title: Tissue-engineered heart valve: future of cardiac surgery.
abstract: BACKGROUND
  Heart valve disease is currently a growing problem, and demand for heart valve replacement is predicted to increase significantly in the future. Existing "gold standard" mechanical and biological prosthesis offers survival at a cost of significantly increased risks of complications. Mechanical valves may cause hemorrhage and thromboembolism, whereas biologic valves are prone to fibrosis, calcification, degeneration, and immunogenic complications.
  
  
  METHODS
  A literature search was performed to identify all relevant studies relating to tissue-engineered heart valve in life sciences using the PubMed and ISI Web of Knowledge databases.
  
  
  CONCLUSIONS
  Tissue engineering is a new, emerging alternative, which is reviewed in this paper. To produce a fully functional heart valve using tissue engineering, an appropriate scaffold needs to be seeded using carefully selected cells and proliferated under conditions that resemble the environment of a natural human heart valve. Bioscaffold, synthetic materials, and preseeded composites are three common approaches of scaffold formation. All available evidence suggests that synthetic scaffolds are the most suitable material for valve scaffold formation. Different cell sources of stem cells were used with variable results. Mesenchymal stem cells, fibroblasts, myofibroblasts, and umbilical blood stem cells are used in vitro tissue engineering of heart valve. Alternatively scaffold may be implanted and then autoseeded in vivo by circulating endothelial progenitor cells or primitive circulating cells from patient's blood. For that purpose, synthetic heart valves were developed.
  
  
  CONCLUSIONS
  Tissue engineering is currently the only technology in the field with the potential for the creation of tissues analogous to a native human heart valve, with longer sustainability, and fever side effects. Although there is still a long way to go, tissue-engineered heart valves have the capability to revolutionize cardiac surgery of the future.
authors.affiliation: UCL Centre for Nanotechnology & Regenerative Medicine, Division of Surgery and Interventional Science, University College London, London, UK. r.rippel@ucl.ac.uk
authors.forename: Radoslaw A
authors.initials: RA
authors.lastname: Rippel
authors.forename: Hossein
authors.initials: H
authors.lastname: Ghanbari
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Seifalian
mesh_terms: D001705:Bioprosthesis / Q000009:adverse effects; D019149:Bioreactors; D042783:Endothelial Cells; D005347:Fibroblasts; D006350:Heart Valve Prosthesis / Q000009:adverse effects; D006801:Humans; D013234:Stem Cells; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds