FIG. 2.

Mineralization of bone-like extracellular matrix (ECM) in MSCs and iPSCs. (A) Calcium deposition per well of MSC and iPSC cultures in control medium (control) or osteogenic induction medium (osteogenic) on days 20 and 30 was evaluated by the calcium measurement assay. The data represent the mean values±SD of triplicate samples [*P<0.001: analysis of variance (ANOVA) with Tukey's multiple-comparison test]. Fourier transform infrared spectroscopy (FTIR) spectra of MSCs (B) and iPSCs (C) during osteogenic induction. After 30 days of osteogenic induction, both MSCs and iPSCs exhibited bands of a similar absorbance for vibrations of phosphate (P: association with the mineral hydroxyapatite), carbonate (C: association with carbonate substitution for hydroxyl and phosphate groups in hydroxyapatite) and amide I (Am I), and II (Am II) (association with the protein constituents of bone). It should be noted that these absorption peaks are not evident on days 0 and 5 of induction.