Transmural pressure is a master regulator of airway branching morphogenesis

Mechanical forces are increasingly recognized to regulate morphogenesis, but how this is accomplished in the context of the multiple tissues present within a developing organ remains unclear. Here we use bioengineered “microfluidic chest cavities” to precisely control the mechanical environment of the fetal lung. We show that transmural pressure controls airway branching morphogenesis and regulates the frequency of airway smooth muscle contraction. Next-generation sequencing analysis shows that lungs held at higher pressure are more mature than lungs held at lower pressure. Timelapse imaging reveals that branching events are synchronized across distant locations within the lung, and are preceded by long-duration waves of airway smooth muscle contraction. Higher transmural pressure decreases the interval between systemic smooth muscle contractions and increases the rate of morphogenesis of the airway epithelium. These data reveal that the mechanical properties of the microenvironment instruct crosstalk between tissues to control the rate of development of the embryonic lung. (i) embryonic mouse lungs at E12.5 were cultured under low or high pressure for 48 hours prior to RNA extraction or (ii) embryonic mouse lungs were isolated from pregnant mice at E12.5, E13.5 and E14.5 prior to RNA extraction