title: Functional and biomechanical evaluation of a completely recellularized stentless pulmonary bioprosthesis in sheep.
abstract: OBJECTIVE
  In a previous study we showed that recellularization of a stentless bioprosthetic valve is stimulated 1 month after implantation in the pulmonary position, when its matrix (acellular photo-oxidized bovine pericardium) was preseeded by intraperitoneal implantation during a 3-day period.
  
  
  METHODS
  The present study reports on the functional and biomechanical properties of such valves (n = 19) in sheep up to 5 months after implantation. Similar valves (n = 20) that were not intraperitoneally preseeded served as controls.
  
  
  RESULTS
  Recellularization was partial in control valves and excessive in preseeded valves: 66% versus 223% of cellularity of native valves, respectively (P < .05). The valves were endothelialized and contained interstitial cells depositing new matrix (collagens and elastin). However, phenotyping revealed an increased proportion of cells with contractile properties (30%-40% alpha smooth muscle actin+) in both groups. Intraperitoneally seeded valves had thicker and shorter leaflets that were associated with mildly increased peak gradients and regurgitation. Characterization of the matrix properties revealed a gradually degrading matrix (+/-25% loss of collagen organization at 5 months) and a concomitant alteration of its biomechanical properties, that is, decreased strength, stiffness, and maximum force. However, overall valve function remained intact, and the biomechanical properties of the whole valves were superior to that of the native valves.
  
  
  CONCLUSIONS
  The ectopic in vivo seeding paradigm provides full recellularization. However, the volume fraction of the cellular phenotypes is not optimal, resulting in inadequate remodeling of the valves.
authors.affiliation: Laboratory for Experimental Cardiac Surgery, Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium. geofrey.devisscher@med.kuleuven.be
authors.forename: Geofrey
authors.initials: G
authors.lastname: De Visscher
authors.forename: Helga
authors.initials: H
authors.lastname: Blockx
authors.forename: Bart
authors.initials: B
authors.lastname: Meuris
authors.forename: Hans
authors.initials: H
authors.lastname: Van Oosterwyck
authors.forename: Erik
authors.initials: E
authors.lastname: Verbeken
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Herregods
authors.forename: Willem
authors.initials: W
authors.lastname: Flameng
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001705:Bioprosthesis; D004195:Disease Models, Animal; D005069:Evaluation Studies as Topic; D005260:Female; D006350:Heart Valve Prosthesis; D011336:Probability; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011664:Pulmonary Valve / Q000601:surgery*; D011897:Random Allocation; D012016:Reference Values; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012756:Sheep; D013718:Tensile Strength; D023822:Tissue Engineering; D014021:Tissue Preservation; D016378:Tissue Transplantation / Q000379:methods