Hampered Lung Maturation in Methimazole-Induced Hypothyroidism in Fetal Chicken: Morphological and Molecular Correlates to Human Fetal Development

Background: Molecular understanding of lung development is crucial for developing therapies and diagnostic tools. Animal models with altered thyroid hormone signaling provide mechanistic insight into thyroid-dependent neonatal lung disease. Repression of Klf2 (Krüppel-like factor 2), a suggested T3 target gene, is associated with disrupted lung development in mice. Klf2 is proposed to be specifically involved in type I pneumocyte differentiation. Objectives: To explore mechanisms of thyroid-dependent lung disease, we studied developing chicken fetuses with experimentally induced hypothyroidism. Methods: Morphology and the expression of a panel of molecules linked to Klf2 were assessed using histology, immunohistochemistry, Western blot and qPCR. Results: Methimazole injections at E14 hampered lung maturation. The effects of methimazole were evident in several tissue compartments, and impacted on both pneumocyte and vascular differentiation, suggesting cellular and molecular pleiotropy. Conclusions: Concomitant expression changes in a panel of selected microRNAs regulated by Klf2 suggest importance in lung development. These microRNAs may thus represent potential clinical targets and diagnostic and prognostic tools in thyroid-dependent lung disease.