Scientists have been able to create - through cell culture in the laboratory - models of early human embryos, using either adult skin cells or pluripotent stem cells. Both techniques are considered revolutionary, as they pave the way for a wide range of research.
The three-dimensional models, which are similar to human blastocysts, were named iBlastoids. Scientists hope iBlastoids can be used to model of biology of early human embryos and in parallel to better study the causes of miscarriage in the early stages of pregnancy, the causes of infertility, as well as the effect of drugs and toxic substances on the development of the fetus.
In the first study, researchers from Australia, USA, China and Singapore, led by Professor Jose Polo of the Australian Institute for Biomedical Discovery University of Mona, who made the relevant publication in the journal «Nature», reprogrammed human skin cells (fibroblasts) to transform them into a three-dimensional spherical cellular structure that is morphologically and molecularly similar (but not exactly the same) to human blastocyst, ie with the initial - just a few days - stage of fetal development.
This laboratory embryo model (iBlastoid) can now be used - instead of a normal embryo - to study fetal biology. So far, the only way to study the first days of the fetus is from blastocysts obtained through donation from the IVF process, which limits their availability. More recently, other scientists have developed blastocyst-like structures in mice, but this is the first time something similar has been done using human cells. "IBlastoids will allow scientists to study the very early stages of human development and some of the causes of infertility, birth defects and the effects of toxins and viruses on early embryos, without the need for the use of human blastocysts, thus accelerating our understanding and the development of new therapies ", said Jose Polo.
Infertility and premature miscarriage occur within the first two weeks after conception, when women do not even know they are pregnant. These "silent" miscarriages probably make up a significant percentage of the total number of miscarriages worldwide. IBlastoids will enable scientists to shed more light on these invisible miscarriages.
In the second study, also published in «Nature», researchers led by Professor Jun Wu of the University of Texas Southwestern Medical Center, followed a different strategy, starting with human pluripotent stem cells, to grow three-dimensional blastocysts in the laboratory. Laboratory blastoids are similar to human blastocysts in morphology, size, cell number, and composition. They stressed, however, that these blastoids are not exactly equivalent to blastocysts and cannot develop into a viable human embryo.
However, this new research, which takes about a week to cultivate blastocyst models in the laboratory, raises bioethics issues. Given that there is no legal precedent for research into blastocyst models such as iBlastoids, and given that the international scientific guidelines are for human blastocysts not to be cultured in vitro beyond the 14th day of embryonic development, Polo and his associates did not cultivate iBlastoids beyond the 11th day.
The new guiding principles of the International Society for Stem Cell Research are expected soon and it is not known whether they will include anything for new laboratory blastocysts such as iBlastoids.
The researchers were able to create iBlastoids using a technique called "Nuclear reprogramming". This allowed them to change the cellular identity of human skin cells that - when placed in a three-dimensional jelly scaffold, known as an extracellular matrix - were organized into blastocyst-like structures that gave them their name.