Does milling one-piece titanium dental implants induce osteocyte and osteoclast changes?

One-piece dental implants avoid adverse effects sometimes associated with the traditional implant-abutment interface and may provide a suitable alternative to two-piece implants; however, one-piece implants often need in situ milling, which may exacerbate cell apoptosis from excessive heat at the bone-implant interface and induce secondary crestal bone loss. Twelve implants were placed in the metaphyses of two sheep under general anesthesia. Six implants were milled with a diamond bur while the other six implants remained intact. Animals were euthanized after four days, and bone blocks were harvested. Bone samples were studied without decalcification. Osteocytes were stained with Hoechst 33342 and osteoclasts by the TRAcP reaction. Both cell types, in the cortical and trabecular bone around the implant's cervical region, were counted utilizing morphometric methods. Values were compared to areas at a distance from the cervical region. No difference was observed between milled and unmilled implants, which suggested that the amount of generated heat did not provoke osteocyte loss or induce osteoclastogenesis. Intraoral abutment preparations did not increase cellular apoptosis at the bone-implant interface after four days in the ovine model.

Cobalt, chromium and nickel affect hydroxyapatite crystal growth in vitro.

Metals are widely used in orthopaedics and recent studies have reported that patients with metal implants have a significant increase of metal levels in serum and synovial fluid. Femoral neck fracture occurred in some patients with metal-on-metal implants for unknown reasons. Recently, bone quality has emerged as an important factor of bone strength and few studies have investigated the effects of metal ions on hydroxyapatite properties. In the present study, we investigated the effects of Co(2+), Cr(3+) and Ni(2+) on hydroxyapatite (HA) growth in vitro, using carboxymethylated poly(2-hydroxyethyl methacrylate) (pHEMA) as a biomaterial for calcification. We have demonstrated that metal ions reduced the quantity of mineral formed at the surface of the polymer and decreased the ratio Ca/P by 1.12-, 1.05- and 1.08-fold for Cr(2+), Cr(3+) and Ni(2+) respectively. Furthermore, the size of calcospherites was significantly increased in the metal-doped HA compared to the controls, indicating a possible effect of metal ions on the crystal lattice. Indeed, the presence of metal ions increased the crystal size as well as the crystallinity of HA and reduce the lattice parameter c of the HA framework. The information obtained from this work suggests that the quality of the mineral around metallic implants could be altered. However, further investigation should be conducted to further elucidate the effects of metal incorporation on bone mineral and the functional consequences.

Influence of fluoride, hydrogen peroxide and lactic acid on the corrosion resistance of commercially pure titanium.

Titanium is widely used in dental implantology and orthopaedics due to its excellent corrosion resistance and mechanical properties. However, it has been reported that Ti is sensitive to F(-), H(2)O(2) and lactic acid. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the corrosion resistance of CP-Ti disks after 9 days immersion in different test solutions, based on artificial saliva containing F(-) (0.5% and 2.5%), H(2)O(2) (0.1% and 10%) and/or lactic acid. Because activated macrophages and bacteria can also release locally some of these oxidative compounds, we investigated the role of these cells when plated onto titanium disks. The surface roughness (R(a)) was highly increased when titanium disks were immersed in artificial saliva containing F(-), H(2)O(2) and lactic acid. After 21 days of cell culture, R(a) was significantly increased on disks incubated with activated-J774.2 cells or Streptococcus mitis. AFM appeared to be more sensitive than SEM in evaluating the corrosion of the titanium. Chemical species, either environmental or those released by macrophages and bacteria, can provoke a marked attack of the titanium surface.

The in vivo calcification capacity of a copolymer, based on methacryloyloxyethyl phosphate, does not favor osteoconduction.

Polymers can be interesting alternatives to bone grafts; they must present suitable mechanical and osteoconductive properties. Biomimetic properties may be a key factor for the recognition by bone cells. Methacryloyloxyethyl phosphate (MOEP) was found to enhance hydroxyapatite deposition. The copolymer containing MOEP and 1-vinyl-2-pyrrolidinone (50-50%) binds large amounts of calcium. Particles of the copolymer were used to fill large cranial bone defects in the rat. After a 12-week healing period, the animals were euthanized and the skulls examined by X-ray, histology, and electron microscopy (EM). The high phosphate content of the polymer conferred a marked calcium-binding capacity, and the particles were heavily calcified. They were embedded in a light fibrous stroma containing numerous capillaries and multinucleated giant cells. The osteoconductive properties were poor: only few trabeculae developed centripetally from the margins of the defects. There was no bone bonding and no osteoblast on the surface of the calcified material. Backscattered EM revealed that the degree of calcification was homogeneous in all particles. Calcium-phosphorus calcospherites were never observed. The material appeared to trap calcium but to impair nucleation because only small hydroxyapatite tablets were occasionally observed. Polyphosphated materials do not represent a suitable source of potentially usable bone substitutes.

Biodegradability of poly (2-hydroxyethyl methacrylate) in the presence of the J774.2 macrophage cell line.

The degradation of cross-linked and linear poly(2-hydroxyethyl methacrylate) (pHEMA), was examined in vitro with J774.2 cells. pHEMA microbeads were prepared with both types of polymers. Only cells in contact with the microbeads increased their production of lysosomal enzymes (TRAcP and ANAE) and released large amounts of reactive oxygen species with both types of pHEMA microbeads. Electron microscopy showed that macrophages were able to erode the surface of linear pHEMA but unable to erode the surface of the cross-linked polymer. Cells appeared wrapped by the linear pHEMA surface, but those cultured on the cross-linked polymer were only laying at the surface. After cell culture, the surface roughness of pHEMA slices was observed by atomic force microscopy (AFM). There was a significant increase in roughness (R(a)) of the surface of linear pHEMA slices cultured with J774.2 cells whereas no difference in R(a) between the surface of cross-linked pHEMA slices could be measured. AFM image of the hydrated materials were done: the surface of linear pHEMA swelled considerably in saline whereas the hydrated cross-linked polymer did not differ from the air-dried appearance. In conclusion, linear pHEMA swells in biological fluids, activates macrophages in close contact with the polymer and can be progressively eroded.

Synthesis of methacryloyloxyethyl phosphate copolymers and in vitro calcification capacity.

Methacryloyloxyethyl phosphate is a methacrylic monomer used to modify different substrates by copolymerisation, in order to enhance hydroxyapatite deposition onto their surfaces. We report the synthesis of two copolymers series using increasing concentrations of methacryloyloxyethyl phosphate with (diethylamino) ethyl methacrylate and 1-vinyl-2-pyrrolidinone. Reactivity ratios were evaluated for the two copolymer systems. The influence of phosphate content and distribution on the capacity to form a calcium-rich layer was evaluated after immersion for 15 days in a synthetic body fluid. Corresponding homopolymers were synthesised as controls. Calcium-phosphorus globules were developed only on samples containing (diethylamino) ethyl methacrylate, and presenting a low density of phosphate groups. The amounts of calcium increased when higher concentrations of methacryloyloxyethyl phosphate were used. The use of 1-vinyl-2-pyrrolidinone was associated with greater calcium amounts, (compared to (diethylamino) ethyl methacrylate). The amine groups may favour the attraction of phosphorus, thus creating another way for the nucleation of calcium/phosphate crystals.

Non-connected versus interconnected macroporosity in poly(2-hydroxyethyl methacrylate) polymers. An X-ray microtomographic and histomorphometric study.

Poly(2-hydroxyethyl methacrylate) (pHEMA) has potentially broad biomedical applications: it is biocompatible and has a hardness comparable to bone when bulk polymerized. Porous biomaterials allow bone integration to be increased, especially when the pores are interconnected. In this study, three types of porogens (sugar fibers, sucrose crystals, and urea beads) have been used to prepare macroporous pHEMA. The pore volume and interconnectivity parameters of the porosity were measured by X-ray microtomography and image analysis. Sucrose crystals, having a high volumetric mass, gave large pores that were located on the block sides. Urea beads and sugar fibers provided pores with the same star volume (2.65 +/- 0.46 mm3 and 2.48 +/- 0.52 mm3, respectively) but which differed in interconnectivity index, fractal dimension, and Euler-Poincarés number. Urea beads caused non-connected porosity, while sugar fibers created a dense labyrinth within the polymer. Interconnectivity was proved by carrying out surface treatment of the pHEMA (carboxymethylation in water), followed by von Kossà staining, which detected the carboxylic groups. Carboxymethylated surfaces were observed on the sides of the blocks and on the opened or interconnected pores. The disconnected pores were unstained. Macroporous polymers can be prepared with water-soluble porogens. X-ray microtomography appears a useful tool to measure porosity and interconnectedness.

Effects of negatively charged groups (carboxymethyl) on the calcification of poly(2-hydroxyethyl methacrylate).

Poly(2-hydroxyethyl methacrylate) (pHEMA) has potentially wide biomedical applications: it is biocompatible, allows immobilization of cells or bioactive molecules and has a hardness comparable to bone. We previously reported that immobilization of alkaline phosphatase (AlkP) in pHEMA can initiate mineralization in a manner that mimics the calcification of cartilage and woven bone. Because numerous proteins known to initiate mineralization possess acidic species, we have modified the neutral electrical surface of pHEMA by carboxymethylation (CM). We have studied the effects of these negative groups on the calcification process in vitro. Calibrated pellets of pHEMA were prepared and carboxymethylated by soaking with 0.5 M bromoacetic acid in 2 M NaOH. Pellets of pHEMA, pHEMA-AlkP and pHEMA-CM were incubated during 5, 10 and 15 days in two types of body fluid: normal (1X) and 1.5X concentration of ions. Nodules of hydroxyapatite developed on pHEMA-AlkP and pHEMA-CM but not on pHEMA. Hydroxyapatite crystals were dissolved in HCl allowing calcium to be dosed. CM significantly increased the amount of deposited Ca by 1.8 folds in the 1X fluid and 15.8 folds in the 1.5X fluid. The presence of AlkP considerably increased the amount of deposited Ca: 25.9 folds in 1X and 23.3 in 1.5X. ROS 17/2.8 osteoblast-like cells were seeded on the materials and examined by confocal microscopy after phalloidin staining. Cells grown on pHEMA alone appeared round, while cells grown on the crystals deposited on the pHEMA-CM or pHEMA-AlkP were flattened. The presence of AlkP favours the mineralization process more than the existence of surface negative groups on the polymer. Cells preferentially adhere to the polymer when hydroxyapatite crystals were developed.

Adherence of osteoblast-like cells on calcospherites developed on a biomaterial combining poly(2-hydroxyethyl) methacrylate and alkaline phosphatase.

The polymer poly(2-hydroxyethyl) methacrylate (pHEMA) can copolymerize with alkaline phosphatase (AlkP) to form a hybrid material. The enzyme retains its biological activity and forms hydroxyapatite nodules (calcospherites) when polymer pellets are incubated with a synthetic body fluid. Osteoblast-like cells (ROS 17/2.8) were seeded on pellets of pHEMA and pHEMA-AlkP on which calcospherites were grown. They were examined by scanning electron microscopy (SEM) with backscattered electron imaging. Cell surface and shape were measured by image analysis combining the SEM images. Cells grown on pHEMA-AlkP had an increased surface area (449 +/- 216 microm(2) vs. 204 +/- 80 microm(2)). The number of filopodia anchoring the cells on the free polymer surface was reduced on pHEMA-AlkP, but numerous thick pseudopodia permitted a direct anchorage on the calcospherites. Pseudopodia were wider and longer than the filopodia. The backscattered images revealed that each cell was seated on 7.1 +/- 1.5 calcospherites and partially covered 10.3 +/- 1.9 others. Antifibronectin and anti-bone sialoprotein antibodies were used to investigate cell attachment. With confocal microscopy, both molecules were located at the interface between the cells and the mineral, inside the cells, and as free molecules on the calcospherites. Immunogold labeling was done with the same antibodies and examined with transmission electron microscopy (TEM). Adsorption of fibronectin and bone sialoprotein was noticeable at the cell/calcospherite interface and on the surface of the hydroxyapatite crystals. Immunogold studies revealed adhesion proteins (bone sialoprotein, fibronectin) to be present at the surface of crystals and at focal points of cell contact.

[In vitro study of the effect of bisphosphonates on mineralization induced by a composite material: poly 2(hydroxyethyl) methacrylate coupled with alkaline phosphatase]. / Etude in vitro de l'influence des bisphosphonates sur la minéralisation induite par un matériau composite: le poly 2(hydroxyéthyl) méthacrylate couplé à la phosphatase alcaline.

We have immobilized the mineralizing agent alkaline phosphatase (AlkP) in a hydrophilic polymer (poly 2(hydroxyéthyl) methacrylate) (pHEMA) in a copolymerization technique. Histochemical study on polymer sections revealed that AlkP has retained its biological activity. The image analysis of sections using a tessellation method showed a lognormal distribution of the area of the tiles surrounding AlkP particles thus confirming a homogeneous distribution of the enzyme in the polymer. Pellets of pHEMA-AlkP were incubated with a synthetic body fluid containing organic phosphates (beta-glycerophosphate). Mineral deposits with a rounded shape (calcospherites) were obtained in about 17 days. We have investigated the effects of three bisphosphonates (etidronate, alendronate and tiludronate) on this system. Bisphosphonates at a concentration of 10(-2) M totally inhibited AlkP in solution at a concentration of 10(-4) mg/ml. Inhibition has been reported being due to the chelation of a metal cofactor (Zn2+). Etidronate and alendronate appeared to inhibit the calcospherite deposition onto the pHEMA-AlkP material in a similar way. Both bisphosphonates possess three sites for mineral complexion. On the other hand, tiludronate having only two sites was associated with a reduced inhibitory effect on mineralization. When used in microgravity conditions, mineralization was impaired with etidronate and larger crystals were obtained with tiludronate. However, these effects were obtained in non-physiological conditions (a 20 degrees C temperature was used during the STS80 flight of the space shuttle). The pHEMA-AlkP material provides an interesting method to study the effects of pharmacological compounds and environmental factors on the bone and cartilage mineralization process.

Poly(2-hydroxy ethyl methacrylate)-alkaline phosphatase: a composite biomaterial allowing in vitro studies of bisphosphonates on the mineralization process.

We have immobilized the mineralizing agent alkaline phosphatase (AlkP) in a hydrophilic polymer: poly(2-hydroxy ethyl methacrylate) - (pHEMA) - in a copolymerization technique. Histochemical study on polymer sections revealed that AlkP has retained its enzymic activity. The image analysis of sections using a tessellation method showed a lognormal distribution of the area of the tiles surrounding AlkP particles, thus confirming a homogeneous distribution of the enzyme in the polymer. Pellets of pHEMA-AlkP were incubated with a synthetic body fluid containing organic phosphates (beta-glycerophosphate). Mineral deposits with a rounded shape (calcospherites) were obtained in about 17 days. We have investigated the effects of three bisphosphonic pharmacological compounds (etidronate, alendronate and tiludronate) on this system which mimics the mineralization process of cartilage and woven bone. Bisphosphonates at a concentration of 10(-2) M totally inhibited AlkP in solution at a concentration of 10(-4) mg/ml. Inhibition has been reported being due to the chelation of a metal cofactor (Zn2+). Etidronate and alendronate appeared to similarly inhibit the calcospherite deposition onto the pHEMA-AlkP material. Both bisphosphonates possess three sites for the mineral complexion by Ca chemisorbtion. On the other hand, tiludronate having only two sites, was associated with a reduced inhibitory effect on mineralization but larger crystals were obtained. The pHEMA-AlkP material contains an immobilized enzyme in a hydrogel and mimics the physiological conditions of matrix vesicles entrapped within the cartilage (or bone) matrix. It provides an interesting method to study the effects of pharmacological compounds on the mineralization process in bone and cartilage in a non cellular and protein-free model.

Development of 5-iodo-2'-deoxyuridine milling process to reduce initial burst release from PLGA microparticles.

The aim of this study was to prepare 5-iodo-2'-deoxyuridine (IdUrd) loaded poly(d,l-lactide-co-glycolide) (PLGA) microspheres with a reduced initial burst in the in vitro release profile, by modifying the drug grinding conditions. IdUrd particle size reduction has been performed using spray-drying or ball milling. Spray-drying significantly reduced drug particle size with a change of the initial crystalline form to an amorphous one and led to a high initial burst. Conversely, ball milling did not affect the initial IdUrd crystallinity. Therefore, the grinding process was optimized to emphasize the initial burst reduction. A first step allowed us to set qualitative parameters such as ball number (7) and cooling with liquid nitrogen to obtain a mean size reduction and a narrow distribution. In a second step, three parameters including milling speed, drug amount and time were studied by a response surface analysis. The interrelationship between drug amount and milling speed was the most significant factor. To reduce particle size it should be necessary to use a moderate speed associated with a sufficient drug amount (400-500 mg). IdUrd release from microparticles prepared by the o/w emulsion/extraction solvent evaporation process with the lowest crystalline particle size (15.3 microns) was studied. Burst effect could be reduced significantly. Concerning the first phase of drug release, the burst was 8.7% for 15.3 microns compared to 19% for 19.5 microns milled drug particles.

Increased nucleolar organizer regions in osteoclast nuclei of Paget's bone disease.

The etiology of Paget's disease of bone is still unknown but several studies have reported a viral origin. At the electron microscopic level, characteristic nuclear and cytoplasmic inclusions have been found and mimic paramyxoviral nucleocapsids in osteoclasts (Oc). Sarcomatous degeneration is observed in 2% of pagetic patients. Nuclear organizer regions are parts of the nucleolus involved in the synthesis of ribosomes, and they contain nonhistone proteins that can be silver stained (AgNORs) on the interphasic nuclei. AgNOR number is known to correlate with the proliferative activity of the cell populations, whether normal or malignant. Cancer cells have an increased demand for (robosomal) rRNA and correlations have been found between AgNORs and proliferative antigens. We have adapted the AgNOR staining method to undecalcified bone biopsies at the light and TEM levels. Bone sections from 10 pagetic patients (without a previous bisphosphonate treatment) were stained for AgNORs. 10 patients having metabolic bone diseases associated with an increased Oc number (i.e., primary and secondary hyperparathyroidism) were used as controls. AgNORs appeared as black dots within the nucleoli of Oc nuclei and were easily numbered. A maximum of two or three dots could be seen in Oc nuclei from control subjects. In pagetic Oc, AgNOR number was greatly increased (6.80 +/- 2.57 dots vs. 2.12 +/- 1.07 in controls). TEM study also showed AgNOR in the nucleoli of pagetic patients' Oc. The viral inclusions within the nuclei appeared faintly stained and could not be confused with AgNORs. The large number of AgNORs in the nuclei of pagetic Oc reflects the need for a greater abundance of ribosomes. With the pagetic Oc being highly active, the cytoplasmic synthesis of proteins is maximized (probably hydrolases involved in the matrix breakdown). An increase in AgNORs does not reflect the proliferative activity of the cell because Oc are made by the fusion of precursors. It is postulated that: (a) other mRNAs (of viral/oncogene origin) could be actively transcribed in pagetic patients and require more numerous ribosomes; or (b) a viral genome/oncogene promotes alteration of the nuclear/nucleolar mechanism.

Expression and identification of a laminin-binding protein in Aspergillus fumigatus conidia.

Adhesion of Aspergillus fumigatus, the causative agent of human aspergillosis, to the extracellular matrix protein laminin has been previously demonstrated. This study investigated the expression of laminin receptors during swelling of conidia, a step leading to germination and subsequent colonization of tissues. Scanning electron microscopy showed that the laminin binding sites were distributed over the external rodlet layer of resting conidia. During swelling, the characteristic rodlet layer progressively disintegrated and conidia surrounded by a smooth cell wall layer appeared. Flow cytometry using fluorescein isothiocyanate-conjugated laminin demonstrated that expression of laminin receptors at the surface of conidia was swelling dependent. Resting conidia expressed high levels of laminin receptors on their surface. A gradual decrease of laminin binding was then observed as swelling occurred, reaching a minimum for 4-h-swollen conidia. This correlated with a loss of adherence of swollen conidia to laminin immobilized on microtiter plates. Trypsin pretreatment of conidia reduced laminin binding. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ligand blotting with laminin identified in a cell wall extract a major 72-kDa cell wall glycoprotein which binds laminin. Thus, one of the initial events in the host colonization may be the recognition of basement membrane laminin by this 72-kDa cell wall surface component.

1,25-Dihydroxyvitamin D3 induces programmed cell death in a rat glioma cell line.

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3), a seco-steroid hormone with potential antitumoral activities, has been recently reported to exert cytotoxic effects on C6 glioma cells. However, the molecular mechanisms which trigger this cell death remain unknown. We show here that this 1,25(OH)2D3-induced cell death is dependent upon protein synthesis and is accompanied by the expression of c-myc, p53, and gadd45 genes. Two other genes, coding for interleukin-6 and vaso-endothelial growth factor, are also upregulated after addition of 1,25(OH)2D3. This programmed cell death can be suppressed when cells are treated with forskolin, a drug which increases intracellular cAMP concentration, or with genistein, an inhibitor of tyrosine protein kinases. However, in spite of the demonstration of fragmented DNA in 1,25(OH)2D3-treated cells, the C6.9 cells used in this study do not show the classical morphological features of apoptosis. These results provide the first evidence for the existence of a programmed cell death triggered by 1,25(OH)2D3 in glioma cells and may provide a basis for the development of new therapeutic strategies. In addition, these data also suggest that the treatment of C6.9 cells with 1,25(OH)2D3 may be a useful model to study the molecular mechanisms involved in the programmed cell death of a cell of glial origin.

[Transmission electron microscopy in the structural study of superparamagnetic contrast agents for MRI]. / Apport de la M.E.T. dans l'étude structurale des agents de contraste superparamagnétiques pour l'IRM.

Iron oxide nanoparticles with different crystal sizes and uniform dextran coating were synthesized and analyzed by T.E.M.. The iron oxide core dimension and homogeneity of the preparation were correlated to magnetic properties. The increasing Fe/Dextran ratio used for the synthesis was well correlated with the mean diameter and the magnetic susceptibility. The comparison of the crystal size with the particle size determined by nanosizer in solution suggest that particles consist in nanoaggregates of many crystal subunits.

[Electron microscopic study of a macroporous calcium phosphate ceramic implanted in an osseous site]. / Etude en microscopie électronique d'une céramique phosphocalcique macroporeuse implantée en site osseux.

Cellular and tissular responses to intraosseous graft of a macroporous calcium phosphate ceramic was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Twelve specimens were implanted in 6 rabbits (tibiae), taken at day 14 after implantation and processed either for TEM (6 samples) or SEM (6 samples). As early as day 14 after implantation osteogenesis so that resorption of the newly formed bone and of the biomaterial, were observed at the surface of the ceramic, inside the macropores. Osteoblasts were clearly visible and well differentiated with abundant rough endoplasmic reticulum and large Golgi zone. The resorption processes were associated with 2 types of multinucleated cells. Based on ultrastructural observations (cellular characteristics and measurement of the microporosity) it appears that incompletely differentiated osteoclast was the major cell responsible of the biodegradation of the ceramic. These results suggest that the cellular events occurring at the surface of a macroporous calcium phosphate ceramic are similar to that observed in physiological bone remodelings.

Osteoclastic resorption of Ca-P biomaterials implanted in rabbit bone.

The nature of the multinucleated cells involved in the resorption processes occurring inside macroporous calcium-phosphate biomaterials grafted into rabbit bone was studied using light microscopy, histomorphometric analysis, enzymatic detection of tartrate-resistant acid phosphatase (TRAP) activity, scanning, and electron microscopy. Samples were taken at days 7, 14, and 21 after implantation. As early as day 7, osteogenesis and resorption were observed at the surface of the biomaterials, inside the macropores. Resorption of both newly formed bone and calcium-phosphate biomaterials was associated with two types of multinucleated cells. Giant multinucleated cells were found only at the surface of the biomaterials; they showed a large number of nuclei, were TRAP negative, developed no ruffled border, and contained numerous vacuoles with large accumulation of mineral crystals from the biomaterials. Osteoclasts exhibited TRAP positivity and well-defined ruffled border. They were observed at the surface of both newly formed bone and biomaterials, around the implant, and inside the macropores. In contract with the biomaterials, infoldings of their ruffled border were observed between the mineral crystals, deeply inside the microporosity. The microporosity of the biomaterials (i.e., the noncrystalline spaces inside the biomaterials) increased underneath this type of cell as compared with underneath giant cells or to the depth of the biomaterials. These observations demonstrate that macroporous calcium-phosphate biomaterials implanted in bone elicit osteogenesis and the recruitment of a double multinucleated cell population having resorbing activity: giant multinucleated cells that resorb biomaterials and osteoclasts that resorb newly formed bone and biomaterials.

Paramyxovirus antigens in osteoclasts from Paget's bone tissue detected by monoclonal antibodies.

The fluorescent antibody technique using both monoclonal and specific polyclonal virus antibodies was applied to investigate the nature of the inclusions seen in the abnormal osteoclasts associated with Paget's bone disease. The results show that antigens of measles virus, simian virus 5 (SV5) and human parainfluenza virus type 3 (PF3) could be detected in the osteoclasts but not in control bone cells. Measles and SV5 nucleoprotein (NP) and haemagglutinin-neuraminidase (HN) antigens were apparently present in all the cases of Paget's disease examined, whereas PF3 NP and HN antigens were present only in some of the cases. These investigations suggest that paramyxoviruses may play a role in the aetiology of the bone disease.