Bleomycin induced type II cell injury in the murine lung: a quantitative and morphometric analysis.

Bleomycin is known to injure the alveolar epithelium in vivo and cause pulmonary fibrosis. There is a need to quantitatively assess this injury in individual cell types. To address this, we did a morphometric analysis of lung tissue from female mice given bleomycin (0.06 U) or saline intratracheally. After 10 days anesthetized mice (C57BL/6, 12 weeks) were measured lung mechanics using a computer‐controlled device (flexiVent, SCIREQ). We found that lung compliance significantly reduced from 0.075 ± 0.005 ml/cmH2O (mean ± SD, n=3) in the control mice compared to 0.045 ± 0.004 ml/cmH2O (n=3) in the bleomycin‐treated mice (P<0.01), suggesting bleomycin induced lung injury. Then, the lung was isolated and injected with 50% OCT under a pressure of 20–25 cmH2O in preparation for cryosectioning of the lungs. We identified alveolar epithelial type II (AT II) cells in lung sections by use of anti‐pro‐SPC and quantified the fluorescence‐labeled pro‐SPC using microscopy and image software (MetaMorph). We randomly imaged different regions (each covered an area of 0.71 x 0.57 mm^2) of the lung sections. The average total pixels of pro‐SPC (+) AT II cells shown in this region was markedly reduced from 18650 ± 2390 in control mouse to 10995 ± 3583 (mean ± SD, n=3) in the bleomycin‐treated mouse (p<0.05), as well as the mean radius of pro‐SPC spots and the shape factors reduced to 60% and 93.5% of control level (P<0.05), respectively. The results suggest that bleomycin‐induced acute lung injury can be easily quantified at the cellular level. This may permit an improved approach to dissecting the underlying mechanisms of injury and repair in acute lung injury.