Question: What are human stem cells?

David Grainger answered on 27 Jun 2018:

Human stem cells is a very broad term. They are defined by their ability to divide and produce exactly the same cell again (scientists call this self-renewal) and by their ability to change (scientists say differentiate) into multiple different cell types.
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Normally we separate stem cells into two groups – embryonic (exist as we are developing inside our mother) and adult (which are present from when we are born to when we die). Some kinds of embryonic stem cells are particularly special because they are able to form all the cell types in the adult body (anything from heart or blood to kidney and liver) and have an incredible ability to divide and form new stem cells forever and ever.
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What my work really aims to do is to take one of these embryonic stem cells and add chemicals to the food we give it to turn it into an adult stem cell – the blood stem cell. These blood stem cells live in our bone marrow and form all of the white and red cells in our bodies. This is important because when somebody has blood cancer, one way this is commonly treated is to give them a drug that kills all their bone marrow (both cancer and healthy as the drug cannot tell them apart) followed by new healthy bone marrow from a donor. This bone marrow transplant is really a blood stem cell transplant. If one day, we could make blood stem cells in a test tube, we would not need to find donors and take bone marrow from them but rather make it in a dish for them!