Expression of aquaporin 8 is diversely regulated by osmotic stress in amnion epithelial cells

Abstract

Water absorption across fetal chorioamniotic membranes is a critical regulatory pathway for amniotic fluid volume homeostasis. Aquaporin 8 (AQP8) is a water channel regulating osmotic water travel across membranes. This study was to investigate the distribution and expression of AQP8 in amnion epithelial cells (AEC) in response to different osmotic stresses. Cells derived from the amnion were subjected to different osmotic culture media. Reverse transcriptase-polymerase chain reaction, Western blotting and immunofluorescence analysis were used to determine expression and localization of AQP8. Immunofluorescent staining confirmed the expression of AQP8 on cytomembrane and in cytoplasm. Hypotonic media increased AQP8 on cytomembrane of AEC. Compared to isosmolar media, hypotonic media significantly enhanced AQP8 mRNA and protein expression (P < 0.05), while hypertonic media significantly decreased expression (P < 0.05). The expression and distribution of AQP8 in AEC are diversely regulated by osmotic loads suggesting a role for AQP8 in intramembranous water transport and the balance of amniotic fluid.