Such models include, for example, human embryonic lung cell lines as well as primary cultures of human lung fibroblasts from either donor or IPF lungs to study the impact of signals inducing their differentiation towards the alveolar fibroblasts/lipofibroblast phenotype, such as with metformin [37] or towards the activated myofibroblasts phenotype (for example, upon treatment with TGF-β1). Here, TGFB1 is linked to idiopathic pulmonary fibrosis.