title: Use of a special bioreactor for the cultivation of a new flexible polyurethane scaffold for aortic valve tissue engineering.
abstract: BACKGROUND
  Tissue engineering represents a promising new method for treating heart valve diseases. The aim of this study was evaluate the importance of conditioning procedures of tissue engineered polyurethane heart valve prostheses by the comparison of static and dynamic cultivation methods.
  
  
  METHODS
  Human vascular endothelial cells (ECs) and fibroblasts (FBs) were obtained from saphenous vein segments. Polyurethane scaffolds (n = 10) were primarily seeded with FBs and subsequently with ECs, followed by different cultivation methods of cell layers (A: static, B: dynamic). Group A was statically cultivated for 6 days. Group B was exposed to low flow conditions (t₁=3 days at 750 ml/min, t₂=2 days at 1100 ml/min) in a newly developed conditioning bioreactor. Samples were taken after static and dynamic cultivation and were analyzed by scanning electron microscopy (SEM), immunohistochemistry (IHC), and real time polymerase chain reaction (RT-PCR).
  
  
  RESULTS
  SEM results showed a high density of adherent cells on the surface valves from both groups. However, better cell distribution and cell behavior was detected in Group B. IHC staining against CD31 and TE-7 revealed a positive reaction in both groups. Higher expression of extracellular matrix (ICAM, Collagen IV) was observed in Group B. RT- PCR demonstrated a higher expression of inflammatory Cytokines in Group B.
  
  
  CONCLUSIONS
  While conventional cultivation method can be used for the development of tissue engineered heart valves. Better results can be obtained by performing a conditioning step that may improve the tolerance of cells to shear stress. The novel pulsatile bioreactor offers an adequate tool for in vitro improvement of mechanical properties of tissue engineered cardiovascular prostheses.
authors.affiliation: Department of Cardiac Surgery, Medical Center Munich University, Marchioninistraße 15, Munich 81377, Germany.
authors.forename: Genoveva
authors.initials: G
authors.lastname: Aleksieva
authors.forename: Trixi
authors.initials: T
authors.lastname: Hollweck
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Thierfelder
authors.forename: Ulrike
authors.initials: U
authors.lastname: Haas
authors.forename: Fabian
authors.initials: F
authors.lastname: Koenig
authors.forename: Cornelia
authors.initials: C
authors.lastname: Fano
authors.forename: Martin
authors.initials: M
authors.lastname: Dauner
authors.forename: Erich
authors.initials: E
authors.lastname: Wintermantel
authors.forename: Bruno
authors.initials: B
authors.lastname: Reichart
authors.forename: Christoph
authors.initials: C
authors.lastname: Schmitz
authors.forename: Bassil
authors.initials: B
authors.lastname: Akra
mesh_terms: D001021:Aortic Valve / Q000166:cytology*; D019149:Bioreactors; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006350:Heart Valve Prosthesis; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D011140:Polyurethanes / Q000494:pharmacology*; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds
chemical_list: D011140:Polyurethanes