Tartrate-resistant acid phosphatase (TRAP) and the osteoclast/immune cell dichotomy

Response of knee fibrocartilage to joint destabilization

OBJECTIVE

A major challenge to understanding osteoarthritis (OA) pathology is identifying the cellular events that precede the onset of cartilage damage. The objective of this study is to determine the effect of joint destabilization on early changes to fibrocartilage in the joint.

DESIGN/METHODS

The anterior cruciate ligament was transected in collagen reporter mice (Col1CFP and ColXRFP). Mineralization labels were given every 2 weeks to measure new mineralized cartilage apposition. Novel fluorescent histology of mineralized tissue was used to characterize the changes in fibrocartilage at 2 and 4 weeks post-injury.

RESULTS

Changes in fibrocartilaginous structures of the joint occur as early as 2 weeks after injury and are well developed by 4 weeks. The alterations are seen in multiple entheses and in the medial surface of the femoral and tibial condyles. In the responding entheses, mineral apposition towards the ligament midsubstance results in thickening of the mineralize fibrocartilage. These changes are associated with increases in ColX-RFP, Col1-CFP reporter activity and alkaline phosphatase enzyme activity. Mineral apposition also occurs in the fibrocartilage of the non-articular regions of the medial condyles by 2 weeks and develops into osteophytes by 4 weeks post-injury. An unexpected observation is punctate expression of tartrate resistant acid phosphatase activity in unmineralized fibrochondrocytes adjacent to active appositional mineralization.

DISCUSSION

These observations suggest that fibrocartilage activates prior to degradation of the articular cartilage. Thus clinical and histological imaging of fibrocartilage may be an earlier indicator of disease initiation and may indicate a more appropriate time to start preventative treatment.

Wear particles derived from metal hip implants induce the generation of multinucleated giant cells in a 3-dimensional peripheral tissue-equivalent model

Multinucleate giant cells (MGCs) are formed by the fusion of 5 to 15 monocytes or macrophages. MGCs can be generated by hip implants at the site where the metal surface of the device is in close contact with tissue. MGCs play a critical role in the inflammatory processes associated with adverse events such as aseptic loosening of the prosthetic joints and bone degeneration process called osteolysis. Upon interaction with metal wear particles, endothelial cells upregulate pro-inflammatory cytokines and other factors that enhance a localized immune response. However, the role of endothelial cells in the generation of MGCs has not been completely investigated. We developed a three-dimensional peripheral tissue-equivalent model (PTE) consisting of collagen gel, supporting a monolayer of endothelial cells and human peripheral blood mononuclear cells (PBMCs) on top, which mimics peripheral tissue under normal physiological conditions. The cultures were incubated for 14 days with Cobalt chromium alloy (CoCr ASTM F75, 1–5 micron) wear particles. PBMC were allowed to transit the endothelium and harvested cells were analyzed for MGC generation via flow cytometry. An increase in forward scatter (cell size) and in the propidium iodide (PI) uptake (DNA intercalating dye) was used to identify MGCs. Our results show that endothelial cells induce the generation of MGCs to a level 4 fold higher in 3-dimentional PTE system as compared to traditional 2-dimensional culture plates. Further characterization of MGCs showed upregulated expression of tartrate resistant alkaline phosphatase (TRAP) and dendritic cell specific transmembrane protein, (DC-STAMP), which are markers of bone degrading cells called osteoclasts. In sum, we have established a robust and relevant model to examine MGC and osteoclast formation in a tissue like environment using flow cytometry and RT-PCR. With endothelial cells help, we observed a consistent generation of metal wear particle- induced MGCs, which heralds metal on metal hip failures.

The clinical spectrum and pathophysiology of skeletal complications in lysosomal storage disorders

Lysosomal storage disorders affect multiple organs including the skeleton. Disorders with prominent skeletal symptoms are type 1 and 3 Gaucher disease, the mucopolysaccharidoses, the glycoproteinoses and pycnodysostosis. Clinical manifestations range from asymptomatic radiographical evidence of bone pathology to overt bone crises (Gaucher), short stature with typical imaging features known as dysostosis multiplex (MPS), with spine and joint deformities (mucopolysaccharidoses, mucolipidosis), or osteopetrosis with pathological fractures (pynodysostosis). The pathophysiology of skeletal disease is only partially understood and involves direct substrate storage, inflammation and other complex alterations of cartilage and bone metabolism. Current treatments are enzyme replacement therapy, substrate reduction therapy and hematopoietic stem cell transplantation. However, effects of these interventions on skeletal disease manifestations are less well established and outcomes are highly dependent on disease burden at treatment initiation. It is now clear that adjunctive treatments that target skeletal disease are needed and should be part of future research agenda.

Erythropoietin promotes bone formation through EphrinB2/EphB4 signaling

Recent studies have demonstrated that erythropoietin (EPO) has extensive nonhematopoietic biological functions. However, little is known about how EPO regulates bone formation, although several studies suggested that EPO can affect bone homeostasis. In this study, we investigated the effects of EPO on the communication between osteoclasts and osteoblasts through the ephrinB2/EphB4 signaling pathway. We found that EPO slightly promotes osteoblastic differentiation with the increased expression of EphB4 in ST2 cells. However, EPO increased the expression of Nfatc1 and ephrinB2 but decreased the expression of Mmp9 in RAW264.7 cells, resulting in an increase of ephrinB2-expressing osteoclasts and a decrease in resorption activity. The stimulation of ephrinB2/EphB4 signaling via ephrinB2-Fc significantly promoted EPO-mediated osteoblastic differentiation in ST2 cells. EphB4 knockdown through EphB4 shRNA inhibited EPO-mediated osteoblastic phenotypes. Furthermore, in vivo assays clearly demonstrated that EPO efficiently induces new bone formation in the alveolar bone regeneration model. Taken together, these results suggest that ephrinB2/EphB4 signaling may play an important role in EPO-mediated bone formation.

Introduction of a mixture of β-tricalcium phosphate into a complex of bone marrow mesenchymal stem cells and type I collagen can augment the volume of alveolar bone without impairing cementum regeneration

BACKGROUND

The purpose of this study is to evaluate whether β-tricalcium phosphate (β-TCP) could be a promising modality to help augment alveolar bone in periodontal tissue regeneration by bone marrow mesenchymal stem cells (BMMSCs).

METHODS

Expanded BMMSCs and atelocollagen (Col) were mixed together (MSC/Col). A combination of β-TCP with MSC/Col was also prepared (MSC/Col/TCP). MSC/Col/TCP or MSC/Col was transplanted into experimental periodontal Class III furcation defects that had been exposed to inflammation in beagle dogs. Periodontal tissue regeneration was evaluated by histologic and morphometric analyses at 4 and 8 weeks after transplantation.

RESULTS

MSC/Col and MSC/Col/TCP enhanced periodontal tissue regeneration compared to Col and TCP/Col according to hematoxylin and eosin staining. The percentage of new cementum length in the MSC/Col/TCP group was not significantly different from that in the MSC/Col group at 4 and 8 weeks. On the other hand, the percentage of new bone area in the MSC/Col/TCP group was much higher than that in the MSC/TCP group at 4 weeks. However, at 8 weeks, no significant difference in new bone area was found between the two groups. In the MSC/Col/TCP group, β-TCP was surrounded by newly formed bone. Multinucleated cells, which were positive for osteopontin and tartrate-resistant acid phosphatase, were present in the interconnected macropores of β-TCP.

CONCLUSION

These findings suggest that β-TCP is applicable as a scaffold for BMMSCs transplantation and helps augment alveolar bone without impairing regeneration of cementum.

Alteration of inflammatory response by shock wave therapy leads to reduced calcification of decellularized aortic xenografts in mice†

OBJECTIVES

Tissue-engineered xenografts represent a promising treatment option in heart valve disease. However, inflammatory response leading to graft failure and incomplete in vitro repopulation with recipient cells remain challenging. Shock waves (SWs) were shown to modulate inflammation and to enhance re-epithelialization. We therefore aimed to investigate whether SWs could serve as a feasible adjunct to tissue engineering.

METHODS

Porcine aortic pieces were decellularized using sodium deoxycholate and sodium dodecylsulphate and implanted subcutaneously into C57BL/6 mice (n = 6 per group). The treatment (shock wave therapy, SWT) group received SWs (0.1 mJ/mm(2), 500 impulses, 5 Hz) for modulation of inflammatory response directly after implantation; control animals remained untreated (CTR). Grafts were harvested 72 h and 3 weeks after implantation and analysed for inflammatory cytokines, macrophage infiltration and polarization, osteoclastic activity and calcification. Transmission electron microscopy (TEM) was performed. Endothelial cells (ECs) were treated with SWs and analysed for macrophage regulatory cytokines. In an ex vivo experimental set-up, decellularized porcine aortic valve conduits were reseeded with ECs with and without SWT (0.1 mJ/mm(2), 300 impulses, 3 Hz), fibroblasts as well as peripheral blood mononuclear cells (all human) and tested in a pulsatile flow perfusion system for cell coverage.

RESULTS

Treated ECs showed an increase of macrophage migration inhibitory factor and macrophage inflammatory protein 1β, whereas CD40 ligand and complement component C5/C5a were decreased. Subcutaneously implanted grafts showed increased mRNA levels of tumour necrosis factor α and interleukin 6 in the treatment group. Enhanced repopulation with recipient cells could be observed after SWT. Augmented macrophage infiltration and increased polarization towards M2 macrophages was observed in treated animals. Enhanced recruitment of osteoclastic cells in proximity to calcified tissue was found after SWT. Consequently, SWT resulted in decreased areas of calcification in treated animals. The reseeding experiment revealed that fibroblasts showed the best coverage compared with other cell types. Moreover, SW-treated ECs exhibited enhanced repopulation compared with untreated controls.

CONCLUSIONS

SWs reduce the calcification of subcutaneously implanted decellularized xenografts via the modulation of the acute macrophage-mediated inflammatory response and improves the in vitro repopulation of decellularized grafts. It may therefore serve as a feasible adjunct to heart valve tissue engineering.

Hydroxyapatite-magnetite-MWCNT nanocomposite as a biocompatible multifunctional drug delivery system for bone tissue engineering

New magnetic hydroxyapatite-based nanomaterials as bone-specific systems for controlled drug delivery have been synthesized. The synthesized hydroxyapatite, HA, decorated with magnetite nanoparticles by a deposition method (HA/Fe3O4) and the nanocomposite system obtained using magnetic multi-walled carbon nanotubes (HA/MWCNT/Fe3O4) as a filler for HA have been characterized by chemical and morphological analyses, and their biological behavior was investigated. The systems have also been doped with clodronate in order to combine the effect of bone biomineralization induced by hydroxyapatite-based composites with the decrease of osteoclast formation induced by the drug. An analysis of the preosteoclastic RAW264.7 cell proliferation by MTT assay confirmed the high biocompatibility of the three systems. TRAP staining of RAW 264.7 conditioned with sRAKL to induce osteoclastogenesis, cultured in the presence of the systems doped and undoped with clodronate, showed the inhibitory effect of clodronate after we counted the MNC TRAP(+)cells but only in the osteoclast formation; in particular, the system HA/Fe3O4-Clo exerted a high inhibitory effect compared to the drug alone. These results demonstrate that the synthesized nanocomposites are a biocompatible magnetic drug delivery system and can represent a useful multimodal platform for applications in bone tissue engineering.

Aconitum pseudo-laeve var. erectum inhibits receptor activator of nuclear factor kappa-B ligand-induced osteoclastogenesis via the c-Fos/nuclear factor of activated T-cells, cytoplasmic 1 signaling pathway and prevents lipopolysaccharide-induced bone loss in mice

Aconitum pseudo-laeve var. erectum (APE) has been widely shown in herbal medicine to have a therapeutic effect on inflammatory conditions. However, there has been no evidence on whether the extract of APE is involved in the biological bone metabolism process, particularly osteoclast-mediated bone resorption. In this study, we confirmed that the administration of APE could restore normal skeletal conditions in a murine model of lipopolysaccharide (LPS)-induced bone loss via a decrease in the receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) ratio and osteoclast number. We then investigated the effect of APE on the RANKL-induced formation and function of osteoclasts to elucidate its underlying molecular mechanisms. APE suppressed the formation of tartrate-resistant acid phosphatase (TRAP)-positive cells, as well as the bone-resorbing activity of mature osteoclasts. Furthermore, APE attenuated nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) and c-Fos without affecting any early signal pathway of osteoclastogenesis. Subsequently, APE significantly downregulated the expression of various genes exclusively expressed in osteoclasts. These results demonstrate that APE restores LPS-induced bone loss through a decrease of the serum RANKL/OPG ratio, and inhibits osteoclast differentiation and function, suggesting the promise of APE as a potential cure for various osteoclast-associated bone diseases.

Immunohistochemical and histochemical analysis of newly formed tissues in root canal space transplanted with dental pulp stem cells plus platelet-rich plasma

INTRODUCTION

Tissue regeneration in root canals after pulpectomy can be achieved by transplantation of autologous dental pulp stem cells and/or platelet-rich plasma. However, the identity of the newly formed tissue in the pulp space has been only examined by histologic analysis. This study aimed to apply immunohistochemistry and histochemistry to detect specific markers in the newly generated tissues after root canal regenerative treatment.

METHODS

In our previous study, 32 root canals in 4 mature dogs were treated with a pulp regeneration procedure after pulpectomy using either blood clot, transplantation of dental pulp stem cells, platelet-rich plasma, or a combination of cells and plasma. In the present study, the tissues were examined for the expression of periostin to detect periodontal ligament tissue, nestin and dentin sialoprotein for odontoblasts, and bone sialoprotein and osteocalcin for bone tissues. Samples were also stained for tartrate-resistant acid phosphatase (TRAP) as a marker for osteoclastic lineages.

RESULTS

Continuous periostin-positive tissue was observed extending from the periodontal ligament into the inner canal surface in which the mineral islands were surrounded by weak periostin staining. There was also positive staining for TRAP, bone sialoprotein, and osteocalcin in the canal space, suggesting the presence of bone tissue. A layer of mineralized tissue along the inner surface of the root canal was negative for TRAP, suggesting the tissue likely to be cementum. In all samples, no nestin-positive reaction was observed, whereas dentin sialoprotein was detected in PDL, dentinal tubules, and intracanal fibrous tissues. There was no difference between any of the 4 groups.

CONCLUSIONS

The tissues formed in the dog mature root canals after regenerative endodontic procedures are not pulp tissues but mainly periodontal tissues.

Osteoclast resorption of beta-tricalcium phosphate controlled by surface architecture

A resorbable bone graft substitute should mimic native bone in its capacity to support bone formation and be remodeled by osteoclasts (OCl) or other multinucleated cells such as foreign body giant cells (FBGC). We hypothesize that by changing the scale of surface architecture of beta-tricalcium phosphate (TCP), cellular resorption can be influenced. CD14(+) monocyte precursors were isolated from human peripheral blood (n = 4 independent donors) and differentiated into OCl or FBGC on the surface of TCP discs comprising either submicron- or micron-scale surface topographical features (TCPs and TCPb, respectively). On submicrostructured TCPs, OCl survived, fused, differentiated, and extensively resorbed the substrate; however, on microstructured TCPb, OCl survival, TRAP activation, and fusion were attenuated. Importantly, no resorption was observed on microstructured TCPb. By confocal microscopy, OCl formed on TCPs contained numerous actin rings allowing for resorption, but not on TCPb. In comparison, FBGC could not resorb either TCP material, suggesting that osteoclast-specific machinery is necessary to resorb TCP. By tuning surface architecture, it appears possible to control osteoclast resorption of calcium phosphate. This approach presents a useful strategy in the design of resorbable bone graft substitutes.

Impact of cigarette smoke on the human and mouse lungs: a gene-expression comparison study

Cigarette smoke is well known for its adverse effects on human health, especially on the lungs. Basic research is essential to identify the mechanisms involved in the development of cigarette smoke-related diseases, but translation of new findings from pre-clinical models to the clinic remains difficult. In the present study, we aimed at comparing the gene expression signature between the lungs of human smokers and mice exposed to cigarette smoke to identify the similarities and differences. Using human and mouse whole-genome gene expression arrays, changes in gene expression, signaling pathways and biological functions were assessed. We found that genes significantly modulated by cigarette smoke in humans were enriched for genes modulated by cigarette smoke in mice, suggesting a similar response of both species. Sixteen smoking-induced genes were in common between humans and mice including six newly reported to be modulated by cigarette smoke. In addition, we identified a new conserved pulmonary response to cigarette smoke in the induction of phospholipid metabolism/degradation pathways. Finally, the majority of biological functions modulated by cigarette smoke in humans were also affected in mice. Altogether, the present study provides information on similarities and differences in lung gene expression response to cigarette smoke that exist between human and mouse. Our results foster the idea that animal models should be used to study the involvement of pathways rather than single genes in human diseases.

Macrophage expression of tartrate-resistant acid phosphatase as a prognostic indicator in colon cancer

Recent research has indicated that separate populations of macrophages are associated with differing outcomes in cancer survival. In our study, we examine macrophage expression of tartrate-resistant acid phosphatase (TRAP) and its effect on survival in colon cancer. Immunohistochemical analysis on colorectal adenocarcinomas confirmed macrophage expression of TRAP. Co-localization of TRAP with CD68, a pan-macrophage marker, revealed that TRAP is present in some but not all sub-populations of macrophages. Further co-localization of TRAP with CD163, an M2 marker, revealed that TRAP is expressed by both M2 and non-M2 macrophages. TRAP expression was then measured using the AQUA method of quantitative immunofluorescence in a tissue microarray consisting of 233 colorectal cancer patients seen at Yale-New Haven Hospital. Survival analysis revealed that patients with high TRAP expression have a 22 % increase in 5-year survival (uncorrected log-rank p = 0.025) and a 47 % risk reduction in disease-specific death (p = 0.02). This finding was validated in a second cohort of older cases consisting of 505 colorectal cancer patients. Patients with high TRAP expression in the validation set had a 19 % increase in 5-year survival (log-rank p = 0.0041) and a 52 % risk reduction in death (p = 0.0019). These results provide evidence that macrophage expression of TRAP is associated with improved outcome and implicates TRAP as a potential biomarker in colon cancer.

Glycosaminoglycan mimetic associated to human mesenchymal stem cell-based scaffolds inhibit ectopic bone formation, but induce angiogenesis in vivo

Tissue engineering approaches to stimulate bone formation currently combine bioactive scaffolds with osteocompetent human mesenchymal stem cells (hMSC). Moreover, osteogenic and angiogenic factors are required to promote differentiation and survival of hMSC through improved vascularization through the damaged extracellular matrix (ECM). Glycosaminoglycans (GAGs) are ECM compounds acting as modulators of heparin-binding protein activities during bone development and regenerative processes. GAG mimetics have been proposed as ECM stabilizers and were previously described for their positive effects on bone formation and angiogenesis after local treatment. Here, we developed a strategy associating the GAG mimetic [OTR4120] with bone substitutes to optimize stem cell-based therapeutic products. We showed that [OTR4120] was able to potentiate proliferation, migration, and osteogenic differentiation of hMSC in vitro. Its link to tricalcium phosphate/hydroxyapatite scaffolds improved their colonization by hMSC. Surprisingly, when these combinations were tested in an ectopic model of bone formation in immunodeficient mice, the GAG mimetics inhibit bone formation induced by hMSC and promoted an osteoclastic activity. Moreover, the inflammatory response was modulated, and the peri-implant vascularization stimulated. All together, these findings further support the ability of GAG mimetics to organize the local ECM to coordinate the host response toward the implanted biomaterial, and to inhibit the abnormal bone formation process on a subcutaneous ectopic site.

Methanol Extract of Euchelus asper Prevents Bone Resorption in Ovariectomised Mice Model

Marine molluscs are widely distributed throughout the world and many bioactive compounds exhibiting antiviral, antitumor, antileukemic, and antibacterial activity have been reported worldwide. The present study was designed to investigate the beneficial effect of methanol extract of Euchelus asper (EAME) on estrogen deficiency induced osteoporosis in ovariectomised mice model. Forty-two female Swiss albino mice were randomly assigned into Sham operated (Sham) group and six ovariectomised (OVX) subgroups such as OVX with vehicle (OVX); OVX with estradiol (2 mg/kg/day); OVX with EAME of graded doses (25, 50, 100, and 200 mg/kg/day). Bone turnover markers like serum alkaline phosphatase (ALP), serum acid phosphatase (ACP), serum calcium, and histological investigations of tibia and uterus were analysed. Metaphyseal DNA content of the femur bone was also studied. Antiosteoclastogenic activity of EAME was examined. Administration of EAME was able to reduce the increased bone turnover markers in the ovariectomised mice. Histomorphometric analysis revealed an increase in bone trabeculation and restoration of trabecular separation by EAME treatment. Metaphyseal DNA content of the femur of the OVX mice was increased by EAME administration. EAME also showed a potent antiosteoclastogenic behaviour. Thus, the present study reveals that EAME was able to successfully reduce the estrogen deficiency induced bone loss.

Doxycycline-induced expression of transgenic human tumor necrosis factor α in adult mice results in psoriasis-like arthritis

Objective

To generate doxycycline-inducible human tumor necrosis factor α (TNFα)–transgenic mice to overcome a major disadvantage of existing transgenic mice with constitutive expression of TNFα, which is the limitation in crossing them with various knockout or transgenic mice.

Methods

A transgenic mouse line that expresses the human TNFα cytokine exclusively after doxycycline administration was generated and analyzed for the onset of diseases.

Results

Doxycycline-inducible human TNFα–transgenic mice developed an inflammatory arthritis– and psoriasis-like phenotype, with fore and hind paws being prominently affected. The formation of “sausage digits” with characteristic involvement of the distal interphalangeal joints and nail malformation was observed. Synovial hyperplasia, enthesitis, cartilage and bone alterations, formation of pannus tissue, and inflammation of the skin epidermis and nail matrix appeared as early as 1 week after the treatment of mice with doxycycline and became aggravated over time. The abrogation of human TNFα expression by the removal of doxycycline 6 weeks after beginning stimulation resulted in fast resolution of the most advanced macroscopic and histologic disorders, and 3–6 weeks later, only minimal signs of disease were visible.

Conclusion

Upon doxycycline administration, the doxycycline-inducible human TNFα–transgenic mouse displays the major features of inflammatory arthritis. It represents a unique animal model for studying the molecular mechanisms of arthritis, especially the early phases of disease genesis and tissue remodeling steps upon abrogation of TNFα expression. Furthermore, unlimited crossing of doxycycline-inducible human TNFα–transgenic mice with various knockout or transgenic mice opens new possibilities for unraveling the role of various signaling molecules acting in concert with TNFα.

Synthetic bone substitute material comparable with xenogeneic material for bone tissue regeneration in oral cancer patients: First and preliminary histological, histomorphometrical and clinical results

Background:

The present study was first to evaluate the material-specific cellular tissue response of patients with head and neck cancer to a nanocrystalline hydroxyapatite bone substitute NanoBone (NB) in comparison with a deproteinized bovine bone matrix Bio-Oss (BO) after implantation into the sinus cavity.

Materials and Methods:

Eight patients with tumor resection for oral cancer and severely resorbed maxillary bone received materials according to a split mouth design for 6 months. Bone cores were harvested prior to implantation and analyzed histologically and histomorphometrically. Implant survival was followed-up to 2 years after placement.

Results:

Histologically, NB underwent a higher vascularization and induced significantly more tartrate-resistant acid phosphatase-positive (TRAP-positive) multinucleated giant cells when compared with BO, which induced mainly mononuclear cells. No significant difference was observed in the extent of new bone formation between both groups. The clinical follow-up showed undisturbed healing of all implants in the BO-group, whereas the loss of one implant was observed in the NB-group.

Conclusions:

Within its limits, the present study showed for the first time that both material classes evaluated, despite their induction of different cellular tissue reactions, may be useful as augmentation materials for dental and maxillofacial surgical applications, particularly in patients who previously had oral cancer.

Bone marrow-derived cell concentrates have limited effects on osteochondral reconstructions in the mini pig

This study investigates the effects of seeding a chondrogenic and osteogenic scaffold with a bone marrow-derived cell concentrate (BMCC) and reports the histological and mechanical properties 3 months after implantation in the miniature pig. Twenty defects (7×10 mm) were created in the femoral condyles of 10 miniature pigs. The defects were left empty (E), filled with the grafted cylinder upside down (U) or with a combined scaffold (S) containing a spongious bone cylinder (Tutobone®) covered with a collagen membrane (Chondrogide®). In a fourth group, the same scaffolds were implanted but seeded with a stem cell concentrate (S+ BMCC). The animals were stained with calcein green after 2 weeks and xylenol orange after 4 weeks. After 3 months, the animals were sacrificed, and a mechanical analysis (Young's modulus), macroscopic, and histologic (ICRS Score) examination of the specimens was conducted. Young's modulus in the periphery was significantly lower for group E (67.5±15.3 kPa) compared with untreated controls (171.7±21.6 kPa, p<0.04). Bone defects were smaller in group S (10%±8%) compared with E (27%±7%; p<0.05). There was a trend toward smaller bony defects on comparing groups E and S+ BMCC (11%±8%; p=0.07). More red fluorescence was detected in group S+ BMCC (2.3%±1.1%) compared with groups E (0.4%±0.2%) and U (0.5%±0.2%, p<0.03). ICRS scores were higher for groups S (25.3±3.8) and S+ BMCC (26.2±5.2, p<0.01). In this animal model of osteochondral defects, stem cell concentrates enhance new bone apposition but fail to improve mechanical properties or histological appearance of cartilage regenerates in critical-sized defects.

Expression of cathepsin K and tartrate-resistant acid phosphatase is not confined to osteoclasts but is a general feature of multinucleated giant cells: systematic analysis

OBJECTIVE

Cathepsin K and tartrate-resistant acid phosphatase (TRAP) are two proteins expressed in osteoclastic giant cells. Recently we showed that lesional multinucleated giant cells (MNGs) in pulmonary granulomatosis with polyangiitis expressed these proteins. We aimed to clarify whether the expression of these two proteins has any specificity or is a general feature of MNGs associated with multiple types of granulomatous inflammation.

METHODS

In total, 7 Crohn's disease (CD), 5 GCA, 5 giant cell myocarditis (GCM), 11 sarcoidosis and 6 tuberculosis cases were examined for expression of cathepsin K and TRAP using immunohistochemistry (IHC). Protein expression was semi-quantitatively classified as none, weak, moderate or strong. In addition, tissue TRAP activity was examined using an enzymatic reaction.

RESULTS

The expression of cathepsin K was robust in >95% of MNGs of all examined disease groups, whereas TRAP expression varied; CD, GCA and tuberculosis showed strong TRAP expression. TRAP expression in sarcoidosis and GCM was weaker (CD vs GCM, P = 0.04; CD vs sarcoidosis, P = 0.06). Compared with IHC, TRAP detection using an enzymatic colour reaction had limited sensitivity.

CONCLUSION

Expression of TRAP and cathepsin K is a general feature of MNGs and their expression might be related to histopathological pattern.

Hyperglycemia induced and intrinsic alterations in type 2 diabetes-derived osteoclast function

Periodontal disease-associated alveolar bone loss is a comorbidity of type-2-diabetes, where the roles of osteoclasts are poorly understood.

OBJECTIVE

To evaluate osteoclast differentiation and function in the context of type-2-diabetes.

MATERIALS AND METHODS

Bone marrow-derived osteoclasts from db/db mice, a model of type-2-diabetes, as well as human osteoclasts derived from peripheral blood of individuals with type-2-diabetes were evaluated for differentiation, resorption, and soluble mediator expression.

RESULTS

While db/db mice were hyperglycemic at time of cell harvest, human participants were glycemically controlled. Although db/db cultures resulted in a higher number of larger osteoclasts, individual cell receptor activator of nuclear factor kappaB ligand (RANKL)-mediated bone resorption was similar to that observed in diabetes-free osteoclasts. Osteoclasts derived from individuals with type-2-diabetes differentiated similarly to controls with again no difference in bone resorbing capacity. Murine and human type-2-diabetes cultures both displayed inhibition of lipopolysaccharide (LPS)-induced deactivation and increased pro-osteoclastogenic mediator expression.

CONCLUSIONS

Hyperglycemia plays a role in aberrant osteoclast differentiation leading to an increased capacity for bone resorption. Osteoclasts derived from murine models of and individuals with type-2-diabetes are unable to be inhibited by LPS, again leading to increased capacity for bone resorption. Here, environmental and intrinsic mechanisms associated with the increased alveolar bone loss observed in periodontal patients with type-2-diabetes are described.

Augmented LPS responsiveness in type 1 diabetes-derived osteoclasts

Bone abnormalities are frequent co-morbidities of type 1 diabetes (T1D) and are principally mediated by osteoblasts and osteoclasts which in turn are regulated by immunologic mediators. While decreased skeletal health in T1D involves alterations in osteoblast maturation and function, the effect of altered immune function on osteoclasts in T1D-associated bone and joint pathologies is less understood. Here T1D-associated osteoclast-specific differentiation and function in the presence and absence of inflammatory mediators was characterized utilizing bone marrow-derived osteoclasts (BM-OCs) isolated from non-obese diabetic (NOD) mice, a model for spontaneous autoimmune diabetes with pathology similar to individuals with T1D. Differentiation and osteoclast-mediated bone resorption were evaluated along with cathepsin K, MMP-9, and immune soluble mediator expression. The effect of lipopolysaccharide (LPS), a pro-inflammatory cytokine cocktail, and NOD-derived conditioned supernatants on BM-OC function was also determined. Although NOD BM-OCs cultures contained smaller osteoclasts, they resorbed more bone concomitant with increased cathepsin K, MMP-9, and pro-osteoclastogenic mediator expression. NOD BM-OCs also displayed an inhibition of LPS-induced deactivation that was not a result of soluble mediators produced by NOD BM-OCs, although a pro-inflammatory milieu did enhance NOD BM-OCs bone resorption. Together these data indicate that osteoclasts from a T1D mouse model hyper-respond to RANK-L resulting in excessive bone degradation via enhanced cathepsin K and MMP-9 secretion concomitant with an increased expression of pro-osteoclastic soluble mediators. Our data also suggest that inhibition of LPS-induced deactivation in NOD-derived BM-OC cultures is most likely due to NOD osteoclast responsiveness rather than LPS-induced expression of soluble mediators.

Effects of lercanidipine on bone density and bone repair in spontaneously hypertensive rats

PURPOSE

To evaluate the effects of the lercanidipine on bone healing (BH) and bone density (BD) in the tibiae of spontaneously hypertensive rats (SHR), using histometric and tartrate-resistant acid phosphatase (TRAP) expression analyses.

MATERIALS AND METHODS

Wistar and SHR were assigned to one of the following groups: normotensive rats (NTR) (n = 15), untreated SHR (n = 15), and lercanidipine-treated SHR (n = 15). The latter group was treated daily with lercanidipine for 6 weeks. Two weeks after the beginning of drug administration, a critical-sized surgical defect was created in the right tibia of all groups, whereas the contralateral tibia remained without defect. The animals were killed 30 days after the creation of the bone defect.

RESULTS

There were no significant differences among the groups for BH, trabecular BD, and the number of TRAP+ cells in the newly formed cortical bone (P > 0.05). SHR presented significantly lower cortical BD and increased cortical levels of TRAP+ cells, when compared with NTR and lercanidipine-treated SHR (P < 0.05).

CONCLUSION

SHR presented a lower cortical BD and increased levels of TRAP+ cells. In addition, the treatment of SHR with lercanidipine during 6 weeks was able to revert the deleterious effects of hypertension on cortical BD and on the number of TRAP+ cells in the tibia of SHR.

Calcium phosphate phases integrated in silica/collagen nanocomposite xerogels enhance the bioactivity and ultimately manipulate the osteoblast/osteoclast ratio in a human co-culture model

A human co-culture model of osteoblasts and osteoclasts, derived from bone marrow stromal cells and monocytes respectively, was used to characterize the influence of biomaterial modification on the bioactivity and ultimately the ratio of bone-forming to bone-resorbing cells cultivated directly on the surface. Nanocomposites of silica and collagen have been shown to function as skeletal structures in nature and were reproduced in vitro by using a sol-gel approach. The resulting xerogels exhibit a number of features that make it a valuable system for the development of innovative materials for bone substitution applications. In the present study, the incorporation of different calcium phosphate phases in silica/collagen-based gels was demonstrated to enhance the bioactivity of these samples. This ability of the biomaterial to precipitate calcium phosphate on the surface when incubated in simulated body fluids or cell culture medium is generally considered to an advantageous property for bone substitution materials. By co-cultivating human osteoblasts and osteoclasts up to 42 days on the xerogels, we demonstrate that the long-term ratio of these cell types depends on the level of bioactivity of the substrate samples. Biphasic silica/collagen xerogels exhibited comparably low bioactivity but encouraged proliferation of osteoblasts in comparison to osteoclast formation. A balanced ratio of both cell types was detected for moderately bioactive triphasic xerogels with 5% calcium phosphate. However, enhancing the bioactivity of the xerogel samples by increasing the calcium phosphate phase percentage to 20% resulted in a diminished number of osteoblasts in favor of osteoclast formation. Quantitative evaluation was carried out by biochemical methods (calcium, DNA, ALP, TRAP 5b) as well as RT-PCR (ALP, BSP II, OC, RANKL, TRAP, CALCR, VTNR, CTSK), and was supported by confocal laser scanning microscopy (cell nuclei, actin, CD68, TRAP) as well as scanning electron microscopy.

Apolipoprotein E inhibits osteoclast differentiation via regulation of c-Fos, NFATc1 and NF-κB

Apolipoprotein E (ApoE) plays a major role in the transport and metabolism of lipid. Other functions of ApoE include modulation of innate and adaptive immune responses. The expression of ApoE in osteoblasts and its relevance with bone formation have also been reported. However, the effect of ApoE on osteoclasts has not yet been examined. Here, we investigated the role of ApoE in osteoclast differentiation using bone marrow-derived macrophages (BMMs) and RAW264.7 cells. We found a down-regulation of ApoE gene expression during osteoclastic differentiation of those cells. Overexpression of ApoE in BMMs and RAW264.7 cells significantly blocked the induction of c-Fos and nuclear factor of activated T cell c1 (NFATc1), transcription factors critical for expression of osteoclast marker genes, by receptor activator of nuclear factor κB ligand (RANKL), the osteoclast differentiation factor. ApoE inhibited osteoclast differentiation, as measured by decreased number of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells (MNCs). In addition, ApoE reduced the expression of dendritic cell-specific transmembrane protein (DC-STAMP) and ATPase, H(+) transporting, lysosomal 38kDa, V0 subunit d2 (ATP6v0d2), genes involved in cell-cell fusion during osteoclastogenesis. Knock-down of ApoE using a specific siRNA promoted the RANKL-mediated induction of osteoclast differentiation. While ApoE did not affect the activation of ERK, JNK, and p38 MAPK signaling pathways by RANKL, the phosphorylation of p65 trans-activation domain on serine 536 and transcription activity of NF-κB were reduced by ApoE overexpression. These findings suggest that ApoE plays an inhibitory role in osteoclast differentiation via the suppression of RANKL-dependent activation of NF-κB and induction of c-Fos and NFATc1.

Complement C1q production by osteoclasts and its regulation of osteoclast development

C1q deficiency is the strongest known risk factor for SLE (systemic lupus erythematosus) but its endogenous cellular origin remains limitedly understood. In the present study we investigate the production of C1q by both cultured and endogenous bone osteoclasts. Blood monocytes were cultured with RANKL (receptor activator of nuclear factor κB ligand) and M-CSF (macrophage colony-stimulating factor) to generate osteoclasts and these cells expressed C1Q mRNA and also secreted C1q protein. Intracellular C1q was detectable in developing osteoclasts at day 3 by Western blotting and was also detectable by flow cytometry. By immunofluorescence microscopy, C1q was preferentially detected in immature osteoclasts. By multiple detection methods, C1q expression was markedly increased after IFNγ (interferon γ) treatment. By immunohistochemistry, C1q was also detected in endogenous bone osteoclasts. When osteoclasts were cultured on immobilized C1q, these cells exhibited 2-7-fold increases in the expression of signature osteoclast genes [TRAP (tartrate-resistant acid phosphatase), cathepsin K, calcitonin receptor, carbonic anhydrase II and NFATc1 (nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1)], suggesting an osteoclastogenic capability. This is the first report of C1q production by osteoclasts. Its ability to enhance osteoclast development implies reduced osteoclastogenesis in patients with SLE as they often experience decreased C1q levels. This is consistent with the non-erosive nature of lupus arthritis.

The role of osteoclasts and tumour-associated macrophages in osteosarcoma metastasis

Osteosarcoma (OS) is the most common primary bone tumour in the paediatric age group. Treatment-refractory pulmonary metastasis continues to be the major complication of OS, reducing the 5-year survival rate for these patients to 10-20%. The mechanisms underlying the metastatic process in OS are still unclear, but undoubtedly, a greater understanding of the factors and interactions involved in its regulation will open new and much needed opportunities for therapeutic intervention. Recent published data have identified a new role for bone-specific macrophages (osteoclasts) and tumour-associated macrophages (TAMs), in OS metastasis. In this review we discuss the contribution of TAMs and osteoclasts in the establishment and maintenance of secondary metastatic lesions, and their novel role in the prevention of metastatic disease in a primary bone cancer such as osteosarcoma.

Immunolocalization of RANK and RANKL along the root surface and in the periodontal membrane of human primary and permanent teeth

OBJECTIVE

Root resorption, impaired tooth eruption and early tooth loss have been described in relation to diseases that involve defects in the RANK-RANKL-OPG-expression. The aim of the present immunhistochemical study was to localize and compare the reactions for RANK and membrane-bound RANKL along root surfaces and in the periodontal membrane in close proximity to the root surface of human primary and permanent teeth.

MATERIALS AND METHODS

The material comprised extracted human teeth (11 primary teeth and six permanent teeth) from 10 different patients. Paraffin sections were prepared of each tooth and sections of each tooth were immunohistochemically stained with antibodies specific for membrane-bound RANKL and RANK.

RESULTS

The root surface and the periodontal membrane in close proximity to the root surface did not show immunoreactivity for RANKL. RANKL was only located in odontoblasts and in cells along denticles in one primary tooth. RANK was located in mononuclear cells in the pulp and in multinucleated odontoclasts along resorbed root surfaces and along resorbed dentin surfaces in the pulp in primary teeth and one permanent tooth.

CONCLUSIONS

This study demonstrated RANK positivity in resorption areas in primary and permanent teeth. RANKL was positive in the pulp of one primary tooth. RANK expression in odontoclasts and RANKL expression in the pulp may indicate that RANK/RANKL play a role during resorption.

A molecular description of acid phosphatase

Acid phosphatase is ubiquitous in distribution in various organisms. Although it catalyzes simple hydrolytic reactions, it is considered as an interesting enzyme in biological systems due to its involvement in different physiological activities. However, earlier reviews on acid phosphatase reveal some fragmentary information and do not give a holistic view on this enzyme. So, the present review summarizes studies on biochemical properties, structure, catalytic mechanism, and applications of acid phosphatase. Recent advancement of acid phosphatase in agricultural and clinical fields is emphasized where it is presented as potent agent for sustainable agricultural practices and diagnostic marker in bone metabolic disorders. Also, its significance in prostate cancer therapies as a therapeutic target has been discussed. At the end, current studies and prospects of immobilized acid phosphatase are included.

ACP5 (Uteroferrin): phylogeny of an ancient and conserved gene expressed in the endometrium of mammals

Type 5 acid phosphatase (ACP5; also known as tartrate-resistant acid phosphatase or uteroferrin) is a metalloprotein secreted by the endometrial glandular epithelium of pigs, mares, sheep, and water buffalo. In this paper, we describe the phylogenetic distribution of endometrial expression of ACP5 and demonstrate that endometrial expression arose early in evolution (i.e., before divergence of prototherian and therian mammals ~166 million years ago). To determine expression of ACP5 in the pregnant endometrium, RNA was isolated from rhesus, mouse, rat, dog, sheep, cow, horse, armadillo, opossum, and duck-billed platypus. Results from RT-PCR and RNA-Seq experiments confirmed that ACP5 is expressed in all species examined. ACP5 was also demonstrated immunochemically in endometrium of rhesus, marmoset, sheep, cow, goat, and opossum. Alignment of inferred amino acid sequences shows a high conservation of ACP5 throughout speciation, with species-specific differences most extensive in the N-terminal and C-terminal regions of the protein. Analysis by Selecton indicated that most of the sites in ACP5 are undergoing purifying selection, and no sites undergoing positive selection were found. In conclusion, endometrial expression of ACP5 is a common feature in all orders of mammals and has been subjected to purifying selection. Expression of ACP5 in the uterus predates the divergence of therians and prototherians. ACP5 is an evolutionary conserved gene that likely exerts a common function important for pregnancy in mammals using a wide range of reproductive strategies.

Sustained release of adiponectin improves osteogenesis around hydroxyapatite implants by suppressing osteoclast activity in ovariectomized rabbits

Lack of estrogen could lead to decreased bone mass and increased risk for osteoporosis, which has a negative influence on biomaterial implantation. Adiponectin (APN), an adipose-derived hormone, has been shown to increase bone density by inhibiting osteoclast formation and promoting the formation of osteoblasts. This study was designed to investigate the direct effects of APN released from the Matrigel controlled-release system on the activity of rabbit mature osteoclasts and osteoclast precursor RAW264.7 cells in vitro, and to determine its effects by improving osteogenesis around the hydroxyapatite (HA) implant in ovariectomized (OVX) rabbits. APN+Matrigel+HA, APN+HA, Matrigel+HA and HA were implanted into mandibular defects of OVX rabbits. At 4 weeks after implantation, the mandibles were examined by histology, microcomputed tomography and biomechanical testing. The results demonstrated that Matrigel extended the length of APN released to achieve long-term persistence. The sustained release of APN suppressed the osteoclastic activity both in vitro and in vivo, and improved the peri-implant osteogenesis in OVX rabbits, while the short-term APN treatment did not. Sustained release of APN may be an effective strategy to improve the restoration of bone defects by the use of HA materials under osteoporotic conditions in which osteoclasts are highly activated.

Monogenic autoimmunity

Monogenic autoimmune syndromes provide a rare yet powerful glimpse into the fundamental mechanisms of immunologic tolerance. Such syndromes reveal not only the contribution of an individual breakpoint in tolerance but also patterns in the pathogenesis of autoimmunity. Disturbances in innate immunity, a system built for ubiquitous sensing of danger signals, tend to generate systemic autoimmunity. For example, defects in the clearance of self-antigens and chronic stimulation of type 1 interferons lead to the systemic autoimmunity seen in C1q deficiency, SPENCDI, and AGS. In contrast, disturbances of adaptive immunity, which is built for antigen specificity, tend to produce organ-specific autoimmunity. Thus, the loss of lymphocyte homeostasis, whether through defects in apoptosis, suppression, or negative selection, leads to organ-specific autoimmunity in ALPS, IPEX, and APS1. We discuss the unique mechanisms of disease in these prominent syndromes as well as how they contribute to the spectrum of organ-specific or systemic autoimmunity. The continued study of rare variants in autoimmune disease will inform future investigations and treatments directed at rare and common autoimmune diseases alike.

Foreign body-type multinucleated giant cells induced by interleukin-4 express select lymphocyte co-stimulatory molecules and are phenotypically distinct from osteoclasts and dendritic cells

Foreign body-type multinucleated giant cells (FBGC), formed by macrophage fusion, are a prominent cell type on implanted biomaterials, although the roles they play at these and other sites of chronic inflammation are not understood. Why lymphocytes are present in this scenario and the effects of fusing macrophages/FBGC on subsequent lymphocyte responses are also unclear. To address the physiological significance of FBGC in this regard, we employed our in vitro system of interleukin (IL)-4-induced human monocyte-derived macrophage fusion/FBGC formation. Initially, we pursued the identities of lymphocyte co-stimulatory molecules on fusing macrophages/FBGC. In addition, we further compared the FBGC phenotype to that currently associated with osteoclasts and dendritic cells using recognized markers. Immunoblotting of cell lysates and immunochemistry of macrophages/FBGC in situ, revealed that IL-4-induced macrophages/FBGC strongly express HLA-DR, CD98, B7-2 (CD86), and B7-H1 (PD-L1), but not B7-1 (CD80) or B7-H2 (B7RP-1). Furthermore, molecules currently recognized to be expressed on osteoclasts (calcitonin receptor, tartrate-resistant acid phosphatase, RANK) or dendritic cells (CD1a, CD40, CD83, CD95/fas) are undetectable. In contrast, fusing macrophages/FBGC strongly express the macrophage markers αX integrin (CD11c), CD68, and dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), whereas CD14 is completely down-modulated with IL-4-induced macrophage fusion. These novel data demonstrate that IL-4-induction of macrophage multinucleation/FBGC formation features the acquisition of a CD14-negative phenotypic profile which is distinguishable from that of dendritic cells and osteoclasts, yet potentially exhibits multiple capacities for lymphocyte interactions with resultant lymphocyte down-modulation.

Characterization of the response of primary cells relevant to dialysis-related amyloidosis to β2-microglobulin monomer and fibrils

The formation of insoluble amyloid fibrils is associated with an array of devastating human diseases. Dialysis-related amyloidosis (DRA) is a severe complication of hemodialysis that results in the progressive destruction of the bones and joints. Elevated concentrations of β₂-microglobulin (β₂m) in the serum of subjects on hemodialysis promote the formation of amyloid fibrils in the osteoarticular tissues, but the cellular basis for the destruction of these tissues in DRA is poorly understood. In this study we performed a systematic analysis of the interaction of monomeric and fibrillar β₂m with primary human cells of the types present in the synovial joints of subjects with DRA. Building upon observations that macrophages infiltrate β₂m amyloid deposits in vivo we demonstrate that monocytes, the precursors of macrophages, cannot degrade β₂m fibrils, and that both monomeric β₂m and fibrillar β₂m are cytotoxic to these cells. β₂m fibrils also impair the formation of bone resorbing osteoclasts from monocytes and reduce the viability of osteoblasts, the cell type that produces bone. As a consequence, we predict that β₂m amyloid will disrupt the remodelling of the bone, which is critical for the maintenance of this tissue. Moreover, we show that β₂m fibrils reduce the viability of chondrocytes, rationalizing the loss of cartilage in DRA. Together, our observations demonstrate that β₂m cytotoxicity has multiple cellular targets in the osteoarticular tissues and is likely to be a key factor in the bone and joint destruction characteristic of DRA.

Impact of ectoenzymes on p2 and p1 receptor signaling

P2 receptors that are activated by extracellular nucleotides (e.g., ATP, ADP, UTP, UDP, Ap(n)A) and P1 receptors activated by adenosine control a diversity of biological processes. The activation of these receptors is tightly regulated by ectoenzymes that metabolize their ligands. This review presents these enzymes as well as their roles in the regulation of P2 and P1 receptor activation. We focus specifically on the role of ectoenzymes in processes of our interest, that is, inflammation, vascular tone, and neurotransmission. An update on the development of ectonucleotidase inhibitors is also presented.

Study of the mechanisms by which Sambucus williamsii HANCE extract exert protective effects against ovariectomy-induced osteoporosis in vivo

The purpose of this study is to investigate the dose-dependent effects of SWH on bone properties and the mechanism involved in mediating the osteoprotective actions of SWH. The results indicated that SWH could improve bone properties by inhibiting the process of bone resorption and stimulating the process of bone formation.

INTRODUCTION

Our previous study showed that Sambucus williamsii HANCE (SWH) improved trabecular bone mass and cortical bone strength in ovariectomized (OVX) rats. The purpose of this study is to investigate the dose-dependent effects of SWH on bone properties and the mechanism involved in mediating the osteoprotective actions of SWH.

METHODS

Three-month-old C57BL/6J mice were fed a phytoestrogen-free diet and subjected to either ovariectomy or sham operation. OVX mice were treated with genistein (50 mg/kg), or a low (200 mg/kg), medium (500 mg/kg), or high (1,000 mg/kg) dose of SWH extract.

RESULTS

SWH could dose-dependently decrease urinary Ca excretion and increase serum Ca level in OVX mice. It could increase tibial bone mineral density and exert beneficial effects on the microarchitecture of trabecular bone in the OVX mice. SWH suppressed the ovariectomy-induced expression of Cbfa1 mRNA and cathepsin K mRNA and enhanced the ratio of OPG/RANKL mRNA expression in the tibia. In vitro study showed that SWH dramatically reduced the number of TRAP-positive cells in RANKL-induced RAW 264.7 cells.

CONCLUSIONS

The present study indicated that SWH could improve bone properties by inhibiting the process of bone resorption and stimulating the process of bone formation.

Osteoclastic metabolism of 25(OH)-vitamin D3: a potential mechanism for optimization of bone resorption

The extrarenal synthesis of 1α,25 dihydroxyvitamin D3 (1,25D) has been demonstrated in a number of cell types including osteoblasts and cells of the monocyte/macrophage lineage. The skeleton appears responsive to serum levels of the 1,25D precursor, 25 hydroxyvitamin D3 (25D), in terms of bone mineralization parameters. The effect of metabolism of 25D into active 1,25D by osteoclast lineage cells is unknown. We found that CYP27B1 mRNA expression increased with exposure of human peripheral blood mononuclear cells (PBMCs) to macrophage colony-stimulating factor in the presence or absence of receptor activator of nuclear factor-κB ligand. Consistent with this, human osteoclast cultures incubated with 25D produced measurable quantities of 1,25D. Osteoclast formation from either mouse RAW264.7 cells or human PBMCs in the presence of physiological concentrations of 25D resulted in significant up-regulation of the key osteoclast transcription factor, nuclear factor of activated T cells-c1 in PBMCs and a number of key osteoclast marker genes in both models. The expression of the osteoblast coupling factor, ephrin-b2, was also increased in the presence of 25D. Levels of CYP27B1 and nuclear factor of activated T cells-1 mRNA correlated during osteoclastogenesis and also in a cohort of human bone samples. CYP27B1 short-hairpin RNA knockdown in RAW264.7 cells decreased their osteoclastogenic potential. 25D dose dependently reduced the resorptive capacity of PBMC-derived osteoclasts without compromising cell viability. 25D also reduced resorption by RAW264.7- and giant cell tumor-derived osteoclasts. Conversely, osteoclasts formed from vitamin D receptor-null mouse splenocytes had increased resorptive activity compared with wild-type cells. We conclude that 25D metabolism is an important intrinsic mechanism for optimizing osteoclast differentiation, ameliorating osteoclast activity, and potentially promoting the coupling of bone resorption to formation.

IL-3 inhibits human osteoclastogenesis and bone resorption through downregulation of c-Fms and diverts the cells to dendritic cell lineage

IL-3 is an important cytokine that regulates hematopoiesis and functions as a link between the immune and the hematopoietic system. In this study, we investigated the role and mechanism of IL-3 action on human osteoclast formation and bone resorption using PBMCs. PBMCs differentiate into functional osteoclasts in the presence of M-CSF and receptor activator of NF-kappaB ligand as evaluated by 23c6 expression and bone resorption. We found that IL-3 dose-dependently inhibited formation of 23c6-positive osteoclasts, bone resorption and C-terminal telopeptide of type I collagen, a collagen degradation product. The inhibitory effect of IL-3 on bone resorption was irreversible. To investigate the mechanism of IL-3 action, we analyzed the effect of IL-3 on the receptor activator of NF-kappaB and c-Fms receptors and c-Fos, PU.1, NFAT cytoplasmic 1, and RelB transcription factors essential for osteoclastogenesis. IL-3 significantly inhibited c-Fms and downregulated both PU.1 and c-Fos at both mRNA and protein level. Furthermore, IL-3-treated cells showed increased expression of dendritic cell markers CD1a and CD80 and decreased expression of monocyte/macrophage marker CD14. Interestingly, IL-3 inhibited formation of human osteoclasts derived from blood monocytes and bone marrow cells of osteoporotic individuals. Thus, IL-3 may have therapeutic potential as an antiosteolytic agent in treatment of osteoporosis.

Carbonic anhydrases II and XII are up-regulated in osteoclast-like cells in advanced human atherosclerotic plaques-Tampere Vascular Study

BACKGROUND AND AIMS

Carbonic anhydrases (CA) play a central role in osteoclast function and bone remodeling by catalyzing the formation of bicarbonate and proton from carbon dioxide. According to previous histochemical studies, advanced atherosclerotic plaques share similarities with bone. However, whether CAs are expressed in plaques is not known.

METHODS AND RESULTS

Whole genome expression array of arterial samples (n = 24) confirmed that several genes indicating osteoblastogenesis and osteoclastogenesis were up-regulated in plaques when compared to control vessel samples from internal thoracic arteries (n = 6), including CA2 and CA12, expression of which was also verified with quantitative reverse transcription polymerase chain reaction (RT-PCR). In atherosclerotic plaques there was 11.6-fold (P < 0.0001) and 11.4-fold (P < 0.0001) up-regulation of CA2 and CA12, compared to controls, respectively. According to quantitative PCR, CA2 expression was elevated in carotid (12.3-fold, P < 0.0001), femoral (13.2-fold, P < 0.01), and aortic plaques (7.5-fold, P < 0.0001). CA12 expression was elevated in carotid (11.6-fold, P < 0.0001), femoral (11.5-fold, P < 0.01), and aortic plaques (9.7-fold, P < 0.0001). CAII, CAXII, and CD68 and tartrate-resistant acid phosphatase (TRAP), a marker of osteoclast-like cells, were found to be co-localized in multinucleated giant cells in the atherosclerotic plaques using immunohistochemistry and double-staining immunofluorescence analysis.

CONCLUSIONS

The present findings provide evidence for the involvement of CAs in advanced atherosclerosis in osteoclast-like cells of monocyte-macrophage lineage.

Dendritic cell-mediated in vivo bone resorption

Osteoclasts are resident cells of the bone that are primarily involved in the physiological and pathological remodeling of this tissue. Mature osteoclasts are multinucleated giant cells that are generated from the fusion of circulating precursors originating from the monocyte/macrophage lineage. During inflammatory bone conditions in vivo, de novo osteoclastogenesis is observed but it is currently unknown whether, besides increased osteoclast differentiation from undifferentiated precursors, other cell types can generate a multinucleated giant cell phenotype with bone resorbing activity. In this study, an animal model of calvaria-induced aseptic osteolysis was used to analyze possible bone resorption capabilities of dendritic cells (DCs). We determined by FACS analysis and confocal microscopy that injected GFP-labeled immature DCs were readily recruited to the site of osteolysis. Upon recruitment, the cathepsin K-positive DCs were observed in bone-resorbing pits. Additionally, chromosomal painting identified nuclei from female DCs, previously injected into a male recipient, among the nuclei of giant cells at sites of osteolysis. Finally, osteolysis was also observed upon recruitment of CD11c-GFP conventional DCs in Csf1r(-/-) mice, which exhibit a severe depletion of resident osteoclasts and tissue macrophages. Altogether, our analysis indicates that DCs may have an important role in bone resorption associated with various inflammatory diseases.

Osteosarcoma is characterised by reduced expression of markers of osteoclastogenesis and antigen presentation compared with normal bone

Background:

Osteosarcoma (OS) is the most common primary bone tumour in children and adolescents. Patients who respond poorly to chemotherapy have a higher risk of metastatic disease and 5-year survival rates of only 10–20%. Therefore, identifying molecular targets that are specific for OS, or more specifically, metastatic OS, will be critical to the development of new treatment strategies to improve patient outcomes.

Methods:

We performed a transcriptomic analysis of chemo-naive OS biopsies and non-malignant bone biopsies to identify differentially expressed genes specific to OS, which could provide insight into OS biology and chemoresistance.

Results:

Statistical analysis of the OS transcriptomes found differential expression of several metallothionein family members, as well as deregulation of genes involved in antigen presentation. Tumours also exhibited significantly increased expression of ID1 and profound down-regulation of S100A8, highlighting their potential as therapeutic targets for OS. Finally, we found a significant correlation between OS and impaired osteoclastogenesis and antigen-presenting activity. The reduced osteoclastogenesis and antigen-presenting activity were more profound in the chemoresistant OS samples.

Conclusion:

Our results indicate that OS displays gene signatures consistent with decreased antigen-presenting activity, enhanced chemoresistance, and impaired osteoclastogenesis. Moreover, these alterations are more pronounced in chemoresistant OS tumour samples.

Erythrina variegata extract exerts osteoprotective effects by suppression of the process of bone resorption

Our previous study showed that Erythrina variegata L. (EV) inhibited bone loss and improved bone properties in ovariectomised rats. The purpose of the present study is to investigate the potential mechanism involved in mediating the osteoprotective actions of EV. Female Sprague–Dawley rats were fed a phyto-oestrogen-free diet and subjected to either ovariectomy or a sham operation. Ovariectomised rats were treated with genistein (40 mg/kg) as well as low (200 mg/kg), medium (500 mg/kg) or high (1000 mg/kg) doses of EV extract. Bone properties and mRNA expressions were evaluated by micro-computed tomography and quantitative RT-PCR, respectively. Osteoclast differentiation in RAW 264·7 cells was studied by tartrate-resistant acid phosphatase (TRAP) staining. High doses of EV could decrease urinary Ca and P excretion, maintain serum Ca and P level, and exert beneficial effects on the micro-structure and morphology of trabecular bone and cortical bone in ovariectomised rats. EV suppressed the up-regulation of cathepsin K mRNA and the down-regulation of osteoprotegrin mRNA in the tibia of ovariectomised rats. TRAP-positive cell numbers were significantly decreased in receptor activator of nuclear factor-κB ligand (RANKL)-induced RAW 264·7 cells when co-cultured with EV extracts. The present study indicated that the protective effects of EV on bone properties in ovariectomised rats are likely to be mediated by its inhibitory actions on the process of bone resorption via the suppression of osteoclast differentiation and maturation.

Biology and clinical significance of tartrate-resistant acid phosphatases: new perspectives on an old enzyme

Type 5 tartrate-resistant acid phosphatase (TRAP) has been a clinically relevant biomarker for about 50 years. It has always been a reliable and specific cytochemical marker for hairy cell leukemia and for differentiated cells of monocytic lineage. Only recently has the test for serum TRAP activity been accepted as sensitive and specific enough for clinical use as a marker of osteoclasts and bone resorption. This has come about through steady advances in knowledge about TRAP enzymology, structure, function, and molecular regulation and a consequent appreciation that TRAP isoforms 5a and 5b have very different clinical significance. As a measure of osteoclast number and bone resorption, TRAP 5b has diagnostic and prognostic applications in osteoporosis, cancers with bone metastasis, chronic renal failure, and perhaps other metabolic and pathologic bone diseases. Serum TRAP 5a, on the other hand, has no relationship to bone metabolism but seems instead to be a measure of activated macrophages and chronic inflammation. Exploration of the real clinical usefulness of serum TRAP 5a for diagnosis and disease management in a wide variety of chronic inflammatory diseases is only now beginning. This perspective traces the important basic scientific developments that have led up to the refinement of serum TRAP isoform immunoassays and their validation as biomarkers of disease. Many unanswered questions remain, providing a wealth of opportunity for continued research of this multifaceted enzyme.

Complex regulation of tartrate-resistant acid phosphatase (TRAP) expression by interleukin 4 (IL-4): IL-4 indirectly suppresses receptor activator of NF-kappaB ligand (RANKL)-mediated TRAP expression but modestly induces its expression directly

Interleukin 4 (IL-4) inhibits receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast formation and functional activity in a STAT6-dependent manner. IL-4 down-regulates expression of tartrate-resistant acid phosphatase (TRAP) in mature osteoclasts. To determine whether IL-4 regulates TRAP promoter activity, RAW264.7 cells were transfected with a TRAP promoter-luciferase reporter. Treatment with IL-4 alone modestly enhanced TRAP luciferase activity. However, IL-4 suppressed the ability of RANKL to up-regulate TRAP-luciferase activity, suggesting that IL-4 has multiple effects on TRAP transcription. IL-4 also reduced the RANKL-induced association of RNA polymerase II with the TRAP gene in osteoclasts. The TRAP promoter contains a STAT6-binding motif, and STAT6 bound to the endogenous TRAP promoter after IL-4 treatment. To determine the impact of STAT6 binding, we transfected cells with STAT6VT, a constitutively active STAT6 mutant. STAT6VT alone up-regulated TRAP-luciferase activity; this effect was abrogated by mutating the STAT6 binding site in the minimal TRAP promoter. STAT6VT did not inhibit the potent up-regulation of TRAP promoter activity caused by overexpression of NFATc1, PU.1, and microphthalmia transcription factor, downstream targets of macrophage colony-stimulating factor and RANKL. IL-4 down-regulated the expression of c-Fos and NFATc1 in mature osteoclasts. Knockdown of NFATc1 by short interfering RNA caused TRAP expression to be down-regulated, and ectopic expression of NFATc1 abrogated the IL-4-induced down-regulation of TRAP. These results suggest that STAT6 plays two distinct roles in TRAP expression. The IL-4-induced activation of STAT6 mediates suppression of the RANKL-induced TRAP promoter activity indirectly by inhibiting NFATc1 expression. However, in the absence of RANKL and osteoclast differentiation, STAT6 binds the TRAP promoter after IL-4 treatment and directly enhances TRAP expression.

Purple acid phosphatase-like sequences in prokaryotic genomes and the characterization of an atypical purple alkaline phosphatase from Burkholderia cenocepacia J2315

Purple acid phosphatases (PAP) are a group of dimetallic phosphohydrolase first identified in eukaryotes. Bioinformatics analysis revealed 57 prokaryotic PAP-like sequences in the genomes of 43 bacteria and 4 cyanobacteria species. A putative PAP gene (BcPAP) from the bacteria Burkholderia cenocepacia J2315 was chosen for further studies. Synteny analysis showed that this gene is present as an independent gene in most of the members of the genus Burkholderia. The predicted 561 a.a. polypeptide of BcPAP was found to harbour all the conserved motifs of the eukaryotic PAPs and an N-terminal twin-arginine translocation signal. Expression and biochemical characterization of BcPAP in Escherichia coli revealed that this enzyme has a relatively narrow substrate spectrum, preferably towards phosphotyrosine, phosphoserine and phosphoenolpyruvate. Interestingly, this enzyme was found to have a pH optimum at 8.5, rather than an acidic optima exhibited by eukaryotic PAPs. BcPAP contains a dimetallic ion centre composed of Fe and Zn, and site-directed mutagenesis confirmed that BcPAP utilizes the invariant residues for metal-ligation and catalysis. The enzyme is secreted by the wild type bacteria and its expression is regulated by the availability of orthophosphate. Our findings suggest that not all members in the PAP family have acidic pH optimum and broad substrate specificity.

Prostatic acid phosphatase, a neglected ectonucleotidase

Two recent papers reveal that the soluble and secreted prostatic acid phosphatase, an enzyme that has long served as a diagnostic marker for prostate cancer, has a membrane-bound splice variant. This enzyme exhibits ecto-5'-nucleotidase activity, is widely distributed, and implicated in the formation of chronic pain. While prostatic acid phosphatase hydrolyzes phosphomonoesters other than 5'-nucleoside monophosphates these novel data suggest that, in addition to ecto-5'-nucleotidase and the alkaline phosphatases, prostatic acid phosphatase must be taken into account in future studies on extracellular adenosine production.