Scientists create first living models of human embryos


Scientists have for the first time grown living reproductions of human embryos in the lab with all the cell types, biochemical activity, and overall structure of real embryos. The research aims to help understand problems that cause miscarriages and birth defects may raise fears over a slippery slope toward human genetic engineering and cloning. But the scientists conducting 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 into a womb.

The research teams reported in the journal Nature their creation of blastoid cellular assemblies resembling blastocysts, the stage of embryonic development five to 10 days after an egg has been fertilized. For ethical reasons, there is an internationally accepted 14-day limit on growing 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 field’s professional body, aims to address ethical concerns by issuing new guidelines soon for creating embryos from stem cells.

Jose Polo, leader of the Monash project said, Blastoids will allow scientists to study the very early steps in human development and some of the causes of infertility, congenital diseases, and the impact of toxins and viruses on early embryos without the use of human blastocysts [from IVF] and, importantly, at an unprecedented scale, accelerating our understanding and the development of new therapies.

Both teams grew 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 lab dishes containing a culture medium designed to make them develop like real embryos.

After being cultured for a week or so, the cells had become blastoids of a similar size and shape to natural blastocysts. They contained more than 100 cells that were beginning to differentiate into the various cell types that would later produce different tissues in an older fetus. Some of the blastoids showed behavior mimicking implantation into the uterus, as they attached to the culture dish and grew new cells that could develop into a placenta.

The scientists insisted that, although blastoids would be very valuable for studying what happens at the start of pregnancy, they should not be regarded as synthetic embryos.

Jun Wu, leader of the Texas team said, Blastoids would not be viable embryos and there are many differences between blastoids and blastocysts.

Last June Naomi Moris and colleagues at the University of Cambridge published groundbreaking research on a later phase of embryonic development. Her lab bypassed the earlier development stages represented by blastoids and produced simplified models of older (18- to 21-days) embryos.

Moris, who has moved to the Crick Institute in London said, this is a very exciting time for human embryology. New tools and stem cell technology are producing an influx of embryo-like models, which give us a chance of understanding how we develop from a single cell into a full human being.

In May the ISSCR international watchdog is due to issue new ethical guidelines for growing embryo models based on stem cells stembryos as some are calling them.

Professor Amander Clark of the University of California Los Angeles, who is on the society’s task force updating research guidelines said, research using these models has the potential to understand a developmental period often referred to as the black box. The models have the potential to improve treatments for infertility and interventions for congenital heart and brain defects and other genetic diseases. As these models continue to advance, research review committees will need a set of criteria for reviewing the permissibility of research proposals.

Meanwhile, research into the artificial reproduction of mice, unconstrained by ethical issues, has moved much further ahead. Scientists at the Weizmann Institute in Israel reported in the same issue of Nature that mouse embryos had grown healthily for 11 days just over half their normal gestation period in an artificial uterus or womb.

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