title: Biological fate of tissue-engineered porcine valvular conduits xenotransplanted in the sheep thoracic aorta.
abstract: The ideal prosthesis to replace the diseased human aortic valve is not yet available. We have previously shown that porcine acellular aortic-valve conduits, obtained by detergent-enzymatic method, display hemodynamic performances similar to those of their native counterparts. Hence, it seemed worthwhile to ascertain whether these tissue-engineered prostheses can be successfully xenotransplanted. Porcine acellular conduits, which immunocytochemistry demonstrated to lack MHC class I and II antigens, were implanted in the thoracic aorta of 9 sheep. Two animals died just after surgery, and the other 7 sheep were sacrificed 1 or 5 months after transplantation. A rather favorable outcome of the implant was observed in 4 sheep. In these animals, aortic valves remained pliable and coaptive, and the luminal surface of the conduits was endothelized just after one month from surgery. An intense inflammatory response was present at 1 month, and, although attennuated, it persisted for 5 months, located mainly between the tunica intima and media and at the border of the implant. Vimentin-positive and smooth muscle actin-positive myofibroblasts proliferated within tunica media and adventitia, and an obvious thickening of the tunica intima was also observed. Small vessels were seen in the adventitia, and elastic fibers were well-preserved in both the aorta wall and valve leaflets. In the cases of unfavorable outcome (3 of 7 survived sheep), implants were detached from the aorta recipient and surrounded by a connective mass that almost completely obstructed their lumen. These masses were composed of a fibromyxoid background where proliferating cells, resembling those occurring in human reactive myofibroblastic lesions (proliferative fascitis), were embedded. Collectively, these rather disappointing findings indicate that acellular valve conduits, obtained by the detergent-enzymatic method, are presently not suitable for clinical applications because of the persistent inflammatory response, which conceivably triggers overgrowth mechanisms that lead to implant failure.
authors.affiliation: Department of Pharmaceutical Sciences, University of Padua, I-35121 Padua, Italy.
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Conconi
authors.forename: Francesco
authors.initials: F
authors.lastname: Rocco
authors.forename: Raffaella
authors.initials: R
authors.lastname: Spinazzi
authors.forename: Mara
authors.initials: M
authors.lastname: Tommasini
authors.forename: Carlo
authors.initials: C
authors.lastname: Valfrè
authors.forename: Roberto
authors.initials: R
authors.lastname: Busetto
authors.forename: Elvio
authors.initials: E
authors.lastname: Polesel
authors.forename: Giovanna
authors.initials: G
authors.lastname: Albertin
authors.forename: Angelo
authors.initials: A
authors.lastname: Dei Tos
authors.forename: Ilaria
authors.initials: I
authors.lastname: Iacopetti
authors.forename: Attilio
authors.initials: A
authors.lastname: Cecchetto
authors.forename: Claudio
authors.initials: C
authors.lastname: Zussa
authors.forename: Mauro
authors.initials: M
authors.lastname: Grigioni
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Parnigotto
authors.forename: Gastone Giovanni
authors.initials: GG
authors.lastname: Nussdorfer
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology* / Q000473:pathology / Q000601:surgery* / Q000648:ultrastructure; D001021:Aortic Valve / Q000166:cytology / Q000637:transplantation*; D004847:Epithelial Cells / Q000166:cytology / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D007249:Inflammation / Q000209:etiology / Q000473:pathology; D008855:Microscopy, Electron, Scanning; D012756:Sheep; D013552:Swine; D023822:Tissue Engineering / Q000009:adverse effects*; D014183:Transplantation, Heterologous / Q000009:adverse effects* / Q000473:pathology; D016896:Treatment Outcome