title: Unstable side population phenotype of mouse spermatogonial stem cells in vitro.
abstract: Stem cells of the side population (SP) phenotype are found in many self-renewing tissues and can be identified by their unique ability to effectively exclude the dye Hoechst 33342. We previously established a method for expanding spermatogonial stem cells (SSCs) in vitro, but the frequency of SSCs is only about 1 to 2%, limiting detailed SSC analyses. In this study, we sought to isolate SSCs from in vitro cultures by exploiting their ability to exclude Hoechst 33342. In contrast to the findings of previous in vivo studies, we found that SP cells developed in a stochastic manner in vitro. Moreover, SP cells in culture were not enriched in SSCs, but they were interconvertible with non-SP cells. Although SP cells were consistently found in testes after transplantation of cultured cells, they were not enriched in SSCs. These results show that SSCs have an unstable SP phenotype and provide evidence that SSCs change their phenotype characteristics in response to their microenvironment.
authors.affiliation: Department of Molecular Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Shinohara
authors.forename: Kei
authors.initials: K
authors.lastname: Ishii
authors.forename: Mito
authors.initials: M
authors.lastname: Kanatsu-Shinohara
mesh_terms: D000818:Animals; D001562:Benzimidazoles; D005456:Fluorescent Dyes; D005854:Germ Cells / Q000637:transplantation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D010641:Phenotype; D018239:Seminoma / Q000473:pathology; D058985:Side-Population Cells / Q000166:cytology*; D013093:Spermatogonia / Q000166:cytology*; D013736:Testicular Neoplasms / Q000473:pathology
chemical_list: D001562:Benzimidazoles; D005456:Fluorescent Dyes; C017807:bisbenzimide ethoxide trihydrochloride