Evidence that multinucleate giant cells are examples of mononuclear phagocytic differentiation

Different Molecular Features of Epithelioid and Giant Cells in Foreign Body Reaction Identified by Single-Cell RNA Sequencing

Although macrophage‒epithelioid cell (EPC)‒giant cell (GC) differentiation is acknowledged in foreign body reaction (FBR), the exact molecular features remain elusive. To discover the molecular profiles of EPC and GC, we analyzed mouse sponge and silk FBRs by integrating single-cell RNA sequencing and spatial sequencing, which identified seven cell types, including macrophages and fibroblasts. Macrophages comprised three subsets with a trajectory from M2-like cell to EPC to GC. They were different in many aspects, including cytokine, extracellular matrix organization/degradation, epithelial modules, and glycolysis that were consistent in both sponge and silk FBRs. EPCs exhibited epithelial modules and extracellular matrix organization, and GCs showed glycolysis, extracellular matrix degradation, and cell fusion signatures. Cellular interactions in GCs and M2-like cells were predicted to be higher than that in EPCs. High expression of inflammation or fusion-related (GPNMB, matrix metalloproteinase 12 gene MMP12, DCSTAMP) and glycolysis-related (PGAM1, ALDOA) genes was identified in GCs of human/mouse tissues, suggesting them as GC-specific markers. Our study identified unique signatures of EPCs and GCs in FBR. Importantly, GCs showed strong glycolysis signatures and cellular interactions, suggesting their activation in FBR. Our data on EPC and GC refinement and GC-specific markers enable the understanding of FBR and help to explore preventive and therapeutic management strategies for skin FBRs.

Degenerative nuclear atypia in pleomorphic adenoma of salivary glands: Histological and immunohistochemical observations

The occurrence and topographical distribution of nuclear changes regarded as degenerative were examined in 84 salivary pleomorphic adenomas (PAs). Haematoxylin and eosin-stained sections from them were light-microscopically studied for unusual variations in size, shape and chromatin pattern of tumour-cell nuclei. Selected cases were further examined by immunohistochemical techniques valuable in characterising cell phenotypes in PA, and cell cycle antigens. A single case (female, 26 years, palate; 1.2 %) showed prominent cells with eosinophilic cytoplasm and variably enlarged or giant, irregularly shaped and occasionally multi-vacuolated nuclei with condensed or stippled chromatin and no mitoses. These cells were variably dyscohesive and did not line lumina; were cytokeratins 5/6, 7 and 14 (+, cytoplasmic), smooth muscle actin (+, cytoplasmic), p63 (+, nuclear), S-100 protein (+, nuclear and cytoplasmic), and WT1 and podoplanin (+/-, cytoplasmic); and did not stain for DOG1, CD63, p16 or Ki67. The nuclear vacuoles were cytokeratin and WT1 (+) - hence, interpreted as cytoplasmic inclusions. Degenerative nuclear atypia in PA seems rare, associated with non-cycling, non-luminal cells of myomatous ('myoepithelial') or schwannomatous phenotype and not related to malignant transformation. The particular phenotype of the affected cells suggests similarities to the degenerative nuclear atypia in pleomorphic leiomyoma and ancient schwannoma.

Intracellular signaling involved in macrophage adhesion and FBGC formation as mediated by ligand-substrate interaction

Fibronectin and RGD- and/or PHSRN-containing oligopeptides were preadsorbed onto physicochemically distinct substrata: polyethyleneglycol-based networks or tissue culture polystyrene (TCPS). The role of selected signaling kinases (namely protein tyrosine kinases, protein serine/threonine kinases, PI3-kinase, Src, and MAPK) in the adhesion of human primary blood-derived macrophages and the formation of foreign-body giant cells (FBGC) on these modified substrata was investigated. The involvement of individual intracellular signaling molecules in mediating macrophage adhesion dynamically varied with the culture time, substrate, and ligand. For example, fibronectin on TCPS or networks involved similar signaling events for macrophage adhesion; however, fibronectin and G(3)RGDG(6)PHSRNG, but not peptides with other RGD and/or PHSRN orientations, mediated similar signaling events for macrophage adhesion on TCPS but mediated different signaling events on networks. Depending on the substrate, a specific molecule (i.e., Src, protein kinase C) within the protein tyrosine kinase or protein serine/threonine kinase family was either an antagonist or agonist in mediating FBGC formation.

Differences in regulation of pH(i) in large (>/=10 nuclei) and small (</=5 nuclei) osteoclasts

Osteoclasts are multinucleated cells that resorb bone by extrusion of protons and proteolytic enzymes. They display marked heterogeneity in cell size, shape, and resorptive activity. Because high resorptive activity in vivo is associated with an increase in the average size of osteoclasts in areas of greater resorption and because of the importance of proton extrusion in resorption, we investigated whether the activity of the bafilomycin A(1)-sensitive vacuolar-type H(+)-ATPase (V-ATPase) and amiloride-sensitive Na(+)/H(+) exchanger differed between large and small osteoclasts. Osteoclasts were obtained from newborn rabbit bones, cultured on glass coverslips, and loaded with the pH-sensitive indicator 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Intracellular pH (pH(i)) was recorded in single osteoclasts by monitoring fluorescence. Large (>/=10 nuclei) and small (</=5 nuclei) osteoclasts differed in that large osteoclasts had a higher basal pH(i), their pH(i) was decreased by bafilomycin A(1) addition or removal of extracellular Na(+), and the realkalinization upon readdition of Na(+) was bafilomycin A(1) sensitive. After acid loading, a subpopulation of large osteoclasts (40%) recovered by V-ATPase activity alone, whereas all small osteoclasts recovered by Na(+)/H(+) exchanger activity. Interestingly, in 60% of the large osteoclasts, pH(i) recovery was mediated by both the Na(+)/H(+) exchanger and V-ATPase activity. Our results show a striking difference between pH(i) regulatory mechanisms of large and small osteoclasts that we hypothesize may be associated with differences in the potential resorptive activity of these cells.

Inflammatory cytokine production by immunological and foreign body multinucleated giant cells

Multinucleated giant cells (MGC) are a common feature of granulomas. The mechanism of their formation has been studied extensively, but their function has not been completely characterized. A new method for the in vivo production of MGC was developed involving subcutaneous injection of microscopic nitrocellulose particles with adsorbed mycobacterial antigens into the footpads of sensitized BALB/c mice (immune [I]-MGC), or by nitrocellulose administration to non-sensitized mice (foreign body [FB]-MGC). The development of granulomas with a highly enriched MGC population was observed 2 weeks after the nitrocellulose injection. MGC were larger with a greater number of nuclei in I-MGC than in FB-MGC. From days 7-28 after nitrocellulose administration, the production of interleukin-1alpha (IL-1alpha) and tumour necrosis factor-alpha (TNF-alpha) was demonstrated in both MGC types by in situ reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. After 2 months, the MGC had ceased production of IL-1alpha and TNF-alpha, but the expression of transforming growth factor-beta (TGF-beta) was very high, occurring together with extensive fibrosis. These results suggest that MGC are an active source of inflammatory cytokines, which can contribute to the initiation, maintenance and down-regulation of granulomatous inflammation induced by immunological and inert substances.

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.

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.

Altered intestinal macrophage phenotype in ovine paratuberculosis

The expression of macrophage surface markers that are likely to be important in antigen presentation and cell interactions was examined in normal sheep and those with clinical paratuberculosis. Immunohistological studies demonstrated that intestinal macrophages in diseased sheep expressed MHC class II, LFA-1 and CR4 antigens weakly compared with normal tissues. Reverse transcriptase-polymerase chain reaction analysis of MHC class II mRNA in intestinal whole tissue samples showed no significant difference between control and diseased groups. A reduction in molecules such as MHC class II and LFA-1 on the surface of infected macrophages could have implications for survival of the intracellular mycobacteria and the persistence of infection.

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.

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.

A quantitative cytochemical investigation of osteoclasts and multinucleate giant cells

Quantitative cytochemical, immunocytochemical, autoradiographic and electron cytochemical investigations have been used to compare osteoclasts with multinucleate giant cells that had been freshly obtained from the same animal. The levels of beta-acid galactosidase activity, the DNA in individual nuclei and the cellular protein content were similar in both cell types. However, osteoclasts generally possessed greater acid phosphatase and NADH dehydrogenase activity but lower levels of fluoride-inhibited non-specific esterase activity than multinucleate giant cells. The acid phosphatase activity in multinucleate giant cells was completely inhibited by 100 mM tartrate, but in osteoclasts only a 20% reduction in activity was observed. Formation of multinucleate giant cells in a "bone microenvironment" (thin bone slices) did not increase their content of tartrate-resistant acid phosphatase activity. Moreover, in osteoclasts, endogenous peroxidase activity was undetectable but present in several granules within the cytoplasm of multinucleate giant cells. Osteoclasts and multinucleate giant cells displayed a similar microtubules distribution, but calcitonin, which induced rearrangement of microtubules and cellular contraction in osteoclasts, had no effect on multinucleate giant cells. Thus, these investigations reveal both similarities and differences between these two syncytia and support the hypothesis that osteoclasts and multinucleate giant cells are related. Possibly osteoclasts arise from monocyte progenitors before commitment to a macrophage lineage has occurred.

Peripheral giant cell granuloma: evidence for osteoclastic differentiation

Nine cases of peripheral giant cell granuloma of the oral cavity have been immunohistochemically analyzed to assess the nature of the giant cells. Giant cells were unreactive when tested with antibodies recognizing myelomonocytic and macrophage markers (lysozyme, MAC 387, HAM 56) but showed strong immunoreactivity with MB1, an antibody reactive with osteoclasts. It is concluded that giant cells characterizing giant cell granuloma exhibit a phenotype distinct from other giant cells found in sites of chronic inflammation and may be true osteoclasts.

Macrophages: current views on their differentiation, structure, and function

Macrophages are large mononuclear phagocytes that represent the major differentiated elements of the mononuclear phagocytic system. They arise from distinct progenitors in the bone marrow, and their immediate precursors, the monocytes, emigrate from the vascular compartment into many tissues and organs where they develop into mature macrophages. The latter display diverse morphological and functional characteristics, depending on the environmental stimuli that they receive. This phenotypic heterogeneity is, therefore, the final consequence of a series of down-regulation of some cellular processes and the up-regulation of others. The kinetics of the production of macrophages and their participation in various physiological and pathological phenomena is the subject of this review.

Macrophages and epithelial cells of the thymus gland. An ultrastructural study in the natterjack, Bufo calamita

In the present study, the ultrastructure of the stromal components, basically epithelial elements and macrophages, of the thymus of adult natterjacks, Bufo calamita has been analyzed. A network of stellate epithelial-reticular cells joined together by desmosomes, constitutes the main component of the thymic parenchyma in both cortex and medulla. In the medulla pale, electron-lucent epithelial cells, sometimes showing surface interdigitations, are striking elements. Moreover, uni- and multicellular epithelial cysts appear in the thymic medulla as well as granulated cells of possible endocrine significance. Remarkably, isolated or grouped gland cells whose morphology and cytoplasmic content resemble that of the skin glands, were occasionally found. Finally, macrophages, multinucleated giant cells and dendritic-like cells, the latter intimately associated to lymphocytes, occur in the thymus of Bufo calamita. The most remarkable morphologic characteristics of all those non-lymphoid cell types, as well as their possible functional significance are comparatively discussed with available information on the amphibian and higher vertebrate thymic cytoarchitecture.

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.

Myelin phagocytosis in Wallerian degeneration. Properties of millipore diffusion chambers and immunohistochemical identification of cell populations

Myelin phagocytosis in Wallerian degeneration was studied using a model of murine sciatic nerve degeneration in millipore diffusion chambers in the peritoneal cavity of host mice. Immunocytological investigations showed the dependence of myelin digestion on the invasion of Fc-positive, Mac-1-positive and partly Ia-positive monocytes. Lymphocytes did not play a prominent role. Compared to Wallerian degeneration in situ, phagocytosis was decreased in nerves enclosed by millipore membranes on both sides of the chamber. The membrane acted as a trap for invading monocytes/macrophages. Neither tissue integrity nor genetic strain influenced the degree of phagocytosis. A modification of the experimental technique is introduced which permits myelin phagocytosis in the peritoneal cavity in a degree comparable to that in Wallerian degeneration in situ.