When building functional organ tissue from the starting point of pluripotent stem cells, a different recipe is required for each different tissue type. Good progress is being made in establishing these recipes, and over the past decade the research community has steadily expanded the number of organs for which tissue engineered organoids can be constructed. An organoid is a millimeter-scale segment of functional organ tissue, only lacking the blood vessel network needed to support larger structures. Organoids are very useful in research, but in many cases can also be used to restore lost organ function when transplanted in sufficient numbers. That has been achieved for the liver and the thymus, and here researchers demonstrate restored function of the thyroid in mice.
Hormones produced by the thyroid gland are essential regulators of organ function. The absence of these hormones either through thyroid dysfunction due to, for example, irradiation, thyroid cancer, autoimmune disease, or thyroidectomy leads to symptoms like fatigue, feeling cold, constipation, and weight gain. Although hypothyroidism can be treated by hormone replacement therapy, some patients have persistent symptoms and/or experience side effects. To investigate potential alternative treatment strategies for these patients, researchers have now for the first time succeeded in generating thyroid mini-organs in the lab.
In a new study researchers used healthy thyroid tissue from patients undergoing surgical removal of the thyroid to grow mini-thyroid organs in a lab which resembled thyroid glands in their structure and protein content. The thyroid mini-organs contained stem cells which re-grew and formed new mini-organs when the structures were dissociated, providing a potentially unlimited source of lab-grown thyroid tissue. Importantly, the thyroid mini-organs could be matured and produced thyroid hormones in the cultures.
Preliminary proof that these structures could potentially replace thyroid tissue came from experiments in mice with hypothyroidism, where transplantation of the mini-organs increased serum levels of thyroid hormones and extended the lifespan of the animals compared to un-transplanted mice. Further studies are required, however the study lays the foundation for generating thyroid mini-organs from surgically removed tissue and may potentially lead to a new therapy for hypothyroidism in the future.