Somatic DNA alterations in lung epithelial barrier cells in COPD patients

Background: Instability of the Microsatellite DNA Instability (MSI) and Loss of Heterozygosity (LOH) have been previously detected in sputum cells of COPD patients. However, the particular cell subpopulation exhibiting genetic instability in COPD was uncertain. The aim of this study was to determine which cell type expresses Microsatellite DNA Instability in sputum and BALF samples from COPD patients.

Methods: Thirty-five COPD patients and 30 non-COPD smokers were studied. Sputum was induced from 20 COPD patients and 20 non-COPD smokers and BALF was obtained from 15 COPD patients and 10 non-COPD smokers. The sputum cell pellet and BALF samples were processed using immunomagnetic technology to separate antibody-specific cell subpopulations, using CD45+ for leukocytes, Epithelial enrich (MACS) for sputum epithelial cells and HEA-human epithelial antigen-(Dynal) for BAL epithelial cells. Microsatellite DNA amplification was performed using specific primers, namely G29802, D6S2223, D6S344, D6S263, D5S207, D13S71, RH70958, and D17S250. The presence of MSI and/or LOH was analyzed with LI-COR Saga GT Microsatellite Analysis Software.

Measurements and main results: None of the non-COPD smokers exhibited any genetic alteration. MSI and LOH were found in 15 cases (8 MSI and 7 LOH) in sputum and BAL samples. MSI and/or LOH were revealed only in the epithelial barrier cells. LOH was detected in D5S207, D6S344, G29802 and D17S250 microsatellite markers, while MSI in D13S71, D5S207 and D6S344. The entire leukocyte subpopulation exhibited no genetic alteration.

Conclusions: Our results support the hypothesis that chronic inflammation and oxidative burden in COPD can lead to DNA damage of the lung epithelial barrier cells, detected at the Microsatellite DNA level. Further studies are required to investigate the significance of these findings in the pathogenesis of COPD.