Lung tissue gene-expression signature for the ageing lung in COPD.

Introduction: COPD is a chronic, progressive, inflammatory disease of the lungs and the third leading cause of death worldwide. The current knowledge of the pathophysiology of COPD is limited and novel insights in underlying disease mechanisms are urgently needed. Since there are clear parallels between ageing and COPD, we investigated genes underlying lung ageing in general and abnormal lung ageing in COPD.

Methods: Whole genome mRNA profiling was performed on lung tissue samples (n=1197) and differential gene expression with increasing age was analysed using an adjusted linear regression model. Subsequent pathway analysis was performed using GeneNetwork and the gene-expression signature was compared with lung ageing in the Genotype-Tissue Expression (GTEx) project. In a subset of patients with COPD (n=311) and non-COPD controls (n=270), we performed an interaction analysis between age and COPD to identify genes differentially expressed with age in COPD compared with controls, followed by gene set enrichment pathway analysis.

Results: We identified a strong gene-expression signature for lung ageing with 3509 differentially expressed genes, of which 33.5% were found nominal significant in the GTEx project. Interestingly, we found as a strong candidate gene for lung ageing. The age*COPD interaction analysis revealed 69 genes significantly differentially expressed with age between COPD and controls.

Conclusions: Our study indicates that processes related to lung development, cell-cell contacts, calcium signalling and immune responses are involved in lung ageing in general. Pathways related to extracellular matrix, mammalian target of rapamycin signalling, splicing of introns and exons and the ribosome complex are proposed to be involved in abnormal lung ageing in COPD.