Quantitative analysis of spermatogenesis and apoptosis in the common marmoset (Callithrix jacchus) reveals high rates of spermatogonial turnover and high spermatogenic efficiency

Spermatogenesis is characterized by the succession in time and space of spe cific germ cell associations (stages), There can be a single stage (e.g., r odents and some macaques) or more than one stage (e.g., chimpanzee and huma n) per tubular cross section. We analyzed the organization of the seminifer ous epithelium and quantified testicular germ cell production and apoptosis in a New World primate, the common marmoset (Callithrix jacchus), Tubule c ross sections contained more than one stage, and the human six-stage system could be applied to marmoset spermatogenesis, Stereological (optical disec tor) analysis (n = 5) revealed high spermatogenic efficiency during meiosis and no loss of spermatids during spermiogenesis. The conversion of type A to type B spermatogonia was several-fold higher than that reported for othe r primates. Highest apoptotic rates were found for S-phase cells (20%) and 4C cells (15%) by flow cytometric analysis (n = 6 animals); histological an alysis confirmed spermatogonial apoptosis, Haploid germ cell apoptosis was <2%, Marmoset spermatogenesis is very efficient and involves substantial sp ermatogonial proliferation. The prime determinants of germ cell production in primates appear to be proliferation and survival of spermatogonia rather than the efficiency of meiotic divisions. Based on the organizational simi larities, common marmosets could provide a new animal model for experimenta l studies of human spermatogenesis.