Figure 2

Morphology of expanded CB-CD34+ cells. A-D. Cytospin preparations of cultured CB-CD34+ cells. A. Day 0. Cells appear lymphocyte-like and uniform in size and shape. B. Day 3; basic medium. Amount of cytoplasm has increased. Mitotic activity is noted (arrow). C-D. Day 15; basic (C) or DEX (D) medium (insets: corresponding phase contrast microscopy images). Cells are larger and more heterogeneous. Many cells display a vacuolated cytoplasm with granular eosinophilic or basophilic cytoplasm. A-D: Giemsa-Wright stain; original magnification X 1,000. E-H. Ultrastructural appearance of expanded CB-CD34+ cells. E. Day 0. Relatively small freshly isolated cells with sparse cytoplasm and scant organelles. Electron dense beads are noted (incidental finding related to MACS cell sorting procedure) (arrows and inset). F-G. Day 15; basic (F) or DEX (G) medium. Cells are larger and more variable in size and shape with more irregular nuclei and more complex cytoplasmic composition. Most cells display specific granules of different size and electron density, suggestive of myeloid differentiation. The arrow in panel F depicts an atypical cell exhibiting a curved nucleus, microvilli, and microvesicular cytoplasmic aggregates (inset). The arrow in panel G depicts an apoptotic cell. H. Day 15, DEX medium. Atypical cell showing irregular curved nucleus, localized cytoplasmic aggregate of microvesicular structures, and microvilli, associated with evidence of exocytosis of lamellated material (arrow and inset). E-H: (uranyl acetate/lead citrate stain; size bar = 2 μm).