BrdU labeling and immunostaining were used to evaluate cell proliferation in mouse lung sections [23 (link), 25 (link)]. BrdU (75mg/kg BW) was administered i.p. to mice at 4h prior to tissue collection. Mouse lung cryosections (5 μm) were stained with FITC-conjugated anti-BrdU using the In Situ Cell Proliferation kit following the manufacturer’s instructions (Roche Applied Science). Endothelial cells were stained with anti-CD31 (1:40, Abcam) and -vWF (1:250, Sigma-Aldrich) antibodies while nuclei were counterstained with DAPI (Invitrogen).