Simulated microgravity modifies intestinal epithelial barrier function and alters expression of tight junction proteins

The integrity of the intestinal epithelial barrier is tight junctiondependent. Previous studies showed that exposure to microgravity compromises the human immune system and increases enteropathogen virulence. However, the effects of microgravity on epithelial barrier function are unknown. Here, we investigated the effects of simulated microgravity on HT‐29 intestinal epithelial cell (IEC) barrier properties. IECs were (i) cultured on microcarrier beads for 18 days while subjected to simulated microgravity in a rotating wall vessel (RWV); (ii) cultured on beads for 18 days in culture plates (static control); (iii) grown in flasks for 18 days (flask control); prior to seeding on inserts. RWV cells displayed reduced transepithelial resistance (TER) on days 2–14 after seeding (−6 ± 3% vs. static day 11; n=4). Confocal analysis revealed increased expression of tight junction proteins Zonula Occludens‐1 (ZO‐1) and Occludin in RWV cells over 2–14 days (ZO‐1: 59–66 ± 11 pixels/unit area; n=3–4) vs. static (40–56 ± 10 p/ua) and flask (38–46 ± 10 p/ua) controls. Moreover, RWV cells showed delayed localization of Occludin and ZO‐1 to the apical junctions suggesting altered intracellular trafficking. In conclusion, cells exposed to simulated microgravity exhibit reduced TER and altered expression and distribution of tight junction proteins suggestive of a functional barrier defect. Supported by NIH UH2 AA019708 ‐01.