Hypobaric Hypoxia 427 427 From: Methods in Molecular Medicine, Vol. 122: Placenta and Trophoblast: Methods and Protocols, Vol. 2 Edited by: M. J. Soares and J. S. Hunt © Humana Press Inc., Totowa, NJ 28 Hypobaric Hypoxia as a Tool to Study Pregnancy- Dependent Responses at the Maternal–Fetal Interface Jennifer K. Ho-Chen, Rupasri Ain, Adam R. Alt, John G. Wood, Norberto C. Gonzalez, and Michael J. Soares Summary Establishment of proper oxygen and nutrient supply to the fetus is essential for a successful pregnancy. The maternal–fetal interface is the site of vascular modifications, providing a con- duit for the delivery of essential nutrients to the developing fetus. Pregnancy-dependent adap- tive vascular responses within the uteroplacental compartment can be exaggerated by exposure to a physiological stressor such as hypoxia. A simple procedure for exposing pregnant rats and mice to hypobaric hypoxia is presented. Key Words: Hypoxia; pregnancy; rat; metrial gland; vascular remodeling; trophoblast. 1. Introduction Oxygen is an essential component of life, and is especially important in pregnancy because oxygen tension has a regulatory role in placental develop- ment (1). Vascular remodeling at the maternal–fetal interface is necessary in order to deliver an adequate oxygen and nutrient supply to the fetus (2–4). Hypoxia has been implicated in pregnancy-associated diseases such as intrauter- ine growth restriction (IUGR) and preeclampsia, which elucidates the impor- tance of oxygen regulation in pregnancy. The rodent has been used as a model to study the role of oxygen in preg- nancy. When rats and mice are exposed to hypoxia, gene expression is altered, impacting placental and fetal development (5–7). The effect of low oxygen can vary—it can lead to IUGR and termination of pregnancy at one extreme or, alternatively, it can elicit maternal adaptations that allow a successful preg- nancy to be achieved. The outcome of maternal hypoxia is dependent on the level of oxygen restriction, the duration of exposure, and the gestational period in which the insult is made.