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Scientists have for the first time cultivated living reproductions of human embryos in the laboratory – with all cell types, biochemical activity and the overall structure of real embryos.
The research, which aims to help understand the problems that cause miscarriages and birth defects, may raise fears of a slippery slope towards human genetic engineering and cloning.
But scientists conducting research at both Monash University in Australia and the University of Texas in the United States say their creations, called blastoids, are not perfect replicas of real embryos and are not suitable. to implantation in the uterus.
Research teams reported in the journal Nature their creation of blastoids – cell assemblages resembling blastocysts, the stage of embryonic development five to 10 days after fertilization of an egg.
For ethical reasons, there is an internationally accepted 14-day limit for the growth of human embryos for research and so far scientists working on living models such as blastoids have observed the same limit.
The International Society for Stem Cell Research, the professional body in the field, aims to address ethical concerns by soon issuing new guidelines for the creation of embryos from stem cells.
“Blastoids will allow scientists to study the very early stages of human development and some of the causes of infertility, birth defects and the impact of toxins and viruses on early embryos – without using human blastocysts. [from IVF] and, most importantly, on an unprecedented scale, accelerating our understanding and development of new therapies, ”said Jose Polo, leader of the Monash project.
Both teams cultured their blastoids from stem cells – derived either by reprogramming adult cells or extracted from embryos. The cells were treated with biochemical cocktails and grown in laboratory dishes containing culture medium designed to make them develop like real embryos.
After being cultured for about a week, the cells had grown into blastoids similar in size and shape to natural blastocysts. They contained over 100 cells that would start to differentiate into different types of cells that would later produce different tissues in an older fetus.
Some of the blastoids showed behavior mimicking implantation in the uterus, as they attached themselves to the culture dish and developed new cells that could develop into a placenta.
Scientists insisted that although blastoids are very useful in studying what happens during early pregnancy, they should not be considered synthetic embryos. “There are many differences between blastoids and blastocysts,” said Jun Wu, team leader from Texas. “The blastoids would not be viable embryos.”
Last June, Naomi Moris and her colleagues at the University of Cambridge published groundbreaking research into a later stage of embryonic development. His lab bypassed the early stages of development represented by blastoids and produced simplified models of older embryos (18 to 21 days).
“It’s a very exciting time for human embryology,” said Moris, who moved to the Crick Institute in London. “New stem cell tools and technology are producing an influx of embryo-like models, which gives us a chance to understand how we develop from a single cell into a full human being.”
In May, the ISSRC’s international watchdog is due to release new ethical guidelines for the cultivation of model embryos based on stem cells – “stembryos” as some call them. “Research using these models has the potential to understand a period of development often referred to as a ‘black box’,” said Professor Amander Clark of the University of California, Los Angeles, who is part of the company’s task force that updates search guidelines.
“The models have the potential to improve infertility treatments and interventions for congenital heart and brain defects and other genetic diseases,” she added. “As these models progress, research review boards will need a set of criteria to review the admissibility of research proposals.”
Meanwhile, research on the artificial reproduction of mice, without ethical constraints, has made great progress. Scientists at the Weizmann Institute in Israel reported in the same issue of Nature that mouse embryos grew healthily for 11 days – just over half of their normal gestation period – in an artificial womb or womb.
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