Comparison of osteogenic differentiation between labeled and unlabeled canine MSCs. UCBMSCs and ATMSCs were cultured in osteogenic differentiation medium for 21 days. Cells were then stained with alizarin red S. Red calcium deposition was observed following osteogenic induction. Osteogenic differentiation was not inhibited by silica nanoparticle labeling as compared with that in unlabeled cells. Magnification, ×200.