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Spermatozoa recovered from testicular biopsies can be used through intracytoplasmic sperm injection (ICSI) to achieve a pregnancy. To assess the likelihood of successful testicular sperm extraction (TESE) in men suffering from severe oligo- or azoospermia, bilateral biopsy specimens were obtained. Following semi-thin sectioning, the morphology of testicular samples was graded according to a modified Johnsen score. TESE was performed in parallel to this histological examination. The number of isolated spermatozoa was assessed in a semiquantitative way. From 103 patients investigated, 64 (62.1%) showed azoospermia in a preceding semen analysis and 29 (28.2%) patients had sperm concentrations between 0.1 and 1 x 10(6)/ml. In 10 patients who had higher sperm counts, most spermatozoa were non-motile. Spermatozoa could be detected after TESE in the testicular tissue of 49 (77%) azoospermic men. When follicle stimulating hormone (FSH) concentration was normal, most patients had detectable spermatozoa after TESE. Nearly one-third of patients with mildly elevated FSH had no spermatozoa. Thirty-nine percent of patients in whom FSH was elevated to more than twice normal and 50% of patients with grossly elevated FSH had no detectable spermatozoa. In all, 82.8% of men with sperm concentrations between 0.1 and 1x10(6)/ml in their ejaculate showed spermatozoa in the tissue sample after TESE. Our data demonstrate that, contrary to previous recommendations, infertile men with azoospermia and high FSH values should be reconsidered for testicular biopsy, provided that tissue samples can be cryopreserved for later TESE/ICSI treatment.

These biomarkers, specifically the surface markers FGFR3 and DSG2, may facilitate the isolation and enrichment of human stem and/or progenitor spermatogonia and thus lay a foundation for studies of long-term maintenance of human SSCs/progenitor cells, spermatogonial self-renewal, clonal expansion and differentiation.

The intermediate filament of mature human Sertoli cells is vimentin. A co-expression of vimentin together with cytokeratin has been demonstrated in Sertoli cells during embryonal development and under pathologic conditions in adult testes. We analysed the presence of vimentin, cytokeratin, and desmin in Sertoli cells of fetal testes (n=20), in seminiferous tubules of cryptorchid testes (n=10) and adjacent to testicular germ cell tumours (n=47) using specific monoclonal antibodies and single and double-labelling immunohistochemistry. During embryonal development prominent cytokeratin expression disappears after the 20th week of gestation. Interestingly, we also found desmin in immature intratubular Sertoli cells between weeks 11 and 14. In adult cryptorchid testes and in peritumour tubules, desmin was also prominently present in Sertoli cells in the vast majority of the cases investigated, as well as vimentin and cytokeratin co-expression. This first description of desmin immunoreactivity may shed some light on the ontogeny of human Sertoli cells and demonstrates that this cell type is able to express three types of intermediate filaments in a complex manner.

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