Mitochondrial reprogramming of alveolar macrophages by umbilical cord mesenchymal stem cells restores immune homeostasis in Porphyromonas gingivalis lipopolysaccharide-induced aspiration pneumonia.

Aspiration pneumonia represents a severe form of acute lung injury (ALI) in which oral pathogen-derived factors disrupt pulmonary immune homeostasis. Lipopolysaccharide (LPS) from Porphyromonas gingivalis (Pg), a key periodontal pathogen, acts as a potent immunogenic stimulus that drives macrophage (MΦ) dysregulation. Human umbilical cord-derived mesenchymal stem cells (UCMSCs) have emerged as living biomaterials with intrinsic immunomodulatory and regenerative properties; however, their mechanisms of action in Pg LPS-induced aspiration pneumonia remain incompletely defined. Here, we integrate in silico transcriptomic analysis, single-cell RNA sequencing, and in vitro and in vivo models to characterize MΦ subset-specific responses to Pg LPS and to evaluate UCMSC-mediated immunomodulation. Pg LPS induces robust M1 polarization programs associated with inflammatory signaling pathways, while single-cell analysis reveals baseline heterogeneity among lung MΦ subsets, including M1-skewed recruited MΦs, mixed interstitial MΦs, and predominantly M2 alveolar MΦs. In vitro, Pg LPS drives M1 polarization across all subsets, which is effectively reversed by UCMSCs. In vivo, Pg LPS exposure predominantly reprograms recruited and alveolar MΦs toward a pro-inflammatory phenotype, whereas UCMSC treatment effectively restores alveolar MΦs to an anti-inflammatory M2 state. Mechanistically, UCMSCs function as bioactive carriers that transfer mitochondria to alveolar MΦs, thereby reprogramming their metabolic and immunological states. This is accompanied by suppression of IL-6 and TNF-α, increased IL-10 production, preservation of alveolar architecture, and improved physiological outcomes. Collectively, these findings identify alveolar macrophages as key immunological targets in Pg LPS-induced lung injury and establish UCMSCs as a next-generation immunomodulatory platform that restores immune homeostasis via mitochondrial transfer. This work highlights the potential of cell-based biomaterials as dynamic immunomodulatory adjuvants for treating aspiration pneumonia and other inflammation-driven diseases.