Distribution of cytokeratin filaments and vimentin in developing human taste buds

Taste buds in humans originate from approximately the 8th postovulatory week under the influence of ingrowing nerve fibers. Since they develop from local epithelium, it is of interest whether or not prospective taste cells maintain or develop characteristics of epithelial cells that are different from those of the adjacent epithelium during differentiation. The aim of this study was to monitor changes of the distribution of the cytokeratin filaments (CKs) 8, 18, 19 and 20 ("gastrointestinal" type), CK 7 ("ductal" type), and CK 13 (maturation "mucosa type"), as well as vimentin in developing human taste buds and adjacent squamous epithelium. With the exception of CK13, which remains negative in taste bud anlagen and adult taste buds, all cytokeratins tested were present in taste cells. With the progress of development, the distribution of CKs becomes more and more restricted to taste cells and salivatory ducts as well as Ebner gland cells. Only CK20 is exclusively specific to taste bud anlagen and sometimes to individual bipolar cells occurring in early stages (week 8-9). Vimentin was located mainly in mesodermal derivatives but also in perigemmal epithelial cells during all stages of development. The occurrence of vimentin in "borderline" epithelia that interface with underlying connective tissue, i.e., in a region of discontinuity, may be associated with particular events in development, cell migration or even dedifferentiation.