Spp1⁺ Macrophages Interact With Mscs Via Spp1–Cd44 In Pulpitis

Aim or purpose To investigate the phenotype of previously identified SPP1⁺ macrophages [1] and their interactions with mesenchymal stem cells (MSCs) in human pulpitis using single-cell RNA sequencing (scRNA-seq). Materials and methods scRNA-seq was performed on inflamed and healthy human dental pulp tissues. Unsupervised clustering identified immune and stromal populations, including a distinct subset of SPP1⁺ macrophages. Cell–cell communication was analyzed using CellChat to explore potential ligand-receptor interactions between macrophages and MSC-like cells. Preliminary investigations into the influence of the SPP1–CD44 axis on in vitro DPSC responses to LPS stimulation were evaluated by qRT-PCR. Results SPP1⁺ macrophages were enriched in inflamed pulp and exhibited a proinflammatory, tissue-remodeling phenotype. Interaction analysis revealed that these macrophages may regulate MSCs via the SPP1–CD44 axis. In vitro, LPS-stimulated DPSCs co-cultured with recombinant SPP1 protein upregulated IL-6 and IL-8 expression, which was attenuated by CD44 neutralizing antibodies. Conclusions Our findings reveal a potential role of SPP1⁺ macrophages in modulating MSC function through SPP1–CD44 signaling during pulpitis. This novel macrophage–MSC interaction highlights a previously unrecognized mechanism within the inflammatory microenvironment of the dental pulp and may offer new targets for controlling inflammation and enhancing regeneration.