Tartrate-resistant acid phosphatase

About: Tartrate-resistant acid phosphatase is a research topic. Over the lifetime, 1115 publications have been published within this topic receiving 45937 citations. The topic is also known as: HPAP & SPENCDI.

Comparative effect of cadmium on osteoblastic cells and osteoclastic cells

Abstract: Cadmium(Cd) has been thought to disturb the bone metabolism directly. The mechanism for the bone lesion is unknown, however. To examine the effects of cadmium on bone metabolism, we compared its effects on osteoblasts and osteoclasts in vitro. We used an established cell line, MC3T3-E1, as osteoblasts and tartrate resistant acid phosphatase (TRACP)-positive multi-nucleated cells (MNC) formed by a bone marrow culture system as osteoclasts. Alkaline phosphatase (ALP) activity was decreased by 10−7 M Cd and DNA content and hydroxyproline content of osteoblastic cells were decreased by 10−5 M Cd. Cadmium at 10−7 M inhibited the osteoclastic cell formation from mouse bone marrow in the presence of 10−8 M 1α,25(OH)2 vitamin D3. A 100-fold higher concentration of zinc(Zn) simultaneously added to the cadmium-containing medium prevented the toxicity of cadmium to osteoclastic cells as observed in the culture of osteoblastic cells. These results indicate that both bone formation and bone resorption are inhibited by cadmium. The responses of osteoclasts and osteoblasts to cadmium in this culture system were the same and the responses of cadmium-damaged osteoblasts and osteoclasts to zinc were also similar. These results suggest that another mechanism by which cadmium could cause bone damage should be considered in addition to the specific induction of osteoclastic cells by Cd.

Role of C-reactive protein in osteoclastogenesis in rheumatoid arthritis.

Abstract: C-reactive protein (CRP) is one of the biomarkers for the diagnosis and assessment of disease activity in rheumatoid arthritis (RA). CRP is not only the by-product of inflammatory response, but also plays proinflammatory and prothrombotic roles. The aim of this study was to determine the role of CRP on bone destruction in RA. CRP levels in RA synovial fluid (SF) and serum were measured using the immunoturbidimetric method. The expression of CRP in RA synovium was assessed using immunohistochemical staining. CD14+ monocytes from peripheral blood were cultured with CRP, and receptor activator of nuclear factor-κB ligand (RANKL) expression and osteoclast differentiation were evaluated using real-time PCR, counting tartrate resistant acid phosphatase (TRAP)-positive multinucleated cells and assessing bone resorbing function. CRP-induced osteoclast differentiation was also examined after inhibition of Fcγ receptors. There was a significant correlation between CRP levels in serum and SF in RA patients. The SF CRP level was correlated with interleukin (IL)-6 levels, but not with RANKL levels. Immunohistochemical staining revealed that compared with the osteoarthritis synovium, CRP was more abundantly expressed in the lining and sublining areas of the RA synovium. CRP stimulated RANKL production in monocytes and it induced osteoclast differentiation from monocytes and bone resorption in the absence of RANKL. CRP could play an important role in the bony destructive process in RA through the induction of RANKL expression and direct differentiation of osteoclast precursors into mature osteoclasts. In the treatment of RA, lowering CRP levels is a significant parameter not only for improving disease activity but also for preventing bone destruction.

The generation of osteoclasts from RAW 264.7 precursors in defined, serum-free conditions

Abstract: Osteoclasts are the unique cell type capable of resorbing bone. The discovery of the TNF-ligand family member, RANKL, has allowed more reliable study of these important cells. The mouse monocytic cell line, RAW 264.7, has been shown to readily differentiate into osteoclasts upon exposure to recombinant RANKL. Unlike primary osteoclast precursors, there is no requirement for the addition of macrophage colony stimulating factor (M-CSF). However, to date, their differentiation has always been studied in the context of added foetal calf serum (FCS). FCS is a complex and largely undefined mixture of growth factors and matrix proteins, and varies between batches. For this reason, osteoclastogenesis would ideally be studied in the context of a defined, serum-free medium. RAW 264.7 cells were cultured in serum-replete α-MEM or serum-deprived medium (SDM) shown previously to support the growth of human osteoclasts in a co-culture with normal osteoblasts. In SDM, in the presence of recombinant RANKL, RAW 264.7 cells readily differentiated into tartrate resistant acid phosphatase (TRAP) positive multinucleated osteoclast-like cells, a process that was enhanced with the addition of 1α,25-dihydroxyvitamin D3 (1,25D). While the osteoclasts grown in SDM were smaller in size compared with those derived in serum-replete media, their resorptive capacity was significantly increased as indicated by a twofold increase in average resorption pit size. In conclusion, we describe a defined model for studying osteoclast differentiation and activity in the absence of serum, which will be ideal for studying the role of agonistic and antagonistic molecules in this process.

Critical Role of β3 Integrin in Experimental Postmenopausal Osteoporosis

Abstract: We show that mice lacking β3 integrin are protected from OVX-induced bone loss. Using a lentiviral-based strategy to express β3 mutants in β3−/− mice, we also show that β3S752, but not β3Y747/Y759, is important for osteoclastic bone resorption in vivo. Introduction: Mice lacking the β3 integrin have dysfunctional osteoclasts and therefore accumulate bone mass with age. Thus, the αvβ3 integrin is a potential anti-osteoporosis target. Identifying components of the β3 integrin that determine its function in vivo is essential for therapeutically exploiting the antiresorptive properties of αvβ3. Materials and Methods: We used DXA and histomorphometry to assess bone loss after ovariectomy in wildtype and β3 integrin null mice. We used lentiviral vectors carrying various human β3 (hβ3) integrin constructs to transduce β3−/− bone marrow and reconstituted lethally irradiated β3−/− mice with the transduced marrow. The expressed constructs include the intact integrin and two mutants, namely hβ3Y747F/Y759F and hβ3S752P, each of which induces the bleeding dyscrasia, Glanzmann's thrombasthenia, in humans. Two months after transplantation, the expression of hβ3 was measured by flow cytometry of marrow-derived macrophages. Osteoclast differentiation and function were assessed ex vivo by TRACP and actin-ring staining, respectively. Reconstituted mice were ovariectomized, and bone loss was assessed by DXA, histomorphometry, and serum TRACP5b assay. Results: β3−/− mice are protected from ovariectomy-induced bone loss, showing no difference in BMD compared with sham-operated controls. We successfully expressed hβ3 integrins in β3−/− hosts using lentiviral transduction of bone marrow. Two months after transplantation, 25–35% of marrow-derived macrophages expressed the hβ3 constructs. Similar to its effect in vitro, hβ3WT completely rescued the osteoclast and platelet phenotype of β3−/− mice. Whereas platelet function remained deranged in β3−/− mice overexpressing hβ3Y747F/Y759F, osteoclast function was fully restored. In contrast, β3−/− mice expressing hβ3S752P continued to exhibit prolonged bleeding times and dysfunctional osteoclasts in vitro and ex vivo. Most importantly, hβ3WT and hβ3Y747F/Y759F transplanted mice underwent equivalent ovariectomy-induced bone loss, whereas, like those bearing the control vector, hβ3S752P transplanted mice were protected. Conclusions: Functional β3 integrin is required for ovariectomy-induced bone loss. β3S752, but not β3Y747/Y759, is critical for osteoclast function in vivo.

Calvarial Osteoclasts Express a Higher Level of Tartrate-Resistant Acid Phosphatase than Long Bone Osteoclasts and Activation Does not Depend on Cathepsin K or L Activity

Abstract: Bone resorption by osteoclasts depends on the activity of various proteolytic enzymes, in particular those belonging to the group of cysteine proteinases. Next to these enzymes, tartrate-resistant acid phosphatase (TRAP) is considered to participate in this process. TRAP is synthesized as an inactive proenzyme, and in vitro studies have shown its activation by cysteine proteinases. In the present study, the possible involvement of the latter enzyme class in the in vivo modulation of TRAP was investigated using mice deficient for cathepsin K and/or L and in bones that express a high (long bone) or low (calvaria) level of cysteine proteinase activity. The results demonstrated, in mice lacking cathepsin K but not in those deficient for cathepsin L, significantly higher levels of TRAP activity in long bone. This higher activity was due to a higher number of osteoclasts. Next, we found considerable differences in TRAP activity between calvarial and long bones. Calvarial bones contained a 25-fold higher level of activity than long bones. This difference was seen in all mice, irrespective of genotype. Osteoclasts isolated from the two types of bone revealed that calvarial osteoclasts expressed higher enzyme activity as well as a higher level of mRNA for the enzyme. Analysis of TRAP-deficient mice revealed higher levels of nondigested bone matrix components in and around calvarial osteoclasts than in long bone osteoclasts. Finally, inhibition of cysteine proteinase activity by specific inhibitors resulted in increased TRAP activity. Our data suggest that neither cathepsin K nor L is essential in activating TRAP. The findings also point to functional differences between osteoclasts from different bone sites in terms of participation of TRAP in degradation of bone matrix. We propose that the higher level of TRAP activity in calvarial osteoclasts compared to that in long bone cells may partially compensate for the lower cysteine proteinase activity found in calvarial osteoclasts and TRAP may contribute to the degradation of noncollagenous proteins during the digestion of this type of bone.