Regulation of Lung Development by miRNAs and Hox Genes.
Abstract: Preterm birth is the leading cause of morbidity in the first year of life. This is due to incomplete lung development that leads to acute and chronic respiratory diseases. MicroRNAs and Hox genes play important roles in regulating biological processes, including organ morphogenesis and maturation. However, little is known about how miRNA and Hox genes regulate lung development. In the ... read morefirst part of this study, we profiled the expression of 376 miRNAs in male and female fetal mouse lungs of gestational days E15 - E18, a time period when several important developmental and cellular events occur. Statistical analyses identified 25 and 37 miRNAs that changed significantly between genders and with gestation, respectively. Ingenuity Pathway Analysis identified miRNA regulated networks, many of which are important to lung development. Next, we examined how anti-angiogenic miR-221 and pro-angiogenic miR-130a affect airway and vascular development in the developing lung. Downregulating miR-221 or upregulating miR-130a in E14 fetal mouse lungs resulted in more distal branch generations and vascular development as evident by increased VEGFR2 and lectin staining around airways. The opposite phenotype was observed with upregulating miR-221 or downregulating miR-130a. Furthermore, some of these effects were mediated through Hoxb5 and Hoxa5, targets of miR-221 and miR-130a, respectively. In vitro, upregulation of miR-221 in endothelial cells resulted in reduced tube formation and cell migration, whereas the reverse was observed with miR-130a upregulation. Based on results, we conclude that miR-221 and miR-130a have opposing effects on airway and vascular morphogenesis of the developing lung. Lastly, we investigated the role of Hoxa5 and Hoxb5 in lung morphogenesis in response to hyperoxia to study mechanisms relevant to clinical scenarios. Compared to E14 fetal mouse lung organ cultures in room air (RA), 48 hours exposure to oxygen significantly altered organization and patterning of airway branching. Lungs returned to RA after 24 h of oxygen exposure had partial structural recovery. Hyperoxia also decreased Hoxb5 and VEGFR2 while altering the cellular distribution of Hoxa5. Overexpression of Hoxb5 promoted lung vascular and airway patterning whereas overexpression of Hoxa5 had the opposite effect on vascular development. We concluded that modest oxygen levels alter expression of Hoxb5 and Hoxa5 proteins, contributing to altered progression of airway and lung microvascular development.
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Cell, Molecular & Developmental Biology.
Advisors: Heber Nielsen, and MaryAnn Volpe.
Committee: Charlotte Kuperwasser, John Castellot, and Carla Kim.
Keywords: Cellular biology, and Developmental biology.read less