The role of oxygen tension in the regulation of embryonic lung development

Oxygen tension is an important physiologic mediator of embryonic and fetal development. In vitro studies have demonstrated that the proper embryonic development is dependent upon low oxygen tension and even short exposure to normoxic environments (21%) can be detrimental to embryonic development. We hypothesized that low oxygen tension promotes lung growth in embryonic organ culture and therefore designed this study to investigate embryonic lung growth in normoxic and hypoxic conditions using simple closed chamber.

Fetal rat lungs were harvested on day 13.5 and placed in organ culture containing serum-free Dulbecco's modified Eagle's medium with antibiotics. The lung cultures were divided into normoxic group, with a 21% oxygen concentration (n = 15), and hypoxic group (n = 15). Hypoxic condition (6% oxygen) was achieved using Oxoid Campygen in a closed chamber. The lungs were placed in 5% carbon dioxide, 37 degrees C incubator for 48 hours. Media were not changed during the incubation period. The morphometric analysis was measured at 0 hour and at 48 hours by counting total terminal buds and entire epithelial contour using Image J software. The fold increase in branching was calculated as the ratio of buds present at 48 hours minus the buds present at 0 hour divided by the number of buds at 0 hour. The increase in entire epithelial contour over 48 hours was calculated in exactly the same way as described above.

There was no significant difference in the increase in total terminal buds count in the hypoxic group (2.06 +/- 0.19) compared with the normoxic group (2.59 +/- 0.21), and no significant difference in the increase in entire epithelial contour in the hypoxic group (1.45 +/- 0.11) compared with the normoxic group (1.63 +/- 0.11).

Although hypoxia has been reported to be an important regulator of murine vascular development, our data show that the embryonic lung growth in whole lung organ culture under hypoxic condition is not significantly different from that in normoxic condition.