Survival and differentiation of pituitary colony-forming cells in vivo

Growth hormone (GH) deficiency is a significant clinical problem, since growth hormone is essential for the regulation of growth, metabolism, and the cardiovascular system. Stem and progenitor cells have been identified in many adult tissues. Recently, our laboratory identified a cell type within the adult pituitary gland with stem cell-like properties, which we have termed pituitary colony-forming cells (PCFCs). Herein we investigate the ability of PCFCs to survive and differentiate in vivo. Enriched populations of PCFCs were transplanted into an in vivo microchamber model. Grafts were harvested at 6 weeks post-transplant and tested for surviving donor cells (LacZ(+)) or for differentiation (GH(+)). The results showed that donor cells survived in chambers (LacZ(+)) and underwent division (phosphohistone-H3-positive). Furthermore, grafted cells showed colocalization of LacZ and GH, suggesting differentiation. To confirm differentiation, donor cells were obtained from a GH-enhanced green fluorescent protein (eGFP) reporter transgenic mouse model that expressed eGFP under control of the GH promoter. Cells that were eGFP(-), that is, GH(-), were selected by fluorescence-activated cell sorting (FACS) and transplanted. After 6 weeks, eGFP(+)GH(+) cells were detected in grafts by immunostaining and by FACS analysis of digested grafts. In conclusion, PCFCs have the capacity to divide and differentiate into GH(+) cells in vivo. The vascularized tissue chamber model is an ideal model to investigate the environmental niche for PCFC expansion and differentiation and has the potential to be developed into a growth hormone-releasing organoid in vivo.