The differentiation of monocytes into macrophages, epithelioid cells, and multinucleated giant cells in subcutaneous granulomas. II. Peroxidatic activity

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.

Monocyte-to-HDL-cholesterol ratio is associated with Ascending Aorta Dilatation in Patients with Bicuspid Aortic Valve

BACKGROUND

The importance of monocyte count-to-HDL-cholesterol ratio (MHR) in cardio- vascular diseases has been shown in various studies. Ascending aortic dilatation (AAD) is a common complication in the patients with bicuspid aortic valve. In this study, we aimed to investigate the relationship between MHR and the presence of aortic dilatation in the patients with bicuspid aortic valve.

METHODS

The study population included totally 347 patients with bicuspid aortic valve.169 patients with aortic dilatation (ascending aorta diameter ≥ 4.0 cm) and 178 patients with no aortic dilatation. Echocardiographic and laboratory measurement was done and compared between groups.

RESULTS

The mean age of the participants was 44.7 ± 15.4 years and average ascending aorta diameter was 3.2 ± 0.3 cm in dilatation negative group and 4.4 ± 0.4 cm in positive group. MHR was significantly increased in in patients with aortic dilatation. MHR and uric acid level was independently associated with the presence of aortic dilatation in the patients with bicuspid aortic valve.

CONCLUSION

We found a significant relationship between MHR and aortic dilatation in the patients with bicuspid aortic valve.

Persistence of Brucella abortus in the Bone Marrow of Infected Mice

Brucellosis is a zoonotic bacterial infection that may persist for long periods causing relapses in antibiotic-treated patients. The ability of Brucella to develop chronic infections is linked to their capacity to invade and replicate within the mononuclear phagocyte system, including the bone marrow (BM). Persistence of Brucella in the BM has been associated with hematological complications such as neutropenia, thrombocytopenia, anemia, and pancytopenia in human patients. In the mouse model, we observed that the number of Brucella abortus in the BM remained constant for up to 168 days of postinfection. This persistence was associated with histopathological changes, accompanied by augmented numbers of BM myeloid GMP progenitors, PMNs, and CD4+ lymphocytes during the acute phase (eight days) of the infection in the BM. Monocytes, PMNs, and GMP cells were identified as the cells harboring Brucella in the BM. We propose that the BM is an essential niche for the bacterium to establish long-lasting infections and that infected PMNs may serve as vehicles for dispersion of Brucella organisms, following the Trojan horse hypothesis. Monocytes are solid candidates for Brucella reservoirs in the BM.

Lens epithelial cell outgrowth and matrix formation on intraocular lenses in rabbit eyes

PURPOSE

To evaluate the presence and distribution of lens epithelial cells (LECs) and extracellular matrix on intraocular lenses (IOLs) implanted in the capsular bag in rabbit eyes.

SETTING

Department of Ophthalmology, Wakayama Medical College, Wakayama, Japan.

METHODS

Five adult albino rabbits had phacoemulsification and IOL implantation in both eyes. Two or 11 months later, the animals were killed by intravenous pentobarbital. The IOLs were removed and observed under scanning and transmission electron microscopy.

RESULTS

In addition to the macrophages and giant cells on the IOLs, all eyes had a monolayer of flattened cells growing out from the residual anterior lens capsule and a fibrous meshwork of extracellular matrix. Unlike those of a macrophagic origin, these cells had no central cytoplasmic elevation of nuclei and few cell surface microvilli and were considered to be proliferating LECs.

CONCLUSION

Lens epithelial cells are involved in the eye's cellular reaction to IOLs and in the formation of extracellular matrix on IOLs. Further study of LEC behavior on IOLs should be done to improve IOL biocompatibility.

Histochemical and electron microscopic characterization of hepatic macrophage subfractions isolated from normal and liposomal muramyl dipeptide treated rats

Subfractions of the hepatic macrophage population, differing in cell size, were isolated from normal rats and rats treated with liposomal muramyl dipeptide (lipMDP) and analyzed histochemically and by ultrastructural peroxidase cytochemistry. The majority of cells in all subfractions of control rats displayed the ultrastructural endogenous peroxidase pattern of resident liver macrophages and showed positive staining with the general macrophage markers nonspecific esterase (NSE) and monoclonal antibody ED1. Heterogeneity in intensity of NSE and ED1 staining was observed among macrophages of different size. Generally, the intensity of NSE and ED1 staining decreased with decreasing cell size. After injection of lipMDP, we observed the appearance of a discrete subpopulation of cells in the liver in addition to the resident macrophages. These cells, containing a nucleus with a characteristic shape, were predominantly recovered in the small-sized fractions and were characterized by an immature ultrastructural macrophage morphology (no or only a few lysosomes and phagosomes) and a lack of ED1 reactivity, NSE, and endogenous peroxidase. We suggest an important role for these cells in lipMDP induced antitumor capacity of the liver.

Uptake, distribution and fate of bacterial lipopolysaccharides in monocytes and macrophages: an ultrastructural and functional correlation

Bacterial lipopolysaccharides (LPS), which are important components of the cell wall of gram-negative bacteria, induce a number of host responses both beneficial and harmful. The present review elucidates the uptake, distribution and functions of LPS in mononuclear phagocytes in an attempt to gain an insight into the mechanisms which control the pathogenesis of LPS mediated septic shock. The unique feature of LPS bilayer structure, the tagged LPS and antibodies to LPS provide means for studying binding, uptake, fate and subcellular distribution of LPS in tissues and cells. LPS bind to monocytes and macrophages by specific interaction via receptors such as scavenger receptors, CD14 and CD18 and by non-specific interactions, and enter the cells via receptor-mediated endocytosis, absorptive pinocytosis, phagocytosis, and diffusion. The ingested LPS are localized in pinocytic vesicles, phagocytic vacuoles, cytoplasm, mitochondria, rough endoplasmic reticulum, Golgi apparatus, and nucleus. The interactions of LPS with monocytes and macrophages trigger a broad spectrum of cellular responses, including production of important bioactive factors or mediators, such as IL-1, TNF, interferons, prostaglandins, and macrophage-derived growth factor, which are implicated in the pathogenesis of septic shock and wound healing. However, there is no conclusive evidence indicating that production of the mediators can only be induced through specific interactions.

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.

Ultrastructural study of the long-term development of two experimental cutaneous calcinoses (topical calciphylaxis and topical calcergy) in the rat

Skin calcification induced by topical calciphylaxis was provoked by a subcutaneous injection of iron chloride in rats previously sensitized by dihydrotachysterol. A cutaneous topical calcergy was induced by an injection of potassium permanganate. An electron-microscopical study of the long-term evolution of both these models of calcification was made. After the initial stages, mineralization of the connective tissue continued by a secondary nucleation process without matrix vesicles. The mineral composed of needle-like structures, apatite in nature, was mainly deposited between and around collagen fibrils, and showed various arrangements in calcified plaques. Intrafibrillar calcification was rarely observed and appeared only in the later stages. The extension of calcified deposits then stopped. Finally, there was a fragmentation of the mineralized area which was progressively surrounded by uncalcified collagen fibrils. A demineralization process, caused by cells such as macrophages and multinucleated giant cells, rather than a resorption of the calcified deposits, was noted. It is important to emphasize that, in both models of ectopic calcification, an evolution toward ectopic ossification was never observed, which is perhaps due to the absence of extensive resorption mechanisms.

Wheat-germ agglutinin binding in four types of mouse peritoneal macrophage

After stimulation of the mouse peritoneal cavity with newborn calf serum (NBCS), four types of monocyte and macrophage were distinguished on the basis of peroxidase (PO) patterns. These cell types showed heterogeneity in their binding of the lectin wheat-germ agglutinin (WGA). At 16 h after stimulation, monocytes and monocyte-derived macrophages (with PO activity in granules) had a high level of WGA binding; PO-negative macrophages showed moderate WGA binding, and resident macrophages (with PO activity in the RER and nuclear envelope) had low WGA binding. At later time-points after stimulation, each of these cell types lost WGA binding sites. This decrease was related to a process of differentiation and to a modulation, affected by environmental factors. The present results also indicated that PO-negative macrophages can give rise to resident macrophages. Whether these PO-negative cells are monocyte derived or originate otherwise needs further investigation. The fourth type of macrophage, the exudate-resident cell (with PO activity both in granules and in the RER and nuclear envelope), with a WGA binding pattern similar to that of monocytes and monocyte-derived macrophages, was considered not to be a resident precursor cell.

Endogenous peroxidase activity in mononuclear phagocytes

The diaminobenzidine (DAB) technique has been used to visualize the subcellular localization of peroxidatic enzymes in mononuclear phagocytes. The latter cells are part of the mononuclear phagocyte system (MPS), which includes the monocytes in the bone marrow and blood, their precursors in the bone marrow, and the resident macrophages in the tissues. The DAB cytochemistry has revealed distinct subcellular distribution patterns of peroxidase in the mononuclear phagocytes. Thus the technique facilitates the identification of the various phagocyte types: Promonocytes contain peroxidase reaction in the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and cytoplasmic granules. Monocytes exhibit the reaction product only in cytoplasmic granules. Most resident macrophages show the activity only in the nuclear envelope and endoplasmic reticulum. Furthermore, new phagocyte types have been detected based on the peroxidase cytochemistry. Intermediate cells between monocytes and resident macrophages contain reaction product in the nuclear envelope, endoplasmic reticulum and cytoplasmic granules. The resident macrophages can be divided into two subtypes. Most of them exhibit the pattern noted above. Some, however, are totally devoid of peroxidase reaction. Most studies on peroxidase cytochemistry of monocytes and macrophages agree that the peroxidase patterns reflect differentiation or maturation stages of one cell line. Some authors, however, still interpret the patterns as invariable characteristics of separate cell lines. As to the function of the peroxidase in phagocytes, the cytochemical findings imply that two different peroxidatic enzymes exist in the latter cells: one peroxidase is synthesized in the endoplasmic reticulum of promonocytes and transported to granules via the Golgi apparatus. The synthesis ceases when the promonocyte matures to the monocyte. Upon phagocytosis the peroxidase is discharged into the phagosomes. Biochemical and functional studies have indicated that this peroxidase (myeloperoxidase) is part of a microbicidal system operating in host defence mechanisms. The other enzyme with peroxidatic activity is confined to the nuclear envelope and endoplasmic reticulum of resident macrophages in-situ and of monocytes at early stages in culture. As suggested by the subcellular distribution, the inhibition by peroxidase blockers, and the localization during phagocytosis studies, the latter peroxidase is functionally different from the myeloperoxidase.(ABSTRACT TRUNCATED AT 400 WORDS)

Endogenous peroxidases in normal human dermis: a marker of fibroblast differentiation

Incubation of unfixed and unfrozen slices of normal human skin allows visualization of a peroxidase activity associated with the perinuclear envelope and with the endoplasmic reticulum of resident dermal macrophages, dermal mastocytes, and also of some dermal fibroblasts. No peroxidase activity can be detected in fibroblasts cultivated in monolayer, while 80% of fibroblasts in an "in vitro" collagen lattice, called a dermal equivalent, express a peroxidase activity in the perinuclear envelope and the endoplasmic reticulum. Hence expression of this peroxidase activity in normal human skin fibroblasts serves as a marker of fibroblast differentiation and seems to depend on an interaction to fibroblast with the elements of a three-dimensional matrix.

Large granular lymphocytes: morphological and functional properties. I. Results in normals

Large granular lymphocytes (LGL) represent a morphologically distinct mononuclear cell type. In healthy individuals an average of 12.5 +/- 5.2% of peripheral mononuclear cells exhibit this morphology. Structurally they are characterized by azurophilic granules, light cell density, low surface adherence and expression of Fc-IgG receptors. Functional analyses on LGL suspensions enriched by means of density gradient fractionation and adherence procedures included testing of T-cell and monocyte-specific in vitro reactions as well as evaluation of their natural cytotoxicity (NC). Results indicated a close correlation between the percentages of LGL and the capacity to bind and to lyse NC-susceptible tumor targets. In agreement with others we would thus conclude that LGL embrace the majority of NK-effector cells. The morphological definition of LGL provides an additional tool for the clinical evaluation of this cell mediated immune reactivity.

Large granular lymphocytes: morphological studies

Large granular lymphocytes from normal human blood were enriched by centrifugation on discontinuous Percoll density gradients. Their capacity for natural killing, but not for phagocytosis of yeast cells, was demonstrated. Large granular lymphocytes are characterized in electron microscopy by their fine structure, especially by typical granules and by inclusions of tubular structures in a parallel array. Their lymphocyte nature is supported by activity of acid-alpha-naphthyl acetate esterase and by the absence of myelo-peroxidase (POX) and of macrophage POX. The Fc gamma receptor of their cell membrane is marked by soluble POX-anti-POX-complexes; labeled parts of their membrane are not incorporated into the cytoplasm as in monocytes.

Heterogeneity of concanavalin A binding by mouse peritoneal macrophages

The binding of the lectin concanavalin A (Con A) to the cell surface of monocytes and macrophages collected from the stimulated peritoneal cavity of mice was investigated electron microscopically with horseradish peroxidase-gold as an indirect marker. Individual cells were identified by the cytochemical localization of peroxidatic (PO) activity. In monocytes and monocyte-derived macrophages with PO activity in cytoplasmic granules, the degree of Con A binding was lower than in resident macrophages with PO activity in the rough endoplasmic reticulum and nuclear envelope. An even higher degree of Con A labelling was found on the surface of cells devoid of PO activity. Since the above-mentioned cell populations show a different degree of lectin binding, it is suggested that lectin labelling methods might offer a new tool for quantitative investigation of the differentiation of monocytes and resident macrophages.

Ultrastructural findings in Hashimoto's thyroiditis and focal lymphocytic thyroiditis with reference to giant cell formation

Ultrastructural findings in two cases of Hashimoto's disease and two cases of focal lymphocytic thyroiditis are reported. Stimulated thyrocytes, oncocytes and degenerating thyrocytes were observed in all cases. Multinucleated thyrocytes and epithelial pseudogiant cells were identified in Hashimoto's disease only. Infiltrating lymphocytes, plasma cells, monocytes and macrophages were present in all cases. The ultrastructure of germinal centres was similar to that seen in lymphatic organs. Giant cells of both intra- and extrafollicular localization were seen in Hashimoto's disease. Most of the giant cells were macrophage-derived. Two different ways of giant cell formation were identified: besides the familiar dissolution of plasma membranes of adjacent macrophages, another mechanism of fusion was observed. At sites of contact, peculiar membrane structures were developed and disintegration of plasma membranes occurred in parts adjacent to these structures. These are not identical to desmosomes and are different from Langerhans' granules. They probably represent special organelles for the initiation of cellular fusion.

Characterization of cells involved in the formation of granuloma. An ultrastructural study on macrophages, epitheloid cells, and giant cells in experimental tubulo-interstitial nephritis

In experimental tubulo-interstitial (anti-basement membrane) nephritis of the rat, granulomatous inflammation develops around immunologically altered tubular basement membranes. The present light- and electron microscopic studies indicate that in the course of the granulomatous reaction, tissue monocytes evolve from blood monocytes and pursue two independent pathways of differentation. On the one hand they may differentiate into macrophages ("distant from tubules") or, alternatively, into epitheloid cells ("adjacent to tubules"). The latter, through cell fusion, develop into multinucleated giant cells of the Langhans' type. The cytoplasmic components of the epitheloid cells and the multinucleated giant cells should be interpreted as an activation of cellular biosynthesis. Its products, upon being secreted at the immunodefective basement membrane, will obviously serve immune defense mechanisms.

Heterogeneity in wheat germ agglutinin binding by mouse peritoneal macrophages

The binding of the lectin wheat germ agglutinin (WGA) to the cell surface of monocytes and macrophages obtained from the stimulated peritoneal cavity of mice was investigated electron microscopically, using ovomucoid-gold as an indirect marker. Resident (tissue) macrophages, identified by the presence of PO activity in the rough endoplasmic reticulum as well as in the nuclear envelope, showed low WGA binding, whereas monocytes and monocyte-derived macrophages with PO activity in the granules showed high WGA binding. Since cells devoid of PO activity showed variable WGA binding, the value of this gold-WGA-binding technique for discrimination on a quantitative basis between resident macrophages and monocytes or monocyte-derived macrophages, is discussed.

The differentiation of monocytes into macrophages, epithelioid cells, and multinucleated giant cells in subcutaneous granulomas. I. Fine structure

The morphological changes occurring in monocytes during their differentiation into macrophages, epithelioid cells, Langhans-type giant cells, and foreign-body-type giant cells were investigated in foreign-body granulomas induced by subcutaneous implantation of pieces of Melinex plastic. Analysis based on Adams's (1974) criteria for discrimination between the several types of cell of the monocyte line, showed that each type has a characteristic type of granule. Primary and secondary granules, numerous in the Golgi area of monocytes were generally found close to the cell membrane and decreased in number in maturing macrophages. This was accompanied by an increase in the number of microtubules. Mature macrophages show numerous characteristic macrophage granules, which are round (average diameter: 280 nm) and have a halo between the limiting membrane and granular matrix. Mature epithelioid cells have characteristic epithelioid cell granules, and multinucleated giant cells a heterogenous population of granules. Fusing macrophages generally have their Golgi areas facing each other, and also show a reduced thickness of the cell coat. The morphology of the multinucleated giant cell is closely related to the number of nuclei present. In Langhans-type giant cells, which generally have two to ten nuclei, a giant centrosphere with numerous aggregated centrioles is found. In transition forms between Langhans-type and foreign-body-type giant cells, which generally contain 10--30 nuclei, the centrioles show less aggregation. In the foreign-body-type giant cells, which generally have more than 30 nuclei, centrioles are virtually absent and never aggregated. These differences between the Langhans-type giant cells, the foreign-body-type giant cells, and the transition forms, support our previous finding that Langhans-type giant cells are the precursors of foreign-body-type giant cells.