Co-expression of cytokeratin and vimentin filaments in rete testis and epididymis. An immunohistochemical study.

In 11 testes of different developmental stages (from 10-week-old embryos to adult) the cytokeratin and vimentin expression patterns of rete testis and epididymis were investigated immunohistochemically in formaldehyde-fixed paraffin-embedded material. In addition, immunofluorescence microscopy including double immunofluorescence was performed on frozen sections of 3 of these 11 cases. Rete testis and epididymis cells displayed a heterogeneous co-expression of cytokeratin and vimentin. In double immunohistochemistry, differences in distribution of keratin and vimentin intermediate filaments with predominance of cytokeratins in the apical cytoplasmic regions and of vimentin filaments in the basal portions of the cells were found. Cytokeratin expression preceded the appearance of vimentin: cytokeratin was already detectable in 10-week-old embryos, while weak vimentin immunoreactivity was first seen in 12-week-old embryos and became conspicuous in testes around the perinatal period. In testes of children up to 2 years of age the cytoplasmic distribution of cytokeratin and vimentin was more homogeneous. Predominance of the basal cell portions for vimentin and the apical regions for cytokeratin staining were less pronounced than in adult testes. In the proximal and distal parts of the epididymis a different intermediate filament expression pattern was found with a clear predominance of cytokeratin near the rete.