Tracheal occlusion: A review of obstructing fetal lungs to make them grow and mature

Fetal lung growth and functional differentiation are affected strongly by the extent that pulmonary tissue is distended (expanded) by liquid that naturally fills developing future airspaces. Methods that prevent normal egress of this lung fluid through the trachea magnify mechanical stretching of lung parenchymal cells, thereby promoting lung development. Indeed, experimental observations demonstrate that in utero tracheal occlusion (TO) performed on fetuses during the late canalicular-early saccular stage potently stimulates pulmonary growth and maturation. In this review, we present the four principle non-human animal models of TO/obstruction and discuss them in relation to their utility in elucidating lung development, in remedying congenital diaphragmatic hernia (CDH) as well as in investigating the stretching effects on growth and remodeling of the fine vasculature.