The Water Permeability Channels Aquaporins 1–4 Are Differentially Expressed in Granulosa and Theca Cells of the Preovulatory Follicle during Precise Stages of Human Ovulation

Context: Changes in vascular permeability and expansion of the fluid-filled antrum are major events in the LH-induced ovulatory process. Objectives: Our objective was to investigate the presence and expression levels of aquaporins (AQPs) in the granulosa and theca cell compartments of the follicle during defined phases of human ovulation. Design and Setting: We conducted a prospective experimental study at the Department of Obstetrics and Gynaecology at a university hospital. Participants: Twenty-eight women underwent laparoscopic sterilization and at the same time follicle retrieval at four periovulatory phases. Main Outcome Measures: mRNA levels of AQP1-4 were measured in separated granulosa and theca cells from preovulatory phase, early ovulatory (EO) phase, late ovulatory phase, and postovulatory phase. Immunohistochemistry was done for AQP1-4 in intact human follicles. Results: All four AQPs were expressed in both the theca and granulosa cells during ovulation. In granulosa cells, AQP1 levels increased in the late ovulatory and postovulatory phases. Expression of AQP2-3 followed a similar pattern with a marked increase in the EO phase, whereas AQP4 levels decreased from preovulatory to the EO phase. The presence of AQP1-4 in the human follicle was verified by immunohistochemistry. Conclusions: The results show for the first time the presence of AQP1-4 in human follicles during ovulation. The marked early rise in expression of AQP2 and AQP3 suggests a role during the process leading to follicular rupture, and the late rise of AQP1 suggests a role in corpus luteum formation.