While we observed an involvement of PDGFRα+ cells in collagen production during the active phase of lung fibrosis development, αSMA+ cells have been shown to play an important role in the resolution phase of bleomycin-induced lung fibrosis (10), suggesting that the contribution of these two cell populations to the lung fibrosis process also depends on their different temporal appearance. Here, PDGFRA is linked to pulmonary fibrosis.