Histologie testiculaire et études méiotiques dans les stérilités de type non obstructif

There has been a renewed interes in testicular biopsy to evaluate infertility since the introduction, in 1993, of ICSI in azoospermic men with testicular sperm extraction (TESE) and intracytoplasmic sperm injection for the treatment of obstructive azoospermia. TESE is now performed for the treatment of nonobstructive azoospermia, and the testicular material sampled for therapeutic purposes can also be used for diagnostic and research purposes. The development of new methods of investigation of spermatogenesis, such as immunocytochemistry and fluorescent in situ hybridization (FISH) have also led to a renewed interest in analysis of spermatogenesis on testicular biopsy. A precise “testicular phenotype” must now be established to propose an aetiological diagnosis, and to determine the mechanisms and risks of nonobstructive azoospermia and severe oligozoospermia for the embryo. We systematically perform testicular histopathology and meiotic study for each patient undergoing testicular biopsy for ICSI. We first describe the histopathological lesions. Examination of the testicular biopsy specimen determines whether the lesion is focal or diffuse. If it is focal, the percentage of altered tubules, evaluated on 50 tubules, should be calculated. Quantitative evaluation of seminiferous epithelium and a qualitative study of cell morphology must also be performed. There are four frequent lesion patterns: 1-Sertoli-cell-only syndrome; 2-tubular hyalinisation; 3-diffuse lesions in spermatogenesis; 4-mixed atrophy. However, the reliability of interpretation of testicular histology presents certain limitations, as no standard method of analysis of testicular biopsies has been defined and there is a marked variability in the histologist’s capacity to recognize the various histological patterns. Meiotic study is performed on the cell suspension remaining after ICSI, which contains immature germ cells. New methods using immunocytochemistry have replaced older methods. The panel of antibodies which detect individual protein components at different stages of meiosis provides a valuable tool for the detection and interpretation of abnormal meiotic profiles. We performed meiotic studies on 41 patients and 13 controls after Giemsa staining, and synaptonemal complexes (SC) from nine of these patients and one control were immunostained with a polyclonal antibody which recognizes the COR1/SCP3 protein of the lateral element of the SC. Nineteen of the patients presented obstructive infertility (O) and 22 presented nonobstructive infertility (NO). We showed that the rate of asynaptic nuclei from the NO group (25.4%) was significantly higher than that of the O group (9.8%) and the controls (9.8%). Two patients of the NO group had a high percentage of asynaptic nuclei (86% and 91.8%), which could arise from a primary meiotic defect. One of these patients had an AZFc microdeletion. The meiotic study in a patient with classical complete AZFb microdeletion revealed a high prevalence of early meiotic stages: leptotene, zygotene and early pachytene stages and marked impairment of the synaptic process in most spermatocytes. In the light of these findings, we conclude that the pachytene checkpoint is localized at the mid-pachytene stage in humans.