Cell proliferation, migration, and specialization in the epithelium of the mouse tongue

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Abstract
The three dimensional structure of the filiform papilla of the mouse tongue is presented.Two distinctly different keratinized cell products are found in the region of the filiform papilla. Evidence for the existence of the two cell types is based on a series of histological, cytological, micro‐manipulative and cell migration studies.A study of the tongues of embryonic and adult mice shows no morphological evidence of heterogeneity in the cells of the basal layer of epithelium which supports the concept that the two different keratinized cell products derive from a homogeneous cell population.Tritiated thymidine autoradiographic studies reveal that the proliferative pool of epithelial cells is limited to the basal cell layer. The avergae cell renewal rate of this layer is presented for the various parts of the tongue. The progenitor cell cycle is also described.The studies indicate that the movement of a cell from the basal layer to the spinous layer is a random event in time and that the movement of a cell out of the basal layer precludes further cell proliferation by that cell.The results indicate that it is positional chance at the time of cell birth which determines whether a cell will specialize into one of two different alternate fates. The fate of the cell in this particular case is based on the particular micro‐environment the cell is forced to occupy. The force is provided by the growth of cellular mass and the subsequent crowding out of those cells not able to remain attached to the basement membrane.