Chronic hypoxia and hyperoxia modifies morphology and VEGF concentration of the lungs of the developing chicken (Gallus gallus variant domesticus)

Embryo body and lung wet and dry mass, pulmonary morphometrics and pulmonary VEGF concentrations were determined in developing chicken embryos at days 16 and 18 (D16, D18) in three populations: incubation in normoxia (21% O2) or in chronic hypoxia (15% O2) or chronic hyperoxia (30% O2). Lung morphology (including parabronchial exchange tissues and parabronchial lumina as a percentage of total lung tissue in cross-sectional area, atrial numbers, atrial density) was determined from morphometric examination of thin sections using light microscopy. VEGF expression was determined with ELISA. Body mass was directly correlated with incubation oxygen level, but neither oxygen level affected lung wet mass on either D16 or D18. Hypoxia had little or no effect on most measured pulmonary morphometric indices in D16 embryos. Hypoxia, however, increased by ∼65% the proportion in cross-section of the total lung occupied by parabronchi on D18. Hyperoxia caused few significant changes in pulmonary morphometrics. Pulmonary VEGF concentration was decreased by ∼30% on day 18 compared to D18 in normoxia. Hypoxia increased pulmonary VEGF concentration by ∼35-75% on both D16 and D18 and, paradoxically, VEGF expression was also similarly increased by hyperoxia on only D18. Collectively, these data suggest that pulmonary gross morphological development in the chicken embryo, while moderately plastic, is not profoundly affected by oxygen incubation level, and that role of VEGF in pulmonary development is not yet well understood.