Decreased expression of endometrial vessel AQP1 and endometrial epithelium AQP2 related to anovulatory uterine bleeding in premenopausal women.

OBJECTIVE: Aquaporins (AQPs) may be involved in the occurrence of abnormal uterine bleeding as the mediators between ovarian steroids and cyclic endometrial changes. The aim of the present study was to investigate the characteristics of endometrial AQPs in women with anovulatory uterine bleeding and explore the relationship between endometrial AQPs and ovarian steroids. DESIGN: Sixty-one women with premenopausal anovulatory uterine bleeding and 108 women with normal cycles were involved in this study. Endometrial biopsies were obtained from the women with anovulatory uterine bleeding and normal control women. Serum estradiol and progesterone concentrations were measured with enzyme-linked immunosorbent assay on the same day as an endometrial biopsy was performed. AQP1 and AQP2 mRNA expression was evaluated using reverse-transcriptase polymerase chain reaction. Immunohistochemistry was used to localize AQP1 and AQP2 in the endometrium, and their expression was quantified by an image analysis/measuring system. RESULTS: AQP1 was located in the endothelium of small vessels, whereas AQP2 was mainly found in luminal and glandular epithelium. The expression levels of AQP1 and AQP2 mRNA and protein were higher in the secretory phase than those in the proliferative phase (P < 0.01) in normal endometrium, and their expression was related to serum steroid hormones (P < 0.01). However, the expression of AQP1 and AQP2 decreased in the endometrium in anovulatory uterine bleeding comparing with normal endometrium (P < 0.01). The correlation between AQP expression and ovarian steroids vanished (P > 0.05) in anovulatory uterine bleeding. CONCLUSIONS: Our findings indicate that cyclic expression of endometrial AQP1/AQP2 correlated with steroid hormone levels may be essential to normal endometrial function and decreased AQP1/AQP2 expression in endometrial vessels or epithelium may be involved in the occurrence of anovulatory uterine bleeding.

Expression of aquaporin-1 in normal, hyperplasic, and carcinomatous endometria.

OBJECTIVE: To explore the relationship between aquaporin-1 (AQP1) and endometrial adenocarcinoma. METHOD: Intratumoral microvessel density (IMD) was assessed as well as AQP1 and vascular endothelial growth factor expression in samples from 117 women, 75 with endometrioid adenocarcinoma, 17 with endometrial hyperplasia, and 25 with normal proliferative endometria. RESULTS: AQP1 was located in the epithelial cells of microvessels and small vessels in all samples. The AQP1/IMD ratio was highest in samples from the first, less in samples from the second, and least in samples from the third group. In samples from endometrioid adenocarcinoma, the AQP1/IMD ratio was significantly correlated with histologic grade, surgical stage, myometrial invasion, and extrauterine metastasis. There was a positive correlation between AQP1 expression and IMD and between AQP1/IMD ratio and VEGF expression. CONCLUSION: AQP1 may be involved in the tumorigenesis and progression of endometrioid adenocarcinoma by promoting angiogenesis, and AQP1 level may be both a tumor indicator and a new therapeutic target.

[Expression profile of aquaporin 1 in patients with menorrhagia].

OBJECTIVE: To investigate the expression of aquaporin 1 (AQP1) in endometrium of patients with menorrhagia. METHODS: RT-PCR and immunohistochemistry were carried out in twenty women with normal menstrual cycle to confirm the expression of AQP1 in endometrium and locate it. Then 51 women with menorrhagia and 40 women with normal menstrual cycle were included in the study. RT-PCR and immunohistochemistry were used to examine the expression of AQP1. RESULT: AQP1 mRNA was expressed in the human endometrium throughout menstruation cycle, which was mainly located in the endothelia of the capillaries and small blood vessels. Quantification of the immunostaining revealed higher density during secretary phase than that in proliferative phase (P<0.01). The staining intensity and density of AQP1-positive microvessel decreased significantly in simple hyperplasia group (P<0.01) and then gradually increased in complex hyperplasia and atypical hyperplasia groups (P<0.001). CONCLUSION: Decreased expression of AQP1 may lead to disturbed endometrial vascular remodeling and may be involved in the occurrence of menorrhagia.

Function of aquaporins in female and male reproductive systems.

The flow of water and some other small molecules across cell membranes is important in many of the processes underlying reproduction. The fluid movement is strongly associated with the presence of aquaporins (AQPs) in the female and male reproductive systems. It has been suggested that AQPs mediate water movement into the antral follicle and play important roles in follicle development. AQPs are known to be involved in the early stage of spermatogenesis, in the secretion of tubule liquid and in the concentration and storage of spermatozoa. Fluid reabsorption in some regions of the male reproductive tract is under steroid hormone control and could be mediated by various AQPs. Also AQPs take part in the processes of fertilization, blastocyst formation (as the pathway for transtrophoectodermal water movement during cavitation) and implantation. Alterations in the expression and function or regulation of AQPs have already been demonstrated in disorders of the male reproductive system, such as abnormal sperm motility, the abnormal epididymis and infertility seen in cystic fibrosis, and varicocele. This article extensively reviews the distribution of AQPs in mammalian reproductive tissues and discusses their possible physiological and pathophysiological roles.