Effects of fibroblast growth factor-2 (FGF-2) expansion on cell proliferation rates and morphology. (a) Cell proliferation rates for passage 2 infrapatellar fat pad-derived cells expanded in normal medium (black bars) and FGF-2-supplemented medium (white bars) at days 2, 4, 6, 8, and 10 are shown. Data are mean ± standard error of the mean (n = 6). *P <0.05 (Student paired t test). Phase-contrast microscopy of cells expanded in normal (b) and FGF-2-supplemented (c) media shows that the latter were smaller, more fibroblastic, and less flattened.