Blood cell development seen in human embryo model

A human embryo model created from adult stem cells shows the production of blood cells during early development.

Researchers at the University of Pittsburgh, Pennsylvania, developed the new embryo model, which they have called the heX-Embryoid model, from induced pluripotent stem cells (iPSCs). The model mimics early post-implantation human embryogenesis, including early haematopoiesis – the generation of blood cells.

'We were able to model something extremely similar to the earliest stages of blood production in humans,' said study lead Dr Mo Ebrahimkhani, associate professor at the University of Pittsburgh. 'This is exciting because there are extensive possibilities to apply this model to better understand how blood is formed and develop better methods for growing cells for blood transfusions, novel cell therapies and haematopoietic stem cell transplants.'

Previously, stem-cell-based embryo models (SCBEMs) have been created to mimic aspects of the post-implantation human embryo (see BioNews 1194, 1195, 1196, 1200 and 1206). Now, the heX-Embryoid model forms structures similar to blood islands, which are the first sites to produce blood cells to support the developing embryo. The researchers observed progenitors of red blood cells, platelets and different types of white blood cells in the model.

Publishing their research in Nature, the researchers generated iPSCs from adult skin cells and programmed them to direct early tissue development when the antibitotic doxycycline is added. The programmed iPSCs were then mixed with standard iPSCs. With the addition of doxycycline, the programmed iPSCs grew and triggered the standard iPSCs to self-organise into embryo-like models, with similarity to an actual human embryo.

HeX-Embryoids self-organise using standard growth media and the addition of a single chemical (doxycycline) with a high level of efficiency. This sidesteps the need for the complicated growth systems involved in creating some other types of SCBEM.

'For a model to be adopted by the scientific community and do its job of contributing to new discoveries, it must be efficient,' explained Dr Ebrahimkhani. 'For example, it will be very difficult to make progress in researching miscarriage if the model itself fails most of the time. Our heX-Embryoid model overcomes this problem.'

Because adult skin cells are used to create the heX-Embryoids, the authors suggest that they could theoretically be made from any individual. This would allow researchers to study different genetic backgrounds.

'Our embryo-like model will unlock this "black box" of human development, which could help solve the mystery of why about 60 percent of pregnancies fail in the first two weeks – before the mother even misses a menstrual period – and pave the way for new therapies,' Dr Ebrahimkhani continued.

HeX-Embryoids mimic embryonic tissue and a yolk sac structure, but not the trophoblast layer of the embryo that ultimately forms the placenta. For this reason, the heX-Embryoids are thought to be non-viable, lacking the capacity to implant in a womb or to develop fully.