Epithelial Vegfa Specifies a Distinct Endothelial Population in the Mouse Lung

Area of Science:

• Pulmonary Biology
• Cell Biology
• Developmental Biology

Background:

• The lung microvasculature, crucial for gas exchange, was previously thought to be uniform.
• Endothelial cells (ECs) form the inner lining of blood vessels and play vital roles in vascular development and function.

Purpose of the Study:

• To investigate the role of Vascular Endothelial Growth Factor A (VEGFA) in specifying distinct endothelial cell (EC) populations within the mouse lung.
• To characterize a novel EC subset marked by Carbonic anhydrase 4 (Car4) and its dependence on epithelial VEGFA.

Main Methods:

• Single-cell RNA sequencing (sc-RNA seq) to identify transcriptionally distinct EC populations.
• Trajectory analysis to infer developmental relationships between EC subsets.
• Genetic deletion of epithelial VEGFA to assess its impact on EC populations and lung structure.

Main Results:

• A subset of approximately 15% of lung ECs, marked by Carbonic anhydrase 4 (Car4), was identified as transcriptionally distinct.
• These Car4+ ECs possess extensive projections and are situated near alveolar type 1 (AT1) cells, separated by a thin basement membrane without pericytes.
• Epithelial VEGFA deletion resulted in the specific loss of Car4+ ECs, leading to enlarged alveolar spaces, despite normal myofibroblast populations.

Conclusions:

• Epithelial VEGFA is essential for specifying a unique lung endothelial cell population (Car4+ ECs).
• These findings highlight a crucial signaling role for AT1 cells in lung microvasculature development and alveologenesis.
• The identified Car4+ ECs share features with retinal tip ECs, suggesting conserved developmental mechanisms.