Figure 2: Immunofluorescence staining of spontaneously formed spheroids. CBDCs were cultured in spheroid-forming conditions for 24 h, and paraffin sections of spheroids were immunostained with primary antibodies specific for SSEA1, Oct4, Nanog, and Sox2 (corresponding to the first horizontal to the fourth horizontal). The positive reaction was distributed among almost all spheroid-forming cells. DAPI (4,6-diamidino-2-phenylindole) was used for nuclear staining. Scale .