Characterization of adherens junction protein expression and localization in pituitary cell networks.

Our view of anterior pituitary organization has been altered with the recognition that folliculo-stellate (FS) and somatotroph cell populations form large-scale three-dimensional homotypic networks. This morphological cellular organization may optimize communication within the pituitary gland promoting coordinated pulsatile secretion adapted to physiological needs. The aim of this study was to identify the molecules involved in the formation and potential functional organization and/or signaling within these cell-cell networks. Here, we have focused on one class of cell adhesion molecules, the cadherins, since beta-catenin has been detected in the GH cell network. We have characterized, by qPCR and immunohistochemistry, their cellular expression and distribution. We have also examined whether their expression could be modulated during pituitary tissue remodeling. The mouse anterior pituitary has a restricted and cell-type specific repertoire of cadherin expression: cadherin-11 is exclusively expressed in TSH cells; N-cadherin displays a ubiquitous expression pattern but with different levels of expression between endocrine cell types; E-cadherin is restricted to homotypic contacts between FS cells; while cadherin-18 is expressed both in somatotrophs and FS cells. Thus, each cell type presents a defined combinatorial expression of different subsets of cadherins. This cell-type specific cadherin expression profile emerges early during development and undergoes major changes during postnatal development. These results suggest the existence within the anterior pituitary of cell-cell contact signaling based on a defined pattern of cadherin expression, which may play a crucial role in cellular recognition during the formation and fate of pituitary cell homotypic networks.