Fig. 2

Effect of vitamin D deficiency on lung structure in air- and CS-exposed mice after 6 and 12 weeks. At the age of 8 weeks, C57Bl/6J vitamin D deficient and control mice were exposed to CS or ambient air for a period of 6 or 12 weeks. a Representative figures of H&E-stained lung sections of paraffinized lungs of each experimental group (100X magnification) after 6 weeks of smoking. b The irregularity of airspaces on histological lung sections was given a semi-quantitative score ranging from 0 to 3 by a pathologist in a blinded manner (0 = absent, 0.5 = minimal, 1 = mild, 2 = moderate and 3 = severe). c The mean linear intercept (Lm), as a measure of the interalveolar wall distance, was determined on histological lung sections (at 200X magnification). The Lm was measured in 15 randomly selected fields per lung slide and calculated as the total length of the grid lines x random fields divided by the sum of the alveolar intercepts. d Relative expression levels of MMP-12 in lung homogenates, analyzed with RT-PCR. Data were normalized using RPL-27 as housekeeping gene and analyzed with the comparative cycle threshold (Ct) method. n = 10–12 per group per timepoint; mean ± SEM; *p < 0.05, **p < 0.01, ****p < 0.0001