The Application of Animal Models in Preservation ofMale Fertility

Spermatogonial s tem cells (SSCs) are a rare group of cells inthe tes tis that undergo self-renewal and complex sequencesof differentiation to es tablish and maintain spermatogenesisthroughout adulthood. The difficulty of unequivocal identificationof SSCs and complexity of replicating their differentiationproperties in vitro have prompted the introduction of novelin vivo models such as germ cell transplantation, tes tis tissuexenografting, and tes tis cell aggregate implantation. Owing tothese unique animal models, our ability to s tudy and manipulateSSCs has dramatically increased, which complements the availabilityof other advanced assis ted reproductive technologiesand various genome editing tools. These animal models can advanceour knowledge of SSCs, tes tis tissue morphogenesis anddevelopment, germ-somatic cell interactions, and mechanismsthat control spermatogenesis. Equally important, these animalmodels can have a wide range of experimental and potentialclinical applications in fertility preservation of prepubertal cancerpatients, and genetic conservation of endangered species.Moreover, these models allow experimentations that are otherwisedifficult or impossible to be performed directly in the targetspecies. Examples include proof-of-principle manipulationof germ cells for correction of genetic disorders or inves tigationof potential toxicants or new drugs on human tes tis formationor function. The primary focus of this presentation is to highlightthe importance, methodology, current and potential futureapplications, as well as limitations of using these novel animalmodels in the s tudy and manipulation of male germline s temcells.