title: Spermatogonial stem cells: questions, models and perspectives.
abstract: This review looks into the phylogeny of spermatogonial stem cells and describes their basic biological features. We are focusing on species-specific differences of spermatogonial stem cell physiology. We propose revised models for the clonal expansion of spermatogonia and for the potential existence of true stem cells and progenitors in primates but not in rodents. We create a new model for the species-specific arrangements of spermatogenic stages which may depend on the variable clonal expansion patterns. We also provide a brief overview of germ cell transplantation as a powerful tool for basic research and its potential use in a clinical setting.
authors.affiliation: Department of Cell Biology and Physiology, Center for Research in Reproductive Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
authors.forename: Jens
authors.initials: J
authors.lastname: Ehmcke
authors.forename: Joachim
authors.initials: J
authors.lastname: Wistuba
authors.forename: Stefan
authors.initials: S
authors.lastname: Schlatt
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002999:Clone Cells / Q000145:classification / Q000166:cytology / Q000502:physiology; D006801:Humans; D008297:Male; D008954:Models, Biological; D039904:Pluripotent Stem Cells / Q000145:classification* / Q000166:cytology / Q000502:physiology*; D051381:Rats; D013093:Spermatogonia / Q000145:classification* / Q000166:cytology / Q000502:physiology*; D033581:Stem Cell Transplantation