The news last week that scientists in Israel had developed a human embryo without sperm, eggs, or a uterus brought to light the Frankenstein-esque experiments going on in laboratories all over the world.
In fact, though scientists led by Jacob Hanna at the Weizmann Institute of Science had garnered laurels for producing a very well-developed human embryo from stem cells, many research groups around the world are working on such projects, some with similar successes.
Even as scientists claim to have found an ethical means of doing research on the earliest stages of human life, their work raises the question, what’s the difference between a human embryo model made of living cells and a living human embryo?
To create what he called an ‘embryo model,’ Hanna started with stem cells and put them back into what is known as the naïve state where they can develop into any kind of cell. Leaving a set aside that would become the embryo itself, they separated the rest into three groups and chemically coaxed them into the three types of cells that form into the placenta, yolk sac, and other biological supports for the embryo. They then stepped back and watched what happened.
“An embryo is self-driven by definition. We don’t need to tell it what to do—we must only unleash its internally encoded potential,” Hanna said in a press release from the institute. “It’s critical to mix in the right kinds of cells initially, which can only be derived from naïve stem cells with no developmental restrictions. Once you do that, the embryo-like model itself says, ‘Go!’”
A few of them—just 1%—indeed came together and were allowed to grow until they were comparable to an embryo 14 days after conception.
The scientist then checked their work against illustrations and microscopic anatomy sections in classical embryology atlases from the 1960s.
The resemblance was not perfect but “uncannily close,” according to the institute’s press release. In the embryo itself, cells were beginning to differentiate into what would become organs and a placenta, yolk sac, chorionic sac, and other external tissues that ensure an embryo’s growth had also formed.
In the process of developing the imperfect embryo, scientists also already started to achieve their additional goal of gaining insight into the causes of pregnancy loss. They had observed that if the embryo was not enveloped by placenta-forming cells in a certain manner on day 3 of the protocol, other structures, such as the yolk sac, failed to properly develop.
After 14 days, Hanna shut down the experiment and destroyed the embryo he had formed, as that time frame is the legal limit on embryo research in Israel and many other countries, though it’s very doubtful the embryo would have been able to reach the next stage of human development—the fetus stage
But the situation brings researchers back to the question of whether an embryo model is an embryo legally, and, more importantly, morally.
Answering the question could redefine the human embryo, further dehumanizing it, some fear.
A paper on the ethical implications of so-called embryo models published in July in the journal Cell called for “a reconsideration of the legal definitions of human embryos” in light of the advances in developing synthetic embryos. Under lead author and embryologist Nicolas Rivron of the Institute of Molecular Biotechnology in Vienna, the paper wants to redefine an embryo as “based on the developmental potential to form a fetus” and having “the provision of a supporting environment integral to realizing this potential.” In other words, as long as it’s on a lab bench and not in a womb, it should not be considered an embryo for legal purposes.
Other ethicists say that Rivron’s definition serves merely to justify experimentation on human embryos, as two Spanish bioethics bodies have responded to the Cell paper and the news of Hanna’s module embryo. They also counter that it denies intrinsic human dignity to human embryos by basing the worth of legal protection on the embryo’s ability to develop to a certain stage and its surrounding environment.
Many embryos are conceived that are not able to develop to the fetal stage. Additionally, the question of whether an embryo in a petri dish is an embryo has already been resolved in the affirmative, even if most countries allow experimentation on such embryos up to 14 days of life.
Rivron also warns of a tipping point at which it will be impossible to distinguish a synthetically developed embryo from one conceived with gametes and they will have to have to be given the same legal protection.
The Spanish ethicists warn that science has already reached that ethical tipping point. Though model embryos may be imperfect, they already share “human genetic endowment and show the ability to develop in their early evolutionary stages.”
What “degree of differences from the human embryos obtained by fertilization must be verified to classify them as true embryos or, on the contrary, as pseudoembryos, embryoids, blastoids or embryo-like models”?
That is the question scientists have laid before humanity, and until it can be resolved, ethicists warn they should err on the side of caution and stop playing with developing embryos in the lab.
