Osteogenic differentiation of particle-loaded cells. Porcine MSCs were exposed to 10 μL/mL iron particles overnight, washed and cultured under MSC conditions for 48 hours, and then changed to osteogenic induction media. After 17 days, unlabeled (A) and iron-labeled (B) cells had the same morphology in culture. Alkaline phophatase expression and pattern were similar in unlabeled (C) and iron-labeled (D) cells. Original magnification for panels A and B, × 60; panels C and D, × 150.