Inflammatory giant cells

Bee venom as an alternative for antibiotics against Staphylococcus aureus infections

The misuse of antibiotics has led to antibiotic-resistant bacterial strains, making it even harder to combat and eliminate their infections. Staphylococcus aureus causes various adverse infections and diseases, including skin abscesses, bloodstream infections, pneumonia, and joint infections. In this study, we aimed to test the cytotoxic and antibacterial effects of bee venom-loaded chitosan nanoparticles (BV-loaded CS-NPs) in comparison to gamma-irradiated BV and native BV from Apis mellifera. The physiochemical characterizations of our treatments were determined by Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscope (TEM), zeta-potential, release rate, and Encapsulation Efficiency (EE). Our study was conducted on both levels, in-vitro and in-vivo. For the in-vitro study, a bacterial model of Staphylococcus aureus with an ATCC number of 6538 was grown in tryptic soy agar (TSA) medium, and the inhibition zones of our drug candidates were measured with the appropriate statistical analysis performed. For the in-vivo study, levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), Creatinine, Urea, and interleukin 6 (IL-6) were analyzed. BV-loaded CS-NPs showed relatively better results than the other alternatives, which are native BV and gamma-irradiated BV. The results showed that the antibacterial effect of BV-loaded CS-NPs was greater than the alternatives. Furthermore, its cytotoxic effect was far less than the native and irradiated bee venom. These outcomes ensure that loading BV on CS-NPs makes it a promising drug candidate for an antibiotic alternative with minimal cytotoxicity and enhanced antibacterial activity.

Surveying the Epigenetic Landscape of Tuberculosis in Alveolar Macrophages

Tuberculosis (TB) remains the leading cause of bacterial disease-related death and is among the top 10 overall causes of death worldwide. The complex nature of this infectious lung disease has proven difficult to treat, and significant research efforts are now evaluating the feasibility of host-directed, adjunctive therapies. An attractive approach in host-directed therapy targets host epigenetics, or gene regulation, to redirect the immune response in a host-beneficial manner. Substantial evidence exists demonstrating that host epigenetics are dysregulated during TB and that epigenetic-based therapies may be highly effective to treat TB. However, the caveat is that much of the knowledge that exists on the modulation of the host epigenome during TB has been gained using in vitro, small-animal, or blood-derived cell models, which do not accurately reflect the pulmonary nature of the disease. In humans, the first and major target cells of Mycobacterium tuberculosis are alveolar macrophages (AM). As such, their response to infection and treatment is clinically relevant and ultimately drives the outcome of disease. In this review, we compare the fundamental differences between AM and circulating monocyte-derived macrophages in the context of TB and summarize the recent advances in elucidating the epigenomes of these cells, including changes to the transcriptome, DNA methylome, and chromatin architecture. We will also discuss trained immunity in AM as a new and emerging field in TB research and provide some perspectives for the translational potential of targeting host epigenetics as an alternative TB therapy.

Host Immune-Metabolic Adaptations Upon Mycobacterial Infections and Associated Co-Morbidities

Mycobacterial diseases are a major public health challenge. Their causative agents include, in order of impact, members of the Mycobacterium tuberculosis complex (causing tuberculosis), Mycobacterium leprae (causing leprosy), and non-tuberculous mycobacterial pathogens including Mycobacterium ulcerans. Macrophages are mycobacterial targets and they play an essential role in the host immune response to mycobacteria. This review aims to provide a comprehensive understanding of the immune-metabolic adaptations of the macrophage to mycobacterial infections. This metabolic rewiring involves changes in glycolysis and oxidative metabolism, as well as in the use of fatty acids and that of metals such as iron, zinc and copper. The macrophage metabolic adaptations result in changes in intracellular metabolites, which can post-translationally modify proteins including histones, with potential for shaping the epigenetic landscape. This review will also cover how critical tuberculosis co-morbidities such as smoking, diabetes and HIV infection shape host metabolic responses and impact disease outcome. Finally, we will explore how the immune-metabolic knowledge gained in the last decades can be harnessed towards the design of novel diagnostic and therapeutic tools, as well as vaccines.

Characterization of macrophages, giant cells and granulomas during muscle regeneration after irradiation

Macrophages play a fundamental role in the different stages of muscle regeneration although the precise mechanisms involved are not entirely understood. Here we investigated the types of macrophages and cytokines that appeared in muscles after local gamma irradiation of mini-pigs that underwent no subsequent treatment or received three successive adipose tissue-derived stem cell (ASC) injections. Although some variability was observed among the three animals included in each study group, a general picture emerged. No macrophages appeared in control muscles from regions that had not been irradiated nor in muscles from irradiated regions derived from two animals. A third irradiated, but untreated animal, with characteristic muscle fibrosis and necrosis due to irradiation, showed invasion of M2 macrophages within small muscle lesions. In contrast, among the three ASC-treated and irradiated animals, one of them had completely recovered normal muscle architecture at the time of sampling with no invading macrophages, muscle from a second one contained mostly M1 macrophages and some M2-like macrophages whereas muscle from a third one displayed granulomas and giant cells. ASC treatment was associated with the presence of similar levels of pro-inflammatory cytokines within the two animals in the process of muscle regeneration whereas the levels of IL-4 and IL-10 expression were distinct from one animal to another. Microspectrofluorimetry and in situ hybridization revealed strong expression of TGF-β1 and TNFα in regenerating muscle. Overall, the data confirm the critical role of macrophages in muscle regeneration and suggest the involvement of a complex network of cytokine expression for successful recovery.

Multinucleated Giant Cells in Experimental Intracerebral Hemorrhage

Macrophage phagocytosis plays an important role in hematoma clearance after intracerebral hemorrhage (ICH). This study examined the characteristics of multinucleated giant cells (MGCs), a group of macrophages with multiple nuclei, in a mouse ICH model. Whether MGCs could be increased by treatment with a CD47 blocking antibody and decreased by treatment with clodronate liposomes were also examined. ICH was induced via autologous blood injection. Male adult C57BL/6 mice in different groups had (1) ICH alone; (2) ICH with anti-CD47 blocking antibody or control IgG; and (3) ICH with anti-CD47 antibody combined with clodronate liposomes or control liposomes. The effect of anti-CD47 antibody on MGC formation was also tested in females. Brains were harvested at days 3 or 7 for brain histology. Many MGCs were found at day 3 post-ICH, but were reduced at day 7. MGCs phagocytosed many red blood cells and were heme oxygenase-1, ferritin, YM-1, and iNOS positive. CD47 blocking antibody injection increased MGC numbers in the peri-hematomal zone and in the hematoma in both sexes. Co-injection of clodronate liposomes depleted MGCs in both the hematoma core and the peri-hematomal area. In conclusion, MGCs represent a macrophage/microglia subtype with strong phagocytosis capacity. MGCs exhibited not only an M2 but also an M1 phenotype and appeared involved in hemoglobin degradation. Anti-CD47 antibody boosted the number of MGCs, which may contribute to enhance hematoma clearance. Understanding the exact roles of MGCs in ICH may reveal novel targets for ICH treatment.

Dual-specificity tyrosine phosphorylation-regulated kinase 2 regulates osteoclast fusion in a cell heterotypic manner

Monocyte fusion into osteoclasts, bone resorbing cells, plays a key role in bone remodeling and homeostasis; therefore, aberrant cell fusion may be involved in a variety of debilitating bone diseases. Research in the last decade has led to the discovery of genes that regulate osteoclast fusion, but the basic molecular and cellular regulatory mechanisms underlying the fusion process are not completely understood. Here, we reveal a role for Dyrk2 in osteoclast fusion. We demonstrate that Dyrk2 down regulation promotes osteoclast fusion, whereas its overexpression inhibits fusion. Moreover, Dyrk2 also promotes the fusion of foreign-body giant cells, indicating that Dyrk2 plays a more general role in cell fusion. In an earlier study, we showed that fusion is a cell heterotypic process initiated by fusion-founder cells that fuse to fusion-follower cells, the latter of which are unable to initiate fusion. Here, we show that Dyrk2 limits the expansion of multinucleated founder cells through the suppression of the fusion competency of follower cells.

In Vitro Biocompatibility Assessment and In Vivo Behavior of a New Osteoconductive βTCP Bone Substitute

OBJECTIVE

Beta-tricalcium phosphate (βTCP) granules (OsproLife) exhibit a pure crystalline phase and a rough microporous surface for promoting cell adhesion and microsized intragranule porosity for improving wettability and resorption necessary for bone regeneration. OsproLife is a fully resorbable, space-maintaining, and osteoconductive synthetic material for the filling of bone defects. To asses OsproLife properties, a similar synthetic biomaterial, already on the market, has been chosen as reference: Cerasorb has the same chemical composition, but different crystal structure, surface morphology, and granule size. The aim of this study is to compare the properties of OsproLife and Cerasorb.

METHODS

Chemical purity, composition and physical properties, in vitro cytotoxicity, and in vivo bone performance in a rabbit model were analyzed. βTCP OsproLife granules (test) were compared with Cerasorb (control). Histological and μCT analyses were performed at 6, 12, and 56 weeks after implantation.

RESULTS

βTCP OsproLife and Cerasorb granules result to be both biocompatible and characterized by the same osteoconductivity and resorption rate.

CONCLUSION

βTCP OsproLife granules are a promising bone substitute for dental and orthopedic applications.

Macrophage form, function, and phenotype in mycobacterial infection: lessons from tuberculosis and other diseases

Macrophages play a central role in mycobacterial pathogenesis. Recent work has highlighted the importance of diverse macrophage types and phenotypes that depend on local environment and developmental origins. In this review, we highlight how distinct macrophage phenotypes may influence disease progression in tuberculosis. In addition, we draw on work investigating specialized macrophage populations important in cancer biology and atherosclerosis in order to suggest new areas of investigation relevant to mycobacterial pathogenesis. Understanding the mechanisms controlling the repertoire of macrophage phenotypes and behaviors during infection may provide opportunities for novel control of disease through modulation of macrophage form and function.

Granulomatous Uveitis Associated with Vaccination in the Atlantic Salmon

This study addressed histologic and immunopathologic changes in ocular tissues and investigated the distribution of major histocompatibility class II (MHC class II)-positive cells in Atlantic salmon ( Salmo salar) suffering from severe postvaccination disease. Twenty-nine fish with generalized inflammation, probably a result of vaccination, were investigated. One individual that had escaped vaccination was included in the study. Material was investigated by cultivation methods for fungi and bacteria. Histology using conventional staining procedures and immunohistochemistry with antisera against MHC class II β chain were performed. No growth was observed from the cultivation investigations. Histology revealed occlusion of the lumen in the larger choroid vessels and in the choriocapillaris, inflammatory infiltrations and loss of structure in the choroid rete, and, in some cases, aggregations of multinucleated giant cells (MGC) and Splendore-Hoeppli material. Immunohistochemistry demonstrated massive MHC class II+ cellular infiltrations in the uveal tract. Such infiltrations were also seen in the ventral ciliary cleft, a condition that is associated with glaucoma. Immunoreactive cells included dendritelike cells, epithelioid cells, and MGCs. The endothelia of smaller vessels were frequently MHC class II+, and immunoreactive infiltrations were seen in the optic nerve in several individuals. No pathologic changes were detected in the unvaccinated individual. In conclusion, generalized inflammatory reactions in fish may lead to severe ocular inflammation, occlusion of uveal vessels, and perivascular changes with MHC class II+ upregulation in cells in the uveal tract and optic nerve.

Bioinspired Materials and Biocompatibility

Material science and engineering are the sources of divergent emerging technologies, since all the modifications and developments are being made to reach a novel biomaterial to fulfill the requirements of biomedical applications, the first important feature is the biocompatibility of the new advanced material. In this chapter, the general biocompatibility concept, test systems to determine biocompatibility, examples of bioinspired materials and their altered biocompatibility and future expectations from these novel bioinspired materials will be discussed.

Modulation of Inflammatory Response and Induction of Bone Formation Based on Combinatorial Effects of Resveratrol

The success of bone tissue engineering strategies critically depends on the rapid formation of a mature vascular network in the scaffolds after implantation. Conventional methods to accelerate the infiltration of host vasculature into the scaffolds need to consider the role of host response in regulation of bone tissue ingrowth and extent of vascularization. The long term goal of this study was to harness the potential of inflammatory response to enhance angiogenesis and bone formation in three dimensional (3D) scaffolds. Towards this goal, we explored the use of resveratrol, a natural compound commonly used in complementary medicine, to enable the concurrently (i) mediate M1 to M2 macrophage plasticity, (ii) impart natural release of angiogenic factors by macrophages and (iii) enhance osteogenic differentiation of human mesenchymal stem cells (hMSCs). We mapped the time-dependent response of macrophage gene expression as well as hMSC osteogenic differentiation to varying doses of resveratrol. The utility of this approach was evaluated in 3D poly (lactide-co-glycolide) (PLGA) sintered microsphere scaffolds for bone tissue engineering applications. Our results altogether delineate the potential to synergistically accelerate angiogenic factor release and upregulate osteogenic signaling pathways by "dialing" the appropriate degree of resveratrol release.

Macrophage heterogeneity in tissues: phenotypic diversity and functions

During development and throughout adult life, macrophages derived from hematopoietic progenitors are seeded throughout the body, initially in the absence of inflammatory and infectious stimuli as tissue-resident cells, with enhanced recruitment, activation, and local proliferation following injury and pathologic insults. We have learned a great deal about macrophage properties ex vivo and in cell culture, but their phenotypic heterogeneity within different tissue microenvironments remains poorly characterized, although it contributes significantly to maintaining local and systemic homeostasis, pathogenesis, and possible treatment. In this review, we summarize the nature, functions, and interactions of tissue macrophage populations within their microenvironment and suggest questions for further investigation.

Embryonic stem cell-derived neural stem cells fuse with microglia and mature neurons

Transplantation of neural stem cells (NSCs) is a novel strategy to restore function in the diseased brain, acting through multiple mechanisms, for example, neuronal replacement, neuroprotection, and modulation of inflammation. Whether transplanted NSCs can operate by fusing with microglial cells or mature neurons is largely unknown. Here, we have studied the interaction of a mouse embryonic stem cell-derived neural stem (NS) cell line with rat and mouse microglia and neurons in vitro and in vivo. We show that NS cells spontaneously fuse with cocultured cortical neurons, and that this process requires the presence of microglia. Our in vitro data indicate that the NS cells can first fuse with microglia and then with neurons. The fused NS/microglial cells express markers and retain genetic and functional characteristics of both parental cell types, being able to respond to microglia-specific stimuli (LPS and IL-4/IL-13) and to differentiate to neurons and astrocytes. The NS cells fuse with microglia, at least partly, through interaction between phosphatidylserine exposed on the surface of NS cells and CD36 receptor on microglia. Transplantation of NS cells into rodent cortex results in fusion with mature pyramidal neurons, which often carry two nuclei, a process probably mediated by microglia. The fusogenic role of microglia could be even more important after NSC transplantation into brains affected by neurodegenerative diseases associated with microglia activation. It remains to be elucidated how the occurrence of the fused cells will influence the functional outcome after NSC transplantation in the diseased brain.

Giant cell polymyositis and myocarditis associated with myasthenia gravis and thymoma

We describe an unusual case of myasthenia gravis. Our patient had been diagnosed as having myasthenia gravis with thymoma at the age of 64 years, and died of acute respiratory failure at the age of 80 years. Post mortem examination revealed CD8-positive lymphocytic infiltration with numerous giant cells in the skeletal muscles and myocardium. Immunohistochemical and ultrastructural studies revealed that there were two types of giant cells: histiocytic and myocytic in origin. Furthermore, both types of giant cells were immunopositive for proteins implicated in the late endosome and lysosome-protease systems, suggesting that endocytosis may be the key mechanism in the formation of giant cells. The present case, together with a few similar cases reported previously, may represent a particular subset of polymyositis, that is, giant cell polymyositis and myocarditis associated with myasthenia gravis and thymoma.

Senescence and quiescence induced compromised function in cultured macrophages

Implants are predisposed to infection even years after implantation, despite ostensibly being surrounded by innumerable macrophages as part of the host foreign body response. The local implant environment could adversely influence the implant-associated macrophage phenotype, proliferative capacity, activation states, and ability to neutralize pathogens. This study monitored cultured macrophage proliferative states and phagocytotic competence on tissue culture plastic to address the hypothesis that extended contact with foreign materials alters macrophage phenotype. That such macrophage alterations might also occur around implants has significance to the foreign body response, infection, cancer, autoimmune and other diseases. Specifically, multiple indicators of macrophage proliferation in various culture conditions, including cell confluence, long-term culture (21 days), lipopolysaccharide (LPS) stimulation, passaging, and mitogenic stimulation are reported. Importantly, primary murine macrophages became quiescent at high confluence and senescent during long-term culture. Senescent macrophages significantly reduced their ability to phagocytose particles, while quiescent macrophages did not. Cell senescence and quiescence were not observed with repeated passaging. Primary macrophage stimulation with LPS delayed senescence but did not eliminate it. These results prompt the conclusion that both cell quiescence and senescence are observed under common macrophage culture conditions and could alter macrophage behavior and phenotypes in extended in vitro culture, such as the ability to phagocytose. Such macrophage transitions around foreign bodies in vivo are not documented: quiescence and senescence reported here in macrophage culture could be relevant to macrophage behavior both in vitro in bioassays and in vivo in the foreign body response and implant-centered infection.

Frequent upregulation of cyclin D1 and p16 expression with low Ki-67 scores in multinucleated giant cells

BACKGROUND/AIMS

Multinucleated giant cells are formed from the fusion of macrophages and are classified into foreign body-type giant cells (FBGCs), osteoclast-type giant cells (OCGCs) and Langhans-type giant cells (LHGCs). OCGCs display upregulated cyclin D1 expression with low Ki-67 activity. However, little is known about the expression of cell cycle regulators in the other types of multinucleated giant cells. We aimed to investigate the cell cycle status of multinucleated giant cells.

METHODS

The immunohistochemical expressions of cyclin D1, p16(INK4a) and Ki-67 were analyzed in a total of 127 cases showing multinucleated giant cells.

RESULTS

Cyclin D1 was overexpressed in 45 (88%) of 51 FBGC cases, 25 (86%) of 29 OCGC cases and 22 (47%) of 47 LHGC cases. p16(INK4a) showed diffuse nuclear and/or cytoplasmic overexpression in 45 (88%) of 51 FBGC cases, 27 (93%) of 29 OCGC cases and 24 (51%) of 47 LHGC cases. Ki-67 immunostaining was negative in almost all FBGC, OCGC and LHGC cases.

CONCLUSION

This study demonstrates that FBGCs and OCGCs frequently show upregulation of cyclin D1 and p16(INK4a) expression with low Ki-67 scores. This suggests that multinucleated giant cells are arrested in the G1/S cell cycle transition.

Macrophage fusion and multinucleated giant cells of inflammation

Macrophages undergo fusion with other macrophages to form the hallmark multinucleated giant cells of chronic inflammation. However, neither the existence of distinct morphological types of giant cells, the signaling pathways that induce their formation, the molecular mechanism(s) of macrophage fusion, nor the significance of macrophage multinucleation at chronic inflammatory sites are well understood. Our efforts have been focused on these unknowns, particularly as they relate to the foreign body-type giant cells that form on implanted biomaterials and biomedical devices. We have pursued the discoveries of human macrophage fusion factors (interleukin-4, interleukin-13, α-tocopherol) with emphasis on foreign body giant cells, and identified adhesion receptors and signaling intermediates, as well as an adhesion protein substrate (vitronectin) that supports macrophage fusion. Studies on the molecular mechanism of macrophage fusion have revealed it to be a mannose receptor-mediated phagocytic process with participation of the endoplasmic reticulum. Further phenotypic and functional investigations will foster new perspectives on these remarkable multinucleated cells and their physiological significances in multiple inflammatory processes.

Prevalence, number and morphological types of multinucleated histiocytic giant cells in equine inflammatory dermatoses: a retrospective light microscopic study of skin-biopsy specimens from 362 horses

REASONS FOR PERFORMING STUDY

Multinucleated histiocytic giant cells (MHGC) are seen frequently in skin-biopsy specimens from horses with inflammatory dermatoses. However, the prevalence, number and morphological types of these cells have not been reported.

OBJECTIVE

To determine the prevalence, number and morphological types of MHGC in equine inflammatory dermatoses, and the association of these cells with specific conditions.

METHODS

Skin-biopsy specimens from 335 horses with inflammatory dermatoses and from 27 horses with normal skin were evaluated for the prevalence, number and morphological types of MHGC.

RESULTS

The prevalence and number of MHGC were greater in granulomatous dermatoses than in nongranulomatous dermatoses. Infectious and noninfectious dermatoses were not different in terms of prevalence or morphological types of MHGC. Foreign-body MHGC were the predominant type in almost all cases. MHGC were not seen in normal skin.

CONCLUSIONS

MHGC are seen in a wide variety of equine inflammatory dermatoses, especially those that are granulomatous. Number and morphological types of MHGC are of no apparent diagnostic significance.

POTENTIAL RELEVANCE

MHGC are frequently present in a wide variety of inflammatory dermatoses in the horse. Because the prevalence, number and morphological types of MHGC are of minimal diagnostic significance, special stains and tissue cultures are necessary to confirm specific diagnoses.

Defense system by mesenchyme cells in bipinnaria larvae of the starfish, Asterina pectinifera

Here we characterize starfish larval mesenchyme cells, in terms of not only their phagocytic behavior, but also their structural and functional properties as a defense system. Our study reveals the following: (1) most mesenchyme cells construct a dynamic network structure beneath the body wall; (2) mesenchyme cells phagocytically respond to almost all foreign materials and form syncytial aggregates to conceal relatively large amounts and large sizes of foreign material; (3) the morphologies of the syncytial aggregates differ from one another depending on the species and the surface configuration of the cellular foreign material; (4) no mesenchyme cells respond to live mesenchyme cells even though they phagocytose chemically fixed cells; (5) mesenchyme cells phagocytose both cellular constituents effluxed from the ectodermal cells and foreign materials taken into the blastocoel through the body wall. Together, these results suggest that mesenchyme cells are equipped with a spectrum of abilities to engage in a defense system in starfish larva.

The scavenger receptor CD36 plays a role in cytokine-induced macrophage fusion

Multinucleated giant cells, characteristic of granulomatous infections, originate from the fusion of macrophages. Using an antibody screening strategy we found that the scavenger receptor CD36 participates in macrophage fusion induced by the cytokines IL-4 and GM-CSF. Our results demonstrate that exposure of phosphatidylserine on the cell surface and lipid recognition by CD36 are required for cytokine-induced fusion of macrophages. We also show that CD36 acts in a heterotypic manner during giant-cell formation and that the formation of osteoclasts is independent of CD36. The discovery of molecules involved in the formation of multinucleated giant cells will enable us to determine their functional significance. Furthermore, our results suggest that lipid capture by cell surface receptors may be a general feature of cell fusion.

Essential role of DAP12 signaling in macrophage programming into a fusion-competent state

Multinucleated giant cells, formed by fusion of macrophages, are a hallmark of granulomatous inflammation. With a genetic approach, we show that signaling through the adaptor protein DAP12 (DNAX activating protein of 12 kD), its associated receptor triggering receptor expressed by myeloid cells 2 (TREM-2), and the downstream protein tyrosine kinase Syk is required for the cytokine-induced formation of giant cells and that overexpression of DAP12 potentiates macrophage fusion. We also present evidence that DAP12 is a general macrophage fusion regulator and is involved in modulating the expression of several macrophage-associated genes, including those encoding known mediators of macrophage fusion, such as DC-STAMP and Cadherin 1. Thus, DAP12 is involved in programming of macrophages through the regulation of gene and protein expression to induce a fusion-competent state.

Carcinogenesis induced by foreign bodies

This review deals with the contemporary investigations of carcinogenesis induced by foreign bodies. The main attention is given to the interactions of macrophages with an implanted foreign body and their possible role in tumorigenesis.

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.

Foreign body-type multinucleated giant cell formation requires protein kinase C beta, delta, and zeta

Multinucleated giant cells are a classic cellular feature of chronic inflammation, although the mechanism of macrophage fusion leading to their formation is not well understood. Here, we investigate the participation of protein kinase C (PKC) in the interleukin (IL)-4-induced fusion of human monocyte-derived macrophages and foreign body giant cell (FBGC) formation in vitro. The PKC inhibitors H-7 and calphostin C attenuated macrophage fusion, whereas H-8, which is more selective for PKA and PKG, did not. Macrophage fusion was also prevented by the phospholipase C inhibitor, Et-18-OCH(3), the PKC isoform inhibitors GO6983 or rottlerin and by peptide inhibitors for PKC (20-28), PKCbeta, or PKCzeta but not by HBDDE or peptide inhibitors for PKCvarepsilon or PKA. In cultures of fusing macrophages/FBGC, we detected only PKCalpha, beta, delta, and zeta by immunoprecipitation and immunoblotting, and we also observed strong expression of these isoforms by immunocytochemistry. Our collective results suggest that the gamma, epsilon, eta, mu, theta, or iota PKC isoforms are not required in the mechanism of IL-4-induced macrophage fusion; whether PKCalpha is required is unclear. However, new evidence is provided that FBGC formation is supported by PKCbeta, PKCdelta, and PKCzeta in combined diacylglycerol-dependent (PKCbeta and PKCdelta) and -independent (PKCzeta) signaling pathways.

The molecular basis of macrophage fusion

Multinucleated giant cells (MGCs), characteristic of granulomatous infections as well as multinucleated osteoclasts originate from fusion of macrophages. While intracellular and viral membrane fusion have been studied in detail, much less is known about the machinery which mediates cell-to-cell fusion, in particular macrophage polykaryon formation. Several molecules have been implicated in this process which may involve the action of multiple glycoproteins mediating membrane attachment and fusion. Macrophage fusion can be induced by soluble mediators such as cytokines and growth factors, even though several other stimuli may be involved, especially for the induction of granuloma-associated giant cells. The function of MGCs during granulomatous diseases is currently unknown. However, a better understanding of the mechanistic basis of macrophage fusion may lead to a better understanding of the function of MGCs found in granulomas.

Macrophage-mediated biodegradation of poly(DL-lactide-co-glycolide) in vitro

Biodegradation of poly-DL-lactide-co-glycolide (PLGA) both in vitro and in vivo has been well documented. However, the roles that macrophages and their fused multinucleated giant cells (MNGCs) play in this biodegradation are still unclear. The current study aimed to investigate macrophage-mediated biodegradation of PLGA thin films and of PLGA composites with hydroxyapatite (HA) and tricalcium phosphate (TCP) ceramic powders in vitro using a murine macrophage cell line (RAW 264.7). The interactions were analyzed by using cell viability assays, scanning electron microscopy, and focused ion beam microscopy. The results showed that RAW 264.7 cells effectively attached and proliferated on the PLGA films and PLGA-HA, PLGA-TCP composites. The RAW 264.7 cells were observed to aggregate and fuse to form MNGCs. The cell processes on the membrane, or pseudopodia, penetrated into the PLGA films and evidently eroded the surface. We conclude that macrophages and fused MNGCs actively respond to PLGA films as substratum and degrade the surface of this polymer.

Multinucleate cells (MNC) as sensitive semiquantitative biomarkers of the toxic effect after experimental fibrous dust and cigarette smoke inhalation by rats

Changes in the counts of binucleate (BNC) and multinucleate cells (MNC) in cell mixtures from lung tissue and bronchoalveolar lavage fluid (BALF) as well as in proportions of four types of BALF cells: Alveolar macrophages (AM), lymphocytes, polymorphonuclears (PMN), BNC and in total BALF protein were followed in a study comparing the toxicity of wollastonite with that of amosite asbestos in Fischer 344 rats. Both of the fibrous dusts were inhaled every second day at 30 or 60 mg/m3 air combined with daily exposure to cigarette smoke at 30 mg of total particulate matter (TPM)/m3 air for 1 h. The exposures lasted 175 days. Both, proportions of BNC as well as of MNC in lung cell mixtures rose significantly after exposure to cigarette smoke only. After inhalation of wollastonite the BNC proportions in all except the lower dust exposure group compared to controls showed a significant rise with the maximal factor value of 2.1 in the higher dust plus smoke exposure group. Wollastonite caused only marginal changes in MNC and other inflammation parameters. After inhalation of amosite at comparing to controls the proportion of BNC rose 8 times in the 30 mg/m3 and 11 times in the 60 mg/m3 exposure group, respectively. The effect of smoking was additive. The proportions of MNC were 39 times higher in the 30 mg/m3 and 41 times higher in the 60 mg/m3 amosite exposure group than in controls. In the higher exposure group the effect of smoking was synergic in that the MNC proportion rose about 58 times over control values from 0.05% up to about 3.0% (99% confidence interval--CI = 2.7-3.3%). The other followed inflammation parameters showed the presence of inflammation in the lung. It could be concluded that wollastonite at the same inhalation exposure concentration caused in rats less toxic effects than amosite, and, that the number of MNC, as well as BNC in lung cell mixtures and in BALF may serve as an important semiquantitative biomarker of inflammation.

B-1 cells are pivotal for in vivo inflammatory giant cell formation

The mechanisms that govern giant cell (GC) formation in inflammatory, neoplastic and physiologic conditions are far from being understood. Here, we demonstrate that B-1 cells are essential for foreign-body GC formation in the mouse. GCs were analysed on the surface of glass cover slips implanted into the subcutaneous tissue of the animals. It was demonstrated that GCs are almost absent on cover slips implanted into the subcutaneous tissue of BALB/c or CBA/N X-linked immunodeficient mice. As these animals do not have B-1 cells in the peritoneal cavity, they were reconstituted with B-1 cells obtained from cultures of adherent mouse peritoneal cells. Results showed that in B-1-reconstituted animals, the number of GCs on the implant surface surpassed the values obtained with preparations from wild animals. In animals selectively irradiated (pleural and peritoneal cavities) to deplete these cavities of B-1 cells, GCs were also not formed. Enriched suspensions of B-1 cells grown in culture were labelled with [(3)H]-tymidine and injected into the peritoneal cavity of naive mice before implantation of glass cover slips. After 4 days, about 17% of mononuclear cells had their nuclei labelled, and almost 70% of GCs had one or more of their nuclei labelled when analysed by histoautoradiographic technique. A few GCs expressed an immunoglobulin M when analysed by immunostaining and confocal microscopy. Overall, these data demonstrate that B-1 cells are pivotal in the mechanisms of foreign-body GC formation in the mouse.

Spontaneous cell transformation: karyoplasts derived from multinucleated cells produce new cell growth in senescent human epithelial cell cultures

Previously, it was shown that SV40-induced cell transformation of human diploid (2N), epithelial cells was a dynamic process of nuclear and cellular events. In this process, nuclei of polyploid (above 2N) cells broke down into multinucleated cells (MNCs) by amitotic division. An induced mass karyoplast (i.e., small cell with reduced amount of cytoplasm) budding process from the MNCs produced transformed cells with extended life span (EL) and altered morphology. In this study, without the use of SV40 and no induction of karyoplast budding, the same sequence of cellular events was found to occur spontaneously for the same type of cells at replicative senescence (no mitosis). These cell transformation events were followed by phase-contrast photography of living cell cultures. Primary, diploid, epithelial cell cultures grew for two to three passages and then entered senescence. Cells remaining in the cultures after widespread cell death (mortality stage 1; M1) developed the typical large, flat-cell morphology of senescence with increased cytoplasmic volume. Some of these cells were MNCs, mostly with two to four nuclei. Cytokinesis in MNCs and spontaneous karyoplast budding from MNCs were observed, and new, limited EL cell growth was present either in foci of cells or as prolonged cell growth over one to two passages. At the end of their replicative phase, the EL cells entered another death crisis (M2) from which no cells survived. In M2-crisis, rarely transformed cells appear with immortal cell growth characteristics (i.e., cell lines). Numerous examples of fragmentation or amitosis of polyploid nuclei in the production of multinucleated cells (MNCs) are presented. Such nuclear divisions produced nuclei with unequal sizes, which suggest unbalanced chromosomal segregations. The nuclear and cellular events in cell transformation are compared with a natural (no induction) occurrence of MNC-offspring cells in mammalian placentas. The possibility of a connection between these two processes is discussed. And finally the difference in the duration of EL cell growth from SV40-MNCs versus from senescent-MNCs is ascribed to increased mutational load in SV40-induced MNCs as compared with that in senescence MNCs.

Effects of adsorbed proteins and surface chemistry on foreign body giant cell formation, tumor necrosis factor alpha release and procoagulant activity of monocytes

The adhesion and activation of monocytes and macrophages are thought to affect the foreign body response to implanted medical devices. However, these cells interact with devices indirectly, because of the prior adsorption of proteins. Therefore, we preadsorbed several "model" biomaterial surfaces with proteins and then measured foreign body giant cell (FBGC) formation, tumor necrosis factor alpha (TNFalpha) release, and procoagulant activity. The model surfaces were tissue culture polystyrene (TCPS), untreated polystyrene (PS), and Primaria, whereas the proteins used were albumin, fibronectin, fibrinogen, and immunoglobulin. FBGC formation, TNFalpha release, and procoagulant activity of monocytes were the highest for surfaces preadsorbed with IgG. FBGC formation was lower on surfaces with adsorbed fibrinogen and fibronectin than on uncoated surfaces. TNFalpha release and procoagulant activity of monocytes were similar on surface adsorbed with fibrinogen, fibronectin, or albumin. Monocyte activation was also affected by the surface chemistry of the substrates, because FBGC formation was the highest on PS and the lowest on TCPS. Monocyte procoagulant activity was the highest on Primaria. Adsorbed proteins and surface chemistry were found to have strong effects on FBGC formation, monocyte TNFalpha release, and procoagulant activity in vitro, providing support for the idea that these same variables could affect macrophage-mediated foreign body response to biomaterials in vivo.

Synthesis and degradation of sodium iron phosphate glasses and theirin vitro cell response

The degradation profiles of six sodium iron phosphate glass formulations have been investigated using simple dissolution trials in deionized water. The glasses were produced from the appropriate phosphate salts by melting at 1200 degrees C in 5% Au/95% Pt crucibles. Dissolution rates varied from 0.2 gcm(-2)h(-1) for the 1% Fe glass to essentially zero over the 6-week test period for the 15% Fe and 20% Fe glasses. The overall degradation rate was found to vary according to the approximate relation: rate = 1.3e(-0.79x) gcm(-2)h(-1), where x is the percentage iron content of the glass. Glasses with 10% or greater iron content were observed to maintain a constant density over the course of the tests and thus appeared to degrade from the surface and not the bulk. In vitro cell response tests were conducted on the glasses using macrophages and primary craniofacial osteoblasts. These tests were performed on the glasses with 10% or greater iron content because glasses with lower iron content degraded too quickly. Confocal microscopy revealed a rounded macrophage morphology and IL-1beta production was low, suggesting little macrophage activation. However, a significant level of peroxide production was observed. Osteoblasts were observed to attach to the glass surfaces and spread, exhibiting a similar cytosketetal organization to the cells on the Thermanox controls, with a high level of F-actin organization. On balance, the 15% Fe glass performed slightly better than the 20% Fe glass in these assays.

Controlled degradation and macrophage responses of a fluoride-treated polycaprolactone

We have developed a new bone replacement material based on polycaprolactone (PCL), which can act as a suitable matrix for monomer transfer molding of degradable composites. A boron trifluoride catalyst with glycerol additive was used to produce PCL with a degradation rate that can be altered by treatment with fluoride ions. The effect of cations on the degradation of the polymer and macrophage cell responses are discussed. We found that treatment with fluoride ions reduced the degradation rate. No significant difference between these three fluorides was observed although a general trend was seen where KF-treated PCL appeared to degrade slower than NaF-treated PCL which was slower than NH(4)F-treated PCL. Variation in solubilities of the salts was observed where the K(+) cation had the highest solubility and the Na(+) cation had the lowest solubility, which suggests that NaF was able to degrade the polymer more efficiently than the other fluorides. No significant macrophage activation was observed after culture on the polymer surfaces as determined by peroxide and IL-1 beta release, whereas some activation occurred after culture in degradation products.

Inhibition of monocyte adhesion and fibrinogen adsorption on glow discharge plasma deposited tetraethylene glycol dimethyl ether

Monocytes and macrophages play important roles in host responses to implanted biomedical devices. Monocyte and macrophage interactions with biomaterial surfaces are thought to be mediated by adsorbed adhesive proteins such as fibrinogen and fibronectin. Non-fouling surfaces that minimize protein adsorption may therefore minimize monocyte adhesion, activation, and the foreign body response. Radio-frequency glow discharge plasma deposition (RF-GDPD) of tetraethylene glycol dimethyl ether (tetraglyme) was used to produce polyethylene oxide (PEO)-like coatings on a fluorinated ethylene-propylene (FEP) surface. Electron spectroscopy for chemical analysis (ESCA) and static time of flight secondary ion mass spectrometry (ToF-SIMS) were used to characterize the surface chemistry of tetraglyme coating. Fibrinogen adsorption to the tetraglyme surface was measured with 125I-labeled fibrinogen and ToF-SIMS. Adsorption of fibrinogen to plasma deposited tetraglyme was less than 10 ng cm(-2), a 20-fold decrease compared to untreated FEP or tissue culture polystyrene (TCPS). Monocyte adhesion to plasma deposited tetraglyme was significantly lower than adhesion to FEP or TCPS. In addition, when the surfaces were preadsorbed with fibrinogen, fibronectin, or blood plasma, monocyte adhesion to plasma deposited tetraglyme after 2 h or 1 day was much lower than adhesion to FEP. RF-GDPD tetraglyme coating provides a promising approach to make non-fouling biomaterials that can inhibit non-specific material-host interactions and reduce the foreign body response.

Synthesis, degradation, and in vitro cell responses of sodium phosphate glasses for craniofacial bone repair

This report outlines the initial synthesis, degradation, and short-term biocompatibility of sodium phosphate glasses, for use in the drawing of fibers and manufacture of biodegradable composites. Biocompatibility studies were performed using a macrophage cell line and primary human craniofacial osteoblasts. Sodium hydrogen phosphate and sodium dihydrogen phosphate glass synthesized for less than 1 h, resulted in a higher degradation rate than glass synthesized for 3 h or more (0.015 mg cm(-2) h(-1)). Glasses with high and low ratios of hydrogen phosphate to dihydrogen phosphate had very similar degradation rates. A condensation route for the formation of the glass should give rise to varying degradation rates with varying ratios of starting materials. It is suggested that the degradation rate of the glass is independent of the concentrations of the initial reagents and that ring-opening polymerization, which reaches an equilibrium state, occurs. Biocompatibility studies suggest minimal macrophage activation (low levels of peroxide and interleukin-1beta release and rounded morphology) and high osteoblast biocompatibility. The ultimate aim of our studies is to produce a biocompatible soluble phosphate glass that can be drawn into fibers for incorporation into a polycaprolactone matrix for craniofacial bone repair. This report demonstrates the successful production of a soluble glass, which is biocompatible with regard to osteoblasts and macrophages. Recent data from our laboratory have demonstrated successful fiber drawing and production of a novel polycaprolactone.

Beta1 and beta2 integrins mediate adhesion during macrophage fusion and multinucleated foreign body giant cell formation

An in vitro system of interleukin (IL)-4-induced human monocyte-derived macrophage fusion was used to investigate the cell/substrate adhesive mechanisms that support multinucleated foreign body giant cell (FBGC) formation. Monocytes were cultured for 3 days and IL-4 was added to induce macrophage fusion and FBGC formation by day 7. Functionally defined anti-integrin antibodies demonstrated that initial monocyte adhesion is mediated by beta2 integrins, whereas during the induction of macrophage fusion by IL-4, an additional dependence on beta1 integrins is acquired. The combination of anti-beta1 plus anti-beta2 was most effective, reducing macrophage/FBGC adhesion to 10% of controls. Consistent with integrin-mediated signaling, the tyrosine kinase inhibitor genistein and the phosphatidylinositol-3-kinase inhibitors wortmannin and LY294002 also attenuated macrophage/FBGC adhesion. Confocal microscopic analysis revealed that beta2 integrins are present on monocytes after initial adhesion and are strongly expressed on fusing macrophages, particularly in peripheral cell areas, and on FBGCs. In contrast, beta1 integrins are not detected on monocytes but begin to appear during macrophage development and are strongly expressed on fusing macrophages and FBGCs. For the first time, these results demonstrate the IL-4-induced acquisition of cooperation between beta1 and beta2 integrins in the cell/substrate adhesive interactions that are required for multinucleated FBGC formation.

IL-4, but not vitamin D(3), induces monoblastic cell line UG3 to differentiate into multinucleated giant cells on osteoclast lineage

The formation of multinucleated giant cells (MGCs) from monocytes/macrophages is controlled by various cytokines, the roles of which are not fully understood. Both interleukin (IL)-4 and 1alpha,25(OH)(2) vitamin D(3) (D(3)) are known to induce MGC formation from monocytes/macrophages. D(3) is also known as a stimulator of osteoclast formation in the presence of stroma cells, and IL-4 as an inhibitor. Previously, we showed that IL-4-induced MGCs from monocytes/macrophages expressed tartrate resistant acid phosphatase (TRAP) activity and hydroxyapatite-resorptive activity in the presence of M-CSF without stroma cells. In this study, we examined the effects of D(3) and/or IL-4 on MGC formation and the characteristics of these MGCs using a monoblastic cell line (UG3), to elucidate the involvement of these factors in osteoclast development without stroma cells. D(3)-induced MGCs showed none of the markers of osteoclasts, such as TRAP activity, calcitonin receptor (cal-R) expression, hydroxyapatite-resorptive activity, and bone-resorptive activity. A low concentration of D(3) synergistically stimulated IL-4-induced TRAP-positive MGC formation, whereas a high concentration of D(3) inhibited it. When IL-4 was added on day 7 of the 2-week culture with D(3), TRAP positivity reached maximum. On the other hand, delayed addition of D(3) on day 7 of culture did not increase the TRAP positivity. Although the fusion rate increased during the first week of the 2-week culture in the presence of D(3), it increased further in the second week following the addition of IL-4 on day 7. Furthermore, IL-4-induced, or IL-4- and D(3)-induced MGCs differentiated into functional osteoclasts with bone-resorptive activity following coculture with osteoblastic cells, whereas D(3)-induced MGCs did not acquire bone-resorptive activity even after coculture with osteoblastic cells in the presence of D(3). These findings suggest that IL-4 initiates osteoclast development of UG3 cells, although stroma cells were necessary for development of functional osteoclasts. On the other hand, D(3) had only a "supportive" effect on this differentiation. IL-4 and direct contact with stroma cells may regulate different stages in the multistep process of osteoclastogenesis of UG3 cells.

Alloplastic implantation

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Define an alloplastic material and know the differences between an alloplast and other types of implants available for surgical use. 2. Determine the biologic response to alloplastic implantation and the material and host characteristics that contribute to long-term reconstruction success with their use. 3. Review the criteria for choosing a specific alloplastic material for a reconstruction site and the principles of surgical technique for its proper placement. 4. Evaluate the various alloplastic material types that are currently available for surgical use and be able to discuss several physical properties of each as they relate to handling and clinical implantation. 5. Discuss the complication of alloplastic infection, its pathogenesis, preoperative and intraoperative measures for its avoidance, and the postoperative management of its occurrence.

Disruption of filamentous actin inhibits human macrophage fusion

The foreign body reaction to implanted biomaterials, characterized by the presence of macrophages and foreign body giant cells (FBGC), can result in structural and functional failure of the implant. Recently, we have shown that interleukin-4 and interleukin-13 can independently induce human macrophage fusion to form FBGC via a macrophage mannose receptor (MR) -mediated pathway. The MR is believed to mediate both endocytosis of glycoproteins and phagocytosis of microorganisms, which bear terminal mannose, fucose, N-acetylglucosamine, or glucose residues. Polarization of microfilaments to closely apposed macrophage membranes as observed with fluorescence confocal microscopy led us to ask whether MR-mediated fusion occurred via a filamentous actin-dependent pathway. Cytochalasins B and D and latrunculin-A, agents that disrupt microfilaments, inhibited macrophage fusion in a concentration-dependent manner. The concentrations of cytochalasins D and B that inhibited fusion did not significantly decrease macrophage adhesion, spreading, or motility but did inhibit internalization of Candida albicans during interleukin-13-enhanced, MR-mediated phagocytosis. Very low concentrations of cytochalasin B (< 2 microM) induced a slight enhancement of macrophage fusion. Taken together, the results of this study suggest that cytokine-induced, MR-mediated macrophage fusion requires an intact F-actin cytoskeleton and that the mechanism of fusion is similar to phagocytosis.--DeFife, K. M., Jenney, C. R., Colton, E., Anderson, J. M. Disruption of filamentous actin inhibits human macrophage fusion.

Cytoskeletal and adhesive structural polarizations accompany IL-13-induced human macrophage fusion

During the inflammatory response to an implanted biomaterial, monocytes undergo a striking phenotypic progression of differentiation into macrophages, which may subsequently fuse to form foreign body giant cells (FBGCs). Taking advantage of an in vitro system of cytokine-induced FBGC formation together with the optical slicing capabilities of a confocal microscope, we investigated the cytoskeletal reorganization and adhesive structure development during this dramatic morphological progression. Human monocytes demonstrated diffuse cytoplasmic staining of adhesive structural proteins. Punctate filamentous (F)-actin structures appeared along the ventral cell membrane of macrophages and were identified as the core of podosome adhesive structures by the distinctive ring staining of vinculin, talin, and paxillin around the F-actin. Cytokine-induced FBGCs were characterized by a restriction of podosomes to the extreme periphery of the ventral cell surface. Although macrophages and FBGC contained equivalent amounts of F-actin, significantly more F-actin was located within 1 micron of the ventral plasma membrane in FBGCs compared to macrophages. Taken together, these results provide new information on the dynamic cytoskeletal reorganization and adhesive structure development that occur during phenotypic progression from human monocytes to macrophages to FBGC. Furthermore, they suggest the acquisition of functional specializations on FBGC formation, which may enhance our understanding of chronic inflammatory processes.

IL-13 as well as IL-4 induces monocytes/macrophages and a monoblastic cell line (UG3) to differentiate into multinucleated giant cells in the presence of M-CSF

The formation of multinucleated giant cells (MGCs) from monocytes/macrophages is controlled by various cytokines whose crucial roles are not fully understood. In this study, we found that interleukin (IL)-13 as well as IL-4 induced peripheral blood monocytes (PBMs) and monoblastic cell line, UG3, to differentiate into MGCs in the presence of macrophage colony-stimulating factor (M-CSF), while IL-2, IL-7 or IL-10 did not. The presence of M-CSF was essential to this MGC formation, because IL-3 or granulocyte-macrophage colony-stimulating factor (GM-CSF) could not replace M-CSF. IL-4 and IL-13 have been known to inhibit the formation of osteoclast-like cells in the presence of stroma cells or osteoblastic cells. But in our system without stroma cells, IL-4 or IL-13 induced some of characteristics of osteoclasts such as tartrate-resistant acid phosphatase (TRAP) activity, vitronectin receptor (vit-R) expression and resorptive activity for hydroxyapatite, but not the expression of receptors for parathyroid hormone or calcitonin. These results suggest possible involvement of IL-4 and IL-13 in MGCs and osteoclasts development, and UG3 may be useful to further investigate the roles of IL-4 and IL-13 in the formation and physiology of MGCs, and the relationship between these MGCs and osteoclasts.

Inhibition of the tissue reaction to a biodegradable biomaterial by monoclonal antibodies to IFN-gamma

Biomaterials are increasingly used for clinical applications. However, loss of function may occur owing to tissue reactions, which are mainly caused by a variety of inflammatory reactions. Recently, we demonstrated that macrophages (MO) and T cells play key roles in these reactions. Since immunological studies showed that the T cell-derived cytokine interferon-gamma (IFN-gamma) activates MO, the aim of this study was to investigate the possibility of modulating tissue reactions to biodegradable biomaterials by inactivating IFN-gamma. Dermal sheep collagen (DSC) was used as a test biomaterial. DSC impregnated with anti-IFN-gamma or phosphate-buffered saline (control) was implanted in rats. The results showed that cellular ingrowth and formation and function of giant cells were strongly delayed by anti-IFN-gamma. Also, MHC class II expression was strongly inhibited. In the treated DSC, some huge giant cells were formed at the interface but association with the DSC bundles did not occur. Finally, in both the control and treated DSC, T cells and NK cells were rarely detected. This study demonstrates that IFN-gamma plays an important role in the inflammatory reaction to biomaterials. This reaction can be modulated by anti-IFN-gamma, which warrants further studies of anti-IFN-gamma for clinical application to prevent unwanted tissue reactions to biomaterials.

Selective expansion and continuous culture of macrophages from adult pig blood

Macrophages were selectively expanded and continuously cultured from adult pig blood. One-half ml of heparinized adult pig blood was inoculated directly into the medium overlaying a feeder layer of STO mouse fibroblasts. After attachment to the feeder cells for 24 h, the culture was washed several times with the medium to remove most of any unattached blood cells and re-fed. Approximately 7 x 10(4) blood monocytes were initially detected and enumerated by specific binding of DiI-labeled acetylated low density lipoprotein (DiI-Ac-LDL). Macrophage outgrowths appeared in the primary culture after 6-7 days. The macrophages grew to relatively high density in 2-3 weeks (2-3 x 10(6) cells/T25 flask), and the culture was passaged on to fresh STO feeder layers to begin secondary culture. Over 2-3 months of culture the macrophage replication produced as many as 1.4 x 10(9) DiI-Ac-LDL-positive cells. The macrophages grew on top of the feeder cells in two forms: either a semi-attached, round morphology, or a closely adherent, flat ameboid morphology with several extended pseudopods. Electron microscopic examination revealed the cells to be uniformly of macrophage character and that 4-5% were giant cells. The macrophages were phagocytic and expressed CD14 on their surfaces. They also reacted positively with pig macrophage-specific monoclonal antibody (mAb), and were negative for reactivity with pig T- and B-cell-specific mAb. This simple method for isolating and propagating macrophages may indicate the replicative capacity of either adult pig blood monocytes or circulating blood stem cells, and it may be useful in providing macrophages for general research, virological assay, adoptive-immunotherapy models, and somatic gene therapy models.

Continuous cultures of macrophages derived from the 8-day epiblast of the pig

Secondary macrophage cell cultures were generated from the primary culture of epiblasts of 8-d-old pig blastocysts. The epiblast-derived macrophagelike (EDM) cells have a morphology and ameboid behavior that is typical of tissue histocytes. The cells reacted positively with monoclonal antibodies specific for pig granulocyte-macrophage lineage cells, and were not reactive with monoclonal antibodies specific for pig B and T lymphocytes. Marked phagocytic behavior and the formation of phagosomes were demonstrated following incubation with FITC-labeled bacteria. The EDM cells stained positively for nonspecific acid esterase that was not inhibited by sodium fluoride. DiI-acetylated-LDL was rapidly taken up by the cells. Transmission electron microscopy of the EDM cells showed phagolysosomes, numerous cytoplasmic vacuoles, large, lobed nuclei, and numerous pseudopods or filopodia at the cell surface. Strong reactivity of the cells with anti-CD14 monoclonal antibody was observed. Further, cytotoxic activity was produced from the EDM cells after exposure to lipopolysaccharide in a concentration and time-dependent manner. The cultures could be maintained and expanded for several months on STO co-culture. Their derivation from the epiblast of the pig demonstrates the possibility of obtaining hemopoietic cell cultures from the preimplantation blastocysts of all mammals.

Are retroviruses involved in the aetiology of human breast cancer?

To further investigate the possibility for retroviral involvement in the etiology of human breast cancer we processed peripheral blood monocytes and malignant breast tissue biopsies from 10 patients with breast cancer (infiltrating ductal carcinoma or infiltrating lobular carcinoma; ages 40-80 years) and 20 normal healthy women (with no evidence or family history of breast cancer. 10 age-matched controls and 10 women age 22-27 years) for the assay of the retroviral enzyme, reverse transcriptase, using an ELISA and for election microscopy examination for the detection of retroviral-like particles. Reverse transcriptase activity was detected in 5 out of 10 samples of monocyte culture medium and in 1 out of 10 of malignant tissue biopsies from the patients with breast cancer. In contrast, reverse transcriptase was not detected in the culture medium of the monocytes from any of the control subjects. Electron microscopy did not reveal the presence of any retroviral-like particles in any sample of monocyte culture medium or in any of the malignant or normal breast tissue biopsies. Despite evidence for the presence of reverse transcriptase in a subsample of the monocyte culture medium and breast tissue biopsies from the cohort of breast cancer patients who participated in this study, the role of retroviruses in human breast cancer remains unclear.

Multinucleated giant cells elicited around hydroxyapatite particles implanted in craniotomy defects are not osteoclasts

BACKGROUND

The nature of the multinucleated giant cells (MNGC) elicited in contact with implantable biomaterials is still indecisive.

METHOD

In Wistar rats the MNGC recruited after the implantation of hydroxyapatite (HA) particles in standardized skull defects were examined morphologically (at both the light and electron microscope levels), enzymatically (tartrate-resistant acid phosphatase and non-specific esterase), and after a challenge with salmon calcitonin.

RESULTS

The MNGC were of great size and contained abundant mitochondria, vacuoles, and vesicles throughout the cytoplasm; they were either tightly apposed to the HA surface or had long and thin processes penetrating the material. When processed for tartrate-resistant acid phosphatase, only a few cells were weakly stained. The staining was totally suppressed when samples were pretreated with cyanuric chloride in the MNGC but not in the host osteoclasts. Calcitonin induced the withdrawal of the host osteoclasts from the bone surface while the MNGC remained in contact with the HA material.

CONCLUSION

The MNGC recruited to HA particles did not exhibit the morphologic, enzymatic and functional characteristics of the osteoclasts, and consequently must be regarded as macrophage polykaryons.