The differences in microbiota between periodontitis and health have been extensively studied; however, knowledge about how the microbiota shifts from shallow to deep periodontal pockets remains limited despite its clinical importance in disease progres-sion and management. Patients diagnosed with stage III periodontitis commonly pre-sent varied probing depths (PD) within the same oral cavity, reflecting localized disease severity. This study aims to analyze the microbiome of subgingival plaques at various PDs in periodontitis patients. Subgingival plaques were collected from sixteen healthy subjects (health group) and periodontal pockets of sixteen stage III periodontitis pa-tients (PD 0–3 mm, PD 4–5 mm and PD 6–9 mm groups). A total of 64 subgingival plaque samples underwent 16S rRNA gene sequencing. The PD 6–9 mm group exhib-ited significantly higher alpha diversity than the health group, and distinct subgingival microbial community structures were observed in periodontitis patients, regardless of probing depth. The relative abundance of specific genera differed notably between health and periodontitis states; Corynebacterium and Cardiobacterium decreased, whereas Schaalia increased in shallow pockets (PD 0–3 mm) of periodontitis relative to the health group. Co-occurrence network analysis on the species level revealed that the PD 4–5 mm group had the most complex interspecies interactions, followed by the PD 6–9 mm and PD 0–3 mm groups. These findings indicate significant variations in mi-crobial diversity, composition, and interspecies interactions associated with periodon-tal health and periodontitis severity, highlighting their potential relevance for clinical diagnosis and targeted therapeutic strategies.

Periodontal bone regeneration depends on the coordinated interplay between osteogenesis and angiogenesis; however, the molecular regulation underlying osteogenic–angiogenic coupling remains incompletely understood. Despite previous evidence that miR-508-5p downregulation enhances the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) in vitro, its role in regulating angiogenesis and bone formation in vivo remains unclear. In the present study, miR-508-5p was modulated using synthetic inhibitor and mimic oligonucleotides, and its effects on osteogenesis, angiogenesis, and osteogenic–angiogenic coupling were investigated by the use of alkaline phosphatase and alizarin red S staining, conditioned-medium assays, a chicken chorioallantoic membrane assay, and a nude mouse ectopic bone formation model. The responses to miR-508-5p inhibition differed by cell type: osteogenic differentiation increased in hPDLSCs, while human umbilical vein endothelial cells (HUVECs) showed greater proliferative, migratory, and tube-forming activity. Conditioned medium experiments further revealed that miR-508-5p inhibition enhanced the reciprocal paracrine effects between hPDLSCs and HUVECs, thereby promoting both osteogenic and angiogenic responses. In vivo, miR-508-5p inhibition enhanced bone-like tissue formation and collagen deposition, accompanied by the elevated expression of collagen type I alpha 1 chain, bone morphogenetic protein 2, and the angiogenic marker CD31. Taken together, the findings support a potential regulatory role for miR-508-5p in osteogenic–angiogenic coupling and indicate that this microRNA may warrant consideration as a candidate target in therapeutic strategies for periodontal bone regeneration.