Monocyte-derived alveolar macrophages drive lung fibrosis and persist in the lung over the life span

Area of Science:

• Immunology
• Pulmonary Medicine
• Cell Biology

Background:

• The roles of different macrophage populations in lung fibrosis remain unclear.
• Understanding these roles is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the distinct contributions of monocyte-derived and tissue-resident alveolar macrophages to lung fibrosis.
• To identify molecular differences between these macrophage populations during fibrosis.

Main Methods:

• Genetic deletion of specific macrophage populations in a mouse model of lung fibrosis.
• Transcriptomic profiling of flow-sorted alveolar macrophages.
• Analysis of human alveolar macrophages from fibrotic and normal lungs.

Main Results:

• Specific deletion of monocyte-derived alveolar macrophages ameliorated lung fibrosis.
• Tissue-resident alveolar macrophages did not contribute to fibrosis development.
• Monocyte-derived alveolar macrophages expressed profibrotic genes during fibrosis, differing from tissue-resident macrophages.
• A persistent population of monocyte-derived alveolar macrophages was observed post-fibrosis resolution.
• Human studies showed upregulated profibrotic genes in alveolar macrophages from fibrotic lungs.

Conclusions:

• Monocyte-derived alveolar macrophages are key drivers of lung fibrosis.
• Targeting alveolar macrophage differentiation offers a potential therapeutic strategy for lung fibrosis.
• This approach may avoid adverse effects of global immune cell depletion.