Endocrine Abstracts

SOX9-positive pituitary stem cells differ according to their position in the gland and maintenance of their progeny depends on context. We and others have previously characterised a population of adult stem cells (SCs) in the murine pituitary gland. We showed that while these SCs are relatively quiescent in normal conditions, they undergo activation following target organ ablation, providing a well-characterized paradigm to study an adaptative response in the context of the endocrine axes. We have here used single cell technologies to characterize SC heterogeneity and mobilization. We show that the transcriptional profile of SCs varies according to their localization in the gland, revealing different compartemnts and properties. Following target organ ablation, analyses of mobilized SCs reveal that differentiation occurs more frequently than previously thought, and that their progeny is more diverse than demonstrated by the lineage tracing experiments. Comparison of SC progeny following short and long term lineage tracing suggests that maintenance of selected nascent cells underlies SC output, highlighting a trophic role for the microenvironment. Consequently, analyses of cell trajectories further predict pathways and potential new regulators. In conclusion, our data highlight the herogeneity of the adult pituitary SC population while our mobization paradigm provides a valuable model to study the influence of evolving states on the mechanisms of SC mobilization and the role of local interactions.