title: CD117-positive cells and mast cells in adult human cardiac valves--observations and implications for the creation of bioengineered grafts.
abstract: BACKGROUND
  There is no report to date of stem cells in human cardiac valves. We examined their possible presence, number, and distribution in valves removed at cardiac surgery from patients with a variety of underlying valve pathologies.
  
  
  METHODS
  Grossly normal aortic and mitral valves were obtained from live heart transplant patients. Surgically excised valves with rheumatic mitral stenosis, aortic valve age-related degeneration, aortic valve changes of aortoannular ectasia, and mitral valves with myxomatous degeneration were studied. Immunohistochemical and histochemical studies were performed on sequential valve sections, including hematoxylin and eosin, hematoxylin phloxine saffron, Movat pentachrome, toluidine blue, CD31, CD34, and CD117.
  
  
  RESULTS
  There were small clusters of CD117-positive cells in the fibrosa and spongiosa of mitral and aortic valves from all groups of valves. Sequential sectioning and staining showed that almost all of these cells were mast cells. However, in the mitral myxomatous valves and the mitral rheumatic valves, there were rare CD117-positive cells that did not have corresponding toluidine blue staining and thus could be valve mesenchymal stem cells.
  
  
  CONCLUSIONS
  Most of the CD117-positive cells in normal and diseased adult heart valves are mast cells. These valve cells could play a role in valve pathology and injury. A very small number of possible valve stem cells were also identified. It is unlikely that these valve stem cells are sufficient in number to allow isolation and expansion for tissue engineering purposes.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, Canada. jpveinot@ottawahospital.on.ca
authors.forename: John P
authors.initials: JP
authors.lastname: Veinot
authors.forename: Wendy
authors.initials: W
authors.lastname: Prichett-Pejic
authors.forename: Jianming
authors.initials: J
authors.lastname: Song
authors.forename: Geeta
authors.initials: G
authors.lastname: Waghray
authors.forename: William
authors.initials: W
authors.lastname: Parks
authors.forename: Thierry G
authors.initials: TG
authors.lastname: Mesana
authors.forename: Marc
authors.initials: M
authors.lastname: Ruel
mesh_terms: D001705:Bioprosthesis; D006350:Heart Valve Prosthesis; D006351:Heart Valves / Q000166:cytology* / Q000276:immunology; D006801:Humans; D007150:Immunohistochemistry; D008407:Mast Cells / Q000276:immunology / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D023822:Tissue Engineering
chemical_list: D019009:Proto-Oncogene Proteins c-kit