Abstract
BackgroundThe molecular mechanisms of acute otitis media (AOM) development, and the intercellular crosstalk within the multicellular ecosystem of AOM, are not clear.MethodsWe established a model of AOM in rats (with normal rats as controls) and undertook single-cell RNA sequencing (scRNA-seq) for the middle-ear mucosa (MEM). Cell clustering and trajectory analyses were undertaken using Seurat and Monocle 2 packages in R software. Pathway analyses were done by gene set enrichment analysis (GSEA). Cell–cell interactions were inferred by CellChat. Cell scores were calculated to identify cells with dual-feature.ResultsA total of 7023 cells from three samples of inflamed MEM and 5258 cells from three samples of healthy MEM underwent scRNA-seq, which identified 20 cell clusters belonging to eight major cell types. After exposure to lipopolysaccharide, the MEM underwent significant conversion of cell types characterized by rapid infiltration of macrophages and neutrophils. M2 macrophages seemed to play a key part in inflammatory intercellular crosstalk, which facilitated the maintenance and proliferation of macrophages, cell chemotaxis, and regulation of the proinflammatory activities of cytokines. Three rare cell clusters with phagocytosis-related dual-feature were also identified. They coexisted with professional phagocytes in the MEM, and displayed distinct immunoregulatory functions by maintaining a normal immune microenvironment or influencing inflammation progression.ConclusionsMacrophages might be the “master” initiators and regulators of the inflammatory response of the MEM to external stimuli. And their functions are fulfilled by a specific polarization status (M2) and sophisticated intercellular crosstalk via certain signaling pathways. Besides, the coexistence of professional phagocytes and non-professional phagocytes as well as their interplay in the MEM provides new clues for deciphering the underlying pathogenic mechanisms of AOM.
Highlights
Acute otitis media (AOM) is a common disease among children
To systematically investigate the cellular diversity of the inflamed middle-ear mucosa (MEM) in rats as well as the sophisticated intercellular crosstalk within its multicellular ecosystem
A model of AOM in rats was established (Figure 1A), which was examined by histology using hematoxylin and eosin (H&E) staining (Figures 1B, C)
Summary
Acute otitis media (AOM) is a common disease among children. It poses a heavy health burden on clinical practice worldwide, especially in developing countries [1].In healthy individuals, the middle ear (ME) cavity is lined with a modified respiratory epithelium with ciliated and secretory cells, along with underlying loose connective tissue and vasculature [2]. Acute otitis media (AOM) is a common disease among children. It poses a heavy health burden on clinical practice worldwide, especially in developing countries [1]. The response of the MEM to acute inflammation at single-cell resolution has not been illustrated. This knowledge gap prevents further understanding of maintenance of homeostasis of the MEM microenvironment and related disease-specific pathophysiologic mechanisms. The molecular mechanisms of acute otitis media (AOM) development, and the intercellular crosstalk within the multicellular ecosystem of AOM, are not clear
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