Multipotent adult spermatogonial-derived stem cells (MASCs) cultured on JK1 cells maintain multipotency. (A): Phase-contrast images of MASC colonies on JK1 cells (A inset) and mouse embryonic fibroblasts (original magnification, ×100). (B–C): Immunohistochemistry revealed (B) OCT4 and (C) NANOG expression was preserved in MASCs passaged on JK1 cells for more than 2 weeks. (D–I): MASC-derived teratomas expressed markers for all three germ layers by immunofluorescence. (D) CD31, (E) HNF3β, (F) mucin, (G) VE-cadherin, (H) GFAP, and (I) GCNA. Antibody staining is green. Nuclear counterstain is blue. All size bars = 50 μm.