Folliculo-stellate cells in the human anterior pituitary express cytokeratin

Recent studies have suggested that the anterior pituitary is derived not from Rathke's pouch, but instead from neuroectoderm. To address this controversy and the differentiation of the adenohypophysis, we evaluated folliculo-stellate cells from 7 human pituitaries using a panel of immunohistochemical stains. The panel included antibodies to a low molecular weight cytokeratin (CK-8), a broad spectrum of cytokeratins (AE 1/AE 3), S-100 protein, vimentin, and glial fibrillary acid protein. The most intense immunostaining was observed with the antibody to broad spectrum cytokeratins. Less intense immunohistochemical staining of folliculo-stellate cells was observed with the antibodies against glial fibrillary acidic protein and S-100 protein. Immunoblotting of anterior pituitary tissue obtained from 3 autopsied patients showed that cytokeratins identified in the anterior pituitary were of low molecular weight (40 to 56 Kd). These results indicate that folliculo-stellate cells show epithelial differentiation, and support the hypothesis that the anterior pituitary is derived from Rathke's pouch.