Analysis of adipocyte differentiation. A) The table shows the percentage of Oil Red O positive cells treated with OS or HS and then induced to differentiate into adipocytes. The percentage of Oil Red O positive cells was calculated by counting at least 500 cells in different microscope fields. Data are expressed as mean values with standard deviations (*P <0.05). The picture shows a representative field of oil-red positive cells. B) RT-PCR expression analysis of early and late adipocyte differentiation markers in MSCs treated with OS or HS and then induced to differentiate into adipocytes. mRNA levels were normalized with respect to GAPDH, which was chosen as an internal control. Each experiment was repeated at least three times. The histogram shows the changes in mRNA expression levels 14 days after incubation in differentiation conditions of MSCs grown in OS (red bars) or HS (black bars). They are expressed as arbitrary units (*P <0.05). HS, healthy weight sera; MSCs, mesenchymal stem cells; OS, overweight sera.