We are arguably a long way from transplanting a miniature brain into humans (Although some tried to put it in rodents). But we’re getting closer to transplanting other organoids — potentially those that look like lungs, livers or intestines, for example.
Recent progress has been made by Mirianne Romiti at the Université Libre de Bruxelles in Belgium and colleagues, who He succeeded in creating a mini-transplantable thyroid gland from stem cells.
The thyroid gland is a butterfly-shaped structure in the neck that makes hormones. A deficiency of these hormones can make people very ill. About 5% of people have hypothyroidism, or hypothyroidism, which can lead to fatigue, aches and pains, weight gain, and depression. It can affect brain development in children. Those affected often have to take hormone replacement therapy every day.
After culturing thyroid organelles in the laboratory for 45 days, Rometty and her colleagues were able to transplant them into mice lacking thyroid glands. The operation appears to have restored production of thyroid hormones, and primarily cured hypothyroidism in the animals. “The animals were very happy,” Romiti said.
The focus now is on finding a way to safely transplant similar organoids into humans. There’s a lot of demand—Romiti says her colleague is constantly getting calls and emails from people desperate to get a small thyroid gland transplanted. But we haven’t gotten there yet.
Rometty and her colleagues made miniature thyroids from stem cells in a flexible “naive” state that could be encouraged to form any of several cell types. It took scientists a decade of research and multiple attempts to find a way to get the cells to form a thyroid-like structure. The end result required genetic modification using a virus to infect cells, and the team used several drugs to help the organelles grow in a dish.
The stem cells the team used were embryonic stem cells — a strain of cells originally taken from a human embryo. These cells cannot be used clinically for several reasons – for example, the recipient’s immune system will reject the cells as foreign, and destroying the embryos to treat diseases would be considered unethical. The next step is to use stem cells generated from the person’s own skin cells. In theory, miniature organs could be made from these cells specifically for individuals. Rometty says her team has made “promising” progress.
Of course, we will also have to make sure that these organelles are safe. No one knows what they are likely to do to the human body. Will they grow? shrink and disappear? constitute a type of cancer? We’ll need more long-term studies to get a better idea of what might happen.