The Effects of Simulated Spaceflight Conditions on the Myometrium of the Mouse Uterus

As scientific discovery and human presence push further into space, it is necessary to investigate the effects of spaceflight on physiological systems. Research into the effects of the space flight environment on the human body is still in its relative infancy. Although initial studies have indicated harmful effects of spaceflight environments on certain body systems, this phenomenon still needs illumination with regards to the female reproductive system. Better understanding of these consequences can change the way society views space travel and colonization of other planets. The spaceflight environment consists of at least two major factors that could confer negative effects on physiology, namely radiation and microgravity. In this experiment, uterine smooth muscle, or the myometrium, was analyzed in 6-month old female C57BL/6 mice that were exposed to 21 days of low dose/low dose rate whole-body radiation with γ-radiation using  57 Co plates (0.04 Gy at 0.01 cGy/h) and/or simulated microgravity (via hind limb unloading). Tissue samples were harvested 4 months after the 21-day simulated spaceflight period. Following embedding, sectioning, and hematoxylin and eosin staining (H&E), the tissues were examined, and the average thicknesses of the myometrial layers were measured. Three types of measurements were made 1 – outer longitudinal layer, 2 – inner circular layer, and 3 –total muscle layer thickness (outer and inner combined). Two-way ANOVA statistical tests were used to compare the thicknesses of the myometrial muscle layers between the various treatment groups. A statistical difference was found between the thicknesses in the outer longitudinal layer of smooth muscle between the control animals and the unloaded animals (P: 0.051).