We are arguably a long way from transplanting miniature brain blobs into humans (although some have attempted to insert them into rodents). But we’re getting closer to implanting other organoids — possibly ones resembling lungs, livers, or intestines, for example.
The most recent advances have been made by Mírian Romitti at the Université libre de Bruxelles in Belgium and her colleagues, who have succeeded in creating miniature transplantable thyroid glands from stem cells.
The thyroid is a butterfly-shaped structure in the neck that produces hormones. A lack of these hormones can make people very ill. About 5% of people have an underactive thyroid, or hypothyroidism, which can lead to fatigue, pain, weight gain, and depression. It can affect brain development in children. And those affected often have to take hormone replacement therapy every day.
transplantation of organoids
After 45 days of growing thyroid organoids in a lab, Romitti and her colleagues were able to transplant them into mice that lacked their own thyroid gland. The surgery appeared to restore thyroid hormone production and essentially cure the animals’ hypothyroidism. “The animals were very happy,” as Romitti puts it.
The focus now is on finding a way to safely transplant similar organoids into humans. Demand is high — Romitti says her colleague is constantly getting calls and emails from people desperate for a mini-thyroid transplant. But we are not there yet.
Romitti and her teammates made their mini-thyroids from stem cells — cells in a “naïve,” flexible state that can be stimulated to form one of many cell types. It took scientists a decade of research and multiple attempts to find a way to get the cells to form a structure that looks like a thyroid gland. The end result required genetic modification with a virus to infect the cells, and the team used several drugs to help the organoids grow in a dish.
The stem cells used by the team were embryonic stem cells – derived from a cell line originally derived from a human embryo. These cells could not be used clinically for a number of reasons — the recipient’s immune system would reject the cells as foreign, for example, and destroying embryos to treat disease would be considered unethical. The next step is to use stem cells obtained from a person’s own skin cells. In theory, mini-organs made from these cells could be custom-made for individuals. Romitti says her team has made “promising” progress.
Of course, we also need to make sure these organoids are safe. No one knows what they are likely to do in a human body. will they grow flinch and disappear? Form some kind of cancer? We need more long-term studies to get a better idea of what might be happening.