Simulated Microgravity Interferes with Oocyte Meiotic Maturation in a 3D Ex Vivo Mouse Folliculogenesis System

Simulated Microgravity Interferes with Oocyte Meiotic Maturation in a 3D Ex Vivo Mouse Folliculogenesis System 

Smithika Reddy Karru1, Begum Aydogan Mathyk2, Matthew Anderson2, Jiyang Zhang3,4,5, and Shuo Xiao3,4,5 

1Department of Cell Biology and Neuroscience, School of Arts and Sciences, Rutgers University, Piscataway, NJ; 2Department of Obstetrics and Gynecology, University of South Florida, Tampa, FL; 3Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ; 4Environmental and Occupational Health Sciences Institute (EOHSI), Rutgers University, Piscataway, NJ; 5Center for Environmental Exposures and Disease, Rutgers University, Piscataway, NJ 


Abstract Text: The percentage of female astronauts has been steadily increasing over the past decades, and it is projected to escalate in coming years. Spaceflight introduces environmental stressors, such as radiation and microgravity, which can profoundly affect human physiology. Prior research studying the health effects of spaceflight has been focused on cardiovascular, neurological, and musculoskeletal systems, but the impacts on female reproductive health remain elusive. This knowledge gap is particularly pressing considering the growing number of female astronauts and other tourism travelers going to space. Radiation has been shown to alter genes related to sex hormone secretion and cause DNA damage in the ovary, indicating potential adverse female reproductive effects. However, microgravity, the feeling of “weightlessness,” is another critical environmental factor in space, but its impact on female reproductive health has been minimally researched. In the current study, we used a 3D hydrogel encapsulated in vitro follicle growth (eIVFG) system to culture immature mouse preantral follicles under a simulated microgravity condition, aiming to explore the ovarian impacts of microgravity. Secondary follicles isolated from female mice were encapsulated using 0.5% alginate hydrogel for eIVFG. Microgravity was simulated using a rotary cell culture system (RCCS) operating at 7.1 rotations per minute (rpm). Follicles were cultured for 6 days under both static and simulated microgravity using RCCS, with key follicle and oocyte endpoints evaluated. Follicles were imaged on day 0, 3, and 6 for assessing follicle survival and development. Conditioned follicle culture media was collected on days 3 and 6 for measuring the hormonal secretion of estradiol. On day 6, grown antral follicles were treated with human chorionic gonadotropin (hCG) to induce in vitro ovulation. Oocyte maturation was assessed by evaluating the polar body extrusion, spindle morphology, and chromosome alignment. The results showed that compared to the control, follicles cultured under simulated microgravity exhibited comparable survival rates, growth patterns, hormonal secretion of estradiol, and numbers of oocytes with extruded polar bodies. However, oocytes from simulated microgravity exhibited significantly larger size of polar bodies, abnormal spindle morphology, and misaligned chromosomes, which have been associated with impaired oocyte quality and heightened risks of aneuploidy, birth defects, and infertility. Ongoing studies are focused on elucidating the underlying mechanisms. In summary, the results of our study suggest that simulated microgravity compromises oocyte meiotic maturation during eIVFG, highlighting a potential adverse impact of space travel on the reproductive health and fertility of female astronauts and other space travelers (This work is supported by NASA South Carolina Space Grant Consortium and NIH K01ES030014, R01ES032144).