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

ABSTRACT 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.