Proacrosin as a marker of meiotic and post-meiotic germ cell differentiation: quantitative assessment of human spermatogenesis with a monoclonal antibody.

A quantitative immunohistochemical study of human spermatogenesis was performed using the 4D4 anti-proacrosin monoclonal antibody (mAb 4D4) as a marker of meiotic and post-meiotic germ cell differentiation. Cells from 15 testicular biopsies with normal spermatogenesis, 18 with slight and nine with marked hypospermatogenesis and six with maturation arrest were assigned to spermatogenic stages according to both nuclear maturation and proacrosin labelling patterns. The results showed that four spermatogenesis steps (mid- and late-pachytene primary spermatocytes, early and late spermatids) have to be separately considered for the classification of a given biopsy. Conversely, data from primary spermatocytes in the metaphase, anaphase and telophase stages and secondary spermatocytes did not show significant differences between biopsies. We conclude that: (1) slight hypospermatogenesis is due only to fewer cells entering meiosis, whereas in marked hypospermatogenesis there is also germ cell loss during the later meiotic steps and spermiogenesis; (2) the sloughing of germ cells from the epithelium could be of pathological significance; and (3) immunodetection with mAb 4D4 improves the assessment of spermatogenesis because it can label a protein expressed as early as meiotic prophase. In addition, mAb 4D4 labels a protein which is a marker of the Golgi complex allowing the detection of disturbances of cytoplasmic events during meiosis or spermiogenesis. Such an analysis is facilitated by mAb 4D4 labelling of paraffin-embedded sections.