Cell cycle progression during adipogenic differentiation of hBMSCs. (A) Post-confluence hBMSCs with or without induction (MDI+Indo treatment for one, two or three cycles) were counted and plotted on day 0 and day 21. (B) Cells with parallel treatment in (A) were also stained with oil red O on day 21 and photographed (magnification 100×). (C) 10 μg/ml BrdU was added to 3T3-L1 cells at 18 h after MDI treatment for 30 h, and added to hBMSC at 24 h for 48 h. BrdU incorporation was detected by immunocytochemistry and photographed with both a halogen and mercury lamp switched on (magnification 200×). In 3T3-L1 cells (D) and hBMSCs (E) with or without induction (control), incorporated BrdU (FITC) and fat lipids (TRITC) were shown by confocal microscopy.