B77-21 Senomorphic Effects of Metformin Promotes Resolution of Age-Associated Lung Fibrosis

Rationale Aging is accompanied by a decline in tissue repair mechanisms and the development of non-resolving fibrosis across organ systems, contributing significantly to morbidity and mortality in the elderly. Idiopathic pulmonary fibrosis (IPF) is detrimental, progressive and aging-related lung disease characterized by excessive extracellular matrix deposition and loss of respiratory function. This study investigates whether AMPK activator metformin reverses established fibrosis and to delineate the underlying cellular and molecular mechanisms of fibrosis resolution in aging. Methods Lung fibrosis was induced in young (10-week) and aged (72-week) mice by orthopharyngeal administration of bleomycin (1.25 U/kg). Metformin (65 mg/kg, i.p.) was administered every other day for 14 days beginning 21 days post-bleomycin, coinciding with the peak of fibrosis. Lung tissues were analyzed using H&E, Masson’s Trichrome, and hydroxyproline assay. Flow cytometry, immunofluorescence, and microscopy characterized alveolar and interstitial macrophage subsets. Protein expression and cytokine profiles were evaluated using Western blotting, ELISAs, and proteome arrays. Selected mechanistic findings were validated in lung tissues and bronchoalveolar lavage fluids from IPF patients (n=6) and healthy control (n=6). Results Fibrotic lungs from both mice and IPF patients displayed increased infiltration of monocyte-derived alveolar macrophages (Mo-dAM). Metformin effectively reduced macrophage-dependent production of TGF-β1, a key driver of fibroblast activation, while promoting secretion of hepatocyte growth factor (HGF), a pro-resolving mediator. In aged mice, metformin attenuated markers of inflammaging and decreased fibroblast release of senescence-associated secretory phenotype (SASP) factors. This intervention promoted fibrosis resolution comparable to that seen in younger animals. Mechanistically, metformin activated AMP-activated protein kinase (AMPK), which restored efferocytosis (clearance of apoptotic cells) and supported a macrophage phenotype competence to tissue repair. Conclusions Metformin facilitates resolution of established, aging-associated lung fibrosis by reprogramming macrophage function, reducing profibrotic signaling, and restoring tissue homeostasis through AMPK activation. These findings highlight metformin’s potential as a senomorphic therapeutic strategy to counteract persistent fibrosis and age-related decline in tissue repair. This abstract is funded by: 2R01HL139617/NIH/NHLBI; HT9425-24-1-0304/US DOD