The length of telomeres in the lung of young WT, old WT and Terc ko/ko mice was measured using the Absolute Mouse Telomere Length Quantification qPCR Assay Kit (ScienCell research Laboratories, Carlsbad, CA, USA) according to the manufacturer's protocol. Genomic DNA from the lungs was extracted by DNeasy Blood & Tissue Kit (Qiagen, Venlo, Netherlands) according to the manufacturer's protocol. For the PCR 2ng of each sample used. Average telomere length per chromosome end was calculated as described by the manufacturer.