O'Reilly M, Hooper SB, Allison BJ, Flecknoe SJ, Snibson K, Harding R, Sozo F
Persistent bronchiolar remodeling following brief ventilation of the very immature ovine lung. [JOURNAL ARTICLE]
Am J Physiol Lung Cell Mol Physiol 2009 Aug 28.
Children and adults who were mechanically ventilated following preterm birth are at increased risk of reduced lung function, suggesting small airway dysfunction. We hypothesized that short periods of mechanical ventilation of very immature lungs can induce persistent bronchiolar remodeling that may adversely affect later lung function. Our objectives were to characterize the effects of brief, positive-pressure ventilation per se on the small airways in very immature, surfactant-deficient lungs, and to determine whether the effects persist after the cessation of ventilation. Fetal sheep (0.75 of term) were mechanically ventilated in-utero with room air (PIP 40cmH2O, PEEP 4cmH2O, 65 breaths/min) for 6h or 12h, after which tissues were collected; another group was studied 7d after 12h of ventilation. Age-matched unventilated fetuses were controls. The mean basement membrane perimeter of airways analyzed was 548.6+/-8.5microm, and was not different between groups. Immediately after ventilation, 21% of airways had epithelial injury; in airways with intact epithelium, there was more airway smooth muscle (ASM) and less collagen, and the epithelium contained more mucin-containing and apoptotic cells and fewer proliferating cells. Seven days after ventilation epithelial injury was absent but the epithelium was thicker, with greater cell turnover; there were increased amounts of bronchiolar collagen and ASM, and fewer alveolar attachments. The increase in ASM was likely due to cellular hypertrophy rather than hyperplasia. We conclude that brief mechanical ventilation of the very immature lung induces remodeling of the bronchiolar epithelium and walls which lasts for at least 7d; such changes could contribute to later airway dysfunction. Key words: epithelium, airway smooth muscle, collagen, proliferation.
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