Scientists at the University of Edinburgh have grown a fully-functional organ inside a mouse; opening the possibility of one day manufacturing compatible organs for transplant without the need for donors. Using mouse embryo cells, scientists at the MRC Centre for Regenerative Medicine created an artificial thymus gland with the same structure and function as an adult organ.

Organ transplants are one of the great medical success stories of the 20th century. Where patients once faced disability or even death, they've been given new life in the form of donated organs to replace their damaged or diseased ones. The problem is that the supply of suitable donor organs has always been in a state of severe shortage. For decades, scientists have worked on producing lab-grown organs and even though such research has produced simple organs such as an artificial esophagus and "mini-kidneys," the creation of whole, complex, functional organs has remained out of reach – until now.

The University of Edinburgh team produced the artificial thymus gland using a technique that the scientists call "reprogramming." It involves fibroblast cells, which form connective tissue in animals, being removed from a mouse embryo and then treated with a protein called FOXN1, so that they changed into thymic epithelial cells (iTEC). These were then mixed with other thymus cells and transplanted into living mice by grafting them to the animal’s kidneys.

There, over a period of four weeks, the cells grew into a complete, functioning thymus gland that can produce T cells, which are an important part of the immune system. According to the scientists, the development goes beyond previous efforts because the thymus serves such a key part in protecting the body against infection and in eliminating cancer cells.

The team is currently working on refining the reprogramming technique in the hope of developing a practical medical procedure, such as creating bespoke thymus glands made to match a patient’s own T cells. They see the development of a lab-grown thymus as a way of treating cancer patients whose immune system has been compromised by radiation or chemotherapy, and children born with malfunctioning thymuses.

"Growing 'replacement parts' for damaged tissue could remove the need to transplant whole organs from one person to another, which has many drawbacks – not least a critical lack of donors," says Rob Buckle, Head of Regenerative Medicine at the MRC. "This research is an exciting early step towards that goal, and a convincing demonstration of the potential power of direct reprogramming technology, by which one cell type is converted to another. However, much more work will be needed before this process can be reproduced in the lab environment, and in a safe and tightly controlled way suitable for use in humans.”

The team’s results were published in Nature Cell Biology.

The video below discusses the lab-grown thymus project.