INTERMEDIATE FILAMENTS IN THE SERTOLI CELLS OF THE AGING HUMAN TESTIS

The presence and distribution of intermediate filaments (vimentin, ker atin, desmin) was studied in the Sertoli cells of elderly men by means of quantitative immunohistochemical methods. Sertoli cells from young men showed moderate immunogold labelling to vimentin throughout the e ntire cytoplasm between the cell organelles in tubules showing complet e spermatogenesis. Immunogold particles were more numerous in the peri nuclear cytoplasm and beneath the plasma membrane in all its faces. Th e testes from elderly men showed different tubule types; some showed c omplete spermatogenesis and a normal lamina propria, while others had spermatogenic arrest at different levels (spermatids, spermatocytes, s permatogonia). The immunohistochemical reaction to vimentin in the Ser toli cells of tubules with complete spermatogenesis (type a) was simil ar to that in the cells of young men. In the Sertoli cells of severely damaged tubules (type b) the immunohistochemical reaction was more in tense and immunogold particles extended in similar proportions through out the whole cytoplasm. When immunolabelling intensity was compared b etween the three groups of tubules, by counting the number of immunogo ld particles per square micrometre of cytoplasm, it was found to be si gnificantly higher (P less than or equal to 0.05) in type b tubules of elderly men than either in tubules of young men or in type a tubules of elderly men. Since the average cell surface of Sertoli cells was si milar in all tubule types, these data suggest that an actual vimentin increase occurs in Sertoli cells of germ-cell-depleted tubules. Sertol i cell immunogold labelling to keratin was found neither in young men nor in type a tubules of ageing men, whereas a positive immunohistoche mical reaction was observed in the Sertoli cells of type b tubules of elderly men. Immunogold particles were localized mainly in the perinuc lear cytoplasm, and beneath the lateral and basal cell surfaces. The o bservation of vimentin increase and keratin re-expression in ageing Se rtoli cells only in germ-cell-depleted tubules suggests that the chang es in intermediate filaments are related to the local factors associat ed with completion of spermatogenesis, causing functional changes in S ertoli cells.