Steady-state level of messenger RNA and immunolocalization of aquaporins 3, 7, and 9 during in vitro growth of ovine preantral follicles

Aquaporins (AQPs) are a well-conserved family of small (approximately 30 kDa) membrane channel proteins that facilitate rapid movement of fluids and have a unique tissue-specific pattern of expression. These proteins have been found in the female reproductive systems of humans, rats, and mice. However, the expression and cellular localization of AQPs have not extensively been studied in the female reproductive system of sheep. Therefore, this study aimed to evaluate, by real-time polymerase chain reaction and immunohistochemistry respectively, the levels of messenger RNA and the immunolocalization of AQP3, AQP7, and AQP9 in large isolated ovine secondary follicles over a period of IVC. Our analysis revealed that AQP3 and AQP9 were present predominately in follicles that exhibited antrum formation, suggesting a crucial role of these AQPs in the formation of the antrum. Interestingly, AQP7 was only expressed in follicles that had not formed an antrum by Day 12 of culture. In conclusion, the presence of protein channels (AQP3 and AQP9) seems to be essential for the formation of the antrum in isolated ovine secondary follicles cultured in vitro and thus plays an important role during folliculogenesis in this species.