A Mouse Model of Asthma

<p><strong>Introduction</strong>: Mouse models show that prolonged transforming growth factor alpha (TGFα) expression promotes chronic lung disease particularly in early growth response-1 (Egr-1) deficient mice. Notably, airway smooth muscle (ASM) is thickened and the exaggerated increase in lung resistance following bronchoconstrictor challenge supports a role in airway disease.</p> <p><strong>Aim</strong>: We aimed to determine the effect of short-term TGFα expression on ASM thickening and the development of airway hyperresponsiveness (AHR).</p> <p><strong>Method</strong>: TGFα was conditionally expressed in the airway epithelium of transgenic mice (Clara cell secretory protein-rtTA(+/−)/[tetO](7)-TGFα(+/−)) following 10 d exposure to doxycycline in chow. Egr-1 deficient mice on doxycycline (n = 5) were compared with a control group (n = 4) that were wild type for Egr-1 and did not receive doxycycline. Airway and lung mechanics were assessed by the forced oscillation technique and lungs fixed for subsequent airway morphometry.</p> <p><strong>Results</strong>: ASM thickening was detected in TGFα transgenic Egr-1 deficient mice (P < 0.05) following doxycycline treatment for 10 d. AHR was also demonstrated, defined by an exaggerated increase in Newtonian resistance after methacholine challenge (P < 0.05) compared with controls. In comparison, there was no effect on lung elastance or tissue damping before or after methacholine.</p> <p><strong>Conclusion</strong>: Doxycycline induced-TGFα expression in Egr-1 deficient mice, after 10 d, produces ASM remodelling and AHR with no change in parenchymal mechanics. Short-term TGFα expression in airway epithelial cells promotes features characteristic of asthma.</p>