Correlated scanning and transmission electron microscopy of cell surfaces at various levels in human gingival epithelium

Abstract

The surfaces and cellular interdigitations of cells at defined levels in human gingival epithelium were investigated by correlated scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The epithelium of critical point-dried or freeze-dried specimens of gingiva was stripped with adhesive tape and the SEM and TEM appearances compared for each level. The undersurfaces of the epithelial cells removed by the adhesive tape were examined by SEM. Critical point-dried specimens were fractured vertically and the fractured epithelial surfaces examined by SEM. Epithelial cells stripped or scraped from the gingiva were also examined. The superficial surfaces of cells of the stratum corneum had a reticular pattern of ridges. Microvilli were present on their undersurface in a reciprocal arrangement. Desmosomes are included in these processes of the plasma membrane which are concluded to be remnants of the cellular interdigitation from a deeper level. Cell separation is an orderly process starting a few layers below the surface, and is possibly controlled by desmosomal attachments. At deeper levels the stripping tape technique uncovered isodiametric cells with fine processes, thought to be prickle or basal cells. Smooth featureless zones were detected at this level which, it is suggested, may represent portions of the basement membrane or cytoplasmic faces of intracellularly fractured keratinocytes. The fractured specimens enabled cells at different levels in the epithelium to be identified and their SEM appearances compared.