An Electron Microscopic Study of Cell Death in Molar Tooth Germ Epithelia of Mouse Embryos

Abstract

Cell death in the epithelial tooth germs of mouse mandibular molars from the 12th to the 14th day of gestation was investigated by electron and light microscopy. Light microscopy revealed granular substances in the epithelial portion of the tooth germ on the 12th day, and an increase in their number to the 14th day when the enamel knot developed. In the areas where granular substances were observed by the light microscope, electron microscopy revealed cells with condensed chromatin. The cytoplasm of these cells increased in electron density, the cisterns of rough endoplasmic reticulum were dilated and the cristae of mitochondria disappeared. These cells were comparable to the physiologically degenerative cells reported in other organs.
These degenerative cells are joined to adjacent cells by desmosomes and are believed to be derived from the epithelial cells.
Further, degenerative bodies, composed of amorphous structures and enveloped by a limiting membrane, were observed in the epithelial cells. They are presumed to be derived from the degenerated cells engulfed by neighboring cells. From this evidence, phagocytic ability is attributed to the epithelial cells of the tooth germ.