Hormonal regulation of pigment epithelium-derived factor (PEDF) expression in the endometrium

Pigment epithelium-derived factor (PEDF) is highly expressed in the female reproductive system and is subjected to regulation by steroid hormones in the ovary. As the uterine endometrium exhibits morphological and functional changes in response to estrogen (E₂) and progesterone (P4), we aimed at characterizing the expression of PEDF in this component of the female reproductive tract and further at exploring the hormonal regulation of its expression. We found that PEDF is expressed in human and mouse endometrium. We further showed that this expression is subjected to regulation by steroid hormones, both in vivo and in vitro, as follows: E₂ decreased PEDF expression and P4 increased its levels. In human endometrial samples, PEDF levels were dynamically altered along the menstrual cycle; they were low at the proliferative and early secretory phases and significantly higher at the late secretory phase. The expression levels of PEDF were inversely correlated to that of vascular endothelial growth factor (VEGF). We also showed that PEDF receptor was expressed in the endometrium and that its stimulation reduced VEGF expression. Illustrating the pattern of PEDF expression during the menstrual cycle may contribute to our understanding of the endometrial complexity.