Male Germ Line Stem Cells Have an Altered Potential to Proliferate and Differentiate During Postnatal Development in Mice

Abstract Spermatogonial stem cells (SSCs) continuously support spermatogenesis after puberty. However, accumulating evidence suggests that SSCs differ functionally during postnatal development. For example, mutant mice exist in which SSCs support spermatogenesis in the first wave after birth but cease to do so thereafter, resulting in infertility in adults. Studies using a retroviral vector have shown that the vector transduces pup SSCs more efficiently than adult SSCs, which suggests that pup SSCs divide more frequently. Thus, it is hypothesized that the SSCs in pup and adult testes have different characteristics. As an approach to testing this hypothesis in the present study, we investigated the proliferation kinetics of pup SSCs (6–9 days old) and their self-renewal/differentiation patterns for the first 2 mo after transplantation, and compared them to those of adult SSCs. Using serial transplantation, we found that the number of pup SSCs declined over the first week after transplantation. Thereafter, ...