Reproduction Abstracts

Introduction: The anterior pituitary lobe is a key endocrine tissue composed of five types of endocrine-cells and non-hormonal cells. Among non-endocrine-cells, Sox2-expressing cells exist as stem/progenitor cells and play a role in the regeneration of endocrine-cells in the adult pituitary. Recently, we have reported that transcription factors, Prop1, Prrx1 and Prrx2, are expressed in the pituitary stem/progenitor cells and these cells contact via a tight-junction protein CAR to construct a stem/progenitor cell niche. However, the micro-environment of niche for maintenance of stemness and self-renewal in the pituitary is still obscure. In this study, we attempted to identify the expression of juxtacrine factor Ephrin (Efn) and its receptor (Eph) in the pituitary stem/progenitor cells.

Materials and methods: Real-time PCR for Efn/Eph was performed using cDNA libraries of the pituitary and pituitary derived cell lines. Immunohistochemistry was examined to determine localization of EFN/EPH in the pituitary.

Results and discussion: Real-time PCR demonstrated that some Efns and Ephs related to EfnB-signaling are expressed in the postnatal pituitary. Immunohistochemistry for EFNs detected the cells positive for EFN-B2 and SOX2 in the marginal cell layer. Recently, we identified a candidate cell line of pituitary stem/progenitor cells, Tpit/E, which maintains stemness and self-renewal. Notably, Tpit/E cells express not only Efn-B2 but also its receptors, such as EphA4, EphB3, EphB4 and EphB6, indicating that reciprocal EFN-B2 signaling within Tpit/E cells themselves might maintain their stemness and self-renewal. Thus, the environment of pituitary stem/progenitor cell niche might be preserved by EFN-B2 signaling.