Hypertensive Arterial Change in Hindlimb Unloading Rats

Hwang, Sang Ho; Koo, Ja Seung

Abstract

BACKGROUND: In a condition of microgravity, arteries of upper body part are exposed to relative hypertensive stress, which is induced by headward fluid shift. We already have reported the increase of monocyte adhesion and intercellular adhesion molecule-I (ICAM-I) expression in carotid artery and thoracic aorta in the simulated microgravity. The purpose of this study was to identify the evidence of hypertensive arterial change in hindlimb unloading rats.
METHODS
A total of 16 Sprague-Dawley rats were divided into the 2 and the 4 weeks hindlimb unloading groups and their control groups, respectively. After experimental exposure, the carotid artery, the thoracic/abdominal aorta, and the femoral artery were obtained from each experimental and control groups. The degree of matrix metalloproteinase (MMP)-2, MMP-9, and tissue inhibitor of MMPs type 1 (TIMP-1) expression were analyzed by immunohistochemical stain.
RESULTS
The increase of MMP-2, 9 expression was noted in the carotid artery and the thoracic aorta from the 4 weeks hindlimb unloading group. On the other hand, the MMP-2, 9 expression was negligible in the abdominal aorta and the femoral artery of this group. In general, the findings of the 2 weeks hindlimb unloading group were similar to those of the control group. The TIMP expression was not found in all groups.
CONCLUSION
We found the evidence of hypertensive arterial change by increased shear stress on upper body part's arteries in simulated microgravity. Considering the possible development of this change into hypertensive arterial damage with other cardiovascular risk factors, our findings can be highlighted as an important medical concern, especially in a long-term spaceflight.