title: Time-lapse microscopy of macrophages during embryonic vascular development.
abstract: BACKGROUND
  Macrophages are present before the onset of blood flow, but very little is known about their function in vascular development. We have developed a technique to concurrently label both endothelial cells and macrophages for time-lapse microscopy using co-injection of fluorescently conjugated acetylated low-density lipoprotein (AcLDL) and phagocytic dye PKH26-PCL.
  
  
  RESULTS
  We characterize double-labeled cells to confirm specific labeling of macrophages. Double-labeled cells circulate, roll along the endothelium, and extravasate from vessels. Most observed macrophages are integrated into the vessel wall, showing an endothelial-like morphology. We used transgenic quail that express a fluorescent protein driven by the endothelial-specific promoter Tie1 in conjugation with the phagocytic dye to analyze these cells. Circulating PKH26-PCL-labeled cells are mostly Tie1-, but those which have integrated into the vessel wall are largely Tie1+. The endothelial-like phagocytic cells were generally stationary during normal vascular development. We, therefore, induced vascular remodeling and found that these cells could be recruited to sites of remodeling.
  
  
  CONCLUSIONS
  The active interaction of endothelial cells and macrophages support the hypothesis that these cells are involved in vascular remodeling. The presence of phagocytic endothelial-like cells suggests either a myeloid-origin to certain endothelial cells or that circulating endothelial cells/hematopoietic stem cells have phagocytic capacity.
authors: Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada.
authors: Sarah
authors: S
authors: Al-Roubaie
authors: Jasmine H
authors: JH
authors: Hughes
authors: Michael B
authors: MB
authors: Filla
authors: Rusty
authors: R
authors: Lansford
authors: Stephanie
authors: S
authors: Lehoux
authors: Elizabeth A V
authors: EA
authors: Jones
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000166:cytology / Q000196:embryology* / Q000502:physiology; D003370:Coturnix / Q000196:embryology; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000196:embryology / Q000502:physiology; D005456:Fluorescent Dyes / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology* / Q000502:physiology* / Q000648:ultrastructure; D008853:Microscopy / Q000379:methods; D009930:Organic Chemicals / Q000494:pharmacology; D059008:Time-Lapse Imaging / Q000379:methods
chemical_list: D005456:Fluorescent Dyes; D009930:Organic Chemicals; C070080:PKH 26