Retinoic acid signaling regulates the energy metabolism of embryonic lung branching

Abstract

Background: Lung branching morphogenesis is characterized by epithelial-mesenchymal interactions and mediated by complex signaling that ultimately defines the airway conducting system. Retinoic Acid (RA) signaling is crucial for lung organogenesis and modulates proximal-distal patterning and branching morphogenesis. However, how signaling networks and energy metabolism work together to shape embryonic lung development remains unexplored. Here, we investigate how RA signaling influences the metabolic profile of lung branching. Methods: We performed ex vivo lung explant culture using embryonic chicken lungs (Gallus gallus) treated with DMSO, 1 uM RA (stimulation), or 10 uM of BMS493 (inhibition). Explant culture media was collected, and the consumption/production of extracellular metabolites was evaluated by 1H-NMR spectroscopy. Lung explants were analyzed to determine mitochondrial respiration and biogenesis. Proliferation was assessed using an EdU‐based assay. Western blot, qPCR, and in situ hybridization were performed to assess the expression of metabolic/signaling components. Results: Upon stimulation, RA signaling increases lung branching, maintaining proper morphology. Besides, there is an increase in the amount of glucose directed into pyruvate and succinate rather than into alanine or lactate production. On the other hand, RA signaling inhibition decreases lung branching, induces a cystic-like phenotype, and promotes mitochondrial function. Proliferation status and lactate dehydrogenase expression are both regulated by RA signaling. Furthermore, RA signaling controls fatty acid metabolism through an AMPK-dependent mechanism. Conclusions: This report shows that RA signaling modulates the energy metabolism of lung branching morphogenesis and highlights the importance of metabolic regulation in this phase, contributing to understanding the etiology of congenital lung disorders.