Fig. 1.

Elastin remodeling over the course of lung development. A: to quantify elastin remodeling during development, we performed elastin in situ zymography (green) and normalized the signal to tropoelastin (red). A lung image at postnatal day 10 (PND10) is shown. Scale bar = 1,000 μm. B: an example of the elastin surface created based on the tetramethylrhodamine isothiocyanate channel (red) and the manual exclusion mask for debris, nonpulmonary organs, and folded tissue (gray). C: within this elastin surface, the elastase (green) and elastin (not shown) signals were quantified. D: the lungs of three different animals per time point were imaged. Lung elastin remodeling began increasing with the onset of alveolarization [between PND3 and PND7, peaked at PND10, and then decreased to embryonic levels by postnatal week 8 (PN 8wk)]. This level of remodeling (normalized to 1) represents the baseline signal of the assay (dashed line). Only differences by t-test are shown. Elastase activity values were significantly different by ANOVA (P < 0.001).