Avian Blood Vessel Formation in Space: Both Microgravity in Space and Mechanical Loading during the Launch Might Affect Vascular Development in the Quail Chorioallantoic Membrane

INTRODUCTION: On earth, gravitational forces seem to play a major role in the initial stages of embryonic development, such as proper orientationof the embryo, separation of yolk from albumen, etc. Previous studies indicated that exposure to weightlessness (microgravity) during space flight might result in abnormalities in embryonic and fetal development in birds, amphibians and mammals, especially when eggs are sent into space immediately after fertilization. By contrast, embryos sent into space after being incubated under "normal" conditions for 7-10 days in 1-g on earth, seemed to be unaffected by microgravity and developed normally. Based on these observations, we hypothesized that microgravity in space and/or other parameters associated with space flight, such as mechanical forces during the launch, and/or the incubation conditions aboard the space vehicles might also adversely affect embryonic development by interfering with the development of the vasculature (angiogenesis) during early stages of embryogenesis. A well characterized model system for studying angiogenesis is the chorioallantoic membrane (CAM), a highly vascularized extra-embryonic membrane, which in avians provides for gas exchange with the outside environment and the transport of minerals (calcium) from the egg shell to the embryo.