A human embryo being implanted into a uterus has been pictured in real time and in 3D footage for the first time by a team of scientists.
It shows images of an embryo implanting into a synthetic uterus, demonstrating how the process occurs naturally.
The groundbreaking footage was released by researchers at the Institute for Bioengineering of Catalonia (IBEC) in collaboration with Dexeus University hospital in Barcelona, which donated the embryos.
Samuel Ojosnegros, the principal investigator of the IBEC’s bioengineering for reproductive health group and lead author of the study, said the work was significant because it revealed how the implementation process happened in detail.
“We have observed that human embryos burrow into the uterus, exerting considerable force during the process,” Ojosnegros said. “These forces are necessary because the embryos must be able to invade the uterine tissue, becoming completely integrated with it. It is a surprisingly invasive process. Although it is known that many women experience abdominal pain and slight bleeding during implantation, the process itself had never been observed before.”
Embryo implantation occurs when a fertilised egg attaches to the lining of the uterus about six to 12 days after ovulation.
A platform that allows embryos to implant outside the uterus under controlled conditions was developed by the researchers. This platform, based on a gel made partly by collagen and uterine tissue, then enabled real-time fluorescence imaging and analysis of the embryo’s interactions with its environment.
After this, researchers carried out experiments with human and mouse embryos to compare the two implantation processes. They discovered that while a mouse embryo sticks to its surface, a human embryo penetrates the uterine tissue completely before growing from the inside out.
The study also showed that during the implantation process, the human embryo released enzymes that broke down the surrounding tissue, and that this embryo also exerted traction forces on its environment.
The failure of the implantation process is one of the main causes of infertility, accounting for about 60% of miscarriages. According to the researchers, this study, which helps to improve understanding of the implantation process, could have a significant impact on fertility rates.
Amélie Godeau, a researcher and co-first author of the study, said: “We observe that the embryo pulls on the uterine matrix, moving and reorganising it. It also reacts to external force cues. We hypothesise that contractions occurring in vivo may influence embryo implantation.”