Mural cell composition and functional analysis in the healing process of human gingiva from periodontal intrabony defects

Objective: To evaluate the composition and function of mural cell populations in human gingival tissues. Design: A cross-sectional study was conducted on seven periodontitis (stage Ⅲ) patients. Gingival tissues were collected two months after scaling and root planing and divided into 3 groups: 1, h_h group (horizontal bone resorption, residual pocket depth ≤3 mm); 2, v_h group (vertical bone resorption >4 mm, residual pocket depth ≤3 mm); 3, v_i group (vertical bone resorption >4 mm, residual pocket depth ≥6 mm). Single-cell RNA sequencing (10X genomics) and subsequent bioinformatics analysis were performed. Protein expression of selected genes was confirmed by histological staining. Results: Two mural cell clusters, RGS5+THY1+ and ACTA2+MYH11+ subpopulations, were identified and confirmed by histological staining and cross-validation with three different single-cell RNA sequencing datasets in the GEO database. RGS5+THY1+ cluster in perivascular areas possessed cellular protrusions and exhibited immunomodulatory and synthetic phenotypes. In contrast, the ACTA2+MYH11+ cluster strictly distributed around vessel walls was characterized by a contractile phenotype. Mural cells closely interacted with endothelial cells through PDGF and NOTCH3 signaling. Mural cell loss was detected in the v_i group and in hopeless periodontal teeth, which might be caused by tumor necrosis factor-alpha induced apoptosis. Conclusions: Gingival mural cells can be classified into two distinct clusters according to their gene signatures and cell morphology. The loss of mural cells may indicate periodontitis progression.