Osteoclasts from human giant cell tumors of bone lack estrogen receptors

Non‑surgical outcomes and risk factors for pulmonary metastasis from giant cell tumor of bone

The present study detailed four factors associated with an increased risk of pulmonary metastasis, age, pathological fracture, local recurrence and mode of treatment. Local recurrence and pathological fracture were independent risk factors for developing metastasis. From January 2016 to December 2021, data from 50 patients diagnosed with giant cell tumor of bone (GCTB) treated in Khon Kaen Hospital, Thailand, were retrospectively analyzed. The risk factors, including age at diagnosis, location of GCTB, clinical presentation, Campanacci stage and no. of local recurrences, for GCTB-induced pulmonary metastasis were evaluated using univariate and multivariable logistic regression analyses. Of the 50 patients analyzed, 9 patients (18%), with a mean age of 46.3 years (range, 18-68 years), developed pulmonary metastasis. No patients died from pulmonary metastasis in the present study. Statistically significant associations were observed between the development of metastasis and both clinical fracture [odds ratio (OR), 6.107; 95% confidence interval (CI), 1.08-34.70] and local recurrence (OR, 6.48; 95% CI, 1.03-40.87). Patients presenting with both a clinical fracture and local tumor recurrence require more rigorous clinical observation due to the significantly elevated risk of disease progression.

Diagnosing giant cell tumor of the bone using positron emission tomography/computed tomography: A retrospective study of 20 patients from a single center

The aim of the present study was to evaluate the sensitivity of positron emission tomography/computed tomography (PET/CT) in the diagnosis of giant cell tumor of the bone (GCTB) using the maximum standard uptake value (SUVmax), which indicates the metabolic rate of tissue. Patients diagnosed with pathologically confirmed GCTB between January 2006 and July 2015 were included in the study. Data from PET/CT scans and pathological and clinical reports for all patients were retrospectively reviewed. The SUVmax value from the PET/CT scan of each patient was retrieved and analyzed. A total of 20 patients [12 male and 8 female; age range, 12–45 years; mean age ± standard deviation (SD), 33.5±15.7] with complete PET/CT data and a pathologically and clinically confirmed diagnosis were examined. The SUVmax of GCTB was between 1.8 and 18.6, with a mean ± SD of 9.2±3.8. Although GCTB is not considered to be a malignant lesion, PET/CT scans of the tumors reveal high-grade malignant osseous sarcomas. It is, therefore, important not to mistake such lesions for osteosarcomas or metastatic malignancies of the bone.

A study of the relationship of metabolic MR parameters to estrogen dependence in breast cancer xenografts

(1)H MRS, (31)P MRS and diffusion-weighted MRI (DW-MRI) were applied to study the metabolic changes associated with estrogen dependence in estrogen receptor (ER)-positive BT-474 and triple-negative HCC1806 breast cancer xenografts supplemented with or without 17β-estradiol (E2) at a dose of 0.18 or 0.72 mg/pellet. Furthermore, the effect of estrogen withdrawal on the metabolism of BT-474 and HCC1806 breast cancer xenografts was studied on day 0, day 2 and day 10. Increasing the dose of E2 resulted in a rapid growth and increases in the lactate level and phosphomonoester/β-nucleoside triphosphate (PME/βNTP), phosphocreatine/inorganic phosphate (PCr/Pi) and βNTP/Pi ratios in BT-474 breast cancer xenografts; however, no significant changes were found in HCC1806 breast cancer xenografts. Estrogen withdrawal resulted in a marked decrease in lactate level and PME/βNTP ratio and an observed increase in βNTP/Pi, PCr/Pi and apparent diffusion coefficient (ADC) values of BT-474 breast cancer xenografts on day 10. These data suggest that the lactate level and PME/βNTP, PCr/Pi and βNTP/Pi ratios of ER-positive tumors are closely related to ER dependence.

Pulmonary metastasis of giant cell tumor of bones

Giant cell tumor of bone (GCTB) accounts for 5% of primary skeletal tumors. Although it is considered to be a benign lesion, there are still incidences of pulmonary metastasis. Pulmonary metastasis of GCTB may be affected by tumor grading and localization as well as the age, gender and overall health status of the patient. Patients with local recurrence are more likely to develop pulmonary metastasis of GCTB. High expression of some genes, cytokines and chemokines may also be closely related to the metastatic potential and prognosis of GCTB. The treatment of the primary GCTB is key to the final outcome of the disease, as intralesional curettage has a significantly higher local recurrence and pulmonary metastasis rate than wide resection. However, even patients with pulmonary metastasis seem to have a good prognosis after timely and appropriate surgical resection. It is hoped that with the development of novel surgical methods and drugs, pulmonary metastasis of GCTB can be prevented and treated more effectively.

Increased OPG/RANKL ratio in the conditioned medium of soybean-treated osteoblasts suppresses RANKL-induced osteoclast differentiation

Soybean is a major dietary source of isoflavones, particularly daidzein and genistein, which stimulate osteoblastic functions that are initiated by binding to estrogen receptor (ER)-α and ER-β found on osteoblasts. However, coupled with a low expression of ER-α and ER-β in osteoclasts, the inhibitory effects of soy isoflavones on osteoclast differentiation is likely mediated through paracrine factors produced by osteoblasts. Therefore, in this study, we investigated whether soybean can indirectly inhibit osteoclast differentiation through the modulation of osteoclastic factors produced by osteoblasts. Treatment with soybean extracts increased the levels of osteoprotegerin (OPG) and decreased those of receptor activator of nuclear factor-κB ligand (RANKL) in the conditioned medium (CM) of MC3T3-E1 osteoblasts. Subsequently, the RANKL-induced RAW264.7 osteoclast formation was markedly inhibited by treatment with CM collected from MC3T3-E1 osteoblasts incubated with soybean extracts (S-CM). Similarly, S-CM significantly attenuated the RANKL-induced increase in the mRNA and protein levels of matrix metalloproteinase-9 (MMP-9), a potential biomarker gene of osteoclast differentiation, through the suppression of nuclear factor of activated T cells c1 (NFATc1) activation. Of note, a soybean concentration of 0.001 mg/ml further increased the OPG/RANKL ratio compared to treatment with a 0.1 mg/ml soybean concentration and was overall, more effective at inhibiting RANKL-induced osteoclast formation and MMP-9 expression. Taken together, our data demonstrate that treatment with soybean extracts stimulates the secretion of OPG and inhibits that of RANKL, thus inhibiting RANKL-induced osteoclast differentiation through the suppression of NFATc1 activation.

Giant cell tumor of bone: a basic science perspective

Comprehending the pathogenesis of giant cell tumor of bone (GCT) is of critical importance for developing novel targeted treatments for this locally-aggressive primary bone tumor. GCT is characterized by the presence of large multinucleated osteoclast-like giant cells distributed amongst mononuclear spindle-like stromal cells and other monocytes. The giant cells are principally responsible for the extensive bone resorption by the tumor. However, the spindle-like stromal cells chiefly direct the pathology of the tumor by recruiting monocytes and promoting their fusion into giant cells. The stromal cells also enhance the resorptive ability of the giant cells. This review encompasses many of the attributes of GCT, including the process of giant cell formation and the mechanisms of bone resorption. The significance of the receptor activator of nuclear factor-κB ligand (RANKL) in the development of GCT and the importance of proteases, including numerous matrix metalloproteinases, are highlighted. The mesenchymal lineage of the stromal cells and the origin of the hematopoietic monocytes are also discussed. Several aspects of GCT that require further understanding, including the etiology of the tumor, the mechanisms of metastases, and the development of an appropriate animal model, are also considered. By exploring the current status of GCT research, this review accentuates the significant progress made in understanding the biology of the tumor, and discusses important areas for future investigation.

Cell-based resorption assays for bone graft substitutes

The clinical utilization of resorbable bone substitutes has been growing rapidly during the last decade, creating a rising demand for new resorbable biomaterials. An ideal resorbable bone substitute should not only function as a load-bearing material but also integrate into the local bone remodeling process. This means that these bone substitutes need to undergo controlled resorption and then be replaced by newly formed bone structures. Thus the assessment of resorbability is an important first step in predicting the in vivo clinical function of bone substitute biomaterials. Compared with in vivo assays, cell-based assays are relatively easy, reproducible, inexpensive and do not involve the suffering of animals. Moreover, the discovery of RANKL and M-CSF for osteoclastic differentiation has made the differentiation and cultivation of human osteoclasts possible and, as a result, human cell-based bone substitute resorption assays have been developed. In addition, the evolution of microscopy technology allows advanced analyses of the resorption pits on biomaterials. The aim of the current review is to give a concise update on in vitro cell-based resorption assays for analyzing bone substitute resorption. For this purpose models using different cells from different species are compared. Several popular two-dimensional and three-dimensional optical methods used for resorption assays are described. The limitations and advantages of the current ISO degradation assay in comparison with cell-based assays are discussed.

Modulation of osteoclast formation

Osteoclasts are derived following the fusion of precursors of hematopoietic and myelomonocytic origin after appropriate stimulus, such as that afforded by RANKL and M-CSF. Thus the osteoclast can be considered as a specialized type of macrophage, and several of the factors that affect osteoclast formation also have affects upon macrophage differentiation. Inhibitors of osteoclast formation may perturb RANKL or M-CSF signalling or affect other signalling pathways. Several of these inhibitors are discussed with the view of their capacity to influence osteoclast differentiation, but not necessarily their activity.

Androgens and bone

Loss of estrogens or androgens increases the rate of bone remodeling by removing restraining effects on osteoblastogenesis and osteoclastogenesis, and also causes a focal imbalance between resorption and formation by prolonging the lifespan of osteoclasts and shortening the lifespan of osteoblasts. Conversely, androgens, as well as estrogens, maintain cancellous bone mass and integrity, regardless of age or sex. Although androgens, via the androgen receptor (AR), and estrogens, via the estrogen receptors (ERs), can exert these effects, their relative contribution remains uncertain. Recent studies suggest that androgen action on cancellous bone depends on (local) aromatization of androgens into estrogens. However, at least in rodents, androgen action on cancellous bone can be directly mediated via AR activation, even in the absence of ERs. Androgens also increase cortical bone size via stimulation of both longitudinal and radial growth. First, androgens, like estrogens, have a biphasic effect on endochondral bone formation: at the start of puberty, sex steroids stimulate endochondral bone formation, whereas they induce epiphyseal closure at the end of puberty. Androgen action on the growth plate is, however, clearly mediated via aromatization in estrogens and interaction with ERalpha. Androgens increase radial growth, whereas estrogens decrease periosteal bone formation. This effect of androgens may be important because bone strength in males seems to be determined by relatively higher periosteal bone formation and, therefore, greater bone dimensions, relative to muscle mass at older age. Experiments in mice again suggest that both the AR and ERalpha pathways are involved in androgen action on radial bone growth. ERbeta may mediate growth-limiting effects of estrogens in the female but does not seem to be involved in the regulation of bone size in males. In conclusion, androgens may protect men against osteoporosis via maintenance of cancellous bone mass and expansion of cortical bone. Such androgen action on bone is mediated by the AR and ERalpha.

Fibroblasts from the inner granulation tissue of the pseudocapsule in hips at revision arthroplasty induce osteoclast differentiation, as do stromal cells

BACKGROUND

It has previously been shown that many osteoclast precursors are included in the granulation tissue within the pseudocapsule obtained at revision arthroplasty from hips with osteolysis. In vitro culture of only cells isolated from the granulation tissue has been previously shown to generate many mature osteoclasts.

OBJECTIVE

To investigate the presence or otherwise of supporting cells, similar to stromal cells, which differentiate osteoclasts within the granulation tissue.

METHODS

Cells isolated from the granulation tissue were cultured alone, and after four weeks fibroblast-like cells (granulation fibroblasts) remained. Rat non-adherent bone marrow cells (NA-BMCs) were co-cultured with the granulation fibroblasts with or without 1alpha,25(OH)2D3 (10(-8) M) or heat treated ROS 17/2.8 cell conditioned medium (ht ROSCM), or both. Multinucleated cells (MNCs), which formed, were assessed by biochemical and functional characterisation of osteoclasts. Receptor activator of NFkappaB ligand (RANKL) was investigated by immunohistochemistry.

RESULTS

Co-culture of NA-BMCs and granulation fibroblasts caused the formation of tartrate resistant acid phosphatase (TRAP) positive MNCs, which had the calcitonin receptor (CTR), the Kat-1 antigen, which is specific to the surface of rat osteoclasts, and the ability to form pits in the presence of both 1alpha,25(OH)2D3 and ht ROSCM or in the presence of just ht ROSCM. RANKL was detected in fibroblast-like cells in the granulation tissue.

CONCLUSION

These data suggest that granulation fibroblasts support osteoclast differentiation, as do osteoblasts/stromal cells, and may play a part in aseptic loosening.

Deletion of estrogen receptors reveals a regulatory role for estrogen receptors-beta in bone remodeling in females but not in males

To determine the contributions of estrogen receptor (ER)alpha and ERbeta in bone growth and remodeling in male and female mice, we generated and analyzed full knockouts for each receptor, and a double ER knockout. Although suppression of the ligand to the ERs (i.e., estradiol) after menopause or gonadectomy in females led to a catastrophic increase in bone turnover and concomitant bone loss, deletion of one or both ERs failed to show such an effect. Complete deletion of ERalpha led to a decrease, not an increase, in bone turnover and an increase, not a decrease, in trabecular bone volume in both male and female animals. Deletion of ERbeta led to different responses in males, where bone was unaffected, and in females, where bone resorption was decreased and trabecular bone volume increased. In contrast, deletion of both ERs led to a profound decrease in trabecular bone volume in females, which was associated with a decrease, not an increase, in bone turnover. Finally, deletion of ERalpha, but not ERbeta, led to major changes in circulating levels of estradiol and/or testosterone, indirectly affecting bone remodeling and bone mass. Thus, only ERalpha was shown to regulate bone remodeling in males, whereas in females both receptor subtypes influenced this process and could, at least under basal knockout conditions, compensate for each other.

Microisolated mouse osteoclasts express VIP-1 and PACAP receptors

Skeletal tissue contains a network of nerve fibers expressing several neuropeptides, including vasoactive intestinal peptide (VIP) and the related peptide pituitary adenylate cyclase activating peptide (PACAP). These peptides have been demonstrated to regulate osteoclast formation and osteoclast activity. Using atomic force microscopy and by analysing changes of the intracellular calcium concentrations, we have recently demonstrated that multinucleated rat osteoclasts have cell membrane binding sites recognising VIP and PACAP. In the present study, we have further studied the expression of VIP receptor subtypes in mouse bone marrow cultures and isolated osteoclasts. A micromanipulation technique was used to isolate pure populations of osteoclasts formed in PTH-stimulated mouse bone marrow cultures. By reverse transcriptase polymerase chain reaction (RT-PCR), we studied the expression of mRNA for VIP-1, VIP-2, and PACAP receptors. The purity of the microisolated osteoclasts was determined by studying the expression of specific mRNA associated with the phenotypic trait of osteoclasts or osteoblasts/stromal cells. In this study, we show that mouse osteoclasts express VIP-1 and PACAP, but not VIP-2, receptor mRNA.

Gene expression of osteoprotegerin ligand, osteoprotegerin, and receptor activator of NF-kappaB in giant cell tumor of bone: possible involvement in tumor cell-induced osteoclast-like cell formation

Giant cell tumor of bone (GCT) is a rare primary osteolytic tumor of bone that is characterized by massive tissue destruction at the epiphysis of long bones. There is no evidence that tumor cells themselves are capable of bone destruction; instead, it appears that the tumor cells of GCT act by promoting osteoclastogenesis and, as a consequence, osteoclastic bone resorption. However, the mechanism by which this is achieved is not understood. Here we attempted to determine whether osteoprotegerin ligand (OPGL), the factor that is necessary and essential for osteoclastogenesis, is involved in tumor cell-recruited osteoclast-like giant cell formation in GCT. Using fluorescence in situ hybridization, we sought to determine mRNA expression of OPGL, its receptor RANK, and its decoy receptor OPG in three major cell types of GCT. We demonstrated that OPG mRNA was expressed in all three cell types of GCT, OPGL transcripts were mainly detected in spindle-shaped stromal-like tumor cells, whereas RANK was expressed only in macrophage-like mononuclear cells and multinuclear osteoclast-like giant cells. By semiquantitative RT-PCR, we also showed that the level of OPGL mRNA in GCT is much higher than that in normal bone and osteogenic osteosarcoma. In contrast, a similar level of OPG transcripts was detected in these three kinds of tissues, and RANK mRNA was detectable only in GCT tissues. We have further examined the regulation of gene expression of OPGL and OPG in tumor cells in response to osteotropic hormones. Administration of 1,25(OH)(2)D(3) and dexamethasone resulted in maximum up-regulation of OPGL level and down-regulation of OPG level in cultured GCT stromal-like tumor cells and the mouse bone marrow-derived ST-2 stromal cell line. Furthermore, we have shown that tumor cells of GCT induce differentiation of RANK-expressing myeloid RAW(264.7) cells into osteoclast-like cells in the presence of 1,25(OH)(2)D(3) and dexamethasone. Our findings suggest that OPGL is involved in the tumor cell-induced osteoclast-like cell formation in GCT. The ratio of OPGL/OPG by tumor cells may contribute to the degree of osteoclastogenesis and bone resorption.

Expression of functional RANK on mature rat and human osteoclasts

Although the important roles of RANK/RANKL in osteoclastogenesis have been established, their roles in the regulation of mature osteoclasts remain uncertain. Microisolation has been used to obtain pure populations of rat and human osteoclasts for RT-PCR analysis. RANK and calcitonin receptor mRNA was detected in all the samples whereas OPG and ALP mRNA was not present in any. RANKL mRNA was detected in two of eight rat and one of four human samples. Treatment of osteoclasts with soluble RANKL resulted in translocation of NF-kappaB to the nucleus and elevation of cytosolic and nuclear calcium levels. We have shown that RANK is highly expressed in mature osteoclasts and that its stimulation by RANKL results in activation of NF-kappaB and calcium signalling.

Role of the osteoclast at the bone-implant interface

A thorough understanding of the processes of healing, repair, and remodeling of bone is critical for the establishment and maintenance of osseointegration of dental implants. In this regard, much attention has been paid to the anabolic aspects of bone remodeling, including the cell biology of the osteoblast and the various cytokines and growth factors which regulate these processes. In contrast, there is little information on the bone-resorptive activity that occurs around implants during osseointegration, and of the role of osteoclasts, macrophages, and stromal cells in those catabolic processes associated with bone remodeling. This paper reviews osteoclast cell biology, the interaction of osteoclasts and biomaterials, and the information available on osteoclasts and dental implants, and poses some questions for future research.

Estrogen's bone-protective effects may involve differential IL-1 receptor regulation in human osteoclast-like cells

Declining estrogen levels during the first postmenopausal decade lead to rapid bone loss and increased fracture risk that can be reversed by estrogen replacement therapy. The bone-protective effects of estrogen may involve suppression of inflammatory cytokines that promote osteoclastogenesis and bone resorption, such as IL-1, TNF-alpha, and IL-6. We investigated whether estrogen modulates IL-1 actions on human osteoclasts (OCs) and other bone cell types. Isolated human OCs and primary bone marrow-derived OC-like cells expressed both the signaling (IL-1RI) and decoy (IL-1RII) IL-1 receptors, whereas only IL-1RI was detected in osteoblasts. IL-1RII/IL-1RI mRNA ratios and release of soluble IL-1RII (sIL-1RII) were lower in OC-like cells derived from women in the late postmenopausal period compared with younger women, but were unrelated to male donor age, suggesting that estrogen might play a role in regulating IL-1 receptor levels in vivo. Estrogen directly reduced in vitro OC-like cell IL-1RI mRNA levels while increasing IL-1RII mRNA levels and sIL-1RII release. These estrogenic events were associated with inhibited IL-1-mediated cytokine (IL-8) mRNA induction and cell survival, i.e., increased apoptosis. In contrast, estrogen did not alter IL-1R levels or IL-1 responsiveness in primary human osteoblasts or bone marrow stromal cells. We conclude that one novel mechanism by which estrogen exerts bone-protective effects may include a selective modulation of IL-1R isoform levels in OC or OC-like cells, thereby reducing their IL-1 responsiveness and cell survival. Conversely, this restraint on IL-1 actions may be lost as estrogen levels decline in aging women, contributing to an enhanced OC-mediated postmenopausal bone loss.

Fra-1 potentiates osteoclastic differentiation in osteoclast-macrophage precursor cell lines

c-Fos, a component of the dimeric transcription factor AP-1, is necessary for osteoclast formation. To determine whether c-Fos can substitute for any or all of the stimuli needed for osteoclast induction, we infected osteoclast precursors with retroviral vectors expressing c-Fos or the Fos-related protein, Fra-1. The infected cells were incubated with or without osteoclast-inductive stimuli. Osteoclast formation from retroviral-infected precursors remained completely dependent on osteoclast-inductive stromal cells. Unexpectedly, infection of bipotential osteoclast-macrophage precursor cell lines with retroviruses expressing Fra-1 but not c-Fos caused a 10-100-fold increase in the number of precursors that developed calcitonin receptors associated with an increase in bone resorption. These observations suggest that, in the precursor cell lines, Fra-1 is a limiting factor for full responsiveness to the osteoclast-inductive environment. Fra-1 is therefore likely to play a role in osteoclast differentiation which is distinct from that of c-Fos.