Fig. 3.

CELA1 is expressed in lung fibroblasts or fibroblast-like cells. A: immunohistochemistry for CELA1 demonstrated CELA1⁺ cells near the pulmonary artery (art) of PND1 mice. Scale bar = 50 μm. B: in PND5 lung, CELA1⁺ cells were predominantly located in alveolar walls and bases. Scale bar = 20 μm. C: CELA1⁺ cells remained in the adventitia of the adult lung. Scale bar = 50 μm. D: Dermo1-cre/Tomato heterozygous mice express green fluorescent protein (GFP) in mesenchymal cells and red fluorescent protein in nonmesenchymal cells. PND9 lung sections costained for CELA1 (purple) demonstrated expression only in green mesenchymal cells (white arrows). Scale bar = 20 μm. E: by flow sorting of PN 8 wk Dermo1-cre/Tomato lung cell suspension, CELA1 mRNA was present only in GFP⁺ cells. Cells were from one mouse. F: in PN 8 wk frozen sections, CELA1 (green) localized to a subset of cells expressing the fibroblast marker desmin (red). Red arrows identify cells only positive for desmin, and yellow arrows identify cells strongly positive for desmin and CELA1. Some CELA1⁺ cells (green arrows) stained only weakly for desmin; 71% of CELA1⁺ cells were strongly positive for desmin. Scale bar = 50 μm.