Real-time footage of a human embryo implanting into an artificial uterus has been captured for the first time.
The remarkable feat, published in the journal Science Advances, offers an unprecedented view into one of the most critical steps in human development.
Implantation failure in the uterus is one of the main contributors to infertility, accounting for 60 per cent of miscarriages. The researchers hope that a better understanding of the implantation process could help improve fertility outcomes, both in natural conception and in vitro fertilisation (IVF).
“Because implantation happens inside the mother, we can’t see it,” Dr Samuel Ojosnegros, head of bioengineering in reproductive health at the Institute for Bioengineering Catalonia (IBEC) and lead author of the new study, told BBC Science Focus.
“So we needed a system where we could see how it works. That way, we can tackle the main roadblock in human fertility.”
Implantation is the stage in early pregnancy when a fertilised egg, now a developing embryo, attaches itself to the lining of the uterus. This step allows the embryo to draw nutrients and oxygen from the mother, making it essential for a successful pregnancy.
To study the process, the team built a platform that mimics the lining of a real uterus, consisting of a scaffold made of collagen and a mixture of proteins necessary for development.
They then studied how both human and mouse embryos implant on the platform, revealing some key differences. Unlike mouse embryos, which adhere to the surface of the uterus, human embryos penetrate the tissue completely before growing from the inside out.
“The human embryo is very invasive,” Ojosnegros said. “It burrows into the matrix and embeds itself, and then grows inside.”
The footage revealed that in order to do this, the embryo exerts a considerable force on the uterus.
“We observe that the embryo pulls on the uterine matrix, moving and reorganising it,” Dr Amélie Godeau, co-first author of the study, said in a statement. “It also reacts to external force cues. It also reacts to external force cues. We hypothesise that contractions occurring in vivo may influence embryo implantation.”
According to Ojosnegros, the force applied during this stage could explain the pain and bleeding many women experience during implantation, the reasons for which were not fully understood before.
The researchers are now developing ways to make the implantation platform more lifelike, including by integrating living cells. The hope is that by creating a realistic window into the implantation process, they will be able to improve the odds of success in IVF, for example, by selecting embryos with better implantation potential.
“We know more about the development of flies and worms than of our own species,” Ojosnegros said. “So watch the movies, and enjoy.”
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