Scientists have created a model of an early human embryo from skin cells, a discovery which they say will revolutionise research into the causes of early miscarriage, infertility and early human development.
Researchers have successfully reprogrammed these fibroblasts or skin cells into a 3D cellular structure that is similar to human blastocysts.
Called iBlastoids, these can be used to model the biology of early human embryos in the laboratory, according to a new study.
Scientists say this is a significant breakthrough for the future study of early human development and infertility.
A few days after an egg has been fertilised, it develops into a blastocyst.
This is a spherical structure made up of an outer layer of cells surrounding a fluid-filled cavity that contains a mass of embryonic cells
To date, the only way to study these first days has been through the use of difficult to obtain, and scarce, blastocysts obtained from IVF procedures.
Professor Jose Polo from Monash University in Melbourne, Australia, led the team.
He 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 and, importantly, at an unprecedented scale, accelerating our understanding and the development of new therapies.’
Researchers succeeded in generating the iBlastoids using a technique called ‘nuclear reprogramming’.
This allowed them to change the cellular identity of human skin cells that – when placed in a 3D jelly scaffold known as an extracellular matrix – organised into blastocyst-like structures which they named iBlastoids.
According to the study published in Nature, iBlastoids model the overall genetics and architecture of human blastocysts.
This includes an inner cell mass-like structure made up of epiblast-like cells, surrounded by an outer layer of trophectoderm-like cells and a cavity resembling the blastocoel.
In human embryos, the epiblast goes on to develop into the embryo proper while the trophectoderm becomes the placenta.
However, Prof Polo said that iBlastoids are not completely identical to a blastocyst.
Lead author Dr Xiaodong (Ethan) Liu, a post-doctoral researcher in the Polo Lab, said: ‘Only when all the data came together and pointed to the same place, we could believe that we had made such a discovery.’
Co-first author and PhD student in the Polo Lab, Jia Ping Tan, added: ‘We are really amazed that skin cells can be reprogrammed into these 3D cellular structures resembling the blastocyst.’
Prof Polo and colleagues reprogrammed human fibroblasts – the main cell type found in connective tissue – to produce three-dimensional models of the human blastocyst in the laboratory.
In a separate paper, also published in Nature, Jun Wu from the University of Texas Southwestern Medical Centre and colleagues developed a three-dimensional culture strategy that allowed them to generate blastocyst-like structures, which they term human blastoids.
Researchers note that although these two models reproduce key aspects of early human development, they present a number of differences to actual human embryos and therefore should not be considered as such.