Endocrine Abstracts

Folliculostellate (FS) cells constitute around 10% of the adenohypophyseal cell population. Various functions of these non-endocrine cells have been elucidated, including the paracrine control of the function of local endocrine cells. FS cell development is currently very poorly understood. In this study FS cell appearance during embryonic chick development between pre-natal stages (st)17-37 was examined. Gene and protein expression of the FS marker proteins annexin A1 (AnxA1) and S100β were detected by in situ hybridisation and immunohistochemistry/immunogold staining respectively. In addition, the emergence of cells with FS-like morphology was investigated by electron microscopy (EM). EM analysis of st30-35 pituitary glands revealed the pre-natal appearance of FS-like cells. Expression of Islet1 in st30-37, known to be expressed in the embryonic chick pituitary gland, was verified. However, in situ hybridisation and immunohistochemistry/immunogold staining for AnxA1 and S100β at the same stages demonstrated a lack of expression. AnxA1 expression was observed elsewhere in choroid plexus, mesonephros and pro-epicardium. These findings support the idea that a subset of FS cells, act as progenitors in the pituitary before differentiated marker expression is evident.