Stereological studies of differentiation in hamster cheek pouch epithelium: variations in the volume and frequency of mitochondria.

The present report describes quantitative studies of mitochondria from stratified squamous epithelial cells from hamster cheek pouch mucosa in differentiating compartments. Mucosa was processed for electron microscopy and, using strict sampling procedures, electron micrographs of epithelium from defined basal, spinous and granular strata were acquired. Using stereological and other morphometric methods, the volume density, numerical density and volume-to-surface ratio of mitochondria were estimated in each cellular layer, and these data were transformed into absolute values characterising the average cell in these layers. The results suggest that both volumetric and numerical densities of mitochondria decreased progressively during epithelial differentiation; conversely, the total volume and number of mitochondria present in granular cells were consistently higher than in basal cells, as was the volume of individual mitochondria. These quantitative changes may reflect functional alterations in the metabolism of epithelial cells during differentiation and provide a base line for further work on experimental epithelial biology and pathology.