Epithelial-fibroblast interactions in IPF: Lessons from in vitro co-culture studies

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial disease that is characterized by increased cellular proliferation and differentiation together with excessive extracellular matrix (ECM) deposition leading to buildup of scar tissue (fibrosis) and remodeling in the lungs. The activated and differentiated (myo)fibroblasts are one of the main sources of tissue remodeling in IPF and a crucial mechanism known to contribute to this feature is an aberrant crosstalk between pulmonary fibroblasts and the abnormal or injured pulmonary epithelium. This epithelial-fibroblast interaction mimics the temporal, spatial and cell-type specific crosstalk between the endoderm and mesoderm in the so-called epithelial-mesenchymal trophic unit (EMTU) during lung development that is proposed to be activated in healthy lung repair and dysregulated in various lung diseases including IPF. To study the dysregulated lung EMTU in IPF, various complex in vitro models have been established. Hence, in this review, we will provide a summary of studies that have used complex (3-dimensional) in vitro co-culture, and organoid models to assess how abnormal epithelial-fibroblast interactions in lung EMTU contribute to crucial features of the IPF including defective cellular differentiation, proliferation and migration as well as increased ECM deposition.

Understanding fibroblast-immune cell interactions via co-culture models and their role in asthma pathogenesis

Asthma is a chronic lung disease involving airway inflammation and fibrosis. Fibroblasts are the main effector cells important for lung tissue production which becomes abnormal in asthmatics and is one of the main contributors to airway fibrosis. Although fibroblasts were traditionally viewed solely as structural cells, they have been discovered to be highly active, and involved in lung inflammatory and fibrotic processes in asthma. In line with this, using 2D and 3D in vitro co-culture models, a complex interaction between lung fibroblasts and various immune cells important for the pathogenesis of asthma have been recently uncovered. Hence, in this review, we provide the first-ever summary of various studies that used 2D and 3D in vitro co-culture models to assess the nature of aberrant immune cell-fibroblast interactions and their contributions to chronic inflammation and fibrotic mechanisms in asthma pathogenesis.