title: Signaling hierarchy regulating human endothelial cell development.
abstract: OBJECTIVE
  Our present knowledge of the regulation of mammalian endothelial cell differentiation has been largely derived from studies of mouse embryonic development. However, unique mechanisms and hierarchy of signals that govern human endothelial cell development are unknown and, thus, explored in these studies.
  
  
  RESULTS
  Using human embryonic stem cells as a model system, we were able to reproducibly and robustly generate differentiated endothelial cells via coculture on OP9 marrow stromal cells. We found that, in contrast to studies in the mouse, bFGF and VEGF had no specific effects on the initiation of human vasculogenesis. However, exogenous Ihh promoted endothelial cell differentiation, as evidenced by increased production of cells with cobblestone morphology that coexpress multiple endothelial-specific genes and proteins, form lumens, and exhibit DiI-AcLDL uptake. Inhibition of BMP signaling using Noggin or BMP4, specifically, using neutralizing antibodies suppressed endothelial cell formation; whereas, addition of rhBMP4 to cells treated with the hedgehog inhibitor cyclopamine rescued endothelial cell development.
  
  
  CONCLUSIONS
  Our studies revealed that Ihh promoted human endothelial cell differentiation from pluripotent hES cells via BMP signaling, providing novel insights applicable to modulating human endothelial cell formation and vascular regeneration for human clinical therapies.
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Kelly
authors.forename: Karen K
authors.initials: KK
authors.lastname: Hirschi
mesh_terms: D055415:Bone Morphogenetic Protein 4 / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D042783:Endothelial Cells / Q000502:physiology*; D053823:Hedgehog Proteins / Q000502:physiology*; D006801:Humans; D018919:Neovascularization, Physiologic / Q000502:physiology; D015398:Signal Transduction
chemical_list: C525809:BMP4 protein, human; D055415:Bone Morphogenetic Protein 4; D053823:Hedgehog Proteins; C509246:IHH protein, human