TNF and periapical periodontitis: In addition to OSM, our scRNA-seq data showed that periodontal neutrophils highly expressed IL-1 and TNF, suggesting that neutrophils may act as an important source of osteoclastogenic cytokines in periodontal bone loss.41,42 Since the marked accumulation of neutrophils was also reported in an apical periodontitis model,43 the neutrophil-osteogenic cell axis may have a role in bone damage associated with endodontic infection.