Because of the loss of various DNA repair pathways in progenitor and mesenchymal cells, we next assessed the expression of PRKDC (encoding for DNA-PKcs), which is required for DNA damage signaling, double strand break repair, telomere maintenance and resistance to oxidative stress [11, 12, 27, 28] in rapid- and slow-IPF SSEA4+ progenitors and SSEA4− fibroblasts. This evidence concerns the gene PRKDC and idiopathic pulmonary fibrosis.