Concordant pattern of radiologic, morphologic, and genomic changes during compensatory lung growth.

BACKGROUND: Although compensatory lung growth (CLG) after lung resection has been reported in various mammalian species, it has generally been thought that the lung cannot regenerate in adult humans. We recently developed a method for evaluating lung weight using a radiologic analysis and demonstrated that the lung was heavier than expected in adult humans after pulmonary resection. In this study, we serially evaluated the morphologic, radiologic, and genomic status during CLG in pneumonectomized mice.

METHODS: The serial changes in morphology and gene expression of the remnant right lung after left pneumonectomy were examined in adult male mice. The alveolar density was determined by the mean linear intercept, and the weight was estimated using the Hounsfield value and volumetric data from micro-computed tomography. The parameters were obtained on days 3, 7, and 30 after left pneumonectomy or thoracotomy only (sham control).

RESULTS: After left pneumonectomy, the right lung became significantly progressively larger in volume and weight on postoperative days 3, 7, and 30 in comparison to the sham controls (P < 0.01). The estimated weight also significantly increased in association with the real volume on postoperative days 3, 7, and 30 (P < 0.01). The cardiac lobe markedly increased in size. During the observation period, the alveolar density was always lower in the pneumonectomized mice than in controls. A microarray analysis revealed that multiple genes related to proliferation (but not specific alveolar development) were initially upregulated until postoperative day 7 and then returned to normal after 1 mo. The morphologic and genomic changes were more evident in the cardiac lobe than in the upper lobe during the observation period.

CONCLUSIONS: The morphologic, radiologic, and genomic changes during CLG were related to each other in pneumonectomized mice. The present study revealed an association between the radiologically estimated weight and other parameters, indicating a marked CLG reaction of the cardiac lobe.