Primary cell-based phenotypic assays to pharmacologically and genetically study fibrotic diseases in vitro

Ongoing tissue repair and formation and deposition of collagen-rich extracellular matrix in tissues and organs finally lead to fibrotic lesions and destruction of normal tissue/organ architecture and function. In the lung, scarring is observed in asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis to various degrees. At the cellular level immune cells, fibroblasts and epithelial cells are all involved in fibrotic processes. Mechanistically, fibroblast to myofibroblast transformation and epithelial to mesenchymal transition are major drivers of fibrosis. Amongst others, both processes are controlled by transforming growth factor beta-1 (TGFβ-1), a growth factor upregulated in idiopathic pulmonary fibrosis lungs. Phenotypic assays with primary human cells and complex disease-relevant readouts become increasingly important in modern drug discovery processes. We describe high-content screening based phenotypic assays with primary normal human lung fibroblasts and primary human airway epithelial cells. For both cell types, TGFβ-1 stimulation is used to induce fibrotic phenotypes in vitro, with alpha smooth muscle actin and collagen-I as readouts for FMT and E-cadherin as a readout for EMT. For each assay, a detailed image analysis protocols is described. Treatment of both cell types with TGFβ-1 and a transforming growth factor beta receptor inhibitor verifies the suitability of the assays for pharmacological interventions. In addition, the assays are compatible for siRNA and Cas9-ribonucleoprotein transfections, and thus are useful for genetic target identification/validation by modulating gene expression.