We assayed the effects of phenol red (pr), estrogen (Es), and progesterone (Pg) in three-dimensional organotypic cultures of human uterine endocervix. Small intact fragments deposited on sponges submerged in DMEM with 10% fetal bovine serum were cultured in three different conditions: with pr (DMEMpr+), without pr (DMEMpr-), and without pr but with the addition of physiological concentrations of Es and Pg [DMEMpr-(Es + Pg)]. Cell viability and cellular responses were assayed after 4, 10, and 21 days using immunohistochemistry for the expression and distribution of the following markers: mucins and mucopolysaccharides (PAS staining), pan-cytokeratins (AE1/AE3), CK19, p63, Ki-67, vimentin, estrogen receptor-alpha (ER-alpha), and progesterone receptor (PR). The fragments cultivated in DMEMpr+ Showed a cuboidal, poorly differentiated epithelial phenotype and signs of stroma degeneration. In DMEMpr-, both tissue architecture and cellular heterogeneity were much better preserved: epithelial cells showed a more columnar shape, and stroma was very well conserved, maintaining cell density. The addition of Es and Pg further improved the histology and physiology of the fragments: in DMEMpr-(Es + Pg), epithelial cells retained a columnar shape, secreted mucins, and formed areas of squamous hyperplasia. (c) 2005 Elsevier GmbH. All rights reserved.