Science scores a major win, as a new study shows that a team of researchers has grown a fully functioning thymus organ in mice by transplanting lab-grown cells. They say this advance could help in future developments of replacement organs that are grown in a lab.

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For the first time, scientists have grown a fully functioning thymus in mice using lab-grown cells.

The study, published in the journal Nature Cell Biology, was conducted by scientists from the MRC Centre for Regenerative Medicine at the University of Edinburgh in the UK.

They note that the thymus is a vital immune organ that produces T cells to guard against disease by searching the body for faulty cells and infections. These T cells lead an immune response to eliminate harmful cells – such as cancer – or bacteria and viruses when they detect a problem.

However, individuals who do not have a fully functioning thymus are unable to generate enough T cells and are therefore vulnerable to infections and diseases.

Although thymus disorders can sometimes be remedied by extra immune cells or thymus transplantation soon after birth, the researchers say both options are limited by a lack of donors and problems with tissue matching.

As such, the ability to create a complete thymus from lab-grown cells would be a major boost in treating these conditions. While it is possible to produce distinct cell types in a dish, until now, researchers have been unable to grow a fully functioning organ from cells created outside the body.

To carry out their research, the team – led by Prof. Clare Blackburn – used cells called fibroblasts from a mouse embryo and converted them into a different type of cell called specialized thymus cells by “reprogramming” them.

This involved increasing levels of FOXN1, a protein that guides thymus development during organ development in the embryo. The new, resulting cells provide the “specialist functions” of the thymus, which enable it to make T cells.

Next, the team combined the induced thymic epithelial cells (iTEC) with other thymus cells and grafted them onto the kidneys of genetically identical mice.

They observed that 4 weeks later, the cells had created well-formed organs with the same structure as a healthy thymus – complete with clearly-defined regions called the cortex and medulla. Additionally, the iTEC cells produced different types of T cells from immature blood cells in the lab.

Commenting on their findings, Prof. Blackburn says:

The ability to grow replacement organs from cells in the lab is one of the ‘holy grails’ in regenerative medicine. But the size and complexity of lab-grown organs has so far been limited. By directly reprogramming cells, we’ve managed to produce an artificial cell type that, when transplanted, can form a fully organized and functional organ. This is an important first step towards the goal of generating a clinically useful artificial thymus in the lab.”

She and her team note that with further research, they hope their lab-made cells could help create a readily available treatment for thymus transplantation for individuals with a weakened immune system.

Prof. Blackburn explains their findings further in the video below:

Head of Regenerative Medicine at MRC Dr. Rob Buckle says that growing such parts for damaged tissue “could remove the need to transplant whole organs from one person to another, which has many drawbacks.”

However, he cautions that more work needs to be done before this technique can be reproduced in the lab and is safe for use in humans.