Expression of aquaporin-1 in endometrial blood vessels in menorrhagia.

Aquaporin-1 (AQP1) is a water channel protein expressed in vascular endothelia and involved in impaired angiogenesis in tumors. Since angiogenesis is an essential component of the regeneration of the endometrium, we sought to analyze the expression of AQP1 in endometrial blood vessels in normal cyclic endometrium as well as in endometrial biopsies of menorrhagia patients. Endometrial biopsies from 16 patients with menorrhagia and 21 healthy fertile women were used for immunohistochemistry assessment of AQP1-stained endothelial structures. RT-PCR was used to confirm the presence of AQP1 mRNA. We detected the expression of AQP1 solely in endometrial blood vessels in the control group, as well as in menorrhagic endometrium. There was no difference between proliferative and secretory endometrium. Furthermore, we observed that the vascular expression of AQP1 in endometrial blood vessels in the menorrhagia group was significantly lower than in controls (p=0.002). There was also a significantly lower number of stained vessels per unit area in the menorrhagia group than in the controls (p=0.006). Thus, the deregulation of aquaporin-1 in menorrhagia may be involved in abnormal endometrial vascular growth and permeability.