Exploring Periodontitis-Associated Fibroblast Interactions via Single-Cell RNA Sequencing

Periodontitis is a chronic inflammatory disease associated with dysbiotic plaque biofilm and is characterized by the progressive destruction of the tooth-supporting apparatus. The purpose of this study was to utilize single-cell RNA sequencing (scRNA-seq) to profile gene expression patterns from gingival tissues affected by periodontitis, and to analyze the interactions between fibroblasts, which remodel the extracellular matrix (ECM), and other cell types at the single-cell level. Our hypothesis is that periodontitis induces significant transcriptional changes in fibroblasts resulting in dysregulated interactions between fibroblasts and other cell types. The raw scRNAseq data of human periodontitis samples was obtained from the National Center for Biotechnology Information database (GSE171213). The data was re-analyzed using RStudio and R packages Seurat and CellChat. We identified specific cell types, including fibroblasts and epithelial, endothelial, and immune cells, and their unique gene expression patterns in both diseased and healthy states. We utilized CellChat to decode complex intercellular communication pathways, focusing on the ligand-receptor interactions involving fibroblasts with other cell types. Fibroblasts presented with the highest outgoing interaction strength compared to all other cell types. They were highly active within the context of periodontal disease, especially in their signaling toward epithelial, endothelial, and immune cells. Specific ECM molecules, such as specialized collagen subtypes (COL4A1/2, COL6A1/3) and the provisional ECM molecule fibronectin (FN1), were most highly upregulated in periodontitis-associated fibroblasts compared to fibroblasts in healthy tissues, with a parallel upregulation of receptor CD44 in all target cells. Our findings indicate an upregulation of fibroblast-mediated ECM signaling in periodontitis, and we identified unique ECM molecules that are known to be important in inflammatory and fibrotic processes. These results pave the way for mechanistic studies exploring the role of periodontitis-associated fibroblasts in disease progression.