Scientists have grown a human embryo-like structure in a lab which replicates very early human development - including the production of blood stem cells.
The lab-grown embryo model could help researchers produce blood stem cells for transplants, screen drugs and understand blood disorders like leukaemia.
Human blood stem cells, also known as hematopoietic stem cells, are immature cells that can develop into any type of blood cell, including red blood cells that carry oxygen and various types of white blood cells crucial to the immune system.
“It was an exciting moment when the blood red colour appeared in the dish – it was visible even to the naked eye,” said Dr Jitesh Neupane, a researcher at the University of Cambridge’s Gurdon Institute and first author of the study published in the journal Cell Reports.
The embryo-like structures, which scientists at the University of Cambridge have named “hematoids”, start producing blood after around two weeks of development in the lab - mimicking the development process in human embryos.
Although it produces blood stem cells, unlike real embryos it doesn’t have several embryonic tissues, as well as the supporting yolk sac and placenta needed for further development.
Dr Geraldine Jowett at the University of Cambridge’s Gurdon Institute, a co-first author of the study, said: “Hematoids capture the second wave of blood development that can give rise to specialised immune cells or adaptive lymphoid cells, like T cells, opening up exciting avenues for their use in modelling healthy and cancerous blood development.”
The human stem cells used to develop hematoids can be created from any cell in the body, meaning there is potential to make blood that is compatible with a patient's body.
Although there are other ways of creating stem cells in a lab, this method mimics the natural developmental process and doesn’t require extra proteins to support stem cell growth.
The findings revealed that the blood cells in hematoids develop to a stage that roughly corresponds to week four to five of human embryonic development, when our organs and blood system first begin to form.
This very early stage of life cannot be directly observed in a real human embryo, because it has implanted in the mother’s womb by this time.
The team observed that by the second day of the hematoids growing, they had self-organised into three germ layers - called the ectoderm, mesoderm, and endoderm - the foundations of the human body plan that are crucial for shaping every organ and tissue, including blood.
By day eight, beating heart cells had formed, which eventually give rise to the heart in a developing human embryo. By day thirteen, the team saw red patches of blood appearing in the hematoids.
Researchers also developed a method that showed the blood stem cells could differentiate into various blood cell types, including specialised immune cells, such as T-cells.
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