Idiopathic pulmonary fibrosis: immunohistochemical analysis provides fresh insights into lung tissue remodelling with implications for novel prognostic markers.

AIM

This study explored the cellular and biological interrelationships involved in Idiopathic Pulmonary Fibrosis (IPF) lung tissue remodelling using immunohistochemical analysis.

METHODS AND RESULTS

IPF and control lung tissues were examined for localisation of Epithelial Mesenchymal Transition (EMT), proliferation and growth factor markers assessing their relationship to key histological aberrations. E-cadherin was expressed in IPF and control (Alveolar type II) ATII cells (>75%). In IPF, mean expression of N-cadherin was scanty (<10%): however 4 cases demonstrated augmented expression in ATII cells correlating to histological disease status (Pearson correlation score 0.557). Twist was expressed within fibroblastic foci but not in ATII cells. Transforming Growth Factor- β (TGF-β) protein expression was significantly increased in IPF ATII cells with variable expression within fibroblastic foci. Antigen Ki-67 was observed within hyperplastic ATII cells but not in cells overlying foci. Collagen I and α-smooth muscle actin (α-SMA) were strongly expressed within fibroblastic foci (>75%); cytoplasmic collagen I in ATII cells was present in 3 IPF cases. IPF ATII cells demonstrated variable Surfactant Protein-C (SP-C).

CONCLUSIONS

The pathogenesis of IPF is complex and involves multiple factors, possibly including EMT. Histological analysis suggests TGF-β-stimulated myofib rob lasts initiate a contractile response within established fibroblastic foci while proliferating ATII cells attempt to instigate alveolar epithelium repair. Marker expression (N-cadherin and Ki-67) correlation with histological disease activity (as reflected by fibroblastic foci extent) may emerge as future prognostic indicators for IPF.