Front Cover

Cover Art: Endothelial differentiation of bone marrow cells in vitro is visualized by a vessel‐like structure formation assay based on the number of branches displaying immunoreactivity to a PECAM1 antibody (red), nuclei (blue). The presence of green fluorescent protein (beta‐actin promoter, green) in PECAM1‐immunoreactive structures (red) demonstrates the possibility of tracking these cells in vivo. Primary KDR‐enriched bone marrow cells at passage 0 start vessel‐like structure formation after 1 week of culture, whereas unsorted cells at passage 12 after 77 days of culture demonstrate formation of vessel‐like structures the day after induction with vascular endothelial growth factor. See Firsova et al. beginning on page 2094 .