Adipogenic differentiation of human ASC clones in early and late passage. (A) Morphology of an ASC clone (B2) at P7 and at senescence (Ps). Arrow points to the nucleus of a large and flattened single cell at Ps. These phenotypes are typical for early passage and senescent human ASCs cultured clonally or as polyclones. (B) Three ASC clones (B1, B2, B3) were induced to differentiate toward the adipogenic pathway for three weeks, starting at P7 (B) or Ps (C). Ps corresponded to P18 (clone B1), P16 (clone B2) and P17 (clone B3). Cells were stained with Oil Red-O to visualize lipid droplets and with hematoxylin to visualize nuclei. Bars, 100 μm.