In vitro, although AEC-II cells can give rise to alveolar-like colonies, they possess limited clonogenic capacity that decreases with passaging.47 Importantly, their number and function decline with age and in certain pathological conditions,48,49 including IPF.50 To determine whether interrupted reprogramming is able to rescue the in vitro limited clonogenic capacity of AEC-II cells, we isolated AEC-II cells from R26-rtTA/Col1a1::tetO-4F2A double transgenic mice51 enabling expression of OSKM following treatment with doxycycline (Dox). Here, COL1A1 is linked to idiopathic pulmonary fibrosis.