Generation of multipotent cell lines from a distinct population of male germ line stem cells

Abstract

Spermatogonial stem cells (SSCs) maintain spermatogenesis by self-renewal and generation of spermatogonia committed to differentiation. Under certain in vitro conditions, SSCs from both neonatal and adult mouse testis can reportedly generate multipotent germ cell (mGC) lines that have characteristics and differentiation potential similar to embryonic stem (ES) cells. However, mGCs generated in different laboratories showed different germ cell characteristics, i.e., some retain their SSC properties and some have lost them completely. This raises an important question: whether mGC lines have been generated from different subpopulations in the mouse testes. To unambiguously identify and track germ line stem cells, we utilized a transgenic mouse model expressing green fluorescence protein under the control of a germ cell-specific Pou5f1 (Oct4) promoter. We found two distinct populations among the germ line stem cells with regard to their expression of transcription factor Pou5f1 and c-Kit receptor. Only the POU5F1C/c-KitC subset of mouse germ line stem cells, when isolated from either neonatal or adult testes and cultured in a complex mixture of growth factors, generates cell lines that express pluripotent ES markers, i.e., Pou5f1, Nanog, Sox2, Rex1, Dppa5, SSEA-1, and alkaline phosphatase, exhibit high telomerase activity, and differentiate into multiple lineages, including beating cardiomyocytes, neural cells, and chondrocytes. These data clearly show the existence of two distinct populations within germ line stem cells: one destined to become SSC and the other with the ability to generate multipotent cell lines with some pluripotent characteristics. These findings raise interesting questions about the relativity of pluripotency and the plasticity of germ line stem cells.

Brief History, Pitfalls, and Prospects of Mammalian Spermatogonial Stem Cell Research

“…1d) (Takehashi et al 2007b). The pluripotency of SSCs was subsequently confirmed by several other groups (Guan et al 2006;Seandel et al 2007;Izadyar et al 2008;Ogawa 2008). However, there are pronounced differences in the phenotypic and functional characteristics of these ES-like cells, which will be the focus of future studies.…”

Spermatogonial Stem Cells: An Alternate Source of Pluripotent Stem Cells for Regenerative Medicine

“…However, the iconoclastic finding of Kanatsu-Shinohara et al (Kanatsu-Shinohara et al 2004) demonstrated that neonatal murine SSCs produced ESC-like cells when isolated from the testis and grown for extended periods in ESC culture conditions. Although initial work was done with neonatal SSCs (Kanatsu-Shinohara et al 2004;Simon et al 2009), subsequent work showed that adult murine SSCs (Glaser et al 2008;Izadyar et al 2008;Seandel et al 2007;Guan et al 2006) grown for 4-7 weeks in vitro also produced a low frequency of ESC-like colonies. These ESC-like cells can give rise to cell types derived from all three embryonic germ layers, and also produce teratomas when injected subcutaneously into nude mice.…”

Pluripotency of Male Germline Stem Cells

“…Izadyar et al (2008) suggested that the Oct4 + /c-Kit + subset of mouse GSCs in the in vitro culture generated a distinct cell population whose properties are very similar to those of pluripotent stem cells.…”