Immunohistochemical localization of proliferating cell nuclear antigen as a tool to study cell proliferation in rodent and primate testes

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Abstract
Summary: The immunohistochemical localization of proliferating cell nuclear antigen (PCNA) has become a widely used method for the detection of proliferating cells in cancerous tissues. PCNA expression is maximal around the S phase of the cell cycle. This study has evaluated the applicability of PCNA localization for the analysis of germ cell proliferation in rats, Djungarian hamsters, rhesus and cynomolgus monkeys and men, using Bouin's‐fixed, paraplast‐embedded tissue. In addition, involuted testes from photoinhibited hamsters, testes from immature rhesus monkeys and from GnRH antagonist‐treated rats and cynomolgus monkeys were included. Monoclonal mouse anti‐PCNA antibody (clone: PC10) was used for detection of the antigen. Visualization was performed by immunogold‐silver staining or avidin‐biotin staining. PCNA labelling was confined to the nuclei of spermatogonia and early spermatocytes within the seminiferous epithelium of all species. The distribution of PCNA among the different types of A‐spermatogonia in primates is in good agreement with the previously described proliferation pattern of these cells. No staining was observed in resting A‐dark spermatogonia, while differentiating A‐pale spermatogonia were positive at distinct stages of the seminiferous epithelium cycle. In the rodent species the pattern of labelled A‐spermatogonia was stage‐specific, but agreed only partly with the previously described pattern of mitotic figures of A‐spermatogonia. Hormonal withdrawal induced a decrease in the number of PCNA‐positive cells in adult rats, hamsters and monkeys. In immature testes from rhesus monkeys positive staining was present in spermatogonia but also in some Sertoli cells, indicating proliferative activity of Sertoli cells in the prepubertal stage. It is concluded that PCNA localization can be used to assess the proliferative status of the renewing spermatogonia in the primate testis and to analyse the proliferative activity of the seminiferous epithelium under various endocrine conditions.