Age-related changes in cytoskeletal components of the BDF1 mouse Sertoli cell

Age-related changes in mouse Sertoli cell cytoskeletal components (F-actin, vimentin and cytokeratin) were investigated by light and transmission electron microscopy and immunofluorescence using BDF1 mice from 3-33 months of age. In old mice (30 and 33 months of age), the testicular seminiferous epithelia were extremely thin, containing scarce round spermatids and spermatocytes with no elongated spermatids. In these epithelia, the Sertoli cells had lost their polarity and had become flattened. F-actin was detectable at the junction between adjoining Sertoli cells and around the spermatid head in young mice. In old mice, F-actin was distributed at the junction between adjacent Sertoli cells, around the spermatid head, and at the luminal side of the Sertoli cell cytoplasm. Vimentin was detected around the Sertoli cell nucleus and extended into the Sertoli cell trunk towards the tubular lumen in young mice. In old mice testes, however, vimentin was recognized around the Sertoli cell nucleus, but not in the Sertoli cell trunk. Additionally, sheet-like reactions of vimentin, running parallel to the basement membrane, were detected near the luminal surface. Although cytokeratin was not detected in the Sertoli cells of mice until 27 months of age, it was obvious in the extremely thin seminiferous epithelia of older mice. Cytokeratin was randomly distributed within the Sertoli cell cytoplasm. In these Sertoli cells, the expression of vimentin was concurrently detected. Detection of cytokeratin in the extremely thin seminiferous epithelia is one of the most characteristic phenomena of age-related testicular changes in Sertoli cells of older mice.