Single-cell RNA sequencing reveals functional heterogeneity of glioma-associated brain macrophages

Abstract

Microglia are resident myeloid cells in the central nervous system (CNS) that control homeostasis and protect CNS from damage and infections. Microglia and peripheral myeloid cells accumulate and adapt tumor supporting roles in human glioblastomas that show prevalence in men. Cell heterogeneity and functional phenotypes of myeloid subpopulations in gliomas remain elusive. Here we show single-cell RNA sequencing (scRNA-seq) of CD11b+ myeloid cells in naïve and GL261 glioma-bearing mice that reveal distinct profiles of microglia, infiltrating monocytes/macrophages and CNS border-associated macrophages. We demonstrate an unforeseen molecular heterogeneity among myeloid cells in naïve and glioma-bearing brains, validate selected marker proteins and show distinct spatial distribution of identified subsets in experimental gliomas. We find higher expression of MHCII encoding genes in glioma-activated male microglia, which was corroborated in bulk and scRNA-seq data from human diffuse gliomas. Our data suggest that sex-specific gene expression in glioma-activated microglia may be relevant to the incidence and outcomes of glioma patients.

A Novel Oral Arginase 1/2 Inhibitor Enhances the Antitumor Effect of PD-1 Inhibition in Murine Experimental Gliomas by Altering the Immunosuppressive Environment

“…High expression of ARG1 and ARG2 was detected in malignant cells and tumor-infiltrating microglia/macrophages (MG/MΦ) ( Figure 1B and Supplementary Figure 1B ). We took advantage of having in-house sc-RNA-seq data of CD11b + immunosorted from murine GL261 gliomas, which provided resolution to distinguish resident microglia from CNS-border associated macrophages (BAMs) or monocytes/macrophages (Mo/MΦ) ( 34 ). Using these data, we analyzed Arg1 and Arg2 expression in the discrete myeloid subpopulations.…”

In Vitro Glioblastoma Models: A Journey into the Third Dimension

“…The genetic diversity is an effective way that GBM cells inside the tumor mass use to develop treatment resistance, a selection process that in turn supports the most typical and deadly factor in GBM malignity: disease recurrence [ 81 ]. However, it should be noticed that this classification is no longer in line with recent, dramatic technological advancements, such as the growing field of single cell RNA sequencing, that have introduced an additional layer of complexity demonstrating that GBM tumors actually contain a wide variety of tumor and non-tumor cells of all three subtypes [ 82 ]. In terms of tumoral diversity and heterogeneity, the process of culturing GBM cells remains incredibly complicated, because current culture techniques often promote homogeneity in cells, thereby limiting their utility.…”

Microglia: A Double-Edged Sword in Intracerebral Hemorrhage From Basic Mechanisms to Clinical Research

“…In this experiment, multiple microglial clusters were obtained, and gene expression profiles underlying a specific cluster could reflect different functions. Hom-MG and activated microglia (Act-MG) were identified, which shows the distinct spatial distribution in experimental gliomas ( 43 ). Furthermore, an environment-dependent transcriptional network specifying microglia-specific programs have been developed, which identified substantial subsets of microglia associate with neurodegenerative and behavioral diseases ( 44 ).…”