Decoding the role of macrophages in periodontitis and type 2 diabetes using single‐cell RNA‐sequencing

Abstract

Macrophages are resident myeloid cells in the gingival tissue which control homeostasis and play a pivotal role in orchestrating the immune response in periodontitis. Cell heterogeneity and functional phenotypes of macrophage subpopulations in periodontitis remain elusive. Here, we isolated gingival tissue from periodontitis‐affected and healthy sites of patients with and without type 2 diabetes mellitus (T2DM). We then used single‐cell RNA‐sequencing (scRNA‐seq) to define the heterogeneity of tissue‐resident macrophages in gingival tissue in health vs. periodontitis. scRNA‐seq demonstrated an unforeseen gene expression heterogeneity among macrophages in periodontitis and showed transcriptional and signaling heterogeneity of identified subsets in an independent cohort of patients with periodontitis and T2DM. Our bioinformatic inferences indicated divergent expression profiles in macrophages driven by transcriptional regulators CIITA, RELA, RFX5, and RUNX2. Macrophages in periodontitis expressed both pro‐inflammatory and anti‐inflammatory markers and their polarization was not mutually exclusive. The majority of macrophages in periodontitis expressed the monocyte lineage marker CD14, indicating their bone marrow lineage. We also found high expression and activation of RELA, a subunit of the NF‐κB transcription factor complex, in gingival macrophages of periodontitis patients with T2DM. Our data suggested that heterogeneity and hyperinflammatory activation of macrophages may be relevant to the pathogenesis and outcomes of periodontitis, and may be further augmented in patients with T2DM.

Overview of Transcriptomic Research on Type 2 Diabetes: Challenges and Perspectives

“…Using the association rule mining method, the authors analyzed microarray data and identified CDC42SE2 as a DEG in patients with decompensated T2D, dyslipidemia, and periodontitis—chronic inflammatory diseases [ 29 ]. An increased expression of RELA, the p65 subunit of the NF-kappa-B complex which regulates DNA transcription, cell survival, and immune response to infection, were also revealed in gingival tissue affected by periodontitis in T2D patients [ 74 ]. The activation of components of the NF-kB signaling pathway was also noted in a study by Saxena et al [ 27 ] and by Lv and colleagues [ 37 ].…”

Single‐cell RNA sequencing in oral science: Current awareness and perspectives

“…The scRNA‐seq study by Qian et al reported that Major Histocompatibility Complex class II cell surface receptor HLA‐DR+ endothelial cells, CXCL13+ fibroblasts, and NLR Family Pyrin Domain Containing 3 (NLRP3) + macrophages were involved in the development of periodontitis 113 . In addition, another study using scRNA‐seq revealed heterogeneity in macrophage populations between periodontitis‐affected and normal gingival tissues in individuals with and without type 2 diabetes 114 . In the research from Chen et al, samples from healthy individuals and severe chronic periodontitis patients, as well as samples from severe chronic periodontitis patients prior to and following initial periodontal therapy, were analyzed by scRNA‐seq.…”

“…The study by Qian et al showed that increased intercellular communication arose between macrophages and T/B cells in periodontitis‐affected tissues 113 . Signals that interacted with macrophages and other cell types were enriched in immune checkpoint pathways associated with exhaustion of T cells 114 . Activation of Ephrin‐Eph signaling mediating crosstalk between endothelial cells and pre‐osteoblasts maybe responsible for pathological bone loss in periodontitis 115 .…”

“… 113 In addition, another study using scRNA‐seq revealed heterogeneity in macrophage populations between periodontitis‐affected and normal gingival tissues in individuals with and without type 2 diabetes. 114 In the research from Chen et al, samples from healthy individuals and severe chronic periodontitis patients, as well as samples from severe chronic periodontitis patients prior to and following initial periodontal therapy, were analyzed by scRNA‐seq. Studying cell clusters in osteoimmunology microenvironments, TNF Receptor Superfamily Member 21 (TNFRSF21) + fibroblast subpopulations were identified as proinflammatory phenotype and CXCL12+ MSC‐like pericytes were recognized as contributing to pre‐osteoblasts during inflammation after periodontal therapy.…”

Dissecting B/Plasma Cells in Periodontitis at Single-Cell/Bulk Resolution

“…Single-cell transcriptomic atlas studies on periodontitis, by numerous research centers (Caetano et al 2021; Qian et al 2021; Williams et al 2021; Agrafioti et al 2022; Chen et al 2022), identified cell subpopulations and analyzed the possible interactions between immune and nonimmune cells. Some studies reported immune cell subpopulations of myeloid lineage cells and NK/T cells (Qian et al 2021; Agrafioti et al 2022), but none of them further analyzed B/plasma cell subpopulations. Therefore, it is necessary to connect these findings at a single-cell level with their clinical significance.…”