Establishment and evaluation of an experimental animal model of high altitude cerebral edema

The aim of our study was to develop a model of high altitude cerebral edema (HACE) using an acute, hypobaric hypoxia environment combined with exhaustive exercise. Forty healthy male Sprague-Dawley rats were randomly divided into a plains control group (PC group) and a plateau altitude hypoxia group (AH group). After 2 days of treadmill adaptation under normoxic conditions, the AH group was housed in hypobaric conditions (simulating 4000 m above sea level) for 2 days while performing exhaustive exercise. The simulated altitude was then increased to 8000 m for 3 days of simple hypobaric hypoxia exposure. Compared with the PC group, the AH group showed significantly greater (P<0.01) water content and Evans blue staining in their brain tissue. Furthermore, the hippocampal formation was seriously damaged, and the number of pyramidal cells decreased. In addition, the brain structure was altered into a loose state with notable edema, which was demonstrated by the leakage of lanthanum nitrate particles from brain microvessels into the surrounding tissue through widened tight junctions. Some neurons and glial cell organelles were swollen and some nerve fibers were demyelinated as well. We have shown that acute hypobaric hypoxia exposure with exhaustive exercise increases the permeability of the blood-brain barrier and leads to cerebral edema, making this a valid animal model of HACE.