The origin of ciliated cell cysts of the anterior pituitary

Summary Rats were decapitated and the heads were stored at 4° C for 24 h. The anterior pituitaries were then removed and incubated for 5 days. On the 1st, 3rd and 5th days of incubation, explants were studied by electron microscopy and immunohistochemistry using antiserum against S-100 protein. In the explant many granulated cells underwent necrosis; folliculo-stellate (FS) cells formed many cyst-like structures (CLSs) and became squamous epithelioid cells (CLS-forming cells). After incubation for 5 days the explants were isotransplanted under the renal capsules of male rats in order to observe morphological changes in the CLSs. Immediately after transplantation, the CLSs were encircled by a basement membrane, but from the 8th to 14th day, ciliation occured in CLS-forming cells and ciliated cell cysts were formed. The ciliated cells were immunostained with antiserum against S-100 protein. The present study suggests that FS cells are related to CLS formation and have the potential to trans-differentiate to ciliated cells.