Formation Of Multinucleated Giant Cells Research Articles

Serglycin induces osteoclastogenesis and promotes tumor growth in giant cell tumor of bone

Giant cell tumor of bone (GCTB) is an aggressive osteolytic bone tumor characterized by the within-tumor presence of osteoclast-like multinucleated giant cells (MGCs), which are induced by the neoplastic stromal cells and lead to extensive bone destruction. However, the underlying mechanism of the pathological process of osteoclastogenesis in GCTB is poorly understood. Here we show that the proteoglycan Serglycin (SRGN) secreted by neoplastic stromal cells plays a crucial role in the formation of MGCs and tumorigenesis in GCTB. Upregulated SRGN expression and secretion are observed in GCTB tumor cells and patients. Stromal-derived SRGN promotes osteoclast differentiation from monocytes. SRGN knockdown in stromal cells inhibits tumor growth and bone destruction in a patient-derived orthotopic xenograft model of mice. Mechanistically SRGN interacts with CD44 on the cell surface of monocytes and thus activates focal adhesion kinase (FAK), leading to osteoclast differentiation. Importantly, blocking CD44 with a neutralizing antibody reduces the number of MGCs and suppresses tumorigenesis in vivo. Overall, our data reveal a mechanism of MGC induction in GCTB and support CD44-targeting approaches for GCTB treatment.

Guanylate-Binding Protein-Dependent Noncanonical Inflammasome Activation Prevents Burkholderia thailandensis-Induced Multinucleated Giant Cell Formation.

ABSTRACTInflammasomes are cytosolic multiprotein signaling complexes that are activated upon pattern recognition receptor-mediated recognition of pathogen-derived ligands or endogenous danger signals. Their assembly activates the downstream inflammatory caspase-1 and caspase-4/5 (human) or caspase-11 (mouse), which induces cytokine release and pyroptotic cell death through the cleavage of the pore-forming effector gasdermin D. Pathogen detection by host cells also results in the production and release of interferons (IFNs), which fine-tune inflammasome-mediated responses. IFN-induced guanylate-binding proteins (GBPs) have been shown to control the activation of the noncanonical inflammasome by recruiting caspase-4 on the surface of cytosolic Gram-negative bacteria and promoting its interaction with lipopolysaccharide (LPS). The Gram-negative opportunistic bacterial pathogen Burkholderia thailandensis infects epithelial cells and macrophages and hijacks the host actin polymerization machinery to spread into neighboring cells. This process causes host cell fusion and the formation of so-called multinucleated giant cells (MNGCs). Caspase-1- and IFN-regulated caspase-11-mediated inflammasome pathways play an important protective role against B. thailandensis in mice, but little is known about the role of IFNs and inflammasomes during B. thailandensis infection of human cells, particularly epithelial cells. Here, we report that IFN-γ priming of human epithelial cells restricts B. thailandensis-induced MNGC formation in a GBP1-dependent manner. Mechanistically, GBP1 does not promote bacteriolysis or impair actin-based bacterial motility but acts by inducing caspase-4-dependent pyroptosis of the infected cell. In addition, we show that IFN-γ priming of human primary macrophages confers a more efficient antimicrobial effect through inflammasome activation, further confirming the important role that interferon signaling plays in restricting Burkholderia replication and spread.

Inhibitory effect of traditional herbal (kampo) medicines on the replication of human parainfluenza virus type 2 in vitro.

Thirteen herbal medicines, Kakkonto (TJ-001), Kakkontokasenkyushin'i (TJ-002), Hangekobokuto (TJ-016), Shoseiryuto (TJ-019), Maoto (TJ-027), Bakumondoto (TJ-029), Hochuekkito (TJ-041), Goshakusan (TJ-063), Kososan (TJ-070), Chikujountanto (TJ-091), Gokoto (TJ-095), Saibokuto (TJ-096), and Ryokankyomishingeninto (TJ-119) were tested for human parainfluenza virus type 2 (hPIV-2) replication. Eight (TJ-001, TJ-002, TJ-019, TJ-029, TJ-041, TJ-063, TJ-095 and TJ-119) out of the thirteen medicines had virus growth inhibitory activity. TJ-001 and TJ-002 inhibited virus release, and largely inhibited genome, mRNA and protein syntheses. TJ-019 slightly inhibited virus release, inhibited gene and mRNA syntheses, and largely inhibited protein synthesis. TJ-029 slightly inhibited virus release, largely inhibited protein synthesis, but gene and mRNA syntheses were unaffected. TJ-041 only slightly inhibited virus release, the gene and mRNA syntheses, but largely inhibited protein synthesis. TJ-091 largely inhibited gene, mRNA and protein syntheses. TJ-095 largely inhibited gene synthesis, but NP and HN mRNAs were slightly detected, and protein syntheses were observed. TJ-119 inhibited gene, mRNA and protein syntheses. TJ-001, TJ-002, TJ-091, TJ-095 and TJ-119 inhibited multinucleated giant cell formation derived from cell-to-cell spreading of virus. However, in TJ-019, TJ-029 and TJ-041 treated infected cells, only small sized fused cells with some nuclei were found. TJ-019 and TJ-041 slightly disrupted actin microfilaments, and TJ-001 and TJ-002 destroyed them. TJ-041 slightly disrupted microtubules, and TJ-001 and TJ-002 disrupted them. In general, the medicines effective on common cold and bronchitis inhibited hPIV-2 replication.

Isolation of Bovine leukemia virus from cows with persistent lymphocytosis in Iraq

This is the first study to report on the isolation of bovine leukemia virus (BLV) from peripheral blood mononuclear cells of two cross bred cows in Iraq. The cattle were seropositive by ELISA when selected while being surveyed for the detection of BLV. Among six cows, two were cases of persistent lymphocytosis (PL). Cytopathology was characterized by the formation of multinucleated giant cells (syncytia) and cytoplasmic vacuoles. Moreover, the viruses produced clear plaques on the monolayer of the primary fetal calf kidney (FCK) cells. Inhibition of plaque formation by BLV-antisera suggested a diagnosis of BLV, which was further confirmed by PCR. Cells infected with the isolates were positive to a monoclonal antibody against the viral gp51 trans-membrane glycoprotein by immunocytochemistry. Both isolates replicated and induced cytopathic effects in bovine and human cell line cultures. Phylogenetic analysis based on partial gp51 env gene sequences revealed that Iraqi strain highly homogenous with Turkey strain (100%) and had 1% distance value with other world strains. In conclusion, this present study found that BLV-infected cattle with PL can be a source for viral isolation, and the cytopathological features of the virus infection are arranged and differ depending on the cell type. This is the first study to report on the isolation of the EBL virus in Iraq, and it provides the basis for further studies about a BLV Iraqi strain that can help control this disease.

Novel cetacean morbillivirus in a rare Fraser\u2019s dolphin (Lagenodelphis hosei) stranding from Maui, Hawai\u2018i

Cetacean morbillivirus (CeMV) is a global threat to cetaceans. We report a novel morbillivirus from a Fraser’s dolphin (Lagenodelphis hosei) that stranded in Maui, Hawaii in 2018 that is dissimilar to the beaked whale morbillivirus previously identified from Hawaii and to other CeMV strains. Histopathological findings included intranuclear inclusions in bile duct epithelium, lymphoid depletion, rare syncytial cells and non-suppurative meningitis. Cerebellum and lung tissue homogenates were inoculated onto Vero.DogSLAMtag cells for virus isolation and cytopathic effects were observed, resulting in the formation of multinucleated giant cells (i.e., syncytia). Transmission electron microscopy of infected cell cultures also revealed syncytial cells with intracytoplasmic and intranuclear inclusions of viral nucleocapsids, consistent with the ultrastructure of a morbillivirus. Samples of the cerebellum, lung, liver, spleen and lymph nodes were positive for morbillivirus using a reverse transcription-polymerase chain reaction. The resulting 559 bp L gene sequence had the highest nucleotide identity (77.3%) to porpoise morbillivirus from Northern Ireland and the Netherlands. The resulting 248 bp P gene had the highest nucleotide identity to porpoise morbillivirus in Northern Ireland and the Netherlands and to a stranded Guiana dolphin (Sotalia guianensis) in Brazil (66.9%). As Fraser’s dolphins are a pelagic species that infrequently strand, a novel strain of CeMV may be circulating in the central Pacific that could have additional population impacts through transmission to other small island-associated cetacean species.

Peptide Inhibitor of Complement C1, RLS-0071, Reduces Zosteriform Spread of Herpes Simplex Virus Type 1 Skin Infection and Promotes Survival in Infected Mice.

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen primarily transmitted through skin-to-skin contact, especially on and around mucosal surfaces where there is contact with contaminated saliva during periods of viral shedding. It is estimated that 90% of adults worldwide have HSV-1 antibodies. Cutaneous HSV-1 infections are characterized by a sensation of tingling or numbness at the initial infection site followed by an eruption of vesicles and then painful ulcers with crusting. These symptoms can take ten days to several weeks to heal, leading to significant morbidity. Histologically, infections cause ballooning degeneration of keratinocytes and formation of multinucleated giant cells, ultimately resulting in a localized immune response. Commonly prescribed treatments against HSV-1 infections are nucleoside analogs, such as acyclovir (ACV). However, the emergence of ACV-resistant HSV (ACVR-HSV) clinical isolates has created an urgent need for the development of compounds to control symptoms of cutaneous infections. RLS-0071, also known as peptide inhibitor of complement C1 (PIC1), is a 15-amino-acid anti-inflammatory peptide that inhibits classical complement pathway activation and modulates neutrophil activation. It has been previously shown to aid in the healing of chronic diabetic wounds by inhibiting the excessive activation of complement component C1 and infiltration of leukocytes. Here, we report that treatment of cutaneous infections of HSV-1 and ACVR-HSV-1 in BALB/cJ mice with RLS-0071 significantly reduced the rate of mortality, decreased zosteriform spread, and enhanced the healing of the infection-associated lesions compared to control-treated animals. Therefore, RLS-0071 may work synergistically with other antiviral drugs to aid in wound healing of HSV-1 cutaneous infection and may potentially aid in rapid wound healing of other pathology not limited to HSV-1.

The Interaction between Integrin Mac-1 (αMβ2, CD11b/CD18) and Sirpα Mediates Macrophage Fusion

Macrophage fusion leading to the formation of multinucleated giant cells is a hallmark of chronic inflammation. While a number of membrane proteins have been implicated in mediating cell-cell attachement during fusion, their binding partners are not yet clear. Recently, we have demonstrated that IL-4-induced fusion of mouse peritoneal macrophages depends on integrin Mac-1 (αMβ2, CD11b/CD18). Surprisingly, the genetic deficiency of ICAM-1, an established ligand of Mac-1, resulted in no decrease of macrophage fusion, suggesting the involvement of other counter-receptors for Mac-1. In the present study, we demonstrated that SIRPα, which like ICAM-1 belongs to the Ig superfamily and was previously implicated in fusion, interacts with Mac-1. Expression of Mac-1 on the surface of HEK293 cells resulted in their adhesion to recombinant ectodomain of SIRPα and this process was mediated through the αMI-domain of Mac-1. In addition, adhesion of RAW264.7 mouse macrophages to SIRPα was dependent on Mac-1. Direct interaction between the αMI-domain and SIRPα was shown by biolayer interferometry. Analyses of the interaction of αMI-domain with a peptide library spanning the ectodomain of SIRPα showed that recognition of SIRPa conforms to general principles that govern binding by Mac-1 of many of its ligands. SIRPα reportedly interacts with CD47; however, adhesion of Mac-1-expressing HEK293 cells, which express CD47, to SIRPα was not dependent on CD47 and an anti-CD47 function-blocking mAb produced only a limited inhibition of adhesion of RAW264.7 cells. Co-immunoprecipitation experiments revealed that Mac-1 forms a complex with CD47 on the surface of RAW264.7 and Mac-1-expressing HEK293 cells. Finally, co-culturing of SIPRα- and Mac-1-expressing HEK293 cells resulted in cell fusion. Collectively, these data identify SIRPα as a novel counter-receptor for Mac-1 and suggest that the Mac-1-SIRPα interaction may be involved in macrophage fusion. DisclosuresNo relevant conflicts of interest to declare.

Covalent linkage of sulfated hyaluronan to the collagen scaffold Mucograft® enhances scaffold stability and reduces proinflammatory macrophage activation in vivo

Sulfated glycosaminoglycans (sGAG) show interaction with biological mediator proteins. Although collagen-based biomaterials are widely used in clinics, their combination with high-sulfated hyaluronan (sHA3) is unexplored. This study aims to functionalize a collagen-based scaffold (Mucograft®) with sHA3 via electrostatic (sHA3/PBS) or covalent binding to collagen fibrils (sHA3+EDC/NHS). Crosslinking without sHA3 was used as a control (EDC/NHS Ctrl). The properties of the sHA3-functionalized materials were characterized. In vitro growth factor and cytokine release after culturing with liquid platelet-rich fibrin was performed by means of ELISA. The cellular reaction to the biomaterials was analyzed in a subcutaneous rat model. The study revealed that covalent linking of sHA3 to collagen allowed only a marginal release of sHA3 over 28 days in contrast to electrostatically bound sHA3. sHA3+EDC/NHS scaffolds showed reduced vascular endothelial growth factor (VEGF), transforming growth factor beta 1 (TGF-β1) and enhanced interleukin-8 (IL-8) and epithelial growth factor (EGF) release in vitro compared to the other scaffolds. Both sHA3/PBS and EDC/NHS Ctrl scaffolds showed a high proinflammatory reaction (M1: CD-68+/CCR7+) and induced multinucleated giant cell (MNGC) formation in vivo. Only sHA3+EDC/NHS scaffolds reduced the proinflammatory macrophage M1 response and did not induce MNGC formation during the 30 days. SHA3+EDC/NHS scaffolds had a stable structure in vivo and showed sufficient integration into the implantation region after 30 days, whereas EDC/NHS Ctrl scaffolds underwent marked disintegration and lost their initial structure. In summary, functionalized collagen (sHA3+EDC/NHS) modulates the inflammatory response and is a promising biomaterial as a stable scaffold for full-thickness skin regeneration in the future.

Apoptotic mesenchymal stromal cells support osteoclastogenesis while inhibiting multinucleated giant cells formation in vitro

In bone regeneration induced by the combination of mesenchymal stromal cells (MSCs) and calcium-phosphate (CaP) materials, osteoclasts emerge as a pivotal cell linking inflammation and bone formation. Favorable outcomes are observed despite short-term engraftments of implanted MSCs, highlighting their major paracrine function and the possible implication of cell death in modulating their secretions. In this work, we focused on the communication from MSCs towards osteoclasts-like cells in vitro. MSCs seeded on a CaP biomaterial or undergoing induced apoptosis produced a conditioned media favoring the development of osteoclasts from human CD14+ monocytes. On the contrary, MSCs’ apoptotic secretion inhibited the development of inflammatory multinucleated giant cells formed after IL-4 stimulation. Components of MSCs’ secretome before and after apoptotic stress were compared using mass spectrometry-based quantitative proteomics and a complementary immunoassay for major cytokines. CXCR-1 and CXCR-2 ligands, primarily IL-8/CXCL-8 but also the growth-regulated proteins CXCL-1, -2 or -3, were suggested as the major players of MSCs’ pro-osteoclastic effect. These findings support the hypothesis that osteoclasts are key players in bone regeneration and suggest that apoptosis plays an important role in MSCs’ effectiveness.

Conducting a comprehensive mycological study to prevent the occurrence of aspergillosis in chickens

Diseases of poultry aspergillosis are recorded in many poultry farms, the causes of the disease are the violation of the sanitary and hygienic conditions of hatcheries and poultry houses (unfavorable microclimate, affected feed and litter by microscopic fungi). To prevent the development of infection, it is necessary to control air pollution and equipment in hatcheries; determine the safety indicators of feed and water (the level of their mycological contamination) in poultry houses; monitor the status of feed storage facilities and water supply systems. According to the results of our research, in 15.1% of dead chickens at the age of 3 to 5 days and 6.6% at the age of 7-10 days, according to the results of mycological examination of pathological material, the diagnosis of aspergillosis was established. Aspergillus flavus (47%) Aspergillus fumigatus (34.5%), Aspergillus niger (10%) were isolated from the lungs of dead chickens. Macroscopically revealed edema and hyperemia of the lungs in chickens of 3-5 days of age. The formation of granulomas in the lungs and serous membranes was not detected, which may indicate an acute form of the pathological process. Chickens 7-10 days old showed a strong thickening of the air sacs, lungs with multiple spherical granulomas up to 2 mm in diameter. Spores of fungi entering the lungs cause a local inflammatory reaction - acute pneumonia. Histologically, in chickens of 3-5 days of age, a thickening of the parabronchial wall due to hyperplasia of local lymphoid formations (providing local immunity), signs of the development of interstitial pneumonia were revealed. Pathognomonic signs were found in the parenchyma - the formation of giant multinucleated cells, which is a characteristic sign of mycotic infections in poultry. The fusion of local pulmonary macrophages, histiocytes, into multinucleated cells is a prerequisite for the formation of granulomas, being a specific immune response in birds to the penetration of a pathogen. According to the development of the infectious process, caseous granulomas and fungal hyphae can be detected microscopically in the lungs. According to the results of histological examination, the formation of mycotic granulomas was found in the lung parenchyma in 7-10 days old chickens, which was accompanied by the formation of a zone of coagulation necrosis, in which the fungal hyphae were found. On the periphery, giant multinucleated epithelioid cells are located, the detection of which by histological examination is the basis for suspecting bird infection with microscopic fungi. Microscopic fungi Aspergillus flavus and Aspergillus fumigatus have been found in washes from hatchery ventilation cabinets, and Aspergillus flavus was found in the air from the chick sorting room and in washes from the feed mixer. Key words: aspergillosis, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, micromycete, mold fungi, histiocytes, granulomas, phylaids, conidia, hyphae.

Stereological analysis and transcriptome profiling of testicular injury induced by di-(2-ethylhexyl) phthalate in prepubertal rats

Di-(2-ethylhexyl) phthalate (DEHP) is the most common phthalate that can affect the male reproductive system. DEHP exposure at the prepubertal stage could lead to the injury of immature testes, but the mechanism has not been fully clarified. In the present study, we elucidated the possible underlying mechanism of DEHP-induced prepubertal testicular injury through stereological analysis and transcriptome profiling. Compared with the control group, the DEHP-treated rats had lower body weight gain and decreased testicular weight and organ coefficient. Moreover, lower serum levels of testosterone and LH were observed in the DEHP group, in contrast to the increased FSH level. Additionally, the serum level of estradiol had no significant difference after DEHP exposure. Stereological analysis showed significant reduction in volumes of most testicular structures, especially in the seminiferous tubule and seminiferous epithelium, along with a vast decrease of spermatogenic cells and obvious structural damages with substantial pathological signs (germ cracks, cytoplasmic vacuolization, sloughing, multinucleated giant cell formation, chromatolysis desquamation and dissolution, pyknosis of nuclei) in the seminiferous tubule upon DEHP exposure at the prepubertal stage. Furthermore, transcriptome profiling identified 5548 differentially expressed genes (DEGs) upon DEHP exposure. Pathway enrichment analysis revealed several crucial signaling pathways related to retinol metabolism, oxidative phosphorylation, steroid hormone biosynthesis, and cell adhesion molecules (CAMs). In addition, seven DEGs selected from RNA-seq data were validated by quantitative real-time polymerase chain reaction (qRT-PCR), and the results showed the same trends as the RNA-seq results. In conclusion, the above findings provide basic morphological data and lay a foundation for systematic research on transcriptome profiling in prepubertal testicular injury induced by DEHP.

Macrophage-specific responses to human- and animal-adaptedtubercle bacilli reveal pathogen and host factors drivingmultinucleated cell formation.

The Mycobacterium tuberculosis complex (MTBC) is a group of related pathogens that cause tuberculosis (TB) in mammals. MTBC species are distinguished by their ability to sustain in distinct host populations. While Mycobacterium bovis (Mbv) sustains transmission cycles in cattle and wild animals and causes zoonotic TB, M. tuberculosis (Mtb) affects human populations and seldom causes disease in cattle. The host and pathogen determinants underlying host tropism between MTBC species are still unknown. Macrophages are the main host cell that encounters mycobacteria upon initial infection, and we hypothesised that early interactions between the macrophage and mycobacteria influence species-specific disease outcome. To identify factors that contribute to host tropism, we analysed blood-derived primary human and bovine macrophages (hMϕ or bMϕ, respectively) infected with Mbv and Mtb. We show that Mbv and Mtb reside in different cellular compartments and differentially replicate in hMϕ whereas both Mbv and Mtb efficiently replicate in bMϕ. Specifically, we show that out of the four infection combinations, only the infection of bMϕ with Mbv promoted the formation of multinucleated giant cells (MNGCs), a hallmark of tuberculous granulomas. Mechanistically, we demonstrate that both MPB70 from Mbv and extracellular vesicles released by Mbv-infected bMϕ promote macrophage multinucleation. Importantly, we extended our in vitro studies to show that granulomas from Mbv-infected but not Mtb-infected cattle contained higher numbers of MNGCs. Our findings implicate MNGC formation in the contrasting pathology between Mtb and Mbv for the bovine host and identify MPB70 from Mbv and extracellular vesicles from bMϕ as mediators of this process.

Primary differentiated respiratory epithelial cells respond to apical measles virus infection by shedding multinucleated giant cells

Significance Measles virus (MeV) is highly infectious by the respiratory route, but respiratory epithelial cells are thought to be resistant to infection through the exposed apical surface and to require infection through the basolateral surface. We show that differentiated respiratory epithelial cells are actually highly susceptible to apical infection and that infection leads to formation of multinucleated giant cells that are shed from the epithelial sheet into the lumen leaving the epithelium intact and devoid of infected cells. These results are consistent with the hypothesis that MeV infection is initiated in respiratory epithelial cells with subsequent infection of lymphoid tissue and systemic spread.

Mechanotransduction via a TRPV4-Rac1 signaling axis plays a role in multinucleated giant cell formation

Multinucleated giant cells are formed by the fusion of macrophages and are a characteristic feature in numerous pathophysiological conditions including the foreign body response (FBR). Foreign body giant cells (FBGCs) are inflammatory and destructive multinucleated macrophages and may cause damage and/or rejection of implants. However, while these features of FBGCs are well established, the molecular mechanisms underlying their formation remain elusive. Improved understanding of the molecular mechanisms underlying the formation of FBGCs may permit the development of novel implants that eliminate or reduce the FBR. Our previous study showed that transient receptor potential vanilloid 4 (TRPV4), a mechanosensitive ion channel/receptor, is required for FBGC formation and FBR to biomaterials. Here, we have determined that (a) TRPV4 is directly involved in fusogenic cytokine (interleukin-4 plus granulocyte macrophage–colony stimulating factor)–induced activation of Rac1, in bone marrow–derived macrophages; (b) TRPV4 directly interacts with Rac1, and their interaction is further augmented in the presence of fusogenic cytokines; (c) TRPV4-dependent activation of Rac1 is essential for the augmentation of intracellular stiffness and regulation of cytoskeletal remodeling; and (d) TRPV4-Rac1 signaling axis is critical in fusogenic cytokine–induced FBGC formation. Together, these data suggest a novel mechanism whereby a functional interaction between TRPV4 and Rac1 leads to cytoskeletal remodeling and intracellular stiffness generation to modulate FBGC formation.

First person – Patricia Joyce Brooks

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Patricia Joyce Brooks is first author on ‘CD301 mediates fusion in IL-4-driven multinucleated giant cell formation’, published in JCS. Patricia conducted the research described in this article while a PhD student in Christopher A. McCulloch and Michael Glogauer's lab at the Faculty of Dentistry, University of Toronto, Canada. Patricia is now a postdoctoral research fellow in the lab of Scott Bratman at the Princess Margaret Research Institute, Toronto, Canada, where she is bringing clinical oral pathology diagnostic challenges to the benchtop to establish better testing at the basic science level.

CD301 mediates fusion in IL-4-driven multinucleated giant cell formation

Multinucleated giant cells (MGCs) are prominent in foreign body granulomas, infectious and inflammatory processes, and auto-immune, neoplastic and genetic disorders, but the molecular determinants that specify the formation and function of these cells are not defined. Here, using tandem mass tag-mass spectrometry, we identified a differentially upregulated protein, C-type lectin domain family 10 member (herein denoted CD301, also known as CLEC10A), that was strongly upregulated in mouse RAW264.7 macrophages and primary murine macrophages undergoing interleukin (IL-4)-induced MGC formation. CD301+ MGCs were identified in biopsy specimens of human inflammatory lesions. Function-inhibiting CD301 antibodies or CRISPR/Cas9 deletion of the two mouse CD301 genes (Mgl1 and Mgl2) inhibited IL-4-induced binding of N-acetylgalactosamine-coated beads by 4-fold and reduced MGC formation by 2.3-fold (P<0.05). IL-4-driven fusion and MGC formation were restored by re-expression of CD301 in the knockout cells. We conclude that in monocytes, IL-4 increases CD301 expression, which mediates intercellular adhesion and fusion processes that are required for the formation of MGCs.This article has an associated First Person interview with the first author of the paper.

Multinucleated Giant Cells in Adipose Tissue Are Specialized in Adipocyte Degradation.

Obesity is associated with chronic low-grade inflammation of visceral adipose tissue (AT) characterized by an increasing number of AT macrophages (ATMs) and linked to type 2 diabetes. AT inflammation is histologically indicated by the formation of so-called crown-like structures, as ATMs accumulate around dying adipocytes, and the occurrence of multinucleated giant cells (MGCs). However, to date, the function of MGCs in obesity is unknown. Therefore, the aim of this study was to characterize MGCs in AT and unravel the function of these cells. We demonstrated that MGCs occurred in obese patients and after 24 weeks of a high-fat diet in mice, accompanying signs of AT inflammation and then representing ∼3% of ATMs in mice. Mechanistically, we found evidence that adipocyte death triggered MGC formation. Most importantly, MGCs in obese AT had a higher capacity to phagocytize oversized particles, such as adipocytes, as shown by live imaging of AT, 45-µm bead uptake ex vivo, and higher lipid content in vivo. Finally, we showed that interleukin-4 treatment was sufficient to increase the number of MGCs in AT, whereas other factors may be more important for endogenous MGC formation in vivo. Most importantly, our data suggest that MGCs are specialized for clearance of dead adipocytes in obesity.

Multinucleated Giant Cell Formation as a Portal to Chronic Bacterial Infections.

This review provides a snapshot of chronic bacterial infections through the lens of Burkholderia pseudomallei and detailing its ability to establish multi-nucleated giant cells (MNGC) within the host, potentially leading to the formation of pyogranulomatous lesions. We explore the role of MNGC in melioidosis disease progression and pathology by comparing the similarities and differences of melioidosis to tuberculosis, outline the concerted events in pathogenesis that lead to MNGC formation, discuss the factors that influence MNGC formation, and consider how they fit into clinical findings reported in chronic cases. Finally, we speculate about future models and techniques that can be used to delineate the mechanisms of MNGC formation and function.

Mesenchymal stromal cells' secretome enhances osteoclastogenesis but reduces multinucleated giant cells formation in vitro

Mesenchymal stromal cells' secretome enhances osteoclastogenesis but reduces multinucleated giant cells formation in vitro

Genomic loss in environmental and isogenic morphotype isolates of Burkholderia pseudomallei is associated with intracellular survival and plaque-forming efficiency.

BackgroundBurkholderia pseudomallei is an environmental bacterium that causes melioidosis. A facultative intracellular pathogen, B. pseudomallei can induce multinucleated giant cells (MNGCs) leading to plaque formation in vitro. B. pseudomallei can switch colony morphotypes under stress conditions. In addition, different isolates have been reported to have varying virulence in vivo, but genomic evolution and the relationship with plaque formation is poorly understood.Methodology/Principle findingsTo gain insights into genetic underpinnings of virulence of B. pseudomallei, we screened plaque formation of 52 clinical isolates and 11 environmental isolates as well as 4 isogenic morphotype isolates of B. pseudomallei strains K96243 (types II and III) and 153 (types II and III) from Thailand in A549 and HeLa cells. All isolates except one environmental strain (A4) and K96243 morphotype II were able to induce plaque formation in both cell lines. Intracellular growth assay and confocal microscopy analyses demonstrated that the two plaque-forming-defective isolates were also impaired in intracellular replication, actin polymerization and MNGC formation in infected cells. Whole genome sequencing analysis and PCR revealed that both isolates had a large genomic loss on the same region in chromosome 2, which included Bim cluster, T3SS-3 and T6SS-5 genes.Conclusions/SignificanceOur plaque screening and genomic studies revealed evidence of impairment in plaque formation in environmental isolates of B. pseudomallei that is associated with large genomic loss of genes important for intracellular multiplication and MNGC formation. These findings suggest that the genomic and phenotypic differences of environmental isolates may be associated with clinical infection.