title: Challenges in developing a reseeded, tissue-engineered aortic valve prosthesis.
abstract: OBJECTIVE
  Biological heart valve prostheses are characterized by a limited durability due to the degenerative processes after implantation. Tissue engineering may provide new approaches in the development of optimized valvular grafts. While re-endothelialization of decellularized heart valves has already been successfully implemented, interstitial repopulation still remains an unaccomplished objective although it is essential for valvular functionality and regeneration potential. The aim of this study was to compare different concepts for an improved in vitro interstitial repopulation of decellularized heart valves. A novel 3D heart valve model has been developed to investigate the cell behaviour of valvular interstitial cells (VIC) in their physiological environment and to evaluate the potential of in vitro repopulation of acellular heart valves.
  
  
  METHODS
  Ovine aortic heart valves were decellularized by detergent solutions and additionally treated with trypsin or laser perforation. Subsequently, the decellularized extracellular matrices (dECM) were reseeded with ovine VIC using reseeding devices to provide a repopulation of the matrix on a defined area under controlled conditions. After an initial attachment of the VIC, reseeded dECM were transferred into a transwell system to improve the nutrient supply inside the valvular matrix. Cell migration and expression of cell markers were analysed histologically. The results were compared with VIC cultivation in a biological scaffold.
  
  
  RESULTS
  VIC did not migrate into the matrix of untreated dECM and reseeding in laser perforated dECM showed inconsistent results. However, trypsinization increased the susceptibility of the valvular cusps to VIC penetration and repopulation of superficial areas. Additionally, the cultivation of reseeded dECM in a transwell system significantly increased the total number of cells repopulating the valvular matrix and their mean migration distance, representing the best repopulation results. Immunohistological analysis and in situ zymography revealed a low activation status of repopulating VIC after 7 days of culture.
  
  
  CONCLUSIONS
  A comparison of different techniques for increasing interstitial repopulation of detergent dECM revealed that an additional limited trypsin treatment was most effective. Nevertheless, a complete interstitial repopulation of decellularized heart valves remains a challenging endeavour. Additional experimental fine-tuning may improve the in vitro results of heart valve tissue engineering.
authors.affiliation: Department of Cardiovascular Surgery, Heinrich-Heine-University, Medical Faculty, Düsseldorf, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Hof
authors.affiliation: Department of Cardiovascular Surgery, Heinrich-Heine-University, Medical Faculty, Düsseldorf, Germany.
authors.forename: Silja
authors.initials: S
authors.lastname: Raschke
authors.affiliation: Department of Cardiovascular Surgery, Heinrich-Heine-University, Medical Faculty, Düsseldorf, Germany.
authors.forename: Karina
authors.initials: K
authors.lastname: Baier
authors.affiliation: Department of Cardiovascular Surgery, Heinrich-Heine-University, Medical Faculty, Düsseldorf, Germany.
authors.forename: Laura
authors.initials: L
authors.lastname: Nehrenheim
authors.affiliation: Department of Cardiovascular Surgery, Heinrich-Heine-University, Medical Faculty, Düsseldorf, Germany.
authors.forename: Jessica Isabel
authors.initials: JI
authors.lastname: Selig
authors.affiliation: Department of Biomedical Optics, Laser Zentrum Hannover e.V., Hannover, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Schomaker
authors.affiliation: Department of Cardiovascular Surgery, Heinrich-Heine-University, Medical Faculty, Düsseldorf, Germany artur.lichtenberg@med.uni-duesseldorf.de.
authors.forename: Artur
authors.initials: A
authors.lastname: Lichtenberg
authors.affiliation: Department of Biomedical Optics, Laser Zentrum Hannover e.V., Hannover, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Meyer
authors.affiliation: Department of Cardiovascular Surgery, Heinrich-Heine-University, Medical Faculty, Düsseldorf, Germany.
authors.forename: Payam
authors.initials: P
authors.lastname: Akhyari
mesh_terms: D000818:Animals; D001021:Aortic Valve / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D001705:Bioprosthesis; D019149:Bioreactors; D002465:Cell Movement; D002478:Cells, Cultured; D003902:Detergents / Q000494:pharmacology; D005109:Extracellular Matrix / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D006350:Heart Valve Prosthesis; D020007:Implants, Experimental; D007834:Lasers; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008955:Models, Cardiovascular; D012756:Sheep; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds; D014357:Trypsin / Q000494:pharmacology
chemical_list: D003902:Detergents; D014357:Trypsin; D020782:Matrix Metalloproteinases
keywords: Decellularization; Heart valve; Tissue engineering; Valvular interstitial cell