Irregularity of airway branching in a mouse bronchial tree: a 3-D morphometric study

Limited information on the degree of irregularity of branching patterns of a bronchial tree may obscure the cause of heterogeneous distribution of the lesions in a variety of lung diseases. We reconstructed three dimensional (3-D) images from hilum to terminal bronchioles of a mouse lung, and defined the irregularity of airway branching by diameter-based morphometric analysis. The relative diameter ratios of a daughter to the parent branch (D1/D0) and those of a minor to major daughter branches (D1/D2) were calculated, and irregular dichotomies were found to be distributed in 48% of bifurcations. D1/D0 is well correlated with D1/D2, and is proved to indicate regular and irregular branching, as well as D1/D2. Irregular branches with D1/D0 smaller than 0.4 correspond to typical lateral branches, taking off from major bronchi. Our novel 3-D morphometric analysis showed the first portrayal of the 3-D structures of mouse bronchial airways, which provides a quantitative description of branching patterns leading to the correlation with distribution of lesions in the diseased lung.