Idiopathic pulmonary fibrosis: misunderstandings between epithelial cells and fibroblasts?

Idiopathic pulmonary fibrosis is a complex disease of unknown etiology which produces a progressive and irreversible destruction of the alveolar-capillary units leading ultimately to death from respiratory failure. For a long time the pathogenesis of the disease was attributed to an unresolved chronic alveolitis. However, a growing body of evidence suggests that inflammation does not play a major role in this disease, and that the pivotal pathogenic mechanisms include epithelial cell microinjuries/activation, and fibroblast migration, proliferation, and differentiation in myofibroblasts forming discrete foci in the injured areas. Active fibroblasts/myofibroblasts from these foci may in turn disturb alveolar re-epithelialization, by provoking basement membrane disruption and epithelial cell apoptosis finally resulting in exaggerated extracellular matrix accumulation. This aberrant repair process annihilates the lung architecture leading to the honeycomb remodeling.