulating mononuclear precursor cells of haematopoietic origin. In this study, we have determined whether there are gender- and age-related differences in osteoclast formation from circulating precursors. Peripheral blood mononuclear cells (PBMCs) were co-cultured with UMR106 osteoblast-like cells in the presence of macrophage-colony stimulating factor (M-CSF) and 1,25 dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) or cultured alone in the presence of sRANKL (soluble receptor activator of nuclear factor kappa B ligand) and M-CSF. As assessed by the formation of tartrate resistant acid phosphatase (TRAP)-positive (TRAP(+)) and vitronectin receptor-positive (VNR(+)) multinucleated cells (MNCs), there was no difference in the number of circulating osteoclast precursors in males and females. Lacunar resorption carried out by osteoclasts formed from these precursors was generally increased in males compared with females (P=0.03). An increase in the number of TRAP(+) and VNR(+) MNCs formed from male PBMCs was noted in response to 1,25(OH)(2)D(3) (P<0.005). An increase in lacunar resorption in cultures of PBMCs (10(5) per well) from males was also noted in response to 10(-9) M 1,25(OH)(2)D(3) (P<0.05) and sRANKL (P=0.05), but not M-CSF. The addition of dexamethasone resulted in a marked increase in osteoclast formation and lacunar resorption in both males and females. Post-menopausal females and males of comparable age showed similar levels of osteoclastogenesis. Pre-menopausal women showed similar levels of osteoclastogenesis but less resorption (P=0.01) compared with males of comparable age. These results show that there are specific gender/age-related differences in osteoclast formation and bone resorption and have implications for evaluating osteoclastogenesis in skeletal diseases such as primary osteoporosis and Paget's disease.     

Human osteoclast formation and bone resorption by monocytes and synovial macrophages in rheumatoid arthritis.

OBJECTIVE: To determine whether synovial macrophages and monocytes isolated from patients with rheumatoid arthritis patients are capable of differentiating into osteoclastic bone resorbing cells; and the cellular and humoral conditions required for this to occur. METHODS: Macrophages isolated from the synovium and monocytes from the peripheral blood of rheumatoid arthritis patients were cultured on bone slices and coverslips, in the presence and absence of UMR 106 rat osteoblast-like cells, 1,25-dihydroxy vitamin D3 (1,25(OH)2D3) and macrophage colony stimulating factor (M-CSF), and assessed for cytochemical and functional evidence of osteoclast differentiation. RESULTS: Isolated calcitonin receptor (CTR), tartrate resistant acid phosphatase (TRAP), and vitronectin receptor (VNR) negative, CD11b and CD14 positive monocytes and macrophages differentiated into CTR, TRAP, and VNR positive multinucleated cells capable of extensive lacunar bone resorption when co-cultured for 14 d with UMR 106 cells in the presence 1,25(OH)2D3 and M-CSF. CONCLUSIONS: Mononuclear phagocytes (monocytes and macrophages) from rheumatoid arthritis patients are capable of differentiating into multinucleated cells showing all the cytochemical and functional criteria of mature osteoclasts. Synovial macrophage-osteoclast differentiation may represent an important cellular mechanism in the bone destruction associated with rheumatoid arthritis.     

Computed tomography of the knee joint as an indicator of intraarticular tophi in gout

Objective. To evaluate the utility of computed tomography (CT) of the knee joint for detecting intraarticular tophaceous deposits. Methods. A prospective study of 16 patients with gout affecting the knee was conducted. A condition for inclusion in the study was the presence of needle-shaped crystals with negative birefringence in the knee joint synovial fluid. Conventional radiography and CT were performed in each case. Results. Intraarticular opacities in the capsule and the synovium, consistent with the presence of tophaceous deposits, were found in 5 of the 16 patients (9 knee joints). The mean duration of gout was longer in the patients with intraarticular tophi than in those without tophi, and 2 of the patients with tophi had poor tolerance to antihyperuricemic therapy. Conclusion. Intraarticular opacities considered to represent tophi were observed in approximately one-third of the patients. The presence of tophi correlated with a longer duration of the disease and a poor tolerance to medication. We therefore suggest that CT of the knees could be useful in the assessment and followup of certain patients with gout.