Pituitary stem cells: Where do we stand?

• Pituitary stem cells were discovered 5-10 years ago, but urge for further detailed characterization.
• New molecular flavors have recently been added, but a pituitary stem cell signature is still absent.
• Pituitary stem cells are activated during early-postnatal maturation of the gland, suggestive of dynamic participation.
• New research models support a stem cell role in pituitary regeneration, and suggest a link with pituitary tumorigenesis.
• How pituitary stem cells differentiate to new hormonal cells is unknown, but gene expression data support embryonic-like paths.

Some 5 years ago, the stem cells of the adult pituitary gland were discovered. Subsequent in-depth characterization revealed expression of several stemness markers and embryo-typical factors. Now, the quest is open to decipher their role in the gland.When and how pituitary stem cells differentiate to contribute to the mature hormone-producing cell populations is not known. New research models support their involvement in cell regeneration after injury in the gland, and suggest a possible role in pituitary tumor formation. From their expression phenotype, pituitary stem cells seem to re-use embryonic developmental programs during the creation of new hormonal cells.Here, we will review the latest progression in the domain of pituitary stem cells, including the uncovering of some new molecular flavors and of the first potential functions. Eventually, we will speculate on their differentiation programs towards hormonal cells, with a particular focus on gonadotropes.