A two-step human culture system replicates intestinal monocyte maturation cascade: Conversion of tissue-like inflammatory monocytes into macrophages

Insights of immune cell heterogeneity, tumor-initiated subtype transformation, drug resistance, treatment and detecting technologies in glioma microenvironment

BACKGROUND

With the gradual understanding of glioma development and the immune microenvironment, many immune cells have been discovered. Despite the growing comprehension of immune cell functions and the clinical application of immunotherapy, the precise roles and characteristics of immune cell subtypes, how glioma induces subtype transformation of immune cells and its impact on glioma progression have yet to be understood.

AIM OF THE REVIEW

In this review, we comprehensively center on the four major immune cells within the glioma microenvironment, particularly neutrophils, macrophages, lymphocytes, myeloid-derived suppressor cells (MDSCs), and other significant immune cells. We discuss (1) immune cell subtype markers, (2) glioma-induced immune cell subtype transformation, (3) the mechanisms of each subtype influencing chemotherapy resistance, (4) therapies targeting immune cells, and (5) immune cell-associated single-cell sequencing. Eventually, we identified the characteristics of immune cell subtypes in glioma, comprehensively summarized the exact mechanism of glioma-induced immune cell subtype transformation, and concluded the progress of single-cell sequencing in exploring immune cell subtypes in glioma.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In conclusion, we have analyzed the mechanism of chemotherapy resistance detailly, and have discovered prospective immunotherapy targets, excavating the potential of novel immunotherapies approach that synergistically combines radiotherapy, chemotherapy, and surgery, thereby paving the way for improved immunotherapeutic strategies against glioma and enhanced patient outcomes.

The relationship between extreme inter-individual variation in macrophage gene expression and genetic susceptibility to inflammatory bowel disease

The differentiation of resident intestinal macrophages from blood monocytes depends upon signals from the macrophage colony-stimulating factor receptor (CSF1R). Analysis of genome-wide association studies (GWAS) indicates that dysregulation of macrophage differentiation and response to microorganisms contributes to susceptibility to chronic inflammatory bowel disease (IBD). Here, we analyzed transcriptomic variation in monocyte-derived macrophages (MDM) from affected and unaffected sib pairs/trios from 22 IBD families and 6 healthy controls. Transcriptional network analysis of the data revealed no overall or inter-sib distinction between affected and unaffected individuals in basal gene expression or the temporal response to lipopolysaccharide (LPS). However, the basal or LPS-inducible expression of individual genes varied independently by as much as 100-fold between subjects. Extreme independent variation in the expression of pairs of HLA-associated transcripts (HLA-B/C, HLA-A/F and HLA-DRB1/DRB5) in macrophages was associated with HLA genotype. Correlation analysis indicated the downstream impacts of variation in the immediate early response to LPS. For example, variation in early expression of IL1B was significantly associated with local SNV genotype and with subsequent peak expression of target genes including IL23A, CXCL1, CXCL3, CXCL8 and NLRP3. Similarly, variation in early IFNB1 expression was correlated with subsequent expression of IFN target genes. Our results support the view that gene-specific dysregulation in macrophage adaptation to the intestinal milieu is associated with genetic susceptibility to IBD.

Behind the monocyte's mystique: uncovering their developmental trajectories and fates

Monocytes are circulating myeloid cells that are derived from dedicated progenitors in the bone marrow. Originally thought of as mere precursors for the replacement of tissue macrophages, it is increasingly clear that monocytes execute distinct effector functions and may give rise to monocyte-derived cells with unique properties from tissue-resident macrophages. Recently, the advent of novel experimental approaches such as single-cell analysis and fate-mapping tools has uncovered an astonishing display of monocyte plasticity and heterogeneity, which we believe has emerged as a key theme in the field of monocyte biology in the last decade. Monocyte heterogeneity is now recognized to develop as early as the progenitor stage through specific imprinting mechanisms, giving rise to specialized effector cells in the tissue. At the same time, monocytes must overcome their susceptibility towards cellular death to persist as monocyte-derived cells in the tissues. Environmental signals that preserve their heterogenic phenotypes and govern their eventual fates remain incompletely understood. In this review, we will summarize recent advances on the developmental trajectory of monocytes and discuss emerging concepts that contributes to the burgeoning field of monocyte plasticity and heterogeneity.

Cell-penetrating TLR inhibitor peptide alleviates ulcerative colitis by the functional modulation of macrophages

Toll-like receptors (TLRs) have a crucial role not only in triggering innate responses against microbes but in orchestrating an appropriate adaptive immunity. However, deregulated activation of TLR signaling leads to chronic inflammatory conditions such as inflammatory bowel disease (IBD). In this study, we evaluated the immunomodulatory potential of a TLR inhibitor in the form of a cell-penetrating peptide using an ulcerative colitis animal model. A peptide derived from the TIR domain of the TLR adaptor molecule TIRAP that was conjugated with a cell-penetrating sequence (cpTLR-i) suppressed the induction of pro-inflammatory cytokines such as TNF-α and IL-1β in macrophages. In DSS-induced colitis mice, cpTLR-i treatment ameliorated colitis symptoms, colonic tissue damage, and mucosal inflammation. Intriguingly, cpTLR-i attenuated the induction of TNF-α-expressing proinflammatory macrophages while promoting that of regulatory macrophages expressing arginase-1 and reduced type 17 helper T cell (Th17) responses in the inflamed colonic lamina propria. An in vitro study validated that cpTLR-i enhanced the differentiation of monocyte-driven macrophages into mature macrophages with a regulatory phenotype in a microbial TLR ligand-independent manner. Furthermore, the cocultivation of CD4 T cells with macrophages revealed that cpTLR-i suppressed the activation of Th17 cells through the functional modulation of macrophages. Taken together, our data show the immunomodulatory potential of the TLR inhibitor peptide and suggest cpTLR-i as a novel therapeutic candidate for the treatment of IBD.

The Conversion of Human Tissue-Like Inflammatory Monocytes Into Macrophages

Classical circulating LyC6^high murine monocytes differentiate progressively from inflammatory tissue monocytes to mature macrophages (Mϕ) after entry into gut mucosa. This protocol provides a two-step in vitro culture method that replicates the human monocyte maturation cascade. First, purified circulating CD14⁺ CD16^- monocytes exposed to granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon gamma (IFNγ), and interleukin 23 (IL-23) differentiate into tissue-like inflammatory monocytes. Next, addition of transforming growth factor beta (TGFβ) plus interleukin 10 (IL-10) promotes their maturation into tissue-like Mϕ. Methods to sort these cells after culture are also provided. The fine-tuning of this system might open therapeutic avenues for chronic inflammatory disorders. © 2021 Wiley Periodicals LLC Basic Protocol 1: Isolation of human monocytes from peripheral blood Basic Protocol 2: First step culture for generation of inflammatory monocyte-like cells Basic Protocol 3: Second step culture for differentiation of inflammatory monocyte-like cells into macrophages Alternate Protocol: Sorting and culturing of inflammatory monocyte-like cells.

Differential Changes in Inflammatory Mononuclear Phagocyte and T-Cell Profiles within Psoriatic Skin during Treatment with Guselkumab vs. Secukinumab

Cellular sources of IL-23 and IL-17A driving skin inflammation in psoriasis remain unclear. Using high-dimensional unsupervised flow cytometry analysis, mononuclear phagocytes and T cells were examined in the same lesions of patients before and during guselkumab (IL-23p19 blocker) or secukinumab (IL-17A blocker) treatment. Among CD11c⁺HLA-DR⁺ mononuclear phagocytes, CD64^brightCD163^-CD14^brightCD1c^-CD1a^‒ inflammatory monocyte‒like cells were the predominant IL-23-producing cells and, together with CD64^-CD163^-CD14^-IL-23p19^-TNF-α⁺ inflammatory dendritic cell‒like cells, were increased in lesional compared with those in nonlesional skin taken from the same patient. Within T cells, CD8⁺CD49a⁺ and/or CD103⁺ tissue-resident memory T cells, CD4⁺CD25⁺FoxP3⁺ regulatory T cells, and CD4⁺CD49a^-CD103^- T cells were increased. Moreover, CD4⁺CD49a^-CD103^- T cells and the relatively rare CD8⁺ memory T cells equally contributed to IL-17A production. Both treatments decreased the frequencies of inflammatory monocyte‒like, inflammatory dendritic cell‒like, and CD4⁺CD49a^-CD103^- T cells. In contrast, guselkumab reduced memory T cells while maintaining regulatory T cells and vice versa for secukinumab. Neither drug modified the frequencies of IL-17A⁺IL^‒17F⁺/^- CD4⁺ or CD8⁺ T cells. This study reveals the identity of the major IL-23⁺ mononuclear phagocyte and IL-17⁺ T-cell subsets in psoriatic skin lesions and paves the way for a better understanding of the mode of action of drugs targeting the IL-23/IL-17A pathway in psoriasis.

Single-Cell Protein and RNA Expression Analysis of Mononuclear Phagocytes in Intestinal Mucosa and Mesenteric Lymph Nodes of Ulcerative Colitis and Crohn's Disease Patients

Inflammatory bowel diseases (IBDs), which include Crohn's disease (CD) and ulcerative colitis (UC), are driven by an abnormal immune response to commensal microbiota in genetically susceptible hosts. In addition to epithelial and stromal cells, innate and adaptive immune systems are both involved in IBD immunopathogenesis. Given the advances driven by single-cell technologies, we here reviewed the immune landscape and function of mononuclear phagocytes in inflamed non-lymphoid and lymphoid tissues of CD and UC patients. Immune cell profiling of IBD tissues using scRNA sequencing combined with multi-color cytometry analysis identifies unique clusters of monocyte-like cells, macrophages, and dendritic cells. These clusters reflect either distinct cell lineages (nature), or distinct or intermediate cell types with identical ontogeny, adapting their phenotype and function to the surrounding milieu (nurture and tissue imprinting). These advanced technologies will provide an unprecedented view of immune cell networks in health and disease, and thus may offer a personalized medicine approach to patients with IBD.