During morphogenesis, embryonic progenitors proliferate, differentiate and establish the shape of the future organs and tissues. In the mature organism, a certain degree of plasticity and potential for regeneration is retained as most organs maintain a population of adult stem cells sharing important similarities with embryonic progenitors; they are characterized by the ability to both self-renew and differentiate into the full range of the specialized cell types corresponding to the organ in which they reside. It is important to understand how these cells participate in organ cell turnover and regeneration, particularly because adult tissue stem cells can give rise to cancer stem cells. However, it is also relevant to regenerative medicine because stem cells can be transplanted once differentiated into the desired cell type or be manipulated in vivo to restore missing cells. In the last 12 years we and others have characterized a population of adult pituitary stem cells. While lineage tracing experiments have firmly established their adult stem cell properties, they have also shown that the cells are relatively quiescent in unchallenged animals. This is perhaps not surprising because the pituitary gland is an organ with a relatively low turn-over. In addition, endocrine cells can divide and this may be enough to maintain a functional pituitary. Therefore, the role of stem cells during homeostasis remains unclear. In contrast, when the gland is challenged, pituitary stem cells are mobilized. Endocrine cell ablation experiments show that stem cells react by actively proliferating and suggest that they also give rise to new endocrine cells, to replenish the depleted population. Moreover, pituitary target organ ablations, representing physiological challenges for the gland, have also been shown to stimulate both the proliferative and differentiation potential of the stem cells, demonstrating their regenerative potentialities. Characterization of the molecular mechanisms underlining mobilization of the stem cells is now required to be able to manipulate their fate.
27 - 29 Sep 2018
European Society for Paediatric Endocrinology