Fibrotic Signaling in the Lung

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring of the lung parenchyma, which ultimately leads to impaired gas exchange, respiratory failure, and death. Studies of patients, cells, and laboratory animals over the last 30 years have led to an ever-increasing corpus of knowledge, based on studies of ever-increasing degrees of sophistication and on the signaling events that occur during lung injury and fibrosis. This review summarizes many of the signaling mechanisms that occur in, arguably, the three principal cellular actors in the fibrotic lung: the epithelial cell, the macrophage, and the fibroblast. The growth of lung fibrosis research, coupled with an intense interest on the part of industry to devise therapies, suggests that new therapies are coming that are rationally designed to target these critical signaling events. This chapter will focus on both the cellular players and the signaling events that contribute to pulmonary fibrosis.