Co-culture of MSC and FEMX-I cells shows uptake of prominin-1 by MSC. MSC and FEMX-I cells were cultured for 24 h at 1:5 ratio. After fixation and permeabilization, expression of prominin-1 was analyzed by immunofluorescence employing phycoerythrin-conjugated AC133 anti-prominin-1 antibody. Since MSC do not express prominin-1, there could be no interference from an endogenous MSC prominin-1 pool. Insets in the upper panels were enlarged in the lower panels. Arrows indicate some areas of prominin-1 positivity inside a MSC. Red, prominin-1; blue, DAPI. Bars, 25 μm.