Sertoli and Leydig cells of the human testis express neurofilament tripletproteins

Using RT-PCR, western blot and enzyme and fluorescence immunocytochemical t echniques, the three isoforms of neurofilament proteins (NFPs), namely NF-L (NFP-68 kDa), NF-M (NFP-160 kDa) and NF-H (NFP-200 kDa) were found in Sert oli and Leydig cells of human testes. RT-PCR showed specific for the three NFP fragments in testicular tissue, in isolated seminiferous tubules and in isolated Leydig cells. In protein preparations from the same testicular co mponents, western blot analysis detected bands with molecular weights chara cteristic for NF-H, NF-M and NF-L. Application of immunofluorescence and im munoenzyme methods on cryostat and paraffin sections resulted in difference s in the staining pattern in Sertoli cells and Leydig cells. In these cells , the NFPs showed predominantly a perinuclear location from which bundles e merge that were directed towards the basal, apical and lateral extensions o f the Sertoli cells as well as the periphery of Leydig cells. NF-H coexists with vimentin-type filaments as seen by dual staining and staining of cons eccutive serial sections of material embedded in paraffin. In Sertoli cells , vimentin and NF-H showed distinct dynamic changes depending on the stage of spermatogenesis and some structural variations of seminiferous tubules. Although in some tubules both vimentin and NF-H immunoreactivity was presen t at high levels, in the Sertoli cells from most individuals an inverse rel ationship in the staining intensity of vimentin and NF-H was observed. The strongest NF-H immunoreactivity was detected in Sertoli cells associated wi th stage 3 spermatids, whereas vimentin immunoreactivity was most abundant in association with stage 5 spermatids. The leydig cells did not show funct ional changes of the NFP immunoreactivity. The results obtained provide new evidence for the heterogeneous phenotype of human Sertoli cells and raise the question of their exact nature and origin.