Perspectives: Methods for Evaluating Primate Spermatogonial Stem Cells

Mammalian spermatogenesis is a complex, highly productive process generating millions of sperm per day. Spermatogonial stem cells (SSCs) are at the foundation of spermatogenesis and can either self-renew, producing more SSCs, or differentiate to initiate spermatogenesis and produce sperm. The biological potential of SSCs to produce and maintain spermatogenesis makes them a promising tool for the treatment of male infertility. However, translating knowledge from rodents to higher primates (monkeys and humans) is challenged by different vocabularies that are used to describe stem cells and spermatogenic lineage development in those species. Furthermore, while rodent SSCs are defined by their biological potential to produce and maintain spermatogenesis in a transplant assay, there is no equivalent routine and accessible bioassay to test monkey and human SSCs or replicate their functions in vitro. This chapter describes progress characterizing, isolating, culturing, and transplanting SSCs in higher primates.