According to several studies, one in three pregnancies results in a miscarriage and one in 33 babies born will have a birth defect, due to the improper formation of the embryo in the womb. Studying the development of the embryo can help us find ways to reduce these numbers. In 2022, we will see progress in this research through embryo-like structures made from stem cells that can be grown in the lab.
Stem cells offer a powerful way to study the early development of the embryo. They can be grown in the lab in large numbers and can be tricked into making a wide assortment of cell types including brain, blood, bone, and muscle.
Recently, several researchers have found ways to join stem cells together into small balls of 3D cells, which makes it easier to create tiny structures resembling embryos. These are currently rudimentary – structures can be variable, they are inefficient to create, and cannot expand much further. Next year we’ll likely see improvements, with more advanced embryonic-like structures made from stem cells. And we’re also likely to see scientists using these models to study specific issues, such as how the embryo implants in the uterus, how organs start to develop, or how the embryo makes sure that the cells are in the correct positions.
Such research has traditionally been difficult to perform with human embryos. Parents using in vitro fertilization can donate their excess embryos, but regulations (confirmed internationally and made into law in the UK) prevent researchers from growing them beyond 14 days. This makes it impossible to directly study the evolution of the human embryo when it passes from a cluster of cells to a structure with the organization of a rudimentary body, when it is between two and four weeks old. The International Society for Stem Cell Research, which represents researchers in this field, called for a public dialogue on whether this limit should be changed. He suggests expanding the culture of human embryos on a case-by-case basis. It remains to be seen how regulators will react to this.
In the meantime, embryo-type stem cell models may alleviate some of the need to use “real” human embryos. They will allow researchers to carry out precise studies of embryonic development, to see how they react when a gene is mutated, for example, or when they are exposed to dangerous chemicals. Because they are made from stem cells, they could even be generated by taking blood or skin samples from patients who themselves have a birth defect and going back in time to a state similar to that of an embryo. This could help us understand how the defect happened, and perhaps even take steps to reduce the incidence of such disorders in the future.
The development of embryonic-type models will raise many new ethical questions. Along with the possibility of moving down a slippery slope towards cloning, stem cell-based embryo models are starting to blur the line between what we consider human and what not. An early stage human embryo, when it is only a small group of 16 cells, is it more valuable if it comes from the union of sperm and egg? Or is it the same as if it were derived in the laboratory from stem cells? Should the moral status often applied to human embryos also apply to groups of cells, even in arrangements that might only vaguely reflect elements of actual embryonic development?
As we move more towards role models that could alleviate the devastating conditions encountered early in life, we will also find ourselves challenged as a society to ask big questions, including the fundamental question of what it means to be. human.
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