In the first week of fertilisation human embryos form a ball of cells called a blastocyst, which must implant into the uterine wall for a pregnancy to continue. Models of the human blastocyst have previously been created by other labs from stem cells but had shortcomings as they contained cells not normally found in the human blastocyst and it was not known if they could implant into a human uterus (see BioNews 1020). The new 'blastoid' model created in this study more faithfully imitated early embryo development spatially and temporally, and successfully attached to uterine cells in vitro, researchers said.
Lead author Dr Nicolas Rivron, from the Institute of Molecular Biotechnology of the Austrian Academy of Sciences in Vienna, said: 'These experiments clearly point out the fact that we are able to model in the dish the first touch between the embryo and the mother.'
In the study published in Nature, scientists used two types of human stem cells to create the blastoids: embryonic stem cells from previously established cell lines or pluripotent stem cells, reprogrammed from adult cells.
The blastoids reliably replicated the key phases of early embryo development, in the correct sequence and time frame and with the correct cellular composition. When they were placed in contact with cells from the lining of the uterus that had been stimulated with hormones, about half of the blastoids attached to the uterine cells and started to grow in the same way blastocysts would, modelling implantation of an embryo to the uterus.
The researchers believe their model could advance our understanding of early development and be used to develop contraceptives or fertility treatments, being able to use the lab-grown blastoids in large numbers for drug discovery and screening. Dr Rivron's group is already using their blastoids to test an FDA-approved drug which could disrupt embryo implantation, and thus could be used as a non-hormonal contraceptive. 'Now that we have formed a reliable embryo model, we can uniquely understand the molecules at play, and I believe that these molecules will actually become tomorrow's medicines to enhance fertility or to be used as contraceptives,' said Dr Rivron.
The study and the use of blastoids already have implications for IVF. Researchers identified the molecule lysophosphatidic acid increased the rate of blastoid formation from stem cells and implantation, and further research could clarify if this could be used by IVF clinics as a medium to culture embryos in to improve their chances of successful implantation.