Clonality analysis of fibroblast proliferation in patients with idiopathic pulmonary fibrosis / 대한내과학회지

ABSTRACT

BACKGROUND/AIMS: Idiopathic pulmonary fibrosis (IPF) is defined pathologically by usual interstitial pneumonia (UIP), and contains characteristic discrete areas of fibroblasts, myofibroblasts, and newly formed collagen, termed "fibroblast foci". A new hypothesis postulates that IPF results from epithelial injury and abnormal wound repair without preceding chronic inflammation. We explored the hypothesis that fibroblasts in the fibroblast foci of IPF undergo neoplastic monoclonal proliferation rather than reactive polyclonal proliferation. METHODS: We obtained fibroblasts from 24 fibroblast foci in seven female patients with IPF, endothelial cells from ten plexiform lesions of two female patients with idiopathic pulmonary arterial hypertension (IPAH) as a positive control for monoclonality, and lung parenchymal cells by microdissection of each formalin-fixed paraffin-embedded block of lung. To analyze clonality, we performed the human androgen-receptor gene methylation assay (HUMARA). DNA released by protein K digestion was subjected to polymerase chain reaction (PCR) amplification with prior digestion with and without the methylation-sensitive restriction enzyme HhaI. Then, we calculated the clonality ratio after electrophoretic analysis of the PCR amplification product. A clonality ratio 0.25, suggesting polyclonality, whereas 7 of 10 plexiform lesions had clonality ratios <0.25 suggesting monoclonality. CONCLUSIONS: The polyclonality of the fibroblast foci in IPF suggests that the fibroblast proliferation in IPF is not neoplastic, but is reactive in nature