Scientists have grown live reproductions of human embryos in the laboratory for the first time – with all cell types, biochemical activity and general structure of real embryos.
The research, which aims to help understand problems that cause miscarriages and birth defects, may raise concerns about a slippery slope to human genetic engineering and cloning.
But the scientists who do research at both Monash University in Australia and the University of Texas in the US say their creations, called blastoids, are not perfect replicas of real embryos and are not suitable for implantation in a womb.
The research teams reported in the journal Nature their creation of blastoids – cellular assemblies resembling blastocysts, the stage of embryonic development five to 10 days after an egg is fertilized.
For ethical reasons, there is an internationally accepted limit of 14 days for culturing human embryos for research and so far scientists working on living models such as blastoids have adhered to the same limit.
The International Society for Stem Cell Research, the field’s professional body, aims to address ethical issues by soon issuing new guidelines for making embryos from stem cells.
Blastoids will allow scientists to study the very early steps in human development and some of the causes of infertility, congenital disease and the impact of toxins and viruses on early embryos – without the use of human blastocysts. [from IVF] and, most importantly, on an unprecedented scale, accelerate our understanding and development of new therapies, ”said Jose Polo, leader of the Monash project.
Both teams grew their blastoids from stem cells – either by reprogramming from adult cells or from embryos. The cells were treated with biochemical cocktails and grown in laboratory dishes containing a culture medium designed to allow them to develop like real embryos.
After about a week of culture, the cells had become blastoids of a similar size and shape to natural blastocysts. They contain over 100 cells that began to differentiate into the different cell types that would later produce different tissues in an older fetus.
Some blastoids exhibited behavior similar to implantation in the uterus because they attached to the culture dish and grew new cells that could develop into a placenta.
The scientists insisted that while blastoids would be very valuable for studying what happens at the beginning of pregnancy, they should not be viewed as synthetic embryos. “There are many differences between blastoids and blastocysts,” said Jun Wu, leader of the Texas team. “Blastoids would not be viable embryos.”
Last June, Naomi Moris and colleagues from the University of Cambridge published groundbreaking research into a later stage of embryonic development. Her lab bypassed the earlier stages of development represented by blastoids and produced simplified models of older (18 to 21 days) embryos.
“This is a very exciting time for human embryology,” said Moris, who has moved to the Crick Institute in London. “New tools and stem cell technology are generating an influx of embryo-like models that allow us to understand how we evolve from a single cell to a complete human.”
In May, the ISSCR international watchdog will issue new ethical guidelines for the cultivation of embryo models from stem cells – “ballot embryos” as some call them. “Research using these models has the potential to understand a developmental period often referred to as the ‘black box’,” said Professor Amander Clark of the University of California Los Angeles, who is part of the association’s task force. updates research guidelines.
“The models have the potential to improve treatments for infertility and interventions for congenital heart and brain defects and other genetic diseases,” she added. “As these models evolve, committees of inquiry will need a set of criteria to assess the admissibility of research proposals.”
Meanwhile, research on the assisted reproduction of mice, not limited by ethical issues, has gone much further. Scientists at the Weizmann Institute in Israel reported in the same issue of Nature that mouse embryos had grown healthy for 11 days – just over half their normal gestation period – in an artificial womb or womb.