Effects of intrauterine human chorionic gonadotropin administration on endometrial receptivity and embryo implantation

Aims: Even though major advances have occurred in in vitro fertilization-embryo transfer (IVF-ET) techniques in recent years, low efficacy of embryo implantation rates after fresh cycle of IVF-ET around 25-30 % is still a biggest challenge to physicians. To address this, clinicians have used intrauterine administration of human chorionic gonadotropin (hCG), one of the initial arrays of molecular crosstalk occurred at maternal-fetal interface. However, many reports have demonstrated the conflicting outcomes with various efficacy. This study aims to provide evidence of the optimal timing of hCG administration to enhance the rates of embryo implantation via improving the uterine environment. Main methods: hCG was administered into one side of mouse uterine horns and saline was infused into the other side of horns as a control. Alterations in the endometrial thickness, endometrial receptivity and angiogenesis-related gene expression, responses of progesterone receptor, and subsequent in vitro fertility assessment were evaluated in hCG-treated endometrium in mice. Key findings: hCG administration induced a serial induction of endometrial receptivity and angiogenesis-related genes and maximally enhanced their expression levels around 72 h after treatment with no significant morphological alterations in the numbers of endometrial glands and thickness. Moreover, using an in vitro model of embryo attachment, hCG treatment significantly promoted the stability of attached embryos, supporting the positive effect of hCG on the initial stage of embryo implantation. Significance: Our findings suggest a new consensus criteria providing a potential strategy of clinical use of hCG for the cleavage-stage ET rather than blastocyst-stage ET to achieve maximal effects of IVF-ET.

Automated summary

This study aimed to investigate the optimal timing of hCG administration to enhance embryo implantation rates. The results showed that hCG administration induced a significant increase in endometrial receptivity and angiogenesis-related gene expression levels within 72 hours, and promoted the stability of embryo attachment in an in vitro model.