Neutrophil-Mediated Inflammatory Response to Zinc Bone Implants: A Single-Cell Transcriptomic Landscape

Zinc (Zn)-based metals have been considered as promising materials for bone regeneration and repair. Neutrophils, as the initial responders in the acute inflammatory phase, play a critical role by generating specialized mediators that facilitate the natural resolution of inflammation. Nevertheless, the mechanisms governing neutrophil-driven inflammation following the implantation of Zn-based metals are not fully elucidated. This study investigated neutrophil-macrophage crosstalk around Zn-based implants using single-cell transcriptomic profiling. A high-resolution cellular atlas of the peri-implant bone marrow microenvironment was generated in a rat femoral model comparing Zn-based implants with the titanium (Ti) ones. The results revealed that Zn implants induced a distinct neutrophil (Neu) subset heterogeneity, including Cd177⁺ Neu, Ifit1bl⁺ Neu, RatNP-3b⁺ Neu, and Prtn3⁺ Neu, the latter demonstrating enhanced tissue repair ability through osteoclast differentiation pathways. Zn-based metallic implants reduced macrophage (Mac) reactivity and promoted Hp⁺ Mac dominance compared to Ti implants, which showed higher Apoe⁺ Mac proportions. Crosstalk analysis identified a significant interaction between the neutrophil subset Ifit1bl⁺ Neu and the macrophage subset Eno3⁺ Mac under Zn implantation, mediated by the Lgals9-Ighm ligand-receptor axis. These findings suggested that degradation products of Zn-based implants modulated immune cell differentiation and interaction networks, thereby modulating biological response.