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J. Tombran–Tink, C.J. Barnstable; Space Shuttle Flight Microgravity Environment Induces Loss of Photoreceptor Outer Segments and other Pathomorphological Changes in the Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1656.
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Purpose: Retinal degenerations can be promoted by many factors including ageing, ischemia, neovascularization, constant bright light, and genetic predisposition. We present new evidence showing that the space shuttle flight microgravity environment disrupts normal retinal development and mimics stimuli that induce earth–based degenerations in the retina. Methods: An in–cabin Payload consisting of six litters of Sprague Dawley rats were launched on STS–72 on a 9 day mission. Each litter consisted of one nursing dam and 10 neonates. Two age–matched litters each were launched with neonates ages at PN5, PN8, and PN15. The rats were housed in an Animal Enclosure Module Nursing Facility (AEM–NF). In–flight rodent conditions consisted of daily health checks, water and normal rat chow refill, and exposed to on/off light conditions. Earth based groups were housed similarly and served as ground controls. In–flight and ground control rats were sacrificed 3 hrs after the shuttle returned to earth. Eyes from age and weight matched neonates were dissected, fixed in 10 % formalin, and retinal sections were stained with H&E or labeled with various antibodies and lectins to identify biochemical and morphological changes in the retina. Results: At all time points of development in the retina of in–flight neonates, there was loss of photoreceptor outer segments, retinal detachment and loss of RPE cells. We observed a decrease in the thickness of the IPL and abnormalities in the ganglion cells. There was also an overall increase in size and numbers of blood vessels in the outer retina. Conclusions: These findings are the first to show pathomorphological changes in the retina during space travel and may provide clues into how the retina adapts to space related assaults such as warp in gravity, solar radiation, muscular atrophy, cardiovascular stress, edema, cephalad fluid shifts, and rapid bone loss. The studies may also lead to the development of strategies that protect the eye from the consequences of space travel and help those with similar earth–based retinal disorders.
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