Introduction: The Why's and How's for Studying Spermatogenesis and Spermatogonial Stem Cells.

Spermatogenesis is maintained throughout adulthood by a pool of adult stem cells termed spermatogonial stem cells (SSCs). Research investigations into spermatogenesis can provide insight into the etiology of certain types of male infertility (e.g., Sertoli cell only syndrome), elucidate means of improving food animal production, reveal new therapeutic avenues to address naturally occurring defects in sperm production, mitigate iatrogenic male infertility (e.g., arising from cancer therapy), and potentially intervene for male contraception. This chapter will serve as a commentary about why studying spermatogenesis is important, including a high-level overview of spermatogonia and SSCs, and make the case for a critical need for use of stringent definitions for SSCs and experimental platforms that allow for clear distinction of the multiple types of spermatogonia that exist in testes of mammals.