Functional and biochemical studies of multinucleated giant cells derived from the culture of human monocytes

Factors influencing multinucleated giant cell formation in vitro

Macrophages fuse together to form multinucleated giant cells (MGC) in granulomas associated with various pathological conditions. Improved in vitro methods are required to better enable investigations of MGC biology and potential contribution to disease. There is a need for standardization of MGC quantification, purification of MGC populations, and characterization of how cell culture variables influence MGC formation. This study examined solutions to address these needs while providing context with other current and alternative methods. Primary mouse bone marrow-derived macrophages were treated with interleukin-4, a cytokine known to induce fusion into MGC. This model was used to systematically assess the influence of cell stimulant timing, cell seeding density, colony stimulating factors, and culture vessel type. Results indicated that MGC formation is greatly impacted by alterations in certain culture variables. An assessment of previously published research showed that these culture conditions varied widely between different laboratories, which may explain inconsistencies in the literature. A particularly novel and unexpected observation was that MGC formation appears to be greatly increased by silicone, which is a component of a chamber slide system commonly used for MGC studies. The most successful quantification method was fluorescent staining with semi-automated morphological evaluation. The most successful enrichment method was microfiltration. Overall, this study takes steps toward standardizing in vitro methods, enhancing replicability, and guiding investigators attempting to culture, quantify, and enrich MGC.

The Formation and Function of Granulomas

Granulomas are organized aggregates of macrophages, often with characteristic morphological changes, and other immune cells. These evolutionarily ancient structures form in response to persistent particulate stimuli-infectious or noninfectious-that individual macrophages cannot eradicate. Granulomas evolved as protective responses to destroy or sequester particles but are frequently pathological in the context of foreign bodies, infections, and inflammatory diseases. We summarize recent findings that suggest that the granulomatous response unfolds in a stepwise program characterized by a series of macrophage activations and transformations that in turn recruit additional cells and produce structural changes. We explore why different granulomas vary and the reasons that granulomas are protective and pathogenic. Understanding the mechanisms and role of granuloma formation may uncover new therapies for the multitude of granulomatous diseases that constitute serious medical problems while enhancing the protective function of granulomas in infections.

A Role for CD154, the CD40 Ligand, in Granulomatous Inflammation

Granulomatous inflammation is a distinctive form of chronic inflammation in which predominant cells include macrophages, epithelioid cells, and multinucleated giant cells. Mechanisms regulating granulomatous inflammation remain ill-understood. CD154, the ligand of CD40, is a key mediator of inflammation. CD154 confers a proinflammatory phenotype to macrophages and controls several macrophagic functions. Here, we studied the contribution of CD154 in a mouse model of toxic liver injury with carbon tetrachloride and a model of absorbable suture graft. In both models, granulomas are triggered in response to endogenous persistent liver calcified necrotic lesions or by grafted sutures. CD154-deficient mice showed delayed clearance of carbon tetrachloride-induced liver calcified necrotic lesions and impaired progression of suture-induced granuloma. In vitro, CD154 stimulated phagocytosis of opsonized erythrocytes by macrophages, suggesting a potential mechanism for the altered granulomatous inflammation in CD154KO mice. These results suggest that CD154 may contribute to the natural history of granulomatous inflammation.

Multinucleated Giant Cells Are Specialized for Complement-Mediated Phagocytosis and Large Target Destruction

Multinucleated giant cells (MGCs) form by fusion of macrophages and are presumed to contribute to the removal of debris from tissues. In a systematic in vitro analysis, we show that IL-4-induced MGCs phagocytosed large and complement-opsonized materials more effectively than their unfused M2 macrophage precursors. MGC expression of complement receptor 4 (CR4) was increased, but it functioned primarily as an adhesion integrin. In contrast, although expression of CR3 was not increased, it became functionally activated during fusion and was located on the extensive membrane ruffles created by excess plasma membrane arising from macrophage fusion. The combination of increased membrane area and activated CR3 specifically equips MGCs to engulf large complement-coated targets. Moreover, we demonstrate these features in vivo in the recently described complement-dependent therapeutic elimination of systemic amyloid deposits by MGCs. MGCs are evidently more than the sum of their macrophage parts.

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MGCs are specialized for phagocytosis of large and complement-opsonized particles

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MGCs show extensive membrane ruffles containing pre-activated complement receptor 3

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Membrane ruffles provide excess membrane for ingestion of large materials

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MGCs eliminate systemic amyloid deposits after immunotherapeutic targeting

Pathophysiologie der Leberkrankheiten

In der sinusoidalen Membran beginnt die Gallebildung. Rezeptoren und Transporter erleichtern die Aufnahme und den Eintritt von Gallensäuren, Bilirubin, Fettsäuren und anderen Gallekomponenten in die Leberzelle. Diese enthält Rezeptoren für Glykoproteine, Asialoglykoprotein, Immunglobulin A (Ig A), vasoaktives intestinales Peptid (VIP), Insulin, Glukagon und „epidermal growth factor“ (EGF). Ein primär aktiver Transport erfolgt durch die Na+-K+-ATPase, die einen Ionengradienten an der Zellmembran aufbaut und innerhalb der Zelle ein negatives elektrisches Potenzial erzeugt (wodurch die Diffusion erleichtert wird). Dieser Ionengradient ermöglicht die Arbeit anderer Carrier gegen das Konzentrationsgefälle, z. B. von NTCP (Natrium-Taurocholsäure-Kotransport-Polypeptid), das auch für zahlreiche Medikamente, Östrogene und zyklische Oligopeptide spezifisch ist. Transporter für organische Anionen (OATP1) und anorganische Ionen wurden ebenfalls nachgewiesen.

Biocompatibility issues with modern implants in bone - a review for clinical orthopedics

Skeletal defects may result from traumatic, infectious, congenital or neoplastic processes and are considered to be a challenge for reconstructive surgery. Although the autologous bone graft is still the "gold standard", there is continuing demand for bone substitutes because of associated disadvantages, such as limited supply and potential donor side morbidity [1]. This is not only true for indications in orthopedic and craniomaxillofacial surgeries, but also in repairing endodontic defects and in dental implantology.Before clinical use all new bone substitute materials have to be validated for their osseoconductive and - depending on the composition of the material also -inductive ability, as well as for their long-term biocompatibility in bone. Serving this purpose various bone healing models to test osteocompatibility and inflammatory potential of a novel material on one hand and, on the other hand, non-healing osseous defects to assess the healing potential of a bone substitute material have been developed. Sometimes the use of more than one implantation site can be helpful to provide a wide range of information about a new material [2].Important markers for biocompatibility and inflammatory responses are the cell types appearing after the implantation of foreign material. There, especially the role of foreign body giant cells (FBGC) is discussed controversial in the pertinent literature, such that it is not clear whether their presence marks an incompatibility of the biomaterial, or whether it belongs to a normal degradation behavior of modern, resorbable biomaterials.This publication is highlighting the different views currently existing about the function of FBGC that appear in response to biomaterials at the implantation sites. A short overview of the general classes of biomaterials, where FBGC may appear as cellular response, is added for clarity, but may not be complete.

Suppressive Effect of Iron on Concanavalin A‐Induced Multinucleated Giant Cell Formation by Human Monocytes

Immune dysfunction in patients with iron overload has been reported. Iron disturbed CD2 expression on T-cells, cell-mediated immunity by Th1 cells and monocyte functions including phagocytosis and natural killer activity. In the present study, we examined the effects of iron and desferrioxamine (DFX, an iron chelator) on generation of multinucleated giant cells (MGC) by human monocytes in vitro. Human monocytes were isolated from venous blood and cultured with concanavalin A (Con A) stimulation with additives, ferric citrate (Fe-citrate) or sodium citrate (Na-citrate) or DFX for 4 days. The cells were fixed and subjected to Wright staining. MGC formation was observed under light microscopy. Con A induced MGC formation in a dose-dependent manner, and reached a plateau after 3 days of incubation. MGC formation was suppressed when Con A-stimulated monocytes were cultured with the co-addition of Fe-citrate but not Na-citrate only in the early phase of culture (less than 24 hours). DFX also suppressed MGC formation in a dose-dependent manner. Using flow cytometry analysis, the co-addition of Fe-citrate significantly suppressed CD18 (beta2 integrin) and CD54 (ICAM-I) but not CD11a (alpha integrin) expression on Con A-stimulated monocytes. Iron supressed the generation of MGC by human monocytes in vitro. These observations suggested that iron might affect MGC generation by down-regulation of adhesion molecule expression on monocytes.

Formation of short-lived multinucleated giant cells (MGCS) from cultured gilthead seabream macrophages

Monocytes/macrophages obtained from the head kidney and peritoneal cavity of gilthead seabream (Sparus aurata) were cultured using plates from three different manufacturers, and were maintained under different conditions. The effects on the morphology and fusion of monocytes/macrophages of initial cell loading, removal of non-adherent cells at different times after plating, and addition of serum and antibiotics were evaluated by light microscopy, and transmission (TEM) and scanning (SEM) electron microscopy. Despite variations in adherence, the behaviour and the morphological changes in kidney monocytes/macrophages were similar in all three types of plates. When foetal calf serum (FCS) was added to the incubation medium, most of the cells resembling monocytes/macrophages were connected by cytoplasmic extensions that formed bridges after 24 hr in culture. After 30 hr, the monocytes/macrophages started to fuse, forming multinucleated giant cells (MGCs) which gradually increased in size until the culture was 4-5 days old. After 5 days the MGCs started to die, and after a week most had disappeared from the cultures. Cells incubated with medium without serum showed changes similar to those fed with FCS, but some cells survived for 3 weeks. The addition of fish serum to the medium appeared to accelerate all processes: the monocytes/macrophages and MGCs died after 3 days in culture. Antibiotics had no apparent effect on the cultures. Removal of non-adherent cells at different times after plating did not appear to affect cell fusion. Coating the wells with extracellular matrix proteins reduced adherence but did not inhibit cell fusion. Curiously, not all macrophages fused with MGCs, and, unlike MGCs, these macrophages phagocytosed sheep red blood cells (SRBCs). Peritoneal macrophages also fused and formed MGCs in culture, similarly to kidney cells.

Human macrophages synthesize type VIII collagen in vitro and in the atherosclerotic plaque

Type VIII collagen is a short-chain collagen that is present in increased amounts in atherosclerotic lesions. Although the physiological function of this matrix protein is unclear, recent data suggest an important role in tissue remodeling. Type VIII collagen in the atherosclerotic lesion is mainly derived from smooth muscle cells. We now show that macrophages in the atherosclerotic vessel wall and monocytes in adjacent mural thrombi also express type VIII collagen. We demonstrated this using a novel combined fluorescence technique that simultaneously stains, within the same tissue section, specific RNAs by in situ hybridization and proteins by indirect immunofluorescence. In culture, human monocyte/macrophages expressed type VIII collagen at all time points from 1 h to 3 wk after isolation. Western blotting and immunoprecipitation also revealed secretion of type VIII collagen into the medium of 14-day-old macrophages. Because this is the first report of secretion of a collagen by macrophages, we tested the effect of lipopolysaccharide (LPS) and interferon gamma, substances that stimulate macrophages to secrete lytic enzymes, on macrophage expression of type VIII collagen. LPS and interferon gamma decreased expression of type VIII collagen. By contrast, secretion of matrix metalloproteinase 1 (MMP 1) was increased, indicating a switch from a collagen-producing to a degradative phenotype. Double in situ hybridization studies of expression of type VIII collagen and MMP 1 in human coronary arteries showed that in regions important for plaque stability, the ratio of MMP 1 RNA to macrophage type VIII collagen RNA varies widely, indicating that the transition from one phenotype to the other that we observed in vitro may also occur in vivo.

The biological relevance of polykaryons in the immune response

Peripheral blood monocyte-derived multinucleated giant cells are a well-known feature of chronic inflammatory conditions. Similarly, virus-induced syncytia derived from CD4+ cells are considered to be typical of human immunodeficiency virus infection under culture conditions. Here, Stefano Fais and colleagues summarize recent experimental results comparing the mechanisms underlying the formation and fate of these two different polykaryons, discussing their putative role in the immune response.

Formation of Multinucleated Giant Cells In Vitro Is Dependent on the Stage of Monocyte to Macrophage Maturation

Multinucleated giant cells (MGC) are a common feature of granulomas that develop during various inflammatory reactions. MGC originate from fusion of monocytes or macrophages, but the exact mechanism of their generation is still unclear. In the present study, we investigated the influence of monocyte to macrophage maturation on the ability of human monocytes/macrophages to fuse with each other. MGC were generated in vitro by stimulation of human peripheral blood monocytes with cytokine containing supernatants. With freshly isolated monocytes, fusion rates of up to 90% were obtained. When monocyte to macrophage maturation was induced by culturing the cells in human serum, fusion rates gradually decreased with advancing time of the preceding culture (corresponding to the stage of differentiation) and almost no MGC formation could be obtained with 8-day-old macrophages. In contrast, fusion rates did not decrease when monocytes had been cultured under serum free conditions before stimulation. When freshly isolated monocytes were added to 1-week cultured macrophages, which had been membrane-labeled with a fluorochrome, fusion between the two populations could be induced. Because the ability for intracellular killing of certain pathogens is reduced in macrophages, fusion with monocytes (newly arriving at the site of inflammation) may represent an attempt to restore this capacity.

Interleukin-4-induced macrophage fusion is prevented by inhibitors of mannose receptor activity

A potential role for the macrophage mannose receptor in human monocyte-derived macrophage fusion was explored by testing the effects of previously described inhibitors of its activity on the formation of interleukin-4-induced foreign body giant cells in vitro Giant cell formation was prevented or reduced in the presence of alpha-man-nan and synthetic neoglycoprotein conjugates according to the following pattern of relative inhibition: mannose-bovine serum albumin (BSA) > N-acetylgucosamine-BSA congruent to glucose-BSA. Laminarin (beta-glucan) or galactose-BSA were not inhibitory. Swainsonine and castanospermine, inhibitors of glycoprotein processing that interfere with the arrival of newly synthesized mannose receptors at the cell surface, also attenuated macrophage fusion and the formation of giant cells, whereas another glycosidase inhibitor, deoxymannojirimycin, was without effect. Mannose receptors were confirmed to be specifically up-regulated by interleukin-4 in this culture system and also demonstrated to be present and concentrated at macrophage fusion interfaces. These data suggest that the macrophage mannose receptor may be an essential participant in the mechanism of interleukin-4-induced macrophage fusion and implicate a novel function for this endocytic/phagocytic receptor in mediating foreign body giant cell formation at sites of chronic inflammation.

Monocyte aggregation and multinucleated giant-cell formation in vitro in Crohn's disease. The effect of cell adhesion molecules

BACKGROUND

Multinucleated giant-cell (MGC) formation is a common histopathologic feature of various granulomatous diseases, including Crohn's disease (CD).

METHODS

We have investigated monocyte aggregation and subsequent MGC formation by in vitro culturing peripheral monocytes from 25 CD patients, 15 ulcerative colitis (UC) patients, and 10 healthy controls. The effect of cell adhesion molecules on the monocyte aggregation and MGC formation in CD patients was investigated by using anti-beta 2 integrin and anti-ICAM-1 antibodies.

RESULTS

The monocyte aggregation and MGC formation were significantly higher in CD than those seen in UC and controls (p < 0.05). In CD, antibody to beta 2 integrin could inhibit not only the monocyte aggregation but also the subsequent MGC formation. In contrast, the antibody to ICAM-1 could inhibit the monocyte aggregation; however, it could not inhibit the MGC formation.

CONCLUSIONS

Monocyte aggregation and MGC formation are increased in CD. beta 2 Integrin may play an important role in the monocyte aggregation and MGC formation of CD patients.

Receptor-mediated gene transfer into macrophages

Gene transfer systems targeting various receptors have been developed to introduce functional genes into cells in culture and into intact animals. A synthetic molecular conjugate, consisting of mannosylated polylysine that exploits endocytosis via the macrophage mannose receptor, was constructed and complexed to expression plasmids containing either the Photinus pyralis luciferase or Escherichia coli beta-galactosidase (lacZ) reporter genes. The DNA complexes were used to transfect murine macrophages isolated from peritoneal exudates in vitro. Luciferase and beta-galactosidase activity was found in transfected cells in culture, whereas complexes consisting of an irrelevant plasmid bound to mannosylated polylysine or the expression plasmid bound to galactosylated polylysine resulted in no detectable transgene expression. Gene transfer was inhibited by the addition of excess mannosylated bovine serum albumin to the culture medium before transfection. Reporter genes were also transferred into macrophages residing in the spleen and liver of adult animals using this system. Luciferase activity was maximal at 4 days after transfection and decreased to lower levels by 16 days. Transgene expression conformed to the distribution of cells that had nonspecific esterase, a cytochemical marker for macrophages. Thus, this system can be used to introduce functional genes into macrophages and may be an approach to the treatment of storage diseases that affect the reticuloendothelial system.

Theoretical analysis of in vivo macrophage adhesion and foreign body giant cell formation on strained poly(etherurethane urea) elastomers

Quantitative description of foreign body giant cell (FBGC) formation on poly(etherurethane urea) (PEUU) surfaces as a function of time can conceivably predict the effects of polymer characteristics on cellular responses in vivo. In the present study, the formation of FBGCs on strained and unstrained PEUUs was quantified with two parameters: the density of adherent macrophages present initially that participate in FBGC formation (d(o)) and the rate constant for cell fusion (k); both kinetic parameters were used to calculate the time-dependent FBGC density (dfc). Relationships were sought between results of the cellular analysis and the extent of environmental stress cracking (ESC), as characterized by scanning electron microscopy. Surface degradation was semiquantified with percent light transmittance. The materials used were: base PEUU, base PEUU with 1% Santowhite antioxidant powder, base PEUU with 5% Methacrol 2138F antifume agent, and base PEUU with both 1% Santowhite and 5% Methacrol 2138F. A comparison of unstrained base PEUU with base PEUU strained to 400% elongation indicated that the rate of cell fusion, but not d(o) and dfc, increased in the presence of strain. In all strained samples, additives that strongly affected the ESC also influenced FBGC kinetic parameters. Strained PEUU containing Santowhite had the lowest d(o), the slowest rate of cell fusion, and lowest dfc, and the least incidence of ESC. The results suggest that the incidence of ESC in PEUU was decreased in the presence of Santowhite, which also lowered the number of adherent macrophages participating in FBGC formation, the rate of FBGC formation and the subsequent FBGC density. These studies also indicate that strain in PEUUs does not directly modulate the adherent macrophage and FBGC density. Further studies are necessary to delineate the relationship between PEUU strain and adherent macrophage and FBGC activation, which leads to the exocytosis of degrading agents and the observed incidence of biodegradation.

Ultrastructural interaction between multinucleate giant cells and the fungus in aspergillomas of human paranasal sinuses

The interaction between multinucleate giant cells (MGCs) and the fungus Aspergillus flavus as seen by transmission electron microscopy (TEM) is described in paranasal granulomas occurring in a Saudi patient dying from chronic aspergillosis. Two morphologically different types of MGCs were recognized; these were: a) 'Unhealthy looking' type I cells, rich in well organized organelles and containing few, partially degenerated and necrotic fungal elements. b) 'Healthy looking' type II cells that contained scanty, randomly dispersed cell organelles and normal, or partially degenerated fungal hyphae. The fungal elements had very thick and multilayered cell walls, and were found either in close contact to the host cell cytoplasm, or enclosed within phagosomes. The mechanism of the fungus destruction by the host MGCs is described and compared with that previous reports of MGCs involved in the elimination of extracellular microorganisms. The morphology and the various physiological activities of MGCs seems to depend mainly on whether the pathogen is extra- or intracellular. However, this study showed that MGCs are the cells best suited for killing pathogenic fungi.

Zinc supplementation impairs monocyte function

Zinc has been shown to be involved in many functions of the immune system. This study was conducted to examine the effect of zinc supplementation on phagocytic, fungicidal and metabolic activity of blood monocytes of marasmic infants during nutritional rehabilitation. A controlled, double-blind design was used in which 19 infants fed a zinc-fortified formula were compared with 20 infants fed the same, unfortified formula. Evaluation of phagocytic-fungicidal capacity, growth, zinc, copper and iron status was performed in both groups on admission and after 60 and 105 days of nutritional rehabilitation. Although energy, copper and iron intakes were similar in the two groups, a decrease in the number of infants able to phagocytose one or more Candida buds was observed after 60 days of zinc supplementation compared to admission (p < 0.03). No change in phagocytic ability was detected between admission and 60 days in the control group. The number of infants with depressed fungicidal activity increased significantly after 105 days of nutritional rehabilitation in the zinc-fortified group as compared to controls (p < 0.04). The number and duration of impetigo episodes was significantly greater in the group fed the zinc-fortified formula. These results suggest that zinc supplements at the RDA level may impair monocyte function.

Macrophages (histiocytes) in various reactive and inflammatory conditions express different antigenic phenotypes

The purpose of this study was to determine whether human tissue macrophages (M phi s) in various inflammatory/reactive conditions express different immunophenotypes. Using a large panel of monoclonal antibodies to monocyte/M phi-related antigens and a frozen-section immunoperoxidase technique, the following conditions were studied: granulomatous inflammation of unknown etiology, sarcoidosis, cat-scratch fever, toxoplasmosis, Gaucher's disease, and juvenile xanthogranulomas. The results show that there is immunophenotypic variation of the M phi s among the various inflammatory/reactive conditions. For example, the M phi s in cat-scratch fever are nearly unique in the expression of the "early inflammation" antigen identified by antibody 27E10, and the M phi s in juvenile xanthogranulomas, unlike those in most of the other conditions, lacked the antigen detected by antibody 25F9. The M phi s in Gaucher's disease differed from those in the other disorders by the combined absence of CD11b, CD14, G16/1, CD1a, CD25, and CD30. The inflammatory/reactive M phi s also exhibited differences from those in "normal" tissues, namely, a tendency toward acquisition of the antigens identified by antibodies Mac 387 and G16/1 and the more uniform expression of the "activation" antigens CD25, CD30, and CD71. The antigenic variations described here probably reflect differences in antigenic stimuli and M phi function. In addition to the possible biologic implications, this M phi immunophenotypic diversity may have practical diagnostic applications.

Impairment of macrophage activation and granuloma formation by protein deprivation in mice

Protein-calorie malnutrition predisposes to infection by intracellular pathogens, but the basis for this predisposition is unclear. We studied the effect of protein deprivation on mouse peritoneal macrophage function and on granuloma formation during infection by bacille Calmette-Gueŕin (BCG). Injection of lipopolysaccharide (LPS) to induce inflammation elicited fewer peritoneal cells from mice fed a 2.5% protein diet than from mice fed an isocaloric chow in which protein calories constituted 24% of the total. LPS-elicited macrophages from protein-deprived mice demonstrated a reduction in spreading, total cell protein, cell lactate dehydrogenase, and release of superoxide anion (O2-) in response to stimulation. Priming in vitro by interferon (IFN)-gamma for enhanced release of O2- was also significantly impaired in protein-deprived mice. This defect was reversible by repletion with 24% protein diet for 10 days. Impairment of macrophage function in protein-deprived mice was further evidenced by an impaired capacity to express Ia antigen in response to IFN-gamma and by reduced production of IL-1 activity in response to LPS. Infection by BCG in protein-deprived mice was characterized by impaired granuloma development in liver, lungs, and spleen. Thus, in this model, protein deprivation significantly impaired macrophage activation, as assessed by morphologic, metabolic, and functional criteria. This impairment might compromise immune effector mechanisms dependent on macrophage activation, including rejection of intracellular pathogens.

Induction of multinucleated giant cell formation from in vitro culture of human monocytes with interleukin-3 and interferon-gamma: comparison with other stimulating factors

One of the hallmarks of the granulomatous response to infection is the formation of multinucleated giant cells (MGC.) In an effort to study MGC, we examined the fusion-promoting effects of a variety of stimulating factors on human peripheral blood monocytes cultured on plastic surfaces in serum-supplemented media. MGC formation was minimally to moderately enhanced by interferon-gamma (IFN-gamma), interleukin (IL)-3, granulocyte/macrophage colony-stimulating factor (GM-CSF), 1,25-dihydroxycholecalciferol (1,25-(OH)2D3), retinoic acid (RA), and IL-6. IL-4 (which has been reported to promote MGC formation from murine macrophages) had an inhibitory effect. IFN-gamma was not required for MGC formation but it significantly increased the fusion-promoting activity of GM-CSF, 1,25-(OH)2D3, RA, and IL-6, IL-3, a hematopoietic growth factor, has been recently shown to induce osteoclast formation from murine bone marrow mononuclear cells. The most striking effect was seen with the combination of IL-3 and IFN-gamma. Fusion index is defined as a percentage of nuclei found within MGC, and an index of 67% at 1 wk was found. The formation of some very large cells with 50 to 100 nuclei was noted. Both Langhans' and foreign-body type cells were seen. Transmission electron micrographs clearly demonstrate the absence of plasma membrane between nuclei. Induction of MGC from peripheral human blood monocytes by IL-3 and IFN-gamma provides an in vitro system for the study of the formation and function of these cells.

Cyclophosphamide affects the dynamics of granuloma formation in experimental visceral leishmaniasis

We observed histopathological and ultrastructural hepatic changes following the intracardiac inoculation of Leishmania donovani amastigotes into inbred LHC hamsters (group I). Since granuloma formation is known to be T-cell-dependent, we also examined infected hamsters under cyclophosphamide immunosuppressive treatment (group ICy) and evaluated the production of interleukin-2 (IL-2) by their cells. Group I showed more intense hepatocyte and endothelial cell clasmatosis as well as hepatocyte degeneration and necrosis, deposits of connective tissue fibers, granulomas with multinucleated giant cells (MGCs) of foreign-body and Langhans' types and reduced production of IL-2 by spleen cells. In contrast, group ICy hamsters exhibited larger eosinophil and lymphocyte populations within sinusoids and peri-sinusoidal areas but showed no MGCs in granulomas. A striking decline in IL-2 production was noted. These results suggest that cyclophosphamide induces a delay in the natural evolution of L. donovani-induced granulomatous hepatic inflammation.

Porous polymer implant for repair of meniscal lesions: a preliminary study in dogs

Artificial meniscal lesions extending into the avascular part of the meniscus, which do not heal by any other means, were repaired by suturing either a porous polymer implant or a synovial flap into the defect. The implant guided the ingrowth of vascular repair tissue into the defect. This fibrous tissue later on transformed into fibrocartilage. Reconstruction with a synovial flap was not successful. It appeared that healing can be achieved by implantation of a porous polymer implant in a large number of cases. Future research will be aiming at improvement of the results of meniscal repair and application of this type of polymer for repair of cartilage defects.

Temporal artery morphology and morphometry in giant cell arteritis

Paraffin sections and more than 7,000 plastic cross-sections of temporal arteries from 27 patients with a clinical diagnosis of polymyalgia rheumatica (PMR), 16 patients with a clinical diagnosis of temporal arteritis (TA) and 18 age- and sex-matched postmortem controls were studied using light microscopy. A new method was developed to permit a morphometric comparison between biopsies and autopsy specimens. Two stages of inflammation were discerned in TA. In atrophic arterial segments there was a focal, foreign-body, giant-cell reaction to the calcified internal elastic membrane (IEM) with a spatially correlated, mononuclear cell infiltration. Isolated giant cells were also found to attack the IEM in these cases. The majority of the biopsies displayed a different picture with a diffuse macrophage attack on media and intima with numerous and apparently macrophage-derived giant cells, which did not attack calcifications. The latter arteries were significantly widened (p less than 0.02), which indicates that this phase is the later one. Non-inflamed segments of PMR vessels displayed a significant, non-reactive media atrophy compared with controls (p less than 0.03) and their IEM calcifications were significantly larger (p less than 0.02). The circumference was smaller in atrophic PMR arteries than in inflamed TA arteries (p less than 0.006), which contradicts post-inflammatory scarring.

Characteristics of giant cells and factors related to the formation of giant cells in myocarditis

Giant cell myocarditis is a serious and frequently fatal inflammatory heart disease of which the etiology remains unknown. In the present study, we investigated the origin of multinucleated giant cells in myocarditis with the use of an experimental model. We also examined the factors relating to the formation of giant cells in myocarditis. Severe myocarditis characterized by the appearance of multinucleated giant cells was induced in Lewis rats by immunization with cardiac myosin in complete Freund's adjuvant. Two types of giant cells, foreign body giant cell-like and myocytelike, were observed in this myocarditis. Immunohistochemical studies revealed that both types of multinucleated giant cells were stained with OX42 and ED1 (macrophage markers) and were not stained with anti-desmin antibody and HHF35 (markers for muscle fibers). Therefore, it is likely that multinucleated giant cells in this myocarditis are derived from macrophages. During the course of the disease, the appearance of multinucleated giant cells was restricted to a period corresponding with the fulminant phase of inflammation. When the severity of the disease was modulated by immunization with various doses of the antigen, multinucleated giant cells appeared only in severe myocarditis after inoculation of a large dose of the antigen. Administration of immunoadjuvants also affected the formation of giant cells. Most of the rats injected with cardiac myosin in complete Freund's adjuvant developed giant cell myocarditis.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo degradation of processed dermal sheep collagen evaluated with transmission electron microscopy

The in vivo degradation of hexamethylenediisocyanate-tanned dermal sheep collagen was studied with transmission electron microscopy. Discs of hexamethylenediisocyanate-tanned dermal sheep collagen were subcutaneously implanted in rats. Both an intra- and an extracellular route of degradation could be distinguished. In addition to normal components of a typical foreign body reaction, remarkable phenomena, such as locally deviant neutrophil morphology, infiltration of basophil-like cells, indications of foreign body multinucleate giant cells formed from different cell types, aluminium silicate accumulations and calcium phosphate depositions, were observed. Foreign body multinucleate giant cells intracellularly degraded hexamethylenediisocyanate-tanned dermal sheep collagen after internalization. Both internalized and cellularly enveloped hexamethylenediisocyanate-tanned dermal sheep collagen degraded by the detachment of fibrils. Another extracellular route of degradation was characterized by calcium phosphate depositions in large bundles of hexamethylenediisocyanate-tanned dermal sheep collagen. From 6 wk, the hexamethylenediisocyanate-tanned dermal sheep collagen implant was replaced by rat connective tissue, which was subsequently also degraded. After 15 wk, the presence of basophil-like foreign body multinucleated giant cells containing aluminium/silicon-crystalline accumulations still persisted. These phenomena were related to the specific nature of the material used and suggest cytotoxicity. They emphasize the need for detailed evaluation at the ultrastructural level of newly developed biomaterials before they can be used for medical applications.

Selective differences in macrophage populations and monokine production in resolving pulmonary granuloma and fibrosis

Alveolar macrophages (AM) and their production of interleukin-1-like activity (IL-1) and macrophage-derived growth factor for fibroblasts (MDGF) were examined during chronic inflammatory reactions leading to either granuloma formation or fibrosis. Groups of five rats each received, respectively, a single transtracheal injection of xonotlite, attapulgite, short chrysotile 4T30, UICC chrysotile B asbestos, or saline. One month later, such treatments induced either no change (xonotlite), granuloma formation (attapulgite and short chrysotile 4T30), or fibrosis (UICC chrysotile B). By 8 months, however, the granulomatous reactions had resolved or greatly diminished, whereas the fibrosis persisted irreversibly. Parallel examination of cell populations obtained by bronchoalveolar lavage revealed that multinucleated giant macrophages (MGC) were present in lavage fluids of animals with resolving granulomatous reactions but absent in those obtained from animals with lung fibrosis. Evaluation of monokine production by inflammatory macrophages also revealed significant differences. Enhanced production of IL-1-like activity was seen in both types of lung injury, although especially during the early stage (1 month) and decreased thereafter (8 months). By contrast, augmentation of MDGF production was observed in animals with lung fibrosis only and persisted up to 9 months. Taken together, these data indicate that production of selected cytokines, as well as AM differentiation along a given pathway, may modulate the outcome of a chronic inflammatory response.

Anti-RMA, a murine monoclonal antibody, activates rat macrophages: II. Induction of DNA synthesis and formation of multinucleated giant cells

Anti-RMA is a murine anti-rat monoclonal antibody that binds to a 120-kD surface membrane antigen expressed primarily by alveolar macrophages. Saline-lavaged alveolar macrophages (AM) formed clusters after incubation with anti-RMA. Anti-RMA produced multinucleated giant cells (MGC) in approximately 15% of adherent AM, and the F (ab')2 fragment of anti-RMA yielded MGC in approximately 9% of AM. The Fab fragment of anti-RMA did not promote MGC formation, nor did the murine anti-rat monoclonal antibodies OX41 and W3/25 (anti-CD4). Although anti-RMA produced a tenfold increase in [3H]thymidine incorporation by AM, it yielded a minimal increase in the number of AM. Autoradiography of AM stimulated with anti-RMA showed heterogeneous labeling of nuclei in MGC, suggesting that 3H-labeled AM may fuse with AM that are not actively synthesizing DNA. These findings suggest that binding of anti-RMA to AM may activate DNA synthesis, and promote clustering and fusion of AM, leading to MGC formation.

Characterization of the binucleated giant cells generated in the autologous mixed leucocyte reaction from patients with rheumatoid arthritis

Binucleated giant cells several times larger than lymphocytes or monocytes were generated in an autologous mixed leucocyte reaction (AMLR) independent of DNA synthesis in patients with rheumatoid arthritis (RA). The AMLR giant cells with multiple cytoplasmic granules were non-specific esterase-staining positive, phagocytic, non-adherent, HLA-DR+, CD11b+, CD14+, 4F2+, CDW29+, and anti-transferrin receptor positive, but negative for T, B, or NK markers. RA patients aged less than 60 years from more giant cells: 12.6 +/- 13.5% (n = 33) as compared with 0.4 +/- 1.5% in age- and sex-matched normals (n = 38, (P less than 0.001). More giant cells were seen over age 60 in both groups: RA 20.1 +/- 15.5% (n = 5) and healthy controls 3.0 +/- 3.2% (n = 8) (P less than 0.01). Neither disease activity nor treatment appear to influence the result in RA. The giant cells that are probably derived from monocytes in AMLR may explain the formation of the giant cells in rheumatoid granulation tissues.

Recombinant murine interferon-gamma inhibits the fusion of mouse alveolar macrophages in vitro but stimulates the formation of osteoclastlike cells on implanted syngeneic bone particles in mice in vivo

Osteoclasts are multinucleated cells that originate from the fusion of mononuclear precursors and are responsible for bone resorption. Indirect evidence from in vitro studies suggests that IFN-gamma and TNF-alpha inhibit and stimulate bone resorption, respectively, but contradictory results have emerged from the literature regarding the effects of IFN-gamma on macrophage multinucleation. Using highly sensitive model systems, the present work demonstrates that, in mice, rMuIFN-gamma inhibits the fusion of alveolar macrophages in vitro but augments the number of osteoclastlike cells on implanted syngeneic bone particles in vivo. Although rMuTNF-alpha fails to stimulate macrophage multinucleation in either system, treatment of implanted animals with rMuIFN-gamma appears to limit the inflammatory reaction and favor tissue repair.

Macrophage multinucleation is accompanied by the expression of new soluble and membrane antigens in mice

Polyclonal antibodies were raised against mouse multinucleated giant cells to identify proteins specifically associated with multinucleated macrophages. A 115 kd membrane protein and a 160 kd soluble protein were detected by immunoprecipitation of radiolabeled giant cells and were not seen in mononucleated macrophages. This study demonstrated that giant cells express de novo synthesized proteins that are not present in macrophages and identified a new immunization technique to generate antibodies directed against cell surface components.

Multinucleated giant cells generated in vitro. Terminally differentiated macrophages with down-regulated c-fms expression

Although multinucleated giant cells (MGCs) are a known feature of granulomatous reactions, little is known about their destination and function. In this study human blood monocyte (BM)-derived giant cells were generated by lymphokine stimulation in vitro. Their immunophenotype and ultrastructural morphology resembled that of MGCs occurring in vivo. Mitotic activity within MGCs could not be established either in vitro or in vivo. Enzyme equipment of MGCs was elevated in comparison with monocyte-macrophages. In comparison with unfused monocyte-macrophages, MGCs did not reveal a higher level of interleukin-1 production or cytostatic activity. They showed, however, a 20-30-fold increase in the production of oxygen-free radicals in response to zymosan. Transcription of the proto-oncogene c-fms was enhanced in short-term cultivated BM and was rapidly down-regulated in MGCs after fusion had occurred. It is concluded that MGCs represent highly stimulated cells of monocyte-macrophage lineage at a terminal stage of maturation.

Interleukin 4 induces cultured monocytes/macrophages to form giant multinucleated cells

Giant multinucleated cells (GMCs) are associated with granulomatous lesions that form in response to various infectious and noninfectious agents. The present study shows that mouse IL-4 induces the in vitro formation of GMCs by factor-dependent bone marrow and alveolar monocytes via cell fusion. GMCs appear 2 d after incubation of cell cultures with 20 U/ml or more of IL-4. Anti-IL-4 mAbs block the appearance of GMCs in these cultures, indicating that IL-4 acts directly on monocytes to promote fusion and does not secondarily induce the production of other soluble fusion factors. In soft agar cultures, IL-4 also causes the aggregation of macrophages and diminishes their migration. The role of IL-4 in a granulomatous inflammatory response is discussed.

In vitro and in vivo interactions of cells with biomaterials

The biocompatibility of materials at an implant site involves a complex interaction of cells and tissues with the biomaterial. This cell-cell and cell-polymer interaction evokes the release of mediators such as chemotactic and growth factors that elicit and sustain inflammatory responses at the implant site. In this review, we summarize the interaction of cells with biomaterials in vitro and in vivo.

Alteration of uptake and distribution of eicosanoid precursor fatty acids by aspirin

Aspirin is an important drug in the treatment of numerous disorders, especially rheumatic diseases. Its several mechanisms of action include inhibition of prostaglandin production by acetylation of prostaglandin synthetase. To explore further the modulatory effect of aspirin on eicosanoid production, we examined its effect on uptake and incorporation of fatty acids into phospholipids of human peripheral blood monocytes. Aspirin ingestion by normal volunteers inhibited uptake of arachidonic acid and linoleic acid in monocytes cultured for 3 days. Similar inhibition was observed when cultured normal human peritoneal macrophages were treated with aspirin for 3 days. In contrast, monocytes cultured for 12 days from both normal volunteers who had ingested aspirin and normal cells treated with aspirin in vitro for the first 3 days of a 12-day culture period expressed an increased uptake of both arachidonic and linoleic acids. Similarly, incorporation of fatty acid into phosphatidylcholine was depressed in 3-day cultured cells but was increased in 12-day cultured cells. Thus, aspirin, whether administered in vivo or added in vitro, modulates cellular uptake and incorporation of eicosanoid precursor fatty acids and their insertion into membrane phospholipids in cultured human monocytes and macrophages.

Size dependent enzyme activities of multinucleated (osteoclastic) giant cells in bone tumors

In osteoclastic giant cells of six different tumors of bones and joints (fibrous dysplasia, proliferating giant cell tumor, malignant giant cell tumor, osteosarcoma after chemotherapy, malignant synovioma and Ewing's sarcoma) activities of tartrate-resistant acid phosphatase, NADH-tetrazolium-oxidoreductase and, in three of them, of non-specific esterase are determined by enzyme histochemical methods. Quantitative microphotometry makes it possible to determine relative enzyme activities in the cut sections of giant cells of different sizes. Giant cells of the various tumors reveal similar trends: With an increase in cell size, mean extinctions of NADH-tetrazolium-oxidoreductase and non-specific esterase decrease. Mean extinctions of tartrate-resistant acid phosphatase increase in cells of medium size, whereas the large cells reveal in part low activities. An additional ultrastructural examination of the giant cells in the proliferating giant cell tumor as well as in the osteosarcoma shows morphological signs of degeneration in the large cells. Electron probe microanalysis of the proliferating giant cell tumor exhibits evidence of phagocytosis of Ca and/or Fe containing particles. The similar size dependent reaction pattern of enzymes in osteoclastic giant cells of different tumors favors the concept of a common histogenesis, i.e. a host reaction.

Studies on the differentiation of the human myelomonocytic cell line RC-2A in response to lymphocyte-derived factors

Cells of the human myelomonocytic line RC-2A were induced to differentiate toward macrophages by culturing for up to 12 days in the presence of supernatant from phytohaemagglutinin stimulated human peripheral blood mononuclear cells (PHA-LCM). The process of differentiation was monitored by changes in expression of two-macrophage related enzymes (alpha-naphthol butyrate esterase and acid phosphatase), the changes in expression of the monocyte-macrophage cell surface markers detected by the monoclonal antibodies anti-Mo1 and anti-Mo2, HLA class 2 antigen detected by FMC-14, and alteration in cell morphology. Maturation induced by PHA-LCM was accompanied by a marked decrease in the proliferative potential of the cell population, and a reduced ability to form colonies in semi-solid medium. Induced RC-2A cells were able to stimulate in one-way mixed leukocyte culture more effectively than control cells.

Human macrophage hybrid forming spontaneous giant cells

Thymidine kinase-deficient clones of the human monocyte/macrophage cell line U-937 were established and used for fusion experiments with separated normal human blood monocytes. A hybrid (H 29) was generated during HAT-selection procedure, about 50% of which formed spontaneous giant cells, as shown by morphological, immunocytochemical, and chromosomal analyses. It is concluded that giant cells originate from monocytes and display mitotic activity. Macrophage hybrids are the basic requirement for the elucidation of monocyte/macrophage heterogeneity and immortalization of their functional properties.

Uptake of fatty acids and their mobilization from phospholipids in cultured monocyte-macrophages from rheumatoid arthritis patients

Prostaglandins (PG) and related eicosanoids which derive from essential fatty acids are important mediators and modulators of inflammation. Macrophages (M phi), which derive from peripheral blood monocytes (PBM), are prominent cells in the synovium of patients with rheumatoid arthritis (RA), and are a major source of synovial PGE2. In addition, fresh and cultured PBM from RA patients produce more PG than normal control cells. When allowed to mature in culture PBM exhibit many characteristics of macrophages (M-M phi). We examined uptake by M-M phi of eicosanoid precursor fatty acids (FA), their incorporation into cellular phospholipid (PL), and mobilization of FA after cell stimulation. Cultured M-M phi from treated and untreated RA patients (RA M-M phi) took up significantly more linoleic acid (LA), dihomogammalinolenic acid (DHLA) and arachidonic acid (AA) than M-M phi from normal volunteers (N M-M phi). The enhanced uptake of FA observed in 12-day cultures of RA M-M phi was similar to uptake seen in normal human peritoneal macrophages (PM phi). After uptake FA were incorporated mainly into phosphatidylcholine (PC). M-M phi from untreated RA patients incorporated a smaller proportion of [14C]LA into PC (37.0 +/- 12.7% of total PL label) than normal cells (86.0 +/- 4.2%), and a greater proportion of [3H]AA into PC (57.1 +/- 7.1%) than normals (23.9 +/- 6.9%). Stimulation of M-M phi with calcium ionophore A23187 resulted in significantly greater hydrolysis of LA and AA from PC in RA M-M phi from both treated and untreated patients than from PC in N M-M phi. The data indicate that M-M phi from RA patients mature more rapidly in vitro than M-M phi from controls as uptake of FA by RA M-M phi increases with duration of culture and by 12 days in culture equals uptake by normal human peritoneal M phi. Also, RA M-M phi exhibit differences from N M-M phi in uptake, PL distribution, and hydrolysis of eicosanoid precursor FA. Such changes in FA metabolism might influence cell function and inflammatory responses.

Electrophysiology of phagocytic membranes. Role of divalent cations in membrane hyperpolarizations of macrophage polykaryons

The electrophysiological properties of the membrane of mouse peritoneal macrophage polykaryons are studied. Slow hyperpolarizations can be elicited by iontophoretic injections of either Ca2+ or Sr2+ into the cytoplasm. The effect of both cations is identical, since: it is invariably triggered by the cation injection, the amplitude is dependent on the K+ gradient, quinine blocks reversibly the response to both cation injections. Mg2+, Ba2+ and Mn2+ did not elicit responses when injected into the cytoplasm. Ca2+ induced slow hyperpolarizations were reversibly blocked by the addition of Ba2+ to the external saline, but were not affected by the presence of external tetraethylammonium chloride. Cells maintained in saline containing high concentrations of Ca2+, Sr2+ or Mn2+ exhibited sustained hyperpolarizations. Quinine blocked the hyperpolarization induced by high Ca2+ or Sr2+, but was ineffective for the case of Mn2+. Cells hyperpolarized by external Mn2+ frequently exhibited nonlinear, voltage-current characteristics. Similar patterns could also be observed in a small fraction (less than 10%) of the cells in control conditions. Current-induced shifts between two stable membrane potentials were seen either in high Ca2+ or normal medium. The great variability of the responses described for this phagocytic membrane is discussed. The evidence supports the assumption that Ca2+ and Sr2+ can induce transient or persistent hyperpolarized states by activating a potassium permeability. External Mn2+ may act in part by reducing impalement-related current leakage from the phagocytic membrane.

Mononuclear macrophage (M-CFC) colony formation in semisolid media in the absence of exogenous GM-CSF

Human fetal bone marrow (FBM) cells were examined for the ability to form colonies in the absence of exogenous colony-stimulating factor (CSF) in double layer agar, methylcellulose (MC), and in agar-MC (agar underlayer, MC overlayer) culture systems. Without exogenous CSF, macrophage colonies (M-CFC) were formed in a combined culture of agar and MC. Aggregates of 5-40 cells were observed on day 7. Gradually, large compact colonies which survived for 10-12 weeks of cultivation, were formed. They were composed of mononuclear monocytes and multinucleated cells. M-CFC progenitors were nonadherent, but their progeny became adherent during differentiation within the colony. Colony formation was cell-dose-dependent. Depletion of monocytes increased the number of colonies in agar-MC cultures and stimulated the development of some macrophage colonies in MC. Survival of monocyte progenitors was not dependent on CSF. Neither was their proliferation nor partial differentiation in agar-MC cultures. CSF increased M-CFC colony efficiency, however, if it was present when cultures were initiated. Addition of CSF to M-CFC growing for 2-5 weeks in CSF-deprived medium stimulated monocytes proliferation and transformation into macrophages. Epithelioid cells, an increase in the number of giant multinucleated cells, and granulocyte multiplication were also observed. The absolute dependence of macrophage colony formation on CSF described by others might be a result of inadequate culture conditions due to agar rather than an intrinsic physiological requirement.