The expression of osteoclast markers on foreign body giant cells

Long-term bone response to particulate injectable ceramic

Biphasic calcium phosphate particles (BCP), alone or combined with a cellulosic ether vehicle in an injectable composite material (COMP), were implanted in femurs of rabbits. The long-term follow-up (up to 78 weeks) indicated: (1) BCP and COMP induced a foreign-body inflammatory reaction but without fibrous encapsulation. Phagocytosis was mediated by mononucleated macrophages (MC) and giant multinucleated cells (GMNC). Phagocytosis was stronger with COMP and required the recruitment of GMNC while it primarily involved MC in the case of BCP. (2) There appeared to be no significant difference between the bone ingrowth in the defects packed with BCP (dBCP) and in those filled with COMP (dCOMP). Bone reconstruction mostly was achieved after 4 weeks in dBCP but took more time to reach the center of dCOMP. High bone remodeling was observed at the last evaluation times, especially in the case of COMP. (3) Degradation of the materials occurred mainly during the first 4 weeks and was more severe for COMP, which probably was related to the smaller granulometry of its mineral phase. Cell-mediated degradation went on for the 78 weeks and followed two processes: phagocytosis and/or extracellular dissolution of the calcium phosphate particles.

Primary lung tumors infiltrated by osteoclast-like giant cells

Six primary lung tumors with numerous multinucleated osteoclast-like giant cells (OLGCs) and no osteogenic component were evaluated histologically and immunohistochemically to examine pulmonary lesions inciting an OLGC response. The patients comprised four women and two men ranging in age from 61 to 80 years (average age, 69 years). The tumors consisted of one adenocarcinoma, two sarcomatoid carcinomas, and three giant cell variants of malignant fibrous histiocytoma. One tumor was endobronchial in location, while five were situated peripherally. Tumor diameter spanned from 1 to 6.5 cm (average, 2.7 cm). In addition to the giant cells, common characteristics included the malignant nature of the neoplasms and, in five of six cases, histologically malignant mesenchyme. This array of cases exemplifies the variability of lung lesions which may elicit an OLGC inflammatory response resulting in areas resembling the giant cell variant of malignant fibrous histiocytoma. The results of this study suggest that OLGCs occur preferentially in malignant rather than benign nonosteogenic lung tumors and that sarcomatoid regions of malignant tumors are more likely to be infiltrated by OLGCs than epithelial regions.

Ovariectomy augments B lymphopoiesis and generation of monocyte-macrophage precursors in rat bone marrow

To investigate the effects of estrogen depletion on hematopoiesis and bone turnover, female rats were either ovariectomized (OVX) or sham operated and killed at 1, 2, 3, and 4 wk postsurgery. Flow cytometric analysis of bone marrow cells (BMC) revealed that, in close temporal association with the rise in bone turnover as measured by bone histomorphometry, the number of Thy 1.1+ and KiB1R+ BMC increased two- to threefold in OVX rats relative to sham controls. The Thy 1.1+ BMC were further characterized as Thy 1.1+/KiB1R+ and Thy 1.1+/HIS24+ double-positive cells of the B cell lineage. A transient rise in ED1+ myeloid cells expressing a lysosomal antigen specific for the monocyte-macrophage and osteoclast lineage coincided with the upregulation of osteoclast numbers in OVX rats at 2 wk postsurgery, but the number of ED8+ myelomonocytic BMC remained unchanged. Administration of estradiol prevented the rise in Thy 1.1+, KiB1R+, and ED1+ BMC in OVX animals. Our study indicates that ovariectomy upregulates B lymphopoiesis in rat bone marrow and increases myeloid cell differentiation into the monocyte-macrophage and possibly also the osteoclast lineage.

Wear particulate species and bone loss in failed total joint arthroplasties

The aim of this study was to evaluate the relative contribution of polyethylene, metal, and polymethylmethacrylate (cement) particles to the overall bone loss in aseptic loosening. Twenty-four interface tissues with adjacent bone were obtained during 17 revision total joint arthroplasties (11 hips and six knees). Osteoclasts and macrophages were identified immunohistochemically on the bone surface. The length of the bone surface in contact with these cell types was measured and analyzed with reference to the particulate species present within the fibrous interface. The presence of abundant polyethylene particles significantly increased the proportion of the bone surface in contact with macrophages but did not have a significant influence on that of osteoclasts. Osteoclastic bone resorption was significantly more extensive in the presence of metal particles. In contrast, the presence of cement particles did not have a significant influence on macrophage or osteoclast coverage of the bone surface. These results highlight the significance of polyethylene particles in macrophage recruitment and subsequent osteolysis and suggest a different mechanism of bone loss related to metal, namely mediation through osteoclastic activities. The relative contribution of cement particles was negligible and needs reevaluation in light of evidence provided by others.

Human arthroplasty derived macrophages differentiate into osteoclastic bone resorbing cells

OBJECTIVE

In aseptic loosening, a heavy macrophage response to biomaterial wear particles is commonly found in arthroplasty tissues. The aim of this study was to discover if these cells contribute to the bone resorption of aseptic loosening by differentiating into osteoclasts.

METHODS

Macrophages were isolated from the pseudocapsule and pseudomembrane of loose cemented and uncemented hip arthroplasties at the time of revision surgery and then co-cultured on glass coverslips and dentine slices with UMR 106 rat osteoblast-like cells, both in the presence and absence of 1,25 dihydroxyvitamin D3 [1,25(OH)2D3]. Macrophages isolated from the synovial membrane of patients with osteoarthritis (OA) undergoing hip replacements were similarly studied as a control group.

RESULTS

After 24 hours incubation, most cells isolated from the above periprosthetic tissues strongly expressed macrophage (CD11b, CD14) but not osteoclast markers. However, after 14 days incubation, numerous multinucleated cells showing the phenotypic features of osteoclasts (that is, positive for tartrate resistant acid phosphatase, the vitronectin receptor, and capable of extensive lacunar resorption) formed in co-cultures of arthroplasty derived macrophages and UMR 106 cells, in the presence of 1,25(OH)2D3. The addition of an antibody to macrophage colony stimulating factor (M-CSF) considerably reduced macrophage-osteoclast differentiation and hence the lacunar resorption seen in these co-cultures. In contrast, OA synovial macrophage/UMR 106 co-cultures showed little or no evidence of macrophage-osteoclast differentiation and this was only seen when human M-CSF was added to the co-cultures.

CONCLUSION

This is the first report showing that human macrophages isolated directly from periprosthetic tissues surrounding loosened implants can differentiate into multinucleated cells showing all the functional and cytochemical characteristics of osteoclasts. In contrast with other macrophage populations, exogenous M-CSF is not required for this to occur. In the context of the heavy macrophage response to wear particles in periprosthetic tissues macrophage-osteoclast differentiation may represent an important cellular mechanism whereby osteolysis is effected in aseptic loosening.

Embedding of bone samples in methylmethacrylate: an improved method suitable for bone histomorphometry, histochemistry, and immunohistochemistry

Methylmethacrylate (MMA) embedding of undecalcified bone biopsies is a technique widely used for bone histomorphometry. However, conventional MMA embedding causes almost complete loss of enzyme activity and protein antigenicity in the tissues. Recently, an MMA embedding technique has been reported that preserves enzyme activity and antigenic determinants in bone tissue. We describe here a modification of this embedding method. For our modified MMA embedding process, commercially available methacrylates can be used without purification, and the histologic quality of bone sections is comparable to that of conventionally MMA-embedded bone specimens. The technique reported here can be employed for embedding of larger bone samples and is suitable for histochemical and immunohistological applications as well as for routine bone histomorphometry. By addition of methylbenzoate during infiltration and polymerization of the plastic, the antigenicity of the tissue was improved. As applications of this novel technique, demonstration of alkaline phosphatase and tartrate-resistant acid phosphatase as well as positive labeling of Kupffer cells and osteoclasts with the monoclonal antibody ED1 in sections of liver, tibiae, and vertebrae of 3-month-old rats was demonstrated. The method described here might be useful for the inclusion of histochemical and immunohistological methods into bone histomorphometry.

Biological reaction to debris in relation to joint prostheses

Bone loss induced by the inflammatory response to wear particles is a major cause of long-term failure of total joint replacement. This review describes the cellular reaction occurring in response to these particles and what is currently known about the inflammatory mechanisms contributing to bone resorption.

Biologic effects of cobalt chrome in cell and animal models

The literature on animal and cellular models used to study the response to cobalt chrome alloy implants and wear and corrosion products is reviewed. Animal studies show that in solid form cobalt chrome alloy is relatively well tolerated. Injections of large numbers of particles in a single bolus lead to acute inflammation and necrosis, followed by a chronic inflammatory response. Macrophages are the predominant cell type and may persist in the tissues for years. Long term studies have failed to confirm the induction of tumors. In vitro studies confirm the toxic effects of cobalt chrome alloy corrosion products and wear particles, especially cobalt, and show that intracellular corrosion is an important mechanism for early release of cobalt ions. In vitro studies show that cobalt chrome alloy particles induce the release of inflammatory mediators from macrophages before causing cell death. These mediators have significant effects on osteoblastlike cells, as well as inducing bone resorption. Variations in the cell types, implantation site, and characteristics of the particles used in experimental models make interpretation of the results difficult. Standardized methods to control for size, shape, and number of particles for testing are proposed. It is important that in vitro and in vivo findings not be taken in isolation, but be compared with the results of human studies.

Bone formation and bone resorption in failed total joint arthroplasties: histomorphometric analysis with histochemical and immunohistochemical technique

To elucidate the reactions of bone around aseptically loosened total joint arthroplasties, 24 interface tissues with adjacent bone were obtained in 17 revision operations (11 hips and six knees). The morphology of the bone surface next to the interface membrane was investigated with histochemical and immunohistochemical techniques and then histomorphometrically analysed. One-third of the total bone surface. 32.69 +/- 5.16% (mean +/- SE) (n = 24), showed positive alkaline phosphatase activity. The bone surface in contact with the cells positive for CD11b (a macrophage marker) amounted to 19.33 +/- 5.16% (n = 24). The proportion of the osteoclastic bone resorption estimated by vitronectin receptor expression was 7.67 +/- 1.82% (n = 21). Tissues retrieved from the sites where radiographic evidence of osteolysis was present (n = 12) had a significantly larger extent of the bone surface in contact with CD11b-positive cells than did the tissues from areas without osteolysis (n = 12, p = 0.0067, Mann-Whitney U test), whereas no significant difference was observed in the extent of osteoclastic bone resorption. These data demonstrate that active bone formation, regarded as a repair process, is the most common feature even in revised cases. They also highlight the role played by macrophages, not as cells producing inflammatory mediators that could activate osteoclasts, but as cells primarily responsible for the bone loss in osteolytic lesions.

Extracellular matrix of the synovial intimal cell layer

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