Figure 7. Neutrophil elastase inhibits expression of elastic fiber assembly components by saccular-stage mouse lung fibroblasts.

(A) Quantification of neutrophil elastase (NE) by ELISA in P5 control and IKTA lung homogenates. Data are expressed as mean ± SEM, n = 4–6 per group, *P < 0.05 by 2-tailed Student’s t test. (B and C) P5 mouse lung fibroblasts were cultured with or without IKTA neutrophils for 4 hours (B) or purified human neutrophil elastase (HNE) 1 μg/mL for 24 hours (C) and Eln and Fbln5 expression was quantified. Where indicated, cells were also pretreated with 10 μM N-methoxysuccinyl-Ala-Ala-Pro-Val-chloromethyl ketone (HNE inhibitor). Data expressed as mean ± SEM, n = 4 per group. Data are representative of 4 independent experiments. *P < 0.05 compared with control by 1-way ANOVA and post hoc Tukey test. (D and E) Saccular-stage mouse lung fibroblasts were cultured with tracheal aspirate exosomes (10⁹ exosomes/mL) isolated from preterm infants with severe BPD or from term-born control infants (CTRL) and Eln (D) and Fbln5 (E) expression was quantified. Data are expressed as mean ± SEM, n = 3 per group, *P < 0.05 by 2-tailed Student’s t test.