Recapitulating Hypothalamus and Pituitary Development Using Embryonic Stem/Induced Pluripotent Stem Cells

The hypothalamic-pituitary system is essential for maintaining life and controlling systemic homeostasis. However, it can be negatively affected by various diseases, resulting in life-long serious symptoms. Pluripotent stem cells, such as embryonic stem (ES) cells and induced pluripotent stem (iPS) cells, differentiate into neuroectodermal progenitors when cultured as floating aggregates under serum-free conditions. Recent results have shown that strict removal of exogenous patterning factors during the early differentiation period induces efficient generation of rostral hypothalamic-like progenitors from mouse ES cell-derived neuroectodermal cells. The use of growth factor-free, chemically defined medium was critical for this induction. The ES cell-derived hypothalamic-like progenitors generated rostral-dorsal hypothalamic neurons, in particular magnocellular vasopressinergic neurons, which release hormones upon stimulation. We subsequently reported efficient self-formation of three-dimensional adenohypophysis tissues in aggregate cultures of mouse ES cells. The ES cells were stimulated to differentiate into non-neural head ectoderm and hypothalamic neuroectoderm in adjacent layers within the aggregate, followed by treatment with a Sonic Hedgehog agonist. Self-organization of Rathke’s pouch-like structures occurred at the interface of the two epithelia in vivo, and various endocrine cells, including corticotrophs and somatotrophs, were subsequently produced. The corticotrophs efficiently secreted adrenocorticotropic hormone in response to corticotropin-releasing hormone. Furthermore, when engrafted in vivo, these cells rescued systemic glucocorticoid levels in hypopituitary mice. The present study aimed to prepare hypothalamic and pituitary tissues from human pluripotent stem cells and establish effective transplantation techniques for future clinical applications. Preliminary results indicated differentiation using human ES/iPS cells, and the culture method replicated stepwise embryonic differentiation. Therefore, these methods could potentially be used as developmental and disease models as well as for future regenerative medicine.