Imagine a tiny clump of cells that looks just like a human embryo. Scientists have created this amazing model using stem cells—no eggs, sperm, or womb involved. This lab-made embryo has a yolk sac and a proto-placenta, which are features seen in real human embryos about 14 days after fertilization. Remarkably, it even produces hormones that can turn a pregnancy test positive!
Jacob Hanna, a professor at the Weizmann Institute of Science in Israel, was thrilled when two students rushed into his office to show him this breakthrough. While he knew this model wasn’t perfect and couldn’t grow into a baby, he recognized that his team had unlocked a vital door to understanding a crucial stage of human development. However, with this discovery comes a significant question: what are the ethical implications of creating such models?
The Mystery of Early Human Development
You may remember from biology class how a fertilized egg transforms into a tiny baby through various stages. However, the earliest stages of this process remain largely unknown because embryos are too small to see clearly and can only be kept alive for a short time in the lab. For decades, scientists have followed a guideline that limits how long embryos can be cultured in a lab to 14 days. This is because, at this stage, embryos can no longer split into twins and start to develop individual characteristics.
Hanna and other researchers believe that these embryo models could be a game-changer for studying some of the toughest problems in human development, such as why miscarriages happen or what causes developmental disorders. They have made incredible progress in growing stem cells that mimic the structure and function of real embryos. However, as they advance scientifically, they also face tough moral questions. At what point does a model become too realistic, and how should society treat it?
The 14-Day Rule Under Scrutiny
At around 14 days of development, a crucial process called gastrulation begins. This is when cells start organizing into layers that will form organs, and it marks the point when the embryo can no longer become a twin. Because of this, many countries have established the “14-day rule,” limiting how long human embryos can be kept alive in a lab. This rule was put in place because scientists believed that before this point, an embryo was just a collection of cells without the potential for individual identity or rights.
However, advancements in creating embryo models have prompted some scientists to question this long-held belief. In 2021, the International Society for Stem Cell Research suggested that research could continue past 14 days with ethical review and national regulations. Meanwhile, in the U.K., some researchers proposed similar guidelines for models. But Australia recently decided that more realistic embryo models should be treated like actual embryos, prohibiting them from developing past 14 days.
In the U.S., there are no federal laws governing experiments with real or model embryos, even though federal funding for human-embryo research has been banned since 1996. This raises a pressing question: Are these models really embryos?
Growing Models and Their Implications
Most scientists agree that today’s models are unlikely to develop into fully formed human beings. Creating embryos in a lab is far more complex than traditional methods, and only about 1% of these models resemble real embryos. Since researchers don’t fully understand what a nine-day-old embryo looks like inside the body, they cannot be sure if their models are developing accurately.
Despite this, recent achievements in science are astonishing. Hanna and another researcher, Magdalena Żernicka-Goetz, have created models for mice with fully functioning brains and beating hearts. This raises new ethical questions: What happens when scientists can grow models that resemble real embryos, and could they eventually be implanted into a womb?
Exploring the Benefits of Lab-Grown Embryos
Creating more realistic embryo models could revolutionize our understanding of early human life. A century ago, scientists collected thousands of embryo samples, which were categorized into 23 stages that describe the first eight weeks of development. However, there are still many unknowns about what happens between these stages. Most birth defects occur in the first trimester, and scientists are eager to understand why.
Better knowledge of the earliest stages of development could help answer questions about miscarriage, infertility, and how external factors like viruses and medications affect pregnancy. For example, Hanna has started a company focused on testing drug safety on these embryo models, which could lead to safer treatments for pregnant individuals. He envisions a future where these models could help tackle infertility by growing embryos to a certain stage and using their eggs for in-vitro fertilization (IVF).
A Balancing Act of Science and Ethics
While researchers like Aryeh Warmflash are exploring gastrulation without creating overly complex models, they also recognize that the more advanced the models become, the more ethical dilemmas they might spark. Bioethicist Insoo Hyun warns scientists against creating extremely realistic models to avoid controversy, especially in a world divided over when life begins.
Despite the challenges, the potential medical breakthroughs from studying realistic embryo models are enormous. The journey to understanding the mysteries of human development is just beginning, and the implications of these discoveries could change the way we think about life itself. As scientists push the boundaries of knowledge, society must grapple with the profound questions these advancements raise.
