Researchers from the Francis Crick Institute (FCI) and University College London (UCL) have rebuilt a human thymus, an essential organ of the immune system, using human stem cells and a bioengineered scaffold. Their work is an important step towards being able to grow artificial thymi for use as transplants.

The thymus – located in the upper front part of the chest, behind the sternum – is a lymphoid organ where T cells mature. These play a vital role in the body’s immune system. If the thymus does not work properly or does not form during foetal development in the womb, it can result in severe immunodeficiency and other conditions where the body cannot fight infectious diseases or cancerous cells, or autoimmunity, where the immune system mistakenly attacks the patient’s own healthy tissue.

In their proof-of-concept study, published in Nature Communications, the scientists rebuilt thymi using stem cells taken from patients who had to have the organ removed during surgery. When transplanted into mice, the bioengineered thymi were able to support the development of mature and functional human T cells.