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A4635 - The Lung Microenvironment Shapes the Alveolar Macrophage Transcriptome During Aging
Author Block: A. C. Mc Quattie-Pimentel1, C. Chen1, Z. Ren1, P. A. Reyfman1, K. M. Ridge1, H. Perlman2, A. Misharin1, G. Budinger1; 1Pulmonary and Critical Care, Northwestern University, Chicago, IL, United States, 2Rheumatology, Northwestern University, Chicago, IL, United States.
Rationale: Aging is associated with increased morbidity and mortality attributable to influenza infection. We used unbiased transcriptional profiling of flow sorted cell populations to identify a reproducible age-related signature in mouse alveolar macrophages and alveolar type II cells that persists during influenza infection. We sought to determine whether age related changes in the transcriptional profiles of alveolar macrophages are cell autonomous or driven by the aged microenvironment. Methods: We optimized protocols to adoptively transfer tissue resident macrophages, and used these protocols to perform heterochronic adoptive transfer of tissue-resident alveolar macrophages from aged CD45.2 mice (18 months) into the lungs of young naïve CD45.1 mice (4 months) and vice versa. Sixty days after transfer mice were infected with influenza A virus (A/WSN/33, 25 pfu/mouse). Alveolar macrophages and alveolar type 2 cells were FACSorted. After RNA extraction and poly (A) enrichment libraries were constructed and single-end RNA-seq was performed. Principal component analysis and K-mean clustering were performed and were used to guide functional enrichment analysis of the RNA-seq data. Results: Principal component analysis of the RNA-seq data demonstrated that 32.8% of the variance within the data in alveolar macrophages was explained by age. Old cells transferred into a young microenvironment clustered between the young and old control samples. K-means clustering revealed similarities between the old transferred cells and the young controls, as well as the young transfer cells with the old controls. Functional analysis of genes upregulated in old cells transferred to a young microenvironment using GO annotation pathways identified enrichment for genes involved in cell cycle, cell division and cellular component organization. Principal component analysis and K-means clustering of alveolar type 2 cells revealed no difference between controls and recipients. Conclusion: This finding suggests that aged lung microenvironment is primarily responsible for the age related changes in alveolar macrophages during homeostasis and after influenza A infection.