Molecular and cellular aspects of endometrial receptivity

Endocrine and paracrine controls regulate the endometrium during the luteal phase of the cycle to permit implantation. Part of this differentiation pr ocess is the production of a specific secretion which fills the intrauterin e cavity and glandular lumen. Its molecular composition originates from the gland secretion, from transudations from stroma, from the endometrial bloo d vessels, and last, but not least, from cellular components of apoptotic a nd exfoliated cells. We have studied the secretions of all phases during th e menstrual cycle using patterns evaluated by SDS-PAGE, by laser densitomet ry or Western blots. Uterine secretion electrophoresis (USE) permits detail ed analyses of the intrauterine micromilieu and allows clinical assessment of the receptive stage of endometrium during the luteal phase, Several indi vidual protein bands have been defined as characteristic markers for such r eceptive pattern. We have isolated and identified the molecular structure o f several of these proteins, e.g. histones, cyclophilin, transthyretin, hap toglobin and uteroglobin, Investigations on the endocrine regulation of the se proteins, were carried out on the uterine secretions of patients treated with progesterone antagonists (mifepristone and onapristone), The results; demonstrate how progesterone-dependent components produce a receptive patt ern, which can serve as a useful and precise marker in the clinical diagnos is of the luteal phase. Essential progesterone-dependent components differe ntiating during the luteal phase may provide new tal gets for contraceptive interventions by preventing the physiological changes typical of receptivi ty.