Identification and enrichment of colony-forming cells from the adult murine pituitary

Stem and progenitor cells have been identified in many adult tissues including bone marrow, the central nervous system, and skin. While there is direct evidence to indicate the activity of a progenitor cell population in the pituitary gland, this putative subpopulation has not yet been identified. Herein we describe the isolation and characterization of a novel clonogenic cell type in the adult murine pituitary, which we have termed Pituitary Colony-Forming Cells (PCFCs). PCFCs constitute 0.2% of pituitary cells, and generate heterogeneous colonies from single cells. PCFCs exhibit variable proliferative potential, and may exceed 11 population doublings in 14 days. Enrichment of PCFCs to 61.5-fold with 100% recovery can be obtained through the active uptake of the fluorescent dipeptide, β-Ala-Lys-Nε-AMCA. PCFCs are mostly contained within the large, agranular subpopulation of AMCA⁺ cells, and constitute 28% of this fraction, corresponding to 140.5-fold enrichment. Interestingly, the AMCA⁺ population contains rare cells that are GH⁺ or PRL⁺. GH⁺ cells were also identified in PCFC single cell colonies, suggesting that PCFCs have the potential to differentiate into GH⁺ cells. Together, these data show that the pituitary contains a rare clonogenic population which may correspond to the somatotrope/lactotrope progenitors suggested by previous experiments.