Researchers Grow Thymus from Embryonic Cells
One of the major goals of regenerative medicine is the technology for growing entire organs from stem cells. This type of organ replacement would be a game-changer for many diseases and benefit countless people.
Scottish researchers recently published in Nature Cell Biology a paper detailing the first published success of growing an entire organ from cells. In this case they grew a working thymus from mouse embryonic fibroblasts.
The thymus is an organ that sits in the anterior chest and is a critical part of the immune system, producing the various types of T-cells. The organ degenerates as we get older, which is usually not a problem, unless you need to reconstitute your immune system following a procedure that wipes out the immune system.
The promising news is that the researchers were able to get embryonic fibroblasts to develop into thymus tissue using a single trigger – Foxn1 expression. The fibroblasts were able to become an entirely different type of cell. Further, the resulting thymus was completely formed and functional.
But don’t get too excited, there are many reasons to be conservative in interpreting the significance of this advance. First, the thymus is a very simple organ (as organs go). Previously, organs such as trachea and bladders have been grown using a scaffold on which to grow the cells. But there are more complex organs still, like lungs, hearts, and kidneys, that will prove the ultimate challenge for growing organs.
Further, the thymus was grown from embryonic cells, rather than adult-derived cells. This means this technique cannot use a patient’s own cells, and therefore rejection is still an issue. This might be particularly problematic for a thymus, which is part of the immune system.
Finally, there still remains obstacles to transplanting stem cells into patients for any indication. One huge technical obstacle is keeping the new tissue from becoming a tumor.
While this latest study is a milestone and important step along the path to growing organs therapeutically, it is a baby step and significant obstacles remain. We are still a long way away from growing a new complex organ (heart or kidney), either in the final recipient or in a host and then transplanting it, from a person’s own cells, eliminating rejection.
Even simple organs like the thymus require much more study. However, we continue to advance down this path. There is meaningful progress, we just have to be patient.