Adult pituitary stem cells

Underlying mechanisms leading to pituitary plasticity by which the gland adapts the number of hormone-producing cell to the continuously changing physiological requirements, are still poorly understood. Adult stem cells were shown to direct homeostatic cell maintenance, regeneration and functional plasticity in several organs and tissues. Only recently potential stem cells were identified and phenotypically characterized in adult pituitary. Multiple possible stem/progenitor cell candidates were proposed but different studies have been only partially reconciled. Here, we critically analyzed the reports addressing the identification of adult pituitary stem cells, trying, when possible, to reunite the results of the different studies. Nonetheless, in light of the still non-complete characterization of these cells, some discrepancies among the published studies are still apparent. Importantly, long-term in vitro self-renewal, a defining features of stem cells, remains to be unequivocally demonstrated. Finally, the potential role of adult pituitary stem (or progenitor) cells in pituitary adenoma development will be discussed.