Function of normal oral mucosa revealed by single-cell RNA sequencing.

The functions of oral mucosa include barrier, sensation, and secretion. The barrier protection function is particularly important, which includes physical barrier and immunological barrier. Few studies have revealed the function of oral mucosa by displaying the map of normal oral mucosal cells from the perspective of single cells. Here, single-cell transcriptome sequencing was used to bring a relatively comprehensive map of the normal oral mucosal cells. In total, 26,398 cells from three cases of normal oral mucosa were analyzed by single-cell RNA-sequencing and 14 distinct cell groups were defined, 7 of which were immune cells. We performed subgroup classification and heterogeneity analysis of epithelial cells, T cells, and macrophagocytes, which found a subpopulation of epithelial cells with high expression of major histocompatibility complex class II molecules, a subpopulation CD8 GZMK T cells, and two kinds of active macrophagocytes. Meanwhile, we identified ligand-receptor pairs among the major cell types to explore the interactions and how they maintain the homeostasis of normal oral mucosa. Based on these results, the epithelial barrier function, immunological barrier function, and potential maintenance function of stromal cells in the oral mucosa were described at the single-cell level, which provides basic data resources for further studies of oral mucosal diseases.