Endometrial receptivity: changes in cell-surface morphology.
Ovulation and fertilization trigger embryonic development and endometrial differentiation by corpus luteum progesterone production. These two synchronous processes couple about 1 week later, when the blastocyst begins to implant in the now receptive endometrium (implantation window). Receptivity is a state of endometrial differentiation marked by a change in epithelial morphology: the hairy-like cell microvilli fuse to a single flower-like membrane projection called the "pinopode." Scanning electron microscopy of sequential endometrial biopsies shows that pinopodes form briefly (1-2 days), and their numbers correlate with implantation. On average, the formation of pinopodes is earlier in stimulated (days 19-20) and later in artificial (days 21-22) compared with natural cycles (days 20-21). There is, however, a wide (up to 5 days) variation between women in the cycle days on which pinopodes form. These results suggest the existence of a narrow and discrete implantation window in humans. Detection of pinopodes is a potential clinical marker to assess endometrial receptivity.
Nikas
G
G
Department of Obstetrics & Gynecology, Karolinska Institute, Huddinge Hospital K57, S-18164 Stockholm, Sweden.
D002462:Cell Membrane / Q000648:ultrastructure; D010064:Embryo Implantation; D004717:Endometrium / Q000502:physiology* / Q000648:ultrastructure*; D004848:Epithelium / Q000648:ultrastructure; D005260:Female; D006801:Humans; D008597:Menstrual Cycle; D008855:Microscopy, Electron, Scanning; D008871:Microvilli / Q000648:ultrastructure; D010062:Ovulation Induction; D011247:Pregnancy; D013997:Time Factors