We applied this technique to segregate CTFR-hi and CTFR-lo fibroblasts from IPF lungs (from patients undergoing lung transplantation), and qPCR demonstrated significant enrichment of p16INK4a expression in the CTFR-hi population (but not p14ARF encoded in the same locus) along with other pathologic fibroblast markers such as p21, CTHRC1, HAS1, and PostN (Figure 6F, Supplemental Figure 7D). This evidence concerns the gene HAS1 and idiopathic pulmonary fibrosis.