Heterogeneity of Fibroblasts and Myofibroblasts in Pulmonary Fibrosis

Purpose of Review Idiopathic pulmonary fibrosis (IPF) is the most common form of interstitial lung disease of unknown etiopathogenesis with mean survival of 3-5 years and limited therapeutics. IPF is characterized by a loss of alveolar type II epithelial cells and aberrant activation of stromal cells, leading to a considerable effort to characterize the origin and activation mechanisms of fibroblasts and myofibroblasts in IPF lungs. In this review, the origin and contribution of fibroblast and myofibroblasts in lung fibrosis will be summarized. Recent Findings Lineage tracing experiments suggested that interstitial lung fibroblasts and lipofibroblasts, pericytes, and mesothelial cells differentiate into myofibroblasts. However, epithelial- and bone marrow-derived cells may give rise to collagen expressing cells but may not contribute to the pool of myofibroblasts. Summary There is great heterogeneity in fibroblasts and myofibroblasts in fibrotic lungs. Further, there is evidence for the expansion of pericyte-derived myofibroblasts and loss of lipofibroblasts and lipofibroblast-derived myofibroblasts in IPF.