In vitro primary human alveolar epithelium/endothelium and fibroblast model: a tool for investigating IPF and treatment strategies

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease. While the etiology of IPF remains unknown, it is characterized by recurrent injuries and the dysregulated release of fibrotic and inflammatory factors, leading to progressive scarring of the alveoli. The current paradigm suggests that TGF-β1 plays a crucial role in the initiation of fibrosis by inducing extracellular matrix stiffening through the fibroblast-to-myofibroblast transition (FMT) and epithelial-to-mesenchymal transition (EMT). This study aims to develop an IPF model using human primary cells. We use AlveolAir™, a tight epithelium composed of type I and II pneumocytes, cultured at the air-liquid interface, along with endothelial cells and fibroblasts. AlveolAir™ and fibroblasts were stimulated with TGF-β1 and TNF-α. AlveolAir™ received daily apical stimulation for 72 hours. Nintedanib and Pirfenidone, used as reference antifibrotics, were tested concomitantly with the stimulation in the basal culture medium. FMT, was assessed via α-SMA analysis, and EMT through cytokines quantification. The expression of α-SMA in the stress fibers were observed after stimulation, quantified by immunofluorescence, resulting in a significant increase in mean intensity. Following stimulation, the co-culture exhibited a significant increase in the release of matrix metalloproteinases, MMP1 and MMP3—biomarkers also observed in patients with IPF. Exposing the stimulated model to Nintedanib or Pirfenidone significantly reduced α-SMA expression and cytokine secretion. This IPF-induced model could improve preclinical antifibrotic screening and deepen the understanding of IPF molecular mechanisms.