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Structural Remodeling of the Post‐pneumonectomy Lung is Characterized by Septal Retraction and Alveolar Duct Dilation

Murine pneumonectomy (PNX) is an established model of adult compensatory lung growth, involving structural remodeling of the peripheral parenchyma. Following left PNX, positron emission tomography and computerized tomography have demonstrated heterogeneous growth patterns within the remaining right lung. To characterize the structural changes associated with these observations, we analyzed histological sections of the right lung between 3 and 22 days after PNX. Within 3 days of PNX, alveolar septae were significantly shorter (p<0.05) in a majority of alveolar ducts, while septal angle remained unchanged. Septal retraction resulted in an apparent dilation of the alveolar duct with a significantly decreased alveolar duct diameter ratio (Dout:Din; p<0.01). The greatest percentage of dilated alveolar ducts was seen at day 3, with 46% of alveolar ducts in the most dilated alveolar duct ratio quintile. Heterogeneous septal lengthening was observed between 4 and 22 days after PNX, with average septal length returning to baseline levels 7 days after PNX. Alveolar duct diameter ratio gradually increased from 3 to 22 days after PNX, returning to baseline levels by day 22. Lungs washed with detergent to remove surfactant demonstrated comparable changes in alveolar duct microstructure. We conclude that remodeling of the post‐PNX lung involves septal retraction and duct dilation, likely as a result of increased alveolar surface forces.