Endometrial Glands Are Essential for Blastocyst Implantation and Decidualization in the Mouse Uterus

Uterine glands and their secretions are hypothesized to be essential for blastocyst implantation and decidualization in the uterus of rodents and humans. One factor solely expressed by uterine glands in mice is leukemia inhibitory factor (LIF), and Lif null mice are infertile because of defective blastocyst attachment to the uterine luminal epithelium (LE). Progesterone treatment of neonatal mice permanently ablates differentiation of uterine glands, resulting in an aglandular uterus in the adult. Progesterone-induced uterine gland knockout (PUGKO) mice were used to investigate the biological role of uterine glands in blastocyst implantation and stromal cell decidualization. As compared to controls, PUGKO mice cycled normally but were infertile. Histological assessment of PUGKO uteri on Days 5.5 and 8.5 postmating found a hatched blastocyst apposed to an intact LE without evidence of implantation or stromal cell decidualization. Expression of several implantation-related factors, including Lif and PTGS2, were altered in the PUGKO uterus, whereas expression of steroid hormone receptors and their regulated genes was not different. Artificial decidualization was observed in the uteri of control but not PUGKO mice. Further, intrauterine administration of LIF failed to promote artificial decidualization in the uterus of PUGKO mice. Thus, uterine glands and their secretions have important biological roles in blastocyst implantation and stromal cell decidualization in the uterus.