Temporal effects of Sprouty on lung morphogenesis

Area of Science:

• Developmental biology
• Cell signaling
• Pulmonary medicine

Background:

• Fibroblast growth factor (FGF) signaling, specifically involving FGF-10 and FGF receptor 2 (FGF-R2IIIb), is essential for lung formation.
• Intracellular antagonists like Sprouty-4 (Spry-4) can modulate FGF receptor activity.

Purpose of the Study:

• To investigate the temporal requirements of FGF signaling during pulmonary morphogenesis.
• To understand the impact of inhibiting FGF signaling at different developmental stages on lung development.

Main Methods:

• A doxycycline-inducible system was used to express Sprouty-4 (Spry-4) in the epithelial cells of fetal lungs.
• Spry-4 expression was controlled across various embryonic and postnatal time points (E6.5-E18.5, E12.5-birth, E16.5-E18.5, E18.5-P21).
• Lung morphology, lobulation, branching, and overall growth were assessed.

Main Results:

• Early Spry-4 expression (E6.5-E13.5) led to severe lung hypoplasia and lobulation defects.
• Reversing Spry-4 expression at E12.5 partially rescued branching defects, but not when reversed at E13.5.
• Late Spry-4 expression (E16.5-E18.5) reduced lung growth, causing respiratory failure and perinatal death.
• Spry-4 expression during saccular/alveolar stages (E18.5-P21) resulted in mild emphysema.

Conclusions:

• The embryonic-pseudoglandular stage is a critical period for Spry-sensitive FGF pathways in branching morphogenesis, lobulation, and lung parenchyma formation.
• FGF signaling is required throughout lung development, with distinct sensitivities at different stages.
• Disruption of FGF signaling at later stages impacts lung growth and can lead to respiratory failure or emphysema.