OR03-02 Identification of a Novel Stem/Progenitor Population of the Adrenal Medulla

The adrenal glands regulate multiple physiological processes including the stress response, the immune system and metabolism. The adrenal is composed of an outer cortex that produces steroids, and an inner medulla that produces catecholamines. Tissue-specific stem/progenitor populations have been identified in the adrenal cortex, while the presence of a functional stem/progenitor population in the adrenal medulla is unclear. The adrenal medulla derives from the neural crest and contains chromaffin cells, neurons and sustentacular (support) cells. Establishing cell hierarchy and elucidating mechanisms of regulation of the different cell types is important to understand normal homeostasis and disease pathogenesis, such as of pheochromocytomas. Using genetic approaches in mouse, we have established that a subpopulation of sustentacular cells express the stem/progenitor marker SOX2. Through genetic lineage-tracing using the Sox2-CreERT2 strain, we demonstrate that these are an expanding population, capable of giving rise to chromaffin cells and neurons throughout life, consistent with a stem/progenitor role in vivo. We further demonstrate the self-renewal and differentiation potential of SOX2+ cells through in vitro isolation and expansion. Through analysis of FFPE sections of human adrenals, we confirm the presence of SOX2+ cells in the normal adult organ, as well as in pheochromocytomas. Taken together, our data support the identification of a previously undescribed stem/progenitor cell in the mammalian adrenal medulla, and confirm its functional relevance.