2.4. Human Lung Slices

Peripheral lung tissue from COPD GOLD 1 (n = 5, all ex-smokers, two females) and GOLD 2 (n = 2, one ex-smoker and one current smoker) patients and from non-COPD control subjects (n = 5) was obtained from subjects (n = 4, three ex-smokers, one current smoker, one female) undergoing surgery for lung cancer using tumor-free tissue far from the tumor site and one control that was obtained from a non-transplanted donor lung (smoking status unknown). Median age was 64 (42–71) years for the COPD groups and 66 (42–69) years for the control group. All tissue was collected according to the Research Code of the University Medical Center Groningen (https://www.umcg.nl/SiteCollectionDocuments/English/Researchcode/umcg-research-code-2018-en.pdf, accessed on 19 April 2021) and national ethical and professional guidelines (‘Code of conduct’, Dutch federation of biomedical scientific societies, http://www.coreon.org, accessed on 19 April 2021). Precision cut lung slices were prepared as previously described [3,22]. After placing the lung tissue on a metal plate on ice, 2% low-melting agarose in slicing buffer was slowly and evenly injected at several sites of the tissue and the tissue was covered with ice for 15 min. Cylindrical cores of 15 mm in diameter were prepared, cut with a tissue slicer into 500 μm thin slices, and processed as described above for guinea pig lung slices.