Op/Op mice develop progressive, age-dependent pulmonary emphysema.
In the histologic evaluation, lungs of Op/Op and control mice of various ages were obtained and stained with hematoxylin and eosin. Representative photomicrographs of lung parenchyma are shown for Op/Op (A,C,E) and control mice (B,D,F) aged 20 days (A-B), 120 days (C-D). and 210 days (E-F). Progressive emphysema with enlarging air spaces occurred in lungs of Op/Op mice but not control mice (× 40). In the morphometric evaluation, digital images of lung tissues from Op/Op and control mice were captured during microscopy (above) and assessed by quantitative morphometry to determine the fractional area of airspace (airspace fraction). In young mice (n = 6/group; age, 20 ± 0 days), the corresponding values for airspace fraction were similar in Op/Op and control mice (P = .89; G,H). In marked contrast, in adult mice (n = 11/group; mean age, 165.3 ± 10.3 days in Op/Op mice and 161.5 ± 9.1 days in controls), the airspace fraction in Op/Op mice was increased significantly compared with that in littermate controls (P < .001). (G) The airspace fraction in adult Op/Op mice was also increased compared with that in young Op/Op mice (P < .0001). (H) In control mice, the airspace fraction did not change with age (P = .38). Linear regression defined the progressive increase in the airspace fraction as 3.6 ± 0.6 × 10−2 %/day in Op/Op mice (R = 0.82; slope significantly different from zero;P = .0001), whereas there was no significant change in controls (−5.4 ± 7.3 × 10−3 %/day; R = 0.18; slope not different from zero; P = .48).
