Screening of Integrin Heterodimers Expressed Functionally on the Undifferentiated Spermatogonial Stem Cells in the Outbred ICR Mice

BACKGROUND AND OBJECTIVES: Outbred mice are widely used in toxicology, pharmacology, and fundamental biomedical research. However, there have been no reports of in vitro culture systems for spermatogonial stem cells (SSCs) derived from these mice. METHODS: As a step towards constructing a non-cellular niche supporting the in vitro maintenance of outbred mouse SSC self-renewal, we systematically investigated the types of integrin heterodimers that are expressed transcriptionally, translationally, and functionally in SSCs derived from Imprinting Control Region (ICR) mice. RESULTS: Among the genes encoding 25 integrin subunits, integrin α(1), α(5), α(6), α(9), α(V), and α(E), and integrin β(1) and β(5) had significantly higher transcriptional levels than the other subunits. Furthermore, at the translational level, integrin α(5), α(6), α(9), α(V), α(E), and β(1) were localized on the surface of SSCs, but integrin α(1) and β(5) not. Moreover, significantly stronger translational expression than integrin α(9) and α(E) was observed in integrin α(5), α(6), α(V), and β(1). SSCs showed significantly increased adhesion to fibronectin, laminin, tenascin C and vitronectin, and functional blocking of integrin α(5)β(1), α(6)β(1), α(9)β(1) or α(V)β(1) significantly inhibited adhesion to these molecules. CONCLUSIONS: We confirmed that integrin α(5)β(1), α(6)β(1), α(9)β(1) and α(V)β(1) actively function on the surface of undifferentiated SSCs derived from outbred ICR mice.