Generation of functional thyroid tissue from stem cells

Thyroid hormones are a class of iodide-containing molecules that play a critical role in the regulation of various body function including growth, metabolism and heart function and that are crucial for normal brain development. The thyroid gland, an endocrine organ that has been specialized in trapping iodide, is the only organ where these hormones are produced. It is, however, of note that one out of 3000 human newborns is born with congenital hypothyroidism, a condition characterized by insufficient production of thyroid hormones. In the absence of a medical treatment with thyroid hormones -- initiated during the first days after birth -- the child will be affected by an irreversible mental retardation. Moreover, a life-long hormonal treatment is necessary in order to maintain proper regulation of growth and general metabolism.

By employing a protocol in which two important genes can be transiently induced in undifferentiated stem cells, the researchers at IRIBHM were able to efficiently push the differentiation of stem cells into thyrocytes, the primary cell type responsible for thyroid hormone production in the thyroid gland.

A first exciting finding of these studies was the development of functional thyroid tissue already within the culture dishes. As a next step, the team of Sabine Costagliola transplanted the stem-cell-derived thyrocytes into mice lacking a functional thyroid gland. Four weeks after transplantation, the researchers observed that transplanted mice had re-established normal levels of thyroid hormones in their blood and were rescued from the symptoms associated with thyroid hormone deficiency. These findings have several important implications. First, the cell system employed by the IRIBHM group provides a vital tool to better characterize the molecular processes associated with embryonic thyroid development. Second, the results of the transplantation studies open new avenues for the treatment of thyroid hormone deficiency but also for the replacement of thyroid tissue in patients suffering from thyroid cancer.

The researchers are currently developing a similar protocol based on human stem cells and explore ways to generate functional human thyroid tissue by reprogramming pluripotent stem cells (iPS) derived from skin cells.