Fra-2 negatively regulates postnatal alveolar septation by modulating myofibroblast function

Area of Science:

• Pulmonary biology
• Cellular and molecular biology
• Developmental biology

Background:

• Global overexpression of Fos-related antigen-2 (Fra-2) in mice induces pulmonary fibrosis and vascular remodeling.
• The role of Fra-2 in specific lung cell types, particularly vascular smooth muscle cells and myofibroblasts, remained unclear.

Purpose of the Study:

• To investigate whether Fra-2 overexpression specifically in vascular smooth muscle cells and myofibroblasts causes pulmonary fibrosis and vascular remodeling.
• To elucidate the cellular and molecular mechanisms underlying Fra-2's effects on lung development and function.

Main Methods:

• Generation of transgenic mice overexpressing Fra-2 specifically in α-smooth muscle actin (SMA)-expressing cells (myofibroblasts).
• Histological analysis of lung tissue to assess alveolar structure and septation.
• Lineage tracing to identify the origin of alveolar myofibroblasts.
• RNA sequencing to analyze gene expression changes in myofibroblasts overexpressing Fra-2.
• Assessment of primary myofibroblast migration capacity.

Main Results:

• Specific Fra-2 overexpression in myofibroblasts did not cause pulmonary fibrosis or vascular remodeling.
• Mice developed an emphysema-like phenotype with enlarged alveoli and reduced secondary septa formation.
• Fra-2 overexpression altered the expression of genes involved in extracellular matrix (ECM) production, secretion, and cell adhesion, including integrins and their ligands.
• Primary myofibroblasts exhibited reduced migration capacity.

Conclusions:

• Fra-2 overexpression in lung myofibroblasts impairs their function, leading to defective secondary septa formation and emphysema.
• Altered expression of ECM and cell adhesion molecules by Fra-2 may disrupt myofibroblast migration and lung development.
• These findings highlight a novel role for Fra-2 in regulating myofibroblast behavior crucial for lung alveolarization.